JPH092879A - Aluminum nitride granules and method for producing the same - Google Patents

Abstract

(57) [Abstract] [PROBLEMS] To provide aluminum nitride granules having a uniform density, suitable for producing a press-formed product capable of obtaining a sintered product having small deformation and high dimensional accuracy. [Structure] A binder is added in an amount of 0.1 to 30 parts by weight, preferably 2 to 15 parts by weight, based on 100 parts by weight of aluminum nitride powder, and has a bulk specific gravity of 0.5 to 1.5 g / cm ³ .
Preferably 0.8-1.3 g / cm ³ , average particle size 20
˜500 μm, preferably 25 to 300 μm, puncture strength of 0.5 to 5 g, preferably 0.7 to 4 g, and fluidity of 5 measured according to JIS Z-2502.
The aluminum nitride granules are characterized in that they are 0 s / 50 g or less, preferably 25 to 45 s / 50 g or less.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to novel aluminum nitride granules. More specifically, the present invention relates to aluminum nitride granules suitable for manufacturing a press-molded body which has a uniform density, is small in deformation, and has high dimensional accuracy, and a manufacturing method thereof.

[0002]

2. Description of the Related Art Due to the recent increase in the amount of heat generated by IC chips accompanying the dramatic improvement in the degree of integration of LSIs, the conventionally used alumina has insufficient thermal characteristics and is reaching the limit of heat dissipation.

On the other hand, aluminum nitride powder has a high thermal conductivity and a high insulating property, and is in the spotlight as a raw material of an aluminum nitride sintered body which is extremely useful as an electronic material such as a package material.

[0004] Conventionally, as one method of obtaining an aluminum nitride sintered body, after granulating aluminum nitride powder into granules, the aluminum nitride granules are packed in a mold and pressed by a press molding machine, a so-called dry press. There is known a method of forming a press-molded product by using the above method and firing it. Further, in the above method, a spray dryer method is generally adopted for producing aluminum nitride granules.

[0005]

However, when press molding is performed using aluminum nitride granules obtained by the conventionally employed method, the obtained aluminum nitride sintered body is largely deformed, and high dimensional accuracy is obtained. It has the problem of being difficult to realize.

[0006]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies to solve the above problems. As a result, it was found that the fluidity of the aluminum nitride granules at the time of press molding affects the uniformity of the obtained press-molded product, which in turn causes the deformation of the obtained molded product.

As a result of further research, aluminum nitride granules having various physical properties such as bulk specific gravity, average particle size, fracture strength and the like, and the fluidity of which is adjusted to a specific value or more, have the above-mentioned object. It has been found that the above can be achieved, and the present invention has been proposed.

That is, the present invention relates to aluminum nitride powder 1
0.1 to 30 parts by weight of a binder is added to 100 parts by weight, the bulk specific gravity is 0.5 to 1.5 g / cm ³ , the average particle size is 20 to 500 μm, and the breaking strength is 0.5 ~
The aluminum nitride granules are characterized in that they are 5 g and have a fluidity of 50 s / 50 g or less.

As the aluminum nitride powder constituting the aluminum nitride granules of the present invention, known aluminum nitride powder can be used without any limitation. In particular, 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, an aluminum nitride powder having an oxygen content of 1.5% by weight or less and a cationic impurity of 0.3% by weight or less is preferable. Furthermore, the oxygen content is 0.4 to 1.3% by weight, and the cation impurities are less than 0.1%.
Aluminum nitride powder of 2% by weight or less is more preferable.

In the above description of impurities, aluminum nitride 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 Al-
The N bond is replaced with an Al-O bond, but this bond A
l was not regarded as a cation impurity, and metallic aluminum having no Al—N or Al—O bond was treated as a cation impurity.

The particles of the aluminum nitride powder used in the present invention are preferably particles having a small particle size. For example, the average particle size measured by a centrifugal particle size distribution measuring device is 5 μm or less, and further 0.5 to 3 μm.
It is preferred that

As the binder constituting the aluminum nitride granules of the present invention, those generally used for molding ceramic powder can be used without any limitation. For example, polyvinyl butyral, polymethylmethacrylate, polyethylmethacrylate, poly-2-ethylhexylmethacrylate,
Oxygen-containing organic compounds such as polybutyl methacrylate, polyacrylate, cellulose acetate butyrate, nitrocellulose, methylcellulose, hydroxymethylcellulose, polyvinyl alcohol, polyoxyethylene oxide and polypropylene oxide. Polymers; hydrocarbon type synthetic resins such as petroleum resin, polyethylene, polypropylene and polystyrene; polyvinyl chloride; organic polymers such as wax and emulsions thereof are used alone or in admixture of two or more. The molecular weight of the organic polymer used as the binder is not particularly limited, but is generally 3000.
˜1,000,000, preferably 5,000 to 30,000
It is preferable to use those of 0 because the density of the aluminum nitride powder compact obtained by press molding increases.

