JP4344934B2 - High thermal conductivity / low thermal expansion composite material, heat dissipation substrate and manufacturing method thereof - Google Patents
High thermal conductivity / low thermal expansion composite material, heat dissipation substrate and manufacturing method thereof Download PDFInfo
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- Ceramic Products (AREA)
- Manufacture Of Alloys Or Alloy Compounds (AREA)
- Cooling Or The Like Of Electrical Apparatus (AREA)
- Cooling Or The Like Of Semiconductors Or Solid State Devices (AREA)
Description
本発明は、高熱伝導・低熱膨張複合材及びそれからなる放熱基板、並びにそれらの製造方法に関し、特に多孔質黒鉛化押出成形体とアルミニウム又は銅との複合材からなり、高熱伝導率、低熱膨張率及び低固有抵抗を有するとともに熱履歴が実質的にないために電子機器用のヒートシンク等に好適な高熱伝導・低熱膨張複合材、及びかかる複合材からなるヒートシンク等の放熱基板、並びにそれらの製造方法に関する。 The present invention relates to a high thermal conductivity / low thermal expansion composite material, a heat dissipation substrate comprising the same, and a method for producing the same, and in particular, a composite material of a porous graphitized extruded product and aluminum or copper, and has a high thermal conductivity and a low thermal expansion coefficient. High thermal conductivity / low thermal expansion composite material having low specific resistance and substantially no thermal history, heat dissipation substrate such as heat sink made of such composite material, and method for manufacturing the same About.
電子部品の高集積化、大容量化、高出力化等に伴い発熱量が増加しつつあり、高熱伝導率で熱膨張率の小さい材料が要求されている。CPU、発光ダイオード等の半導体素子は大量の熱を発生するので、通常ヒートシンクが取り付けられている。半導体素子からヒートシンクに伝達された熱はファンや冷却媒体等により強制的に放散されている。ヒートシンクには通常熱伝導性に優れたアルミニウム、銅又はこれらの合金が使用されている。 The amount of heat generation is increasing as electronic parts become highly integrated, have a large capacity, and have a high output, and a material having a high thermal conductivity and a low coefficient of thermal expansion is required. Since semiconductor elements such as CPUs and light emitting diodes generate a large amount of heat, a heat sink is usually attached. The heat transmitted from the semiconductor element to the heat sink is forcibly dissipated by a fan, a cooling medium, or the like. As the heat sink, aluminum, copper, or an alloy thereof, which is usually excellent in thermal conductivity, is used.
また例えばCPUはヒートシンクより遥かに小型であるので、通常両者の間にヒートスプレッダーと呼ばれる高熱伝導体を介在させている。ヒートスプレッダーの材質としては、高熱伝導率を有するのみならず、シリコンからなるCPUと同程度の低熱膨張率を有するものが望まれている。これは、化合物半導体（GaAs，GaN等）からなる発光ダイオードの場合も同様である。このような目的で、熱膨張率の小さなセラミックスである炭化珪素、アルミナ、窒化珪素又は窒化アルミニウムとアルミニウム又は銅との複合材からなる基板が数多く提案されているが、これらの複合材基板は、セラミックスを含むため加工が難しいという難点がある。また熱膨張率の小さな金属であるタングステン又はモリブデンと銅とからなる複合材基板も提案されているが、これらの複合材基板にも加工が難しいという問題点がある。 For example, since the CPU is much smaller than the heat sink, a high heat conductor called a heat spreader is usually interposed between the two. As a material of the heat spreader, a material having not only high thermal conductivity but also a low thermal expansion coefficient comparable to that of a CPU made of silicon is desired. The same applies to light-emitting diodes made of compound semiconductors (GaAs, GaN, etc.). For this purpose, many substrates made of a composite material of silicon carbide, alumina, silicon nitride, or aluminum nitride and aluminum or copper, which are ceramics having a low coefficient of thermal expansion, have been proposed. Since ceramics are included, there is a difficulty that processing is difficult. A composite material substrate made of tungsten or molybdenum, which is a metal having a small coefficient of thermal expansion, and copper has also been proposed. However, these composite material substrates also have a problem that processing is difficult.
以上の事情に鑑み、最近炭素粒子又は炭素繊維と金属との複合材を放熱基板として使用する試みが数多く提案されている。例えば特開平10-168502号（特許文献１）は、黒鉛、炭素繊維、カーボンブラック、フラーレン又はカーボンナノチューブから選ばれた１種類以上からなる結晶性カーボン材１〜200重量部と、Fe、Cu、Al、Ag、Be、Mg、Ｗ、Ni、Mo、Si、Zn及びこれらの合金からなる群から選ばれた金属の粉末100重量部とを混合し、ホットプレス成形することにより得られた高熱伝導率複合材を開示している。しかしながら、この複合材は金属マトリックスに結晶性カーボン材が分散した構造を有し、熱伝導率が高いものの、熱膨張率が金属マトリックスと同程度に高いという問題を有する。 In view of the above circumstances, many attempts have recently been made to use a composite material of carbon particles or carbon fibers and metal as a heat dissipation substrate. For example, JP-A-10-168502 (Patent Document 1) discloses that 1 to 200 parts by weight of a crystalline carbon material selected from graphite, carbon fiber, carbon black, fullerene or carbon nanotube, Fe, Cu, High thermal conductivity obtained by mixing 100 parts by weight of a metal powder selected from the group consisting of Al, Ag, Be, Mg, W, Ni, Mo, Si, Zn, and alloys thereof, and hot pressing. Rate composites are disclosed. However, this composite material has a structure in which a crystalline carbon material is dispersed in a metal matrix and has a high thermal conductivity, but has a problem that the thermal expansion coefficient is as high as that of the metal matrix.
特開2000-203973号（特許文献２）は、炭素質マトリックス中にアルミニウム、マグネシウム、錫、亜鉛、銅、銀、鉄、ニッケル及びこれらの合金からなる群から選ばれた少なくとも１種の金属が含浸されてなる炭素基金属複合材であって、炭素質マトリックスの気孔の90体積％以上に前記金属が含浸し、前記金属の含有量が前記炭素基金属複合材全体の35体積％以下である炭素基金属複合材を開示している。 Japanese Patent Application Laid-Open No. 2000-203973 (Patent Document 2) discloses that at least one metal selected from the group consisting of aluminum, magnesium, tin, zinc, copper, silver, iron, nickel and alloys thereof is contained in a carbonaceous matrix. A carbon-based metal composite material impregnated, wherein 90% by volume or more of the pores of the carbonaceous matrix is impregnated with the metal, and the content of the metal is 35% by volume or less of the total carbon-based metal composite material. A carbon-based metal composite is disclosed.
また、特開2001-58255号（特許文献３）は、黒鉛結晶を含む炭素粒子又は炭素繊維を含む炭素成形体にアルミニウム、銅、銀又はこれらの合金を溶湯鍛造法で加圧含浸させることにより製造された炭素基金属複合材であって、室温における厚さ方向の熱伝導率が150 W/mK以上であり、熱膨張率が４×10-6／K〜12×10-6／Kである炭素基金属複合材を開示している。これらの炭素基金属複合材は、高剛性で高熱伝導率及び低熱膨張率を有する黒鉛マトリックスを骨格とし、その気孔に金属が含浸した構造を有するので、黒鉛の低熱膨張率と金属の高熱伝導率を兼備する。 Japanese Patent Laid-Open No. 2001-58255 (Patent Document 3) discloses a method in which aluminum, copper, silver, or an alloy thereof is pressure impregnated by a molten metal forging method into a carbon molded body including carbon particles including carbon crystals or carbon fibers. a carbon base metal composite material produced, and a thermal conductivity of the thickness direction at room temperature of 0.99 W / mK or more, the thermal expansion coefficient in the 4 × 10 -6 / K~12 × 10 -6 / K A carbon-based metal composite is disclosed. These carbon-based metal composites have a structure in which a graphite matrix having high rigidity, high thermal conductivity, and low thermal expansion coefficient is used as a skeleton, and the pores are impregnated with metal. Therefore, the low thermal expansion coefficient of graphite and the high thermal conductivity of metal Combined.
以上の利点にもかかわらず、これらの炭素基金属複合材には、シリコンや化合物半導体より遥かに大きな熱膨張率を有するという欠点がある。シリコンや化合物半導体との熱膨張率の差が大きいと、CPUや発光ダイオードに放熱基板を接合するための半田付けやろう付けの作業時にCPUや発光ダイオードに大きな熱応力がかかるのみならず、CPUや発光ダイオードの動作時にもCPUや発光ダイオードに大きな熱応力がかかるので、好ましくない。そのため、通常CPUや発光ダイオードと放熱基板との間に応力緩和材を介在させることが行われている。しかしながら、応力緩和材の熱伝導率は必ずしも十分に大きくないので、せっかく高熱伝導率の炭素基金属複合材を放熱基板に用いても、その効果が十分に発揮されないという問題がある。 Despite the above advantages, these carbon-based metal composites have the disadvantage of having a much larger coefficient of thermal expansion than silicon and compound semiconductors. If the difference in coefficient of thermal expansion from silicon or compound semiconductor is large, not only the CPU or light emitting diode is subjected to large thermal stress during soldering or brazing work to join the heat dissipation board to the CPU or light emitting diode, but also the CPU Further, it is not preferable because the CPU and the light emitting diode are subjected to a large thermal stress during the operation of the light emitting diode. Therefore, a stress relaxation material is usually interposed between the CPU or light emitting diode and the heat dissipation substrate. However, since the thermal conductivity of the stress relaxation material is not necessarily sufficiently high, there is a problem that even if a carbon-based metal composite material having a high thermal conductivity is used for the heat dissipation substrate, the effect is not sufficiently exhibited.
さらにCPUや発光ダイオードに放熱基板を接合する場合、例えばアルミニウム含浸黒鉛基板の場合には半田付け（通常200〜300℃程度）が行われ、銅含浸黒鉛基板の場合にはろう付け（通常700〜800℃程度）が行われる。ところが、このような高温に曝されると、アルミニウム又は銅を含浸した複合基板は残留応力により加熱前の寸法と加熱後の寸法とに著しい差が生じることが分かった。このような熱履歴があると、CPUや発光ダイオードと接合した放熱基板には反りが生じ、最終的には破壊に至ることもあり、またCPUやレーザダイオード等も熱応力により損傷することがある。 Furthermore, when joining a heat dissipation board to a CPU or light emitting diode, for example, in the case of an aluminum-impregnated graphite board, soldering (usually about 200-300 ° C) is performed, and in the case of a copper-impregnated graphite board, brazing (usually 700-- 800 ° C). However, it has been found that when exposed to such a high temperature, the composite substrate impregnated with aluminum or copper has a significant difference between the dimension before heating and the dimension after heating due to residual stress. If there is such a thermal history, the heat sink board joined to the CPU or light emitting diode may be warped, eventually resulting in destruction, and the CPU or laser diode may be damaged by thermal stress. .
従って、本発明の目的は、高熱伝導率を有するとともに、シリコン又は化合物半導体と同程度の小さな熱膨張率を有し、熱履歴が実質的にない高熱伝導・低熱膨張複合材を提供することである。 Accordingly, an object of the present invention is to provide a high thermal conductivity / low thermal expansion composite material having a high thermal conductivity, a small thermal expansion coefficient comparable to that of silicon or a compound semiconductor, and substantially no thermal history. is there.
本発明のもう一つの目的は、かかる特性を有する高熱伝導・低熱膨張複合材からなる放熱基板を提供することである。 Another object of the present invention is to provide a heat dissipation substrate made of a high thermal conductivity / low thermal expansion composite material having such characteristics.
本発明のさらにもう一つの目的は、かかる高熱伝導・低熱膨張複合材及び放熱基板を製造する方法を提供することである。 Still another object of the present invention is to provide a method for manufacturing such a high thermal conductivity / low thermal expansion composite material and a heat dissipation substrate.
上記目的に鑑み鋭意研究の結果、本発明者は、多孔質黒鉛化押出成形体に溶融金属を含浸させた後、熱処理することにより、(a) 熱伝導率を増大させるとともに熱膨張率をシリコン又は化合物半導体の熱膨張率と同程度まで低下させることができ、かつ(b) 熱膨張率の熱履歴を実質的に除去することができるので、加熱時に良好な寸法安定性が得られることを発見し、本発明に想到した。 As a result of diligent research in view of the above object, the present inventor found that the porous graphitized extrudate was impregnated with molten metal and then heat-treated to increase (a) the thermal conductivity and the thermal expansion coefficient of silicon. Alternatively, the thermal expansion coefficient can be reduced to the same level as that of the compound semiconductor, and (b) the thermal history of the thermal expansion coefficient can be substantially removed, so that good dimensional stability can be obtained during heating. Discovered and came up with the present invention.
