JP3820674B2 - Resin-sealed electronic device and manufacturing method thereof - Google Patents

Resin-sealed electronic device and manufacturing method thereof Download PDF

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JP3820674B2
JP3820674B2 JP10340197A JP10340197A JP3820674B2 JP 3820674 B2 JP3820674 B2 JP 3820674B2 JP 10340197 A JP10340197 A JP 10340197A JP 10340197 A JP10340197 A JP 10340197A JP 3820674 B2 JP3820674 B2 JP 3820674B2
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sealing resin
resin
stress
coating film
electronic device
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JPH10294404A (en
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昌弘 山本
太一 谷方
将 愛知後
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Denso Corp
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Denso Corp
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2224/00—Indexing scheme for arrangements for connecting or disconnecting semiconductor or solid-state bodies and methods related thereto as covered by H01L24/00
    • H01L2224/01—Means for bonding being attached to, or being formed on, the surface to be connected, e.g. chip-to-package, die-attach, "first-level" interconnects; Manufacturing methods related thereto
    • H01L2224/26—Layer connectors, e.g. plate connectors, solder or adhesive layers; Manufacturing methods related thereto
    • H01L2224/31—Structure, shape, material or disposition of the layer connectors after the connecting process
    • H01L2224/32—Structure, shape, material or disposition of the layer connectors after the connecting process of an individual layer connector
    • H01L2224/321—Disposition
    • H01L2224/32151—Disposition the layer connector connecting between a semiconductor or solid-state body and an item not being a semiconductor or solid-state body, e.g. chip-to-substrate, chip-to-passive
    • H01L2224/32221—Disposition the layer connector connecting between a semiconductor or solid-state body and an item not being a semiconductor or solid-state body, e.g. chip-to-substrate, chip-to-passive the body and the item being stacked
    • H01L2224/32245—Disposition the layer connector connecting between a semiconductor or solid-state body and an item not being a semiconductor or solid-state body, e.g. chip-to-substrate, chip-to-passive the body and the item being stacked the item being metallic
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2224/00—Indexing scheme for arrangements for connecting or disconnecting semiconductor or solid-state bodies and methods related thereto as covered by H01L24/00
    • H01L2224/01—Means for bonding being attached to, or being formed on, the surface to be connected, e.g. chip-to-package, die-attach, "first-level" interconnects; Manufacturing methods related thereto
    • H01L2224/42—Wire connectors; Manufacturing methods related thereto
    • H01L2224/47—Structure, shape, material or disposition of the wire connectors after the connecting process
    • H01L2224/48—Structure, shape, material or disposition of the wire connectors after the connecting process of an individual wire connector
    • H01L2224/481—Disposition
    • H01L2224/48151—Connecting between a semiconductor or solid-state body and an item not being a semiconductor or solid-state body, e.g. chip-to-substrate, chip-to-passive
    • H01L2224/48221—Connecting between a semiconductor or solid-state body and an item not being a semiconductor or solid-state body, e.g. chip-to-substrate, chip-to-passive the body and the item being stacked
    • H01L2224/48245—Connecting between a semiconductor or solid-state body and an item not being a semiconductor or solid-state body, e.g. chip-to-substrate, chip-to-passive the body and the item being stacked the item being metallic
    • H01L2224/48247—Connecting between a semiconductor or solid-state body and an item not being a semiconductor or solid-state body, e.g. chip-to-substrate, chip-to-passive the body and the item being stacked the item being metallic connecting the wire to a bond pad of the item
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2224/00—Indexing scheme for arrangements for connecting or disconnecting semiconductor or solid-state bodies and methods related thereto as covered by H01L24/00
    • H01L2224/73—Means for bonding being of different types provided for in two or more of groups H01L2224/10, H01L2224/18, H01L2224/26, H01L2224/34, H01L2224/42, H01L2224/50, H01L2224/63, H01L2224/71
    • H01L2224/732—Location after the connecting process
    • H01L2224/73251—Location after the connecting process on different surfaces
    • H01L2224/73265—Layer and wire connectors
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L24/00—Arrangements for connecting or disconnecting semiconductor or solid-state bodies; Methods or apparatus related thereto
    • H01L24/73—Means for bonding being of different types provided for in two or more of groups H01L24/10, H01L24/18, H01L24/26, H01L24/34, H01L24/42, H01L24/50, H01L24/63, H01L24/71
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
    • H01L2924/10—Details of semiconductor or other solid state devices to be connected
    • H01L2924/102—Material of the semiconductor or solid state bodies
    • H01L2924/1025—Semiconducting materials
    • H01L2924/10251—Elemental semiconductors, i.e. Group IV
    • H01L2924/10253—Silicon [Si]

Abstract

PROBLEM TO BE SOLVED: To provide a highly reliable resin sealed type electronic device by relieving the stresses applied between a primary sealing resin and a secondary sealing resin. SOLUTION: An IC package body 5 is constituted in such a way that a silicon chip 2 is mounted on a lead frame 1 and electrically connected to a lead frame 1a through a bonding wire 3. In addition, the wire 3 and chip 2 are molded with a primary sealing resin 4. Then the lead frame and chip 2 are molded with a secondary sealing resin 8. Between the primary and secondary sealing resins 4 and 8, a stress relaxing coating film 9 is arranged. Since the film 9 is made of rubber 10 containing scattered bubbles 11, the film 9 relaxes the stresses caused by the resins 4 and 8.

