JP2004031577A

JP2004031577A - Radiator for semiconductor device

Info

Publication number: JP2004031577A
Application number: JP2002184710A
Authority: JP
Inventors: Masanori Yamagiwa; 山際　正憲
Original assignee: Nissan Motor Co Ltd
Current assignee: Nissan Motor Co Ltd
Priority date: 2002-06-25
Filing date: 2002-06-25
Publication date: 2004-01-29

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radiator for a semiconductor device which has a good heat dissipating efficiency without an increase in size. <P>SOLUTION: The radiator 1 has a side wall portion 3 standing up from an end part 2 of a placement section 2 to the semiconductor device 5 side. There are bottom face fins 11 on a bottom surface of the placement section 2 and side face fins 12 on an outer surface of the side wall portion 3. The bottom face fins 11, the side face fins 12, the bottom face of the placement section 2, and the outer surface of the side wall section 3 are made to face a liquid 10 for cooling to dissipate heat generated by the semiconductor device 5. Due to this structure, the radiator for a semiconductor device can be reduced in size, compared with the conventional radiator with an increased area for the placement section with added bottom face fins. Furthermore, the radiator 1 can secure required dissipating performance in a shape corresponding to a dimensional margin of an installation site of the radiator 1 mounted with the semiconductor device 5. <P>COPYRIGHT: (C)2004,JPO

Description

【０００１】
【発明の属する技術分野】
本発明は、半導体素子の放熱を行う半導体素子用放熱器に関する。
【０００２】
【従来の技術】
近年、半導体素子の微細加工技術がより一層進歩し、高密度化によって動作時の発熱量が増大しているため、その熱を効果的に放熱するための新しい放熱器が種々提案されている。このような放熱器の例として、たとえば特開２００１−１６８２５６号公報記載のようなものがある。この放熱器は、半導体素子を載置する載置部と、載置部の半導体を載置した側を表面としてその裏面から伸びる複数の放熱フィンからなる。この載置部の裏面と放熱フィンを冷却用液体に臨ませることにより、半導体素子で発生した熱は載置部表面へ伝わり、放熱器の内部で拡散して放熱フィンを伝って冷却用液体へと放熱される。
【０００３】
【発明が解決しようとする課題】
このような上記従来の放熱器にあっては、十分な放熱効果を得るためには放熱フィンを追加する必要があり、また同時に放熱フィンを冷却する冷却用液体の流路も拡大せざるを得ない。
さらに、放熱フィンを追加した場合、放熱面積が増加し冷却用液体への伝熱量は全体的には増加する傾向になるが、熱源である半導体素子から放熱フィンにおける冷却用液体と接する放熱面までの距離が遠くなるため、熱源から運ばれる熱量はその距離が遠いほど少なくなる。したがって追加した放熱フィンほど、そこでの冷却用液体への伝熱量は少なくなる。
