JPH02225307A - Production of aluminum nitride powder and sintered material of aluminum nitride. - Google Patents

Abstract

PURPOSE:To obtain highly purified and fine granular sinterable aluminum nitride powder in a low cost by burning mixture of aluminum-containing compound and tannic acid and/or gluconic acid in nitrogen-containing, non-oxidizing atmosphere. CONSTITUTION:A mixture of aluminum-containing compound and tannic acid and/or gluconic acid is burnt in non-oxidizing atmosphere containing nitrogen to obtain aluminum nitride powder. Besides, a molded material having fixed shape composed of said mixture is burnt in non-oxidizing atmosphere containing nitrogen to readily afford sufficiently sintered, dense sintered material of aluminum nitride in a low cost. Preferably water-soluble compound as aluminum- containing compound is uniformly mixed with tannic acid and/or gluconic acid in a state of aqueous solution and water is removed to afford said mixture. At least one of aluminum polynuclear complex and aluminum alkoxide is preferably used as aluminum compound.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for producing aluminum nitride powder for producing, for example, a highly thermally conductive (insulating) substrate; ) A method for manufacturing an aluminum nitride sintered body for use as a substrate.

[Conventional technology and problems]

BACKGROUND ART As semiconductor devices such as ICs have become more highly integrated and have higher power, electrical insulating materials with good heat dissipation properties have become required. In response to this demand, various highly thermally conductive substrates have been proposed. Among them, aluminum nitride ceramic substrates in particular are being put into practical use because they are excellent in terms of thermal conductivity, thermal expansion, electrical insulation, and the like.

This aluminum nitride ceramic substrate is a sintered body obtained using aluminum powder. The aluminum nitride powder used here is produced by direct nitriding of aluminum, carbon reduction of alumina, etc. However, for example, it is difficult to obtain powder with high purity and small particle size using the direct nitriding method of aluminum. However, in the carbon reduction method of alumina, there are problems such as the reaction requires high temperature and the cost of raw materials is high. As an improvement to the carbon reduction method of alumina, a method of reducing the aluminum source with a carbon-containing compound has been proposed, but it is still not sufficient in terms of reduction efficiency.

[Problem to be solved by the invention]

In view of these circumstances, the first objective of this invention is to provide a method that can inexpensively obtain highly pure, fine-grained, easily sinterable aluminum nitride powder. The second object of the present invention is to provide a method for obtaining an aluminum nitride sintered body easily and inexpensively.

[Means to solve the problem]

In order to solve the first problem, in the method for producing aluminum nitride powder according to claim 1, a mixture of an aluminum-containing compound and tannic acid and/or gluconic acid,
The firing is done in a non-oxidizing atmosphere containing nitrogen.

In order to solve the second problem, in the method for producing an aluminum nitride sintered body according to claim 2, a molded body of a predetermined shape made of a mixture of an aluminum-containing compound and tannic acid and/or gluconic acid is prepared by adding nitrogen to the aluminum nitride sintered body. The firing is done in a non-oxidizing atmosphere.

As the mixture of the aluminum-containing compound and tannic acid and/or gluconic acid used in both production methods of the present invention, for example, as in the invention according to claim 3, the aluminum-containing compound is a water-soluble compound, and the aluminum-containing compound is a water-soluble compound; Examples include those obtained by uniformly mixing acid and/or gluconic acid in an aqueous solution state and then removing water.

The aluminum-containing compound used in the production method of the present invention includes at least one of an aluminum polynuclear complex and an aluminum alkoxide.

In the method for producing an aluminum nitride sintered body according to the present invention, for example, as in the fifth aspect of the invention, the molded body may contain a sintering aid and then be fired.

This will be explained in more detail below.

The aluminum-containing compound is a source of aluminum, which is the main component of aluminum nitride. Therefore, as long as it is a compound containing aluminum, it is not particularly limited, and examples thereof include aluminum nitrate, aluminum chloride, aluminum sulfate, aluminum hydroxide, aluminum lactate, alumina, aluminum polynuclear complex, aluminum alkoxide, and the like.

Examples of the aluminum polynuclear complex include basic aluminum chloride, basic aluminum lactate, and basic aluminum nitrate.

