JPS61143686A - Silicon carbide sintered body for heat-resistant jig having excellent dimensional accuracy - 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 Industrial Application] The present invention relates to a silicon carbide sintered body i for heat-resistant jigs with excellent dimensional accuracy. For example, diffusion oxidation treatment of semiconductors, junction of diodes,
The present invention relates to a silicon carbide sintered body for a heat-resistant jig with excellent dimensional accuracy suitable for applications such as glass sealing and brazing of lead frames of puff cages.

[Conventional technology]

Heat-resistant jigs for the electronics industry are mainly used for applications that handle high-purity products such as semiconductors, and are characterized by high purity, no product contamination, excellent wear resistance, and excellent dimensional accuracy. It is important to be present.

The heat-resistant jig for the electronic industry is a recrystallized silicon carbide material manufactured from highly purified silicon carbide powder and high-purity silicon for the electronic industry, or a high-purity graphite material whose surface is made of silicon carbide. There are known products manufactured from graphite materials coated with silicon carbide.

[Problem that the invention seeks to solve]

However, the recrystallized silicon carbide material is expensive because it uses high-purity silicon for the electronic industry as a part of the starting material, and also uses relatively coarse grained silicon carbide as another part of the starting material. Heat-resistant jigs with large surface roughness and requiring high dimensional accuracy have the disadvantage of being difficult to manufacture (without special machining); however, the silicon carbide-coated graphite The material is graphite material surface 8i0
It is manufactured by reacting with a gas to convert it into 8iC, and the silicon carbide coating layer is relatively thin and porous, so it has the drawback of poor oxidation resistance and wear resistance.

[Means for solving problems]

The present inventors have developed a heat-resistant jig material for the electronic industry that has been improved by eliminating the drawbacks of conventionally known materials as described above, that is, a heat-resistant jig material for the electronic industry that has excellent oxidation resistance, abrasion resistance, and dimensional accuracy. With the aim of providing materials for sex jigs at low cost, we have conducted a variety of research and found that silicon carbide fine powder with low impurity components, which is used in normal pressureless sintering, is used as a starting material, and it is The present invention was completed based on the new finding that a high-strength silicon carbide sintered body with high surface precision can be produced by sintering within a temperature range without causing substantial sintering shrinkage. did.

The present invention is a silicon carbide sintered body that is sintered without substantially shrinking, and has an average bending strength of 7 kl/Wd or more, for use in heat-resistant jigs with excellent dimensional accuracy. It is a silicon carbide sintered body.

The present invention will be explained in detail below.

The silicon carbide sintered body of the present invention must be made of a silicon carbide sintered body sintered without substantially shrinking. The reason for this is that silicon carbide sintered bodies produced by normal pressureless sintering that are shrunk during sintering are preferable in terms of strength and wear resistance; The dimensions are greatly affected by the density of the formed body and the amount of shrinkage during sintering, so in order to produce a sintered body with excellent dimensional accuracy, the shrinkage during sintering must occur uniformly. By the way, in order to cause the above-mentioned contraction uniformly, it is important to obtain a formed body with a uniform density, but it is extremely difficult to obtain a formed body with such a uniform density, and this study This is because it is difficult to produce a sintered body with extremely excellent dimensional accuracy, which is the object of the invention, by causing firing shrinkage.

In addition, it is advantageous that the firing shrinkage rate of the silicon carbide sintered body sintered without substantially shrinking according to the present invention is 2% or less, and more preferably 1% or less. be.

The silicon carbide sintered body of the present invention has an average bending strength of 7 med.
It is necessary that it is above. The reason for this is that if the average bending strength of the silicon carbide sintered body is smaller than 7 to 97 d, it will easily break or crack during use and will not be able to withstand practical use.

