JP2004063898A

JP2004063898A - Heat radiating material and its manufacturing method

Info

Publication number: JP2004063898A
Application number: JP2002221884A
Authority: JP
Inventors: Makoto Hori; 堀　誠; Takashi Suzumura; 鈴村　隆志
Original assignee: Hitachi Cable Ltd
Current assignee: Hitachi Cable Ltd
Priority date: 2002-07-30
Filing date: 2002-07-30
Publication date: 2004-02-26

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat radiating material that is high in thermal conductivity, good in heat radiating property, and low in thermal strain, can be manufactured efficiently, and can be reduced in manufacturing cost. <P>SOLUTION: The heat radiating material 1 is provided with a heat receiving layer 2 which absorbs the heat generated from a heating element, and a heat radiating layer 3 which is integrated with the heat receiving layer 2 and discharges the heat conducted from the heat receiving layer 2 to the outside, in a sintered compact formed by sintering a mixture of metal powder and the powder of an inorganic compound having a smaller coefficient of thermal expansion than the metal powder has. On the surface of the material 1, a plurality of pyramidal or conical pin-like fins 4 is provided integrally with the heat radiating layer 3. The concentration of the inorganic compound in the heat receiving layer 2 is made higher than that of the compound in the heat radiating layer 3. <P>COPYRIGHT: (C)2004,JPO