As the aluminum alkoxide, aliphatic alkoxides having 10 or less carbon atoms such as aluminum methoxide, aluminum ethoxide, aluminum propoxide, and aluminum butoxide can be suitably used. Used alone or in combination.

Tannic acid and gluconic acid serve to remove the oxygen element contained in the aluminum-containing compound in the form of CC01Co in the aluminum nitride production reaction in the firing process. Tannic acid and gluconic acid are usually used alone, but they may be used in combination.

When the aluminum-containing compound is a water-soluble compound and a mixture is obtained by uniformly mixing it with tannic acid and/or gluconic acid in an aqueous solution state and then drying to remove moisture, the drying temperature is, for example, 80 to 80°C. 200℃,
Furthermore, a range of about 100 to 200°C is appropriate.

In the case of powder production, the mixture obtained by drying is in a powder state or in a bulk state. If it is in a bulk state, it is fired as it is or after it is pulverized. When the aluminum nitride powder is fired in the bulk state, the aluminum nitride powder is usually in such a clump-like state that it easily crumbles at the stage of firing.

Also in the case of producing a sintered body, the mixture obtained by drying is in a powder state or a bulk state. In the production of sintered bodies, the mixture is formed into a molded body of a predetermined shape, but if the mixture obtained by drying is in bulk form, it is preferable to first crush and powder it before molding. , it may also be molded in bulk form.

The molding method may be, for example, a pressure molding method using a mold, but is not particularly limited as long as it does not cause undesirable deterioration of components or flow holes.

Examples of the sintering aid contained in the compact include salts and oxides of alkaline earth or rare earth elements. Specific examples include yttrium nitrate, yttrium chloride, basic yttrium acetate, yttrium oxide, calcium nitrate, calcium chloride, calcium oxide, etc., but are not limited thereto. Note that the content of the sintering aid is preferably about 3 to 10% by weight based on the aluminum contained.

The timing of adding the sintering aid is not particularly limited, and may be at the aqueous solution stage where the aluminum-containing compound and tannic acid or gluconic acid are mixed, or at the powder stage after drying the aqueous solution.

Furthermore, in the method for producing aluminum nitride powder, calcium salts, yttrium salts, or salts of lanthanide group elements, etc., are also added to the mixture in order to promote nitriding and facilitate carbon removal. You can also do this.

As the non-oxidizing atmosphere, an atmosphere of argon containing nitrogen, carbon monoxide containing nitrogen, nitrogen, ammonia, or the like is used. In the method for producing aluminum nitride powder, the firing temperature is 1200°C or higher, preferably 1200°C or higher.
The temperature is about 400 to 1800°C, and in the method for producing an aluminum nitride sintered body, the temperature is 1200°C or higher, preferably about 1400 to 2000°C. In addition, when removing residual carbon in the powder or sintered body, for example, after nitriding, 600
Further heat treatment is performed in an oxidizing atmosphere at about ~700°C.

[For production]

As in the method for producing aluminum nitride powder according to the present invention, when an aluminum-containing compound, such as an aluminum polynuclear complex or a mixture of aluminum alkoxide and tannic acid and/or gluconic acid, is fired in a non-oxidizing atmosphere containing nitrogen, Even if the firing temperature is not high, aluminum nitride powder with high purity (nitridation rate) and sufficiently small particle size can be obtained at low cost. Powder with a small particle size is easily sintered when producing a highly thermally conductive insulating substrate.

As in the method for producing an aluminum nitride sintered body according to the present invention, a molded body of a predetermined shape made of an aluminum-containing compound, such as an aluminum polynuclear complex or a mixture of aluminum alkoxide and tannic acid and/or gluconic acid, is formed into a molded body containing nitrogen. By firing in a non-oxidizing atmosphere, an aluminum nitride sintered body with high purity (nitridation rate), density, and good thermal conductivity can be easily obtained without going through a complicated powder process.

The aluminum-containing compound is a water-soluble compound, and the mixture obtained by uniformly mixing the aluminum-containing compound with tannic acid and/or gluconic acid in an aqueous solution state and then removing water is the aluminum-containing compound and tannic acid and/or gluconic acid. Since the acids are mixed on a molecular order, a more pure and homogeneous powder or sintered body can be obtained.

〔Example〕

Hereinafter, specific examples will be described.

First, an example of a method for producing aluminum nitride powder will be described.