Description

【０００１】
【発明の属する技術分野】
この発明は、樹脂封止型電子装置及びその製造方法に関するものである。
【０００２】
【従来の技術】
図１０に示すように、シリコンチップ等の電子部品４１をリードフレーム４０の上に搭載し、電子部品４１を一次封止樹脂４２にてモールドしてＩＣパッケージ体４３とするとともに、このＩＣパッケージ体４３をエポキシ等の二次封止樹脂４４にてモールドすることが行われている。つまり、ＩＣパッケージ体４３を更に二次成形（トランスファー成形、ポッティング成形）することが行われている。
【０００３】
この樹脂封止型電子装置においては、硬化収縮応力あるいは硬化後の熱応力により電子部品４１が過大な応力を受け、その機能が低下するおそれがある。つまり、図１０に示すように、ＩＣパッケージ体４３が二次封止樹脂４４にて覆われている状態から図１１に示すように高温になったり図１２に示すように低温になった場合を考える。一次封止樹脂４２の熱膨張率をαM とし二次封止樹脂４４の熱膨張率をαE としたときαE ＞αM を満足する場合、図１１の如く高温になると、二次封止樹脂４４はＩＣパッケージ体４３から離れる方向に膨張する。また、図１２の如く低温になると、二次封止樹脂４４はＩＣパッケージ体４３を圧迫する方向に収縮する。このように、温度変化によりＩＣパッケージ体４３に応力が加わることになる。
【０００４】
そこで、応力緩和のために、エポキシ等の二次封止樹脂自身の低応力化を図ったり、二次封止樹脂のボリュームを減らすといった構造的工夫が行われているが、製品のフレキシビリティ、その他の部位の信頼性確保といった点から限界があった。
【０００５】
一方、２つの部材間に生じる応力を低減する一手法として２つの部材間にゴムを挟み込むことが一般的に行われている。
この手法を樹脂封止型電子装置において用いようとすると、一次封止樹脂４２と二次封止樹脂４４との間にゴムを介在させることとなり、この場合、本来ゴムは非圧縮性物質（ポアソン比がほぼ０．５）のため、ＩＣパッケージ体４３を二次封止樹脂４４で完全に覆う樹脂封止型電子装置においては、変形空隙のない構造であるので、応力緩和の効果が現れない。即ち、二次封止樹脂４４はその硬化時に収縮力を発生するとともに硬化後の冷熱サイクルを受けた時に多大な応力を発生するが、ゴム材において外部からの応力を分散させる効果があるのはゴムが変形しうる空隙が確保されている場合に限られている。
【０００６】
【発明が解決しようとする課題】
そこで、この発明の目的は、一次封止樹脂と二次封止樹脂間に加わる応力を緩和して信頼性の高い樹脂封止型電子装置を提供することにある。
【０００７】
【課題を解決するための手段】
請求項１に記載の発明は、一次封止樹脂と二次封止樹脂との間に配置される応力緩衝用コーティング膜として、母材として弾性体（例えばゴム）を用いるとともに、この母材中に気体を封止した中空球フィラーを混入させることにより容積が変化する気泡を散在させたものを用いたことを特徴としている。
【０００８】
よって、温度変化等によって一次封止樹脂と二次封止樹脂との間に応力が加わった際に、応力緩衝用コーティング膜における母材である弾性体が変形して、散在した気泡の容積が変化する。この気泡の容積変化にて一次封止樹脂と二次封止樹脂との間の応力が吸収され、半導体チップ等の電子部品に加わる応力が緩和される。
【０００９】
つまり、温度変化等により一次と二次の封止樹脂の間に応力が加わった際において、応力緩衝用コーティング膜中の気泡が変形代（潰し代）になって応力緩和が図られる。また、請求項２に記載のように、前記中空球フィラーは、前記応力緩衝用コーティング膜の内側に存在する。
【００１０】
請求項３に記載の発明によれば、第１工程により、基材の上に配置された電子部品が一次封止樹脂にてモールドされる。そして、第２工程により、一次封止樹脂の表面が、母材としての弾性体中に気体を封止した中空球フィラーを混入させることにより容積が変化する気泡を散在させた応力緩衝用コーティング膜にてコーティングされる。さらに、第３工程により、前記応力緩衝用コーティング膜の外周側において前記基材および電子部品が二次封止樹脂にてモールドされる。
【００１１】
その結果、請求項１に記載の樹脂封止型電子装置が製造される。
ここで、請求項４に記載のように、前記第２工程において、液状弾性素材に中空球フィラーを混入させた溶液を、前記一次封止樹脂の表面にコーティングすると、実用上好ましいものになる。
【００１２】
【発明の実施の形態】
以下、この発明を具体化した実施の形態を図面に従って説明する。
図１には、本実施形態における樹脂封止型電子装置の断面図を示す。本装置は、ガソリンエンジンの点火コイルおよび点火回路を樹脂モールドしたものである。
【００１３】
図１において、基材としてのリードフレーム１の上には電子部品としてのシリコンチップ２が搭載され、ボンディグワイヤ３にてシリコンチップ２とリードフレーム１ａとが電気的に接続されている。このボンディグワイヤ３とシリコンチップ２とは一次封止樹脂４にてモールドされている。このようしてＩＣパッケージ体（モールド体）５が構成されている。
【００１４】
なお、シリコンチップ２以外にも、アルミナ基板を用いた回路基板（プリント基板）をリードフレーム１上に搭載したパッケージ体に具体化してもよい。
