JPH10258479A - Manufacture of functionally gradient material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the occurrence of cracks or deformations positively at the laminated place by controlling a ratio of thermal expansion between a ceramic composition part and a metal composition part to be specific %, and effecting simultaneous calcination in a laminated state of the ceramic side material and metal side material set in this manner. SOLUTION: Each thermal expansion coefficient of a ceramics composition part and a metallic composition part is substantially the same during the calcination period, i.e., at a temperature of the manufacture, and set to be the same at a temperature of the use. In this manner, separation or the like in the lamination place can be precluded effectively. Herein, the thermal expansion coefficient uses a combination of W-Cu and MoCu as a metal side composition to be controlled by changing each composition ratio; on the other hand, as a ceramics side composition, metallic aluminum, aluminum nitride and other additives are controlled by changing each composition ratio. Thus, selection is done to be a thermal expansion coefficient of the ceramics composition part/a thermal expansion coefficient of the metallic composition part × 100=75-125%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a functionally gradient material having a ceramic side composition and a metal side composition.

[0002]

2. Description of the Related Art Generally, in a semiconductor circuit, in order to stabilize semiconductor characteristics, the semiconductor circuit is mounted on a ceramic substrate, and a device for efficiently discharging heat generated in the semiconductor circuit to the outside is provided. ing.

At this time, when the heat generated from the semiconductor circuit is relatively large, the ceramic substrate alone cannot sufficiently cope with the heat, and a copper or aluminum heat sink is brazed or soldered to the ceramic substrate. Has been done. Furthermore, MPU and large capacity power IGBT
In such a case, a device is provided for providing heat radiation fins and forcibly releasing heat.

Here, the ceramic substrate is required to have high thermal conductivity in order to maintain the characteristics of the semiconductor circuit at a high level, and is required to have insulation properties, light shielding properties, low dielectric properties, and the like. On the other hand, a heat sink is also required to have high thermal conductivity. Generally, both the ceramic substrate and the heat sink have a thermal conductivity of 150 W / mK or more, and the coefficient of thermal expansion is close to the coefficient of thermal expansion of the semiconductor chip. Is set to

[0005]

However, the brazing material or solder material for connecting the ceramic substrate and the heat sink has a coefficient of thermal expansion of at least twice that of the ceramic substrate and the heat sink, and a thermal conductivity of 20 W / mK. ~
70W / mK or less, which is a low value of 1/2 to 1/7 of the ceramic substrate and the heat sink. For this reason, the joint where the brazing material or the solder material is provided has a low thermal conductivity, a larger coefficient of thermal expansion than other parts, and a considerably large stress is generated in this joint, and the joint reliability is reduced. Has been pointed out.

In addition, heat tends to accumulate in the joint, and the function of the heat sink may not be effectively exhibited. Accordingly, it is necessary to provide a considerably large heat sink and heat radiation fins to always increase the thermal gradient, and there is a problem that it is not possible to cope with a demand for miniaturization.

SUMMARY OF THE INVENTION The present invention solves this kind of problem, and provides a functionally graded material having a high bonding reliability and a high thermal conductivity while integrating metal and ceramics without providing a bonding portion. The purpose is to provide.

[0008]

In order to solve the above-mentioned problems, a method for producing a functionally graded material according to the present invention has a ceramic side composition and a metal side composition, and has a thermal expansion coefficient of a ceramic composition portion. The thermal expansion coefficient of the metal composition portion is adjusted to be substantially the same, and then the co-firing treatment is performed in a state where the ceramic-side raw material and the metal-side raw material thus set are laminated. For this reason, it is possible to reliably prevent cracks, deformation, peeling, and the like from occurring at the lamination portion of the ceramic-side raw material and the metal-side raw material due to the difference in the thermal expansion coefficient during the firing treatment.

Here, the coefficients of thermal expansion of the ceramic composition portion and the metal composition portion are substantially the same at the time of firing treatment, that is, at the manufacturing temperature, and are also set at the same operating temperature. This makes it possible to effectively prevent peeling of the laminated portion during use, in addition to firing.

Here, the thermal expansion coefficient of the metal composition portion and the thermal expansion coefficient of the ceramic composition portion can be changed by selecting the respective compositions. That is, Table 1 shows a change in the coefficient of thermal expansion when a combination of tungsten and copper (W-Cu) and a combination of molybdenum and copper (Mo-Cu) were used as the metal side composition and the respective composition ratios were changed. Have been.

[0011]

[Table 1]

On the other hand, as shown in Table 2, the coefficient of thermal expansion of the ceramic composition portion can be changed by changing the composition ratio of metallic aluminum, aluminum nitride, and other additives as the ceramic composition.

[0013]

[Table 2]

Therefore, the coefficient of thermal expansion of the ceramic composition portion / the coefficient of thermal expansion of the metal composition portion × 100 = 75 to 12
If the composition on the metal side and the composition on the ceramic side are selected so as to be 5 (%), it is possible to prevent peeling at the laminated portion due to a difference in thermal expansion coefficient.

Further, the sintering temperature ranges of metal and ceramics are different from each other. For example, the difference in sintering temperature between copper (metal) and aluminum nitride (ceramic) is 750 ° C. to 1100 ° C. Has occurred.
Therefore, the densification temperature of ceramics is reduced by reaction sintering. In this case, the respective sintering temperature ranges according to the metal side composition and the ceramic side composition are shown in Table 3.
The respective compositions are selected such that the sintering temperature ranges of the metal side composition and the ceramic side composition are the same.

[0016]

[Table 3]

Further, as shown in Table 4, in order to effectively densify the reaction sintered ceramics, a composition for lowering the nitriding temperature is set.

[0018]

[Table 4]

Next, the ceramic-side raw material and the metal-side raw material set as described above are laminated and subjected to a simultaneous firing treatment, whereby the diffusion of the metal layer into the ceramic layer and the ceramic layer From the metal to the metal layer, and the ceramic and the metal are mutually diffused and integrated.

Further, since reaction nitridation is involved, unreacted portions are diffused inside, and there is no need to form a multilayer. For this reason, it is only necessary to laminate the ceramic side raw material and the metal side raw material in two layers, and it is possible to manufacture at low cost by a simple molding process. Thereby, there is an effect that the thermal conductivity, the heat resistance, and the stress resistance are excellent, and the joining reliability is improved.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for producing a functionally gradient material according to an embodiment of the present invention will be described below.

In this embodiment, a process for manufacturing a functionally graded material in which a ceramic substrate as a heat dissipation substrate and a heat sink base are integrated will be described. Usually, this type of process includes a substrate manufacturing process, a processing process thereof, a process of directly arranging copper on a matching surface of the substrate, a process of applying nickel plating to a portion where the copper is arranged, a manufacturing process of a heat sink base, a processing process thereof, And a step of soldering by interposing solder between the heat sink base and the heat sink base. In the present embodiment, these steps are collectively performed in two steps of a manufacturing step of the functionally graded material and a processing step thereof. . The processing step is a step of setting the surface roughness on the ceramic substrate side to 0.8 S or more, and can be performed in one step by shot blasting or the like.

As the ceramic side composition, aluminum nitride is selected from the viewpoint of heat conduction and thermal expansion coefficient. On the other hand, as the metal side composition on the heat sink base side, copper alloy is selected from the viewpoint of heat conduction and thermal expansion coefficient. Among them, copper-tungsten (-Ag) was set.

Therefore, in consideration of making the thermal expansion coefficients of the ceramic side composition and the metal side composition substantially the same at the production temperature and the use temperature, and taking into account the sintering temperature range of the ceramic side and the metal side, Ceramic side raw materials and metal side raw materials having the composition ratios shown in Tables 5 and 6 were set.

[0025]

[Table 5]

[0026]

[Table 6]

Next, in Table 5, No. 1 to No. 4 and No. 4 in Table 6. a-No. The ratio of the coefficient of thermal expansion in the sintering temperature range, that is, the coefficient of thermal expansion of ceramics / the coefficient of thermal expansion of metal × 100
(%) Was calculated, and the results are shown in Table 7.

