JP4223730B2 - Heat sink plate - Google Patents

Description

【０００９】
本課題を達成する為、表―１に示す複合材料をさらに組合わせて使用することを考えた。熱伝導度について、例えば２種の複合材料を組合わせた場合、総括熱伝導度U（W／ｍK）は１種の熱伝導度A（W／ｍK）、その厚さX（ｍｍ）とし、他種の熱伝導度B（W／ｍK）、その厚さY（ｍｍ）とする時、
Ｕ＝（Ｘ+Ｙ）／（Ｘ／Ａ+Ｙ／Ｂ）という式が成り立つ。
【００１０】
上式のＵが４００Ｗ／ｍＫ以上になるためには少なくとも一種は10、11を採用し、他種との兼合いからその厚さを調整すれば良い訳である。例えば他種に４を選択し、その厚さを１ｍｍ、11の厚さを３ｍｍとする時、Ｕは４０８Ｗ／ｍＫとなる。別の例としては、1の厚さを１ｍｍ、10の厚さを２ｍｍとする時、Ｕは４０７Ｗ／ｍＫとなり、それぞれ熱伝導度の目標を満足する。
【００１１】
次に熱膨張率であるが、10あるいは11を使用する場合、直角方向での熱膨張率を採用せねばならない。この理由はヒートシンク板としては、熱伝導度が板の厚さ方向に良好なことが必要であるのに対して、熱膨張率は板の平面方向に関係してくるからである。
【００１２】
9、10および11は、繊維方向をヒートシンク板の厚み方向とする時、板の平面方向は、繊維の直角方向となるがその直角方向の引張強度はいずれも小さいので、例えば1と10の組合わせの場合、熱膨張は1が支配的となり熱膨張率として、１２ｐｐｍ／Ｋとなる。又、4と11の組合わせの場合は、８ｐｐｍ／Ｋとなり例えば、電気自動車などのパワーモジュール系のヒートシンク板として満足されるものとなる。
【００１３】
一方で、10と12、11と13の組合わせでは、板の平面方向の熱膨張率はそれぞれ、4.５〜4.１となり光通信用などの放熱基板として最適なものとなる。
【００１４】
【課題を解決するための手段】
本発明は、炭化珪素粒子又は立方晶窒化ほう素粒子からなる層と炭素粒子又は炭素繊維からなる層の２層から構成される無機物層に溶融金属を含浸させることによって得られるヒートシンク板を提供するものである。
【実施例】
以下、実施例によって本発明を更に具体的に説明するが、本発明はこれらの実施例に限定されるものではない。
【００１５】
【実施例１】
ピッチ系の炭素繊維をフェノール樹脂にて一方向に揃うように成形し、これを真空中で３０００℃に焼成し、１方向のグラファイト質の炭素繊維成形体を得た。このものの繊維体積率は５５％フェノール樹脂から炭化したものは１８％であった。
【００１６】
他方、炭化珪素粒子を２０００℃にて焼結した炭化珪素焼結体を体積率７２％で得た。黒鉛化炭素繊維成形体（1）と炭化珪素焼結体（4）とを繊維方向が炭化珪素板面に直角になるよに配置して図―１に示すようにそれぞれ８００℃に予熱した後、所定の金型に入れ（3、4）、その上に８００℃のJIS Ａ1050溶湯を注ぎプランジャーで圧力９８ＭＰaにて加圧し凝固完了後、黒鉛化炭素繊維と炭化珪素を強化材とするアルミニウム基複合材を得た。
【００１７】
このように得られた複合材の物性は、図―２に示すように炭素繊維の複合材層が２ｍｍ炭化珪素の複合材層が１ｍｍの厚さの加工すると、熱膨張率が４.５ｐｐｍ／K、熱伝導度が４０７W／ｍKであった。これと同様のものを図―３―１（断面図）、図―３―２（平面図）のように加工し、ヒートシンクパッケージ（14）を得た。このものは炭素繊維とアルミニウムからなる複合材層が機械加工性に優れているので、容易に加工でき、かつ、サブマウント（13）が一体成形できるので、サブマウント頂上からパッケージの最下面までの熱伝導度も極めて良好であり、かつサブマウントを基板にロー付けする必要のないものであった。
【００１８】
【実施例２】
実施例１と同様の黒鉛化炭素繊維成形体を用いて他方は炭化珪素焼結体の替わりに炭化珪素粒子を用いて、JIS A1050の替わりにJIS C1020を、予熱温度１２００℃、溶湯温度１２５０℃にした以外は同様にして行った。
その結果、熱膨張率は８ｐｐｍ／K、熱伝導度は４０８W／ｍKであった。
【００１９】
【実施例３】
予め６５０℃に加熱した炭化珪素焼結体の上に、これも予め６００℃加熱した黒鉛粒子を金型内に配置して、７５０℃のJIS ＡＤＣ14溶湯を流し図―４のようにプランジャーで圧力７０ＭPaにて加圧し、凝固後、炭化珪素と黒鉛粒子の２層からなる金属基複合材料を得た。
【００２０】
このものを、幅７０ｍｍ長さ１５０mmで炭化珪素の複合材層の厚みが１ｍｍ、黒鉛粒子との複合材層の厚みが２ｍｍになるように作成した。このものの引張強度は、板の平面方向で３１０MPaであり、熱伝導度は３１０W／ｍK、熱膨張率は４.３ｐｐｍ／Kであった。
これを図―５のように黒鉛粒子の複合材層の部分を切削加工して６ヶのセクションに分かれたパワーモジュール用の基板が得られた。このものは黒鉛粒子との複合材層の部分だけの切削なので容易に加工でき、しかも一体成形物であるので６ヶ所の凸部分をロー付けの必要もなく、より熱伝導度の良好なものが得られた。
