JP2004266003A

JP2004266003A - Radiator, power module substrate, power module and radiator manufacturing method using the radiator

Info

Publication number: JP2004266003A
Application number: JP2003053117A
Authority: JP
Inventors: Kazuaki Kubo; 和明久保; Toshiyuki Nagase; 敏之長瀬
Original assignee: Mitsubishi Materials Corp
Current assignee: Mitsubishi Materials Corp
Priority date: 2003-02-28
Filing date: 2003-02-28
Publication date: 2004-09-24
Anticipated expiration: 2023-02-28
Also published as: JP3885745B2

Abstract

【課題】絶縁基板及び放熱体の双方の熱膨張係数差があっても、これに拘わることなく反りを低減できると共に、熱伝導率が低下することを抑制できる放熱体並びにこの放熱体を用いたパワーモジュール用基板及びパワーモジュール並びに放熱体の製造方法を提供すること。
【解決手段】被放熱体の熱を放熱させる放熱体１６であって、放熱体本体１７と，放熱体本体１７の熱膨張係数より低い材質からなる低熱膨張材１８とを備え、放熱体本体１７は、板状体１７ａ，及び鋳造体１７ｂを少なくとも備えた積層体をなし、かつ板状体１７ａが放熱体本体１７の各最外層に各々配設された構成をなし、低熱膨張材１８はＳｉ粒子の集合体からなり、かつ板状体１７ａ同士の間にＳｉ粒子同士の間隙を介して鋳造体１７ｂにより鋳包まれて配設されている。
【選択図】図１A heat radiator capable of reducing warpage and suppressing a decrease in thermal conductivity even if there is a difference in thermal expansion coefficient between an insulating substrate and a heat radiator, and the heat radiator To provide a power module substrate, a power module, and a method of manufacturing a radiator.
A heat dissipating body for dissipating heat from a heat dissipating body, comprising a heat dissipating body and a low thermal expansion material made of a material having a coefficient of thermal expansion lower than that of the heat dissipating body. Is a laminated body including at least a plate-like body 17a and a cast body 17b, and the plate-like body 17a is disposed on each outermost layer of the radiator body 17, and the low thermal expansion material 18 is made of Si. It consists of an aggregate | assembly of particle | grains, and it is cast and arrange | positioned by the casting body 17b between the plate-shaped bodies 17a through the gap | interval of Si particles.
[Selection] Figure 1