【０００４】
式で表すと、放熱器の材料の熱伝導率をλ、熱の流れる断面積をＳ１、その熱伝導距離をＸ、放熱面における冷却用液体への熱伝達係数をα、その伝達面積（放熱面積）をＳ２とした場合、放熱器内での熱源から放熱面までの熱の流れやすさは、
λ×Ｓ１／Ｘ　　　　　　　　　　　　　　　　　　　　　　式（１）
で表され、放熱器の放熱面から冷却用液体への熱の伝わりやすさは、
α×Ｓ２　　　　　　　　　　　　　　　　　　　　　　　　式（２）
で表される。
【０００５】
したがって、どれだけ伝達面積Ｓ２を増やしても、それにあわせて熱伝道距離Ｘの値も上昇してしまえば、全体の放熱効果は小さくなる。すなわち、追加した放熱フィンでは、式（１）に含まれる熱伝導距離Ｘの値が大きくなり放熱フィン先端まで十分に熱が伝わらないため、式（２）であらわされる冷却用液体への伝熱量は非常に少ないものとなる。
【０００６】
特に液冷の場合、式（２）に含まれる熱伝達係数αの値が空冷に比べて大きいにもかかわらず、熱伝導距離Ｘの値が大きいほど式（１）で算出されるように放熱フィンの放熱面まで熱が到達しにくくなり、その結果、放熱フィンの追加による半導体素子の最大温度Ｔｊｍａｘの低減には限界が生じていた。
【０００７】
そこで本発明はこのような問題点に鑑み、大型化を避け、放熱効率のよい半導体素子用放熱器を提供することを目的とする。
【０００８】
【課題を解決するための手段】
本発明は、半導体素子を備える基板を載置する載置部の端部を、半導体素子側に伸ばして側壁部を形成する。載置部の半導体素子を載置していない側の面と、側壁部の外側の面および載置部の側面の少なくとも一方を冷却用媒体に臨ませて、半導体素子で発生する熱の放熱を行うものとした。
【０００９】
【発明の効果】
本発明によれば、半導体素子を載置する載置部の端部に側壁部を備えたので、半導体素子によって発生した熱は、載置部だけでなく側壁部および載置部の側面からも冷却用媒体へ放熱できる構造となっている。よって従来は、放熱器を載置部の面積方向へ拡大して放熱性能を確保していたが、本発明では側壁部を設けて放熱を行うことにより、従来よりも小型な放熱器を得ることができる。
【００１０】
【発明の実施の形態】
次に本発明の実施の形態を実施例により説明する。
図１に本発明の断面図を示す。
放熱器１の載置部２に、半導体素子５を備える半導体モジュール１３が接合されている。放熱器１は、載置部２の端部から半導体素子５側に立ち上がる側壁部３を有している。また側壁部３の端部が外方に向けて９０度折り曲げられ、その先端に取付穴４Ａが開けられて取付部４を形成している。放熱器１は、載置部２の半導体素子５が載置されていない側の面から下方に伸びる下面フィン１１を有している。また放熱器１は、最外側の下面フィン１１における外側面、側壁部３の外側面および載置部２の側面から、外側方向に伸びる側面フィン１２を有している。
【００１１】
一方、半導体モジュール１３は半導体素子５、半田６および絶縁基板７からなる。絶縁基板７は、十分な絶縁性を保ち熱伝導率の高いセラミックス基板７Ｂを備え、セラミックス基板７Ｂの上面には半導体素子５を半田付けするための銅回路７Ａを直接またはろう材を用いて接合してある。半導体素子５は半田６によって銅回路７Ａに取り付けられる。またセラミックス基板７Ｂの下面は、直接またはろう材を用いて載置部２に接合される。
【００１２】
放熱器１の下方には、下面フィン１１および側面フィン１２を囲う図示しない流路が形成され、下面フィン１１、側面フィン１２、載置部２の下面および側面、側壁部３の外方側面は、流路を流れる冷却媒体としての冷却用液体１０に接している。半導体素子５で発生した熱は、半田６と絶縁基板７を経由して載置部２の上面へと伝わり、放熱器１の載置部２および側壁部３で拡散し、下面フィン１１、側面フィン１２を伝って冷却用液体１０へと放熱される。
【００１３】
放熱器１は熱伝導率や、加工性、信頼性の観点から、アルミニウムまたはアルミニウム合金によって形成される。これらは比較的熱伝導率が高く（２００Ｗ／ｍＫ前後）、加工も容易でありさらにヤング率が低く塑性変形しやすいために、載置部２に接合したセラミックス基板７Ｂにかかる応力の緩和が図れ、半導体モジュール１３としての高い信頼性を確保することができる。
【００１４】
図１に示すように、冷却用液体１０の流路の幅を２６ｍｍ、放熱器１の取付部４の上面から、冷却用液体１０の流路の底面までの高さを１０．４ｍｍとする。また半導体素子５の発熱量を２００Ｗ、放熱器１の熱伝導率を２００Ｗ／ｍＫ、冷却用液体１０の温度を８０℃とし、冷却用液体１０に接する放熱面の熱伝達係数を６０００Ｗ／ｍ^２Ｋ、半田６の熱伝導率を７０Ｗ／ｍＫ、半田６の厚みを０．０８ｍｍとする。さらに絶縁基板７の絶縁層であるセラミックス基板７Ｂの熱伝導率を１７０Ｗ／ｍＫ、その厚みを０．６ｍｍとした場合の、半導体素子５の熱シュミレーションを行った。
