JP3837858B2 - Conductive adhesive and method of using the same - Google Patents
Conductive adhesive and method of using the same Download PDFInfo
- Publication number
- JP3837858B2 JP3837858B2 JP22683197A JP22683197A JP3837858B2 JP 3837858 B2 JP3837858 B2 JP 3837858B2 JP 22683197 A JP22683197 A JP 22683197A JP 22683197 A JP22683197 A JP 22683197A JP 3837858 B2 JP3837858 B2 JP 3837858B2
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- silver powder
- conductive adhesive
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- H05K3/30—Assembling printed circuits with electric components, e.g. with resistor
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- Engineering & Computer Science (AREA)
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- Conductive Materials (AREA)
Description
【０００１】
【発明の属する技術分野】
本発明はＩＣ等の半導体素子およびチップ抵抗、チップＬＥＤ等のチップ部品をリ−ドフレ−ムや放熱板等に接着する際に使用されるもので、作業性、接着性、導電性、耐熱性、熱伝導性に優れた導電性接着剤に関するものである。
【０００２】
【従来の技術】
近年ＩＣ、ＬＳＩ、ＬＥＤ等をはじめとする半導体素子は著しい発展をしており、大量生産が行われている。それに伴い、その量産における作業性の向上、および製造費の削減が重要な問題となっている。
【０００３】
従来、これらの半導体素子をリ−ドフレ−ムや基板等に接着する方法としては金−シリコン共晶ハンダや錫−鉛ハンダ等のハンダを用いることが主流であった。しかし、今までの方法は、金が高価であること、半導体素子とリ−ドフレ−ムや基板の熱膨張の差を吸収しきれず、半導体素子やハンダ類にクラックが発生すること、耐熱性に欠けること、作業温度が比較的高温であること、半導体素子の電極を汚染しやすいことなどから、導電性接着剤を使用する方法が主流となってきている。
【０００４】
一般に使用されている導電性接着剤は、導電性粉体、有機樹脂、溶剤、触媒等から構成され、導電性粉体には、金、銀、銅、カ−ボン等が用いられ、特にフレ−ク状の銀粉が導電性に優れているため多く使用されている。また、有機樹脂にはエポキシ樹脂、フェノ−ル樹脂等の熱硬化性樹脂が多く使用されている。これらの導電性接着剤は前述のハンダの欠点を克服する一方、熱伝導を比べた場合、金属の固体であるハンダ類には劣ることがわかっている。
【０００５】
【発明が解決しようとする課題】
半導体素子やチップ部品は、近年、小型化、高精度化、高性能化が求められている。中でも半導体素子であるＩＣやＬＳＩは多ピン化、小型化、高周波数化の要求が高まり、それに伴い発生する熱は数年前に比べ数倍の熱量となっている。また同様に、ＬＥＤにおいても高輝度化が求められ、熱の発生量はますます増大してきている。
【０００６】
すなわち、高い発熱を生じる半導体素子の接続には、高熱伝導性を有する材料が要求されるために、導電性接着剤は使用せず、熱伝導に優れているハンダ類が使用されているのが一般的である。しかし、ハンダ類の使用には、前述の欠点が存在しており、高熱伝導性を有する導電性接着剤が強く望まれている。
【０００７】
本発明の目的は、ハンダ類と同等の熱伝導を有し、なおかつ今までの導電性接着剤の利点を併せ持つ導電性接着剤を提供することにある。
【０００８】
【課題を解決するための手段】
上記の目的を達成するために鋭意努力した結果、導電性粉体と有機樹脂とを含有する導電性接着剤において、該導電性粉体として最大粒径が１μｍ以下でかつ平均粒径が０．２μｍ以下の球状銀粉のみを含有し、該有機樹脂としてエポキシ樹脂あるいはポリイミド樹脂を含有し、かつ、導電性粉体を５０〜９０質量％、有機樹脂を４〜３６質量％を含有させることにより、高い熱伝導性が得られることを見出したのである。
【０００９】
あるいは、少なくとも導電性粉体と有機樹脂とを含有する導電性接着剤において、該導電性粉体として最大粒径が１μｍ以下でかつ平均粒径が０．２μｍ以下の球状銀粉と、最大粒径が５０μｍ以下のフレ−ク状銀粉との混合物を含有し、該有機樹脂としてエポキシ樹脂あるいはポリイミド樹脂を含有し、球状銀粉に対するフレ−ク状銀粉の質量混合比（＝フレ−ク状銀粉の質量／球状銀粉の質量）が０．１以上１．３３未満の範囲であり、かつ、該導電性粉体が５０〜９０質量％、該有機樹脂が４〜３６質量％含有されることにより、接触により高導電性が得られるフレーク状銀粉の利点も併せ持たせることができる。
【００１０】