Description

【０００１】
【発明の属する技術分野】
この発明は、被放熱体の熱を放熱させる放熱体並びにこの放熱体を用いたパワーモジュール用基板及びパワーモジュール並びに放熱体の製造方法に関するものである。
【０００２】
【従来の技術】
半導体装置としてのパワーモジュールは、一般に、半導体チップがパワーモジュール用基板に搭載され、半導体チップの熱がパワーモジュール用基板に伝導されることから、パワーモジュール用基板に伝わる熱を放熱する必要がある。
このような被放熱体としてのパワーモジュール用基板は、セラミックス材料からなる絶縁基板（セラミックス基板）に金属薄板が直接積層され、この金属薄板に可塑性多孔質金属層を介し、ヒートシンクからなる放熱体が積層接着される（例えば、特許文献１参照）。可塑性多孔質金属層は、気孔率２０〜５０％のＣｕの多孔質焼結体であって、絶縁基板が、これに搭載されている半導体チップからの熱を受けたとき、その熱変形を吸収する応力緩和層をなす構成であり、これにより、絶縁基板及び放熱体の反りや割れを防止でき、放熱体が良好な放熱作用を果たすこともできるようになっている。
【０００３】
【特許文献１】
特開平８−３３５６５２号公報（第４−１２頁、図１〜図５）
【０００４】
【発明が解決しようとする課題】
ところで、前記従来では、被放熱体としてのパワーモジュール用基板に設けられた可塑性多孔質金属層が、絶縁基板や放熱体の熱変形を吸収するので、絶縁基板と放熱体との熱膨張係数が異なっても、絶縁基板，放熱体に反りや割れが起こるのを防止できるようにしているものの、絶縁基板と放熱体との間に可塑性多孔質金属層が介在しているので、その分だけ熱抵抗が上昇して熱伝導率が低下してしまい、そのため、放熱体の放熱効果が悪くなっていた。
【０００５】
一般に、放熱体は、被放熱体との間で互いに熱膨張係数の異なる材質で構成する場合、両者の熱膨張係数の差による反りを防止するために、両者の熱膨張係数を合わせることが容易に考えられる。この場合、熱膨張係数の低い方（被放熱体）に合わせることになるが、そうすると、反りを低減できる反面、その分だけ熱伝導率が低下して放熱効果の低下をきたしてしまい、反り対策と良好な放熱効果との双方を兼ね備えたものの要請に応えることができない問題があった。
【０００６】
この発明は、このような事情を考慮してなされたもので、その目的は、被放熱体と間で熱膨張係数差があっても、これに拘わることなく反りを低減することができるとともに、熱伝導率が低下することも抑制することができる放熱体並びにこの放熱体を用いたパワーモジュール用基板及びパワーモジュール並びに放熱体の製造方法を提供することにある。
【０００７】
【課題を解決するための手段】
前記目的を達成するために、この発明は以下の手段を提案している。
請求項１に係る発明は、被放熱体の熱を放熱させる放熱体であって、放熱体本体と，該放熱体本体の熱膨張係数より低い材質からなる低熱膨張材とを備え、前記放熱体本体は、板状体，及び鋳造体を少なくとも備えた積層体をなし、かつ前記板状体が前記放熱体本体の各最外層に各々配設された構成をなし、前記低熱膨張材はＳｉ粒子の集合体からなり、かつ前記板状体同士の間にＳｉ粒子同士の間隙を介して前記鋳造体により鋳包まれて配設されていることを特徴とする。
【０００８】
この発明に係る放熱体によれば、前記低熱膨張材としてＳｉ粒子の集合体が配設されているので、放熱体に低熱膨張材を備えた構成においても熱伝導率の低下が最小限に抑制されるとともに、放熱体全体の熱膨張係数が確実に低下する。すなわち、Ｓｉは、熱伝導率がおよそ１５０Ｗ／ｍ・Ｋのいわゆる高熱伝導材であるとともに、熱膨張係数がおよそ２．２×１０−６／℃のいわゆる低熱膨張材であるため、Ｓｉ粒子集合体が放熱体内部に埋設されることにより、この放熱体の熱伝導率の低下が抑制されるとともに、熱膨張係数が可及的に低下することになる。従って、被放熱体と放熱体とをはんだ等によって接合した際、放熱体に被放熱体に向かう反りが発生することを確実に抑制するとともに、このような構成においても放熱体の熱伝導率の低下を最小限に抑制することになる。また、板状体が放熱体本体の各最外層に配設されているので、放熱体の被放熱体との当接面が平滑面となり、放熱体と被放熱体とが良好に密着することになるため、被放熱体からの熱が放熱体に良好に伝導されることになる。さらに、低熱膨張材がＳｉ粒子の集合体からなるので、前記鋳造体を形成する際に、鋳造体となる溶湯がＳｉ粒子集合体の全体に浸透する，すなわちＳｉ粒子同士の間の間隙が鋳造体により充密されることになる。従って、被放熱体からの熱は放熱体の内部に滞ることなく良好に低温側へ向かって伝導することになる。
以上により、放熱体の熱膨張係数を可及的に小さくでき、放熱体の前記反りの発生を抑制することができるとともに、このような構成においても放熱体の熱伝導率の低下を最小限に抑制することができるようになる。
【０００９】
請求項２に係る発明は、請求項１記載の放熱体において、前記板状体及び鋳造体が、純Ａｌ，Ａｌ合金，純Ｃｕ又はＣｕ合金からなることを特徴とする。
【００１０】
この発明に係る放熱体によれば、板状体及び鋳造体が、純Ａｌ，Ａｌ合金，純Ｃｕ又はＣｕ合金から形成されているので、放熱性に優れた放熱体を容易且つ確実に形成することができるようになる。すなわち、鋳造体が純Ａｌ又はＡｌ合金により形成された場合では、良好な湯流れを実現する等，鋳造性に優れた材料であるため鋳造欠陥の発生が抑制され、従って、放熱体全体の熱伝導率の低下が最小限に抑制される。一方、鋳造体が純Ｃｕ又はＣｕ合金により形成された場合では、熱伝導率が大きい材料であるため放熱性に優れた放熱体を提供できるようになる。
【００１１】
請求項３に係る発明は、請求項１記載の放熱体において、前記板状体が純Ｃｕ又はＣｕ合金からなり、前記鋳造体が純Ａｌ又はＡｌ合金からなることを特徴とする。
【００１２】
この発明に係る放熱体によれば、板状体が純Ｃｕ又はＣｕ合金からなり、鋳造体が純Ａｌ又はＡｌ合金からなるので、被放熱体側の熱膨張係数，発熱量等に応じて、放熱体全体の熱膨張係数，及び熱伝導率の調整を容易になすことができるようになる。従って、放熱体と被放熱体とをはんだ接合する際，及び放熱体と被放熱体とを接合した状態で使用する際に放熱体に反りが発生することが確実に抑制される。また、純Ａｌ又はＡｌ合金は、鋳造性に優れているため鋳造欠陥の発生が抑制され、従って、放熱体全体の熱伝導率の低下が最小限に抑制される。
【００１３】
請求項４に係る発明は、請求項１から３のいずれかに記載の放熱体において、前記板状体が圧延材であることを特徴とする。
【００１４】
この発明に係る放熱体によれば、板状体が圧延材であるため、板状体に内在する空孔等の内部欠陥の含有が最小限に抑制され、放熱体の熱伝導率の低下が抑制される。すなわち、放熱体本体全体が例えば，鋳造体である場合、巣を始めとする内部欠陥が発生する場合があり、この内部欠陥が放熱体内部における熱の伝導を阻害することになるため、放熱体全体の熱伝導率の低下を招くことがある。しかしながら、前述したように板状体が圧延材の場合、前記内部欠陥が形成される場合が少ないため、前記熱伝導率の低下が最小限に抑制される。
【００１５】
請求項５に係る発明は、請求項１から４のいずれかに記載の放熱体において、前記各板状体の厚さは、放熱体において、被放熱体側の熱膨張係数が放熱体側の熱膨張係数より小さいとき、被放熱体側の板状体の厚さを放熱体側の板状体の厚さより厚く形成する一方、被放熱体側の熱膨張係数が放熱体側の熱膨張係数より大きいとき、被放熱体側の板状体の厚さを放熱体側の板状体の厚さより薄く形成することを特徴とする。
【００１６】
この発明に係る放熱体によれば、各板状体の厚さが前述のように設定されているので、鋳造体を形成する際に放熱体に発生した反りと、この放熱体と被放熱体とをはんだ接合した際に放熱体に発生しようとする反りとが互いに相殺し合い、結果として放熱体と被放熱体との双方が平坦となる。従って、被放熱体と放熱体との密着性が確保されることになるため、被放熱体の熱を放熱体に確実に伝導できるようになる。
【００１７】
請求項６に係る発明は、絶縁基板と，該絶縁基板の一方の面側に設けられた放熱体とを備えたパワーモジュール用基板であって、前記放熱体は、請求項１から５のいずれかに記載の放熱体であることを特徴とする。
【００１８】
この発明に係るパワーモジュール用基板によれば、放熱体が請求項１から５のいずれかに記載の放熱体であるので、この放熱体の熱膨張係数を可及的に小さくでき、放熱体の前記反りの発生を抑制することができるとともに、このような構成においても放熱体の熱伝導率の低下を最小限に抑制することができるため、反り発生抑制効果と熱伝導率の低下抑制効果との双方を有するパワーモジュール用基板を提供できるようになる。
【００１９】
請求項７に係る発明は、請求項６記載のパワーモジュール用基板において、前記絶縁基板の前記一方の面に金属層を、他方の面に回路層を各々備え、前記金属層及び前記回路層は、純Ａｌ，Ａｌ合金，純Ｃｕ，又はＣｕ合金からなることを特徴とする。
【００２０】
この発明に係るパワーモジュール用基板によれば、絶縁基板と放熱体との熱膨張係数の差に拘わることなく、両者の反りを可及的に抑えつつ良好な熱伝導率を有するパワーモジュール用基板が確実に得られる。
【００２１】
請求項８に係る発明は、請求項６又は７に記載のパワーモジュール用基板の前記絶縁基板の他方の面側に、チップを搭載してなることを特徴とする。
【００２２】
この発明に係るパワーモジュールによれば、絶縁基板と放熱体との熱膨張係数の差に拘わることなく、両者の反りを可及的に抑えつつ良好な熱伝導率を有するパワーモジュールが得られる。
【００２３】
請求項９に係る発明は、被放熱体の熱を放熱させる放熱体の製造方法であって、板状体同士の間にＳｉ粒子を配し、前記板状体と前記Ｓｉ粒子の集合体とを備えた積層体を形成した後、前記各板状体により前記Ｓｉ粒子の集合体を狭持した状態で、前記板状体同士の間に溶湯を注入し、前記Ｓｉ粒子の集合体を鋳包むことを特徴とする。
【００２４】
この発明に係る放熱体の製造方法によれば、前記低熱膨張材を放熱体本体に鋳包む際に予め、板状体により低熱膨張材としてのＳｉ粒子の集合体を狭持しておき、この状態でＳｉ粒子集合体に溶湯を注入しＳｉ粒子集合体を放熱体本体に鋳包むため、低熱膨張材が高精度に形成，及び位置決めされる。すなわち、Ｓｉ粒子集合体に溶湯を注入してこの集合体を放熱体本体に鋳包む際に、Ｓｉ粒子集合体に作用する溶湯の注入圧により、前記集合体が型崩れする，或いは放熱体本体に対する配設位置がずれる等し易いが、溶湯注入時にＳｉ粒子集合体を狭持しておき、この状態で溶湯を注入するため、前記注入圧によるＳｉ粒子集合体の型崩れ等の発生が抑制されることになる。これにより、熱膨張係数，熱伝導率等の特性を安定させて放熱体を形成することができ、量産品質を確保することができるようになる。
また、放熱体と，この放熱体の熱膨張係数と異なる熱膨張係数の被放熱体とをはんだ接合した際に放熱体に発生する反りと略同等且つ反対方向の反りが、低熱膨張材を鋳包む際に放熱体に生じるように、板状体の厚さを各別に異ならせる設定を容易に行うことができるようになる。このように板状体の厚さを各別に設定することにより、低熱膨張材を鋳包む際に放熱体に発生した反りと、この放熱体と被放熱体とをはんだ接合した際に放熱体に発生しようとする反りとが互いに相殺し合い、結果として放熱体と被放熱体との双方が平坦となり、被放熱体と放熱体とを良好に密着させることができるようになるため、被放熱体の熱を放熱体に確実に伝導できるようになる。
さらに、低熱膨張材としてＳｉ粒子の集合体としたので、Ｓｉ粒子同士の間に溶湯が良好に浸透するため、形成された放熱体においては、鋳造体が放熱体の厚さ方向及び沿面方向の双方に連続することになる。従って、放熱体自体の熱伝導率の低下抑制をより確実に図ることができるようになる。
【００２５】
【発明の実施の形態】
以下、図面を参照し、この発明の実施の形態について説明する。図１はこの発明の一実施形態に係るパワーモジュール用基板を適用したパワーモジュールを示す全体図である。
本実施形態のパワーモジュールＰにおいて、パワーモジュール用基板１０は、大別すると図１に示すように、絶縁基板１１と，放熱体１６とを備える。
絶縁基板１１は、例えばＡｌＮ，Ａｌ２Ｏ３，Ｓｉ３Ｎ４，ＳｉＣ等により所望の大きさに形成され、絶縁基板１１の上面に回路層１２が，下面に金属層１３がそれぞれ積層接合される。回路層１２及び金属層１３は、純Ａｌ，Ａｌ合金，純Ｃｕ，Ｃｕ合金等により形成され、はんだ付け又はろう付け等により絶縁基板１１上下面に積層接合されている。
【００２６】
絶縁基板１１上面に設けられた回路層１２上面に、はんだ１４によって半導体チップ３０が搭載される一方、絶縁基板１１下面に設けられた金属層１３の下面に、はんだ１５によって或いはろう付けや拡散接合等によって放熱体１６が接合され、更に、この放熱体１６下面に冷却シンク部３１が設けられている。このように構成されたパワーモジュールＰにおいては、絶縁基板１１側から放熱体１６に伝導された熱が、冷却シンク部３１内の冷却液（或いは冷却空気）３２により外部に放熱される構成となっている。尚、放熱体１６は、冷却シンク部３１に取付ねじ３３によって密着した状態で取付けられている。
【００２７】
ここで、放熱体１６は放熱体本体１７と，放熱体本体１７の熱膨張係数より低い材質からなる低熱膨張材１８とを備えている。
放熱体本体１７は、純Ａｌ，Ａｌ合金，純Ｃｕ又はＣｕ合金のいずれかからなる，板状体１７ａ及び鋳造体１７ｂを備えた積層体をなし、且つ板状体１７ａが放熱体本体１７の各最外層，すなわち絶縁基板１１側，及び冷却シンク部３１側に各々配設された構成となっている。ここで、板状体１７ａは圧延材により形成されている。
【００２８】
一方、低熱膨張材１８は、Ｓｉ粒子の集合体からなり、かつ板状体１７ａ同士の間にＳｉ粒子同士の間隙を介して鋳造体１７ｂにより鋳包まれて配設されている。すなわち、鋳造体１７ｂはＳｉ粒子同士の間隙に充密するように配されるとともに、Ｓｉ粒子の集合体の厚さ方向及び沿面方向に連続して配設され、さらに各板状体１７ａの低熱膨張材１８側の表面と接合した構成となっている。
【００２９】
ここで、放熱体本体１７は、前述したように、純Ａｌ若しくはＡｌ合金，好ましくは純度９９．５％以上のＡｌ合金、又は純Ｃｕ若しくはＣｕ合金，好ましくは純度９９．９％以上の高純度Ｃｕのような変形抵抗が小さく，且つ熱伝導性の良好な材質，いわゆる高熱伝導材によって形成されている。高熱伝導材としては、熱伝導率が例えば、１００Ｗ／ｍ・Ｋ以上，好ましくは１５０Ｗ／ｍ・Ｋ以上のものである。
【００３０】
一方、低熱膨張材１８であるＳｉ粒子の集合体は、放熱体本体１７の熱膨張係数より低い熱膨張係数，およそ２．２×１０−６／℃の材質からなっており、鋳造体１７ｂに鋳包む，すなわち放熱体本体１７の内部に埋設することで、放熱体１６全体の熱膨張係数と絶縁基板１１の熱膨張係数との差を可及的に近づける構成となっている。また、このＳｉ粒子集合体は、熱伝導率がおよそ１５０Ｗ／ｍ・Ｋであり、放熱体本体１７の熱伝導率と同等となっており、互いに異種材料である放熱体本体１７と低熱膨張材１８とが積層されたことによる放熱体１６全体の熱伝導率の低下を最小限に抑制できる構成となっている。
以上のように構成されたパワーモジュールＰにおいては、絶縁基板１１側の熱膨張係数が放熱体１６側の熱膨張係数より小さくなっており、この場合、絶縁基板１１側の板状体１７ａの厚さが冷却シンク部３１側の板状体１７ａの厚さより厚く形成されている。
【００３１】
以上のように構成された放熱体１６を形成する製造方法について説明する。
まず、純Ａｌ，Ａｌ合金，純Ｃｕ又はＣｕ合金のいずれかからなる圧延材の板状体１７ａ同士の間に、板状体１７ａ表面の略全面に亘って所定の厚さになるようにＳｉ粒子を配した後、各板状体１７ａにより低熱膨張材１８であるＳｉ粒子集合体を狭持する。そして、この状態で低熱膨張材１８側面側から純Ａｌ，Ａｌ合金，純Ｃｕ又はＣｕ合金のいずれかからなる溶湯を注入する。この際、溶湯はＳｉ粒子同士の間隙を縫って、低熱膨張材１８の厚さ方向及び沿面方向に流れ、さらに、Ｓｉ粒子集合体を狭持している各板状体１７ａの低熱膨張材１８との当接面にまで至る。そして、この溶湯を冷却硬化することで、放熱体１６の最外層を構成する各板状体１７ａ同士を接合するとともに，低熱膨張材１８を鋳包む鋳造体１７ｂが形成され、放熱体１６が形成される。
【００３２】
以上説明したように、本実施形態による放熱体１６によれば、放熱体１６が、放熱体本体１７の熱膨張係数より低い熱膨張係数の材質からなる低熱膨張材１８を備えているので、放熱体１６全体としての熱膨張係数を確実に下げることができ、絶縁基板１１と放熱体１６全体との熱膨張係数の差を可及的に小さくすることができる。
【００３３】
このため、絶縁基板１１と放熱体１６とをはんだ１５（若しくはろう付けや拡散接合等）によって接合した場合、放熱体１６に絶縁基板１１に向かう反りが発生することを確実に抑制することができる。これにより、放熱体１６を冷却シンク部３１に取り付けても、冷却シンク部３１と放熱体１６との間に間隙が発生することを防止することができ、放熱体１６から冷却シンク部３１へ高効率に熱を伝導することができる。従って、パワーモジュールＰ全体としての熱伝導率の低下を抑制することができ、結果として、半導体チップ３０の温度上昇をも抑制することができる。
【００３４】
また、低熱膨張材１８としてＳｉ粒子の集合体が配設されているので、放熱体１６が低熱膨張材１８を備えた構成においても熱伝導率の低下を最小限に抑制することができるとともに、放熱体１６全体の熱膨張係数を確実に低下することができる。すなわち、Ｓｉは、熱伝導率がおよそ１５０Ｗ／ｍ・Ｋのいわゆる高熱伝導材であるとともに、熱膨張係数がおよそ２．２×１０−６／℃のいわゆる低熱膨張材であるため、Ｓｉ粒子集合体を放熱体１６内に埋設することにより、この放熱体１６の熱膨張係数を可及的に低下することができるとともに、熱伝導率の低下を抑制することができる。
【００３５】
また、低熱膨張材１８がＳｉ粒子の集合体からなるので、鋳造体１７ｂを形成する際に、鋳造体１７ｂとなる溶湯がＳｉ粒子集合体の全体に確実に浸透し、Ｓｉ粒子同士の間の間隙に鋳造体１７ｂを充密させて配することができる。従って、絶縁基板１１からの熱が放熱体１６内部に滞ることなく良好に冷却シンク部３１側へ伝導することになるため、放熱体１６の熱膨張係数の低下と，熱伝導率の低下抑制との双方を図ることができる。
【００３６】
また、板状体１７ａ及び鋳造体１７ｂが、純Ａｌ，Ａｌ合金，純Ｃｕ又はＣｕ合金のいずれかから形成されているので、放熱性の優れた放熱体１６を備えたパワーモジュール用基板１０を容易且つ確実に形成することができる。すなわち、鋳造体１７ｂが純Ａｌ又はＡｌ合金により形成された場合では、良好な湯流れを実現する等，鋳造性に優れた材料であるため鋳造欠陥の発生が抑制され、従って、放熱体１６全体の熱伝導率の低下が最小限に抑制される。一方、鋳造体１７ｂが純Ｃｕ又はＣｕ合金により形成された場合では、熱伝導率が大きい材料であるため放熱性に優れた放熱体１６を有するパワーモジュール用基板１０を確実に提供できるようになる。
【００３７】
