JPS62108772A - Manufacture of cubic boron nitride sintered body - 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 (Industrial Application Field) The present invention relates to a method for producing a dense cubic boron nitride sintered viscous material having properties suitable for use as a heat sink for electronic devices such as microwave devices and as a cutting tool insert. be.

(Prior technology) Cubic boron nitride has hardness and thermal conductivity close to that of diamond, and also has excellent electrical insulation properties, so in addition to its conventional use as abrasive grains for difficult-to-cut materials, Various attempts have been made to use them as heat sinks for electronic devices such as microwave devices, and dense sintered bodies of cubic boron nitride have attracted particular attention. Furthermore, it is expected that such a sintered body will exhibit excellent properties as a cutting tool insert, and development of cubic boron nitride sintered bodies is progressing.

Conventional methods for producing cubic boron nitride sintered viscous materials include (a) a method in which low-crystalline hexagonal boron nitride powder is treated as a starting material under high-temperature and high-pressure conditions without using a catalyst (temperature: 1250°C or higher, preferably 1450-1600
℃ or more, pressure crab 5Qkbar or more; Materials Research Buricia (Mat, Res, Bull,)
7, 999-1004 (1972)).

(b) A method in which a low-crystalline hexagonal boron nitride powder bundle mixed with AIN, etc. is used as a starting material and treated under high temperature and high pressure conditions (temperature: 1700°C to 1800°C, pressure crab).
75 kbar; JP-A-49-22925).

(c) Pyrolytic boron nitride (pyrolytic boron nitride), which is hexagonal boron nitride precipitated from the gas phase.
A method of directly processing the molded body under high temperature and high pressure (temperature: 1
800° C. or higher, preferably 2100 to 2500° C., and a pressure of 60 kbar or higher, preferably 55 kbar or higher; JP-A-54-33510).

(d) Mg5 in a hot-pressed sintered body of hexagonal boron nitride
A method in which a catalyst such as B2L is diffused and impregnated with high temperature and high pressure treatment (temperature: 1510-1550°C, pressure 5.2-5
．． 7 GPa; Japanese Patent Publication No. 60-28782).

etc. are known.

(Problems to be Solved by the Invention) However, each of these methods has its own problems, and the cubic boron nitride obtained by these methods is not suitable for industrially producing cubic boron nitride sintered viscous bodies for heat sinks. It was inappropriate. First, in method (a), unconverted hexagonal boron nitride remains in the cubic boron nitride matrix after high-temperature and high-pressure treatment, which significantly deteriorates the thermal and mechanical properties of the cubic boron nitride sintered viscous body. things tend to happen. In order to avoid this, extremely severe high temperature and high pressure treatment at 1700° C. and 70,000 atmospheres is required, so this method is unsuitable for industrial production. In addition, in the method (mouth), the added A
Since 1 etc. act as a catalyst, conversion to cubic boron nitride is possible under milder high temperature and high pressure conditions than in method (a), but the amount of AIN added needs to be about lθ ~ 20% by weight. Yes, a large amount of AI after conversion to cubic boron nitride
Since N remains in the sintered body, the excellent thermal conductivity of cubic boron nitride is impaired. Although method (c) can produce a dense cubic boron nitride sintered viscous material with high thermal conductivity, it requires severe conditions such as a pressure of 50,000 atmospheres or more and a temperature of 1,800°C or more, so this method is different from method (a). as well as unsuitable for industrial production. In method (d), the catalyst is extremely uniformly contained in the raw material hexagonal boron nitride, so a uniform cubic boron nitride sintered viscous body can be obtained under mild high-pressure and high-temperature conditions. The raw hot-pressed sintered body contains a binder in the form of an oxide,
If the cubic boron nitride sintered viscous body is made into a sintered viscous body, the uniformity of the structure will be impaired, so a step of heat-treating the hot-pressed sintered body at a high temperature in an inert atmosphere to reduce the oxygen content is required in advance. As this heat treatment, for example, heating is performed at 2100° C. for 2 hours or more in a nitrogen stream. As mentioned above, in method (d), a cubic boron nitride sintered viscous material with excellent properties can be obtained under mild high-pressure and high-temperature conditions, but this method has the disadvantage of requiring a long deoxidation pretreatment step. be.

