JPH02137787A - Glass-coated sintered silicon carbide and production thereof - Google Patents

Abstract

PURPOSE:To obtain the subject material free from cracks and voids, exhibiting high surface electric resistance and usable as substrate of various integrated circuits, etc., by forming a glass layer having specific component and composition on a surface of sintered silicon carbide. CONSTITUTION:A glass-coated sintered silicon carbide is produced by applying a glass layer composed of 15-23wt.% of Al2O3, 30-55wt.% of SiO2, 20-40wt.% of B2O3, 5-10wt.% of CaO and l-3wt.% of ZrO2 to a surface of sintered silicon carbide. It can be produced by melting the above composition in a platinum crucible at 1450-1500 deg.C, quenching the molten composition, crushing to a particle size of about 44mum, mixing the obtained glass powder with an organic binder to form a paste, applying the paste to a sintered silicon carbide and sintering at 850-1100 deg.C or applying the paste, subjecting to primary sintering at 1000-1450 deg.C, applying the paste again and carrying out the secondary sintering at 850-1000 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a glass-coated silicon carbide sintered body used for electrical circuit nozzle plates, heat-sensitive head substrates, etc., and a method for manufacturing the same.

(Prior art) Silicon carbide sintered bodies have excellent strength, heat resistance, and thermal conductivity, but their volume resistivity is 102 to 06ΩC1, which is poor electrical insulation. Since there are a large number of pores of about 2 to 2 cm in size, it is necessary to coat the surface of the sintered body in order to use it for large electric circuit boards or thermal head substrates.

The method involves applying a paste consisting of glass powder and an organic binder to the surface of a silicon carbide sintered body and firing it to form a glass layer on the surface of the sintered body. The glass used was lead borosilicate glass, which is used in alumina ceramics.

(Invention or Problem to be Solved) Since conventionally used glass has a large coefficient of thermal expansion,
Silicon carbide sintered bodies are prone to rear cracks due to differences in thermal expansion.
Or, due to the generation of bubbles due to the reaction with the silicon carbide sintered body,
There was a drawback that the adhesion between the silicon carbide sintered body and the glass was poor, and the formed glass layer could not be used effectively.

An object of the present invention is to provide a glass-coated silicon carbide sintered body that forms a specific glass layer on the surface of a sintered silicon carbide body, prevents cracks from occurring, and has good bonding properties with the surface of the sintered body, and a method for manufacturing the same. It is in.

(Means for Solving the Problems) The present invention has investigated a glass that has a relatively low melting point, has a thermal expansion coefficient that is not significantly different from that of silicon carbide sintered bodies, and does not react with silicon carbide sintered bodies. The summary of the completed result is: AIJt15-23g1% by weight (hereinafter % is based on weight), 5in2:to-55%, B, 0,2
It is a silicon carbide sintered body whose surface is coated with glass having a composition of 0 to 40% CaO, 3 to 1% CaO, and 1 to 3% lrO. Apply to the surface of silicon carbide sintered body 8
A method of heating to 50 to 1000°C, and after coating the paste by heating it to 1000 to 1450°C late in the coating process, the same paste is further applied on top of the coating to a temperature of 850 to 1000°C.
This method involves heating to 0°C.

Since the glass of the above composition does not contain alkali oxides and PbO, its coefficient of thermal expansion and dielectric constant are relatively small.However, glasses that do not contain these generally have a high glass melting temperature and are difficult to manufacture and manufacture. The firing temperature of the coating becomes high, which is disadvantageous for coating a silicon carbide sintered body with glass. However, in the case of undeveloped IJI, it has become possible to melt it at temperatures below 1450°C by using specific ingredients and compositions. The thermal expansion coefficient of silicon carbide sintered body is usually 40 to 42X 10
-'/'C or so, the glass composition of the present invention is approximately 33
~40x 10-'/°C.

The glass composition of the present invention contains 30 to 55% of SiO□, which is a glass-forming oxide, in order to make the coefficient of thermal expansion of the glass close to that of the silicon carbide sintered body.

If SiO□ is less than 30%, the coefficient of thermal expansion of the glass becomes large and the glass tends to undergo phase separation, making it impossible to form a smooth coating. Moreover, if it exceeds 55%, it becomes difficult to melt the glass, the glass baking temperature becomes high, and a reaction between the silicon carbide sintered body and the glass occurs, which tends to cause foaming.

Does the addition of B2O3 have the effect of lowering the thermal expansion coefficient and viscosity of the glass? In the present invention, BxCh is 20%.
If it is less than 40%, it becomes difficult to melt the glass, and if it exceeds 40%, the glass tends to undergo phase separation and its water resistance deteriorates.

