JP3420415B2 - High thermal conductive composite material - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has a thermal expansion coefficient similar to that of alumina and a high thermal conductivity, and is suitable as a radiator such as a heat sink material of a semiconductor device. The present invention relates to a high thermal conductivity composite material. 2. Description of the Related Art In recent years, the amount of heat generated in a semiconductor element at the time of driving has increased due to an increase in the operation speed of an IC or LSI, an increase in the electric capacity of a transistor, the appearance of a semiconductor element or FET using GaAs, and the like. Therefore, how to dissipate this heat is a major issue. In general, heat generated in a semiconductor device is discharged from a package such as a package through a heat radiator such as a heat sink through a package substrate on which the semiconductor device is mounted.
Therefore, in a package or the like on which a semiconductor element generating a large amount of heat is mounted, the package substrate and the heat sink material need to have high thermal conductivity. Further, a heat radiator to be joined to a package substrate or a semiconductor element needs to have a coefficient of thermal expansion close to that of the semiconductor element or the package substrate. Heretofore, alumina-based sintered bodies have been most frequently used as package substrates because of their high reliability. Heretofore, as a radiator material suitable for such a condition, for example, a Cu-W or Cu-Mo composite material as described in JP-A-59-141247 has been known. In the heat radiator material in which Cu, W, and Mo are combined, the thermal expansion coefficient and the thermal conductivity can be arbitrarily selected by changing the Cu content. Therefore, the optimal Cu content is adjusted according to the material of the semiconductor element to be mounted, the material of the ceramics constituting the package substrate, the shape and size of the package, etc., so that it has an appropriate coefficient of thermal expansion and has a thermal conductivity. Excellent heat dissipating material can be manufactured. [0006] However, with the recent increase in the degree of integration of semiconductor devices, the weight of the heat radiator used in the semiconductor devices has been required to be reduced. Further, since the specific gravity of each of the Cu-Mo-based composite materials is as large as 10 or more, it has been impossible at the present time to satisfy the demands and respond. Further, in order to prevent minute cracks and peeling due to mechanical stress caused by a difference in thermal expansion of a substrate on which a heat sink is mounted, the substrate must have a thermal expansion coefficient similar to that of an alumina substrate or the like. Accordingly, an object of the present invention is to provide a low specific gravity,
An object of the present invention is to provide a high thermal conductive composite material having a thermal expansion characteristic similar to that of alumina. The present inventors have conducted various studies in order to achieve the above-mentioned object, and as a result, have found that one of the Cu-W or Cu-Mo conventionally used is one of W and Mo. By replacing the part with silicon having a low coefficient of thermal expansion, good thermal conductivity and low specific gravity, it has been found that a high-thermal-conductivity composite material that is lighter than conventional materials can be obtained, leading to the present invention. That is, the high thermal conductivity composite material of the present invention contains 20 to 50% by weight of copper, 15 to 70% by weight of silicon, and 10 to 50% by weight of nickel and tungsten in total. It has a specific gravity of 7.5 or less, a thermal conductivity of 60 W / m · K or more, and a coefficient of thermal expansion from room temperature to 800 ° C. of 7 to 8 ppm / ° C. According to the present invention, Cu, W and / or Mo
For a high thermal conductive material consisting of:
High thermal conductivity that combines high thermal conductivity of Cu and low specific gravity of silicon by replacing with silicon having a lower specific gravity by replacing silicon with a silicon having a lower specific gravity than W and Mo and controlling the amount of silicon to a specific range. A composite material can be easily obtained. Further, by making the coefficient of thermal expansion of the high thermal conductive composite material close to that of alumina (7 ppm / ° C.), it is possible to prevent the occurrence of minute cracks or peeling due to mechanical stress generated by the difference in thermal expansion. it can. BEST MODE FOR CARRYING OUT THE INVENTION The highly thermally conductive composite material of the present invention
The sintered body contains 20 to 50% by weight of copper, 15 to 70% by weight of silicon, and 10 to 50% by weight of nickel and tungsten in total in terms of composition. The content of these elements is limited to the above range, because the sintered body having a composition outside this range does not have a thermal expansion coefficient falling within the range of 7 to 8 ppm / ° C. from room temperature to 800 ° C., or has a specific gravity. This is because the thermal conductivity exceeds 7 or the thermal conductivity becomes smaller than 60 W / m · K. Note that W and Ni are for improving sinterability. The preferred composition range of the high thermal conductive composite material in the present invention is that copper is 35 to 50% by weight and silicon is 30% by weight.
