JP2004207619A - Power module and substrate therefor - Google Patents

Power module and substrate therefor Download PDF

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Publication number
JP2004207619A
JP2004207619A JP2002377387A JP2002377387A JP2004207619A JP 2004207619 A JP2004207619 A JP 2004207619A JP 2002377387 A JP2002377387 A JP 2002377387A JP 2002377387 A JP2002377387 A JP 2002377387A JP 2004207619 A JP2004207619 A JP 2004207619A
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Prior art keywords
radiator
power module
insulating substrate
heat
thermal expansion
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JP2002377387A
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Japanese (ja)
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Yoshiyuki Nagatomo
義幸 長友
Toshiyuki Nagase
敏之 長瀬
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Mitsubishi Materials Corp
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Mitsubishi Materials Corp
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Priority to JP2002377387A priority Critical patent/JP2004207619A/en
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2224/00—Indexing scheme for arrangements for connecting or disconnecting semiconductor or solid-state bodies and methods related thereto as covered by H01L24/00
    • H01L2224/01—Means for bonding being attached to, or being formed on, the surface to be connected, e.g. chip-to-package, die-attach, "first-level" interconnects; Manufacturing methods related thereto
    • H01L2224/26—Layer connectors, e.g. plate connectors, solder or adhesive layers; Manufacturing methods related thereto
    • H01L2224/31—Structure, shape, material or disposition of the layer connectors after the connecting process
    • H01L2224/32—Structure, shape, material or disposition of the layer connectors after the connecting process of an individual layer connector
    • H01L2224/321—Disposition
    • H01L2224/32151—Disposition the layer connector connecting between a semiconductor or solid-state body and an item not being a semiconductor or solid-state body, e.g. chip-to-substrate, chip-to-passive
    • H01L2224/32221—Disposition the layer connector connecting between a semiconductor or solid-state body and an item not being a semiconductor or solid-state body, e.g. chip-to-substrate, chip-to-passive the body and the item being stacked
