JP2001053203A - Heat radiating plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat radiating plate wherein, efficiently radiating the heat accumulated at a module, a deformation of a substrate caused by the difference in thermal expansion from a ceramic substrate is reduced even when directly jointed to the ceramic substrate. SOLUTION: Silicon carbide powder is mixed with phenol resin, which is compression-molded into a plate and then carbonized in vacuum (about 900 deg.C), and baked in vacuum at 1500-1700 deg.C. Or, silicon carbide powder is mixed with carbon powder, which is molded into a plate and then baked at 1500-1700 deg.C in vacuum so that a porous performs in formed. The perform contacts the ingot of high-purity metal silicon and is thermally processed at 1500-1700 deg.C in argon so that a molten metal silicon penetrates into the preform for reactive sintering with the phenol resin or carbon powder to form a silicon carbide. At the same time the voids in the preform is filled with the molten metal silicon to provide a tight heat radiation plate. The porosity of the heat radiation plate is preferred to be 10% or less for a sufficient heat conductivity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat radiating plate for suppressing a high temperature of a circuit board, especially a ceramic substrate using many ICs.

[0002]

2. Description of the Related Art Conventionally, in a high-current module such as a large-current power module, a large amount of current flows through a small wiring resistance, so that the module itself generates heat. as a result,
There is a problem that the mounted IC runs away from heat or the IC itself is damaged in severe cases. Therefore, a ceramic substrate having excellent heat resistance is used for the module, and a heat radiating plate made of metal such as Cu or Al is provided to efficiently radiate generated heat.

[0003]

However, since this module has a difference in thermal expansion between the ceramic substrate and the metal radiator plate, it is used repeatedly when the ceramic substrate and the radiator plate are directly joined. As a result, there has been a problem that heat is repeatedly generated and deformation such as warpage is caused. For this reason, a method of mechanically joining the ceramic substrate and the metal radiator plate has been adopted, which has been dealt with by providing a relief for a difference in expansion caused by a rise in temperature. As a result, there is a problem that the contact between the two is limited and the entire surface cannot be joined, thereby reducing the contact area between the two and making it impossible to fully utilize the characteristics of the heat sink.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the module, and has as its object to efficiently radiate heat generated in the module and to directly connect the ceramic substrate to the ceramic substrate. Another object of the present invention is to provide a heat radiating plate for reducing deformation of a substrate caused by a difference in thermal expansion between the heat radiating plate and the heat radiating plate.

[0005]

[Means to solve the problem] Therefore, the present inventors,
As a result of diligent research to achieve the above objective, the use of a composite material of ceramic powder and metal as a heat radiating plate efficiently dissipates the heat generated in the module and ensures that even if the module is directly bonded to the ceramic substrate, The present inventors have found that the deformation of the substrate caused by the difference in thermal expansion between them can be reduced, and have completed the present invention.

That is, the present invention resides in using a composite material in which silicon carbide is impregnated with silicon carbide powder as a heat sink. By combining silicon carbide powder and metallic silicon, it is possible to approximate the thermal expansion of the ceramic substrate used and to provide high thermal conductivity, making it an excellent heat sink. become.

Usually, alumina (Al2O3), aluminum nitride (AlN), beryllia (BeO), etc. are used as the ceramic substrate. The radiator plate of the present invention can be used for any substrate. In particular, aluminum nitride is the most suitable substrate because the difference in thermal expansion between the radiator plate and the radiator plate of the present invention can be made very close and residual stress is hardly accumulated.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The method of manufacturing a heat sink of the present invention is not particularly limited, but is manufactured by the following method, for example.

First, a silicon carbide powder and a phenol resin are mixed, molded into a plate by press molding, carbonized in a vacuum (about 900 ° C.), and then 1500 to 170 vacuum.
By sintering at 0 ° C. or by mixing silicon carbide powder and carbon powder, forming it into a plate,
By firing at 00 to 1700 ° C., a porous preform is formed. An ingot of high-purity metallic silicon was brought into contact with the obtained preform,
Heat treatment at 700 ° C allows molten metal silicon to penetrate into the preform and react and sinter with the phenolic resin or carbon powder to form silicon carbide, and the voids in the preform are filled with molten metal silicon and dense. Thus, a good heat sink can be obtained.

