JP3237965B2 - Method for producing aluminum nitride powder - 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 powder.
The present invention relates to a technique useful for applying to a raw material for sintering an aluminum nitride sintered body.

[0002]

2. Description of the Related Art Aluminum nitride (AlN) is a high-temperature material having high strength and excellent heat resistance and corrosion resistance, and also has excellent properties in thermal conductivity and electrical insulation. Therefore, in recent years, it has attracted attention as a substrate material used for electronic devices, particularly for integrated circuits and the like.

[0003] Since aluminum nitride is difficult to sinter, it must be fired in a temperature environment of 1800 ° C or more or in an ultra-high pressure environment to obtain a dense sintered body. Reduction of body manufacturing cost and IC
To perform simultaneous firing of aluminum nitride and metal at the time of manufacturing a substrate or a package, a lower temperature (1800
(° C. or lower). In general, sinterability mainly depends on the particle size of the raw material powder for sintering, so to improve sinterability, increase the grain growth rate during sintering, and prevent the generation of structural defects in the sintered body It is a condition that the powders have a fine particle size on the order of submicrons and have a uniform particle size.

On the other hand, aluminum nitride is theoretically 300 W
/ M · K or higher, but at present, its sintered body is at least 150W
/ M · K only. this is,
It is considered that oxygen or metal impurities form a solid solution in the aluminum nitride sintered body, which causes phonon scattering. In addition, the presence of these impurities adversely affects other physical properties of the sintered body, for example, appearance and strength. Therefore, in order to improve the properties of the aluminum nitride sintered body, particularly the thermal conductivity, it is necessary to use a high-purity aluminum nitride powder as a raw material for sintering.

In general, reduction nitriding and direct nitriding are known as industrial methods for producing aluminum nitride powder.
Either method requires pulverization or the like in order to adjust the particle size of the powder to obtain a fine powder having a particle size of several μm or less. As a pulverizing method of aluminum nitride, a ball mill or a rod mill, in which a ball or a rod and a raw material powder of aluminum nitride are placed in a pulverizer and used as a pulverizer, is used. In these ball mills and the like, there are a dry pulverization method and a wet pulverization method, but in order to satisfy the above-mentioned condition of fineness and uniform particle size, a wet pulverization method is selected.

[0006] The reason is that the wet pulverization method has an advantage that it is effective in lowering the surface energy of particles and preventing agglomeration of particles, and is suitable for obtaining powder having a particle size on the order of submicrons. Because there is. On the other hand, in the wet grinding method, the crushed material (coarse raw material) is liable to be contaminated by abrasion of the crusher and balls during the crushing process, or the surface of the crushed material is oxidized by activation of the surface. There are drawbacks such as ease of use. Therefore, in the aluminum nitride powder obtained by pulverization, the amounts of metal impurities and oxygen in the powder increase, and high thermal conductivity cannot be obtained.

[0007] In order to solve the above-mentioned disadvantages, studies have been made on balls and pulverizers made of a low wear material. For example, in JP-A-61-146703,
It has been proposed that the layer constituting the inner surface of the pulverizer be an aluminum nitride layer. According to this, since the layer has the same composition as the raw material powder (aluminum nitride), it is possible to eliminate the contamination of impurities. I have. In Japanese Patent Publication No. 4-78563 and Japanese Patent Publication No. 5-10298,
It has been proposed that the material of the ball be zirconia, which can eliminate the mixing of oxygen and metal impurities, shorten the grinding time, and suppress the surface oxidation of aluminum nitride during grinding. .

[0008]

However, it has been clarified by the present inventors that the above-described technology has the following problems. That is, JP-A-61-146
In the technique described in Japanese Patent Application Publication No. 703, the aluminum nitride layer of a pulverizer is severely worn and the pulverization efficiency is low. Since the aluminum nitride layer is covered with an oxide, It is disadvantageous in that the amount of oxygen in the aluminum powder is not significantly reduced. Further, in the technology described in Japanese Patent Publication No. 4-78563 or Japanese Patent Publication No. 5-10298, zircon is mixed into the aluminum nitride powder obtained by pulverization, and the powder is obtained by using the powder. This has the disadvantage that the properties of the aluminum nitride sintered body, particularly the color tone, are affected.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object thereof is to provide a submicron device.
For high-purity sintering with orderly and uniform particle size
Aluminum nitride powder that enables the production of raw material powder
It is to provide a manufacturing method.

