JP2675149B2 - Surface treatment method for aluminum nitride powder - Google Patents

Description

TECHNICAL FIELD The present invention relates to a surface treatment method for aluminum nitride powder.

2. Related Art Problems to be solved by the prior art and the invention It is known that aluminum nitride has high thermal conductivity, and its sintered body is used as a high thermal conductive ceramic. It has also been proposed to use the powder as a filler for a resin kneading material including an IC sealing material and an adhesive.

However, aluminum nitride has a strong reactivity with water, is hydrolyzed when contacted with water, and has a property of being decomposed into hydrated alumina while generating ammonia.
Therefore, the following problem occurs.

a) When forming and sintering aluminum nitride powder to form an aluminum nitride sintered body, water cannot be used as a forming medium. Therefore, there is a problem that casting and tape molding using a water slurry cannot be used, and the molding method must be limited. In addition, since water cannot be used as a forming medium, an organic solvent has been used instead of water as a forming medium in the past, but the use of an organic solvent increases the cost and there is a risk of explosion. .

Even if water is used as the molding medium, a sintered body having a desired thermal conductivity cannot be obtained because the oxygen content in the aluminum nitride powder increases due to the reaction with water.

b) Hydrolysis of aluminum nitride is also promoted by moisture in the atmosphere. If storage conditions are poor, ammonia odor is generated during storage and handling, and the oxygen content increases. Therefore, when aluminum nitride powder is used as a filler, the quality of the filler may significantly change over time.

To solve the above problem, aluminum nitride
A method of improving the water resistance of aluminum nitride by heating at 0 to 800 ° C. to form an aluminum oxide film on the surface has been proposed, but this method also maintains the water resistance of aluminum nitride stably for a long time. Can not do.

An object of the present invention is to provide an aluminum nitride powder having stable water resistance over a long period of time.

Another object of the present invention is to provide an aluminum nitride powder having excellent water resistance, which can be appropriately used as a raw material for producing an aluminum nitride sintered body and as a filler for an IC encapsulating material or a resin kneading material.

An object of the present invention is to provide a surface treatment method for obtaining an aluminum nitride powder having excellent water resistance.

Means for Solving the Problems This time, it was found that the aluminum nitride powder obtained by adding a specific amount of an organic phosphoric acid compound to the aluminum nitride powder and then heat-treating the aluminum nitride powder has excellent water resistance. .

Therefore, the excellent water-resistant aluminum nitride powder provided by the present invention, after treating by adding 0.1 to 10 parts by weight of an organic phosphoric acid compound per 100 parts by weight of the aluminum nitride powder to the aluminum nitride powder, It is characterized by being surface-treated by heat treatment at a temperature of 150 to 800 ° C.

In order to obtain an aluminum nitride powder having excellent water resistance of the present invention, first, the aluminum nitride powder is dispersed in a solvent, and the organic phosphoric acid compound is added dropwise to the dispersion under stirring to nitride a predetermined amount of the organic phosphoric acid compound. React with aluminium. The temperature for reacting the aluminum nitride and the organic phosphoric acid compound is not particularly limited, but is usually selected in the range of room temperature to 800 ° C, preferably 40 to 60 ° C.

Moreover, the aluminum nitride powder having excellent water resistance of the present invention can be obtained by dry-mixing the aluminum nitride powder at room temperature in the coexistence of an organic phosphoric acid compound and then heat-treating at a temperature of about 150 to 800 ° C.

The aluminum nitride powder treated with the organic phosphoric acid compound is not particularly limited, and nitride produced by a method such as a direct nitriding method of heating powdered aluminum in nitrogen or an alumina reduction method of heating a mixture of alumina and carbon in nitrogen. It can be an aluminum powder. Normally, the average particle size is about 0.1 μm to about 1 mm
Aluminum nitride powder of is used.

As the organic phosphoric acid compound, an acid represented by (RO) ₂ P (O) OH or ROP (O) (OH) ₂ [wherein R is an alkyl, alkenyl or aryl group having 1 to 18 carbon atoms] Phosphate esters such as methyl acid phosphate, ethyl acid phosphate, butyl acid phosphate, 2-ethylhexyl acid phosphate, lauryl acid phosphate, palmityl acid phosphate, stearyl acid phosphate, oleyl acid phosphate, phenyl acid phosphate, nonylphenyl acid phosphate, etc. Mono- or dialkyl, alkenyl or aryl esters of pyrophosphoric acid or polyphosphoric acid, eg di-2
-Ethylhexylpyrophosphate, etc .; Phosphonic acids and their esters such as methylenephosphonic acid, aminomethylenephosphonic acid, t-butylnitrilobismethylenephosphonic acid, n-butylnitrilobismethylenephosphonic acid, nitrilotrimethylenephosphonic acid, ethylenediaminetetramethylenephosphonic acid Acid, 1-hydroxyethylidene-1,1-diphosphonic acid, butylhydrogen phosphite, 2-ethylhexyl hydrogen phosphite, lauryl hydrogen phosphite, dibutyl hydroxymethylphosphonate, and the like; and mixtures thereof.

