JP3552587B2 - Composite materials and semiconductor devices - Google Patents

Description

【００３２】
一方、ミクロ組織は図１（２００倍）より明らかなように、Ｃｕ_２Ｏ は混合工程において凝集，焼結工程において肥大成長するが、粒径は５０μｍ以下であり、Ｃｕ相とＣｕ_２Ｏ 相が均一に分散した緻密な組織となっている。なお、写真中の白い部分がＣｕ相，黒い部分がＣｕ_２Ｏ 相である。Ｃｕ_２Ｏ 粒子のほとんどが１０μｍ以下の粒径であり、それ以上のものは複数個のＣｕ_２Ｏ 粒子が連なり、１００μｍ平方当り１０個以下の１５体積％である。硬さ測定の結果、Ｃｕ相はＨｖ７５〜８０，Ｃｕ_２Ｏ がＨｖ２１０〜２３０の硬さであった。また、機械加工性を旋盤及びドリル加工で評価した結果、加工性は非常に良好であり、形状付与が容易であることがわかった。
【００３３】
次いで、得られた焼結体を室温で３ｍｍの厚さまでプレスし、組織観察した。鍛造材は、側面に多少の耳割れが観察されたが、それ以外では割れが観察されず健全であり、本発明の銅複合材料は、塑性加工性に優れることが判明した。
【００３４】
図２は、鍛造材の鍛伸方向に平行な面のミクロ組織（２００倍）を示す。 Ｃｕ_２Ｏ 相は、変形して鍛伸方向に配向する傾向が認められるが、Ｃｕ相、 Ｃｕ_２Ｏ 相及びその境界にはクラック等の欠陥は認められない。Ｃｕ_２Ｏ 粒子は９５％が２０μｍ以下の粒径である。それ以上の粒径のものは複数個連らなったものである。
【００３５】
（実施例２）
粉末の混合をＶミキサーで行った以外は、実施例１と同一の条件でＮｏ．３ （Ｃｕ−１５体積％Ｃｕ_２Ｏ ）と同一組成の焼結体を作成し、実施例１と同様に組織観察，熱膨張係数及び熱伝導率の測定に供した。
【００３６】
図３にＣｕ−１５体積％Ｃｕ_２Ｏ 焼結体のミクロ組織（２００倍）を示す。写真から明らかなように、サイズが大きく異なるＣｕ_２Ｏ が混在した組織となっている。大きなサイズのＣｕ_２Ｏ 粒子は、Ｖミキサーによる混合中にＣｕ_２Ｏ 粒子同士が凝集して生成したものである。熱膨張係数及び熱伝導率の値は、Ｃｕ及びＣｕ_２Ｏ がそれぞれ均一に分散した同一組成の焼結体と明らかな差が認められなかったが、測定場所によるばらつきが若干大きくなる傾向が認められた。１つ大きな塊があるが、５０μｍ以下がほとんどである。分散が不足したものと思われる。他の細かい粒子は１０μｍ以下の粒径である。
【００３７】
（実施例３）
原料粉として、７４μｍ以下の電解Ｃｕ粉末と粒径１〜２μｍのＣｕ_２Ｏ 粉末を用い、Ｃｕ−１５体積％Ｃｕ_２Ｏ の組成比で３００ｇ調合した後、直径８ｍｍの鋼球を入れた直径１２０ｍｍの遊星ボールミル容器中で２５時間メカニカルアロイング（ＭＡ）した。その後、混合粉末を直径８０ｍｍの金型に注入し、１０００ｋｇ／ｃｍ^２ の圧力で冷間プレスして予備成形体を得た。その後、予備成形体をアルゴンガス雰囲気中で８００℃×２時間の焼結を行い、実施例１と同様に組織観察，熱膨張係数及び熱伝導率の測定，酸化物Ｘ線回折に供した。
【００３８】
ミクロ組織は実施例１あるいは２に比べて、Ｃｕ_２Ｏ 粒子が微細であり、粒径１０μｍ以下のＣｕ_２Ｏ が均一分散していた。組織の微細化は、強度の向上や冷間圧延性の改善に好適である。
【００３９】
（実施例４）
原料粉として、７４μｍ以下の電解Ｃｕ粉末と粒径１〜２μｍのＣｕＯ粉末を用いた。Ｃｕ粉末とＣｕＯ粉末を表２に示す比率で１４００ｇ調合した後、スチールボールを入れた乾式のポットミル中で１０時間以上混合した。混合粉末を直径１５０ｍｍの金型に注入し、ＣｕＯ含有量に応じて４００〜１０００ｋｇ／ｃｍ^２ の圧力で冷間プレスして予備成形体を得た。予備成形体をアルゴンガス雰囲気中で焼結させた後、酸化物Ｘ線回折，組織観察，熱膨張係数及び熱伝導率の測定に供した。なお、焼結温度はＣｕＯ含有量に応じて９００℃〜１０００℃の間で変化させ、各温度で３時間保持した。熱膨張係数は室温から３００℃の温度範囲でＴＭＡ（Ｔｈｅｒｍａｌ Ｍｅｃｈａｎｉｃａｌ Ａｎａｌｙｓｉｓ）装置を用いて行い、熱伝導率はレーザーフラッシュ法により測定した。その結果を表２に併記した。
【００４０】
【表２】

【００４１】
焼結体について、Ｘ線回折により酸化物の同定を行った結果、検出された銅酸化物の回折ピークはＣｕ_２Ｏ のみであり、焼結中にＣｕＯからＣｕ_２Ｏ への変態が完全になされたことを確認した。図４に得られた試料Ｎｏ．７のミクロ組織 （２００倍）を示すが、実施例１の同一組成のものと同様の組織を呈しており、Ｃｕ_２Ｏ 相はＣｕとＣｕＯの酸化反応により生成したＣｕ_２Ｏ とＣｕＯが分解して生成したＣｕ_２Ｏ からなっている。Ｃｕ_２Ｏ 粒子は５％複数個の粒子が連なったものがあり、他は２０μｍ以下の粒子からなる。
【００４２】
次いで、得られた焼結体を９００℃で２ｍｍの厚さに熱間圧延及び酸洗後、３０μｍの厚さまで冷間圧延して塑性加工性を検討した。Ｃｕ相中にそれよりも硬さの高いＣｕ_２Ｏ 相が分散しているために、純Ｃｕに比べて変形抵抗が大きくなり、圧延性が劣る傾向が認められた。組織観察の結果、Ｃｕ相，Ｃｕ_２Ｏ 相及びその境界にはクラック等の欠陥は認められず、本発明の銅複合材料は、塑性加工性により薄板化が可能であることが判明した。