The mixing ratio of the aluminum nitride powder and the binder is 0.1 to 30 parts by weight of the binder with respect to 100 parts by weight of aluminum nitride. When the amount of the binder is less than the above range, a good press-molded product cannot be molded due to insufficient strength, and when the amount is large, the physical properties of the aluminum nitride sintered product obtained by press-molding and firing are high. It is not preferable because it decreases.

Within the above range, in order to obtain granules having particularly good fluidity, the mixing ratio of the binder is more preferably 2 to 15 parts by weight.

The bulk specific gravity of the aluminum nitride granules of the present invention is in the range of 0.5 to 1.5 g / cm ³ . Bulk specific gravity is 0.
When it is less than 5 g / cm ³ , many voids remain inside the sintered body and the density of the sintered body becomes low, so that a good sintered body cannot be obtained. On the other hand, it is difficult to produce aluminum nitride granules having a bulk specific gravity of more than 1.5 g / cm ³ . In order to suppress the generation of voids in the obtained aluminum nitride powder compact, the bulk specific gravity is preferably in the range of 0.8 to 1.3 g / cm ³ .

The average particle size of the aluminum nitride granules of the present invention is in the range of 20 to 500 μm. Average particle size is 2
If it is less than 0 μm, it becomes bulky due to electrostatic repulsion, etc., and as a result, sufficient bulk specific gravity cannot be obtained, resulting in the inconvenience as described above. On the other hand, when it exceeds 500 μm, the voids between the individual granules become large, and the internal voids remain after sintering, so that a good sintered body cannot be obtained.

In order to obtain a high-density aluminum nitride powder compact, the average particle diameter of the aluminum nitride granules is 25 to
The range of 300 μm is particularly preferable. Further, since coarse particles and fine particles adversely affect the density of the obtained aluminum nitride powder compact, the particle diameter is 10 μm.
Aluminum nitride granules below and above 800 μm are
It is preferably 5% by weight or less.

The fracture strength of the aluminum nitride granules of the present invention should be in the range of 0.5-5 g. If the breaking strength is less than 0.5 g, the aluminum nitride granules will be broken during handling such as transportation, or the granules will be broken early during press molding, which prevents close packing due to movement of the granules. However, this is not preferable because the density of the press-formed product does not increase. Further, when the breaking strength exceeds 5 g, many voids due to the grain boundaries of the aluminum nitride granules remain when the aluminum nitride powder compact is manufactured by press molding, which is not preferable. The breaking strength of the above-mentioned aluminum nitride granules is particularly preferably in the range of 0.7 to 4 g in consideration of the improvement in the density of the press-formed product.

The fluidity of the aluminum nitride granules of the present invention is measured according to JIS Z-2502 and is 50 s.
The greatest feature is that it is in the range of (sec) / 50 g or less. That is, since aluminum nitride granules having a fluidity of more than 50 s / 50 g are not uniformly packed in the mold during press molding and the density in the aluminum nitride powder compact is not uniform, firing after firing is not performed. Due to the large deformation of the bonded body, it is not possible to obtain an aluminum nitride sintered body having high dimensional accuracy.

The fluidity of the aluminum nitride granules may be 50 s / 50 g or less as described above, but in order to obtain an aluminum nitride powder compact having a uniform density,
The range of 25 to 45 s / 50 g is more preferable. By the way,
According to the manufacturing method of the present invention described later, it is possible to manufacture up to about 20 s / 50 g.

The shape of the aluminum nitride granules of the present invention is not particularly limited and may be any shape, but it is generally spherical or close to that due to the production method. In the present invention, the high-density aluminum nitride granules with few voids are preferably spherical, and for example, those having a sphericity of 0.93 or more determined from the ratio of the short diameter to the long diameter are preferably used. Aluminum nitride granules of the present invention,
Although it may be produced by any method, the following method is preferably adopted. That is, it is a method of producing aluminum nitride granules by granulating a mixture of aluminum nitride powder, a binder and an organic solvent, and then allowing the granules to stay in a turbulent gas.

Organic solvents preferably used in the production of the aluminum nitride granules of the present invention include, for example, ketones such as acetone, methyl ethyl ketone and methyl isobutyl ketone; alcohols such as ethanol, propanol and butanol. Examples thereof include aromatic hydrocarbons such as benzene, toluene and xylene; and halogenated hydrocarbons such as trichloroethylene, tetrachloroethylene and bromochloromethane, or a mixture of two or more thereof. The amount of the organic solvent is selected from the range of 20 to 200 parts by weight and used.

