JPH0995745A - Low thermal expansion-high thermal conductivity copper composite material and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a low thermal expansion-high thermal expansion copper composite material by subjecting a powdery mixture composed of specified ratios of copper powder and silicon carbide powder to press sintering. SOLUTION: By volume, 20 to 80% silicon carbide powder is added to 80 to 20% copper powder, which are mixed, and press sintering is executed at 600 to 950 deg.C under >=1,000kg/cm<2> pressure. Thus, the copper composite material whose thermal expansion coefficient is regulated to 5×10<-6> to 14×10<-6> /K and thermal conductivity to 150 to 380W/(m.K) can be obtd. Furthermore, preferably, the purity of the copper powder is regulated to ∞99%, the concn. of iron impurities therein to <=0.001%, the purity of the silicon carbide powder to >=99%, and the average grain size thereof to >=10μ, respectively.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a copper composite material having a low coefficient of thermal expansion and high thermal conductivity and a method for manufacturing the same, and more particularly to a material suitable for a heat dissipation plate of a semiconductor device and a method for manufacturing the same.

[0002]

2. Description of the Related Art In recent years, in the field of semiconductor technology, large capacity of transistors, high integration of LSI, high speed and high performance, etc.
The performance of semiconductor devices is remarkably improved. Therefore, how to efficiently dissipate the heat energy generated from the semiconductor element by the heat dissipation plate material is an important issue. As a conventional heat sink material for a semiconductor device, copper (Cu),
Molybdenum (Mo) is used for a large substrate, plastic or alumina (Al ₂ O ₃ ) is used for a package, and aluminum nitride (AlN) is used for a package having a large capacity.

[0003]

In the conventional heat dissipation plate material for semiconductor devices, the heat conductivity is 390 W / (m
・ K) and high copper have excellent heat dissipation, whereas the coefficient of thermal expansion of silicon (Si) used in semiconductor materials such as transistors and LSI chips is 4.2 × 10 ^-6 / K. Copper has a large coefficient of thermal expansion of 17.0 × 10 ^-6 / K, so the solder joint surface such as Pb-Sn between the heat dissipation plate and the semiconductor material peels off due to the thermal stress repeatedly applied during the operation of the circuit. There is a problem that there is a risk of doing. vice versa,
Mo having a thermal expansion coefficient of 5.l × 10 ^-6 / K is excellent in reliability at the solder joint surface because it is close to the thermal expansion coefficient of semiconductor materials, but has a thermal conductivity of 150 W / (m・ There is a problem that the heat dissipation is not sufficient because it is as low as K). 170 W /
AlN, which is a ceramic having a good balance between the thermal conductivity of (m · K) and the thermal expansion coefficient of 4.5 × 10 ⁻⁶ / K, has a problem that it is costly and economically disadvantageous. Further, since these conventional materials are composed of a single material, there is a problem that it is difficult to arbitrarily control both characteristics of the thermal expansion coefficient and the thermal conductivity.

Therefore, it is an object of the present invention to provide a copper composite material which is inexpensive, has a low thermal expansion coefficient and a high thermal conductivity.

[0005]

As a result of intensive studies in view of the above problems, the present inventors have found that a composite material composed of copper and silicon carbide has high thermal conductivity and low thermal expansion,
The present invention has been completed.

That is, the low thermal expansion and high thermal conductivity copper composite material of the present invention is obtained by pressure sintering a mixed powder obtained by adding 20 to 80% by volume of silicon carbide powder to 80 to 20% by volume of copper powder. It is characterized by being

Further, the method of the present invention for producing a copper composite material having a low thermal expansion and a high thermal conductivity is 20 to 80% by volume of copper powder.
Add 80% by volume of silicon carbide powder and mix to 600-950
It is characterized by performing pressure sintering at a temperature of ℃ and a pressure of 1000 kg / cm ² or more.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below. (1) Copper powder Copper powder having a purity of 99% or more is preferable. If the purity of the copper powder is less than 99%, the heat transfer coefficient of the obtained composite material becomes small, which is not preferable. The average particle size of copper powder is
The thickness is preferably 10 to 300 μm, more preferably 20 to 100 μm, and particularly preferably 20 to 50 μm. The copper powder content is 80 to 20% by volume based on the total volume of the raw material powder. When the content of the copper powder exceeds 80% by volume, the coefficient of thermal expansion increases, and when the content is less than 20% by volume, the thermal conductivity decreases, which is not preferable.