【００４３】
（実施例５）
実施例１〜４に記載の本発明の銅複合材料を放熱板として、半導体素子が樹脂封止される半導体装置に適用した実施例を述べる。
【００４４】
一例として、ＩＧＢＴ（Ｉｎｓｕｌａｔｅｄ Ｇａｔｅ Ｂｉｐｏｌａｒ Ｔｒａｎｓｉｓｔｏｒ）などのパワー半導体素子を複数個搭載し、樹脂封止した半導体装置への適用例を示す。図５は本発明による半導体装置の断面構成図を示す。パワー半導体素子１１，１２がはんだ接着層１４を介してＣｕ製のリードフレームの電極板部１３の一方の主面上に固着され搭載される。電極板部１３の他方の主面すなわち上記部品が搭載された主面の裏面は、絶縁層２を介して実施例１〜４に記載の本発明の係る全表面にＮｉめっきされたＣｕ−Ｃｕ_２Ｏ 複合材からなる放熱板６に接着される。次いで、パワー半導体素子１１，１２は、アルミニウムのワイヤボンデイング部１５によりリード電極部４，５と電気的に接続され、リード電極部４，５の一部が端子として外部に導出され、主回路を構成する。さらに主回路はエポキシ系樹脂からなる樹脂層１によって被覆され構造体をなし、リード電極部４，５の端子部、並びに放熱板６の裏面を露出する形で構造体全体がエポキシ系樹脂からなる樹脂層３により一体モールド封止される。
【００４５】
本実施例では、樹脂層３の材料としてエポキシ系樹脂材料を用いたが、例えばポリフェニレン系樹脂など熱可塑性樹脂であってもよい。また、樹脂層２には良好な熱伝導性を得るために、アルミナ，マグネシア，シリカなどの無機材料フィラーが含まれることが望ましい。
【００４６】
放熱板は、モールド樹脂の熱膨張係数を考慮して、室温から３００℃における熱膨張係数が１４×１０^−６〜１７×１０^−６／℃の範囲となるように、Ｃｕ−５〜２０体積％Ｃｕ_２Ｏ の範囲内で組成を変えて作製し、機械加工及びＮｉめっき処理を施して供した。
【００４７】
上記のようにして実装された半導体装置について、反りやモールド樹脂あるいは素子のクラックの有無を観察した。その結果、モールド樹脂と放熱板との熱膨張差が０．５×１０^−６／℃以下となるように、放熱板のＣｕ_２Ｏ量を調節することで、問題がなく実装できることがわかった。
【００４８】
本実施例ではパワー半導体素子１１として、ＩＧＢＴ素子を用いた半導体装置の例について示したが、例えばＭＯＳ系トランジスタ，ダイオードなど他の種類の半導体素子であってもよい。さらに、これら複数素子の組み合わせによる特定の回路、例えばインバータ用パワーモジュールなどであっても良い。また回路中に抵抗やコンデンサなどの受動素子が含まれていても良い。これら、電気素子または電子素子はプリント基板のような回路基板上に搭載されていても良い。
【００４９】
本実施例では、放熱板がモールド樹脂の外部に露出したタイプについて述べたが、放熱板内蔵型のパッケージであっても良い。
【００５０】
【発明の効果】
本発明の複合材料は、低熱膨張で高熱伝導性を有するとともに高い塑性加工性を有することから製造工程が短縮され多量生産が可能となる顕著な効果を有する。
【００５１】
また、本発明の複合材料は、特に高熱伝導性を有するＣｕ相と低熱膨張性のＣｕ_２Ｏ 相からなる混合組織を有するために、両方の特性を兼ね備えている。また、本発明の複合材料は、Ｃｕ及びＣｕ_２Ｏ 両者の含有量を調整することにより、低熱膨張係数で高熱伝導率を得ることができる。本発明の用途として、半導体装置に搭載される放熱板として広い範囲にわたって適用が可能である。
【００５２】
また、本発明材料の特性から鑑みて、半導体装置分野以外に熱変形の抑制や熱放散が厳しく要求される精密機械，電子部品などへの適用が可能である。
【図面の簡単な説明】
【図１】本発明の実施例１に係る試料Ｎｏ．３（Ｃｕ−１５体積％Ｃｕ_２Ｏ ）焼結体のミクロ組織を示す光学顕微鏡写真。
【図２】本発明の実施例１に係るＣｕ−１５体積％Ｃｕ_２Ｏ の鍛造材の鍛伸方向に平行な面のミクロ組織を示す光学顕微鏡写真。
【図３】本発明の実施例２に係るＣｕ−１５体積％Ｃｕ_２Ｏ 焼結体のミクロ組織を示す光学顕微鏡写真。
【図４】本発明の実施例４に係る試料Ｎｏ．７（Ｃｕ−１５体積％Ｃｕ_２Ｏ ）焼結体のミクロ組織を示す光学顕微鏡写真。
【図５】本発明の実施例５に係るパワー半導体装置の断面構成図。
【符号の説明】
６…放熱板。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a copper composite material having low thermal expansion, high thermal conductivity and high electrical conductivity, and a resin-sealed semiconductor device using the same.
[0002]
[Prior art]