[0010]

Means for Solving the Problems To achieve the above object, the present inventors minimized contamination of raw material powder by metal impurities and oxygen during pulverization, and sintered the original high thermal conductivity of aluminum nitride. Various methods and conditions were studied for the purpose of developing an aluminum nitride powder having a particle size on the order of submicron which can sufficiently exhibit the effects of the present invention, and as a result, the present invention was completed.

Production of aluminum nitride powder according to the present invention
In the method , a particle diameter (D50) of a particle corresponding to 50% of the total number of particles in a particle size distribution curve obtained by calculating a particle diameter and the number of particles corresponding to the particle diameter by a laser diffraction method is 1. The ratio of the particle size (D90) of the particle corresponding to 90% of the total number of particles in the above curve and the particle size (D10) of the particle corresponding to 10% of the total number of particles in the same curve. There is four or less, and the total amount of impurity consisting of cations is 0.1 wt% or less, more per the amount of oxygen to produce aluminum nitride powder is 1.7 wt% or less
Raw aluminum coarse powder alone, or
Add the binder, dispersant, plasticizer and sintering aid
A mixture of one or more substances selected from the group consisting of
The compound is an organic polymer, aluminum having a purity of 99.5% or more.
Inside a pulverizer having an inner surface made of sialon or sialon
Alumina with a purity of 99.5% or more, or Sialon
Wet grinding in an organic solvent.
To make sense.

In the method for producing an aluminum nitride powder according to the present invention, the water content of the organic solvent
Was 1000 ppm or less.

The contents of the present invention will be described in more detail. In the present invention, a wet method is employed for pulverizing the raw material coarse powder of aluminum nitride. As long as the crusher is a rotary cylindrical mill (ball mill), a vibrating ball mill, a centrifugal ball mill, a solvent agitation mill, or the like, there is no restriction on the model and size (scale). In order to increase the purity of the aluminum nitride powder as the raw material powder for sintering, it is necessary to use a wear-resistant material containing no harmful elements for a pulverizer, a ball (a pulverizer) or the like.

Examples of the wear-resistant material include organic polymers having solvent resistance and wear resistance. An abrasion-resistant organic polymer is an ideal material because it can be removed during heating even if it is mixed during the milling of the raw material coarse powder, but its specific gravity is low, so it is limited to the use of the inner wall material of the mill. Can be If the material is specifically illustrated, nylon, polyethylene,
Examples include polycarbonate, polyethylene terephthalate, and resins. Alternatively, high-purity alumina (purity 99.5% or more), sialon (SiAlO)
N: an oxynitride ceramic composed of silicon, aluminum, oxygen and nitrogen).

Since the above organic polymer is unsuitable for use in a ball as described above, the above high-purity alumina or sialon is used for a ball. This high-purity alumina ball is a general-purpose alumina ball (purity 9).
(Less than 9.5%), it has excellent properties such as high wear resistance, high strength and high toughness. Sialon balls have the highest abrasion resistance among commercially available balls. Note that the silicon (Si) component in the sialon does not affect the characteristics of the aluminum nitride sintered body at all if the amount is small. Ball diameter is usually from 1mm to 2
It is about 0 mm, preferably about 3 mm or more and 10 mm or less.

The organic solvent preferably has a low water content and does not contain harmful elements such as chlorine.
Specific examples include aromatic compounds such as toluene, ketone compounds such as acetone, paraffin compounds such as hexane, and alcohol compounds such as isopropyl alcohol. As the raw material coarse powder proceeds, the powder becomes more chemically active and easily reacts with the water in the solvent. Therefore, the water in the solvent is removed as much as possible in advance. The dehydration method at this time is not particularly limited, but depends on the use of distillation, a dehydrating agent and the like.

The aluminum nitride raw material powder used in the present invention is aluminum nitride powder obtained by a direct nitridation method, a reduction nitridation method, or another method. Having an average particle size of preferably 10
It does not exceed μm. Then, depending on the type of the crusher, the crusher is filled with the raw material coarse powder of aluminum nitride up to about 5 to 30% of its volume, and the crusher has a volume of 3%.
Fill the ball to about 0-70%. The treatment temperature in the pulverization treatment is room temperature, the treatment time is 1 to 100 hours, and there is no particular limitation, but the treatment atmosphere is preferably a gas containing no water vapor, for example, an inert gas atmosphere.