ここで、絶縁基板１１側の板状体１７ａの厚さを冷却シンク部３１側の板状体１７ａの厚さより厚く形成しているので、鋳造体１７ｂを形成する際、放熱体１６には、絶縁基板１１へ向かう反りが発生することになる。また、この放熱体１６を絶縁基板１１と接合する際、絶縁基板１１の熱膨張係数は放熱体１６の熱膨張係数より小さいので、放熱体１６には、絶縁基板１１へ向かう方向に反りが発生しようとする。この際、放熱体１６には、鋳造体１７ｂを形成した際に絶縁基板１１から遠ざかる方向に反りが生じているので、これらの各反りが互いに相殺し合うことになり、結果として放熱体１６と絶縁基板１１との双方を平坦とすることができ、これらを良好に互いに密着させることができる。
すなわち、放熱体１６と，この放熱体１６の熱膨張係数と異なる熱膨張係数の絶縁基板１１とをはんだ接合した際に放熱体１６に発生する反りと略同等且つ反対方向の反りが、低熱膨張材１８を鋳造体１７ｂに鋳包む際に放熱体１６全体に生じるように、板状体１７ａの厚さを絶縁基板１１側と冷却シンク部３１側とで各別に異ならせる設定を容易になすことができるようになり、放熱体１６と絶縁基板１１とを良好に密着させることができ、絶縁基板１１の熱を放熱体１６に確実に伝導させる構成を容易に形成することができる。
【００３８】
また、低熱膨張材１８を放熱体本体１７に鋳包む際に予め、板状体１７ａにより低熱膨張材１８としてのＳｉ粒子集合体を狭持しておき、この状態でＳｉ粒子集合体の側面側から溶湯を注入するため、低熱膨張材１８を高精度に形成することができるとともに、放熱体１６の厚み方向，及び沿面方向に対する低熱膨張材１８の配設位置を高精度に位置決めすることができる。すなわち、低熱膨張材１８を放熱体本体１７に鋳包む際に、低熱膨張材１８に作用する溶湯の注入圧により、低熱膨張材１８の放熱体本体１７に対する配設位置がずれる，Ｓｉ粒子集合体が型崩れする等し易いことになるが、この際、低熱膨張材１８は板状体１７ａにより狭持されているので、前記注入圧による低熱膨張材１８の前記位置ずれ，型崩れ等の発生を抑制することができる。従って、熱膨張係数，熱伝導率等の特性を安定させてパワーモジュール用基板１０を形成することができ、量産品質の確保を図ることができる。
【００３９】
さらに、形成された放熱体１６の最外層が圧延材の板状体１７ａとなるので、絶縁基板１１が載置される放熱体本体１７表面が平滑面となり、これにより、放熱体１６と絶縁基板１１との各当接面を互いに一様に密着させることができ、絶縁基板１１の熱を放熱体１６に確実に伝導することができる。
【００４０】
また、板状体１７ａが圧延材であるため、板状体１７ａに内在する空孔等の内部欠陥の含有を最小限に抑制することができ、放熱体１６の熱伝導率の低下を抑制することができる。すなわち、放熱体本体１７全体が例えば，鋳造体である場合、巣を始めとする内部欠陥が発生し易いが、この場合、放熱体１６内部を熱が伝導する際、前記内部欠陥が熱伝導を阻害することになるため、放熱体１６全体の熱伝導率の低下を招くことになる。しかしながら、前述したように板状体１７ａが圧延材の場合、前記内部欠陥が発生する場合が少ないため、前記熱伝導率の低下を最小限に抑制することができる。
【００４１】
なお、本発明は前記実施形態に限定されるものではなく、本発明の趣旨を逸脱しない範囲において種々の変更を加えることが可能である。例えば、放熱体１６表面に冷却シンク部３１を設けた構成を示したが、この構成に限らず、コルゲートフィンを設けた構成としてもよい。すなわち、放熱体１６表面にろう材を介して接合された接合部と、接合部の一端に設けられ接合部と直交して立上がる立上がり部と、立上がり部の上端に設けられ接合部に平行且つ離間する方向に延びる平坦部と、平坦部の一端に設けられ平坦部に直交且つ放熱体１６に向かって折返る折返し部とを備えた突出部を、放熱体１６の沿面方向に沿って繰返し連続して設けた構成としてもよい。なお、この構成においては、立上がり部と平坦部と折返し部と放熱体１６表面とが空間を形成することになる。
【００４２】
また、放熱体１６が取り付けられるパワーモジュール用基板１１として、放熱体１６側の面に金属層１３が設けられた例を示したが、金属層１３を設けず絶縁基板１１をろう材を介して放熱体１６に直接接合しても、同様の作用効果が得られる。
【００４３】
さらに、絶縁基板１１側の板状体１７ａにおいて、絶縁基板１１側の表面を平坦面としたが、この表面において、絶縁基板１１が接合される領域を、絶縁基板１１側へ凸とする台座部を形成してもよい。この場合、板状体１７ａは圧延材ではなく鋳造により形成してもよい。また、各板状体１７ａの低熱膨張材１８側の表面において、任意の領域を凹ませて形成してもよく、さらに、波形の凹凸形状を付与する等してもよく、平坦面に限らない。
【００４４】
さらにまた、放熱体本体１７が、純Ａｌ，Ａｌ合金，純Ｃｕ又はＣｕ合金のいずれかからなる板状体１７ａ及び鋳造体１７ｂを備えた構成を示したが、板状体１７ａを純Ｃｕ又はＣｕ合金とし、鋳造体１７ｂを純Ａｌ又はＡｌ合金としてもよい。この場合においても、前述と同様の作用効果を奏することができる。さらに、板状体１７ａと鋳造体１７ｂとを各々異なる材料で形成することにより、絶縁基板１１側の熱膨張係数，及び発熱量等に応じて、放熱体１６全体の熱膨張係数，及び熱伝導率等の調整を容易になすことができるようになる。従って、前述した放熱体１６の反り発生抑制効果をより確実に実現できることになる。
【００４５】
【発明の効果】
以上説明したように、請求項１に係る発明によれば、絶縁基板と放熱体とをはんだ等によって接合した際、放熱体に絶縁基板に向かう反りが発生することを確実に抑制するとともに、このような構成においても放熱体の熱伝導率の低下を最小限に抑制することができる。また、板状体が放熱体本体の各最外層に配設されているので、放熱体の絶縁基板との当接面が平滑面となり、放熱体と絶縁基板とが良好に密着することになるため、絶縁基板からの熱を放熱体に良好に伝導することができる。さらに、Ｓｉ粒子同士の間の間隙に鋳造体が充密して配されることになるため、絶縁基板からの熱が放熱体の内部に滞ることなく良好に低温側へ向かって伝導することになる。以上により、放熱体の熱膨張率の低下と、熱伝導率の低下抑制との双方が図られることになる。
【００４６】
請求項２に係る発明によれば、板状体及び鋳造体が、純Ａｌ，Ａｌ合金，純Ｃｕ又はＣｕ合金から形成されているので、放熱性の優れた放熱体を容易且つ確実に形成することができるようになる。
【００４７】
請求項３に係る発明に係る発明によれば、放熱体と絶縁基板とをはんだ接合する際，及び放熱体と絶縁基板とを接合した状態で使用する際に放熱体に反りが発生することを確実に抑制することができる。また、純Ａｌ又はＡｌ合金は、鋳造性に優れているため鋳造欠陥の発生が抑制され、従って、放熱体全体の熱伝導率の低下を最小限に抑制することができる。
【００４８】
請求項４に係る発明によれば、板状体が圧延材により形成されているので、板状体に内在する，空孔等の内部欠陥の含有を最小限に抑制でき、放熱体の熱伝導率の低下を抑制できる。
【００４９】
請求項５に係る発明によれば、鋳造体を形成する際に放熱体に発生した反りと、この放熱体と被放熱体とをはんだ接合した際に放熱体に発生しようとする反りとが互いに相殺し合い、結果として放熱体と被放熱体との双方が平坦となる。従って、被放熱体と放熱体との密着性が確保されることになるため、被放熱体の熱を放熱体に確実に伝導することができる。
【００５０】
請求項６に係る発明によれば、この放熱体の熱膨張係数を可及的に小さくでき、放熱体の前記反りの発生を抑制することができるとともに、このような構成においても放熱体の熱伝導率の低下を最小限に抑制することができるため、反り発生抑制効果と熱伝導率の低下抑制効果との双方を有するパワーモジュール用基板を提供することができる。
【００５１】
請求項７に係る発明によれば、絶縁基板と放熱体との熱膨張係数の差に拘わることなく、両者の反りを可及的に抑えつつ良好な熱伝導率を有するパワーモジュール用基板が確実に得られる。
【００５２】
請求項８に係る発明によれば、絶縁基板と放熱体との熱膨張係数の差に拘わることなく、両者の反りを可及的に抑えつつ良好な熱伝導率を有するパワーモジュールが得られる。
【００５３】
請求項９に係る発明によれば、低熱膨張材を高精度に形成することができるとともに、その配設位置を高精度に位置決めすることができ、熱膨張係数，熱伝導率等の特性を安定させてパワーモジュール用基板を形成することができるため、量産品質を確保することができる。また、絶縁基板が載置される放熱体表面を平滑面とすることを容易且つ確実に実現することができ、放熱体と絶縁基板とを互いに一様に密着させることができるため、絶縁基板からの熱を放熱体に確実に伝導することができる。さらに、放熱体と，この放熱体の熱膨張係数と異なる熱膨張係数の絶縁基板とをはんだ接合した際に放熱体に発生する反りと略同等且つ反対方向の反りが、低熱膨張材を鋳包む際に放熱体に生じるように、板状体の厚さを各別に異ならせて設定することが容易になる。
【図面の簡単な説明】
【図１】この発明の一実施形態に係る放熱体を適用したパワーモジュールを示す全体図である。
【符号の説明】
１０パワーモジュール用基板
１１絶縁基板
１６放熱体
１７放熱体本体
１７ａ板状体
１７ｂ鋳造体
１８低熱膨張材（Ｓｉ粒子集合体）
３０半導体チップ（チップ）
Ｐパワーモジュール[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a radiator that dissipates heat from a radiator, a power module substrate using the radiator, a power module, and a method of manufacturing the radiator.
[0002]
[Prior art]
Generally, a power module as a semiconductor device has a semiconductor chip mounted on a power module substrate, and heat of the semiconductor chip is conducted to the power module substrate. Therefore, it is necessary to dissipate heat transmitted to the power module substrate. .
In such a power module substrate as a radiator, a metal thin plate is directly laminated on an insulating substrate (ceramic substrate) made of a ceramic material, and a heat sink made of a heat sink is interposed on the metal thin plate with a plastic porous metal layer. Laminated and bonded (see, for example, Patent Document 1). The plastic porous metal layer is a porous sintered body of Cu having a porosity of 20 to 50%, and when the insulating substrate receives heat from the semiconductor chip mounted thereon, it absorbs the thermal deformation. Thus, it is possible to prevent warping and cracking of the insulating substrate and the heat radiating body, and the heat radiating body can also perform a good heat radiating action.
[0003]
[Patent Document 1]
JP-A-8-335652 (page 4-12, FIGS. 1 to 5)
[0004]
[Problems to be solved by the invention]
By the way, in the prior art, the plastic porous metal layer provided on the power module substrate as the heat radiating member absorbs thermal deformation of the insulating substrate and the heat radiating member, so that the thermal expansion coefficient between the insulating substrate and the heat radiating member is large. Although it is possible to prevent warping and cracking of the insulating substrate and the heat sink even if they are different, since the plastic porous metal layer is interposed between the insulating substrate and the heat sink, heat is increased accordingly. The resistance is increased and the thermal conductivity is lowered, so that the heat dissipation effect of the radiator is deteriorated.
[0005]
In general, when the heat dissipating body is made of a material having a different thermal expansion coefficient with respect to the heat radiating body, it is easy to match the thermal expansion coefficients of both in order to prevent warping due to the difference in the thermal expansion coefficient of both. Can be considered. In this case, the thermal expansion coefficient will be adjusted to the lower one (heat radiating body). However, if this is done, the warpage can be reduced, but the thermal conductivity will be reduced by that much, resulting in a reduction in the heat dissipation effect. However, there is a problem that it is impossible to meet the demands of what has both good heat dissipation effect.
[0006]
This invention was made in consideration of such circumstances, and its purpose is to reduce warpage without regard to this even if there is a difference in thermal expansion coefficient between the heat radiating body and An object of the present invention is to provide a heat radiating body capable of suppressing a decrease in thermal conductivity, a power module substrate using the heat radiating body, a power module, and a method for manufacturing the heat radiating body.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, the present invention proposes the following means.
The invention according to claim 1 is a heat radiator that dissipates heat of the heat radiating body, and includes a heat radiator body and a low thermal expansion material made of a material having a thermal expansion coefficient lower than that of the heat radiator body. The main body is a laminate including at least a plate-like body and a cast body, and the plate-like body is arranged in each outermost layer of the heat radiating body. The low thermal expansion material is made of Si particles. And is disposed by being cast by the cast body through a gap between Si particles between the plate-like bodies.
[0008]
