JP4421081B2 - Power module and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power module which is excellent in radiation and suitable for high-density miniaturization and manufacture thereof. SOLUTION: There are provided an insulator layer 104, leads 102 formed in a surface of the insulator layer 104, a semiconductor chip 101 electrically connected with the leads 102, and a heat sink 105 formed on the rear surface of the insulator layer 104. The insulator layer 104 contains 70-95 weight parts of inorganic filler and 5-30 weight parts of thermosetting resin composition. The semiconductor chip 101 is sealed in the insulator layer 104 and mounted on the insulator layer side surface of the leads 102 by flip chip bonding.

Description

【０１１９】
ここで、エポキシ樹脂組成物としては、ビスフェノールＦ型エポキシ樹脂（油化シェルエポキシ社製）９０重量％、硬化剤としてアミン付加物（味の素社製「ＭＹ−Ｈ（商品名）」）３重量％、硬化促進剤としてイミダゾール７重量％を含む組成物を使用した。
【０１２０】
また、Ａｌ₂Ｏ₃としては昭和電工社製「ＡＳ−４０（商品名）」を、ＳｉＯ₂、ＭｇＯおよびＢＮとしては関東化学社製の試薬を使用した。着色剤としては東洋カーボン社製のカーボンブラックを、分散剤としては第一工業製薬社製「プライサーフ、Ｆ−２０８Ｆ（商品名）」を、カップリング剤としてはチタネート系カップリング剤である味の素社製「プレンアクト（商品名）」を使用した。
【０１２１】
作製した板状絶縁体について、弾性率、熱膨張係数および熱伝導率を測定した。なお、測定方法は以下の通りである。
【０１２２】
弾性率： ＪＩＳ Ｃ ６４８１に記載の方法に準じて測定した。
【０１２３】
熱膨張係数： 熱分析装置にて試験片（５ｍｍ×５ｍｍ、厚み１．０ｍｍ）を、５℃／分の割合で昇温させて厚み方向の熱膨張量を測定し、測定した熱膨張量を１℃当たりの値に換算し、これを０℃における試験片の寸法に対する百万分率で表した。測定は４０〜１００℃の温度で行い、前記温度範囲における平均値を求めて熱膨張係数とした。
【０１２４】
熱伝導率： 試験片（５ｍｍ×５ｍｍ、厚み１．０ｍｍ）の表面を加熱ヒータに接触させ、試験片の裏面を室温に冷却した放熱フィンに固定した。この状態で試験片表面を一定電力で加熱し、試験片の表裏面の温度差を測定し、電力当たりの温度差として熱抵抗値を算出した。また、熱抵抗値の逆数をとり、熱伝導率を算出した。
【０１２５】
また、表１に示す各組成の絶縁体ペーストを使用すること以外は、実施例１と実質的に同様の方法により１０種のパワーモジュールを作製した。作製したパワーモジュールについて、ヒートサイクル試験を行った後、絶縁耐圧を測定した。なお、ヒートサイクル試験は、パワーモジュールを−５５℃の低温条件下で３０分間保持した後、１２５℃の高温条件下で３０分間保持するという操作を、１０００回繰り返すことにより実施した。
【０１２６】
各測定結果を、表２に示す。
【０１２７】
【表２】

【０１２８】
表２に示すように、無機フィラー７０〜９５重量部および熱硬化性樹脂組成物５〜３０重量部を含有する場合（試料番号２〜１０）は、熱伝導率に優れるうえに、弾性率が高く、半導体と同程度の熱膨張係数を有する絶縁体を得られることが確認できた。また、このような絶縁体層を使用したパワーモジュールは、ヒートサイクル信頼性が良好であることが確認できた。
【０１２９】
（実施例３）
図１に示す構造を有するパワーモジュールを、以下の要領で作製した。まず、実施例１と同様にして、離型キャリア上にリードフレームを形成し、リードフレーム上に半導体チップをフリップチップ実装した。
【０１３０】
次に、下記の組成を有する樹脂組成物にメチルエチルケトン溶剤を加え、アルミナボールを入れたポット中で４８時間５００ｒｐｍの速度で回転混合させて、スラリーを調製した。なお、メチルエチルケトン溶剤の添加量は、スラリーの粘度を約２０Ｐａ・ｓに調整することができる量とした。
（１）無機フィラー：ＡｌＮ（ダウケミカル社製、平均粒子径１２μm）８５重量部
（２）熱硬化性樹脂組成物：シアネート樹脂組成物（旭チバ社製、「ＡｒｏＣｙＭ−３０（商品名）」）１４重量部
（３）添加剤：カーボンブラック（東洋カーボン社製）０．３重量部、分散剤（第一工業製薬社製「プライサーフ Ｆ−２０８Ｆ（商品名）」）０．２重量部
次に、造膜用離型キャリアとして７５μｍ厚のポリエチレンテレフタレート（ＰＥＴ）フィルムを準備し、この造膜用離型キャリア上に、上記スラリーをドクターブレード法でギャップ（ブレードと造膜用離型キャリアとの間の距離）を約１．４ｍｍとして造膜した。次に、造膜シートを１００℃の温度で１時間放置し、造膜シート中のメチルエチルケトン溶剤を乾燥させた。次いで、造膜用離型キャリアを剥離し、可撓性を有する絶縁体シート（７５０μｍ厚）を得た。
【０１３１】
次いで、半導体チップを実装したリードフレームと、絶縁体シートと、ヒートシンクとしてのアルミニウム板とを積層した。この積層体を、温度２６０℃、圧力９．８ＭＰａの条件で１時間加熱加圧し、絶縁体シートの熱硬化性樹脂を硬化させるとともに、絶縁体層、半導体チップ、リードフレームおよびヒートシンクを一体化した。その後、離型キャリアを剥離し、パワーモジュールを得た。
【０１３２】
得られたパワーモジュールの熱伝導性を評価したところ、０．７５℃／Ｗの熱抵抗値が得られた。また、絶縁耐圧を測定したところ、１０ＫＶ／ｍｍ以上の耐圧が得られた。
【０１３３】
（実施例４）
図２と同様の構造を有するパワーモジュールを、次の要領で作製した。まず、離型キャリアとして７０μｍ厚の銅箔を使用し、その表面に電解銅メッキ法により２５０μｍ厚の銅メッキ層を形成した。この離型キャリアの銅メッキ層表面にドライフィルムを接着した後、配線パターンを形成したマスクを介してドライフィルムを露光し、露光部分以外のドライフィルムを除去するように現像した。次いで、塩化第２鉄溶液中に浸漬して銅メッキ層をエッチング除去し、更にドライフィルムを苛性ソーダで除去して、離型キャリア上に銅メッキ層によるリードフレーム配線パターンを形成した。
【０１３４】
次に、リードフレーム上に半導体チップをフリップチップ実装した。半導体チップとしては、電流５０Ａ仕様のＩＧＢＴ（松下電子工業社製）を使用した。半導体チップの表面電極に、直径１００μｍ、高さ４０μｍのバンプを金メッキ法によって形成し、更にバンプに共晶半田を印刷した。半導体チップを、表面電極がリードフレーム側を向くように、リードフレーム上に配置した。半導体チップを固定した状態で半田リフロー装置にて共晶半田を溶融させ、半導体チップの表面電極とリードフレームとを電気的に接続した。
【０１３５】
続いて、前記半導体チップの背面電極とリードフレームとを、内部リードを介して接続した。内部リードは、銅板を打ち抜き加工した後、その表面に１μｍ厚の金メッキ層を形成することにより作製した。超音波ボンディング装置により、この内部リードを半導体チップの背面電極およびリードフレームに接着させた。
【０１３６】
次に、リードフレームおよび半導体チップを備えた離型キャリア上に、絶縁体ペーストを印刷して絶縁体層を形成した。絶縁体ペーストとしては、実施例１と同様のものを使用した。次に、絶縁体層上にヒートシンクとしてアルミニウム板（１．０ｍｍ厚）を積層し、温度１７５℃、圧力４．９ＭＰａの条件で３０分間加熱加圧し、絶縁体層中の熱硬化性樹脂を硬化させるとともに、絶縁体層、半導体チップ、リードフレームおよびヒートシンクを一体化した。その後、離型キャリアを剥離し、パワーモジュールを得た。得られたパワーモジュールにおいて、内部リードは絶縁体層内に埋設され、且つ、絶縁体層の硬化による変形は認められなかった。
【０１３７】
得られたパワーモジュールの熱伝導性を評価したところ、０．７５℃／Ｗの熱抵抗値が得られた。また、信頼性の評価として、最高温度が２６０℃で１０秒間のリフロー試験を行った。このとき、絶縁体層とリードフレームとの界面、絶縁体層と半導体チップとの界面、および、絶縁体層と内部リードとの界面に、間隙発生などの異常は認められず、強固な密着が得られていることが確認できた。
【０１３８】
【発明の効果】
以上説明したように、本発明のパワーモジュールによれば、無機フィラーおよび熱硬化性樹脂組成物を含有する絶縁体層と、前記絶縁体層の表面に形成されたリードと、前記リードの前記絶縁体層側の面に実装された少なくとも１つの半導体チップと、前記絶縁体層の裏面に形成されたヒートシンクとを備え、前記半導体チップが、フリップチップボンディングにより前記リードに実装されており、且つ、前記絶縁体層内に封止されているため、放熱効率に優れ、且つ、高密度実装が可能なパワーモジュールとすることができる。
【図面の簡単な説明】
【図１】 本発明のパワーモジュールの一例を示す断面図である。
【図２】 本発明のパワーモジュールの別の一例を示す断面図である。
【図３】 本発明のパワーモジュールの別の一例を示す断面図である。
【図４】 本発明のパワーモジュールの製造方法の一例を示す工程別断面図である。
【図５】 本発明のパワーモジュールの製造方法の別の一例を示す工程別断面図である。
【符号の説明】
１０１、１１１、２０１ 半導体チップ
１０２、１１２、２０２ リード
１０３、１１３、２０３ バンプ
１０４、１１４、２０４ 絶縁体層
１０５、１１５、２０５ ヒートシンク
１０６、１１６、２０６ 表面実装型電子部品
１１７ 内部リード
２０７ 回路基板
３０１、４０１ 離型キャリア
３０２、４０２ リードフレーム
３０３、４０３ 半導体チップ
３０４、４０４ バンプ
３０５、４０５ 未硬化の絶縁体層
３０６、４０６ ヒートシンク
３０７、４０７ 硬化した絶縁体層
３０８、４０８ 表面実装型電子部品[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a power module mounted with a semiconductor chip and a method for manufacturing the same.
[0002]
[Prior art]
In recent years, with the demand for higher performance and smaller size of electronic devices, power supply circuits in the power electronics field are also required to be smaller and save energy. Therefore, the heat dissipation structure of the power module is an important issue.
[0003]
As a method of improving the heat dissipation of the power module, use a substrate with good thermal conductivity, and contact the semiconductor chip on this substrate and the back of the semiconductor chip (the surface opposite to the device formation surface) on the substrate surface. There has been proposed a method of dissipating heat from the substrate by mounting in such a manner.
[0004]
As such a method, for example, a method using a metal base substrate in which a wiring pattern is formed on a surface of a metal plate such as aluminum via an insulator layer has been proposed. A method of using a substrate in which a copper plate is bonded to the surface of a ceramic plate such as aluminum oxide or aluminum nitride has been proposed.
[0005]