【００２１】
【発明の効果】
本発明により充分に高い熱伝導度を有し、かつ適正な熱膨張率を有する、易加工の一体型ヒートシンクが得られた。
【図面の簡単な説明】
【図１】４００W／ｍK以上の熱伝導度を有し、熱膨張率が４〜５ｐｐｍのヒ
ートシンクパッケージを製造する概念図
【図２】図―１から取り出された複合材料
【図−３―１】一体型のサブマウントを有するヒートシンクパッケージの断面図
【図−３−２】同上の平面図
【図―４】 ３００W／ｍK以上の熱伝導度を有するパワーモジュール用のヒートシンク板を製造する概念図
【図―５】 パワーモジュール
【符号の説明】
１ 黒鉛化炭素繊維成形体
２、２２ 炭化珪素焼結体
３、４、２３、２４ 金型
５、２５ 加圧プランジャ
６、２６ アルミニウム又はアルミニウム合金溶湯
１１ 炭素繊維複合材層
１２、３２ 焼結炭化珪素複合材層
１３ サブマウント
２１ 黒鉛粒子層
３１ 黒鉛粒子複合材層[0001]
[Industrial application fields]
The present invention is applied to a member having excellent strength and thermal conductivity and having an appropriate coefficient of thermal expansion as a substrate requiring heat dissipation such as a semiconductor or an integrated circuit.
[0002]
[Prior art]
In the past, when alumina ceramics or epoxy resin was used as a semiconductor substrate, heat generation from the semiconductor itself was not a problem. Recently, however, semiconductor cooling has become indispensable as the calculation speed increases and the amount of heat generated by the light heat of high-speed communication, so-called optical communication, increases. Correspondingly, the substrate has been selected by a material having a good thermal conductivity and a material having an appropriate coefficient of thermal expansion.
[0003]
That is, a composite material of copper tungsten, copper molybdenum, silicon carbide and aluminum has been invented and used as a material having high thermal conductivity and an appropriate thermal expansion coefficient. They have a thermal conductivity of approximately 150-200 W / mK and a coefficient of thermal expansion of 8-12 ppm / K.
[0004]
[Problems to be solved by the invention]
Recently, however, the amount of heat generated from semiconductors has increased, and the one having higher thermal conductivity has become necessary. In addition, a compound semiconductor used for optical communication is required to have a coefficient of thermal expansion of 4 to 5 ppm / K. Copper tungsten, copper molybdenum, or a composite material of silicon carbide and aluminum cannot satisfy both the thermal conductivity and thermal expansion characteristics required for a new substrate.
