JPH02275768A - Production of sintered aluminum nitride - Google Patents

Abstract

PURPOSE:To improve the thermal conductivity of sintered AIN without deteriorating the other properties by adding Y2O3 powder and Y powder as sintering assistants to AIN powder and calcining the mixture. CONSTITUTION:The objective sintered AIN is produced by mixing 100 pts. wt. of powder composed mainly of AIN with 0.05 to 5 pts.wt. of Y2O3 powder and 0.05 to 5 pts.wt. of Y powder (preferably surfacecoated with Y2O3 layer of >=10nm thick) as sintering assistants, forming the mixture and calcining the formed product at 1400 to 2000 deg.C in a non-oxidizing atmosphere.

Description

[Detailed Description of the Invention] [Industrial field] The present invention relates to a method for producing an aluminum nitride sintered body, and particularly to a method for producing an aluminum nitride sintered body with high density and high thermal conductivity, which is highly demanded in industry. Regarding the method.

[Prior Art] Aluminum nitride sintered body has high thermal conductivity and high insulation properties, and is a material that is attracting attention as a four-plate material for highly integrated and high output semiconductors.

What are the desirable properties of the sintered body as a base plate material? ■ High insulation resistance.

■High thermal conductivity.

■High strength.

That is the condition.

However, if aluminum nitride powder is molded and fired without adding a sintering aid, sintering will be insufficient and impurities such as oxygen will not be completely removed, resulting in less of the desired characteristics mentioned above. It was impossible to obtain.

For this reason, yttrium oxide is generally used as a sintering aid (for example, JP-A-49-111909), and although it has been somewhat effective, it has been desired to have the above-mentioned characteristics in the direction of -F.

[Problems to be Solved by the Invention] In view of the above-mentioned prior art, the present invention seeks to provide a manufacturing method that improves the characteristics of an aluminum nitride sintered body.

[Means for Solving the Problems] The present inventors have arrived at the present invention as a result of various researches in order to solve the above problems by developing a method for producing an aluminum nitride sintered body with excellent properties. In the present invention, 0.05 to 5 parts by weight of yttrium oxide powder and 0.05 to 5 parts by weight of yttrium powder as sintering aids are mixed with 31 parts of aluminum nitride powder as the main component, and the mixture is After molding, the molded body was heated to 1400°C in a non-oxidizing atmosphere.
A method for producing an aluminum nitride sintered body characterized by firing at ~2000°C, in which yttrium powder is used as yttrium powder.
Yttrium powder whose surface is covered with a yttrium oxide layer having a thickness of lonm or more can be used.

[Function] There are no particular restrictions on the manufacturing method or purity of the aluminum nitride powder, which is the main component, but in order to obtain a high sintered body density, it is preferable that the powder be as fine as possible and have a uniform particle size. In order to obtain conductivity, it is preferable to use a material with a low amount of oxygen and metal impurities.

The manufacturing method, purity, etc. of the yttrium oxide powder and yttrium powder to be mixed as a sintering aid are not particularly limited, but they are preferably as fine as possible and have uniform particle size so that they can be evenly mixed with the main component, aluminum nitride powder. In addition, it is preferable to use a material containing a low amount of metal impurities.

The amount of yttrium oxide powder mixed is 0.05 to 5 parts by weight per 100 parts by weight of aluminum nitride powder. 0,
If the amount is less than 0.05 parts by weight, the effect will be insufficient, and if it is mixed in more than 5 parts by weight, no improvement in the effect will be observed.

Yttrium oxide combines with oxygen contained as an impurity in AJ2N, removes oxygen from the particles, and forms a liquid phase during firing to promote sintering.

On the other hand, yttrium also has the above effect, but since it does not entrain oxygen, it has the effect of significantly reducing the amount of residual rvI elementary compounds within one grain and at grain boundaries, and as a result, it has an extremely high thermal conductivity. A (IN sintered body is obtained.

The mixing amount of yttrium powder is 1 part of aluminum nitride powder.
The amount is 0.05 to 5 parts by weight per 00 parts by weight. 0.05
Aluminum nitride, yttrium oxide, and yttrium powders are insufficiently effective when mixed in less than 5 parts by weight, and no improvement in effectiveness is seen even when mixed in more than 5 parts by weight.
Thoroughly mix and knead using a dispersion medium such as toluene, trichloroethylene, or dioxane. At this time, a suitable dispersant may be added if necessary. In this way (1
An appropriate amount of binder is added to the resulting slurry, and the slurry is molded into the desired shape. As a molding method, a doctor blade method is often used when manufacturing a substrate, but it is also possible to use a press method, a roll coating method, and the like.