A1□03 improves the chemical durability of glass by 15%
If it is less than 23%, the glass tends to undergo phase separation, and if it exceeds 23%, the glass tends to undergo phase separation and the coefficient of thermal expansion becomes large, making it easy for cracks to occur in the glass coating.

CaO is an important component for reducing the viscosity of the glass melt and obtaining a homogeneous glass, but if it is less than 5%, the viscosity decreases insufficiently and devitrification occurs when the glass is baked. If it exceeds 10%, the coefficient of thermal expansion of the glass increases, causing cracks in the glass coating and making it impossible to obtain a smooth coating.

Does Zr0t have an effect on the chemical durability of glass?If it exceeds 3%, the melting temperature of the glass will increase and the coefficient of thermal expansion of the glass will also increase, while if it is less than 1%, the chemical durability of the glass will deteriorate. I don't like either of them.

From these things, 5i02 is 30-55%, Al20f
f 15-23%, +120:l 20-40%, C
It is necessary to set aO to 5 to 10% and ZrO to 21 to 3%.

Next, the invention of the manufacturing method will be explained.

The glass powder is prepared by melting the above-mentioned composition in a platinum crucible, preferably rapidly cooling it, and then pulverizing it to adjust the particle size.

Melting is carried out at 1450 to 1500'C, and rapid cooling is carried out, for example, by pouring the melt into water. The cooled and solidified glass is crushed in an alumina or agate mortar to a particle size of about 44 gm or less.

A one-step method is possible in which the glass powder and organic binder are mixed to make a paste, applied to a silicon carbide sintered body, and cooled after firing to solidify the glass layer, but it is preferable to apply the paste and bake in two steps. By carrying out the process in stages, a glass coating with excellent properties can be formed on the silicon carbide sintered body.

In the one-step firing method, a paste is prepared by mixing glass powder and an organic binder so that the glass powder content is preferably 50 to 60% depending on the thickness of the coating film or the uniformity of the coating film.
This is applied to the surface of a silicon carbide sintered body or a silicon carbide sintered body that has undergone surface oxidation treatment, and heated to an appropriate temperature in the range of 80 to 400°C depending on the type of organic binder to remove the binder. The method involves removing the glass, heating it for 5 to 30 minutes at a constant temperature in the range of 850 to 1000°C, and then rapidly cooling it to form a homogeneous glass coating.

The surface oxidation treatment of the silicon carbide sintered body in this method involves heating the silicon carbide sintered body at 1300 to 1400°C in air, for example.
This is carried out by heating for 0.5 to 2 hours at a temperature of .

This surface oxidation treatment facilitates adhesion of the glass layer to the surface of the silicon carbide sintered body.

Furthermore, since the firing temperature after applying the paste is the softening temperature of this glass, which is 76°C to 850°C, the firing temperature is suitably in the range of 850 to 1000''C, which is the melting and softening temperature.

The thickness of the glass coating layer after firing is 50 mm for the above applications.
~100 gm is desirable.

The two-step firing method consists of a first fired glass coating and a second fired glass coating.The first fired glass coating is made by mixing glass powder with an organic binder to create a paste containing 5 to 20% glass powder, which is then fired with silicon carbide. It consists of coating the surface of the compact, heating to a temperature in the range of 80 to 400 DEG C. to remove the binder, and then heating at 1000 to 145 G'C for 5 to 0 minutes. The purpose of this heating is to lower the viscosity of the glass, wet the pores on the surface of the silicon carbide sintered body, and form a glass layer, and for this purpose, the above temperature range is appropriate. In this case, the amount of glass powder to be applied is Q,S ~1.0 mg/
cr rn' is desirable, and the amount of glass powder is 0.5B/
If it is less than cm', the coated glass will be non-uniform, and 1
．． If it exceeds 0 mg/cm', bubbles tend to remain in the glass coating.6 The reason for setting the glass powder in the paste to 10 to 20% is that if it does not reach 10%, the glass coating will be uneven. If it exceeds it, it becomes difficult to apply a thin layer.

In the first firing glass coating, the glass penetrates into the pores on the surface of the silicon carbide sintered body, and prevents the generation of bubbles during the second firing described below.

The secondary fired glass coating is the above-mentioned 1.
Similar to the step firing method, this is a method in which a paste is applied, the binder is removed by heating, and a glass coating m is formed by firing.

