JP2000264738A - Production of aluminum nitride sintered compact - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a dense aluminum nitride sintered compact having high strength and high heat conductivity by adding a yttrium-containing material, a calcium-containing material and a silicon-containing material to aluminum nitride powder and carrying out sintering. SOLUTION: The aluminum nitride powder is preferably high purity fine aluminum nitride powder but commercially available powder may be used. Any material may be applied as the silicon-containing material if it can form SiO2 at high temperature, but since the heat conductivity of aluminum nitride is liable to lower remarkably when excess SiO2 enters into solid solution, a small amount of silica or an SiO2-Al2O3 compound such as mullite is suitable for use as the silicon-containing material. The preferred amount is 100 ppm to 1 wt.% in the case of silica and 5,000 ppm to 5 wt.% in the case of mullite. The yttrium-containing material is 1-5 wt.% (expressed in terms of Y2O3) yttrium oxide. The calcium-containing material is 0.1-1 wt.% (expressed in terms of CaO) calcium carbonate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an aluminum nitride sintered body, and more particularly, to an electric insulating material having high thermal conductivity and high strength for manufacturing a semiconductor circuit board or a printed wiring board. The present invention relates to a method for producing a high strength aluminum nitride sintered body suitable for use as a structural material for producing mechanical parts such as bearings requiring high heat conductivity and high strength.

[0002]

2. Description of the Related Art Aluminum nitride has attracted attention as a heat-dissipating substrate material for semiconductor mounting because of its high thermal conductivity, thermal expansion coefficient close to that of silicon, and high electrical insulation, and further improvements are being studied. For example, Journal of Materia
In ls Science Letter, vol. 11, 1508 (1992), a small amount of yttria, rare earth oxide or alkaline earth metal oxide was added to aluminum nitride powder in order to improve the sinterability and thermal conductivity of aluminum nitride. And sintering is described. In this case, the addition amount of the oxide is several percent, and the calcination is performed at 1800 ° C. or more for several hours.

[0003]

However, the strength of the obtained sintered body is low, for example, the strength of the sintered body obtained by the above-mentioned conventional method is generally 200 to 350 MPa (for example, the Journal of American Ceramics Society). , 7
8, 2335 (1995)). For these reasons, aluminum nitride sintered bodies have not been widely used as structural component materials.

[0004] The present invention has been made in view of these circumstances, and has as its object to provide a dense aluminum nitride sintered body having high strength.

[0005]

The method for producing an aluminum nitride sintered body according to the present invention comprises the steps of:
The gist of the present invention is to add an yttrium-containing substance, a calcium-containing substance, and a silicon-containing substance and sinter them.

The silicon-containing substance added to the aluminum nitride powder may be 100 ppm to 1% by weight of silica or 5000 ppm to 5% by weight of mullite.

[0007] The sintering temperature can be 1400 to 1800 ° C.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Various factors affecting the strength of an aluminum nitride sintered body can be considered. Various attempts have been made to improve the strength of the aluminum nitride sintered body under various conditions. Alternatively, it has been found that the strength of a sintered body can be improved while maintaining the high thermal conductivity obtained when mullite, particularly a small amount of silica or mullite, is added. It is not clear how silica and mullite work, but in sintered bodies to which these are added, the aluminum nitride particle size tends to decrease, and the strength of the sintered body is affected by the particle size. Considering that, the addition of silica and mullite causes the SiO ₂ component to form a solid solution in the aluminum nitride particles, which has the effect of promoting the miniaturization of the aluminum nitride particles of the sintered body, thereby reducing the strength of the sintered body. It is thought to improve.

As a result of repeated studies in view of the above, according to the present invention, in order to provide a high-strength aluminum nitride, the aluminum nitride powder to which a silicon-containing substance such as silica or mullite is added is sintered. A method for manufacturing an aluminum sintered body is proposed. According to this method, the strength of the obtained aluminum nitride sintered body can be improved, and an aluminum nitride sintered body having both high strength and high thermal conductivity can be manufactured.

