JP3905363B2 - Liquid epoxy resin composition for sealing filler - Google Patents

Description

【００４９】
（式中、Ｒ２は、一価の鎖式炭化水素基であり、Ｒ３は、一価の鎖式炭化水素基であり、Ｒ６は、水素原子または鎖式炭化水素基である）で示される環上に置換を有するテトラヒドロフタル酸型の二カルボン酸の分子内酸無水物、あるいは、一般式（II）：
【００５０】
【化２】

【００５１】
（式中、Ｒ２は、一価の鎖式炭化水素基であり、Ｒ３は、一価の鎖式炭化水素基である）で示される環上に置換と架橋鎖を有するテトラヒドロフタル酸型二カルボン酸の分子内酸無水物など、相対的な嵩高い６員環を有するものも、好適な酸無水物の一例として挙げられる。
【００５２】
加えて、得られるエポキシ樹脂硬化物において、その可撓性を増進するため、用いられる酸無水物自体の炭素骨格内に不飽和炭素結合を含まないものを用いることができる。例えば、熱硬化性エポキシ樹脂に対する硬化剤として利用されている酸無水物のうち、−ＣＯ−Ｏ−ＣＯ−を含む環構造が５員環を構成し、しかも、この５員環は、環状の炭化水素骨格と縮合する形状を有し、その際、環状の炭化水素骨格は、その環内に不飽和炭素結合を含まないものが好適である。より具体的には、飽和な環状の炭化水素二カルボン酸の分子内酸無水物であり、−ＣＯ−Ｏ−ＣＯ−を含む環構造が５員環を構成するものが好ましい。一例として、先に述べた脂環族酸無水物、例えば、ヘキサヒドロ無水フタル酸（ＨＨＰＡ）、メチルテトラヒドロ無水フタル酸（ＭＴＨＰＡ）、無水メチルナジック酸（ＮＭＴ）などに含まれる、環状の炭化水素骨格中の不飽和炭素結合に水素添加を施した、飽和な脂環族酸無水物が、かかる目的ではより好ましく、水素添加ナジック酸（ＨＮＡ）の酸無水物を代表例として挙げることができる。
【００５３】
下記する飽和な環状炭素骨格を有する水素添加ナジック酸（ＨＮＡ）の酸無水物、ビシクロ［２．２．１］ヘプタン−２，３−ジカルボン酸由来の酸無水物：
【００５４】
【化３】

【００５５】
と同様に、ビシクロ［２．２．１］ヘプタン（ノルボルナン）骨格を含む、飽和な環状炭素骨格を有する酸無水物である、ビシクロ［２．２．１］ヘプタン−２，３，５，６−テトラカルボン酸由来の酸無水物：
【００５６】
【化４】

【００５７】
あるいは、分子内に鎖状のシロキサン構造（−（Ｈ₂ＳｉＯ）_n−ＳｉＨ₂−）を含んでいる、末端にビシクロ［２．２．１］ヘプタン−２，３−ジカルボン酸由来の酸無水物構造が置換したポリシロキサン：
【００５８】
【化５】

