JP2886003B2 - Aluminum nitride composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum nitride composition suitable for continuous punching of a sheet formed mainly of aluminum nitride powder.

[0002]

2. Description of the Related Art Aluminum nitride sintered bodies have a high thermal conductivity and have been spotlighted as electronic materials.
As a method for obtaining an aluminum nitride sintered body, there are a method in which aluminum nitride powder is formed by dry pressing and firing, and a method in which aluminum nitride powder is wet-formed to obtain a green sheet and fired. The latter method of producing a green sheet generally employs a method in which a binder, a deflocculant, an organic solvent, and the like are mixed with aluminum nitride powder and formed into a sheet by a togger blade method or the like. Here, the binder is used for imparting strength and flexibility to the green sheet, improving processability and facilitating handling.

[0003] The green sheet is punched and cut into a predetermined shape. When the size of the green sheet piece after cutting is too small, the green sheet piece can be cut into a relatively large size and easily cut into a predetermined size later. In this manner, an operation of forming a break line (groove) in a green sheet and cutting along the break line after firing is adopted.

[0004]

However, when a break line is to be formed in the green sheet punching process, a phenomenon occurs in which the green sheet adheres to the blade of the punching machine, and the green sheet rises as the blade rises. There was a problem. For this reason, it has been impossible to continuously perform punching of a green sheet having a break line.

[0005]

In order to obtain a green sheet which can be continuously punched with a break line, the present inventors obtain a green sheet which does not easily adhere to the blade of a punching machine. We have continued our research for the purpose. As a result, they have found that a composition of a polyvinyl butyral resin having a specific degree of butyralization and aluminum nitride powder is a raw material for a green sheet that has achieved the above-mentioned object, and has led to the present invention.

That is, the present invention relates to an aluminum nitride powder 1
An aluminum nitride composition comprising 00 parts by weight and 4 to 30 parts by weight of a polyvinyl butyral resin having a degree of butyralization of 80% by weight or more.

As the aluminum nitride powder, which is one component of the aluminum nitride composition of the present invention, known ones can be used without any limitation. Generally, in order to obtain an aluminum nitride sintered body having excellent thermal conductivity, it is preferable that the oxygen content and the amount of cationic impurities be small. That is, when AlN has an aluminum nitride composition, the oxygen content as an impurity is 1.5%.
Aluminum nitride powder with less than 0.3% by weight and less than 0.3% by weight of cationic impurities is preferred. Further, an aluminum nitride powder having an oxygen content of 0.4 to 1.3% by weight and a cation impurity of 0.2% by weight or less is more preferable. The aluminum nitride in the present invention is a 1: 1 compound of aluminum and nitrogen, and all other compounds are treated as impurities. However, the surface of the aluminum nitride powder is inevitably oxidized in air, and the Al—N bond is replaced by an Al—O bond. However, this bonded Al is not regarded as a cationic impurity. Therefore, Al-N, Al
Metallic aluminum having no -O bond is a cationic impurity.

Further, it is preferable that the particles of the aluminum nitride powder used in the present invention have a small particle diameter. For example, the average particle diameter (meaning the average particle diameter of aggregated particles measured by a centrifugal particle size distribution analyzer, for example, CAPA500 manufactured by HORIBA, Ltd.) is preferably 5 μm or less, more preferably 3 μm or less.

Next, another component of the aluminum nitride composition of the present invention is a polyvinyl butyral resin having a degree of butyralization of 80% by weight or more. If the degree of butyralization of the polyvinyl butyral resin is outside the above range, continuous punching of the obtained green sheet cannot be performed, which is not preferable. The butyralization degree of the polyvinyl butyral resin is up to 88% by weight at present. In the present invention, the degree of butyralization is determined according to JIS.
It is a value calculated from the following formula by determining a vinyl acetate component and a vinyl alcohol component by K6728.