Description

【０００１】
【発明の属する技術分野】
本発明は、半導体素子やこの素子を用いた半導体モジュールなどの半導体装置から発生する熱を放熱する放熱材及びその製造方法に関する。
【０００２】
【従来の技術】
半導体回路（ＬＳＩ）の高容量化、高速化に伴い、その回路が形成される半導体素子の発熱量はさらに増大する傾向にある。このため、発熱に起因する半導体素子の特性劣化、短寿命化を防止するために、放熱材を設け、半導体素子及びその近傍での温度上昇を抑制する必要がある。
【０００３】
Ｃｕ（銅）は、熱伝導率が３９３Ｗ／（ｍ・Ｋ）と大きく、かつ低価格であるため、ＬＳＩの放熱材として一般に用いられている。一方、各種オン・オフ機能を持つ電力やエネルギーの変換、制御用の半導体素子は、発熱量が特に大きいことから、放熱材として、熱膨張率が、半導体素子の構成材料であるＳｉ（シリコン）の熱膨張率に近い材料、例えばＭｏ（モリブデン）やＷ（タングステン）が使われている。
【０００４】
しかし、このＣｕは、熱伝導率が大きいものの、熱膨張係数が１７×１０^−６／Ｋと大きいため、発熱量が多く熱膨張率が小さい半導体素子用の放熱材には熱歪み等の点から直接利用することができない。また、ＭｏやＷは、熱膨張率が小さいが、高価格で熱伝導性が低い欠点がある。このため、発熱量が多い半導体素子用の放熱材には、熱伝導率が大きく、かつ価格の安いＣｕがＭｏ、Ｗと組み合わされて使用されている。このＣｕ、Ｍｏ、Ｗを組合せて放熱材を生成する場合、高圧でかつ時間を要するプレス成形や熱処理研磨仕上げが必要であることから、製造工程が複雑になり、製造コストが高くなる。
【０００５】
そこで、低価格で経済的に有利な銅製放熱材の熱膨張の問題を解決する放熱材として、良伝熱性の金属粉末（例えばＣｕ粉末）と、この金属より低熱膨張率を有する無機材料（例えばＣｕＯ：酸化銅）の粉末とを混合して焼結し、これによって得られるＣｕとＣｕ_２Ｏの複合金属による放熱材が提案開発されている。この放熱材は、半導体装置等の発熱体から発生される熱を吸収する受熱層と、この受熱層と一体化され、受熱層からの熱を外部に放出する放熱層とを有して構成されている。
【０００６】
この放熱材において、Ｃｕ_２Ｏの割合を多くすると熱膨張率は低くなるが、熱伝導率及び強度も低くなるので、熱膨張率及び熱伝導率がほぼ中間的な単一酸化銅濃度複合材（例：酸化銅濃度が約５０％）を使用する場合が多い。また、更なる半導体素子の発熱量増大に対し、上記提案開発中の放熱材の放熱性能を上げるため、放熱側に伝熱効率の良い連続フィンを設け、放熱材の放熱性能を向上させることが図られている。
【０００７】
この連続フィンを設けた従来の放熱材の例を、図１７及び図１８に示す。図１７に斜視図で示す放熱材５１は、方形の薄板上に断面が三角の細長いフィン（連続フィン）５２を複数平行に設けたものである。この放熱材５１は、半導体装置の絶縁板２１に接合されて用いられる。矢印２０で示す半導体装置からの熱は、絶縁板２１を介して放熱材５１から放射される。この際、矢印２３で示す空気などの冷却流体が、矢印２２で示すように、連続フィン５２を乗り越え、又は冷却流体２３が多い場合は、連続フィン５２の間に沿って流れることにより、半導体装置の熱で熱くなった放熱材５１を冷却する。
【０００８】
また、図１８に断面図で示す放熱材５１ａは、方形の薄板上に円柱状のピン（ピン状フィン）５２ａを多数点在させて作製したものである。この放熱材５１ａも、半導体装置の絶縁板２１に接合されて用いられ、矢印２０で示す半導体装置からの熱を、矢印２２ａで示すように放射する。
【０００９】
【発明が解決しようとする課題】
しかし、従来の連続フィンを設けた放熱材５１においては、熱膨張率が小さい半導体装置の絶縁板２１との高温接合後、放熱材５１と絶縁板２１との熱膨張率の差による反りが発生し、放熱性が低下する。また、冷却流体２３が連続フィン５２間を通る際の圧損が大きいので、放熱材５１の放熱性が低下するという問題がある。さらに、連続フィン５２は、フライスや旋盤により加工されるが、この加工方法は、製造コストが高く、量産性が低いという問題がある。
【００１０】
また、ピン状フィン５２ａは、連続フィン５２に比べ圧損が小さく伝熱性能が良いなどの利点があるが、フライスや旋盤による製作はほとんど不可能であり、精密鋳造、プレスなどにより製作される為、製造コストが格段に高いという問題がある。
【００１１】
本発明は、かかる点に鑑みてなされたものであり、熱伝導性が高くて放熱性が良く、熱歪みが少なく、効率良く製造することができ、製造コストを低減させることができる放熱材及びその製造方法を提供することを目的とする。
【００１２】
【課題を解決するための手段】
上記課題を解決するために、本発明の放熱材は、金属粉末とこの金属粉末より低い熱膨張率を有する無機化合物粉末とを混合した焼結体であり、この焼結体に、発熱体から発生された熱を吸収する受熱層と、この受熱層と一体化され、前記受熱層から伝導されてくる熱を外部に放出する放熱層とを備えて成る放熱材において、前記放熱層の表面に、角錐又は円錐型の突起手段を前記放熱層と一体に複数設けたことを特徴としている。
【００１３】
また、前記受熱層は、前記放熱層よりも前記無機化合物の濃度が高いことを特徴としている。
【００１４】
また、前記焼結体は、銅、アルミニウム、銀、金又はこれらの合金から選択される金属粉末と、室温〜３００℃における熱膨張率が５×１０^−６／Ｋ以下の酸化銅、酸化錫、酸化亜鉛、酸化鉛、酸化ニッケル、酸化アルミニウムの何れかによる無機化合物粉末の混合物を焼結して成ることを特徴としている。
【００１５】
また、前記焼結体は、前記金属粉末に銅、前記無機化合物粉末に酸化第二銅を用い、前記受熱層の酸化第一銅の濃度が７０％以下、前記放熱層の酸化第一銅の濃度が０％以上であることを特徴としている。