【００５９】
なども、利用可能な飽和な脂環族酸無水物に含まれる。なお、かかるビシクロ［２．２．１］ヘプタン−２，３−ジカルボン酸由来の酸無水物のように、ジカルボン酸のカルボキシ基が存在する炭素原子に対して、その隣接する炭素原子との間で炭素−炭素二重結合を構成する上で、立体障害となる炭素骨格を有するものでは、より高温において熱硬化反応を行う際、かかるジカルボン酸からの熱的な脱炭酸に伴う二酸化炭素の生成もなく、その点にも、利点を有している。
【００６０】
前記酸無水物はその大半は硬化剤として消費されるが、フラックス成分として、若干量が消費されるので、その消費量を考慮し、液状エポキシ樹脂の１当量に対して、例えば、酸無水物を０．８当量以上、好ましくは、０．９当量以上、多くとも、若干等量を超える量、具体的には、１．１当量を超えない範囲、０．９〜１．１当量の範囲に選択することがより好ましい。
【００６１】
なお、酸化皮膜の形成が多い劣悪な条件では、より高いフラックス活性が必要となり、その点を考慮して、前記（Ｂ）の硬化剤の酸無水物の添加率範囲上限に近い値を選択すると好ましい。現実的には、過度の自然酸化が生じないように当業者が通常の注意を払う限り、（Ａ）の熱硬化性エポキシ樹脂の１当量に対して、酸無水物を０．８５〜０．９５当量含む組成範囲に選択しても、必要とされるフラックス活性に伴う消費量を賄い、更に残る酸無水物の量は、熱硬化に適当な０．８当量〜０．９当量の範囲に概ね収まる。なお、バンプ電極間の間隔が狭くなることも考えあわせると、表面酸化皮膜の除去で消費される酸無水物の割合が相対的に増す傾向にある。その際には、安全を見て、当初の含有比率をやや高め、例えば、１．１当量までに選択することで、フラックス作用を発揮して消費される量を除いても、熱硬化に適当な０．８当量〜１．０当量の範囲により確実に収めることができる。
【００６２】
前記する種々の酸無水物から、上記（Ａ）の各種液状の熱硬化性エポキシ樹脂に応じて選択される酸無水物を（Ｂ）の硬化剤として用い、（Ａ）液状の熱硬化性エポキシ樹脂と共に開環重合を起こさせ、熱硬化を起こさせる。その際、熱硬化温度が比較的に低い場合は、エポキシ環の開環を適度に促進する目的で、硬化促進剤を少量添加することが望ましい。すなわち、本発明の封止充填剤用液状エポキシ樹脂組成物では、（Ｂ）の硬化剤として酸無水物は、適正な重合の伸長に適する比率であるものの、その熱硬化の開始に、硬化促進剤の作用を利用し、その添加量を硬化温度に応じて選択することで、全体的な熱硬化速度を所望の範囲に調整することが容易になる。
【００６３】
この硬化促進剤は、エポキシ基の開環反応を促進し、酸無水物自体と反応を起こさないものである限り、特に制限はなく、酸無水物とアミドの形成を起こさないアミン化合物、ルイス酸、ならびにイミダゾール類が利用できる。前記の要件を満たすアミン化合物としては、具体的には、第三級アミン、例えば、ベンジルジメチルアミン（ＢＤＭＡ）、２，４，６−トリス（ジメチルアミノメチル）フェノール（ＤＭＰ−３０）など、ルイス酸としては、例えば、ＢＦ₃・モノエチルアミン、ＢＦ₃・ピペラジンなど、また、イミダゾール類としては、１−ベンジル−２−メチルイミダゾール、２−エチル−４−メチルイミダゾール（ＥＭ１２４）、２−ヘプタデシルイミダゾール（ＨＤ１２）など、これらを一例として挙げることができる。
【００６４】
これら硬化促進剤の内でも、イミダゾール類は、付加的成分として添加されているジカルボン酸と含有される窒素原子間での複合体（付加塩）を形成する懸念が少なく、本発明の目的により適するものである。
【００６５】
硬化促進剤として、前記するアミン化合物、ルイス酸、ならびにイミダゾール類などを用いる際には、これら求核性化合物のエポキシ環の開環促進作用により、反応が誘起・促進された、エポキシ樹脂と酸無水物との重付加反応により、樹脂鎖の延長がなされる。従って、熱硬化性エポキシ樹脂の１分子当たり、０．００１〜０．０２分子の硬化促進剤を混合することが好ましい。例えば、硬化促進剤として、具体的には、例えば、エポキシ当量１９０のエポキシ樹脂の１００ｇ当たり、イミダゾール類では０．５〜１０ｍｍｏｌ（ミリモル）の範囲に選択するとよい。硬化促進剤個々の分子量にもよるが、例えば、液状エポキシ樹脂の１００質量部当たり、０．１〜２質量部の範囲で添加することもできる。なお、硬化処理温度を高くするに伴い、硬化促進剤の添加比率を下げても、硬化剤の酸無水物との反応は進行するので、この熱硬化反応と平行して進行されるフラックス処理の反応と、その反応速度の均衡が図られるように、硬化処理温度を高く選択する際には、硬化促進剤の添加比率を相対的に下げ、液状エポキシ樹脂の１００質量部当たり、０．１〜１．２質量部の範囲の範囲とすることがより望ましい。
【００６６】
以上に説明した、熱硬化反応に関与する主要成分を均一に混合した液状エポキシ樹脂組成物中に、付加的成分として、（Ｃ）プロトン供与能を有するフラックス活性増強成分としての機能を有する、ジカルボン酸を少量添加する。
【００６７】
前記ジカルボン酸は、その融点は、液状エポキシ樹脂組成物の熱硬化温度より低く、常温では固体であり、その沸点は、前記液状エポキシ樹脂組成物の熱硬化温度よりも高いことが好ましい。加えて、液状エポキシ樹脂組成物中の主成分であるエポキシ樹脂と均一に混和できる、相溶性に富むジカルボン酸が好ましい。
【００６８】
すなわち、ジカルボン酸は、酸無水物と同様に、液状エポキシ樹脂組成物中に均一に溶解・混和した状態で使用されるが、熱硬化の進行とともに、溶媒としても機能している液状エポキシ樹脂自体、重合を起こし、溶媒として機能する液状エポキシ樹脂量が減少していく際にも、ジカルボン酸が液状エポキシ樹脂組成物中に均一な溶解状態を維持することが好ましい。
【００６９】
従って、用いるジカルボン酸は、その沸点は、液状エポキシ樹脂組成物の熱硬化温度よりも有意に高いことがより好ましい。熱硬化とともに、フラックス処理も進行するが、仮に、熱硬化温度よりも、用いるジカルボン酸の沸点が低いと、液状エポキシ樹脂組成物中に溶解しているので、沸点上昇が生じて、実効的に気泡を生じて気化するには至らないものの、蒸散が進み、残留濃度が減少すると、目標とするフラックス活性増強作用を達成できない事態も生じる。用いるジカルボン酸の沸点が、液状エポキシ樹脂組成物の熱硬化温度よりも有意に高いならば、前記の蒸散に伴うフラックス活性増強作用の低下は、問題とならないものとなる。また、熱硬化が完了した時点で、重合反応の終端において消費されず、なお、残留しているジカルボン酸は、その融点が熱硬化温度よりも低いと、硬化物の重合体分子間に浸漬し、均一に分散した状態がより確実に達成できる。勿論、熱硬化の際、気化したジカルボン酸が気泡を形成して、ボイドの発生させる要因ともならない。
【００７０】
加えて、ジカルボン酸は、その分子形状によっては、加熱する間に、自らの分子内で、二つのカルボキシ基間で脱水縮合が生じ、酸無水物へと変換されることもある。具体的には、生成する環状無水物が、無水コハク酸、無水マレイン酸、無水フタル酸のように、５員環を形成するもの、あるいは、グルタル酸無水物のように、６員環を形成するものは、加熱温度が増すに従って、脱水縮合による酸無水物へと変換が進行する。その際、フラックス活性増強作用を有するジカルボン酸の含有比率は結果として減少する、すなわち、フラックス活性増強作用の低下が引き起こされる。生成する酸無水物自体は、エポキシ樹脂に対する硬化剤として機能するものが多く、問題となることはないものの、当初添加するジカルボン酸量を予め増すことが必要となり、決して好ましいものではない。加えて、この５員環、あるいは、６員環の環状酸無水物を生成するに付随して、副生物の水分子が気化し、気泡を形成すると、ボイド発生の要因となり、封止充填剤の機能上好ましものではない。
【００７１】
それとは別に、ジカルボン酸のうち、水に対する溶解性に富む、フマル酸（trans−ブタン二酸）、シュウ酸（エタン二酸）、マロン酸（プロパン二酸）などは、前記環状酸無水物を生成する懸念はないものの、封止充填剤の耐水性、あるいは、高湿環境における保護特性の観点では、硬化物表面に存在した際、水に溶解して、酸として機能する懸念があり、その利用範囲は制限がある。
【００７２】
対象とするハンダ材料は、その融点が２００℃以上、高くとも、２３０℃を超えない範囲の鉛フリーハンダであるため、封止充填剤用液状エポキシ樹脂組成物の熱硬化処理の温度は、鉛フリーハンダの融解温度よりは有意に、例えば１０℃程度以上は高いものの、通常、高くとも２６０℃を超えない範囲に選択し、フラックス処理を併せて実施する。従って、かかる熱硬化処理の温度を、２３０℃〜２６０℃の範囲に選択する際にも、以上の種々の条件を全て満たし、制約なく、好適に利用可能なジカルボン酸は、ジカルボン酸の融点は、例えば、組成がＳｎ：９５．８％、Ａｇ：３．５％、Ｃｕ：０．７％のＳｎ−Ａｇ系ハンダの融解温度（２１７℃）よりも有意に低く、沸点は、かかるＳｎ−Ａｇ系ハンダの融解温度よりも十分に高く、また、水に対する溶解性が乏しいもので、加えて、含まれる二つのカルボキシ基の間に、少なくとも、炭素数で４以上の炭素鎖長に相当する隔たりがある構造を有するジカルボン酸である。
【００７３】
例えば、飽和脂肪族ジカルボン酸であれば、二つのカルボキシ基を両端に含む鎖（ＨＯＯＣ−（Ｃ）_n−ＣＯＯＨ）を母体鎖とする際、この鎖長（ｎ＋２）の母体鎖は、少なくとも、炭素数６以上の鎖長を有するもの、好ましくは、炭素数９〜１５の範囲の鎖長を有するもの、より好ましくは、炭素数１０〜１３の範囲の鎖長を有するものを、好適な例として挙げることができる。なお、この母体鎖に対して、若干数の分岐鎖が存在するものであっても、その融点が極端に上昇するものでなければ、同様に好適なものとなる。飽和脂肪族ジカルボン酸のなかでも、側鎖を持たない、直鎖のアルカン二酸であり、その炭素数は、Ｃ９〜Ｃ１５の範囲、より好ましくは、Ｃ１０〜Ｃ１３の範囲であると、より好ましいものとなる。
【００７４】
また、不飽和脂肪族ジカルボン酸においても、前記飽和脂肪族ジカルボン酸に対応する、二つのカルボキシ基を両端に含む鎖を母体鎖（ＨＯＯＣ−（Ｃ）_n−ＣＯＯＨ）が、炭素数９〜１５の範囲の鎖長を有するもの、より好ましくは、炭素数１０〜１３の範囲の鎖長を有するものを、好適な例として挙げることができる。この場合も、その母体鎖に対して、若干数の分岐鎖が存在するものであっても、その融点が極端に上昇するものでなければ、同様に好適なものとなる。なお、母体鎖中に存在する−ＣＨ＝ＣＨ−などの炭素−炭素二重結合における絶対配置によっては、二つのカルボキシ基が互いに近接して、分子内で酸無水物の生成が可能となる場合もあるが、この種の環状無水物が容易に生成する配置は、好適な範囲からは除かれる。不飽和脂肪族ジカルボン酸においても、側鎖を持たない、直鎖のジカルボン酸であり、その炭素数は、Ｃ９〜Ｃ１５の範囲、より好ましくは、Ｃ１０〜Ｃ１３の範囲であると、より好ましいものとなる。
【００７５】
さらには、上記の鎖状の脂肪族ジカルボン酸における、二つのカルボキシ基を両端に含む鎖を母体鎖に代えて、鎖中に環構造を含み、その実効的な鎖長が炭素数６以上の鎖長に相当するものの、好適なジカルボン酸となる。具体的には、含まれる環構造としては、芳香環、例えば、フェニレン基（−Ｃ₆Ｈ₄−）など、あるいは、脂環炭化水素に由来する環構造、例えば、シクロヘキサンジイル（−Ｃ₆Ｈ₁₀−）などが挙げられる。なお、これらの環構造；Ｒに直接、一つのカルボキシ基が結合するものでなく、ＨＯＯＣ−（Ｃ）_n1−Ｒ−（Ｃ）_n2−ＣＯＯＨ型の環構造上の二つの側鎖にそれぞれカルボキシ基が存在する形状のものがより好ましい。
【００７６】
なお、飽和脂肪族ジカルボン酸であれば、母体鎖の炭素数が１５を超えると、炭素数が増しても、然程上昇しなくなり、添加比率が少ない際には、母体鎖の炭素数が４０程度に達するものであっても、利用可能なものとなる。なお、不必要に炭素数の大きなものとすることは好ましいものとは言えず、一般に、母体鎖の炭素数が１５以下の範囲に留めることが望ましい。
【００７７】
また、不飽和脂肪族ジカルボン酸においても、前記飽和脂肪族ジカルボン酸に対応する、二つのカルボキシ基を両端に含む鎖を母体鎖（ＨＯＯＣ−（Ｃ）_n−ＣＯＯＨ）が、炭素数９以上の範囲の鎖長を有するものが好ましく、添加比率や処理温度の選択に応じて、場合によっては、母体鎖の炭素数が４０程度であっても、利用可能なものとなる。なお、同じく、不必要に炭素数の大きなものとすることは好ましいものとは言えず、一般に、母体鎖の炭素数が１５以下の範囲に留めることが望ましい。
【００７８】
加えて、不飽和脂肪酸にアクリル酸などの短鎖のα，β−不飽和カルボン酸が付加した、炭素数２０程度までのダイアシッド（付加ジカルボン酸）や、長鎖の不飽和カルボン酸が相互に付加した炭素数３８〜４４のダイマー酸なども、鉛フリーハンダが対象となる場合には、利用可能となる。なお、前記炭素数３８〜４４のダイマー酸は、若干のモノマー酸、トリマー酸が混入するものであるが、一般に、室温付近でも、高粘度の液状を示すが、これら混入物を含め、その沸点は、前記鉛フリーハンダの融解温度よりは十分に高いものである。
【００７９】
ジカルボン酸の添加比率は、酸無水物に応じて、また、フラックス処理を行う温度をも考慮して、適宜選択するものである。つまり、フラックス処理を行う温度を高く選択する際には、主な役割が硬化剤である酸無水物は、熱硬化に急速に消費されるため、フラックス処理速度をかかる熱的な硬化速度と匹敵するものとする上では、ジカルボン酸の添加比率を増す必要がある。一方、フラックス処理を行う温度をそれほど高くしない場合には、熱的な硬化速度もそれほど速くなっていないので、ジカルボン酸の添加比率が低くとも、フラックス処理速度をかかる熱的な硬化速度と匹敵するものとすることができる。
【００８０】
鉛フリーハンダ材料としては、その融点は、高くとも、２３０℃を超えない範囲のものが主に利用されており、例えば、組成がＳｎ：９５．８％、Ａｇ：３．５％、Ｃｕ：０．７％のＳｎ−Ａｇ系ハンダの融解温度は２１７℃であり、その際、熱硬化処理の温度は、２３０℃以上、２５０℃以下の範囲に選択する。従って、本発明においては、前記熱硬化処理の温度に対応させて、一般に、（Ｂ）硬化剤の酸無水物の１モルに対して、前記ジカルボン酸を５×１０^-2〜５×１０^-1モルの範囲となる量、好ましくは、５×１０^-2〜３×１０^-1モルの範囲となる量に選択することが好ましい。あるいは、樹脂組成物全体に対して、ジカルボン酸の含有量が５〜１５質量％の範囲に選択することがより望ましい。
【００８１】
なお、本発明の封止充填剤用液状エポキシ樹脂組成物においては、鉛フリー錫合金ハンダ材に対するフラックス処理は、主に、上記する付加的成分のジカルボン酸が示すフラックス活性増強作用を活用し、酸無水物を利用して行われるものであるが、場合によっては、更にフラックス活性増強作用を示す成分を副次的に添加することができる。例えば、この副次的に添加することが可能な、フラックス活性増強作用を示す成分としては、アクリル酸などを付加した酸変性ロジン、例えば、アクリル変性ロジン、あるいは、アミン化合物の塩基性窒素原子上にハロゲン化水素付加塩を形成してなるアミンのハロゲン化水素付加塩など、加熱した際、初めてプロトン供与能を示すものを、補足的な量を添加して利用することもできる。
【００８２】
すなわち、本発明において、（Ｃ）プロトン供与能を有するフラックス活性増強成分として、上記のジカルボン酸を主に利用するが、補足的に、ジカルボン酸の含有比率を超えない範囲で、例えば、高い沸点を有するモノカルボン酸をも用いることもできる。具体的には、熱硬化処理の温度を、２３０℃〜２６０℃の範囲に選択する際にも、補足的なフラックス活性増強成分として、好適に利用可能なモノカルボン酸は、かかるモノカルボン酸の融点は、例えば、組成がＳｎ：９５．８％、Ａｇ：３．５％、Ｃｕ：０．７％のＳｎ−Ａｇ系ハンダの融解温度（２１７℃）よりも有意に低く、沸点は、かかるＳｎ−Ａｇ系ハンダの融解温度よりも十分に高く、また、水に対する溶解性が乏しいものである。前記の条件を満たし、補足的なフラックス活性増強成分として、好適に利用可能なモノカルボン酸の一例は、樹脂酸の主成分である、アビエチン酸、ピマル酸などのジテンペル酸Ｃ₁₉Ｈ₂₉ＣＯＯＨ等を水素添加処理したもの、あるいは、これらのジテンペル酸を主成分とするロジンを水素添加処理した水添ロジンなどを挙げることができる。これらの高い沸点のモノカルボン酸をも利用する際には、ジカルボン酸の含有比率に対して、モノカルボン酸の含有比率が有意に低い範囲、例えば、ジカルボン酸１０質量部に対して、モノカルボン酸は５質量部を超えない範囲に選択することがより望ましい。少なくとも、ジカルボン酸１分子に対して、モノカルボン酸が１／２分子を超えない範囲に選択することがより望ましい。
【００８３】
一方、前記モノカルボン酸は、副次的なフラックス活性増強成分としての機能に加え、エポキシ樹脂の硬化反応に伴う重合鎖長の延長に際し、末端封止の役割をも有する。その結果、フラックス処理後、ハンダ付けとエポキシ樹脂の熱硬化が進む過程において、得られる架橋・重合構造における鎖長の延長が過度に進み、樹脂粘度が必要以上に増すことを回避する作用をも示す。加えて、過度な鎖長の延長に至らないので、得られる熱硬化体の低温における脆性の改善にも、寄与を示すものとなる。かかる補足的に添加されるモノカルボン酸も、樹脂組成物中に均一に溶解することが望ましく、加えて、得られる熱硬化体において、その吸水率を増す、あるいは、末端封止を行った際、かかるモノカルボン酸の炭素骨格自体がＴｇの上昇の要因となるなどの不具合を引き起こさないものが望ましい。従って、例えば、分子内に付加重合可能な不飽和炭素結合や、熱分解を引き起こす部位を有するロジンに対して、予め水添処理を施した水添ロジンは、前記の観点でも好適なモノカルボン酸の一つとなる。また、エポキシ樹脂における溶解特性に優れ、高沸点でありつつ、高温領域における高いプロトン供与能も示す、酸性度の高い安息香酸類、例えば、ｐ−ヒドロキシ安息香酸、ｍ−ブロモ安息香酸などを用いることもできる。
【００８４】
なお、酸無水物の含有比率が増すにつれ、酸無水物自体にフラックス活性が増すので、ジカルボン酸の添加比率を低くしても、所望のフラックス処理速度が達成できる。一方、酸無水物の含有比率が低い際には、前記の上限値を超えない範囲で、ジカルボン酸の添加比率をより高い範囲に選択し、所望のフラックス処理速度となるように一層の活性増強を図ることが好ましいものである。
【００８５】
さらには、残余のジカルボン酸は、ハンダ付けが終了した後もアンダーフィル中に留まるが、接触している配線金属などに対して、不要な反応を起こして、動作不良を引き起こす要因を形成することもない。
【００８６】
封止充填剤は、特に、バンプ電極近傍、すなわち、チップ部品とプリント配線基板との接合固定領域の補強を主な機能とするので、バンプ電極近傍において、硬化に実際に関与する、熱硬化性エポキシ樹脂と硬化剤の最終的な含有率が好ましい範囲、具体的には、重付加型の硬化剤、例えば、酸無水物が０．８当量程度となるのが最適である。熱硬化を進めるため、高温に維持される間に、表面酸化皮膜の除去に伴い、酸無水物の一部は消費される。そのため、バンプ電極近傍において、酸無水物についてみるならば、その局所的な含有率は、フラックス処理が進むにつれて、しだいに低下していく。その結果、エポキシ樹脂と硬化剤との重合付加反応の伸長を一旦遅延されるので、フラックス処理の完了する前は、エポキシ樹脂組成物の流動性が損なわれ、フラックス処理の阻害要因となってしまうことを防止している。フラックス処理が終わると、その後、熱硬化に要する期間、ハンダの融点付近の温度で一定に保つ間に、拡散により必要な酸無水物は供給される。従って、バンプ電極近傍においても、得られる熱硬化物の特性は、従来の封止充填剤と比較して、全く遜色のないものとなる。
【００８７】
本発明の封止充填剤用液状エポキシ樹脂組成物は、上述する（Ａ）液状の熱硬化性エポキシ樹脂と（Ｂ）の硬化剤の酸無水物、ならびに付加的成分の（Ｃ）プロトン供与能を有するフラックス活性増強成分として利用するジカルボン酸の必須成分に加えて、通常、先に述べた硬化促進剤を副次的な成分として添加することが多いが、それ以外も、この種のエポキシ樹脂組成物に慣用される副次的な成分を添加することもできる。具体的には、その他の副次的な成分として、応力緩和剤、レベリング剤、カップリング剤、酸化防止剤など、さらには、可塑剤、チキソ剤などをも添加できる。いずれを添加するか、また、その添加量は、必須成分に用いる熱硬化性エポキシ樹脂と酸無水物に応じて、適宜選択するとよい。
【００８８】
酸化防止剤は、封止充填した後、熱硬化処理の際、エポキシ樹脂の耐熱性を向上する目的で、予めエポキシ樹脂中に混入しておくことができる。この酸化防止剤としては、酸素除去・還元作用を有するヒドロキノン、亜リン酸エステル類などを用いることができ、その添加量は、熱処理環境、例えば、リフロー加熱炉内の残留酸素濃度・温度などを考慮して適宜選択する。
【００８９】
レベリング剤は、封止充填剤用液状エポキシ樹脂組成物自体の粘度、従って、必須成分に用いる熱硬化性エポキシ樹脂と硬化剤の種類、含有比率に応じて、適宜添加量を選択するとよい。例えば、レベリング剤としては、ＳＴ８０ＰＡ（商品名；東レ・ダウ=コーニング・シリコーン社製）などを用いることができ、液状エポキシ樹脂組成物全体に対して、０〜５質量％の範囲で添加することができる。応力緩和剤としては、アデカレジンＥＰＲ−１３０９（商品名；旭電化工業社製、エポキシ当量２８０）などを用いることができ、液状エポキシ樹脂組成物全体に対して、０〜１０質量％の範囲で添加することができる。
【００９０】
また、カップリング剤は、プリント配線基板の材質、チップ部品裏面の表面に露出している材料の種類を考慮し、用いるエポキシ樹脂の種類に応じて、必要に応じて、適宜好ましいものを選択して添加する。汎用されるカップリング剤としては、例えば、シラン系カップリング剤のγ−グリシドキシプロピルトリメトキシシランなどがあるが、これらから前記の選択基準に従って好適なカップリング剤を適量添加するとよい。一般に、カップリング剤は、液状エポキシ樹脂組成物全体に対して、０〜１０質量％の範囲で添加することができる。
【００９１】
可塑剤やチキソ剤は、液状エポキシ樹脂組成物の塗布加工性を考慮して、必要に応じて、添加される。可塑剤としては、例えば、フタル酸ジブチルなどがあるが、エポキシ樹脂の種類に応じて、好ましい可塑剤を適量添加するとよい。チキソ剤としては、例えば、ヒドロキシステアリン酸のトリグリセライド、ヒュームドシリカなどがあるが、エポキシ樹脂の種類に応じて、好ましいチキソ剤を適量添加するとよい。
【００９２】
本発明の封止充填剤用液状エポキシ樹脂組成物は、その熱硬化処理の温度は、例えば、２３０℃〜２６０℃の範囲に選択されるので、その加熱昇温の過程で、一旦は次第に粘度が低下し、封止充填すべき隙間を均一に満たし、塗布する際に仮に部分的に濡れていない箇所も、この段階で液状エポキシ樹脂組成物により覆われた状態となる。従って、室温における液状エポキシ樹脂組成物自体の液粘度は、所望とする液量を鉛フリーハンダ製のバンプ電極を覆うように塗布可能な程度に流動性を満足する範囲に選択すればよい。例えば、塗布手段として、ディスペンサーを利用する際には、液状エポキシ樹脂組成物自体の液粘度は、ディスペンサーのノズル径に応じて、０．５〜５０Ｐａ・ｓの範囲に調整することが好ましい。本発明の封止充填剤用液状エポキシ樹脂組成物は、必須成分の熱硬化性エポキシ樹脂と硬化剤、付加的成分のジカルボン酸、ならびに必要に応じて添加される上述の慣用される副次的な成分とを含むが、主な成分である、熱硬化性エポキシ樹脂と硬化剤の液粘度の組み合わせによって、全体の液粘度を前記の範囲に調整することが望ましい。例えば、熱硬化性エポキシ樹脂として、例えば、微粒子状の熱可塑性樹脂の分散や熱可塑性樹脂分子の付加修飾による変性を施した液状エポキシ樹脂を用いると、これらは一般に液粘性が増すが、硬化剤に利用する酸無水物として、相対的に液粘度の低いものを選択することで、全体として、好適な液粘度範囲の液状エポキシ樹脂組成物に調製することができる。
【００９３】
本発明の封止充填剤用液状エポキシ樹脂組成物は、必須成分の熱硬化性エポキシ樹脂と硬化剤、付加的成分のジカルボン酸、ならびに必要に応じて添加される上述の慣用される副次的な成分とを十分に混合した後、その調製工程の攪拌等により内部に発生したあるいは取り込まれた気泡を減圧脱泡して製造することができる。加えて、本発明の封止充填剤用液状エポキシ樹脂組成物中に含有される、硬化剤の酸無水物や、ジカルボン酸をなどは、硬化反応前から、水分が存在する環境に置くと、その本来の機能が失われる化合物であり、また、金属材料表面の酸化皮膜の除去作用を維持するためにも、製造された液状エポキシ樹脂組成物への水分混入を抑制して、調製・保存を行う。
【００９４】
本発明の封止充填剤用液状エポキシ樹脂組成物は、フリップチップ実装における封止充填に用いて、その効果を発揮するものである。具体的には、フリップチップ実装において、鉛フリーハンダ製のバンプ電極の熔融を、アンダーフィルを充填した後、その熱硬化とともに行う方式において、その効果を発揮する。
【００９５】
液状エポキシ樹脂組成物の充填方式に依らず、鉛フリー錫合金ハンダ製のバンプなどの金属表面に残留する酸化皮膜のその場除去作用は得られるが、例えば、以下の手順をとる封止充填方法をとる際、その効果はより高くなる。具体的には、フリップチップ実装における封止充填の方法として、
（１）基板用電極を有するプリント配線基板とチップ部品用電極を有するチップ部品とをハンダ製のバンプ電極を用いて両電極間の相互導通をとるべく、前記プリント配線基板上の所定の領域に前記チップ部品を配置後、前記ハンダ製のバンプ電極と電極間の接触を図る工程、
（２）前記ハンダ製のバンプ電極と電極間の接触を図る工程後、またはその工程と併せて、前記プリント配線基板とその上の所定の領域上に配置される前記チップ部品の間隙に、前記接触を図ったハンダ製のバンプ電極と電極とを被覆するように、上記する本発明の封止充填剤用液状エポキシ樹脂組成物を満たす充填工程、
（３）次いで加熱して、前記所定の領域の間隙に充填した前記液状エポキシ樹脂組成物における、前記エポキシ樹脂の熱硬化を進めるとともに、前記液状エポキシ樹脂組成物が被覆する前記ハンダ製のバンプを熔融させる工程、
所定時間の加熱後、冷却して、一旦熔融したハンダの再固化を行い、バンプ電極と電極とをハンダ付け固着・接合させ、同時に熱硬化したエポキシ樹脂により封止充填を完了する工程、
上記（１）〜（３）の一連の工程により、封止充填を行うと好ましいものとなる。
【００９６】
つまり、所定の粘性を有する液状エポキシ樹脂組成物をプリント配線基板上に予め厚めに塗布しておき、その上からチップ部品を押し付けることで、金属配線の電極とバンプ電極との物理的な接触を行い、同時に、押しつぶされ、広がった液状エポキシ樹脂組成物が、金属配線の電極とバンプ電極をも覆った状態となる。この際、塗布されている液状エポキシ樹脂組成物の上面はほぼ平坦であるので、その上からチップ部品を押し付けることで、未充填部分、ボイドとなる部分が発生することはない。また、物理的な接触を果たした金属配線の電極とバンプ電極の表面を、液状エポキシ樹脂組成物が密に覆っている状態とできる。この状態において、ハンダ製のバンプを熔融させるべく加熱を行うので、上で説明したように、金属表面に残留している酸化皮膜の除去がなされる。
【００９７】
従って、本発明にかかる電子部品は、上に説明した本発明の封止充填剤用液状エポキシ樹脂組成物を利用して、フリップチップ実装し、その間に封止充填がなされてなる実装組み立て済み電子部品であり、基板用電極を有するプリント配線基板とチップ部品用電極を有するチップ部品との接合を、両電極間の相互導通を融点が２００℃以上、高くとも、２３０℃を超えない範囲の鉛フリー錫合金ハンダ材料製のバンプ電極を利用した際、金属表面に残留している酸化皮膜の除去が効果的に行え、高い再現性で良好な導通特性が達成できる。加えて、フラックス処理が終わり、鉛フリー錫合金ハンダ材料の溶融、ハンダ付けが可能となった時点で、エポキシ樹脂の熱硬化も進むため、未充填部分、ボイドとなる部分が発生することもなく、ハンダ付けと封止充填がなされたものとなる。また、本発明にかかる電子部品は、鉛フリー錫合金ハンダ材料を利用してフリップチップ実装可能な半導体素子チップをプリント配線基板上に、少ない工程で実装したものとできる。加えて、用いる本発明の封止充填剤用液状エポキシ樹脂組成物を、
（Ｂ）硬化剤の酸無水物として、飽和な環状炭化水素ジカルボン酸由来の分子内酸無水物を用いる、あるいは、
（Ａ）の熱硬化性エポキシ樹脂として、熱可塑性樹脂成分の少量添加、微粒子状の熱可塑性樹脂の分散、熱可塑性樹脂分子の付加修飾による変性のいずれかの処理により、かかる熱可塑性樹脂に由来する強靭性が付与された熱硬化性エポキシ樹脂成分を、少なくとも部分的に含む組成とすることで、得られるエポキシ樹脂硬化物の示す柔軟性、あるいは、靭性の強化を行うと、過酷な冷却条件、例えば、−６５℃の冷却条件と１２５℃の加熱条件において、冷熱サイクル処理を施しても、封止充填されている樹脂硬化物におけるクラックの発生が効果的に抑制されたものとできる。また、その際、接着性不良などの不良も抑制でき、本発明にかかる電子部品は、寒暖差の大きな環境下、外部からの水分の浸入を長期にわたり防護された、耐環境性に優れたものとなる。
【００９８】
【実施例】
以下に、具体例を挙げて、本発明の封止充填剤用液状エポキシ樹脂組成物、それを用いた封止充填において達成される酸化皮膜の除去効果に関して、より具体的に説明する。なお、以下に示す実施例などは、本発明における最良の実施形態の一例ではあるものの、本発明は、これら実施例に限定されるものではない。
【００９９】
本発明の封止充填剤用液状エポキシ樹脂組成物の示す特徴である、鉛フリーハンダ材料表面に生成する酸化皮膜の除去作用を検証した。具体的には、付加的成分として添加されている、ジカルボン酸によって、フラックス活性の増強が所望の程度に達成することを検証した。
【０１００】
加えて、本発明の構成をとることにより、鉛を含まない錫合金ハンダの融点より有意に高い温度まで加熱を進めた際にも、含有されている成分の熱的分解等に起因するボイドの発生を十分に抑制されることを検証した。
【０１０１】
ジカルボン酸の添加に伴う、液状エポキシ樹脂組成物中に必須成分として含まれる、（Ｂ）硬化剤の酸無水物が関与する、ハンダ材料の酸化皮膜の除去効率の差異は、封止充填剤を充填硬化させた試料について、ハンダ不良が要因と推察される、電極間の導通試験において、導通不良発生の有無により判定した。
【０１０２】
（比較例１）
バンプを形成するハンダ材料として、鉛を含まないスズ合金ハンダ、所謂、鉛フリーハンダの一つ、組成がＳｎ：９５．８％、Ａｇ：３．５％、Ｃｕ：０．７％（熔融点：２１７℃）のＳｎ−Ａｇハンダを用いる場合、その融点を大きく超えない温度で使用可能なアンダーフィル用のエポキシ樹脂として、液状エポキシ樹脂として、ビスフェノールＡ型エポキシ樹脂のエピコート８２８（商品名、ジャパンエポキシレジン社製、エポキシ当量 約１９０）１００質量部当たり、硬化剤の酸無水物として、テトラヒドロフタル酸無水物誘導体のＹＨ−３０７（商品名；ジャパンエポキシレジン社製、酸無水物当量 約２３０）１２０質量部と、硬化促進剤として、少量の、イミダゾール類の一つ、１−ベンジル−２−メチルイミダゾールのＢＭＩ１２（商品名、ジャパンエポキシレジン社製、分子量 １７２）０．８質量部を添加した液状エポキシ樹脂組成物を調製した。
【０１０３】
前記の三成分を均一に混合した後、減圧脱泡処理して、液状エポキシ樹脂組成物を調製した。この液状エポキシ樹脂組成物は、熱硬化条件として、硬化温度２５０℃において、２〜５分間で所望の硬化がなされる。
【０１０４】
（実施例１）
本発明の封止充填剤用液状エポキシ樹脂組成物の一例であり、すなわち、バンプを形成するハンダ材料として、前記のＳｎ−Ａｇハンダ（熔融点：２１７℃）が利用される際に好適な組成比を有する、液状エポキシ樹脂と酸無水物に、付加的成分のフラックス活性増強成分として、ジカルボン酸を含む液状エポキシ樹脂組成物とした。このジカルボン酸として、この実施例１においては、直鎖状アルカン二酸；ω，ω’−アルカンジカルボン酸（ＨＯＯＣ−（ＣＨ₂）_n−ＣＯＯＨ）の一つであるドデカン二酸（宇部興産（株）製、 分子量２３０．３、融点１２９℃、沸点２４５℃（１０ｍｍＨｇ））を用いた。
【０１０５】
液状エポキシ樹脂として、ビスフェノールＡ型エポキシ樹脂のエピコート８２８（前出）１００質量部当たり、硬化剤の酸無水物として、テトラヒドロフタル酸無水物誘導体のＹＨ−３０７（前出）１２０質量部と、硬化促進剤として、少量の、イミダゾール類の一つ、１−ベンジル−２−メチルイミダゾールのＢＭＩ１２（前出）０．８質量部を添加した液状エポキシ樹脂組成物を調製した。加えて、ドデカン二酸１０質量部を、フラックス活性増強成分として、液状エポキシ樹脂組成物中に均一に分散した。その後、減圧脱泡処理して、目的の封止充填剤用液状エポキシ樹脂組成物を調製した。この液状エポキシ樹脂組成物は、熱硬化条件として、硬化温度２５０℃において、２〜５分間で所望の硬化がなされる。
【０１０６】
（実施例２）
前記実施例１と比べて、ドデカン二酸の添加比率を高くした液状エポキシ樹脂組成物を調製した。具体的には、液状エポキシ樹脂として、ビスフェノールＡ型エポキシ樹脂のエピコート８２８（前出）１００質量部当たり、硬化剤の酸無水物として、テトラヒドロフタル酸無水物誘導体のＹＨ−３０７（前出）１２０質量部と、硬化促進剤として、少量の、イミダゾール類の一つ、１−ベンジル−２−メチルイミダゾールのＢＭＩ１２（前出）０．８質量部を添加した液状エポキシ樹脂組成物を調製した。加えて、ドデカン二酸２０質量部を、フラックス活性増強成分として、液状エポキシ樹脂組成物中に均一に分散した。その後、減圧脱泡処理して、目的の封止充填剤用液状エポキシ樹脂組成物を調製した。この液状エポキシ樹脂組成物は、熱硬化条件として、硬化温度２５０℃において、２〜５分間で所望の硬化がなされる。
【０１０７】
（実施例３）
前記実施例１において用いたドデカン二酸に代えて、セバシン酸（デカン二酸；１，８−オクタンジカルボン酸）を付加的成分のフラックス活性増強成分として利用する、液状エポキシ樹脂組成物を調製した。具体的には、液状エポキシ樹脂として、ビスフェノールＡ型エポキシ樹脂のエピコート８２８（前出）１００質量部当たり、硬化剤の酸無水物として、テトラヒドロフタル酸無水物誘導体のＹＨ−３０７（前出）１２０質量部と、硬化促進剤として、少量の、イミダゾール類の一つ、１−ベンジル−２−メチルイミダゾールのＢＭＩ１２（前出）０．８質量部を添加した液状エポキシ樹脂組成物を調製した。加えて、セバシン酸（デカン二酸：豊国製油（株）製、 分子量２０２．２５、融点１３５℃、沸点２９４．５℃（１００ｍｍＨｇ））１０質量部を、フラックス活性増強成分として、液状エポキシ樹脂組成物中に均一に分散した。その後、減圧脱泡処理して、目的の封止充填剤用液状エポキシ樹脂組成物を調製した。この液状エポキシ樹脂組成物は、熱硬化条件として、硬化温度２５０℃において、２〜５分間で所望の硬化がなされる。
【０１０８】
（参考例１）
前記比較例１と比べて、酸無水物の含有比率を高め、フラックス活性の増強を図った液状エポキシ樹脂組成物を調製した。具体的には、液状エポキシ樹脂として、ビスフェノールＡ型エポキシ樹脂のエピコート８２８（前出）１００質量部当たり、硬化剤の酸無水物として、テトラヒドロフタル酸無水物誘導体のＹＨ−３０７（前出）１３０質量部と、硬化促進剤として、少量の、イミダゾール類の一つ、１−ベンジル−２−メチルイミダゾールのＢＭＩ１２（前出）０．８質量部を添加した液状エポキシ樹脂組成物を調製した。この液状エポキシ樹脂組成物は、熱硬化条件として、硬化温度２５０℃において、２〜５分間で所望の硬化がなされる。
【０１０９】
次いで、実施例１〜３の液状エポキシ樹脂組成物と比較例１ならびに参考例１の液状エポキシ樹脂組成物について、それぞれ同様の条件でフリップチップ実装を行い、得られた実装済み半導体装置について、チップ部品とプリント回路基板の電極間の導通不良の有無を評価した。加えて、実装済みのプリント回路基板について、透視観察して、空隙（ボイド）の有無を検査した。
【０１１０】
なお、用いた硬化条件は、２０℃から２５０℃まで急速に昇温（１．５℃／ｓ）し、２５０℃で２０秒間保持した。この保持後、強制冷却した。
【０１１１】
表１に、導通試験結果を併せて示す。導通試験結果は、全試料数５０に対して、導通不良の無い合格品数の比率をもって、その指標とする。
【０１１２】
【表１】

