JPH0627033B2 - Black aluminum nitride sintered body - Google Patents

Description

TECHNICAL FIELD The present invention relates to a black aluminum nitride sintered body, and more specifically, it has high density and high thermal conductivity, and is particularly suitable for electronic equipment substrate materials. Regarding the body

[Prior Art] In recent years, with high integration and high density of LSI, an insulating substrate material having good thermal conductivity has been demanded.

As such an insulating substrate material, conventionally, an alumina sintered body is most often used. However, the alumina substrate has many problems such as low thermal conductivity (about 20 W / mk) and a large thermal expansion coefficient compared to silicon, resulting in poor bondability. Therefore, attention has been paid to an aluminum nitride (AIN) sintered body which has a good thermal conductivity and a thermal expansion coefficient close to that of silicon. Furthermore, the aluminum nitride sintered body has high mechanical strength (40 to 50 kg
/ mm ² ), it has a small dielectric constant and excellent electrical characteristics, so it is also suitable as a substrate material in this respect.

However, aluminum nitride has a strong covalent bond,
Since it is a material that is difficult to sinter, it is difficult to obtain a dense sintered body. Therefore, until now, various attempts have been made to obtain a dense aluminum nitride sintered body by a method using a sintering aid or a hot pressing method. For example, a rare earth oxide or an alkaline earth oxide as a sintering aid is added to aluminum nitride powder and the mixture is sintered in a non-oxidizing atmosphere by atmospheric pressure or hot pressing. The density of the aluminum nitride sintered body obtained at this time shows a relatively high value, but it is insufficient in terms of thermal conductivity. Further, the sintering temperature is usually as high as 1800 ° C. or higher, which causes an increase in manufacturing cost.

Recently, high-purity aluminum nitride powder has come to be obtained, and JP-A-60-71575 describes that a translucent aluminum nitride sintered body can be obtained by atmospheric pressure or hot pressing. Has been done. Such an aluminum nitride sintered body tends to cause uneven burning or uneven color, and
The color tone of the sintered body may change due to sunlight (ultraviolet rays), etc. When used as a package substrate, the internal I
It is fully conceivable that the C memory will be adversely affected.

[Problems to be Solved by the Invention] The present invention is intended to obtain a black aluminum nitride sintered body having high density, high thermal conductivity, and excellent light-shielding properties by relatively low temperature sintering. .

[Means for Solving Problems] The present invention is a sintered body of black aluminum nitride, which is characterized in that Ca ₃ WO ₆ is added to aluminum nitride and fired.

The present invention will be specifically described below.

First, the aluminum nitride powder is fine with an average particle size of 10 μm or less, preferably 2 μm or less. Ca ₃ WO ₆ powder used as a sintering aid has an average particle size of 10 μm.
Fine particles having a diameter of m or less are preferable, and those having a diameter of 5 μm or less are particularly preferable.

The amount of Ca ₃ WO ₆ added is 0.01 to 20% by weight, and particularly preferably 1 to 10% by weight based on the total amount of the aluminum nitride powder. If the addition amount is less than 0.01% by weight, a dense sintered body cannot be obtained, and the sintered body is gray, which is not preferable. On the other hand, if the addition amount is more than 20% by weight, the growth of crystal grains becomes remarkable, the density is lowered, the strength of the sintered body is lowered, and the thermal conductivity is lowered, which is not preferable.

When producing the sintered body of the present invention, it is necessary to perform it in a non-acidic atmosphere. As the non-oxidizing atmosphere, a nitrogen gas, an argon gas, a helium gas, a carbon monoxide gas, a hydrogen gas, an ammonia gas or the like or a mixed atmosphere thereof or a vacuum can be used. Particularly, nitrogen gas is preferable.

The firing temperature is preferably 1500 to 2000 ° C, preferably 1550 to 1700
℃ is good. Further, the sintering is usually carried out by the normal pressure sintering method, but the reduced pressure sintering method or the pressure sintering method may be used.

It has been found that the use of Ca ₃ WO ₆ as a sintering aid improves the thermal conductivity compared to other calcium tungstates (CaWO ₄ ).