There has also been proposed a method in which leads are formed on the surface of a substrate in which an inorganic filler is dispersed in a thermoplastic resin, and a semiconductor chip is mounted on the leads. However, since this substrate is produced by melt-kneading a thermoplastic resin and an inorganic filler and injection-molding it, it is difficult to fill the inorganic filler in a high concentration, which improves the thermal conductivity. There are limits.
[0006]
Also, a method has been proposed in which leads are formed on the surface of a substrate in which an inorganic filler is dispersed in a thermosetting resin composition, and a semiconductor chip is mounted on the leads (Japanese Patent Laid-Open No. 9-270005). This substrate is made by laminating a flexible sheet in an uncured state containing a thermosetting resin and an inorganic filler and a lead frame, and then curing the sheet, and filling the inorganic filler in a high concentration It is possible to achieve good thermal conductivity.
[0007]
[Problems to be solved by the invention]
As a method for mounting a semiconductor chip in the signal circuit field, flip chip bonding or wire bonding is employed. In flip chip bonding, a semiconductor chip is mounted such that the substrate surface and the semiconductor chip surface (element formation surface) face each other, that is, mounted face down, and can be mounted at a higher density than wire bonding. is there.
[0008]
However, in the power supply circuit field, heat radiation from the back surface of the semiconductor chip is required. Therefore, in the conventional power module, in order to radiate heat from the substrate, it is necessary to bring the substrate surface and the semiconductor chip back surface into contact with each other. Therefore, in the conventional power module, when flip chip bonding is employed, improvement in heat dissipation cannot be expected.
[0009]
Therefore, the conventional power module employs wire bonding in which the semiconductor chip is mounted on the substrate so that the back surface of the semiconductor chip and the surface of the substrate are in contact with each other. In this wire bonding, the electrode of the semiconductor chip and the lead formed on the substrate surface are electrically connected through a fine metal wire. However, since the conductor resistance of the thin metal wire is so large that it cannot be ignored compared to the on-resistance of the semiconductor element, when the semiconductor chip is mounted by wire bonding, power loss increases and the amount of heat generation increases. Therefore, when wire bonding is employed, there is a problem that further heat dissipation is required for the substrate.
[0010]
An object of this invention is to provide the power module excellent in heat dissipation and suitable for high-density miniaturization, and its manufacturing method.
[0011]
[Means for Solving the Problems]
In order to achieve the above object, the power module of the present invention includes an insulator layer containing an inorganic filler and a thermosetting resin composition, a lead formed on the surface of the insulator layer, and the insulator of the lead. At least one semiconductor chip mounted on the surface on the layer side, and a heat sink formed on the back surface of the insulator layer, wherein the semiconductor chip is mounted on the lead by flip chip bonding, and Sealed within the insulator layer.
[0012]
In the power module having such a configuration, the semiconductor chip is built in the insulating layer having thermal conductivity with the back surface thereof facing the heat sink. Therefore, heat can be efficiently radiated from the back surface of the semiconductor chip to the heat sink via the insulator layer. In addition, the semiconductor chip can be protected from moisture absorption and the like. In addition, since the semiconductor chip is mounted by flip chip bonding, resistance loss at the connection portion between the semiconductor chip and the lead can be reduced and high-density mounting can be achieved as compared with mounting by wire bonding.
[0013]
In the power module, the semiconductor chip includes a first electrode formed on a surface on the lead side and a second electrode formed on a surface on the heat sink side. It is preferable that an electrode is connected to the lead by flip-chip bonding, and the second electrode is connected to the lead via an internal lead disposed in the insulator layer. This is because it is possible to cope with an increase in current by using a semiconductor chip configured so that a current flows in the thickness direction.
[0014]
In the power module, in the insulator layer, the proportion of the inorganic filler is preferably 70 to 95% by weight, and the proportion of the thermosetting resin composition is preferably 5 to 30% by weight. According to this preferable example, the heat conductivity of the insulator layer can be improved, and the heat dissipation can be further improved. Further, the thermal expansion coefficient of the insulator layer can be made comparable to that of a semiconductor, and a power module having excellent reliability can be obtained.
[0015]
In the power module, the insulator layer preferably has a thermal conductivity in the range of 1 to 10 W / (m · K). This is because the heat dissipation can be further improved.
[0016]
In the power module, the thermal expansion coefficient of the insulator layer is 8 to 20 × 10. ^-6 K ^-1 It is preferable to be in the range. This is because, by setting the thermal expansion coefficients of the insulator layer and the semiconductor chip to the same level, a power module having excellent reliability against thermal shock can be obtained.
[0017]
In the power module, the insulator layer preferably has an elastic modulus in a range of 20 to 50 MPa. This is because a power module having excellent reliability against thermal shock can be obtained.