【０１１３】
表１に示す通り、ドデカン二酸を添加している、実施例２の液状エポキシ樹脂組成物においては全数合格、実施例１の液状エポキシ樹脂組成物においても、導通不良は２０％程度であった。また、セバシン酸を用いた実施例３の液状エポキシ樹脂組成物においても、導通不良は３５％程度に抑制されていた。一方、比較例１の液状エポキシ樹脂組成物では、凡そ９５％程度に導通不良が発生している。なお、参考例１の液状エポキシ樹脂組成物においては、酸無水物の含有量を増すことでフラックス活性が増しているものの、なお、導通不良は９０％以上に達している。従って、本発明の液状エポキシ樹脂組成物においては、フラックス活性増強成分のドデカン二酸、あるいはセバシン酸の添加により、酸無水物の示す、フラックス活性が付与・増進されている結果、リフロー処理によって前記の様に良好なバンプ電極による接合がなされていると判断される。
【０１１４】
一方、ボイド発生は、実施例１、２の液状エポキシ樹脂組成物においては、全く見出されず、また、実施例３の液状エポキシ樹脂組成物においても、この温度範囲では見出されていない。勿論、参考例１、比較例１の液状エポキシ樹脂組成物においても、ボイド発生は見出されていない。
【０１１５】
（実施例４）
前記の結果に基づき、実施例１に記載する組成の封止充填剤用液状エポキシ樹脂組成物を用いて、以下の手順によりアンダーフィルの充填を行った。その結果、上記Ｓｎ−Ａｇ系ハンダ・バンプの熔融（２１７℃）時、表面酸化皮膜に由来するハンダ付け不良もなく、また、充填不良、ボイドの発生もないものであった。
【０１１６】
プリント配線基板上にバンプ電極が設けられているフリップチップ実装に適用した。まず、前記のバンプ電極を予め形成したプリント配線基板に、上記アンダーフィル用エポキシ樹脂組成物をスクリーン印刷により所定のパターンに塗布する。これも裏面にバンプ電極を形成してあるチップ部品を、このアンダーフィル剤パターンを印刷した配線基板上のバンプ電極に対して、両者の電極位置が整合するように位置合わせする。この位置において、電極相互が接触するようにチップ部品を押し付ける。その過程で、塗布されているアンダーフィル剤層は押し広げられ、チップ部品の裏面とも密着する。また、接触しているバンプ電極、対応する基板上の配線表面、チップ部品の裏面電極面もしっかり、押し広げられたアンダーフィル剤で被覆される。
【０１１７】
このチップ部品の上面から押圧した状態で、リフロー炉内に入れ、例えば、温度２５０℃まで昇温してバンプ熔融を行う。バンプハンダ付けが済み、更にアンダーフィル剤のエポキシ樹脂の熱硬化が進行する。
【０１１８】
上述する通り、この手順に従うとチップ部品を押圧するので、チップ部品裏面との間に気泡が残ることもないので、ボイドは発生しない。また、既に説明した通り、酸化被膜もその場で除去されるのでハンダ付け不良もない。このように、電極の接合不良もなく、しかも、アンダーフィルの充填・硬化も過不足なく達成される。
【０１１９】
なお、用いているハンダ材料が、その融点が２１７℃の上述のＳｎ−Ａｇ系ハンダであるため、このリフロー工程における昇温過程は、かかる２１７℃より有意に高い２５０℃まで一定速度で昇温する過程を用いており、その際、１３０℃を超えると、徐々に熱硬化反応が進み始めるが、添加されているドデカン二酸の作用により、前記２１７℃近くに達するまでに十分にフラックス処理が進み、加えて、系内に残余する酸無水物濃度が相当低くなった状態となった時点でも、なお、必要とするフラックス活性の確保することが可能である。
【０１２０】
（実施例５）
本発明の封止充填剤用液状エポキシ樹脂組成物の一例であり、すなわち、バンプを形成するハンダ材料として、前記のＳｎ−Ａｇハンダ（熔融点：２１７℃）が利用される際に好適な組成比を有する、液状エポキシ樹脂と酸無水物に、付加的成分のフラックス活性増強成分として、ジカルボン酸を含む液状エポキシ樹脂組成物とした。このジカルボン酸として、この実施例５においても、直鎖状アルカン二酸の一つであるドデカン二酸（前出）を用いた。
【０１２１】
液状エポキシ樹脂として、ビスフェノールＡ型エポキシ樹脂のエピコート８２８（前出）１００質量部当たり、硬化剤の酸無水物として、テトラヒドロフタル酸無水物誘導体のＹＨ−３０７（前出）１２０質量部と、硬化促進剤として、少量の、イミダゾール類の一つ、１−（２−シアノエチル）−２−エチル−４−メチルイミダゾールの２Ｅ４ＭＺ−ＣＮ（商品名、四国化成社製、分子量 １６３）０．３質量部を添加した液状エポキシ樹脂組成物を調製した。加えて、ドデカン二酸２０質量部を、フラックス活性増強成分として、液状エポキシ樹脂組成物中に均一に分散した。その後、減圧脱泡処理して、目的の封止充填剤用液状エポキシ樹脂組成物を調製した。この液状エポキシ樹脂組成物は、熱硬化条件として、硬化温度２５０℃において、２〜５分間で所望の硬化がなされる。
【０１２２】
（実施例６）
前記実施例５と比べると、フラックス活性増強成分として、ドデカン二酸の添加に加え、水添ロジン：フォーラルＡＸＥ（商品名、日商岩井ケミカル社製、平均分子量 ３１０）をも少量添加する変更を施し、液状エポキシ樹脂組成物を調製した。具体的には、液状エポキシ樹脂として、ビスフェノールＡ型エポキシ樹脂のエピコート８２８（前出）１００質量部当たり、硬化剤の酸無水物として、テトラヒドロフタル酸無水物誘導体のＹＨ−３０７（前出）１２０質量部と、硬化促進剤として、少量の２Ｅ４ＭＺ−ＣＮ（前出）０．３質量部を添加した液状エポキシ樹脂組成物を調製した。加えて、ドデカン二酸２０質量部ならびに水添ロジン（前出）１０質量部を、フラックス活性増強成分として、液状エポキシ樹脂組成物中に均一に分散した。その後、減圧脱泡処理して、目的の封止充填剤用液状エポキシ樹脂組成物を調製した。この液状エポキシ樹脂組成物は、熱硬化条件として、硬化温度２５０℃において、２〜５分間で所望の硬化がなされる。
【０１２３】
（実施例７）
本発明の封止充填剤用液状エポキシ樹脂組成物の一例であり、すなわち、バンプを形成するハンダ材料として、前記のＳｎ−Ａｇハンダ（熔融点：２１７℃）が利用される際に好適な組成比を有する、液状エポキシ樹脂と酸無水物に、付加的成分のフラックス活性増強成分として、前記実施例６と同じく、直鎖状アルカン二酸の一つであるドデカン二酸（前出）と、少量の水添ロジン（前出）を含む液状エポキシ樹脂組成物とした。加えて、硬化剤の酸無水物として、テトラヒドロフタル酸無水物誘導体のＹＨ−３０７（前出）に代えて、水添ナジック酸の酸無水物：ＨＮＡ（商品名、新日本理化社製、酸無水物当量 ９５）を利用した。
【０１２４】
液状エポキシ樹脂として、ビスフェノールＡ型エポキシ樹脂のエピコート８２８（前出）１００質量部当たり、硬化剤の酸無水物として、ＨＮＡ（前出）８７質量部と、硬化促進剤として、少量の２Ｅ４ＭＺ−ＣＮ（前出）０．３質量部を添加した液状エポキシ樹脂組成物を調製した。加えて、ドデカン二酸２０質量部ならびに水添ロジン（前出）１０質量部を、フラックス活性増強成分として、液状エポキシ樹脂組成物中に均一に分散した。その後、減圧脱泡処理して、目的の封止充填剤用液状エポキシ樹脂組成物を調製した。この液状エポキシ樹脂組成物は、熱硬化条件として、硬化温度２５０℃において、２〜５分間で所望の硬化がなされる。
【０１２５】
次いで、実施例５〜７の液状エポキシ樹脂組成物について、それぞれ、上記実施例２の液状エポキシ樹脂組成物と同様の条件でフリップチップ実装を行い、得られた実装済み半導体装置について、チップ部品とプリント回路基板の電極間の導通不良の有無を評価した。加えて、実装済みのプリント回路基板について、透視観察して、空隙（ボイド）の有無を検査した。
【０１２６】
なお、用いた硬化条件は、２０℃から２５０℃まで急速に昇温（１．５℃／ｓ）し、２５０℃で２０秒間保持した。この保持後、強制冷却した。
【０１２７】
表２に、導通試験結果を併せて示す。導通試験結果は、全試料数５０に対して、導通不良の無い合格品数の比率をもって、その指標とする。
【０１２８】
【表２】

【０１２９】
表２に示す通り、硬化促進剤として、ＢＭＩ１２に代えて、２Ｅ４ＭＺ−ＣＮを用いる結果、同量のドデカン二酸を添加している実施例２の液状エポキシ樹脂組成物と比較すると、若干導通不良の比率は増すものの、実施例５の液状エポキシ樹脂組成物においても、導通不良は２０％程度に抑えられている。なお、補足的なフラックス活性増強成分として、さらに、水添ロジン（前出）を少量添加することで、実施例６の液状エポキシ樹脂組成物においては、導通不良はもはや見出されなくなっている。また、硬化剤の酸無水物として、テトラヒドロフタル酸無水物誘導体のＹＨ−３０７に代えて、水添ナジック酸の酸無水物ＨＮＡ（前出）を採用した際にも、補足的なフラックス活性増強成分として、さらに、水添ロジン（前出）を少量添加することで、実施例７の液状エポキシ樹脂組成物においては、導通不良はもはや見出されなくなっている。
【０１３０】
従って、硬化促進剤として利用する、イミダゾール類の硬化促進作用の相違がある場合においても、本発明の液状エポキシ樹脂組成物においては、フラックス活性増強成分のドデカン二酸の添加により、酸無水物の示す、フラックス活性が付与・増進されている結果、リフロー処理によって前記の様に良好なバンプ電極による接合がなされていると判断される。
【０１３１】
一方、ボイド発生は、実施例２の液状エポキシ樹脂組成物と比較して、より硬化が促進されている、これら実施例５〜７の液状エポキシ樹脂組成物においても、全く見出されていない。
【０１３２】
加えて、得られるエポキシ樹脂硬化物は、それを構成するエポキシ樹脂成分と硬化剤の酸無水物の骨格構造に応じて、可撓性、接着性に違いが生じ、特に、氷点以下の温度に冷却した際、剪断強度、剥離強度の低下が生じると、反復的に加熱・冷却を繰り返す間に、封止充填した樹脂硬化物の内部分的な剥離、あるいは、樹脂硬化物の表面における微細なクラック発生の有無に差異が生じる。この冷却における樹脂硬化物の可撓性、接着性の相違を比較するため、前記実施例５〜７の液状エポキシ樹脂組成物を用いて、前記実施例４に記載する実装と同じ要領で、アンダーフィルの充填・硬化と、ハンダ材のリフロー工程を施したプリント基板上に実装された半導体素子について、冷熱サイクル試験を実施した。
【０１３３】
冷熱サイクル試験は、温度条件を、冷却状態−４５℃、加熱状態１２５℃の条件と、特に、冷却時の条件をより過酷とした、冷却状態−６５℃、加熱状態１２５℃の条件とで行った。表３に、実施例５〜７の液状エポキシ樹脂組成物を用いて、アンダーフィルの充填・硬化と、ハンダ材のリフロー工程を施した実装半導体素子の冷熱サイクル試験における結果、特に、封止充填剤部の劣化に起因する不良発生比率、ならびに、サイクル試験終了時における封止充填剤部の硬化樹脂に微細なクラック発生の有無に関する評価結果を示す。冷熱サイクル試験結果は、全試料数５０に対して、不良発生の無い品数の比率をもって、その指標とする。
【０１３４】
【表３】

【０１３５】
樹脂硬化物を構成するエポキシ樹脂成分とその硬化剤の酸無水物が同一組成である、実施例５、６の液状エポキシ樹脂組成物の間では、得られる樹脂硬化物の可撓性、接着性など、特に、冷却した際、剪断強度、剥離強度の低下の程度は同程度であるため、上記の冷熱サイクル試験結果において、実質的な差異は見出されていない。冷却状態が−４５℃の条件では、樹脂硬化物自体は、極端な脆さを示さず、樹脂硬化物とプリント基板と熱膨張率の差異に由来する歪応力によるクラック発生も、問題となる頻度ではない。一方、冷却状態が−６５℃の条件では、かかるエポキシ樹脂硬化物自体は、柔軟性に乏しく、脆さを示す状態となり、冷熱サイクル時の歪応力によるクラック発生がより顕著となっている。
【０１３６】
一方、硬化剤の酸無水物として、ＨＮＡを採用している実施例７の液状エポキシ樹脂組成物においては、そのエポキシ樹脂硬化物自体は、この酸無水物に由来する構造には、不飽和炭素結合を有してなく、テトラヒドロフタル酸無水物誘導体のＹＨ−３０７を利用する実施例５、６の液状エポキシ樹脂組成物によるエポキシ樹脂硬化物と比較して、より柔軟性に富むものとなる。その相違により、冷却状態が−４５℃の条件では、未だ脆さを示さず、不良発生もなく、歪応力によるクラック発生が回避されている。さらに、冷却状態が−６５℃の条件でも、樹脂硬化物自体は、極端な脆さを示さず、僅かに不良発生、歪応力によるクラック発生は見られるものの、問題となる頻度ではない。
【０１３７】
樹脂硬化物自体の可撓性、接着性、特に、冷却した際、剪断強度、剥離強度の低下をより小さなものとするため、利用する硬化剤の酸無水物として、不飽和炭素結合を持たない水添ナジック酸の酸無水物ＨＮＡを利用した上に、エポキシ樹脂成分自体も、可撓性、接着性の向上が図られるニトリル変性エポキシ樹脂の利用、あるいは、少量のアクリルゴムなど、熱可塑性樹脂成分の添加、微粒子状の熱可塑性樹脂の分散など、柔軟性を付加することで、脆さを改善し、より高靭性を発揮する上で効果を持つものを利用して、液状エポキシ樹脂組成物を調製した。
【０１３８】
（実施例８）
本発明の封止充填剤用液状エポキシ樹脂組成物の一例であり、すなわち、バンプを形成するハンダ材料として、前記のＳｎ−Ａｇハンダ（熔融点：２１７℃）が利用される際に好適な組成比を有する、液状エポキシ樹脂と酸無水物に、付加的成分のフラックス活性増強成分として、前記実施例７と同じく、直鎖状アルカン二酸の一つであるドデカン二酸（前出）と、少量の水添ロジン（前出）を含む液状エポキシ樹脂組成物とした。硬化剤の酸無水物として、ＨＮＡ（前出）を用い、エポキシ樹脂成分として、エピコート８２８（前出）に代えて、ビスフェノールＦ型エポキシ樹脂を主成分とする低粘度エポキシ樹脂であるＥＸＡ−８３５ＬＶ（商品名；大日本インキ化学工業社製、 エポキシ当量： １６５）とＣＴＢＮ変性エポキシ樹脂であるＥＰＲ−４０２３（商品名；旭電気化学工業社製、
エポキシ当量： ２３０）とを混合して用いた。
【０１３９】
液状エポキシ樹脂として、ＥＸＡ−８３５ＬＶ（前出）５０質量部：ＥＰＲ−４０２３（前出）５０質量部の比率で混合される、エポキシ樹脂１００質量部当たり、硬化剤の酸無水物として、ＨＮＡ（前出）８０質量部と、硬化促進剤として、少量の２Ｅ４ＭＺ−ＣＮ（前出）０．３質量部を添加した液状エポキシ樹脂組成物を調製した。加えて、ドデカン二酸２０質量部ならびに水添ロジン（前出）１０質量部を、フラックス活性増強成分として、液状エポキシ樹脂組成物中に均一に分散した。その後、減圧脱泡処理して、目的の封止充填剤用液状エポキシ樹脂組成物を調製した。この液状エポキシ樹脂組成物は、熱硬化条件として、硬化温度２５０℃において、２〜５分間で所望の硬化がなされる。
【０１４０】
（実施例９）
本発明の封止充填剤用液状エポキシ樹脂組成物の一例であり、すなわち、バンプを形成するハンダ材料として、前記のＳｎ−Ａｇハンダ（熔融点：２１７℃）が利用される際に好適な組成比を有する、液状エポキシ樹脂と酸無水物に、付加的成分のフラックス活性増強成分として、前記実施例７と同じく、直鎖状アルカン二酸の一つであるドデカン二酸（前出）と、少量の水添ロジン（前出）を含む液状エポキシ樹脂組成物とした。硬化剤の酸無水物として、ＨＮＡ（前出）を用い、エポキシ樹脂成分として、エピコート８２８（前出）に代えて、ビスフェノールＦ型エポキシ樹脂を主成分とする低粘度エポキシ樹脂であるＥＸＡ−８３５ＬＶ（前出）とコアシェル型の平均粒径０．５μｍゴム成分微粒子を分散したエポキシ樹脂であるＹＲ−６２８（商品名；東都化成社製、 エポキシ当量： ２２５）とを混合して用いた。
【０１４１】
液状エポキシ樹脂として、ＥＸＡ−８３５ＬＶ（前出）３０質量部：ＹＲ−６２８（前出）７０質量部の比率で混合される、エポキシ樹脂１００質量部当たり、硬化剤の酸無水物として、ＨＮＡ（前出）８６質量部と、硬化促進剤として、少量の２Ｅ４ＭＺ−ＣＮ（前出）０．３質量部を添加した液状エポキシ樹脂組成物を調製した。加えて、ドデカン二酸２０質量部ならびに水添ロジン（前出）１０質量部を、フラックス活性増強成分として、液状エポキシ樹脂組成物中に均一に分散した。その後、減圧脱泡処理して、目的の封止充填剤用液状エポキシ樹脂組成物を調製した。この液状エポキシ樹脂組成物は、熱硬化条件として、硬化温度２５０℃において、２〜５分間で所望の硬化がなされる。
【０１４２】
（実施例１０）
本発明の封止充填剤用液状エポキシ樹脂組成物の一例であり、すなわち、バンプを形成するハンダ材料として、前記のＳｎ−Ａｇハンダ（熔融点：２１７℃）が利用される際に好適な組成比を有する、液状エポキシ樹脂と酸無水物に、付加的成分のフラックス活性増強成分として、前記実施例９と同じく、直鎖状アルカン二酸の一つであるドデカン二酸（前出）と、少量の水添ロジン（前出）を含む液状エポキシ樹脂組成物とした。硬化剤の酸無水物として、テトラヒドロフタル酸無水物誘導体のＹＨ−３０７（前出）を用い、エポキシ樹脂成分として、エピコート８２８（前出）に代えて、ビスフェノールＦ型エポキシ樹脂を主成分とする低粘度エポキシ樹脂であるＥＸＡ−８３５ＬＶ（前出）とコアシェル型の平均粒径０．５μｍゴム成分微粒子を分散したエポキシ樹脂であるＹＲ−６２８（前出）とを混合して用いた。
【０１４３】
液状エポキシ樹脂として、ＥＸＡ−８３５ＬＶ（前出）３０質量部：ＹＲ−６２８（前出）７０質量部の比率で混合される、エポキシ樹脂１００質量部当たり、硬化剤の酸無水物として、ＹＨ−３０７（前出）１１０質量部と、硬化促進剤として、少量の２Ｅ４ＭＺ−ＣＮ（前出）０．３質量部を添加した液状エポキシ樹脂組成物を調製した。加えて、ドデカン二酸２０質量部ならびに水添ロジン（前出）１０質量部を、フラックス活性増強成分として、液状エポキシ樹脂組成物中に均一に分散した。その後、減圧脱泡処理して、目的の封止充填剤用液状エポキシ樹脂組成物を調製した。この液状エポキシ樹脂組成物は、熱硬化条件として、硬化温度２５０℃において、２〜５分間で所望の硬化がなされる。
【０１４４】
次いで、実施例８〜１０の液状エポキシ樹脂組成物の液状エポキシ樹脂組成物について、それぞれ、上記実施例７の液状エポキシ樹脂組成物と同様の条件でフリップチップ実装を行い、得られた実装済み半導体装置について、チップ部品とプリント回路基板の電極間の導通不良の有無を評価した。加えて、実装済みのプリント回路基板について、透視観察して、空隙（ボイド）の有無を検査した。
【０１４５】
なお、用いた硬化条件は、２０℃から２５０℃まで急速に昇温（１．５℃／ｓ）し、２５０℃で２０秒間保持した。この保持後、強制冷却した。
【０１４６】
表４に、導通試験結果を併せて示す。導通試験結果は、全試料数５０に対して、導通不良の無い合格品数の比率をもって、その指標とする。
【０１４７】
【表４】

【０１４８】
表４に示す通り、硬化剤、ならびにフラックス活性の主体として機能する、酸無水物として、ＨＮＡ（前出）を用い、主なフラックス活性増強成分として、ドデカン二酸を、補足的なフラックス活性増強成分として、さらに、水添ロジン（前出）を少量添加することで、実施例７の液状エポキシ樹脂組成物に比較して、酸無水物ＨＮＡの含有比率が若干少ない、実施例８、９の液状エポキシ樹脂組成物においても、導通不良は見出されていない。また、硬化剤の酸無水物として、テトラヒドロフタル酸無水物誘導体のＹＨ−３０７（前出）を用いている実施例１０の液状エポキシ樹脂組成物においても、実施例９の液状エポキシ樹脂組成物と同じく、導通不良は見出されていない。
【０１４９】
従って、利用するエポキシ樹脂の種類は異なるものの、実施例８、９の液状エポキシ樹脂組成物、あるいは、実施例１０の液状エポキシ樹脂組成物においても、先に示す実施例７、あるいは実施例６の液状エポキシ樹脂組成物と同様に、フラックス活性増強成分のドデカン二酸と水添ロジンの添加により、酸無水物の示すフラックス活性が付与・増進されている結果、リフロー処理によって前記の様に良好なバンプ電極による接合がなされていると判断される。また、ボイド発生は、これら実施例８〜１０の液状エポキシ樹脂組成物においても、全く見出されていない。
【０１５０】
加えて、これら実施例８、９の液状エポキシ樹脂組成物は、得られるエポキシ樹脂硬化物は、それを構成する硬化剤の酸無水物の骨格構造に不飽和炭素結合を含まず、同時に、エポキシ樹脂成分にも、ニトリルゴム成分付加による変性、あるいは、ゴム質の微粒子分散によって、可撓性、接着性の向上を図る成分を利用することで、特に、冷却した際、剪断強度、剥離強度の低下をより緩和することを、主な目的としている。この冷却における樹脂硬化物の可撓性、接着性の向上を検証するため、実施例８〜１０の液状エポキシ樹脂組成物を用いて、前記実施例４に記載する実装と同じ要領で、アンダーフィルの充填・硬化と、ハンダ材のリフロー工程を施したプリント基板上に実装された半導体素子について、冷熱サイクル試験を実施した。
【０１５１】
冷熱サイクル試験は、温度条件を、冷却状態−４５℃、加熱状態１２５℃の条件と、特に、冷却時の条件をより過酷とした、冷却状態−６５℃、加熱状態１２５℃の条件とで行った。表５に、実施例８〜１０の液状エポキシ樹脂組成物を用いて、アンダーフィルの充填・硬化と、ハンダ材のリフロー工程を施した実装半導体素子の冷熱サイクル試験の結果を示す。冷熱サイクル試験結果は、全試料数５０に対して、不良発生の無い品数の比率をもって、その指標とする。
【０１５２】
【表５】