一方、樹脂封止型電子装置の筐体（ハウジング）６の内部における下部には点火コイル７が配置されるとともに、同じく筐体６の内部における点火コイル７の上方には前述のＩＣパッケージ体５が配置されている。筐体６の内部には二次封止樹脂８が充填され、点火コイル７および前述のＩＣパッケージ体５が二次封止樹脂８にてモールドされている。二次封止樹脂８には注型エポキシ樹脂を用いている。この注型エポキシにおいては、硬化収縮応力や硬化後の熱応力によりＩＣパッケージ体５が過大な応力を受け、その機能が低下するおそれがある。これについては図１０〜図１２を用いて説明したのでここでは説明は省略するが、要は図１１の如く高温になると、二次封止樹脂８はＩＣパッケージ体５から離れる方向に膨張し、図１２の如く低温になると、二次封止樹脂８はＩＣパッケージ体５を圧迫する方向に収縮する。このように、温度変化によりＩＣパッケージ体５に応力が加わることになる。
【００１５】
そこで、図１に示すように、一次封止樹脂４と二次封止樹脂８との間には、両封止樹脂間に加わる応力を緩和するための応力緩衝用コーティング膜９が配置されている。応力緩衝用コーティング膜９は、図２に示すように、母材として弾性体、本実施形態ではゴム１０を用いるとともに、この母材中に気泡１１を散在させたものを用いている。応力緩衝用コーティング膜９の膜厚は、０．５ｍｍ程度である。
【００１６】
この応力緩衝用コーティング膜９は、図１０〜図１２において緩衝領域となり、ＩＣパッケージ体５の熱的変形および二次封止樹脂８の熱的変形に伴いその体積が変化する。
【００１７】
つまり、各部の熱的変形は拘束のない場合には定変位量だけ変形することから、例えば緩衝領域が全くその変形に拘束を与えないなら、一次封止樹脂４と二次封止樹脂８との熱膨張率の不整合による熱応力は発生しない。これを満足させる緩和層としては体積変化できることが必要となる。
【００１８】
即ち、図３に示すように、応力緩衝用コーティング膜９が無い場合には、特性線Ｐ１にて示す如くＩＣパッケージ体５には歪み量δに比例した力Ｆが加わるが、応力緩衝用コーティング膜９を設けることにより気泡１１が潰れ代となり、特性線Ｐ２にて示す如く所定の歪み量δ１までは殆ど力ＦがＩＣパッケージ体５に加わらない。
【００１９】
また、図１に示すように、リードフレーム１ａは筐体６を貫通するリード端子１２に接続され、リード端子１２にて外部からの接続が行われるようになっている。また、リードフレーム１は点火コイル７のリード端子７ａと接続されている。そして、リード端子１２を介してシリコンチップ２に形成された回路にバッテリ電圧が供給され、所定の点火タイミングにて点火コイル７により高電圧を生成して点火プラグに高電圧を供給するようになっている。
【００２０】
次に、製造方法を説明する。
図４に示すように、リードフレーム１の上にシリコンチップ２を搭載し、ワイヤ３にてシリコンチップ２とリードフレーム１ａとをボンディングする。そして、ボンディグワイヤ３とシリコンチップ２とを一次封止樹脂４にてモールドして、ＩＣパッケージ体５とする。
【００２１】
引き続き、図５に示すように、ＩＣパッケージ体５を応力緩衝用コーティング膜９にて被覆する。応力緩衝用コーティング膜９によるコーティグ処理は、図６に示す３つの工程よりなる。
【００２２】
まず、液状弾性素材である液状シリコーン樹脂を用意するとともに、図７に示す中空球フィラー（カプセル）２０を用意する。中空球フィラー２０は、その径Ｄが８０μｍ程度の微粒体である。液状シリコーン樹脂としては、例えば、東レ社製ＣＹ５２ー２２７を用い、また、中空球フィラー２０としては、例えば、日本フィライト社製ＤＵ−８０を用いる。そして、液状シリコーン樹脂と適量の中空球フィラー２０とを混合させる。ここで、液状シリコーン樹脂に対する中空球フィラー２０の混合比は、４０ｖｏｌ％程度とする。
【００２３】
そして、液状シリコーン樹脂に中空球フィラー２０を混入させた溶液中にＩＣパッケージ体５をディッピングして一次封止樹脂４の表面にコーティングする（図６に示す塗膜工程）。引き続き、１５０℃、２０分間の加熱にて硬化させる（図６に示す熱硬化工程）。その結果、液状シリコーン樹脂に中空球フィラー２０が分散した状態のまま固化される。なお、応力緩衝用コーティング膜９においてゴム１０中に気泡１１が散在することは応力緩衝用コーティング膜９の断面写真により確認している。
【００２４】
このように中空球フィラー２０を液状樹脂に混合させ塗膜することにより下記のような効果を奏する。
（１）中空球フィラー２０の添加量を調整することにより、応力緩衝用コーティング膜９中の気泡１１の総量を調整でき、適切な応力緩和が可能となる。
【００２５】
このように、中空球フィラー２０の含有率、粒径を選択することにより、目的とする塗膜の体積変化率を設定でき、材料混合により応力緩和効果を容易にコントロールできる。
（２）液状樹脂を用いた塗膜であるため（例えばディッピング法により塗膜するため）、ＩＣパッケージ体５のリード端子１ａの部分等も完全にコーティングすることができる。つまり、ディッピング法ではなく図８に示すように弾性を有するキャップ材３０にてＩＣパッケージ体５を覆う場合には、ＩＣパッケージ体５のリード端子１ａの部分はキャップ材３０にて覆いにくい部分となるが、ディッピング法を用いればリード端子１ａの部分も完全に覆うことができる。このことは、その後の二次成形時液状樹脂ポッティングを例えば真空注入する場合、コーティング膜９の内部に樹脂が浸入することなく緩衝効果が確保できる。
【００２６】
このように、塗膜される構造物は、必要部位を塗膜形成することができる。
（３）液状樹脂を用いた塗膜であるため（例えばディッピング法により塗膜するため）、角部を有するＩＣパッケージ体５においてもその角部になだらかな曲面をもたせて成形できる。このことから、応力集中が緩和でき、二次ポッティング材のクラック発生を抑制することができる。