【００１６】
また、前記受熱層の表面及び内部に、焼結温度より低い融点の低融点金属を、被覆及び含浸したことを特徴としている。
【００１７】
また、前記突起手段の先端及び根本に湾曲面を形成したことを特徴としている。
【００１８】
また、本発明の放熱材の製造方法は、発熱体に接合され、発熱体ら発生する熱を放熱する放熱材を製造する放熱材の製造方法において、金属粉末とこの金属粉末より低い熱膨張率を有する無機化合物粉末との混合粉末を、逆角錐又は逆円錐型に凹部が独立して複数設けられた金型に充填して焼結し、この焼結体の上面に、前記焼結の温度より低い融点の低融点金属粉末を載せて加圧しながら加熱し、この加熱後に冷却により固化された放熱材を取り出すことを特徴としている。
【００１９】
【発明の実施の形態】
以下、本発明の実施の形態について、図面を参照して詳細に説明する。
【００２０】
（実施の形態）
図１は、本発明の実施の形態に係る放熱材の構成を示す断面図、図２は、その平面図である。
【００２１】
この図１及び図２に示す放熱材１は、方形薄板形状の受熱層２及び放熱層３から成る本体の放熱層３の上面に、三角錐形のピン状フィン４を多数点在させて作製したものである。このピン状フィン４が設けられた面の裏面、即ち半導体装置又は半導体装置の絶縁板に接合される受熱層２の面は、平滑面となっている。また、図３の拡大断面図に示すように、ピン状フィン４の根本１１と先端１３にはアール１２が設けられており、先端１３は、僅かな平滑面となっている。更に、放熱層３及びピン状フィン４は、後述の製造方法で説明する無機材料低濃度複合材４９から成り、受熱層２は、無機材料高濃度複合材から成り、受熱層２の表面部分には低融点金属４７が被膜及び含浸されている。
【００２２】
また、放熱材１は、金属と、この金属よりも熱膨張係数が小さい無機化合物粒子とを有し、金属の中に無機化合物粒子が分散している。金属中に分散する無機化合物粒子は、直径が２００μｍ以下で、好ましくは６０μｍ以下とされている。これは、金属中に無機化合物粒子が分散することによって、はじめて低熱膨張性の放熱材が得られるためである。
【００２３】
ここで、放熱材１は、例えば金属がＣｕの場合、無機化合物の１つであるＣｕ_２Ｏ（酸化第一銅）を０〜７０体積％含むＣｕ合金からなり、室温から３００℃における熱膨張係数が７〜１８×１０^−６／Ｋおよび熱伝導率が８０〜３９０Ｗ／ｍ・Ｋである。Ｃｕ_２Ｏ量が０体積％以下では、熱膨張率が１８×１０^−６／Ｋ以上となり、また、Ｃｕ_２Ｏ量が７０体積％以上では、熱伝導率が８０Ｗ／ｍ・Ｋ以下となるが、平均で見ると熱伝導率が２３０Ｗ／ｍ・Ｋの低熱膨張性の放熱材１を得ることが可能となる。
【００２４】
次に、放熱材１の製造方法を、図４〜図７を参照して説明する。
【００２５】
放熱材１の原料粉末として、平均粒径１０μｍの電解Ｃｕ粉末と粒径５０μｍ以下のＣｕＯ粉末とを用い、電解Ｃｕ粉とＣｕＯ粉末を下記表１の測定例１〜１０に示す比率で調合した後、さらに粉バインダー３１（図４参照）を０〜５重量％調合混入し、スチールボールを入れた乾式ボールミルで１０時間混合する。これによって得られる混合粉末２９を用いた。
【００２６】
従って、この実施の形態では、放熱材１において、ピン状フィン４が設けられた放熱層３の無機材料低濃度複合材４９が酸化第一銅低濃度銅複合材となり、受熱層２の無機材料高濃度複合材５０が酸化第一銅高濃度銅複合材となっており、また、受熱層２の表面及び内部に低融点金属４７が被覆及び含浸されている。
【００２７】
図４に示すように、放熱材製造装置において、ダイ２７と下パンチ１５により構成された粉末充填部４４に金型１６を挿入し、この金型１６に離型剤３０を塗布した後、無機材料（酸化銅）低濃度混合粉末４５及び無機材料（酸化銅）高濃度混合粉末４６から成る混合粉末２９を充填する。この充填後、粉末充填上面をスキーパですりきり、圧紛体４１（図５参照）を生成するための粉末充填量を一定にする。そして、上パンチ２６をプレス押し棒２５で矢印２４の示す方向に加圧し、所定の厚さまで圧紛する。
【００２８】
次に、図５に示すように、プレス押し棒２５を上昇させ、図４に示したダイサポート２８を取りはずし、ダイ２７面にガイド３５をセットする。次いでプレス押し棒２５を矢印３３で示す方向に下降させ、ダイ２７を金型１６の低部が見える位置まで矢印３４で示す方向に押し下げる。次にプレス押し棒２５を上昇させ、ガイド３５を取り外す。次に、上パンチ２６を圧紛体４１から取り上げ、次いで圧紛体４１を金型１６から取り外す。この工程における焼結温度はＣｕＯ含有量に応じて８５０〜１０００℃の間で変化させ、焼結温度を３時間保持する。その後、焼結体を充分に冷却する。なお、放熱材１のＣｕ_２Ｏ濃度を、放熱層３で低く、受熱層２で高くする場合は、先ず、粒径の小さい電解Ｃｕ粉を金型１６に一定量充填し、次いでＣｕＯ高濃度の混合粉を粉末充填部４４迄一杯に充填し、その後すりきりし、加振によって、受熱層２側（上パンチ側）に混合粉末２９のＣｕＯ濃度を高め、粉末成形する。
【００２９】
また、低融点金属４７を焼結体４２の表面及び内部に、被覆及び含浸する場合は、圧粉体４１を焼結した後、図６に示すように、粉末成形時と同様に金型１６の中に焼結体４２をセットする。次いで、低融点金属４７の粉末を焼結体４２上面に一定量充填し、加熱しながら、上パンチ２６により矢印２４で示す方向に加圧し、低融点金属４７を、焼結体４２の表面及び内部に、被覆及び含浸する。
【００３０】
次に、図７に示すように、プレス押し棒２５を上昇させ、ダイ２７面にガイド３５をセットし、矢印４３で示すように加熱しながら、プレス押し棒２５を矢印３３で示す方向に下降させ、ダイ２７を金型１６の低部が見える位置まで矢印３４で示す方向に押し下げる。これによって、無機材料高濃度複合材５０に低融点金属層３６が形成される。
【００３１】
【表１】