The resin-sealed package has a structure in which a lead frame and terminals of a semiconductor element are connected by a bonding wire, and this is sealed with a resin. 2. Description of the Related Art The degree of integration and the operation speed of semiconductor elements increase year by year, and accordingly, the amount of heat generated has also increased. Therefore, the performance of a heat sink mounted to efficiently dissipate generated heat is important. High heat conductive Cu or lightweight Al or the like is used as a heat radiating material for the heat radiating plate. However, a mismatch with a package forming material such as a semiconductor element, a lead frame, and a sealing resin having a large coefficient of thermal expansion is caused by heat. Since the resin or the element is cracked due to the accumulation of stress, a heat-radiating material that has good compatibility with the resin of the sealing material and has a large thermal conductivity, particularly in terms of the coefficient of thermal expansion, is desired.
[0003]
At present, an epoxy resin is mainly used as a semiconductor sealing resin, and a resin having a thermal expansion coefficient of 10 × 10 ^{−6 to} 20 × 10 ⁻⁶ / ° C. has been developed. The coefficient of thermal expansion of the resin is adjusted by adding a filler having low thermal expansion represented by fused silica. However, the use of a filler increases the cost by 13 × 10 in consideration of compatibility with other package constituent materials. Resins having a coefficient of thermal expansion of about ⁻⁶ to 18 × 10 ⁻⁶ / ° C. are frequently used.
[0004]
[Problems to be solved by the invention]
An object of the present invention is to provide a copper composite material having low thermal expansion, high thermal conductivity, and easy processability, and excellent in compatibility with a package sealing resin, and a semiconductor device using the same.
[0005]
[Means for Solving the Problems]
The present invention has a metal and inorganic compound particles having a smaller coefficient of thermal expansion than the metal, and the compound particles are formed into a complex-shaped mass in which the cross-sectional area ratio is 50% or less of the entire particles connected to each other. And a composite material characterized by being dispersed.