(Means for Solving the Problems) The present inventors have conducted extensive research with the aim of solving the above-mentioned drawbacks of conventional methods for producing cubic boron nitride sintered viscous materials, and have found that We have discovered a method for manufacturing dense cubic boron nitride sintered bodies under mild conditions of high temperature and high pressure, without causing any problems, with extremely low content of impurities that could cause deterioration of properties.

The method for producing a cubic boron nitride sintered viscous body of the present invention includes adding 0.1 to 5 mo/% of an alkali metal or alkaline earth metal nitride or boron nitride to a pyrolytic boron nitride assembly.
It is characterized in that it is diffused into cubic boron nitride at a ratio of 1,300° C. or higher and at a pressure of 40,000 atmospheres or higher under thermodynamically stable conditions for cubic boron nitride.

The pyrolytic boron nitride (PBN) molded body used in the present invention is
It is a highly oriented hexagonal boron nitride synthesized by chemical vapor deposition (CVD), and is commercially available as a plate with a thickness of several micrometers. The synthesis of pyrolytic boron nitride by the CVD method uses boron halide gas such as boron trichloride (BCl2) and ammonia gas as raw materials, as disclosed in, for example, U.S. Pat. No. 3,152,006. Toshi, 50To
This is achieved by depositing boron nitride from the gas phase on the surface of a substrate such as graphite at a temperature of 1400 to 2300°C under reduced pressure below rr, and this method produces an extremely high purity pyrolytic boron nitride assembly. You get a body.

Such pyrolytic boron nitride has a highly anisotropic structure with a layered structure extending perpendicular to the direction of precipitation growth, and the C axis of the hexagonal boron nitride S crystal lattice is It is highly oriented in the direction of precipitation growth of decomposed boron nitride (ie, in the thickness direction).

Pyrolytic boron nitride is very stable in air and can ignore the surface oxidation phenomenon observed in commercially available hexagonal boron nitride powder bundles, so it has an extremely low oxygen content without special treatment and handling. It can be considered as a boron nitride number type field. Since pyrolytic boron nitride is produced by the CVD method, it is difficult to obtain thick samples, but a thickness of several mm is sufficient to use it as a starting material for cubic boron nitride sintered viscous bodies. A commercially available pyrolytic boron nitride plate-shaped molded body can be used without any problem.

The pyrolytic boron nitride plate is processed into the desired shape and dimensions, and then the nitride or boron nitride of an alkali metal or alkaline earth metal, which is a conversion catalyst to cubic boron nitride, is heated in pyrolytic boron nitride. Diffuse and impregnate. The diffusion impregnation method involves embedding a pyrolytic boron nitride number type body in powder of a catalyst or a substance that reacts with boron nitride to become a catalyst, and heating it in a non-oxidizing atmosphere to form a pyrolytic boron nitride number type body. An example is a method of reaction-diffusion.

At this time, by adjusting the heating temperature and time,
The catalyst content in the pyrolytic boron nitride can be adjusted.

Examples of alkali metal or alkaline earth metal nitrides or boronitrides useful as catalysts include 13N+M
g3N2. Ca3N2,5r3N2. Ba3N2. Mg
5N4B2. Ca3N4B2.

5r3N4B2.5r3N4B2. Ba3N4B2, etc. When used alone, these catalysts tend to react with moisture in the air and decompose, but when they are diffused and impregnated into a pyrolytic boron nitride molded product, their stability is significantly improved and handling is extremely easy.

