JP3935090B2 - Wiring board - Google Patents

Wiring board Download PDF

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JP3935090B2
JP3935090B2 JP2003048346A JP2003048346A JP3935090B2 JP 3935090 B2 JP3935090 B2 JP 3935090B2 JP 2003048346 A JP2003048346 A JP 2003048346A JP 2003048346 A JP2003048346 A JP 2003048346A JP 3935090 B2 JP3935090 B2 JP 3935090B2
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conductive member
semiconductor element
insulating substrate
high thermal
wiring board
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JP2004288662A (en
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直樹 堀之内
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Kyocera Corp
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Kyocera 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
    • H01L2224/42—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
    • H01L2224/4805—Shape
    • H01L2224/4809—Loop shape
    • H01L2224/48091—Arched
    • 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
    • H01L2224/48225—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 non-metallic, e.g. insulating substrate with or without metallisation
    • H01L2224/48227—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 non-metallic, e.g. insulating substrate with or without metallisation 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
    • H01L2224/01—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
    • H01L2224/49—Structure, shape, material or disposition of the wire connectors after the connecting process of a plurality of wire connectors
    • H01L2224/491—Disposition
    • H01L2224/4912—Layout
    • H01L2224/49175—Parallel arrangements
    • 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
    • H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
    • H01L2924/15—Details of package parts other than the semiconductor or other solid state devices to be connected
    • H01L2924/151—Die mounting substrate
    • H01L2924/1517—Multilayer substrate
    • H01L2924/15172—Fan-out arrangement of the internal vias
    • H01L2924/15174—Fan-out arrangement of the internal vias in different layers of the multilayer substrate
    • 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
    • H01L2924/15—Details of package parts other than the semiconductor or other solid state devices to be connected
    • H01L2924/161—Cap
    • H01L2924/1615—Shape
    • H01L2924/16195—Flat cap [not enclosing an internal cavity]

Landscapes

  • Production Of Multi-Layered Print Wiring Board (AREA)

Description

【０００１】
【発明の属する技術分野】
本発明は、半導体素子等の電子部品を搭載するために用いられる配線基板に関し、特に、半導体素子から発生する熱を効率良く吸収し、外部に放散するための高熱伝導部材の熱の吸収性および高熱伝導部材と絶縁基板との接合信頼性を改善した配線基板に関するものである。
【０００２】
【従来の技術】
近年、半導体素子等の電子部品の高集積化・高速化に伴い、半導体素子等が動作した際に発生する熱量は増加する傾向にある。そして、この発生した熱が半導体素子等に蓄積されると、半導体素子等の回路の誤動作を発生させたり、さらには回路自身を破壊したりするという問題がある。そこで従来から、半導体素子等を搭載する配線基板には、半導体素子等から発生する熱を効率良く吸収し、外部に放散するための放熱板を設けるといった工夫がなされている。
【０００３】
このような放熱板は、一般に、銅やその他の金属から成る高熱伝導部材で形成されており、半導体素子等を搭載する配線基板の裏面または両面に面接合したり、あるいは半導体素子等を放熱板に直接搭載することによって、半導体素子等に発生した熱をこの放熱板に吸収させるとともに吸収した熱を外部に放散させることにより半導体素子等を熱から保護している。そして、このような配線基板における半導体素子等が発する熱の放熱構造においては、放熱板に半導体素子等を直接搭載した構造のものが特に放熱性に優れている。
【０００４】
放熱板に半導体素子等を直接搭載した従来の配線基板としては、例えば、図５に断面図で示すような構造が一般的である（例えば、特許文献１参照。）。
【０００５】
図５において、従来の配線基板107は、中央部に貫通穴102が形成され、ビアホール導体103ａと配線回路層103ｂとから成る配線導体103が配設された、複数の絶縁層101ａ〜101ｈから成る絶縁基板101の下側主面に、貫通穴102を塞ぐようにして、その上側主面に半導体素子104が接着剤109により接着されて搭載される板状の高熱伝導部材105が、ロウ材106を介して接合されて構成されている。
【０００６】
このような従来の配線基板107に使用される絶縁基板101としては、各種のセラミック材料または有機絶縁樹脂材料、あるいは無機絶縁物粉末を有機絶縁樹脂で結合したもの等が使用され、配線導体103にはタングステン・モリブデン等の高融点金属や銅・銀・金等の低抵抗金属が用いられている。
【０００７】
【特許文献１】
特開平６−296084号公報
【０００８】
【発明が解決しようとする課題】
しかしながら、上記のような従来の配線基板107においては、前述のように、絶縁基板101には各種のセラミック材料および有機絶縁樹脂材料あるいは無機絶縁物粉末を有機絶縁樹脂で結合したもの等が使用されるのに対して、高熱伝導部材105には熱伝導性が高い金属等が使用されるため、熱膨張係数が異なる異種の材料がロウ材106を介して接合されることとなる。
【０００９】
そして、高熱伝導部材105の上側主面と絶縁基板101の下側主面とが互いにロウ材106を介して接合される平行な面のみで接合される構造となっていることから、高熱伝導部材105に枠状の絶縁基板101をロウ材106により接合する際の加熱とその後の冷却過程において高熱伝導部材105と絶縁基板101では熱膨張ならびに熱収縮挙動が異なることから、例えば、高熱伝導部材105よりも絶縁基板101の熱膨張係数が大きい場合には、冷却時の熱収縮量が大きな絶縁基板101が、ロウ材106で接合されている面を力点として高熱伝導部材105を配線基板107の中心方向へ圧縮する応力を発生させるために、配線基板107全体が凹形に反ってしまうこととなる。
【００１０】
また、これとは反対に、高熱伝導部材105よりも絶縁基板101の熱膨張係数が小さい場合には、冷却時の熱収縮量の大きな高熱伝導部材105が、ロウ材106で接合されている面を力点として絶縁基板101を配線基板107の内側方向へ引っ張る応力を発生させるために、配線基板107全体が凸形に反ってしまうこととなる。
【００１１】
このような、絶縁基板101と高熱伝導部材105のロウ材106による接合時に、特に、冷却過程における熱収縮挙動の違いによって発生する配線基板107の反りは、絶縁基板101と高熱伝導部材105の接合界面であるロウ材106の内部や、高熱伝導部材105の上側主面とロウ材106との接合界面または絶縁基板101の下側主面とロウ材106との接合界面に大きな応力を集中させることとなり、ロウ材106が破壊したり、ロウ材106と高熱伝導部材105の上側主面または絶縁基板101の下側主面との接合界面が剥離したり、一般に高熱伝導部材105よりも延性が低い絶縁基板101の内部にロウ材106との接合界面の端部を起点としたクラック等が発生するという問題点があった。
【００１２】
また、配線基板107の反りにより、高熱伝導部材105も反るため、半導体素子104を高熱伝導部材105に接着して固定すると、熱伝導率の低い接着剤109の厚みが接着面全体で不均一でかつ厚くなることとなり、半導体素子104の動作時に発生する熱が厚みの厚い接着剤109により、高熱伝導部材105に伝わりにくくなるため、半導体素子104の熱の吸収・放散性が低下するという問題点があった。
【００１３】
また、接着剤109の種類としては、金−錫・半田・銀エポキシ樹脂等があるが、熱伝導率は、５〜150Ｗ／ｍ・Ｋの範囲であり、高熱伝導部材105の材料である銀や銅の380〜400Ｗ／ｍ・Ｋより小さく、このような低熱伝導率の接着剤109が半導体素子104と高熱伝導部材105との間の全面にあるため、半導体素子104の動作時に発生する熱が接着剤109によって高熱伝導部材105に伝わりにくくなり、半導体素子104の熱の吸収・放散性が低下するという問題点があった。
【００１４】
また、半導体素子104の動作時における発熱および冷却のサイクルにおいては、前述のような高熱伝導部材105と絶縁基板101との熱膨張係数の差に起因する熱応力が、高熱伝導部材105および絶縁基板101の接合界面に繰り返し、かつ、長期間作用することから、これによっても同様に、ロウ材106が破壊したり、ロウ材106と高熱伝導部材105の上側主面または絶縁基板101の下側主面との接合界面が剥離したり、一般に高熱伝導部材105よりも延性が低い絶縁基板101の内部にロウ材106との接合界面の端部を起点としたクラック等が徐々に発生し進行したりすることから、配線基板107における絶縁基板101と高熱伝導部材105との接合信頼性が低いという問題点があった。
【００１５】
そこで、以上のような高熱伝導部材105と絶縁基板101との熱膨張係数の差に起因する熱応力による接合信頼性の低下を防止するために、ロウ材106の接合状態を調整することによって熱応力を分散させたり、高熱伝導部材105と絶縁基板101との熱膨張係数の差を小さくするために、高熱伝導部材105および絶縁基板101の材料組成等を調整したりすることが種々試みられているが、近年の配線基板に要求されている機械的・電気的特性の多様化や、増加傾向にある半導体素子104の発熱量に十分対応できているとは言えないのが現状である。
【００１６】
さらに、上記のような従来の配線基板107においては、高熱伝導部材105が絶縁基板101から下方に突出しているため、高熱伝導部材105の側面と絶縁基板101下側主面で形成される段差部および絶縁基板101の貫通穴102の内面と高熱伝導部材105上側主面で形成される段差部に応力が集中しやすい構造となっており、配線基板107が落下する等の機械的衝撃が加わった際に、この機械的衝撃が高熱伝導部材105と絶縁基板101との間の段差部に集中して作用してしまうことから、ここを起点としたクラック等の破壊が絶縁基板101に発生しやすいという問題点もあった。
【００１７】
また、高熱伝導部材105が絶縁基板101から突出した構造の従来の配線基板107においては、小型・薄型化が困難であり設計的に大きな制約があるという問題点もあった。
【００１８】
本発明は、上記問題点を解決するために案出されたものであり、その目的は、高熱伝導部材と絶縁基板との熱膨張係数の差に起因する熱応力によって、ロウ材を用いた接合時に高熱伝導部材と絶縁基板との界面が破壊したり、半導体素子等の電子部品の動作時に絶縁基板にクラックが発生したりすることによる接合信頼性の低下や、機械的衝撃による高熱伝導部材と絶縁基板との界面の破壊等を防止し、高熱伝導部材と絶縁基板とを強固に接合するとともに、半導体素子が発生する熱を効率良く吸収・放散し、半導体素子を長期にわたり正常、かつ安定に作動させることができる信頼性の高い配線基板を提供することにある。
【００１９】
【課題を解決するための手段】
本発明の配線基板は、上下主面間を貫通する貫通穴を有するとともにこの貫通穴の周辺に配線導体が配設された絶縁基板に、上側主面の中央部に半導体素子が接着される、外周部に複数個の貫通孔が形成された板状の高熱伝導部材が、前記絶縁基板の前記上下主面と前記高熱伝導部材の上下主面とがそれぞれ同一面をなすように、前記貫通穴の内面と前記高熱伝導部材の側面との間にロウ材を介して接合されて成ることを特徴とするものである。