[0006]
The present invention has a metal and inorganic compound particles having a smaller coefficient of thermal expansion than the metal, wherein the compound particles are 10 or less in a lump of complicated shape connected to each other within 100 μm square, and the remaining compound particles Is a composite material characterized by being present alone and dispersed.
[0007]
The present invention provides a composite material comprising a metal and 5 to 20% by volume of inorganic compound particles having a smaller coefficient of thermal expansion than the metal, wherein the compound particles have a Vickers hardness of 300 or less. .
[0008]
The present invention has a metal and 5 to 20% by volume of inorganic compound particles having a smaller coefficient of thermal expansion than the metal, and has a coefficient of thermal expansion of 13 × 10 ^{−6 to} 17 × 10 ^{−6 at} 20 ° C. to 300 ° C. / C, a thermal conductivity of 270 to 375 W / m · K, and a conductivity of 60 to 85% IACS.
[0009]
The present invention has a metal and inorganic compound particles having a smaller coefficient of thermal expansion than the metal, wherein the compound particles are dispersed as a continuous mass of 10% or less, and the mass is stretched by plastic working. The composite material is characterized by extending in a different direction.
[0010]
The present invention provides a composite material comprising copper and copper oxide particles, wherein the copper oxide particles are dispersed as a complex-shaped mass in which 10% or less of the whole particles are connected to each other. is there.
[0011]
The present invention contains 5 to 20% by volume of cuprous oxide (Cu ₂ O), the balance being copper (Cu) and unavoidable impurities, and having a structure in which the Cu ₂ O phase and the Cu phase are dispersed, The coefficient of thermal expansion from room temperature to 300 ° C. is 13 × 10 ^{−6 to} 17 × 10 ⁻⁶ / ° C., the thermal conductivity is 270 to 375 W / m · K, and the conductivity is 60 to 85% IACS. Features.
[0012]
The present invention resides in a heat sink for a semiconductor device, comprising the composite material described above. Further, there is provided a heat sink for a semiconductor device having a Ni plating layer on a surface thereof.
[0013]
The present invention provides an electrode plate on which a semiconductor element is mounted, a lead electrode electrically connected to the semiconductor element, a radiator plate on which the semiconductor element, the electrode plate, and the lead electrode are mounted, and the electrode plate. And sealing the structure having an insulating layer between the lead electrode and the heat sink with resin, and opening a part of the lead electrode and at least a surface of the heat sink opposite to a bonding surface of the element. In the semiconductor device described above, the radiator plate is formed of the radiator plate described above.
[0014]
That is, the composite material according to the present invention uses Au, Cu, Al having high electric conductivity as a metal, and Cu is most excellent in that it has a high melting point and a high strength. In addition, the particles constituting the composite material are not soft compounds such as conventional SiC and Al ₂ O ₃ having extremely different hardnesses from the base metal, but are relatively soft particles which are stable after sintering and have a hardness of 20 to 20. The average coefficient of thermal expansion in the range of 150 ° C. is preferably 5.0 × 10 ⁻⁶ / ° C. or less, more preferably 3.5 × 10 ⁻⁶ / ° C. or less, and Vickers hardness of 300 or less. By using soft particles as described above, high plastic workability by hot and cold after sintering can be obtained, and especially since these rolling becomes possible, high productivity can be obtained and the same as pure copper Can be obtained. Copper oxide (Cu ₂ O), tin oxide, lead oxide, nickel oxide and the like can be considered as composite particles. However, copper oxide (Cu ₂ O), which has the smallest coefficient of thermal expansion and is soft, is particularly preferable.
Further, the composite material of the present invention is preferably strengthened by containing 5% by volume or less of fine ceramic particles having a Vickers hardness of 1000 or more and a hard average particle size of 3 μm or less, such as SiC, Al ₂ O ₃ , and SiO _2. preferable.
[0015]
The heat sink in the present invention can be formed into a final shape by plastic working by a mold press after sintering or subsequent working by rolling or the like.
[0016]
The method for producing a composite material according to the present invention includes a step of press-molding a mixed powder having copper oxide (Cu ₂ O) as an example of the composite compound particles and copper (Cu) powder as an example of the metal. The method is characterized by including a step of sintering at 800 ° C. to 1050 ° C. and a step of plastic working at least either cold or hot.
[0017]
Further, the method for producing a copper composite material according to the present invention comprises press-molding a mixed powder containing 2.7 to 10.8% by volume of copper dioxide (CuO) and the balance being copper (Cu) and unavoidable impurities. , A sintering step of reacting CuO with Cu and transforming it into Cu ₂ O together with solidification at 800 ° C. to 1050 ° C., a step of plastic working at least one of cold and hot, and subsequent annealing Preferably, a step is included.
