JP2774386B2 - Method for producing cubic boron nitride sintered body - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a cubic boron nitride (cBN) sintered body by a static high-pressure high-temperature method without using a catalyst.

[0002]

2. Description of the Related Art cBN, which is a high-pressure phase of boron nitride (BN), has hardness and thermal conductivity next to diamond and is chemically stable. The use as a heat dissipation substrate of a semiconductor device is being promoted.

In general, cBN is produced by maintaining hexagonal BN (hBN) or BN (tBN), which is a low-pressure phase of boron nitride, under thermodynamically stable conditions of cBN. c
In the case where static ultra-high-temperature and high-pressure treatment is used as a method for obtaining the thermodynamic stability conditions of BN, the conversion pressure and temperature conditions may be, for example, 6.5 GPa and 2000 ° C. or higher.

According to a direct conversion method without a catalyst or a sintering aid (hereinafter referred to as a direct conversion method), the obtained cB
N sintered body is a polycrystalline body composed of fine particles and has features such as high hardness, high purity, high thermal conductivity, and high toughness, so it is expected as a tool material and a heat dissipation substrate that exhibit excellent performance. .

Japanese Patent Publication No. Sho 63-394 discloses that a cBN sintered body having excellent machinability and heat conductivity without producing cracks, chips or the like in a cBN sintered body by a direct conversion method. It has been proposed to chamfer or bevel the circumferential edge of a raw material disc. However, in this method, when the raw material disc is filled in the ultra-high pressure space, voids are formed in the chamfered or obliquely cut portion, and the utilization efficiency of the expensive ultra-high pressure space is deteriorated. The shape is restricted to those having no corners, and in particular, when used as a tool or the like, there is a problem that the processing cost for providing a cutting edge by polishing or the like increases.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to produce a cBN sintered body free from cracks, chips or the like by a direct conversion method while increasing the utilization efficiency of an ultra-high pressure space.

[0007]

The present inventors have conducted various studies on a method for producing a cBN sintered body by a direct conversion method, and in particular, on the conditions for high-temperature and high-pressure treatment of low-pressure phase boron nitride used as a raw material. By performing a high-temperature and high-pressure treatment with a carbon film or a carbon plate interposed between the phase-boron nitride compacts, it is possible to manufacture a cBN sintered body without cracks, chips, etc., significantly more efficiently than before. And completed the present invention.

That is, the present invention provides a method for producing a cubic boron nitride sintered body by treating a raw low-pressure phase boron nitride compact at a static ultrahigh pressure and high temperature without using a catalyst. A cubic boron nitride sintered body, wherein the treatment is performed with a carbon film or a carbon plate interposed therebetween.

Hereinafter, the present invention will be described in more detail.
The low-pressure phase boron nitride compact (hereinafter simply referred to as a raw compact) used as a raw material in the present invention is produced, for example, by any of the following methods. 1) Particles consisting of hBN, tBN, rBN alone or a mixture thereof are formed into a desired shape. 2) The particles made of a single substance of hBN, tBN, and rBN or a mixture thereof are formed into a desired shape and then sintered. 3) hBN and tB, which are pyrolytic boron nitride (PBN)
A desired shape is cut out from a plate made of a single substance of N or rBN or a mixture thereof.

[0010] hBN and tBN particles, plates and the like are substances that are industrially widely produced and can be easily obtained. Further, rBN particles are also described in, for example, Japanese Patent Publication No. 60-22.
As described in Japanese Patent Publication No. 44-44, it can be synthesized by reacting a boron compound containing oxygen with cyan gas. rBN
For the plate, the rBN particles can be formed by pressure molding or, for example, by supplying a boron source gas and a nitrogen source gas onto a heated substrate and depositing them as described in JP-B-64-3948. it can. hBN and / or tBN
Together with PBN obtained by precipitating rBN
Can be produced, for example, according to Example 2 of Japanese Patent Publication No. 64-3948.

In the present invention, for example, the following method can be used as a method of interposing a carbon film or a carbon plate between the raw material compacts. 1) A carbon film is formed by spraying a carbon spray on the surface of the raw material compact. 2) A liquid carbon, such as tar or pitch, or a solution prepared by dissolving or dispersing carbon powder in a solvent is applied to the surface of the raw material compact to form a carbon film. 3) The raw material compact is placed in a carbon heater, and carbon plates are arranged above and below the raw material compact. When there are a plurality of raw material compacts, carbon plates are arranged above and below each raw material compact, and a carbon plate is interposed between each raw material compact. The thickness of the carbon film and the carbon plate interposed between the raw material compacts is not particularly limited, but is preferably 0.1 μm to 2 mm. The reason is that if the carbon film is too thin, the effect of preventing cracking, chipping, and the like is small, and if the carbon film is too thick, the utilization efficiency of the ultrahigh-pressure high-temperature reactor decreases.

As used herein, the term "carbon" broadly refers to all carbonaceous materials, and may be graphite or amorphous. Further, carbon spray is a carbon powder that can be sprayed by dissolving or dispersing in a solvent or the like,
Any material may be used as long as it can form a carbon film on its surface by removing the solvent after spraying the raw material compact. The size and concentration of the carbon particles contained in the spray, the solvent and gas used for the spray, and the like are not particularly limited. As a commercially available carbon spray, for example, “dgf123” (Miracle Power Product (MIRA
CLEPOWER PRODUCTS). Further, tar and pitch may be those generally available on the market, and the grade and the like are not particularly limited. The tar and the pitch are dissolved in a suitable organic solvent, for example, a volatile oil such as benzene, to facilitate application and drying, and are adjusted to have a viscosity that can be applied with a brush or the like. The carbon plate may be graphite or amorphous, may be obtained in the form of a plate on the market, or may be processed from massive carbon into a plate shape.