In order to obtain sufficient heat conductivity as the heat radiating plate, the porosity of the heat radiating plate is desirably 10% or less, and the porosity is desirably low. Therefore, the porosity is desirably 5% or less.

The ceramic substrate and the heat sink may be joined by a method using an active metal, a method using solder, or the like. Alternatively, the preform described above may be arranged on a ceramic substrate, and the molten metal silicon may be attached to the preform. At the same time, the radiating plate and the ceramic substrate may be joined by fusing the molten metal silicon and the ceramic substrate that have been infiltrated with the silicon. The point is that it is sufficient that the ceramic substrate and the heat radiating plate can be joined on the entire surface so that the characteristics of the heat radiating plate can be fully utilized, so that heat from the ceramic substrate can be efficiently transmitted to the heat radiating plate.

[0012]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples of the present invention and Comparative Examples.

(1) Example 1 Silicon Carbide (GC # 180, manufactured by Shinano Electric Refining Co., Ltd.) 100
Parts by weight and 10 parts by weight of a phenol resin (BRL-101, manufactured by Showa Polymer Co., Ltd.) are mixed, molded into a size of 60 mm × 4 mmt, and baked at 1600 ° C. for 3 hours in a vacuum to obtain a relative density of 65%.
% Of the preform was formed. Then, after placing the obtained preform on the silicon metal ingot, the metal silicon is melted at 1600 ° C. in argon to infiltrate the molten metal silicon into the preform, and then cooled to process it.
A heat sink of mm × 2 mmt was prepared. The resulting heat sink had a porosity of 2% and a thermal conductivity of 150 W / K · m.
Also, a 40 mm square 1.5 mmt aluminum nitride substrate having a copper plate attached to the surface thereof using an active metal was bonded to a heat sink using solder to produce a simulated module without mounting a silicon chip.

(2) Example 2 An simulated module without mounting a silicon chip was manufactured by bonding an alumina substrate having a copper plate attached to a radiator plate manufactured in the same manner as in Example 1 in the same manner as in Example 1.

(3) Example 3 A 40 mm square was placed on a preform manufactured in the same manner as in Example 1.
With a 1.5 mmt aluminum nitride substrate placed and a metal silicon ingot placed under the preform, the silicon metal is melted at 1600 ° C. in argon to infiltrate the preform with the molten metal silicon. Simultaneously with the production of the radiator plate, the radiator plate was joined to the aluminum nitride substrate, and then a copper plate was attached to the upper surface of the aluminum nitride substrate using an active metal, thereby producing a simulated module without mounting a silicon chip.

(4) Comparative Example 1 A 40 mm square with a copper plate attached using an active metal
1.5mmt aluminum nitride substrate was soldered to 5
A simulated module without a silicon chip mounted thereon was fabricated by bonding to a copper radiator plate of 0 mm square x 2 mm ^t .

The evaluation method is as follows:
THERMAL SHOCK CHAMB made by ESPEC
Using ER, 16 ° C./sec between −40 ° C. and + 125 ° C.
The temperature was raised and lowered by c, and 50 cycles of a temperature cycle of 5 minutes holding time at both temperatures were loaded, and the flatness of the substrate before and after loading was measured by a surface roughness meter (Surfcom 205C, manufactured by Tokyo Seimitsu Co., Ltd.).
Was measured in accordance with JIS B0601, and the difference in maximum height (Rmax) before and after the load was defined as a change in flatness, and was used as an index of the degree of deformation of the substrate due to a change in temperature. Table 1 shows the obtained results.
Shown in

As is evident from Table 1, the heat sink of the present invention showed less heat deformation and smaller thermal stress distortion than the comparative example.

[0019]

As described above, by using the heat sink of the present invention as a heat sink for electronic circuits (so-called heat sink), the heat generated by driving the silicon chip can be efficiently dissipated, and the heat generated by the module itself (in the heat cycle) )
Deformation due to thermal stress distortion is small, and thus, separation between the driving electronic circuit board and the heat sink is suppressed, and a more reliable electronic circuit module can be obtained.

[Table 1]

Claims (2)

[Claims] 1. A radiator plate comprising a composite material in which silicon carbide is impregnated into silicon carbide powder. 2. The heat sink according to claim 1, wherein the porosity is 10% or less.