JPS6374934A - Glass coated sintered silicon carbide and production thereof - Google Patents

Abstract

PURPOSE:To produce a glass coated sintered SiC having low dielectric constant, causing neither foams nor cracks, by coating the surface of a sintered SiC with paste of glass powder having a specific composition and an organic binder, calcining and repeating these processes. CONSTITUTION:The surface of sintered SiC is coated with paste consisting of glass powder containing 9-15wt.% Al2O3, 20-30wt.% B2O2, 40-60wt.% SiO2, 3-15wt.% CaO and, if necessary, <=3pts.wt. ZrO2 and an organic binder. The coated sintered SiC is heated to remove the binder, further heated at 1,100-1,500 deg.C and then cooled to form a primary calcined glass layer. Further the surface is coated with similar paste, heated to remove the binder, further heated to 850-1,100 deg.C and then cooled to form a secondary calcined glass layer. Consequently, uniform sintered SiC having a glass coat and high electrical resistance of surface causing neither foams nor cracks is obtained.

Description

Detailed Description of the Invention (Industrial Application Fields) Silicon carbide sintered bodies have excellent strength at high temperatures and are useful as heat-resistant materials. Also, due to their high thermal conductivity, they are useful as substrates for integrated circuits. However, since the volume resistivity is as low as 102 to 106 Ω, the electrical insulation is low, and there are many pores with a diameter of about 1 to 2 μm on the surface. The sintered body is coated and put into practical use.

(Prior art) Glass coating is a method of smoothing the surface of a silicon carbide sintered body and increasing its electrical insulation. Conventionally, the glass used for this purpose is a low melting point glass containing PBO. The drawback is that it has a high dielectric constant.Another method for forming a glass coating by firing is to mix glass powder and an organic binder, apply it as a paste to the surface of the silicon carbide sintered body, and then dry and fire it. (There is a coating method. Although this method is easy and industrially convenient, it has the disadvantage that bubbles and cracks are likely to occur in the glass coating formed by firing.

(Problems to be Solved by the Invention) The disadvantages of conventional glass coating films formed on silicon carbide sintered bodies, namely the high dielectric constant and the tendency for bubbles and cracks to occur, have been improved. An object of the present invention is to provide a glass-coated silicon carbide sintered body and a method for manufacturing the same.

(Means for solving the problems) The present invention for achieving the above object is based on At2039-1
5% by weight, Bo 20-30% by weight, 510240-6
A glass-coated silicon carbide sintered body having a glass coating film consisting of 0% by weight, 0003-15% by weight and a glass coating film containing approximately 25 parts by weight or less of ZrO per 100 parts by weight of the composition, and the glass coating. A paste consisting of a glass powder having composition 3 corresponding to the film and an organic binder is applied to the surface of the silicon carbide sintered body, first heated to remove the binder, and then heated to 1100°C to 1500°C.
The first fired glass layer is formed by heating to a temperature range of After that, further 850℃
The present invention relates to a method for manufacturing a glass-coated silicon carbide sintered body, which comprises heating to a temperature range of ~1100 C and then cooling to form a second fired glass layer.

Since the glass of said composition is free of alkali fluoride and pbo, its coefficient of thermal expansion and dielectric constant are relatively small. However, since this type of glass generally has a high glass melting temperature, the manufacturing temperature of the glass and the firing temperature of the glass coating become high, which is disadvantageous for coating silicon carbide sintered bodies with glass. However, in the present invention, it has become possible to melt at a temperature of 1450C or lower, and it has also become possible to form a glass coating by firing at a temperature of 1000C or lower.

Let's further explain the glass composition.

The content of 51o2 should be 40wt.1% or more to make the thermal expansion coefficient of the glass close to that of silicon carbide, and 60wt.1% to keep the melting temperature of the glass below 1450C. It is necessary to do the following. O
α0 is essential for reducing the viscosity of the melt during glass melting and producing homogeneous glass, and if it does not reach 1%, the viscosity is insufficiently reduced, and 15ffiffi
If it exceeds %, the coefficient of thermal expansion will be larger than that of the silicon carbide sintered body, and cracks will occur in the glass coating. cause

When ZrO□ is contained in an amount of 3 parts by weight or less, it has the effect of causing emulsification of the glass during firing and forming the glass coating and improving the chemical durability of the formed glass coating. However, if it exceeds 3 parts by weight, homogeneous glass melting will result in sticking. 2r02 is included if necessary.

If the amount of At203 is less than 9%, the moisture resistance will be poor;
If the temperature is exceeded, the melting temperature will increase. The B20° content is 2
If it is less than 0%, the melting temperature will become too high, and if it exceeds 30%, the chemical stability of the glass will decrease, which is not desirable.

The glass-coated silicon carbide sintered body of the present invention is produced by a one-step method in which a paste prepared by mixing glass powder with the above composition and a binder is applied to a silicon carbide sintered body, and after firing, the glass layer is cooled to solidify the glass layer. A glass coating of excellent properties can be formed on the silicon carbide sintered body by preferably performing the firing in two stages.