    • H01L2224/32225—Disposition the layer connector connecting between a semiconductor or solid-state body and an item not being a semiconductor or solid-state body, e.g. chip-to-substrate, chip-to-passive the body and the item being stacked the item being non-metallic, e.g. insulating substrate with or without metallisation

Abstract

<P>PROBLEM TO BE SOLVED: To reduce warping, and to inhibit the lowering of a heat transfer coefficient even when there is the difference of a coefficient of thermal expansion in both an insulating substrate and a radiator. <P>SOLUTION: The radiator 16 is formed in a multilayer structure in which a radiator body 17 and a low thermal-expansion material 18 are joined. The radiator body 17 is formed of a high heat-conduction material having an excellent thermal conductivity such as Al, Cu or the like. The difference of a coefficient of thermal expansion of the whole radiator 16 and that of the insulating substrate 11 is brought close as much as possible by a laminating on the radiator body 17 in the low thermal-expansion material 18, and the low thermal-expansion material 18 is composed of high carbon steel (Fe-C) when the insulating substrate 11 and the radiator body 17 consist of AlN and Al respectively. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
この発明は、大電圧・大電流を制御する半導体装置に用いられるパワーモジュール用基板に係り、特に半導体チップの発熱体から発生する熱を放散させる放熱体を有するパワーモジュール用基板及びパワーモジュールに関する。
【０００２】
【従来の技術】
従来のこの種のパワーモジュール用基板にあっては、図５に示すように、酸化アルミニウム焼結体からなる絶縁基板１の両面に、Ｃｕからなる回路層２、金属層３がそれぞれ積層されている。回路層２には、半導体チップ１００を搭載するための回路パターンが形成されている。
【０００３】
そして、絶縁基板１の金属層３にはんだ４、或いはろう付け等によって放熱体５が接合されている。この放熱体５は、下方が例えば冷却シンク部（図示せず）に取り付けられて使用されたとき、該冷却シンク部内の冷却水（若しくは冷却空気）が放熱体５に伝達される熱を外部に放熱させ、これによって、回路層２に搭載された半導体チップ１００の熱が回路層２、絶縁基板１、金属層３、はんだ４、放熱体５を介して伝達されることで、良好な熱伝達が得られるようになっている（例えば、特許文献１参照。）。
【０００４】
【特許文献１】
特開平４−１２５５４号公報（第１−３頁、第１図、第２図）
【０００５】
【発明が解決しようとする課題】
ところで、上記に示す従来のパワーモジュール用基板は、絶縁基板１と放熱体５との熱膨張係数が互いに異なるので、両者１、５がはんだ４によって接合された後、冷却して常温に戻すと、絶縁基板１の熱膨張係数が小さく、放熱体５の収縮寸法が大きいことから、図６に示すように、放熱体５が絶縁基板１側に向けて凸状に反ってしまう現象が起こる。放熱体５に絶縁基板１側に向かう反りが発生すると、放熱体５が図６の鎖線に示す冷却シンク部６に取り付けられたとき、放熱体５と冷却シンク部６間に隙間が生じてしまうので、熱伝達の低下をきたし、そのため、発熱量の大きい半導体チップを用いた場合、熱により半導体チップ１００が機能しなくなるという問題があった。
【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、絶縁基板と放熱体との熱膨張係数の差を少なくして反りを低減でき、しかも熱伝達率が低下するのを抑制できるパワーモジュール用基板及びパワーモジュールを提供することにある。
【０００７】
【課題を解決するための手段】
上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、絶縁基板と、該絶縁基板の一方の面に接合される放熱体とを備えたパワーモジュール用基板において、前記放熱体は、高熱伝導材からなる放熱体本体と、該放熱体本体の熱膨張係数より低い低熱膨張材とを複数接合させて多層構造としたことを特徴とする。
【０００８】
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、放熱体本体と低熱膨張材とを互いに積層して多層に形成されると、放熱体全体としての熱膨張係数を確実に下げることができるので、絶縁基板と放熱体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、そのため、絶縁基板と放熱体とをはんだ等によって接合した場合、放熱体に絶縁基板に向かう反りが発生するのを確実に低減することができる。