[0018]
As the plastic working method according to the present invention, cold or hot rolling, forging, pressing, extrusion, or the like, or plate working or forming into a desired shape by using a mold is possible.
[0019]
The copper composite material according to the present invention has Cu having a thermal expansion coefficient of 17.6 × 10 ⁻⁶ / ° C. and a high thermal conductivity of 391 W / m · K, and a thermal conductivity of 12 W / m · K and 2.7. This is a composite material of Cu ₂ O having a low coefficient of thermal expansion of × 10 ⁻⁶ / ° C., and has a composition of Cu-5 to 20% by volume as a sintered body composition applied to a heat sink of a resin-sealed semiconductor package.
It is selected in the composition range of Cu ₂ O, has a coefficient of thermal expansion from room temperature to 300 ° C. of 13 × 10 ^{−6 to} 17 × 10 ⁻⁶ / ° C., and has a thermal conductivity of 270 to 375 W / m · K. Can be. When the content of Cu ₂ O is 5% or more, the thermal expansion coefficient required for the heat sink is obtained, and when it is 20% by volume or less, sufficient thermal conductivity and strength as a structure are obtained.
[0020]
In the present invention, the composite material is basically obtained by powder metallurgy. In the case of the copper composite material, Cu powder and Cu ₂ O powder or CuO powder are mixed at a predetermined ratio as a raw material powder, and are cold-pressed in a mold. After that, it is manufactured by sintering. Then, if necessary, at least one of cold and hot plastic working is performed.
[0021]
The mixing of the raw material powder is performed by a V mixer, a pot mill, mechanical alloying, or the like. However, since the particle size of the raw material powder affects the press moldability and the dispersibility of Cu ₂ O after sintering, the Cu powder is 100 μm. Hereinafter, the particle diameter of the Cu ₂ O and CuO powders is preferably 10 μm or less, particularly preferably 1 to 2 μm.
[0022]
Next, the mixed powder is cold-pressed using a mold at a pressure of 400 to 1000 kg / cm ² , and the pressure is desirably increased as the Cu ₂ O content increases.
[0023]
The preform of the mixed powder is sintered under normal pressure, HIP or hot pressing in an argon gas atmosphere, preferably at 800 ° C. to 1050 ° C. for about 3 hours, and increases the Cu ₂ O content. As the temperature increases. The sintering temperature varies depending on the base metal. Particularly, at 800 ° C. or lower, a sintered body having a high density cannot be obtained at Cu below 800 ° C., and at 1050 ° C. or higher, there is a risk of partial melting due to the eutectic reaction between Cu and Cu ₂ O. For this reason, it is not preferable, and 900 ° C. to 1000 ° C. is preferable.
[0024]
The copper composite material of the present invention has a low hardness of Cu and Cu ₂ O constituting it, and is rich in ductility, so that cold or hot working such as rolling and forging extrusion can be performed. Will be applied. By imparting processing, the material exhibits heat conduction anisotropy, but it is effective for applications requiring strength improvement and heat transfer in a certain direction.
[0025]
In the present invention, CuO is used as a raw material powder, and after mixing and press molding with Cu powder, Cu is internally oxidized in a sintering process, and finally a sintered structure having a structure in which Cu phase and Cu ₂ O phase are dispersed is obtained. Can be a body. That is, when CuO coexists with Cu, it utilizes the fact that it is more thermally stable to transform to Cu ₂ O according to the equation (1) at a high temperature.
[0026]
2Cu + CuO → Cu + Cu ₂ O (1)
It takes a predetermined time for the equation (1) to reach equilibrium. For example, when the sintering temperature is 900 ° C., about 3 hours is sufficient.
[0027]
The particle size of Cu ₂ O in the sintered body is preferably fine because it affects density, strength or plastic workability. However, the particle size is strongly affected by the method of mixing the powders, and the larger the mixing energy, the less the agglomeration between the powders, and a fine Cu ₂ O phase is obtained after sintering.
[0028]
In the present invention, the particle size of the Cu ₂ O phase after sintering is 50 to 200 μm in the V ₂ mixer having a small mixing energy, the particle size is 50 to 200 μm, and the balance is 50%.
μm or less, 50 μm or less for a pot mill containing steel balls, and 10 μm or less for mechanical alloying with the largest mixing energy. When the particle size is 200 μm or more, the porosity increases, and the plastic workability is impaired. When the amount is 50% by volume or more of the Cu ₂ O phase, variation in the heat conduction characteristics is increased, and the heat sink of the semiconductor device is increased. Is unsuitable for A preferred structure is a structure in which a Cu ₂ O phase of 50 μm or less is uniformly dispersed in the Cu phase. The Cu ₂ O phase is more preferably 10 μm or less.