また、本発明の導電性接着剤を使用する際、塗布された導電性接着剤を２００〜３５０℃に加熱することにより、球状銀粉の焼結が生じ、導電性と熱伝導性が向上することを見出した。
【００１１】
【発明の実施の形態】
本発明の導電性接着剤には、最大粒径が１μｍ以下でかつ平均粒径が０．２μｍ以下の球状銀粉を導電性粉体として用いている。一般に導電性接着剤の導電性粉体の多くには銀粉が用いられ、なおかつフレ−ク状銀粉かフレーク状銀粉と球状銀粉の混合物がよく用いられていた。これは今までの導電性接着剤がフレーク状銀粉の接触によって高導電性を得ており、球状銀粉だけでは高い導電性が得られなかったことによる。しかし、フレーク状銀粉を用いたのでは高熱伝導は得られなかった。
【００１２】
本発明で使用する最大粒径が１μｍ以下でかつ平均粒径が０．２μｍ以下の球状銀粉は、非常に細かい銀粉であるため焼結し易い。そのため本発明の導電性接着剤では、銀粉が焼結し、金属固体に近づくため、熱伝導性、導電性が向上するのである。
【００１３】
特に本発明の導電性接着剤は２００℃〜３５０℃に加熱することにより、高熱伝導性、高導電性が得られる。銀粉の焼結は１５０℃程度でも生じるが、１５０℃では焼結が不十分であり、得られる導電性および熱伝導性の向上も十分とは言えない。２００℃〜３５０℃に加熱することで銀粉の焼結が促進し、より高い導電性および熱伝導性が得られるのである。また、この温度範囲であれば導電性接着剤に用いる有機樹脂の変質も生じない。
【００１４】
本発明に用いる銀粉は様々な方法で製造できるが、上記の条件を満たせばどのような銀粉でもよい。一例としては、水酸化ナトリウムと硝酸銀を同当量づつ攪拌しながら反応させ、酸化銀を生成させ、得られた酸化銀を良く洗浄し、７５℃に保温しながらロジンとトリエタノ−ルアミンを加え酸化銀を完全に還元し、得られた銀粉を吸引ろ過しながら水で良く洗浄することにより得られる。また、銀粉は細かいほど焼結開始温度が低くなるのでより細かい粉の方が好ましく、望むべくは最大粒径０．２μｍ以下で、平均粒径０．１μｍ以下が望ましい。
【００１５】
本発明においては、上記球状銀粉とフレ−ク状銀粉を混合して用いてもよい。これにより焼結によって高導電性、高熱伝導性が得られる球状銀粉と、接触によって高導電性が得られるフレ−ク状銀粉の利点を得ることができる。その場合、フレ−ク状銀粉は最大粒径が５０μｍ以下であることが望ましい。
【００１６】
細かい球状銀粉を用いるとチクソ比が上昇し、印刷には適しているが、ディスペンスやスタンピングなどには不向きである。しかし、フレ−ク状銀粉を混合するとチクソ比は適度に下がり、ディスペンスやスタンピングに適した導電性接着剤になる。フレ−ク状銀粉を適量混合しても高導電性や高熱伝導性においては球状銀粉のみからなる導電性接着剤と同程度の性能が得られる。
【００１７】
また、球状銀粉に対するフレ−ク状銀粉の質量混合比（＝フレ−ク銀粉の質量／球状銀粉の質量）を０．１以上１．３３未満の範囲で配合しているが、これは０．１未満だとフレ−ク状銀粉の効果が全く得られず、１．３３以上では球状銀粉の効果が得られず、熱伝導性が低下するためである。
【００１８】
本発明に用いる有機樹脂としては、ポリイミド樹脂あるいはエポキシ樹脂が用いられる。また、ポリイミド樹脂とエポキシ樹脂の混合物を有機樹脂に用いても構わない。
【００１９】
本発明に用いるポリイミド樹脂としては、公知のポリイミド樹脂全てが使用でき、特に制限は無いが、使用方法を勘案すると液体か、溶剤に溶けうる固体が望ましい。公知のポリイミド樹脂として市販品の例を挙げると宇部興産株式会社製のＵＰＡシリ−ズやユピコ−トシリ−ズ、東レ株式会社製のセミコファインシリ−ズ、丸善石油化学株式会社製のビスアルケニル置換ナジイミド等が挙げられる。ポリイミド樹脂をエポキシ樹脂と混合して使用する場合は、エポキシ樹脂と相溶性があることが望ましい。
【００２０】
ポリイミド樹脂に対して溶剤を加える場合は、ポリイミド樹脂に希釈効果があるものを使用する。例えば、Ｎ−メチル−２−ピロリドン、Ｎ，Ｎ−ジメチルホルムアミド、Ｎ，Ｎ−ジメチルアセトアミド、トルエン、キシレン、石油エ−テル等が挙げられる。これらは単独でも複数種を混合して用いてもよい。また一部のポリイミド樹脂ではエチレングリコ−ルジグリシジルエ−テルや、フェニルグリシジルエ−テル、３−アミノプロピルトリエトキシシラン、３−グリシドキシプロピルトリメトキシシラン、３−グリシドキシプロピルメチルジメトキシシラン、２−（３，４−エポキシシクロヘキシル）エチルトリメトキシシランなど使用しても差し支えない。
【００２１】
本発明に用いられるエポキシ樹脂としては、公知のエポキシ樹脂全てが使用でき、特に制限はない。公知のエポキシ樹脂の例を挙げると、主に電子材料の注形や接着に使用されているビスフェノ−ルＡジグリシジルエ−テルをはじめに、ビスフェノ−ルＦジグリシジルエ−テル、ノボラックグリシジルエ−テル、エポキシ化大豆油、３，４エポキシ−６メチルシクロヘキシルメチルカルボキシレ−ト、３，４エポキシシクロヘキシルメチルカルボキシレ−ト、テトラグリシジルジアミノジフェニルメタン等が挙げられる。使用用途を考えると液状のものが望ましく、また、電子材料に使われることを考えると、塩素イオンをはじめとするイオン性不純物が８００ｐｐｍ以下であることが望ましい。また、これらのエポキシ樹脂は単独でも複数種を混合して用いても差し支えない。
【００２２】