[0005]
On the other hand, in recent years, automobiles have become a substrate for integrated circuits as a result of electrification. In addition to the required characteristics as a heat sink material with a thermal expansion coefficient of 8 to 12 ppm / K and a thermal conductivity of 300 W / mK or more, the mechanical strength is 250 MPa or more. Things are needed.
[0006]
For this reason, as a subject of this development, the thermal expansion coefficient was set to two levels of 4 to 5 ppm / K and 8 to 12 ppm / K, and a heat sink plate having a thermal conductivity of 300 to 400 W / mK was completed.
[0007]
Prior to this task, we investigated the mechanical strength, thermal conductivity, and thermal expansion characteristics of metal matrix composites that were pre-impregnated with various types of inorganic materials as reinforcing materials. The characteristic values shown were obtained.
[0008]

[0009]
In order to achieve this task, we considered using the composite materials shown in Table 1 in combination. Regarding thermal conductivity, for example, when two types of composite materials are combined, the overall thermal conductivity U (W / mK) is one type of thermal conductivity A (W / mK) and its thickness X (mm), When other types of thermal conductivity B (W / mK), thickness Y (mm),
The equation U = (X + Y) / (X / A + Y / B) holds.
[0010]
In order for U in the above equation to be 400 W / mK or more, at least one of them should adopt 10, 11 and the thickness should be adjusted in consideration of the balance with other types. For example, when 4 is selected for the other species, the thickness is 1 mm, and the thickness of 11 is 3 mm, U is 408 W / mK. As another example, when the thickness of 1 is 1 mm and the thickness of 10 is 2 mm, U is 407 W / mK, each satisfying the target of thermal conductivity.
[0011]
Next, regarding the thermal expansion coefficient, when 10 or 11 is used, the thermal expansion coefficient in the perpendicular direction must be adopted. This is because, as a heat sink plate, it is necessary that the thermal conductivity is good in the thickness direction of the plate, whereas the coefficient of thermal expansion is related to the plane direction of the plate.
[0012]
9, 10 and 11, when the fiber direction is the thickness direction of the heat sink plate, the plane direction of the plate is the perpendicular direction of the fiber, but the tensile strength in the perpendicular direction is small. In the case of combination, the thermal expansion is 1 and the thermal expansion coefficient is 12 ppm / K. Further, in the case of the combination of 4 and 11, it becomes 8 ppm / K, and is satisfied as a heat module plate of a power module system such as an electric vehicle.
[0013]
On the other hand, in the combination of 10 and 12, 11 and 13, the coefficient of thermal expansion in the plane direction of the plate is 4.5 to 4.1, respectively, which is optimal as a heat dissipation substrate for optical communication or the like.
[0014]
[Means for Solving the Problems]
The present invention provides a heat sink plate obtained by impregnating a molten metal into an inorganic layer composed of a layer composed of silicon carbide particles or cubic boron nitride particles and a layer composed of carbon particles or carbon fibers. Is.
【Example】
EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.
[0015]
[Example 1]
Pitch-based carbon fibers were molded with a phenol resin so as to be aligned in one direction, and fired at 3000 ° C. in a vacuum to obtain a unidirectional graphitic carbon fiber molded body. The fiber volume fraction of this product was 18% carbonized from 55% phenol resin.
[0016]
On the other hand, a silicon carbide sintered body obtained by sintering silicon carbide particles at 2000 ° C. was obtained at a volume ratio of 72%. Graphitized carbon fiber molded body (1) and silicon carbide sintered body (4) are placed so that the fiber direction is perpendicular to the silicon carbide plate surface and preheated to 800 ° C as shown in Fig. Then, put it in a predetermined mold (3, 4), pour 800 ℃ JIS A1050 molten metal onto it and pressurize with a plunger at a pressure of 98 MPa, and after solidification is completed, aluminum with graphitized carbon fiber and silicon carbide as reinforcement A matrix composite was obtained.