Example 1 Tannic acid (
(manufactured by Nacalai Tesque) was mixed in an amount of 0.65 parts by weight to prepare an aqueous solution. The basic aluminum chloride used had an aluminum content of 50% by weight in terms of Altos and a basicity of 84%. Next, this aqueous solution was evaporated to dryness at a drying temperature of 120°C. The obtained solid was pulverized and calcined in a nitrogen atmosphere (non-oxidizing atmosphere) at 1550°C for 8 hours, and then heat-treated for 1 hour in an air atmosphere (oxidizing atmosphere) at a temperature of 700°C. Aluminum nitride powder was obtained.

Example 2 - Tannic acid (1 part by weight of basic aluminum lactate)
An aqueous solution was prepared by mixing 0.47 parts by weight of the following ingredients (manufactured by Nacalai Tesque). In addition, basic aluminum lactate has an aluminum content of Af□0. The lactic acid content was 37% by weight and the lactic acid content was 56%. Next, this aqueous solution was evaporated to dryness at a drying temperature of 120°C. The obtained solid material was pulverized and calcined in a nitrogen atmosphere at 1550°C for 8 hours, and then heat-treated at a temperature of 700°C in an air atmosphere for 1 hour to obtain aluminum nitride powder.

Example 3 - 1 part by weight of aluminum triisopropoxide (aluminum triisopropoxide) and 0.32 parts by weight of tannic acid (manufactured by Nacalai Tesque) were mixed into 2.97 parts of a 15% aqueous solution of tetramethylammonium hydroxide! !
After stirring at room temperature for 1 hour, this solution was
It was evaporated to dryness at a drying temperature of 20°C. The obtained solid material was pulverized and calcined in a nitrogen atmosphere at 1550°C for 8 hours, and then heat-treated at a temperature of 700°C in an air atmosphere for 1 hour to obtain aluminum nitride powder.

Example 4 - 1 part by weight of alumina powder with a purity of 99.9% and an average particle size of 0.4 ha was added to an aqueous solution in which 1.28 parts by weight of tannic acid (manufactured by Nacalai Tesque) was dissolved, and the mixture was heated at room temperature. After standing for 10 minutes, the solution was evaporated to dryness at a drying temperature of 120°C. The obtained solid was pulverized and calcined in a nitrogen atmosphere at 1600°C for 8 hours, and then heat-treated at 700°C in an air atmosphere for 1 hour to obtain aluminum nitride powder, Example 5- 1 gluconic acid (50% aqueous solution) instead of tannic acid
．． Aluminum nitride powder was obtained in the same manner as in Example 1 except that the amount was 97 parts by weight.

Example 6 - 1 gluconic acid (50% aqueous solution) instead of tannic acid
Aluminum nitride powder was obtained in the same manner as in Example 2 except that the amount was changed to 44 parts by weight.

Example 7 - Gluconic acid (50% aqueous solution) in place of tannic acid
．． Aluminum nitride powder was obtained in the same manner as in Example 3 except that the amount was 97 parts by weight.

Example 8 - 3 gluconic acid (50% aqueous solution) instead of tannic acid
．． Aluminum nitride powder was obtained in the same manner as in Example 4 except that the amount was 88 parts by weight.

- Comparative Example 1 An aqueous solution was prepared by mixing 1 part by weight of basic aluminum chloride used in Example 1 with 0.70 parts by weight of hexamethylenetetramine.

Next, this aqueous solution was evaporated to dryness at a drying temperature of 120°C. The obtained solid material was pulverized and calcined in a nitrogen atmosphere at 1600°C for 8 hours, and then heat-treated at 700°C in an air atmosphere for 1 hour to obtain aluminum nitride powder.

- Comparative Example 2 - Carbon black (Mitsubishi Kasei ■ #40
10B) 0.50 parts by weight was suspended and stirred at room temperature for 30 minutes. Next, this aqueous solution was evaporated to dryness at a drying temperature of 120°C. The obtained solid was pulverized and
The product was fired for 8 hours in a nitrogen atmosphere at 700°C, and then heat-treated for 1 hour in an air atmosphere at 700°C to obtain aluminum nitride lamb powder.

Examples 1 to 8 and Comparative Example 1.
The nitridation rate (purity) and average particle size of the aluminum nitride powder of No. 2 were measured. The measurement results are shown in Table 1.