The silicon carbide sintered body of the present invention has an average crystal grain size of ~1
It is preferably made of a silicon carbide sintered body having a diameter of 0 μm and a density of 1.4 to 2.6 da/i. The reason why it is preferable that the average grain size of the crystals is within the range of 0 to 10 μm is that a sintered body in which the average grain size of the crystals is smaller than O and Sμ has weak bonding between crystal grains, and the present invention Objective 7#
This is because it is difficult to obtain a sintered body having an average bending strength of /- or more, and on the other hand, if it is larger than 10 μm, the surface roughness of the sintered body surface becomes large and dimensional accuracy deteriorates. The reason why the density is preferably within the range of 1.4 to 2.6 f/d is that a sintered body with a density smaller than t, 4 f/d has fewer bonding points between silicon carbide particles, This is because it is difficult to form a sintered body having an average bending strength of more than 'Ik (i/-), which is the objective of the present invention;
．． When actually manufacturing a sintered body larger than 6 g/di, a formed body with a density commensurate with the sintered body is required, but 2
．． This is because it is extremely difficult and impractical to obtain a formed body having a density greater than 6 f/d.

The silicon carbide sintered body of the present invention needs to have excellent dimensional accuracy, and is better than a silicon carbide sintered body having a three-dimensional network structure composed of silicon carbide crystals with an average aspect ratio of 5 or less. It is preferable that the

Next, a method for manufacturing a heat-resistant silicon carbide sintered body for a jig with excellent dimensional accuracy according to the present invention will be described.

The silicon carbide sintered body for heat-resistant jigs of the present invention has an average grain size of 5
It can be manufactured by a method of sintering silicon carbide powder with a size of .mu.m or less into a green body in a non-oxidizing atmosphere within a molding range without substantially shrinking it.

The reason for using a silicon carbide powder bed with an average particle size of 5 μm or less is that silicon carbide with a particle size larger than 5 μm is preferable for suppressing firing shrinkage, but it reduces the number of bonding points between grains of the sintered weight. Therefore, the high strength, that is, the average bending strength is 71
This not only makes it difficult to obtain the silicon carbide sintered body described above, but also deteriorates the surface roughness.

By the way, the crystal system of silicon carbide includes α type, β type and amorphous type, and any of them or a mixture thereof can be used. Among them, β type is 5.
It can be advantageously used because it is easy to obtain particles of micrometers or smaller in the form of fine powder, and it is also possible to produce sintered bodies with relatively high strength. Among them, silicon carbide containing β-type silicon carbide in an amount of 50% by weight or more can be used advantageously. It is advantageous to use silicon carbide powder.

The silicon carbide powder preferably has a total content of boron, aluminum, and iron of 0.3% by weight or less in terms of elements. The reason for this is that if the total content of boron, aluminum and iron is more than 0.3% by weight in terms of elements, sintering will occur during sintering due to interaction with free carbon contained in silicon carbide powder. This is because the sintered body tends to shrink and it is difficult to produce a sintered body without causing substantial shrinkage, which is the objective of the present invention.

In addition, when the content of boron, aluminum, and iron in the silicon carbide powder is within the above range, a carbonaceous substance can be added to make the starting material contain 5% by weight or less of free carbon. The free carbon has the effect of suppressing the coarsening of crystal grains, and by making it present in the starting raw material, it is possible to make the crystal grain size of the sintered body uniform and obtain a sintered body with relatively high strength. can. The reason why the free carbon content is set to 5% by weight or less is that if it is more than 5% by weight, excessive carbon will exist between the silicon carbide powder particles, which will significantly inhibit the bonding between the particles. This is because the strength of the sintered body deteriorates.

The carbonaceous material may be any material that allows carbon to be present at the start of sintering, such as phenol resin, lignin sulfonate, polyvinyl alcohol, cornstarch, sugar, coal tar pitch, and alginate. Organic substances or pyrolytic carbons such as carbon black, acetylene black can advantageously be used.