すなわち、本発明の高熱伝導・低熱膨張複合材は、多孔質黒鉛化押出成形体に金属が含浸した高熱伝導・低熱膨張複合材であって、前記金属がアルミニウム又はその合金であり、前記複合材は前記金属を含浸させた後に（前記金属の融点−10℃）以下で、かつ200℃以上の温度で熱処理してなり、前記熱処理後の押出方向及び前記押出方向と直交する方向における熱履歴による寸法変化率が±0.1%以内であることを特徴とする。
前記熱処理は昇温速度30℃／分以下、冷却速度20℃／分以下の条件で行うのが好ましい。より好ましくは昇温速度10℃／分以下、冷却速度10℃／分以下である。
前記金属は11〜14質量％の珪素、残部がアルミニウム及び不可避不純物からなるアルミニウム合金であり、その金属組織中に析出した珪素（Si）リッチ相のうち、長径が30μｍ以下でアスペクト比（長径／短径）が10以上の針状組織の割合（顕微鏡写真における面積率）が10％以下であるのが好ましい。より好ましくは５％以下である。前記アルミニウム合金中の酸素量は400 ppm以下であるのが好ましい。
本発明のもう一つの高熱伝導・低熱膨張複合材は、多孔質黒鉛化押出成形体に金属が含浸した高熱伝導・低熱膨張複合材であって、前記金属が銅又はその合金であり、前記複合材は前記金属を含浸させた後に（前記金属の融点−10℃）以下で、かつ300℃以上の温度で熱処理してなり、前記熱処理後の押出方向及び前記押出方向と直交する方向における熱履歴による寸法変化率が±0.1%以内であることを特徴とする。
前記熱処理は昇温速度30℃／分以下、冷却速度20℃／分以下の条件で行うのが好ましい。より好ましくは昇温速度10℃／分以下、冷却速度10℃／分以下である。
前記金属が銅又はその合金の場合、前記金属中の酸素量は400 ppm以下であるのが好ましく、より好ましくは250 ppm以下である。
前記高熱伝導・低熱膨張複合材は、熱伝導率及び熱膨張率に異方性を有し、押出方向の熱伝導率が250 W/mK以上で熱膨張率が４×10-6／K未満であり、前記押出方向と直交する方向の熱伝導率が150 W/mK以上で熱膨張率が10×10-6／K以下であるのが好ましい。
That is, the high thermal conductivity / low thermal expansion composite material of the present invention is a high thermal conductivity / low thermal expansion composite material obtained by impregnating a porous graphitized extruded body with a metal, wherein the metal is aluminum or an alloy thereof, and the composite material Is heat-treated at a temperature of 200 ° C. or more after impregnating the metal (melting point of the metal −10 ° C.), and depending on the heat history in the extrusion direction after the heat treatment and in the direction perpendicular to the extrusion direction The dimensional change rate is within ± 0.1%.
The heat treatment is preferably performed under conditions of a heating rate of 30 ° C./min or less and a cooling rate of 20 ° C./min or less. More preferably, the heating rate is 10 ° C./min or less and the cooling rate is 10 ° C./min or less.
The metal is an aluminum alloy composed of 11 to 14% by mass of silicon, the balance being aluminum and inevitable impurities. Of the silicon (Si) -rich phases precipitated in the metal structure, the major axis is 30 μm or less and the aspect ratio (major axis / It is preferable that the ratio (area ratio in the micrograph) of the acicular structure having a minor axis) of 10 or more is 10% or less. More preferably, it is 5% or less. The amount of oxygen in the aluminum alloy is preferably 400 ppm or less.
Another high thermal conductivity / low thermal expansion composite material of the present invention is a high thermal conductivity / low thermal expansion composite material obtained by impregnating a porous graphitized extruded body with a metal, wherein the metal is copper or an alloy thereof. The material is heat-treated at a temperature of 300 ° C. or higher after impregnating the metal (melting point of the metal −10 ° C.), and heat history in the extrusion direction after the heat treatment and in the direction perpendicular to the extrusion direction. It is characterized in that the dimensional change rate due to is within ± 0.1%.
The heat treatment is preferably performed under conditions of a heating rate of 30 ° C./min or less and a cooling rate of 20 ° C./min or less. More preferably, the heating rate is 10 ° C./min or less and the cooling rate is 10 ° C./min or less.
When the metal is copper or an alloy thereof, the amount of oxygen in the metal is preferably 400 ppm or less, more preferably 250 ppm or less.
The high thermal conductivity / low thermal expansion composite material has anisotropy in thermal conductivity and thermal expansion coefficient, thermal conductivity in the extrusion direction is 250 W / mK or more, and thermal expansion coefficient is less than 4 × 10 −6 / K. It is preferable that the thermal conductivity in the direction orthogonal to the extrusion direction is 150 W / mK or more and the thermal expansion coefficient is 10 × 10 −6 / K or less .
本発明の好ましい実施例では、押出方向の熱伝導率が250 W/mK以上で熱膨張率が0.1×10-6／K以上、４×10-6／K未満であり、前記押出方向と直交する方向の熱伝導率が150 W/mK以上で熱膨張率が4×10-6／K以上、10×10-6／K以下である。 In a preferred embodiment of the present invention, the thermal conductivity in the extrusion direction is 250 W / mK or more and the thermal expansion coefficient is 0.1 × 10 −6 / K or more and less than 4 × 10 −6 / K, and is orthogonal to the extrusion direction. The thermal conductivity in the direction of the flow is 150 W / mK or more, and the thermal expansion coefficient is 4 × 10 −6 / K or more and 10 × 10 −6 / K or less.
本発明の放熱基板は、上記高熱伝導・低熱膨張複合材からなり、基板の板厚方向が多孔質黒鉛化押出成形体の押出方向に一致しており、押出方向と直交する面に発熱体を接合するようになっていることを特徴とする。
Heat sink substrate of the present invention consists of the high thermal conductivity and low thermal expansion composite material, the thickness direction of the substrate coincides with the direction of extrusion of the multi-porous graphitized extrudate, heating element on a surface perpendicular to the extrusion direction It is characterized by joining.
本発明の高熱伝導・低熱膨張複合材の製造方法は、(1) 炭素粒子及び／又は炭素繊維とタールピッチとの押出成形体を焼成することにより黒鉛化し、(2) 得られた多孔質黒鉛化押出成形体に、アルミニウム又はその合金の溶融金属を、前記溶融金属の融点より10℃以上高い温度及び10 MPa以上の圧力で含浸させ、(3) 得られた黒鉛／金属複合材に（前記金属の融点−10℃）以下で、かつ200℃以上の温度で熱処理を施すことを特徴とする。
本発明のもう一つの高熱伝導・低熱膨張複合材の製造方法は、(1) 炭素粒子及び／又は炭素繊維とタールピッチとの押出成形体を焼成することにより黒鉛化し、(2) 得られた多孔質黒鉛化押出成形体に、銅又はその合金の溶融金属を、前記溶融金属の融点より10℃以上高い温度及び10 MPa以上の圧力で含浸させ、(3) 得られた黒鉛／金属複合材に（前記金属の融点−10℃）以下で、かつ300℃以上の温度で熱処理を施すことを特徴とする。
前記熱処理は昇温速度30℃／分以下、冷却速度20℃／分以下の条件で行うのが好ましい。より好ましくは昇温速度10℃／分以下、冷却速度10℃／分以下である。
The method for producing a high thermal conductivity / low thermal expansion composite material of the present invention includes: (1) graphitization by firing an extruded product of carbon particles and / or carbon fibers and tar pitch; and (2) the obtained porous graphite. the reduction extruded body, the molten metal of aluminum or its alloys, the impregnated at a pressure of 10 ° C. or higher high temperature and 10 MPa or more than the melting point of the molten metal, (3) the obtained graphite / metal composite material (the It is characterized in that the heat treatment is performed at a temperature not higher than the melting point of the metal −10 ° C.) and not lower than 200 ° C.
Another method for producing a high thermal conductivity / low thermal expansion composite material of the present invention is (1) graphitized by firing an extruded product of carbon particles and / or carbon fibers and tar pitch, and (2) obtained. (3) Obtained graphite / metal composite material by impregnating a porous graphitized extrudate with a molten metal of copper or an alloy thereof at a temperature of 10 ° C. or higher and a pressure of 10 MPa or higher than the melting point of the molten metal. (The melting point of the metal is −10 ° C.) or less, and heat treatment is performed at a temperature of 300 ° C. or more.
The heat treatment is preferably performed under conditions of a heating rate of 30 ° C./min or less and a cooling rate of 20 ° C./min or less. More preferably, the heating rate is 10 ° C./min or less and the cooling rate is 10 ° C./min or less.
本発明の放熱基板の製造方法は、上記方法により高熱伝導・低熱膨張複合材を製造した後、前記多孔質黒鉛化押出成形体の押出方向と垂直な面に沿って切り出すことを特徴とする。前記垂直面を発熱体を接合する面として使用するのが好ましい。
Method for manufacturing a heat sink substrate of the present invention is characterized in that cut out after producing a high thermal conductivity and low thermal expansion composite by the above methods, along the extrusion direction and vertical surface of the porous graphitized extrudate . The vertical surface is preferably used as a surface for joining the heating elements.
このようにして得られた高熱伝導・低熱膨張複合材は、厚さ0.1〜100 ｍｍ程度の板状に切り出して、ヒートシンク等として用いるのが望ましい。金属含浸後の複合体を熱処理した後で、板状に切り出すのが通常であるが、超高精度の形状が要求されるような場合には金属含浸後の複合体から板状に切り出した後で熱処理を施し、再度目的とする形状に加工するのが好ましい。何れにしても多孔質黒鉛化押出成形体からなる放熱基板は、押出方向及び直交方向における熱履歴による寸法変化率が±0.1％以内であるので、ろう付け等の際に熱応力がかかっても、冷却後に反りや接合界面での剥離等の問題がない。 The thus obtained high thermal conductivity / low thermal expansion composite material is preferably cut into a plate shape having a thickness of about 0.1 to 100 mm and used as a heat sink or the like. After the metal-impregnated composite is heat-treated, it is usually cut into a plate shape. However, if an ultra-high precision shape is required, the metal-impregnated composite is cut into a plate shape. It is preferable to heat-treat and process into the desired shape again. In any case, the heat dissipation substrate made of a porous graphitized extruded product has a dimensional change rate within ± 0.1% due to thermal history in the extrusion direction and in the orthogonal direction, so even if thermal stress is applied during brazing, etc. There are no problems such as warping or peeling at the bonding interface after cooling.
本発明の高熱伝導・低熱膨張複合材は熱伝導率及び熱膨張率に異方性を有し、具体的には、押出方向において熱伝導率は250 W/mK以上で熱膨張率は４×10-6／K未満であり、また押出方向と直交する方向において熱伝導率は150 W/mK以上で熱膨張率は10×10-6／K以下である。そのため、半導体素子用のヒートシンク又はヒートスプレッダー等に使用する場合、熱応力による影響が抑制され、熱は横方向に広がるとともに厚さ方向に良好に伝導し、効率的に熱放散を行うことができる。また厚さ方向の熱膨張率が低いので、パッケージに組立てる時に厚さ方向の寸法精度が良く、高気密性のパッケージを得ることができる。 The high thermal conductivity / low thermal expansion composite material of the present invention has anisotropy in thermal conductivity and thermal expansion coefficient. Specifically, in the extrusion direction, the thermal conductivity is 250 W / mK or more and the thermal expansion coefficient is 4 ×. less than 10 -6 / K, and the thermal conductivity in the direction perpendicular to the extrusion direction is the thermal expansion coefficient at 0.99 W / mK or more and less 10 × 10 -6 / K. Therefore, when used in a heat sink or heat spreader for semiconductor elements, the influence of thermal stress is suppressed, heat spreads in the lateral direction and conducts well in the thickness direction, and can efficiently dissipate heat. . Further, since the coefficient of thermal expansion in the thickness direction is low, the dimensional accuracy in the thickness direction is good when assembled into a package, and a highly airtight package can be obtained.
以下、本発明の高熱伝導・低熱膨張複合材の好ましい構成について述べる。本発明の高熱伝導・低熱膨張複合材は嵩密度1.9 g/cm3以上を有し、前記金属の含有量は10〜30体積％であるのが好ましい。 Hereinafter, a preferable configuration of the high thermal conductivity / low thermal expansion composite material of the present invention will be described. The high thermal conductivity / low thermal expansion composite of the present invention preferably has a bulk density of 1.9 g / cm 3 or more, and the metal content is preferably 10 to 30% by volume.
高熱伝導・低熱膨張複合材の押出方向における固有抵抗は４μΩｍ以下であり、直交方向における固有抵抗は７μΩｍ以下であるのが好ましい。より好ましくは押出方向における固有抵抗は２μΩｍ以下であり、直交方向における固有抵抗は3.5μΩｍ以下である。 The specific resistance in the extrusion direction of the high thermal conductivity / low thermal expansion composite material is preferably 4 μΩm or less, and the specific resistance in the orthogonal direction is preferably 7 μΩm or less. More preferably, the specific resistance in the extrusion direction is 2 μΩm or less, and the specific resistance in the orthogonal direction is 3.5 μΩm or less.