In addition to the above composition, a surfactant is generally employed to enhance the dispersibility of mud. The surfactant is
Known ones are used without any limitation, and particularly, the hydrophilic / lipophilic balance (hereinafter abbreviated as HLB) is 4.5 to 1.
No. 8 and more preferably 6.0 to 10.0 are preferably used 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 surfactant that can be preferably used in the present invention include carboxylated trioxyethylene tridecyl ether, dixerine monooleate,
Diglycerin monostearate, carboxylated heptaoxyethylene tridecyl ether, tetraglycerin monooleate, hexaglycerin monooleate, polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monooleate Etc. The surfactants in the present invention may be used as a mixture of two or more, and the HLB at that time is the H of each surfactant.
It can be calculated by the arithmetic mean of LB.

In order to produce good aluminum nitride granules, these surfactants are usually used in an amount of 0.01 to 10 parts by weight, preferably 0.02 to 3.0 parts by weight, based on 100 parts by weight of aluminum nitride. It is a department. The surfactant is 0.
When the amount is less than 01 parts by weight, the dispersion of mud is insufficient and the effect of the present invention is not achieved. When the amount is more than 10 parts by weight, intergranular blocking may occur, which is not preferable.

Further, in addition to the above composition, known sintering aids used for sintering aluminum nitride powder, for example,
Alkaline earth metal oxides such as calcium oxide and strontium oxide; rare earth oxides such as yttrium oxide and lanthanum oxide; complex oxides such as calcium aluminate in the total amount with the aluminum nitride powder in a ratio of 0.1.
You may use it in the range of 10 to 10 parts by weight.

The above components are mixed and made into a viscous slurry generally called mud, and then granulated by a known granulation method such as a spray dryer method.

The granulated aluminum nitride granules are then fluidized by allowing the granules to stay in a turbulent gas so as to have a fluidity within the range specified in the present invention.

The gas used for this fluidization is preferably a gas which does not substantially react with the additives such as aluminum nitride powder and a binder, and examples thereof include air, oxygen and nitrogen. The wind speed of the supplied gas may be any wind speed required for fluidizing the granules. The wind speed required for fluidizing the granules is, for example, the equation of fluidization start speed described in “Chemical Engineering Handbook 4th Edition”, edited by Chemical Engineering Society, page 176, and 1056
It is arbitrarily selected from the range of values calculated by the terminal velocity formula described on the page. The residence time of the granules is preferably selected from the range of 1 minute to 36 hours. Any temperature may be adopted as the temperature of the supplied gas, but in order to obtain aluminum nitride granules having an appropriate breaking strength, it is preferable to select from a range of 0 to 250 ° C.

The bulk specific gravity, which is one of the constituent requirements of the aluminum nitride granules of the present invention, is
It can be adjusted depending on the mixing conditions and the amount of solvent used during mixing.

The average particle size, which is one of the constituent requirements of the aluminum nitride granules of the present invention, can be adjusted mainly by the operating conditions of the spray dryer in the above production method.

Further, the breaking strength, which is one of the constituent requirements of the aluminum nitride granules of the present invention, can be adjusted mainly by the kind and amount of the binder in the above-mentioned production method. Further, after granulation, the breaking strength is also increased by heating to 50 to 250 ° C., for example, so that it is possible to adjust the above range by such means. The heating may be performed simultaneously in the fluidizing process.

The aluminum nitride granules thus obtained can be dry press-molded by known methods and conditions, and the obtained aluminum nitride powder compact is degreased and fired by a known method to obtain a sintered body. It
The above degreasing is generally performed in an atmosphere of air or nitrogen, and the degreasing temperature is 30 depending on the type of binder and the atmosphere.
It is arbitrarily selected from the range of 0 to 1000 ° C. The degreased aluminum nitride powder compact is fired in a non-oxidizing atmosphere at any temperature in the range of 1700 to 1950 ° C.

In this way, it is possible to obtain an aluminum nitride sintered body having a small deformation and high dimensional accuracy.

[0035]

The aluminum nitride granules of the present invention are suitable as a raw material for producing aluminum nitride powder compacts by dry press molding. That is, when an aluminum nitride powder compact is manufactured by dry press molding using the aluminum nitride granules of the present invention, an aluminum nitride powder compact having a uniform density can be obtained. Since this aluminum nitride powder compact has a small deformation at the time of sintering that occurs due to uneven density, it is possible to obtain an aluminum nitride sintered compact having high dimensional accuracy.