【０００９】
請求項２に係る発明は、請求項１記載のパワーモジュール用基板において、前記放熱体は、放熱体本体と低熱膨張材とが互い違いに接合されて、計５〜７枚の多層構造としたことを特徴とする。
【００１０】
この発明に係るパワーモジュール用基板によれば、放熱体本体と、低熱膨張材とを５〜７枚接合した多層構造に形成されるので、反りの抑制をいっそう的確に行うことができる。
【００１１】
請求項３に係る発明は、請求項１又は２記載の絶縁基板上にチップを搭載してなることを特徴とする。
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を可及的に小さくでき、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。
【００１２】
【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。
＜第一の実施形態＞
図１及び図２はこの発明の第一の実施の形態に係るパワーモジュール及びパワーモジュール用基板を示す図であって、図１はパワーモジュールの全体図、図２は放熱体の破断拡大図である。
この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、その上面及び下面に回路層１２及び金属層１３がそれぞれ積層して接合される。回路層１２及び金属層１３は、Ａｌ、Ｃｕ等により形成されている。
【００１３】
絶縁基板１１の回路層１２上にはんだ１４によって半導体チップ３０が搭載される一方、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が直接接合され、更に、この放熱体１６が冷却シンク部２０に取り付けられて使用され、該冷却シンク部２０内の冷却水（或いは冷却空気）２１によって放熱体１６に伝達される熱が外部に放熱されるようになっている。放熱体１６は、冷却シンク部２０に取付ねじ２２によって密着した状態で取り付けられる。
【００１４】
この実施形態は、放熱体１６が、放熱体本体１７と低熱膨張材１８とを複数接合させて多層構造に形成されている。
放熱体本体１７は、例えばＡｌ、Ｃｕ等のような熱伝導率の良好な材質、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１８０Ｗ／ｍＫ以上、好ましくは２００Ｗ／ｍＫ以上のものである。
一方、低熱膨張材１８は、放熱体本体１７に積層することで、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ためのものであり、熱膨張係数が例えば１０ｐｐｍ／℃以下、好ましくは７ｐｐｍ／℃以下であり、本例では絶縁基板１１がＡｌＮで、放熱体本体１７がＡｌのとき、例えば高炭素鋼（Ｆｅ−Ｃ）からなっている。
【００１５】
上記の材質からなる低熱膨張材１８は、図１及び図２に示すように、放熱体本体１７と１７との間に接合されている。従って、放熱体１６が二枚の放熱体本体１７と一枚の低熱膨張材１８との三層構造であって、絶縁基板１１側と冷却シンク部２０側とに放熱体本体１７が配置されている。
なお、図２において、符号１９は、放熱体１６に穿設された取付ねじ２２の挿通孔である。
【００１６】
このように、パワーモジュール用基板１０を構成する放熱体１６が、放熱体本体１７と低熱膨張材１８とを互いに積層して多層に形成すると、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るので、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。
そのため、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に従来のように絶縁基板１１に向かう反りが発生するのを確実に低減することができるので、放熱体１６を冷却シンク部２０に取り付けても、冷却シンク部２０と放熱体１６との間に隙間が発生するのを防止することができる。
【００１７】
しかも、低熱膨張材１８が金属であってかつ相応の熱伝導率を有しているので、絶縁基板１１上の半導体チップ３０からの発熱が、回路層１２、絶縁基板１１、金属層１３、はんだ１５、放熱体１６及び冷却シンク部２０を介して外部に放熱される結果、熱伝達率が低下するのを抑制することもできる。
その結果、絶縁基板１１と放熱体１６との材質の膨張係数に差があっても、反りの抑制と熱伝達率の低下の抑制とを両立させた、良好なパワーモジュール基板１０を得ることができる。
【００１８】
また、放熱体１６が、二層からなる放熱体本体１７、１７の間に低熱膨張材１８が挟まれた状態で接合されているので、つまり、放熱体１６において絶縁基板１１側と冷却シンク部２０側との層に放熱体本体１７がそれぞれ配置して形成されているので、絶縁基板１１からの熱を良好に受けると共に、その熱を冷却シンク部２０に対して良好に伝達させることができ、これによって、放熱体１６本来の放熱効果を的確に果たすことができる。
【００１９】
＜第２の実施形態＞
図３は、この発明の第２の実施の形態に係るパワーモジュール用基板の放熱体を示している。この実施形態では、低熱膨張材１８として、インバー合金を用いている。そして、この低熱膨張材１８と、Ａｌからなる高熱伝導材としての放熱体本体１７とが、図３に示すように下方に順次互い違いに接合されることで、六層構造の放熱体１６が形成されている。絶縁基板は、ＡｌＮからなっている。
【００２０】