As described above, the raw material compact is filled in a belt-type high-temperature high-pressure generator with a carbon film or a carbon plate interposed between the compacts. The high-temperature and high-pressure processing is performed while maintaining the apparatus at a predetermined temperature and pressure for a certain time. As an example of the conditions, the pressure is 65,000 atm, the temperature is 2000 ° C or more, and the holding time is 5
Minutes to 1 hour. After the treatment, first, the temperature is continued, the pressure is returned to room temperature and 1 atm, respectively, and the cBN sintered body is taken out.

[0014]

The reason why cracks, chips and the like do not occur in the cBN sintered body obtained by the present invention is considered as follows.

When the raw material compacts are subjected to high-temperature and high-pressure treatment in a state where they are directly in contact with each other as in the related art without interposing a carbon film or a carbon plate between the raw material compacts, conversion into cBN and While sintering proceeds, sintering also occurs at the interface between the raw material compacts, and the compacts adhere to each other. When such adhesion occurs, complicated forces such as tension, compression, and shear act on the cBN sintered body due to internal stress generated at the time of temperature reduction and pressure reduction, external frictional force due to deformation of the reaction vessel, and the like. However, this cannot be alleviated, and cracks, chips and the like occur in the sintered body. On the other hand, if a carbon film or a carbon plate is interposed between the raw material compacts and sintered, the fusion of the compacts does not occur, so that such a problem can be avoided.

In addition, carbon has the following properties, and is the most suitable substance for practicing the present invention. 1) Under the high-temperature and high-pressure processing conditions as in the present invention, it is stable without causing phase transformation or the like. 2) Does not react with BN and does not inhibit the conversion of hBN to cBN. 3) Since it has the function of a solid lubricant, the frictional force generated between the cBN sintered body and the reaction vessel or the like is reduced.

[0017]

The present invention will be described more specifically below with reference to examples and comparative examples. Example 1 A disk having a diameter of 20 mm and a thickness of 1 mm was cut out from a commercially available PBN plate to obtain a raw material molded body. A commercially available carbon spray (trade name “dgf123” manufactured by Miracle Power Products Co., Ltd.) was sprayed on the surface of the raw material compact, and dried at normal temperature to form a carbon film.

Twenty sheets of the raw material compact having the carbon film formed thereon were stacked and filled in a graphite heater having an inner diameter of 20 mm, and then placed in a belt-type high-temperature high-pressure generator. Then, first raise the pressure to 7.5 GPa, then raise the temperature to 2300 ° C.
After high-temperature and high-pressure treatment for 30 minutes, the pressure is first increased, the temperature is returned to room temperature and 1 atm, respectively, and the sintered body is taken out.
The state of cracks and chips was visually observed. Table 1 shows the results.

[0019]

[Table 1]

Comparative Example 1 This example was performed in the same manner as in Example 1 except that no carbon film was formed on the surface of the raw material molded body.

Example 2 This example was performed in the same manner as in Example 1 except that tar was applied instead of carbon spray. Tar was used after dissolving and diluting it with 10-fold benzene.

Example 3 This example was performed in the same manner as in Example 1 except that a pitch was applied instead of the carbon spray. Pitch is 10
It was used after dissolving and diluting with 1-fold benzene.

Example 4 In this example, the same raw material compacts as in Example 1
13mm graphite discs with a thickness of 0.5mm and a thickness of 0.5mm
Was carried out in the same manner as in Example 1 except that the graphite heater was alternately stacked and filled.

Example 5 In this example, a PB plate was used as a raw material compact instead of a PBN plate.
The procedure was performed in the same manner as in Example 1 except that a pressure-molded body of N particles was used.

Example 6 In this example, hBN was used as a raw material molded body instead of a PBN plate.
The procedure was performed in the same manner as in Example 1 except that a pressure-formed body of particles was used.

Example 7 In this example, a hBN instead of a PBN plate was used as a raw material compact.
The procedure was performed in the same manner as in Example 1 except that a sintered body of particles was used.

Example 8 In this example, the conditions for high-temperature and high-pressure treatment were as follows: temperature 2000 ° C., pressure 6.5 GP.
a, and the same procedure as in Example 1 was carried out except that the holding time was 60 minutes.

Example 9 In this example, high-temperature and high-pressure processing conditions were set to a temperature of 2400 ° C. and a pressure of 8.5 GP.
a, and the same procedure as in Example 1 was carried out except that the holding time was 5 minutes.

Comparative Examples 2 to 6 These examples were carried out in the same manner as in Examples 5 to 9 except that no carbon film was formed on the surface of the raw material molded product.

[0030]

According to the present invention, c without cracks, chips, etc.
A BN sintered body can be efficiently manufactured by a direct conversion method.

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Hiroaki Tanji 3-5-1 Asahicho, Machida-shi, Tokyo Denki Kagaku Kogyo Co., Ltd. (56) References JP-A-1-208371 (JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) C04B 35/583 B01J 3/06

Claims (1)

(57) [Claims] 1. A method for producing a cubic boron nitride sintered body by treating a raw low-pressure phase boron nitride compact at a static ultra-high pressure and high temperature without using a catalyst, comprising the steps of: A method for producing a cubic boron nitride sintered body, wherein the above treatment is performed with a film or a carbon plate interposed.