【００２７】
このように、塗膜される構造物は、その形状によらなず塗膜形成することができる。
（４）塗膜中の気泡１１は単独で存在するため、後工程での例えばエポキシ含浸等の工程においても気泡１１が埋まることはない。
【００２８】
なお、ディップ材は特に液状シリコーン樹脂である必要はなく、液状柔エポキシ剤（例えば、セメンダイン社製ＥＰー００１）でもよい。このようにすると、二次ポッティング材がエポキシの場合、共材のためその化学的密着性が確保でき、熱伝導及び応力分散の観点から更に優れたものとなる。
【００２９】
製造工程の説明に戻り、ＩＣパッケージ体５を応力緩衝用コーティング膜９にてコーティングした後において、図１に示すように、筐体６内に点火コイル７を装着するとともに、ＩＣパッケージ体５を配置する。さらに、液状のエポキシ樹脂８を筐体６内に充填して硬化（固化）させる。
【００３０】
なお、応力緩衝用コーティング膜９のコーティングはディップ以外にもスプレー、キャスティング、リキッドインジェクションモールド等にて行ってもよい。次に、図９を用いてエポキシ樹脂８の硬化収縮応力の低減効果について説明する。
【００３１】
まず、図９（ａ）に示すように、応力緩衝用コーティング膜９のない場合には、ＩＣパッケージ体５において受ける応力により発生する表面歪εは、−２００μｓである。ここで、表面歪εとは、単位長さの材料が２０℃から１５０℃に温度変化した際の材料の長さの変化量を指す。即ち、２０℃において長さＬであったものが１５０℃において長さＬ’に変化した場合においては、
ε＝（Ｌ−Ｌ’）／Ｌ
にて定義されるものである。
【００３２】
また、図９（ｂ）に示すように、中空球フィラーを含有しないシリコーンゴム３５を厚さ０．５ｍｍ塗膜した場合には、上記表面歪εは、−１２０μｓとなる。
【００３３】
さらに、図９（ｃ）に示すように、中空球フィラーを含有したシリコーンゴム（コーティング膜９）を厚さ０．５ｍｍ塗膜した場合には、上記表面歪εは、０〜−１０μｓとなる。
【００３４】
このように、通常上記液状シリコーン樹脂を硬化してなる硬化物は、ゴム弾性を示すが、その機械的性質は非弾性変形、非圧縮性変形をもつことになるが、応力緩和層としてのゴム弾性体は体積変化が求められるが、その非圧縮性により応力緩和性が十分発揮できないが、気泡１１を散在することにより応力を緩和することができようになる。つまり、シリコーンゴム等の非圧縮性物質を緩衝層として使用するに際し、気体を封止した中空球フィラー２０を混入させることにより、そのゴム弾性を残しつつ、緩衝層として圧縮性をもたせることにより応力緩和層として優れたものとなる。
【００３５】
このように本実施の形態は、下記の特徴を有する。
（イ）一次封止樹脂４と二次封止樹脂８との間に配置される応力緩衝用コーティング膜９として、母材としてゴム１０を用いるとともに、この母材中に気泡１１を散在させたものを用いたので、温度変化等によって一次封止樹脂４と二次封止樹脂８との間に応力が加わった際に、応力緩衝用コーティング膜９における母材であるゴム１０が変形して、散在した気泡１１の容積が変化する。この気泡１１の容積変化にて一次封止樹脂４と二次封止樹脂８の間の応力が吸収され、シリコンチップ２に加わる応力が緩和される。つまり、温度変化等により一次と二次の封止樹脂４，８との間に応力が加わった際において、応力緩衝用コーティング膜９中の気泡１１が変形代（潰し代）になって応力緩和が図られる。
（ロ）リードフレーム１の上に配置されたシリコンチップ２を一次封止樹脂４にてモールドし、一次封止樹脂４の表面を、母材としてのゴム１０中に気泡１１を散在させた応力緩衝用コーティング膜９にてコーティングし、さらに、応力緩衝用コーティング膜９の外周側においてリードフレーム１およびシリコンチップ２を二次封止樹脂８にてモールドするようにした。その結果、上記（イ）の樹脂封止型電子装置が得られる。
（ハ）応力緩衝用コーティング膜９の成膜工程として、液状弾性素材に中空球フィラー２０を混入させた溶液を、一次封止樹脂４の表面にコーティングすると、前述したように実用上好ましいものになる。
【００３６】
なお、封止樹脂の硬化は加熱を用いたが、紫外線照射等の手法により行ってもよい。
【図面の簡単な説明】
【図１】 実施の形態における樹脂封止型電子装置の断面図。
【図２】 応力緩衝用コーティング膜の断面図。
【図３】 歪み量と力との関係を示す図。
【図４】 樹脂封止型電子装置の製造工程を説明するための断面図。
【図５】 樹脂封止型電子装置の製造工程を説明するための断面図。
【図６】 樹脂封止型電子装置の製造工程を説明するための工程図。
【図７】 中空球フィラーの断面図。
【図８】 比較のための樹脂封止型電子装置の断面図。
【図９】 封止樹脂により加わる応力を説明するための断面図。
【図１０】 封止樹脂により加わる応力を説明するための断面図。
【図１１】 封止樹脂により加わる応力を説明するための断面図。
【図１２】 封止樹脂により加わる応力を説明するための断面図。
【符号の説明】
１…リードフレーム、２…シリコンチップ、４…一次封止樹脂、８…二次封止樹脂、９…応力緩衝用コーティング膜、１０…ゴム、１１…気泡[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a resin-sealed electronic device and a method for manufacturing the same.