なお、インバー合金とは、室温付近でほとんど熱膨張が生じない合金であって、Ｆｅが６４．６ｍｏｌ％で、Ｎｉが３５．４ｍｏｌ％の組成率となっている。但し、Ｆｅ中には、それ以外の不可避不純物が含まれたものもインバー合金と呼ばれている。
【００２１】
＜第３の実施形態＞
図示しないが、この実施形態では、低熱膨張材１８として４２合金を用い、これを図３に示す第２の実施形態と同様、Ａｌからなる放熱体本体１７に互い違いに積層して六層構造とすることで、放熱体１６が形成されている。
なお、４２合金は、Ｆｅが５８ｍｏｌ％で、Ｎｉが４２ｍｏｌ％の組成率となったＦｅ系合金である。
【００２２】
＜第４の実施形態＞
図４は、この発明の第４の実施の形態に係るパワーモジュール用基板の放熱体を示している。
図４に示す実施形態では、低熱膨張材１８としてＭｏを用い、この低熱膨張材１８と、Ｃｕからなる放熱体本体１７とが互い違いに接合されることで、全体として五層構造の放熱体１６が構成されている。この場合、放熱体１６において、絶縁基板１１側の層と冷却シンク部２０側の層とにそれぞれ放熱体本体１７が配置される。
【００２３】
＜第５の実施形態＞
図示しないが、この実施形態では、低熱膨張材１８としてＷを用い、この低熱膨張材１８と、Ｃｕからなる放熱体本体１７とが互い違いに積層されることで、全体として図４のような五層構造の放熱体１６が構成される。この場合も、放熱体１６の絶縁基板１１側の層と冷却シンク部２０側の層とにそれぞれ放熱体本体１７が配置される。
上記した各実施形態及び比較例の試験結果を表１にまとめた。
【００２４】
【表１】

Figure 2004207619
【００２５】
なお、表１において、「接合方法」とは、放熱体と絶縁基板との接合方法を表している。また、比較例の放熱体は、ＣｕにＭｏを分散させたものである。
【００２６】
上記表１において、第４の実施形態が比較例と対応するものであり、第４の実施形態の反り量が比較例の反り量より遙かに小さな値となっており、反り量を大幅に低減できることが明らかである。
表紙１における「反り量」とは、測定長さ２００ｍｍの範囲内で、反りが最も大きくなっている部分を測定したときの数値である。
【００２７】
なお、上記表１において、第２及び第３の実施形態の反り量が他の実施形態より大きい値となっているが、これは放熱体１６が、表に示す材質からなる六層構造であること等に起因するものである。また、これら第２及び第３の実施形態は、比較例と条件が大幅に異なるため、比較例との測定結果の比較は適切でない。
試験結果から、放熱体１６が、高熱伝導材としての放熱体本体１７と、低熱膨張材１８とを５〜７枚接合した多層構造に形成される場合にも、反りの抑制を的確に行うことができることを確認した。
【００２８】
そして、放熱体１６における放熱体本体１７の全体厚みと、低熱膨張材１８の全体厚みとは、概略的には適宜の割合に規定してもよいが、これに限らず、それぞれの厚みのみならず大きさを任意に変えたりしても良いのは勿論である。
なお、図示実施形態では、絶縁基板１１において放熱体１６側の面に金属層１３が積層された例を示したが、これに限らず、金属層１３が設けられていない絶縁基板１１を放熱体１６に直接接合しても、同様の作用効果が得られる。
【００２９】
【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、放熱体が、放熱体本体と低熱膨張材とを互いに積層して多層に形成されることで、絶縁基板と放熱体全体との熱膨張係数の差を可及的に小さくできるように構成したので、放熱体に絶縁基板に向かう反りが発生するのを確実に低減することができる結果、絶縁基板と放熱体との材質の膨張係数に差があっても、反りの抑制と熱伝達率の低下の抑制とを両立させた、良好なパワーモジュール基板が得られるという効果がある。
【００３０】
請求項２に係る発明によれば、放熱体本体と、低熱膨張材とを５〜７枚接合した多層構造に形成されるので、反りの抑制をいっそう的確に行うことができるという効果が得られる。
【００３１】
請求項３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を可及的に小さくすることができ、両者の反りを可及的に抑えつつ良好な熱伝達率を有するパワーモジュールが得られる効果がある。
【図面の簡単な説明】
【図１】この発明の第一の実施の形態に係るパワーモジュールを示す全体構成図である。
【図２】図１における放熱体の破断拡大図である。
【図３】この発明の第２の実施の形態に係るパワーモジュール用基板を示す破断拡大図である。
【図４】この発明の第４の実施の形態に係るパワーモジュール用基板の放熱体を示す破断拡大図である。
【図５】従来のパワーモジュール用基板を示す概略図である。
【図６】従来のパワーモジュール用基板に反りが発生した説明図である。
【符号の説明】
Ｐ パワーモジュール
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（高熱伝導材）
１８ 低熱膨張材[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a power module substrate used for a semiconductor device for controlling a large voltage and a large current, and more particularly to a power module substrate and a power module having a heat radiator for dissipating heat generated from a heat generator of a semiconductor chip.