本発明に使用する多孔質黒鉛化押出成形体は、コークス等の炭素粒子とタールピッチとからなり、前記炭素粒子は平均粒径50μｍ以上であるのが好ましい。押出成形体の灰分は0.5質量％以下であるのが好ましく、より好ましくは0.3質量％である。 The porous graphitized extruded product used in the present invention comprises carbon particles such as coke and tar pitch, and the carbon particles preferably have an average particle size of 50 μm or more. The ash content of the extruded product is preferably 0.5% by mass or less, and more preferably 0.3% by mass.
本発明に使用する多孔質黒鉛化押出成形体の固有抵抗は、押出方向で７μΩｍ未満であり、押出方向と直交する方向で７μΩｍ以上であり、前記固有抵抗の押出方向／直交方向比は0.9以下であるのが好ましい。より好ましくは、多孔質黒鉛化押出成形体の固有抵抗は押出方向で６μΩｍ以下、押出方向と直交する方向で８μΩｍ以上、前記固有抵抗の押出方向／直交方向比は0.6以下である。 The specific resistance of the porous graphitized extruded product used in the present invention is less than 7 μΩm in the extrusion direction, 7 μΩm or more in the direction orthogonal to the extrusion direction, and the extrusion direction / orthogonal direction ratio of the specific resistance is 0.9 or less. Is preferred. More preferably, the specific resistance of the porous graphitized extrudate is 6 μΩm or less in the extrusion direction, 8 μΩm or more in the direction orthogonal to the extrusion direction, and the extrusion direction / orthogonal direction ratio of the specific resistance is 0.6 or less.
本発明に使用する多孔質黒鉛化押出成形体の熱膨張率は、押出方向で3×10-6／K以下であり、押出方向と直交する方向で4×10-6／K以下であり、前記熱膨張率の押出方向／直交方向比は0.8以下であるのが好ましい。より好ましくは、多孔質黒鉛化押出成形体の熱膨張率は押出方向で1×10-6／K以下、押出方向と直交する方向で3×10-6／K以下、前記熱膨張率の押出方向／直交方向比は0.5以下である。 The thermal expansion coefficient of the porous graphitized extrudate used in the present invention is 3 × 10 −6 / K or less in the extrusion direction, and 4 × 10 −6 / K or less in the direction orthogonal to the extrusion direction. The ratio of the thermal expansion coefficient in the extrusion direction / orthogonal direction is preferably 0.8 or less. More preferably, the porous graphitized extrudate has a thermal expansion coefficient of 1 × 10 −6 / K or less in the extrusion direction and 3 × 10 −6 / K or less in the direction orthogonal to the extrusion direction. The direction / orthogonal ratio is 0.5 or less.
本発明に使用する多孔質黒鉛化押出成形体の熱伝導率は押出方向で150 W/mK以上であり、前記押出方向と直交する方向で80 W/mK以上であり、より好ましくは100 Ｗ／ｍＫ以上である。前記熱伝導率の押出方向／直交方向比は1.3以上であり、より好ましくは1.5以上である。 The thermal conductivity of the porous graphitized extrudate used in the present invention is 150 W / mK or more in the extrusion direction, 80 W / mK or more in the direction orthogonal to the extrusion direction, and more preferably 100 W / mK. mK or more. The extrusion direction / orthogonal direction ratio of the thermal conductivity is 1.3 or more, more preferably 1.5 or more.
前記金属としてアルミニウム又はその合金を使用する場合、前記多孔質黒鉛化押出成形体への前記溶融金属の含浸をその融点より10℃以上高い温度及び10MPa以上の圧力で行うのが好ましい。
When aluminum or an alloy thereof is used as the metal, it is preferable to impregnate the porous graphitized extrudate with the molten metal at a temperature higher than its melting point by 10 ° C. or higher and a pressure of 10 MPa or higher.
前記金属として銅又はその合金を使用する場合、前記多孔質黒鉛化押出成形体への前記溶融金属の含浸をその融点より10℃以上高い温度及び10MPa以上の圧力で行うのが好ましい。
When copper or an alloy thereof is used as the metal, it is preferable to impregnate the porous graphitized extrudate with the molten metal at a temperature higher than its melting point by 10 ° C. or higher and a pressure of 10 MPa or higher.
以上より、本発明の黒鉛／金属複合材は、(a) 黒鉛からなる骨格とその空孔内に含浸された高熱伝導率の金属とからなるので、黒鉛の特性（小さな熱膨張率）と金属の特性（大きな熱伝導率）を保持するとともに、(b) 熱処理により熱伝導率が幾分向上しているとともに、熱膨張率が著しく低下したという特徴を有する。また本発明の黒鉛／金属複合材は、黒鉛化した押出成形体を骨格としているので、押出方向と直交方向とで特性値に差がある。そのため、用途に応じて切り出し方向を押出方向又は直交方向に平行にすることにより、所望の熱伝導率及び熱膨張率を有する放熱基板を得ることができる。さらに、本発明の黒鉛／金属複合材は熱処理により熱膨張の熱履歴が実質的になくなっているので、半田やろう付けの後でも寸法精度が良好であるという利点も有する。 From the above, the graphite / metal composite material of the present invention is composed of (a) a skeleton made of graphite and a metal having a high thermal conductivity impregnated in the pores. (B) The heat conductivity is somewhat improved by the heat treatment, and the coefficient of thermal expansion is remarkably reduced. Moreover, since the graphite / metal composite material of the present invention has a graphitized extruded product as a skeleton, there is a difference in characteristic values between the extrusion direction and the orthogonal direction. Therefore, a heat dissipation substrate having a desired thermal conductivity and thermal expansion coefficient can be obtained by making the cutting direction parallel to the extrusion direction or the orthogonal direction according to the application. Furthermore, the graphite / metal composite material of the present invention has an advantage that the dimensional accuracy is good even after soldering or brazing because the thermal history of thermal expansion is substantially eliminated by heat treatment.
[1] 高熱伝導・低熱膨張複合材
(A) 構成
(1) 多孔質黒鉛化押出成形体
本発明に使用する多孔質黒鉛化押出成形体は、２g/cm3以下、特に1.6〜1.95 g/cm3の嵩密度を有するのが好ましい。嵩密度が２g/cm3超であると、溶融金属の含浸が不十分であり、熱伝導率の十分な向上効果が得られない。また1.6 g/cm3未満であると、黒鉛骨格の強度が不十分であり、複合材全体の熱膨張率が金属の熱膨張率により大きく影響を受けて増大する。多孔質黒鉛化押出成形体のより好ましい嵩密度は1.65〜1.85 g/cm3である。
[1] High thermal conductivity / low thermal expansion composite
(A) Configuration
(1) Porous graphitized extrudate The porous graphitized extrudate used in the present invention preferably has a bulk density of 2 g / cm 3 or less, particularly 1.6 to 1.95 g / cm 3 . When the bulk density is more than 2 g / cm 3 , the impregnation with the molten metal is insufficient, and the effect of sufficiently improving the thermal conductivity cannot be obtained. If it is less than 1.6 g / cm 3 , the strength of the graphite skeleton is insufficient, and the thermal expansion coefficient of the entire composite material is greatly influenced by the thermal expansion coefficient of the metal and increases. A more preferable bulk density of the porous graphitized extruded product is 1.65 to 1.85 g / cm 3 .
(2) 含浸金属
多孔質黒鉛化押出成形体に含浸させる溶融金属は、アルミニウムもしくはその合金、又は銅もしくはその合金である。特にアルミニウムの合金としては、11〜14質量％の珪素を含有するアルミニウム−珪素合金が好ましい。この理由は、11〜14質量％の珪素を含有することにより、溶融金属の融点が低下し、その結果アルミニウム炭化物の生成が抑えられて、熱伝導率の低下が防止されたものと考えられる。さらに、合金内に含まれる針状の珪素粒子が熱処理により粒状化したことにより、熱抵抗が低下し、その結果熱伝導率が向上したものと考えられる。
(2) Impregnated metal The molten metal impregnated into the porous graphitized extrudate is aluminum or an alloy thereof , or copper or an alloy thereof . In particular, the aluminum alloy is preferably an aluminum-silicon alloy containing 11 to 14% by mass of silicon. The reason is considered to be that the melting point of the molten metal is lowered by containing 11 to 14% by mass of silicon, and as a result, the formation of aluminum carbide is suppressed, and the decrease in thermal conductivity is prevented. Furthermore, it is considered that the needle-like silicon particles contained in the alloy were granulated by heat treatment, so that the thermal resistance was lowered, and as a result, the thermal conductivity was improved.
また、銅合金としてはクロム銅合金が好ましい。この理由は、合金内に含まれるクロムに黒鉛と銅の界面の強度を向上させる効果があり、その結果複合材強度が向上したものと考えられる。クロムの含有量は0.1〜10質量％であり、好ましくは0.1〜5質量％、より好ましくは0.1〜2質量％である。 Moreover, as a copper alloy, a chromium copper alloy is preferable. The reason for this is considered that chromium contained in the alloy has an effect of improving the strength of the interface between graphite and copper, and as a result, the strength of the composite material is improved. The chromium content is 0.1 to 10% by mass, preferably 0.1 to 5% by mass, and more preferably 0.1 to 2% by mass.
複合材中の金属の割合は10〜30体積％であるのが好ましい。多孔質黒鉛化押出成形体に含浸した金属が複合材の10体積％未満であると、嵩密度が1.9g/cm3未満となり、金属含浸による熱伝導率の向上効果が不十分である。また金属が30体積％超であると、黒鉛骨格に対して金属の含浸量が多すぎるので、複合材全体の熱膨張率が金属の熱膨張率により大きく影響され、シリコンや化合物半導体の熱膨張率との差が大きくなりすぎる。複合材中の金属のより好ましい割合は15〜25体積％である。
The proportion of metal in the composite is preferably 10-30% by volume. When the metal impregnated into the porous graphitized extruded product is less than 10% by volume of the composite material, the bulk density becomes less than 1.9 g / cm 3, and the effect of improving the thermal conductivity by the metal impregnation is insufficient. If the metal content exceeds 30% by volume, the amount of impregnation of the metal with the graphite skeleton is too large, so the thermal expansion coefficient of the entire composite material is greatly influenced by the thermal expansion coefficient of the metal, and the thermal expansion of silicon and compound semiconductors. The difference from the rate is too large. A more desirable ratio of the metal in the composite material is 15 to 25% by volume.
多孔質黒鉛化押出成形体の空孔にできるだけ緻密に金属が充填されるのが好ましいので、複合材の嵩密度は1.9g/cm3以上であるのが好ましい。嵩密度が1.9g/cm3未満であると、複合材の空孔率が高すぎるので、熱伝導率を十分に高くすることができない。また嵩密度が５g/cm3超になると加圧含浸工程での温度／圧力条件が厳しくなりすぎ、製造が困難になるのみならずコスト高にもなる。複合材のより好ましい嵩密度は1.9〜４g/cm3である。 Since it is preferable that the pores of the porous graphitized extruded product are filled with the metal as densely as possible, the bulk density of the composite material is preferably 1.9 g / cm 3 or more. When the bulk density is less than 1.9 g / cm 3 , the porosity of the composite material is too high, so that the thermal conductivity cannot be sufficiently increased. On the other hand, if the bulk density exceeds 5 g / cm 3 , the temperature / pressure conditions in the pressure impregnation step become too severe, which not only makes the production difficult but also increases the cost. A more preferable bulk density of the composite material is 1.9 to 4 g / cm 3 .
(B) 製造方法
(1) 多孔質黒鉛化押出成形体の製造
多孔質黒鉛化押出成形体自体は公知の方法により製造することができる。典型的には、コークス等の炭素原料を粉砕し、適当な粒度に分級した後、バインダーとしてピッチを添加し、溶融混練する。混練物を所定の形状の押出口を有するダイから押し出し、所定の長さに切断後焼成し、黒鉛化させる。なお炭素粉末の代わりに炭素繊維を使用しても良いし、炭素粉末と炭素繊維との混合物を使用しても良い。
(B) Manufacturing method
(1) Production of porous graphitized extruded product The porous graphitized extruded product itself can be produced by a known method. Typically, a carbon raw material such as coke is pulverized and classified to an appropriate particle size, and then pitch is added as a binder and melt-kneaded. The kneaded product is extruded from a die having an extrusion port having a predetermined shape, cut into a predetermined length, fired, and graphitized. Carbon fiber may be used instead of carbon powder, or a mixture of carbon powder and carbon fiber may be used.
コークス粉等の炭素粉末の平均粒径は50μｍ以上であるのが好ましい。炭素粉末の平均粒径が50μｍ未満であると、得られる多孔質黒鉛化押出成形体の熱伝導率が不十分である。また炭素粉末の平均粒径が３mm超であると、機械的強度が不十分という問題がある。炭素粉末のより好ましい平均粒径は50μｍ〜３mm程度である。また炭素繊維の場合、ピッチ系の炭素繊維が好ましく、その平均長さは50μｍ〜５mm程度が好ましい。 The average particle size of carbon powder such as coke powder is preferably 50 μm or more. When the average particle size of the carbon powder is less than 50 μm, the heat conductivity of the obtained porous graphitized extruded product is insufficient. Further, if the average particle size of the carbon powder is more than 3 mm, there is a problem that the mechanical strength is insufficient. A more preferable average particle size of the carbon powder is about 50 μm to 3 mm. In the case of carbon fibers, pitch-based carbon fibers are preferable, and the average length is preferably about 50 μm to 5 mm.