According to the heat dissipating body according to the present invention, since the aggregate of Si particles is disposed as the low thermal expansion material, even in a configuration in which the heat dissipating material includes the low thermal expansion material, a decrease in thermal conductivity is minimized. In addition, the thermal expansion coefficient of the entire radiator is surely reduced. That is, since Si is a so-called high thermal conductivity material having a thermal conductivity of approximately 150 W / m · K and a so-called low thermal expansion material having a thermal expansion coefficient of approximately 2.2 × 10 −6 / ° C., When the body is embedded in the radiator, a decrease in the thermal conductivity of the radiator is suppressed, and the thermal expansion coefficient is reduced as much as possible. Therefore, when the heat radiating body and the heat radiating body are joined by solder or the like, it is possible to reliably suppress the heat radiating body from warping toward the heat radiating body, and even in such a configuration, the heat conductivity of the heat radiating body is reduced. The decrease will be minimized. In addition, since the plate-like body is disposed on each outermost layer of the radiator body, the contact surface of the radiator with the radiator body is a smooth surface, and the radiator and the radiator body are in good contact with each other. Therefore, the heat from the heat radiating body is favorably conducted to the heat radiating body. Furthermore, since the low thermal expansion material is composed of an aggregate of Si particles, when the cast body is formed, the molten metal that becomes the cast body penetrates the entire Si particle aggregate, that is, a gap between the Si particles is cast. It will be packed by the body. Therefore, the heat from the heat radiating member is favorably conducted toward the low temperature side without stagnation inside the heat radiating member.
As described above, the thermal expansion coefficient of the heat radiating body can be made as small as possible, the occurrence of the warpage of the heat radiating body can be suppressed, and even in such a configuration, the decrease in the thermal conductivity of the heat radiating body can be minimized. It becomes possible to suppress.
[0009]
The invention according to claim 2 is characterized in that, in the heat radiating body according to claim 1, the plate-like body and the cast body are made of pure Al, Al alloy, pure Cu or Cu alloy.
[0010]
According to the heat radiator according to the present invention, since the plate-like body and the cast body are made of pure Al, Al alloy, pure Cu or Cu alloy, a heat radiator excellent in heat dissipation can be easily and reliably formed. Will be able to. That is, when the cast body is made of pure Al or Al alloy, it is a material with excellent castability such as realizing a good hot water flow, so that the occurrence of casting defects is suppressed. The decrease in conductivity is minimized. On the other hand, when the cast body is formed of pure Cu or a Cu alloy, since it is a material having a high thermal conductivity, it is possible to provide a heat radiating body with excellent heat dissipation.
[0011]
The invention according to claim 3 is the heat dissipating body according to claim 1, wherein the plate-like body is made of pure Cu or a Cu alloy, and the cast body is made of pure Al or an Al alloy.
[0012]
According to the heat radiator according to the present invention, the plate-like body is made of pure Cu or a Cu alloy, and the cast body is made of pure Al or an Al alloy. It becomes possible to easily adjust the coefficient of thermal expansion and the thermal conductivity of the whole body. Therefore, when soldering the heat radiator and the heat radiating member, and when using the heat radiator and the heat radiating member in a joined state, warpage of the heat radiating member is reliably suppressed. Moreover, since pure Al or Al alloy is excellent in castability, generation | occurrence | production of a casting defect is suppressed, Therefore, the fall of the thermal conductivity of the whole heat radiator is suppressed to the minimum.
[0013]
The invention according to claim 4 is the radiator according to any one of claims 1 to 3, wherein the plate-like body is a rolled material.
[0014]
According to the heat radiator according to the present invention, since the plate-like body is a rolled material, the inclusion of internal defects such as voids in the plate-like body is suppressed to a minimum, and the thermal conductivity of the heat radiator is reduced. It is suppressed. That is, when the entire heat dissipating body is, for example, a cast body, internal defects such as nests may occur, and this internal defect obstructs heat conduction inside the heat dissipating body. May reduce overall thermal conductivity. However, as described above, when the plate-like body is a rolled material, the internal defects are rarely formed, so that the decrease in the thermal conductivity is minimized.
[0015]
According to a fifth aspect of the present invention, in the radiator according to any one of the first to fourth aspects, the thickness of each plate-like body is such that the thermal expansion coefficient on the radiator side is the thermal expansion on the radiator side. When the coefficient of thermal expansion is smaller than the coefficient of thermal expansion, the thickness of the plate on the side of the radiator is larger than the thickness of the plate on the side of the radiator while the coefficient of thermal expansion on the side of the radiator is greater than the coefficient of thermal expansion on the side of the radiator. The thickness of the plate-like body on the body side is made thinner than the thickness of the plate-like body on the radiator side.
[0016]
According to the heat dissipating body according to the present invention, since the thickness of each plate-like body is set as described above, the warp generated in the heat dissipating body when forming the cast body, the heat dissipating body and the heat dissipating body And the warp that is to occur in the heat dissipating member when they are soldered to each other, and as a result, both the heat dissipating member and the heat dissipating member become flat. Accordingly, since the adhesion between the heat radiating body and the heat radiating body is ensured, the heat of the heat radiating body can be reliably conducted to the heat radiating body.
[0017]
The invention according to claim 6 is a power module substrate comprising an insulating substrate and a radiator provided on one surface side of the insulating substrate, wherein the radiator is any one of claims 1 to 5. It is a heat radiator as described in the above.
[0018]
According to the power module substrate of the present invention, since the radiator is the radiator according to any one of claims 1 to 5, the thermal expansion coefficient of the radiator can be made as small as possible. In addition to being able to suppress the occurrence of the warp, and even in such a configuration, it is possible to suppress a decrease in the thermal conductivity of the heat radiating body to a minimum, Thus, a power module substrate having both of the above can be provided.
[0019]
The invention according to claim 7 is the power module substrate according to claim 6, wherein the one surface of the insulating substrate is provided with a metal layer, and the other surface is provided with a circuit layer. It consists of pure Al, Al alloy, pure Cu, or Cu alloy.
[0020]
According to the power module substrate according to the present invention, the power module substrate having good thermal conductivity while suppressing the warpage of both as much as possible regardless of the difference in thermal expansion coefficient between the insulating substrate and the radiator. Is definitely obtained.
[0021]
The invention according to claim 8 is characterized in that a chip is mounted on the other surface side of the insulating substrate of the power module substrate according to claim 6 or 7.
[0022]
According to the power module of the present invention, it is possible to obtain a power module having good thermal conductivity while suppressing the warpage of both as much as possible regardless of the difference in thermal expansion coefficient between the insulating substrate and the radiator.
[0023]