エポキシ樹脂の硬化剤としては、加熱時（６０〜３００℃）にエポキシ樹脂と速やかに硬化反応を生じ、かつ室温で長期間の貯蔵安定性を満足できるものであれば特に制限はない。一般にはイミダゾ−ル類の２−エチル−４−メチルイミダゾ−ル、２−フェニル−４，５−ジヒドロキシメチルイミダゾ−ル、２−フェニル−４−メチル−５−ヒドロキシメチルイミダゾ−ル、２−ヘプタデシルイミダゾ−ルや、フェノ−ルノボラック化合物、ジシアンジアミド、酸無水物系のテトラヒドロメチル無水フタル酸、ヘキサヒドロ無水フタル酸、メチル無水ハイミック酸、ルイス酸錯体のＢＦ3塩などが考えられる。これらは単独でも複数種混合して用いても良い。これらの硬化剤は種類によって添加量が異なるので、特に量の規定はしないが、エポキシ樹脂と化学両論組成にあった量が望ましい。この他に、本発明では硬化促進作用が認められるもの、例えば、アミン塩、ブロックイソシアネ−ト等も使用できる。
【００２３】
また、本発明では特に規定しないが、エポキシ樹脂に溶剤を加える場合は、エポキシ樹脂と相溶性があり、硬化後には液体として存在しないものを使用することが望ましい。一般にはエポキシ樹脂、硬化剤と反応しない、２，２，４−トリメチル３−ヒドロキシジペンタンイソブチレ−ト、２，２，４−トリメチルペンタン１，３−イソブチレ−ト、イソブチルブチレ−ト、ジエチレングリコ−ルモノブチルエ−テル、エチレングリコ−ルモノブチルエ−テル等が挙げられる。また、加熱時にエポキシ樹脂および硬化剤と反応し得る、フェニルグリシジルエ−テル、エチレングリコ−ルジグリシジルエ−テルや、３−アミノプロピルトリエトキシシラン、３−グリシドキシプロピルトリメトキシシラン、３−グリシドキシプロピルメチルジメトキシシラン、２−（３，４−エポキシシクロヘキシル）エチルトリメトキシシランなどが挙げられる。
【００２４】
本発明において導電性接着剤中に導電性粉体を５０〜９０質量％としているのは、５０質量％以下だと満足のいく電気導電性、熱伝導性が得られず、９０質量％以上だと接着力弱く、接着剤としての機能を持ち合わせないからである。また、樹脂成分を４〜３６質量％としているのは、４質量％未満であると接着強度が著しく低下し、３６質量％を超えると導電性、熱伝導性が低下するためである。
【００２５】
【実施例】
［試料の作製］
以下、実施例により本発明を更に詳細に説明する。表１に実施例１〜１３と表２に比較例１〜７を示す。なお、表１、２中における組成は重量％で示している。
【００２６】
表１および表２において、銀粉末には、球状銀粉Ａとして平均粒径０．０５μｍ、最大粒径が０．１０μｍの微細球状銀粉、球状銀粉Ｂとして平均粒径０．１２μｍ、最大粒径が０．５０μｍの微細球状銀粉、球状銀粉Ｃとして平均粒径が０．３０μｍ、最大粒径が１．１２μｍの球状銀粉を使用した。また、フレ−ク状銀粉Ｄとして平均粒径が１．４５μｍ、最大粒径が３７μｍのフレ−ク状銀粉を使用した。
【００２７】
ポリイミド樹脂には、ポリイミド樹脂ＡとしてＮ，Ｎ−ヘキサメチレン−ビス（アリルビシクロ［２．２．１］ヘプト−５−エン−２，３−ジカルボキシイミド、ポリイミド樹脂Ｂとしてビス［４−（アリルビシクロ［２，２，１］ヘプト−５−エン−２，３−ジカルボキシイミド）フェニル］メタンを使用した。
【００２８】
エポキシ樹脂には、エポキシ樹脂Ａとしてビスフェノ−ルＡジグリシジルエ−テル、エポキシ樹脂Ｂとしてノボラックグリシジルエ−テルを使用した。また、エポキシ樹脂の硬化剤には、硬化剤Ａとしてフェノ−ルノボラック、硬化剤Ｂとしてジシアンジアミドを使用し、その他に硬化促進剤として２−フェニル−４，５ジヒドロキシメチルイミダゾ−ルを使用した。
【００２９】
希釈剤は、希釈剤ＡとしてＮ−メチル−２−ピロリドン、希釈剤Ｂとしてフェニルグリシジルエ−テル、希釈剤Ｃとしてジエチレングリコ−ルモノブチルエ−テルを使用した。
【００３０】
表１および表２中の質量割合に従って上記原料を配合し、３本ロ−ル型混練機で混練することにより、導電性接着剤の試料を作製した。得られた導電性接着剤試料については下記の各項目について測定用の試料を作製し、各評価を行った。
【００３１】
［試料の評価］
（１）シ−ト抵抗値の測定
アルミナ基板上の２ｍｍ離れた電極間に、該電極に重ねて幅２ｍｍ、長さ５ｍｍの長方形状に導電性接着剤を印刷し、２００℃のオ−ブン中に３０分間放置して樹脂を乾燥もしくは硬化させ、３００℃のホットプレ−トにのせ１５分間放置し焼結および樹脂の本硬化をさせた後、室温まで冷却し電極間の抵抗値を測定した。
【００３２】
（２）接着強度の測定
銀メッキを施した２．５ｃｍ角の銅基板上に導電性接着剤を滴下し、１．５ｍｍ角のシリコンチップを載せ、２００℃のオ−ブン中に３０分間放置して樹脂を乾燥もしくは硬化させ、３００℃のホットプレ−トにのせ１５分間放置して焼結および樹脂の本硬化をさせた。室温まで冷却した後、上記基板に対し、水平方向から上記シリコンチップに力を加え、該シリコンチップがはがれたときの力を接着強度として測定した。
【００３３】
（３）耐熱強度の測定
銀メッキを施した２．５ｃｍ角の銅基板上に導電性接着剤を滴下し、１．５ｍｍ角のシリコンチップを載せ、２００℃のオ−ブン中に３０分間放置して樹脂を乾燥もしくは硬化させ、３００℃のホットプレ−トにのせ１５分間放置して焼結および樹脂の本硬化をさせた。室温まで冷却した後、２５０℃に加熱してあるホットプレ−ト上に上記基板を３０秒間放置し、その後加熱しながら該基板に対し、水平方向から上記シリコンチップに力を加え、該シリコンチップが剥がれたときの力を耐熱強度として測定した。
【００３４】
（４）耐熱耐湿性の評価