【０１５３】
実施例８、９の液状エポキシ樹脂組成物を用いた場合も、上記実施例７の液状エポキシ樹脂組成物を用いた際と同様に、冷却状態が−４５℃の条件では、樹脂硬化物自体は、脆さを示さず、樹脂硬化物とプリント基板と熱膨張率の差異に由来する歪応力によるクラック発生もなく、不良が見出されていない。加えて、実施例８、９の液状エポキシ樹脂組成物を用いた場合、硬化剤の酸無水物の骨格構造に不飽和炭素結合を含まず、同時に、エポキシ樹脂成分にも、ニトリルゴム成分付加による変性、あるいは、ゴム質の微粒子分散によって、可撓性、接着性の向上を図る成分を利用する結果、冷却状態が−６５℃の条件でも、かかるエポキシ樹脂硬化物自体は、脆さを示さず、高い靭性を保持し、冷熱サイクル時の歪応力によるクラック発生も回避でき、不良が見出されていない。
【０１５４】
また、実施例１０の液状エポキシ樹脂組成物を用いた場合も、エポキシ樹脂成分に、ゴム質の微粒子分散によって、可撓性、接着性の向上を図る成分を利用する結果、冷却状態が−４５℃の条件では、樹脂硬化物自体は、脆さを示さず、樹脂硬化物とプリント基板と熱膨張率の差異に由来する歪応力によるクラック発生もなく、不良が見出されていない。なお、用いている硬化剤の酸無水物は、その骨格構造に不飽和炭素結合を残す結果、冷却状態が−６５℃の条件では、低温における脆さの改善がやや不足し、冷熱サイクルを繰り返すとともに、クラック発生が若干生じ、同時に、一部に不良も見出されている。
【０１５５】
【発明の効果】
本発明の封止充填剤用液状エポキシ樹脂組成物は、必須成分として、（Ａ）液状の熱硬化性エポキシ樹脂と（Ｂ）前記の熱硬化性エポキシ樹脂に対する硬化剤として酸無水物、さらに付加的成分として、付加的成分として、（Ｃ）プロトン供与能を有するフラックス活性増強成分となる、ジカルボン酸、例えば、母体鎖の炭素数が９〜１５の鎖状ジカルボン酸を少量、具体的には、（Ｂ）硬化剤の酸無水物１モル当たり、この（Ｃ）フラックス活性増強成分のジカルボン酸の含有量を、５×１０^-2〜５×１０^-1モルの範囲となるように添加した液状エポキシ樹脂組成物である。この液状エポキシ樹脂組成物が充填された状態において、チップ部品とプリント配線基板の電極間に互いに物理的な接触を形成する配置されている、融点が２００℃以上、２３０℃を超えない鉛フリー錫合金ハンダ製、特には、Ｓｎ−Ａｇ系ハンダ製のバンプ電極を加熱熔融した際、ジカルボン酸のカルボキシ基より供与されるプロトンによって、（Ｂ）硬化剤の酸無水物が有するフラックス活性の増強がなされ、バンプ電極などの表面の酸化皮膜、例えば、錫の酸化物の除去を行うことができる。一方、前記の（Ｂ）硬化剤の酸無水物は、前記錫の酸化物との反応により、若干量が消費されるものの、過度な含有量の減少でなく、例えば、副次的な成分として添加されている、硬化促進剤の含有量を少量に留めるなどして、用いる鉛フリー錫合金ハンダに適合する比較的に高い熱硬化温度で加熱処理をした際にも、酸化物皮膜の除去とともに、適正な速度で熱硬化が進行し、所望の熱硬化物とできる。また、添加されるジカルボン酸の沸点は熱硬化温度より十分に高いので、その気化による気泡の形成もなく、ボイドの発生の要因ともならない。また、利用する母体鎖の炭素数は比較的に長いジカルボン酸は、エポキシ樹脂との相溶性も優れており、熱硬化が次第に進行していく間も、樹脂組成物中に均一に分散して、（Ｂ）硬化剤の酸無水物が有するフラックス活性の増強作用を維持でき、従って、予めバンプ電極などの表面の酸化皮膜を除去するため、フラックスによる処理を施さなくとも、バンプ電極に用いるハンダの良好な熔融、ハンダ付けによる電極間の接合ができ、同時に封止充填剤の熱硬化が行えるという利点が得られる。加えて、この方式の封止充填は、高い作業効率性を持ち、特に、プリント配線基板上にスクリーン印刷などの手段で所望の液状エポキシ樹脂組成物層を塗布形成するので、プリント配線基板の形状・材質に依らず、全般的な工程の短縮化、ならびにボイド発生などの不良要因の根絶が可能となる。加えて、（Ｂ）硬化剤の酸無水物として、その分子骨格内に不飽和炭素結合を含まないものを利用し、さらには、（Ａ）液状の熱硬化性エポキシ樹脂成分として、熱可塑性樹脂成分の少量添加、微粒子状の熱可塑性樹脂の分散、熱可塑性樹脂分子の付加修飾による変性などによって、得られる樹脂硬化物において、靭性を増し、特に、低温脆性が改善された、接着性、可撓性に富み、特に、冷却した際、剪断強度、剥離強度の低下がより緩和されたものとできる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a liquid epoxy resin composition for a sealing filler, which is used in sealing and filling in flip chip mounting, and a sealing and filling method using the same. More specifically, a bump used for flip chip mounting using a lead-free tin alloy solder material having a melting point of 200 ° C. or higher as a bump electrode material when the sealing filler is thermally cured by heating. Liquid epoxy resin composition suitable for sealing filler that covers lead-free tin alloy solder bumps in the process of soldering and bonding and bonding between electrodes and bumps. Liquid epoxy resin composition more suitably used as a sealing filler that can achieve sufficient flux activity even when tin-silver alloy solder is used as the solder material for forming About.
[0002]
[Prior art]
In order to reduce the weight, size, and thickness of electronic devices, a flip chip mounting method is being adopted as a method for mounting semiconductor chip components on a printed wiring board. In this flip chip mounting method, a chip component electrode is formed on the mounting surface (back surface) of the chip component, and this is opposed to a predetermined region (mounting region) of the substrate electrode formed on the printed wiring board. Bump electrodes are used to place and achieve the desired conduction between the electrodes. For example, a bump electrode prepared in advance by a spherical solder is provided on a chip component electrode formed on the mounting surface (back surface) of the chip component, and this bump electrode is provided in a predetermined region (mounting region) of the substrate electrode. Make contact. In this arrangement, when the solder is melted, soldering and bonding are performed at a desired position in contact with the substrate electrode. Thus, desired conduction is achieved between the chip component and the printed wiring board via the bump electrodes. Or, conversely, a method of providing bump electrodes on the electrodes of the printed wiring board may be used.
[0003]
In this flip chip mounting method, the chip component is fixed only by the bump electrode that connects between the chip component and both electrodes of the printed wiring board. Since this is a mounting method aimed at miniaturization and thinning, this bump electrode is made as small as possible. Chip components and printed wiring boards have different thermal expansion coefficients. When the thermal expansion or shrinkage of the printed wiring board occurs relatively with the temperature change during operation, the bump electrode has its thermal displacement. There is no play or deflection that absorbs or relaxes. When the temperature change (thermal cycle) is repeated, the stress distortion resulting from the thermal displacement is repeated, and as a result, peeling at the joint portion (soldering portion) between the bump electrode and the electrode may be caused.
[0004]
In order to suppress this thermal cycle deterioration, filling and sealing are performed with a resin having a role of reducing relative thermal displacement by bonding and fixing each other in the gap between the chip component and the printed wiring board. Although this sealing filler is called underfill, from the purpose of use, the gap between the chip component and the printed wiring board is tightly filled, and an unfilled residue (void) called void is not generated. Filled. Further, filling and sealing are performed so as to cover the periphery of the bump electrode densely.
[0005]
Conventionally, a technique has been used in which bonding (soldering) between a bump electrode and an electrode is performed first, and then a liquid epoxy resin composition is injected and soaked into the gap between the chip component and the printed wiring board. With this method, the chip component itself becomes larger with higher integration, and the number of electrodes (number of terminals) to be connected to the substrate electrode of the printed wiring board increases, the distance between the bump electrodes, the chip component and the printed wiring board. There is a concern that the occurrence frequency of voids will increase if the gap between the gaps is further narrowed. Moreover, the injection | pouring process of a liquid epoxy resin composition has also become an obstacle at the time of raising working efficiency further.
[0006]
As a technique for avoiding these problems, a liquid epoxy resin composition layer is previously formed in accordance with a predetermined area on the printed wiring board by means of screen printing or the like, and chip components are arranged on the printed wiring board. And when making a contact between a bump electrode and an electrode, the method of extending the layer of a liquid epoxy resin composition with the mounting surface (back surface) of a chip component is proposed (Unexamined-Japanese-Patent No. 11-354555 etc.). In the step of press-contacting the chip component, the liquid epoxy resin composition is filled with no gap between the chip component and the printed wiring board, together with the contact between the bump electrode and the electrode. Next, in order to perform bonding (soldering) between the bump electrodes and the electrodes, heating is performed to melt the solder bumps in a reflow furnace. During this heat treatment, the filled liquid epoxy resin composition is also thermally cured, and bonding between the bump electrodes and the electrodes (soldering) and curing of the underfill (sealing filler) are achieved at the same time. The Since underfill (sealing filler) can be produced in advance by means such as screen printing with high reproducibility and workability, and the heating process can be integrated, the working efficiency is greatly improved.
[0007]
The above-described method for bonding (soldering) the bump electrode to the electrode and curing and bonding the underfill (sealing filler) in the same process is an excellent method in terms of workability, and particularly high integration. This has the great advantage that it can easily cope with the increase in size of the chip component itself and the increase in the number of electrodes (number of terminals) accompanying the increase in size. On the other hand, if the oxide film remains on the surface of the bump (spherical solder) or on the electrode surface of the circuit during bonding formation (soldering) between the bump electrode and the electrode, the bump (spherical solder) itself melts uniformly. There will be a number of problems such as failure of wetting between the electrode surface of the circuit and the solder. The problem of poor soldering is eliminated by performing flux treatment.
[0008]
However, in the method in which the heat treatment is performed in one step, the underfill is filled so as to cover the bumps (spherical solder) itself, and thus it is necessary to perform a flux treatment in advance. Nevertheless, the effect of the oxide film formed after the flux treatment remained, and the effect increased with the passage of time after the treatment. For this reason, even if the flux treatment is performed in advance, there are not a few occurrences of poor soldering and poor conduction due to poor wetting with solder.
[0009]
In addition, conventionally, a Pb—Sn eutectic alloy solder material has been widely used for the production of the bump (spherical solder), but instead of this Pb—Sn eutectic alloy, tin containing no lead is used. The use of a bump (spherical solder) using an alloy, so-called lead-free solder, is also being studied. By removing the oxide film on the surface of this lead-free solder bump (spherical solder), joint formation between the bump electrode and the electrode (soldering) and curing of the underfill (sealing filler) are performed simultaneously. Therefore, even under relatively high melting temperatures of this lead-free solder, sufficient flux activity is exhibited, and the reflow temperature is increased, and underfill (encapsulation) in which moderate thermosetting proceeds under the high temperature conditions. Stop filler) is required.
[0010]
[Problems to be solved by the invention]
Even in the method in which the underfill filling is performed in one process in combination with the placement and pressure contact of the chip parts on the printed wiring board, if the flux treatment is performed immediately before this process, the influence of the oxide film is almost eliminated. However, instead of the means for limiting the time freedom of such a process, a component having a flux activity is added to the thermosetting resin composition used for underfill filling, and the influence of the oxide film is sufficiently affected. A new means that eliminates and does not limit the temporal freedom of the process is desired.
[0011]
In addition, instead of the Pb—Sn alloy solder that has been conventionally used, the use of a tin alloy solder that does not contain lead, that is, the so-called lead-free solder is used for the purpose of avoiding environmental pollution caused by the contained lead when discarded. It is being advanced. When adopting the bump electrode using this lead-free solder, the reflow temperature must be selected higher because the melting point of the lead-free solder is higher than that of the Pb—Sn alloy solder. Even under the reflow temperature (thermosetting temperature) condition, it is an underfill (sealing filler) that has a high flux activity that allows the oxide film on the solder surface to be removed quickly, and that thermosetting proceeds at an appropriate rate. There is a need.
[0012]
When an acid anhydride is used as the curing agent for the thermosetting epoxy resin as the main component of the sealing filler, the acid anhydride itself, an oxide film on the surface of the tin alloy solder, more specifically, The inventors have previously found that they react with a surface oxide film of tin, which is a metal component, at a high temperature and function as a flux component, and utilize both the flux action of the acid anhydride and the function as a curing agent. The invention of the liquid epoxy resin composition for sealing filler was filed as Japanese Patent Application No. 2000-72184.
[0013]
In such a liquid epoxy resin composition for sealing filler, an acid anhydride is contained as a curing agent in a ratio higher than 1 equivalent with respect to 1 equivalent of a thermosetting epoxy resin, and the flux action of the acid anhydride is exhibited. I am letting. High reflow temperature that is compatible with the relatively high melting temperature of lead-free solder, although the fluxing action of acid anhydride, specifically, the reaction rate between tin oxide and acid anhydride increases with increasing temperature. In (thermosetting temperature), in order to achieve a desired flux activity, it has been necessary to significantly increase the content ratio of the acid anhydride contained in the epoxy resin composition.
[0014]
A small amount of acid anhydride is consumed by the reaction between the tin oxide and the acid anhydride, resulting in a slight decrease in concentration, but it still remains at a high content ratio. Fortunately, if the amount of oxide film present on the surface of the solder material is small, the amount of acid anhydride consumed is also small, and the content ratio of acid anhydride remains at the initial high content ratio. Become.
[0015]
On the other hand, the thermosetting reaction of the thermosetting epoxy resin that proceeds at the same time, when the content ratio of the acid anhydride as a curing agent is high, the induction of the epoxy ring opening reaction by the acid anhydride starts more frequently. become. As a result, when the thermal curing proceeds more rapidly than the flux processing speed, the viscosity of the epoxy resin composition due to the curing reaction is not completed while the reaction between the tin oxide and the acid anhydride is not completed. Increase and decrease in fluidity occur. That is, while the target flux treatment is not sufficiently performed, thermosetting of the thermosetting epoxy resin proceeds. In some cases, a conduction failure may occur. In addition, the resin strength and adhesive strength of the final cured product to be sealed and filled depend on the ratio between the thermosetting epoxy resin and the acid anhydride that is the curing agent, and a more suitable ratio depending on the thermosetting temperature. However, as the content ratio of the acid anhydride becomes higher, the resin properties of the obtained cured product gradually become different from the desired optimum properties. On the other hand, when the thermosetting reaction proceeds rapidly, the concentration of the remaining acid anhydride rapidly decreases, so the flux activity also decreases accordingly, and the maintenance of the intended flux activity becomes more difficult. come.
[0016]
Actually, when the heat curing temperature (reflow temperature) is selected to be relatively high, the addition amount of a curing accelerator having an action of promoting the ring-opening polymerization reaction between the thermosetting epoxy resin and the acid anhydride is increased. While suppressing the curing rate from becoming excessively high, it remains unreacted as the content ratio of the acid anhydride serving as the curing agent becomes higher than the equivalent ratio with respect to the thermosetting epoxy resin. The ratio of the acid anhydride to be increased will increase. At this time, if the amount of the remaining acid anhydride becomes excessive, it is not always preferable from the viewpoint of function as a sealing filler, for example, maintenance of durability under high humidity and high temperature conditions.
[0017]
Therefore, in the flux treatment, although an acid anhydride is used, a desired flux treatment can be achieved without unnecessarily increasing the content ratio of the acid anhydride contained in the liquid epoxy resin composition for a sealing filler, In addition, the development of a liquid epoxy resin composition capable of obtaining appropriate curing characteristics becomes a new development target. More specifically, with the adoption of bump electrodes using lead-free solder, even when a relatively high thermosetting temperature (reflow temperature) is selected, there is a balance between the thermosetting speed and the flux processing speed. Furthermore, it is necessary to maintain the required flux activity even after reaching the temperature at which the lead-free solder is melted.
[0018]
In addition, the cured epoxy resin obtained by sealing filling fills the gap between the chip component and the printed wiring board, and can maintain its sealing characteristics even when the ambient temperature repeatedly changes, for example. More specifically, it is possible to suppress the occurrence of cracks due to thermal strain stress in the resin itself even when the sealing properties are deteriorated due to temperature changes at an accelerated rate by a thermal cycle test, and peeling, etc. It is also desired that defects in sealing properties can be suppressed.
[0019]
The present invention solves the above-mentioned problems, and an object of the present invention is to provide a flux activity possessed by the acid anhydride in a liquid epoxy resin composition using a thermosetting epoxy resin and an acid anhydride as its curing agent. In addition to the above, by adding a flux activity enhancing component as an additional component, it is possible to achieve a desired flux treatment without obtaining an excessively high content of acid anhydride, and to obtain appropriate curing characteristics. An object of the present invention is to provide a liquid epoxy resin composition for a sealing filler having a novel composition and a sealing filling method using such a liquid epoxy resin composition for a sealing filler. More specifically, the object of the present invention is to select, for example, a reflow temperature / thermosetting temperature at a relatively high temperature that matches the melting temperature of a so-called lead-free tin alloy solder, When the joint formation (soldering) and curing of the underfill (sealing filler) are performed in the same heating process, the content ratio of the acid anhydride that is the curing agent to the thermosetting epoxy resin is In order to demonstrate excellent flux activity that can effectively prevent the occurrence of poor soldering and poor conduction due to poor wetting with solder, while keeping it within a suitable range due to good curing characteristics, a flux activity enhancing component is used. An object of the present invention is to provide a liquid epoxy resin composition for a sealing filler having a novel composition which is added as an additional component.
[0020]
Furthermore, as a final object, the present invention uses a lead-free tin alloy solder as a solder material without depending on the type of the lead-free tin alloy solder and the reflow temperature (thermosetting temperature). By using the liquid epoxy resin composition for sealing filler that also has the above-mentioned flux treatment effect, sealing filling in flip chip mounting that can prevent the occurrence of poor soldering and poor conduction due to poor wetting with solder A method, for example, to provide an effective sealing and filling method even when using Sn-Ag alloy solder as a solder material.
[0021]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the present inventors compared the temperature at which the thermosetting is carried out according to the melting temperature in a range not exceeding 230 ° C. at the maximum of 200 ° C. or higher, which is indicated by lead-free tin alloy solder. Liquid epoxy resin composition for sealing filler that can maintain the desired thermosetting properties while maintaining appropriate thermosetting properties even when the temperature is selected at a high temperature. In particular, when the content ratio of the acid anhydride serving as the curing agent to the thermosetting epoxy resin is kept at an equivalent ratio or slightly lower than the equivalent ratio, the acid anhydride itself As a flux activity-enhancing component that enhances the flux activity mainly related to the flux activity to the desired flux activity, we have eagerly studied and studied what components should be added as additional components.
[0022]
If the above-mentioned flux action is not required, for example, when the thermosetting temperature is about 250 ° C., the liquid epoxy resin and the curing agent acid that are usually recommended for underfill (sealing filler) applications are used. The mixing ratio with the anhydride is selected to be, for example, an amount of the acid anhydride slightly less than 1 equivalent, preferably about 0.8 equivalent, with respect to 1 equivalent of the liquid epoxy resin. Considering this point, in the liquid epoxy resin composition for sealing fillers also having a flux action, the acid anhydride itself is equivalent to the acid anhydride consumed in the process in order to be mainly involved in the flux activity. Although it is necessary to include an excessive amount, the mixing ratio of the liquid epoxy resin and the curing agent is significantly higher than the above 0.8 equivalent with respect to 1 equivalent of the liquid epoxy resin, but very little 1 equivalent. It is concluded that it is desirable to select a flux activity-enhancing component that can achieve a desired flux activity at a relatively low content ratio. Obtained.
[0023]
In addition, the flux activity enhancing component to be additionally added is a component that has essentially no influence on the thermosetting properties and the properties of the resulting cured product when added to the liquid epoxy resin composition. It is desirable to be. At least, the flux treatment activity that mainly involves the acid anhydride itself will be enhanced, but the reaction with the acid anhydride that is the curing agent for the epoxy resin will not be excessively promoted, or conversely will not be inhibited. It is desirable to be. Furthermore, even if the flux activity enhancing component remains at the time of completion of the flux treatment and thermosetting treatment, it has a substantial influence on the properties of the resulting cured epoxy resin, such as insulation properties. It also needs to be non-existent.
[0024]
Under these constraints, when contained in a liquid epoxy resin composition, the thermosetting property, adhesiveness, and resin strength after curing can be maintained within a desired range, and surface oxide films such as bump electrodes and electrodes can be maintained. On the other hand, the inventors searched for a component capable of exhibiting the same effect as a general flux treatment and capable of enhancing the flux activity exhibited by the acid anhydride even when the addition concentration is small. As a result, a component having a proton donating ability is suitable for enhancing flux activity, and can be uniformly distributed throughout the liquid epoxy resin composition, that is, miscibility (solubility / It was found that dicarboxylic acid, which is excellent in dispersibility, is one of those that satisfy these requirements.
[0025]
That is, a dicarboxylic acid, for example, a chain dicarboxylic acid, has compatibility with a liquid epoxy resin due to the lipophilicity of the hydrocarbon chain portion of the skeleton constituting the dicarboxylic acid. It exhibits sufficient mixing properties (solubility / dispersibility) and exhibits sufficient proton donating ability when it reaches a temperature at which flux treatment is performed. Therefore, dicarboxylic acid once donates protons to the tin oxide on the surface of the solder material to promote the reaction with the acid anhydride, but the dicarboxylic acid type distribution derived from the acid anhydride. At the time when a complex consisting of a ligand is formed or converted into a metal salt of a dicarboxylic acid derived from an acid anhydride, the proton is restored again to become the original dicarboxylic acid. Because of this catalytic flux activity enhancing action, the amount of addition can be small since it is not itself consumed as in the case of ordinary fluxing agents.
[0026]
On the other hand, when the flux treatment is completed, the terminal in the polymer of an epoxy resin and an acid anhydride generated by a thermosetting reaction gradually progressing in the meantime, specifically, a carboxy anion species derived from an acid anhydride, In addition, a proton derived from dicarboxylic acid and a carboxy anion species are bonded to the carbocation species generated by the ring opening of the epoxy ring, and are used for the termination. Proton liberation from dicarboxylic acid is an equilibrium reaction, and although there is a considerable proportion of dicarboxylic acid in the form of no proton liberation, it is uniformly distributed in the cured product, which may be a cause of some problems. The formation of the dicarboxylic acid aggregate is less. Of course, the dicarboxylic acid itself has a higher solubility in water than the epoxy resin thermoset, but in the end, most of the dicarboxylic acid is consumed at the end of the thermoset polymer, and the remaining dicarboxylic acid is also cured. As a result of being uniformly dispersed in the product, the remaining carboxy group does not function as ionic conductivity and does not have an essential influence on the insulation of the cured product itself. Based on the above series of findings, the present inventors prepared a liquid epoxy resin composition to which a small amount of dicarboxylic acid was added in addition to the liquid epoxy resin and the acid anhydride of the curing agent, and a relatively high thermosetting temperature. The same effect as the target flux treatment is effectively achieved, and at the same time, there is no substantial influence on the thermosetting reaction itself, and the resin strength of the obtained thermoset is also good. The present invention was completed by confirming that it would not be inferior.
[0027]
The liquid epoxy resin composition for sealing filler of the present invention enhances the flux activity of the acid anhydride to the liquid epoxy resin composition containing a thermosetting epoxy resin and an acid anhydride of a curing agent as essential components. Therefore, a small amount (a catalytic amount) of the flux activity enhancing component having proton donating ability is added as an additional component,
That is, the liquid epoxy resin composition for sealing filler of the present invention uses a flip-chip that uses a lead-free tin alloy solder material having a melting point of 200 ° C. or higher and at most 230 ° C. as a bump electrode material. A liquid epoxy resin composition used in a sealing and filling process of mounting,
The liquid epoxy resin composition includes, as essential components, (A) a liquid thermosetting epoxy resin, (B) an acid anhydride as a curing agent for the thermosetting epoxy resin, and (C) as an additional component. ) Comprising a flux activity enhancing component having proton donating ability,
The (C) flux activity enhancing component is a dicarboxylic acid having 9 to 15 carbon atoms,
The content of the dicarboxylic acid of the (C) flux activity enhancing component is 5 × 10 5 per mole of the acid anhydride of the (B) curing agent. ^-2 ~ 5x10 ^-1 It is the liquid epoxy resin composition for sealing fillers characterized by being selected in the range of mole.
[0028]
In the liquid epoxy resin composition for sealing filler of the present invention, in addition to (B) the acid anhydride of the curing agent,
As a secondary additive component, a liquid epoxy resin composition for sealing fillers that also contains a curing accelerator that promotes the ring-opening reaction of the epoxy ring by the acid anhydride is preferable. In addition, as other secondary additive components, one or more additive components selected from stress relaxation agents, leveling agents, coupling agents, antioxidants, and thixotropic agents may be included.
On the other hand, in the liquid epoxy resin composition for sealing filler of the present invention, the thermosetting epoxy resin (A) is diglycidyl ether having a bisphenol type skeleton, polyglycidyl ether of phenol resin, aliphatic carboxylic acid or aromatic. It is preferable that it is 1 or more types of thermosetting epoxy resins selected from the group of the epoxy resin which consists of diglycidyl ester of an aromatic carboxylic acid, and an alicyclic epoxy resin.
[0029]
Furthermore, in the liquid epoxy resin composition for sealing fillers of this invention, the acid anhydride of (B) hardening | curing agent is 0.9-1.1 with respect to 1 equivalent of the thermosetting epoxy resin of (A). It is desirable to make it the liquid epoxy resin composition for sealing fillers characterized by including equivalent. Furthermore, the content of the curing accelerator is preferably selected in the range of 0.1 to 1.2 parts by mass per 100 parts by mass of the thermosetting epoxy resin (A).
[0030]
In the liquid epoxy resin composition for sealing filler of the present invention, the dicarboxylic acid is ω, ω′-linear hydrocarbon dicarboxylic acid, and the carbon number thereof is selected in the range of C10 to C13. Is more preferable. At that time, the content of the C10-C13 ω, ω′-linear hydrocarbon dicarboxylic acid is 5 × 10 5 per mole of the anhydride of the (B) curing agent. ^-2 ~ 3x10 ^-1 It is desirable to be selected in the molar range.
[0031]
In addition, in the liquid epoxy resin composition for sealing fillers of the present invention, an epoxy obtained by using an intramolecular acid anhydride derived from a saturated cyclic hydrocarbon dicarboxylic acid as the acid anhydride of the (B) curing agent. This is preferable for the purpose of enhancing the flexibility or toughness exhibited by the cured resin. Furthermore, as the thermosetting epoxy resin (A),
Thermosetting epoxy that has been provided with toughness derived from such thermoplastic resin by either adding a small amount of thermoplastic resin component, dispersing fine-part thermoplastic resin, or modifying by modification of thermoplastic resin molecules. A composition containing at least a part of the resin component is preferable for the purpose of enhancing the flexibility or toughness of the obtained cured epoxy resin.
[0032]
In the liquid epoxy resin composition for a sealing filler of the present invention described above, an imidazole is contained as the curing accelerator, which is contained as a secondary additive component. It is desirable to use a liquid epoxy resin composition for an agent.
[0033]
In addition, the present invention also provides an invention of a sealing filling method as an effective usage of the liquid epoxy resin composition for a sealing filler of the present invention having the above-described configuration,
That is, the sealing filling method of the present invention is a sealing filling method in flip chip mounting,
(1) Bump electrodes made of a lead-free tin alloy solder material having a melting point of 200 ° C. or higher and at most 230 ° C. are not used for a printed wiring board having a substrate electrode and a chip component having a chip component electrode A step of making contact between the bump electrode and the electrode after disposing the chip component in a predetermined region on the printed wiring board in order to establish mutual conduction between the electrodes.
(2) After the step of making contact between the bump electrode and the electrode, or in combination with the step, the contact is made in the gap between the printed wiring board and the chip component disposed on a predetermined region thereon. A filling step for filling the liquid epoxy resin composition for a sealing filler having any one of the above-described configurations so as to cover the bump electrodes and the electrodes,
(3) Next, heat the epoxy resin in the liquid epoxy resin composition filled in the gaps of the predetermined region by heating, and the solder bumps covered by the liquid epoxy resin composition are advanced. Melting process,
The process of heating for a predetermined time, cooling, re-solidifying the solder once melted, soldering and bonding the bump electrode and the electrode, and simultaneously completing sealing filling with a thermoset epoxy resin,
Having a series of steps (1) to (3) above,
A sealing filling method characterized by using a liquid epoxy resin composition for a sealing filler having any one of the above configurations as a sealing filler. In particular, the sealing and filling method of the present invention is preferably carried out as a sealing and filling method characterized in that the solder material is a Sn-Ag alloy.
[0034]
Further, the present invention provides a liquid epoxy resin composition for a sealing filler according to the present invention, and an invention of a sealed and filled electronic component, the final object of the invention of a sealing and filling method using the same. Of course,
That is, the electronic component according to the present invention is flip-chip mounted on a printed wiring board using a lead-free tin alloy solder material having a melting point of 200 ° C. or higher and not exceeding 230 ° C. , Mounted and assembled electronic parts that are sealed and filled in the meantime,
The printed wiring board is a printed wiring board having a substrate electrode, and the chip component is a chip component having a chip component electrode. In flip chip mounting, mutual conduction between both electrodes is the lead-free. It is made using a bump electrode made of a tin alloy solder material,
The electronic component is characterized in that flip-chip mounting and sealing filling using the lead-free tin alloy solder material are performed by the sealing and filling method according to the present invention. In that case, the electronic component according to the present invention is usually an electronic component characterized in that at least one of the chip components to be flip-chip mounted and sealed and filled on a printed wiring board is a semiconductor element chip. .
[0035]
DETAILED DESCRIPTION OF THE INVENTION
The liquid epoxy resin composition for a sealing filler of the present invention is a semiconductor using a lead-free tin alloy solder, a so-called lead-free solder, for example, a Sn-Ag alloy solder, as a material for a bump electrode. When the device is assembled, the temperature at which the thermosetting is performed is selected to be higher than the melting temperature of the lead-free tin alloy solder, and the above-described bonding between the bump electrode and the electrode (soldering) and underfill (sealing) are performed. In the method of performing the curing and adhesion of the (stop filler) in the same process, the original effect is exhibited.
[0036]
As a means for inducing thermosetting of thermosetting epoxy resins, especially by using acid anhydrides as curing agents, the reaction of acid anhydrides to metal oxides can also be used as the main flux activity. Yes. In addition, for the purpose of enhancing the flux activity of the acid anhydride, a flux activity enhancing component having proton donating ability is added as an additional component, and an oxide film on the surface of the tin alloy solder, specifically, tin Catalytic promotion of the reaction of acid anhydrides with oxides of Specifically, dicarboxylic acid that can be dissolved in a liquid epoxy resin is used as a flux activity enhancing component having proton donating ability. When heating for thermosetting (reflow), by thermally donating a proton from the carboxy group of the dicarboxylic acid to the oxygen atom of the tin oxide, the acid anhydride reacts with the tin oxide, It promotes the formation of a complex consisting of a dicarboxylic acid type ligand derived from an acid anhydride, or the process of conversion to a metal salt of a dicarboxylic acid derived from an acid anhydride. After the reaction, the proton once donated to the oxygen atom of the tin oxide is restored to the original carboxy group after the series of reactions, and the dicarboxylic acid which has not undergone acid dissociation. Thus, it functions as an acid catalyst.
[0037]
Below, the liquid epoxy resin composition for sealing fillers of this invention, its preparation method, and the procedure of the sealing filling using this liquid epoxy resin composition for sealing fillers are demonstrated in detail.
[0038]
The liquid epoxy resin composition for a sealing filler of the present invention includes, as essential components, (A) a liquid thermosetting epoxy resin, (B) an acid anhydride as a curing agent for the thermosetting epoxy resin, In the liquid epoxy resin composition in which both are uniformly mixed, as an additional component, (C) a dicarboxylic acid used as a flux activity enhancing component is selected as a dicarboxylic acid having 9 to 15 carbon atoms, 5 × 10 5 per mole of acid anhydride ^-2 ~ 5x10 ^-1 It is in the range of moles.
[0039]
In the liquid epoxy resin composition for sealing filler of the present invention, as the essential component (A) liquid thermosetting epoxy resin constituting the thermosetting product, as long as it is an epoxy resin that can be used for the sealing filler There is no limit to its type. For example, diglycidyl ether having a bisphenol type skeleton, polyglycidyl ether of phenol resin, diglycidyl ester of aliphatic carboxylic acid or aromatic carboxylic acid, alicyclic epoxy resin, etc. It is widely used in sealing fillers. Also in the present invention, the diglycidyl ether having a bisphenol type skeleton, a polyglycidyl ether of a phenol resin, a diglycidyl ester of an aliphatic carboxylic acid or an aromatic carboxylic acid, or an epoxy resin consisting of an alicyclic epoxy resin is selected. It is more preferable. At that time, a single resin compound can be used, or two or more resin compounds can be mixed and used. More specifically, as a diglycidyl ether having a bisphenol type skeleton, Epicoat 828 (trade name; manufactured by Japan Epoxy Resin Co., Ltd .: epoxy equivalent 190) and the like, as a polyglycidyl ether of a phenol resin, Epicoat 154 (trade name; Japan Epoxy). Resin Co., Ltd .: Epoxy Equivalent 178), etc. As an aliphatic carboxylic acid or aromatic carboxylic acid diglycidyl ester, Epicoat 871 (trade name; Japan Epoxy Resin Co., Ltd .: Epoxy equivalent 430), Epomic R540 (trade name; Mitsui Chemicals) Celoxide 2021 (trade name; manufactured by Daicel Chemical Industries, Ltd .: epoxy equivalent 135) and the like are used as the alicyclic epoxy resin such as Epoxy equivalent (195).
[0040]
In the liquid epoxy resin composition for sealing fillers of the present invention, in order to enhance the flexibility and flexibility of the obtained thermosetting product, the essential component (A) used as a liquid thermosetting epoxy resin is used. Thermosetting that has been provided with toughness derived from such thermoplastic resin by adding a small amount of thermoplastic resin component, dispersing fine-part thermoplastic resin, or modifying by addition modification of thermoplastic resin molecules It is particularly effective to have a composition that at least partially contains the epoxy resin component. In particular, it is desirable to partially use an epoxy resin that has been subjected to either a dispersion of a particulate thermoplastic resin or a modification by addition modification of a thermoplastic resin molecule. A small amount of the thermoplastic resin dispersed in the form of fine particles maintains a uniform dispersion state even during curing in the liquid epoxy resin composition for sealing fillers of the present invention that cures at a relatively high temperature. The toughness derived from the thermoplastic resin fine particles can be imparted to the entire cured product obtained. Similarly, when an epoxy resin that has been modified by addition modification of thermoplastic resin molecules is partially used, the entire cured product obtained can be imparted with toughness derived uniformly from such thermoplastic resin molecules.
[0041]
The epoxy resin in which the particulate thermoplastic resin is dispersed is, for example, a core-shell type particulate so that the shape of the particulate thermoplastic resin is maintained during thermosetting, and the core portion is rubbery. A thermoplastic resin having a glass transition point Tg higher than that of the thermoplastic resin is preferably used for this purpose. As an example, YR-628 (trade name; manufactured by Tohto Kasei Co., Ltd., epoxy equivalent: 225) or EPR-21 (trade name; Asahi Denka Co., Ltd.), which is an epoxy resin in which rubber component fine particles having a core-shell average particle size of 0.5 μm are dispersed. An epoxy equivalent: 210) manufactured by Kogyo Co., Ltd. can be mentioned. Further, examples of the epoxy resin modified by addition modification of thermoplastic resin molecules include those modified by addition modification of nitrile rubber molecules. As an example, EPR-4023 (trade name; manufactured by Asahi Denki Kagaku Kogyo Co., Ltd., epoxy equivalent: 230), YR-450 (trade name; manufactured by Tohto Kasei Co., Ltd., epoxy equivalent: 450), which is a CTBN-modified epoxy resin, NBR modified epoxy EPR-4026 (trade name; manufactured by Asahi Denki Kagaku Kogyo Co., Ltd., epoxy equivalent: 280), EPR-1309 (trade name: manufactured by Asahi Denki Kagaku Kogyo Co., Ltd., epoxy equivalent: 300), and flexibility in the resin skeleton EPR-4000S (trade name; manufactured by Asahi Denki Kagaku Kogyo Co., Ltd., epoxy equivalent: 260), Epicoat 871 (trade name; manufactured by Japan Epoxy Resin Co., Ltd .: epoxy equivalent 430), Epicoat 872 ( Trade name: Japan Epoxy Resin Co., Ltd .: epoxy equivalent 650). Liquid epoxy resins that have been modified by dispersion of these fine-part thermoplastic resins or addition modification of thermoplastic resin molecules generally increase the liquid viscosity, and therefore are necessary in the liquid epoxy resin composition for sealing fillers of the present invention. For the purpose of maintaining liquid fluidity, it is preferable to mix with a low-viscosity liquid epoxy resin component and adjust the liquid viscosity to the target range as a whole. At that time, the mixing ratio can be appropriately selected according to the viscosity range of the entire resin composition that enables uniform application and filling at the site to be filled at around room temperature. In addition, as an example of the low-viscosity liquid epoxy resin component used, EXA-835LV (trade name; manufactured by Dainippon Ink & Chemicals, Epoxy equivalent: 165), which is a low-viscosity liquid epoxy resin of bisphenol F type, etc. Can be mentioned.
[0042]
By using partially the thermosetting epoxy resin component provided with toughness derived from such a thermoplastic resin, the toughness, flexibility, and flexibility derived from the thermoplastic resin as a whole thermosetting product to be obtained In addition, the advantage of the original adhesiveness of the thermosetting epoxy resin can be maintained. In particular, when cooled to a temperature below the freezing point, the difficulty of thermosetting epoxy resins that rapidly become brittle with the cooling temperature is largely due to the flexibility and toughness resulting from the added thermoplastic resin component. Improved. As a result, the thermoset obtained has increased toughness, especially improved low-temperature brittleness, and is highly adhesive and flexible. Especially, when cooled, the decrease in shear strength and peel strength was further alleviated. I can do it.
[0043]
For example, when using an epoxy resin in which a particulate thermoplastic resin is dispersed, the low-temperature brittleness is improved as the content ratio of the particulate thermoplastic resin increases, but the content ratio is excessively high. Then, taking into account the effect on the excellent adhesiveness, moisture resistance, and heat resistance of the cured epoxy resin itself, the entire liquid epoxy resin composition, per 100 parts by mass, contained in a particulate form dispersed therein Although the thermoplastic resin also depends on the particle size of the fine particles, it is desirable that the thermoplastic resin be within a range not exceeding 40 parts by mass. In order to significantly improve the low temperature brittleness while maintaining the excellent properties of the cured epoxy resin itself, the entire liquid epoxy resin composition, 100 parts by mass, is dispersed and contained in a particulate thermoplastic resin The total amount depends on the particle size of the fine particles, but is preferably selected in the range of 2 to 30 parts by mass, more preferably in the range of 4 to 20 parts by mass. In addition, it is more desirable to keep the total amount of the particulate thermoplastic resin as low as possible in the content ratio as long as the target improvement in low-temperature brittleness is achieved. Also, when using an epoxy resin subjected to addition modification such as addition modification of thermoplastic resin molecules, the ratio of the portion corresponding to the thermoplastic resin molecule in the cured product, for example, nitrile added by modification It is desirable that the sum of the parts derived from the rubber molecules corresponds to the content ratio described above. For example, based on the raw material used when preparing the addition-modified epoxy resin itself, the ratio of the portions corresponding to the thermoplastic resin molecules can be added to obtain such a content ratio.
[0044]
As the acid anhydride that can be used as the curing agent (B), a dicarboxylic acid anhydride that causes curing of the thermosetting epoxy resin can be generally used. This acid anhydride causes a polyaddition reaction with the epoxy resin and achieves resin curing. For example, alicyclic acid anhydrides such as hexahydrophthalic anhydride (HHPA), methyltetrahydrophthalic anhydride, such as aliphatic acid anhydrides such as polyazeline acid anhydride (PAPA), dodecenyl succinic anhydride (DDSA), etc. (MTHPA), methyl nadic acid anhydride (NMT), etc., aromatic acid anhydrides, for example, trimetic acid anhydride (TMA), pyromellitic anhydride (PMDA), etc., halogen acid anhydrides, for example, het acid anhydride (HET) ), Tetrabromophthalic anhydride (TBPA) and the like can be mentioned as examples of polyaddition type acid anhydride curing agents.
[0045]
Especially, it is more preferable that the ring structure containing —CO—O—CO— constitutes a 5-membered ring in the acid anhydride itself used. Among acid anhydrides used as curing agents for thermosetting epoxy resins, those having the above-described structure include, for example, tetrahydrophthalic acid, hexahydrophthalic acid, or endomethylenetetrahydrophthalic acid (methanotetrahydrophthalic acid). From acid anhydrides or derivatives having substitution on the hydrocarbon ring, phthalic anhydride or derivatives having substitution on the benzene ring of phthalic anhydride, succinic anhydride or derivatives having substitution on the hydrocarbon chain of succinic anhydride And acid anhydrides. In addition, the derivative of tetrahydrophthalic anhydride or hexahydrophthalic anhydride preferably used in the present invention includes methylhexahydrophthalic anhydride (trade name B-650; manufactured by Dainippon Ink & Chemicals, Inc.), and the like. Examples of the derivative of succinic anhydride include dodecenyl succinic anhydride.
[0046]
For example, when selecting a diglycidyl ether having the bisphenol type skeleton, a polyglycidyl ether of a phenol resin, a diglycidyl ester of an aliphatic carboxylic acid or an aromatic carboxylic acid, or an alicyclic epoxy resin as an epoxy resin, Examples of the acid anhydride that functions as the curing agent include tetrahydrophthalic acid, hexahydrophthalic acid, or an acid anhydride of endomethylenetetrahydrophthalic acid (methanotetrahydrophthalic acid) or a derivative having substitution on the hydrocarbon ring thereof, Selecting either phthalic anhydride or a derivative having substitution on the benzene ring of phthalic anhydride, or a derivative having substitution on the hydrocarbon chain of succinic anhydride or succinic anhydride provides a more preferable combination.
[0047]
In addition, the following general formula (I):
[0048]
[Chemical 1]

