JPH0214189B2 - - Google Patents

Description

[Detailed description of the invention]

[Field of Application of the Invention] The present invention relates to a ceramic substrate and a method for manufacturing the same, and particularly preferably to a ceramic substrate mounted with a semiconductor element whose surface layer is coated with a metal layer that does not inhibit bonding with silicon, which is a semiconductor element, or a heat sink. The present invention relates to a ceramic substrate and a method for manufacturing the same. [Background of the Invention] Ceramic containing a small amount of beryllia in silicon carbide is a new type of ceramic that has both high thermal conductivity and high electrical insulation. Ceramics having such excellent properties are used for substrates for mounting semiconductor elements, etc., but the surface layer must be metallized in order to bond with silicon or the like of the semiconductor element. Conventionally, there are various methods for metallizing ceramic surface layers depending on the use and purpose. For example, the metallization method for alumina ceramic is as described in JP-A No. 55-113683, in which a metal composition paste is applied onto the ceramic, and then sintered in hydrogen or a mixture of hydrogen and nitrogen. A commonly used method is to bond the metal to form a metallized layer, and then apply nickel plating or the like. Therefore, we used a conventional method to metallize the surface layer of ceramics whose main component is silicon carbide, that is, we printed molybdenum powder paste, fired it in a wet hydrogen atmosphere and a dry hydrogen atmosphere at 1300 to 1500°C to metallize it, and then electro-nickel plated it. In this structure, there is a problem in that the reliability of heat treatment depends on the thickness of the nickel plating. Here, problems with conventional manufacturing methods will be discussed. As shown in FIG. 2, the conventional structure in which the surface layer of a ceramic substrate 1 mainly composed of silicon carbide is metallized 22 and electronickel plated 23 tends to peel off from the boundary between the metallized layer and the ceramic. The reason why the metallized layer of the conventional structure shown in FIG. 2 peels off is that silicon carbide, molybdenum, and nickel have different coefficients of thermal expansion. That is, silicon carbide is 3.5×10 ^-6 /℃, molybdenum is 4.9×10 ^-6 /℃
℃ and the coefficient of thermal expansion of silicon carbide and molybdenum are not much different, but the coefficient of thermal expansion of nickel is 13.6 ×
10 ^-6 /℃, the contraction of the nickel layer is greater than that of the ceramic and molybdenum layers during cooling during heat treatment, and the molybdenum layer and the ceramic, which shrink less, are pulled together, and due to their relative strength, the nickel layer shrinks more than the ceramic and molybdenum layers. The problem is that it causes delamination at the ceramic boundary. In particular, if the nickel plating thickness distribution is uneven or thick, the shrinkage stress due to heat treatment will increase, making the metallized layer more likely to peel off. Therefore, there is a restriction that the nickel plating film must be thin and uniformly distributed. On the other hand, ceramics used for semiconductor element mounting substrates are small and produced in large quantities. Generally, barrel plating is a method for plating many small objects at once. However, in barrel plating, since electricity is applied through a dummy, the plating current density is not constant, and the plating film thickness distribution is also not uniform. Therefore, when the surface layer of a ceramic whose main component is silicon carbide is metallized and barrel electroplated with nickel, the nickel plating film thickness distribution is uneven, and metallization occurs due to uneven shrinkage stress during heat treatment. The layers tend to peel off easily.

[Purpose of the invention]