When the total content of boron, aluminum and iron exceeds 0.3% by weight in terms of elements, the silicon carbide powder has a content of carbonaceous substances and free carbon in terms of fixed carbon content. It is preferably 0.6% by weight or less. The reason is that when the total content of boron, aluminum and iron exceeds 0.3% by weight in terms of elements,
As explained earlier, if the content of carbonaceous substances and free carbon is more than 0.6% by weight in terms of fixed carbon amount,
This is because the interaction between boron, aluminum, or iron and carbon tends to cause sintering shrinkage during sintering, making it difficult to obtain a sintered body without causing substantial shrinkage, which is the objective of the present invention. In addition, if the content of boron, aluminum, and iron is too high, it will deteriorate the physical properties of the sintered body, so it is desirable that the content be as low as possible, and the total content should be 2% by weight or less in terms of elements. preferable.

The resulting shaped body is fired within a temperature range of 1700-2100°C. The reason is that if the temperature is lower than 1700'C, it is difficult to sufficiently develop the necks that connect the grains, making it impossible to obtain a sintered body with high strength.
On the other hand, if the temperature is higher than 2100°C, the necks that have grown once and are smaller than a certain size will become constricted, or in severe cases they will disappear, resulting in a decrease in strength.
This is because some of the particles become coarse and the surface roughness deteriorates.

The resulting shaped body is fired in a non-oxidizing atmosphere without substantial shrinkage. The reason for this is that shrinkage during sintering is preferable for improving the strength of the sintered body, but generally speaking, the amount of shrinkage during sintering has a large effect on the density of the formed body, so it is necessary to generate uniform shrinkage. Therefore, it is important to obtain a formed body with uniform density. However, it is extremely difficult to obtain a green body with such uniform density, and therefore it is difficult to produce a sintered body with extremely high dimensional accuracy, which is the object of the present invention, by causing firing shrinkage. It is from.

In addition, in order to obtain a sintered body with high dimensional accuracy as mentioned above, the firing shrinkage rate when sintering without substantially shrinking is 2%.
It is preferably at most 1%, and more preferably at most 1%.

Further, it is preferable that the formed body is fired within a temperature range of 1700 to 2100'C for at least 10 minutes in an atmosphere in which the partial pressure of at least one of the gases 1 and 2 in the surrounding air is maintained at 100 Pa or more. . The reason for this is that by increasing the partial pressure of at least one of CO or N2 in the atmosphere to 100 Pa or higher for at least 10 minutes within the above temperature range, the growth of the neck can be promoted and the This is because shrinkage can be effectively suppressed.

It is advantageous for the heat-resistant sintered silicon carbide body for a jig of the present invention to be fired by charging the formed body into a heat-resistant container in which the firing atmosphere can be controlled.

The reason why it is advantageous to charge the material into a heat-resistant container and fire it while controlling the firing atmosphere is that it can promote the bonding of adjacent silicon carbide crystals and the growth of necks. . The reason why bonding between adjacent silicon carbide crystals and the growth of necks can be promoted by charging the formed body into a heat-resistant container and firing while controlling the firing atmosphere as described above is because silicon carbide particles This is thought to be because the movement of silicon carbide by evaporation-recondensation and/or surface diffusion between the two layers can be promoted.

As the heat-resistant container, materials such as graphite and silicon carbide, and materials having functions equivalent to these materials can be advantageously used.

Furthermore, it is advantageous to control the volatilization rate of silicon carbide to 5% by weight or less during firing by charging the formed body into a heat-resistant container in which the firing atmosphere can be controlled and firing it.

It is advantageous that the formed body for producing the silicon carbide sintered body for a heat-resistant jig is 4.5-b. The reason for this is that when the density of the formed body is lower than 45% by volume, there are fewer points of contact between the silicon carbide particles, which inevitably results in fewer bonding points, resulting in an average of 7 to 9/- or more, which is the objective of the present invention. This is because it is difficult to obtain a sintered body having bending strength, and it is difficult to produce a formed body having a content higher than -80,000% by volume.

Also, one of the temperature increase processes up to 1700'Q mentioned above.
By maintaining the total gas partial pressure of CO and N2 in the atmosphere at 100 Pa or less at 500°C or higher for at least 30 minutes, necks between silicon carbide particles are uniformly generated and firmly bonded. be able to.

Note that carbides other than silicon carbide also have a sintering mechanism similar to that of silicon carbide, so that a sintered body having excellent dimensional accuracy and strength as in the present invention can be obtained.