The concentration of iron impurities in the copper powder is preferably 0.001% or less. If the concentration of iron impurities exceeds 0.001%, the thermal conductivity will decrease.

(2) Silicon Carbide Powder Silicon carbide powder having a purity of 99% or more is preferable.
If the purity of the silicon carbide powder is less than 99%, the heat transfer rate is low, which is not preferable. The content of the silicon carbide powder is 20 to 80% by volume based on the total volume of the raw material powder. When the content of the silicon carbide powder exceeds 80% by volume, the thermal conductivity becomes low, and when the content is less than 20% by volume, the thermal expansion coefficient becomes large, which is not preferable.

The average particle size of the silicon carbide powder is preferably 10 μm or more. If the average particle size is less than 10 μm, the ceramic particles agglomerate and are difficult to uniformly disperse in the metal matrix,
Moreover, since the pores are generated in the particle agglomeration portion, the thermal conductivity is lowered. The average particle size of silicon carbide is more preferably 10 to 300 μm, and particularly preferably 20 to 100 μm.

(3) Manufacturing Method Copper powder and silicon carbide powder are mixed in the above ratio. Mixing can be performed by various known methods, for example, using a ball mill or the like. The mixing time is preferably 3 hours or more. Next, the mixed powder is preformed into a desired shape. Examples of the molding method include a die pressing method.

Next, the preformed body obtained is sintered, and the preferred sintering method is pressure sintering such as HIP or hot pressing. Sintering temperature is 600-950 ° C, pressure is 1000
It is preferably at least kg / cm ² . If the sintering temperature is below 600 ° C, the porosity of the resulting composite material will increase and
If the temperature exceeds 0 ° C, the heat transfer rate becomes small, which is not preferable. Further, if the pressure is less than 1000 kg / cm ² , the porosity of the obtained composite material increases, which is not preferable. A more preferable sintering temperature is 800 to 900 ° C., and a more preferable pressure is 1000 to 2000 kg / cm ² .

(4) Copper Composite Material The composite material thus obtained has a porosity of 10% or less, a coefficient of thermal expansion of 5 to 14 × 10 ⁻⁶ / K, and a thermal conductivity of 150 to 380. It is W / (mK). When the porosity of the composite material exceeds 10%, the thermal conductivity is low. Preferred porosity is 8
% Or less.

The copper composite material of the present invention has the following features. (a) The thermal expansion coefficient and the thermal conductivity can be controlled to desired characteristics by appropriately selecting the content (volume%) of the copper particles and silicon carbide particles serving as the base.

(B) Since it is possible to obtain a thermal expansion coefficient similar to that of the semiconductor material mounted on the heat dissipation plate material, the solder joint surface between the heat dissipation plate and the semiconductor material is not peeled off due to thermal stress, and the solder joint is performed. The reliability of the surface is improved.

(C) Since the base is copper, high thermal conductivity can be obtained, heat energy generated from the semiconductor material can be efficiently dissipated, and malfunctions and thermal damage of transistor chips, LSI chips, etc. can be prevented. .

[0018]

The present invention will be described in more detail with reference to the following specific examples. Example 1 (1) Raw Material Powder Silicon carbide powder having a particle size of 130 μm or less (average particle size 57 μm)
And the purity is 99.3% or more. The particle size of copper powder is 130
The average particle size was 40 μm or less, and the purity was 99.9% or more. The iron impurity concentration in the copper powder was 0.0001% or less.

(2) Molding The above silicon carbide and copper powders were blended in the proportions shown in Table 1 and dry mixed in a ball mill for 24 hours. 5 ton / cm ^{2 of} mixed powder
A molded body having a diameter of 30 mm and a height of 30 mm was manufactured under the pressure.

This molded body was placed in a mild steel cylindrical container,
After vacuum degassing at 650 ℃ for 4 hours, 1400 kg / cm ² and
HIP sintering was carried out at 850 ° C. for 1 hour to obtain five dense sintered bodies in which silicon carbide particles were uniformly dispersed in a copper matrix.

(3) Measurement The following characteristics were measured for each of the obtained five types of sintered bodies. 1. Thermal conductivity After cutting out a test piece with a diameter of 10 mm and a height of 2 mm from each sintered body, use a thermal constant measuring device (LF / TCM-FA8510B, manufactured by Rigaku Denki Co., Ltd.) according to the laser flash method (JIS1606 compliant). The thermal conductivity was measured. The results are shown in Table 1.

