JP2001303151A - Sintered composite material and its producing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a low thermal-expansion and high thermal-conductivity composite material excellent in workability and mechanical strength and provide its a producing method. SOLUTION: In producing a composite material sintered under a pressure of >=10 atm, the low thermal-expansion and high thermal-conductivity composite material excellent in workability and mechanical strength is obtained by preparing a composition consisting of 20-80 vol.% high thermal-conductivity metal and the balance one or more kinds of low thermal expansion compound oxides and high melting point metals. Since a sintered material of what is called a near net-shape is obtained by using a method for sintering a powdery mixture composed of a high thermal-conductivity metal powder and the balance one or more kinds among low thermal-expansion oxide powders and high melting point powders under a pressure of >=10 atm, the sintered composite material having the low thermal-expansion and the high thermal-conductivity can be mass-produced without post-processing and at a low cost.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sintered composite material having high thermal conductivity and low thermal expansion used as a heat sink material for radiating heat of a semiconductor device, and a method of manufacturing the same.

[0002]

2. Description of the Related Art In recent years, with the demand for higher performance and higher reliability such as higher integration and higher speed of electronic devices, improvement of heat radiation capability of heat energy generated from an electronic circuit board has become a major issue. As a heat dissipation material for conventional electronic circuit boards,
Materials with high thermal conductivity such as Cu, Cu clad material, and Cu-W alloy have been used, but have a high density, and furthermore, Si as a semiconductor material, and Al ₂ used for IC substrates and packages.
Since there is a large difference in thermal expansion coefficient as compared with ceramics or plastics such as O ₃ and AlN, there is a problem that a joint surface is peeled off or a base material is broken by thermal stress. In order to solve these problems, a composite material of a metal having excellent thermal conductivity and a ceramic having a small coefficient of thermal expansion has been studied.
In recent years, Al-SiC composite materials as described in JP-A-63-290251 have been used. This composite material has excellent thermal conductivity, a small density, and a small difference in thermal expansion coefficient from the ceramic substrate. However, since this composite material is prepared by infiltrating molten Al into a skeleton of SiC, the content of Al is limited. Therefore, there is a problem that the Al content cannot be increased when a higher thermal conductivity is required. Further, a method of dispersing ceramic particles in a molten metal is also disclosed, but it requires a special device and processing to a product, which is very costly. Also, since the melting point of Al is low,
There is also a problem that the composite material is melted during brazing. By using the conventional powder metallurgy method, a so-called near-net-shape composite material can be obtained. However, a dense composite material cannot be obtained due to poor adhesion between ceramics and metal. Is insufficient, and the mechanical strength is not sufficient.

[0003]

An object of the present invention is to provide a composite material which is dense, has excellent workability and strength, has low thermal expansion and high thermal conductivity, and a method for producing the same.

[0004]

SUMMARY OF THE INVENTION In a sintered composite material which is sintered under a pressure of 10 atm or more, a high heat conductive metal is used.
The above problem can be solved by obtaining a sintered composite material characterized by containing at least 80% by volume and the balance consisting of one or more of a low thermal expansion composite oxide and a high melting point metal. Then, by sintering under a pressure of 10 atm or more by powder metallurgy, mass production can be performed at low cost. Metals such as Cu, Al, Ag, and Au or alloys thereof can be used as the high heat conductive metal. These high thermal conductive metals can be arbitrarily selected according to the required thermal conductivity and thermal expansion coefficient, but a mixture of two or more or an alloy thereof may be used. The content of these high heat conductive metals is desirably from 20% by volume to 80% by volume. 20% by volume
If less, sintering is not promoted and high thermal conductivity is not satisfied. If the content is more than 80% by volume, the effect of lowering the coefficient of thermal expansion by the composite oxide or the high melting point metal is small. As the composite oxide, a composite oxide such as cordierite, spodumene, eucryptite, mullite, zircon, or aluminum titanate can be used. These composite oxides make it possible to obtain raw material powder at a very low price compared to high-purity oxide ceramics.
Their thermal expansion coefficient is 6.0 × 10 ⁻⁶ (1 / ° C.) or less and their density is small. Further, high-purity oxides such as Al ₂ O ₃ and ZrO ₂ have a contact angle with liquid metal of 90 ° or more and cannot be bonded to metal. However, by using a composite oxide with a glass phase, affinity with a metal is improved, so that bonding with a metal becomes possible, and excellent adhesion and denseness can be obtained. It is particularly desirable to use cordierite in consideration of thermal expansion properties, thermal conductivity, denseness, raw materials and production costs, adhesion to metals, and the like. Mo, W, or the like can be used as the high melting point metal. These metals have a lower coefficient of thermal expansion than the high thermal conductive metal, but have a higher thermal conductivity than the low thermal expansion composite oxide, so that a large decrease in the thermal conductivity is suppressed in the sintered composite material. In addition, since these metals have excellent affinity with highly heat conductive metals, they also have an effect as a sintering aid.

The starting material powder having an average particle diameter of about 1 to 50 μm for a high thermal conductive metal, about 1 to 100 μm for a complex oxide, and about 1 to 20 μm for a high melting point metal and having a spherical or irregular shape is used. Can be used. A compact sintered composite material can be obtained by sintering the compact of the powder mixture at a pressure of 10 atm or more at a temperature of 70 to 98% of the melting point of the metal used. In particular,
Sintering under a pressure of 50 atm or more is desirable from the viewpoint of obtaining a dense sintered composite material. When a low coefficient of thermal expansion is required, a sintered composite of a low thermal expansion composite oxide and a high thermal conductivity metal is used. When a high thermal conductivity is required, a high melting point metal and a high thermal conductivity are used. It can be arbitrarily selected according to required characteristics such as a sintered composite material of a metal. In particular, when a higher thermal conductivity and a lower coefficient of thermal expansion are required than the sintered composite material, it is preferable to use a sintered composite material of a low thermal expansion composite oxide, a high melting point metal, and a high thermal conductive metal. .