[0049]
Wherein R2 is a monovalent chain hydrocarbon group, R3 is a monovalent chain hydrocarbon group, and R6 is a hydrogen atom or a chain hydrocarbon group. Intramolecular acid anhydrides of tetrahydrophthalic acid type dicarboxylic acids having the above-mentioned substitution, or general formula (II):
[0050]
[Chemical 2]

[0051]
(Wherein R2 is a monovalent chain hydrocarbon group and R3 is a monovalent chain hydrocarbon group) a tetrahydrophthalic acid type dicarboxylic acid having a substitution and a crosslinking chain on the ring represented by Those having a relatively bulky 6-membered ring such as an acid intramolecular acid anhydride are also examples of suitable acid anhydrides.
[0052]
In addition, in the obtained epoxy resin cured product, in order to enhance its flexibility, a product containing no unsaturated carbon bond in the carbon skeleton of the acid anhydride used can be used. For example, among acid anhydrides used as curing agents for thermosetting epoxy resins, a ring structure containing —CO—O—CO— constitutes a 5-membered ring, and the 5-membered ring is The hydrocarbon skeleton has a shape that condenses, and in this case, the cyclic hydrocarbon skeleton preferably does not contain an unsaturated carbon bond in the ring. More specifically, it is preferably an intramolecular acid anhydride of a saturated cyclic hydrocarbon dicarboxylic acid, in which the ring structure containing —CO—O—CO— constitutes a 5-membered ring. As an example, a cyclic hydrocarbon skeleton contained in the above-described alicyclic acid anhydrides, such as hexahydrophthalic anhydride (HHPA), methyltetrahydrophthalic anhydride (MTHPA), methyl nadic anhydride (NMT), etc. A saturated alicyclic acid anhydride obtained by hydrogenating an unsaturated carbon bond therein is more preferable for this purpose, and a hydrogenated nadic acid (HNA) acid anhydride can be given as a representative example.
[0053]
An acid anhydride of hydrogenated nadic acid (HNA) having a saturated cyclic carbon skeleton described below, an acid anhydride derived from bicyclo [2.2.1] heptane-2,3-dicarboxylic acid:
[0054]
[Chemical 3]

[0055]
As well as bicyclo [2.2.1] heptane-2,3,5,6, which is an acid anhydride having a saturated cyclic carbon skeleton, including a bicyclo [2.2.1] heptane (norbornane) skeleton. -Acid anhydride derived from tetracarboxylic acid:
[0056]
[Formula 4]

[0057]
Alternatively, a chain siloxane structure (-(H ₂ SiO) _n -SiH ₂ -) Containing polysiloxane having a terminal substituted with an acid anhydride structure derived from bicyclo [2.2.1] heptane-2,3-dicarboxylic acid:
[0058]
[Chemical formula 5]

