JP3460156B2 - Manufacturing method of aluminum nitride sintered body - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an aluminum nitride sintered body, particularly an aluminum nitride sintered body suitable for a ceramic substrate for an insulating heat dissipation plate used in a power module for electronic parts.

[0002]

2. Description of the Related Art In recent years, an aluminum nitride substrate as a highly thermal conductive ceramic substrate, particularly a substrate for a high power module in which metal plates are bonded to both surfaces thereof to form a circuit, has been attracting attention with the development of semiconductor elements. Also, with the diversification of circuit boards, it is necessary to prepare a thin aluminum nitride substrate with a thickness of about 0.3 mm to a thickness of about 1 mm or more.

Conventionally, aluminum nitride sintered bodies are obtained by adding aluminum nitride powder to sintering aids such as yttria, calcia and magnesia, organic binders such as ethyl cellulose and polyvinyl butyral, plasticizers such as dibutyl phthalate, and glycerin trioleate. Dispersant, toluene, xylene, isopropanol and other organic solvents are mixed to prepare a slurry, which is formed into a sheet by the doctor blade method and then fired in a non-oxidizing atmosphere such as nitrogen or argon. ing.

However, according to this method, it is difficult to adjust the clearance of the doctor knife, so even if a considerable amount of skill is applied to adjust the thickness, 50 to 7 of the coating width from both sides can be obtained.
The portion up to about 0 mm has a non-uniform thickness and cannot be used, so that the yield is poor. Also,
If the drying speed of the organic solvent is not adjusted properly, wrinkles will occur on the sheet surface or a resin film will be formed and the organic solvent gas inside the sheet will not escape sufficiently, causing pinholes and further worsening the yield. Let Furthermore, the machinery and equipment to be used must have an explosion-proof structure against organic solvents, resulting in a large investment.

To solve the above problems, water may be used in place of the organic solvent to form a sheet, but for that purpose, it is necessary to make the aluminum nitride powder highly durable against hydrolysis. There is. Conventionally, various methods have been proposed, and an example thereof is a hydrophobic treatment with stearic acid (Japanese Patent Publication No. 3-261665). This treatment enabled molding by the doctor blade method and slip casting method using water as a medium, but since the hydrophobized aluminum nitride powder has poor dispersibility in water, a hydrophilic group is added by a surfactant or the like. There was a need.

The present invention solves the above problems, and provides a method for producing an aluminum nitride sintered body, which does not require an explosion-proof structure for machinery and equipment used, which has a very high yield.

[0007]

That SUMMARY OF THE INVENTION The present invention provides nitrogen
Mixed powder containing aluminum oxide powder and sintering aid, and hydrophobic
The above mixed powder is made hydrophobic by mixing with a surfactant having a group.
After the chemical treatment , a water-soluble organic polymer compound, a plasticizer and water are mixed to produce a kneaded product, which is extruded and molded, and then fired in a non-oxidizing atmosphere. This is a method of manufacturing an aluminum nitride sintered body, in which the sintering aid is
And the surfactant having a hydrophobic group is oleic acid.
The water-soluble organic polymer is methyl cellulose or ethyl acetate.
Lulose and the plasticizer is glycerin or phthalate
Of aluminum nitride sintered body characterized by being
It is a manufacturing method .

The present invention will be described in more detail below. The aluminum nitride powder used in the present invention can be produced by an alumina reduction method, a metal aluminum direct nitriding method, a vapor phase method or the like.

As a method for hydrophobizing aluminum nitride powder, a surfactant having a hydrophobic group, for example, stearic acid, aliphatic carboxylic acid of oleic acid, aliphatic carboxylic acid salt and its ester, higher alcohols, sulfonic acids One or two or more selected from the above are mixed in an amount of preferably 0.5 to 5 parts by weight, particularly preferably 1 to 3 parts by weight with respect to 100 parts by weight of aluminum nitride powder, and a ball mill, a vibration mill, a Henschel mixer, etc. It can be performed by mixing. In order to achieve uniform mixing, a surfactant having a hydrophobic group in the aluminum nitride powder is more than 1.
It is preferable to prepare a masterbatch in which the amount is about 5 to 3 times as large as that of the mixture, and mix the masterbatch and the aluminum nitride powder in the above ratio. When the amount of the surfactant is small or the mixing is insufficient, the hydrophobic treatment is insufficient, and conversely, when the amount of the surfactant is large, the aluminum nitride powder aggregates. The hydrophobizing treatment of the aluminum nitride powder can be performed with a mixed powder of the aluminum nitride powder and the sintering aid.

As the sintering aid used in the present invention, oxides of alkaline earth metals such as calcia, magnesia, alumina, yttria, and ceria, IIIa compounds, compounds of rare earth elements, etc. which have been conventionally used. However, yttrium oxides, fluorides, chlorides, nitrates and sulfates are preferable, and yttria is particularly preferable. The amount used is preferably 0.1 to 10 parts by weight and particularly preferably 1 to 5 parts by weight with respect to 100 parts by weight of the aluminum nitride powder.