[Example] Example 1 Ca ₃ W was added to aluminum nitride powder having an average particle size of 2 μm.
0.1% by weight of O ₆ powder was added and mixed. Next, this mixture was pressed at room temperature at about 1200 Kg / cm ² to obtain a molded body. Then, this molded body was sintered in a nitrogen gas atmosphere at 1700 ° C. for 3 hours to obtain an aluminum nitride sintered body. The obtained sintered body was dense, excellent in light-shielding property and excellent in plane smoothness, and exhibited a beautiful black color. Further, the density and the density conductivity were measured, and the results are shown in Table 1.

Examples 2 to 15 Ca ₃ WO was added to the aluminum nitride powder used in Example 1.
₆ powders were added in the amounts shown in Table 1 and sintered at the temperatures shown in Table 1 to obtain aluminum nitride sintered bodies. The density and the thermal conductivity were measured for each, and the obtained results are shown in Table 1 together with the color. By X-ray diffraction,
The constituent phases of these black aluminum nitride sintered bodies are Al
In addition to the constituent phase of Nn, all of Examples 1 to 15 were compounds containing calcium aluminate compound and metallic tungsten as main components, and it was found that blackening was caused by fine dispersion of metallic tungsten. In addition, the volume resistivity was 10 ¹³ Ωcm or more, indicating good insulation.

Comparative Example 1 An aluminum nitride sintered body was produced in the same manner as in Example 1 except that the aluminum nitride powder used in Example 1 was used under the conditions of 1800 ° C. and 3 hours. The obtained sintered body was white and was hardly densified.

Comparative Example 2 CaCO ₃ powder was added to the aluminum nitride powder used in Example 1 in an amount of 1% by weight in terms of CaO, and aluminum nitride firing was performed under the same conditions as in Example 1 at 1800 ° C. for 3 hours. A knot was prepared. The obtained sintered body was gray and partial burning unevenness was observed. In addition, fine pores were generated on the surface of the sintered body.

Comparative Example 3 WO ₃ powder 3 was added to the aluminum nitride powder used in Example 1.
% Was added, and an aluminum nitride sintered body was produced in the same manner as in Example 1 under the conditions of 1800 ° C. and 3 hours. The obtained sintered body exhibited a blackish color, and partial burning unevenness and color unevenness were observed.

Comparative Example 4 CaCO ₃ powder was added to the aluminum nitride powder used in Example 1 so as to be 1 wt% in terms of CaO, and aluminum nitride sintering was performed under the same conditions as in Example 1 at 1700 ° C. for 3 hours. The body was made. The obtained sintered body had a white gray color and was not densified so much.

It can be seen that the aluminum nitride sintered bodies obtained in Comparative Examples 1 to 4 also have lower densities and thermal conductivities as compared with the present invention, as in the examples.

[Effects of the Invention] As shown in Table 1, the aluminum nitride sintered body of the present invention has no burning unevenness and color unevenness, exhibits a black color with excellent light-shielding properties and surface smoothness, and has high density and high thermal conductivity. Therefore, it is useful as a substrate material for heat dissipation. Furthermore, the sintering temperature is 17
Since it can be sintered at a temperature of 00 ° C. or less, which is considerably lower than the conventional temperature, the manufacturing cost is reduced and the industrial value is very large.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Hisashi Sakuramoto Hisashi Sakuramoto No. 3 Nanjimiyama, Narumi-cho, Midori-ku, Aichi Prefecture Narumi Technical Research Institute (72) Inventor Satoshi Nishiyama Nanjimi-cho, Narumi-cho, Midori-ku, Nagoya, Aichi Prefecture Address 3: Narumi Technical Research Institute (56) Reference JP-A-63-319267 (JP, A)

Claims (2)

[Claims] 1. A sintered body of black aluminum nitride, which is prepared by adding Ca ₃ WO ₆ to aluminum nitride and firing the mixture. 2. A balance of 0.01 to 20% by weight of Ca ₃ WO ₆ powder with the balance of aluminum nitride powder added.
The black aluminum nitride sintered body according to the item (1).