The invention which concerns on Claim 9 is a manufacturing method of the thermal radiation body which radiates the heat | fever of a to-be-radiated body, Comprising: Si particle | grains are arrange | positioned between plate-shaped bodies, The aggregate of the said plate-shaped body and the said Si particle, Then, in a state where the aggregates of the Si particles are sandwiched between the plate-like bodies, a molten metal is injected between the plate-like bodies to cast the aggregate of the Si particles. It is characterized by wrapping.
[0024]
According to the method of manufacturing a heat radiator according to the present invention, when the low thermal expansion material is cast into the heat radiator body, an aggregate of Si particles as a low thermal expansion material is sandwiched in advance by a plate-like body, In this state, the molten metal is injected into the Si particle aggregate and the Si particle aggregate is cast into the heat radiating body, so that the low thermal expansion material is formed and positioned with high accuracy. That is, when the molten metal is injected into the Si particle aggregate and the aggregate is cast into the heat radiating body, the aggregate is deformed due to the injection pressure of the molten metal acting on the Si particle aggregate, or the heat radiating body. However, since the Si particle aggregate is held at the time of pouring the molten metal and the molten metal is injected in this state, the occurrence of deformation of the Si particle aggregate due to the injection pressure is suppressed. Will be. Thereby, characteristics, such as a thermal expansion coefficient and heat conductivity, can be stabilized, a heat radiator can be formed, and mass production quality can be secured.
In addition, when the heat sink and a heat radiating body having a thermal expansion coefficient different from the thermal expansion coefficient of the heat sink are soldered together, the warpage in the opposite direction is substantially the same as the warp generated in the heat sink. It is possible to easily set the thickness of the plate-like body to be different from each other so as to be generated in the radiator when wrapping. In this way, by setting the thickness of the plate-like body separately, the warp generated in the heat sink when casting the low thermal expansion material and the heat sink when the heat sink and the heat sink are soldered together. The warpage to be generated cancels each other, and as a result, both the heat radiating body and the heat radiating body become flat, and the heat radiating body and the heat radiating body can be satisfactorily adhered. Heat can be reliably conducted to the radiator.
Furthermore, since the aggregate of Si particles is used as the low thermal expansion material, the molten metal penetrates well between the Si particles. Therefore, in the formed heat radiator, the cast body is in the thickness direction and the creeping direction of the heat radiator. It will be continuous to both sides. Accordingly, it is possible to more reliably suppress the decrease in the thermal conductivity of the radiator itself.
[0025]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an overall view showing a power module to which a power module substrate according to an embodiment of the present invention is applied.
In the power module P of the present embodiment, the power module substrate 10 includes an insulating substrate 11 and a radiator 16 as shown in FIG.
The insulating substrate 11 is formed to have a desired size by using, for example, AlN, Al2O3, Si3N4, SiC, and the like, and the circuit layer 12 is laminated on the upper surface of the insulating substrate 11 and the metal layer 13 is laminated on the lower surface. The circuit layer 12 and the metal layer 13 are formed of pure Al, Al alloy, pure Cu, Cu alloy or the like, and are laminated and bonded to the upper and lower surfaces of the insulating substrate 11 by soldering or brazing.
[0026]
The semiconductor chip 30 is mounted on the upper surface of the circuit layer 12 provided on the upper surface of the insulating substrate 11 by solder 14, while the lower surface of the metal layer 13 provided on the lower surface of the insulating substrate 11 is connected by solder 15 or brazing or diffusion bonding. The heat sink 16 is joined by, for example, and a cooling sink portion 31 is provided on the lower surface of the heat sink 16. In the power module P configured as described above, the heat conducted from the insulating substrate 11 side to the heat radiating body 16 is radiated to the outside by the cooling liquid (or cooling air) 32 in the cooling sink portion 31. ing. The radiator 16 is attached to the cooling sink portion 31 in close contact with the attachment screw 33.
[0027]
Here, the radiator 16 includes a radiator body 17 and a low thermal expansion material 18 made of a material lower than the thermal expansion coefficient of the radiator body 17.
The heat dissipating body 17 is a laminated body including a plate-like body 17a and a casting body 17b made of pure Al, Al alloy, pure Cu or Cu alloy, and the plate-like body 17a is the heat dissipating body main body 17. Each of the outermost layers, that is, the insulating substrate 11 side and the cooling sink portion 31 side, is arranged. Here, the plate-like body 17a is formed of a rolled material.
[0028]
On the other hand, the low thermal expansion material 18 is made of an aggregate of Si particles, and is disposed between the plate-like bodies 17a by being casted by a cast body 17b through a gap between the Si particles. That is, the cast body 17b is arranged so as to be densely packed in the gap between the Si particles, is continuously disposed in the thickness direction and the creeping direction of the aggregate of Si particles, and further the low heat of each plate-like body 17a. It has the structure joined to the surface of the expansion material 18 side.
[0029]
Here, as described above, the radiator body 17 is pure Al or Al alloy, preferably Al alloy having a purity of 99.5% or higher, or pure Cu or Cu alloy, preferably high purity having a purity of 99.9% or higher. It is formed of a material having a small deformation resistance and good thermal conductivity, such as Cu, a so-called high thermal conductive material. The high thermal conductivity material has a thermal conductivity of, for example, 100 W / m · K or more, preferably 150 W / m · K or more.
[0030]
On the other hand, the aggregate of Si particles as the low thermal expansion material 18 is made of a material having a thermal expansion coefficient lower than the thermal expansion coefficient of the heat radiating body 17 and approximately 2.2 × 10 −6 / ° C. By casting or embedding in the radiator body 17, the difference between the thermal expansion coefficient of the entire radiator 16 and the thermal expansion coefficient of the insulating substrate 11 is made as close as possible. In addition, this Si particle aggregate has a thermal conductivity of about 150 W / m · K, which is equivalent to the thermal conductivity of the heat radiating body 17, and the heat radiating body 17 and the low thermal expansion material which are different materials from each other. 18 is configured to be able to suppress a decrease in the thermal conductivity of the entire radiator 16 due to the lamination.
In the power module P configured as described above, the thermal expansion coefficient on the insulating substrate 11 side is smaller than the thermal expansion coefficient on the radiator 16 side. In this case, the thickness of the plate-like body 17a on the insulating substrate 11 side is small. Is formed thicker than the thickness of the plate-like body 17a on the cooling sink portion 31 side.
[0031]
A manufacturing method for forming the radiator 16 configured as described above will be described.
First, between the plate-like bodies 17a of the rolled material made of pure Al, Al alloy, pure Cu or Cu alloy, Si is formed to have a predetermined thickness over substantially the entire surface of the plate-like body 17a. After arranging the particles, each plate-like body 17a sandwiches the Si particle aggregate as the low thermal expansion material 18. In this state, a molten metal made of pure Al, Al alloy, pure Cu or Cu alloy is injected from the side surface of the low thermal expansion material 18. At this time, the molten metal sews the gap between the Si particles, flows in the thickness direction and the creeping direction of the low thermal expansion material 18, and further, the low thermal expansion material 18 of each plate-like body 17a holding the Si particle aggregate. To the contact surface. Then, by cooling and hardening the molten metal, the plate bodies 17a constituting the outermost layer of the heat radiating body 16 are joined together, and a cast body 17b for casting the low thermal expansion material 18 is formed. Is done.