Table 1 The aluminum nitride powders of Examples 1 to 8 have high purity as shown in Table 1. The aluminum nitride powder of Comparative Example 1.2 has very poor purity. Even if the firing temperature is not very high, the powders of the examples have a very high nitridation rate. Of course, as shown in Table 1, the powders of the examples are fine particles with small particle sizes, and it goes without saying that they have excellent sinterability.

In addition, when the powders of Examples 1 to 8 and Comparative Example 1.2 were subjected to X-ray analysis, it was found that the powders of Examples had no unnitrided residual A.
ll! Almost no peak indicating the presence of Os was detected, but on the other hand, in each powder of the comparative example, unnitrided residual A1
A peak indicating the presence of xos was clearly detected, confirming that the purity of the powder of the comparative example was insufficient.

Next, an embodiment of the method for manufacturing an aluminum nitride sintered body according to the present invention will be described.

Example A - An aqueous solution was prepared by mixing 1 part by weight of basic aluminum chloride with 0.43 parts by weight of tannic acid. In addition, basic aluminum chloride has an aluminum content of 50% by weight in terms of AltO* and a basicity of 84.
% was used. Next, this aqueous solution was evaporated to dryness at a drying temperature of 120°C. The obtained solid material was first pulverized, then made into a disc-shaped molded product with a diameter of 25 mm and a thickness of 3 μm using a mold, and then fired in a nitrogen atmosphere at 1900°C for 8 hours to undergo nitriding. An aluminum sintered body was obtained.

Example B - 1 part by weight of basic aluminum chloride used in Example A, 0.43 part by weight of tannic acid, 6 parts by weight of yttrium nitrate.
An aqueous solution containing 0.068 parts by weight of hydrate was prepared. Next, this aqueous solution was evaporated to dryness at a drying temperature of 120°C. The obtained solid material was first pulverized, and then formed into a disc-shaped body with a diameter of 25 mm and a thickness of 3 mm using a mold, and then fired in a nitrogen atmosphere at 1850°C for 4 hours. An aluminum nitride sintered body was obtained.

Example C For 1 part by weight of basic aluminum lactate, 0.32 parts by weight of tannic acid, 0.32 parts by weight of tannic acid, and 0.32 parts by weight of IJium hexahydrate.
An aqueous solution was prepared by mixing 0.05 parts by weight. The basic aluminum lactate used had an aluminum content of 37% by weight in terms of A1xo* and a lactic acid content of 56%. Next, this aqueous solution was evaporated to dryness at a drying temperature of 100°C. The obtained solid material was first pulverized, then made into a disc-shaped body with a diameter of 25 m and a thickness of 3 mm using a molding die, and then pulverized in a nitrogen atmosphere at 1850°C for 40 minutes.
The aluminum nitride sintered body was obtained by firing for several hours.

Example D - 1 part by weight of aluminum triisopropoxide, 0.21 parts by weight of tannic acid, 0°033 parts by weight of yttrium nitrate hexahydrate,
Tetramethylammonium high 1' oxide 15%
After adding to 2.97 parts by weight of the aqueous solution and stirring at room temperature for 1 hour, the solution was evaporated to dryness at a drying temperature of 110°C. After pulverizing the obtained solid, a molded body was obtained in the same manner as in Example A, and then fired at a temperature of 1850° C. in a nitrogen atmosphere for 4 hours to obtain an aluminum nitride sintered body.

Example E For 1 part by weight of aluminum nitrate nonahydrate, 0.11 parts by weight of tannic acid and 0.0 part of yttrium nitrate hexahydrate were added.
An aqueous solution was prepared by mixing the components to have a volume of 19 parts. Next, these four water solutions were evaporated to dryness at a drying temperature of 120°C. After pulverizing the obtained solid material and obtaining a molded body in the same manner as in Example A, the solid material was crushed in a nitrogen atmosphere at a temperature of 1850°C for 4 hours.
The aluminum nitride sintered body was obtained by firing for several hours.

Example F An aluminum nitride sintered body was obtained in the same manner as in Example A except that 0.60 parts by weight of gluconic acid was used instead of tannic acid.

Example G An aluminum nitride sintered body was obtained in the same manner as in Example B except that 0.65 parts by weight of gluconic acid was used instead of tannic acid.