[0002]
[Prior art]
In a conventional power module substrate of this type, as shown in FIG. 5, a circuit layer 2 made of Cu and a metal layer 3 are respectively laminated on both surfaces of an insulating substrate 1 made of an aluminum oxide sintered body. I have. On the circuit layer 2, a circuit pattern for mounting the semiconductor chip 100 is formed.
[0003]
Then, a heat radiator 5 is joined to the metal layer 3 of the insulating substrate 1 by solder 4 or brazing. When the lower part of the radiator 5 is used, for example, attached to a cooling sink (not shown), the cooling water in the cooling sink (or the cooling air) transfers heat transmitted to the radiator 5 to the outside. By dissipating the heat, the heat of the semiconductor chip 100 mounted on the circuit layer 2 is transmitted through the circuit layer 2, the insulating substrate 1, the metal layer 3, the solder 4, and the radiator 5, thereby providing good heat transfer. (For example, see Patent Document 1).
[0004]
[Patent Document 1]
JP-A-4-12554 (pages 1-3, FIG. 1, FIG. 2)
[0005]
[Problems to be solved by the invention]
By the way, in the conventional power module substrate described above, since the thermal expansion coefficients of the insulating substrate 1 and the radiator 5 are different from each other, when the two are joined by the solder 4 and then cooled to room temperature. Since the thermal expansion coefficient of the insulating substrate 1 is small and the shrinkage dimension of the heat radiator 5 is large, a phenomenon occurs in which the heat radiator 5 warps convexly toward the insulating substrate 1 as shown in FIG. When the heat radiator 5 is warped toward the insulating substrate 1, when the heat radiator 5 is attached to the cooling sink portion 6 shown by a chain line in FIG. 6, a gap is generated between the heat radiator 5 and the cooling sink portion 6. As a result, heat transfer is reduced. Therefore, when a semiconductor chip having a large amount of heat is used, there is a problem that the semiconductor chip 100 does not function due to heat.
[0006]
The present invention has been made in view of such circumstances, and an object of the present invention is to reduce the difference in thermal expansion coefficient between an insulating substrate and a radiator, thereby reducing warpage and reducing the heat transfer coefficient. It is an object of the present invention to provide a power module substrate and a power module capable of suppressing the occurrence of the power module.
[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 power module substrate including an insulating substrate and a radiator bonded to one surface of the insulating substrate, wherein the radiator includes a radiator main body made of a high heat conductive material; It is characterized in that a plurality of low thermal expansion materials having a lower thermal expansion coefficient than that of the radiator body are joined to form a multilayer structure.
[0008]
ADVANTAGE OF THE INVENTION According to the board | substrate for power modules which concerns on this invention, when a radiator is formed by laminating a radiator main body and a low-thermal-expansion material mutually, and it can reduce the thermal expansion coefficient as a whole radiator reliably. Since the difference in thermal expansion coefficient between the insulating substrate and the entire radiator can be made as small as possible, when the insulating substrate and the radiator are joined by soldering or the like, the radiator faces the radiator toward the insulating substrate. The occurrence of warpage can be reliably reduced.
[0009]
According to a second aspect of the present invention, in the power module substrate according to the first aspect, the radiator has a multilayer structure of a total of 5 to 7 sheets in which a radiator body and a low thermal expansion material are alternately joined. It is characterized by.
[0010]
ADVANTAGE OF THE INVENTION According to the board | substrate for power modules which concerns on this invention, since a radiator main body and a low-thermal-expansion material are formed in the multilayer structure which joined 5-7 sheets, the suppression of a warp can be performed more exactly.
[0011]
The invention according to claim 3 is characterized in that a chip is mounted on the insulating substrate according to claim 1 or 2.
ADVANTAGE OF THE INVENTION According to the power module which concerns on this invention, the difference of the thermal expansion coefficient of an insulating board and a radiator can be made as small as possible, and the power module which has favorable thermal conductivity, suppressing the curvature of both as much as possible. can get.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
<First embodiment>
1 and 2 are views showing a power module and a power module substrate according to a first embodiment of the present invention. FIG. 1 is an overall view of the power module, and FIG. is there.
In the power module P of this embodiment, the power module substrate 10 includes an insulating substrate 11 and a heat radiator 16 as roughly shown in FIG.
The insulating substrate 11 is formed in a desired size by using, for example, AlN, Al 2 O 3 , Si 3 N 4 , SiC, or the like, and a circuit layer 12 and a metal layer 13 are respectively laminated and joined on the upper and lower surfaces thereof. The circuit layer 12 and the metal layer 13 are formed of Al, Cu, or the like.
[0013]
The semiconductor chip 30 is mounted on the circuit layer 12 of the insulating substrate 11 by the solder 14, while the radiator 16 is directly bonded to the lower surface of the metal layer 13 by the solder 15 or by brazing or diffusion bonding. The radiator 16 is used by being attached to the cooling sink unit 20, and heat transmitted to the radiator 16 by the cooling water (or cooling air) 21 in the cooling sink unit 20 is radiated to the outside. . The radiator 16 is attached to the cooling sink unit 20 in a state in which the radiator 16 is in close contact with the attachment screw 22.
[0014]
In this embodiment, the heat radiator 16 is formed in a multilayer structure by joining a plurality of heat radiator main bodies 17 and low thermal expansion materials 18.
The radiator body 17 is formed of a material having good thermal conductivity such as Al, Cu, or the like, that is, a so-called high thermal conductive material. The high thermal conductive material has a thermal conductivity of, for example, 180 W / mK or more, preferably 200 W / mK or more.
On the other hand, the low thermal expansion material 18 is provided on the radiator body 17 so as to make the difference between the thermal expansion coefficient of the entire radiator 16 and the thermal expansion coefficient of the insulating substrate 11 as close as possible. The expansion coefficient is, for example, 10 ppm / ° C. or less, preferably 7 ppm / ° C. or less. In this example, when the insulating substrate 11 is AlN and the radiator body 17 is Al, it is made of, for example, high carbon steel (Fe—C). .
[0015]
As shown in FIGS. 1 and 2, the low thermal expansion material 18 made of the above-described material is joined between the radiator bodies 17. Therefore, the radiator 16 has a three-layer structure of two radiator bodies 17 and one low-thermal-expansion material 18, and the radiator body 17 is arranged on the insulating substrate 11 side and the cooling sink part 20 side. I have.
In FIG. 2, reference numeral 19 denotes an insertion hole for the mounting screw 22 formed in the heat radiator 16.
[0016]
As described above, when the heat radiator 16 constituting the power module substrate 10 is formed in a multilayer structure by laminating the heat radiator body 17 and the low thermal expansion material 18, the thermal expansion coefficient of the heat radiator 16 as a whole is reliably reduced. Therefore, the difference in the coefficient of thermal expansion between the insulating substrate 11 and the entire radiator 16 can be reduced as much as possible.
Therefore, when the insulating substrate 11 and the radiator 16 are joined by the solder 15 (or brazing, diffusion bonding, or the like), it is possible to reliably reduce the occurrence of warpage of the radiator 16 toward the insulating substrate 11 as in the related art. Therefore, even if the heat radiator 16 is attached to the cooling sink 20, it is possible to prevent a gap from being generated between the cooling sink 20 and the heat radiator 16.
[0017]
Moreover, since the low thermal expansion material 18 is a metal and has a corresponding thermal conductivity, heat generated from the semiconductor chip 30 on the insulating substrate 11 is generated by the circuit layer 12, the insulating substrate 11, the metal layer 13, and the solder. As a result, the heat is radiated to the outside via the radiator 16 and the cooling sink portion 20, so that a decrease in the heat transfer coefficient can be suppressed.