ここで、上記表１に、単体複合材の室温〜３００℃の温度範囲でＴＭＡ（Ｔｈｅｒｍａｌ　Ｍｅｃｈａｎｉｃａｌ　Ａｎａｌｙｓｉｓ）装置を用いて測定した銅複合材の熱膨張率及びレーザーフラッシュ法により求めた熱伝導率の参考データを示す。また、本実施の形態の放熱材１は、実際には連続的にＣｕ_２Ｏ（無機材料）濃度が変化するので境界は見られないが、放熱材１のＣｕ_２Ｏ（無機材料）量が少ない箇所の無機材料低濃度複合材４９と、多い箇所の無機材料高濃度複合材５０との境界を概略的に破線で示した。
【００３２】
このように作製された図８に示す放熱材１を、図９に示すように、空冷式冷却材として半導体装置の絶縁板２１に取り付けた場合、放熱層３に多数のピン状フィン４が設けられているので、平滑面に比べ、放熱伝熱面積は増大する。さらに図８に示したように、冷部流体４０の流れ２２がピン状フィン４により撹拌されるので、図１７に示した従来の連続フィン５２を設けた放熱材５１に比べ、伝熱性能（放熱）は増大する。
【００３３】
この他、図１０に示すように、放熱材１において、ピン状フィン４のフィンピッチ８を小さくた放熱材１ａや、図１１に示すように、形状の異なるピン状フィン４，４ａを、千鳥状に交互に配置した放熱材１ｂも、上記製造方法により容易に作製することができ、冷却流体４０の種類及び冷却方法に合わせて製作することが可能である。なお、図１１に示したピン状フィン頂角５は、フィン両側面の傾向線の交点での角度とし、通常、円柱フィンと考えられる場合のフィン頂角５は、ほぼ０度近くになる。
【００３４】
従来の問題点で指摘した通り、ピン状フィン４は、フライスや旋盤などによる機械加工は困難であり、プレス或いは精密鋳造などにより製造される。この際、ピン状フィンの製造コストは大幅に増大する。従って、製造コストを下げるためには、本実施の形態のように粉末成形し、焼結によりピン状フィン４を製作するのが望ましい。ピン状フィン４は、連続フィン５２に比べ根元から先端になるほどフィン横断面の減歩率が大きく、フィンの金型１６による拘束力は小さくなり、ピン状フィン４は連続フィン５２より、粉末成形後の金型１６からの離型はし易い。
【００３５】
しかし、ピン状フィン４は、連続フィン５２より、根元１１から先端１３になるほどフィン横断面の減少率が大きくなるので、逆にフィン強度は小さくなると考えられる。その結果、粉末成形後の金型１６からの離型時に連続フィン５２が根元１１から剥離するのに対し、ピン状フィン４はフィンの欠けが生じやすいと考えられる。その為、フィン先端１３にアール１２を設けフィン先端の脱落を防止した。又、フィン根元１１にアール１２を設け粉末成形離型時のフィン剥離を防止した。さらに混合粉末２９充填前に金型１６に離型剤３０を塗布し、金型１６と圧紛体４１との接着度を軽減し、圧紛体４１の金型１６からの離型時のフィンに対する金型１６の拘束力を小さくした。即ち、図１２の混合粉末２９充填前の塗布処理に応じた引き抜き力（ＭＰａ）の比較図に示すように、圧紛体４１の金型１９への接着力は離型剤３０が塗布されない場合に比べ、連続フィン５２の場合、約３０％に低減した。
【００３６】
また、金型１６として、図１３に示すように、下パンチ１５に取り付けられたダイ２７に嵌合される孔付き金型１６にコネクテングロッド１７を一体化することにより、金型１６セットの時間短縮或いは確実性の向上を図ることが可能となる。このような金型１６においては、図１に示したフィン高さ６が低く、フィン頂角５（図１１参照）が大きいピン状フィン４を容易に得ることができる。なお、比較のため図１４に従来の金型１８を示す。従来の金型１８は、孔付き下パンチ１９にダイ２７が取り付けられている。
【００３７】
しかし、フィン高さ６がさらに高くなり、フイン頂角５が小さいシャープなピン状フィン４になると、圧紛体４１を孔付き金型１６から取り出す時、連続フィン５２の場合と同様、フィン４が孔付き金型１６に拘束され、フィン４とフィン底肉部３９が分離、あるいは孔付き金型１６によりフィン４が損傷し、シャープなピン状フィン４を取り出すのは困難になる。その為、混合粉末２９に粉バインダーを添加し、ピン状フィン４の強度を向上させることにより、フィン頂角５が０〜４５度及び、フィン高さ６と底肉厚７（図１参照）の比が１〜６であるシャープな高伝熱性能のピン状フィン４を得ることができる。
【００３８】
なお、粉バインダーの濃度は、０．５〜４％で、ピン状フィン４のフィン強度は増大し、シャープなピン状フィンを形成することができるが、粉バインダーの濃度が高くなると、焼結体４２のボイドが多くなり、繊密度低下、腐食促進などの欠陥が生ずる。しかし、本実施の形態では、放熱材１の表面及び内部に、低融点金属４７が、焼結時の粉バインダー欠落後のボイドに含浸及び被覆されるので、流体４０からの防食及び熱伝導性の低下が防止できる。
【００３９】
また、流体４０の流れが連続フィン５２より円滑に流れる。さらにフィン先端１３及び根元１１にアール１２が設けられている為、流体４０の澱みなどによる流体側の熱抵抗増加あるいは腐食などが回避できる。
【００４０】
更に、上記の他の実施の形態として、高さの異なる金型１６を交互に幅方向に並列に配列し、図１５に示すように、放熱フィンをフィン高さ６の異なるピンフィン４ａ及びピンフィン４ｂからなる放熱材１ｃとし、流体４０の圧損をさらに軽減しながら、流体４０の流れをさらに複雑に変化させ、撹拌効果を高め、放熱性能の更なる向上を図ることも可能である。また、図１６に示すように、上記製造方法により、ピン状フィン４の周りに冷却器との取り付け面３７を設けた放熱材１ｄを作製してもよい。但し、取り付け面３７は平滑にし、取り付け穴３８を設ける。
【００４１】
上記の放熱材１，１ａ，１ｂ，１ｃ，１ｄは、金属としてＣｕ以外に電気伝導性の高いＡｕ、Ａｇ、Ａｌも使用可能である。また、無機化合物として室温〜３００℃の温度範囲における熱膨張係数が５×１０^−６／Ｋ以下の酸化錫、酸化亜鉛、酸化鉛、酸化ニッケル、酸化アルミニウム（Ａｌ_２Ｏ_３）等も使用可能である。
【００４２】
以上説明した実施の形態の放熱材によれば、受熱層２に金属と無機材料からなる低熱膨張性金属複合材、放熱層３にピン状フィン４を金型１６で形成することによって次の▲１▼〜▲６▼に記載するような効果が得られる。
【００４３】
▲１▼受熱層２が低熱膨張率、放熱層３がピン状フィン４により伝熱効率が高くなる為、高熱伝導性の放熱材１を提供することができる。
【００４４】
▲２▼放熱材１の放熱側３にピンフィン４を千鳥状に設けることにより、流体４０の流れが良くなり、放熱材１の放熱性能を向上させることができる。
【００４５】
▲３▼受熱層２の表面及び内部に、低融点金属（錫あるいは鉛、ビスマス）４７が被覆及び含浸されていることにより、放熱材１の密度を向上させ、熱伝導性及び耐腐食性を向上させることができる。
【００４６】
▲４▼フィンが粉末成形時に生成される為、焼結後のフィン成形機械加工の省路が可能となり、大幅な製造コストの低減を図ることができる。
【００４７】
▲５▼受熱層２を低熱膨張率、放熱層３を高熱伝導性のピン状フィン４にすることにより、はんだ等を利用した半導体用絶縁材２０との接合後の放熱材１の反りの減少を図ることができる。この理由は、絶縁板２１の接合面である受熱層２は熱膨張率が低く、対向側の放熱層３は熱膨張率が高いので、絶縁板２１と接合面には直接熱が伝わるが、この接合面の受熱層２では熱の伝導速度は遅い。また、受熱層２から伝達されてきた熱は、放熱層３は速く伝導される。このことから、放熱材における接合面側と放熱側との温度差が小さくなる。また、接合面側が放熱側よりも熱膨張率が低いので、双方の側では熱膨張量の差が小さくなる。この結果、放熱材の反りは軽減する。
【００４８】
▲６▼ピンフィン成形時、種々の孔付き金型１６により、種々のピンフィン形状の放熱材１を容易に生成することができる。
【００４９】
【発明の効果】
以上説明したように、本発明によれば、金属粉末とこの金属粉末より低い熱膨張率を有する無機化合物粉末とを混合した焼結体であり、この焼結体に、発熱体から発生された熱を吸収する受熱層と、この受熱層と一体化され、受熱層から伝導されてくる熱を外部に放出する放熱層とを備えて成る放熱材において、放熱層の表面に、角錐又は円錐型の突起手段を放熱層と一体に複数設けた。また、受熱層の無機化合物の濃度を、放熱層よりも高くしたので、発熱体の接合面である受熱層は熱膨張率が低く、対向側の放熱層は熱膨張率が高くなり、これによって熱膨張量の差を小さくすることができるので、放熱材の反りを軽減させることができる。また、熱伝導率の高い突起手段により放熱効果が向上する。また、突起手段は放熱層の形成時に同時に形成されるので、効率良く製造することができ、製造コストを低減させることができる。
【図面の簡単な説明】
【図１】本発明の実施の形態に係る放熱材の構成を示す断面図である。
【図２】上記実施の形態に係る放熱材の構成を示す平面図である。
【図３】上記実施の形態に係る放熱材のピン状フィン部位の拡大図である。
【図４】上記実施の形態に係る放熱材の製造装置による放熱材製造方法を説明するための第１の図である。
【図５】上記実施の形態に係る放熱材の製造装置による放熱材製造方法を説明するための第２の図である。
【図６】上記実施の形態に係る放熱材の製造装置による放熱材製造方法を説明するための第３の図である。
【図７】上記実施の形態に係る放熱材の製造装置による放熱材製造方法を説明するための第４の図である。
【図８】上記実施の形態に係る放熱材の斜視図である。
【図９】上記実施の形態に係る放熱材に半導体装置の絶縁板を接合した際の断面図である。
【図１０】他の実施の形態に係る放熱材であり、ピン状フィンのピッチを狭めた構造を示す断面図である。
【図１１】他の実施の形態に係る放熱材であり、ピン状フィンの先端形状を異なる２種類とした構造を示す断面図である。
【図１２】上記実施の形態に係る放熱材の製造方法において、混合粉末充填前の塗布処理に応じた引き抜き力の比較を示す図である。
【図１３】上記実施の形態に係る放熱材を作製するための金型の構成を示す断面図である。
【図１４】従来の放熱材を作製するための金型の構成を示す断面図である。
【図１５】他の実施の形態に係る放熱材であり、ピン状フィンのフィン高さを異ならせた構造を示す断面図である。
【図１６】他の実施の形態に係る放熱材であり、ピン状フィンの周りに冷却器との取り付け面を設けた構造を示す断面図である。
【図１７】従来の連続フィンを設けた放熱材の構成を示す斜視図である。
【図１８】従来のピン状フィンを設けた放熱材の構成を示す斜視図である。
【符号の説明】
１　本発明の放熱材
２　受熱層
３　放熱層
４　ピン状フィン
５　フィン頂角
６　フィン高さ
７　フィン底肉厚
８　フィンピッチ
９　ワーク幅　１０　ワーク長さ
１１　フィン底部
１２　アール
１３　フィン先端
１４　本発明の金型
１５　下パンチ
１６　孔板（金型）
１７　コネクテングロット
１８　従来の金型
１９　孔付き下パンチ
２０　熱の流れ
２１　半導体（絶縁板）
２２　流体の流れ方向
２３　流体の流れ
２４　プレス方向
２５　プレス押し棒
２６　上パンチ
２７　ダイ
２８　ダイサポート
２９　混合粉
３０　離型剤
３２　プレスベース
３３　押し出し方向
３４　ダイ進行方向
３５　ガイド
３６　低融点金属層
３７　冷却器取り付け面
３８　取り付け穴
３９　フィン底肉部
４０　冷却流体
４１　圧紛体
４２　焼結体
４３　ヒータ加熱方向
４４　粉末充填部
４５　無機材料（酸化銅）低濃度混合粉末
４６　無機材料（酸化銅）高濃度混合粉末
４７　低融点金属
４８　無機材料（酸化銅）
４９　無機材料低濃度複合材（酸化第一銅低濃度銅複合材）
５０　無機材料高濃度複合材（酸化第一銅高濃度銅複合材）
５１　従来の放熱材
５２　連続フィン[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a heat dissipating material that dissipates heat generated from a semiconductor device such as a semiconductor element and a semiconductor module using the element, and a method of manufacturing the same.
[0002]
[Prior art]
As the capacity and speed of a semiconductor circuit (LSI) increase, the amount of heat generated by a semiconductor element on which the circuit is formed tends to further increase. For this reason, in order to prevent deterioration of the characteristics of the semiconductor element due to heat generation and shortening of the service life, it is necessary to provide a heat radiating material to suppress a temperature rise in the semiconductor element and its vicinity.
[0003]
Since Cu (copper) has a large thermal conductivity of 393 W / (m · K) and is inexpensive, it is generally used as a heat dissipation material for LSIs. On the other hand, a semiconductor element for converting and controlling electric power and energy having various on / off functions generates a particularly large amount of heat, and therefore, as a heat dissipating material, has a thermal expansion coefficient of Si (silicon) which is a constituent material of the semiconductor element. For example, a material having a coefficient of thermal expansion close to that of Mo (molybdenum) or W (tungsten) is used.
[0004]
However, although this Cu has a large thermal conductivity, it has a large thermal expansion coefficient of 17 × 10 ⁻⁶ / K. Therefore, a heat-dissipating material for a semiconductor element having a large calorific value and a small thermal expansion coefficient has a problem such as thermal distortion. Not available directly from. In addition, Mo and W have a low coefficient of thermal expansion, but have disadvantages of high cost and low thermal conductivity. For this reason, Cu, which has a large thermal conductivity and is inexpensive, is used in combination with Mo and W as a heat radiating material for a semiconductor element that generates a large amount of heat. When a heat radiating material is generated by combining Cu, Mo, and W, press forming and heat treatment polishing that require high pressure and time are required, so that the manufacturing process is complicated and the manufacturing cost is increased.