First, a one-step firing method [Noperu].

First, At2039-15% by weight with a particle size of 50 μm or less
3020-30% by weight, SiO240-60% by weight, C
A glass powder consisting of α06 to 15% by weight, or a glass powder containing 3 parts by weight or less of ZrO2 based on 100 parts by weight of the composition, 50 to 60% by weight, and 40 to 50% by weight of a binder. The paste which is a mixture is made of silicon carbide sintered body or 1000~1400C
It is applied to the surface of a silicon carbide sintered body whose surface has been oxidized with
Next, the binder is removed by heating in the range of 90 to 400C, and then heated to a constant temperature in the range of 850 to 1.100t:'.
Heat for 5 to 30 minutes and then cool to form a homogeneous glass coating. Next, the two-stage firing method will be described in detail.

First, At2039-15% by weight with a particle size of 50 μm or less, B
o 20-30% by weight, SiO240-60% by weight, 0
Glass powder consisting of 3 to 15% by weight of a0, or glass powder containing 3 parts by weight or less of ZrO2 per 100 parts by weight of the composition (hereinafter referred to as glass powder) containing 10 to 20% by weight The paste, which is a mixture of the glass powder and the binder, is applied to the surface of the silicon carbide sintered body, then heated to a temperature in the range of 90 to 400 C to remove the binder, and heated at 1,100 to 15,000 C for 50 to 60 minutes.
Heat for 0 minutes and then cool to form a homogeneous glass coating. In addition, the glass certificate in this case is α5~t 01n9/c
ffl is preferred. When the amount of glass does not reach α5 da/cal, the glass coating becomes uneven and to+19/cm
When the temperature exceeds 100%, air bubbles remain in the glass coating.

Ethyl cellulose is preferred as the binder, and terpineol and carpitol acetate are preferred as the solvent plasticizer.

The reason for setting the glass powder content in the paste to 10 to 20% by weight is that if it does not reach 10% by weight, the glass coating will become non-uniform. When the amount exceeds 20% by weight, the glass coating becomes thicker and causes bubbles to remain.

In general, the smaller the particle size of the glass powder, the better the properties of the resulting glass film, but practically the particle size is 44 μm or less, preferably 10 μm or less.

The first fired glass film produced in this way penetrates into the pores on the surface of the silicon carbide sintered body to prevent the generation of bubbles in the next second firing. Containing 50 to 60% by weight of glass powder within the composition range used in The binder is removed, and the glass is heated to a constant temperature within the range of 850 to 1100 t:' for 15 to 30 minutes, and finally cooled to form a homogeneous secondary fired glass film.In this case, the amount of glass is 5
It is desirable that it is 0 to 60 .mu./d.

The reason why the glass powder content in the paste is set to 50 to 60% by weight is that if it does not reach 50% by weight, multiple applications are required to form a glass coating of the required thickness. 60
When the weight exceeds 4%, it is difficult to apply the paste uniformly to the required thickness.

Preferable binders are ethyl cellulose,
Solvents, plasticizers, etc. are terpineol and carpitol acetate. The secondary firing is repeated until the thickness of the glass coating reaches the required thickness.

Note that the glass powder used in the above-mentioned firing is obtained by crushing glass produced by a conventional method and, if necessary, classifying it by an appropriate means. The paste is applied by a screen printing method, a doctor blade method, or the like.

(Effects) The glass coating on the silicon carbide sintered body produced according to the present invention has a homogeneous glass phase, and the formation of bubbles and cracks is also improved compared to the past. Depending on the type of glass, the coating can be made colorless and transparent or emulsified. The glass-coated silicon carbide sintered body according to the present invention has a large electrical resistance on the surface of the silicon carbide sintered body due to the glass coating, and is used as a substrate for various integrated circuits. show.

Reference example Production of glass powder The raw material mixture for glass shown in Table 1 is placed in a platinum crucible and heated to 1450C in an electric furnace with a silicon carbide heating element.The resulting melt is poured onto a graphite plate and solidified to form a colorless product. A transparent glass was prepared. Next, this glass was ground to 325 mm and 1 mm (44 μm) or less using an alumina mortar. This glass powder was suspended in ethyl alcohol and classified based on the difference in sedimentation rate to prepare glass powder with a particle size of 10 μm or less. These glass powders are kneaded with a binder to form a paste, which is applied to a silicon carbide sintered body.

Table 1 Example 1 A paste containing 56% by weight of glass powder was produced by mixing powders of tkl, m2, and Nn5 shown in Table 1 with a particle size of 44 μm or less with organic binders such as ethyl cellulose, terpineol, and carpitol acetate. and coated on the surface of a silicon carbide sintered body substrate (hereinafter abbreviated as the substrate), and
After heating to 20C to remove the binder, 750℃~
It was fired at a constant temperature between 1100 C for a certain time.