The water-soluble organic polymer compound used in the present invention functions as a binder, and examples thereof include polyvinyl alcohol, methyl cellulose, alginic acid, polyethylene glycol, carboxymethyl cellulose, ethyl cellulose and the like. The amount used is preferably 4 to 14 parts by weight and particularly preferably 6 to 12 parts by weight with respect to 100 parts by weight of the aluminum nitride powder.

Further, as the plasticizer, phthalic acid esters such as dibutyl phthalate, dimethyl phthalate and diethyl phthalate, glycerin and the like can be used, and the amount of each is 1 to 100 parts by weight of aluminum nitride powder. 8 parts by weight.

The amount of water is 5 to 15 parts by weight based on 100 parts by weight of aluminum nitride powder.

The kneading method of these materials may be a ball mill, a vibration mill, a high speed mixer or the like. However, since the kneaded product is subsequently extruded and molded, kneading using a screw of a molding machine is preferable. The kneaded product is vacuum degassed at about 50 to 200 Pa, then extruded and dried at a temperature at which the water-soluble organic polymer compound does not deteriorate, for example, 100 ° C. or less to form an aluminum nitride green sheet. As an extruder, a screw type extruder is generally adopted.

Next, the aluminum nitride green sheet is fired to produce an aluminum nitride sintered body. The firing conditions are a temperature of 1700 to 2000 ° C. and a time of 0.5 to 5 hours under a non-oxidizing atmosphere such as nitrogen and argon.

[0016]

EXAMPLES The present invention will be described in more detail with reference to Examples and Comparative Examples.

Example 1 100 parts by weight of aluminum nitride powder having an oxygen content of 1.2% by weight and an average particle size of 2.0 μm and 4 parts by weight of yttria powder were mixed in a ball mill for 30 minutes, and then 2 parts by weight of oleic acid. In addition, the mixture was further mixed for 30 minutes to hydrophobize the aluminum nitride powder.

After adding 8 parts by weight of methylcellulose to the obtained mixture and mixing for 1 minute with a high-speed mixer, a mixed solution of 6 parts by weight of glycerin and 14 parts by weight of water was further added with continuous stirring and mixed for 2 minutes, and further rolled. To produce a kneaded product.

This kneaded product was rotary pumped to 130P.
While vacuum degassing to about a, using a screw type extruder to form a sheet with a 120 mm wide die, and then drying in a belt type drying oven at 80 ° C for 20 minutes, 0.75 mm thick aluminum nitride A green sheet was molded.

This was punched with a die into a size of 55 × 55 mm, the surface of each sheet was coated with BN powder, and five sheets were piled up and placed in a degreasing furnace and treated in air at a temperature of 500 ° C. for 3 hours. Degreased.

Then, it is heated at a temperature of 1 in a nitrogen atmosphere at atmospheric pressure.
After holding at 900 ° C for 30 minutes and baking, temperature 1700
The cooling rate to 1.5 ° C. was set to 1.5 ° C./min and the temperature was cooled to room temperature to produce a 43 × 43 × 0.65 mm aluminum nitride sintered body. Honing the surface of the sintered body to 2μ
After removing m, the density (Archimedes method) and the thermal conductivity (“TC-3000” manufactured by Vacuum Riko Co., Ltd.) of the sintered body were measured, and they were 3.26 g / cm ³ and 132 W / mK, respectively.
Met. This value was comparable to the conventional doctor blade method of 3.25 g / cm ³ and 135 W / mK.

Further, in the conventional doctor blade method, the edge portion of the aluminum nitride green sheet was insufficient in thickness, and only about 50% of the obtained sheet could be used in the punching step of the next step. In the case of about 70%, the yield was improved.

Comparative Example 1 When an aluminum nitride sintered body was produced in the same manner as in Example 1 except that oleic acid was not added, the aluminum nitride green sheet was hydrolyzed to generate ammonia. Due to the heat of decomposition, the methyl cellulose deteriorated and could not be punched with a mold.

Example 2 An aluminum nitride sintered body was produced in the same manner as in Example 1 except that ethyl cellulose was used as the water-soluble polymer compound and dimethyl phthalate was used as the plasticizer. Density 3.26 g / cm ³ , thermal conductivity 13
It was 0 W / mK.

[0025]

According to the present invention, it is possible to manufacture aluminum nitride sintered bodies of different thicknesses safely and with good yield without using an explosion-proof structure for machinery and equipment used.

─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Takashi Ikeda 1 Shinkai-cho, Omuta-shi, Fukuoka Electric Chemical Industry Co., Ltd. Omuta factory (56) Reference JP-A-3-261665 (JP, A) JP-A-62- 56376 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) C04B 35/581

Claims (2)

(57) [Claims] 1. An aluminum nitride powder and a sintering aid are included.
Mix the mixed powder with a surfactant having a hydrophobic group and
After hydrophobizing the mixed powder , a water-soluble organic polymer compound, a plasticizer and water are mixed to produce a kneaded product, which is then pressed.
A method for producing an aluminum nitride sintered body, which comprises subjecting the material to extrusion molding and then firing it in a non-oxidizing atmosphere. 2. The sintering aid is yttria and the hydrophobic group is
The surfactant it has is oleic acid,
The child compound is methyl cellulose or ethyl cellulose
The plasticizer is glycerin or phthalate.
The aluminum nitride sintered body according to claim 1, characterized in that
Manufacturing method.