[0059]
Are also included in the available saturated alicyclic acid anhydrides. In addition, like the acid anhydride derived from such bicyclo [2.2.1] heptane-2,3-dicarboxylic acid, the carbon atom in which the carboxy group of the dicarboxylic acid is present is adjacent to the adjacent carbon atom. In the case of having a carbon skeleton that becomes a steric hindrance in constituting a carbon-carbon double bond, the formation of carbon dioxide accompanying thermal decarboxylation from such a dicarboxylic acid when performing a thermosetting reaction at a higher temperature There is also an advantage in that respect.
[0060]
Most of the acid anhydride is consumed as a curing agent, but a small amount is consumed as a flux component. Therefore, for example, an acid anhydride is used with respect to 1 equivalent of a liquid epoxy resin in consideration of the amount consumed. 0.8 equivalents or more, preferably 0.9 equivalents or more, at most slightly more than an equivalent amount, specifically, a range not exceeding 1.1 equivalents, a range of 0.9 to 1.1 equivalents It is more preferable to select.
[0061]
It should be noted that, under poor conditions where there is a lot of oxide film formation, higher flux activity is required, and in consideration of this point, a value close to the upper limit range of the acid anhydride addition ratio of the curing agent (B) is selected. preferable. Practically, as long as a person skilled in the art takes normal care so as not to cause excessive spontaneous oxidation, the acid anhydride is used in an amount of 0.85 to 0.001 per 1 equivalent of the thermosetting epoxy resin (A). Even if the composition range including 95 equivalents is selected, the consumption accompanying the required flux activity is covered, and the amount of the remaining acid anhydride is in the range of 0.8 equivalents to 0.9 equivalents suitable for thermal curing. Generally fits. In consideration of the narrow spacing between the bump electrodes, the proportion of the acid anhydride consumed in the removal of the surface oxide film tends to increase relatively. In that case, considering the safety, the initial content ratio is slightly increased, for example, by selecting up to 1.1 equivalents, it is suitable for thermosetting even if the amount consumed by exhibiting the flux action is excluded. It can be surely accommodated in the range of 0.8 equivalent to 1.0 equivalent.
[0062]
The acid anhydride selected from the above-mentioned various acid anhydrides according to the various liquid thermosetting epoxy resins in (A) above is used as the curing agent in (B), and (A) liquid thermosetting epoxy is used. It causes ring-opening polymerization together with the resin to cause thermosetting. At that time, when the heat curing temperature is relatively low, it is desirable to add a small amount of a curing accelerator for the purpose of appropriately promoting the opening of the epoxy ring. That is, in the liquid epoxy resin composition for a sealing filler of the present invention, although the acid anhydride is a ratio suitable for elongation of proper polymerization as the curing agent of (B), curing is accelerated at the start of the thermal curing. By utilizing the action of the agent and selecting the addition amount according to the curing temperature, it becomes easy to adjust the overall thermosetting rate to a desired range.
[0063]
This curing accelerator is not particularly limited as long as it accelerates the ring-opening reaction of the epoxy group and does not react with the acid anhydride itself, an amine compound that does not cause formation of an amide with the acid anhydride, Lewis acid As well as imidazoles. Specific examples of amine compounds that satisfy the above requirements include tertiary amines such as benzyldimethylamine (BDMA) and 2,4,6-tris (dimethylaminomethyl) phenol (DMP-30). Examples of the acid include BF _Three ・ Monoethylamine, BF _Three -Piperazine and the like, and examples of imidazoles include 1-benzyl-2-methylimidazole, 2-ethyl-4-methylimidazole (EM124), 2-heptadecylimidazole (HD12), and the like. .
[0064]
Among these curing accelerators, imidazoles are less likely to form a complex (addition salt) between the dicarboxylic acid added as an additional component and the nitrogen atom contained therein, and are more suitable for the purpose of the present invention. Is.
[0065]
When using the above-described amine compounds, Lewis acids, imidazoles, etc. as curing accelerators, the epoxy resin and acid whose reaction is induced and promoted by the action of promoting the opening of the epoxy ring of these nucleophilic compounds. The resin chain is extended by a polyaddition reaction with an anhydride. Therefore, it is preferable to mix 0.001 to 0.02 molecule of a curing accelerator per molecule of the thermosetting epoxy resin. For example, specifically as a hardening accelerator, it is good to select in the range of 0.5-10 mmol (mmol) in imidazoles per 100g of epoxy resins of epoxy equivalent 190 specifically, for example. Depending on the molecular weight of the curing accelerator, for example, it can be added in the range of 0.1 to 2 parts by mass per 100 parts by mass of the liquid epoxy resin. As the curing temperature is increased, the reaction with the acid anhydride of the curing agent proceeds even if the addition ratio of the curing accelerator is lowered. In order to balance the reaction and the reaction rate, when selecting a high curing treatment temperature, the addition ratio of the curing accelerator is relatively lowered, and 0.1 to 100 parts by mass of the liquid epoxy resin. It is more desirable to set the range in the range of 1.2 parts by mass.
[0066]
In the liquid epoxy resin composition in which the main components involved in the thermosetting reaction described above are uniformly mixed, as an additional component, (C) a dicarboxylic acid having a function as a flux activity enhancing component having proton donating ability Add a small amount of acid.
[0067]
The dicarboxylic acid has a melting point lower than the thermosetting temperature of the liquid epoxy resin composition, is solid at room temperature, and preferably has a boiling point higher than the thermosetting temperature of the liquid epoxy resin composition. In addition, a highly compatible dicarboxylic acid that can be uniformly mixed with the epoxy resin as the main component in the liquid epoxy resin composition is preferred.
[0068]
That is, the dicarboxylic acid is used in a state where it is uniformly dissolved and mixed in the liquid epoxy resin composition, like the acid anhydride, but the liquid epoxy resin itself that functions as a solvent as the thermosetting progresses. When the amount of the liquid epoxy resin that causes polymerization and functions as a solvent decreases, it is preferable that the dicarboxylic acid maintains a uniform dissolved state in the liquid epoxy resin composition.
[0069]
Therefore, it is more preferable that the dicarboxylic acid to be used has a boiling point significantly higher than the thermosetting temperature of the liquid epoxy resin composition. Along with heat curing, flux treatment also proceeds. However, if the boiling point of the dicarboxylic acid used is lower than the heat curing temperature, it will dissolve in the liquid epoxy resin composition, resulting in an increase in boiling point. Although vaporization does not occur due to generation of bubbles, if transpiration progresses and the residual concentration decreases, the target flux activity enhancing action may not be achieved. If the boiling point of the dicarboxylic acid to be used is significantly higher than the thermosetting temperature of the liquid epoxy resin composition, the decrease in the flux activity enhancing action associated with the transpiration will not be a problem. Further, when the thermosetting is completed, it is not consumed at the end of the polymerization reaction, and the remaining dicarboxylic acid is immersed between the polymer molecules of the cured product when its melting point is lower than the thermosetting temperature. A uniformly dispersed state can be achieved more reliably. Of course, during the thermal curing, the vaporized dicarboxylic acid forms bubbles and does not cause a void.
[0070]
In addition, depending on the molecular shape of the dicarboxylic acid, dehydration condensation may occur between the two carboxy groups within the molecule during heating, and the dicarboxylic acid may be converted into an acid anhydride. Specifically, the cyclic anhydride to be formed forms a 5-membered ring such as succinic anhydride, maleic anhydride, and phthalic anhydride, or a 6-membered ring such as glutaric anhydride. As for what to do, conversion to the acid anhydride by dehydration condensation advances as heating temperature increases. At that time, the content ratio of the dicarboxylic acid having the flux activity enhancing action is reduced as a result, that is, the flux activity enhancing action is lowered. Many of the acid anhydrides themselves that function as a curing agent for the epoxy resin are not problematic, but it is necessary to increase the amount of the dicarboxylic acid initially added, which is not preferable. In addition, when the 5-membered or 6-membered cyclic acid anhydride is generated, water molecules as a by-product are vaporized and bubbles are formed, causing voids, and sealing filler. Is not preferred in terms of functionality.
[0071]
Separately, among the dicarboxylic acids, fumaric acid (trans-butanedioic acid), oxalic acid (ethanedioic acid), malonic acid (propanedioic acid), etc., which are highly soluble in water, are prepared by using the cyclic acid anhydride. Although there is no concern of formation, from the viewpoint of the water resistance of the sealing filler or the protective properties in a high humidity environment, there is a concern that when present on the surface of the cured product, it dissolves in water and functions as an acid. The range of use is limited.
[0072]
The target solder material is lead-free solder whose melting point is 200 ° C. or higher and at most 230 ° C., so the temperature of the thermosetting treatment of the liquid epoxy resin composition for sealing filler is lead Although it is significantly higher than the melting temperature of free solder, for example, about 10 ° C. or higher, it is usually selected within a range not exceeding 260 ° C. at the highest, and the flux treatment is also performed. Therefore, even when the temperature of the thermosetting treatment is selected in the range of 230 ° C. to 260 ° C., the dicarboxylic acid that satisfies all the above-mentioned various conditions and can be suitably used without restriction has a melting point of the dicarboxylic acid. For example, the melting point is significantly lower than the melting temperature (217 ° C.) of Sn—Ag solder having a composition of Sn: 95.8%, Ag: 3.5%, Cu: 0.7%, and the boiling point is such Sn— It is sufficiently higher than the melting temperature of Ag-based solder, has poor solubility in water, and corresponds to a carbon chain length of at least 4 carbon atoms between the two carboxy groups contained. It is a dicarboxylic acid having a structure with a gap.
[0073]
For example, in the case of a saturated aliphatic dicarboxylic acid, a chain containing two carboxy groups at both ends (HOOC- (C) _n When -COOH) is used as a base chain, the base chain of this chain length (n + 2) has at least a chain length of 6 or more, preferably a chain length in the range of 9 to 15 carbon atoms. More preferably, those having a chain length in the range of 10 to 13 carbon atoms can be mentioned as suitable examples. It should be noted that even if some number of branched chains are present with respect to the base chain, it is similarly suitable if the melting point thereof does not rise extremely. Among saturated aliphatic dicarboxylic acids, it is a linear alkanedioic acid having no side chain, and its carbon number is preferably in the range of C9 to C15, more preferably in the range of C10 to C13. It will be a thing.
[0074]
Also in unsaturated aliphatic dicarboxylic acid, a chain containing two carboxy groups at both ends corresponding to the saturated aliphatic dicarboxylic acid is defined as a parent chain (HOOC- (C) _n -COOH) having a chain length in the range of 9 to 15 carbon atoms, more preferably, having a chain length in the range of 10 to 13 carbon atoms can be mentioned as a suitable example. In this case as well, even if some number of branched chains are present with respect to the base chain, it is similarly suitable if the melting point does not rise extremely. Depending on the absolute configuration of the carbon-carbon double bond such as —CH═CH— present in the parent chain, two carboxy groups are close to each other, and an acid anhydride can be generated in the molecule. However, the configuration in which this type of cyclic anhydride readily forms is excluded from the preferred range. Unsaturated aliphatic dicarboxylic acid is also a straight chain dicarboxylic acid having no side chain, and its carbon number is preferably in the range of C9 to C15, more preferably in the range of C10 to C13. It becomes.
[0075]
Further, in the above chain aliphatic dicarboxylic acid, the chain containing two carboxy groups at both ends is replaced with a base chain, the chain contains a ring structure, and the effective chain length is 6 or more carbon atoms. Although it corresponds to the chain length, it is a suitable dicarboxylic acid. Specifically, the included ring structure includes an aromatic ring such as a phenylene group (—C ₆ H _Four -) Or the like, or a ring structure derived from an alicyclic hydrocarbon such as cyclohexanediyl (-C ₆ H _Ten -). In addition, these ring structures; one carboxy group is not directly bonded to R, but HOOC- (C) _n1 -R- (C) _n2 A shape having a carboxy group in each of two side chains on a —COOH type ring structure is more preferred.
[0076]
In the case of a saturated aliphatic dicarboxylic acid, if the number of carbons in the base chain exceeds 15, even if the number of carbons increases, it does not increase so much. When the addition ratio is small, the number of carbons in the base chain is 40. Even those that reach a degree will be usable. Note that it is not preferable that the number of carbon atoms is unnecessarily large. In general, it is preferable that the number of carbon atoms in the base chain be 15 or less.
[0077]
Also in unsaturated aliphatic dicarboxylic acid, a chain containing two carboxy groups at both ends corresponding to the saturated aliphatic dicarboxylic acid is defined as a parent chain (HOOC- (C) _n -COOH) having a chain length in the range of 9 or more carbon atoms is preferable. Depending on the selection of the addition ratio and the treatment temperature, it can be used even if the base chain has about 40 carbon atoms. It will be something. Similarly, it is not preferable that the number of carbon atoms is unnecessarily large. In general, it is desirable that the number of carbon atoms in the base chain be 15 or less.
[0078]
In addition, diacids (added dicarboxylic acids) up to about 20 carbon atoms in which short-chain α, β-unsaturated carboxylic acids such as acrylic acid are added to unsaturated fatty acids, and long-chain unsaturated carboxylic acids are mutually linked. The dimer acid having a carbon number of 38 to 44 added to can be used when lead-free solder is a target. The dimer acid having 38 to 44 carbon atoms is a mixture of some monomeric acid and trimer acid, and generally shows a high-viscosity liquid even near room temperature. Is sufficiently higher than the melting temperature of the lead-free solder.
[0079]
The addition ratio of the dicarboxylic acid is appropriately selected according to the acid anhydride and considering the temperature at which the flux treatment is performed. In other words, when the temperature at which the flux treatment is performed is selected to be high, the acid anhydride, which is a curing agent in the main role, is rapidly consumed for thermal curing, so the flux treatment speed is comparable to the thermal curing speed. In order to do so, it is necessary to increase the addition ratio of the dicarboxylic acid. On the other hand, when the temperature at which the flux treatment is performed is not so high, the thermal curing rate is not so high, so even if the addition ratio of dicarboxylic acid is low, the flux treatment rate is comparable to the thermal curing rate. Can be.
[0080]
As the lead-free solder material, those having a melting point of at most 230 ° C. are mainly used. For example, the composition is Sn: 95.8%, Ag: 3.5%, Cu: The melting temperature of 0.7% Sn—Ag solder is 217 ° C., and the temperature of the thermosetting treatment is selected in the range of 230 ° C. or more and 250 ° C. or less. Therefore, in the present invention, in general, the dicarboxylic acid is added in an amount of 5 × 10 5 to 1 mol of the acid anhydride of the (B) curing agent in accordance with the temperature of the thermosetting treatment. ^-2 ~ 5x10 ^-1 In amounts in the molar range, preferably 5 × 10 ^-2 ~ 3x10 ^-1 It is preferable to select the amount in a molar range. Alternatively, it is more desirable to select the dicarboxylic acid content in the range of 5 to 15% by mass with respect to the entire resin composition.
[0081]
In addition, in the liquid epoxy resin composition for sealing filler of the present invention, the flux treatment for the lead-free tin alloy solder material mainly utilizes the flux activity enhancing action exhibited by the above-mentioned additional component dicarboxylic acid, Although it is performed using an acid anhydride, in some cases, a component exhibiting a flux activity enhancing action can be added as a secondary agent. For example, as a component that can be added as a secondary agent and has a flux activity enhancing action, an acid-modified rosin added with acrylic acid or the like, for example, an acrylic-modified rosin, or a basic nitrogen atom of an amine compound is used. Those which show a proton donating ability for the first time when heated, such as a hydrogen halide addition salt of an amine formed by forming a hydrogen halide addition salt, can be used by adding a supplementary amount.
[0082]
That is, in the present invention, (C) the above-mentioned dicarboxylic acid is mainly used as the flux activity enhancing component having proton donating ability, but supplementally, in the range not exceeding the content ratio of dicarboxylic acid, for example, high boiling point It is also possible to use monocarboxylic acids having Specifically, even when the temperature of the thermosetting treatment is selected in the range of 230 ° C. to 260 ° C., the monocarboxylic acid that can be suitably used as a supplemental flux activity enhancing component is such a monocarboxylic acid. The melting point is significantly lower than the melting temperature (217 ° C.) of Sn—Ag solder having a composition of Sn: 95.8%, Ag: 3.5%, Cu: 0.7%, and the boiling point is, for example, It is sufficiently higher than the melting temperature of Sn-Ag solder and has poor solubility in water. An example of a monocarboxylic acid that satisfies the above conditions and can be suitably used as a supplemental flux activity enhancing component is ditenperic acid C such as abietic acid or pimaric acid, which is the main component of resin acid. ₁₉ H ₂₉ Examples include hydrogenation treatment of COOH or the like, or hydrogenation rosin obtained by hydrogenation treatment of a rosin containing ditenperic acid as a main component. When these high boiling point monocarboxylic acids are also used, the monocarboxylic acid content ratio is significantly lower than the dicarboxylic acid content ratio, for example, 10 parts by mass of the dicarboxylic acid. It is more desirable to select the acid within a range not exceeding 5 parts by mass. It is more desirable to select the monocarboxylic acid so that it does not exceed 1/2 molecule per molecule of dicarboxylic acid.
[0083]
On the other hand, in addition to the function as a secondary flux activity enhancing component, the monocarboxylic acid also has a role of end-capping when extending the polymer chain length accompanying the curing reaction of the epoxy resin. As a result, in the process of soldering and thermal curing of epoxy resin after flux treatment, the chain length in the resulting cross-linked / polymerized structure is excessively advanced, preventing the resin viscosity from increasing more than necessary. Show. In addition, since the chain length is not excessively extended, the resulting thermoset is also improved in brittleness at low temperatures. It is desirable that such a supplemented monocarboxylic acid also dissolves uniformly in the resin composition. In addition, when the resulting thermoset is increased in water absorption or end-capped. It is desirable that the carbon skeleton itself of such a monocarboxylic acid does not cause problems such as an increase in Tg. Therefore, for example, a hydrogenated rosin that has been previously hydrogenated to an unsaturated carbon bond capable of addition polymerization in the molecule or a rosin having a site causing thermal decomposition is a monocarboxylic acid that is also suitable from the above viewpoint. It becomes one of. Also, use of highly acidic benzoic acids such as p-hydroxybenzoic acid, m-bromobenzoic acid, etc., which have excellent solubility in epoxy resin, high boiling point and high proton donating ability in high temperature region You can also.
[0084]
As the content ratio of the acid anhydride increases, the flux activity increases in the acid anhydride itself, so that a desired flux treatment rate can be achieved even if the addition ratio of the dicarboxylic acid is lowered. On the other hand, when the content ratio of the acid anhydride is low, the addition ratio of the dicarboxylic acid is selected within a range that does not exceed the above upper limit value, and the activity is further enhanced so that the desired flux treatment rate is obtained. It is preferable to aim for.
[0085]
Furthermore, the remaining dicarboxylic acid remains in the underfill even after the soldering is completed, but it causes an unnecessary reaction to the wiring metal that is in contact with it, forming a factor that causes malfunction. Nor.
[0086]
The sealing filler is mainly used to reinforce the bonding and fixing area near the bump electrode, that is, the chip component and the printed wiring board. It is optimal that the final content of the epoxy resin and the curing agent is in a preferable range, specifically, a polyaddition type curing agent, for example, an acid anhydride is about 0.8 equivalent. In order to advance thermosetting, a part of the acid anhydride is consumed as the surface oxide film is removed while the temperature is maintained at a high temperature. Therefore, when the acid anhydride is seen in the vicinity of the bump electrode, the local content thereof gradually decreases as the flux treatment proceeds. As a result, since the elongation of the polymerization addition reaction between the epoxy resin and the curing agent is once delayed, the fluidity of the epoxy resin composition is impaired before the flux treatment is completed, which becomes an obstacle to the flux treatment. To prevent that. After the flux treatment is completed, the necessary acid anhydride is supplied by diffusion while keeping constant at a temperature near the melting point of the solder for a period required for heat curing. Accordingly, even in the vicinity of the bump electrode, the properties of the obtained thermoset are completely inferior to those of the conventional sealing filler.
[0087]
The liquid epoxy resin composition for sealing filler of the present invention comprises the above-mentioned (A) liquid thermosetting epoxy resin, (B) acid anhydride of the curing agent, and (C) proton donating ability of an additional component. In addition to the essential component of the dicarboxylic acid used as a flux activity enhancing component having the above, usually the curing accelerator described above is often added as a secondary component, but other than this, this kind of epoxy resin Secondary ingredients commonly used in the composition can also be added. Specifically, as other secondary components, a stress relaxation agent, a leveling agent, a coupling agent, an antioxidant, etc., and further, a plasticizer, a thixotropic agent, and the like can be added. Which is added, and the addition amount thereof may be appropriately selected according to the thermosetting epoxy resin and acid anhydride used as essential components.
[0088]
The antioxidant can be mixed in the epoxy resin in advance for the purpose of improving the heat resistance of the epoxy resin in the thermosetting process after sealing and filling. As this antioxidant, hydroquinone, phosphites and the like having an oxygen removing / reducing action can be used, and the amount of addition depends on the heat treatment environment, for example, the residual oxygen concentration and temperature in the reflow furnace. Select as appropriate.
[0089]
The leveling agent may be appropriately selected depending on the viscosity of the liquid epoxy resin composition itself for the sealing filler, and accordingly the type and content ratio of the thermosetting epoxy resin and the curing agent used as essential components. For example, as a leveling agent, ST80PA (trade name; manufactured by Toray Dow = Corning Silicone Co., Ltd.) or the like can be used, and it should be added in the range of 0 to 5% by mass with respect to the entire liquid epoxy resin composition. Can do. As a stress relaxation agent, Adeka Resin EPR-1309 (trade name; manufactured by Asahi Denka Kogyo Co., Ltd., epoxy equivalent 280) can be used, and it is added in a range of 0 to 10% by mass with respect to the whole liquid epoxy resin composition. can do.
[0090]
In addition, considering the material of the printed wiring board and the type of material exposed on the back surface of the chip component, the coupling agent should be selected as appropriate according to the type of epoxy resin used. Add. Examples of commonly used coupling agents include silane-based coupling agents γ-glycidoxypropyltrimethoxysilane and the like. From these, a suitable amount of a suitable coupling agent may be added according to the above selection criteria. Generally, a coupling agent can be added in 0-10 mass% with respect to the whole liquid epoxy resin composition.
[0091]
A plasticizer or a thixotropic agent is added as necessary in consideration of the coating processability of the liquid epoxy resin composition. Examples of the plasticizer include dibutyl phthalate, and an appropriate amount of a preferable plasticizer may be added depending on the type of epoxy resin. Examples of the thixotropic agent include triglyceride of hydroxystearic acid, fumed silica, and the like, and an appropriate amount of a preferable thixotropic agent may be added depending on the type of epoxy resin.
[0092]
In the liquid epoxy resin composition for sealing filler of the present invention, the temperature of the thermosetting treatment is selected, for example, in the range of 230 ° C. to 260 ° C. , The gaps to be sealed and filled are uniformly filled, and the portions that are not partially wet when applied are also covered with the liquid epoxy resin composition at this stage. Therefore, the liquid viscosity of the liquid epoxy resin composition itself at room temperature may be selected within a range that satisfies the fluidity to the extent that it can be applied so as to cover the bump electrode made of lead-free solder. For example, when a dispenser is used as the application means, the liquid viscosity of the liquid epoxy resin composition itself is preferably adjusted to a range of 0.5 to 50 Pa · s according to the nozzle diameter of the dispenser. The liquid epoxy resin composition for sealing fillers of the present invention comprises the above-mentioned commonly used secondary and thermosetting epoxy resins and curing agents, an additional component dicarboxylic acid, and optionally added. However, it is desirable to adjust the overall liquid viscosity within the above range by the combination of the thermosetting epoxy resin and the liquid viscosity of the curing agent, which are the main components. For example, as a thermosetting epoxy resin, for example, when a liquid epoxy resin subjected to modification by dispersion of fine particle thermoplastic resin or addition modification of a thermoplastic resin molecule is used, these generally increase the liquid viscosity. As the acid anhydride utilized in the above, a liquid epoxy resin composition having a suitable liquid viscosity range can be prepared as a whole by selecting one having a relatively low liquid viscosity.
[0093]
The liquid epoxy resin composition for sealing fillers of the present invention comprises the above-mentioned commonly used secondary and thermosetting epoxy resins and curing agents, an additional component dicarboxylic acid, and optionally added. After sufficiently mixing these components, the bubbles generated or taken in by the stirring in the preparation process can be produced by degassing under reduced pressure. In addition, the acid anhydride of the curing agent, dicarboxylic acid, and the like contained in the liquid epoxy resin composition for sealing filler of the present invention are placed in an environment where moisture exists before the curing reaction. It is a compound that loses its original function, and in order to maintain the removal action of the oxide film on the surface of the metal material, it can be prepared and stored by suppressing the mixing of water into the manufactured liquid epoxy resin composition. Do.
[0094]
The liquid epoxy resin composition for sealing filler of the present invention is used for sealing filling in flip chip mounting and exhibits its effect. Specifically, in flip-chip mounting, the effect is exhibited in a system in which a bump electrode made of lead-free solder is melted with an underfill and then thermally cured.
[0095]
Regardless of the filling method of the liquid epoxy resin composition, an in-situ removal action of an oxide film remaining on a metal surface such as a bump made of lead-free tin alloy solder can be obtained. For example, a sealing filling method that takes the following procedure The effect is higher when taking Specifically, as a method of sealing filling in flip chip mounting,
(1) A printed wiring board having a substrate electrode and a chip component having a chip component electrode are placed in a predetermined region on the printed wiring board in order to establish mutual conduction between both electrodes using solder bump electrodes. After placing the chip component, a step of making contact between the solder bump electrode and the electrode,
(2) After the step of making contact between the solder bump electrode and the electrode, or together with the step, the gap between the printed wiring board and the chip component disposed on a predetermined region on the printed wiring board, Filling step for filling the liquid epoxy resin composition for sealing filler of the present invention as described above so as to cover the bump electrode and the electrode made of solder intended to contact,
(3) Next, heat the epoxy resin in the liquid epoxy resin composition filled in the gaps of the predetermined region by heating, and the solder bumps covered by the liquid epoxy resin composition are advanced. Melting process,
The process of heating for a predetermined time, cooling, re-solidifying the solder once melted, soldering and bonding the bump electrode and the electrode, and simultaneously completing sealing filling with a thermoset epoxy resin,
It is preferable to perform sealing and filling by the series of steps (1) to (3).
[0096]
In other words, a liquid epoxy resin composition having a predetermined viscosity is previously applied thickly on a printed wiring board, and a chip component is pressed from above to make physical contact between the metal wiring electrode and the bump electrode. At the same time, the liquid epoxy resin composition that has been crushed and spread also covers the metal wiring electrode and the bump electrode. At this time, since the upper surface of the applied liquid epoxy resin composition is substantially flat, no unfilled portion or void portion is generated by pressing the chip component from above. Further, the surface of the metal wiring electrode and the bump electrode that have achieved physical contact can be in a state in which the liquid epoxy resin composition is densely covered. In this state, heating is performed to melt the solder bumps, so that the oxide film remaining on the metal surface is removed as described above.
[0097]
Therefore, the electronic component according to the present invention is mounted and assembled electronically by flip-chip mounting using the above-described liquid epoxy resin composition for sealing filler of the present invention described above, and sealing filling is performed therebetween. Lead, which is a component, for joining a printed wiring board having a substrate electrode and a chip component having a chip component electrode, and having a mutual conduction between the electrodes of 200 ° C. or higher but not exceeding 230 ° C. When a bump electrode made of a free tin alloy solder material is used, the oxide film remaining on the metal surface can be effectively removed, and good conduction characteristics can be achieved with high reproducibility. In addition, when the flux treatment is completed and the lead-free tin alloy solder material can be melted and soldered, the epoxy resin is thermally cured, so there is no occurrence of unfilled or voided parts. , Soldering and sealing filling are performed. In addition, the electronic component according to the present invention can be obtained by mounting a semiconductor element chip that can be flip-chip mounted on a printed wiring board using a lead-free tin alloy solder material in a few steps. In addition, the liquid epoxy resin composition for sealing filler of the present invention to be used,
(B) As an acid anhydride of the curing agent, an intramolecular acid anhydride derived from a saturated cyclic hydrocarbon dicarboxylic acid is used, or
The thermosetting epoxy resin of (A) is derived from such a thermoplastic resin by any treatment of addition of a small amount of a thermoplastic resin component, dispersion of a particulate thermoplastic resin, or modification by addition modification of a thermoplastic resin molecule. When the composition of the thermosetting epoxy resin component to which the toughness is imparted is at least partially included, and the flexibility or toughness of the resulting cured epoxy resin is enhanced, severe cooling conditions For example, even if a cooling cycle treatment is performed under a cooling condition of −65 ° C. and a heating condition of 125 ° C., the generation of cracks in the sealed resin filled product can be effectively suppressed. At that time, defects such as poor adhesion can also be suppressed, and the electronic component according to the present invention has excellent environmental resistance in which moisture ingress from the outside is protected for a long time in an environment with a large temperature difference. It becomes.
[0098]
【Example】
Below, a specific example is given and it demonstrates more concretely about the liquid epoxy resin composition for sealing fillers of this invention, and the removal effect of the oxide film achieved in sealing filling using the same. In addition, although the Example shown below is an example of the best embodiment in this invention, this invention is not limited to these Examples.
[0099]
The removal action of the oxide film formed on the surface of the lead-free solder material, which is a characteristic of the liquid epoxy resin composition for sealing filler of the present invention, was verified. Specifically, it was verified that the enhancement of flux activity was achieved to a desired degree by the dicarboxylic acid added as an additional component.
[0100]
In addition, by adopting the configuration of the present invention, even when heating is proceeded to a temperature significantly higher than the melting point of the lead-free tin alloy solder, voids resulting from thermal decomposition of the contained components are not caused. It was verified that the occurrence was sufficiently suppressed.
[0101]
The difference in the removal efficiency of the oxide film of the solder material involved in the acid anhydride of the (B) curing agent, which is included as an essential component in the liquid epoxy resin composition due to the addition of the dicarboxylic acid, About the filling and hardening sample, it was judged by the presence or absence of the conduction | electrical_connection defect in the conduction | electrical_connection test between electrodes presumed to be a solder defect.
[0102]
(Comparative Example 1)
As a solder material for forming bumps, a tin alloy solder not containing lead, one of so-called lead-free solders, the composition is Sn: 95.8%, Ag: 3.5%, Cu: 0.7% (melting point) : When using Sn-Ag solder of 217 ° C), as an epoxy resin for underfill that can be used at a temperature that does not greatly exceed its melting point, as a liquid epoxy resin, Epicoat 828 of bisphenol A type epoxy resin (trade name, Japan) Epoxy resin, epoxy equivalent of about 190) per 100 parts by mass of the acid anhydride of the curing agent, tetrahydrophthalic anhydride derivative YH-307 (trade name; Japan Epoxy Resin, acid anhydride equivalent of about 230) 120 parts by mass and a small amount of BMI of 1-benzyl-2-methylimidazole as one of imidazoles as a curing accelerator 2 (trade name, manufactured by Japan Epoxy Resins Co., Ltd., molecular weight 172) and the liquid epoxy resin composition was added 0.8 part by weight were prepared.
[0103]
After mixing the above three components uniformly, vacuum degassing treatment was performed to prepare a liquid epoxy resin composition. This liquid epoxy resin composition is cured as desired in 2 to 5 minutes at a curing temperature of 250 ° C. as thermosetting conditions.
[0104]
Example 1
It is an example of the liquid epoxy resin composition for sealing filler of this invention, ie, a composition suitable when said Sn-Ag solder (melting | fusing point: 217 degreeC) is utilized as a solder material which forms bump. A liquid epoxy resin composition containing a dicarboxylic acid as a flux activity enhancing component as an additional component in a liquid epoxy resin and acid anhydride having a ratio. As this dicarboxylic acid, in this Example 1, linear alkanedioic acid; ω, ω′-alkanedicarboxylic acid (HOOC— (CH ₂ ) _n -COOH), dodecanedioic acid (manufactured by Ube Industries, Ltd., molecular weight 230.3, melting point 129 ° C., boiling point 245 ° C. (10 mmHg)) was used.
[0105]
As a liquid epoxy resin, per 100 parts by mass of bisphenol A type epoxy resin Epicoat 828 (supra), as a curing agent acid anhydride, 120 parts by mass of tetrahydrophthalic anhydride derivative YH-307 (supra) As an accelerator, a liquid epoxy resin composition was prepared by adding a small amount of 0.8 part by mass of BMI12 (supra) of 1-benzyl-2-methylimidazole, one of imidazoles. In addition, 10 parts by mass of dodecanedioic acid was uniformly dispersed in the liquid epoxy resin composition as a flux activity enhancing component. Then, the defoaming process was carried out under reduced pressure, and the target liquid epoxy resin composition for sealing fillers was prepared. This liquid epoxy resin composition is cured as desired in 2 to 5 minutes at a curing temperature of 250 ° C. as thermosetting conditions.
[0106]
(Example 2)
Compared with Example 1, a liquid epoxy resin composition having a higher dodecanedioic acid addition ratio was prepared. Specifically, tetrahydrophthalic anhydride derivative YH-307 (supra) 120 per 100 parts by mass of bisphenol A type epoxy resin Epicoat 828 (supra) as a liquid epoxy resin. A liquid epoxy resin composition was prepared by adding 0.8 part by mass of BMI12 (supra) of 1 part of imidazole, 1-benzyl-2-methylimidazole as a part of mass part and a curing accelerator. In addition, 20 parts by mass of dodecanedioic acid was uniformly dispersed in the liquid epoxy resin composition as a flux activity enhancing component. Then, the defoaming process was carried out under reduced pressure, and the target liquid epoxy resin composition for sealing fillers was prepared. This liquid epoxy resin composition is cured as desired in 2 to 5 minutes at a curing temperature of 250 ° C. as thermosetting conditions.
[0107]
(Example 3)
Instead of dodecanedioic acid used in Example 1, a liquid epoxy resin composition was prepared using sebacic acid (decanedioic acid; 1,8-octanedicarboxylic acid) as an additional component for increasing flux activity. . Specifically, tetrahydrophthalic anhydride derivative YH-307 (supra) 120 per 100 parts by mass of bisphenol A type epoxy resin Epicoat 828 (supra) as a liquid epoxy resin. A liquid epoxy resin composition was prepared by adding 0.8 part by mass of BMI12 (supra) of 1 part of imidazole, 1-benzyl-2-methylimidazole as a part of mass part and a curing accelerator. In addition, 10 parts by mass of sebacic acid (decanedioic acid: manufactured by Toyokuni Oil Co., Ltd., molecular weight 202.25, melting point 135 ° C., boiling point 294.5 ° C. (100 mmHg)) as a flux activity enhancing component was used as a liquid epoxy resin composition Evenly dispersed in the product. Then, the defoaming process was carried out under reduced pressure, and the target liquid epoxy resin composition for sealing fillers was prepared. This liquid epoxy resin composition is cured as desired in 2 to 5 minutes at a curing temperature of 250 ° C. as thermosetting conditions.
[0108]
(Reference Example 1)
Compared to Comparative Example 1, a liquid epoxy resin composition was prepared in which the content ratio of the acid anhydride was increased and the flux activity was enhanced. Specifically, tetrahydrophthalic anhydride derivative YH-307 (supra) 130 as a liquid epoxy resin per 100 parts by mass of bisphenol A type epoxy resin Epicoat 828 (supra). A liquid epoxy resin composition was prepared by adding 0.8 part by mass of BMI12 (supra) of 1 part of imidazole, 1-benzyl-2-methylimidazole as a part of mass part and a curing accelerator. This liquid epoxy resin composition is cured as desired in 2 to 5 minutes at a curing temperature of 250 ° C. as thermosetting conditions.
[0109]
Next, the liquid epoxy resin compositions of Examples 1 to 3 and the liquid epoxy resin compositions of Comparative Example 1 and Reference Example 1 were each flip-chip mounted under the same conditions. The presence or absence of poor conduction between the components and the electrodes of the printed circuit board was evaluated. In addition, the mounted printed circuit board was observed through and examined for the presence of voids.
[0110]
The curing conditions used were a rapid temperature increase from 20 ° C. to 250 ° C. (1.5 ° C./s), and the temperature was maintained at 250 ° C. for 20 seconds. After this holding, forced cooling was performed.
[0111]
Table 1 also shows the results of the continuity test. The continuity test result is used as an index with the ratio of the number of accepted products without continuity failure to the total number of samples 50.
[0112]
[Table 1]