[0029]
BEST MODE FOR CARRYING OUT THE INVENTION
(Example 1)
As the raw material powder, an electrolytic Cu powder having a particle size of 75 μm or less and a Cu ₂ O powder having a particle size of 1 to ₂ μm were used. After mixing 1400 g of Cu powder and Cu ₂ O powder at the ratio shown in Table 1, they were mixed in a dry pot mill containing steel balls for 10 hours or more. The mixed powder was poured into a mold having a diameter of 150 mm and cold-pressed at a pressure of 400 to 1000 kg / cm ² depending on the Cu ₂ O content to obtain a preform having a diameter of 150 mm and a height of 15 to 17 mm. Thereafter, the preformed body was sintered in an argon gas atmosphere and subjected to chemical analysis, structure observation, measurement of thermal expansion coefficient, thermal conductivity, conductivity, and Vickers hardness. The sintering temperature was varied between 900 ° C. and 1000 ° C. in accordance with the content of Cu ₂ O, and was maintained at each temperature for 3 hours. The coefficient of thermal expansion is TMA in the temperature range from room temperature to 300 ° C.
(Thermal Mechanical Analysis) apparatus, thermal conductivity was measured using a laser flash method, and conductivity was measured using a sigma tester. The results are shown in Table 1. In addition, the obtained sample No. FIG. 1 shows the microstructure of the three sintered compact.
[0030]
As a result of chemical analysis, the composition of the sintered body was consistent with the composition. As is clear from Table 1, the thermal expansion coefficient, the thermal conductivity, and the electrical conductivity are varied over a wide range by adjusting the composition ratio of Cu and Cu ₂ O, and are required for the heat sink. It was found that thermal characteristics could be controlled.
[0031]
[Table 1]

[0032]
On the other hand, microstructure as is clear from FIG. 1 (200 times), _Cu 2 O is agglomerated in the mixing step, although hypertrophic growth during the sintering process, the particle size is at 50μm or less, Cu phase and _Cu 2 O phase Are uniformly dispersed. The white part in the photograph is the Cu phase, and the black part is the Cu ₂ O phase. Most Cu ₂ O particles are particle size of less than 10 [mu] m, it is continuous with a plurality of _Cu 2 O particles, a 100 [mu] m 10 or fewer 15 vol% per square more. As a result of the hardness measurement, the Cu phase had a hardness of 75 to 80 Hv, and the Cu ₂ O had a hardness of 210 to 230 Hv. In addition, as a result of evaluating the machinability with a lathe and a drill, it was found that the machinability was very good and the shape was easily imparted.
[0033]
Next, the obtained sintered body was pressed at room temperature to a thickness of 3 mm, and the structure was observed. The forged material had some edge cracks observed on the side surface, but no cracks were observed in other areas, indicating that the copper composite material of the present invention was excellent in plastic workability.
[0034]
FIG. 2 shows the microstructure (200 times) of a plane parallel to the forging direction of the forged material. The Cu ₂ O phase has a tendency to be deformed and oriented in the forging direction, but no defects such as cracks are found in the Cu phase, the Cu ₂ O phase and boundaries thereof. 95% of the Cu ₂ O particles have a particle size of 20 μm or less. Those having a particle size larger than that are a plurality of continuous ones.
[0035]
(Example 2)
No. 5 was prepared under the same conditions as in Example 1 except that the mixing of the powder was performed with a V mixer. 3 (Cu-15% by volume Cu ₂ O), a sintered body having the same composition as that of Example 1 was prepared, and subjected to structure observation, measurement of thermal expansion coefficient, and measurement of thermal conductivity in the same manner as in Example 1.
[0036]
FIG. 3 shows the microstructure (200 times) of the Cu-15 volume% Cu ₂ O sintered body. As is clear from the photograph, the structure has a mixed structure of Cu ₂ O having greatly different sizes. The large-sized Cu ₂ O particles are formed by aggregation of Cu ₂ O particles during mixing by a V mixer. The values of the coefficient of thermal expansion and the coefficient of thermal conductivity were not clearly different from those of the same composition in which Cu and Cu ₂ O were uniformly dispersed, but there was a tendency that the variation depending on the measurement location was slightly increased. Was done. There is one large lump, but most of it is 50 μm or less. It seems that dispersion was insufficient. Other fine particles have a particle size of 10 μm or less.