その結果、半導体素子５の最大温度Ｔｊｍａｘは１３４．０℃となった。
【００１５】
ここで従来の放熱器、すなわち載置部と、載置部から下方に伸びる放熱フィンからなる放熱器に、半導体素子を取り付けた際の熱シュミレーション結果を示す。この放熱器に取り付けられる半導体モジュールは、第１の実施例と同じ構成であるものとする。また、載置部の下面からは７個の放熱フィンが伸び、放熱フィンの左右最外側間は３２ｍｍである。さらに、冷却用液体を流す流路の幅を３２ｍｍに形成して、流路に放熱フィンを臨ませ、放熱フィンと載置部の下面を冷却用液体に臨ませる。冷却用液体の流路の下面から半導体素子の上面までの高さは１０．４ｍｍであるとする。
【００１６】
半導体素子の発熱量を２００Ｗ、放熱器の熱伝導率を２００Ｗ／ｍＫ、冷却用液体の温度を８０℃とし、それと接する放熱面における熱伝達係数を６０００Ｗ／ｍ^２Ｋとする。また、半田の熱伝導率を７０Ｗ／ｍＫ、厚みを０．０８ｍｍ、絶縁基板の絶縁層であるセラミックス基板の熱伝導率を１７０Ｗ／ｍＫ、その厚みを０．６ｍｍとした場合に半導体素子の熱シュミレーションを行った。
その結果、半導体素子の最大温度Ｔｊｍａｘは１３４．０℃となった。
【００１７】
このように、本実施例および従来の放熱器における半導体素子の熱シュミレーションより、半導体素子の最大温度Ｔｊｍａｘを同じ値としながら、取付部４を除く放熱器の横方向の幅を、従来の幅３２ｍｍから幅２６ｍｍに縮小することができ、モジュール全体の約２０％の小型化を達成することができる。
【００１８】
図２の（ａ）に、本実施例における放熱器１の放熱面から冷却用液体１０へ伝達される熱の伝達量を、放熱器１の横方向の単位長さ（１ｍｍ）毎に計算した値をグラフにしたものを示す。放熱器１の奥行きは１ｍとする。同様に図２の（ｂ）に、上記従来の放熱器の放熱面から冷却用液体へ伝達される熱の伝熱量を、放熱器の横方向の単位長さ（１ｍｍ）毎に計算した値をグラフにしたものを示す。これによると、従来の放熱器である図２の（ｂ）に比べ、本実施例における放熱器内において全体的に均一に熱拡散が行われ、両脇の放熱フィンで効果的な放熱が実施されていることがわかる。
【００１９】
さらに同様な熱シュミレーションにおいて、図１における放熱器１の左右の側面フィン１２を両側に互いに３ｍｍずつ伸ばし、冷却用液体１０の流路幅を従来と同様の３２ｍｍにした場合、半導体素子５の最大温度Ｔｊｍａｘは１３２．２℃となり、上記従来の放熱器と同じ横幅寸法で、モジュール全体の熱抵抗を約３．３％改善できる結果が得られた。
本実施例において、下面フィン１１および側面フィン１２が本発明における放熱フィンを構成する。
【００２０】
本実施例は以上のように構成され、下面フィン１１を備える載置部２、および側面フィン１２を備える側壁部３を冷却用液体１０に臨ませて、半導体素子５で発生する熱の放熱を行うことにより、従来の下面フィンを追加した放熱器に比べ、小型の半導体素子用放熱器を得ることができ、半導体素子５を備えた放熱器１と冷却用液体の流路の設置場所の縦横寸法の制限範囲内で、必要な放熱性能を確保することができる。
【００２１】
これにより、半導体素子の最大温度Ｔｊｍａｘは上げずに半導体素子用放熱器を小型化することや、半導体素子用放熱器の大きさは大型化せずに半導体素子の最大温度Ｔｊｍａｘを下げることが可能である。
熱を放熱する放熱フィンとしての下面フィン１１や側面フィン１２を備えたことにより放熱面積が増加し、より効果的な放熱を行うことができる。
【００２２】
次に本発明の第２の実施例を説明する。
図３は第２の実施例の断面図である
放熱器１Ａの載置部２に、半導体素子５を備える半導体モジュール１３が接合されている。放熱器１Ａは、載置部２の端部から半導体素子５側に立ち上がる側壁部３を有している。また側壁部３の端部が外方に向けて９０度折り曲げられ、その先端に取付穴４Ａが開けられて取付部４を形成している。放熱器１Ａは、載置部２の半導体素子５が載置されていない側の面から下方に伸びる下面フィン１１（１１Ａ、１１Ｂ）を有している。
【００２３】
載置部２の下面から伸びる下面フィン１１（１１Ａ、１１Ｂ）のうち左右最外側の下面フィン１１Ａは、載置部２の下面からの突出量を中央部の下面フィン１１Ｂと同じに形成されている。また下面フィン１１Ａの内側面１１ａは、下面フィン１１Ａの先端から階段状に、隣接する下面フィン１１Ｂの根元近傍につながっている。このように下面フィン１１Ａは、先端に向かうにつれて他の下面フィン１１Ｂの幅と同じとなる先細り形状に形成してある。