The purpose of the present invention is to achieve high reliability through heat treatment,
Another object of the present invention is to provide a ceramic substrate with improved productivity and a method for manufacturing the same. [Summary of the Invention] To summarize the present invention, the first invention of the present invention relates to a ceramic substrate, which includes a ceramic substrate made of insulating silicon carbide, and a copper or aluminum substrate bonded onto this substrate. It is characterized by comprising a carbon fiber composite material layer and a metal coating layer formed on this composite material layer. A second invention of the present invention relates to a method for manufacturing a ceramic substrate, which includes a step of bonding a copper or aluminum-carbon fiber composite material layer to a ceramic substrate made of insulating silicon carbide; It is characterized by including the following steps: a step of treating the surface of the composite material layer so that the carbon fibers are not exposed before or after, and a step of finally performing metal plating. The copper or aluminum-carbon fiber composite material in the form of carbon fiber embedded in a copper or aluminum matrix used in the method of the present invention has characteristics such as good thermal conductivity and electrical conductivity, and a low coefficient of thermal expansion. The flexibility of the copper or aluminum matrix also makes it a stress reliever. The present inventors have discovered that in the ceramic substrate according to the present invention, the shrinkage stress generated in the metal plating layer due to heat treatment is alleviated by the copper (or aluminum)-carbon fiber composite material, so that peeling of the metal plating layer can be prevented. I found out. The composite materials used in the present invention are known materials; for example, the copper-carbon fiber composite material is described in Japanese Patent Application Laid-Open No. 128274/1982, and the aluminum-carbon fiber composite material is described in Japanese Patent Application Laid-Open No. 49-18891. It is stated in the official gazette. However, as mentioned above, copper (or aluminum)-carbon fiber composite materials are in the form of carbon fibers embedded in a copper (or aluminum) matrix, and when the carbon fibers are exposed on the surface, uniform metal plating occurs. I can't. Therefore, by forming the copper (or aluminum)-carbon fiber composite material so that the carbon fibers are not exposed on the surface, a uniform metal plating layer can be obtained. In addition, the copper (or aluminum)-carbon fiber composite material bonded to the ceramic substrate not only does not have a negative effect on the metal plating film, but also can be used as a substrate for mounting semiconductor elements, which is one use of the ceramic substrate of the present invention. It does not have any adverse effect on the characteristics of Therefore, the ceramic substrate of the present invention has a novel structure that not only does not impair the original characteristics of ceramic, but also has the characteristics of a copper (or aluminum)-carbon fiber composite material. It has also been found that even if barrel plating is used as a means for metal plating, the substrates can be mass-produced because the reliability due to heat treatment is not reduced. Therefore, the step of treating the carbon fibers so that they are not exposed, which is important in the method of the present invention, may be carried out by a method known per se. For example, before or after joining the composite material, the composite material may be It can be foiled or covered with plating, or the composite can be sandwiched in a hot press. [Examples of the Invention] Hereinafter, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to these Examples. Note that FIG. 1 shows one of the ceramic substrates of the present invention.
FIG. 2 is a cross-sectional schematic diagram showing an example structure. In FIG. 1, reference numeral 1 means a ceramic substrate, 2 means a copper (or aluminum)-carbon fiber composite material, 3 means a bonding material, and 4 means a plated metal material. Example 1 Granulation - Hot press - Cutting and grinding thickness 0.6
Ceramic substrate containing a small amount of beryllia in silicon carbide with a thickness of 0.1 mm, a width of 8 mm, and a length of 12 mm with a surface covered with a 20 μm thick copper foil containing 45% carbon fiber with a diameter of 6 μm. Copper-carbon fiber composite materials of 25 μm thick were bonded together in an argon atmosphere at a temperature of 870°C for a holding time of 1 second, and after surface activation treatment in an acidic bath, 240 g of nickel sulfate was added to the composite material. Nickel chloride 45g/,
Using a Watts bath consisting of 30 g of boric acid or a nickel sulfamate plating bath consisting of 375 g of nickel sulfamate, 30 g of boric acid, and 0.4 g of sodium lauryl sulfate, the temperature was 50°C and the plating current density was 1 A/dm ² . Ceramic/copper-carbon fiber composite material/nickel composite plates were prepared by barrel nickel plating to average thicknesses of 2, 5, and 10 μm at a rotation speed of 5 rpm. The ceramic/copper-carbon fiber composite material/nickel composite plate produced by the above method was heated in a hydrogen atmosphere.
As a result of heat treatment at a temperature of 500℃ and a holding time of 5 minutes,
As shown in Table 2, no deformation such as peeling of the metallized layer was observed. The circle mark in the table indicates that there is no deformation in the metallized layer.

〔Effect of the invention〕

As explained above, according to the present invention, remarkable effects have been achieved in that a ceramic substrate and a method for manufacturing the same are provided which have high reliability through heat treatment and high productivity due to omission of steps and the like.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view showing the structure of an example of a ceramic substrate of the present invention, and FIG. 2 is a schematic cross-sectional view showing the structure of an example of a conventional ceramic substrate. 1: ceramic substrate, 2: copper (or aluminum)-carbon fiber composite material, 3: bonding material, 4: plated metal material, 22: metallized layer, 23: nickel plated material.

Claims (1)

[Scope of Claims] 1. A ceramic substrate made of insulating silicon carbide, a copper or aluminum-carbon fiber composite material layer bonded to the substrate, and a metal coating layer formed on the composite material layer. A ceramic substrate characterized by: 2. A step of bonding a copper or aluminum-carbon fiber composite material layer to a ceramic substrate made of insulating silicon carbide, and a step of treating the surface of the composite material layer so that the carbon fibers are not exposed before or after this step. , and finally metal plating.