上記（１）で作製したシ−ト抵抗値の測定試料を、温度８５℃、湿度８５％ＲＨで１００時間保持した後、室温まで冷却し、（１）と同様にしてシ−ト抵抗値を測定した。（１）で求めたシ−ト抵抗値をもとに、ここで求めたシ−ト抵抗値の倍率を求めた。
【００３５】
また、上記（２）で作製した接着強度の測定試料と同様に作製した試料を温度８５℃、湿度８５％ＲＨで１００時間保持した後、室温まで冷却し、（２）と同様にして接着強度を測定した。（２）で求めた接着強度をもとに、ここで求めた接着強度の倍率を求めた。
【００３６】
これら求められたシ−ト抵抗値と接着強度の倍率に対し、シ−ト抵抗値の倍率が１．２倍以内、かつ接着強度に対する倍率が０．５倍以上であれば良（○）とし、それ以外であれば不可（×）とした。
【００３７】
（５）作業性の評価
得られた導電性接着剤を、２５０メッシュのスクリ−ンを用い０．３ｍｍ幅の線を０．５ｍｍ間隔で銅基板上に印刷した。この際、印刷された基板上に印刷かすれがないかを目視にて確認した。
【００３８】
また、導電性接着剤をシリンジ中に充填し、空気圧によって導電性接着剤を押出し、銅板上に吐出し（ディスペンス）、その形状を観察した。
【００３９】
以上の作業性評価において、印刷時にかすれがあり、かつディスペンス時に糸が引き、横に倒れたり、高さが１ｍｍ以上あるものは不可（×）、印刷もしくはディスペンスのどちらかで使用できる場合、または両方とも可能な場合は良（○）とした。
【００４０】
（６）熱伝導性の評価
リ−ドフレ−ム上に導電性接着剤を滴下し、半導体チップをマウントし、２００℃のオ−ブン中で３０分間放置し樹脂を乾燥もしくは硬化させたのち、３００℃のホットプレ−ト上に１５分間放置し焼結および樹脂の本硬化をさせた。室温に冷却後、リ−ドフレ−ムおよび半導体チップの電極部にマイクロプロ−ブをあて、最初５ｍＡの電流を３ｍＳ間流し、電圧を測定する。この時の電圧値をＶ１とする。続けて３００ｍＡの電流を５０ｍＳ間流し、半導体チップを発熱させ、その後再び５ｍＡの電流を３ｍＳ流し電圧を測定する。この時の電圧値をＶ２とし、Ｖ１−Ｖ２の値が３０ｍＶ以下であれば熱伝導性は良（○）、それ以外は不可（×）とした。
【００４１】
（７）総合評価
上記の６項目において、シ−ト抵抗値は２００ｍΩ以下、接着強度は４０Ｎ以上、耐熱強度は５Ｎ以上、耐熱耐湿性、作業性、熱伝導性については良（○）の条件を満たしたもののみ良（○）とし、１つでも条件が満たさないものは不可（×）とした。
【００４２】
［評価結果］
表１から明らかなように、実施例１〜１３の導電性接着剤は、導電性、接着性、耐熱性、作業性、熱伝導性に優れた性能を有している。
【００４３】
【表１】
一方、表２に示す本発明の組成範囲外の比較例１〜７は全ての条件を満足していない。
【００４５】
比較例１および２は、球状銀粉の平均粒径が０．２μｍより大きく、最大粒径が１．０μｍより大きい銀粉を使用した場合の例である。このような銀粉を使用すると銀粉の焼結が生じず、また、球状銀粉であるため銀粉同士の接触も少なく、シ−ト抵抗値が非常に高くなり熱伝導性も悪くなってしまった。
【００４６】
比較例３および４は、銀粉量が本発明の組成範囲の上限より多く、樹脂成分が組成範囲の下限より少ない場合である。比較例３、４では、樹脂量が少ないため、接着強度、耐熱強度が弱くなり、耐熱耐湿性も悪くなっている。また銀粉量が多すぎるために印刷、ディスペンスともにできず作業性も悪くなった。
【００４７】
比較例５および６は、銀粉量が本発明の組成範囲の下限より少なく、樹脂成分が組成範囲の上限より大きい場合である。比較例５，６では、銀粉量が足りないためシ−ト抵抗値が高くなり、熱伝導性も悪くなっている。
【００４８】
比較例７は、銀粉がフレ−ク状銀粉のみの場合であり、市場に出ている一般的な導電性接着剤の組成である。比較例７はフレーク状銀粉同士の接触により高導電性は確保できるが、熱伝導性が悪い結果となっている。
【００４９】
【表２】
【発明の効果】
本発明の導電性接着剤は、従来の銀粉の接触により導電性を得る導電性接着剤と異なり、銀粉を焼結させて導電性を得るため、高導電性が得られるとともに、熱伝導性も飛躍的に向上したものとなった。[0001]
BACKGROUND OF THE INVENTION
The present invention is used when bonding a semiconductor element such as an IC and a chip component such as a chip resistor or a chip LED to a lead frame or a heat radiating plate. The workability, adhesion, conductivity, heat resistance The present invention relates to a conductive adhesive excellent in thermal conductivity.
[0002]
[Prior art]
In recent years, semiconductor elements such as IC, LSI, LED, etc. have been remarkably developed, and mass production has been carried out. Accordingly, improvement of workability in mass production and reduction of manufacturing costs are important issues.