また放熱器１Ａは、最外側の下面フィン１１Ａにおける外側面、側壁部３の外側面および載置部２の側面から、外側方向に伸びる側面フィン１２を有している。
他の構成は上記第１の実施例と同様であり、同じ番号を付して説明を省略する。
なお、下面フィン１１Ａの内側面１１ａの形状は、階段状に限らず、斜めや曲線等の形状であってもかまわない。
【００２４】
図３に示すように、冷却用液体１０の流路の幅を２６ｍｍ、放熱器１Ａの取付部４の上面から、冷却用液体１０の流路の底面までの高さを１０．４ｍｍとし、上記第１の実施例で行った各種の条件と同じ条件で、第２の実施例における放熱器１Ａを用いて、半導体素子５の熱シュミレーションを行った。
その結果、半導体素子５の最大温度Ｔｊｍａｘは１３２．４℃となり、上記従来の放熱器を用いた場合に比べ、モジュール全体の約２０％の小型化とともに、モジュール全体の熱抵抗を約３．０％改善することが同時に可能である結果が得られた。
【００２５】
図４に、第２の実施例における放熱器１Ａの放熱面から冷却用液体１０へ伝達される熱の伝達量を、放熱器１Ａの横方向の単位長さ（１ｍｍ）毎に計算した値をグラフにしたものを示す。放熱器１Ａの奥行きは１ｍとする。これによると、放熱器１Ａ内で全体的に満遍なく熱拡散が行われ、階段状の内側面１１ａを備えた下面フィン１１Ａで特に伝熱量が多く、効果的な放熱が実施されていることがわかる。
【００２６】
本実施例は以上のように構成され、下面フィン１１Ａは、内側面１１ａを階段状に形成され、先端に向かうにつれて他の下面フィン１１Ｂの幅と同じとなる先細り形状に形成される。よって放熱器１Ａにおいて、半導体素子５を備える半導体モジュール１３との接合面から伝わる熱は、下面フィン１１Ａの先端まで十分に広い断面積を通って運ばれてくるため、下面フィン１１Ａおよび側面フィン１２の放熱面において、熱を冷却用液体１０に効果的に放熱することができる。
【００２７】
なお本実施例において、下面フィンのうち左右最外側の下面フィン１１Ａのみを先細り形状に形成したが、これに限定されず他の下面フィン１１Ｂや側面フィン１２の形状を先細り形状に形成してもよい。これにより、より効率よく熱を放熱することができる。
【００２８】
なお上記各実施例において、絶縁基板７の上面に備えた銅回路７Ａに代り、応力緩和を図ったアルミニウム回路を用いてもよい。また半導体モジュール１３と放熱器１との取り付けの際に、セラミックス基板７Ｂと載置部２とを直接またはろう材を用いて取り付けたが、これに限定されず、セラミックス基板７Ｂの下面に銅回路を備えたセラミックス絶縁基板や、前記セラミックス絶縁基板を搭載したベース、または、その他全ての半導体モジュールを接合してもよい。
【００２９】
また、放熱器の材料として、高い熱伝導率で放熱性を向上した無酸素銅（３６０Ｗ／ｍＫ前後、１６ｐｐｍ／℃前後）を用いてもよい。また、熱膨張係数がよりセラミックスの値に近く、セラミックス基板７Ｂにかかる応力の緩和が図れるモリブデンを用いた銅合金（２２０Ｗ／ｍＫ前後、８ｐｐｍ／℃前後）やその他の銅合金、炭化ケイ素等を分散材とした金属基複合材料（１８０Ｗ／ｍＫ前後、８ｐｐｍ／℃前後）や、１００Ｗ／ｍＫ以上の熱伝導率を持った窒化アルミニウム、窒化ケイ素等のセラミックス材料を用いてもよい。
【００３０】
このように放熱器を熱伝導率の高い金属材料によって形成することにより、放熱器内で熱の伝達がよくなり、より一層冷却用液体に熱を伝達し、半導体素子を冷却することができる。また絶縁基板に用いられるセラミックスと比較的熱膨張係数が近い金属基複合材料やセラミックス材料を放熱器の材料として用いた場合は、高温と低温との間で繰り返されるヒートサイクルによって絶縁基板に与える熱応力を小さくすることができ、モジュールの信頼性の向上を図ることができる。
【図面の簡単な説明】
【図１】本発明における第１の実施例を示す断面図である。
【図２】第１の実施例における放熱器から冷却用液体への伝熱量を示す図である。
【図３】本発明における第２の実施例を示す断面図である。
【図４】第２の実施例における放熱器から冷却用液体への伝熱量を示す図である。
【符号の説明】
１、１Ａ　　放熱器
２　　載置部
３　　側壁部
５　　半導体素子
７　　絶縁基板
１０　　冷却用液体
１１、１１Ａ、１１Ｂ　　下面フィン
１２　　側面フィン
１３　　半導体モジュール[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a semiconductor device radiator that radiates heat from a semiconductor device.