Hereinafter, the present invention will be described in detail.

In the production of the high-strength aluminum nitride sintered body of the present invention, first, a silicon-containing substance is added to aluminum nitride powder. It is desirable that the raw material aluminum nitride powder has as high a purity as possible and fine particles, but a commercially available powder generally used is sufficient. The silicon-containing substance to be added in the present invention is a substance which dissolves the SiO ₂ component in the aluminum nitride particles during the sintering process at a high temperature to make the particles finer, so that the silicon-containing substance capable of generating the SiO ₂ component at a high temperature Anything is applicable. However, if the SiO ₂ component is excessively dissolved, the thermal conductivity of aluminum nitride may be significantly reduced. Therefore, a small amount of silica, SiO ₂ —Al ₂ which is relatively stable even at a high temperature and does not excessively generate the SiO ₂ component. It is preferable to use an O ₃ compound (for example, mullite (2SiO ₂ · 3Al ₂ O ₃ )) or a polytypoid which is a reaction product of aluminum nitride and SiO ₂ . Also, S
It is also possible to add a solution in which a silicon-containing alkoxide (methyl silicate, ethyl silicate, or the like) that can be a precursor of iO ₂ is dissolved in an organic solvent. Silica and mullite can be appropriately selected from commonly used ones, and it is preferable to use mullite having a fine particle, particularly a fine powder having a particle size of 1 μm or less. The effect of the addition of silica and mullite is particularly remarkable when the addition amount is small, and in the case of silica, the content is 100 pp.
It is preferable that the amount be from m to 1% by weight, and in the case of mullite be from 5000 ppm to 5% by weight. More preferably, 100 to 2000 ppm for silica and 500 for mullite.
0 ppm to 3% by weight. When silica is used and the amount of addition is very small and control is difficult, for example, when the content of silica is set to several hundred to 1,000 ppm, it can be added as a solution in which an alkoxide such as methylsilicate is dissolved in a solvent. Alternatively, mullite can be used. When the content is set to 1000 to 5000 ppm, the addition amount can be suitably controlled by using a commercially available silica powder. However, when the content of silica exceeds 3000 ppm, the thermal conductivity of the aluminum nitride sintered body tends to decrease, and when it is necessary to increase the amount of addition, mullite is used instead of silica. Good.

The aluminum nitride powder is further added with an yttrium-containing substance and a calcium-containing substance as auxiliaries. This yttrium-containing substance is a substance that can provide the same effect as yttrium oxide during sintering, such as yttrium oxide and a compound that generates yttrium oxide when heated. The calcium-containing compound is a substance that has the same effect as calcium oxide during sintering, and includes calcium oxide, a compound that generates calcium oxide when heated, and the like. Typical compounds actually used include yttrium oxide and calcium carbonate (which generates calcium oxide at a temperature of 1000 ° C. or higher). It is preferable to adjust the amount of the yttrium-containing compound to be 1 to 10% by weight in terms of yttrium oxide and the amount of the calcium-containing compound to be 0.1 to 3% by weight in terms of calcium oxide. More preferably, it is 1 to 5% by weight in terms of yttrium oxide, and 0.1 to 1% in terms of calcium oxide.
% By weight.

The above additives are uniformly mixed with the aluminum nitride powder. At this time, ethanol, alcohol such as propanol and other solvents can be mixed as a dispersion medium by a mixing means such as a ball mill, and after the powder is uniformly mixed, the dispersion medium may be removed by appropriately drying. .

The mixed powder is preformed into a desired shape. The molding may be appropriately performed by a method such as compression molding such as uniaxial pressing or cold isostatic pressing (CIP), or tape molding such as a doctor blade method.

The preformed compact is heated and sintered.
Sintering is performed at about 1400 to 1800 ° C., preferably 160
This is performed at a temperature of about 0 to 1800 ° C. in a non-oxidizing atmosphere such as a nitrogen atmosphere.