炭素粉末及び／又は炭素繊維とピッチとの混合比（重量基準）は、10：1〜10：4が好ましく、10：2〜10：3がより好ましい。混合比が10：1未満、また10：4超であると、混練物の粘度が不適となり押出成形が困難になる。 The mixing ratio (weight basis) of carbon powder and / or carbon fiber and pitch is preferably 10: 1 to 10: 4, and more preferably 10: 2 to 10: 3. If the mixing ratio is less than 10: 1 or more than 10: 4, the viscosity of the kneaded product becomes inappropriate and extrusion molding becomes difficult.
炭素粉末及び／又は炭素繊維とタールピッチとの溶融混練物は100〜140℃の温度で押出ダイから押し出すのが好ましい。 The melt-kneaded product of carbon powder and / or carbon fiber and tar pitch is preferably extruded from an extrusion die at a temperature of 100 to 140 ° C.
優れた熱伝導率及び熱膨張率を有する黒鉛／金属複合材を得るためには、多孔質黒鉛化押出成形体は高純度の黒鉛からなるのが好ましい。具体的には、多孔質黒鉛化押出成形体中の灰分は0.5質量％以下であるのが好ましく、0.3質量％以下がより好ましい。まず多孔質黒鉛化押出成形体は、押出成形後700〜1000℃により焼成する。焼成後の成形体には多数の気孔があるので、嵩密度1.65 g/cm3以上とするには、焼成後の成形体の気孔内へピッチを含浸し再焼成する。この後、黒鉛化成形体とするために2600〜3000℃の温度で熱処理することにより、炭素質から黒鉛質に変化し多孔質黒鉛化押出成形体とする。高熱伝導率及び低熱膨張率を有する黒鉛／金属複合材を得るためには、多孔質黒鉛化押出成形体を燃焼させたときに残る不燃性の鉱物質（灰分）は0.5質量％以下とし、純度の高い黒鉛質となすことが肝要である。 In order to obtain a graphite / metal composite material having excellent thermal conductivity and coefficient of thermal expansion, the porous graphitized extrudate is preferably made of high-purity graphite. Specifically, the ash content in the porous graphitized extruded product is preferably 0.5% by mass or less, and more preferably 0.3% by mass or less. First, the porous graphitized extrudate is fired at 700 to 1000 ° C. after extrusion. Since the fired compact has a large number of pores, pitch is impregnated into the pores of the fired compact and refired in order to obtain a bulk density of 1.65 g / cm 3 or more. Thereafter, heat treatment is performed at a temperature of 2600 to 3000 ° C. to obtain a graphitized molded body, whereby the carbonaceous material is changed to a graphite material to obtain a porous graphitized extruded product. In order to obtain a graphite / metal composite material having high thermal conductivity and low thermal expansion coefficient, the non-combustible mineral (ash) remaining after burning the porous graphitized extruded product should be 0.5% by mass or less, and the purity It is important to make it high in graphite.
(2) 金属の含浸
多孔質黒鉛化押出成形体への溶融金属の含浸は溶湯鍛造法により行うことができる。溶湯鍛造法を行うのに好ましい金型装置の一例を図１に示す。図１(a) に示すように、金型装置１は、中央にキャビティ11aを有する上型11と、上型11の下に配置され、中央に開口部12aを有する下型12と、上型11のキャビティ11a内に配置された下パンチ13と、下パンチ13の底部に連結して下型12の開口部12aを貫通するシャフト14と、上型11のキャビティ11a内に進入する上パンチ15と、上パンチ15の上面に連結したプランジャーシャフト16とを有する。
(2) Impregnation of metal Impregnation of the molten metal into the porous graphitized extrudate can be performed by a molten metal forging method. An example of a mold apparatus preferable for performing the molten metal forging method is shown in FIG. As shown in FIG. 1 (a), a mold apparatus 1 includes an upper mold 11 having a cavity 11a at the center, a lower mold 12 disposed below the upper mold 11 and having an opening 12a at the center, and an upper mold. A lower punch 13 disposed in the cavity 11a of the eleventh shaft, a shaft 14 connected to the bottom of the lower punch 13 and penetrating through the opening 12a of the lower mold 12, and an upper punch 15 entering the cavity 11a of the upper mold 11 And a plunger shaft 16 connected to the upper surface of the upper punch 15.
図１(a) に示すように、まず上パンチ15を取り外し、かつ多孔質黒鉛化押出成形体20を載置した下パンチ13を上型11のキャビティ11a内の最下部まで降下させた状態で、取鍋２より溶融金属Mをキャビティ11a内に注入する。このとき上下型11，12及び多孔質黒鉛化押出成体等を所定の温度に加熱しておくとともに、含浸中に凝固しないように十分な量の溶融金属Mをキャビティ11a内に注入するのが好ましい。また、溶融金属を注入した時に、多孔質黒鉛化押出成体20が浮上するのを防止するために、鉄製材料などの重しをするとより好ましい。 As shown in FIG. 1 (a), the upper punch 15 is first removed, and the lower punch 13 on which the porous graphitized extruded product 20 is placed is lowered to the lowermost part in the cavity 11a of the upper die 11. The molten metal M is poured into the cavity 11a from the ladle 2. At this time, it is preferable that the upper and lower molds 11 and 12 and the porous graphitized extruded product are heated to a predetermined temperature and a sufficient amount of molten metal M is injected into the cavity 11a so as not to solidify during the impregnation. . In order to prevent the porous graphitized extruded product 20 from floating when the molten metal is injected, it is more preferable to weight the iron material or the like.
図１(b) に示すように、上パンチ15をキャビティ11a内に進入させ、プランジャーシャフト16を介して高圧で上パンチ15を押圧すると、高圧になった溶融金属Mは多孔質黒鉛化押出成形体20の空孔内に浸入する。多孔質黒鉛化押出成形体20に浸入した溶融金属Mが凝固した後、図１(c) に示すように、上パンチ15を除去し、次いで下パンチ13を上昇させて、得られた金属含浸多孔質黒鉛化押出成形体21を取り出す。最後に図１(d) に示すように、金属含浸多孔質黒鉛化押出成形体21を凝固金属M’から切り出す。なお溶融金属Mが多孔質黒鉛化押出成形体20の空孔に十分に加圧浸入しないうちに凝固するのを防止するために、溶湯鍛造の間上下の金型11，12及びパンチ13，15を所定の温度に加熱しているのが好ましい。 As shown in FIG. 1 (b), when the upper punch 15 enters the cavity 11a and presses the upper punch 15 at a high pressure via the plunger shaft 16, the molten metal M at a high pressure becomes porous graphitized extrusion. It penetrates into the pores of the molded body 20. After the molten metal M that has entered the porous graphitized extrudate 20 has solidified, as shown in FIG. 1 (c), the upper punch 15 is removed, and then the lower punch 13 is raised to obtain the resulting metal impregnation. The porous graphitized extruded product 21 is taken out. Finally, as shown in FIG. 1 (d), the metal-impregnated porous graphitized extrudate 21 is cut out from the solidified metal M '. In order to prevent the molten metal M from solidifying before sufficiently intruding into the pores of the porous graphitized extrudate 20, the upper and lower molds 11 and 12 and the punches 13 and 15 during the forging of the molten metal. Is preferably heated to a predetermined temperature.
溶湯鍛造温度は溶融金属の種類により異なるが、一般に溶融金属の融点より10℃以上高い温度であるのが好ましい。具体的には、各金属又はその合金の溶湯鍛造温度は下記表１に示す通りである。いずれの溶融金属の場合でも、溶湯鍛造温度が下限温度未満であると、溶融金属の多孔質黒鉛化押出成形体の空孔への浸入が不十分である。また溶湯鍛造温度を上昇することにより得られる効果は上限温度でほぼ飽和し、それより高くしてもそれに伴う効果の向上は得られない。また、いずれの溶融金属の場合でも、含浸する前に、多孔質黒鉛化押し出し成形体の温度を溶融金属の融点と同等か、好ましくは溶融金属の融点以上に予め加熱しておくと、成形体の空孔中への溶融金属の十分な浸入が達成されるので好ましい。
溶湯鍛造圧力は溶融金属の種類によらず10 MPa以上必要である。より好ましくは50 MPa以上である。いずれの溶融金属の場合でも、溶湯鍛造圧力が下限温度未満であると、溶融金属の多孔質黒鉛化押出成形体の空孔への浸入が不十分である。また溶湯鍛造圧力を上昇することにより得られる効果は上限圧力でほぼ飽和し、それより高くしてもそれに伴う効果の向上は得られない。 The forging pressure of molten metal must be 10 MPa or more regardless of the type of molten metal. More preferably, it is 50 MPa or more. In any case of the molten metal, if the molten metal forging pressure is less than the lower limit temperature, the molten metal does not sufficiently enter the pores of the porous graphitized extruded product. Further, the effect obtained by increasing the melt forging pressure is almost saturated at the upper limit pressure, and even if it is higher than that, the improvement of the effect cannot be obtained.
加圧時間は溶融金属の種類、温度及び圧力によらず、一般に１分〜30分もあれば良い。加圧時間が１分未満の場合、多孔質黒鉛化押出成形体は十分に溶融金属で含浸されず、また30分超では溶融金属の温度が低下してしまい、さらに含浸が進むことはない。 The pressurization time is generally from 1 minute to 30 minutes regardless of the type of molten metal, temperature and pressure. When the pressurization time is less than 1 minute, the porous graphitized extrudate is not sufficiently impregnated with the molten metal, and when it exceeds 30 minutes, the temperature of the molten metal is lowered and the impregnation does not proceed further.
(3) 熱処理
図２は本発明に好ましい黒鉛／金属複合材の熱処理パターンを示す。黒鉛／金属複合材の昇温速度は30℃／分以下であるのが好ましく、10℃／分以下であるのがより好ましい。昇温速度が30℃／分超であると、複合材の温度が均一にならないという問題がある。なお昇温速度の下限は、熱処理効率を考慮して0.5℃／分程度であれば良い。
(3) Heat treatment FIG. 2 shows a heat treatment pattern of the graphite / metal composite material preferred in the present invention. The temperature rising rate of the graphite / metal composite is preferably 30 ° C./min or less, and more preferably 10 ° C./min or less. If the rate of temperature rise exceeds 30 ° C./min, there is a problem that the temperature of the composite material does not become uniform. The lower limit of the heating rate may be about 0.5 ° C./min in consideration of the heat treatment efficiency.
黒鉛／金属複合材の保持温度は、一般に（各金属の融点−10℃）以下で、かつ200℃以上であるのが好ましい。保持温度が（各金属の融点−10℃）超であると、金属が軟化又は溶融して、多孔質黒鉛化押出成形体から滲出する恐れがある。また保持温度が200℃未満では、熱処理効果が十分に得られない。なお保持時間は1〜120分程度であれば良い。
The holding temperature of the graphite / metal composite is generally (melting point of each metal −10 ° C.) or lower and preferably 200 ° C. or higher. If the holding temperature is higher than (melting point of each metal −10 ° C.) , the metal may be softened or melted and ooze out from the porous graphitized extruded product. If the holding temperature is less than 200 ° C., the heat treatment effect cannot be obtained sufficiently. The holding time may be about 1 to 120 minutes.
上記温度に保持した黒鉛／金属複合材は徐冷するのが好ましいので、その冷却速度は20℃／分以下であるのが好ましく、10℃／分以下であるのがより好ましい。冷却速度が20℃／分超であると、含浸した金属の熱履歴が残る。なお冷却速度の下限は、熱処理効率を考慮して0.5℃／分程度であれば良い。 Since the graphite / metal composite maintained at the above temperature is preferably slowly cooled, the cooling rate is preferably 20 ° C./min or less, more preferably 10 ° C./min or less. When the cooling rate exceeds 20 ° C./min, the heat history of the impregnated metal remains. The lower limit of the cooling rate may be about 0.5 ° C./min in consideration of the heat treatment efficiency.
なお、これらの熱処理は金属含浸多孔質黒鉛化押出成形体21の状態で施してもよく、押出方向と垂直な面に沿って切り出した金属含浸黒鉛／金属複合材を熱処理しても良い。製造工程上は前者の方が好ましい。 These heat treatments may be performed in the state of the metal-impregnated porous graphitized extrudate 21 or the metal-impregnated graphite / metal composite material cut out along a plane perpendicular to the extrusion direction may be heat-treated. The former is preferable in the manufacturing process.