[0018]
In the power module, it is preferable that an electronic component is mounted on a surface of the lead opposite to the surface on which the semiconductor chip is mounted. This is because the power module can be further miniaturized and miniaturized.
[0019]
In the power module, it is preferable that the lead is embedded in the insulator layer with at least a part thereof exposed on the surface of the insulator layer. This is because the lead itself contributes to heat dissipation, so that the heat dissipation efficiency can be further improved. Further, there is an advantage that misalignment hardly occurs when an electronic component is mounted on the surface of the lead opposite to the insulator layer side.
[0020]
In the power module, a circuit board formed by laminating a wiring layer and a substrate layer is embedded in the insulator layer with at least one of the wiring layers exposed on the surface of the insulator layer. It is preferable. According to this preferred example, not only the power supply circuit but also peripheral circuits such as a control circuit and a protection circuit can be integrated, and higher-density mounting is possible.
[0021]
Moreover, in the said power module, it is preferable that the said thermosetting resin composition contains a thermosetting resin, a hardening | curing agent, and a hardening accelerator.
[0022]
In this case, in the thermosetting resin composition, the ratio of the thermosetting resin is 50 to 95% by weight, the ratio of the curing agent is 4.9 to 45% by weight, and the ratio of the curing accelerator is 0.1 to 0.1%. It is preferably 5% by weight.
[0023]
Moreover, in the power module, it is preferable that the thermosetting resin composition contains at least one thermosetting resin selected from the group consisting of an epoxy resin, a phenol resin, and a cyanate resin. This is because these thermosetting resins are excellent in heat resistance and electrical insulation.
[0024]
Moreover, in the said power module, it is preferable that the said thermosetting resin composition contains an epoxy resin, a novolak resin, and imidazole. In particular, it is preferable to contain a brominated polyfunctional epoxy resin, a bisphenol A type novolac resin, and imidazole. This is because such a composition is excellent in heat resistance, electrical insulation and flame retardancy.
[0025]
In this case, in the thermosetting resin composition, the ratio of the epoxy resin is 60 to 80% by weight, the ratio of the novolak resin is 18 to 39.9% by weight, and the ratio of the imidazole is 0.1 to 2% by weight. % Is preferred.
[0026]
In the power module, the inorganic filler is Al. ₂ O _Three , SiO ₂ It is preferably at least one selected from the group consisting of MgO, BN and AlN. This is because these inorganic fillers are particularly effective in improving the thermal conductivity of the insulator layer. In particular, AlN and BN are effective in improving the thermal conductivity of the insulator layer and lowering the thermal expansion coefficient.
[0027]
Moreover, in the power module, it is preferable that an average particle diameter of the inorganic filler is in a range of 0.1 to 100 μm. This is because the inorganic filler can be filled with high density. In particular, if inorganic fillers having different average particle diameters within the above range are used in combination, the filler can be filled at a higher density and the thermal conductivity can be further improved.
[0028]
In the power module, the lead is preferably at least one metal selected from the group consisting of copper, aluminum, nickel, and iron. This is because the electrical conductivity is high and resistance loss is small even when a large current is passed. In particular, copper is not only excellent in electrical conductivity, but also has good thermal conductivity, which is advantageous for improving heat dissipation.
[0029]
In the power module, it is preferable that the lead has a thickness in a range of 0.05 to 1.00 mm. This is because it can cope with a large current.
[0030]
In the power module, it is preferable that a metal plating layer made of at least one selected from the group consisting of nickel, tin, solder and gold is formed on the surface of the lead on the insulator layer side. This is because the adhesion with the insulator layer is improved and the reliability such as thermal shock is improved.
[0031]
In the power module, it is preferable that a surface of the lead on the insulator layer side is roughened. This is because the adhesion with the insulator layer is improved and the reliability such as thermal shock is improved.
[0032]
In the power module, the heat sink is preferably aluminum or copper. This is because these metals are excellent in thermal conductivity. In particular, since copper is excellent in thermal conductivity, good heat dissipation can be obtained. In addition, aluminum is lightweight and can be obtained at low cost, and is excellent in workability. Therefore, it is possible to increase the surface area by making the heat sink into a complicated shape, and good heat dissipation can be obtained.
[0033]
In the power module, it is preferable that the heat sink includes a heat radiating fin. This is because the heat dissipation efficiency can be further improved.
[0034]
Moreover, in the power module, it is preferable that a surface on the insulator layer side of the heat sink is roughened. This is because the adhesion with the insulator layer is improved and the reliability such as thermal shock is improved.
[0035]
As the semiconductor chip, for example, a chip such as a silicon semiconductor or a silicon carbide semiconductor can be used. Specifically, IGBT (insulated gate bipolar transistor), MOS-FET (metal oxide semiconductor-field effect transistor), etc. can be used.
[0036]
In order to achieve the above object, a method of manufacturing a power module according to the present invention includes a step of forming a lead on a release carrier, a step of mounting a semiconductor chip on the lead by flip chip bonding, and a step on the release carrier. A step of forming an uncured insulator layer containing an inorganic filler and a thermosetting resin composition so as to cover the leads and the semiconductor chip, and a heat sink on the uncured insulator layer And a step of heating the laminate to cure the insulator layer, and a step of peeling the release carrier.
[0037]
With such a configuration, the power module of the present invention can be efficiently manufactured. Further, in the manufacturing method of the present invention, since the leads are formed on the release carrier, it is possible to form a fine wiring pattern and an independent wiring pattern, and to further reduce the size of the module.
[0038]
In the said manufacturing method, it is preferable in the said insulator layer that the ratio of the said inorganic filler is 70 to 95 weight%, and the ratio of the said thermosetting resin composition is 5 to 30 weight%. This is because the heat conductivity of the insulator layer can be improved and the heat dissipation of the power module can be further improved.
[0039]
Moreover, in the said manufacturing method, it is preferable that the process of forming the said insulator layer is a process of apply | coating the paste containing the said inorganic filler and the said thermosetting resin composition on the said mold release carrier. . This is because the insulator layer can be filled with an inorganic filler at a high concentration, and the heat dissipation of the power module can be further improved.
[0040]
In this case, it is preferable that the paste is applied by screen printing or metal mask printing. This is because the insulator layer can be formed with simple equipment.
[0041]
Further, in the manufacturing method, the step of forming the insulator layer includes removing the flexible sheet in the uncured state containing the inorganic filler and the thermosetting resin composition. A step of laminating on the mold carrier is preferable. This is because the insulator layer can be filled with an inorganic filler at a high concentration, and the heat dissipation of the power module can be further improved.
[0042]
In the manufacturing method, during the step of forming the insulator layer, or after the step of forming the insulator layer and before the step of curing the insulator layer, It is preferable to expose the formed product formed on the release carrier in a vacuum. This is because voids in the insulator layer that cause a decrease in the withstand voltage can be reduced.
[0043]
Further, the manufacturing method preferably includes a step of mounting an electronic component on a surface of the lead opposite to the insulator layer side after the step of peeling the release carrier. This is because the power module can be further reduced in density and size.
[0044]
In the manufacturing method, after forming the leads on the release carrier, a circuit board formed by laminating a wiring layer and a substrate layer is disposed on the release carrier, and the insulator layer is It is preferable to form so as to cover the circuit board. This is because by forming peripheral circuits such as a control circuit and a protection circuit on a circuit board, it is possible to realize further high-density and miniaturization of the module.
[0045]
Moreover, in the said manufacturing method, it is preferable to make heating temperature into the range of 130-260 degreeC in the process of heating the said laminated body. This is because the thermosetting resin composition constituting the insulator layer can be cured in a short time.
[0046]
Moreover, in the said manufacturing method, it is preferable to apply the pressure of 19.6 Mpa or less to the said laminated body in the process of heating the said laminated body. This is because the gap between the semiconductor chip and the lead can be easily filled with the thermosetting resin composition constituting the insulator layer.
[0047]
Moreover, in the said manufacturing method, it is preferable that the said thermosetting resin composition contains a thermosetting resin, a hardening | curing agent, and a hardening accelerator.
[0048]
In this case, in the said thermosetting resin composition, the ratio of a thermosetting resin is 50 to 95 weight%, the ratio of a hardening | curing agent is 4.9 to 45 weight%, and the ratio of a hardening accelerator is 0.00. It is preferably 1 to 5% by weight.
[0049]
Moreover, in the said manufacturing method, it is preferable that the said thermosetting resin composition contains at least 1 type of thermosetting resin chosen from an epoxy resin, a phenol resin, and cyanate resin. It is because it is excellent in heat resistance and electrical insulation.
[0050]
Moreover, in the said manufacturing method, it is preferable that the said thermosetting resin composition contains a liquid thermosetting resin at room temperature. This is because it is easy to produce a paste having an appropriate viscosity for coating or a sheet having moderate flexibility. In addition, room temperature is 20 degreeC normally.
[0051]
In this case, the thermosetting resin which is liquid at room temperature is preferably at least one selected from the group consisting of bisphenol A type epoxy resins, bisphenol F type epoxy resins and liquid phenol resins. This is because an insulating layer having excellent heat resistance can be obtained, and the gap between the flip chip mounted semiconductor chip and the lead can be easily filled.
[0052]
In the manufacturing method, the inorganic filler is Al. ₂ O _Three , SiO ₂ It is preferably at least one selected from the group consisting of MgO, BN and AlN. This is because it is particularly effective for improving the thermal conductivity of the insulator layer.
[0053]
Moreover, in the said manufacturing method, it is preferable that the average particle diameter of the said inorganic filler is the range of 0.1-100 micrometers. This is because the inorganic filler can be filled with high density.
[0054]
In the manufacturing method, it is preferable that the lead is at least one metal selected from the group consisting of copper, aluminum, nickel, and iron. This is because conductivity is high and resistance loss is small.
[0055]
Moreover, in the said manufacturing method, it is preferable that the thickness of the said lead is the range of 0.05-1.00 mm. This is because it can cope with a large current.
[0056]
Further, in the manufacturing method, before the step of forming the insulator layer, at least one metal selected from the group consisting of nickel, tin, solder, and gold is provided on the surface of the lead in contact with the insulator layer. It is preferable to form a plating layer. This is because the adhesive strength with the insulator layer can be improved and the solder wettability when mounting semiconductor chips and electronic components can be improved.
[0057]
Moreover, in the said manufacturing method, it is preferable to roughen the surface which contact | connects the said insulator layer of the said lead | read | reed before the process of forming the said insulator layer. This is because the adhesive strength with the insulator layer can be improved.
[0058]
Moreover, in the said manufacturing method, it is preferable that the said heat sink is aluminum or copper. Furthermore, it is preferable that the heat sink includes a heat radiating fin. This is because the heat dissipation efficiency is improved.
[0059]
Moreover, in the said manufacturing method, it is preferable to roughen the surface which touches the said insulator layer of the said heat sink before the process of laminating | stacking the said heat sink on the said insulator layer. This is because the adhesive strength with the insulator layer is improved.
[0060]
Moreover, in the said manufacturing method, it is preferable to use an organic film as said mold release carrier. This is because peeling from the insulator layer and the lead is easy and the cost is low. As the organic film, for example, at least one organic film selected from the group consisting of polyphenylene oxide, polyimide, polyethylene, polyethylene terephthalate, and aramid can be used.
[0061]
Moreover, in the said manufacturing method, it is preferable to use metal foil as said mold release carrier. This is because the metal foil has a small dimensional change due to heat, and can suppress a dimensional change in the step of curing the insulator layer. As the metal foil, for example, at least one metal foil selected from the group consisting of copper foil, nickel foil and aluminum foil can be used.
[0062]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a cross-sectional view showing an example of a power module of the present invention. This power module has an insulator layer 104 containing a semiconductor chip 101, a lead frame 102 formed on the surface of the insulator layer 104, and a heat sink 105 formed on the back surface of the insulator layer 104. The semiconductor chip 101 has a surface electrode and is mounted on the surface of the lead frame 102 on the insulator layer side by flip chip bonding. That is, the semiconductor chip 101 is disposed with the front surface (device forming surface) facing the lead frame and the back surface (surface opposite to the device forming surface) facing the heat sink. The frame 102 is electrically connected via the bump 103. A surface mount electronic component 106 is disposed on the surface of the insulator layer 104 and is mounted on the surface opposite to the semiconductor chip side of the lead frame 102.
[0063]
In the power module, the insulating material constituting the insulator layer 104 covers the semiconductor chip 101 mounted on the lead frame 102 from the back surface and fills the gap between the semiconductor chip 101 and the lead frame 102. ing. As a result, the semiconductor chip 101 is embedded inside the insulating layer 104 and is completely shielded from the outside air.
[0064]
The insulating material constituting the insulator layer 104 is also filled in the gap between the lead frames 102. As a result, the lead frame 102 is embedded in the insulator layer 104 with one surface (the surface opposite to the surface on which the semiconductor chip is mounted) exposed to the outside.
[0065]
The insulator layer 104 is a layer in which an inorganic filler is dispersed in a thermosetting resin composition, and preferably has the following characteristics. The thermal conductivity of the insulator layer 104 is 1 to 10 W / (m · K), preferably 3 to 10 W / (m · K), more preferably 5 to 10 W / (m · K). The thermal expansion coefficient of the insulator layer 104 is 8 to 20 × 10. ^-6 K ^-1 , Preferably 8-17 × 10 ^-6 K ^-1 More preferably, 8 to 13 × 10 ^-6 K ^-1 It is. The elastic modulus is 20 to 50 MPa, preferably 20 to 40 MPa, and more preferably 20 to 30 MPa. Note that characteristics such as thermal conductivity, thermal expansion coefficient, and elastic modulus can be adjusted by the composition of the insulator layer 104.
[0066]
FIG. 2 is a cross-sectional view showing another example of the power module according to the present invention. This power module includes an insulator layer 114 containing a semiconductor chip 111, a lead frame 112 formed on the surface of the insulator layer 114, and a heat sink 115 formed on the back surface of the insulator layer 114. The semiconductor chip 111 is configured such that current flows in the thickness direction of the chip, and includes a surface electrode on the surface and a back electrode on the back surface. The semiconductor chip 111 is arranged with the front side facing the lead frame and the back side facing the heat sink.
[0067]
The surface electrode of the semiconductor chip 111 is connected to the lead frame 112 via the bump 113, that is, connected by flip chip bonding. On the other hand, the back electrode of the semiconductor chip 111 is connected to the lead frame 112 via the internal lead 117. The internal lead 117 is embedded in the insulator layer 114.
[0068]
As the internal lead 117, for example, copper, aluminum, nickel, iron or the like can be used. Moreover, it is preferable to form a metal plating layer of nickel, tin, solder, gold or the like on the surface. The thickness of the internal lead 117 is, for example, 0.1 to 2.0 mm, preferably 0.4 to 1.0 mm, and more preferably 0.5 to 0.8 mm.
[0069]
As described above, the semiconductor chip 111 is configured to flow a current in the thickness direction in order to switch a larger current. In order to extract current from the back electrode of the semiconductor chip 111, the electrical resistance of the internal lead 117 must be made as low as possible to minimize resistance loss. The thickness of the internal lead 117 is appropriately set depending on the magnitude of the current extracted from the back electrode of the semiconductor chip 111. For example, the current up to about 5A is 0.2 mm or more, and about 20 A is about 0.5 mm or more and about 40 A. Then, it is 0.8 mm or more.
[0070]
The power module shown in FIG. 2 is the same as the power module shown in FIG. 1 except that the back electrode of the semiconductor chip is connected to the lead frame by internal leads.
[0071]
FIG. 3 is a cross-sectional view showing another example of the power module according to the present invention. The power module shown in FIG. 3 includes an insulator layer 204 containing a semiconductor chip 201, a lead frame 202 formed on the surface of the insulator layer 204, and a heat sink 205 formed on the back surface of the insulator layer 204. A circuit board 207 embedded in the surface of the insulator layer 204 is provided.
[0072]
The insulating material constituting the insulator layer 204 is also filled in the gap between the lead frame 202 and the circuit board 207, so that the circuit board 207 exposes one side to the outside and It will be embedded in the surface.
[0073]
The circuit board 207 is obtained by laminating a conductive layer 207b constituting a wiring pattern on an insulating substrate 207a. As the insulating substrate 207a, for example, a glass-epoxy substrate in which a glass woven fabric is impregnated with an epoxy resin, a paper-phenol substrate in which paper is impregnated with a phenol resin, or the like can be used. Moreover, as the conductor layer 207b, copper, aluminum, etc. can be used, for example. The circuit board 207 is not limited to the double-sided wiring board as shown in FIG. 3 and may be a multilayer wiring board.
[0074]
The power module shown in FIG. 3 is the same as the power module shown in FIG. 1 except that the circuit board 207 is provided.
[0075]
The power module of the present invention can be manufactured, for example, by the method described below. 4A to 4F are process diagrams for explaining an example of a method for manufacturing the power module shown in FIG.
[0076]
First, the lead frame 302 is formed on the surface of the release carrier 301 (FIG. 4A).
[0077]
As the lead frame 302, for example, a metal foil such as copper, aluminum, nickel, and iron can be used. In addition, it is preferable that the surface of the lead frame 302 be subjected to an antioxidant treatment by metal plating such as nickel, tin, solder, and gold.
[0078]
Further, the surface of the lead frame 302 is preferably subjected to a roughening process. As the roughening treatment method, either a chemical treatment method or a physical treatment method can be adopted. Examples of the chemical treatment method include a method of immersing and etching a lead frame in an aqueous solution of iron chloride, copper chloride or the like. Moreover, as a physical processing method, the method of spraying powder, such as aluminum oxide, on a lead frame surface with compressed air, for example is mentioned.
[0079]
By roughening the surface of the lead frame, adhesion to the insulator layer is greatly improved. This is because the surface area increases due to roughening and the adhesive strength increases due to the anchor effect. As a result of improved adhesion to the insulator layer, the reliability against thermal shock such as heat cycle is greatly improved. Since such an effect can be obtained efficiently, it is preferable to employ the physical treatment method as described above as the roughening treatment method.
[0080]
In roughening the lead frame, Rz representing the degree of roughening is preferably in the range of 2 to 20 μm, and more preferably 2 to 5 μm. Here, Rz is an average value of the height of the mountain from the highest mountain to the fifth highest mountain in the rough surface profile, and the depth of the valley from the deepest valley to the fifth deepest valley. It can be said that it is a rough surface, so that Rz is large.
[0081]
When an organic film is used as the release carrier 301, the lead frame 302 is formed by applying an adhesive on the organic film, then laminating a metal foil on the coated surface, and patterning this by photolithography and etching. Can be used. As the adhesive, it is preferable to use a tacky adhesive such as a rubber adhesive.
[0082]
When a metal foil is used as the release carrier 301, the lead frame 302 is formed by applying an adhesive on the metal foil that is the release carrier and laminating the metal foil that becomes the lead frame on the application surface. In addition, a method of patterning this by photolithography and etching can be employed. Alternatively, a metal layer may be formed by electrolytic plating on a metal foil that is a release carrier, and this metal layer may be used as the lead frame 302. According to the latter method, there is no possibility that the adhesive remains on the surface of the lead frame after peeling off the release carrier, and a clean surface can be obtained. Also, the peeling process is easy.
[0083]
Next, the semiconductor chip 303 is mounted at a predetermined position of the lead frame 302 (FIG. 4B). This step is performed by flip chip mounting. First, bumps 304 are formed on the electrode surface of the semiconductor chip 303, and solder is further formed on the bumps 304 surface. Next, the semiconductor chip 303 is mounted face-down on the lead frame 302, solder is reflowed in this state, and the bumps 304 and the lead frame 302 are joined. Alternatively, after bumps 304 are formed on the electrode surface of the semiconductor chip 303, the semiconductor chips 303 are mounted face down on the lead frame 302, and heating and pressurization or ultrasonic wave application is performed in this state, The lead frame 302 may be directly joined.
[0084]
Next, an insulator paste 305 is printed on the surface of the release carrier 301 provided with the lead frame 302 so as to cover the semiconductor chip 303, thereby forming an uncured insulator layer (FIG. 4C).
[0085]
The insulator paste 305 is prepared by mixing a solvent with an insulating material containing an inorganic filler and a thermosetting resin composition as necessary.
[0086]
The thermosetting resin composition constituting the insulator material is a composition containing a thermosetting resin as a main component and appropriately containing additives such as a curing agent and a curing accelerator. As the thermosetting resin, epoxy resin, phenol resin, cyanate resin and the like can be used. In particular, a thermosetting resin that is liquid at room temperature, such as bisphenol A type epoxy resin, bisphenol F type epoxy resin, or liquid phenol resin, may be used alone or mixed with a thermosetting resin that is solid at room temperature. Is preferred.
[0087]
A hardening | curing agent and a hardening accelerator are selected according to the kind of thermosetting resin to be used. For example, when an epoxy resin is used as the thermosetting resin, examples of the curing agent include amines such as aliphatic polyamines and aromatic polyamines, phenolic resins such as acid anhydrides, novolac, and amino resins. Examples of the accelerator include amines such as imidazoles and benzyldimethylamine.
[0088]
Moreover, when the whole thermosetting resin composition is 100 weight part, the preferable range of content of said each component is as follows. The thermosetting resin that is solid at room temperature is 0 to 45 parts by weight, the thermosetting resin that is liquid at room temperature is 5 to 50 parts by weight, and the total of both is 50 to 95 parts by weight, preferably 65 to 90 parts by weight. And The curing agent is 4.9 to 45 parts by weight, preferably 9.9 to 35 parts by weight. The curing accelerator is suitably 0.1 to 5 parts by weight, preferably 0.5 to 3.5 parts by weight.
[0089]
As the inorganic filler, various oxides and nitrides can be used. For example, Al ₂ O _Three , SiO ₂ MgO, BN, AlN and the like. Moreover, it is preferable that the average particle diameter of an inorganic filler is 0.1-100 micrometers, Furthermore, it is 7-12 micrometers.
[0090]
The content of each component in the insulating material is 5-30 parts by weight, preferably 7-15 parts by weight, more preferably 9-12 parts by weight, based on 100 parts by weight of the whole insulating material. It is appropriate that the inorganic filler is 70 to 95 parts by weight, preferably 86 to 93 parts by weight, more preferably 89 to 93 parts by weight.
[0091]
Moreover, it is preferable that the insulating material contains additives, such as a coupling agent, a dispersing agent, a coloring agent, and a mold release agent, as needed. It is because the characteristics of the insulator layer can be improved by containing various additives. For example, the coupling agent is effective in improving the withstand voltage because it improves the adhesion between the inorganic filler and the thermosetting resin. In addition, the dispersant improves the dispersibility of the inorganic filler and is effective in reducing composition unevenness in the insulating layer. Moreover, if a colorant is black colorants, such as carbon powder, for example, it is effective for the improvement of the heat dissipation of an insulator layer.
[0092]
The insulating material obtained by kneading the thermosetting resin composition and the inorganic filler can be used as the insulating paste 305 as it is when it has an appropriate viscosity for application. Moreover, when the viscosity of an insulating material is high, the solvent which can be volatilized by a post process can be mixed and it can adjust to a suitable viscosity. As the solvent, a solvent having a boiling point lower than the curing temperature of the thermosetting resin can be used. Further, the viscosity of the insulator paste 305 is not particularly limited, but about 100 to 300 Pa · s is appropriate.
[0093]
As a method for printing the insulator paste 305, for example, a metal mask printing method, a screen printing method, or the like can be employed. However, when the screen printing method is adopted, it is necessary to repeatedly print until a desired layer thickness is obtained. Also, in order to reliably fill the gap between the lead frames 302 with the insulator paste 305 and reduce voids in the insulator layer, printing is performed in a vacuum, or heat treatment in a vacuum is performed after printing. It is preferable to implement.