As a result, even if there is a difference between the expansion coefficients of the materials of the insulating substrate 11 and the heat radiator 16, it is possible to obtain a good power module substrate 10 that achieves both suppression of warpage and suppression of a decrease in heat transfer coefficient. it can.
[0018]
Further, since the heat radiator 16 is joined in a state where the low thermal expansion material 18 is sandwiched between the heat radiator bodies 17, 17 composed of two layers, in other words, the heat sink 16 and the cooling sink portion are connected to each other. Since the heat radiator main bodies 17 are arranged and formed on the layers on the side of the heat sink 20, respectively, the heat from the insulating substrate 11 can be received well and the heat can be transmitted well to the cooling sink portion 20. Thus, the original heat radiation effect of the heat radiator 16 can be accurately achieved.
[0019]
<Second embodiment>
FIG. 3 shows a radiator of a power module substrate according to a second embodiment of the present invention. In this embodiment, an invar alloy is used as the low thermal expansion material 18. The low-thermal-expansion material 18 and the radiator main body 17 as a high-thermal-conductivity material made of Al are joined alternately downward, as shown in FIG. 3, to form a radiator 16 having a six-layer structure. Have been. The insulating substrate is made of AlN.
[0020]
The invar alloy is an alloy that hardly undergoes thermal expansion near room temperature, and has a composition ratio of 64.6 mol% of Fe and 35.4 mol% of Ni. However, Fe containing other unavoidable impurities is also called an Invar alloy.
[0021]
<Third embodiment>
Although not shown, in this embodiment, a 42 alloy is used as the low thermal expansion material 18, which is alternately stacked on the radiator body 17 made of Al to form a six-layer structure, similarly to the second embodiment shown in FIG. By doing so, the heat radiator 16 is formed.
The 42 alloy is an Fe-based alloy having a composition ratio of 58 mol% of Fe and 42 mol% of Ni.
[0022]
<Fourth embodiment>
FIG. 4 shows a radiator of a power module substrate according to a fourth embodiment of the present invention.
In the embodiment shown in FIG. 4, Mo is used as the low-thermal-expansion material 18, and the low-thermal-expansion material 18 and the radiator body 17 made of Cu are alternately joined, so that the radiator 16 having a five-layer structure as a whole is obtained. Is configured. In this case, in the radiator 16, the radiator main body 17 is disposed on each of the layer on the insulating substrate 11 side and the layer on the cooling sink unit 20 side.
[0023]
<Fifth embodiment>
Although not shown, in this embodiment, W is used as the low thermal expansion material 18, and the low thermal expansion material 18 and the radiator body 17 made of Cu are alternately laminated to form a five-dimensional structure as shown in FIG. A radiator 16 having a layer structure is configured. Also in this case, the radiator body 17 is disposed on each of the layer on the insulating substrate 11 side and the layer on the cooling sink section 20 side of the radiator 16.
Table 1 summarizes the test results of the above embodiments and comparative examples.
[0024]
[Table 1]
Figure 2004207619
[0025]
In Table 1, the term "joining method" indicates a method of joining the heat radiator and the insulating substrate. The heat radiator of the comparative example is one in which Mo is dispersed in Cu.
[0026]
In the above Table 1, the fourth embodiment corresponds to the comparative example. The amount of warpage of the fourth embodiment is much smaller than the amount of warpage of the comparative example, and the amount of warpage is significantly reduced. It is clear that it can be reduced.
The “warp amount” in the cover 1 is a numerical value when a portion where the warp is the largest is measured within the range of the measurement length of 200 mm.
[0027]
In Table 1, the amount of warpage of the second and third embodiments is larger than that of the other embodiments, but this is a six-layer structure in which the radiator 16 is made of the material shown in the table. It is caused by the above. Further, in the second and third embodiments, since the conditions are significantly different from those of the comparative example, the comparison of the measurement results with the comparative example is not appropriate.