[0002]
[Prior art]
As shown in FIG. 10, an electronic component 41 such as a silicon chip is mounted on a lead frame 40, and the electronic component 41 is molded with a primary sealing resin 42 to form an IC package body 43. This IC package body 43 is molded with a secondary sealing resin 44 such as epoxy. That is, the IC package 43 is further subjected to secondary molding (transfer molding or potting molding).
[0003]
In this resin-encapsulated electronic device, the electronic component 41 may be subjected to excessive stress due to curing shrinkage stress or thermal stress after curing, and the function thereof may be degraded. That is, as shown in FIG. 10, when the IC package body 43 is covered with the secondary sealing resin 44, the temperature becomes high as shown in FIG. 11 or low as shown in FIG. Think. When αE> αM is satisfied when the thermal expansion coefficient of the primary sealing resin 42 is αM and the thermal expansion coefficient of the secondary sealing resin 44 is αE, when the temperature becomes high as shown in FIG. It expands in a direction away from the IC package body 43. Further, when the temperature becomes low as shown in FIG. 12, the secondary sealing resin 44 contracts in a direction in which the IC package body 43 is pressed. In this way, stress is applied to the IC package body 43 due to temperature changes.
[0004]
Therefore, in order to relieve stress, structural contrivances such as reducing the stress of the secondary sealing resin itself such as epoxy and reducing the volume of the secondary sealing resin have been performed, but the flexibility of the product, There was a limit in terms of ensuring the reliability of other parts.
[0005]
On the other hand, as a technique for reducing stress generated between two members, it is generally performed to sandwich rubber between the two members.
If this method is used in a resin-sealed electronic device, rubber is interposed between the primary sealing resin 42 and the secondary sealing resin 44. In this case, the rubber is originally an incompressible substance (Poisson). In the resin-encapsulated electronic device that completely covers the IC package body 43 with the secondary encapsulating resin 44, since the structure has no deformation gap, the effect of stress relaxation does not appear. . That is, the secondary sealing resin 44 generates a shrinkage force when it is cured and generates a great amount of stress when it is subjected to a cooling cycle after curing, but the rubber material has an effect of dispersing the external stress. This is limited to the case where a void that can deform the rubber is secured.
[0006]
[Problems to be solved by the invention]
SUMMARY OF THE INVENTION An object of the present invention is to provide a highly reliable resin-encapsulated electronic device by relieving stress applied between a primary sealing resin and a secondary sealing resin.
[0007]
[Means for Solving the Problems]
The invention according to claim 1 uses an elastic body (for example, rubber) as a base material as a stress buffer coating film disposed between the primary sealing resin and the secondary sealing resin, and in the base material. A hollow sphere filler sealed with a gas is mixed with air bubbles that change in volume .
[0008]
Therefore, when a stress is applied between the primary sealing resin and the secondary sealing resin due to a temperature change or the like, the elastic body, which is a base material in the stress buffer coating film, is deformed, and the volume of scattered bubbles is reduced. Change. Due to the volume change of the bubbles, the stress between the primary sealing resin and the secondary sealing resin is absorbed, and the stress applied to the electronic component such as a semiconductor chip is relieved.
[0009]
That is, when a stress is applied between the primary and secondary sealing resins due to a temperature change or the like, the bubbles in the stress buffer coating film become a deformation allowance (squeeze allowance), and stress relaxation is achieved. According to a second aspect of the present invention, the hollow sphere filler is present inside the stress buffer coating film.
[0010]
According to invention of Claim 3 , the electronic component arrange | positioned on a base material is molded by primary sealing resin by a 1st process. Then, in the second step, the surface of the primary sealing resin has a coating film for stress buffering, in which air bubbles whose volume changes are scattered by mixing a hollow sphere filler in which gas is sealed in an elastic body as a base material It is coated with. Further, in the third step, the base material and the electronic component are molded with a secondary sealing resin on the outer peripheral side of the stress buffer coating film.
[0011]
As a result, the resin-sealed electronic device according to claim 1 is manufactured.