【００２０】
本発明の配線基板によれば、上側主面の中央部に半導体素子が接着される、外周部に複数個の貫通孔が形成された板状の高熱伝導部材が、絶縁基板の上下主面と高熱伝導部材の上下主面とがそれぞれ同一面をなすように、貫通穴の内面と高熱伝導部材の側面との間にロウ材を介して接合されていることから、高熱伝導部材と絶縁基板との熱膨張係数の差に起因する、ロウ材による接合時および半導体素子動作時の配線基板の熱収縮挙動は、高熱伝導部材の熱収縮と絶縁基板の熱収縮とが横方向（配線基板の主面に対して平行な方向）に並ぶ状態で発生するため、そのような熱収縮挙動によって配線基板には反りが発生しないものとすることができる。
【００２１】
また、配線基板が反らず、高熱伝導部材も反らないため、半導体素子を高熱伝導部材に接着して固定しても、熱伝導率の低い接着剤の厚みは接着面全体で均一で薄いものとすることができるため、半導体素子の動作時に発生する熱が薄い接着剤を経由して高熱伝導部材に伝わりやすく、接着剤の厚みが不均一で厚い場合に比較して、半導体素子の熱の吸収・放散性を高くすることができる。
【００２２】
また、発生した熱応力は、絶縁基板の上下主面と高熱伝導部材の上下主面とがそれぞれ同一面となっており、両者の間に部分的に応力が集中する箇所が存在しないことから、絶縁基板の貫通穴の内面および高熱伝導部材配線基板の側面に分散され、かつ、両者の間を接合しているロウ材が応力緩和層としても機能するため、効率良く減衰させることができる。
【００２３】
さらに、高熱伝導部材は、上側主面の外周部である半導体素子が接着される部位の外周の外側の領域、つまり、半導体素子の接着部である中央部とロウ材の接合部との間の部位に複数個の貫通孔が形成されていることから、高熱伝導部材と絶縁基板との熱膨張係数の差に起因する、ロウ材による接合時および半導体素子動作時にロウ材接合部に発生する引っ張りおよび圧縮の熱応力は、複数個の貫通孔に分散させることができるため、効率よく減衰させて、配線基板に反りが発生しないものとすることができる。
【００２４】
従って、ロウ材による接合時に高熱伝導部材と絶縁基板との界面が破壊したり、半導体素子等の電子部品の動作時に絶縁基板にクラックが発生したりすることによる絶縁基板と高熱伝導部材との接合信頼性の低下等を効果的に抑制することができる。
【００２５】
また、絶縁基板の上下主面と高熱伝導部材の上下主面とがそれぞれ同一面をなすように絶縁基板の貫通穴の内面と高熱伝導部材の側面とがロウ材を介して接合されていることから、配線基板に落下等により機械的衝撃が加わった場合においても、従来の配線基板のように、応力が集中しやすい高熱伝導部材の側面と絶縁基板の下側主面とで形成される段差部および絶縁基板の貫通穴の内面と高熱伝導部材の上側主面とで形成される段差部が存在しないので、絶縁基板の破壊の起点となる部位が無く機械的衝撃に強いものとすることができる。そして、高熱伝導性部材が配線基板の内部に収納される構造となるため、容易に小型化・薄型化を図ることが可能となる。
【００２６】
また、高熱伝導部材の前記上側主面の前記中央部に前記半導体素子の面積よりも小さい面積の、前記半導体素子の下面に上面が当接する凸部が形成されている場合には、半導体素子が接着剤により接着されて固定されていても、その接着剤から露出した凸部の上面が半導体素子の下面に当接していることから、半導体素子から発生した熱が高熱伝導部材の凸部に直接伝わるため、半導体素子が動作する際に発生する熱を熱伝導率の低い接着剤に阻害されることなく高熱伝導部材に伝えることができ、半導体素子から発生した熱を高熱伝導部材が効率よく吸収し放散することができる。
【００２７】
また、高熱伝導部材が四角形状であり、前記貫通孔が前記外周部の角部に形成されている場合には、角部に発生する局所的な引っ張りおよび圧縮の最大熱応力は、それら四角形状の高熱伝導部材の外周部の角部に形成された複数個の貫通孔に分散するため、極めて効率良く減衰させることができ、さらに確実に配線基板に反りが発生しないものとすることができる。
【００２８】
さらに、凸部が複数形成されている場合には、半導体素子が複数の凸部上に設置されることとなり、硬化後の接着剤の厚みが凸部の厚みよりも低くなるので、凸部が半導体素子に圧縮応力を加えるような場合においても、圧縮応力が複数の凸部に分散されるため、半導体素子への局所的な圧縮応力を低減することができ、半導体素子の動作信頼性をより高いものとすることができる。
【００２９】
【発明の実施の形態】
次に、本発明の配線基板を添付図面に基づき詳細に説明する。
【００３０】
図１は、本発明の配線基板を半導体素子を収容する半導体素子収納用パッケージに適用した場合の実施の形態の一例を示す断面図である。また、図２は、図１に示す本発明の配線基板の実施の形態の一例の平面図である。
【００３１】
これらの図において、本発明の配線基板７は、中央部に上下主面間を貫通する貫通穴２が形成され、ビアホール導体３ａと配線回路層３ｂとから成る配線導体３が配設された、複数の絶縁層１ａ〜１ｄから成る絶縁基板１の下側主面に、貫通穴２を塞ぐようにして、その上側主面の中央部に半導体素子４が接着され、その半導体素子４の接着部である中央部の外側の領域である外周部に複数個の貫通孔８が形成された板状の高熱伝導部材５が、ロウ材６を介して接合されて構成されている。
【００３２】
絶縁基板１は、酸化アルミニウム質焼結体・窒化アルミニウム質焼結体・ムライト質焼結体・炭化珪素質焼結体・ガラスセラミックス焼結体等のセラミックスやエポキシ樹脂等の電気絶縁材料から成り、例えば、ガラスセラミックス焼結体から成る場合には、ガラス粉末・フィラー粉末（セラミック粉末）・有機バインダ・可塑剤・有機溶剤等を混練したガラスセラミックグリーンシートを単層で、または複数積層し、焼焼することで作製される。
【００３３】
ガラス粉末としては、例えばＳｉＯ２−Ｂ２Ｏ３系・ＳｉＯ２−Ｂ２Ｏ３−Ａｌ２Ｏ３系・ＳｉＯ２−Ｂ２Ｏ３−Ａｌ２Ｏ３−ＭＯ系（但し、ＭはＣａ，Ｓｒ，Ｍｇ，ＢａまたはＺｎを示す）・ＳｉＯ２−Ａｌ２Ｏ３−Ｍ１Ｏ−Ｍ２Ｏ系（但し、Ｍ１およびＭ２は同一または異なってＣａ，Ｓｒ，Ｍｇ，ＢａまたはＺｎを示す）・ＳｉＯ２−Ｂ２Ｏ３−Ａｌ２Ｏ３−Ｍ１Ｏ−Ｍ２Ｏ系（但し、Ｍ１およびＭ２は前記と同じである）・ＳｉＯ２−Ｂ２Ｏ３−Ｍ３ ２Ｏ系（但し、Ｍ３はＬｉ，ＮａまたはＫを示す）・ＳｉＯ２−Ｂ２Ｏ３−Ａｌ２Ｏ３−Ｍ３ ２Ｏ系（但し、Ｍ３は前記と同じである）・Ｐｂ系ガラス・Ｂｉ系ガラス等が挙げられる。
【００３４】
また、フィラー粉末としては、例えばＡｌ２Ｏ３，ＳｉＯ２，ＺｒＯ２とアルカリ土類金属酸化物との複合酸化物・ＴｉＯ２とアルカリ土類金属酸化物との複合酸化物・Ａｌ２Ｏ３およびＳｉＯ２から選ばれる少なくとも１種を含む複合酸化物（例えばスピネル，ムライト，コージェライト）等が挙げられる。
【００３５】
これらガラスとフィラーとの混合割合は質量比で40：60〜99：１であるのが好ましい。
【００３６】
また、有機バインダとしては、従来からセラミックグリーンシートに使用されているものが使用可能であり、例えばアクリル系（アクリル酸，メタクリル酸またはそれらのエステルの単独重合体または共重合体、具体的にはアクリル酸エステル共重合体，メタクリル酸エステル共重合体，アクリル酸エステル−メタクリル酸エステル共重合体等）・ポリビニルブチラール系・ポリビニルアルコール系・アクリル−スチレン系・ポリプロピレンカーボネート系・セルロース系等の単独重合体または共重合体が挙げられる。
【００３７】
ガラスセラミックグリーンシートは、上記ガラス粉末・フィラー粉末・有機バインダに必要に応じて所定量の可塑剤・溶剤（有機溶剤，水等）を添加してスラリーを得て、これをドクターブレード・圧延・カレンダーロール・金型プレス等により厚さ約50〜500μｍに成形することにより得られる。
【００３８】
このようにして得られたガラスセラミックグリーンシートにビアホール導体３ａや貫通穴２を作製するため打ち抜き加工を行ない、切断して適当な形状の絶縁層１ａ〜１ｄを作製する。
【００３９】
なお、絶縁層１ａ〜１ｄがガラスセラミックスから成る場合は、例えば、銅・銀・金・銀−パラジウム等の銀系合金等の金属粉末に適当な有機バインダや溶剤を添加し混練して作製した金属ペーストをスクリーン印刷法等により所定パターンに埋め込むとともに印刷することにより、ビアホール導体３ａおよび配線回路層３ｂを形成する。
【００４０】
配線導体３が埋め込まれ印刷された絶縁層１ａ〜１ｄを複数枚積層した後、有機成分の除去および焼成を行なう。有機成分の除去は、例えば100〜500℃の温度範囲でこの積層体を加熱することにより行ない、有機成分を分解し揮散させる。また、焼成温度はガラスセラミックスの組成により異なるが、通常は800〜1000℃の範囲内であり、配線導体３および絶縁層１ａ〜１ｄが焼結することにより、貫通穴２を有するとともに貫通穴２の周辺にビアホール導体３ａと配線回路層３ｂとから成る配線導体３が配設された絶縁層１ａ〜１ｄから成る絶縁基板１が得られる。
【００４１】
高熱伝導部材５は、半導体素子４が接着される部位の外周の外側の領域の部位、つまり、半導体素子４の接着部の外周とロウ材６接合部との間の領域の中央に、円形状または楕円形状の、その半導体素子４の接着部の外周とロウ材６の接合部との間隔の半分程度の大きさの孔径を有する複数個の貫通孔８を打ち抜き加工により作製することによって、複数個の貫通孔８が形成された板状の部材として得られる。
【００４２】
貫通孔８は、多角形状であると、ロウ材の接合時や半導体素子４の発熱時に貫通孔８に分散した応力が高熱伝導部材５の角部に集中し、高熱伝導部材５が劣化しやすくなるため、角部の無い円または楕円の形状であることが好ましい。
【００４３】
また、貫通孔８が、ロウ材６の接合部や半導体素子４の接着部の外周の近辺に位置すると、貫通孔８に分散した応力がロウ材６の接合部や半導体素子４の接着部の外周に影響し、接合強度および接着強度を低下させるため、貫通孔８はロウ材６の接合部と半導体素子４の接着部の外周との間の領域の中央に位置することが好ましい。
【００４４】
また、貫通孔８の孔径が、ロウ材６の接合部と半導体素子４の接着部の外周との間隔とほぼ同じ大きさであると、貫通孔８に分散した応力がロウ材６の接合部や半導体素子４の接着部の外周に影響を与え、接合強度および接着強度を低下させることがある。逆に、ロウ材６の接合部と半導体素子４の接着部の外周との間隔に比較して非常に小さい大きさであると、貫通孔８に分散する応力が小さくなり、十分な応力の分散効果が得られないこととなる。従って、貫通孔８の孔径は、ロウ材６の接合部と半導体素子４の接着部の外周との間隔の半分程度の大きさであることが好ましい。
【００４５】
さらに、高熱伝導部材５が四角形状である場合には、ロウ材６による接合時や半導体素子４の発熱時にロウ材６の接合部の角部に最大の熱応力が発生するため、貫通孔８は、この発生した最大の熱応力を分散させるために、上記の条件に加え、高熱伝導部材５の角部に形成することが好ましい。
【００４６】
次に、絶縁基板１の貫通穴２に絶縁基板１の上下主面と高熱伝導部材５の上下主面がそれぞれ同一面をなすように高熱伝導部材５を埋設した後、ロウ材６を絶縁基板１の貫通穴２の内面と高熱伝導部材５の側面との間に充填して600〜800℃で加熱することによりロウ材６が溶融し、その後、冷却することによってロウ材６が固化し、これによって絶縁基板１と高熱伝導部材５とがロウ材６を介して接合される。
【００４７】
ここで、絶縁基板１の上下主面と、外周部に複数個の貫通孔８が形成された板状の高熱伝導部材５の上下主面とがそれぞれ同一面をなすように、絶縁基板１の貫通穴２の内面と高熱伝導部材５の側面との間にロウ材６を介して接合することが重要である。
【００４８】
絶縁基板１の上下主面と高熱伝導部材５の上下主面とがそれぞれ同一面をなすため、ロウ材６による接合時および半導体素子４の動作時において、高熱伝導部材５と絶縁基板１との熱膨張係数の差に起因して発生する引っ張りおよび圧縮応力は、高熱伝導部材５の側面と絶縁基板１の貫通穴２の内面の接合面において、局所的な偏りがない均等な応力分布をもつため、配線基板７には反りが発生せず、また、両者の間を接合しているロウ材６が応力緩和層として機能するため、高熱伝導部材５と絶縁基板１との熱膨張係数の差に起因して発生する引っ張りおよび圧縮応力を効率良く減衰させることができる。さらに、発生した引っ張りおよび圧縮応力は、高熱伝導部材５に形成された貫通孔８に分散するため、ロウ材６の接合面での引っ張りおよび圧縮応力をより一層低減させることができる。また、高熱伝導部材５が四角形状であり、貫通孔８が外周部の角部に形成されている場合には、貫通孔８が外周部の角部に形成されていることから、角部に発生する局所的な引っ張りおよび圧縮の最大の熱応力は、これら角部に形成された複数個の貫通孔８に分散するため、効率よく減衰させることができる。
【００４９】
また、配線基板７に落下等により機械的衝撃が加わった場合においても、従来の配線基板のように、応力が集中しやすい高熱伝導部材５の側面と絶縁基板１の下側主面とで形成される段差部および絶縁基板１の貫通穴２の内面と高熱伝導部材５の上側主面とで形成される段差部が存在しないことから、絶縁基板１の破壊の起点となる部位が無く機械的衝撃に強いものとすることができる。
【００５０】
なお、このように絶縁基板１の上下主面と高熱伝導部材５の上下主面とがそれぞれ同一面をなすようにする場合、その上側主面同士および下側主面同士は、高熱伝導部材５の側面と絶縁基板１の貫通穴２の内面との接合面において、局所的な偏りがない均等な応力分布をもたせるため、可能な限り同一平面をなすようにしておくことが好ましいが、絶縁基板１と高熱伝導部材５の厚みが各々の加工精度により寸法誤差が生じた場合でも、そのことにより、絶縁基板１と高熱伝導部材５の接合信頼性が著しく低下するようなことはない。
【００５１】
貫通穴２は、板状の高熱伝導部材５を絶縁基板１の内部に収容し、絶縁基板１の上下主面と高熱伝導部材５の上下主面とがそれぞれ同一面をなすように、絶縁基板１の貫通穴２の内面と高熱伝導部材５の側面との間をロウ材６を介して接合するために形成される。従って、貫通穴２は高熱伝導部材５と同形状となっており、さらに、その内面と高熱伝導部材５との間に適量のロウ材６を充填できる程度の間隔が開けられるような開口寸法を有している。
【００５２】
一方、高熱伝導部材５は、半導体素子４を直接搭載し半導体素子４が発生する熱を効率良く吸収し、外部に放散する機能を有する。このような高熱伝導部材５には、銅・銀・アルミニウム・ニッケル・ベリリウム・マグネシウム・銅−タングステン合金・銅−モリブデン合金等の熱伝導性に優れた金属や合金が使用され、例えば、銅−タングステン合金から成る場合には、タングステンの粉末を約98ＭＰａの圧力で加圧成形するとともにこれを還元雰囲気中にて約2000℃の温度で焼成して多孔質のタングステン焼結体を得た後に、約900℃の温度で加熱溶融させた銅をタングステン焼結体の多孔質部分に毛管現象を利用し含浸させることにより作製できる。
【００５３】
なお、高熱伝導部材５の材質は、絶縁基板１の材質に応じて種々選択することが可能であるが、特に、高周波用配線基板として絶縁基板１にガラスセラミックス焼結体を用いた場合には、一般にガラスセラミックス焼結体の熱膨張係数は10×10−６／℃程度と比較的小さいことから、他の高熱伝導部材に比べ熱膨張係数が５×10−６／℃程度と小さいタングステンを用いることが好ましい。
【００５４】
また、高熱伝導部材５の上下主面の面積は、半導体素子４の搭載面積よりも全方向に渡って広く、かつ、半導体素子４の端部から高熱伝導部材５の上側主面の端部までの幅が絶縁基板１の厚み以上になるようにしておくと、半導体素子４から発生した熱は高熱伝導部材５の下側主面の方向におよそ45°の角度をもって放射状に伝熱する性質があることから、半導体素子４から発生した熱が高熱伝導部材５に吸収された後に低い熱伝導率を有する絶縁基板１で阻害されずに配線基板７の外部に効率良く放散されるため、より好ましいものとなる。
【００５５】
また、高熱伝導部材５の上下主面の形状は、搭載する半導体素子４の形状や搭載形態に応じて任意の形状を選択することができるが、熱応力および機械的衝撃等の影響を抑制するという観点からは円形状であることが望ましく、四角形状等の多角形状を用いる際は、各角部に丸み（Ｒ面）を設けたりすることによって応力の集中を避けるようにしてもよい。
【００５６】
また、高熱伝導部材５の熱膨張係数が絶縁基板１の熱膨張係数よりも小さくなるようにすると、絶縁基板１の熱収縮が高熱伝導部材５の熱収縮より大きくなり、ロウ材６による接合時の冷却過程において、絶縁基板１が高熱伝導部材５の周囲を圧縮し、かしめる効果があり、絶縁基板１と高熱伝導部材５との接合強度をより向上させることができる点で好ましい。
【００５７】
なお、図１および図２に示す例では、貫通穴２および高熱伝導部材５は絶縁基板１の中央部に１つ設けた例を示しているが、複数個の半導体素子を搭載する混成集積回路基板や複数個のＬＥＤを収容するＬＥＤ収納用容器等に適用する場合においては、貫通穴２および高熱伝導部材５は所定の部位にそれぞれ複数個設けてもよい。
【００５８】
ロウ材６は、絶縁基板１と高熱伝導部材５とを接合し、さらに発生した熱応力を緩和する機能を有しており、一般的な銀・銀−銅等のロウ材や、Ｔｉ・ＺｒまたはＨｆの少なくとも１種を含有する銀−銅系の活性金属ロウ材等を用いることができる。
【００５９】
また、絶縁基板１の貫通穴２の内面に、例えば絶縁基板１がガラスセラミックス焼結体から成る場合には、予め焼成前に銅・銀・金・銀−パラジウム等の銀系合金等の金属粉末に適当な有機バインダや溶剤を添加し混練して作製した金属ペーストを塗布しておいてメタライズ層を形成し、このメタライズ層とロウ材６を介して絶縁基板１と高熱伝導部材５とを接合すると、応力緩和層がメタライズ層とロウ材６との二重となって、より強固に絶縁基板１と高熱伝導部材５とを接合することができるので好ましい。
【００６０】
以上によって、絶縁基板１の上下主面と高熱伝導部材５の上下主面とがそれぞれ同一面をなすように、絶縁基板１の貫通穴２の内面と高熱伝導部材５の側面との間にロウ材６を介して接合された配線基板７が作製され、次に、高熱伝導部材５の上側主面に半導体素子４を銀エポキシ樹脂等の接着剤９で接着して固定した後、配線導体３の絶縁基板１の上側主面に露出した部位と半導体素子４の電極とを金・アルミニウム等のボンディングワイヤを介して電気的に接続し、さらに、絶縁基板１の上側および下側主面に金属やセラミックスから成る蓋体（図示せず）をガラスや樹脂・ロウ材等の封止材を介して接合させ、絶縁基板１と蓋体とから成る容器内部に半導体素子４を気密に収容したり、樹脂等の封止材（図示せず）により、直接、半導体素子４や貫通孔８を封止して半導体素子４を気密に収容したりすることによって製品としての半導体装置が完成する。
【００６１】
次に、図３は、本発明の配線基板を半導体素子を収容する半導体素子収納用パッケージに適用した場合の実施の形態の他の例を示す断面図である。また、図４は、図３に示す本発明の配線基板の実施の形態の他の例の平面図である。なお、図３および図４においては、図１および図２と同様の箇所には同じ符号を付してある。また、この図４においては、凸部10および接着剤９の配置が分かるように、半導体素子４は破線で示している。
【００６２】
図３および図４に示す例においては、本発明の配線基板７’の高熱伝導部材５’には、その上側主面の中央部の半導体素子４の接着部の内側に、半導体素子４の面積よりも小さい面積の、半導体素子４の下面にその上面が当接する凸部10が、接着剤９の硬化後の厚みに等しい高さで形成されている。これにより、半導体素子４が接着剤９により高熱伝導部材５’の上側主面に接着されて固定されていても、その接着剤９から露出した凸部10の上面が半導体素子４の下面に当接していることから、半導体素子４から発生した熱が高熱伝導部材５’の凸部10に直接伝わるため、半導体素子４が動作する際に発生する熱を熱伝導率の低い接着剤９に阻害されることなく高熱伝導部材５’に伝えることができ、半導体素子４から発生した熱を高熱伝導部材５’が効率よく吸収し放散することができる。
【００６３】
このような高熱伝導部材５’は、上側主面の半導体素子４の接着部内に接着剤９の硬化後の厚みに等しい高さの凸部10を、物理的な切削加工や化学的なエッチング加工等の方法により形成することによって作製される。凸部10の平面形状は、半導体素子４の動作時に発生する熱を効率よく吸収するために、半導体素子４の形状に合わせて四角形状であることが好ましいが、半導体素子４の接着時にはこの凸部10の角部に局所的な熱応力が発生することを考慮して、四角形状の角部に丸み（Ｒ面）をつけてもよい。また、半導体素子４の下面に当接する凸部10の上面は、半導体素子４と隙間無く密着し、発生する熱を効率よく吸収するために、平坦になっていることが好ましい。また、半導体素子４の下面に当接する凸部10の上面の面積は、半導体素子４の下面の面積の40％から90％であることが好ましい。凸部10の半導体素子４の下面に当接する凸部10の上面の面積が半導体素子４の下面の面積の40％未満であると、半導体素子４の動作時に発生する熱が直接、十分に高熱伝導部材５’に伝わりにくくなるため、熱の吸収・放散性が低下することとなる。他方、半導体素子４の下面に接する凸部10の上面の面積が半導体素子４の下面の面積の90％を超えると、半導体素子４を接着剤９で高熱伝導部材５’の上側主面に接着する面積が半導体素子４の下面の面積の10％未満となり、高熱伝導部材５’に接着固定する力が不十分となってしまう。
【００６４】
凸部10の高さは、接着剤９の硬化後の厚みに等しいことが好ましい。凸部10の高さが接着剤９の硬化後の厚みより大きいと、接着剤９で半導体素子４を高熱伝導部材５’に十分な強度で接着できなくなるうえに、凸部10が半導体素子４に圧縮応力を与えることになり、半導体素子４の動作信頼性および高熱伝導部材５’への接着固定力を低下させることになる。他方、凸部10の高さが接着剤９の硬化後の厚みより小さいと、凸部10の上面と半導体素子４の下面との間に隙間が生じることになり、半導体素子４の動作時に発生する熱の吸収・放散性が低下することになる。
【００６５】
なお、図３および図４に示す例では、凸部10を高熱伝導部材５’の上側主面に１つ設けた例を示しているが、半導体素子４の動作信頼性をより向上させる目的等により、凸部10を複数形成してもよい。凸部10を複数形成することにより、半導体素子４が複数の凸部10上に設置されることとなり、硬化後の接着剤９の厚みが凸部10の厚みよりも低くなり、凸部10が半導体素子４に圧縮応力を加えるような場合においても、圧縮応力が複数の凸部10に分散されるため、半導体素子４への局所的な圧縮応力を低減することができ、半導体素子４の動作信頼性をより向上させることができる。
【００６６】
このように凸部10を複数形成する場合には、高熱伝導部材５’は、上側主面の半導体素子４の接着部内に接着剤９の硬化後の厚みに等しい高さの複数の凸部10を、物理的な切削加工や化学的なエッチング加工等の方法により形成することによって作製される。凸部10の平面形状は、半導体素子４の動作時に発生する熱を効率よく吸収するために、半導体素子４の形状に合わせて四角形状を複数に分割する形であることが好ましいが、半導体素子４の接着時にはこの複数の凸部10の角部に局所的な熱応力が発生することを考慮して、複数の凸部10の角部に丸み（Ｒ面）をつけてもよい。複数の凸部10の平面形状は、半導体素子４が高熱伝導部材５’上に均等な接着力で接着されるように、同形状・同寸法で、半導体素子４の接着部の中心に対して点対称に配置されることが好ましく、半導体素子４が正方形である場合には、複数の同形状・同寸法の正方形の凸部10が半導体素子４の接着部内に等間隔で配置されることが好ましい。また、半導体素子４の下面に当接する複数の凸部10の上面は、半導体素子４と隙間無く密着して発生する熱を効率よく吸収するために、平坦になっていることが好ましい。また、半導体素子４の下面に当接する複数の凸部10の上面の面積の合計は、半導体素子４の下面の面積の40％から90％であることが好ましい。半導体素子４の下面に当接する複数の凸部10の上面の面積の合計が半導体素子４の下面の面積の40％未満であると、半導体素子４の動作時に発生する熱が直接、十分に高熱伝導部材５’に伝わりにくくなるため、熱の吸収・放散性が低下することとなる。他方、半導体素子４の下面に接する複数の凸部10の上面の面積の合計が半導体素子４の下面の面積の90％を超えると、半導体素子４を接着剤９で高熱伝導部材５’の上側主面に接着する面積が半導体素子４の下面の面積の10％未満となり、高熱伝導部材５’に接着固定する力が不十分となってしまう。
【００６７】
複数の凸部10の相互の間隔は、半導体素子４が高熱伝導部材５’上に均等な接着力で接着されるように全て等しい間隔であることが好ましく、間隔の大きさは、前述のように、複数の凸部10が同形状・同寸法で、半導体素子４の接着部の中心に対して点対称に配置されることと、複数の凸部10の上面の面積の合計が半導体素子４の下面の面積の40％から90％であることから決められる。
【００６８】
複数の凸部10の高さは、全て等しく、接着剤９の硬化後の厚みに等しいことが好ましい。複数の凸部10の高さが全て等しくないと、部分的に高い凸部10が有る場合には、半導体素子４に局所的な圧縮応力を与えることになる。他方、部分的に低い凸部10が有る場合には、半導体素子４との間に隙間が生じ、半導体素子４の動作時に発生する熱の吸収・放散性が低下することになる。また、複数の凸部10の高さが接着剤９の硬化後の厚みより大きいと、接着剤９で半導体素子４を高熱伝導部材５’に十分な強度で接着できなくなるうえに、凸部10が半導体素子４に圧縮応力を与えることになり、半導体素子４の動作信頼性および高熱伝導部材５’への接着固定力を低下させることになる。他方、凸部10の高さが接着剤９の硬化後の厚みより小さいと、凸部10の上面と半導体素子４の下面との間に隙間が生じることになり、半導体素子４の動作時に発生する熱の吸収・放散性が低下することになる。
【００６９】
この例のような本発明の配線基板７’について、高熱伝導部材５’の上面に半導体素子４を接着剤９で接着して固定するときには、接着剤９は、銀エポキシ樹脂・半田・金−錫等の各種接着剤が使用できるが、接着時に半導体素子４に加えられる熱および熱応力を少なくするために、低温で接着可能な銀エポキシ樹脂を使用することが好ましい。
【００７０】
【実施例】
以下、本発明の実施例および比較例の試験結果を挙げて本発明の配線基板を詳細に説明するが、本発明は以下の実施例のみに限定されるものではない。
【００７１】
絶縁基板には、ガラスセラミックス焼結体を用い、ガラス粉末・フィラー粉末（セラミック粉末）・有機バインダ・可塑剤・有機溶剤等を混練したガラスセラミックグリーンシートを焼成することで作製した。
【００７２】
ガラスセラミック成分としては、ＳｉＯ２−Ａｌ２Ｏ３−ＭｇＯ−Ｂ２Ｏ３−ＺｎＯ系ガラス粉末60質量％，ＣａＺｒＯ３粉末20質量％，ＳｒＴｉＯ３粉末17質量％およびＡｌ２Ｏ３粉末３質量％を使用した。このガラスセラミック成分100重量部に有機バインダとしてアクリル樹脂12重量部，フタル酸系可塑剤６重量部および溶剤としてトルエン30重量部を加え、ボールミル法により混合しスラリーとした。このスラリーを用いてドクターブレード法により厚さ300μｍのガラスセラミックグリーンシートを作製した。
【００７３】
このガラスセラミックグリーンシートにビアホール導体や貫通穴を作製するための打ち抜き加工を行ない、切断して適当な形状の絶縁層を作製した。
【００７４】
そして、銀の金属粉末に有機バインダや溶剤を添加し混練して作製した金属ペーストをスクリーン印刷法により絶縁層上の所定パターンに埋め込むとともに印刷し、ビアホール導体および配線回路層を作製した。
【００７５】
この配線導体が埋め込まれ印刷された絶縁層を複数枚積層した後、この積層体を約300℃に加熱して有機成分を分解・揮散させた後、約900℃で焼成することにより、配線導体および絶縁層を焼結させて、中央部に上下主面を貫通する貫通穴を有するとともに貫通穴の周辺に配線導体が配設された絶縁基板を作製した。
【００７６】
高熱伝導部材は、四角形状で、熱膨張係数が20×10−６／℃の銀から成るものを使用し、半導体素子の接着部の外側の領域の４つの角部およびそれら角部間の中央部に、ロウ材の接合部と半導体素子の接着部との間の中央にその間隔の半分の大きさの孔径を持つ円形状の８個の貫通孔を打ち抜き加工した。
【００７７】
次に、絶縁基板の上下主面と高熱伝導部材の上下主面とがそれぞれ同一面をなすように、高熱伝導部材を絶縁基板の貫通穴に埋設した後、約700℃で加熱して冷却することにより、銀−銅ロウ材を絶縁基板の貫通穴の内面と高熱伝導部材の側面との間に充填し固化させることによって、絶縁基板と高熱伝導部材とを接合した。なお、絶縁基板には熱膨張係数が９×10−６／℃のガラスセラミックスを使用した。
【００７８】
半導体素子は、高熱伝導部材の上側主面に搭載し、銀エポキシ樹脂接着剤で接着し固定して、配線導体の絶縁基板の上面に露出した部位に半導体素子の電極をアルミニウムのボンディングワイヤを介して電気的に接続した。
