JPH0790413A - Composite material - Google Patents

Abstract

PURPOSE:To obtain a functional material having a small thermal expansion coefft. so as to obtain reliability of joining with a semiconductor element and also having thermal conductivity capable of obtaining sufficient heat radiating property. CONSTITUTION:Quartz particles of <=500mum average particle size are uniformly dispersed in a metal material having high thermal expansion such as Cu, Cu- alloy, Al, Al-alloy to decrease the thermal expansion coefft. By properly selecting the volume proportion of quartz particles in the metal material from the range of 40 to 70%, a desirable thermal expansion coefft. can be obtd. while sufficient thermal radiating property is maintained. Thus, both of low thermal expansion and high thermal conductivity can be obtd. The material can easily be produced into a desired form by powder metallurgical processing, and composite material having proper characteristics and a shape according to the purpose can easily be obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composite material used for a heat dissipation substrate for a semiconductor element, etc., in which quartz particles are dispersed in a Cu material which is a metal having high thermal conductivity and high thermal expansion to obtain a volume ratio of quartz. The present invention relates to a composite material which controls the thermal expansion coefficient by selection and has both low thermal expansion and high thermal conductivity and excellent properties.

[0002]

2. Description of the Related Art Integrated circuit chips for semiconductor packages, especially LSIs and ULSIs for large computers,
The trend is toward higher integration and higher calculation speeds, and the amount of heat generated during operation increases significantly with the increase in power consumption, and the coefficient of thermal expansion of the substrate material is silicon or gallium arsenide, which is a chip material. There is a problem that the chip may peel off or crack. The design of the semiconductor package also takes into consideration the heat dissipation property, the substrate on which the chip is mounted is required to have the heat dissipation property, and the substrate material is required to have a high thermal conductivity.

Therefore, the substrate is required to have a coefficient of thermal expansion close to that of the chip and a large thermal conductivity. For example, a Mo material having a coefficient of thermal expansion close to that of the chip and an alumina material constituting the package substrate are required. There is a structure in which Kovar alloy materials with a thermal expansion coefficient close to each other are brazed and laminated, a chip is mounted on Mo material, bonded to the package substrate via the Kovar alloy material, and a radiation fin is attached, which may cause peeling or cracking. However, since the material that controls heat dissipation is Kovar alloy material with low thermal conductivity, even if a heat dissipation fin is attached,
There was a problem that sufficient heat dissipation could not be obtained.

[0004]

Therefore, as a material satisfying the contradictory requirements of matching the coefficient of thermal expansion of the chip and having a large thermal conductivity, a clad plate or Cu-
Composite materials for heat spreaders such as Mo or Cu-W alloy have been proposed. As the clad plate for the heat spreader, a material in which a copper plate and an Invar alloy plate are laminated is used. The clad plate can be made to have almost the same thermal expansion coefficient as the chip, but the thermal conductivity in the plate thickness direction is not always sufficient because the Invar alloy plate is interposed.

For Cu-Mo and Cu-W alloy substrates, sintered Mo and W powders having a coefficient of thermal expansion substantially equal to that of a chip are sintered to produce a sintered body having a large porosity, and then molten copper is melted. Mo or W and Cu obtained by impregnating and manufacturing (Japanese Patent Publication No. 5-38457) or sintering Mo and W powder and copper powder (Japanese Patent Laid-Open No. 62-294147). Is a complex of. Both the thermal expansion coefficient and the thermal conductivity of the composite satisfy practically satisfactory conditions, but they are heavy because of high density of Mo, W, etc., and must be mechanically molded to obtain a predetermined dimension. In addition, the processing cost is high and the yield is poor.

An object of the present invention is to provide a functional material having a small coefficient of thermal expansion so as to obtain reliability of bonding with a semiconductor element and having a thermal conductivity capable of obtaining sufficient heat dissipation.

[0007]

As a result of various studies, the inventor has made various studies as to whether a material having a small coefficient of thermal expansion and a thermal conductivity capable of obtaining sufficient heat dissipation can be manufactured at low cost. The inventors have found that a material having desired characteristics can be obtained by uniformly dispersing particles and controlling the volume ratio, and completed the present invention. That is, the present invention is a composite material in which quartz particles are dispersed in a high thermal expansion metal material, and the volume ratio of the quartz particles is 40% to 70%. Further, the present invention is the above-mentioned structure, wherein the composite material has an average particle diameter of quartz of 500 μm or less,
A composite material in which the high thermal expansion metal material is any one of Cu, Cu alloy, Al, and Al alloy is also proposed.