[0005]
Therefore, as a heat dissipating material that solves the problem of thermal expansion of a copper heat dissipating material that is economically advantageous at low cost, a metal powder having good thermal conductivity (for example, Cu powder) and an inorganic material having a lower coefficient of thermal expansion than this metal (for example, A heat radiator made of a composite metal of Cu and Cu ₂ O obtained by mixing and sintering a powder of CuO (copper oxide) has been proposed and developed. The heat dissipating material includes a heat receiving layer that absorbs heat generated from a heating element such as a semiconductor device, and a heat dissipating layer that is integrated with the heat receiving layer and that emits heat from the heat receiving layer to the outside. ing.
[0006]
In this heat dissipating material, when the proportion of Cu ₂ O is increased, the coefficient of thermal expansion is reduced, but the thermal conductivity and strength are also reduced. (Eg, copper oxide concentration of about 50%) is often used. In order to further increase the heat dissipation of the semiconductor element, in order to improve the heat dissipation performance of the heat dissipation material under development proposed above, continuous fins with good heat transfer efficiency are provided on the heat dissipation side to improve the heat dissipation performance of the heat dissipation material. Have been.
[0007]
FIGS. 17 and 18 show examples of conventional heat dissipating materials provided with the continuous fins. The heat dissipating material 51 shown in a perspective view in FIG. 17 is formed by providing a plurality of elongated fins (continuous fins) 52 having a triangular cross section on a rectangular thin plate. The heat radiating material 51 is used by being joined to the insulating plate 21 of the semiconductor device. Heat from the semiconductor device indicated by the arrow 20 is radiated from the radiator 51 via the insulating plate 21. At this time, a cooling fluid such as air indicated by an arrow 23 passes over the continuous fins 52 as shown by an arrow 22 or flows along the space between the continuous fins 52 when the cooling fluid 23 is large. The heat dissipating material 51 heated by the heat is cooled.
[0008]
The heat dissipating material 51a shown in the cross-sectional view of FIG. 18 is formed by arranging a large number of cylindrical pins (pin-shaped fins) 52a on a rectangular thin plate. The heat dissipating material 51a is also used by being joined to the insulating plate 21 of the semiconductor device, and radiates heat from the semiconductor device indicated by the arrow 20 as indicated by the arrow 22a.
[0009]
[Problems to be solved by the invention]
However, in the heat dissipating material 51 provided with the conventional continuous fins, after the high-temperature bonding with the insulating plate 21 of the semiconductor device having a small thermal expansion coefficient, warpage due to the difference in the thermal expansion coefficient between the heat dissipating material 51 and the insulating plate 21 occurs. And the heat radiation is reduced. Further, since the pressure loss when the cooling fluid 23 passes between the continuous fins 52 is large, there is a problem that the heat dissipation of the heat radiating material 51 is reduced. Further, the continuous fin 52 is processed by a milling machine or a lathe. However, this processing method has a problem that manufacturing cost is high and mass productivity is low.
[0010]
Further, the pin-shaped fins 52a have advantages such as a small pressure loss and a good heat transfer performance as compared with the continuous fins 52, but are almost impossible to be manufactured by a milling machine or a lathe. However, there is a problem that the manufacturing cost is extremely high.
[0011]
The present invention has been made in view of the above points, and has a high heat conductivity, good heat dissipation, little heat distortion, can be manufactured efficiently, and can reduce the manufacturing cost. It is an object of the present invention to provide a manufacturing method thereof.
[0012]
[Means for Solving the Problems]
In order to solve the above problems, the heat radiating material of the present invention is a sintered body obtained by mixing a metal powder and an inorganic compound powder having a lower coefficient of thermal expansion than the metal powder. A heat-receiving layer that absorbs generated heat, and a heat-dissipating material that includes a heat-dissipating layer that is integrated with the heat-receiving layer and that emits heat conducted from the heat-receiving layer to the outside; And a plurality of pyramidal or conical projections are provided integrally with the heat dissipation layer.
[0013]
Further, the heat receiving layer is characterized in that the concentration of the inorganic compound is higher than that of the heat radiation layer.
[0014]
Further, the sintered body is made of a metal powder selected from copper, aluminum, silver, gold or an alloy thereof, and copper oxide or tin oxide having a coefficient of thermal expansion at room temperature to 300 ° C. of 5 × 10 ⁻⁶ / K or less. , And a mixture of inorganic compound powders of any of zinc oxide, lead oxide, nickel oxide, and aluminum oxide.
[0015]
Further, the sintered body uses copper as the metal powder and cupric oxide as the inorganic compound powder, and the concentration of cuprous oxide in the heat receiving layer is 70% or less, and the concentration of cuprous oxide in the heat radiation layer is less than 70%. It is characterized in that the concentration is 0% or more.
[0016]
Further, the invention is characterized in that the surface and the inside of the heat receiving layer are coated and impregnated with a low melting point metal having a melting point lower than a sintering temperature.
[0017]
Further, a curved surface is formed at a tip and a root of the projection means.
[0018]
In addition, the method for manufacturing a heat radiating material of the present invention is a method for manufacturing a heat radiating material that is joined to a heating element and radiates heat generated from the heating element, wherein the metal powder has a lower coefficient of thermal expansion than the metal powder. The mixed powder with the inorganic compound powder having the following formula is filled into a mold provided with a plurality of inverted pyramids or inverted cone-shaped concave parts independently and sintered, and the upper surface of the sintered body is subjected to the sintering temperature. The method is characterized in that a low melting point metal powder having a lower melting point is placed and heated while being pressed, and after this heating, a heat radiation material solidified by cooling is taken out.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0020]