【００７９】
以上により、絶縁基板と高熱伝導部材とが、絶縁基板の上下主面と高熱伝導部材の上下主面とがそれぞれ同一面をなすように、絶縁基板の貫通穴の内面と高熱伝導部材の側面との間にロウ材を介して接合されて成ることを特徴とする本発明の配線基板の実施例１の試料を作製した。
【００８０】
次に、同様にして、高熱伝導部材に、四角形状で、熱膨張係数が20×10−６／℃で熱伝導率が400Ｗ／ｍ・Ｋの銀を使用し、切削加工により、高熱伝導部材の上側主面の中央部に、半導体素子の下面に当接する上面の面積を半導体素子の下面の面積の70％とした、高さが20μｍの四角形状の凸部を形成した。また、高熱伝導部材の半導体素子の接着部の外周の外側の領域の４つの角部およびそれら角部間の中央部に、ロウ材の接合部と半導体素子の接着部との間の中央にその間隔の半分の大きさの孔径を持つ円形状の８個の貫通孔を打ち抜き加工し、この高熱伝導部材を用いて本発明の配線基板の実施例２の試料を作製した。
【００８１】
また、比較例として、上記と同じ材料および作製方法によって、絶縁基板に形成した貫通穴の内面と高熱伝導部材の側面との間ではなく、絶縁基板の貫通穴の周囲の下面とその貫通穴を覆うような大きさの高熱伝導部材の外周部の上面とをロウ材を介して接合した従来の構造の配線基板（以下、比較例という）を作製した。
【００８２】
そして、本発明の実施例１・２および比較例について応力の集中特性を評価するために、ロウ材付け接合試験、半導体素子発熱試験、機械的衝撃試験を実施したところ、各試験においてロウ材接合部の剥離というような重大な問題は両者とも発生しなかった。
【００８３】
そこで、さらに詳細な比較を行なうために、ロウ材の接合部における絶縁基板側のクラックの発生の有無を評価した。その評価結果を表１に示す。
【００８４】
表１に示す結果において、ロウ付け接合試験については、高熱伝導部材と絶縁基板とをロウ材を介して接合する際に700℃まで加熱し、次いで25℃まで冷却した後に、絶縁基板の表面を倍率10〜40倍の顕微鏡を用いて観察し、クラックが有れば接合信頼性に問題が発生する可能性があるため「×」とし、クラックが無ければ実用上問題のない接合信頼性を有すると考えられることから「○」として評価した。
【００８５】
また、半導体素子発熱試験については、高熱伝導部材の上側主面に半導体素子を搭載して、半導体素子を初めの１サイクルに動作開始後５秒間で125℃まで上昇し、次いで停止後15秒間で25℃まで下降するように半導体素子への印加電流を初期設定し、これを連続で5000サイクル繰り返して行なった後に、絶縁基板の表面を倍率10〜40倍の顕微鏡を用いて観察し、上記と同様にクラックが有れば「×」、無ければ「○」として評価した。
【００８６】
また、機械的衝撃試験については、高熱伝導部材の上側主面に半導体素子を搭載した配線基板を10ｃｍの高さから落とした後に、絶縁基板の表面を倍率10〜40倍の顕微鏡を用いて観察し、上記と同様にクラックが有れば「×」、無ければ「○」として評価した。
【００８７】
【表１】

Figure 0003935090
【００８８】
表１に示す結果から明らかなように、いずれの試験においても、比較例においてはクラックの発生が観察されたが、本発明の実施例１および２においては絶縁基板にクラックは発生しておらず、これにより本発明の実施例１および２においては、絶縁基板と高熱伝導部材との間のロウ材を介した接合部への応力の集中度が低く、絶縁基板と高熱伝導部材とが強固に接合されていることが確認できた。
【００８９】
次に、本発明の実施例１・２および比較例について、熱の吸収・放散特性を評価するために、半導体素子の動作試験を行なった。この半導体素子の動作試験は、高熱伝導部材の上側主面に半導体素子を搭載して、半導体素子が125℃で一定になるように半導体素子への印加電流を設定し、半導体素子の上面および高熱伝導部材の下側主面の温度を測定することにより、実施例１・２および比較例の配線基板としての熱抵抗を求めた。比較例に対して実施例1は10％、実施例２は20％、それぞれ配線基板の熱抵抗が低下しており、本発明の配線基板によれば、高熱伝導部材による半導体素子の熱の吸収・放散特性が改善されていることが確認された。
【００９０】
なお、本発明は上記の実施の形態の例に限定されるものではなく、本発明の要旨を逸脱しない範囲であれば種々の変更は可能である。例えば、上記の例では本発明の配線基板を半導体素子を収容する半導体素子収納用パッケージに適用したが、混成集積回路基板やＬＥＤ収納用容器等の他の用途に適用してもよい。
【００９１】
【発明の効果】
本発明の配線基板によれば、上側主面の中央部に半導体素子が接着される、外周部に複数個の貫通孔が形成された板状の高熱伝導部材が、絶縁基板の上下主面と高熱伝導部材の上下主面とがそれぞれ同一面をなすように、絶縁基板の上下主面間を貫通する貫通穴の内面と高熱伝導部材の側面との間にロウ材を介して接合されていることから、高熱伝導部材と絶縁基板との熱膨張係数の差に起因して発生する、ロウ材による接合時および半導体素子動作時の配線基板の引っ張りおよび圧縮の熱応力は、高熱伝導部材の側面と絶縁基板の貫通穴の内面との接合面において、局所的な偏りがない均等な応力分布をもつこととなり、配線基板の熱収縮挙動は、高熱伝導部材の熱収縮と絶縁基板の熱収縮とが横方向（配線基板の主面に対して平行な方向）に並ぶ状態で発生するため、そのような熱収縮挙動によって配線基板には反りが発生しないものとすることができる。
【００９２】
また、配線基板が反らず、高熱伝導部材も反らないため、半導体素子を高熱伝導部材に接着して固定しても、熱伝導率の低い接着剤の厚みは接着面全体で均一で薄いものとすることができるため、半導体素子の動作時に発生する熱が薄い接着剤を経由して高熱伝導部材に伝わりやすく、接着剤の厚みが不均一で厚い場合に比較して、半導体素子の熱の吸収・放散性を高くすることができる。
【００９３】
また、発生した熱応力は、絶縁基板の上下主面と高熱伝導部材の上下主面とがそれぞれ同一面となっており、両者の間に部分的に応力が集中する箇所が存在しないことから、絶縁基板の貫通穴の内面および高熱伝導部材配線基板の側面に分散され、かつ、両者の間を接合しているロウ材が応力緩和層としても機能するため、効率良く減衰させることができる。
【００９４】
さらに、高熱伝導部材は、上側主面の外周部である半導体素子が接着される部位の外周の外側の領域、つまり、半導体素子の接着部である中央部とロウ材の接合部との間の部位に複数個の貫通孔が形成されていることから、高熱伝導部材と絶縁基板との熱膨張係数の差に起因する、ロウ材による接合時および半導体素子動作時にロウ材接合部に発生する引っ張りおよび圧縮の熱応力は、複数個の貫通孔に分散させることができるため、効率よく減衰させて、配線基板に反りが発生しないものとすることができる。
【００９５】
従って、ロウ材による接合時に高熱伝導部材と絶縁基板との界面が破壊したり、半導体素子等の電子部品の動作時に絶縁基板にクラックが発生したりすることによる絶縁基板と高熱伝導部材との接合信頼性の低下等を効果的に抑制することができる。
【００９６】
また、絶縁基板の上下主面と高熱伝導部材の上下主面とがそれぞれ同一面をなすように絶縁基板の貫通穴の内面と高熱伝導部材の側面とがロウ材を介して接合されていることから、配線基板に落下等により機械的衝撃が加わった場合においても、従来の配線基板のように、応力が集中しやすい高熱伝導部材の側面と絶縁基板の下側主面とで形成される段差部および絶縁基板の貫通穴の内面と高熱伝導部材の上側主面とで形成される段差部が存在しないので、絶縁基板の破壊の起点となる部位が無く機械的衝撃に強いものとすることができる。そして、高熱伝導性部材が配線基板の内部に収納される構造となるため、容易に小型化・薄型化を図ることが可能となる。
【００９７】
また、高熱伝導部材の前記上側主面の前記中央部に前記半導体素子の面積よりも小さい面積の、前記半導体素子の下面に上面が当接する凸部が形成されている場合には、半導体素子が接着剤により接着されて固定されていても、その接着剤から露出した凸部の上面が半導体素子の下面に当接していることから、半導体素子から発生した熱が高熱伝導部材の凸部に直接伝わるため、半導体素子が動作する際に発生する熱を熱伝導率の低い接着剤に阻害されることなく高熱伝導部材に伝えることができ、半導体素子から発生した熱を高熱伝導部材が効率よく吸収し放散することができる。
【００９８】
また、高熱伝導部材が四角形状であり、貫通孔が外周部の角部に形成されている場合には、角部に発生する局所的な引っ張りおよび圧縮の最大熱応力は、それら四角形状の高熱伝導部材の外周部の角部に形成された複数個の貫通孔に分散するため、極めて効率よく減衰させることができ、さらに確実に配線基板に反りが発生しないものとすることができる。
【００９９】
さらに、凸部が複数形成されている場合には、半導体素子が複数の凸部上に設置されることとなり、硬化後の接着剤の厚みが凸部の厚みよりも低くなるので、凸部が半導体素子に圧縮応力を加えるような場合においても、圧縮応力が複数の凸部に分散されるため、半導体素子への局所的な圧縮応力を低減することができ、半導体素子の動作信頼性をより高いものとすることができる。
【０１００】
以上により、本発明によれば、高熱伝導部材と絶縁基板とを強固に接合するとともに、半導体素子が発生する熱を効率良く吸収・放散し、半導体素子を長期にわたり正常、かつ安定に作動させることができる信頼性の高い配線基板を提供することができる。
【図面の簡単な説明】
【図１】本発明の配線基板の実施の形態の一例を示す断面図である。
【図２】本発明の配線基板の実施の形態の一例を示す平面図である。
【図３】本発明の配線基板の実施の形態の他の例を示す断面図である。
【図４】本発明の配線基板の実施の形態の他の例を示す平面図である。
【図５】従来の配線基板の例を示す断面図である。
【符号の説明】
１・・・・・・・絶縁基板
１ａ〜１ｄ・・・絶縁層
２・・・・・・・貫通穴
３・・・・・・・配線導体
３ａ・・・・・・ビアホール導体
３ｂ・・・・・・配線回路層
４・・・・・・・半導体素子
５、５’・・・・高熱伝導部材
６・・・・・・・ロウ材
７、７’・・・・配線基板
８・・・・・・・貫通孔
９・・・・・・・接着剤
10・・・・・・・凸部[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a wiring board used for mounting an electronic component such as a semiconductor element, and in particular, absorbs heat generated from a semiconductor element efficiently and dissipates it to the outside. The present invention relates to a wiring board having improved bonding reliability between a high thermal conductive member and an insulating board.
[0002]
[Prior art]
In recent years, with the increase in integration and speed of electronic components such as semiconductor elements, the amount of heat generated when the semiconductor elements operate tends to increase. When the generated heat is accumulated in a semiconductor element or the like, there is a problem that a malfunction of the circuit such as the semiconductor element occurs or the circuit itself is destroyed. Thus, conventionally, a wiring board on which a semiconductor element or the like is mounted has been devised such that a heat radiating plate for efficiently absorbing heat generated from the semiconductor element or the like and dissipating it to the outside is provided.
[0003]
Such a heat sink is generally formed of a high heat conductive member made of copper or other metal, and is bonded to the back surface or both surfaces of a wiring board on which a semiconductor element or the like is mounted, or the semiconductor element or the like is heat sink. By directly mounting on the semiconductor device, the heat generated in the semiconductor element or the like is absorbed by the heat radiating plate and the absorbed heat is dissipated to the outside to protect the semiconductor element or the like from the heat. And in the heat dissipation structure of the heat | fever which the semiconductor element etc. in such a wiring board emit, the thing of the structure which mounted the semiconductor element etc. directly on the heat sink is excellent in heat dissipation.