When an aluminum nitride sintered body is manufactured according to the above, when the silica content is about 1200 ppm,
A sintered body having high thermal conductivity of about 147 W / mK and high strength of about 400 MPa can be obtained. When the mullite content is 1% by weight, a sintered body having high thermal conductivity of about 154 W / mK and high strength of about 520 MPa can be obtained. Although the thermal conductivity of the aluminum nitride sintered body according to the conventional method is 100 to 250 W / mK, but the strength is about 200 to 350 MPa, the improvement of the strength of the sintered body obtained by the present invention is remarkable. It is easily understood.

Further, as for the aluminum nitride sintered body substrate, a substrate having a thickness of about 2 to 4 mm has been conventionally manufactured in order to secure the reliability of the substrate. Since the strength of the body can be improved, the thickness of the substrate can be reduced, and there are advantages such as being effective in reducing the size of electronic components and the like. Furthermore, even in applications other than the substrate material, the use value of the aluminum nitride sintered body as a structural component material can be dramatically increased by increasing the strength.

[0018]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to examples, but the present invention is not limited to the following examples.

(Sample 1) 210 ppm (0.
0. 21% by weight of methyl silicate was dissolved in ethanol, and 96.95% by weight of aluminum nitride powder (manufactured by Tokuyama Corporation, specific surface area: 3 m ² / g) and yttria powder (manufactured by Hokuko Chemical Industry Co., Ltd.) 2 Calcium carbonate powder (manufactured by Wako Pure Chemical Industries, Ltd.) in an amount of .29% by weight and 0.76% by weight in terms of calcia was added, and the mixture was mixed for 6 hours using a plastic ball and a pot. The obtained slurry was heated to about 60 ° C. in a reduced-pressure atmosphere and stirred and dried, and then heated again to 600 ° C. in a nitrogen atmosphere and calcined for 2 hours to obtain a mixed powder.

The obtained mixed powder is 9 mm long, 10 mm wide,
After preforming into a prism having a length of 45 mm, it was cold isostatically pressed at a pressure of 200 MPa, and was heated to 1700 ° C. in a nitrogen atmosphere.
And baked for 3 hours.

The thermal conductivity of the obtained aluminum nitride sintered body was determined from the density, the thermal diffusivity measured by a laser flash method, and the specific heat. Further, the strength was measured by a three-point bending test. Table 1 shows the obtained thermal conductivity and strength.

(Samples 2 to 5) The amount of methyl silicate used was 0.030% by weight in terms of silica (sample 2).
049% by weight (sample 3), 0.070% by weight (sample 4)
Alternatively, the same operation as in Sample 1 was repeated except that the amount was changed to 0.125% by weight (Sample 5) to produce an aluminum nitride sintered body, and the thermal conductivity and strength were determined.
Table 1 shows the obtained results.

(Sample 6) Commercially available mullite fine powder 0.5% by weight, aluminum nitride powder (manufactured by Tokuyama Corp., specific surface area: 3 m ² / g) 96.95% by weight, yttria powder (manufactured by Hokuko Chemical Industry Co., Ltd.) 2 Calcium carbonate powder (manufactured by Wako Pure Chemical Industries, Ltd.) in an amount of .29% by weight and 0.76% by weight in terms of calcia was added to ethanol, and mixed for 6 hours using a plastic ball and a pot. The obtained slurry was heated to about 60 ° C. in a reduced-pressure atmosphere and stirred and dried, and then heated again to 600 ° C. in a nitrogen atmosphere and calcined for 2 hours to obtain a mixed powder.

The obtained mixed powder was 9 mm long, 10 mm wide,
After preforming into a prism having a length of 45 mm, it was cold isostatically pressed at a pressure of 200 MPa, and was heated to 1700 ° C. in a nitrogen atmosphere.
And baked for 3 hours.

The thermal conductivity and strength of the obtained aluminum nitride sintered body were measured in the same manner as in Sample 1. Table 1 shows the obtained thermal conductivity and strength.

