JPS6141538A - Ceramic substrate and manufacture thereof - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

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.
Particularly preferably, the present invention relates to a ceramic substrate for mounting a semiconductor element, in which the surface layer of the ceramic substrate is completely coated with a metal layer that does not completely inhibit the bonding with silicon, which is a semiconductor element, and a heat sink, and a method for manufacturing the same.

[Background of the invention]

Ceramic containing a small amount of beryllia gold in silicon carbide is a new type of ceramic that has both high thermal conductivity and high electrical insulation. Ceramics having all of these excellent properties are used for substrates for mounting semiconductor elements, etc., but the surface layer needs to be metallized in order to bond with silicon or the like of the semiconductor element.

Conventionally, there are various methods for metallizing ceramic surfaces depending on the application and purpose. For example, the metallization method for alumina ceramics is as described in JP-A-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 metallize the entire structure and then apply nickel plating, etc. Therefore, we used a conventional method to fully metalize the surface layer of a ceramic whose main component was silicon carbide, that is, to print the entire surface layer on a molybdenum powder base.
In a structure in which metallization is performed by firing in a wet hydrogen atmosphere or a dry hydrogen atmosphere at 00° C., and electronickel plating is performed, there is a problem in that the reliability due to heat treatment depends on the thickness of the nickel plating.

Here, problems with conventional manufacturing methods will be discussed. As shown in FIG. 2, in the conventional structure in which the surface layer of a ceramic substrate 1 whose main components are carbon, silicon, and the entire surface layer is metallized 22 and electrolytically nickel plated 23, peeling easily occurs from the boundary between the metallized layer and the ceramic.

The reason why the metallized layer of the conventional structure shown in FIG. 2 separates is that silicon carbide, molybdenum, and nickel have different coefficients of thermal expansion. That is, silicon carbide is 3.5
X 10 = / u, molybdenum 4.9 X 10-6
/ ℃ There is not much difference in the coefficient of thermal expansion of silicon carbide and molybdenum, but the coefficient of thermal expansion of nickel is 13.6 × 1
o-6/r: Because of the large size, the shrinkage of the nickel layer during cooling during heat treatment is greater than that of ceramic and molybdenum, and due to the shrinkage rate of the molybdenum layer and the ceramic total tensile strength, and the relative strength, the metallized layer This causes delamination at the ceramic interface. 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, the barrel plating method is used to plate many small objects at once. However, in barrel plating, since all dummy valves are energized, the plating current density is not constant and the plating film thickness distribution is also not uniform. Therefore, if the surface layer of a ceramic containing silicon carbide is completely metallized and barrel electroplated with nickel,
Since the nickel plating film thickness distribution is non-uniform, the metal 1 layer tends to peel off due to non-uniform shrinkage stress during heat treatment.

Table 1 Table 1 shows nickel sulfate 2409/l, nickel chloride 4
5 t/l, watts bath consisting of 3 t/7 t of boric acid or 375 f/l of nickel sulfamate, 30 f/l of boric acid
After barrel plating using a nickel sulfamate plating bath consisting of 0.4 f/l of sodium lauryl sulfate at a temperature of 50°C, a plating current density of IA/dm", a rotation speed of 5 rpm, and a plating thickness of 2.5.10 μm. All the results are shown after heat treatment in a hydrogen atmosphere at a temperature of 500°C for a holding time of 5 minutes, and the Δ marks indicate that the metallized layer has peeled off in some cases.
The x marks indicate that the metallization layer has mostly separated. As a result, both when using a Watt bath or a sulfamino acid nickel plating bath, there is a tendency for the metallized layer to peel off, especially when the nickel plating becomes thick. Therefore, the nickel plating after the entire surface layer of the ceramic whose main component is silicon carbide has been made into molybdenum metal requires that the nickel plating thickness be uniformly distributed. However, in barrel plating, a uniform plating thickness cannot be obtained because the plating current density is non-uniform. Therefore, nickel plating after the entire surface layer of a ceramic whose main component is silicon carbide has been metallized with molybdenum has to be performed one by one, resulting in poor productivity.

[Purpose of the invention]

An object of the present invention is to provide a ceramic substrate that has high reliability through heat treatment and is highly productive, and a method for manufacturing the same.

[Summary of the invention]

Kaito Himi To summarize, the first invention of the present invention relates to a ceramic substrate, which comprises a ceramic base, a copper or aluminum-carbon fiber composite material layer bonded onto the base, and this composite material layer. The composite material Ivi is characterized in that the surface of the composite material Ivi, which includes the entire metal plating layer formed thereon, has a structure in which the carbon fibers do not touch the plating layer.

A second invention of the present invention relates to a method for manufacturing a ceramic substrate, including a step of bonding all copper or aluminum-carbon fiber composite layers to a ceramic substrate, and a step of bonding the composite material before or after the step. Process to prevent the carbon fiber from being exposed on the surface of the material layer, and finally metal plating? It is characterized by including all of the steps involved.

The copper or aluminum-carbon fiber composite material used in the method of the present invention, in which carbon fibers are embedded in a copper or aluminum matrix, has good thermal conductivity and electrical conductivity.
In addition to having characteristics such as a low coefficient of thermal expansion, the copper or aluminum matrix also has flexibility, so it can also be used as a stress relief material.

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 the peeling of the metal layer can be completely prevented. Ta.

The composite material used in the present invention is a known material, for example, a copper-carbon fiber composite material is disclosed in Japanese Patent Publication No. 55-12
8274, while an aluminum-carbon fiber composite material is described in JP-A-49-18891.