In this case, it is desirable that the glass powder content of the paste be 50 to 60%. In the present invention, the paste used in the paste is a fiber derivative such as ethyl cellulose or nitrocellulose, and the organic solvent is terpineol or carpitol acetate. The glass powder may be used by pulverizing glass made by melting and solidifying the glass components to a size of about 44 ILm or less, or preferably by classifying it to a size of 10 μm or less.
Use as less than m.

The paste can be applied to the surface of the silicon carbide sintered body by screen printing or the Dr.Frede method.

[Example 1] Raw material powders having the glass composition shown in Table 1 were weighed and mixed, and the mixed powder was placed in a platinum crucible and heated in an electric heating furnace at 1500 m
℃, the melt is poured into water and rapidly cooled to produce a glass, firstly the glass is ground in an alumina mortar to form a powder of 44JL or less, further this glass powder is suspended in ethyl alcohol, Glass powder with a particle size of 10 gm or less was prepared by classifying based on the difference in sedimentation speed.

A paste was prepared by kneading 1001 parts of the glass powder with 10 parts by weight of ethyl cellulose as a binder, a solvent, 60 parts by weight of terpineol, and 5 parts by weight of carpitol acetate. Next, the glass paste was screen printed on one side of a silicon carbide sintered body (0.7 mm thick x 50 mm x 50 mm) which had been previously degreased and washed, and then fired in the air. Firing was carried out by heating at 350°C for 1 hour to remove the binder, then holding at a temperature of 900°C for 20 minutes, followed by rapid cooling to form a glass coating with a thickness of 100 μl.

The resulting glass coating was examined for bubbles, cracks, and smoothness, and the results are shown in Table 2. Regarding bubbles, cracks, and smoothness in the table, bubbles 1. Those with cracks or poor slipperiness are marked with an x mark, those with good properties are marked with an ○ mark, and those with somewhat good slipperiness are marked with a Δ mark.
It was marked as a mark.

The composition of the comparative example had 1 phase separation, devitrification, and cracks.
Although bubbles and smoothness are poor, the glass composition of the present invention has no phase separation 5 devitrification and has good cracks, bubbles, and smoothness.

(Example 2) A paste containing 10% of glass powder with an average particle size of 1.3 ILm was prepared using the glass composition of No. 8.9.1O111 used in Example 1 and the binder and solvent of the same composition as in Example. 0.7% silicon carbide sintered body by screen printing method.
A paste was applied to one side of a glass having a thickness of X 5 (lx 50 mg) so that the amount of glass powder was 0.8 sg/cm'' and fired in the air.

Firing was performed at 350°C for 1 hour to remove the binder, then heated to 1400°C for 30 minutes, left to cool to form a glass layer, and then glass powder with an average particle size of 3μ dust was used as an example. A paste was prepared using the same binder and solvent as in 1, and applied to the glass-coated surface by screen printing, heated at a temperature of 350°C for 1 hour to remove the binder, and then heated at a temperature of 900°C for 15 minutes. , ]000°
Firing was performed by heating at a temperature of C for 5 minutes, followed by rapid cooling to form a glass coating. The results are numbered 13.14 in order.
．． It is shown in Table 3 as 15.16. The thickness of the second stage glass coating is 1004 rs. By using this method, the pores on the surface of the silicon carbide sintered body can be covered, and a smooth glass coating with good adhesion without bubbles and cracks can be obtained.

Table 1 Table 2 (Effects of the Invention) The glass coating on the silicon carbide sintered body according to the present invention has no cracks or bubbles, and is formed into a uniform glass coating, which reduces the electrical resistance of the surface of the silicon carbide sintered body. Because of its large size, this sintered body has excellent properties as a substrate for various integrated circuits, and its practical effects are remarkable.

Table 3

Claims (3)

[Claims] (1) Al_2O_315~2 on the surface of silicon carbide sintered body
3% by weight, SiO_230-55% by weight, B_2O_3
20-40% by weight, CaO5-10% by weight, ZrO_2
A silicon carbide sintered body coated with glass having a composition of 1 to 3% by weight. (2) Applying a paste consisting of the glass powder and organic binder of claim 1 to the surface of the silicon carbide sintered body;
A method for producing a glass-coated silicon carbide sintered body, which comprises heating to 50 to 1000°C. (3) Applying a paste consisting of the glass powder and organic binder of claim 1 to the surface of the silicon carbide sintered body;
000 to 1450°C to form a primary glass coating, and then apply the paste on top of the primary glass coating.
1. A method for producing a glass-coated silicon carbide sintered body, which comprises heating to a temperature of 0.degree. C. to form a secondary glass coating.