Table 2 shows the conditions of bubbles, cracks, and emulsion in the obtained glass coating. The respective degree is indicated by A-11. A indicates none, B indicates a very small amount, 0 indicates a small amount, D indicates a large amount, and E indicates an extremely large amount. There are cracks on floor 1, but Nn2
．． In No. 3, there are no cracks. Furthermore, the number of bubbles tends to increase as the firing temperature increases. Note that the glass coating had a thickness of 2X.

Table 2 Example 2 Glass powder with a glass composition of m2 shown in Table 1 with a particle size of 10 μm or less, and 4 with a glass powder particle size of 10 μm or less classified and separated.
The following procedures were carried out for each case of 4 μm or less.

That is, each glass powder was mixed with organic binders such as ethyl cellulose, terpineol, and carpitol acetate to prepare a paste with a glass powder content of 10% by weight, and the paste was coated on a silicon carbide substrate by screen printing and heated to 400C. After heating and removing the binder,
A glass coating was formed by baking at 1400C for 30 minutes. The relationship between the powder particle size, coating amount, and the properties of the resulting glass coating (heterogeneity, bubble formation, etc.) is shown in FIG.

Table 3 Regarding heterogeneity, there is no mu and D indicates a large amount.
The bubbles are the same as in Example 1.

Note that no cracks were generated in this example.

This example shows that a homogeneous, bubble-free glass coating can be obtained when glass powder with a particle size of 10 μm or less is used and the amount of glass is α5 to toe/cm.

Example 3 A glass coating was formed on a silicon carbide sintered body by firing a glass powder having the glass composition of positive 2 using a two-step firing method. First, a paste containing 10% by weight of glass powder prepared by glass powder with a particle size of 10 μm or less and organic binders such as ethyl cellulose, terpineol, and carpitol acetate was applied to the surface of the substrate by screen printing, and heated to 400C. After removing the binder 14
00 t:' for 30 minutes and cooled to form a glass coating. Next, a paste containing 56% by weight of glass powder prepared by removing glass powder with a particle size of 10 μm or less and glass powder with a particle size of 44 μm or less and organic binders such as ethyl cellulose, terpineol, and carpitol acetate is applied to the glass-coated surface. After applying by screen printing method and heating to 120C to remove the binder,
A glass coating was formed by firing at a constant temperature between 925 and 10251:' for 15 minutes and cooling. The results are shown in Table 4. No cracks were formed at any of the firing temperatures, and no bubbles were formed at the secondary firing temperature of 975C. The higher the firing temperature, the more bubbles tend to increase.

The thickness of the glass coating was 0.0811 m.

Example 4.5 Two-stage firing was carried out under the same conditions as in Example 3 using glass powders having compositions of N14 and N15. In either case, a colorless and transparent glass coating without bubbles or cracks could be formed.

Claims (4)

[Claims] (1) Al_2O_39-15% by weight, B_2O_32
0-30% by weight, SiO_240-60% by weight, CaO
A glass-coated silicon carbide sintered body having a glass coating film consisting of 3 to 15% by weight. (2) Al_2O_39-15% by weight, B_2O_32
0-30% by weight, SiO_240-60% by weight, CaO
A glass-coated silicon carbide sintered body having a glass coating film consisting of 3 to 15% by weight and further containing 3 parts by weight or less of ZrO_2 based on 100 parts by weight of the above composition. (3) Al_2O_39~ on the surface of the silicon carbide sintered body
15% by weight, B_2O_320-30% by weight, SiO_
A paste consisting of glass powder consisting of 240 to 60% by weight and 3 to 15% by weight of CaO and an organic binder was applied, first heated to remove the binder, and then heated to 1100% by weight.
The glass powder is heated to a temperature range of 1500°C to 1500°C, then cooled to form a primary fired glass layer, and then a paste consisting of a glass powder within the composition range of the glass powder and an organic binder is applied, and heated to form a first fired glass layer. After removing the binder,
A method for producing a glass-coated silicon carbide sintered body, which further comprises heating to a temperature range of 850°C to 1100°C and then cooling to form a second fired glass layer. (4) Al_2O_39-1 on the surface of the silicon carbide sintered body
5% by weight, B_2O_320-30% by weight, SiO_2
A glass powder paste consisting of a glass powder consisting of 40 to 60% by weight, 3 to 15% by weight of CaO, and further containing 3 parts by weight or less of ZrO_2 per 100 parts by weight of the above composition, and an organic binder is applied, and heated first. After removing the binder, it is further heated to a temperature range of 1100°C to 1500°C, and then cooled to form a first fired glass layer, which is further composed of a glass powder within the composition range of the glass powder and an organic binder. , glass-coated silicon carbide characterized by applying a glass powder paste, removing the binder by heating, further heating to a temperature range of 850°C to 1100°C, and then cooling to form a second fired glass layer. A method for producing a sintered body.