[0032]
As described above, according to the radiator 16 according to the present embodiment, the radiator 16 includes the low thermal expansion material 18 made of a material having a thermal expansion coefficient lower than the thermal expansion coefficient of the radiator body 17. The coefficient of thermal expansion of the entire body 16 can be reliably reduced, and the difference in coefficient of thermal expansion between the insulating substrate 11 and the entire radiator 16 can be made as small as possible.
[0033]
For this reason, when the insulating substrate 11 and the heat radiating body 16 are joined by the solder 15 (or brazing, diffusion bonding, or the like), it is possible to reliably suppress the heat radiating body 16 from warping toward the insulating substrate 11. . As a result, even if the radiator 16 is attached to the cooling sink portion 31, it is possible to prevent a gap from being generated between the cooling sink portion 31 and the radiator 16 and to increase the height from the radiator 16 to the cooling sink portion 31. Heat can be conducted efficiently. Therefore, a decrease in the thermal conductivity of the power module P as a whole can be suppressed, and as a result, an increase in the temperature of the semiconductor chip 30 can also be suppressed.
[0034]
In addition, since the aggregate of Si particles is disposed as the low thermal expansion material 18, it is possible to minimize a decrease in thermal conductivity even in the configuration in which the radiator 16 includes the low thermal expansion material 18. The thermal expansion coefficient of the entire radiator 16 can be reliably reduced. That is, since Si is a so-called high thermal conductivity material having a thermal conductivity of approximately 150 W / m · K and a so-called low thermal expansion material having a thermal expansion coefficient of approximately 2.2 × 10 −6 / ° C., By burying the body in the heat radiating body 16, the thermal expansion coefficient of the heat radiating body 16 can be reduced as much as possible, and the decrease in thermal conductivity can be suppressed.
[0035]
Further, since the low thermal expansion material 18 is composed of an aggregate of Si particles, when the cast body 17b is formed, the molten metal that becomes the cast body 17b surely penetrates the entire Si particle aggregate, and between the Si particles. The casting 17b can be densely arranged in the gap. Therefore, the heat from the insulating substrate 11 is favorably conducted to the cooling sink portion 31 without stagnation inside the radiator 16, so that the thermal expansion coefficient of the radiator 16 is reduced and the thermal conductivity is suppressed from being reduced. Both can be aimed at.
[0036]
Further, since the plate-like body 17a and the cast body 17b are made of pure Al, Al alloy, pure Cu or Cu alloy, the power module substrate 10 provided with the heat radiating body 16 having excellent heat radiating properties is provided. It can be formed easily and reliably. That is, when the cast body 17b is formed of pure Al or an Al alloy, it is a material excellent in castability, such as realizing a good hot water flow, so that the occurrence of casting defects is suppressed. The decrease in the thermal conductivity of is minimized. On the other hand, when the cast body 17b is formed of pure Cu or a Cu alloy, the power module substrate 10 having the heat dissipating body 16 having excellent heat dissipating property can be reliably provided because the material has a high thermal conductivity. .
[0037]
Here, since the thickness of the plate-like body 17a on the insulating substrate 11 side is thicker than the thickness of the plate-like body 17a on the cooling sink portion 31 side, when forming the cast body 17b, Warping toward the insulating substrate 11 occurs. Further, when the heat radiating body 16 is joined to the insulating substrate 11, the thermal expansion coefficient of the insulating substrate 11 is smaller than the thermal expansion coefficient of the heat radiating body 16, so that the heat radiating body 16 warps in the direction toward the insulating substrate 11. try to. At this time, since the heat sink 16 is warped in the direction away from the insulating substrate 11 when the cast body 17b is formed, these warpages cancel each other. As a result, the heat sink 16 and Both the insulating substrate 11 and the insulating substrate 11 can be made flat, and these can be satisfactorily adhered to each other.
That is, when the heat radiating body 16 and the insulating substrate 11 having a thermal expansion coefficient different from the thermal expansion coefficient of the heat radiating body 16 are solder-bonded, a warpage substantially equal to and opposite to the warpage generated in the heat radiating body 16 is low thermal expansion. The thickness of the plate-like body 17a can be easily set differently between the insulating substrate 11 side and the cooling sink portion 31 side so that the material 18 is formed in the entire heat radiating body 16 when the material 18 is cast into the cast body 17b. As a result, the heat dissipating body 16 and the insulating substrate 11 can be satisfactorily adhered to each other, and a configuration for reliably conducting the heat of the insulating substrate 11 to the heat dissipating body 16 can be easily formed.
[0038]
Further, when the low thermal expansion material 18 is cast into the heat radiating body 17, the Si particle aggregate as the low thermal expansion material 18 is held in advance by the plate-like body 17 a, and in this state, the side surface side of the Si particle aggregate Therefore, the low thermal expansion material 18 can be formed with high accuracy, and the disposition position of the low thermal expansion material 18 with respect to the thickness direction and the creeping direction of the radiator 16 can be positioned with high accuracy. . That is, when the low thermal expansion material 18 is cast into the heat radiating body 17, the arrangement position of the low thermal expansion material 18 with respect to the heat radiating body 17 is shifted due to the injection pressure of the molten metal acting on the low thermal expansion material 18. However, at this time, since the low thermal expansion material 18 is sandwiched by the plate-like body 17a, the low displacement of the low thermal expansion material 18 due to the injection pressure, the occurrence of loss of shape, etc. Can be suppressed. Accordingly, it is possible to form the power module substrate 10 while stabilizing the characteristics such as the thermal expansion coefficient and the thermal conductivity, and to secure the mass production quality.
[0039]
Furthermore, since the outermost layer of the formed radiator 16 is a rolled plate-like body 17a, the surface of the radiator body 17 on which the insulating substrate 11 is placed becomes a smooth surface, whereby the radiator 16 and the insulating substrate are arranged. 11 can be brought into close contact with each other uniformly, and the heat of the insulating substrate 11 can be reliably conducted to the radiator 16.
[0040]
In addition, since the plate-like body 17a is a rolled material, the inclusion of internal defects such as vacancies in the plate-like body 17a can be suppressed to a minimum, and a decrease in the thermal conductivity of the radiator 16 can be suppressed. be able to. That is, if the entire radiator body 17 is, for example, a cast body, internal defects such as nests are likely to occur. In this case, when heat is conducted through the radiator 16, the internal defects conduct heat. Therefore, the heat conductivity of the entire radiator 16 is reduced. However, as described above, when the plate-like body 17a is a rolled material, the internal defects are rarely generated, so that a decrease in the thermal conductivity can be minimized.
[0041]