[0003]
Conventionally, as a method for adhering these semiconductor elements to a lead frame, a substrate or the like, it has been the mainstream to use solder such as gold-silicon eutectic solder or tin-lead solder. However, the conventional methods are expensive in gold, cannot absorb the difference in thermal expansion between the semiconductor element and the lead frame or the substrate, the semiconductor element and solder are cracked, and the heat resistance is improved. A method using a conductive adhesive has become mainstream because it lacks, the working temperature is relatively high, and the electrodes of the semiconductor element are easily contaminated.
[0004]
Commonly used conductive adhesives are composed of conductive powder, organic resin, solvent, catalyst, etc., and gold, silver, copper, carbon, etc. are used for the conductive powder. -A lot of silver powder is used because of its excellent conductivity. In addition, thermosetting resins such as epoxy resins and phenol resins are often used as organic resins. While these conductive adhesives overcome the aforementioned drawbacks of solder, they have been found to be inferior to metallic solid solders when compared to heat conduction.
[0005]
[Problems to be solved by the invention]
In recent years, semiconductor elements and chip parts have been required to be downsized, highly accurate, and high performance. In particular, ICs and LSIs, which are semiconductor elements, are increasingly required to have a large number of pins, a small size, and a high frequency, and the heat generated therewith is several times the amount of heat generated several years ago. Similarly, higher brightness is also demanded for LEDs, and the amount of heat generation is increasing.
[0006]
In other words, since a material having high thermal conductivity is required for connection of semiconductor elements that generate high heat generation, a conductive adhesive is not used, and solders having excellent thermal conductivity are used. It is common. However, the use of solders has the above-mentioned drawbacks, and a conductive adhesive having high thermal conductivity is strongly desired.
[0007]
An object of the present invention is to provide a conductive adhesive having a thermal conductivity equivalent to that of solders and also having the advantages of conventional conductive adhesives.
[0008]
[Means for Solving the Problems]
As a result of diligent efforts to achieve the above object, in a conductive adhesive containing a conductive powder and an organic resin, the conductive powder has a maximum particle size of 1 μm or less and an average particle size of 0.1. 2μm contains only the following spherical silver powder, and an epoxy resin or polyimide resin as the organic resin, and an electrically conductive powder 50 to 90 wt%, by the organic resin Ru is contained from 4 to 36 wt% They have found that high thermal conductivity can be obtained.
[0009]
Alternatively, in a conductive adhesive containing at least a conductive powder and an organic resin, a spherical silver powder having a maximum particle size of 1 μm or less and an average particle size of 0.2 μm or less as the conductive powder, and a maximum particle size There following frame 50 [mu] m - comprises a mixture of click-like silver powder, and an epoxy resin or polyimide resin as the organic resin, frame for spherical silver powder - weight mixing ratio of the click-shaped silver powder (= frame - the mass of the click-shaped silver powder / mass of spherical silver powder) is Ri range der of 0.1 or more and less than 1.33, and the conductive powder is 50 to 90 wt%, by organic resin is contained 4 to 36% by weight, The advantage of the flaky silver powder that provides high conductivity by contact can also be provided.
[0010]
In addition, when the conductive adhesive of the present invention is used, by heating the applied conductive adhesive to 200 to 350 ° C., the spherical silver powder is sintered, and the conductivity and thermal conductivity are improved. I found.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
In the conductive adhesive of the present invention, spherical silver powder having a maximum particle size of 1 μm or less and an average particle size of 0.2 μm or less is used as the conductive powder. In general, silver powder is used for many of the conductive powders of conductive adhesives, and flake silver powder or a mixture of flaky silver powder and spherical silver powder is often used. This is because conventional conductive adhesives have obtained high conductivity by contact with flaky silver powder, and high conductivity has not been obtained with spherical silver powder alone. However, high thermal conductivity could not be obtained by using flaky silver powder.
[0012]
The spherical silver powder having a maximum particle size of 1 μm or less and an average particle size of 0.2 μm or less used in the present invention is a very fine silver powder and is easily sintered. Therefore, in the conductive adhesive of this invention, since silver powder sinters and approximates a metal solid, thermal conductivity and electroconductivity improve.
[0013]
In particular, when the conductive adhesive of the present invention is heated to 200 ° C. to 350 ° C., high thermal conductivity and high conductivity can be obtained. Sintering of silver powder occurs even at about 150 ° C., but at 150 ° C., the sintering is insufficient, and the resulting conductivity and thermal conductivity cannot be improved sufficiently. By heating to 200 ° C. to 350 ° C., the sintering of silver powder is promoted, and higher conductivity and thermal conductivity are obtained. Further, within this temperature range, the organic resin used for the conductive adhesive is not deteriorated.
[0014]
The silver powder used in the present invention can be produced by various methods, but any silver powder may be used as long as the above conditions are satisfied. As an example, sodium hydroxide and silver nitrate are reacted with stirring at the same equivalent amount to form silver oxide, and the obtained silver oxide is washed well, and rosin and triethanolamine are added while keeping the temperature at 75 ° C. Can be obtained by thoroughly washing the obtained silver powder with water while suction filtration. Further, the finer the silver powder, the lower the sintering start temperature, so the finer powder is preferable. If desired, the maximum particle diameter is 0.2 μm or less and the average particle diameter is preferably 0.1 μm or less.
[0015]
In the present invention, the spherical silver powder and the flake silver powder may be mixed and used. Thereby, the advantage of spherical silver powder from which high electroconductivity and high heat conductivity are obtained by sintering, and flake-like silver powder from which high electroconductivity is obtained by contact can be acquired. In that case, it is desirable that the flake-shaped silver powder has a maximum particle size of 50 μm or less.