~ 55% by weight, the total amount of copper and silicon is 55-80% by weight
And the total amount of nickel and tungsten is 10 to 50
Those consisting of weight% have a coefficient of thermal expansion of 7 to 7.5 ppm.
/ ° C and a thermal conductivity of 70 W / m · k or more. Note that the Ni content is desirably 1 to 3% by weight in order to enhance sinterability. In order to produce the high heat conductive composite material of the present invention, copper powder, silicon powder, nickel powder and tungsten powder are weighed and mixed in the above-mentioned range, and then mixed with a desired molding means, for example, After being formed into an arbitrary shape by a die press, a cold isostatic press, an extrusion molding or the like, it is fired. The calcination is performed at 1100 ° C. or more,
By firing at 1250 ° C., it is possible to densify to a relative density of 95% or more. When firing, it is necessary to fire in a vacuum or in a non-oxidizing atmosphere such as N ₂ or Ar so that copper and silicon are not oxidized. In particular, 1 × 1
Firing at a vacuum of 0 ^-2 to 10 ^-6 Torr is desirable.
This is because when the degree of vacuum is lower than 1 × 10 ⁻² Torr, the metal in the raw material is oxidized, and when the degree of vacuum is higher than 10 ⁻⁶ Torr, copper is easily evaporated. is there. EXAMPLE Copper powder having a purity of 99.5% and purity of 99.9%
Was weighed at a ratio shown in Table 1 using silicon powder having a purity of 99.9%, and nickel powder and tungsten powder having a purity of 99.9%, mixed with a ball mill for 24 hours, and formed into a green compact at a pressure of 1 ton / cm ² . Then, the molded body was fired under the firing conditions shown in Table 1. In addition, the vacuum is 1 × 10 ⁻⁶ torr.
It is an order. The obtained sintered body was measured for specific gravity by Archimedes method, thermal expansion coefficient in a temperature range from room temperature to 800 ° C., and thermal conductivity by laser flash method with a sample thickness of 3 mm. The results are shown in Table 1. [Table 1] As is clear from the results shown in Table 1, in Sample No. 1 having a copper content of less than 20% by weight, the thermal conductivity was low and the thermal expansion coefficient was as low as 6.6 ppm / ° C. Sample No. 10 containing less than 5% by weight
Then, the specific gravity is large. Sample No. 8 having a copper content of more than 50% by weight had a coefficient of thermal expansion of 8.5 ppm / ° C., and sample No. 9 having a silicon content of more than 70% by weight.
Has a low coefficient of thermal expansion of 6.8 ppm / ° C. or less. In contrast to these comparative examples, the sample of the present invention has a specific gravity of 7.5 or less as compared with the conventional Cu-W and Cu-Mo-based materials, and can realize a lighter weight. Conductivity is 60 W / m · k or more, thermal expansion coefficient is 7 ~
A highly thermally conductive composite material having an alumina content of 8 ppm / ° C. was obtained. As described in detail above, according to the present invention,
A high-thermal-conductivity composite material having a lower specific gravity than that of a conventional Cu-W-based or Cu-Mo-based composite material can be obtained. for that reason,
When used for a heat sink material or a heat dissipation substrate of a semiconductor device, a very lightweight package can be supplied.

Claims (1)

(57) [Claim 1] 20 to 50% by weight of copper and 15 to 7% of silicon
0% by weight, nickel and tungsten in a total amount of 10 to 5
A sintered body containing 0% by weight and having a specific gravity of 7.
5 or less, thermal conductivity of 60 W / m · K or more, from room temperature to 80
A highly thermally conductive composite material having a coefficient of thermal expansion up to 0 ° C of 7 to 8 ppm / ° C.