From the test results, even when the heat radiator 16 is formed in a multilayer structure in which five to seven radiator bodies 17 as high thermal conductive materials and the low thermal expansion material 18 are joined, it is necessary to accurately control the warpage. I confirmed that I can do it.
[0028]
The overall thickness of the radiator body 17 and the overall thickness of the low-thermal-expansion material 18 in the radiator 16 may be roughly defined at an appropriate ratio, but is not limited to this. Needless to say, the size may be arbitrarily changed.
In the illustrated embodiment, the example in which the metal layer 13 is laminated on the surface of the insulating substrate 11 on the side of the heat radiator 16 is shown. However, the present invention is not limited to this. The same operation and effect can be obtained by directly joining to the base member 16.
[0029]
【The invention's effect】
As described above, according to the first aspect of the invention, the heat radiator is formed in a multilayer structure by laminating the heat radiator body and the low thermal expansion material to each other, so that the heat radiation between the insulating substrate and the heat radiator as a whole. Since the difference in expansion coefficient is configured to be as small as possible, it is possible to reliably reduce the occurrence of warping toward the insulating substrate in the heat radiator, and as a result, the expansion coefficient of the material between the insulating substrate and the heat radiator is reduced. However, there is an effect that a good power module substrate that achieves both suppression of warpage and suppression of a decrease in heat transfer coefficient can be obtained.
[0030]
According to the second aspect of the present invention, since the radiator body and the low-thermal-expansion material are formed in a multilayer structure in which five to seven sheets are joined, the effect that the warpage can be suppressed more accurately can be obtained. .
[0031]
According to the third aspect of the present invention, the difference in the coefficient of thermal expansion between the insulating substrate and the radiator can be made as small as possible, and a good heat transfer coefficient can be obtained while minimizing the warpage of both. There is an effect that a power module can be obtained.
[Brief description of the drawings]
FIG. 1 is an overall configuration diagram showing a power module according to a first embodiment of the present invention.
FIG. 2 is an enlarged cutaway view of a heat radiator in FIG. 1;
FIG. 3 is an enlarged cutaway view showing a power module substrate according to a second embodiment of the present invention.
FIG. 4 is an enlarged cutaway view showing a heat radiator of a power module substrate according to a fourth embodiment of the present invention.
FIG. 5 is a schematic view showing a conventional power module substrate.
FIG. 6 is an explanatory view in which warpage has occurred in a conventional power module substrate.
[Explanation of symbols]
P Power module 10 Power module substrate 11 Insulating substrate 16 Heat radiator 17 Heat radiator body (high thermal conductive material)
18 Low thermal expansion material

Claims (3)

絶縁基板と、該絶縁基板の一方の面に接合される放熱体とを備えたパワーモジュール用基板において、
前記放熱体は、高熱伝導材からなる放熱体本体と、該放熱体本体の熱膨張係数より低い低熱膨張材とを複数接合させて多層構造としたことを特徴とするパワーモジュール用基板。In a power module substrate including an insulating substrate and a radiator bonded to one surface of the insulating substrate,
A power module substrate, wherein the radiator has a multilayer structure in which a plurality of radiator main bodies made of a high thermal conductive material and a low thermal expansion material having a lower thermal expansion coefficient than the radiator main body are joined. 請求項１記載のパワーモジュール用基板において、
前記放熱体は、放熱体本体と低熱膨張材とが互い違いに接合されて、計５〜７枚の多層構造としたことを特徴とするパワーモジュール用基板。The power module substrate according to claim 1,
A power module substrate, wherein the radiator has a radiator body and a low thermal expansion material which are alternately joined to form a total of 5 to 7 multilayer structures. 請求項１又は２記載の絶縁基板上にチップを搭載してなることを特徴とするパワーモジュール。A power module comprising a chip mounted on the insulating substrate according to claim 1.
JP2002377387A 2002-12-26 2002-12-26 Power module and substrate therefor Pending JP2004207619A (en)

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