However, as mentioned above, copper (or aluminum)-carbon fiber composite materials have carbon fibers embedded in a copper (or aluminum) matrix, and if the carbon fibers are exposed on the surface, uniform metal plating cannot be achieved. Can not. 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 has characteristics as a substrate for mounting semiconductor elements, which is one use of the ceramic substrate of the present invention. It does not have any negative effect on the

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 characteristic sound of a copper (or aluminum)-carbon fiber composite material. And the barrel plating method as a means of meeting metal plating? It has also been found that the substrates can be mass-produced because the reliability is not degraded by heat treatment even when the substrates are used.

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, All you have to do is cover it with foil or plate it.
Alternatively, the whole composite material can be sandwiched in a hot press.

[Embodiments of the invention]

EXAMPLES 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 is a schematic cross-sectional view showing the structure of one example of the ceramic substrate of the present invention. In FIG. 1, numeral 1 means a ceramic substrate, 2 means a copper (or aluminum)-carbon fiber composite material, 5 means a bonding material, and 4 means a plated metal material.

Example 1 Granulation - Hot pressing - Cutting and grinding thickness [16111
1% Width 91111% Length 15 am (7) Carbonized Ke(
'XK Ceramic substrate containing a small amount of beryllia and diameter 6
A copper-carbon fiber composite material with a thickness of 0.1 = 8 m in width and 12 cm in length, which contains 45% of carbon fibers with a total surface thickness of 20 μm, is placed in an argon atmosphere using a manganese wax with a thickness of 25 μm. , bonded at a temperature of 870°C and a holding time of 1 second, and after surface activation treatment in an acidic bath, a Watts bath consisting of 240t/t of nickel sulfate, 451/l of nickel chloride, and 50f/t of boric acid or sulfamic acid. A nickel sulfamate plating bath consisting of 575 t/l of nickel, 509/l of boric acid, and 0-4 f/l of sodium pentauryl sulfate was used at a temperature of 50°C and a plating current density of I.
A/am”, rotation speed 5 rpm, average thickness 2.5.
10μm barrel nickel plated ceramic/1I
A complete composite plate of iIl-carbon fiber composite material/nickel was prepared.

Ceramic/copper-carbon sterile composite material/nickel composite plate prepared by the above method, in a hydrogen atmosphere at a temperature of 500°C,
As a result of heat treatment for a holding time of 5 minutes, no deformation such as peeling of the metallized layer was observed as shown in Table 2. The O mark in the table indicates that there is no deformation in the metallized layer.

Table 2 Next, as a result of investigating all the characteristics of the ceramic/copper-carbon fiber composite material/nickel composite plate produced in the same manner, it was found to be sufficiently satisfactory for use as a substrate for mounting a semiconductor element.

Further, according to the present invention, it is possible to omit steps such as preparing, applying, and sintering a metallization composition paste when fully metallizing the ceramic surface layer.

Therefore, according to the present invention, charcoal 1 can be used for semiconductor element mounting substrates that have high reliability through heat treatment and high productivity.
Ceramic substrates containing 1Z silicon as a main component can be efficiently manufactured.

Example 2 Thickness 0.6m+, width 9 manufactured by the same method as Example 1
Ceramic substrate containing a small amount of beryllia in silicon carbide with a length of 13 cm and 45% carbon fiber with a diameter of 6 μm
A copper-carbon fiber composite material with a thickness of 8 mm, a width of 8 mm, and a length of 12 mm was bonded using manganese solder with a thickness of 25 μm in an argon atmosphere at a temperature of 870°C and a holding time of 1 second, and in an acid bath. After surface activation treatment with copper sulfate 20
0 tll, sulfuric acid 50 g/l, hydrochloric acid α15 g/l copper sulfate plating bath, temperature 30°C, plating current density 1A
/ dm”, rotation speed 5 rpm, first layer thickness 5 μm
Then, under the same conditions as the nickel plating in the second layer VC Example 1, barrel nickel plating was performed to a thickness of 2.5.10 μm to produce a complete ceramic/copper-carbon fiber composite/nickel composite plate. did.

The ceramic/copper-carbon fiber composite material/nickel plate produced by the above method was heat-treated in a hydrogen atmosphere at a temperature of 500°C for 5 minutes in the same manner as in Example 1. Similarly, no phenomena such as peeling of the metallized layer were observed.

As described above, in Examples 1 and 2, the carbon fibers were treated to prevent the surface VC from being exposed before or after brazing the copper-carbon fiber composite material to the ceramic substrate containing a small amount of beryllia in silicon carbide with manganese. Although we have described the production of a nickel-plated ceramic/@-carbon fiber composite material/nickel composite board, the fundamental purpose of the present invention is to improve reliability through heat treatment of a ceramic substrate for mounting semiconductor elements with a metalized surface layer. The goal is to increase productivity without reducing productivity. Therefore, in the present invention, in addition to the copper-carbon fiber composite material explained in Examples 1 and 2, aluminum-
Bonding carbon fiber composite materials etc. and plating with metal such as nickel? The present invention can be applied to composite plates having a structure consisting of ceramic/fiber-reinforced composite material/metal plating layer, and to general methods of manufacturing such composite plates.

〔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 the drawing]

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 entire structure of an example of a conventional ceramic substrate. 1: Ceramic substrate, 2: Copper (or aluminum)-carbon fiber composite material, 5: Bonding material, 4: Plated metal material, 2
2: Metalized layer, 23: Nickel plating material

Claims (1)

[Claims] 1. A ceramic substrate, a copper or aluminum-carbon fiber composite material layer bonded onto the substrate, and a metal plating layer formed on the composite material layer, the composite material comprising: A ceramic substrate characterized in that a layer surface has a structure in which the carbon fibers do not touch the plating layer. 2. A step of bonding a copper or aluminum-carbon fiber composite material layer to a ceramic substrate, 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 a step of bonding a metal A method for manufacturing a ceramic substrate, characterized by including each step of plating.