After the molded body is dried, the binder is decomposed and volatilized by heating (degreasing process).

Firing is generally performed at 1400°C to 2°C in a non-oxidizing atmosphere that does not contain molecular oxygen, such as nitrogen, ammonia, or argon.
It is carried out in the range of 000°C. When fired in an oxidizing atmosphere, aluminum nitride powder oxidizes to aluminum oxide,
If the firing iRf degree is less than 1400'C, sintering will be insufficient, and if it exceeds 2000°C, aluminum nitride will volatilize and the sintered body will have a lower heat conductivity.

In the present invention, as yttrium powder, one surface has a thickness of lOn.
Yttrium powder covered with a layer of yttrium oxide with a thickness of m or more can be used.

Yttrium is highly active and easily reacts with oxygen and water vapor in the air, changing into hydroxide, etc., so by covering it with a layer of yttrium oxide, which is stable in the atmosphere,
Its handling performance can be improved.

If the thickness of the yttrium layer is less than 1 nm, the above effect is insufficient, and the upper limit is not particularly limited, but
In order to suppress the same amount of oxygen band as the yttrium powder, it is better to make it as thin as possible.

[Example] Example 1 100 parts by weight of aluminum nitride (AffN) powder with an average particle size ILLm was mixed with yttrium oxide (Y2O2) with an average particle size (18 μm) as a sintering aid in the amount shown in Table 1.
After charging the powder and yttrium (Y) powder with an average particle size of 0.3 μm prepared by the in-gas evaporation method into a ball mill together with trichlorethylene and thoroughly mixing and crushing it, polyvinyl butyral resin was added as a binder. A slurry was prepared. Using this slurry, a green sheet was prepared by a doctor blade method and punched into a 65 x 65 mm square to obtain a green molded body.

The green molded body was degreased in N2 at 700°C for 1 hour, and then fired at 1800°C for 3 hours under normal pressure in N2 atmosphere to obtain a sintered plate.

Regarding the obtained sintered plate, appearance, relative density, thermal conductivity,
Properties generally required for an insulating substrate, such as insulation resistance and surface roughness, were measured. The results are shown in Table 1.

Among the characteristics, the relative density was determined by calculating the density of the sintered body using the Archimedes method, divided by the true density, and expressed as a percentage. Thermal conductivity was measured using the laser flash method, and insulation resistance was measured using an insulation meter.
The surface roughness (Ra) was measured using a stylus type surface roughness meter.

Example 2 The yttrium powder used in Example 1 was treated with dry oxygen.
Heated in argon mixed gas.

Its surface was covered with a layer of yttrium oxide with a thickness of about 50 nm. This powder was used as yttrium powder, and the prescribed amounts shown in Table 2 were mixed with 100 parts by weight of the aluminum nitride powder and 2.5 parts by weight of the yttrium oxide powder used in Example 1. A sintered plate was created using the same method.

Its appearance, relative density, thermal conductivity, insulation resistance, and surface roughness were measured, and the results are shown in Table 2.

Comparative Example A sintered plate was prepared in the same manner as in Example 1 except that only yttrium oxide powder was used as a sintering aid, and its appearance, relative density, thermal conductivity, insulation resistance, and surface roughness were evaluated. measure,
The results are shown in Table 3.

[Effect of the invention] By adding yttrium l- to yttrium oxide as a sintering aid, the thermal conductivity of the sintered body can be significantly improved without impairing the properties of the bale. By covering the powder with a layer of yttrium oxide, the yttrium powder can be easily handled without damaging the properties of the sintered body.

Applicant: Kawasaki '9J Iron Co., Ltd.

Claims (1)

[Claims] 1. 100 parts by weight of aluminum nitride powder as the main component, 0.05 to 5 parts by weight of yttrium oxide powder and 0.05 to 5 parts by weight of yttrium powder as sintering aids.
5 parts by weight of aluminum nitride, molding the mixture, and then firing the molded product at 1400 to 2000°C in a non-oxidizing atmosphere. 2. The method for producing an aluminum nitride sintered body according to claim 1, wherein the yttrium powder is a yttrium powder whose surface is covered with a yttrium oxide layer having a thickness of 10 nm or more.