各金属含浸黒鉛／金属複合材の好ましい熱処理条件を以下の表２にまとめて示す。
(C) 特性
(1) 熱伝導率
本発明の黒鉛／金属複合材は、多孔質黒鉛化押出成形体の空孔に高熱伝導率の金属が加圧浸入した構造を有するので、黒鉛より著しく高い熱伝導率を有する。また黒鉛骨格自体は押出成形体からなり、異方性を有するので、押出方向とその直交方向とで熱伝導率に差がある。多孔質黒鉛化押出成形体自体の熱伝導率は押出方向で150W/mK以上であり、その直交方向で80 W/mK以上である。そのため、含浸する金属の種類に関わらず、複合材の熱伝導率は押出方向で250 W/mK以上であり、その直交方向で150 W/mK以上の熱伝導率を発揮できる。さらに、本発明の特徴として黒鉛／金属複合材は熱処理を施すことにより熱伝導率はさらに向上する。
(C) Characteristics
(1) Thermal conductivity The graphite / metal composite of the present invention has a structure in which a metal with high thermal conductivity is pressed into the pores of the porous graphitized extruded product, and therefore has a significantly higher thermal conductivity than graphite. Have. Further, the graphite skeleton itself is made of an extruded product and has anisotropy, so that there is a difference in thermal conductivity between the extrusion direction and the orthogonal direction. The thermal conductivity of the porous graphitized extruded product itself is 150 W / mK or more in the extrusion direction and 80 W / mK or more in the orthogonal direction. Therefore, regardless of the type of metal to be impregnated, the thermal conductivity of the composite material is 250 W / mK or more in the extrusion direction, and can exhibit a thermal conductivity of 150 W / mK or more in the orthogonal direction. Furthermore, as a feature of the present invention, the thermal conductivity of the graphite / metal composite is further improved by heat treatment.
各黒鉛／金属複合材の熱処理前後の熱伝導率を以下の表３にまとめて示す。
(2) 熱膨張率
本発明の黒鉛／金属複合材は、骨格が多孔質黒鉛化押出成形体からなるので、全体的に黒鉛の熱膨張率に近い熱膨張率を有する。また黒鉛骨格は押出成形体からなるので、押出方向とその直交方向とで熱膨張率に差がある。多孔質黒鉛化押出成形体自体の熱膨張率は押出方向で3.0×10-6／K以下であり、その直交方向で4.0×10-6／K以下である。そのため、含浸する金属の種類に応じて多少異なるが、複合材の熱膨張率は押出方向で4.0×10-6／K未満であり、その直交方向で10×10-6／K以下の低熱膨張率を発揮できる。さらに本発明の特徴として、黒鉛／金属複合材は熱処理を施すことにより熱膨張率がさらに低下する。
(2) Coefficient of thermal expansion The graphite / metal composite of the present invention has a coefficient of thermal expansion generally close to that of graphite because the skeleton is made of a porous graphitized extruded product. Further, since the graphite skeleton is made of an extruded product, there is a difference in the coefficient of thermal expansion between the extrusion direction and the orthogonal direction. The thermal expansion coefficient of the porous graphitized extrudate itself is less 3.0 × 10 -6 / K in the extrusion direction is less that in the orthogonal direction 4.0 × 10 -6 / K. Therefore, although it varies somewhat depending on the type of metal to be impregnated, the thermal expansion coefficient of the composite material is less than 4.0 × 10 −6 / K in the extrusion direction, and low thermal expansion of 10 × 10 −6 / K or less in the orthogonal direction. The rate can be demonstrated. Further, as a feature of the present invention, the thermal expansion coefficient of the graphite / metal composite material is further lowered by performing a heat treatment.
各黒鉛／金属複合材の熱処理前後の熱膨張率と寸法変化率を以下の表４にまとめて示す。
(3) 熱膨張の熱履歴
熱処理前の黒鉛／金属複合材の熱膨張は熱履歴を有する。すなわち、熱処理前の黒鉛／金属複合材を加熱すると、黒鉛／金属複合材は熱膨張するが、加熱冷却後、室温で元のサイズに戻らず、寸法安定性に劣るという欠点がある。ところが、本発明の熱処理を施すと、寸法変化率が著しく低減することが分かった。寸法安定性に優れていると、黒鉛／金属複合材を放熱基板として使用した場合に半田やろう付けの熱を受けても、寸法の変化が実質的になく、放熱基板が反ったり、半導体素子又はレーザ素子等の発熱素子に不要な応力がかかったりすることがない。
(3) Thermal history of thermal expansion The thermal expansion of the graphite / metal composite before heat treatment has a thermal history. That is, when the graphite / metal composite material before heat treatment is heated, the graphite / metal composite material thermally expands, but after heating and cooling, it does not return to its original size at room temperature and has a disadvantage of poor dimensional stability. However, it has been found that when the heat treatment of the present invention is applied, the dimensional change rate is significantly reduced. Excellent dimensional stability means that when a graphite / metal composite is used as a heat dissipation board, even if it receives heat from soldering or brazing, there is virtually no change in dimensions, and the heat dissipation board warps, Alternatively, unnecessary stress is not applied to the heating element such as a laser element.
(4) その他の性質
黒鉛／金属複合材の固有抵抗は熱処理により若干低下する。固有抵抗の低下は特に押出方向において顕著である。一般に黒鉛／金属複合材の固有抵抗は、押出方向で４μΩm以下であるのが好ましく、また直交方向で７μΩm以下であるのが好ましい。各黒鉛／金属複合材の熱処理前後の固有抵抗を以下の表５にまとめて示す。
(4) Other properties The specific resistance of graphite / metal composites is slightly reduced by heat treatment. The decrease in specific resistance is particularly remarkable in the extrusion direction. In general, the specific resistance of the graphite / metal composite material is preferably 4 μΩm or less in the extrusion direction, and preferably 7 μΩm or less in the orthogonal direction. The specific resistance before and after heat treatment of each graphite / metal composite is summarized in Table 5 below.
黒鉛／金属複合材の固有抵抗が熱処理により低下するのは、含浸金属中の酸素量が熱処理により低下するため高純度化が進むためであると推定される。含浸金属中の酸素量は金属の種類により異なる。一般に熱処理前の黒鉛／金属複合材では、アルミニウム又はその合金の場合には200〜400 ppmであり、銅又はその合金の場合には500〜1000 ppmであり、銀又はその合金の場合には200〜600 ppmであり、マグネシウム又はその合金の場合には200〜600 ppmであり、亜鉛又はその合金の場合には500〜2000 ppmである。特に銅又はその合金の場合、熱処理により酸素含有量は著しく低下する。具体的には、熱処理後の黒鉛／銅複合材の酸素含有量は400 ppm以下に低下している。 It is presumed that the specific resistance of the graphite / metal composite is lowered by the heat treatment because the oxygen content in the impregnated metal is lowered by the heat treatment, so that the purification is advanced. The amount of oxygen in the impregnated metal varies depending on the type of metal. In general, the graphite / metal composite before heat treatment is 200 to 400 ppm in the case of aluminum or its alloy, 500 to 1000 ppm in the case of copper or its alloy, and 200 in the case of silver or its alloy. ~ 600 ppm, in the case of magnesium or its alloys 200-600 ppm, and in the case of zinc or its alloys 500-2000 ppm. In particular, in the case of copper or an alloy thereof, the oxygen content is significantly reduced by heat treatment. Specifically, the oxygen content of the graphite / copper composite after the heat treatment is reduced to 400 ppm or less.
黒鉛／金属複合材のヤング率は熱処理前後でほとんど変わらず、放熱基板として使用するときに必要なレベルの面方向で５GPa以上である。また黒鉛／金属複合材の曲げ強さも熱処理前後でほとんど変わらず、放熱基板として使用するときに必要なレベルの10 MPa以上である。熱処理による高熱伝導率化、低熱膨張率化及び寸法安定性の向上は、主に溶湯鍛造時の残留歪が消滅したためであると考えられる。特にAl-Si合金を使用した場合、熱抵抗を増大させる針状組織が熱処理により粒状化することも、熱伝導率の向上に寄与していると考えられる。また銅又は銅合金を使用した場合、熱抵抗を増大させる酸素量が熱処理により減少することも、熱伝導率の向上に寄与していると考えられる。 The Young's modulus of the graphite / metal composite material hardly changes before and after the heat treatment and is 5 GPa or more in the plane direction necessary for use as a heat dissipation substrate. Further, the bending strength of the graphite / metal composite material is almost the same before and after the heat treatment, and is 10 MPa or more, which is a required level when used as a heat dissipation substrate. It is considered that the increase in thermal conductivity, lower thermal expansion coefficient and improvement in dimensional stability by heat treatment are mainly due to the disappearance of residual strain during molten forging. In particular, when an Al—Si alloy is used, it is considered that the acicular structure that increases the thermal resistance is granulated by heat treatment, which contributes to the improvement of the thermal conductivity. Moreover, when copper or copper alloy is used, it is thought that the oxygen amount that increases the thermal resistance is reduced by the heat treatment, which contributes to the improvement of the thermal conductivity.
[2] 放熱基板
放熱基板は、熱処理した黒鉛／金属複合材を所定のサイズに切り出したものである。放熱基板はヒートシンク又はヒートスプレッダー等として用いるのが好ましいが、黒鉛／金属複合材の優れた加工性により放熱フィンとヒートスプレッダーを一体化した構造とすることも可能である。半導体素子又はレーザ素子等の発熱素子を接合する面は黒鉛／金属複合材の押出方向と直交する面であるのが好ましいが、押出方向と平行な面であっても良い。
[2] Heat dissipation substrate The heat dissipation substrate is obtained by cutting a heat-treated graphite / metal composite material into a predetermined size. The heat dissipating substrate is preferably used as a heat sink or a heat spreader, but it is also possible to have a structure in which the heat dissipating fin and the heat spreader are integrated due to the excellent workability of the graphite / metal composite material. A surface to which a heating element such as a semiconductor element or a laser element is bonded is preferably a plane orthogonal to the extrusion direction of the graphite / metal composite material, but may be a plane parallel to the extrusion direction.
例えば図３に示すように、半導体素子３が接合する面が押出方向に対して垂直な放熱基板４の場合、放熱基板４の熱伝導率は厚さ方向の方が面方向より大きいので、半導体素子３の熱は素早く放熱基板４の他面に接合されたヒートシンク５に伝達される。一方、放熱基板４の熱膨張率は面方向の方が厚さ方向より大きいので、放熱基板４の面方向における熱膨張率は半導体素子３の熱膨張率とヒートシンクの熱膨張率の両方に近い。そのため、半導体素子３の動作時に放熱基板４との接合面とヒートシンクの接合面の両方に大きな熱応力がかかることがない。 For example, as shown in FIG. 3, when the surface to which the semiconductor element 3 is joined is a heat dissipation substrate 4 perpendicular to the extrusion direction, the heat conductivity of the heat dissipation substrate 4 is greater in the thickness direction than in the surface direction. The heat of the element 3 is quickly transmitted to the heat sink 5 bonded to the other surface of the heat dissipation substrate 4. On the other hand, the thermal expansion coefficient of the heat dissipation substrate 4 is larger in the thickness direction in the surface direction, and therefore, the thermal expansion coefficient in the surface direction of the heat dissipation substrate 4 is close to both the thermal expansion coefficient of the semiconductor element 3 and the heat expansion coefficient of the heat sink. . Therefore, a large thermal stress is not applied to both the bonding surface with the heat dissipation substrate 4 and the bonding surface of the heat sink during the operation of the semiconductor element 3.
また、半導体素子３を放熱基板４に接合するための半田やろう付けの際の加熱によっても、半導体素子３に大きな熱応力がかかることがない。
さらに、放熱基板の熱膨張率は面方向より厚さ方向の方が半分以下と小さいので、パッケージ作製時の加熱時に、高さ方向の膨張率が小さくなり組み立て工程において、位置決めしやすく好ましい。
Further, even when solder for joining the semiconductor element 3 to the heat dissipation substrate 4 or heating during brazing, the semiconductor element 3 is not subjected to a large thermal stress.
Furthermore, since the thermal expansion coefficient of the heat dissipation substrate is less than half in the thickness direction than in the surface direction, the expansion coefficient in the height direction is small during heating during package fabrication, and positioning is easy in the assembly process.
放熱基板の製造方法は、黒鉛／金属複合材を熱処理後に切り出すことを特徴とする。熱処理前に黒鉛／金属複合材を切削すると、寸法安定性に劣るので、半田やろう付けの際の加熱や動作時の昇温により、放熱基板の寸法が変化してしまう。そのため、寸法精度を出すために仕上げ加工が必要になったり、放熱基板接合部の信頼性が低下するという問題がある。 The manufacturing method of the heat dissipation substrate is characterized by cutting out the graphite / metal composite material after the heat treatment. If the graphite / metal composite material is cut before the heat treatment, the dimensional stability is inferior. Therefore, the dimensions of the heat dissipation substrate change due to heating during soldering or brazing or temperature rise during operation. For this reason, there is a problem that finishing is required to obtain dimensional accuracy, and the reliability of the heat dissipation substrate joint is lowered.