The use of alkali metal salts as organophosphate compounds should be avoided. This is because the metal salt is insoluble in the solvent and there is a problem that the metal remains.

The amount of the organophosphate compound is important, and if the amount is less than 0.1 parts by weight relative to 100 parts by weight of the aluminum nitride powder, the desired effect cannot be obtained, while if it exceeds 10 parts by weight, the oxygen content in the aluminum nitride powder increases. Is not preferred.
Preferably, the organophosphate compound is an aluminum nitride powder
Use 0.2 to 3 parts by weight per 100 parts by weight.

As a solvent for dispersing the aluminum nitride powder, a low boiling point solvent is preferable, and a lower alcohol having 1 to 4 carbon atoms such as ethanol, isopropyl alcohol and butanol is used, or a middle or lower alkane miscible with the lower alcohol ( For example, n-hexane, n-octane or n
-Decane) or acetone may be used in combination. It is not necessary to make the solvent dry, but inclusion of water in the solvent should be avoided.

The above-mentioned solvent acts as a solvent for the aluminum nitride powder as well as a solvent for the organic phosphoric acid compound. Therefore, when the organic phosphoric acid compound is added dropwise, it is preferable to add the organic phosphoric acid compound in a state of being dissolved in the same solvent in which the aluminum nitride powder is dispersed.

In order to obtain an aluminum nitride powder having excellent water resistance, which is the object of the present invention, it is necessary to add a specific amount of the organic phosphoric acid compound to the aluminum nitride powder as described above, and then further heat-treat. By this heat treatment, the organic phosphoric acid compound is thermally decomposed, and a hydrophilic film is formed on the surface of the aluminum nitride powder. The heat treatment temperature is about 150 to 800 ° C, preferably about 350 to 600 ° C. If the heat treatment temperature is lower than 150 ° C, thermal decomposition of the organic phosphoric acid compound is insufficient, while if it exceeds 800 ° C, the aluminum nitride powder is likely to be oxidized or aggregated, which is not preferable. The heat treatment atmosphere is usually air, vacuum or an inert gas atmosphere. The heat treatment time is selected from the range of about 30 minutes to 24 hours depending on the type of organic phosphoric acid compound and the heat treatment method.

Examples The following are non-limiting examples of the present invention.

Example 1 After introducing 250 ml of isopropyl alcohol / n-hexane (1: 1) into a container having a volume of 1, 100 g of aluminum nitride powder (average particle size 4.3 μm, oxygen content 0.66%) was added and stirred to disperse aluminum nitride. A liquid was created. The dispersion was warmed to about 60 ° C. with agitation by shaking the container on a hot water bath. Then, a solution prepared by dissolving 3 g of butyl acid phosphate in 50 ml of isopropyl alcohol / n-hexane (1: 1) was added dropwise to cause a gentle reaction. During the reaction, a dry inert gas was kept flowing through the vessel at a small flow rate so that water did not enter the system.

After sufficient reaction, heat treatment was performed at 500 ° C. for 5 hours in the atmosphere.

A surface-treated aluminum nitride powder was obtained in the same manner as above except that other organic phosphoric acid compound or various surface-treating agents soluble in isopropyl alcohol or n-hexane were used instead of butyl acid phosphate. However, when a surface treating agent other than the organic phosphoric acid compound was used, heat treatment was not performed.

The water resistance of the aluminum nitride powder thus surface-treated was tested as follows.

4.1 g of aluminum nitride powder heated to 80 ° C in pure water (pH
(5.6) Add to 54g, stir and mix to make aluminum nitride dispersion, and adjust the pH (80
° C) changes were examined using pH test paper.

 The results are shown in the table below.

As is clear from the table, in the case of aluminum nitride powder which has been treated with an organic phosphoric acid compound and then heat-treated, there is no or almost no change in pH even at least 2 hours after the dispersion is prepared. In the case of aluminum nitride powder treated with a surface treatment material other than
After 10 to 30 minutes, the pH reached 9.6 or higher, and the smell of ammonia was also detected.

In addition, when treated with butyl acid phosphate but not subjected to heat treatment for connection, the pH already reached 9.6 or more 30 minutes after the dispersion was prepared, and β (3,4-epoxycyclohexyl) ethyl was used. Even after the treatment with trimethoxysilane and the heat treatment in the air at 500 ° C. for 5 hours in the same manner as in the present invention, the pH reached 9.6 or more one hour after the aqueous solution was prepared. From this, it is clear that the combination of the treatment with the organic phosphoric acid compound and the heat treatment is very important in the present invention.

Example 2 After introducing 200 ml of isopropyl alcohol into an evaporator flask having a volume of 1, 100 g of aluminum nitride powder (average particle size: 1.1 μm, oxygen content: 1.39%) was added and stirred to prepare an aluminum nitride dispersion liquid. Next, 0.5 g of butyl acid phosphate is added to 50 ml of isopropyl alcohol.
What was melt | dissolved in was added, and the dispersion liquid was made to react slowly, heating at about 60 degreeC, stirring a rotating water bath.