(Embodiment)
FIG. 1 is a cross-sectional view showing a configuration of a heat dissipating material according to an embodiment of the present invention, and FIG. 2 is a plan view thereof.
[0021]
The heat dissipating material 1 shown in FIGS. 1 and 2 is manufactured by dispersing a large number of triangular pyramid pin-shaped fins 4 on the upper surface of the heat dissipating layer 3 of the main body composed of the heat receiving layer 2 and the heat dissipating layer 3 each having a rectangular thin plate shape. It was done. The back surface of the surface on which the pin-shaped fins 4 are provided, that is, the surface of the heat receiving layer 2 joined to the semiconductor device or the insulating plate of the semiconductor device is a smooth surface. As shown in the enlarged cross-sectional view of FIG. 3, a radius 12 is provided at the root 11 and the tip 13 of the pin-shaped fin 4, and the tip 13 has a slight smooth surface. Further, the heat radiation layer 3 and the pin-like fins 4 are made of a low-concentration composite material 49 of an inorganic material, which will be described in a later-described manufacturing method, and the heat-receiving layer 2 is made of a high-concentration composite material of an inorganic material. Is coated and impregnated with a low melting point metal 47.
[0022]
The heat radiating material 1 includes a metal and inorganic compound particles having a smaller coefficient of thermal expansion than the metal, and the inorganic compound particles are dispersed in the metal. The inorganic compound particles dispersed in the metal have a diameter of 200 μm or less, preferably 60 μm or less. This is because the heat dissipating material having low thermal expansion can be obtained only by dispersing the inorganic compound particles in the metal.
[0023]
Here, for example, when the metal is Cu, the heat radiating material 1 is made of a Cu alloy containing 0 to 70% by volume of Cu ₂ O (cuprous oxide), which is one of inorganic compounds, and has a thermal expansion from room temperature to 300 ° C. The coefficient is 7 to 18 × 10 ⁻⁶ / K and the thermal conductivity is 80 to 390 W / m · K. When the amount of Cu ₂ O is 0% by volume or less, the coefficient of thermal expansion becomes 18 × 10 ⁻⁶ / K or more, and when the amount of Cu ₂ O is 70% by volume or more, the thermal conductivity becomes 80 W / m · K or less. However, on average, it becomes possible to obtain a low-thermal-expansion radiator 1 having a thermal conductivity of 230 W / m · K.
[0024]
Next, a method for manufacturing the heat dissipating material 1 will be described with reference to FIGS.
[0025]
As raw material powder of the heat dissipating material 1, an electrolytic Cu powder having an average particle diameter of 10 μm and a CuO powder having a particle diameter of 50 μm or less were used, and the electrolytic Cu powder and the CuO powder were mixed at the ratios shown in Measurement Examples 1 to 10 in Table 1 below. Thereafter, the powder binder 31 (see FIG. 4) is further mixed and mixed in an amount of 0 to 5% by weight and mixed in a dry ball mill containing steel balls for 10 hours. The mixed powder 29 thus obtained was used.
[0026]
Therefore, in this embodiment, in the heat radiating material 1, the inorganic material low concentration composite material 49 of the heat radiation layer 3 provided with the pin-shaped fins 4 becomes the cuprous oxide low concentration copper composite material, and the inorganic material of the heat receiving layer 2 The high-concentration composite material 50 is a cuprous oxide high-concentration copper composite material, and the surface and the inside of the heat receiving layer 2 are covered and impregnated with a low-melting metal 47.
[0027]
As shown in FIG. 4, in the heat radiating material manufacturing apparatus, the mold 16 is inserted into the powder filling portion 44 formed by the die 27 and the lower punch 15, and the mold 16 is coated with the release agent 30. A mixed powder 29 composed of a material (copper oxide) low concentration mixed powder 45 and an inorganic material (copper oxide) high concentration mixed powder 46 is filled. After this filling, the upper surface of the powder filling is scraped off with a skeper to make the powder filling amount for producing the compact 41 (see FIG. 5) constant. Then, the upper punch 26 is pressed by the press push rod 25 in the direction indicated by the arrow 24 to crush it to a predetermined thickness.
[0028]
Next, as shown in FIG. 5, the press push rod 25 is raised, the die support 28 shown in FIG. 4 is removed, and the guide 35 is set on the die 27 surface. Next, the press push rod 25 is lowered in the direction shown by the arrow 33, and the die 27 is pushed down in the direction shown by the arrow 34 to a position where the lower part of the mold 16 can be seen. Next, the press push rod 25 is raised, and the guide 35 is removed. Next, the upper punch 26 is removed from the compact 41, and then the compact 41 is removed from the mold 16. The sintering temperature in this step is varied between 850 and 1000 ° C. according to the CuO content, and the sintering temperature is maintained for 3 hours. Thereafter, the sintered body is sufficiently cooled. When the Cu ₂ O concentration of the heat radiating material 1 is low in the heat radiating layer 3 and high in the heat receiving layer 2, first, a fixed amount of electrolytic Cu powder having a small particle size is filled into the mold 16, and then the CuO high concentration The powder mixture is filled up to the powder filling portion 44, and thereafter, the powder is shaved and vibrated to increase the CuO concentration of the mixed powder 29 on the heat receiving layer 2 side (upper punch side) to form a powder.
[0029]
When the low-melting point metal 47 is coated and impregnated on the surface and inside of the sintered body 42, after sintering the green compact 41, as shown in FIG. The sintered body 42 is set inside. Next, a certain amount of the powder of the low-melting metal 47 is filled in the upper surface of the sintered body 42, and while being heated, the upper punch 26 is pressed in a direction indicated by an arrow 24 to apply the low-melting metal 47 to the surface of the sintered body 42. Cover and impregnate inside.
[0030]
Next, as shown in FIG. 7, the press push rod 25 is raised, the guide 35 is set on the surface of the die 27, and the press push rod 25 is lowered in the direction shown by the arrow 33 while heating as shown by the arrow 43. Then, the die 27 is pushed down in the direction indicated by the arrow 34 to a position where the lower part of the mold 16 can be seen. Thereby, the low melting point metal layer 36 is formed on the inorganic material high concentration composite material 50.
[0031]
[Table 1]