所定の寸法に切削加工した放熱基板の表面には、パッケージの気密性を確保するために金属層を設けるのが好ましい。通常は放熱基板の全面に金属層を設けるのが好ましいが、パッケージの気密性を確保する目的からすれば少なくとも半導体素子等を搭載する面（及び裏面）に設ければ良い。気密性としては、1×10−2 Pa・cm3/s以下のリーク量となるものであれば良い。 It is preferable to provide a metal layer on the surface of the heat dissipation board that has been cut into a predetermined dimension in order to ensure the hermeticity of the package. In general, it is preferable to provide a metal layer on the entire surface of the heat dissipation substrate, but it may be provided at least on the surface (and the back surface) on which a semiconductor element or the like is mounted for the purpose of ensuring the airtightness of the package. As the airtightness, any leakage amount of 1 × 10 −2 Pa · cm 3 / s or less may be used.
金属層の形成方法としては、CVD法、蒸着法、スパッタ法、金属ペースト印刷・焼成法、メッキ法等が挙げられる。気密性確保のために、金属層の厚さは0.5μｍ〜10μｍであるのが好ましい。メッキの場合、電界メッキより無電解メッキの方が、放熱基板の外周に均一に金属層を形成できるので好ましい。 Examples of the method for forming the metal layer include a CVD method, a vapor deposition method, a sputtering method, a metal paste printing / firing method, and a plating method. In order to ensure airtightness, the thickness of the metal layer is preferably 0.5 μm to 10 μm. In the case of plating, electroless plating is preferable to electroplating because a metal layer can be uniformly formed on the outer periphery of the heat dissipation substrate.
メッキ層としては、Ni-P、Ni-B、Cuメッキ等が好ましい。含浸金属が銅又はその合金であって、700℃以上の耐熱性が要求される場合、特に金属と拡散反応し難いNi-Bメッキが安定的であるので好ましい。これらの金属層は気密性確保だけでなく、他部品との接合用下地としても利用可能である。このような金属層を設けることにより、半導体素子のような発熱体やパッケージとの密着性が向上するので望ましい。 As the plating layer, Ni-P, Ni-B, Cu plating or the like is preferable. When the impregnated metal is copper or an alloy thereof and heat resistance of 700 ° C. or higher is required, Ni—B plating that is difficult to diffuse and react with the metal is particularly preferable because it is stable. These metal layers can be used not only for airtightness but also as a base for bonding with other components. Providing such a metal layer is desirable because adhesion to a heating element such as a semiconductor element or a package is improved.
特に含浸金属がアルミニウム又はその合金である放熱基板は大きな熱伝導率を有するとともに、シリコンや化合物半導体の熱膨張率に近い熱膨張率を有し、かつ半田付け性が良いので、接合に半田付けを用いる半導体素子用のヒートスプレッダー等に好適である。また黒鉛／アルミニウム複合材は溶湯鍛造温度及び熱処理温度が低いので、製造コストが低いという利点を有する。さらに、従来の銅、アルミニウムからなるヒートスプレッダーよりも半導体素子に近い熱膨張率を有し、かつ軽量なので、グリースなどを介したヒートスプレッダーにも好ましい。 In particular, a heat dissipation board in which the impregnated metal is aluminum or an alloy thereof has a large thermal conductivity, a thermal expansion coefficient close to that of silicon or a compound semiconductor, and good solderability. It is suitable for a heat spreader for semiconductor elements using Further, the graphite / aluminum composite material has an advantage that the manufacturing cost is low because the melt forging temperature and the heat treatment temperature are low. Furthermore, since it has a coefficient of thermal expansion closer to that of a semiconductor element than a conventional heat spreader made of copper or aluminum and is lightweight, it is also preferable for a heat spreader via grease.
また含浸金属が銅又はその合金である放熱基板は、大きな熱伝導率を有するとともに、小さい熱膨張率を有し、寸法安定性が良好である。その上、比較的高融点の銅で含浸されているので耐熱性が高く、ろう付け温度でも変化しない。そのため、銀ろうを用いたろう付けを行うレーザ素子の放熱を含む光通信用パッケージ等の用途に好適である。 Moreover, the heat dissipation board | substrate whose impregnation metal is copper or its alloy has a small thermal expansion coefficient while having a large thermal conductivity, and its dimensional stability is favorable. In addition, since it is impregnated with a relatively high melting point copper, it has high heat resistance and does not change even at a brazing temperature. Therefore, it is suitable for uses such as an optical communication package including heat radiation of a laser element that is brazed using silver brazing.
また、締結用の貫通孔を有する放熱基板の場合は、この貫通孔に金属のパイプ部材を嵌合すると、補強部材として働き、高い締結トルクをかけてもクラックなどの損傷を防止することができ、高い締め付けトルクを得ることができる。また、金属パイプ部材は貫通孔周辺に集中する熱応力を分散させる熱伝導部材としても働き、放熱基板としての効果も高くなる。 In addition, in the case of a heat dissipation board having a fastening through-hole, when a metal pipe member is fitted into the through-hole, it works as a reinforcing member and can prevent damage such as cracks even when a high fastening torque is applied. High tightening torque can be obtained. Further, the metal pipe member also functions as a heat conduction member that disperses the thermal stress concentrated around the through hole, and the effect as a heat dissipation substrate is enhanced.
含浸金属が銀又はその合金である放熱基板は、大きな熱伝導率を有するとともにアルミニウムと銅の間の融点を有する銀で含浸されているので、900℃程度の耐熱性が必要とされる用途に好適である。 The heat dissipation substrate whose impregnated metal is silver or an alloy thereof is impregnated with silver having a large thermal conductivity and a melting point between aluminum and copper, so that the heat resistance of about 900 ° C. is required. Is preferred.
含浸金属がマグネシウム又はその合金である放熱基板は、アルミニウムと銀の間の融点を有するマグネシウムで含浸されているので、アルミニウムより高い耐熱性が必要となる部品に好適である。 The heat dissipation substrate in which the impregnated metal is magnesium or an alloy thereof is impregnated with magnesium having a melting point between aluminum and silver, and thus is suitable for a component that requires higher heat resistance than aluminum.
含浸金属が亜鉛又はその合金である放熱基板は、アルミニウム、銅、銀、マグネシウム等が含浸された基板より大きな熱膨張率を有するので、アルミニウムや銅等のヒートシンク等と接合される場合のように、大きな熱膨張率を有する部材に接合する用途に好適である。また含浸温度が低いので、コスト的にも有利である。 A heat dissipation substrate whose impregnated metal is zinc or an alloy thereof has a larger coefficient of thermal expansion than a substrate impregnated with aluminum, copper, silver, magnesium, etc., so that it is joined with a heat sink such as aluminum or copper. It is suitable for use in joining to a member having a large coefficient of thermal expansion. Further, since the impregnation temperature is low, it is advantageous in terms of cost.
本発明を以下の実施例によりさらに詳細に説明するが、本発明はそれらに限定されるものではない。 The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto.
実施例１
平均粒径500μｍのコークス粒子とピッチとの溶融混練物を押出成形し、黒鉛化してなる多孔質黒鉛化押出成形体（嵩比重：1.70、灰分0.3質量％、押出方向及び押出方向と直交する方向における固有抵抗がそれぞれ5.0μΩｍ及び8.5μΩｍ、押出方向及び押出方向と直交する方向における熱膨張係数がそれぞれ0.6×10−６／K及び2.0×10−６／K、押出方向及び押出方向と直交する方向における熱伝導率がそれぞれ230 W/mK及び120 W/mK）と、12質量％のSiを含有するAl-Si合金とを用いて、下記の条件により黒鉛／Al-Si複合材を製造した。
Example 1
A porous graphitized extruded product obtained by extruding and graphitizing a melt-kneaded product of coke particles having an average particle diameter of 500 μm and pitch (bulk specific gravity: 1.70, ash content of 0.3% by mass, direction of extrusion and direction orthogonal to the direction of extrusion) Specific resistance is 5.0 μΩm and 8.5 μΩm, respectively, and thermal expansion coefficients in the extrusion direction and the direction orthogonal to the extrusion direction are 0.6 × 10 −6 / K and 2.0 × 10 −6 / K, respectively, and are orthogonal to the extrusion direction and the extrusion direction. The graphite / Al-Si composite was manufactured under the following conditions using an Al-Si alloy having a thermal conductivity in the direction of 230 W / mK and 120 W / mK, respectively, and 12 mass% of Si. .
まず図１(a) に示す金型装置（750℃に保持）のキャビティ内に上記多孔質黒鉛化押出成形体を載置し、上記Al-Si合金の溶湯（750℃）を注入した後で、上パンチを押し下げて、100 MPaで５分間溶湯鍛造を行った。余分のAl-Si合金を切削により除去することにより黒鉛／Al-Si複合材を得た。この黒鉛／Al-Si複合材に対して下記条件で熱処理を行った。
昇温速度：２℃／分
保持条件：500℃×60分
冷却速度：２℃／分
First, after placing the porous graphitized extrudate in the cavity of the mold apparatus (held at 750 ° C) shown in Fig. 1 (a) and pouring the molten Al-Si alloy (750 ° C). The upper punch was pushed down, and the molten metal was forged at 100 MPa for 5 minutes. Excess Al-Si alloy was removed by cutting to obtain a graphite / Al-Si composite. The graphite / Al—Si composite material was heat-treated under the following conditions.
Temperature rising rate: 2 ° C / min Holding condition: 500 ° C x 60 minutes Cooling rate: 2 ° C / min
熱処理後の黒鉛／Al-Si複合材を40.0 mm×20.0 mm×2.0 mmのサイズに切り出し、放熱基板用サンプルとした。なお放熱基板の厚さ方向は複合材の押出方向と一致させた。 The heat-treated graphite / Al-Si composite material was cut into a size of 40.0 mm x 20.0 mm x 2.0 mm, and used as a heat dissipation substrate sample. The thickness direction of the heat radiating substrate was matched with the extrusion direction of the composite material.
熱処理前後の黒鉛／Al-Si複合材のサンプルに対して、Al-Si合金の含有量、Al-Si合金のSiリッチ相のうちの針状組織の含有量、嵩密度、熱伝導率、熱膨張率、固有抵抗、弾性率（ヤング率）、曲げ強度、及び寸法変化率を下記方法により測定した。測定結果を下記表６に示す。 For graphite / Al-Si composite samples before and after heat treatment, the content of Al-Si alloy, the content of needle-like structure in the Si-rich phase of Al-Si alloy, bulk density, thermal conductivity, heat The expansion coefficient, specific resistance, elastic modulus (Young's modulus), bending strength, and dimensional change rate were measured by the following methods. The measurement results are shown in Table 6 below.
(1) 嵩密度は、見掛けの単位体積当たりの重量とした。
(2) 熱伝導率は、JIS R 1611に基づきアルバック理工（株）製のTC-7000H型レーザフラッシュ法熱定数測定装置により測定した。
(3) 熱膨張率及び寸法変化率は、セイコーインスツルメンツ（株）製のEXSTAR6000熱分析システムによる熱機械分析装置により測定した。
(4) 固有抵抗は、アルバック理工（株）製のZEM-2を使用して、４端子法により測定した。
(5) ヤング率は、シンクアラウンドユニットUVM-2及びデジタルオシロスコープを用い、超音波の透過波を受信する二探触子法により測定した。
(6) 曲げ強度は、JIS R 1601に基づき（株）島津製作所製のオートグラフAG-G型を用い、３点曲げ試験法により測定した。
(1) The bulk density was the weight per apparent unit volume.
(2) The thermal conductivity was measured with a TC-7000H laser flash method thermal constant measuring device manufactured by ULVAC-RIKO, based on JIS R 1611.
(3) The coefficient of thermal expansion and the rate of dimensional change were measured by a thermomechanical analyzer using an EXSTAR6000 thermal analysis system manufactured by Seiko Instruments Inc.
(4) The specific resistance was measured by the 4-terminal method using ZEM-2 manufactured by ULVAC-RIKO.
(5) Young's modulus was measured by a two-probe method using a sink-around unit UVM-2 and a digital oscilloscope to receive ultrasonic transmitted waves.
(6) The bending strength was measured by a three-point bending test method using an autograph AG-G type manufactured by Shimadzu Corporation based on JIS R 1601.
比較例１
下記条件で熱処理を行った以外実施例１と同様にして黒鉛／Al-Si複合材を作製し、評価した。結果を下記表６に示す。
昇温速度：２℃／分
保持条件：150℃×60分
冷却速度：２℃／分
Comparative Example 1
A graphite / Al—Si composite was prepared and evaluated in the same manner as in Example 1 except that heat treatment was performed under the following conditions. The results are shown in Table 6 below.
Temperature rising rate: 2 ° C / min Holding conditions: 150 ° C x 60 minutes Cooling rate: 2 ° C / min
表６から明らかなように、熱処理により黒鉛／Al-Si複合材の熱伝導率は増大し、熱膨張率、寸法変化率は著しく減少した。また抵抗、ヤング率及び曲げ強度については、熱処理の前後でほとんど変化はなかった。以上の結果から、熱処理により黒鉛／Al-Si複合材は放熱基板として望ましい性能を獲得したと言うことができる。一方比較例１では、熱伝導率、熱膨張率及び寸法変化率が熱処理前とほとんど変わらなかった。 As is clear from Table 6, the thermal conductivity of the graphite / Al—Si composite increased with the heat treatment, and the thermal expansion coefficient and dimensional change rate decreased significantly. Further, the resistance, Young's modulus and bending strength were almost unchanged before and after the heat treatment. From the above results, it can be said that the graphite / Al—Si composite material has achieved desirable performance as a heat dissipation substrate by heat treatment. On the other hand, in Comparative Example 1, the thermal conductivity, thermal expansion coefficient, and dimensional change rate were almost the same as before heat treatment.