(Samples 7 and 8) The same operation as in Sample 6 was repeated except that the amount of the mullite fine powder used was changed to 1 part by weight (Sample 7) or 2 parts by weight (Sample 8). A sintered body was manufactured, and the thermal conductivity and strength were determined. Table 1 shows the obtained results.

(Sample 9) The same operation as in Sample 6 was repeated except that no mullite fine powder was used to produce an aluminum nitride sintered body, and the thermal conductivity and strength were determined. Table 1 shows the obtained results.

(Samples 10 to 11) The sintering temperature was 1750 ° C.
The same operation as in Sample 9 was repeated except that the temperature was changed to (Sample 10) or 1800 ° C. (Sample 11) to produce an aluminum nitride sintered body, and the thermal conductivity and strength were determined. Table 1 shows the obtained results.

[0029]

Table 1 Sample sintering conditions Thermal conduction in sintered body----------------- Rate Strength Temperature Time Additive amount (° C) (hr) (W / mK) (MPa) -------------------------- ----------- 1 1700 3 silica 210 ppm 161 285 2 1700 3 silica 300 ppm 160 320 3 1700 3 silica 490 ppm 160 360 360 1700 3 silica 700 ppm 154 372 5 1700 3 silica 1250 ppm 147 400 5700 500 wt. 7 17003 Mullite 1 wt% 154 520 8 17003 Mullite 2 wt% 150 518 9 1700 3-165 240 10 1750 3-178 250 11 1800 3- 185 290 -------------------------------------------------------------------------

As is clear from the results shown in Table 1, by adding a small amount of silica or mullite, a dense aluminum nitride sintered body having high thermal conductivity and high strength can be obtained.

[0031]

As described above, according to the present invention, by adding a small amount of silica or mullite to aluminum nitride powder and sintering, aluminum nitride having both high thermal conductivity and high strength is sintered. The body can be provided.
Therefore, the aluminum nitride sintered body can be used as a highly reliable structural material, and its industrial value is extremely large.

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[Procedure amendment]

[Submission date] April 26, 2000 (200.4.2
6)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0006

[Correction method] Change

[Correction contents]

[0006] The silicon-containing substance added to the aluminum nitride powder may be 5000 to 5 wt% mullite.

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Manuel E. Burito 3-2-4, 17-302, Chikusa-ku, Nagoya, Aichi Prefecture (72) Inventor Tomoyama Tomohiro 6-3-1, Chuodai, Kasugai-shi, Aichi Prefecture (72) Inventor Shuzo Kanzaki 8-12, Fujiyamadai, Kasugai-shi, Aichi Prefecture -4 (72) Inventor Fumio Ueno 1 Toshiba-cho, Komukai-shi, Kawasaki-shi, Kanagawa Prefecture Inside the Toshiba R & D Center (72) Inventor Akihiro Horiguchi 1 Toshiba-cho, Komukai-shishi-ku, Kawasaki-shi, Kanagawa Toshiba Corporation Inside the R & D Center (72) Inventor Mitsuo Kasori 1 Tokoba, Komukai Toshiba-cho, Saiwai-ku, Kawasaki-shi, Kanagawa Prefecture F-term in Toshiba R & D Center (reference) 4G001 BA04 BA07 BA09 BA36 BA65 BA81 BA85 BB03 BB07 BB09 BB36 BC11 BC52 BD03 BD13 BD23 5F036 AA01 BB01 BD14

Claims (3)

[Claims] 1. A method for producing an aluminum nitride sintered body, comprising adding an yttrium-containing substance, a calcium-containing substance, and a silicon-containing substance to aluminum nitride powder and sintering. 2. The method according to claim 1, wherein the silicon-containing substance added to the aluminum nitride powder is 100 ppm to 1% by weight of silica or 5000 ppm to 5% by weight of mullite. 3. The method according to claim 1, wherein the sintering temperature is 1400 to 1800 ° C.