[0037]
(Example 3)
As raw material powder, with a _Cu 2 O powder of the following electrolytic Cu powder and the particle diameter 1 to 2 [mu] m 74 .mu.m, after 300g formulated in a composition ratio of Cu-15 vol% _Cu 2 O, was charged with steel balls having a diameter of 8mm diameter Mechanical alloying (MA) was performed in a 120 mm planetary ball mill container for 25 hours. Thereafter, the mixed powder was poured into a mold having a diameter of 80 mm, and was cold-pressed at a pressure of 1000 kg / cm ² to obtain a preform. Thereafter, the preformed body was sintered at 800 ° C. for 2 hours in an argon gas atmosphere, and subjected to structure observation, measurement of thermal expansion coefficient and thermal conductivity, and oxide X-ray diffraction in the same manner as in Example 1.
[0038]
Microstructure as compared with Example 1 or 2, _Cu 2 O particles are fine, the particle size 10μm or less of _Cu 2 O was found to be uniformly dispersed. Refinement of the structure is suitable for improving strength and cold rolling properties.
[0039]
(Example 4)
As the raw material powder, an electrolytic Cu powder having a size of 74 μm or less and a CuO powder having a particle size of 1 to 2 μm were used. After mixing 1400 g of Cu powder and CuO powder at the ratio shown in Table 2, they were mixed for 10 hours or more in a dry pot mill containing steel balls. The mixed powder was poured into a mold having a diameter of 150 mm, and cold-pressed at a pressure of 400 to 1000 kg / cm ² depending on the CuO content to obtain a preform. After sintering the preform in an argon gas atmosphere, it was subjected to oxide X-ray diffraction, microstructure observation, and measurement of thermal expansion coefficient and thermal conductivity. The sintering temperature was varied between 900 ° C. and 1000 ° C. in accordance with the CuO content, and was maintained at each temperature for 3 hours. The coefficient of thermal expansion was measured in a temperature range from room temperature to 300 ° C. using a TMA (Thermal Mechanical Analysis) apparatus, and the thermal conductivity was measured by a laser flash method. The results are shown in Table 2.
[0040]
[Table 2]

[0041]
For sintered bodies, results of identification of the oxide by X-ray diffraction, diffraction peaks of the detected cuprates are only Cu ₂ O, transformation completely from CuO during sintering to Cu ₂ O I confirmed that it was done. The sample No. obtained in FIG. 7 shows a microstructure (200 times), but shows the same structure as that of Example 1 with the same composition. The Cu ₂ O phase is decomposed by Cu ₂ O and CuO generated by the oxidation reaction of Cu and CuO. Made of Cu ₂ O. Some of the Cu ₂ O particles include 5% of a plurality of continuous particles, and the other particles are particles of 20 μm or less.
[0042]
Next, the obtained sintered body was hot-rolled and pickled at 900 ° C. to a thickness of 2 mm, and then cold-rolled to a thickness of 30 μm to examine plastic workability. Since the Cu ₂ O phase having a higher hardness is dispersed in the Cu phase, the deformation resistance is larger than that of pure Cu, and the rollability tends to be inferior. As a result of the microstructure observation, no defects such as cracks were observed in the Cu phase, Cu ₂ O phase and boundaries thereof, and it was found that the copper composite material of the present invention can be made thin by plastic workability.
[0043]
(Example 5)
An example in which the copper composite material of the present invention described in Examples 1 to 4 is used as a heat sink and applied to a semiconductor device in which a semiconductor element is resin-sealed.
[0044]
As an example, an application example to a semiconductor device in which a plurality of power semiconductor elements such as an IGBT (Insulated Gate Bipolar Transistor) are mounted and resin-sealed will be described. FIG. 5 is a sectional view showing the configuration of a semiconductor device according to the present invention. Power semiconductor elements 11 and 12 are fixed and mounted on one main surface of electrode plate portion 13 of a lead frame made of Cu via solder adhesive layer 14. The other main surface of the electrode plate portion 13, that is, the back surface of the main surface on which the above components are mounted, is Cu-Cu Ni-plated on the entire surface according to the present invention described in Examples 1 to 4 via the insulating layer 2. It is bonded to a heat radiating plate 6 made of a ₂ O composite material. Next, the power semiconductor elements 11 and 12 are electrically connected to the lead electrode sections 4 and 5 by the aluminum wire bonding section 15, and a part of the lead electrode sections 4 and 5 is led out as terminals to form a main circuit. Constitute. Further, the main circuit is covered with a resin layer 1 made of an epoxy resin to form a structure, and the entire structure is made of an epoxy resin so as to expose the terminal portions of the lead electrode portions 4 and 5 and the back surface of the heat sink 6. The resin layer 3 is integrally molded and sealed.