[0017]
The physical properties of the composite material thus obtained are as follows. When the carbon fiber composite material layer is processed with a 2 mm silicon carbide composite material layer with a thickness of 1 mm, the coefficient of thermal expansion is 4.5 ppm / K and thermal conductivity were 407 W / mK. A heat sink package (14) was obtained by processing the same as shown in Fig. 3-1 (sectional view) and Fig. 3-2-2 (plan view). This composite layer made of carbon fiber and aluminum is excellent in machinability, so it can be easily processed, and the submount (13) can be formed integrally, so that from the top of the submount to the bottom of the package. The thermal conductivity was also very good and it was not necessary to braze the submount to the substrate.
[0018]
[Example 2]
Using the same graphitized carbon fiber molded body as in Example 1 and using silicon carbide particles instead of the silicon carbide sintered body, JIS C1020 instead of JIS A1050, preheating temperature 1200 ° C., molten metal temperature 1250 ° C. The procedure was the same except for the above.
As a result, the coefficient of thermal expansion was 8 ppm / K, and the thermal conductivity was 408 W / mK.
[0019]
[Example 3]
On the silicon carbide sintered body heated in advance to 650 ° C., graphite particles heated in advance to 600 ° C. are placed in a mold, and a 750 ° C. JIS ADC14 molten metal is flowed with a plunger as shown in FIG. After pressurizing at a pressure of 70 MPa and solidifying, a metal matrix composite material comprising two layers of silicon carbide and graphite particles was obtained.
[0020]
This was prepared so that the width of the composite material layer of 70 mm in width and 150 mm in length, the silicon carbide composite material layer was 1 mm, and the composite material layer with graphite particles was 2 mm. The tensile strength of this product was 310 MPa in the plane direction of the plate, the thermal conductivity was 310 W / mK, and the thermal expansion coefficient was 4.3 ppm / K.
As shown in Fig. 5, the composite layer of graphite particles was cut to obtain a power module substrate divided into six sections. Since this is only a part of the composite material layer with graphite particles, it can be easily processed, and since it is an integrally molded product, there is no need to braze the six convex parts, and it has better thermal conductivity. Obtained.
[0021]
【The invention's effect】
According to the present invention, an easily machined integrated heat sink having a sufficiently high thermal conductivity and an appropriate coefficient of thermal expansion was obtained.
[Brief description of the drawings]
FIG. 1 is a conceptual diagram for manufacturing a heat sink package having a thermal conductivity of 400 W / mK or more and a thermal expansion coefficient of 4 to 5 ppm. FIG. 2 is a composite material taken out from FIG. ] Cross-sectional view of heat sink package with integrated submount [Fig. 3-2] Plan view of the above [Fig. 4] Conceptual diagram for manufacturing a heat sink plate for a power module having a thermal conductivity of 300 W / mK or more [Figure-5] Power module [Explanation of symbols]
1 Graphitized carbon fiber molded body 2, 22 Silicon carbide sintered body 3, 4, 23, 24 Mold 5, 25 Pressure plunger 6, 26 Aluminum or aluminum alloy molten metal 11 Carbon fiber composite material layer 12, 32 Sintered carbonization Silicon composite material layer 13 Submount 21 Graphite particle layer 31 Graphite particle composite material layer

Claims (5)

The heat sink plate obtained by the impregnating molten metal into constructed inorganic layer of two layers of the silicon carbide particles or cubic a layer of carbon particles or carbon fiber comprising boron nitride particles layer. The layer made of silicon carbide particles or cubic boron nitride particles is made of a layer made of powder of silicon carbide particles or cubic boron nitride particles, or a sintered body of powder of silicon carbide particles or cubic boron nitride particles. 2. The heat sink plate according to claim 1, wherein the heat sink plate is a layer made of a pre-sintered body using alumina sol or silica sol of silicon carbide particles or cubic boron nitride particles as a binder. 2. The heat sink plate according to claim 1, wherein the layer composed of carbon particles or carbon fibers is a unidirectional graphitic carbon fiber molded body obtained by molding carbon fibers so as to be aligned in one direction with a phenol resin and firing the carbon fibers . The heat sink plate according to claim 1, wherein the metal of the molten metal is aluminum, copper, silver, or an alloy thereof. The heat sink plate according to claim 1, wherein the heat sink plate is obtained by impregnating a molten metal by press-fitting and solidifying at a high pressure.

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