JPS6241768A - Manufacture of aluminum 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] [4 Requirements] An aluminum nitride pre-fired body is subjected to hot isostatic pressing (Ho
t rsostatic Pressing) in a silica glass bath.

[Industrial application field]

The present invention relates to a method for manufacturing a high-density aluminum nitride sintered body having high thermal conductivity.

[Prior art and problems to be solved by the invention] Conventionally, aluminum nitride pre-sintered bodies were sintered at normal pressure.

However, pressureless sintering does not compress the material, so the sintered density is not high enough, and the thermal conductivity is also low. Also, during sintering, the sintering aid evaporates and scatters near the surface of the pre-sintered body. As a result, there was a problem that grain growth was not uniform.

As a sintering aid for aluminum nitride, Japanese Patent Application Laid-open No. 59
No. 131,583 discloses boron nitride or oxides, and mentions calcium, magnesium, aluminum, titanium, zirconium, chromium, silicon, rare earth metals, and yttrium as oxides.

According to the inventor's findings, boron nitride alone does not actually have a sufficient effect as a sintering aid, and when yttrium oxide is used alone as a typical oxide, the diffusion of yttrium oxide is uneven. Therefore, the sintering effect is also non-uniform.

[Means for solving problems]

The above problem can be solved by heating an aluminum nitride powder compact in a nitrogen atmosphere to thermally decompose and scatter the organic binder to form a pre-fired body, then burying this pre-fired body in silica powder and removing the silica by vacuum heating. The problem can be solved by a method for manufacturing an aluminum nitride sintered body, which is characterized in that the prefired body is softened and wrapped in silica glass, and the prefired body is sintered in a fused silica bath by hot isostatic pressing. can.

It is advantageous to coat the prefired body with a coating layer containing a sintering aid to prevent failure of the sintering aid, to prevent oxidation of aluminum nitride by silica, and to prevent diffusion of impurities.

The sintering aid contains an oxide or carbonate of an alkaline earth metal or a rare earth metal, especially yttrium oxide as a main component, and further contains semimetals or semiconductors of Group IIIb or Group II of the periodic table, or semiconductors thereof. It is expedient to use a mixture containing nitrides, especially boron nitride.

〔Example〕

99.5% by weight of aluminum nitride on a chisel, 0.25% by weight of yttrium oxide and 0.2% by weight of boron nitride as sintering aids.
Add 2 parts by weight of paraffin as an organic binder to 100 parts by weight of the mixed powder with 5% by weight, knead, granulate, hot press, and form a cylindrical aluminum nitride with a diameter of 151 layers and a length of Ion. As a body.

This molded body was heated in nitrogen gas to 600° C. over 10 hours, and further heated to 1200° C. over 1.5 hours to remove the burr, thereby obtaining a pre-fired body with a density of 60%.

The pre-fired body was buried in silica powder filled in a crucible made of nitrided boron, heated under vacuum to a temperature of 1535°C to soften the silica, and the pre-fired body was wrapped in silica glass. The crucible was placed in a hot isostatic pressurizer, heated to 1535°C in vacuum, and from that point pressurization with argon gas was started, and the temperature was increased to 1800°C and 2000°C.
kg/cn! was held for 1 hour.

In the obtained sintered body, particles of 10 to 20 μm were uniformly grown, and the density was 99.5% of the theoretical density.

Further, the thermal conductivity is 100 to 140 W/m,k, which is more than twice that of conventional pressureless sintered bodies.

Daishi 1 A pre-fired body is pre-sintered from an aluminum nitride molded body mixed with a sintering aid in the same manner as in Example 1, and 95 parts by weight of boron nitride powder as a sintering aid and yttrium oxide are added to the surface of the pre-fired body. Aluminum nitride was sintered by hot isostatic pressing in the same manner as in Example 1, except that 5 parts by weight of the powder was suspended in 100 parts by weight of acetone, kneaded and applied, and after drying, it was buried in silica powder. Obtained a body.

The density of the sintered body is 99.5% of the theoretical density, and 1
Particles of 5-20 μm were grown uniformly, and the thermal conductivity was 110-150 W/m, k. This is because boron nitride in the surface layer prevents oxidation of aluminum nitride by silica, yttrium oxide in the surface layer increases the concentration of yttrium oxide on the surface of the sintered body, enhancing the sintering effect, and impurities in the silica. This is thought to be due to the prevention of the spread of

[Effects of the Invention] According to the method of manufacturing an aluminum nitride sintered body by hot isostatic pressing of the present invention, not only the density is increased but also the evaporation and scattering of the sintering aid near the surface of the prefired body is prevented. Therefore, the distribution of the sintering aid in the sintered body can be made uniform, grain growth can be made uniform, density can be uniformly increased, and thermal conductivity can also be increased.

Claims (1)

[Claims] 1. An aluminum nitride powder compact is heated in a nitrogen atmosphere to thermally decompose and scatter the organic binder to form a pre-fired product;
This pre-fired body is buried in silica powder, the silica is softened by vacuum heating, and the pre-fired body is wrapped in silica glass.
A method for producing an aluminum nitride sintered body, which comprises sintering this pre-fired body in a fused silica bath by hot isostatic pressing. 2. The method according to claim 1, wherein the pre-fired body is coated with a coating layer containing a sintering aid and embedded in silica glass powder. 3. The sintering aid mainly contains an oxide or carbonate of an alkaline earth metal or a rare earth metal, and further contains a semimetal or semiconductor of Group III_b or Group IV_b of the periodic table, or a nitride thereof. 3. The method according to claim 1 or 2, comprising a mixture comprising: 4. The method according to claim 3, wherein the sintering aid is a mixture of yttrium oxide and boron nitride.