[0045]
In this embodiment, an epoxy-based resin material is used as the material of the resin layer 3, but a thermoplastic resin such as a polyphenylene-based resin may be used. Further, it is desirable that the resin layer 2 contains an inorganic material filler such as alumina, magnesia, and silica in order to obtain good thermal conductivity.
[0046]
In consideration of the thermal expansion coefficient of the mold resin, the radiator plate has a Cu-5 to 20 volume ratio such that the thermal expansion coefficient from room temperature to 300 ° C. is in the range of 14 × 10 ^{−6 to} 17 × 10 ⁻⁶ / ° C. % Cu ₂ O was prepared with a different composition, machined and subjected to Ni plating.
[0047]
With respect to the semiconductor device mounted as described above, the presence or absence of warpage, mold resin, or cracks in elements was observed. As a result, it was found that mounting was possible without any problem by adjusting the amount of Cu ₂ O in the heat sink so that the difference in thermal expansion between the mold resin and the heat sink was 0.5 × 10 ⁻⁶ / ° C. or less. .
[0048]
In this embodiment, an example of a semiconductor device using an IGBT element as the power semiconductor element 11 has been described. However, another type of semiconductor element such as a MOS transistor or a diode may be used. Furthermore, a specific circuit formed by combining these plural elements, for example, a power module for an inverter may be used. Further, a passive element such as a resistor or a capacitor may be included in the circuit. These electric or electronic elements may be mounted on a circuit board such as a printed board.
[0049]
In the present embodiment, the type in which the heat sink is exposed to the outside of the mold resin has been described, but a package with a built-in heat sink may be used.
[0050]
【The invention's effect】
Since the composite material of the present invention has low thermal expansion, high thermal conductivity and high plastic workability, the composite material has a remarkable effect of shortening the manufacturing process and enabling mass production.
[0051]
In addition, the composite material of the present invention has both characteristics because it has a mixed structure composed of a Cu phase having high thermal conductivity and a Cu ₂ O phase having low thermal expansion. The composite material of the present invention can obtain a high thermal conductivity with a low coefficient of thermal expansion by adjusting the content of both Cu and Cu ₂ O. The present invention can be applied to a wide range as a heat sink mounted on a semiconductor device.
[0052]
In addition, in view of the characteristics of the material of the present invention, the present invention can be applied to precision machines, electronic components, and the like, in which suppression of thermal deformation and heat dissipation are strictly required, in addition to the semiconductor device field.
[Brief description of the drawings]
FIG. 1 shows a sample No. 1 according to Example 1 of the present invention. 3 is an optical microscope photograph showing a microstructure of a 3 (Cu-15 volume% Cu ₂ O) sintered body.
FIG. 2 is an optical microscope photograph showing a microstructure of a plane parallel to a forging direction of a forged material of Cu-15% by volume Cu ₂ O according to Example 1 of the present invention.
FIG. 3 is an optical micrograph showing a microstructure of a Cu-15% by volume Cu ₂ O sintered body according to Example 2 of the present invention.
FIG. 4 shows a sample No. 4 according to Example 4 of the present invention. 7 is an optical microscope photograph showing a microstructure of a 7 (Cu-15 volume% Cu ₂ O) sintered body.
FIG. 5 is a sectional configuration diagram of a power semiconductor device according to a fifth embodiment of the present invention.
[Explanation of symbols]
6 ... heat sink.

Claims (6)

A copper composite material having copper and copper oxide particles, comprising 5 to 20% by volume of the copper oxide particles, and having a coefficient of thermal expansion at 20 ° C to 300 ° C of 13 × 10 ^{−6 to} 17 × 10 ⁻⁶ / ° C. A copper composite material having a thermal conductivity of 270 to 375 W / mK and a conductivity of 60 to 85% IACS. 2. The copper composite material according to claim 1, wherein 10 or less of the copper oxide particles have a particle size of 10 μm or more in a 100 μm square. 3. 3. The copper composite material according to claim 1, wherein particles having a particle size of 10 μm or more in the copper oxide particles are 10% or less of the whole. 4. A heat sink for a semiconductor device, comprising the composite material according to claim 1. The heat sink for a semiconductor device according to claim 4, further comprising a Ni plating layer on a surface. An electrode plate on which a semiconductor element is mounted, a lead electrode electrically connected to the semiconductor element, a radiator plate on which the semiconductor element, the electrode plate and the lead electrode are mounted, the electrode plate and the lead electrode A semiconductor device having a structure having an insulating layer between the substrate and the heat radiating plate is resin-sealed, and a part of the lead electrode and a surface of the heat radiating plate opposite to at least a bonding surface of the element are opened. 6. The semiconductor device according to claim 1, wherein the heat radiating plate comprises the heat radiating plate according to claim 4.

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