[0016]
Using fine spherical silver powder increases the thixotropy and is suitable for printing, but is not suitable for dispensing or stamping. However, when the flake silver powder is mixed, the thixo ratio is lowered moderately, and a conductive adhesive suitable for dispensing and stamping is obtained. Even when a suitable amount of flake-shaped silver powder is mixed, the same performance as that of a conductive adhesive consisting only of spherical silver powder can be obtained in high conductivity and high thermal conductivity.
[0017]
Also, frame for spherical silver powder - weight mixing ratio of the click-shaped silver powder - although the (= deflection mass click silver powder mass / spherical silver powder) were blended in a range of 0.1 or more and less than 1.33, which is 0. If it is less than 1, the effect of the flake-shaped silver powder cannot be obtained at all, and if it is 1.33 or more, the effect of the spherical silver powder cannot be obtained and the thermal conductivity is lowered.
[0018]
As the organic resin used in the present invention, a polyimide resin or an epoxy resin is used. A mixture of a polyimide resin and an epoxy resin may be used for the organic resin.
[0019]
As the polyimide resin used in the present invention, all known polyimide resins can be used, and there is no particular limitation. However, considering the method of use, a liquid or a solid that can be dissolved in a solvent is desirable. Examples of commercially available polyimide resins that are commercially available are UPA series and Upico series manufactured by Ube Industries, Semicofine series manufactured by Toray Industries, and bisalkenyl substituted manufactured by Maruzen Petrochemical Co., Ltd. Nadiimide and the like can be mentioned. When using a polyimide resin mixed with an epoxy resin, it is desirable that the resin be compatible with the epoxy resin.
[0020]
When adding a solvent with respect to a polyimide resin, what has a dilution effect in a polyimide resin is used. Examples thereof include N-methyl-2-pyrrolidone, N, N-dimethylformamide, N, N-dimethylacetamide, toluene, xylene, petroleum ether and the like. These may be used alone or as a mixture of two or more. In some polyimide resins, ethylene glycol diglycidyl ether, phenyl glycidyl ether, 3-aminopropyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane or the like may be used.
[0021]
As an epoxy resin used for this invention, all the well-known epoxy resins can be used and there is no restriction | limiting in particular. Examples of known epoxy resins include bisphenol A diglycidyl ether, bisphenol F diglycidyl ether, novolac glycidyl ether, epoxidation, which are mainly used for casting and bonding of electronic materials. Examples include soybean oil, 3,4 epoxy-6 methyl cyclohexyl methyl carboxylate, 3,4 epoxy cyclohexyl methyl carboxylate, and tetraglycidyl diaminodiphenylmethane. Considering the intended use, a liquid one is desirable, and considering that it is used for an electronic material, it is desirable that ionic impurities including chlorine ions be 800 ppm or less. These epoxy resins may be used alone or in combination of a plurality of types.
[0022]
The curing agent for the epoxy resin is not particularly limited as long as it can rapidly cure with the epoxy resin during heating (60 to 300 ° C.) and can satisfy long-term storage stability at room temperature. In general, imidazoles such as 2-ethyl-4-methylimidazole, 2-phenyl-4,5-dihydroxymethylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, 2- Examples include heptadecyl imidazole, phenol novolak compounds, dicyandiamide, acid anhydride tetrahydromethyl phthalic anhydride, hexahydrophthalic anhydride, methyl hymic anhydride, and BF 3 salt of Lewis acid complex. These may be used alone or in combination. Since the addition amount of these curing agents varies depending on the type, the amount is not particularly specified, but an amount suitable for the stoichiometric composition with the epoxy resin is desirable. In addition, in the present invention, those which are recognized to have a curing accelerating action, such as amine salts and block isocyanates, can also be used.
[0023]
Although not particularly defined in the present invention, it is desirable to use a solvent that is compatible with the epoxy resin and does not exist as a liquid after curing when a solvent is added to the epoxy resin. Generally, 2,2,4-trimethyl 3-hydroxydipentane isobutylate, 2,2,4-trimethylpentane 1,3-isobutylate, isobutyl butyrate, which does not react with epoxy resin or curing agent , Diethylene glycol monobutyl ether, ethylene glycol monobutyl ether, and the like. In addition, phenylglycidyl ether, ethylene glycol diglycidyl ether, 3-aminopropyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, Examples thereof include glycidoxypropylmethyldimethoxysilane and 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane.
[0024]
In the present invention, the conductive powder in the conductive adhesive is 50 to 90% by mass. If it is 50% by mass or less, satisfactory electric conductivity and thermal conductivity cannot be obtained, and 90% by mass or more. This is because the adhesive strength is weak and it does not have an adhesive function. Further, the resin components are a 4 to 36 wt%, the adhesive strength is less than 4% by weight is significantly reduced, electrical conductivity exceeds 36 wt%, because the thermal conductivity decreases.
[0025]
【Example】
[Preparation of sample]
Hereinafter, the present invention will be described in more detail with reference to examples. Table 1 shows Examples 1 to 13 and Table 2 shows Comparative Examples 1 to 7. In addition, the composition in Tables 1 and 2 is shown by weight%.
[0026]
In Tables 1 and 2, the silver powder has an average particle size of 0.05 μm as the spherical silver powder A and a fine spherical silver powder having a maximum particle size of 0.10 μm, and an average particle size of 0.12 μm and a maximum particle size as the spherical silver powder B. As the fine spherical silver powder and spherical silver powder C of 0.50 μm, spherical silver powder having an average particle diameter of 0.30 μm and a maximum particle diameter of 1.12 μm was used. Further, as the flake silver powder D, a flake silver powder having an average particle diameter of 1.45 μm and a maximum particle diameter of 37 μm was used.