In the present invention, quartz does not necessarily have to have an ideal chemical composition, and it may be completely crystalline to amorphous or contain impurities. However, in order to obtain a desired coefficient of thermal expansion, quartz is used only in the amount of impurities. It becomes necessary to increase the amount. In the composite material according to the present invention, if the volume ratio of quartz is less than 40%, the coefficient of thermal expansion of the obtained composite material becomes too large, and if the volume ratio of quartz exceeds 70%, the heat of the obtained composite material is increased. The volume ratio of quartz is 40 to 70% because the conductivity becomes too small, and the quartz particles coalesce during sintering and the quartz particles do not randomly disperse in the copper.
And When the average particle diameter of quartz exceeds 500 μm, the quartz particles coalesce with each other during sintering, and the quartz particles are not randomly dispersed in copper or the like which is a high thermal expansion metal material. In some cases, the metal material becomes dispersed in the lump of quartz, and the thermal conductivity becomes too small.
It is set to 0 μm or less. The lower limit of the average particle size of quartz is not particularly limited, but is preferably 20 μm to 300 μm, more preferably 50 μm to 200 μm.

As a method for producing a composite material according to the present invention, as shown in the examples, quartz having a predetermined average particle diameter and high thermal expansion metal material powder are mixed and kneaded and molded into a predetermined shape by pressure molding or injection molding. After that, a powder metallurgy method of sintering in a non-oxidizing atmosphere such as a hydrogen atmosphere can be adopted. In order to uniformly disperse the quartz during the production, the high thermal expansion metal material powder is preferably equal to or smaller than the average particle diameter of quartz, preferably 200 μm or less, and more preferably 10 μm or less.
It is 0 μm or less.

[0010]

The composite material according to the present invention is made of Cu, Cu alloy,
The average particle size is 50 in the high thermal expansion metal material such as Al or Al alloy.
Quartz particles of 0 μm or less are dispersed uniformly to reduce the coefficient of thermal expansion, and the volume ratio of the quartz particles in the metal material is appropriately selected within the range of 40% to 70%. It is possible to obtain a desired coefficient of thermal expansion while ensuring heat dissipation, has both excellent properties such as low thermal expansion and high thermal conductivity, and is most suitable for a heat dissipation substrate for semiconductor elements. In addition, since the desired shape can be easily produced directly by a powder metallurgy method, a substrate or the like having characteristics and a shape according to the application can be provided at low cost.

[0011]

【Example】

Example 1 Quartz particles having an average particle size of 150 μm and copper powder having an average particle size of 100 μm were mixed in a volume ratio of quartz of 20%, 40%, 60%, 80.
% So that a small amount of stearic acid was added and kneaded. Then, it was pressure-molded into a plate having a thickness of 1.5 mm × 60 mm square and sintered at 1000 ° C. for 3 hours in a hydrogen atmosphere to obtain a composite material. A test piece was cut out from the obtained composite material, the thermal expansion coefficient and the thermal conductivity were measured, and the results are shown in Table 1. In Table 1, the case where the volume ratio of quartz is 20% is Comparative Example 4, the case where 40% is the present invention 1, the case where 60% is the present invention 2, and the case where the ratio is 80% is the comparative example 5.
Is.

Example 2 Quartz particles having an average particle size of 15 μm and copper powder having an average particle size of 10 μm were mixed so that the volume ratio of quartz was 50%, and a polypropylene binder of 40% by volume was added to the mixture. Then kneaded. This is injection molded with a thickness of 2 mm x 2
It was molded into a 0 mm square plate, degreased, and then sintered in a hydrogen atmosphere at 1000 ° C. for 3 hours to obtain a composite material. A test piece was cut out from the obtained composite material, the coefficient of thermal expansion and the thermal conductivity were measured, and the results are shown in Table 1 as Invention 3 of the present invention.

Comparative Example Quartz particles having an average particle size of 600 μm and copper powder having an average particle size of 100 μm were mixed so that the volume ratio of quartz was 50%. Thereafter, a composite material was obtained in the same manner as in Example 1. . A test piece was cut out from the obtained composite material, the thermal expansion coefficient and the thermal conductivity were measured, and the results are shown in Table 1 as Comparative Example 6.

[0014]

[Table 1]

[0015]

The composite material according to the present invention is made of Cu, Al.
The reliability of bonding with a semiconductor element can be obtained by uniformly dispersing quartz particles of a predetermined average particle size in a high thermal expansion metal material such as, and by appropriately selecting the volume ratio of the quartz particles in the metal material. Has a small coefficient of thermal expansion, and
A functional material that combines thermal conductivity with sufficient heat dissipation can be easily obtained, and since a powder metallurgical method can be adopted, mechanical molding processing is unnecessary and yield is good to obtain a predetermined dimension, It has the advantage of being extremely manufacturable.

Claims (3)

[Claims] 1. A composite material in which quartz particles are dispersed in a high thermal expansion metal material, and the volume ratio of the quartz particles is 40% to 70%. 2. The composite material according to claim 1, wherein the average particle size of quartz is 500 μm or less. 3. The high thermal expansion metal material is Cu, Cu alloy, A
The composite material according to claim 1 or 2, which is one of Al and Al alloy.