熱処理前後の黒鉛／Al-Si複合材からなるサンプルについて、Al-Si部分の組織を日立製作所（株）製の走査イオン顕微鏡（SIM）FB-2000Aを用いて観察した。SIM写真を図４に示す。図４の(a) から明らかなように、熱処理前の黒鉛／Al-Si複合材からなるサンプルでは、Siリッチ相からなる針状組織が析出していた。これに対して、図４の(b) から明らかなように、熱処理後の黒鉛／Al-Si複合材からなるサンプルでは、針状組織は球状化していた。本実施例では、珪素リッチ相のうち、長径が30μｍ以下、アスペクト比（長径／短径）が10以上の針状組織の割合（顕微鏡写真における面積率）は５％に減少していた。Siリッチ相は低熱伝導なので、球状化することにより熱抵抗が減少し、熱伝導率の向上に寄与していると推定される。珪素リッチ相のうち、長径が30μｍ以下でアスペクト比が10以上の針状組織の面積率が10％以下、特に5％以下となると、熱伝導率が著しく増大することが分かった。 About the sample which consists of a graphite / Al-Si composite material before and behind heat processing, the structure | tissue of the Al-Si part was observed using the Hitachi, Ltd. scanning ion microscope (SIM) FB-2000A. A SIM photograph is shown in FIG. As apparent from FIG. 4 (a), in the sample made of the graphite / Al—Si composite material before the heat treatment, an acicular structure made of the Si-rich phase was precipitated. On the other hand, as apparent from FIG. 4B, in the sample made of the graphite / Al—Si composite material after the heat treatment, the acicular structure was spheroidized. In this example, the ratio (area ratio in the micrograph) of the acicular structure having a major axis of 30 μm or less and an aspect ratio (major axis / minor axis) of 10 or more in the silicon-rich phase was reduced to 5%. Since the Si-rich phase has low thermal conductivity, it is estimated that spheroidizing reduces thermal resistance and contributes to improvement in thermal conductivity. It has been found that the thermal conductivity increases remarkably when the area ratio of a needle-like structure having a major axis of 30 μm or less and an aspect ratio of 10 or more in the silicon-rich phase is 10% or less, particularly 5% or less.
熱処理前後の黒鉛／Al-Si複合材からなるサンプルについて、室温から500℃まで加熱した後、放冷し、それぞれ押出方向及び直交方向における熱膨張の履歴を測定した。結果を図５及び６に示す。図５(a) 及び図６(a) から明らかなように、熱処理前の黒鉛／Al-Si複合材は、熱履歴後に押出方向で0.18％、直交方向で0.32％の寸法変化率を示した。一方、図５(b) 及び図６(b) から明らかなように、熱処理後の黒鉛／Al-Si複合材では、熱履歴後に押出方向及び直交方向のいずれでも寸法変化率は僅か0.01％であり、寸法変化は実質的になかったことが分かる。以上の結果から、金属含浸後に熱処理してなる本発明の黒鉛／Al-Si複合材は、熱履歴後でも寸法変化が少なく、寸法安定性に優れていることが分かる。 About the sample which consists of a graphite / Al-Si composite material before and behind heat processing, after heating from room temperature to 500 degreeC, it stood to cool, and the log | history of the thermal expansion in an extrusion direction and an orthogonal direction was measured, respectively. The results are shown in FIGS. As is clear from FIGS. 5 (a) and 6 (a), the graphite / Al—Si composite material before heat treatment exhibited a dimensional change rate of 0.18% in the extrusion direction and 0.32% in the orthogonal direction after the heat history. . On the other hand, as is clear from FIGS. 5 (b) and 6 (b), the heat-treated graphite / Al-Si composite has a dimensional change rate of only 0.01% in both the extrusion direction and the orthogonal direction after the thermal history. It can be seen that there was virtually no dimensional change. From the above results, it can be seen that the graphite / Al—Si composite material of the present invention, which is heat-treated after metal impregnation, has little dimensional change even after heat history and is excellent in dimensional stability.
実施例２
実施例１に用いたのと同じ多孔質黒鉛化押出成形体と、純銅（純度99.9％以上）とを用いて、下記のように黒鉛／銅複合材を製造した。まず図１(a) に示す金型装置（1000℃に保持）のキャビティ内に上記多孔質黒鉛化押出成形体を載置し、上記純銅の溶湯（1350℃）を注入した後で、上パンチを押し下げて、100 MPaで５分間溶湯鍛造を行った。余分の純銅を切削により除去することにより黒鉛／銅複合材を得た。この黒鉛／銅複合材に対して、下記条件で熱処理を行った。
昇温速度：５℃／分
保持条件：900℃×120分
冷却速度：５℃／分
Example 2
Using the same porous graphitized extrudate as used in Example 1 and pure copper (purity 99.9% or more), a graphite / copper composite was produced as follows. First, the porous graphitized extrudate is placed in the cavity of the mold apparatus (maintained at 1000 ° C.) shown in FIG. 1 (a), and the above-described pure copper molten metal (1350 ° C.) is poured into the upper punch. Was pushed down and forged for 5 minutes at 100 MPa. Excess pure copper was removed by cutting to obtain a graphite / copper composite. This graphite / copper composite was heat-treated under the following conditions.
Temperature increase rate: 5 ° C / min Holding conditions: 900 ° C x 120 minutes Cooling rate: 5 ° C / min
熱処理後の黒鉛／銅複合材を40.0 mm×20.0 mm×2.0 mmのサイズに切り出し、放熱基板用サンプルとした。なお放熱基板の厚さ方向は複合材の押出方向と一致していた。各サンプルに対して、実施例１と同様にして、銅の含有量、嵩密度、熱伝導率、熱膨張率、寸法変化率（加熱・放冷した後の寸法変化率）、固有抵抗、弾性率（ヤング率）、曲げ強度、及び銅中の酸素量を測定した。測定結果を下記表７に示す。 The heat-treated graphite / copper composite material was cut into a size of 40.0 mm × 20.0 mm × 2.0 mm, and used as a heat dissipation substrate sample. The thickness direction of the heat radiating substrate coincided with the extrusion direction of the composite material. For each sample, in the same manner as in Example 1, the copper content, bulk density, thermal conductivity, thermal expansion coefficient, dimensional change rate (dimensional change rate after heating / cooling), specific resistance, elasticity The rate (Young's modulus), bending strength, and oxygen content in copper were measured. The measurement results are shown in Table 7 below.
参考例１
多孔質黒鉛化押出成形体（嵩比重：1.58、灰分0.7質量％、押出方向及び押出方向と直交する方向における固有抵抗がそれぞれ9.0μΩｍ及び9.5μΩｍ、押出方向及び押出方向と直交する方向における熱膨張係数がそれぞれ4.0×10−６／K及び4.2×10−６／K、押出方向及び押出方向と直交する方向における熱伝導率がそれぞれ130 W/mK及び80 W/mK）を用いた以外実施例２と同様にして、黒鉛／銅複合材を製造し、実施例２と同じ測定を行った。測定結果を下記表７に示す。
Reference example 1
Porous graphitized extrudate (bulk specific gravity: 1.58, ash content 0.7% by mass, specific resistance in extrusion direction and direction orthogonal to extrusion direction is 9.0μΩm and 9.5μΩm, respectively, thermal expansion in extrusion direction and direction orthogonal to extrusion direction Examples except that the coefficients are 4.0 × 10 −6 / K and 4.2 × 10 −6 / K, respectively, and the thermal conductivities in the extrusion direction and the direction orthogonal to the extrusion direction are 130 W / mK and 80 W / mK, respectively. In the same manner as in Example 2, a graphite / copper composite material was produced, and the same measurement as in Example 2 was performed. The measurement results are shown in Table 7 below.
表７から明らかなように、熱処理により黒鉛／銅複合材の熱伝導率は若干増大するとともに、熱膨張率は著しく減少した。また抵抗、ヤング率及び曲げ強度については、熱処理の前後でほとんど変化はなかった。以上の結果から、熱処理により黒鉛／銅複合材は放熱基板として望ましい性能を獲得したと言うことができる。一方参考例１では、寸法変化率が熱処理により低減されたが、熱処理後でも熱伝導率が低く、熱膨張率は大きかった。
As is apparent from Table 7, the heat conductivity of the graphite / copper composite slightly increased and the coefficient of thermal expansion significantly decreased by the heat treatment. Further, the resistance, Young's modulus and bending strength were almost unchanged before and after the heat treatment. From the above results, it can be said that the graphite / copper composite has obtained desirable performance as a heat dissipation substrate by heat treatment. On the other hand, in Reference Example 1 , the dimensional change rate was reduced by the heat treatment, but even after the heat treatment, the thermal conductivity was low and the thermal expansion coefficient was large.
熱処理前後の黒鉛／銅複合材からなるサンプルについて、銅部分を走査イオン顕微鏡（SIM）により観察した。SIM写真を図７に示す。図７の(a) から明らかなように、熱処理前の黒鉛／銅複合材からなるサンプルでは、銅相は典型的な鋳造組織を呈していた。これに対して、図７の(b) から明らかなように、熱処理後の黒鉛／銅複合材からなるサンプルでは、銅相は等軸晶に変化していた。また酸素量が著しく減少していた。熱抵抗を増大させる酸素量の低減は熱伝導率の向上をもたらしたと推定される。 About the sample which consists of a graphite / copper composite material before and behind heat processing, the copper part was observed with the scanning ion microscope (SIM). A SIM photograph is shown in FIG. As apparent from FIG. 7 (a), in the sample made of the graphite / copper composite material before the heat treatment, the copper phase exhibited a typical cast structure. On the other hand, as apparent from FIG. 7 (b), in the sample made of the graphite / copper composite material after the heat treatment, the copper phase was changed to equiaxed crystals. In addition, the amount of oxygen was significantly reduced. It is estimated that the reduction in the amount of oxygen that increases the thermal resistance resulted in an improvement in thermal conductivity.
熱処理前後の黒鉛／銅複合材からなるサンプルについて、室温から900℃まで加熱した後、放冷し、それぞれ押出方向及び直交方向における熱膨張の履歴を測定した。結果を図８及び図９に示す。図８(a) 及び図９(a) から明らかなように、熱処理前の黒鉛／銅複合材では冷却後に押出方向、直交方向がそれぞれ0.35％及び0.40％の寸法変化率であったが、図８(b) 及び図９(b) から明らかなように、熱処理後の黒鉛／銅複合材では押出方向、直交方向それぞれ0.02％及び0.01％の寸法変化率となり、寸法変化は実質的になかった。これから、本発明の黒鉛／銅複合材は加熱されても寸法変化が小さく、寸法安定性に優れていることが分かる。 About the sample which consists of a graphite / copper composite material before and behind heat processing, after heating from room temperature to 900 degreeC, it stood to cool, and the log | history of the thermal expansion in an extrusion direction and an orthogonal direction was measured, respectively. The results are shown in FIGS. As is clear from FIGS. 8 (a) and 9 (a), the graphite / copper composite before heat treatment had dimensional change rates of 0.35% and 0.40% in the extrusion direction and the orthogonal direction after cooling, respectively. As is clear from FIG. 8 (b) and FIG. 9 (b), the graphite / copper composite after the heat treatment had a dimensional change rate of 0.02% and 0.01% in the extrusion direction and the orthogonal direction, respectively, and there was substantially no dimensional change. . From this, it can be seen that the graphite / copper composite of the present invention has a small dimensional change even when heated, and is excellent in dimensional stability.
実施例３
実施例１に用いたのと同じ多孔質黒鉛化押出成形体（嵩比重：1.70、灰分0.3質量％、押出方向及び押出方向と直交する方向における固有抵抗がそれぞれ5.0μΩｍ及び8.5μΩｍ、押出方向及び押出方向と直交する方向における熱膨張係数がそれぞれ0.6×10−６／K及び2.0×10−６／K、押出方向及び押出方向と直交する方向における熱伝導率がそれぞれ230 W/mK及び120 W/mK）と、70質量％のCu及び30質量％のZnからなる黄銅を用いて、下記の条件により黒鉛／黄銅複合材を製造した。
Example 3
The same porous graphitized extruded product used in Example 1 (bulk specific gravity: 1.70, ash content 0.3% by mass, specific resistance in the extrusion direction and direction orthogonal to the extrusion direction is 5.0 μΩm and 8.5 μΩm, respectively, The thermal expansion coefficients in the direction orthogonal to the extrusion direction are 0.6 × 10 −6 / K and 2.0 × 10 −6 / K, respectively, and the thermal conductivities in the extrusion direction and the direction orthogonal to the extrusion direction are 230 W / mK and 120 W, respectively. / mK), and a brass made of 70% by mass of Cu and 30% by mass of Zn, a graphite / brass composite material was manufactured under the following conditions.
