JPH06107465A - Aluminum nitride composition - Google Patents

Abstract

PURPOSE:To make it possible to continuously blank a sheetlike molded body by adding specified polyvinyl butyral resin to aluminum nitride powder. CONSTITUTION:Aluminum nitride powder having 1:1 molar ratio of aluminum: nitrogen and <=5mum average particle diameter and contg. <=1.5wt.% oxygen as an impurity and <=0.3wt.% cationic impurities is prepd. and 100 pts.wt. of this powder is blended with 4-30 pts.wt. polyvinyl butyral resin having >=80wt.% degree of butyral formation and 3,000-1,000,000 mol.wt., 0.01-10 pts.wt. one or more kinds of surfactants having 4.5-18 HLB such as carboxylated trioxyethylene tridecyl ether, <=15 pts.wt. plasticizer such as polyethylene glycol, 20-200 pts.wt. one or more kinds of org. solvents such as acetone and 0.1-10wt.% sintering aid such as calcium oxide basing on the total amt. of the aluminum nitride powder and the sintering aid. The resulting blend is molded into a sheet shape.

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 molded product containing aluminum nitride powder as a main component.

[0002]

2. Description of the Related Art Sintered aluminum nitride has a high thermal conductivity and is in the spotlight as an electronic material.
As a method of obtaining an aluminum nitride sintered body, there are a method of forming aluminum nitride powder by dry pressing and firing, a method of wet forming aluminum nitride powder to obtain a green sheet, and firing this. In the latter case, a green sheet is generally produced by mixing aluminum nitride powder with a binder, a deflocculant, an organic solvent and the like and forming the sheet by the Togter blade method or the like. Here, the binder is used for imparting strength and flexibility to the green sheet, improving processability and facilitating handling.

The green sheet is punched and cut into a predetermined shape. When the size of the cut green sheet becomes too small, it can be cut relatively large and easily cut into a predetermined size later. In this way, a break line (groove) is formed on the green sheet, and after firing, cutting is performed along the break line.

[0004]

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

[0005]

DISCLOSURE OF THE INVENTION The inventors of the present invention obtain a green sheet which does not easily adhere to the blade of a punching machine in order to obtain a green sheet which can be continuously punched with a break line. For that purpose, I have continued my earnest research. As a result, they have found that a composition of a polyvinyl butyral resin having a specific degree of butyralization and an aluminum nitride powder is a raw material for a green sheet that has achieved the above object, and has proposed the present invention.

That is, the present invention relates to 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 butyralization degree 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 cation impurities are small. That is, when AlN has an aluminum nitride composition, the oxygen content as an impurity is 1.5
An aluminum nitride powder having a weight percentage of less than or equal to 0.3 and a cationic impurity amount of less than or equal to 0.3 is preferable. Furthermore, an aluminum nitride powder having an oxygen content of 0.4 to 1.3% by weight and a cationic 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 with the Al—O bond, but this bonded Al is not regarded as a cation impurity. Therefore, Al-N, Al
Metallic aluminum without a -O bond is a cationic impurity.

The particles of the aluminum nitride powder used in the present invention preferably have a small particle size. For example, the average particle diameter (meaning the average particle diameter of the agglomerated particles measured by a centrifugal particle size distribution measuring device such as CAPA500 manufactured by Horiba Ltd.) is preferably 5 μm or less, and 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 butyralization degree of 80% by weight or more. When the butyralization degree of the polyvinyl butyral resin is outside the above range, it is not preferable because the obtained green sheet cannot be continuously punched. The butyralization degree of polyvinyl butyral resin is currently up to 88% by weight. In the present invention, the degree of butyral is JIS
It is a value calculated from the following formulas by calculating the vinyl acetate component and the vinyl alcohol component by K6728.

Degree of butyralization = 100- {vinyl acetate component (% by weight) + vinyl alcohol component (% by weight)} The blending amount of the polyvinyl butyral resin having a degree of butyralization of 80% by weight or more to the aluminum nitride powder is nitriding. It should be 4 to 30 parts by weight, preferably 5 to 15 parts by weight, based on 100 parts by weight of the aluminum powder. When 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 when punching the green sheet,
When the amount is more than the above range, the physical properties of the aluminum nitride sintered body obtained from the aluminum nitride composition are deteriorated, 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 preferably 50,000, preferably 5,000 to 300,000 because the green sheet is flexible and rich in toughness and easy to handle during processing.