[0113]
As shown in Table 1, in the liquid epoxy resin composition of Example 2 to which dodecanedioic acid was added, the total number passed, and also in the liquid epoxy resin composition of Example 1, the conduction failure was about 20%. . Also, in the liquid epoxy resin composition of Example 3 using sebacic acid, the conduction failure was suppressed to about 35%. On the other hand, in the liquid epoxy resin composition of Comparative Example 1, conduction failure occurs in about 95%. In the liquid epoxy resin composition of Reference Example 1, although the flux activity is increased by increasing the content of the acid anhydride, the conduction failure reaches 90% or more. Accordingly, in the liquid epoxy resin composition of the present invention, the flux activity indicated by the acid anhydride is imparted / enhanced by the addition of the flux activity enhancing component dodecanedioic acid or sebacic acid. Thus, it is judged that the bonding by the good bump electrode is made.
[0114]
On the other hand, no void generation was found in the liquid epoxy resin compositions of Examples 1 and 2, and no liquid generation was found in this temperature range in the liquid epoxy resin composition of Example 3. Of course, no voids were found in the liquid epoxy resin compositions of Reference Example 1 and Comparative Example 1.
[0115]
Example 4
Based on the above results, underfill filling was performed by the following procedure using the liquid epoxy resin composition for sealing filler having the composition described in Example 1. As a result, when the Sn-Ag solder / bump was melted (at 217 ° C.), there was no soldering failure derived from the surface oxide film, and there was no filling failure or void generation.
[0116]
The present invention was applied to flip chip mounting in which bump electrodes are provided on a printed wiring board. First, the underfill epoxy resin composition is applied to a predetermined pattern by screen printing on a printed wiring board on which the bump electrodes are formed in advance. In this case, the chip component having the bump electrode formed on the back surface is aligned with the bump electrode on the wiring board on which the underfill agent pattern is printed so that the positions of both electrodes are aligned. At this position, the chip component is pressed so that the electrodes come into contact with each other. In the process, the applied underfill agent layer is spread and closely contacts the back surface of the chip component. Further, the bump electrode that is in contact, the wiring surface on the corresponding substrate, and the back electrode surface of the chip component are also firmly covered with the underfill agent that has been spread out.
[0117]
In a state of being pressed from the upper surface of the chip component, it is placed in a reflow furnace, and for example, the temperature is raised to 250 ° C. to perform bump melting. Bump soldering is completed, and the thermosetting of the epoxy resin as the underfill agent proceeds.
[0118]
As described above, if this procedure is followed, the chip component is pressed, so that no bubbles remain between the chip component and the back surface of the chip component. Further, as already described, since the oxide film is also removed in situ, there is no poor soldering. In this way, there is no defective bonding of the electrodes, and underfill filling / curing can be achieved without excess or deficiency.
[0119]
Since the solder material used is the above-mentioned Sn—Ag solder having a melting point of 217 ° C., the temperature raising process in this reflow process is performed at a constant rate up to 250 ° C., which is significantly higher than 217 ° C. In this case, when the temperature exceeds 130 ° C., the thermosetting reaction gradually begins to proceed. However, due to the action of the added dodecanedioic acid, the flux treatment is sufficiently performed until the temperature approaches 217 ° C. In addition, even when the concentration of the acid anhydride remaining in the system becomes considerably low, it is possible to ensure the required flux activity.
[0120]
(Example 5)
It is an example of the liquid epoxy resin composition for sealing filler of this invention, ie, a composition suitable when said Sn-Ag solder (melting | fusing point: 217 degreeC) is utilized as a solder material which forms bump. A liquid epoxy resin composition containing a dicarboxylic acid as a flux activity enhancing component as an additional component in a liquid epoxy resin and acid anhydride having a ratio. As this dicarboxylic acid, also in Example 5, dodecanedioic acid (above), which is one of linear alkanedioic acids, was used.
[0121]
As a liquid epoxy resin, per 100 parts by mass of bisphenol A type epoxy resin Epicoat 828 (supra), as a curing agent acid anhydride, 120 parts by mass of tetrahydrophthalic anhydride derivative YH-307 (supra) As a promoter, a small amount of one of imidazoles, 1E (2-cyanoethyl) -2-ethyl-4-methylimidazole 2E4MZ-CN (trade name, manufactured by Shikoku Kasei Co., Ltd., molecular weight 163) 0.3 parts by mass A liquid epoxy resin composition to which was added was prepared. In addition, 20 parts by mass of dodecanedioic acid was uniformly dispersed in the liquid epoxy resin composition as a flux activity enhancing component. Then, the defoaming process was carried out under reduced pressure, and the target liquid epoxy resin composition for sealing fillers was prepared. This liquid epoxy resin composition is cured as desired in 2 to 5 minutes at a curing temperature of 250 ° C. as thermosetting conditions.
[0122]
(Example 6)
Compared to Example 5, in addition to the addition of dodecanedioic acid as a flux activity enhancing component, a change was also made in which a small amount of hydrogenated rosin: Foral AX (trade name, manufactured by Nissho Iwai Chemical Co., Ltd., average molecular weight 310) was also added. And a liquid epoxy resin composition was prepared. Specifically, tetrahydrophthalic anhydride derivative YH-307 (supra) 120 per 100 parts by mass of bisphenol A type epoxy resin Epicoat 828 (supra) as a liquid epoxy resin. The liquid epoxy resin composition which added a mass part and 0.3 mass part of 2E4MZ-CN (above) small amount as a hardening accelerator was prepared. In addition, 20 parts by mass of dodecanedioic acid and 10 parts by mass of hydrogenated rosin (supra) were uniformly dispersed in the liquid epoxy resin composition as a flux activity enhancing component. Then, the defoaming process was carried out under reduced pressure, and the target liquid epoxy resin composition for sealing fillers was prepared. This liquid epoxy resin composition is cured as desired in 2 to 5 minutes at a curing temperature of 250 ° C. as thermosetting conditions.
[0123]
(Example 7)
It is an example of the liquid epoxy resin composition for sealing filler of this invention, ie, a composition suitable when said Sn-Ag solder (melting | fusing point: 217 degreeC) is utilized as a solder material which forms bump. In the same manner as in Example 6, dodecanedioic acid (supra), which is one of linear alkanedioic acids, as a flux activity enhancing component as an additional component to the liquid epoxy resin and acid anhydride having a ratio, A liquid epoxy resin composition containing a small amount of hydrogenated rosin (supra) was used. In addition, instead of tetrahydrophthalic anhydride derivative YH-307 (supra), acid anhydride of hydrogenated nadic acid: HNA (trade name, manufactured by Shin Nippon Rika Co., Ltd. Anhydride equivalent 95) was utilized.
[0124]
As a liquid epoxy resin, per 100 parts by mass of bisphenol A type epoxy resin Epicoat 828 (supra), as an acid anhydride of a curing agent, 87 parts by mass of HNA (supra), and as a curing accelerator, a small amount of 2E4MZ-CN (Id.) A liquid epoxy resin composition to which 0.3 part by mass was added was prepared. In addition, 20 parts by mass of dodecanedioic acid and 10 parts by mass of hydrogenated rosin (supra) were uniformly dispersed in the liquid epoxy resin composition as a flux activity enhancing component. Then, the defoaming process was carried out under reduced pressure, and the target liquid epoxy resin composition for sealing fillers was prepared. This liquid epoxy resin composition is cured as desired in 2 to 5 minutes at a curing temperature of 250 ° C. as thermosetting conditions.
[0125]
Next, for the liquid epoxy resin compositions of Examples 5 to 7, flip chip mounting was performed under the same conditions as the liquid epoxy resin composition of Example 2 above, and the obtained mounted semiconductor device The presence or absence of poor conduction between the electrodes of the printed circuit board was evaluated. In addition, the mounted printed circuit board was observed through and examined for the presence of voids.
[0126]
The curing conditions used were a rapid temperature increase from 20 ° C. to 250 ° C. (1.5 ° C./s), and the temperature was maintained at 250 ° C. for 20 seconds. After this holding, forced cooling was performed.
[0127]
Table 2 also shows the results of the continuity test. The continuity test result is used as an index with the ratio of the number of accepted products without continuity failure to the total number of samples 50.
[0128]
[Table 2]