In addition, this invention is not limited to the said embodiment, A various change can be added in the range which does not deviate from the meaning of this invention. For example, although the structure which provided the cooling sink part 31 in the heat radiator 16 surface was shown, it is good also as a structure which provided not only this structure but a corrugated fin. That is, a joined portion joined to the surface of the radiator 16 via a brazing material, a rising portion that is provided at one end of the joining portion and rises perpendicular to the joining portion, and is provided at the upper end of the rising portion and is parallel to the joining portion and A projecting portion including a flat portion extending in a separating direction and a folded portion provided at one end of the flat portion and orthogonal to the flat portion and folded back toward the radiator 16 is continuously repeated along the creeping direction of the radiator 16. It is good also as a structure provided. In this configuration, the rising portion, the flat portion, the folded portion, and the surface of the radiator 16 form a space.
[0042]
Moreover, although the example in which the metal layer 13 was provided on the surface on the heat radiating body 16 side as the power module substrate 11 to which the heat radiating body 16 is attached was shown, the insulating substrate 11 is not provided through the brazing material without providing the metal layer 13. Even if it is directly joined to the radiator 16, the same effect can be obtained.
[0043]
Further, in the plate-like body 17a on the insulating substrate 11 side, the surface on the insulating substrate 11 side is a flat surface. On this surface, a pedestal portion that projects the region to which the insulating substrate 11 is bonded toward the insulating substrate 11 side. May be formed. In this case, the plate-like body 17a may be formed by casting instead of a rolled material. Further, on the surface on the low thermal expansion material 18 side of each plate-like body 17a, an arbitrary region may be formed to be concave, and a corrugated uneven shape may be added, and the surface is not limited to a flat surface. .
[0044]
Furthermore, although the heat dissipating body main body 17 is configured to include the plate-like body 17a and the cast body 17b made of pure Al, Al alloy, pure Cu or Cu alloy, the plate-like body 17a is made of pure Cu or A Cu alloy may be used, and the cast body 17b may be pure Al or an Al alloy. Even in this case, the same effects as described above can be obtained. Furthermore, by forming the plate-like body 17a and the cast body 17b from different materials, the thermal expansion coefficient and the heat conduction of the entire radiator 16 according to the thermal expansion coefficient on the insulating substrate 11 side, the heat generation amount, and the like. It is possible to easily adjust the rate and the like. Therefore, the effect of suppressing the occurrence of warpage of the heat radiating body 16 can be more reliably realized.
[0045]
【The invention's effect】
As described above, according to the first aspect of the invention, when the insulating substrate and the heat radiating body are joined by solder or the like, it is possible to reliably suppress the warping of the heat radiating member toward the insulating substrate, Even in such a configuration, it is possible to minimize a decrease in the thermal conductivity of the radiator. In addition, since the plate-like body is disposed on each outermost layer of the radiator body, the contact surface of the radiator with the insulating substrate becomes a smooth surface, and the radiator and the insulating substrate are in good contact with each other. Therefore, heat from the insulating substrate can be conducted well to the radiator. Furthermore, since the casting is densely arranged in the gap between the Si particles, the heat from the insulating substrate is favorably conducted toward the low temperature side without stagnation inside the radiator. Become. As described above, both the reduction of the thermal expansion coefficient of the heat radiating body and the suppression of the reduction of the thermal conductivity are achieved.
[0046]
According to the invention of claim 2, since the plate-like body and the cast body are made of pure Al, Al alloy, pure Cu or Cu alloy, a heat radiating body with excellent heat dissipation is easily and reliably formed. Will be able to.
[0047]
According to the invention of claim 3, when the radiator and the insulating substrate are joined by soldering, and when the radiator and the insulating substrate are used in a joined state, the radiator is warped. It can be surely suppressed. Moreover, since pure Al or Al alloy is excellent in castability, generation | occurrence | production of a casting defect is suppressed, Therefore Therefore, the fall of the thermal conductivity of the whole heat radiator can be suppressed to the minimum.
[0048]
According to the invention of claim 4, since the plate-like body is formed of a rolled material, the inclusion of internal defects such as vacancies existing in the plate-like body can be minimized, and the heat conduction of the radiator. Reduction in rate can be suppressed.
[0049]
According to the invention which concerns on Claim 5, the curvature which generate | occur | produced in the heat radiator when forming a casting and the curvature which is going to generate | occur | produce in a heat radiator when this heat radiator and a to-be-heat-dissipated body are soldered mutually. As a result, both the heat radiating body and the heat radiating body become flat. Therefore, since the adhesiveness between the heat radiating body and the heat radiating body is ensured, the heat of the heat radiating body can be reliably conducted to the heat radiating body.
[0050]
According to the invention of claim 6, the thermal expansion coefficient of the radiator can be made as small as possible, the occurrence of the warp of the radiator can be suppressed, and even in such a configuration, the heat of the radiator can be reduced. Since a decrease in conductivity can be suppressed to a minimum, a power module substrate having both a warp generation suppressing effect and a thermal conductivity decrease suppressing effect can be provided.
[0051]
According to the invention of claim 7, a power module substrate having a good thermal conductivity while suppressing the warpage of both as much as possible regardless of the difference in thermal expansion coefficient between the insulating substrate and the heat radiating member is ensured. Is obtained.
[0052]
According to the eighth aspect of the invention, it is possible to obtain a power module having a good thermal conductivity while suppressing the warpage of both as much as possible regardless of the difference in thermal expansion coefficient between the insulating substrate and the radiator.
[0053]
According to the invention of claim 9, the low thermal expansion material can be formed with high accuracy, and the position of the low thermal expansion material can be positioned with high accuracy, and characteristics such as thermal expansion coefficient and thermal conductivity can be stabilized. Thus, the power module substrate can be formed, so that mass production quality can be ensured. In addition, it is possible to easily and reliably realize a smooth surface on the surface of the radiator on which the insulating substrate is placed, and the radiator and the insulating substrate can be uniformly adhered to each other. This heat can be reliably conducted to the heat radiating body. Further, when the heat sink and the insulating substrate having a thermal expansion coefficient different from the thermal expansion coefficient of the heat sink are soldered together, the warpage in the opposite direction is substantially equal to the warp generated in the heat sink and casts the low thermal expansion material. In this case, the thickness of the plate-like body can be easily set differently so as to be generated in the radiator.
[Brief description of the drawings]
FIG. 1 is an overall view showing a power module to which a heat radiator according to an embodiment of the present invention is applied.
[Explanation of symbols]
10 Power module substrate
11 Insulating substrate
16 Radiator
17 Heat sink body
17a Plate
17b Cast body
18 Low thermal expansion material (Si particle aggregate)
30 Semiconductor chip (chip)
P power module