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 surface active agent, any known surface active agent can be used without any limitation, but particularly, a surface active agent having a hydrophilic-lipophilic balance (hereinafter abbreviated as HLB) of 4.5 to 18, more preferably 6 is used. Those of 0.0 to 10.0 are preferably adopted because the molding density of the aluminum nitride powder compact increases. The HLB in the present invention is a value calculated by the Davis equation.

Specific examples of the surfactants that can be preferably 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 used to process a specific molded product, it is preferable to use a plasticizer for the purpose of imparting flexibility to the processed product. As the plasticizer, those known to be used for the above-mentioned purpose in molding a general ceramic powder can be used without particular limitation. Specific examples of typical ones that are particularly preferably used include polyethylene glycol and its derivatives; phthalic acid esters such as dimethyl phthalate, dibutyl phthalate, butylbenzyl phthalate and dioctyl phthalate; stearic acid such as butyl stearate. Esters; tricresole phosphate; tri-N-butyl phosphate; glycerin and the like.

Further, as the organic solvent, for example, 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; or trichloroethylene,
It is possible to use one kind or a mixture of two or more kinds of halogenated hydrocarbons such as tetrachloroethylene and bromochloromethane.

The amount of these surfactants, plasticizers and organic solvents used is usually 0.01 to 100 parts by weight of aluminum nitride powder in order to produce a good aluminum nitride green sheet. -10 parts by weight, preferably 0.02-3.0 parts by weight, plasticizer 15 parts by weight or less, preferably 0.4-15 parts by weight, organic solvent 20
˜200 parts by weight.

In addition to the above composition, a sintering aid known to be used for sintering aluminum nitride powder, for example, an alkaline earth metal oxide such as calcium oxide or strontium oxide; yttrium oxide or lanthanum oxide. Rare earth oxides such as; complex oxides such as calcium aluminate may be used in the range of 0.1 to 10% by weight in the total amount with the aluminum nitride powder.

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

The aluminum nitride green sheet thus obtained is fired by a known method to form 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 molding using the aluminum nitride composition of the present invention and punching with a break line is performed, the aluminum nitride green sheet is prevented from adhering to the upper blade of the punching machine. Therefore, the green sheet punched body of aluminum nitride can be continuously manufactured for a long period of time.

[0021]

EXAMPLES In order to describe the present invention more specifically, examples and comparative examples are given below, but the present invention is not limited to these examples.

Various physical properties in the following examples and comparative examples were measured by the following methods.

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

("Flowsorb 2300" manufactured by Shimadzu Corporation)
2) Average aggregate particle size: determined by a centrifugal sedimentation method. (Use "CAPA 500" manufactured by HORIBA, Ltd.) 3) Impurity amount Cation impurities: After melting the powder with alkali, neutralize with acid,
The solution was quantified by ICP emission spectroscopy. (“ICPS-1000” manufactured by Shimadzu Corporation is used) Impurity carbon amount: The powder was burned in an oxygen stream, and quantified from the generated CO and CO ₂ gas amounts. (Using "EMIA-110" manufactured by Horiba Ltd.) Impurity oxygen amount: determined from the amount of CO gas generated by the high temperature thermal decomposition method of the powder in the graphite crucible. (Using "EMGA-2800" manufactured by Horiba Ltd.) 4) Sheet molded product density (dg): Calculated by the following formula.

[0025]

[Equation 1]

5) AlN sintered body density (dg): Determined by the Archimedes method. ("Toyo Seiki's high-precision specific gravity meter D-
H ”) Example 1 Nylon balls with an iron core were placed in a nylon pot having an internal capacity of 10 L, 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, and sufficiently mixed in a ball mill. , Got white mud.

The mud thus obtained was desolvated, the viscosity was adjusted to 20000 cps, and the sheet was formed by the doctor blade method, and dried at room temperature for 2 hours and at 60 ° C. for 5 hours to obtain a width of 10 cm and a thickness of 0. A sheet molded body (green sheet) having a size of 0.8 mm was produced and the apparent density was measured.

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

This sheet was fired in air at 600 ° C. for 5 hours, then placed 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 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 in succession. Firing was performed 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 a polyvinyl butyral resin having a butyralization degree of 88% by weight was added in the amount shown in Table 3, and further, as in Example 1. A punched sheet was obtained in the same manner. The results are shown in Table 3.

[0035]

[Table 3]

Claims (1)

[Claims] 1. An aluminum nitride composition comprising 100 parts by weight of aluminum nitride powder and 4 to 30 parts by weight of polyvinyl butyral resin having a butyralization degree of 80% by weight or more.