[0018]

According to the above-mentioned means, the organic polymer, 99.5
% Or more of the raw material of aluminum nitride together with a crusher (ball) of 99.5% or higher purity in an crusher having an inner surface of alumina or sialon of higher purity than 9%. Since the wet milling treatment is performed inside, the solvent resistance and abrasion resistance of the crusher and the ball are remarkably improved, and contamination of metal impurities from the crusher and the ball during the crushing is suppressed as much as possible. Further, since the water content in the organic solvent is 1000 ppm or less, oxidation of the aluminum nitride powder during pulverization is prevented. Accordingly, a high-purity aluminum nitride powder having a particle size on the order of submicrons and having a uniform particle size can be obtained.

[0019]

EXAMPLES The features of the present invention will be clarified below with reference to examples and comparative examples. (Examples 1 to 4) 90 g of dehydrated organic solvent, 100 g of aluminum nitride raw powder (average particle size: 5.71 μm) and diameter were placed in a 1-liter ball mill whose inner surface was made of nylon resin (organic polymer). 1000g of 5mm ball
And wet-pulverizing treatment was performed at room temperature for 24 to 36 hours, followed by drying at 70 ° C. for 4 hours to obtain fine aluminum nitride powder. In Examples 1 and 2, high-purity alumina (99.9% purity) balls were used.
Used sialon (purity 99.9%) balls.
In Examples 1 and 3, isopropyl alcohol (IPA) was used as an organic solvent, and in Examples 2 and 4, acetone was used.

Here, a molecular sieve (molecular sieve) was used for the dehydration treatment of the organic solvent, and the rotation speed of the ball mill was set to 100 rpm. Table 1 shows the results obtained by measuring the powder properties of the aluminum nitride powders obtained in Examples 1 to 4, such as the particle size, the amount of oxygen, and the amount of metal impurities. For reference, Table 1 also shows the results of measurement of powder characteristics of the oxygen content and the metal impurity content of the aluminum nitride raw material coarse powder before the pulverization treatment. In Table 1, “D ₅₀ ” is the particle size of a particle corresponding to 50% of the total number of particles in a particle size distribution curve obtained by determining the particle size and the number of particles corresponding to the particle size by a laser diffraction method. , That is, the average particle size.

[Table 1]

(Comparative Examples 1 to 3) In Comparative Example 1, general-purpose alumina (purity 93.0%) balls were used, and in Comparative Example 2, aluminum nitride (purity 99.5%) balls were used. In Comparative Example 3, balls made of zirconia (purity: 95.0%) were used. Other pulverization conditions were the same as in Example 1 above (however, in Comparative Examples 2 and 3, the pulverization time was 36 hours). Table 1 shows the results obtained by measuring the powder properties of the aluminum nitride powders obtained from Comparative Examples 1 to 3, such as the particle size, the amount of oxygen, and the amount of metal impurities.

Comparative Example 4 A general-purpose organic solvent, that is, a solvent which had not been subjected to a dehydration treatment in advance was used. Other pulverization conditions were the same as in Example 1 above. Table 1 shows the measurement results of the powder characteristics such as the particle size, the amount of oxygen, and the amount of metal impurities of the obtained aluminum nitride powder.

As is apparent from Table 1, in Examples 1 to 4 according to the present invention, the average particle diameter is 1.2 μm or less, and the total amount of cation impurities is 0.1% by weight or less. Aluminum nitride powder having an oxygen content of 1.7% by weight or less was obtained, and these powders had an average particle diameter (D) as compared with the powders obtained from Comparative Examples 1 to 4.
₅₀ ), the total amount of oxygen and metal impurities was excellent.