Claims

A radiator that dissipates the heat of the radiator,
A radiator body, and a low thermal expansion material made of a material lower than the thermal expansion coefficient of the radiator body,
The heat dissipating body has a laminated body including at least a plate-like body and a casting body, and the plate-like body is disposed in each outermost layer of the heat dissipating body.
The low thermal expansion material is an aggregate of Si particles, and is disposed between the plate-like bodies by being cast by the cast body through a gap between Si particles. .

The heat radiator according to claim 1,
The heat dissipation body, wherein the plate-like body and the cast body are made of pure Al, Al alloy, pure Cu or Cu alloy.

In the heat radiator according to claim 1 or 2,
The radiator is characterized in that the plate-like body is made of pure Cu or Cu alloy, and the cast body is made of pure Al or Al alloy.

In the heat radiator in any one of Claim 1 to 3,
The radiator is characterized in that the plate-like body is a rolled material.

In the heat radiator in any one of Claim 1 to 4,
The thickness of each plate-like body is such that when the thermal expansion coefficient on the radiator side is smaller than the thermal expansion coefficient on the radiator body, the thickness of the plate-like body on the radiator side is the thickness of the radiator body. While forming thicker than the thickness,
When the thermal expansion coefficient on the radiator side is larger than the thermal expansion coefficient on the radiator side, the thickness of the plate on the radiator side is made thinner than the thickness of the plate on the radiator side.

A power module substrate comprising an insulating substrate and a heat dissipator provided on one surface side of the insulating substrate,
The power module substrate according to claim 1, wherein the heat radiator is the heat radiator according to claim 1.

The power module substrate according to claim 6,
A metal layer is provided on the one surface of the insulating substrate, and a circuit layer is provided on the other surface, and the metal layer and the circuit layer are made of pure Al, Al alloy, pure Cu, or Cu alloy. Power module substrate.

A power module comprising a chip mounted on the other surface side of the insulating substrate of the power module substrate according to claim 6.

A method of manufacturing a radiator that dissipates heat from a radiator,
After arranging Si particles between the plate-like bodies and forming a laminate including the plate-like bodies and the aggregate of the Si particles,
A heat radiator manufactured by injecting molten metal between the plate-like bodies in a state where the aggregate of the Si particles is sandwiched between the plate-like bodies and casting the aggregate of the Si particles. Method.