The content of the catalyst is required to be 0.1 to 5 mol% relative to the pyrolytic boron nitride as a raw material. If it is less than 0.1 mol%, the conversion to cubic boron nitride will not be completed, and if it exceeds 5 mol%, an excessive amount of catalyst will remain in the grain boundaries of the sintered body, and the original cubic boron nitride will not be converted. properties are impaired.

When the catalyst-containing pyrolytic boron nitride number type body obtained in this way is converted into a cubic boron nitride sintered viscous body by treating it at high temperature and high pressure as a starting material, it is possible to convert Various advantages can be obtained that cannot be achieved with other methods. first,
Since the cubic boron nitride conversion catalyst is extremely uniformly dispersed in the starting material of the present invention, the conversion to cubic boron nitride occurs extremely uniformly throughout the pyrolytic boron nitride molding, resulting in a uniform structure. A cubic boron nitride sintered viscous material with excellent properties is obtained. Furthermore, since the starting material contains a catalyst for converting cubic boron nitride, the high temperature and high pressure conditions required for conversion to cubic boron nitride may be mild conditions within the thermodynamic stability range of cubic boron nitride. Therefore, the conditions necessary to produce a cubic boron nitride sintered viscous body by subjecting a conventionally known pyrolytic boron nitride number type body to high temperature and high pressure treatment without adding a catalyst, such as 2000 to 2300°C, 65 to 75K, are necessary.
A dense cubic boron nitride sintered viscous material with excellent thermal conductivity is produced under conditions much milder than bar. Therefore,
The high temperature and high pressure equipment is less likely to be damaged, the life of the equipment can be extended, and industrial productivity can be significantly improved. In addition, due to the anisotropy of pyrolytic boron nitride, the cubic boron nitride sintered viscous body after conversion becomes a sintered body in which the <ILD orientation, which is a high thermal conductivity orientation, is highly oriented in the thickness direction. A cubic boron nitride sintered viscous body with optimal properties for use as a heat sink is obtained. Furthermore, the starting material used in the present invention is synthesized using a method that essentially does not cause oxygen contamination, and has excellent stability and oxidation resistance in the air, so it has an extremely low oxygen content (commonly used as a starting material). There is an advantage that the deoxidizing heat treatment step that is necessary when using a hexagonal boron nitride hot press molded body is unnecessary.

The temperature and pressure conditions for converting cubic boron nitride to a sintered viscous body in the present invention vary depending on the type and amount of the nitride catalyst contained, but in order to obtain a dense highly thermally conductive cubic boron nitride sintered viscous body, a temperature of 1300°C or higher is required. and a pressure of 40,000 atmospheres or more is required.

In the present invention, there is no need to perform any special pretreatment such as deoxidation of the starting material. A sintered viscous body of crystalline boron nitride is obtained, and this sintered body does not contain excessive impurities that would cause deterioration of properties, so it has properties suitable as a heat sink.

(Example) The present invention will be described below with reference to Examples and Comparative Examples.

Examples 1 to 3 and Comparative Examples 1 to 3 A commercially available pyrolytic boron nitride plate having a thickness of l a+m was processed into a pyrolytic boron nitride mounting plate having a diameter of 25+ nm using an ultrasonic processing machine. This pyrolytic boron nitride mounting plate was embedded in Mg5L powder and heat-treated at a temperature of 1350°C for a predetermined period of time in a nitrogen atmosphere to produce a pyrolytic boron nitride mounting plate for cubic boron nitride sintered viscous raw materials with various catalyst contents. Got the board. Multiple specimens were produced under each heat treatment condition, and some of them were
, N, and Mg.

The specimen thus obtained was used as a starting material and treated in a belt-type high-pressure device at a temperature of 1400° C. and a pressure of 55,000 atmospheres for 1 hour to obtain a sintered body. The generated phases of these sintered bodies were identified by X-ray diffraction, and the thermal conductivity was also measured.

These results are summarized in Table 1. Incidentally, in Table 1, the amount of metal nitride in the starting material is as follows: Mg is M g 3
This is a calculated value obtained from measurements of Mg-containing pots assuming that it exists as N 2 .