[0002]
[Prior art]
In recent years, fine processing technology for semiconductor elements has been further advanced, and the amount of heat generated during operation has been increased due to higher density. Therefore, various new radiators for effectively dissipating the heat have been proposed. As an example of such a radiator, there is one described in, for example, JP-A-2001-168256. The radiator includes a mounting portion on which a semiconductor element is mounted, and a plurality of heat dissipating fins extending from the back surface of the mounting portion on the side where the semiconductor is mounted. The heat generated by the semiconductor element is transmitted to the surface of the mounting part, and diffuses inside the radiator and travels through the radiating fin to the cooling liquid by exposing the back surface of the mounting part and the radiation fin to the cooling liquid. Is dissipated.
[0003]
[Problems to be solved by the invention]
In such a conventional radiator, it is necessary to add a radiation fin in order to obtain a sufficient heat radiation effect, and at the same time, the flow path of the cooling liquid for cooling the radiation fin must be enlarged. Absent.
Furthermore, when a heat radiating fin is added, the heat radiating area increases and the amount of heat transferred to the cooling liquid tends to increase as a whole, but from the semiconductor element, which is the heat source, to the heat radiating surface of the heat radiating fin that contacts the cooling liquid. , The amount of heat transferred from the heat source decreases as the distance increases. Therefore, the more heat radiation fins are added, the smaller the amount of heat transfer to the cooling liquid there.
[0004]
In terms of the equation, the thermal conductivity of the material of the radiator is λ, the cross-sectional area of heat flow is S1, the heat conduction distance is X, the heat transfer coefficient to the cooling liquid on the heat radiating surface is α, and the transfer area (radiation) If the area) is S2, the easiness of heat flow from the heat source to the heat dissipation surface in the radiator is
λ × S1 / X Equation (1)
The heat transfer from the radiator surface to the cooling liquid is
α × S2 Equation (2)
Is represented by
[0005]
Therefore, no matter how much the transmission area S2 is increased, if the value of the heat conduction distance X increases accordingly, the overall heat radiation effect becomes smaller. That is, with the added radiating fin, the value of the heat conduction distance X included in Expression (1) becomes large, and heat is not sufficiently transmitted to the tip of the radiating fin. Therefore, the amount of heat transfer to the cooling liquid represented by Expression (2) Will be very few.
[0006]
In particular, in the case of liquid cooling, although the value of the heat transfer coefficient α included in the equation (2) is larger than that of the air cooling, the larger the value of the heat conduction distance X is, the more the heat is dissipated as calculated by the equation (1). It is difficult for heat to reach the radiating surface of the fin, and as a result, there has been a limit in reducing the maximum temperature Tjmax of the semiconductor element by adding the radiating fin.
[0007]
SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide a semiconductor device radiator having high heat dissipation efficiency while avoiding an increase in size.
[0008]
[Means for Solving the Problems]
According to the present invention, an end of a mounting portion on which a substrate having a semiconductor element is mounted is extended toward the semiconductor element to form a side wall. The surface of the mounting portion on which the semiconductor element is not mounted, and at least one of the outer surface of the side wall portion and the side surface of the mounting portion are exposed to the cooling medium to radiate heat generated by the semiconductor element. It was done.
[0009]
【The invention's effect】
According to the present invention, since the side wall is provided at the end of the mounting portion on which the semiconductor element is mounted, the heat generated by the semiconductor element can be transmitted not only from the mounting portion but also from the side wall and the side surface of the mounting portion. It has a structure that can radiate heat to the cooling medium. Therefore, in the past, the heat radiator was expanded in the area direction of the mounting portion to secure the heat radiation performance. However, in the present invention, by providing the side wall portion to perform the heat radiation, it is possible to obtain a heat radiator smaller than the conventional one. Can be.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, embodiments of the present invention will be described with reference to examples.
FIG. 1 shows a sectional view of the present invention.
The semiconductor module 13 including the semiconductor element 5 is joined to the mounting portion 2 of the radiator 1. The radiator 1 has a side wall 3 that rises from the end of the mounting portion 2 toward the semiconductor element 5. Further, the end of the side wall portion 3 is bent outward by 90 degrees, and a mounting hole 4A is formed at the end thereof to form the mounting portion 4. The radiator 1 has a lower surface fin 11 extending downward from a surface of the mounting portion 2 on which the semiconductor element 5 is not mounted. The radiator 1 also has side fins 12 extending outward from the outer surface of the outermost lower surface fin 11, the outer surface of the side wall portion 3, and the side surface of the mounting portion 2.