Examples 5 and 6 High-purity alumina (purity 9)
9.9%) balls or sialon (purity 99.9%) balls, each aluminum nitride powder of Example 2 or Example 4 obtained by wet grinding with 5% by weight of a sintering aid Y203. (Average particle size: 1.2 μm) was wet-mixed for 12 hours, and then dried at 70 ° C. for 4 hours to obtain a mixed powder. 1000kgf / c using these mixed powders
After press molding under a hydrostatic pressure of m ² , normal pressure sintering was performed at 1790 ° C. for 3 hours in a nitrogen atmosphere. Table 2 shows the density and thermal conductivity of the obtained sintered body. In Table 2, "D
₁₀ , D ₅₀ , D ₉₀ ”are 10%, 50%, and 90% of the total number of particles in a particle size distribution curve obtained by calculating the particle size and the number of particles corresponding to the particle size by the laser diffraction method. % Means the particle size of the particles.

[Table 2]

(Comparative Examples 5 to 7) In Comparative Example 5, the aluminum nitride powder of Comparative Example 1 obtained by wet grinding with a general-purpose alumina (purity: 93.0%) ball was used. Aluminum nitride powder obtained by dry milling with a mill was used. In Comparative Example 6, classification was performed. Other sintering conditions were the same as in Example 5 above. Table 2 shows the density and thermal conductivity of the obtained sintered body.

[0026] As apparent from Table 2, baked in Examples 5-6 of the present invention, D ₉₀ / D ₁₀ ratio is obtained 4 or less aluminum nitride powder, also obtained by using them powder The sintered body was superior to the sintered bodies of Comparative Examples 5 to 7 in density and thermal conductivity, and in particular, a high thermal conductivity of 180 W / m · K or more was obtained.

In this example, the particle size distribution of the aluminum nitride powder was measured by a laser diffraction method, and the quantitative analysis of oxygen in the aluminum nitride powder was performed by an inert gas melting method. ICP emission spectrometry (indu
Ctively coupled plasma at
omic emission spectrometer
The laser flash method was used to measure the thermal conductivity of the aluminum nitride sintered body using the y) method.

[0028]

The production of the aluminum nitride powder according to the present invention
According to the manufacturing method , aluminum nitride powder is contaminated with impurities coming out of the pulverizers and pulverizers during the pulverization process by using wear-resistant materials containing no harmful elements on the inner surface of the pulverizer and the pulverizers. Can be suppressed as much as possible. In addition, by preliminarily dehydrating the organic solvent, it is possible to minimize the occurrence of a hydration reaction of the aluminum nitride powder during the pulverization. Therefore, the average particle diameter of 1.2 μm with a very small amount of metal impurities and oxygen mixed therein.
m of aluminum nitride powder can be easily obtained.

Further, in the sintering using the fine powder, the sinterability is improved, and sintering at a lower temperature (1800 ° C. or lower) becomes possible. Therefore, in manufacturing an aluminum nitride sintered body, the manufacturing cost can be reduced, and industrial mass productivity is extremely excellent. Also,
The thermal conductivity of the obtained aluminum nitride sintered body is 180 W
/ MK or more. Such a high thermal conductivity has not been conventionally achievable, and the present invention has an extremely high practical value.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C01B 21/072 CA (STN)

Claims (2)

(57) [Claims] 1. A particle diameter (D50) of a particle corresponding to 50% of the total number of particles in a particle size distribution curve obtained by calculating a particle diameter and the number of particles corresponding to the particle diameter by a laser diffraction method is 1 .2 μm or less and the particle diameter (D90) of the particle corresponding to 90% of the total number of particles in the above curve and the particle diameter (D10) of the particle corresponding to 10% of the total number of particles in the same curve. A method for producing an aluminum nitride powder wherein the ratio is 4 or less, the total amount of impurities composed of cations is 0.1% by weight or less, and the amount of oxygen is 1.7% by weight or less.
In producing aluminum nitride powder, aluminum nitride
Raw material coarse powder consisting solely of
Select from the group consisting of binders, dispersants, plasticizers and sintering aids.
The mixture of one or more of the substances
Coalescence, 99.5% or higher purity alumina or sialo
99.5% or more in a pulverizer having an inner surface consisting of
With a crusher made of alumina or sialon with a purity of
In addition, it is characterized by wet grinding in an organic solvent.
Of producing aluminum nitride powder. 2. The water content of the organic solvent is 100
2. The nitriding material according to claim 1, wherein the content is 0 ppm or less.
Manufacturing method of aluminum powder.