Degree of butyralization = 100- {vinyl acetate component (% by weight) + vinyl alcohol component (% by weight)} The blending amount of polyvinyl butyral resin having a degree of butyralization of 80% by weight or more with aluminum nitride powder is as follows: It must be 4 to 30 parts by weight, preferably 5 to 15 parts by weight, per 100 parts by weight of aluminum powder. If the blending amount of the polyvinyl butyral resin having a butyralization degree of 80% by weight or more is less than the above range, cracks occur at the time of green sheet punching,
If the amount is larger than the above range, the physical properties of the aluminum nitride sintered body obtained from the aluminum nitride composition deteriorate, which is not preferable. Although the molecular weight of the polyvinyl butyral resin is not particularly limited, it is generally 3,000 to 1,000.
It is suitable for the green sheet to be flexible and rich in toughness and to be easy to handle at the time of processing, preferably 5,000, preferably 5,000 to 300,000.

When a green sheet is produced using the aluminum nitride composition of the present invention, a surfactant, a plasticizer, and an organic solvent are usually used.

As the surfactant, known surfactants can be used without any limitation, and in particular, those having a hydrophilic / lipophilic balance (hereinafter abbreviated as HLB) of 4.5 to 18, more preferably 6 A value of from 0.0 to 10.0 is preferably employed because the molding density of the aluminum nitride powder compact increases. Note that HLB in the present invention is a value calculated by the Davis formula.

Specific examples of surfactants that can be suitably used in the present invention include carboxylated trioxyethylene tridecyl ether, diglycerin monooleate, diglycerin monostearate, and carboxylated heptaoxyethylene tridecyl ether. , Tetraglycerin monooleate, hexaglycerin monooleate, polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monooleate, and the like. The surfactant in the present invention may be used as a mixture of two or more kinds, and the HLB at that time can be calculated by the arithmetic average of the HLB of each surfactant.

When the aluminum nitride composition of the present invention is processed into a specific molded product, a plasticizer is preferably used for the purpose of imparting flexibility to the processed product. As the plasticizer, those known to be used for the above-mentioned purpose when molding general ceramic powder can be used without particular limitation. Specific examples of the particularly preferable examples include polyethylene glycol and derivatives thereof; phthalic acid esters such as dimethyl phthalate, dibutyl phthalate, butyl benzyl phthalate and dioctyl phthalate; stearic acid such as butyl stearate; Esters; tricresole phosphate; tri-N-butyl phosphate; glycerin and the like.

Examples of the organic solvent include ketones such as acetone, methyl ethyl ketone and methyl isobutyl ketone; alcohols such as ethanol, propanol and butanol; aromatic hydrocarbons such as benzene, toluene and xylene;
One or more halogenated hydrocarbons such as tetrachloroethylene and bromochloromethane can be used in combination.

In order to produce a good aluminum nitride green sheet, the surfactant, plasticizer and organic solvent are usually used in an amount of 0.01 to 0.01 parts by weight of the surfactant per 100 parts by weight of aluminum nitride powder. 10 to 10 parts by weight, preferably 0.02 to 3.0 parts by weight, the plasticizer 15 parts by weight or less, preferably 0.4 to 15 parts by weight, and the organic solvent 20 parts by weight.
It is selected from the range of ~ 200 parts by weight.

Furthermore, in addition to the above composition, sintering aids known to be used for sintering aluminum nitride powder, for example, alkaline earth metal oxides such as calcium oxide and strontium oxide; yttrium oxide, lanthanum oxide Or a composite oxide such as calcium aluminate may be used in a proportion of 0.1 to 10% by weight in the total amount with the aluminum nitride powder.

The above-described components are mixed to form a viscous paint-like slurry generally called a slurry. And
The sheet is formed into a sheet using a sheet forming machine such as a doctor blade. Next, the sheet-like molded product is dried by evaporating the solvent at a temperature from room temperature to the boiling point of the solvent to obtain an aluminum nitride green sheet.

The thus obtained aluminum nitride green sheet is fired by a known method to obtain an aluminum nitride sintered body.