Therefore, the aluminum nitride sintered body obtained by using the aluminum nitride granules of the present invention is an industrially extremely useful material for substrates such as electronic materials with extremely high precision and products with complicated shapes. Become.

[0037]

EXAMPLES In order to explain the present invention more specifically, the following examples and comparative examples are given, 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) Bulk Density "A / B / D powder characteristic measuring instrument" manufactured by Tsutsui Rikagaku Kikai Co., Ltd.
Was used to measure the bulk bulk density.

2) Density of pressed compact The raw density was determined from the size and weight of the pressed compact, and the density of the pressed compact of only AlN powder was calculated from this value.

[0041]

[Equation 1]

3) Fracture strength Three granules with an average particle size of ± 5 μm or less are placed on the vertices of an equilateral triangle with a side of 5 mm, and a load is gently applied from above to break the granules by one or more. The breaking strength was used. The measurement was repeated 10 times, and an 8-point average value excluding the lowest value and the highest value was used.

4) Average particle size The average particle size was calculated from the 50% value of the cumulative distribution of the particle size distribution described in "Chemical Engineering Handbook, 4th edition," edited by the Chemical Engineering Society, page 973.

5) Fluidity In accordance with JIS Z-2502, fluidity was measured using a product manufactured by Kuramochi Kagaku Kikai Seisakusho. The sample before the measurement was dried at 60 ± 5 ° C. for 3 hours. Flow rate is JIS
It was determined by Z-8401.

6) Density of sintered body The density was determined by the Archimedes method using "High Precision Densitometer DH" manufactured by Toyo Seiki Co., Ltd.

7) Shrinkage of Sintered Body The dimensions before and after sintering were measured, and the shrinkage was calculated from the average value of the shrinkage on four sides. The shrinkage rate of each side was calculated by the following formula.

[0047]

[Equation 2]

8) Deformation Degree of Sintered Body The degree of shrinkage of the sintered body on the four sides was calculated from the difference between the maximum value and the minimum value.

Example 1 A nylon pot having an inner volume of 2 l was filled with an iron core in a nylon pot.
Aluminum nitride powder 1 shown in Table 1
00 parts by weight (average particle size is CAPA500 manufactured by Horiba Ltd.
4 parts by weight of yttrium oxide, 1 part by weight of hexaglycerin monooleate, 5 parts by weight of butyl methacrylate, and 100 parts by weight of a toluene solvent were added, and the mixture was thoroughly mixed with a ball mill and then white. Got the mud.

[0050]

[Table 1]

The mud thus obtained was granulated by a spray dryer method and then fluidized at room temperature for 2 hours to prepare aluminum nitride granules. The bulk specific gravity, particle size, breaking strength, fluidity and sphericity of the obtained granules were measured.

Using this granule, a corner of 3 at 1.0 t / cm ²
A press-molded body having a thickness of 0 mm and a thickness of 1 mm was produced and the density of the press-molded body was measured. Then, it was fired in air at 600 ° C. for 5 hours, then placed in a carbon crucible having an inner surface coated with boron nitride, and fired in a nitrogen atmosphere at 1800 ° C. for 10 hours to obtain a sintered body. The density, shrinkage and deformation of the sintered body were measured, and the results are shown in Table 2.

Comparative Example 1 Aluminum nitride granules were produced in the same manner as in Example 1 except that the fluidizing treatment was not carried out, and further, a pressed body and a sintered body were obtained. Table 2 shows these properties.
It was also described in.

[0054]

[Table 2]

Example 2 Aluminum nitride granules were produced in the same manner as in Example 1 except that butyl methacrylate was added in the amount shown in Table 3, and press-formed products and sintered products were prepared in the same manner as in Example 1. Got The results are shown in Table 3.

[0056]

[Table 3]

Example 3 Various aluminum nitride granules were produced by changing the spray dryer and the flow treatment conditions. Further, a press molded body and a sintered body were obtained in the same manner as in Example 1, and the properties are shown in Table 4.

[0058]

[Table 4]

Claims (2)

[Claims] 1. A binder is mixed in an amount of 0.1 to 30 parts by weight with respect to 100 parts by weight of aluminum nitride powder, the bulk specific gravity is 0.5 to 1.5 g / cm ³ , and the average particle size is 20 to. Fifty
0 μm and breaking strength of 0.5 to 5 g, and JI
The fluidity measured according to S Z-2502 is 50 s / 5.
Aluminum nitride granules characterized by being 0 g or less. 2. The method for producing aluminum nitride granules according to claim 1, wherein after granulating a mixture of aluminum nitride powder, a binder and an organic solvent, the granules are retained in a turbulent gas.