Example 11 An aluminum nitride sintered body was obtained in the same manner as in Example C, except that 0.45 parts by weight of gluconic acid was used instead of tannic acid.

Example I - An aluminum nitride sintered body was obtained in the same manner as in Example 1, except that 0.30 parts by weight of gluconic acid was used instead of tannic acid and the aqueous solution drying temperature was 120°C.

Example J - An aluminum nitride sintered body was obtained in the same manner as in Example E except that 0.16 ml of gluconic acid was used instead of tannic acid.

To Comparative Example - An aqueous solution was prepared by mixing 1 part by weight of basic aluminum chloride with 1 part by weight of hexamethylenetetramine. In addition, basic aluminum chloride is
Aluminum content is 50% by weight in terms of Al1t O1
and the basicity was 84%. Next, the aqueous solution was evaporated to dryness at a drying temperature of 120°C. The obtained solid material was first pulverized, and then formed into a disc-shaped compact with a diameter of 25 am and a thickness of 311 A using a molding die, and then fired in a nitrogen atmosphere at 1900°C for 8 hours to undergo nitriding. An aluminum sintered body was obtained.

The density and thermal conductivity of the aluminum nitride sintered bodies of Examples A-J and Comparative Example A thus obtained were measured.

The measurement results are shown in Table 2.

As shown in Table 2, the aluminum nitride sintered bodies of Examples A and -J in Table 2 are dense sintered bodies with larger densities than those of Comparative Example A. It is conductivity. When the sintered bodies of Examples A to J were subjected to X-ray analysis, almost no peak indicating the presence of unnitrided residual Aβ2° was detected, but when the sintered bodies of Comparative Example A were subjected to X-ray analysis, A peak indicating the presence of unnitrided residual Al s O* was clearly detected.

〔Effect of the invention〕

As described above, in the method for producing aluminium nitride powder according to the present invention, powder with high purity and small particle size can be obtained quickly and inexpensively even if the firing temperature is low. Therefore, an excellent high thermal conductivity (insulating) substrate can be obtained easily and inexpensively.

Further, in the method for producing an aluminum nitride sintered body according to the present invention, a dense and highly thermally conductive sintered body can be directly produced without going through the state of aluminum nitride powder. Therefore, an excellent high thermal conductivity (insulating) substrate can be obtained easily and inexpensively.

In both of these production methods, if the mixture is obtained by uniformly mixing an aluminum-containing compound and tannic acid and/or gluconic acid in an aqueous solution state and then removing water, the aluminum-containing compound and tannin Since the acid and/or gluconic acid are sufficiently mixed, a more pure and homogeneous powder or sintered body can be obtained.

Agency Lentinum Takeshi Matsumoto 2 ゜ 3 ゜ "Itroku Nena ILI Masao 7 (1 distribution Heisei 1st LO Moon 6 [] Specially application flat 1 = 201823 Invention Name Aluminum Nitride Powl) and Aluminum Nitride Fortune) Relationship with the Case of Person Who Amends the Manufacturing Capacity Act Patent Applicant Address 1048 Kadoma, Kadoma City, Osaka Name (583) Matsushita Electric Works Co., Ltd.

Claims (1)

[Scope of Claims] 1. A method for producing aluminum nitride powder, which comprises firing a mixture of an aluminum-containing compound and tannic acid and/or gluconic acid in a non-oxidizing atmosphere containing nitrogen. 2. A method for producing an aluminum nitride sintered body, in which a molded body of a predetermined shape made of a mixture of an aluminum-containing compound and tannic acid and/or gluconic acid is fired in a non-oxidizing atmosphere containing nitrogen. 3. The aluminum nitride powder or aluminum nitride powder according to claim 1 or 2, wherein the aluminum-containing compound is a water-soluble compound, and the mixture is obtained by uniformly mixing tannic acid and/or gluconic acid in an aqueous solution state and then removing water. A method for producing an aluminum nitride sintered body. 4. The method for producing aluminum nitride powder or aluminum nitride sintered body according to any one of claims 1 to 3, wherein the aluminum-containing compound is at least one of an aluminum polynuclear complex and an aluminum alkoxide. 5. The method for producing an aluminum nitride sintered body according to any one of claims 2 to 4, wherein the molded body contains a sintering aid.