[0020]

The aluminum nitride composition of the present invention is suitable as a raw material for producing an aluminum nitride powder compact by green sheet molding. That is, when an aluminum nitride green sheet is manufactured by sheet forming using the aluminum nitride composition of the present invention and punching with a break line is performed, adhesion of the aluminum nitride green sheet to the upper blade of the punching machine is prevented. Therefore, a green sheet blank of aluminum nitride can be manufactured continuously for a long period of time.

[0021]

EXAMPLES The present invention will be described more specifically with reference to the following Examples and Comparative Examples, but the present invention is not limited to these Examples.

In the following examples and comparative examples, various physical properties were measured by the following methods.

1) Specific surface area: determined by the BET method using N ₂ adsorption.

("Flowsorb 2300" manufactured by Shimadzu Corporation)
2) Average aggregate particle size: determined by centrifugal sedimentation. (Use HORIBA “CAPA 500”) 3) Impurity amount Cation impurity: After powder is alkali-melted, neutralized with acid,
The solution was quantified by ICP emission spectroscopy. (Using “ICPS-1000” manufactured by Shimadzu Corporation) Impurity carbon amount: The powder was burned in an oxygen stream and quantified from the amount of generated CO and CO ₂ gases. (Using "EMIA-110" manufactured by Horiba, Ltd.) Impurity oxygen content: It was determined from the amount of CO gas generated by a high-temperature pyrolysis method of powder in a graphite crucible. (Using "EMGA-2800" manufactured by Horiba, Ltd.) 4) Density of sheet compact (dg): Determined by the following formula.

[0025]

(Equation 1)

5) Density of AlN sintered body (dg): Determined by Archimedes' method. (Toyo Seiki “High-precision hydrometer D-
Example 1 A nylon ball containing an iron core was placed in a nylon pot having a content of 10 L, and then 100 parts by weight of aluminum nitride powder shown in Table 1 and polyvinyl butyral resin 10 having various butyralization degrees shown in Table 2 were used. Parts by weight, 4.0 parts by weight of yttrium oxide, 2.0 parts by weight of hexaglycerin monooleate as a surfactant, 6.0 parts by weight of dibutyl phthalate as a plasticizer, and 100 parts by weight of toluene. , Got a white plasma.

After the solvent obtained was desolvated and the viscosity was adjusted to 20,000 cps, the sheet was formed by a doctor blade method and dried at room temperature for 2 hours and at 60 ° C. for 5 hours to obtain a sheet having a width of 10 cm and a thickness of 0 cm. A sheet molded body (green sheet) having a thickness of 0.8 mm was prepared, and its apparent density was measured.

This green sheet was continuously punched with a 68 mm square mold having a 5 mm square break line,
A punched sheet was obtained. The number of times of punching until the aluminum nitride green sheet adhered to the upper blade of the punching machine was 400 or more.

This sheet was fired in air at 600 ° C. for 5 hours, then put in a boron nitride crucible, and fired in a nitrogen atmosphere at 1800 ° C. for 10 hours to obtain an aluminum nitride sintered body.

Table 2 shows the measurement results of the density of the aluminum nitride sintered body.

[0031]

[Table 1]

Comparative Example 1 An aluminum nitride green sheet was prepared in the same manner as in Example 1 except that a polyvinyl butyral resin having a butyralization degree of 75% by weight was used.
Further, punching was performed to obtain a punched sheet. It was impossible to punch two or more sheets continuously. It was fired in the same manner as in Example 1, and the density of the obtained sintered body was measured. The results are shown in Table 2.

[0033]

[Table 2]

Example 2 An aluminum nitride green sheet was prepared in the same manner as in Example 1 except that the polyvinyl butyral resin having a butyralization degree of 88% by weight was added in the amount shown in Table 3. Similarly, a punched sheet was obtained. The results are shown in Table 3.

[0035]

[Table 3]

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) C04B 35/581 C04B 35/632

Claims (1)

(57) [Claims] An aluminum nitride composition comprising 100 parts by weight of aluminum nitride powder and 4 to 30 parts by weight of a polyvinyl butyral resin having a degree of butyralization of 80% by weight or more.