Here, as described in claim 4 , it is practically preferable to coat the surface of the primary sealing resin with a solution in which a hollow sphere filler is mixed in a liquid elastic material in the second step.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a cross-sectional view of a resin-encapsulated electronic device according to this embodiment. In this apparatus, an ignition coil and an ignition circuit of a gasoline engine are resin-molded.
[0013]
In FIG. 1, a silicon chip 2 as an electronic component is mounted on a lead frame 1 as a base material, and the silicon chip 2 and the lead frame 1 a are electrically connected by a bonding wire 3. The bonding wire 3 and the silicon chip 2 are molded with a primary sealing resin 4. In this way, an IC package body (mold body) 5 is configured.
[0014]
In addition to the silicon chip 2, a circuit board (printed board) using an alumina substrate may be embodied in a package body mounted on the lead frame 1.
On the other hand, an ignition coil 7 is disposed in the lower part of the housing (housing) 6 of the resin-encapsulated electronic device, and the IC package 5 is also disposed above the ignition coil 7 in the housing 6. Is arranged. The casing 6 is filled with a secondary sealing resin 8, and the ignition coil 7 and the IC package 5 described above are molded with the secondary sealing resin 8. A cast epoxy resin is used for the secondary sealing resin 8. In this cast epoxy, the IC package 5 is subjected to excessive stress due to curing shrinkage stress or thermal stress after curing, and its function may be reduced. Since this has been described with reference to FIGS. 10 to 12, the description thereof is omitted here. In short, when the temperature becomes high as shown in FIG. 11, the secondary sealing resin 8 expands away from the IC package body 5. When the temperature becomes low as shown in FIG. 12, the secondary sealing resin 8 contracts in the direction of pressing the IC package body 5. In this way, stress is applied to the IC package body 5 due to temperature changes.
[0015]
Therefore, as shown in FIG. 1, a stress buffer coating film 9 is disposed between the primary sealing resin 4 and the secondary sealing resin 8 to relieve stress applied between the two sealing resins. Yes. As shown in FIG. 2, the stress buffer coating film 9 uses an elastic body as a base material, rubber 10 in this embodiment, and a material in which bubbles 11 are scattered in the base material. The film thickness of the stress buffer coating film 9 is about 0.5 mm.
[0016]
The stress buffer coating film 9 becomes a buffer region in FIGS. 10 to 12, and its volume changes with the thermal deformation of the IC package body 5 and the thermal deformation of the secondary sealing resin 8.
[0017]
That is, since the thermal deformation of each part is deformed by a constant displacement amount when there is no constraint, for example, if the buffer region does not constrain the deformation at all, the primary sealing resin 4 and the secondary sealing resin 8 Thermal stress due to the mismatch of the thermal expansion coefficient of each other does not occur. As a relaxation layer that satisfies this requirement, it is necessary that the volume can be changed.
[0018]
That is, as shown in FIG. 3, when there is no stress buffering coating film 9, a force F proportional to the strain amount δ is applied to the IC package 5 as indicated by the characteristic line P1, but the stress buffering coating is applied. By providing the film 9, the bubble 11 becomes a crushing margin, and almost no force F is applied to the IC package 5 up to a predetermined strain amount δ1 as shown by the characteristic line P2.
[0019]
As shown in FIG. 1, the lead frame 1 a is connected to a lead terminal 12 that penetrates the housing 6, and the lead terminal 12 is connected from the outside. The lead frame 1 is connected to a lead terminal 7 a of the ignition coil 7. Then, the battery voltage is supplied to the circuit formed on the silicon chip 2 via the lead terminal 12, and a high voltage is generated by the ignition coil 7 at a predetermined ignition timing to supply the high voltage to the spark plug. ing.
[0020]
Next, a manufacturing method will be described.
As shown in FIG. 4, the silicon chip 2 is mounted on the lead frame 1, and the silicon chip 2 and the lead frame 1 a are bonded by the wire 3. Then, the bonding wire 3 and the silicon chip 2 are molded with the primary sealing resin 4 to form an IC package body 5.
[0021]
Subsequently, as shown in FIG. 5, the IC package body 5 is covered with a stress buffer coating film 9. The coating process using the stress buffer coating film 9 includes three steps shown in FIG.
[0022]
First, a liquid silicone resin, which is a liquid elastic material, is prepared, and a hollow sphere filler (capsule) 20 shown in FIG. 7 is prepared. The hollow sphere filler 20 is a fine particle having a diameter D of about 80 μm. As the liquid silicone resin, for example, CY52-227 manufactured by Toray Industries, Inc. is used. As the hollow sphere filler 20, for example, DU-80 manufactured by Nippon Philite Co., Ltd. is used. Then, the liquid silicone resin and an appropriate amount of the hollow sphere filler 20 are mixed. Here, the mixing ratio of the hollow sphere filler 20 to the liquid silicone resin is about 40 vol%.
[0023]
Then, the IC package body 5 is dipped in a solution in which the hollow sphere filler 20 is mixed in a liquid silicone resin to coat the surface of the primary sealing resin 4 (coating process shown in FIG. 6). Subsequently, it is cured by heating at 150 ° C. for 20 minutes (thermosetting step shown in FIG. 6). As a result, the hollow sphere filler 20 is solidified while being dispersed in the liquid silicone resin. It is confirmed from the cross-sectional photograph of the stress buffer coating film 9 that the bubbles 11 are scattered in the rubber 10 in the stress buffer coating film 9.