まず図１(a) に示す金型装置（1000℃に保持）のキャビティ内に上記黒鉛を載置し、上記黄銅の溶湯（1350℃）を注入した後で、上パンチを押し下げて、100 MPaで５分間溶湯鍛造を行った。余分の純銅を切削により除去することにより黒鉛／黄銅複合材を得た。この黒鉛／黄銅複合材に対して下記条件で熱処理を行った。
昇温速度：５℃／分
保持条件：900℃×120分
冷却速度：５℃／分
First, the graphite is placed in the cavity of the mold apparatus (maintained at 1000 ° C) shown in Fig. 1 (a), the molten brass (1350 ° C) is injected, and the upper punch is pushed down to 100 MPa. And forged the melt for 5 minutes. Excess pure copper was removed by cutting to obtain a graphite / brass composite material. This graphite / brass composite material was heat-treated under the following conditions.
Temperature increase rate: 5 ° C / min Holding conditions: 900 ° C x 120 minutes Cooling rate: 5 ° C / min
得られた黒鉛／黄銅複合材のサンプルに対して、実施例１と同様にして、黄銅の含有量、嵩密度、熱伝導率、熱膨張率、寸法変化率（加熱・放冷した後の寸法変化率）、固有抵抗、ヤング率、曲げ強度、及び黄銅中の酸素量を測定した。測定結果を下記表８に示す。 For the obtained graphite / brass composite sample, the brass content, bulk density, thermal conductivity, thermal expansion coefficient, dimensional change rate (dimensions after heating / cooling) in the same manner as in Example 1. Change rate), specific resistance, Young's modulus, bending strength, and oxygen content in brass. The measurement results are shown in Table 8 below.
比較例２
下記条件で熱処理を行った以外実施例３と同様にして黒鉛／黄銅複合材を作製し、測定した。結果を表８に示す。
昇温速度：５℃／分
保持条件：250℃×120分
Comparative Example 2
A graphite / brass composite material was prepared and measured in the same manner as in Example 3 except that heat treatment was performed under the following conditions. The results are shown in Table 8.
Temperature increase rate: 5 ° C / min Holding conditions: 250 ° C x 120 minutes
実施例４
表６に示す実施例１の黒鉛／Al-Si合金複合体（熱処理後）から切り出してなる40.0 mm×20.0 mm×2.0 mmの放熱基板の表面に、ジンケート処理後無電解Ni-Pメッキを施した。また表７に示す実施例２の黒鉛／Cu複合体（熱処理後）から切り出してなる40.0 mm×20.0 mm×2.0 mmの放熱基板の表面に、無電解Ni-Bメッキを施した。各メッキ済放熱基板に対して、メッキ層の有無と気密性との相関を評価するために、
JIS C 7021 A-6に基づき、日本真空製のヘリウムリークディテクターDLMS-33型を用い、メッキ済放熱基板を貫通するヘリウムガスの量を測定した。メッキ済放熱基板を貫通するヘリウムガスの量をリーク量として、気密性のパラメータとした。結果を下記表９に示す。
Example 4
Electroless Ni-P plating after zincate treatment was applied to the surface of a 40.0 mm x 20.0 mm x 2.0 mm heat dissipation board cut out from the graphite / Al-Si alloy composite of Example 1 shown in Table 6 (after heat treatment). did. Further, electroless Ni—B plating was applied to the surface of a 40.0 mm × 20.0 mm × 2.0 mm heat dissipation substrate cut out from the graphite / Cu composite (after heat treatment) of Example 2 shown in Table 7. In order to evaluate the correlation between the presence of the plating layer and airtightness for each plated heat dissipation board,
Based on JIS C 7021 A-6, a helium leak detector model DLMS-33 made by Nippon Vacuum was used to measure the amount of helium gas penetrating the plated heat dissipation substrate. The amount of helium gas penetrating through the plated heat dissipation substrate was taken as the leak amount and used as an airtight parameter. The results are shown in Table 9 below.
黒鉛／Al-12Si及び黒鉛／Cuのいずれも、メッキを施すことにより気密性が著しく向上することが分かった。なおメッキ厚さが0.5μｍ未満だと十分な気密性が得られない。また20μｍを超えると残留応力の増大により、メッキ膜が剥離する。なお黒鉛／Al-12Si複合体等は、Al蒸着膜も密着力が高くなり好ましい。また黒鉛／Cu複合体等は、Agペーストを印刷したのち、900℃で焼成した膜を形成しても良い。この場合、膜応力が低いので、膜厚は30μｍ程度でもよい。 It was found that the airtightness of graphite / Al-12Si and graphite / Cu was remarkably improved by plating. If the plating thickness is less than 0.5 μm, sufficient airtightness cannot be obtained. On the other hand, if the thickness exceeds 20 μm, the plating film peels off due to an increase in residual stress. In addition, graphite / Al-12Si composite is preferable because the Al deposited film also has high adhesion. The graphite / Cu composite or the like may form a film fired at 900 ° C. after printing an Ag paste. In this case, since the film stress is low, the film thickness may be about 30 μm.
実施例５
本発明の黒鉛／金属複合材（Cu）を半導体素子搭載用モジュールに用いた例を図10に示す。図の半導体素子搭載用モジュールは、縦100 mm×横100 mm×厚さ2 mmの黒鉛／Cu複合体からなる放熱基板4aと、縦30 mm×横30 mm×厚さ0.8 mmの窒化珪素基板からなる絶縁基板６と、ヒートシンク５とからなる。
Example 5
An example in which the graphite / metal composite material (Cu) of the present invention is used in a module for mounting a semiconductor element is shown in FIG. The module for mounting a semiconductor device shown in the figure is a heat dissipation substrate 4a made of graphite / Cu composite of length 100 mm x width 100 mm x thickness 2 mm, and silicon nitride substrate 30 mm long x 30 mm wide x 0.8 mm thick The insulating substrate 6 is made of a heat sink 5.
放熱基板4aと絶縁基板６をろう付けし、絶縁基板６にNiメッキを施した後、10 mm×10mmの半導体チップ３を絶縁基板６にはんだ付けした。また、放熱基板4aとヒートシンク５は高熱伝導グリースを介してボルト等で機械的に締結しモジュールとした。 The heat radiating substrate 4a and the insulating substrate 6 were brazed, and the insulating substrate 6 was plated with Ni, and then the 10 mm × 10 mm semiconductor chip 3 was soldered to the insulating substrate 6. Further, the heat radiating board 4a and the heat sink 5 were mechanically fastened with bolts or the like via high thermal conductive grease to form a module.
放熱基板4aは黒鉛／Cu複合体からなるが、ここではCrを1.0質量％含有するクロム銅合金に含浸し、基板の厚み方向の熱伝導率が250W/mK以上、熱膨張係数が0.1×10−６／Kより大きく４×10−６／K未満、厚み方向と直交する方向（素子搭載面側）の熱伝導率が150W/mK以上、熱膨張係数が４×10−６／K以上、10×10−６／K以下の放熱基板4aとした。 The heat dissipation substrate 4a is made of a graphite / Cu composite. Here, a chromium copper alloy containing 1.0% by mass of Cr is impregnated, the thermal conductivity in the thickness direction of the substrate is 250 W / mK or more, and the thermal expansion coefficient is 0.1 × 10. Greater than −6 / K and less than 4 × 10 −6 / K, thermal conductivity in the direction perpendicular to the thickness direction (element mounting surface side) is 150 W / mK or more, thermal expansion coefficient is 4 × 10 −6 / K or more, The heat dissipation board 4a was 10 × 10 −6 / K or less.
この例の半導体モジュールの放熱特性の評価を行った。放熱特性は、通電時の半導体チップの表面温度と半導体チップ３とヒートシンク５の裏面との間の熱抵抗（℃／Ｗ）を測定し、さらに−40℃〜125℃までの昇降温試験を3000サイクル行った後の半導体チップ３とヒートシンク５の裏面との間の熱抵抗を測定した。尚、3000サイクルの温度サイクル試験後の熱抵抗は温度サイクル試験前の熱抵抗からの上昇率で示した。 The heat dissipation characteristics of the semiconductor module of this example were evaluated. For the heat dissipation characteristics, the surface temperature of the semiconductor chip during energization and the thermal resistance (° C / W) between the semiconductor chip 3 and the back surface of the heat sink 5 were measured, and a temperature increase / decrease test from -40 ° C to 125 ° C was measured. The thermal resistance between the semiconductor chip 3 after cycling and the back surface of the heat sink 5 was measured. The thermal resistance after the 3000-cycle temperature cycle test is shown by the rate of increase from the thermal resistance before the temperature cycle test.
その結果、半導体素子表面温度は52.1℃、熱抵抗は0.23℃／Ｗ、サイクル試験後上昇率は2.5％という特性が得られ、従来に比べて、半導体素子の表面温度および熱抵抗は総じて低くなり、サイクル試験後の上昇率も小さくなった。 As a result, the surface temperature of the semiconductor element was 52.1 ° C, the thermal resistance was 0.23 ° C / W, and the rate of increase after the cycle test was 2.5%. The surface temperature and thermal resistance of the semiconductor element were generally lower than before. The rate of increase after the cycle test was also reduced.
また、本発明の黒鉛／金属複合材を放熱基板4aに用いる場合、上記実施例のようにヒートシンク５との締結のために放熱基板4aに貫通孔40を設けることがある。このとき、貫通孔40の内周部に金属パイプ部材7を嵌合することが望ましい。パイプ部材7の形状は、貫通孔40の内周面に嵌合されるものであれば特に制限されるものではなく、図12(a)及び(b)のような形状、又は図12(c)のように鍔70があっても良い。両端部に鍔70があると貫通孔40を起点とするクラックの発生をより抑制することができるので好ましい。鍔70を一方の端部のみに形成する場合には、ボルト頭部が接触する側に形成する。 Further, when the graphite / metal composite material of the present invention is used for the heat dissipation substrate 4a, a through hole 40 may be provided in the heat dissipation substrate 4a for fastening with the heat sink 5 as in the above embodiment. At this time, it is desirable to fit the metal pipe member 7 to the inner peripheral portion of the through hole 40. The shape of the pipe member 7 is not particularly limited as long as it can be fitted to the inner peripheral surface of the through hole 40. The shape shown in FIGS. 12 (a) and 12 (b), or FIG. ) As in). It is preferable that there are ridges 70 at both ends because cracks starting from the through hole 40 can be further suppressed. When the collar 70 is formed only on one end, it is formed on the side where the bolt head contacts.
さらには、図12(d)のようにスリット71入り、図12(e)のようにノッチ72入りのパイプ部材7とすることもできる。このようなスリット71やノッチ72が入っていると円周方向で弾性変形が可能となるのでパイプ部材７を貫通孔40に容易に嵌合することができる。また、スリット71やノッチ72は、基板の加熱に伴うパイプ部材７の膨張による基板への負荷を緩衝する役割も有する。このようなパイプ部材７は冷熱サイクル、はんだリフロー工程に対して十分な耐久性がある。また、パイプ部材７と基板の界面をろう材などを用い金属接合することにより、密着性が向上し、より放熱性を向上させることができるので好ましい。 Furthermore, the pipe member 7 can be made into the slit 71 as shown in FIG. 12 (d) and the notch 72 as shown in FIG. 12 (e). When such slits 71 and notches 72 are included, elastic deformation is possible in the circumferential direction, so that the pipe member 7 can be easily fitted into the through hole 40. Further, the slit 71 and the notch 72 also have a role of buffering a load on the substrate due to expansion of the pipe member 7 accompanying heating of the substrate. Such a pipe member 7 has sufficient durability against a cooling / heating cycle and a solder reflow process. In addition, it is preferable to perform metal bonding at the interface between the pipe member 7 and the substrate using a brazing material or the like because adhesion can be improved and heat dissipation can be further improved.
１・・・溶湯鍛造用金型装置
２・・・取鍋
３・・・半導体素子
４・・・放熱基板（ヒートスプレッダー）
４ａ・・・放熱基板
５・・・ヒートシンク
６・・・絶縁基板（窒化珪素基板）
７・・・パイプ部材
11・・・上型
12・・・下型
13・・・下パンチ
14，16・・・プランジャー
15・・・上パンチ
20・・・多孔質黒鉛化押出成形体
21・・・黒鉛／金属複合材
M・・・溶融金属
40・・・貫通孔
71・・・スリット
72・・・ノッチ
DESCRIPTION OF SYMBOLS 1 ... Mold apparatus 2 for molten metal forging ... Ladle 3 ... Semiconductor element 4 ... Heat dissipation board (heat spreader)
4a ... heat dissipation substrate 5 ... heat sink 6 ... insulating substrate (silicon nitride substrate)
7 ... Pipe member
11 ... Upper mold
12 ... Lower mold
13 ... Bottom punch
14, 16 ... Plunger
15 ... Upper punch
20 ... Porous graphitized extruded product
21 ... Graphite / metal composite
M ... Molten metal
40 ... through hole
71 ... Slit
72 ... Notch
Claims (21)
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