After a sufficient reaction, it was confirmed that the pH had reached 4.5 or more with a pH test paper, and isopropyl alcohol was volatilized by a vacuum pump. After fully volatilized, 450 ℃ in air
And heat treated for 1 hour.

When the water resistance of the aluminum nitride powder thus obtained was tested according to the method of Example 1, the pH reached 9.6 or higher 12 hours after the dispersion was prepared, and in the case of the untreated aluminum nitride powder it was 1.5 hours. Later the pH already reached above 9.6.

In order to test the water resistance of the aluminum nitride obtained as described above by another method, the change in oxygen content immediately after heat treatment of aluminum nitride powder and after being immersed in water at 40 ° C for 5 hours was used. HORIBA, Ltd. Ceramic Oxygen Nitrogen Analyzer
It was measured using EMGA-2800. The oxygen content of the aluminum nitride powder immediately after heating was 1.77%, and the oxygen content after being immersed in water at 40 ° C. for 5 hours was 1.74%, and the aluminum nitride powder surface-treated with butyl acid phosphate was heat-treated. No change in oxygen content was observed even when immersed in water at 40 ° C. On the other hand, when untreated aluminum nitride powder was immersed in water under the same conditions, the oxygen content was 20.4.
Increased to%.

5% yttrium oxide as a sintering aid, a water-soluble acrylic binder (manufactured by Chuo Rika Kogyo KK, ESZ-1311,
Solid content 42%) as solid content 3% and peptizer 1% as ammonium salt of acrylic oligomer (Aron A-61
14) and an appropriate amount of water were mixed for 1 hour and a half in a ball mill, and the mixture was vacuum degassed to prepare a water slurry having a solid content of 70%. The obtained slurry was formed into a sheet using a doctor blade method and dried for 48 hours to obtain an aluminum nitride green sheet having a thickness of 0.8 mm. The plate obtained by degreasing the obtained sheet and sintering at 1850 ° C. for 3 hours under normal pressure was a laser flash method thermal constant measuring device (manufactured by Rigaku Denki Co., Ltd., LF / TCM-
8510), the high thermal conductivity (15
4 W / mk). This value is the thermal conductivity (147W / mk) of a plate obtained by sintering untreated aluminum nitride powder under the same conditions.
It was confirmed that the effect on the thermal conductivity of the treated film was small.

In order to examine the P content of the sintered plate, a small amount of the sintered plate was heated and divided in concentrated hydrochloric acid, and the eluate was mixed with ICP (Inductive
Coupled plasma (high-frequency inductive coupling) emission analysis revealed that there was almost no P content (50 ppm or less).

Example 3 3.75 kg (85% by volume) of 10 mmφ high-purity alumina balls were introduced into an alumina pot having a capacity of 2, then 390 g of aluminum nitride powder (average particle size 4.3 μm, oxygen content 0.66%) was added, and then butyl acid phosphate. 2g was added and crushed for 5 hours with a batch type vibration mill manufactured by Chuo Kakoki Co., Ltd., and the aluminum nitride powder finely crushed was crushed in the air.
It heat-processed at 450 degreeC for 1 hour.

The aluminum nitride powder thus obtained (average particle size 1.
Water resistance of 2 μm, oxygen content 1.5%) was tested as follows.

Pure water obtained by heating 4.1 g of aluminum nitride powder to 40 ° C (pH
≈5.6) 54 g, and mixed with stirring to prepare an aluminum nitride dispersion liquid, and pH was changed with time (40 ° C.) as in Example 1.
The change was investigated using pH test paper. As a result, the pH reached 9.6 or higher, and 12 hours passed before the smell of ammonia was detected. On the other hand, in the case of aluminum nitride powder that has not been heat-treated, the pH reaches 9.6 or higher after 1.5 hours,
Ammonia odor was also detected.

Effect of the Invention Since the aluminum nitride powder heat-treated after treatment with the organophosphate compound of the present invention has excellent water resistance,
There is no danger of generating ammonia or increasing oxygen content during storage and handling. Further, since the ammonium nitride powder of the present invention hardly agglomerates, it can be suitably used as an IC sealing material or a filler for resin kneading.

Since the aluminum nitride powder of the present invention has excellent water resistance, it is possible to use water as a molding medium when producing a sintered body, and in addition, a hydrophilic film is formed on the surface. Because it is also excellent in water dispersibility,
When manufacturing an aluminum nitride sintered body, various molding methods can be used. Further, even if water is used as the molding medium, the oxygen content of the raw material aluminum nitride powder does not increase, so that a sintered body having a desired thermal conductivity can be manufactured. Therefore, the aluminum nitride powder of the present invention is suitable as a raw material for producing an aluminum nitride sintered body.

Furthermore, the aluminum nitride powder of the present invention does not require a special production process, and can be obtained at low cost.

Claims (1)

(57) [Claims] 1. A method in which 0.1 to 10 parts by weight of organic phosphorus oxide is added to aluminum nitride powder per 100 parts by weight of aluminum nitride powder for treatment, and then heat treatment is performed at a temperature of about 150 to 800 ° C. A method for surface treatment of aluminum nitride powder.