[0011]
On the other hand, the semiconductor module 13 includes the semiconductor element 5, the solder 6, and the insulating substrate 7. The insulating substrate 7 includes a ceramic substrate 7B having sufficient thermal conductivity and high thermal conductivity, and a copper circuit 7A for soldering the semiconductor element 5 is bonded directly or using a brazing material to the upper surface of the ceramic substrate 7B. I have. The semiconductor element 5 is attached to the copper circuit 7A by the solder 6. The lower surface of the ceramic substrate 7B is joined to the mounting portion 2 directly or by using a brazing material.
[0012]
Below the radiator 1, a flow path (not shown) surrounding the lower fin 11 and the side fin 12 is formed, and the lower fin 11, the side fin 12, the lower surface and the side surface of the mounting portion 2, and the outer side surface of the side wall portion 3 are formed. And a cooling liquid 10 as a cooling medium flowing through the flow path. The heat generated in the semiconductor element 5 is transmitted to the upper surface of the mounting portion 2 via the solder 6 and the insulating substrate 7, diffused in the mounting portion 2 and the side wall portion 3 of the radiator 1, Heat is radiated to the cooling liquid 10 along the fins 12.
[0013]
The radiator 1 is formed of aluminum or an aluminum alloy from the viewpoint of thermal conductivity, workability, and reliability. These have relatively high thermal conductivity (around 200 W / mK), are easy to process, and have low Young's modulus and are easily plastically deformed, so that the stress applied to the ceramic substrate 7B joined to the mounting portion 2 can be relaxed. Thus, high reliability as the semiconductor module 13 can be ensured.
[0014]
As shown in FIG. 1, the width of the flow path of the cooling liquid 10 is 26 mm, and the height from the upper surface of the mounting portion 4 of the radiator 1 to the bottom of the flow path of the cooling liquid 10 is 10.4 mm. Further, the heat value of the semiconductor element 5 is 200 W, the thermal conductivity of the radiator 1 is 200 W / mK, the temperature of the cooling liquid 10 is 80 ° C., and the heat transfer coefficient of the heat radiation surface in contact with the cooling liquid 10 is 6000 W / m ^2. K, the thermal conductivity of the solder 6 is 70 W / mK, and the thickness of the solder 6 is 0.08 mm. Further, the thermal simulation of the semiconductor element 5 was performed when the thermal conductivity of the ceramic substrate 7B as the insulating layer of the insulating substrate 7 was 170 W / mK and the thickness was 0.6 mm.
As a result, the maximum temperature Tjmax of the semiconductor element 5 became 134.0 ° C.
[0015]
Here, a heat simulation result when a semiconductor element is attached to a conventional radiator, that is, a radiator including a mounting portion and a radiating fin extending downward from the mounting portion, is shown. The semiconductor module attached to this radiator has the same configuration as that of the first embodiment. Also, seven radiating fins extend from the lower surface of the mounting portion, and the distance between the left and right outermost fins is 32 mm. Further, the width of the flow path through which the cooling liquid flows is formed to be 32 mm, and the radiation fin faces the flow path, and the lower surface of the radiation fin and the mounting portion faces the cooling liquid. The height from the lower surface of the cooling liquid flow path to the upper surface of the semiconductor element is 10.4 mm.
[0016]
The heat value of the semiconductor element is 200 W, the thermal conductivity of the radiator is 200 W / mK, the temperature of the cooling liquid is 80 ° C., and the heat transfer coefficient on the heat dissipating surface in contact therewith is 6000 W / m ² K. When the thermal conductivity of the solder is 70 W / mK, the thickness is 0.08 mm, and the thermal conductivity of the ceramic substrate, which is the insulating layer of the insulating substrate, is 170 W / mK and the thickness is 0.6 mm, the heat of the semiconductor element is A simulation was performed.
As a result, the maximum temperature Tjmax of the semiconductor element became 134.0 ° C.
[0017]
As described above, from the heat simulation of the semiconductor element in the present embodiment and the conventional radiator, while keeping the maximum temperature Tjmax of the semiconductor element to the same value, the width in the lateral direction of the radiator excluding the mounting part 4 is reduced to the conventional width of 32 mm. To 26 mm in width, and a size reduction of about 20% of the entire module can be achieved.