[0129]
As shown in Table 2, as a result of using 2E4MZ-CN as a curing accelerator in place of BMI12, the conductivity is slightly poor compared to the liquid epoxy resin composition of Example 2 in which the same amount of dodecanedioic acid is added. In the liquid epoxy resin composition of Example 5, however, the conduction failure is suppressed to about 20%. As a supplementary flux activity enhancing component, a small amount of hydrogenated rosin (supra) is added, and in the liquid epoxy resin composition of Example 6, poor conduction is no longer found. In addition, when the acid anhydride HNA (supra) of hydrogenated nadic acid is used in place of the tetrahydrophthalic anhydride derivative YH-307 as the acid anhydride of the curing agent, supplementary flux activity enhancement Further, by adding a small amount of hydrogenated rosin (supra) as a component, in the liquid epoxy resin composition of Example 7, poor conduction is no longer found.
[0130]
Therefore, even when there is a difference in the curing acceleration effect of imidazoles used as a curing accelerator, in the liquid epoxy resin composition of the present invention, the addition of dodecanedioic acid, a flux activity enhancing component, causes acid anhydrides to be added. As shown in the figure, as a result of imparting and promoting the flux activity, it is determined that the bonding by the good bump electrode is performed as described above by the reflow process.
[0131]
On the other hand, generation of voids has not been found at all in the liquid epoxy resin compositions of Examples 5 to 7, which are more cured than the liquid epoxy resin composition of Example 2.
[0132]
In addition, the resulting cured epoxy resin has a difference in flexibility and adhesiveness depending on the skeleton structure of the epoxy resin component and the acid anhydride of the curing agent, particularly at temperatures below freezing point. If the shear strength and peel strength decrease during cooling, the resin cured material that has been sealed and filled may be partially peeled off or the surface of the resin cured product may be minutely repetitively heated and cooled repeatedly. There is a difference in the presence or absence of cracks. In order to compare the difference in flexibility and adhesiveness of the cured resin in this cooling, using the liquid epoxy resin composition of Examples 5-7, the same procedure as in the mounting described in Example 4 was used. A thermal cycle test was performed on the semiconductor elements mounted on the printed circuit board that had been filled and cured with fill and the solder material reflow process.
[0133]
The thermal cycle test is performed under the conditions of the cooling state of −45 ° C. and the heating state of 125 ° C., and particularly the cooling state of −65 ° C. and the heating state of 125 ° C., where the cooling conditions are more severe. It was. Table 3 shows results in a thermal cycle test of a mounted semiconductor element subjected to underfill filling / curing and a solder material reflow process using the liquid epoxy resin compositions of Examples 5 to 7, particularly sealing filling. The evaluation results regarding the occurrence ratio of defects due to deterioration of the agent part and the presence or absence of fine cracks in the cured resin of the sealing filler part at the end of the cycle test are shown. The result of the thermal cycle test is used as an index of the ratio of the number of products with no defect to the total number of samples 50.
[0134]
[Table 3]

[0135]
Between the liquid epoxy resin compositions of Examples 5 and 6 in which the epoxy resin component constituting the cured resin and the acid anhydride of the curing agent have the same composition, the flexibility and adhesiveness of the resulting cured resin In particular, when cooled, the degree of decrease in shear strength and peel strength is comparable, and thus no substantial difference has been found in the above-described thermal cycle test results. Under the condition where the cooling state is −45 ° C., the cured resin itself does not show extreme brittleness, and the occurrence of cracks due to strain stress resulting from the difference in thermal expansion coefficient between the cured resin and the printed board is also a problem frequency. is not. On the other hand, under the condition where the cooling state is −65 ° C., the cured epoxy resin itself has poor flexibility and exhibits brittleness, and the occurrence of cracks due to strain stress during the cooling and heating cycle is more remarkable.
[0136]
On the other hand, in the liquid epoxy resin composition of Example 7 which employs HNA as the acid anhydride of the curing agent, the epoxy resin cured product itself has an unsaturated carbon in the structure derived from this acid anhydride. Compared with the epoxy resin hardened | cured material by the liquid epoxy resin composition of Example 5 and 6 which does not have a coupling | bonding and utilizes YH-307 of a tetrahydrophthalic anhydride derivative, it becomes richer in flexibility. Due to the difference, under the condition where the cooling state is −45 ° C., the brittleness is not yet exhibited, no defect is generated, and crack generation due to strain stress is avoided. Furthermore, even when the cooling state is −65 ° C., the cured resin itself does not exhibit extreme brittleness, and although it is slightly defective and cracks are generated due to strain stress, it is not a problem frequency.
[0137]
The resin cured product itself has flexibility and adhesiveness, especially when it is cooled, so that the decrease in shear strength and peel strength is reduced, so it does not have unsaturated carbon bonds as the acid anhydride of the curing agent used. In addition to using hydrogenated nadic acid anhydride HNA, the epoxy resin component itself is also made of a nitrile-modified epoxy resin that improves flexibility and adhesion, or a small amount of thermoplastic resin such as acrylic rubber. A liquid epoxy resin composition that uses an effect to improve brittleness and to exhibit higher toughness by adding flexibility such as addition of components and dispersion of particulate thermoplastic resin. Was prepared.
[0138]
(Example 8)
It is an example of the liquid epoxy resin composition for sealing filler of this invention, ie, a composition suitable when said Sn-Ag solder (melting | fusing point: 217 degreeC) is utilized as a solder material which forms bump. In the same manner as in Example 7, dodecanedioic acid (supra), which is one of linear alkanedioic acids, as a component for increasing flux activity as an additional component to liquid epoxy resin and acid anhydride having a ratio, A liquid epoxy resin composition containing a small amount of hydrogenated rosin (supra) was used. EXA-835LV, which is a low-viscosity epoxy resin containing bisphenol F type epoxy resin as a main component, instead of Epicoat 828 (above) as an epoxy resin component, using HNA (above) as the acid anhydride of the curing agent. (Trade name; manufactured by Dainippon Ink & Chemicals, Inc., epoxy equivalent: 165) and EPR-4023 (trade name; manufactured by Asahi Denki Kagaku Kogyo Co., Ltd.)
Epoxy equivalent: 230) was used as a mixture.
[0139]
As a liquid epoxy resin, EXA-835LV (supra) 50 parts by mass: EPR-4023 (supra) 50 parts by mass of epoxy resin mixed per 100 parts by mass of epoxy resin as an acid anhydride of a curing agent, HNA ( A liquid epoxy resin composition was prepared by adding 80 parts by mass and a small amount of 2E4MZ-CN (above) 0.3 part by mass as a curing accelerator. In addition, 20 parts by mass of dodecanedioic acid and 10 parts by mass of hydrogenated rosin (supra) were uniformly dispersed in the liquid epoxy resin composition as a flux activity enhancing component. Then, the depressurization process was carried out under reduced pressure, and the target liquid epoxy resin composition for sealing fillers was prepared. This liquid epoxy resin composition is cured as desired in 2 to 5 minutes at a curing temperature of 250 ° C. as thermosetting conditions.
[0140]
Example 9
It is an example of the liquid epoxy resin composition for sealing filler of this invention, ie, a composition suitable when said Sn-Ag solder (melting | fusing point: 217 degreeC) is utilized as a solder material which forms bump. In the same manner as in Example 7, dodecanedioic acid (supra), which is one of linear alkanedioic acids, as a component for increasing flux activity as an additional component to liquid epoxy resin and acid anhydride having a ratio, A liquid epoxy resin composition containing a small amount of hydrogenated rosin (supra) was used. EXA-835LV, which is a low-viscosity epoxy resin containing bisphenol F type epoxy resin as a main component, instead of Epicoat 828 (above) as an epoxy resin component, using HNA (above) as the acid anhydride of the curing agent. (Above) and YR-628 (trade name; manufactured by Tohto Kasei Co., Ltd., epoxy equivalent: 225), which is an epoxy resin in which core-shell type rubber particle fine particles having an average particle size of 0.5 μm are dispersed, were used.
[0141]
As a liquid epoxy resin, EXA-835LV (supra) 30 parts by mass: YR-628 (supra) mixed at a ratio of 70 parts by mass, and per 100 parts by mass of epoxy resin, HNA ( The liquid epoxy resin composition which added 86 mass parts and a small amount of 2E4MZ-CN (above) 0.3 mass part as a hardening accelerator was prepared. In addition, 20 parts by mass of dodecanedioic acid and 10 parts by mass of hydrogenated rosin (supra) were uniformly dispersed in the liquid epoxy resin composition as a flux activity enhancing component. Then, the depressurization process was carried out under reduced pressure, and the target liquid epoxy resin composition for sealing fillers was prepared. This liquid epoxy resin composition is cured as desired in 2 to 5 minutes at a curing temperature of 250 ° C. as thermosetting conditions.
[0142]
(Example 10)
It is an example of the liquid epoxy resin composition for sealing filler of this invention, ie, a composition suitable when said Sn-Ag solder (melting | fusing point: 217 degreeC) is utilized as a solder material which forms bump. In the same manner as in Example 9, dodecanedioic acid (supra), which is one of linear alkanedioic acids, as a flux activity enhancing component as an additional component to the liquid epoxy resin and acid anhydride having a ratio, A liquid epoxy resin composition containing a small amount of hydrogenated rosin (supra) was used. Tetrahydrophthalic anhydride derivative YH-307 (supra) is used as the acid anhydride of the curing agent, and the epoxy resin component is based on bisphenol F type epoxy resin instead of Epicoat 828 (supra). A low-viscosity epoxy resin EXA-835LV (supra) and a core-shell type epoxy resin YR-628 (supra) in which rubber component fine particles having an average particle size of 0.5 μm were dispersed were used.
[0143]
As a liquid epoxy resin, EXA-835LV (supra) 30 parts by mass: YR-628 (supra) mixed at a ratio of 70 parts by mass, and 100 parts by mass of epoxy resin, YH- A liquid epoxy resin composition was prepared by adding 110 parts by mass of 307 (above) and 0.3 part by mass of 2E4MZ-CN (above) as a curing accelerator. In addition, 20 parts by mass of dodecanedioic acid and 10 parts by mass of hydrogenated rosin (supra) were uniformly dispersed in the liquid epoxy resin composition as a flux activity enhancing component. Then, the depressurization process was carried out under reduced pressure, and the target liquid epoxy resin composition for sealing fillers was prepared. This liquid epoxy resin composition is cured as desired in 2 to 5 minutes at a curing temperature of 250 ° C. as thermosetting conditions.
[0144]
Next, the liquid epoxy resin compositions of the liquid epoxy resin compositions of Examples 8 to 10 were each flip-chip mounted under the same conditions as the liquid epoxy resin composition of Example 7 above, and the obtained mounted semiconductors About the apparatus, the presence or absence of the conduction | electrical_connection defect between a chip component and the electrode of a printed circuit board was evaluated. In addition, the mounted printed circuit board was observed through and examined for the presence of voids.
[0145]
The curing conditions used were a rapid temperature increase from 20 ° C. to 250 ° C. (1.5 ° C./s), and the temperature was maintained at 250 ° C. for 20 seconds. After this holding, forced cooling was performed.
[0146]
Table 4 also shows the results of the continuity test. The continuity test result is used as an index with the ratio of the number of accepted products without continuity failure to the total number of samples 50.
[0147]
[Table 4]

[0148]
As shown in Table 4, HNA (supra) is used as an acid anhydride, which functions as a main component of the curing agent and flux activity, and dodecanedioic acid is supplemented as a main flux activity enhancement component. As a component, by adding a small amount of hydrogenated rosin (supra), the content ratio of acid anhydride HNA is slightly less than that of the liquid epoxy resin composition of Example 7, Even in the liquid epoxy resin composition, no conduction failure has been found. Also, in the liquid epoxy resin composition of Example 10 using the tetrahydrophthalic anhydride derivative YH-307 (supra) as the acid anhydride of the curing agent, the liquid epoxy resin composition of Example 9 and Similarly, no conduction failure has been found.
[0149]
Accordingly, although the types of epoxy resins used are different, the liquid epoxy resin compositions of Examples 8 and 9 or the liquid epoxy resin composition of Example 10 are the same as those of Example 7 or Example 6 described above. As with the liquid epoxy resin composition, the addition of flux activity enhancing components dodecanedioic acid and hydrogenated rosin imparts and enhances the flux activity exhibited by the acid anhydride. It is determined that the bonding by the bump electrode is performed. In addition, no void generation has been found in the liquid epoxy resin compositions of Examples 8 to 10.
[0150]
In addition, in the liquid epoxy resin compositions of Examples 8 and 9, the obtained epoxy resin cured product does not contain an unsaturated carbon bond in the skeleton structure of the acid anhydride of the curing agent constituting the epoxy resin composition, and at the same time, The resin component is also modified by adding a nitrile rubber component, or a component that improves flexibility and adhesion by dispersing fine particles of rubber. Especially when cooled, the shear strength and peel strength are improved. The main purpose is to further ease the decline. In order to verify the improvement in flexibility and adhesiveness of the cured resin in this cooling, using the liquid epoxy resin composition of Examples 8 to 10, the underfill is performed in the same manner as the mounting described in Example 4 above. A thermal cycle test was performed on the semiconductor element mounted on the printed circuit board that had been filled and cured with solder and the solder material was reflowed.
[0151]
The thermal cycle test is performed under the conditions of the cooling state of −45 ° C. and the heating state of 125 ° C., and particularly the cooling state of −65 ° C. and the heating state of 125 ° C., where the cooling conditions are more severe. It was. Table 5 shows the results of a thermal cycle test of a mounted semiconductor element subjected to underfill filling / curing and a solder material reflow process using the liquid epoxy resin compositions of Examples 8 to 10. The result of the thermal cycle test is used as an index of the ratio of the number of products with no defect to the total number of samples 50.
[0152]
[Table 5]

[0153]
Even when the liquid epoxy resin compositions of Examples 8 and 9 were used, similarly to the case of using the liquid epoxy resin composition of Example 7 above, the cured resin product itself under the condition where the cooling state was −45 ° C. No brittleness was observed, no cracks were generated due to strain stress resulting from the difference in thermal expansion coefficient between the cured resin and the printed circuit board, and no defect was found. In addition, when the liquid epoxy resin compositions of Examples 8 and 9 are used, the skeleton structure of the acid anhydride of the curing agent does not contain an unsaturated carbon bond, and at the same time, the epoxy resin component is also added by adding a nitrile rubber component. As a result of using a component that improves the flexibility and adhesiveness by modification or rubber fine particle dispersion, the cured epoxy resin itself does not show brittleness even in a cooling state of −65 ° C. In addition, it maintains high toughness, can avoid the occurrence of cracks due to strain stress during the thermal cycle, and no defect has been found.
[0154]
Moreover, also when the liquid epoxy resin composition of Example 10 was used, as a result of using a component for improving flexibility and adhesiveness by dispersing rubber-like fine particles in the epoxy resin component, the cooling state was −45. Under the condition of ° C., the cured resin itself does not show brittleness, no cracks are generated due to strain stress resulting from the difference in thermal expansion coefficient between the cured resin and the printed circuit board, and no defect is found. The acid anhydride of the curing agent used leaves an unsaturated carbon bond in its skeleton structure. As a result, when the cooling state is −65 ° C., the brittleness improvement at a low temperature is slightly insufficient and the cooling cycle is repeated. At the same time, some cracks occur, and at the same time, some defects have been found.
[0155]
【The invention's effect】
The liquid epoxy resin composition for a sealing filler of the present invention includes, as essential components, (A) a liquid thermosetting epoxy resin and (B) an acid anhydride as a curing agent for the thermosetting epoxy resin, and further addition As an additional component, as an additional component, (C) a small amount of a dicarboxylic acid, for example, a chain dicarboxylic acid having 9 to 15 carbon atoms in the base chain, which becomes a flux activity enhancing component having proton donating ability, specifically, (B) The content of the dicarboxylic acid of the flux activity enhancing component (C) is 5 × 10 5 per mole of the anhydride of the curing agent. ^-2 ~ 5x10 ^-1 It is the liquid epoxy resin composition added so that it might become the range of a mole. Lead-free tin with a melting point of 200 ° C. or higher and 230 ° C. or higher which is disposed to form physical contact between the chip component and the electrodes of the printed wiring board in a state filled with the liquid epoxy resin composition When a bump electrode made of an alloy solder, in particular, a Sn-Ag solder is heated and melted, the flux activity of the acid anhydride of the curing agent (B) is enhanced by protons donated from the carboxy group of the dicarboxylic acid. Thus, the oxide film on the surface of the bump electrode or the like, for example, tin oxide can be removed. On the other hand, although the acid anhydride of the (B) curing agent is consumed in a slight amount due to the reaction with the tin oxide, it is not an excessive decrease in the content, for example, as a secondary component. Even when heat treatment is performed at a relatively high heat curing temperature that is compatible with the lead-free tin alloy solder used, such as by adding a small amount of hardening accelerator, the oxide film is removed. Then, thermosetting proceeds at an appropriate speed to obtain a desired thermoset. In addition, since the boiling point of the added dicarboxylic acid is sufficiently higher than the thermosetting temperature, there is no formation of bubbles due to its vaporization, and no generation of voids. In addition, the dicarboxylic acid having a relatively long base chain carbon number has excellent compatibility with the epoxy resin, and is uniformly dispersed in the resin composition while the thermal curing gradually proceeds. (B) Solder used for the bump electrode without the treatment with the flux in order to maintain the enhancing action of the flux activity of the acid anhydride of the curing agent and thus remove the oxide film on the surface of the bump electrode or the like in advance. It is possible to bond the electrodes by good melting and soldering, and at the same time, obtain the advantage that the sealing filler can be thermally cured. In addition, this method of sealing and filling has high work efficiency, and in particular, since a desired liquid epoxy resin composition layer is applied and formed on the printed wiring board by means such as screen printing, the shape of the printed wiring board -Regardless of the material, it is possible to shorten the overall process and eradicate defective factors such as voids. In addition, (B) as the acid anhydride of the curing agent, one that does not contain an unsaturated carbon bond in its molecular skeleton, and (A) a thermoplastic resin as a liquid thermosetting epoxy resin component Addition of a small amount of ingredients, dispersion of particulate thermoplastic resin, modification by modification of thermoplastic resin molecules, etc., increased toughness, especially improved low-temperature brittleness, adhesiveness, good It is rich in flexibility, and particularly when cooled, the decrease in shear strength and peel strength can be further alleviated.

Claims (14)

A liquid epoxy resin composition used for a sealing and filling process of flip chip mounting using a lead-free tin alloy solder material having a melting point of 200 ° C. or higher and not exceeding 230 ° C. as a bump electrode material. ,
The liquid epoxy resin composition includes, as essential components, (A) a liquid thermosetting epoxy resin, (B) an acid anhydride as a curing agent for the thermosetting epoxy resin, and (C) as an additional component. ) Comprising a flux activity enhancing component having proton donating ability,
The (C) flux activity enhancing component is a dicarboxylic acid having 9 to 15 carbon atoms,
The content of the dicarboxylic acid of the (C) flux activity enhancing component is selected in the range of 5 × 10 ^{−2 to} 5 × 10 ⁻¹ mol per 1 mol of the acid anhydride of the (B) curing agent. A liquid epoxy resin composition for sealing filler, characterized by (B) In addition to the acid anhydride of the curing agent,
The liquid epoxy resin composition for sealing filler according to claim 1, further comprising a curing accelerator that accelerates a ring-opening reaction of the epoxy ring by the acid anhydride as a secondary additive component. The other secondary additive component includes at least one additive component selected from a stress relaxation agent, a leveling agent, a coupling agent, an antioxidant, and a thixotropic agent. Liquid epoxy resin composition for sealing filler. The thermosetting epoxy resin (A) is an epoxy resin comprising a diglycidyl ether having a bisphenol type skeleton, a polyglycidyl ether of a phenol resin, an aliphatic carboxylic acid or an aromatic carboxylic acid diglycidyl ester, and an alicyclic epoxy resin. The liquid epoxy resin composition for a sealing filler according to claim 1, wherein the liquid epoxy resin composition is one or more thermosetting epoxy resins selected from the group consisting of: 2. The sealing filler according to claim 1, comprising 0.9 to 1.1 equivalents of acid anhydride of (B) curing agent with respect to 1 equivalent of thermosetting epoxy resin of (A). Liquid epoxy resin composition. Furthermore, content of the said hardening accelerator is selected in the range of 0.1-1.2 mass parts per 100 mass parts of thermosetting epoxy resin of (A), The feature of Claim 2 characterized by the above-mentioned. Liquid epoxy resin composition for sealing filler. 2. The sealing filler according to claim 1, wherein the dicarboxylic acid is an ω, ω′-linear hydrocarbon dicarboxylic acid, and the carbon number thereof is selected in the range of C10 to C13. Liquid epoxy resin composition. (B) The liquid epoxy resin composition for sealing fillers according to claim 1, wherein an intramolecular acid anhydride derived from a saturated cyclic hydrocarbon dicarboxylic acid is used as the acid anhydride of the curing agent. As the thermosetting epoxy resin (A),
Thermosetting epoxy that has been provided with toughness derived from such thermoplastic resin by either adding a small amount of thermoplastic resin component, dispersing fine-part thermoplastic resin, or modifying by addition modification of thermoplastic resin molecules The liquid epoxy resin composition for sealing fillers according to claim 1, wherein the resin component is at least partially contained. The liquid epoxy resin composition for sealing filler according to claim 2, wherein the curing accelerator contains imidazoles as a secondary additive component. A method of sealing filling in flip chip mounting,
(1) Bump electrodes made of a lead-free tin alloy solder material having a melting point of 200 ° C. or higher and at most 230 ° C. are not used for a printed wiring board having a substrate electrode and a chip component having a chip component electrode A step of making contact between the bump electrode and the electrode after disposing the chip component in a predetermined region on the printed wiring board in order to establish mutual conduction between the electrodes.
(2) After the step of making contact between the bump electrode and the electrode, or in combination with the step, the contact is made in the gap between the printed wiring board and the chip component disposed on a predetermined region thereon. A filling step for filling the liquid epoxy resin composition for sealing filler according to any one of claims 1 to 10, so as to cover the bump electrode and the electrode,
(3) Next, heat the epoxy resin in the liquid epoxy resin composition filled in the gaps of the predetermined region by heating, and the solder bumps covered by the liquid epoxy resin composition are advanced. Melting process,
The process of heating for a predetermined time, cooling, re-solidifying the solder once melted, soldering and bonding the bump electrode and the electrode, and simultaneously completing sealing filling with a thermoset epoxy resin,
Having a series of steps (1) to (3) above,
A method for sealing and filling, comprising using the liquid epoxy resin composition for a sealing filler according to any one of claims 1 to 10 as the sealing filler. The method of sealing filling according to claim 11, wherein the solder material is a Sn—Ag alloy. A chip component is flip-chip mounted on a printed wiring board using a lead-free tin alloy solder material having a melting point of 200 ° C. or higher and at most 230 ° C., and sealed and filled in between. Mounted and assembled electronic components,
The printed wiring board is a printed wiring board having a substrate electrode, and the chip component is a chip component having a chip component electrode. In flip chip mounting, mutual conduction between both electrodes is the lead-free. It is made using a bump electrode made of a tin alloy solder material,
An electronic component, wherein flip chip mounting and sealing filling using the lead-free tin alloy solder material are performed by the sealing filling method according to claim 11 or 12. The electronic component according to claim 13, wherein at least one of the chip components to be flip-chip mounted and sealed and filled on a printed wiring board is a semiconductor element chip.