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention according to claim 1 contains a high thermal conductive metal in an amount of 20 to 80% by volume, and the balance consists of one or more of a low thermal expansion complex oxide and a high melting point metal. The sintered composite material is a low thermal expansion, high thermal conductivity sintered composite material characterized by sintering under a pressure of 10 atm or more, but a high thermal conductive metal and a low thermal expansion composite oxide,
Made of one or more of the high melting point metals, it has low thermal expansion and high thermal conductivity, is easy to process, has high bending strength, and is sintered at high pressure, so it is dense and has higher thermal conductivity than that of normal pressure sintering Material can be obtained. The present invention according to claim 2 is to provide a mixture of a high thermal conductive metal powder and a powder composed of one or more of the low thermal expansion complex oxide powder and the high melting point metal powder at a pressure of 10 atm or more. This is a method for producing a sintered composite material characterized by sintering. By using this method, a so-called near net shape sintered body is obtained, so that post-processing is almost unnecessary, inexpensive, low thermal expansion, Mass production of sintered composites with high thermal conductivity. Hereinafter, the present invention will be described in detail with reference to examples.

[0007]

EXAMPLE A low-thermal-expansion, high-thermal-conductivity sintered composite material of the present invention using Cu as a high thermal conductive particle, cordierite as a composite oxide and Mo as a high melting point metal will be described as an example. Cu powder having an average particle size of 30 μm and a purity of 99.5% or more and cordierite (2
MgO-2Al ₂ O ₃ -5SiO ₂ composition) and average particle size 4 μm
Of Mo powder was weighed so as to have the composition shown in Table 1, and mixed with a fluid mixer for 30 minutes. This mixed powder was molded in a mold and then sintered at 850 ° C. for 60 minutes under a pressure of 50 atm. Example No. 1 to Example No. 1; 7 is Cu
-Shows the present invention of the cordierite series. Example No. 8
-Example No. 14 shows the present invention of Cu-Mo system.
Example No. 15 to Example No. 25 is Cu-Mo-
Fig. 2 shows a cordierite-based invention. The thermal conductivity, coefficient of thermal expansion, relative density and bending strength of the thus obtained sintered composite material were measured, and the results shown in Table 1 were obtained.

[0008]

[Table 1]

Table 2 shows that the raw materials of the present invention are used, but the amounts of the raw materials are out of the range of the present invention, those of Cu, Mo, and cordierite each consisting of a simple substance, and those of Al-70 vol.
Are shown as comparative examples. Comparative Example No. 1 to Comparative Example Nos. 2 is a Cu-cordierite-based material; 3 to Comparative Example Nos. 4 is a Cu—Mo-based material, Comparative Example No. Comparative Example No. 5 Numeral 7 indicates characteristics of Cu, cordierite, and Mo alone. Comparative Example No. 8
Indicates the characteristics of an Al-70 volume% SiC material.

[0010]

[Table 2]

As a result, in the embodiment No. 1 to Example No. 1; 25 is Comparative Example No. 25. 1 to Comparative Example Nos. Compared to 8, it has a high thermal conductivity and a low coefficient of thermal expansion, and has a high strength value, and has characteristics required for use as a heat sink material for heat dissipation of semiconductor devices. On the other hand, in the comparative example, at least one of the thermal conductivity, the thermal expansion coefficient, the relative density, and the tensile strength does not satisfy the characteristics used for a heat sink material that dissipates heat of the semiconductor device. It could not be used for any purpose.

[0012]

According to the present invention, the following effects can be obtained. 1. INDUSTRIAL APPLICABILITY The sintered composite material of the present invention has high thermal conductivity and excellent heat dissipation, and is therefore effective for high integration and high performance of IC substrates. 2. When a composite of a high thermal conductive metal and a composite oxide is used, the density of the sintered composite material is lower than that of a single material of a high thermal conductive metal or a refractory metal alone, which is effective in reducing the weight of an IC substrate. . 3. Since it has a small coefficient of thermal expansion, it can be used without peeling or destruction due to thermal stress even when bonded to Si, ceramics, low thermal expansion plastic, or the like. 4. By adjusting the type and content of high thermal conductive metal, composite oxide metal and high melting point metal, the coefficient of thermal expansion and thermal conductivity can be adjusted to any value, so it can be widely used as a heat dissipation material for electronic devices Can be. 5. Since it is a dense material, it has excellent mechanical properties and is suitable for use in an environment where reliability such as thermal cycling, vibration, and impact is required. 6. Since the raw material powder is extremely inexpensive and can be manufactured by a usual powder metallurgy method, a so-called near net shape product can be manufactured in a large amount and economically without requiring any special equipment.

Claims (2)

[Claims] A sintered composite material sintered under a pressure of 10 atm or more contains a high thermal conductive metal in an amount of 20 to 80% by volume, and the balance is one of a low thermal expansion composite oxide and a high melting point metal.
A sintered composite material comprising a seed or two or more kinds. 2. A mixture of a high thermal conductive metal powder and a powder comprising at least one of a low thermal expansion composite oxide powder and a high melting point metal powder, the remainder being sintered under a pressure of 10 atm or more. A method for producing a sintered composite material, comprising: