JPS6261558B2 - - Google Patents

Description

[Detailed description of the invention]

Silicon nitride, silicon nitride, silicon carbide, and sintered bodies of silicon carbide (hereinafter referred to as silicon nitride and silicon carbide) both have excellent heat-resistant properties such as thermal shock strength and mechanical strength at high temperatures, and have excellent chemical properties. High-alumina ceramics have been used in high-temperature mechanical parts because of their high mechanical stability and excellent wear resistance, and in particular, as internal combustion engine parts due to their significantly high thermal shock strength. However, it was difficult to create a metallized surface that could be firmly bonded to a different material such as metal, for example when used as a chip for the sliding part of a rocker arm. The reason for this is that the coefficient of thermal expansion of both silicon nitride sintered body and silicon carbide sintered body, which is approximately 4.5×10 ^-6 /℃ or less, is higher than that of a different material, such as 15×10 ^-6 /℃ of steel. ℃, and is approximately 1/2 that of the same ceramic, high alumina porcelain, which is approximately 8.0×10 ^-6 /℃, and this low coefficient of thermal expansion contributes greatly to the heat resistance properties mentioned above. On the other hand, this causes a large difference in thermal expansion between the dissimilar materials being joined, resulting in a significant reduction in joint strength. In other words, in the metallization (thick film) method, which is commonly used as a conventional metallization method, in which a metallization paste is screen printed on the surface of the substrate and then heated in a non-oxidizing atmosphere, the metallized surface generated on the substrate is , Mo or W with high rigidity
Not only is the metallized surface on the substrate unable to absorb the above thermal expansion difference, but the metallized surface is
Since the metallized surface is formed into a thick film of .mu., the difference in thermal expansion between the base and the metallized surface has even become a factor in reducing the bonding strength. The present invention has succeeded in establishing a method for metallizing the surfaces of sintered bodies of silicon nitride and silicon carbide, which exhibit particularly high bonding strength with dissimilar materials. The feature is that the metallized surface is produced by physical vapor deposition. In the present invention, the reason why Al was specified as the metal that generates the metallized surface is that Al easily reacts with the silicon nitride and silicon carbide of the base, and the former silicon nitride easily reacts with free nitrogen and oxygen. This is because the latter carbide easily reacts with free carbon and oxygen, provides a metallized surface that firmly bonds with the substrate, and because Al has great malleability. The reason why this method was adopted is that the film thickness of the metallized surface can be freely controlled, and since the processing temperature is relatively low, the reaction layer can be limited to the vicinity of the boundary between the deposited film and the base, and the size of the deposited layer can be increased. This is because the Al layer having the above-mentioned high malleability is used as the portion, and this malleability absorbs the difference in thermal expansion between the different materials to be joined by brazing. Example 1 Purity 98%, theoretical density ratio 98, manufactured by conventional method
% of a plate-shaped silicon carbide sintered body from 30 x 10 x 5 mm,
Using silicon nitride sintered bodies of the same size with the same purity of 90% and theoretical density ratio of 99% as a base, one main surface of 30 x 10 mm was polished to a surface roughness of 0.17 to 0.48 μRa, and then Cleaning with neutral detergent and running water - Moisture replacement with acetone - 1.1.1 Trichloroethane and acetone washing - Drying, and vacuum evaporation machine (Nippon Vacuum Technology Co., Ltd. EVB)
Various thicknesses were obtained by ^melting and vapor depositing Al by resistance heating on the main surface which had undergone the polishing process described above. In order to examine the bonding strength of the metallized surface made of a thin Al film to each substrate, the metallized surface was made into a rectangular pattern with a width of 1.6 mm and a length of 5.0 mm by photoetching, and a rectangular pattern of 1 mmφ was formed on this metallized surface by photoetching.
A length of about 50 mm of Cu wire is bent at a right angle at a point 6 mm from the end, and the 6 mm long part is fixed so that the bent point is 1 mm away from the outer edge of the pattern, and then the product is called Arsol 45D. After brazing using aluminum solder from Nihon Superior Co., Ltd., the copper wire was pulled vertically and the Al film was peeled off to perform a peel strength test. The results are shown in Table 1.

[Table] From Table 1, there is no major difference in the material of the substrate whether the substrate is a silicon carbide sintered body or a silicon nitride sintered body; If the film thickness of the metallized surface is 1000 Å, the bonding strength with the base as expressed by adhesion strength is insufficient and practical, but it becomes practical when it rapidly increases from 2000 Å, and when it reaches 10000 Å (1.0 μ), it becomes low. It has been confirmed that the film has a strength that is strong enough to peel off from the bonded part, and that it tends to be saturated beyond that point. Therefore, from the viewpoint of mass production, the film thickness should be within the range of 10,000 Å to 20,000 Å, especially
Approximately 10,000 Å is preferable. Example 2 As mentioned earlier, the dense sintered bodies of silicon carbide and silicon nitride both exhibit excellent properties as mechanical parts for high-temperature use, and the coefficient of thermal expansion is also in the unit of 10 ^-6 , with the former silicon carbide being approximately 4.4. , silicon nitride is very similar to about 3.2, and it is possible to create a composite sintered body of silicon carbide and silicon nitride.As before, a composite sintered body of 30 x 10 x 5 mm is made into a plate, Table 2 shows the results of the same test as before. However, the metallized surface formed on the surface of the substrate by Al vapor deposition was fixed at 10,000 Å.

[Table] From Table 2, it was revealed that results almost equivalent to those of the sintered bodies of silicon carbide and silicon nitride can be obtained even when the sintered body of silicon carbide and silicon nitride is used as the base. Example 3 In each of the previous examples, a brazing agent for aluminum was used because the bonding strength with the substrate was tested by directly brazing the metallized surface by vapor deposition of Al. Soldering can be performed by vapor-depositing Cu, Ni, Ag, etc. onto the metallized surface of Al without breaking the vacuum of the vacuum chamber. By this method, the film thickness of the metallized surface by Al vapor deposition can be made thinner than 10,000 Å, which was considered preferable from the viewpoint of practicality in each of the previous examples. Add 20000Å of Cu to the sample No. 5 in Table 1 of 5000Å.
When vapor-deposited, the bond strength exceeds the strength limit of solder soldering, that is, 5.0 kg/
It showed adhesion strength of 1.6mm or more. As described above, the present invention is characterized in that a metallized surface consisting of a thin film of aluminum is formed on the surface of a silicon nitride and carbide sintered body or a composite sintered body of both by physical vapor deposition. The metallization method is
The difference in thermal expansion between dissimilar materials is absorbed by the highly malleable aluminum thin film, which not only provides high bonding strength, but the metallized surface that is generated reacts only at the interface with the base, leaving the surface with a low It has excellent effects such as showing a metal state that can be attached. The materials that can be joined by brazing are not limited to metals, but also include oxides, other nitrides,
It is also possible to provide a metallized surface on the surface of other ceramic sintered bodies such as carbide, and to obtain large-sized silicon nitride and silicon carbide sintered bodies, two of these homogeneous materials can be used.
Although it is possible to divide it into two parts or more and join them together, this is particularly effective for brazing with dissimilar materials having different coefficients of thermal expansion.

Claims (1)

[Scope of Claims] 1. A method for metallizing the surface of a silicon nitride and carbide sintered body, characterized in that a metallized surface consisting of a thin film of aluminum is produced on the surface of the sintered body by physical vapor deposition. 2. The method for metallizing the surface of a sintered body according to claim 1, wherein the silicon nitride is silicon nitride and the silicon carbide is silicon carbide. 3. The silicon nitride and carbide sintered body surface according to claim 1 or 2, wherein the metallized surface made of a thin aluminum film on the sintered body surface has a film thickness of 2000 Å or more. Metallization method. 4. A method for metallizing the surface of a composite sintered body made of silicon nitride and silicon carbide, characterized in that a metallized surface made of a thin film of aluminum is produced on the surface of the sintered body by physical vapor deposition. 5. The method for metallizing the surface of a sintered body according to claim 4, wherein the silicon nitride is silicon nitride and the silicon carbide is silicon carbide. 6. The silicon nitride and carbide sintered body surface according to claim 4 or 5, wherein the metallized surface made of a thin aluminum film on the sintered body surface has a film thickness of 2000 Å or more. Metallization method. 7. On the thin film of aluminum produced by physical vapor deposition on the surface of the sintered body, a thin film of metal with high wettability is deposited by successive vapor deposition in the same vacuum. A method for metallizing the surface of a sintered body of silicon nitride, silicon carbide, or a combination of both. 8. The hardening of silicon nitride and silicon carbide, or both of them, according to claim 7, characterized in that the thin film of aluminum produced on the surface of the sintered body by physical vapor deposition has a thickness of 2000 Å or more. A method of metallizing the surface of a molten sintered body.