[0094]
Next, a heat sink 306 is laminated on the insulator paste 305. Thereafter, this is heated and pressed to cure the thermosetting resin constituting the insulator paste 305, thereby forming the insulator layer 307 (FIG. 4D). Through this process, the insulator layer 307 is integrated with the semiconductor chip 303, the lead frame 302, and the heat sink 306.
[0095]
As the heat sink 306, for example, an aluminum plate, a copper plate, or the like can be used, and it is particularly preferable to use one provided with heat radiation fins. The surface of the heat sink 306 is preferably subjected to a roughening process in advance in the same manner as the roughening process of the lead frame surface described above. The degree of roughening of the heat sink is the same as that of the lead frame. By such roughening of the heat sink, the same effect as the roughening of the lead frame can be obtained.
[0096]
Moreover, the temperature at the time of heat-pressing should just be more than the curing temperature of the thermosetting resin which comprises the insulator paste 305, and is normally 130-260 degreeC, Preferably you may be 170-230 degreeC. The pressure is usually 19.6 MPa or less, preferably 2.94 to 14.7 MPa.
[0097]
Next, the release carrier 301 is peeled from the lead frame 302 and the insulator layer 307 (FIG. 4E). At this time, the adhesive applied to the release carrier 301 is removed from the lead frame 302 together with the release carrier 301.
[0098]
Furthermore, a power module is manufactured by mounting the surface-mounted electronic component 308 at a desired location on the surface of the lead frame 302 from which the release carrier 301 has been removed (FIG. 4F). The mounting method of the surface mount electronic component 308 is not particularly limited. For example, after the solder is formed on the electrode surface of the surface mount electronic component 308, the surface mount electronic component 308 is mounted on the lead frame 302. In this state, the solder can be reflowed. In this case, as the solder, it is preferable to use lead-less solder because cracks are hardly generated in the soldered portion. Also, as a solder formation method, a method of forming a solder resist, a method of printing cream solder, or the like can be employed.
[0099]
In the case of manufacturing the power module as shown in FIG. 2 by the above manufacturing method, after connecting the surface electrode of the semiconductor chip and the lead frame through the metal bump in the step of FIG. The back electrode of the chip and the lead frame are connected via internal leads. Then, what is necessary is just to implement the process of FIG.4 (c).
[0100]
Further, when the power module as shown in FIG. 3 is manufactured by the above manufacturing method, in the process of FIG. 4A, the circuit board is not overlapped with the lead frame on the adhesive-coated surface of the release carrier. In the process of FIG. 4C, an insulating paste may be applied so as to cover the circuit board.
[0101]
Moreover, in the said manufacturing method, although the printing process for insulator layer formation and the hardening process of an insulator layer were implemented separately, this can also be performed continuously as a series of processes.
[0102]
The power module according to the present invention can also be manufactured by the method described below. FIGS. 5A to 5F are process cross-sectional views for explaining another example of the method for manufacturing the power module shown in FIG.
[0103]
First, the lead frame 402 is formed on the surface of the release carrier 401 (FIG. 5A), and the semiconductor chip 403 is mounted at a predetermined position of the lead frame 402 (FIG. 5B). The above steps can be performed in the same manner as in FIGS.
[0104]
Next, an insulator sheet 405 is aligned and laminated on the surface of the lead frame 402 on which the semiconductor chip 403 is mounted, thereby forming an uncured insulator layer (FIG. 5C).
[0105]
The insulator sheet 405 is flexible in an uncured state. This insulator sheet 405 is prepared by mixing a suitable solvent with an insulating material containing an inorganic filler and a thermosetting resin composition to prepare a slurry, and forming this slurry on the surface of a release carrier for film formation. The solvent can be produced by drying. The film forming method is not particularly limited, and a doctor blade method, a coater method, an extrusion molding method and the like can be adopted. Moreover, although the viscosity of a slurry is not specifically limited, For example, when employ | adopting a doctor blade method, about 5-100 Pa.s is suitable. The drying temperature is not lower than the boiling point of the solvent and not higher than the curing temperature of the thermosetting resin, and usually 70 to 100 ° C. is appropriate.
[0106]
As the insulating material, the same insulating material as that described in the description of the step of FIG. 4C can be used. Moreover, as a solvent, it is preferable to use a thing with a boiling point of 100 degrees C or less, such as methyl ethyl ketone, for example. Further, when the insulating material has a viscosity suitable for film formation and the sheet after drying the solvent has flexibility, it is not necessary to add a solvent.
[0107]
Next, after laminating the heat sink 406 on the insulator sheet 405, the thermosetting resin constituting the insulator sheet 405 is cured by heating and pressing to form an insulator layer 407 (FIG. 5D). This step can be performed in substantially the same manner as the step of FIG. However, the pressure when heating and pressurizing is preferably 19.6 MPa or less, more preferably 2.94 to 14.7 MPa. Thereby, the insulator layer 407 is bonded to and integrated with the semiconductor chip 403, the lead frame 402, and the heat sink 406.
[0108]
Thereafter, in the same manner as in the steps of FIGS. 4E and 4F, the release carrier 401 is peeled off and the surface-mounted electronic component 408 is mounted to produce a power module (FIG. 5E and FIG. 5). (F)).
[0109]
In the case of manufacturing the power module as shown in FIG. 2 by the above manufacturing method, after connecting the surface electrode of the semiconductor chip and the lead frame through the metal bump in the step of FIG. The back electrode of the chip and the lead frame are connected via internal leads. Then, what is necessary is just to implement the process of FIG.5 (c).
[0110]
Further, when the power module as shown in FIG. 3 is manufactured by the above manufacturing method, in the process of FIG. 5A, the circuit is provided so as not to overlap the lead frame on the adhesive-coated surface of the release carrier 401. A board | substrate is arrange | positioned and what is necessary is just to laminate | stack an insulator sheet so that a circuit board may also be coat | covered in the process of FIG.5 (c).
[0111]
【Example】
Example 1
A power module having the same structure as that of FIG. 1 was produced in the following manner. First, a 50 μm-thick polyphenylene sulfide (PPS) film was used as a release carrier, and a rubber adhesive was applied to the surface thereof to a thickness of 10 μm. A 250 μm-thick copper foil was bonded to the adhesive-coated surface of the release carrier by a roll laminating method. Furthermore, after laminating a dry film on the surface of the copper foil, the dry film was exposed through a mask on which a wiring pattern was formed, and developed so as to remove the dry film other than the exposed portion. Subsequently, it was immersed in a ferric chloride solution to remove unnecessary portions of the copper foil, and the dry film was further removed with caustic soda to form a lead frame.
[0112]
Next, a semiconductor chip was flip-chip mounted on the lead frame. As the semiconductor chip, an IGBT having a current specification of 50A (manufactured by Matsushita Electronics Co., Ltd.) was used. A bump having a diameter of 100 μm and a height of 40 μm was formed on the electrode of the semiconductor chip by a gold plating method, and eutectic solder was printed on the bump. The semiconductor chip was placed on the lead frame, and the eutectic solder was melted by a solder reflow apparatus in a state where the semiconductor chip was fixed, so that the electrode of the semiconductor chip and the lead frame were electrically connected.
[0113]
Next, an insulator paste was printed on a release carrier having a lead frame and a semiconductor chip to form an insulator layer. As the insulator paste, a resin composition having the following composition was kneaded with three rolls and the viscosity was adjusted to 100 Pa · s (25 ° C.).
(1) Inorganic filler: Al ₂ O _Three (Showa Denko “AS-40” (trade name), spherical, average particle size 12 μm) 90 parts by weight
(2) Thermosetting resin composition: epoxy resin composition (“WE-3025 (trade name)” manufactured by Nippon Pernox Co., Ltd., epoxy resin 50% by weight, curing agent (acid anhydride) 45% by weight, and curing accelerator ( Imidazole) 5% by weight.) 9.5 parts by weight
(3) Additive: 0.3 parts by weight of carbon black (manufactured by Toyo Carbon Co., Ltd.), 0.2 parts by weight of dispersant (“Plysurf F-208F (trade name)” manufactured by Daiichi Kogyo Seiyaku Co., Ltd.)