Here, in Table 1 above, the thermal expansion coefficient of the copper composite material measured using a TMA (Thermal Mechanical Analysis) device in the temperature range of room temperature to 300 ° C. of the simple composite material and the thermal conductivity obtained by the laser flash method are shown. Reference data is shown. Further, in the heat radiating material 1 of the present embodiment, the boundary is not seen because the concentration of Cu ₂ O (inorganic material) continuously changes, but the amount of Cu ₂ O (inorganic material) of the heat radiating material 1 is reduced. The boundary between the inorganic material low-concentration composite material 49 in a small portion and the inorganic material high-concentration composite material 50 in a large portion is schematically indicated by a broken line.
[0032]
When the heat dissipating material 1 thus manufactured as shown in FIG. 8 is attached to the insulating plate 21 of the semiconductor device as an air-cooled cooling material as shown in FIG. 9, a large number of pin-shaped fins 4 are provided on the heat dissipating layer 3. As a result, the heat radiation heat transfer area increases as compared with the smooth surface. Further, as shown in FIG. 8, the flow 22 of the cold part fluid 40 is agitated by the pin-shaped fins 4, so that the heat transfer performance (compared to the conventional heat dissipating material 51 provided with the continuous fins 52 shown in FIG. 17). Heat dissipation) increases.
[0033]
In addition, as shown in FIG. 10, in the heat radiating material 1, a heat radiating material 1a in which the fin pitch 8 of the pin-shaped fins 4 is small, or as shown in FIG. The heat radiating members 1b alternately arranged in a shape can also be easily manufactured by the above manufacturing method, and can be manufactured according to the type of the cooling fluid 40 and the cooling method. Note that the pin-shaped fin apex angle 5 shown in FIG. 11 is an angle at the intersection of the trend lines on both side surfaces of the fin, and the fin apex angle 5 normally considered as a cylindrical fin is almost 0 degrees.
[0034]
As pointed out by the conventional problems, the pin-shaped fins 4 are difficult to machine by a milling machine or a lathe, and are manufactured by press or precision casting. At this time, the manufacturing cost of the pin-shaped fins is greatly increased. Therefore, in order to reduce the manufacturing cost, it is desirable to form the pin-shaped fins 4 by powder molding and sintering as in the present embodiment. As compared with the continuous fins 52, the pin-shaped fins 4 have a larger reduction rate in the cross section of the fins from the root to the tip, and the restraining force of the fins 16 becomes smaller. Release from the mold 16 later is easy.
[0035]
However, the pin-shaped fins 4 are considered to have a smaller fin cross-sectional reduction rate from the root 11 to the tip 13 than the continuous fins 52, so that the fin strength is conversely reduced. As a result, it is considered that the continuous fins 52 peel off from the root 11 at the time of release from the mold 16 after powder molding, whereas the pin-shaped fins 4 are liable to be chipped. Therefore, the radius 12 is provided at the fin tip 13 to prevent the fin tip from falling off. Further, a radius 12 is provided at the fin base 11 to prevent fin peeling during powder molding and release. Further, the mold release agent 30 is applied to the mold 16 before filling the mixed powder 29 to reduce the degree of adhesion between the mold 16 and the compact 41, and the mold for the fins when the compact 41 is released from the mold 16. The restraining force of the mold 16 was reduced. That is, as shown in a comparison diagram of the pull-out force (MPa) according to the coating process before filling the mixed powder 29 in FIG. 12, the adhesive force of the powder body 41 to the mold 19 is higher when the release agent 30 is not applied. In comparison, in the case of the continuous fin 52, it was reduced to about 30%.
[0036]
As shown in FIG. 13, as shown in FIG. 13, the connecting rod 17 is integrated with the holed die 16 that is fitted to the die 27 attached to the lower punch 15, so that a die 16 set is formed. It is possible to shorten the time or improve the reliability. In such a mold 16, the pin-shaped fins 4 shown in FIG. 1 having a low fin height 6 and a large fin apex angle 5 (see FIG. 11) can be easily obtained. FIG. 14 shows a conventional mold 18 for comparison. The conventional die 18 has a die 27 attached to a lower punch 19 having holes.
[0037]
However, when the fin height 6 is further increased and the fin apex angle 5 is reduced to a sharp pin-shaped fin 4, when the compact 41 is taken out from the mold 16 with holes, the fin 4 is removed as in the case of the continuous fin 52. The fin 4 and the fin bottom wall 39 are separated by the holed mold 16 or the fin 4 is damaged by the holed mold 16, making it difficult to take out the sharp pin-shaped fin 4. Therefore, by adding a powder binder to the mixed powder 29 and improving the strength of the pin-shaped fins 4, the fin apex angle 5 is 0 to 45 degrees, the fin height 6 and the bottom thickness 7 (see FIG. 1). Can be obtained, and a sharp pin-shaped fin 4 having a high heat transfer performance having a ratio of 1 to 6 can be obtained.
[0038]
The concentration of the powder binder is 0.5 to 4%, and the fin strength of the pin-shaped fins 4 is increased, and sharp pin-shaped fins can be formed. The voids of the body 42 increase, and defects such as a decrease in fiber density and acceleration of corrosion occur. However, in the present embodiment, the low melting point metal 47 is impregnated and coated on the voids after the powder binder is lost during sintering on the surface and inside of the heat radiating material 1, so that the corrosion prevention from the fluid 40 and the thermal conductivity are prevented. Can be prevented from decreasing.
[0039]
Further, the flow of the fluid 40 flows more smoothly than the continuous fins 52. Further, since the radius 12 is provided at the fin tip 13 and the root 11, an increase in thermal resistance or corrosion of the fluid side due to stagnation of the fluid 40 can be avoided.
[0040]
Further, as another embodiment described above, the molds 16 having different heights are alternately arranged in parallel in the width direction, and as shown in FIG. It is also possible to further reduce the pressure loss of the fluid 40, change the flow of the fluid 40 more complicatedly, enhance the stirring effect, and further improve the heat dissipation performance by using the heat dissipating material 1c made of. Further, as shown in FIG. 16, a heat dissipating material 1d having a mounting surface 37 for attaching a cooler around the pin-shaped fins 4 may be manufactured by the above manufacturing method. However, the mounting surface 37 is made smooth and a mounting hole 38 is provided.
[0041]
For the above-described