[0018]
In FIG. 2A, the amount of heat transferred from the heat radiating surface of the radiator 1 to the cooling liquid 10 in the present embodiment was calculated for each unit length (1 mm) of the radiator 1 in the lateral direction. The values are shown as a graph. The depth of the radiator 1 is 1 m. Similarly, FIG. 2B shows a value obtained by calculating the amount of heat transferred from the heat radiation surface of the conventional radiator to the cooling liquid for each unit length (1 mm) in the lateral direction of the radiator. The graph is shown. According to this, as compared with the conventional radiator of FIG. 2B, the heat is diffused uniformly in the radiator of the present embodiment as a whole, and effective radiation is performed by the radiation fins on both sides. You can see that it is done.
[0019]
Further, in the same heat simulation, when the left and right side fins 12 of the radiator 1 in FIG. 1 are extended to both sides by 3 mm and the flow path width of the cooling liquid 10 is set to 32 mm as in the related art, the maximum of the semiconductor element 5 The temperature Tjmax was 132.2 ° C., and the result was that the thermal resistance of the entire module could be improved by about 3.3% with the same width as the above-mentioned conventional radiator.
In the present embodiment, the lower surface fins 11 and the side fins 12 constitute the heat radiation fins of the present invention.
[0020]
This embodiment is configured as described above. The mounting portion 2 having the lower surface fins 11 and the side wall portion 3 having the side surface fins 12 are exposed to the cooling liquid 10 to radiate heat generated in the semiconductor element 5. By doing so, it is possible to obtain a small-sized radiator for a semiconductor device as compared with a radiator provided with a conventional lower surface fin, and the radiator 1 provided with the semiconductor element 5 and the vertical and horizontal positions of the cooling liquid flow path are installed. The required heat radiation performance can be ensured within the size limit.
[0021]
This makes it possible to reduce the size of the semiconductor device radiator without increasing the maximum temperature Tjmax of the semiconductor device, and to reduce the maximum temperature Tjmax of the semiconductor device without increasing the size of the semiconductor device radiator. It is.
The provision of the lower surface fins 11 and the side surface fins 12 as heat radiation fins for dissipating heat increases the heat radiation area, thereby enabling more effective heat radiation.
[0022]
Next, a second embodiment of the present invention will be described.
FIG. 3 is a cross-sectional view of the second embodiment, in which a semiconductor module 13 having a semiconductor element 5 is joined to a mounting portion 2 of a radiator 1A. The radiator 1 </ b> A has a side wall 3 rising from the end of the mounting section 2 to the semiconductor element 5 side. Further, the end of the side wall portion 3 is bent outward by 90 degrees, and a mounting hole 4A is formed at the end thereof to form the mounting portion 4. The radiator 1A has lower surface fins 11 (11A, 11B) extending downward from a surface of the mounting portion 2 on which the semiconductor element 5 is not mounted.
[0023]
Of the lower surface fins 11 (11A, 11B) extending from the lower surface of the mounting portion 2, the left and right outermost lower surface fins 11A are formed to have the same protruding amount from the lower surface of the mounting portion 2 as the lower surface fin 11B of the central portion. I have. In addition, the inner side surface 11a of the lower fin 11A is connected to the vicinity of the root of the adjacent lower fin 11B stepwise from the tip of the lower fin 11A. As described above, the lower surface fin 11A is formed in a tapered shape having the same width as the other lower surface fins 11B toward the tip.
The radiator 1A has side fins 12 extending outward from the outer surface of the outermost lower surface fin 11A, the outer surface of the side wall 3 and the side surface of the mounting portion 2.
Other configurations are the same as those of the first embodiment, and the same reference numerals are given and the description is omitted.
The shape of the inner side surface 11a of the lower surface fin 11A is not limited to the step shape, and may be an oblique or curved shape.
[0024]
As shown in FIG. 3, the width of the flow path of the cooling liquid 10 is 26 mm, and the height from the top surface of the mounting portion 4 of the radiator 1A to the bottom surface of the flow path of the cooling liquid 10 is 10.4 mm. Under the same conditions as the various conditions performed in the first embodiment, a heat simulation of the semiconductor element 5 was performed using the radiator 1A in the second embodiment.
As a result, the maximum temperature Tjmax of the semiconductor element 5 becomes 132.4 ° C., the size of the module is reduced by about 20% and the thermal resistance of the module is reduced to about 3.0 as compared with the case of using the conventional radiator. % Improvement was obtained at the same time.
[0025]
FIG. 4 shows a value obtained by calculating the amount of heat transmitted from the heat radiation surface of the radiator 1A to the cooling liquid 10 for each unit length (1 mm) in the lateral direction of the radiator 1A in the second embodiment. The graph is shown. The depth of the radiator 1A is 1 m. According to this, it can be seen that heat is diffused uniformly throughout the radiator 1A, and the lower surface fin 11A having the step-like inner surface 11a has a particularly large amount of heat transfer and effective heat radiation is performed. .