2. Coefficient of thermal expansion After cutting out a test piece of 3 mm square x 17 mm long from each sintered body, measure the thermal expansion coefficient using TMA (thermo-mechanical analyzer, Seiko Co., Ltd.) in the temperature range from room temperature to 100 ° C. did. The results are shown together in Table 1.

3. Porosity A test piece of 10 mm square and 2 mm high was cut out from each sintered body, and then each porosity was measured according to the Archimedes method, and the results are shown in Table 1.

Table 1 Example 1 Experimental results Mixed volume% Thermal conductivity Thermal expansion coefficient Porosity Cu SiC W / (m · K) × 10 ⁻⁶ / K% 20:80 150 6.5 5.0 30:70 162 7.1 4.2 40 : 60 185 9.3 3.1 50:50 203 11.0 2.0 80:20 360 13.8 0.1

As can be seen from Table 1, all of the composite materials obtained with the above mixing ratio showed a high thermal conductivity of 150 W / (m · K) or more.

Example 2 In the same manner as in Example 1, 50% by volume of copper powder and 50% by volume of silicon carbide powder were mixed and preformed, and then HIP was performed under the respective sintering conditions shown in Table 2, The thermal conductivity and the porosity of the obtained sintered body were measured in the same manner as in Example 1. The results are shown in Table 2.

Table 2 Experimental results of Example 2 Temperature Pressure Thermal conductivity Porosity ℃ kg / cm ² W / ( mK )% 850 1400 203 2.0 850 1200 155 9.6 850 500 l20 12.0

As can be seen from Table 2, the pressure is 1000 kg / cm.
^{When it was} less than ² , the porosity of the obtained sintered body exceeded 10% and increased, and the thermal conductivity significantly decreased.

Comparative Example 1 After preforming by mixing 50% by volume of copper powder and 50% by volume of silicon carbide powder in the same manner as in Example 1, except that the iron impurity concentration in the copper powder was 0.1%. Sintering was performed under the same sintering conditions as in Example 1, and the thermal conductivity and porosity of the obtained sintered body were measured in the same manner as in Example 1. The results are shown in Table 3.

Table 3 Experimental Results of Comparative Example 1 Iron Impurity Thermal Conductivity % W / (m · K) 0.1 40

As can be seen from Table 3, the iron impurity concentration is 0.
When it exceeds 001%, the thermal conductivity is remarkably reduced.

[0032]

The copper composite material of the present invention has both a low thermal expansion property and a high thermal conductivity because it has a controlled porosity. Further, the copper composite material of the present invention, by appropriately adjusting the content (volume%) of copper particles and silicon carbide particles,
Since the coefficient of thermal expansion and the thermal conductivity can be controlled to desired levels, it can be widely used as a heat dissipation plate material for semiconductor materials.

Claims (7)

[Claims] 1. A low-thermal-expansion / high-thermal-conductivity copper composite obtained by pressure-sintering a mixed powder obtained by adding 20 to 80% by volume of silicon carbide powder to 80 to 20% by volume of copper powder. material. 2. The low thermal expansion / high thermal conductivity copper composite material according to claim 1, wherein the composite material has a thermal expansion coefficient of 5 ×.
10 ^{−6 to} 14 × 10 ⁻⁶ / K, and the thermal conductivity is 150 to 380 W /
A composite material characterized by being (m · K). 3. The low thermal expansion / high thermal conductivity copper composite material according to claim 1 or 2, wherein the silicon carbide powder has an average particle size of 10 μm or more. 4. The low thermal expansion / high thermal conductivity copper composite material according to claim 1, wherein the silicon carbide powder has a purity of 99% or more, and the copper powder has a purity of 99% or more. A composite material characterized by being. 5. The low thermal expansion / high thermal conductivity copper composite material according to any one of claims 1 to 4, wherein the concentration of iron impurities in the copper powder is 0.001% or less. . 6. A method for producing a low thermal expansion and high thermal conductivity copper composite material, wherein 20 to 80% by volume of silicon carbide powder is added and mixed to 80 to 20% by volume of copper powder, and the mixture is heated to 600 to 950 ° C. A method comprising press-sintering at a temperature of 1000 kg / cm ² or more. 7. The method for producing a low thermal expansion / high thermal conductivity copper composite material according to claim 6, wherein the mixed powder is H
A method characterized by performing pressure sintering by IP or hot pressing.