heat radiating materials

1, 1a, 1b, 1c, 1d, Au, Ag, or Al having high electrical conductivity can be used as a metal in addition to Cu. Inorganic compounds such as tin oxide, zinc oxide, lead oxide, nickel oxide, and aluminum oxide (Al ₂ O ₃ ) having a thermal expansion coefficient of 5 × 10 ⁻⁶ / K or less in a temperature range from room temperature to 300 ° C. can also be used. It is.
[0042]
According to the heat dissipating material of the embodiment described above, the heat receiving layer 2 is formed of a low thermal expansion metal composite material composed of a metal and an inorganic material, and the heat dissipating layer 3 is formed with the pin-shaped fins 4 by the mold 16. The effects described in 1) to 6) can be obtained.
[0043]
{Circle around (1)} Since the heat receiving layer 2 has a low coefficient of thermal expansion and the heat radiating layer 3 has high heat transfer efficiency due to the pin-shaped fins 4, the heat radiating material 1 having high thermal conductivity can be provided.
[0044]
(2) By providing the pin fins 4 in a staggered manner on the heat radiation side 3 of the heat radiation material 1, the flow of the fluid 40 is improved, and the heat radiation performance of the heat radiation material 1 can be improved.
[0045]
{Circle over (3)} The low-melting point metal (tin, lead, bismuth) 47 is coated and impregnated on the surface and inside of the heat receiving layer 2 to improve the density of the heat radiating material 1 and improve the heat conductivity and corrosion resistance. Can be improved.
[0046]
{Circle around (4)} Since the fins are generated during the powder molding, the fin molding machining after sintering can be omitted, and the production cost can be greatly reduced.
[0047]
{Circle around (5)} By forming the heat receiving layer 2 with a low thermal expansion coefficient and the heat radiation layer 3 as a high heat conductive pin-like fin 4, the warpage of the heat radiation material 1 after bonding with the semiconductor insulating material 20 using solder or the like is reduced. Can be achieved. The reason is that the heat receiving layer 2 which is the bonding surface of the insulating plate 21 has a low coefficient of thermal expansion and the heat radiation layer 3 on the opposite side has a high coefficient of thermal expansion, so that heat is directly transmitted to the insulating plate 21 and the bonding surface. The heat conduction speed of the heat receiving layer 2 on the bonding surface is low. In addition, heat transmitted from the heat receiving layer 2 is quickly conducted to the heat radiation layer 3. For this reason, the temperature difference between the joint surface side and the heat dissipation side of the heat dissipation material is reduced. In addition, since the joint surface side has a lower coefficient of thermal expansion than the heat radiating side, the difference in the amount of thermal expansion between both sides is smaller. As a result, warpage of the heat radiating material is reduced.
[0048]
{Circle around (6)} When forming the pin fins, the heat radiating material 1 having various pin fin shapes can be easily generated by the various molds 16 having holes.
[0049]
【The invention's effect】
As described above, according to the present invention, it is a sintered body in which a metal powder and an inorganic compound powder having a lower coefficient of thermal expansion than the metal powder are mixed, and the sintered body is generated from a heating element. In a heat dissipating material comprising a heat receiving layer that absorbs heat and a heat dissipating layer that is integrated with the heat receiving layer and emits heat conducted from the heat receiving layer to the outside, a pyramid or cone type heat sink is provided on the surface of the heat dissipating layer. Are provided integrally with the heat radiation layer. In addition, since the concentration of the inorganic compound in the heat-receiving layer is higher than that of the heat-radiating layer, the heat-receiving layer, which is the bonding surface of the heating element, has a low coefficient of thermal expansion, and the heat-radiating layer on the opposite side has a high coefficient of thermal expansion. Since the difference in the amount of thermal expansion can be reduced, the warpage of the heat radiating material can be reduced. Further, the heat radiation effect is improved by the projection means having a high thermal conductivity. Further, since the projection means is formed simultaneously with the formation of the heat radiation layer, it can be manufactured efficiently, and the manufacturing cost can be reduced.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view illustrating a configuration of a heat radiating material according to an embodiment of the present invention.
FIG. 2 is a plan view showing a configuration of a heat radiating material according to the embodiment.
FIG. 3 is an enlarged view of a pin-like fin portion of the heat radiating material according to the embodiment.
FIG. 4 is a first diagram for explaining a heat radiating material manufacturing method using the heat radiating material manufacturing apparatus according to the embodiment.
FIG. 5 is a second diagram for explaining a heat radiating material manufacturing method by the heat radiating material manufacturing apparatus according to the embodiment.
FIG. 6 is a third diagram illustrating a method of manufacturing a heat radiating material by the heat radiating material manufacturing apparatus according to the embodiment.
FIG. 7 is a fourth diagram illustrating a method of manufacturing a heat radiating material by the heat radiating material manufacturing apparatus according to the embodiment.
FIG. 8 is a perspective view of a heat radiating material according to the embodiment.
FIG. 9 is a cross-sectional view when the insulating plate of the semiconductor device is joined to the heat radiating material according to the embodiment.
FIG. 10 is a cross-sectional view showing a heat radiating material according to another embodiment and showing a structure in which the pitch of pin-shaped fins is narrowed.
FIG. 11 is a cross-sectional view showing a heat dissipating material according to another embodiment, and showing a structure in which two different tip end shapes of pin-shaped fins are used.
FIG. 12 is a diagram showing a comparison of a drawing force according to a coating process before filling a mixed powder in the method of manufacturing a heat dissipation material according to the embodiment.
FIG. 13 is a cross-sectional view showing a configuration of a mold for producing the heat dissipation material according to the embodiment.
FIG. 14 is a cross-sectional view showing a configuration of a mold for producing a conventional heat dissipation material.
FIG. 15 is a cross-sectional view showing a heat dissipating material according to another embodiment, showing a structure in which pin-shaped fins have different fin heights.
FIG. 16 is a cross-sectional view showing a heat dissipating material according to another embodiment, showing a structure in which a mounting surface for a cooler is provided around pin-shaped fins.
FIG. 17 is a perspective view showing a configuration of a heat dissipating material provided with a conventional continuous fin.
FIG. 18 is a perspective view showing a configuration of a heat dissipating member provided with a conventional pin-shaped fin.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Heat radiating material 2 of the present invention 2 Heat receiving layer 3 Heat radiating layer 4 Pin fin 5 Fin apex angle 6 Fin height 7 Fin bottom thickness 8 Fin pitch 9 Work width 10 Work length 11 Fin bottom 12 Round 13 Fin tip 14 Mold 15 Lower punch 16 Hole plate (Mold)
17 Connect Grotto 18 Conventional Die 19 Lower Punch with Hole 20 Heat Flow 21 Semiconductor (Insulating Plate)
22 Fluid flow direction 23 Fluid flow 24 Press direction 25 Press push rod 26 Upper punch 27 Die 28 Die support 29 Mixed powder 30 Release agent 32 Press base 33 Extrusion direction 34 Die advancing direction 35 Guide 36 Low melting point metal layer 37 Cooling Container mounting surface 38 Mounting hole 39 Fin bottom portion 40 Cooling fluid 41 Powder compact 42 Sintered body 43 Heater heating direction 44 Powder filling portion 45 Inorganic material (copper oxide) low concentration mixed powder 46 Inorganic material (copper oxide) high concentration mixing Powder 47 Low melting point metal 48 Inorganic material (copper oxide)
49 Inorganic low-concentration composite material (cuprous oxide low-concentration copper composite material)
50 High-concentration composite material of inorganic material (high-concentration copper-copper composite material)
51 Conventional radiator 52 Continuous fin

Claims

A sintered body obtained by mixing a metal powder and an inorganic compound powder having a lower coefficient of thermal expansion than the metal powder, wherein the sintered body has a heat receiving layer that absorbs heat generated from the heating element, and a heat receiving layer. A heat dissipating material comprising: a heat dissipating layer integrated to release heat conducted from the heat receiving layer to the outside;
A heat dissipating material, wherein a plurality of pyramidal or conical projections are provided integrally with the heat dissipating layer on the surface of the heat dissipating layer.

The heat dissipation material according to claim 1, wherein the heat receiving layer has a higher concentration of the inorganic compound than the heat dissipation layer.

The sintered body includes a metal powder selected from copper, aluminum, silver, gold, or an alloy thereof, and copper oxide, tin oxide, or oxide having a thermal expansion coefficient of 5 × 10 ⁻⁶ / K or less at room temperature to 300 ° C. The heat radiating material according to claim 1, wherein a mixture of inorganic compound powders of any of zinc, lead oxide, nickel oxide, and aluminum oxide is sintered.

The sintered body uses copper as the metal powder and copper oxide as the inorganic compound powder, and the concentration of cuprous oxide in the heat receiving layer is 70% or less, and the concentration of cuprous oxide in the heat radiation layer is 0%. The heat radiating material according to claim 1, wherein:

The heat radiating material according to claim 1, wherein a low melting point metal having a melting point lower than a sintering temperature is coated and impregnated on the surface and inside of the heat receiving layer.

The heat radiating material according to claim 1, wherein a curved surface is formed at a tip and a root of the projection means.

In a method of manufacturing a heat radiating material that is joined to a heating element and radiates heat generated from the heating element,
A mixed powder of a metal powder and an inorganic compound powder having a lower coefficient of thermal expansion than the metal powder is filled in a mold having a plurality of inverted pyramids or inverted cone-shaped recesses independently provided, and sintered. A method for manufacturing a heat dissipating material, comprising: placing a low melting point metal powder having a melting point lower than the sintering temperature on the upper surface of the sintered body; .