[0004]
As a conventional wiring board in which a semiconductor element or the like is directly mounted on a heat sink, for example, a structure as shown in a cross-sectional view in FIG. 5 is common (see, for example, Patent Document 1).
[0005]
In FIG. 5, a conventional wiring board 107 includes a plurality of insulating layers 101a to 101h in which a through hole 102 is formed at the center and a wiring conductor 103 including a via-hole conductor 103a and a wiring circuit layer 103b is disposed. A plate-like high thermal conductive member 105 on which a semiconductor element 104 is bonded and mounted on the upper main surface of the insulating substrate 101 so as to close the through hole 102 on the lower main surface of the insulating substrate 101 is a brazing material 106. It is joined via.
[0006]
As the insulating substrate 101 used for such a conventional wiring substrate 107, various ceramic materials or organic insulating resin materials, or inorganic insulating powders bonded with an organic insulating resin are used. High melting point metals such as tungsten and molybdenum and low resistance metals such as copper, silver, and gold are used.
[0007]
[Patent Document 1]
JP-A-6-296084
[0008]
[Problems to be solved by the invention]
However, in the conventional wiring substrate 107 as described above, as described above, the insulating substrate 101 uses various ceramic materials and organic insulating resin materials or inorganic insulating powders combined with an organic insulating resin. In contrast, since a metal having high thermal conductivity is used for the high thermal conductive member 105, different types of materials having different thermal expansion coefficients are joined via the brazing material 106.
[0009]
Since the upper main surface of the high heat conductive member 105 and the lower main surface of the insulating substrate 101 are joined only by parallel surfaces that are joined to each other via the brazing material 106, the high heat conductive member 105 Since the high thermal conductive member 105 and the insulating substrate 101 have different thermal expansion and thermal contraction behavior in the heating and subsequent cooling processes when the frame-shaped insulating substrate 101 is bonded to the brazing material 106 to 105, for example, the high thermal conductive member 105 In the case where the thermal expansion coefficient of the insulating substrate 101 is larger than that of the insulating substrate 101, the insulating substrate 101 having a large amount of thermal shrinkage at the time of cooling has the high thermal conductivity member 105 as the center of the wiring substrate 107 with the surface joined by the brazing material 106 as a power point. In order to generate a stress that compresses in the direction, the entire wiring board 107 warps in a concave shape.
[0010]
On the contrary, when the thermal expansion coefficient of the insulating substrate 101 is smaller than that of the high heat conductive member 105, the surface where the high heat conductive member 105 having a large amount of heat shrinkage during cooling is joined by the brazing material 106. Since the stress that pulls the insulating substrate 101 toward the inside of the wiring substrate 107 is generated with the force as the power point, the entire wiring substrate 107 is warped in a convex shape.
[0011]
When the insulating substrate 101 and the high thermal conductive member 105 are joined by the brazing material 106, the warpage of the wiring substrate 107 caused by the difference in the heat shrinkage behavior particularly in the cooling process is caused by the joining of the insulating substrate 101 and the high thermal conductive member 105. Concentrate large stresses on the inside of the brazing material 106, which is the interface, the bonding interface between the upper main surface of the high thermal conductive member 105 and the brazing material 106, or the bonding interface between the lower main surface of the insulating substrate 101 and the brazing material 106. Thus, the brazing material 106 is broken, the bonding interface between the brazing material 106 and the upper main surface of the high thermal conductive member 105 or the lower main surface of the insulating substrate 101 is peeled off, and generally has a lower ductility than the high thermal conductive member 105 There is a problem that cracks or the like starting from the end of the bonding interface with the brazing material 106 occur in the insulating substrate 101.
[0012]
Further, since the high thermal conductive member 105 is also warped due to the warping of the wiring substrate 107, when the semiconductor element 104 is bonded and fixed to the high thermal conductive member 105, the thickness of the adhesive 109 having low thermal conductivity is not uniform over the entire bonding surface. The heat generated during the operation of the semiconductor element 104 becomes difficult to be transferred to the high thermal conductive member 105 by the thick adhesive 109, and the heat absorption / dissipation property of the semiconductor element 104 is reduced. There was a point.
[0013]
Further, as the kind of the adhesive 109, there are gold-tin, solder, silver epoxy resin, etc., but the thermal conductivity is in the range of 5 to 150 W / m · K, and silver is the material of the high thermal conductive member 105. Since the adhesive 109 having a low thermal conductivity, which is smaller than 380 to 400 W / m · K of copper or copper, is present on the entire surface between the semiconductor element 104 and the high thermal conductive member 105, heat generated during the operation of the semiconductor element 104 However, it is difficult for the adhesive 109 to be transmitted to the high thermal conductive member 105, and there is a problem in that the heat absorption and dissipation of the semiconductor element 104 is reduced.
[0014]
Further, in the heat generation and cooling cycle during the operation of the semiconductor element 104, the thermal stress resulting from the difference in thermal expansion coefficient between the high thermal conductive member 105 and the insulating substrate 101 as described above is caused by the high thermal conductive member 105 and the insulating substrate. Since this acts repeatedly on the bonding interface of 101 and for a long period of time, this also causes the brazing material 106 to be broken or the upper main surface of the brazing material 106 and the high thermal conductive member 105 or the lower main surface of the insulating substrate 101. The joint interface with the surface is peeled off, or cracks etc. starting from the end of the joint interface with the brazing material 106 are gradually generated and progressed inside the insulating substrate 101 which is generally less ductile than the high thermal conductive member 105. Therefore, there is a problem that the bonding reliability between the insulating substrate 101 and the high thermal conductive member 105 in the wiring substrate 107 is low.
[0015]
Therefore, in order to prevent a decrease in bonding reliability due to thermal stress due to the difference in thermal expansion coefficient between the high thermal conductive member 105 and the insulating substrate 101 as described above, the thermal condition is adjusted by adjusting the bonding state of the brazing material 106. Various attempts have been made to adjust the material composition of the high thermal conductive member 105 and the insulating substrate 101 in order to disperse stress and to reduce the difference in thermal expansion coefficient between the high thermal conductive member 105 and the insulating substrate 101. However, the current situation is that it cannot sufficiently cope with the diversification of mechanical and electrical characteristics required for wiring boards in recent years and the heat generation amount of the semiconductor element 104 which is increasing.
[0016]
Further, in the conventional wiring board 107 as described above, since the high thermal conductive member 105 protrudes downward from the insulating substrate 101, a step portion formed between the side surface of the high thermal conductive member 105 and the lower main surface of the insulating substrate 101. In addition, stress is likely to concentrate on the step formed by the inner surface of the through hole 102 of the insulating substrate 101 and the upper main surface of the high thermal conductive member 105, and mechanical shocks such as dropping of the wiring substrate 107 were applied. At this time, since this mechanical shock is concentrated and acts on the step portion between the high thermal conductive member 105 and the insulating substrate 101, the insulating substrate 101 is likely to be broken such as cracks. There was also a problem.
[0017]
In addition, the conventional wiring board 107 having a structure in which the high thermal conductive member 105 protrudes from the insulating substrate 101 has a problem that it is difficult to reduce the size and thickness, and there is a great design limitation.
[0018]
The present invention has been devised to solve the above-described problems, and its purpose is to join using a brazing material due to thermal stress caused by a difference in thermal expansion coefficient between a high thermal conductive member and an insulating substrate. Sometimes the interface between the high thermal conductive member and the insulating substrate is broken, or the insulating substrate is cracked during the operation of the electronic component such as a semiconductor element. Prevents destruction of the interface with the insulating substrate, firmly bonds the high thermal conductivity member and the insulating substrate, efficiently absorbs and dissipates the heat generated by the semiconductor element, and makes the semiconductor element normal and stable over a long period of time An object of the present invention is to provide a highly reliable wiring board that can be operated.
[0019]
[Means for Solving the Problems]
The wiring board of the present invention has a through-hole penetrating between the upper and lower main surfaces and a semiconductor element is bonded to the central portion of the upper main surface on the insulating substrate in which the wiring conductor is disposed around the through-hole. The plate-like high heat conductive member having a plurality of through holes formed in the outer peripheral portion thereof, wherein the upper and lower main surfaces of the insulating substrate and the upper and lower main surfaces of the high heat conductive member are flush with each other. And an inner surface of the high heat conductive member and a side surface of the high thermal conductive member.
[0020]
According to the wiring board of the present invention, the plate-like high heat conductive member in which the semiconductor element is bonded to the central portion of the upper main surface and the plurality of through holes are formed in the outer peripheral portion is formed on the upper and lower main surfaces of the insulating substrate. Since the upper and lower main surfaces of the high heat conductive member are respectively flush with each other, the inner surface of the through hole and the side surface of the high heat conductive member are joined via a brazing material. The thermal contraction behavior of the wiring board due to the difference in thermal expansion coefficient between the soldering material and the semiconductor element is due to the fact that the thermal contraction of the high thermal conductive member and the thermal contraction of the insulating substrate are lateral ( Therefore, it is possible to prevent the wiring board from warping due to such a heat shrinkage behavior.
[0021]
In addition, since the wiring board does not warp and the high heat conductive member does not warp, even if the semiconductor element is bonded and fixed to the high heat conductive member, the thickness of the adhesive having low heat conductivity is uniform and thin on the entire bonding surface. Therefore, the heat generated during the operation of the semiconductor element is easily transferred to the high thermal conductive member via the thin adhesive, and the heat of the semiconductor element is larger than that in the case where the thickness of the adhesive is uneven and thick. The absorption and dissipation of can be increased.
[0022]
In addition, the generated thermal stress is such that the upper and lower main surfaces of the insulating substrate and the upper and lower main surfaces of the high thermal conductive member are the same surface, and there is no portion where stress is partially concentrated between the two. Since the brazing material that is dispersed on the inner surface of the through hole of the insulating substrate and the side surface of the high thermal conductive member wiring substrate and that joins between them also functions as a stress relaxation layer, it can be attenuated efficiently.
[0023]
Further, the high thermal conductive member is a region outside the outer periphery of the portion to which the semiconductor element that is the outer peripheral portion of the upper main surface is bonded, that is, between the central portion that is the bonded portion of the semiconductor element and the bonding portion of the brazing material. Since a plurality of through-holes are formed in the part, the tensile force generated at the brazing material joining portion when joining with the brazing material and operating the semiconductor element due to the difference in thermal expansion coefficient between the high thermal conductive member and the insulating substrate Since the compressive thermal stress can be dispersed in the plurality of through holes, it can be efficiently attenuated so that the wiring board does not warp.
[0024]
Therefore, the bonding between the insulating substrate and the high thermal conductive member is caused by the destruction of the interface between the high thermal conductive member and the insulating substrate at the time of joining with the brazing material or the generation of cracks in the insulating substrate during the operation of the electronic component such as a semiconductor element. Reduction in reliability and the like can be effectively suppressed.
[0025]
Also, the inner surface of the through hole of the insulating substrate and the side surface of the high heat conductive member are joined via a brazing material so that the upper and lower main surfaces of the insulating substrate and the upper and lower main surfaces of the high heat conductive member are the same surface. Therefore, even when a mechanical shock is applied to the wiring board due to a drop or the like, the step formed between the side surface of the high thermal conductive member where stress is likely to concentrate and the lower main surface of the insulating substrate, as in the conventional wiring board Since there is no step portion formed between the inner surface of the through hole of the insulating portion and the insulating substrate and the upper main surface of the high thermal conductive member, there is no portion that becomes the starting point of the destruction of the insulating substrate, and it should be resistant to mechanical shock. it can. And since it becomes a structure where a highly heat-conductive member is accommodated in the inside of a wiring board, it becomes possible to achieve size reduction and thickness reduction easily.
[0026]
In the case where a convex portion whose upper surface is in contact with the lower surface of the semiconductor element having an area smaller than the area of the semiconductor element is formed in the central portion of the upper main surface of the high heat conductive member, the semiconductor element is Even if it is bonded and fixed by an adhesive, the upper surface of the convex portion exposed from the adhesive is in contact with the lower surface of the semiconductor element, so that the heat generated from the semiconductor element is directly applied to the convex portion of the high thermal conductive member. Therefore, the heat generated when the semiconductor element operates can be transferred to the high thermal conductive member without being hindered by the adhesive having low thermal conductivity, and the high thermal conductive member efficiently absorbs the heat generated from the semiconductor element. Can be dissipated.
[0027]
In addition, when the high heat conductive member has a quadrangular shape and the through hole is formed in the corner portion of the outer peripheral portion, the maximum thermal stress of local tension and compression generated in the corner portion is the square shape. Since it is dispersed in a plurality of through holes formed at the corners of the outer peripheral portion of the high heat conductive member, it can be attenuated extremely efficiently, and further, the wiring board can be surely not warped.
[0028]
Further, when a plurality of protrusions are formed, the semiconductor element is placed on the plurality of protrusions, and the thickness of the adhesive after curing is lower than the thickness of the protrusions. Even when compressive stress is applied to the semiconductor element, the compressive stress is distributed to the plurality of convex portions, so that the local compressive stress on the semiconductor element can be reduced, and the operation reliability of the semiconductor element is further improved. Can be expensive.
[0029]
DETAILED DESCRIPTION OF THE INVENTION
Next, the wiring board of the present invention will be described in detail with reference to the accompanying drawings.
[0030]
FIG. 1 is a cross-sectional view showing an example of an embodiment in which the wiring board of the present invention is applied to a package for housing a semiconductor element that houses a semiconductor element. FIG. 2 is a plan view of an example of the embodiment of the wiring board of the present invention shown in FIG.