For printing, a lead frame is set on a printing stage, a SUS metal mask (0.7 mm thickness) having an opening of a desired printing portion is stacked up to a position in contact with the lead frame, and an insulating paste is dropped on the metal mask. This was carried out by imprinting into the mask opening with a SUS board squeegee. Further, after removing the metal mask, heat treatment was performed in vacuum to remove voids in the insulator layer, and the thermosetting resin constituting the insulator layer was uncured and had no tackiness.
[0114]
Next, an aluminum plate (1.0 mm thickness) is laminated on the insulator layer as a heat sink, and heated and pressurized for 30 minutes under the conditions of a temperature of 175 ° C. and a pressure of 4.9 MPa to cure the thermosetting resin in the insulator layer. In addition, the insulator layer, the semiconductor chip, the lead frame, and the heat sink were integrated. The thickness of the insulator layer after heating and pressing was 0.63 mm. Thereafter, the release carrier was peeled off to obtain a power module.
[0115]
When the thermal conductivity of the obtained power module was evaluated, a thermal resistance value of 0.8 ° C./W was obtained. The thermal resistance value was calculated from the measured value by supplying a current to the semiconductor chip to generate heat and measuring the temperature of the back surface of the heat sink.
[0116]
Further, as a reliability evaluation, a reflow test was performed at a maximum temperature of 260 ° C. for 10 seconds. At this time, it was confirmed that there was no abnormality such as generation of a gap at the interface between the insulator layer and the lead frame and the interface between the insulator layer and the semiconductor chip, and that strong adhesion was obtained.
[0117]
(Example 2)
Insulator pastes having the respective compositions shown in Table 1 were printed on a PPS film (75 μm thick) and dried, and then another PPS film was laminated and cured by hot pressing to produce a plate-like insulator.
[0118]
[Table 1]

[0119]
Here, as an epoxy resin composition, bisphenol F type epoxy resin (manufactured by Yuka Shell Epoxy Co., Ltd.) 90% by weight, and an amine adduct (“MY-H (trade name)” manufactured by Ajinomoto Co.) as a curing agent 3% by weight A composition containing 7% by weight of imidazole was used as a curing accelerator.
[0120]
Al ₂ O _Three For example, “AS-40 (trade name)” manufactured by Showa Denko KK ₂ As the MgO and BN, reagents manufactured by Kanto Chemical Co., Inc. were used. Carbon black manufactured by Toyo Carbon Co., Ltd. as the colorant, “Plisurf, F-208F (trade name)” manufactured by Daiichi Kogyo Seiyaku Co., Ltd. as the dispersant, and Ajinomoto Co., Ltd., which is the titanate coupling agent. “Plenact (trade name)” manufactured by the company was used.
[0121]
About the produced plate-shaped insulator, an elasticity modulus, a thermal expansion coefficient, and thermal conductivity were measured. The measuring method is as follows.
[0122]
Elastic modulus: Measured according to the method described in JIS C 6481.
[0123]
Coefficient of thermal expansion: The test piece (5 mm × 5 mm, thickness 1.0 mm) was heated at a rate of 5 ° C./min with a thermal analyzer to measure the amount of thermal expansion in the thickness direction. It converted into the value per 1 degreeC and this was represented by the part per million with respect to the dimension of the test piece in 0 degreeC. The measurement was performed at a temperature of 40 to 100 ° C., and an average value in the above temperature range was obtained as a thermal expansion coefficient.
[0124]
Thermal conductivity: The surface of the test piece (5 mm × 5 mm, thickness 1.0 mm) was brought into contact with a heater, and the back surface of the test piece was fixed to a radiation fin cooled to room temperature. In this state, the surface of the test piece was heated with a constant power, the temperature difference between the front and back surfaces of the test piece was measured, and the thermal resistance value was calculated as the temperature difference per power. Further, the thermal conductivity was calculated by taking the reciprocal of the thermal resistance value.
[0125]
In addition, 10 types of power modules were produced in the same manner as in Example 1 except that the insulator pastes having the respective compositions shown in Table 1 were used. About the produced power module, after performing the heat cycle test, the withstand voltage was measured. The heat cycle test was performed by repeating the operation of holding the power module for 30 minutes under a low temperature condition of −55 ° C. and then holding the power module for 30 minutes under a high temperature condition of 125 ° C. 1000 times.
[0126]
Table 2 shows the measurement results.
[0127]
[Table 2]

[0128]
As shown in Table 2, when containing 70 to 95 parts by weight of an inorganic filler and 5 to 30 parts by weight of a thermosetting resin composition (sample numbers 2 to 10), the thermal conductivity is excellent and the elastic modulus is It was confirmed that an insulator having a high thermal expansion coefficient comparable to that of a semiconductor could be obtained. Moreover, it has confirmed that the power module using such an insulator layer has favorable heat cycle reliability.
[0129]
(Example 3)
A power module having the structure shown in FIG. 1 was produced in the following manner. First, in the same manner as in Example 1, a lead frame was formed on a release carrier, and a semiconductor chip was flip-chip mounted on the lead frame.
[0130]
Next, a methyl ethyl ketone solvent was added to a resin composition having the following composition, and the mixture was rotated and mixed at a speed of 500 rpm for 48 hours in a pot containing alumina balls to prepare a slurry. The amount of methyl ethyl ketone solvent added was such that the viscosity of the slurry could be adjusted to about 20 Pa · s.
(1) Inorganic filler: 85 parts by weight of AlN (manufactured by Dow Chemical Co., average particle size 12 μm)
(2) Thermosetting resin composition: 14 parts by weight of cyanate resin composition (manufactured by Asahi Ciba, “AroCyM-30 (trade name)”)
(3) Additive: 0.3 parts by weight of carbon black (manufactured by Toyo Carbon Co., Ltd.), 0.2 parts by weight of dispersant (“Plysurf F-208F (trade name)” manufactured by Daiichi Kogyo Seiyaku Co., Ltd.)
Next, a 75 μm-thick polyethylene terephthalate (PET) film was prepared as a film-forming release carrier, and the slurry was placed on the film-forming release carrier with a gap (blade and film-forming release carrier by the doctor blade method). Was formed at a distance of about 1.4 mm. Next, the film-forming sheet was left at a temperature of 100 ° C. for 1 hour to dry the methyl ethyl ketone solvent in the film-forming sheet. Subsequently, the release carrier for film formation was peeled off to obtain a flexible insulator sheet (750 μm thick).
[0131]
Next, a lead frame on which a semiconductor chip was mounted, an insulator sheet, and an aluminum plate as a heat sink were laminated. This laminate was heated and pressurized for 1 hour under the conditions of a temperature of 260 ° C. and a pressure of 9.8 MPa to cure the thermosetting resin of the insulator sheet, and the insulator layer, semiconductor chip, lead frame and heat sink were integrated. . Thereafter, the release carrier was peeled off to obtain a power module.
[0132]
When the thermal conductivity of the obtained power module was evaluated, a thermal resistance value of 0.75 ° C./W was obtained. Further, when the withstand voltage was measured, a withstand voltage of 10 KV / mm or more was obtained.
[0133]
Example 4
A power module having the same structure as that of FIG. 2 was produced in the following manner. First, a copper foil having a thickness of 70 μm was used as a release carrier, and a copper plating layer having a thickness of 250 μm was formed on the surface thereof by an electrolytic copper plating method. After adhering the dry film to the copper plating layer surface of the release carrier, the dry film was exposed through a mask on which a wiring pattern was formed, and developed so as to remove the dry film other than the exposed portion. Next, it was immersed in a ferric chloride solution to remove the copper plating layer by etching. Further, the dry film was removed with caustic soda to form a lead frame wiring pattern with the copper plating layer on the release carrier.