Next, the present invention will be explained with reference to Examples and Comparative Examples.

Example 1 Silicon carbide powder used as starting material was 94.6% by weight
is a β-type crystal, and the rest is suddenly more than a 2H-type crystal.
It mainly contains 0.29% by weight of free carbon, 0.17% by weight of oxygen, 0.03% by weight of iron, and 0.03% by weight of aluminum, and has an average particle size of 0.28%. No boron was detected.

5 parts by weight of polyvinyl alcohol and 300 parts by weight of water were blended with 100 parts by weight of the silicon carbide powder, mixed in a ball mill for 5 hours, and then dried.

An appropriate amount of this dry mixture was taken, granulated, and then molded using a metal mold at a pressure of 3000 kQ/d.

The dimensions of this generated form are 250m x 25 (m x 30 cod,
The density is 2. Ofl/c4 (62% by volume).

The formed body was placed in a graphite crucible and fired in a Tammann type firing furnace in an atmosphere of mainly argon gas at 1 atm. In the temperature raising process, the temperature was raised to 2000°C in 450°Φ hours, and the maximum temperature was held at 2000°C for 10 minutes. The 0013 partial pressure during sintering was controlled by suitably adjusting the argon gas flow rate so that it was within the range of 80 Pa or less from room temperature to 1700''C and 300±50 Pa at higher temperatures than 1700°C.

The density of the obtained sintered body was 2.05 f/d, and its crystal structure was observed using a scanning electron microscope and revealed that silicon carbide plate crystals with an average aspect ratio of 2.5 were intricately intertwined in multiple directions. It has a three-dimensional structure, and the linear shrinkage rate for the produced shape is 0.25 ± 0.0 in any direction.
Within the range of 2%, the dimensional accuracy of the sintered body was within ±0.05 degrees. Moreover, the average bending strength of this sintered body is 18.5
It showed an extremely high value of 1-.

Example 2 The same operation as in Example 1 was repeated to produce a sintered body. The results are shown in Table 1.

As can be seen from the results shown in Table 1, the maximum ζ-line shrinkage rate is about 0.253±0.022%, and according to the sintering conditions shown in Example 1, the linear shrinkage rate is 0.25%. It was confirmed that by molding and sintering the formed body with the setting, it is possible to easily produce a sintered body with extremely high dimensional accuracy within ±0.0551 m.

Comparative Example 1) For 100 parts by weight of the silicon carbide powder described in Example 1, 1 part by weight of boron carbide powder with a specific surface area of 20.5 d/f, 2 parts by weight of carbon black powder with a specific surface area of 128 Wl/f, 0.4 parts by weight of polyoquine ethylene nonylphenol ether and 400 parts by weight of water were mixed in a ball mill for 20 hours and then dried.

An appropriate amount of this dry mixture was taken, granulated, and then pre-molded using a metal press at a pressure of 1501 mm, and then molded using an isostatic press at a pressure of 2000 mm/d. The zero dimensions and density of the resulting green bodies are shown in Table 1.

The resulting green body was fired in the same manner as in Example 1 using a Tammann type firing furnace in an atmosphere of mainly argon gas at 1 atm. The heating process is from room temperature to 1650℃: 5℃/i%1650
After holding at the temperature for 45 minutes, the temperature was further increased at 5°j and held at the maximum temperature of 2100°C for 30 minutes. 0013 during sintering
The partial pressure was controlled by suitably adjusting the argon gas flow rate so that the partial pressure was 5 KPa or less between normal temperature and 1650°C, 500 Pa or less when maintained at 1650°C, and 5 KPa or less in a higher temperature range than 1650°C. The results are shown in Table 1.

As can be seen from the results shown in Table 1, the obtained sintered bodies are all dense and have high strength, but the shrinkage rate varies widely, making it difficult to manufacture sintered bodies with particularly high dimensional accuracy without finishing processing. That was difficult.