[0027]
Polyimide resin includes N, N-hexamethylene-bis (allylbicyclo [2.2.1] hept-5-ene-2,3-dicarboximide as polyimide resin A, and bis [4- ( Allylbicyclo [2,2,1] hept-5-ene-2,3-dicarboximido) phenyl] methane was used.
[0028]
As the epoxy resin, bisphenol A diglycidyl ether was used as the epoxy resin A, and novolak glycidyl ether was used as the epoxy resin B. As the curing agent for the epoxy resin, phenol novolak was used as the curing agent A, dicyandiamide was used as the curing agent B, and 2-phenyl-4,5 dihydroxymethyl imidazole was used as the curing accelerator.
[0029]
Diluents used were N-methyl-2-pyrrolidone as diluent A, phenylglycidyl ether as diluent B, and diethylene glycol monobutyl ether as diluent C.
[0030]
The said raw material was mix | blended according to the mass ratio of Table 1 and Table 2, and the sample of the electrically conductive adhesive was produced by kneading | mixing with a 3 roll type kneader. About the obtained conductive adhesive sample, the sample for a measurement was produced about each following item, and each evaluation was performed.
[0031]
[Sample evaluation]
(1) Measurement of sheet resistance value A conductive adhesive was printed in a rectangular shape with a width of 2 mm and a length of 5 mm between the electrodes 2 mm apart on the alumina substrate. The resin was allowed to dry for 30 minutes and then dried or cured, placed on a hot plate at 300 ° C. for 15 minutes, allowed to sinter and fully cure the resin, then cooled to room temperature and measured for resistance between the electrodes. .
[0032]
(2) Measurement of adhesive strength A conductive adhesive is dropped onto a 2.5 cm square copper substrate with silver plating, a 1.5 mm square silicon chip is placed, and left in an oven at 200 ° C. for 30 minutes. The resin was then dried or cured, placed on a 300 ° C. hot plate and allowed to stand for 15 minutes to sinter and fully cure the resin. After cooling to room temperature, force was applied to the silicon chip from the horizontal direction with respect to the substrate, and the force when the silicon chip was peeled was measured as adhesive strength.
[0033]
(3) Measurement of heat resistance strength A conductive adhesive is dropped onto a 2.5 cm square copper substrate subjected to silver plating, a 1.5 mm square silicon chip is placed, and left in an oven at 200 ° C. for 30 minutes. The resin was then dried or cured, placed on a 300 ° C. hot plate and allowed to stand for 15 minutes to sinter and fully cure the resin. After cooling to room temperature, the substrate is allowed to stand for 30 seconds on a hot plate heated to 250 ° C., and then heated while applying force to the silicon chip from the horizontal direction against the substrate. The force when peeled was measured as the heat resistance strength.
[0034]
(4) Evaluation of heat and humidity resistance After the sheet resistance value measurement sample prepared in (1) above was held at a temperature of 85 ° C. and a humidity of 85% RH for 100 hours, it was cooled to room temperature and the same as (1) Then, the sheet resistance value was measured. Based on the sheet resistance value obtained in (1), the magnification of the sheet resistance value obtained here was obtained.
[0035]
In addition, a sample prepared in the same manner as the measurement sample of adhesive strength prepared in (2) above was held at a temperature of 85 ° C. and a humidity of 85% RH for 100 hours, and then cooled to room temperature. Was measured. Based on the adhesive strength determined in (2), the magnification of the adhesive strength determined here was determined.
[0036]
With respect to the sheet resistance value and the bond strength magnification obtained, the sheet resistance value magnification is within 1.2 times and the bond strength strength is 0.5 times or more. Otherwise, it was determined as impossible (×).
[0037]
(5) Evaluation of workability The obtained conductive adhesive was printed on a copper substrate at intervals of 0.5 mm using a 250-mesh screen with a width of 0.3 mm. At this time, it was visually confirmed whether there was any print fading on the printed substrate.
[0038]
Moreover, the conductive adhesive was filled in the syringe, the conductive adhesive was extruded by air pressure, discharged onto the copper plate (dispensing), and the shape was observed.
[0039]
In the above workability evaluation, when there is fading at the time of printing and the thread is pulled at the time of dispensing and falls to the side, or the height is 1 mm or more is not possible (×), when it can be used for either printing or dispensing, or When both were possible, it was determined to be good (◯).
[0040]
(6) Evaluation of thermal conductivity A conductive adhesive is dropped on a lead frame, a semiconductor chip is mounted, and left in a 200 ° C. oven for 30 minutes to dry or harden the resin. It was allowed to stand on a hot plate at 300 ° C. for 15 minutes to sinter and fully cure the resin. After cooling to room temperature, a microprobe is applied to the lead frame and the electrode part of the semiconductor chip, and a current of 5 mA is first applied for 3 mS to measure the voltage. The voltage value at this time is V1. Subsequently, a current of 300 mA is supplied for 50 mS to heat the semiconductor chip, and then a current of 5 mA is supplied again for 3 mS to measure the voltage. The voltage value at this time was V2, and if the value of V1-V2 was 30 mV or less, the thermal conductivity was good (◯), and the others were not possible (×).
[0041]
(7) Comprehensive evaluation In the above six items, the sheet resistance value is 200 mΩ or less, the adhesive strength is 40 N or more, the heat resistance strength is 5 N or more, the heat and humidity resistance, workability, and thermal conductivity are good (◯) conditions. Only those satisfying the conditions were evaluated as good (◯), and those that did not satisfy even one condition were determined as unacceptable (×).
[0042]
[Evaluation results]
As is clear from Table 1, the conductive adhesives of Examples 1 to 13 have performances excellent in conductivity, adhesiveness, heat resistance, workability, and thermal conductivity.
