JPS62252374A - 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 (Industrial Application Field) The present invention relates to a method for producing a high density, high thermal conductivity aluminum nitride sintered body.

(Prior Art) Substrates made of aluminum nitride sintered bodies are attracting attention as substrates for ICs, LSIs, etc., and as heat sinks for thyristors.

Aluminum nitride itself can be produced using a direct nitriding method in which aluminum is heat-treated at 1300 to 1500°C in a nitrogen atmosphere;
Carbon powder is mixed with Al2O3, and this is heated in a nitrogen atmosphere for 1
It can be synthesized by a reductive nitriding method that involves heat treatment at 400 to 1,700°C.

In order to obtain this sintered body of aluminum nitride, the aluminum nitride itself was formed by hot pressing or under normal pressure. In order to obtain high thermal conductivity, the oxygen content in the aluminum nitride sintered body must be reduced.
It is necessary to control the sintering conditions so that a dense sintered body is obtained. Usually, in sintering under normal pressure, rare earth metal oxides, alkaline earth oxides, etc. are used as sintering aids. This is disclosed, for example, in Japanese Patent Publication No. 47-18655.

(Problem to be solved by the invention) However, in the method of obtaining an aluminum nitride sintered body in a state in which the above-mentioned sintering aid is added, the sintering aid itself is easily evaporated, so that It was not possible to obtain a sintered body, and furthermore, it was not possible to reduce the oxygen content in the sintered body.

For this reason, Japanese Patent Application Laid-Open No. 59-207883 discloses that in order to prevent the sintering aid contained in the aluminum nitride compact from evaporating, powder having the same composition as the compact is used when the compact is fired. A method has been proposed in which the material is coated with aluminum and fired in this state. However, although this method can improve the density of the obtained sintered body, it is difficult to reduce the amount of oxygen contained in this sintered body, and as a result, it is difficult to increase the thermal conductivity. could not.

(Objective of the Invention) Therefore, an object of the present invention is to provide a method for manufacturing an aluminum nitride sintered body that is dense and exhibits good thermal conductivity.

(Structure of the Invention) According to the present invention, aluminum nitride powder obtained in advance by a direct nitriding method, a reductive nitriding method, or the like is used.

Then, a step of mixing the aluminum nitride powder with one or more kinds of rare earth metal compound powder or alkaline earth metal compound powder as a sintering aid, and molding the obtained mixed powder to form a compact 4. ! a step of obtaining the molded body,
Covering with a coating material made of a mixture of powder with the same components as the mixed powder and carbon powder, or a coating material made with a mixture of powder with the same ingredients as the mixed powder and carbon powder containing an excessive amount of a sintering aid. and a step of sintering the molded body coated with the coating material under atmospheric pressure in a nitrogen or inert atmosphere.

The aluminum nitride powder used here has an average particle size of several μm or less, more preferably 1 μm or less. In addition, as a rare earth metal compound, YSLasCes
Oxides and fluorides such as Nd5Er and Sm are used. In general, as an alkaline earth metal compound, Ca%
Oxides such as S r s B a s M g, carbonates, fluorides, etc. are used.

The content of these sintering aids with respect to aluminum nitride is 0.5 to 0.5 to oxide in terms of AIN.
It may be contained within a range of 7.0% by weight.

Further, the amount of the sintering aid contained in the coating material that covers the compact may be the same as the sintering aid in the compact (or 1
It may be contained in 0 times excess.

Furthermore, the amount of carbon powder contained in the coating material that covers the molded body is 0.0 in weight ratio to aluminum nitride.
What is necessary is just to make it contain in the range of 5-1. This is because if the ratio is less than 0.05, the amount of oxygen in the sintered body will not be reduced, while if it exceeds 1, the evaporation of AIN and the sintering aid will become significant.

(Effects) According to the method for producing aluminum nitride according to the present invention, a molded body of aluminum nitride containing a sintering aid is produced using a powder having the same components as the molded body or a powder containing an excessive amount of the sintering aid. Since the powder is coated with a coating material made by adding carbon powder, it is possible to suppress the evaporation of the sintering aid from the compact during firing, and the presence of the carbon powder makes it easier to sinter. At times, the oxygen in the molded body is released from the molded body, and as a result, the amount of oxygen in the aluminum nitride sintered body can be reduced, and a high thermal conductivity can be obtained.

(Example) The present invention will be explained in detail below according to examples.

Example Aluminum nitride powder was mixed with sintering aids Y2O3, YF3, Ca C12, Ca as shown in Table 1.
CO3, Er2O3, and CaF were added at 2% by weight each, and mixed for 16 hours. 10 weight of paraffin was added to this mixture and mixed, and 2 tons of this mixed powder was added.
It was molded into a disk shape with a diameter of 1° lam and a thickness of 3 mm using a pressure of 1.5 oz/cm 2 . This molded body was heated to 800°C in a nitrogen atmosphere.
Paraffin was removed by heat treatment at a temperature of .

On the other hand, in a mixed powder containing 3% by weight of each sintering aid shown in Table 1 based on the aluminum nitride powder, add carbon powder to the aluminum nitride powder in the proportions shown in Table 1. A coating material for the molded body described above was prepared.

This coating material was filled in a container made of graphite, and the molded article was embedded in this coating material. Thereafter, sintering was performed in nitrogen gas at 1850° C. under normal pressure under conditions of opening at 3 o'clock to obtain an aluminum nitride sintered body. The relative density and thermal conductivity of each of the obtained sintered bodies were measured, and the results are shown in Table 1.

Comparative Example 1 The aluminum nitride molded body produced in the above example was used.

On the other hand, 2% by weight of Y2O to aluminum nitride powder
A graphite container was filled with a coating material containing 3 and YF3, and the molded body was embedded in the coating material. and,
Firing was performed in the same manner as in the example to obtain an aluminum nitride sintered body.

When we measured the relative density and thermal conductivity of this sintered body, we found that the one using Y2O3 coating material had a relative density of 9.
8.0%, and the thermal conductivity was 50 w/m·k, and the one using the YF3 coating also had a relative density of 98.0% and a thermal conductivity of 50 w/m−.

Comparative Example 2 The aluminum nitride molded body produced in the above example was used.

On the other hand, a graphite container was filled with a coating material consisting only of carbon, and the molded body was embedded in this coating material. Then, it was fired in the same manner as in the example to obtain an aluminum nitride sintered body.

When the relative density and thermal conductivity of this sintered body were measured, the relative density was 94.0% and the thermal conductivity was 40w/m-
It was.

Claims (1)

[Claims] (1) 1 of aluminum nitride powder and rare earth metal compound powder or alkaline earth metal compound powder that is a sintering aid
a step of mixing the seed or two or more kinds; a step of molding the obtained mixed powder to obtain a molded body; or coating with a coating material that is a mixture of carbon powder and a powder having the same components as the mixed powder containing an excessive amount of a sintering aid; or a step of normal pressure sintering in an inert atmosphere; and a method for producing an aluminum nitride sintered body.