[0024]
Thus, the following effects are produced by mixing the hollow sphere filler 20 with the liquid resin and coating it.
(1) By adjusting the addition amount of the hollow sphere filler 20, the total amount of the bubbles 11 in the stress buffer coating film 9 can be adjusted, and appropriate stress relaxation becomes possible.
[0025]
Thus, the volume change rate of the target coating film can be set by selecting the content rate and particle size of the hollow sphere filler 20, and the stress relaxation effect can be easily controlled by mixing the materials.
(2) Since it is a coating film using a liquid resin (for example, coating by a dipping method), the lead terminal 1a portion of the IC package body 5 and the like can be completely coated. That is, when the IC package body 5 is covered with the cap material 30 having elasticity as shown in FIG. 8 instead of the dipping method, the lead terminal 1a portion of the IC package body 5 is difficult to cover with the cap material 30. However, if the dipping method is used, the portion of the lead terminal 1a can be completely covered. This means that when the liquid resin potting in the subsequent secondary molding is performed by, for example, vacuum injection, a buffering effect can be ensured without the resin entering the coating film 9.
[0026]
As described above, the structure to be coated can form a coating on a necessary portion.
(3) Since it is a coating film using a liquid resin (for example, for coating by a dipping method), the IC package 5 having a corner portion can be molded with a gentle curved surface at the corner portion. From this, the stress concentration can be relaxed, and the occurrence of cracks in the secondary potting material can be suppressed.
[0027]
Thus, the structure to be coated can form a coating regardless of its shape.
(4) Since the air bubbles 11 in the coating film exist alone, the air bubbles 11 are not buried in a subsequent process such as epoxy impregnation.
[0028]
Note that the dip material does not need to be a liquid silicone resin, and may be a liquid soft epoxy agent (for example, EP-001 manufactured by Cementine Co.). In this case, when the secondary potting material is epoxy, its chemical adhesion can be ensured because it is a co-material, which is further excellent from the viewpoint of heat conduction and stress distribution.
[0029]
Returning to the description of the manufacturing process, after the IC package body 5 is coated with the stress buffer coating film 9, as shown in FIG. 1, the ignition coil 7 is mounted in the housing 6, and the IC package body 5 is mounted. Deploy. Furthermore, the liquid epoxy resin 8 is filled in the housing 6 and cured (solidified).
[0030]
The stress buffer coating film 9 may be coated by spraying, casting, liquid injection molding, or the like in addition to dipping. Next, the effect of reducing the curing shrinkage stress of the epoxy resin 8 will be described with reference to FIG.
[0031]
First, as shown in FIG. 9A, in the case where the stress buffer coating film 9 is not provided, the surface strain ε generated by the stress received in the IC package 5 is −200 μs. Here, the surface strain ε refers to the amount of change in the length of the material when the material of the unit length changes in temperature from 20 ° C. to 150 ° C. That is, when the length L at 20 ° C. is changed to the length L ′ at 150 ° C.,
ε = (L−L ′) / L
As defined in.
[0032]
Further, as shown in FIG. 9B, when the silicone rubber 35 containing no hollow sphere filler is coated with a thickness of 0.5 mm, the surface strain ε is −120 μs.
[0033]
Furthermore, as shown in FIG. 9 (c), when a silicone rubber (coating film 9) containing a hollow sphere filler is applied to a thickness of 0.5 mm, the surface strain ε is 0 to −10 μs. .
[0034]
As described above, a cured product obtained by curing the above liquid silicone resin usually exhibits rubber elasticity, but its mechanical properties are inelastic deformation and incompressible deformation, but rubber as a stress relaxation layer. Although the elastic body is required to change in volume, the stress relaxation property cannot be sufficiently exhibited due to its incompressibility, but the stress can be relaxed by scattering the bubbles 11. That is, when an incompressible substance such as silicone rubber is used as a buffer layer, by mixing the hollow sphere filler 20 in which gas is sealed, the rubber elasticity remains and the compressive layer is made compressible. It becomes an excellent relaxation layer.
[0035]
Thus, the present embodiment has the following features.
(A) As the stress buffer coating film 9 disposed between the primary sealing resin 4 and the secondary sealing resin 8, rubber 10 is used as a base material, and bubbles 11 are scattered in the base material. Since a material is used, when a stress is applied between the primary sealing resin 4 and the secondary sealing resin 8 due to a temperature change or the like, the rubber 10 as a base material in the stress buffer coating film 9 is deformed. The volume of the scattered bubbles 11 changes. The stress between the primary sealing resin 4 and the secondary sealing resin 8 is absorbed by the volume change of the bubbles 11 and the stress applied to the silicon chip 2 is relaxed. That is, when stress is applied between the primary and secondary sealing resins 4 and 8 due to temperature change or the like, the bubbles 11 in the stress buffer coating film 9 become deformation allowance (squeeze allowance) to relieve stress. Is planned.
(B) Stress in which the silicon chip 2 disposed on the lead frame 1 is molded with the primary sealing resin 4 and the surface of the primary sealing resin 4 is dispersed with the bubbles 11 in the rubber 10 as the base material. Coating is performed with the buffer coating film 9, and the lead frame 1 and the silicon chip 2 are molded with the secondary sealing resin 8 on the outer peripheral side of the stress buffer coating film 9. As a result, the resin-sealed electronic device of (A) is obtained.