[0134]
Next, a semiconductor chip was flip-chip mounted on the lead frame. As the semiconductor chip, an IGBT having a current specification of 50A (manufactured by Matsushita Electronics Co., Ltd.) was used. A bump having a diameter of 100 μm and a height of 40 μm was formed on the surface electrode of the semiconductor chip by a gold plating method, and eutectic solder was printed on the bump. The semiconductor chip was placed on the lead frame such that the surface electrode was directed to the lead frame side. The eutectic solder was melted by a solder reflow apparatus with the semiconductor chip fixed, and the surface electrode of the semiconductor chip and the lead frame were electrically connected.
[0135]
Subsequently, the back electrode of the semiconductor chip and the lead frame were connected via internal leads. The internal lead was produced by punching a copper plate and forming a 1 μm thick gold plating layer on the surface. This internal lead was bonded to the back electrode of the semiconductor chip and the lead frame by an ultrasonic bonding apparatus.
[0136]
Next, an insulator paste was printed on a release carrier having a lead frame and a semiconductor chip to form an insulator layer. As the insulator paste, the same paste as in Example 1 was used. Next, an aluminum plate (1.0 mm thickness) is laminated on the insulator layer as a heat sink, and heated and pressurized for 30 minutes under the conditions of a temperature of 175 ° C. and a pressure of 4.9 MPa to cure the thermosetting resin in the insulator layer. In addition, the insulator layer, the semiconductor chip, the lead frame, and the heat sink were integrated. Thereafter, the release carrier was peeled off to obtain a power module. In the obtained power module, the internal leads were embedded in the insulator layer, and deformation due to hardening of the insulator layer was not recognized.
[0137]
When the thermal conductivity of the obtained power module was evaluated, a thermal resistance value of 0.75 ° C./W was obtained. Further, as a reliability evaluation, a reflow test was performed at a maximum temperature of 260 ° C. for 10 seconds. At this time, there is no abnormality such as a gap at the interface between the insulator layer and the lead frame, the interface between the insulator layer and the semiconductor chip, and the interface between the insulator layer and the internal lead, and a strong adhesion is observed. It was confirmed that it was obtained.
[0138]
【The invention's effect】
As described above, according to the power module of the present invention, the insulator layer containing the inorganic filler and the thermosetting resin composition, the lead formed on the surface of the insulator layer, and the insulation of the lead At least one semiconductor chip mounted on the body layer side surface, and a heat sink formed on the back surface of the insulator layer, the semiconductor chip is mounted on the lead by flip chip bonding, and Since it is sealed in the insulator layer, it is possible to provide a power module that is excellent in heat dissipation efficiency and capable of high-density mounting.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an example of a power module of the present invention.
FIG. 2 is a cross-sectional view showing another example of the power module of the present invention.
FIG. 3 is a cross-sectional view showing another example of the power module of the present invention.
FIG. 4 is a sectional view by process showing an example of a method for manufacturing a power module of the present invention.
FIG. 5 is a cross-sectional view for each process showing another example of the method for manufacturing the power module of the present invention.
[Explanation of symbols]
101, 111, 201 Semiconductor chip
102, 112, 202 leads
103, 113, 203 Bump
104, 114, 204 Insulator layer
105, 115, 205 heat sink
106, 116, 206 Surface-mount type electronic components
117 Internal lead
207 Circuit board
301, 401 Release carrier
302, 402 Lead frame
303, 403 semiconductor chip
304, 404 Bump
305, 405 Uncured insulator layer
306, 406 heat sink
307, 407 Hardened insulator layer
308, 408 Surface mount electronic components

Claims (21)

An insulator layer containing an inorganic filler and a thermosetting resin composition; a lead formed on a surface of the insulator layer; and at least one semiconductor chip mounted on a surface of the lead on the insulator layer side; A heat sink formed on the back surface of the insulator layer, wherein the semiconductor chip is mounted on the lead by flip chip bonding, and is sealed in the insulator layer, and further includes a wiring A power module in which a circuit board formed by laminating a layer and a substrate layer is embedded in the insulator layer with at least one of the wiring layers exposed on the surface of the insulator layer .   The semiconductor chip has a first electrode formed on the lead side surface and a second electrode formed on the heat sink side surface, and the first electrode is formed by flip chip bonding. 2. The power module according to claim 1, wherein the power module is connected to the lead, and the second electrode is connected to the lead through an internal lead disposed in the insulator layer.   The power module according to claim 1 or 2, wherein in the insulator layer, the proportion of the inorganic filler is 70 to 95 wt%, and the proportion of the thermosetting resin composition is 5 to 30 wt%.   The power module according to claim 1, wherein an electronic component is mounted on a surface of the lead opposite to the surface on which the semiconductor chip is mounted.   5. The power module according to claim 1, wherein the lead is embedded in the insulator layer with at least a part thereof exposed on the surface of the insulator layer. 6. The thermosetting resin composition contains a thermosetting resin, a curing agent and a curing accelerator, the ratio of the thermosetting resin is 50 to 95% by weight, and the ratio of the curing agent is 4.9 to 45% by weight. %, And the ratio of a hardening accelerator is 0.1 to 5 weight%, The power module in any one of Claims 1-5 . The thermosetting resin composition contains an epoxy resin, a novolac resin, and imidazole, the proportion of the epoxy resin is 60 to 80% by weight, and the proportion of the novolac resin is 18 to 39.9% by weight. the power module according to any one of claims 1 to 6 ratio of the imidazole is 0.1 to 2 wt%. Power module according to any of the inorganic _{filler, Al 2 O 3, SiO 2} , MgO, claim 1-7 is at least one selected from the group consisting of BN and AlN. The average particle diameter of the inorganic filler, a power module according to any one of claims 1-8 is in the range of 0.1 to 100 [mu] m. The power module according to any one of claims 1 to 9 , wherein a surface of the heat sink on the insulator layer side is roughened. A step of forming a lead on a release carrier, a step of mounting a semiconductor chip on the lead by flip chip bonding, and an uncured state containing an inorganic filler and a thermosetting resin composition on the release carrier Forming the insulator layer so as to cover the leads and the semiconductor chip, laminating a heat sink on the uncured insulator layer to form a laminate, and heating the laminate The step of curing the insulator layer, and the step of peeling the release carrier ,
After forming the leads on the release carrier, a circuit board formed by laminating a wiring layer and a substrate layer is disposed on the release carrier, and the insulator layer covers the circuit board. A method for manufacturing a power module, comprising: forming a power module. The method for producing a power module according to claim 11 , wherein the step of forming the insulator layer is a step of applying a paste containing the inorganic filler and the thermosetting resin composition on the release carrier. The power module manufacturing method according to claim 11 or 12 , wherein the application of the paste is performed by screen printing or metal mask printing. The step of forming the insulator layer is a step of laminating a sheet containing the inorganic filler and the thermosetting resin composition and having flexibility in an uncured state on the release carrier. The manufacturing method of the power module of Claim 11 . Formed on the release carrier during the step of forming the insulator layer or after the step of forming the insulator layer and before the step of curing the insulator layer. method of manufacturing a power module according to any one of claims 11 to 14, exposing the formations in vacuum. The method for manufacturing a power module according to any one of claims 11 to 15 , further comprising a step of mounting an electronic component on a surface opposite to the insulator layer side of the lead after the step of peeling the release carrier. . Wherein before the step of forming an insulator layer, on the surface in contact with the insulating layer of the lead, nickel, tin, solder and at least one selected from gold claims 11 to 16 for forming a metal plating layer The manufacturing method of the power module in any one. The method for manufacturing a power module according to any one of claims 11 to 17 , wherein a surface of the lead in contact with the insulator layer is roughened before the step of forming the insulator layer. Wherein before the step of laminating the heat sink on the insulator layer, the method for manufacturing power module according to any one of claims 11 to 18 for roughening the surface in contact with the insulator layer of the heat sink. The method for manufacturing a power module according to any one of claims 11 to 19 , wherein the release carrier is at least one organic film selected from the group consisting of polyphenylene oxide, polyimide, polyethylene, polyethylene terephthalate, and aramid. The method for manufacturing a power module according to any one of claims 11 to 19 , wherein the release carrier is at least one metal foil selected from the group consisting of a copper foil, a nickel foil, and an aluminum foil.

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