JPS63295479A - Sintered aluminum nitride body and its production - Google Patents

Abstract

PURPOSE:To obtain the titled sintered body having an excellent thermal conduction property and sinterability adequate for an insulating substrate material, heat radiating material, etc., by adding and mixing a sintering assistant consisting of an alkaline earth metal (compd.) and Al4C3 to and with AlN powder and sintering the molding in a nonoxidizing atmosphere after molding. CONSTITUTION:The sintering assistant powder consisting of (a) >=1 kinds of the compds. of the alkaline earth metals such as Ca, Mg, Sr, Ba, and Ra or the hydrides, carbides, nitrides, etc., thereof (e.g.: CaC2, CaH2, etc.) and (b) Al4C3 and having >=5mu average grain size is added and to and with (A) the AlN powder having <=5mu average grain size and the mixture is pressurized and molded under 500-2,000kg/cm<2>. This molding is then sintered for 0.5-3hr at 1,700-1,950 deg.C under an atm. pressure in the nonoxidizing atmosphere of N2, Al, H2, CO or hydrocarbon, etc., by which the titled sintered body having the extremely high thermal conductivity of >=160W/m.K is obtd.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to thermally conductive ceramics, and in particular to an aluminum nitride sintered body suitable for insulating substrate materials and various heat dissipating materials that require high thermal conductivity, and the like. Regarding the manufacturing method.

[Conventional technology]

Conventionally, sintered alumina has been used as an insulating substrate material for integrated circuits such as large electronic computers.

However, alumina has low thermal conductivity, and as devices become more highly integrated, there is a need to develop materials with higher thermal conductivity.

Aluminum nitride has high thermal conductivity and high resistance,
Furthermore, the coefficient of thermal expansion is close to that of silicon, the element material.
It also has a low dielectric constant, making it ideal as an insulating substrate material for integrated circuits.

However, since aluminum nitride has poor sinterability when used alone, a sintered body is usually obtained by adding a sintering aid.

In general, known sintering aids include alkaline earth metals or compounds thereof (Japanese Patent Application Laid-Open No. 61-10071), rare earth metals or compounds thereof (Japanese Patent Application Laid-open No. 61-127267). Although the density of the sintered body was increased by adding these sintering aids, a sufficient thermal conductivity was not obtained due to the presence of oxygen and other impurities.

[Problem that the invention seeks to solve]

As described above, in the above-mentioned conventional techniques, materials with sufficiently high thermal conductivity have not yet been obtained, and there have been problems in applying them to insulating substrate materials for integrated circuits.

An object of the present invention is to provide an aluminum nitride sintered body that has improved thermal conductivity compared to conventional sintered bodies.

[Means for solving problems]

The above objectives are achieved by:

That is, the first feature is that it consists of a sintered body containing aluminum nitride, at least one of an alkaline earth metal and a compound of an alkaline earth metal, and aluminum carbide as a sintering aid. It is an aluminum nitride sintered body.

In the second method, a powder consisting of at least one of alkaline earth metals and compounds of alkaline earth metals and aluminum carbide is added and mixed as a sintering aid to aluminum nitride powder, and then molded. and a method for producing an aluminum nitride sintered body, characterized in that firing is performed in a non-oxidizing atmosphere.

Examples of alkaline earth metals include Be, Mg, and Ca.

Examples include Sr, Ba, and Ra, with Ca being particularly preferred.

Hydride is a compound of alkaline earth metal.

Examples include borides, carbides, nitrides, oxides, halides, and thiocyanides, with hydrides, carbides, and nitrides being particularly preferred.

Particularly preferred are aacz, CaHz, and the like.

The average particle size of aluminum nitride (AQN) and sintering aid powder is 5 μm or less, preferably 3 μm or less. If the particle size of AQN powder exceeds 5 μm, a dense sintered body cannot be obtained. When the particle size of the sintering aid powder exceeds 5 μm, its action as a sintering aid decreases.

The amount of the sintering aid added is 0.01 to 10% by weight, particularly preferably 0.5 to 3% by weight.

If the amount of the sintering aid added is less than 0.01% by weight, a dense sintered body cannot be obtained, and if it exceeds 10% by weight, the high thermal conductivity, which is the original property of AQN, will be lost.

The AQN sintered body is usually obtained by adding and mixing kQN powder with the above-mentioned sintering aid powder, press-molding the mixture at room temperature, and sintering the mixture under normal pressure in a non-oxidizing atmosphere.

Pressure molding pressure is about 500 to 2000 kg/cd.

Examples of the non-oxidizing atmosphere include Nz, He, and Ar.

The purpose of creating a non-oxidizing atmosphere, which may be an atmosphere of H 2 , G 2 O, various hydrocarbons, or a mixture thereof, or vacuum, is to prevent oxidation of the surface of the pulverized AQN.

The atmospheric pressure may be atmospheric pressure, usually in a nitrogen stream. Further, for the sintering, not only the normal pressure sintering method but also the hot pressing method may be used.

Sintering temperature is 1700-1950℃, special temperature 1800-19
00°C is preferred.

Sintering time is usually 0.5 to 3 hours.

[Effect]

Although there are still many unknowns as to why the sintered body of the present invention has higher thermal conductivity than conventional sintered bodies containing alkaline earth or rare earth metal compounds, the following assumptions can be made: can do.

Among the additives for the sintered body of the present invention, alkaline earth metals or their compounds are effective as sintering aids for densifying AfiN, and aluminum carbide alone has almost no effect as a sintering aid. However, it is thought that when combined with an alkaline earth metal or its compound, it has the effect of increasing purity and thermal conductivity.

〔Example〕

The present invention will be explained in detail below.

Examples 1 to 7 AQN powder with an average particle size of 1.4 μm was added with an average particle size of 3 μm.
Alkaline earth metal compound powder and AQaCδ powder were added in the proportions shown in Table 1 and mixed using a ball mill.Next, this mixture was mixed at room temperature at a rate of 2000 kg/kg.
It was molded at a pressure of J. The obtained molded body was heated in a N2 stream for 1
Pressureless sintering was performed at 800''C for 3 hours.

Comparative Examples 1-3 To the AQN powder used in Examples 1-7, alkaline earth or rare earth metal compound powder with an average particle size of 3 μm was added in the proportions shown in Table 1. Similarly, A
A fiN sintered body was manufactured.

The characteristics of the obtained AQN sintered body were measured as follows.

(1) Density and Relative Density Density was measured by the Archimedes method, and the relative value to the theoretical density was determined.

(2) Thermal conductivity A disk with a diameter of IQm and a thickness of 3 m was cut out from the sintered body, and this was used as a test piece to measure the thermal conductivity by the laser flash method.

〔Effect of the invention〕

As explained above, the AnN sintered body obtained by the present invention has a thermal conductivity of 16. It has a very high OW/m- or more, has excellent sinterability, and is suitable as an insulating substrate material for integrated circuits and various heat dissipation materials.

Claims (1)

[Claims] 1. A sintered body containing at least one of an alkaline earth metal and an alkaline earth metal compound and aluminum carbide as a sintering aid in aluminum nitride. aluminum nitride sintered body. 2. The aluminum nitride sintered body according to claim 1, characterized in that the amount of the sintering aid added is 0.01 to 10% by weight. 3. After adding and mixing a powder consisting of at least one of alkaline earth metals and alkaline earth metal compounds and aluminum carbide as a sintering aid to aluminum nitride powder, molding and non-oxidizing atmosphere 1. A method for producing an aluminum nitride sintered body, the method comprising firing the aluminum nitride sintered body inside.