(C) As a film forming step of the stress buffer coating film 9, when the surface of the primary sealing resin 4 is coated with a solution in which the hollow sphere filler 20 is mixed in a liquid elastic material, as described above, a practically preferable one is obtained. Become.
[0036]
In addition, although hardening was used for hardening of sealing resin, you may carry out by methods, such as ultraviolet irradiation.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a resin-encapsulated electronic device according to an embodiment.
FIG. 2 is a cross-sectional view of a stress buffer coating film.
FIG. 3 is a diagram showing the relationship between strain and force.
FIG. 4 is a cross-sectional view for explaining a manufacturing process of a resin-encapsulated electronic device.
FIG. 5 is a cross-sectional view for explaining a manufacturing process of a resin-encapsulated electronic device.
FIG. 6 is a process diagram for explaining a manufacturing process of a resin-encapsulated electronic device.
FIG. 7 is a cross-sectional view of a hollow sphere filler.
FIG. 8 is a cross-sectional view of a resin-sealed electronic device for comparison.
FIG. 9 is a cross-sectional view for explaining the stress applied by the sealing resin.
FIG. 10 is a cross-sectional view for explaining stress applied by a sealing resin.
FIG. 11 is a cross-sectional view for explaining a stress applied by a sealing resin.
FIG. 12 is a cross-sectional view for explaining the stress applied by the sealing resin.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Lead frame, 2 ... Silicon chip, 4 ... Primary sealing resin, 8 ... Secondary sealing resin, 9 ... Stress-buffering coating film, 10 ... Rubber, 11 ... Air bubble

Claims (4)

基材の上に配置された電子部品をモールドする一次封止樹脂と、
前記一次封止樹脂によりモールドされた前記基材および電子部品をモールドする二次封止樹脂と、
前記一次封止樹脂と二次封止樹脂との間に配置され、両封止樹脂間に加わる応力を緩和するための応力緩衝用コーティング膜と、
を備えた樹脂封止型電子装置において、
前記応力緩衝用コーティング膜として、母材として弾性体を用いるとともに、この母材中に気体を封止した中空球フィラーを混入させることにより容積が変化する気泡を散在させたものを用いたことを特徴とする樹脂封止型電子装置。A primary sealing resin for molding an electronic component disposed on a substrate;
A secondary sealing resin for molding the base material and the electronic component molded by the primary sealing resin;
A stress buffering coating film that is disposed between the primary sealing resin and the secondary sealing resin, and relieves stress applied between the two sealing resins;
In a resin-encapsulated electronic device comprising:
As the stress buffer coating film, an elastic body is used as a base material, and a material in which bubbles whose volume is changed is mixed by mixing a hollow sphere filler sealed with gas in the base material is used. A resin-sealed electronic device. 前記中空球フィラーは、前記応力緩衝用コーティング膜の内側に存在する請求項１記載の樹脂封止型電子装置。The resin-encapsulated electronic device according to claim 1, wherein the hollow sphere filler is present inside the stress buffer coating film. 基材の上に配置された電子部品を一次封止樹脂にてモールドする第１工程と、A first step of molding an electronic component placed on a substrate with a primary sealing resin;
前記一次封止樹脂の表面を、母材としての弾性体中に気体を封止した中空球フィラーを混入させることにより容積が変化する気泡を散在させた応力緩衝用コーティング膜にてコーティングする第２工程と、The surface of the primary sealing resin is coated with a stress buffer coating film in which air bubbles whose volume changes are scattered by mixing a hollow sphere filler in which gas is sealed in an elastic body as a base material. Process,
前記応力緩衝用コーティング膜の外周側において前記基材および電子部品を二次封止樹脂にてモールドする第３工程と、A third step of molding the base material and the electronic component with a secondary sealing resin on the outer peripheral side of the stress buffer coating film;
を備えたことを特徴とする樹脂封止型電子装置の製造方法。A method for manufacturing a resin-encapsulated electronic device, comprising: 前記第２工程は、液状弾性素材に中空球フィラーを混入させた溶液を、前記一次封止樹脂の表面にコーティングするものである請求項３記載の樹脂封止型電子装置の製造方法。4. The method of manufacturing a resin-encapsulated electronic device according to claim 3, wherein the second step is to coat the surface of the primary sealing resin with a solution in which a hollow sphere filler is mixed with a liquid elastic material.
JP10340197A 1997-04-21 1997-04-21 Resin-sealed electronic device and manufacturing method thereof Expired - Lifetime JP3820674B2 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
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Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP10340197A JP3820674B2 (en) 1997-04-21 1997-04-21 Resin-sealed electronic device and manufacturing method thereof

Publications (2)

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JPH10294404A JPH10294404A (en) 1998-11-04
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JP5477301B2 (en) * 2011-01-06 2014-04-23 株式会社デンソー Semiconductor device
JP2014110249A (en) * 2012-11-30 2014-06-12 Shindengen Electric Mfg Co Ltd Structure for embedding semiconductor device, and method of embedding semiconductor device
JP6028592B2 (en) * 2013-01-25 2016-11-16 三菱電機株式会社 Semiconductor device
CN113977835A (en) * 2021-10-26 2022-01-28 海鹰企业集团有限责任公司 Ultrasonic transducer probe encapsulating method

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