A sintered body was manufactured using a mixed gas of Rougon gas and nitrogen gas. The partial pressure of nitrogen gas during sintering is 20 Pa or less at room temperature to 1700°C, and 300 Pa at higher temperatures than 1700°C.
It was set to The 0013 partial pressure during sintering is always 50P3.
The flow rate of the mixed gas of argon gas and nitrogen gas was appropriately adjusted and controlled as follows.

The density of the obtained sintered body is 2.08 f/d, and the linear shrinkage rate of the formed body is 0.26 in any direction.
The dimensional accuracy of the sintered body was within ±o, oao m. Further, the average bending strength of this sintered body was as high as 22.5rc-j.

Comparative Example 2 Same as Example 1, but with silicon carbide powder of 95.7
% by weight of β-type crystals and the remainder substantially of 2H-type crystals, 0.10% by weight of free carbon, 0.15% by weight of oxygen,
A sintered body was obtained using silicon carbide powder mainly containing 0.02% by weight of iron and 0.02% by weight of aluminum and having an average particle size of 8 μm. Note that boron could not be detected from this silicon carbide powder. The density of the obtained sintered body was 1.85j'A, the linear shrinkage rate for the formed body was relatively uneven at 0.248±0.058%, and the dimensional accuracy was also ±0.145ff. Also,
The average bending strength of this sintered body was 6.3 kQ/-, which was relatively low.

] Prisoner 11 Same as Example 1, but the maximum temperature during firing was set to 2200
A sintered body was obtained by increasing the temperature to ℃.

The density of the obtained sintered body is as low as 1.95 f/d (the linear shrinkage rate for the formed body has a relatively large variation of 0.203 ± 0.11%, and the dimensional accuracy is also significantly decreased at ± 0.275 g). The average bending strength of this sintered body was 4.2k.
It was extremely low at V-.

Example 4 Same as Example 1, but 92.8 as silicon carbide powder
% by weight of β-type crystals and the remainder substantially of 2H-type crystals, 0.21% by weight of free carbon, 0.17% by weight of oxygen,
0.05 M% iron, 0.1% by weight Al Znium,
Mainly contains 0.2% by weight of boron, Q, 27pm
Using silicon carbide powder having an average particle size of A sintered body was obtained using a dry mixture obtained by mixing in a ball mill for 5 hours and then drying.

The density of the obtained sintered body was 2.05 f/d, and although the linear shrinkage rate was slightly higher than that of the formed body at 0.52 ± 0.03%, the dimensional accuracy was relatively good at ±0.08 g. Ah tko. The average bending strength of this sintered body is 32.5&G.
A significantly high value of 4 was obtained.

Comparative Example 4 A sintered body was obtained in the same manner as in Example 4, except that the amount of novolak phenol resin was changed to 1.6 parts.

The density of the obtained sintered body was as high as 2.50F/d,
The linear shrinkage rate for the produced shape also varied widely, at 4.47±0.23%, and the dimensional accuracy also decreased significantly, at ±0.575 ff. The average bending strength of this sintered body is 31
．． It was 7#/-.

〔Effect of the invention〕

As described above, the silicon carbide sintered body for heat-resistant jigs of the present invention is sintered without substantially shrinking, has excellent dimensional accuracy and strength, and is suitable for use in exceptional machinery. It can be supplied at low cost without any processing.

Claims (1)

[Claims] 1. A silicon carbide sintered body sintered without substantially shrinking, with excellent dimensional accuracy characterized by an average bending strength of 7 kg/mm^2 or more. Silicon carbide sintered body for heat-resistant jigs. 2. The silicon carbide sintered body for a heat-resistant jig according to claim 1, wherein the silicon carbide sintered body has a shrinkage rate of 2% or less during sintering. 3. The silicon carbide sintered body has an average crystal grain size of 0.5.
10 μm and a density of 1.4 to 2.6 g/cm^2, the heat-resistant silicon carbide sintered body for a jig according to claim 1 or 2. 4. The silicon carbide sintered body has a three-dimensional network structure mainly composed of -silicon carbide-crystals with an average aspect ratio of 5 or less. Silicon carbide sintered body.