[0028]

[Table 7]

Further, after each of the ceramic-side raw material and the metal-side raw material is wet-mixed using an organic solvent, the solvent is prepared up to 13 vol%, and molded using a hydrostatic pressure molding method in a mold. A molded article was obtained. At that time, paper is placed on the lower punch of the mold, and the metal-side raw material powder is filled thereon and compressed at about 20 MPa, and then the ceramic-side raw material powder is filled,
Paper was placed thereon and molded at a pressure of 120 MPa. This paper has a function of preventing the organic solvent from oozing out of the molded body during pressurization and keeping the mold punch and the molded body in close contact with each other, and has a function of maintaining the molding yield.

Next, after being dried, each molded body is heated to 1350 ° C. at 0.5 Torr under a flow of nitrogen gas, and further heated to 90 ° C. at 1450 ° C. with 1 bar of nitrogen gas.
It was nitrided and sintered for only minutes. Here, each sintered body obtained under the above sintering conditions was inspected for defects, and the results are shown in Table 8.

[0031]

[Table 8]

In Table 8, those which have been sufficiently densified from the density and cross-sectional observations and which can be actually used are indicated by "◎", and those which can be used experimentally without generation of defects or the like are indicated by "○". "" Indicates that the formation of cracks and the like was observed but the shape was maintained, and "x" indicates that there were many defects such as cracks and cracks and even handling was difficult. These were tested under different sintering conditions and patterns, but no improvement was achieved from “Δ” and “×” to “◎” and “「 ”. The sintering conditions are 1100 ° C ~
The test was performed by changing the temperature up to 1700 ° C.

As a result, when the thermal expansion coefficient ratio in the vicinity of the use temperature was 75 to 125 (%), it was possible to manufacture the functionally graded material without generating a visible level of defect. Further, the ratio of the coefficient of thermal expansion is 85 to 115 (%).
At this time, an excellent functionally graded material having a desired function was formed.

Further, No. 1 and No. c has a mean thermal conductivity of 180 W
/ MK and a high value. Therefore, a remarkable improvement is realized as compared with the case where the heat conductivity of the heat sink base integrated type semiconductor substrate which has been manufactured by soldering is up to 100 W / mK.

[0035]

As described above, in the method for producing a functionally graded material according to the present invention, in a functionally graded material having a ceramic side composition and a metal side composition, the thermal expansion coefficient of the ceramic composition part and the thermal expansion coefficient of the metal composition part Because the coefficient of expansion is adjusted so that it is almost the same at the production temperature and the use temperature,
Cracks, deformation, and the like do not occur in the laminated portion, and a highly reliable high thermal conductive joint portion in which both components are mutually diffused can be obtained. This makes it possible to reliably obtain a functionally graded material having a desired function with an extremely simple process, and to reduce the manufacturing cost.

Claims (5)

[Claims] 1. A method for producing a functionally graded material having a ceramic-side composition and a metal-side composition, wherein the coefficient of thermal expansion of the 100% ceramic portion and the 100% metal portion is determined by the production temperature and Selecting a ceramic-side raw material and a metal-side raw material that are adjusted so that the thermal expansion coefficient of the ceramic composition portion / the thermal expansion coefficient of the metal composition portion × 100 = 75 to 125 (%) at the operating temperature; Producing a functionally graded material by laminating a raw material and said metal-side raw material and mutually diffusing both components by simultaneous firing treatment to produce a functionally graded material. 2. The method according to claim 1, wherein said ceramic composition portion is aluminum nitride, and said metal composition portion is copper and tungsten. 3. The method according to claim 1, wherein
The ceramic-side raw material has metal aluminum which becomes aluminum nitride by nitriding, and at the time of the nitriding, aluminum nitride and zirconium, tungsten, tungsten carbide, tungsten nitride, molybdenum carbide as other additives. And at least one selected from chromium and alumina, and a method for producing a functionally gradient material. 4. The manufacturing method according to claim 3, wherein the composition ratio of said metal aluminum, said aluminum nitride and said other additive is: metal aluminum: aluminum nitride: other additive = 8
~ 25: 74 ~ 87: 1 ~ 12, a method for producing a functionally gradient material. 5. The method according to claim 1, wherein the ceramic-side raw material and the metal-side raw material are set to have the same firing temperature. Manufacturing method of functionally graded material.