[0031]
In these drawings, the wiring board 7 of the present invention has a through hole 2 penetrating between the upper and lower main surfaces in the center portion, and a wiring conductor 3 composed of a via-hole conductor 3a and a wiring circuit layer 3b. A semiconductor element 4 is bonded to the central portion of the upper main surface of the lower main surface of the insulating substrate 1 composed of a plurality of insulating layers 1 a to 1 d so as to close the through hole 2. A plate-like high heat conductive member 5 in which a plurality of through holes 8 are formed in the outer peripheral portion which is a region outside the central portion is joined via a brazing material 6.
[0032]
The insulating substrate 1 is made of an electrically insulating material such as ceramics such as an aluminum oxide sintered body, an aluminum nitride sintered body, a mullite sintered body, a silicon carbide sintered body, a glass ceramic sintered body, or an epoxy resin. For example, in the case of a glass ceramic sintered body, a glass ceramic green sheet kneaded with a glass powder, a filler powder (ceramic powder), an organic binder, a plasticizer, an organic solvent, or the like is laminated in a single layer or a plurality of layers, It is made by baking.
[0033]
Examples of glass powder include SiO.2-B2O3Series ・ SiO2-B2O3-Al2O3Series ・ SiO2-B2O3-Al2O3-MO system (where M represents Ca, Sr, Mg, Ba or Zn), SiO2-Al2O3-M1OM2O system (however, M1And M2Are the same or different and represent Ca, Sr, Mg, Ba or Zn) .SiO2-B2O3-Al2O3-M1OM2O system (however, M1And M2Is the same as above) · SiO2-B2O3-M3 2O system (however, M3Represents Li, Na or K) .SiO2-B2O3-Al2O3-M3 2O system (however, M3Are the same as those described above), Pb glass, Bi glass and the like.
[0034]
Moreover, as filler powder, for example, Al2O3, SiO2, ZrO2Oxide and TiO of alkaline earth metal oxides2Oxide of Al and alkaline earth metal oxide, Al2O3And SiO2And composite oxides containing at least one selected from (for example, spinel, mullite, cordierite).
[0035]
The mixing ratio of these glass and filler is preferably 40:60 to 99: 1 by mass ratio.
[0036]
In addition, as the organic binder, those conventionally used for ceramic green sheets can be used. For example, acrylic (acrylic acid, methacrylic acid or their homopolymers or copolymers, specifically, Acrylic ester copolymer, methacrylic ester copolymer, acrylic ester-methacrylic ester copolymer, etc.), polyvinyl butyral, polyvinyl alcohol, acrylic-styrene, polypropylene carbonate, cellulose, etc. Examples thereof include a polymer or a copolymer.
[0037]
A glass ceramic green sheet is obtained by adding a predetermined amount of a plasticizer / solvent (organic solvent, water, etc.) to the glass powder / filler powder / organic binder as necessary to obtain a slurry. It can be obtained by molding to a thickness of about 50 to 500 μm with a calender roll, a die press or the like.
[0038]
The glass ceramic green sheet thus obtained is punched to produce via-hole conductors 3a and through-holes 2, and cut to produce appropriately shaped insulating layers 1a to 1d.
[0039]
In addition, when the insulating layers 1a to 1d are made of glass ceramics, for example, an appropriate organic binder or solvent is added to and kneaded with a metal powder such as a silver-based alloy such as copper, silver, gold, or silver-palladium. Via paste conductor 3a and wiring circuit layer 3b are formed by embedding and printing a metal paste in a predetermined pattern by screen printing or the like.
[0040]
After laminating a plurality of insulating layers 1a to 1d in which the wiring conductor 3 is embedded and printed, the organic components are removed and baked. The organic component is removed by heating the laminate in a temperature range of 100 to 500 ° C., for example, to decompose and volatilize the organic component. In addition, although the firing temperature varies depending on the composition of the glass ceramic, it is usually in the range of 800 to 1000 ° C., and the wiring conductor 3 and the insulating layers 1 a to 1 d are sintered to have the through hole 2 and the through hole 2. As a result, an insulating substrate 1 composed of insulating layers 1a to 1d, in which a wiring conductor 3 composed of a via-hole conductor 3a and a wiring circuit layer 3b is disposed, is obtained.
[0041]
The high heat conductive member 5 is formed in a circular shape at a portion of the outer region of the outer periphery of the portion to which the semiconductor element 4 is bonded, that is, at the center of the region between the outer periphery of the bonded portion of the semiconductor element 4 and the brazing material 6 joint. Alternatively, a plurality of through-holes 8 having a hole diameter that is about half the distance between the outer periphery of the bonding portion of the semiconductor element 4 and the bonding portion of the brazing material 6 are formed by punching, thereby forming a plurality of through holes 8. It is obtained as a plate-like member in which a single through hole 8 is formed.
[0042]
If the through-hole 8 has a polygonal shape, the stress dispersed in the through-hole 8 is concentrated at the corners of the high thermal conductive member 5 when the brazing material is joined or when the semiconductor element 4 generates heat, and the high thermal conductive member 5 is likely to deteriorate. Therefore, the shape is preferably a circle or an ellipse having no corners.
[0043]
Further, when the through hole 8 is located in the vicinity of the outer periphery of the bonding portion of the brazing material 6 or the bonding portion of the semiconductor element 4, the stress dispersed in the through hole 8 is applied to the bonding portion of the brazing material 6 or the bonding portion of the semiconductor element 4. In order to affect the outer periphery and reduce the bonding strength and the bonding strength, the through hole 8 is preferably located at the center of the region between the bonding portion of the brazing material 6 and the outer periphery of the bonding portion of the semiconductor element 4.
[0044]
Further, when the hole diameter of the through hole 8 is substantially the same as the distance between the joint portion of the brazing material 6 and the outer periphery of the bonding portion of the semiconductor element 4, the stress dispersed in the through hole 8 is the joint portion of the brazing material 6. Otherwise, the outer periphery of the bonded portion of the semiconductor element 4 may be affected, and the bonding strength and the bonding strength may be reduced. On the contrary, if the size is very small compared to the distance between the joint portion of the brazing material 6 and the outer periphery of the bonding portion of the semiconductor element 4, the stress dispersed in the through-hole 8 becomes small, and the stress is sufficiently dispersed. The effect will not be obtained. Accordingly, the hole diameter of the through hole 8 is preferably about half the distance between the joint portion of the brazing material 6 and the outer periphery of the bonding portion of the semiconductor element 4.
[0045]
Further, when the high heat conductive member 5 is rectangular, the maximum thermal stress is generated at the corner of the joint portion of the brazing material 6 when the brazing material 6 is joined or when the semiconductor element 4 generates heat. In order to disperse the generated maximum thermal stress, it is preferable to form at the corners of the high thermal conductive member 5 in addition to the above conditions.
[0046]
Next, after the high heat conductive member 5 is embedded in the through hole 2 of the insulating substrate 1 so that the upper and lower main surfaces of the insulating substrate 1 and the upper and lower main surfaces of the high heat conductive member 5 are the same surface, the brazing material 6 is attached to the insulating substrate. The brazing material 6 is melted by filling between the inner surface of the through hole 2 of 1 and the side surface of the high thermal conductive member 5 and heating at 600 to 800 ° C., and then the brazing material 6 is solidified by cooling. As a result, the insulating substrate 1 and the high thermal conductive member 5 are joined via the brazing material 6.
[0047]
Here, the upper and lower main surfaces of the insulating substrate 1 and the upper and lower main surfaces of the plate-like high heat conductive member 5 having a plurality of through holes 8 formed on the outer periphery thereof are flush with each other. It is important to join the inner surface of the through hole 2 and the side surface of the high heat conductive member 5 via the brazing material 6.
[0048]
Since the upper and lower main surfaces of the insulating substrate 1 and the upper and lower main surfaces of the high thermal conductive member 5 are the same surface, the high thermal conductive member 5 and the insulating substrate 1 are bonded to each other at the time of joining with the brazing material 6 and the operation of the semiconductor element 4. The tensile and compressive stress generated due to the difference in thermal expansion coefficient has a uniform stress distribution with no local bias on the joint surface between the side surface of the high thermal conductive member 5 and the inner surface of the through hole 2 of the insulating substrate 1. Therefore, the wiring board 7 does not warp, and the brazing material 6 joining the two functions as a stress relaxation layer, so that the difference in thermal expansion coefficient between the high thermal conductive member 5 and the insulating substrate 1 is increased. It is possible to efficiently attenuate the tensile and compressive stress generated due to the above. Furthermore, since the generated tensile and compressive stress is dispersed in the through holes 8 formed in the high thermal conductive member 5, the tensile and compressive stress at the joint surface of the brazing material 6 can be further reduced. In addition, when the high heat conductive member 5 has a quadrangular shape and the through hole 8 is formed at the corner portion of the outer peripheral portion, the through hole 8 is formed at the corner portion of the outer peripheral portion. Since the maximum thermal stress generated by local tension and compression is distributed to the plurality of through-holes 8 formed at these corners, it can be efficiently damped.
[0049]
Further, even when a mechanical shock is applied to the wiring board 7 due to dropping or the like, it is formed by the side surface of the high thermal conductive member 5 where stress is likely to concentrate and the lower main surface of the insulating substrate 1 as in the conventional wiring board. Since there is no step portion formed between the step portion to be formed and the inner surface of the through hole 2 of the insulating substrate 1 and the upper main surface of the high heat conductive member 5, there is no portion that becomes the starting point of the breakdown of the insulating substrate 1 and is mechanical. It can be strong against impact.
[0050]
When the upper and lower main surfaces of the insulating substrate 1 and the upper and lower main surfaces of the high heat conductive member 5 are formed in the same plane as described above, the upper main surfaces and the lower main surfaces are formed of the high heat conductive member 5. In order to have a uniform stress distribution with no local bias in the joint surface between the side surface of the insulating substrate 1 and the inner surface of the through hole 2 of the insulating substrate 1, it is preferable to make the same plane as much as possible. Even if the dimensional errors of the thicknesses of 1 and the high heat conductive member 5 occur due to the respective processing accuracy, the bonding reliability between the insulating substrate 1 and the high heat conductive member 5 is not significantly reduced.
[0051]
The through-hole 2 accommodates the plate-like high heat conductive member 5 in the insulating substrate 1, and the insulating substrate 1 and the upper and lower main surfaces of the insulating substrate 1 and the upper and lower main surfaces of the high heat conducting member 5 are flush with each other. It is formed in order to join between the inner surface of one through hole 2 and the side surface of the high heat conductive member 5 via the brazing material 6. Accordingly, the through hole 2 has the same shape as the high heat conductive member 5, and has an opening size that allows an appropriate amount of brazing material 6 to be filled between the inner surface and the high heat conductive member 5. Have.
[0052]
On the other hand, the high thermal conductive member 5 has a function of directly mounting the semiconductor element 4 and efficiently absorbing the heat generated by the semiconductor element 4 and dissipating it to the outside. For such a high thermal conductive member 5, a metal or alloy having excellent thermal conductivity such as copper, silver, aluminum, nickel, beryllium, magnesium, copper-tungsten alloy, copper-molybdenum alloy is used. In the case of consisting of a tungsten alloy, a tungsten powder is pressure-molded at a pressure of about 98 MPa and fired at a temperature of about 2000 ° C. in a reducing atmosphere to obtain a porous tungsten sintered body. It can be produced by impregnating a porous portion of a tungsten sintered body with copper melted by heating at a temperature of about 900 ° C. using capillary action.
[0053]
The material of the high thermal conductive member 5 can be variously selected according to the material of the insulating substrate 1, but particularly when a glass ceramic sintered body is used for the insulating substrate 1 as a high frequency wiring substrate. In general, the thermal expansion coefficient of glass ceramic sintered body is 10 × 10-6The coefficient of thermal expansion is 5x10 compared to other high heat conducting members because it is relatively small at around / ° C.-6It is preferable to use tungsten as small as about / ° C.
[0054]
Further, the area of the upper and lower main surfaces of the high heat conductive member 5 is wider than the mounting area of the semiconductor element 4 in all directions, and from the end of the semiconductor element 4 to the end of the upper main surface of the high heat conductive member 5. If the width of the semiconductor substrate 4 is equal to or greater than the thickness of the insulating substrate 1, the heat generated from the semiconductor element 4 is transferred in a radial manner at an angle of about 45 ° in the direction of the lower main surface of the high thermal conductive member 5. Therefore, it is more preferable because the heat generated from the semiconductor element 4 is absorbed by the high thermal conductive member 5 and efficiently dissipated outside the wiring substrate 7 without being inhibited by the insulating substrate 1 having low thermal conductivity. It will be a thing.
[0055]
Moreover, although the shape of the upper and lower main surfaces of the high thermal conductive member 5 can be selected according to the shape of the semiconductor element 4 to be mounted and the mounting form, it suppresses the influence of thermal stress, mechanical shock, and the like. From the viewpoint of this, it is desirable to have a circular shape. When a polygonal shape such as a quadrangular shape is used, concentration of stress may be avoided by providing roundness (R surface) at each corner.
[0056]
Further, if the thermal expansion coefficient of the high thermal conductive member 5 is made smaller than the thermal expansion coefficient of the insulating substrate 1, the thermal contraction of the insulating substrate 1 becomes larger than the thermal contraction of the high thermal conductive member 5. In this cooling process, the insulating substrate 1 is preferable in that it has an effect of compressing and caulking the periphery of the high heat conductive member 5 and the bonding strength between the insulating substrate 1 and the high heat conductive member 5 can be further improved.
[0057]
In the example shown in FIGS. 1 and 2, an example is shown in which one through hole 2 and one high thermal conductive member 5 are provided in the central portion of the insulating substrate 1, but a hybrid integrated circuit on which a plurality of semiconductor elements are mounted. When applied to a substrate or an LED storage container for storing a plurality of LEDs, a plurality of through holes 2 and a plurality of high heat conduction members 5 may be provided at predetermined locations.
[0058]
The brazing material 6 has a function of joining the insulating substrate 1 and the high thermal conductive member 5 and further mitigating the generated thermal stress, such as a general brazing material such as silver, silver-copper, or Ti / Zr. Alternatively, a silver-copper based active metal brazing material containing at least one of Hf can be used.
[0059]
When the insulating substrate 1 is made of a glass ceramic sintered body on the inner surface of the through hole 2 of the insulating substrate 1, for example, a metal such as a silver-based alloy such as copper, silver, gold, silver-palladium before firing. A metal paste prepared by adding an appropriate organic binder and solvent to the powder and kneading is applied to form a metallized layer, and the insulating substrate 1 and the high thermal conductive member 5 are connected to each other through the metallized layer and the brazing material 6. Bonding is preferable because the stress relaxation layer becomes a double layer of the metallized layer and the brazing material 6 and the insulating substrate 1 and the high thermal conductive member 5 can be bonded more firmly.
[0060]
As described above, the solder is interposed between the inner surface of the through hole 2 of the insulating substrate 1 and the side surface of the high heat conductive member 5 so that the upper and lower main surfaces of the insulating substrate 1 and the upper and lower main surfaces of the high heat conductive member 5 are the same surface. A wiring board 7 bonded through the material 6 is manufactured. Next, the semiconductor element 4 is bonded and fixed to the upper main surface of the high thermal conductive member 5 with an adhesive 9 such as silver epoxy resin, and then the wiring conductor 3 is fixed. The part exposed on the upper main surface of the insulating substrate 1 and the electrode of the semiconductor element 4 are electrically connected through bonding wires such as gold and aluminum, and further, metal is formed on the upper and lower main surfaces of the insulating substrate 1. A lid (not shown) made of glass or ceramic is joined via a sealing material such as glass, resin, brazing material, etc., and the semiconductor element 4 is hermetically accommodated inside a container made of the insulating substrate 1 and the lid. Directly with a sealing material such as resin (not shown) The semiconductor device as a product is completed by or housing the semiconductor element 4 hermetically sealing the element 4 and the through-hole 8.
[0061]
Next, FIG. 3 is a cross-sectional view showing another example of the embodiment when the wiring board of the present invention is applied to a package for housing a semiconductor element for housing a semiconductor element. FIG. 4 is a plan view of another example of the embodiment of the wiring board of the present invention shown in FIG. 3 and 4, the same reference numerals are given to the same portions as those in FIGS. 1 and 2. Further, in FIG. 4, the semiconductor element 4 is indicated by a broken line so that the arrangement of the convex portions 10 and the adhesive 9 can be understood.
[0062]
In the example shown in FIG. 3 and FIG. 4, the high thermal conductive member 5 ′ of the wiring board 7 ′ of the present invention has an area of the semiconductor element 4 inside the bonding portion of the semiconductor element 4 at the center of the upper main surface. A convex portion 10 whose upper surface abuts on the lower surface of the semiconductor element 4 with a smaller area is formed at a height equal to the thickness after curing of the adhesive 9. Thereby, even if the semiconductor element 4 is bonded and fixed to the upper main surface of the high heat conductive member 5 ′ with the adhesive 9, the upper surface of the convex portion 10 exposed from the adhesive 9 contacts the lower surface of the semiconductor element 4. Since the heat generated from the semiconductor element 4 is directly transferred to the convex portion 10 of the high heat conductive member 5 ′, the heat generated when the semiconductor element 4 operates is obstructed by the adhesive 9 having a low heat conductivity. Therefore, the heat generated from the semiconductor element 4 can be efficiently absorbed and dissipated by the high heat conductive member 5 ′.
[0063]
Such a high thermal conductive member 5 ′ has a convex portion 10 having a height equal to the thickness after curing of the adhesive 9 in the adhesive portion of the semiconductor element 4 on the upper main surface, and is subjected to physical cutting or chemical etching. It is produced by forming by a method such as. The planar shape of the convex portion 10 is preferably a square shape in accordance with the shape of the semiconductor element 4 in order to efficiently absorb the heat generated during the operation of the semiconductor element 4. In consideration of the occurrence of local thermal stress at the corners of the portion 10, the corners of the quadrangular shape may be rounded (R surface). Further, it is preferable that the upper surface of the convex portion 10 in contact with the lower surface of the semiconductor element 4 is flat in order to be in close contact with the semiconductor element 4 without any gap and efficiently absorb the generated heat. Further, the area of the upper surface of the convex portion 10 contacting the lower surface of the semiconductor element 4 is preferably 40% to 90% of the area of the lower surface of the semiconductor element 4. If the area of the upper surface of the convex portion 10 that contacts the lower surface of the semiconductor element 4 of the convex portion 10 is less than 40% of the area of the lower surface of the semiconductor element 4, the heat generated during the operation of the semiconductor element 4 is directly high enough. Since it is difficult to be transmitted to the conductive member 5 ', the heat absorption / dissipation property is lowered. On the other hand, when the area of the upper surface of the convex portion 10 in contact with the lower surface of the semiconductor element 4 exceeds 90% of the area of the lower surface of the semiconductor element 4, the semiconductor element 4 is bonded to the upper main surface of the high heat conductive member 5 ′ with the adhesive 9. The area to be processed is less than 10% of the area of the lower surface of the semiconductor element 4, and the force for bonding and fixing to the high heat conductive member 5 ′ becomes insufficient.
[0064]
The height of the convex portion 10 is preferably equal to the thickness after curing of the adhesive 9. If the height of the convex portion 10 is larger than the thickness of the adhesive 9 after curing, the adhesive 9 cannot bond the semiconductor element 4 to the high thermal conductive member 5 ′ with sufficient strength. Thus, compressive stress is applied to the semiconductor element 4, and the operation reliability of the semiconductor element 4 and the adhesive fixing force to the high thermal conductive member 5 ′ are reduced. On the other hand, if the height of the convex portion 10 is smaller than the thickness after curing of the adhesive 9, a gap is generated between the upper surface of the convex portion 10 and the lower surface of the semiconductor element 4, which occurs during operation of the semiconductor element 4. The heat absorption / dissipation property is reduced.
[0065]
In the example shown in FIGS. 3 and 4, an example in which one convex portion 10 is provided on the upper main surface of the high thermal conductive member 5 ′ is shown. However, the purpose of further improving the operational reliability of the semiconductor element 4 and the like. Thus, a plurality of convex portions 10 may be formed. By forming a plurality of protrusions 10, the semiconductor element 4 is placed on the plurality of protrusions 10, and the thickness of the adhesive 9 after curing becomes lower than the thickness of the protrusions 10. Even when compressive stress is applied to the semiconductor element 4, since the compressive stress is distributed to the plurality of convex portions 10, the local compressive stress on the semiconductor element 4 can be reduced, and the operation of the semiconductor element 4. Reliability can be further improved.
[0066]
When a plurality of convex portions 10 are thus formed, the high heat conductive member 5 ′ has a plurality of convex portions 10 having a height equal to the thickness after curing of the adhesive 9 in the adhesive portion of the semiconductor element 4 on the upper main surface. Is produced by a method such as physical cutting or chemical etching. The planar shape of the convex portion 10 is preferably a shape in which a quadrangular shape is divided into a plurality of shapes in accordance with the shape of the semiconductor element 4 in order to efficiently absorb heat generated during operation of the semiconductor element 4. In consideration of the occurrence of local thermal stress at the corners of the plurality of convex portions 10 at the time of bonding, the corner portions of the plurality of convex portions 10 may be rounded (R surface). The planar shape of the plurality of convex portions 10 has the same shape and the same size so that the semiconductor element 4 is bonded to the high thermal conductive member 5 ′ with a uniform adhesive force, and is centered on the bonding portion of the semiconductor element 4. It is preferable that the semiconductor elements 4 are square, and when the semiconductor elements 4 are square, a plurality of square protrusions 10 having the same shape and the same dimensions may be arranged at equal intervals in the bonding portion of the semiconductor elements 4. preferable. In addition, it is preferable that the upper surfaces of the plurality of convex portions 10 that are in contact with the lower surface of the semiconductor element 4 are flat in order to efficiently absorb heat generated in close contact with the semiconductor element 4 without a gap. In addition, the total area of the upper surfaces of the plurality of protrusions 10 in contact with the lower surface of the semiconductor element 4 is preferably 40% to 90% of the area of the lower surface of the semiconductor element 4. When the total area of the upper surfaces of the plurality of convex portions 10 that contact the lower surface of the semiconductor element 4 is less than 40% of the area of the lower surface of the semiconductor element 4, the heat generated during the operation of the semiconductor element 4 is directly high enough. Since it is difficult to be transmitted to the conductive member 5 ', the heat absorption / dissipation property is lowered. On the other hand, when the total area of the upper surfaces of the plurality of convex portions 10 in contact with the lower surface of the semiconductor element 4 exceeds 90% of the area of the lower surface of the semiconductor element 4, the semiconductor element 4 is bonded to the upper side of the high heat conductive member 5 ′ with the adhesive 9. The area bonded to the main surface is less than 10% of the area of the lower surface of the semiconductor element 4, and the force for bonding and fixing to the high heat conductive member 5 ′ becomes insufficient.
[0067]
The intervals between the plurality of protrusions 10 are preferably all equal so that the semiconductor elements 4 are bonded to the high thermal conductive member 5 ′ with an equal adhesive force. The size of the intervals is as described above. In addition, the plurality of convex portions 10 have the same shape and the same size, are arranged point-symmetrically with respect to the center of the bonding portion of the semiconductor element 4, and the total area of the upper surfaces of the plurality of convex portions 10 is the semiconductor element 4. It is determined from 40% to 90% of the area of the lower surface of the.
[0068]
The heights of the plurality of convex portions 10 are all equal and are preferably equal to the thickness after curing of the adhesive 9. If the heights of the plurality of protrusions 10 are not all equal, a local compressive stress is applied to the semiconductor element 4 when there are partially high protrusions 10. On the other hand, when the convex portion 10 is partially low, a gap is formed between the semiconductor element 4 and heat absorption / dissipation generated during the operation of the semiconductor element 4 is reduced. If the height of the plurality of protrusions 10 is greater than the thickness after curing of the adhesive 9, the adhesive 9 cannot bond the semiconductor element 4 to the high heat conductive member 5 'with sufficient strength, and the protrusion 10 This gives compressive stress to the semiconductor element 4, and decreases the operation reliability of the semiconductor element 4 and the adhesive fixing force to the high heat conductive member 5 ′. On the other hand, if the height of the convex portion 10 is smaller than the thickness after curing of the adhesive 9, a gap is generated between the upper surface of the convex portion 10 and the lower surface of the semiconductor element 4, which occurs during operation of the semiconductor element 4. The heat absorption / dissipation property is reduced.
[0069]
When the semiconductor element 4 is bonded and fixed to the upper surface of the high heat conductive member 5 ′ with the adhesive 9 in the wiring board 7 ′ of the present invention as in this example, the adhesive 9 is silver epoxy resin / solder / gold- Various adhesives such as tin can be used, but in order to reduce the heat and thermal stress applied to the semiconductor element 4 during bonding, it is preferable to use a silver epoxy resin that can be bonded at a low temperature.
[0070]
【Example】
Hereinafter, although the test result of the Example of this invention and the comparative example is given and the wiring board of this invention is demonstrated in detail, this invention is not limited only to the following Examples.
[0071]
A glass ceramic sintered body was used for the insulating substrate, and a glass ceramic green sheet kneaded with glass powder, filler powder (ceramic powder), organic binder, plasticizer, organic solvent, and the like was fired.
[0072]
As a glass ceramic component, SiO2-Al2O3-MgO-B2O3-ZnO-based glass powder 60% by mass, CaZrO320% by mass of powder, SrTiO317% by weight of powder and Al2O33% by weight of powder was used. To 100 parts by weight of the glass ceramic component, 12 parts by weight of an acrylic resin as an organic binder, 6 parts by weight of a phthalic plasticizer and 30 parts by weight of toluene as a solvent were added and mixed by a ball mill method to form a slurry. Using this slurry, a glass ceramic green sheet having a thickness of 300 μm was prepared by a doctor blade method.
[0073]
This glass ceramic green sheet was punched to produce via-hole conductors and through-holes, and cut to produce an insulating layer having an appropriate shape.
[0074]
A metal paste prepared by adding an organic binder or a solvent to silver metal powder and kneading was embedded in a predetermined pattern on the insulating layer by a screen printing method and printed to produce a via-hole conductor and a wiring circuit layer.
[0075]
After laminating a plurality of printed insulating layers embedded with this wiring conductor, the laminated body is heated to about 300 ° C to decompose and volatilize the organic components, and then fired at about 900 ° C. Then, the insulating layer was sintered to produce an insulating substrate having a through hole penetrating the upper and lower main surfaces in the center and a wiring conductor disposed around the through hole.
[0076]
The high thermal conductivity member is rectangular and has a thermal expansion coefficient of 20 × 10.-6Is made of silver at a temperature of / ° C., and is formed between the bonding portion of the brazing material and the bonding portion of the semiconductor element at the four corners of the outer region of the bonding portion of the semiconductor element and the central portion between the corner portions. Eight circular through-holes having a hole diameter half the size of the gap were punched in the center.
[0077]
Next, the high heat conductive member is embedded in the through hole of the insulating substrate so that the upper and lower main surfaces of the insulating substrate and the upper and lower main surfaces of the high heat conductive member are in the same plane, and then heated and cooled at about 700 ° C. Thus, the insulating substrate and the high heat conductive member were joined by filling and solidifying the silver-copper brazing material between the inner surface of the through hole of the insulating substrate and the side surface of the high heat conductive member. The insulating substrate has a thermal expansion coefficient of 9 × 10-6Glass ceramics at / ° C were used.
[0078]
The semiconductor element is mounted on the upper main surface of the high thermal conductive member, bonded and fixed with a silver epoxy resin adhesive, and the electrode of the semiconductor element is placed on the upper surface of the insulating substrate of the wiring conductor via an aluminum bonding wire. Connected electrically.
[0079]
As described above, the inner surface of the through hole of the insulating substrate and the side surface of the high heat conductive member are arranged so that the upper and lower main surfaces of the insulating substrate and the upper and lower main surfaces of the high heat conductive member are flush with each other. A sample of Example 1 of the wiring board according to the present invention, which is characterized by being joined via a brazing material, was prepared.
[0080]
Next, in the same manner, the high thermal conductivity member is rectangular and has a thermal expansion coefficient of 20 × 10.-6Using silver having a thermal conductivity of 400 W / m · K at / ° C. and cutting, the area of the upper surface contacting the lower surface of the semiconductor element at the center of the upper main surface of the high thermal conductive member is A square-shaped convex part having a height of 20 μm and having an area of 70% was formed. In addition, the four outer corners of the outer periphery of the bonded portion of the semiconductor element of the high thermal conductive member and the central portion between the corner portions, the center between the bonding portion of the brazing material and the bonded portion of the semiconductor element Eight circular through-holes having a hole diameter half as large as the interval were punched out, and a sample of Example 2 of the wiring board of the present invention was produced using this high heat conductive member.
[0081]
Further, as a comparative example, the lower surface around the through hole of the insulating substrate and the through hole are not formed between the inner surface of the through hole formed in the insulating substrate and the side surface of the high thermal conductive member by the same material and the same manufacturing method as described above. A wiring board having a conventional structure (hereinafter, referred to as a comparative example) in which the upper surface of the outer peripheral portion of the high heat conductive member having a size that can be covered was joined with a brazing material was produced.
[0082]
In order to evaluate the stress concentration characteristics of Examples 1 and 2 of the present invention and Comparative Examples, a brazing material bonding test, a semiconductor element heat generation test, and a mechanical impact test were performed. Neither of the serious problems such as part peeling occurred.
[0083]
Therefore, in order to make a more detailed comparison, the presence or absence of occurrence of cracks on the insulating substrate side at the joint portion of the brazing material was evaluated. The evaluation results are shown in Table 1.
[0084]
In the results shown in Table 1, in the brazing joint test, when the high thermal conductive member and the insulating substrate are joined via the brazing material, the surface of the insulating substrate is heated to 700 ° C. and then cooled to 25 ° C. When observed with a microscope with a magnification of 10 to 40 times, if there is a crack, there is a possibility that a problem will occur in the bonding reliability. Therefore, it was evaluated as “◯” because it was considered.
[0085]
As for the semiconductor element heat test, a semiconductor element is mounted on the upper main surface of the high thermal conductivity member, and the semiconductor element is raised to 125 ° C. in 5 seconds after starting operation in the first cycle, and then in 15 seconds after stopping. Initially set the applied current to the semiconductor element to lower to 25 ℃, after repeating this 5000 cycles continuously, observe the surface of the insulating substrate using a microscope with a magnification of 10 to 40 times, and Similarly, when there was a crack, it was evaluated as “×”, and when there was no crack, it was evaluated as “◯”.
[0086]
For mechanical impact tests, after dropping the wiring board with the semiconductor elements on the upper main surface of the high thermal conductivity member from a height of 10 cm, observe the surface of the insulating board using a microscope with a magnification of 10 to 40 times. In the same manner as above, when there was a crack, it was evaluated as “X”, and when there was no crack, it was evaluated as “◯”.
[0087]
[Table 1]
Figure 0003935090
[0088]
As is clear from the results shown in Table 1, in all the tests, cracks were observed in the comparative examples, but no cracks occurred in the insulating substrate in Examples 1 and 2 of the present invention. As a result, in the first and second embodiments of the present invention, the concentration of stress on the joint portion between the insulating substrate and the high thermal conductive member via the brazing material is low, and the insulating substrate and the high thermal conductive member are strengthened. It was confirmed that they were joined.
[0089]
Next, with respect to Examples 1 and 2 and Comparative Example of the present invention, an operation test of a semiconductor element was performed in order to evaluate heat absorption / dissipation characteristics. In this semiconductor element operation test, the semiconductor element is mounted on the upper main surface of the high thermal conductive member, the applied current to the semiconductor element is set so that the semiconductor element is constant at 125 ° C. By measuring the temperature of the lower main surface of the conductive member, the thermal resistance of the wiring boards of Examples 1 and 2 and the comparative example was determined. Compared to the comparative example, the thermal resistance of the wiring board is reduced by 10% in Example 1 and 20% in Example 2. According to the wiring board of the present invention, the heat absorption of the semiconductor element by the high thermal conductive member is achieved. -It was confirmed that the emission characteristics were improved.
[0090]
In addition, this invention is not limited to the example of said embodiment, A various change is possible if it is the range which does not deviate from the summary of this invention. For example, in the above example, the wiring board of the present invention is applied to a package for housing a semiconductor element that houses a semiconductor element, but may be applied to other uses such as a hybrid integrated circuit board and an LED storage container.
[0091]
【The invention's effect】
According to the wiring board of the present invention, the plate-like high heat conductive member in which the semiconductor element is bonded to the central portion of the upper main surface and the plurality of through holes are formed in the outer peripheral portion is formed on the upper and lower main surfaces of the insulating substrate. The inner surface of the through hole that penetrates between the upper and lower main surfaces of the insulating substrate and the side surface of the high heat conductive member are joined via a brazing material so that the upper and lower main surfaces of the high heat conductive member are flush with each other. Therefore, the tensile stress and compressive thermal stress at the time of joining with the brazing material and the operation of the semiconductor element caused by the difference in thermal expansion coefficient between the high thermal conductive member and the insulating substrate are the side surfaces of the high thermal conductive member. And the inner surface of the through hole of the insulating substrate have a uniform stress distribution with no local bias, and the thermal contraction behavior of the wiring substrate is the thermal contraction of the high thermal conductive member and the thermal contraction of the insulating substrate. In the horizontal direction (direction parallel to the main surface of the wiring board) To generate a state aligned in, the wiring board by such thermal shrinkage behavior may be assumed that the warpage does not occur.
[0092]
In addition, since the wiring board does not warp and the high heat conductive member does not warp, even if the semiconductor element is bonded and fixed to the high heat conductive member, the thickness of the adhesive having low heat conductivity is uniform and thin on the entire bonding surface. Therefore, the heat generated during the operation of the semiconductor element is easily transferred to the high thermal conductive member via the thin adhesive, and the heat of the semiconductor element is larger than that in the case where the thickness of the adhesive is uneven and thick. The absorption and dissipation of can be increased.
[0093]
In addition, the generated thermal stress is such that the upper and lower main surfaces of the insulating substrate and the upper and lower main surfaces of the high thermal conductive member are the same surface, and there is no portion where stress is partially concentrated between the two. Since the brazing material that is dispersed on the inner surface of the through hole of the insulating substrate and the side surface of the high thermal conductive member wiring substrate and that joins between them also functions as a stress relaxation layer, it can be attenuated efficiently.
[0094]
Further, the high thermal conductive member is a region outside the outer periphery of the portion to which the semiconductor element that is the outer peripheral portion of the upper main surface is bonded, that is, between the central portion that is the bonded portion of the semiconductor element and the bonding portion of the brazing material. Since a plurality of through-holes are formed in the part, the tensile force generated at the brazing material joining portion when joining with the brazing material and operating the semiconductor element due to the difference in thermal expansion coefficient between the high thermal conductive member and the insulating substrate Since the compressive thermal stress can be dispersed in the plurality of through holes, it can be efficiently attenuated so that the wiring board does not warp.
[0095]
Therefore, the bonding between the insulating substrate and the high thermal conductive member is caused by the destruction of the interface between the high thermal conductive member and the insulating substrate at the time of joining with the brazing material or the generation of cracks in the insulating substrate during the operation of the electronic component such as a semiconductor element. Reduction in reliability and the like can be effectively suppressed.
[0096]
Also, the inner surface of the through hole of the insulating substrate and the side surface of the high heat conductive member are joined via a brazing material so that the upper and lower main surfaces of the insulating substrate and the upper and lower main surfaces of the high heat conductive member are the same surface. Therefore, even when a mechanical shock is applied to the wiring board due to a drop or the like, the step formed between the side surface of the high thermal conductive member where stress is likely to concentrate and the lower main surface of the insulating substrate, as in the conventional wiring board Since there is no step portion formed between the inner surface of the through hole of the insulating portion and the insulating substrate and the upper main surface of the high thermal conductive member, there is no portion that becomes the starting point of the destruction of the insulating substrate, and it should be resistant to mechanical shock. it can. And since it becomes a structure where a highly heat-conductive member is accommodated in the inside of a wiring board, it becomes possible to achieve size reduction and thickness reduction easily.
[0097]
In the case where a convex portion whose upper surface is in contact with the lower surface of the semiconductor element having an area smaller than the area of the semiconductor element is formed in the central portion of the upper main surface of the high heat conductive member, the semiconductor element is Even if it is bonded and fixed by an adhesive, the upper surface of the convex portion exposed from the adhesive is in contact with the lower surface of the semiconductor element, so that the heat generated from the semiconductor element is directly applied to the convex portion of the high thermal conductive member. Therefore, the heat generated when the semiconductor element operates can be transferred to the high thermal conductive member without being hindered by the adhesive having low thermal conductivity, and the high thermal conductive member efficiently absorbs the heat generated from the semiconductor element. Can be dissipated.
[0098]
In addition, when the high heat conductive member has a quadrangular shape and the through holes are formed at the corners of the outer peripheral portion, the maximum thermal stress of local tension and compression generated at the corner portions is high. Since it disperse | distributes to the several through-hole formed in the corner | angular part of the outer peripheral part of a conductive member, it can attenuate | dampen very efficiently and it can be set as the thing which does not generate | occur | produce a curvature in a wiring board more reliably.
[0099]
Further, when a plurality of protrusions are formed, the semiconductor element is placed on the plurality of protrusions, and the thickness of the adhesive after curing is lower than the thickness of the protrusions. Even when compressive stress is applied to the semiconductor element, the compressive stress is distributed to the plurality of convex portions, so that the local compressive stress on the semiconductor element can be reduced, and the operation reliability of the semiconductor element is further improved. Can be expensive.
[0100]
As described above, according to the present invention, the high thermal conductivity member and the insulating substrate are firmly bonded, and the heat generated by the semiconductor element is efficiently absorbed and dissipated, so that the semiconductor element can operate normally and stably over a long period of time. Therefore, it is possible to provide a highly reliable wiring board capable of achieving the above.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an example of an embodiment of a wiring board according to the present invention.
FIG. 2 is a plan view showing an example of an embodiment of a wiring board according to the present invention.
FIG. 3 is a cross-sectional view showing another example of the embodiment of the wiring board of the present invention.
FIG. 4 is a plan view showing another example of the embodiment of the wiring board according to the present invention.
FIG. 5 is a cross-sectional view showing an example of a conventional wiring board.
[Explanation of symbols]
1. Insulating substrate
1a-1d ... Insulating layer
2 .... through hole
3. Wiring conductor
3a: Via hole conductor
3b ··· Wiring circuit layer
4 .... Semiconductor element
5, 5 '... High heat conduction member
6 .... Wax
7, 7 '... Wiring board
8 ..... through hole
9 .... Adhesive
10 ...

Claims (5)

上下主面間を貫通する貫通穴を有するとともに該貫通穴の周辺に配線導体が配設された絶縁基板に、上側主面の中央部に半導体素子が接着される外周部に複数個の貫通孔が形成された板状の高熱伝導部材が、前記絶縁基板の前記上下主面と前記高熱伝導部材の上下主面とがそれぞれ同一面をなすように、前記貫通穴の内面と前記高熱伝導部材の側面との間にロウ材を介して接合されて成ることを特徴とする配線基板。  A plurality of through-holes in an outer peripheral portion where a semiconductor element is bonded to the central portion of the upper main surface on an insulating substrate having a through-hole penetrating between the upper and lower main surfaces and a wiring conductor disposed around the through-hole In the plate-like high heat conductive member formed with the upper and lower main surfaces of the insulating substrate and the upper and lower main surfaces of the high heat conductive member, the inner surface of the through hole and the high heat conductive member A wiring board, which is joined to a side surface via a brazing material. 前記高熱伝導部材の前記上側主面の前記中央部に前記半導体素子の面積よりも小さい面積の、前記半導体素子の下面に上面が当接する凸部が形成されていることを特徴とする請求項１記載の配線基板。  The convex part which an upper surface contacts with the lower surface of the said semiconductor element of the area smaller than the area of the said semiconductor element is formed in the said center part of the said upper main surface of the said high heat conductive member. The wiring board described. 前記高熱伝導部材が四角形状であり、前記貫通孔が前記外周部の角部に形成されていることを特徴とする請求項１記載の配線基板。The wiring board according to claim 1, wherein the high heat conductive member has a quadrangular shape, and the through holes are formed at corners of the outer peripheral portion. 前記高熱伝導部材が四角形状であり、前記貫通孔が前記外周部の角部に形成されていることを特徴とする請求項２記載の配線基板。The wiring board according to claim 2, wherein the high heat conductive member has a quadrangular shape, and the through holes are formed at corners of the outer peripheral portion. 前記凸部が複数形成されていることを特徴とする請求項２又は請求項４記載の配線基板。The wiring board according to claim 2, wherein a plurality of the convex portions are formed.
JP2003048346A 2003-01-28 2003-02-25 Wiring board Expired - Fee Related JP3935090B2 (en)

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