[0043]
[Table 1]
On the other hand, Comparative Examples 1 to 7 outside the composition range of the present invention shown in Table 2 do not satisfy all the conditions.
[0045]
Comparative Examples 1 and 2 are examples in which silver powder having an average particle diameter of spherical silver powder larger than 0.2 μm and a maximum particle diameter larger than 1.0 μm is used. When such silver powder is used, the silver powder does not sinter, and since it is a spherical silver powder, there is little contact between the silver powders, the sheet resistance value is very high, and the thermal conductivity is deteriorated.
[0046]
Comparative Examples 3 and 4 are cases where the amount of silver powder is greater than the upper limit of the composition range of the present invention and the resin component is less than the lower limit of the composition range. In Comparative Examples 3 and 4, since the amount of resin is small, the adhesive strength and heat resistance are weak, and the heat and humidity resistance is also poor. Moreover, since there was too much silver powder, neither printing nor dispensing was possible, and workability also deteriorated.
[0047]
In Comparative Examples 5 and 6, the amount of silver powder is less than the lower limit of the composition range of the present invention, and the resin component is larger than the upper limit of the composition range. In Comparative Examples 5 and 6, since the amount of silver powder is insufficient, the sheet resistance value is increased and the thermal conductivity is also deteriorated.
[0048]
The comparative example 7 is a case where silver powder is only flake-like silver powder, and is a composition of a general conductive adhesive on the market. Although the comparative example 7 can ensure high electroconductivity by contact between flaky silver powder, it has a bad thermal conductivity.
[0049]
[Table 2]
【The invention's effect】
Unlike the conventional conductive adhesive that obtains conductivity by contact with silver powder, the conductive adhesive of the present invention obtains conductivity by sintering silver powder, so that high conductivity is obtained and thermal conductivity is also obtained. It became a dramatic improvement.
Claims (3)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP22683197A JP3837858B2 (en) | 1997-08-22 | 1997-08-22 | Conductive adhesive and method of using the same |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP22683197A JP3837858B2 (en) | 1997-08-22 | 1997-08-22 | Conductive adhesive and method of using the same |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH1166953A JPH1166953A (en) | 1999-03-09 |
| JP3837858B2 true JP3837858B2 (en) | 2006-10-25 |
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| Application Number | Title | Priority Date | Filing Date |
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| JP22683197A Expired - Lifetime JP3837858B2 (en) | 1997-08-22 | 1997-08-22 | Conductive adhesive and method of using the same |
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| JP (1) | JP3837858B2 (en) |
Families Citing this family (18)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP4543460B2 (en) * | 1999-11-22 | 2010-09-15 | 住友ベークライト株式会社 | Conductive resin paste and semiconductor device using the same |
| JP5293496B2 (en) * | 2000-11-28 | 2013-09-18 | 日立化成株式会社 | Adhesive composition, adhesive film, and semiconductor device |
| JP4507488B2 (en) * | 2001-11-12 | 2010-07-21 | 日立化成工業株式会社 | Bonding material |
| JP3858902B2 (en) | 2004-03-03 | 2006-12-20 | 住友電気工業株式会社 | Conductive silver paste and method for producing the same |
| CN1320663C (en) * | 2004-04-22 | 2007-06-06 | 复旦大学 | Solar cell based on polymer doped quasi-solid state electrolyte material and its prepn. method |
| CN1320664C (en) * | 2004-04-22 | 2007-06-06 | 复旦大学 | Solar cel adopting organic/inorganic nano doped quasi-solid state electrolyte, and its prepn. method |
| JP2006169288A (en) * | 2004-12-13 | 2006-06-29 | Tdk Corp | Adhesive and method for bonding thin sheet to flat sheet |
| JP4942566B2 (en) * | 2007-06-29 | 2012-05-30 | 富士通コンポーネント株式会社 | Manufacturing method of touch panel |
| JP5311871B2 (en) * | 2008-04-23 | 2013-10-09 | 京セラケミカル株式会社 | Conductive adhesive composition |
| EP2278593A4 (en) * | 2008-04-30 | 2013-08-28 | Hitachi Chemical Co Ltd | CONNECTING MATERIAL AND SEMICONDUCTOR DEVICE |
| CN101805575B (en) * | 2010-04-09 | 2013-06-12 | 连云港昭华科技有限公司 | High-performance conductive silver paste and preparation method thereof |
| DE102010044326A1 (en) * | 2010-09-03 | 2012-03-08 | Heraeus Materials Technology Gmbh & Co. Kg | Use of aliphatic hydrocarbons and paraffins as solvents in silver pastes |
| DE112011103319T5 (en) | 2010-09-29 | 2013-07-11 | Hitachi Chemical Company, Ltd. | Adhesive composition and semiconductor device using the same |
| TW201245364A (en) | 2011-01-28 | 2012-11-16 | Hitachi Chemical Co Ltd | Adhesive composition and semiconductor device using same |
| JP5880300B2 (en) | 2012-06-14 | 2016-03-08 | 日立化成株式会社 | Adhesive composition and semiconductor device using the same |
| WO2014038331A1 (en) | 2012-09-05 | 2014-03-13 | 日立化成株式会社 | Silver paste composition and semiconductor device using same |
| JP5827203B2 (en) * | 2012-09-27 | 2015-12-02 | 三ツ星ベルト株式会社 | Conductive composition |
| JP2018181453A (en) * | 2017-04-04 | 2018-11-15 | 名古屋ファインケミカル株式会社 | Heat proof electroconductive adhesive |
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1997
- 1997-08-22 JP JP22683197A patent/JP3837858B2/en not_active Expired - Lifetime
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| JPH1166953A (en) | 1999-03-09 |
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