[0026]
The present embodiment is configured as described above, and the lower surface fin 11A is formed in a stepped shape on the inner side surface 11a, and is formed in a tapered shape having the same width as the other lower surface fins 11B toward the tip. Therefore, in the radiator 1A, the heat transmitted from the bonding surface with the semiconductor module 13 including the semiconductor element 5 is transferred through a sufficiently wide cross-sectional area to the tip of the lower fin 11A, so that the lower fin 11A and the side fin 12 The heat can be effectively radiated to the cooling liquid 10 on the heat radiating surface.
[0027]
In this embodiment, among the lower fins, only the left and right outermost lower fins 11A are formed in a tapered shape. However, the present invention is not limited to this, and other lower fins 11B and side fins 12 may be formed in a tapered shape. Good. Thereby, heat can be more efficiently dissipated.
[0028]
In each of the above embodiments, an aluminum circuit for reducing stress may be used instead of the copper circuit 7A provided on the upper surface of the insulating substrate 7. In mounting the semiconductor module 13 and the radiator 1, the ceramic substrate 7B and the mounting portion 2 are mounted directly or by using a brazing material. However, the present invention is not limited to this, and a copper circuit is provided on the lower surface of the ceramic substrate 7B. A ceramic insulating substrate provided with the above, a base on which the ceramic insulating substrate is mounted, or all other semiconductor modules may be joined.
[0029]
Further, as a material of the radiator, oxygen-free copper (about 360 W / mK, about 16 ppm / ° C.) having high heat conductivity and improved heat dissipation may be used. In addition, a copper alloy (about 220 W / mK, about 8 ppm / ° C.) using molybdenum whose thermal expansion coefficient is closer to that of ceramics and can relax stress applied to the ceramic substrate 7B, other copper alloys, silicon carbide, etc. A metal-based composite material (around 180 W / mK, around 8 ppm / ° C.) as a dispersing material, or a ceramic material such as aluminum nitride or silicon nitride having a thermal conductivity of 100 W / mK or more may be used.
[0030]
By forming the radiator from a metal material having a high thermal conductivity as described above, heat can be transmitted well in the radiator, and the heat can be further transmitted to the cooling liquid to cool the semiconductor element. When a metal-based composite material or ceramic material having a coefficient of thermal expansion relatively close to that of the ceramic used for the insulating substrate is used as the material for the radiator, the heat applied to the insulating substrate by repeated heat cycles between high and low temperatures The stress can be reduced, and the reliability of the module can be improved.
[Brief description of the drawings]
FIG. 1 is a sectional view showing a first embodiment of the present invention.
FIG. 2 is a diagram showing a heat transfer amount from a radiator to a cooling liquid in the first embodiment.
FIG. 3 is a sectional view showing a second embodiment of the present invention.
FIG. 4 is a diagram showing a heat transfer amount from a radiator to a cooling liquid in a second embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1, 1A Heat sink 2 Mounting part 3 Side wall part 5 Semiconductor element 7 Insulating substrate 10 Cooling liquid 11, 11A, 11B Lower fin 12 Side fin 13 Semiconductor module

Claims

In a semiconductor element radiator used for cooling a semiconductor element,
A mounting portion for mounting the substrate including the semiconductor element, and a side wall portion formed by extending an end of the mounting portion toward the semiconductor element side,
The heat generated in the semiconductor element by exposing at least one of the surface of the mounting portion on which the semiconductor element is not mounted, the outer surface of the side wall portion, and the side surface of the mounting portion to the cooling medium. A radiator for a semiconductor device, which radiates heat.

The heat generated by the semiconductor element is applied to at least one of the surface of the mounting portion on which the semiconductor element is not mounted, the outer surface of the side wall portion, and the side surface of the mounting portion for cooling. The radiator for a semiconductor device according to claim 1, further comprising a radiating fin for radiating heat to the medium.

3. The radiator for a semiconductor device according to claim 1, wherein the radiating fin is formed to have a larger cross-sectional area at a root and a tapered shape having a smaller cross-sectional area toward a tip.

The placing part and the side wall part are described above.
It is characterized by being formed of a metal material such as copper, copper alloy, aluminum and aluminum alloy, a metal matrix composite material using a ceramic dispersing material, or a ceramic material such as aluminum nitride and silicon nitride having high thermal conductivity. The radiator for a semiconductor device according to claim 1, 2 or 3, wherein