Example 4 A pyrolytic boron nitride mounting plate with a diameter of 25 mm and a thickness of 1 mIn was embedded in Mg382N4 powder and heated at a temperature of 1200°C for 5 hours in a nitrogen atmosphere to form a 0.5 mol% M
A pyrolytic boron nitride mounting plate for cubic boron nitride sintered viscous material containing g+BJs was obtained. The obtained specimen is used as a starting material,
Using the same equipment and conditions as in Examples 1 to 3, high-temperature and high-pressure treatment was carried out to convert into a cubic boron nitride burner. According to X-ray diffraction, this sintered body consisted only of cubic boron nitride, and was highly oriented in the <111> direction in the thickness direction of the disk. In addition, Knoop hardness is 6.500kg/mm2
The thermal conductivity was extremely high, exceeding 5 W/cm-.

(Effects of the Invention) According to the present invention, a cubic boron nitride heat-generating body with high orientation, high thermal conductivity, and high hardness can be obtained, and therefore, the cubic boron nitride heat-generating body produced can be used as a heat sink and a cutting tool. suitable for application. In particular, unlike conventional manufacturing methods, the present invention uses a pyrolytic boron nitride molded body as a starting material, so there is no need to pre-treat the starting material for deoxygenation, and the material after impregnating the catalyst is air-filled. It has the advantage of being easy to handle because it does not undergo oxidation even when handled inside. Moreover, since a small amount of cubic boron nitride conversion catalyst is used in the present invention, the conversion to cubic boron nitride sintered viscous material is performed under milder high temperature and high pressure conditions than in conventional methods, and therefore In addition to the advantages of significantly improving industrial productivity by extending the life of the equipment and eliminating the possibility of damage, the sintered body produced does not contain excessive impurities. This has the advantage that properties do not deteriorate.

Procedure Amendment Written by the Commissioner of the Patent Office on October 4, 1986 Black 1) Mr. Akiyu 1. Indication of the case 1985 Patent Application No. 247933 2. Name of the invention Process for manufacturing cubic boron nitride sintered viscous material 3 Amendment Patent applicant (329) Denki Kagaku Kogyo Co., Ltd. Director of Inorganic Materials Research Institute, Science and Technology Agency Yu Goto 4, Agent 1, "L+3N, lAg3" on page 8 of the specification, lines 4-5
N2...5r3N, B2. Ba3N4B2, etc. ” as [l, l:lN, Mg3N2°Ca3N2.
5r3N2. Ba3N2. Mg5N4B2 or! Jg3N3B.

Ca3N4L or Ca3N3B, 5r3N4B
2 or 5r3N3B, (la, N4 [12 or Ba3N38, etc.)".

2. In the same page 9, lines 1 and 2, "Since the raw material... is dispersed," was replaced with "As there are no impurity components in the pyrolytic boron nitride, impregnated cubic nitride is used as the raw material." The elementary conversion catalyst diffuses extremely uniformly during high-temperature, high-pressure treatment, so the correction was made to ``.

3. From the 4th line from the bottom of page 9 to the 2nd line of page 10, ``Also, the anisotropy of pyrolytic boron nitride...the sintered body is i, etc.''

Delete.

4. Delete "Moreover, the <111> orientation was highly oriented in the thickness direction of the disk" on page 14, lines 10-11.

Agent Bu? Physician Akira Sugimura Shugai I
given name

Claims (1)

[Claims] 1. Add 0.1 of alkali metal or alkaline earth metal nitride or boron nitride to the pyrolytic boron nitride molded body.
Diffused in a proportion of ~5 mol% and converted to cubic boron nitride at a temperature of 1300°C or higher and a pressure of 40,000 atmospheres or higher under thermodynamically stable conditions for cubic boron nitride. A method for producing a characteristic cubic boron nitride sintered body.