JPS61146703A - Production of aluminum nitride powder - Google Patents

Abstract

PURPOSE:To obtain AlN powder contg. a small amount of impurities by crushing coarse AlN powder to fine powder by means of a crusher consisting essentially of an AlN layer coated in the inside thereof. CONSTITUTION:The crusher such as a ball mill or a hammer crusher is lined with an AlN-base layer contg., by weight, <=10wt% oxygen, <=1wt% silicon, <=1wt% iron and <=2wt% in the total of other cationic impurities. The coarse AlN powder to be crushed is put in the lined crusher and crushed to fine pow der by collision with the AlN-base layer and by friction.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a method for producing aluminum nitride powder with low impurities.

[Technical background of the invention and its problems]

Aluminum nitride is an industrially promising mechanical material, as it is wettable to molten metal and has excellent high-temperature strength. Aluminum nitride is also known to inherently have a high thermal conductivity of 300 W/mek or more, and it is expected to be used as a material for the electronic industry by utilizing its high thermal conductivity. The thermal conductivity of the obtained aluminum sintered body is as low as 40 W/m.

This is thought to be caused by the solid solution of impurities, particularly impurities such as oxygen, silicon, and iron, into the aluminum nitride sintered body. In other words, these impurities were easily incorporated into aluminum nitride to form a solid solution during sintering). When the amount of solid solution further increases, polymorphs of aluminum nitride are generated. For this reason, phonon conduction is inhibited and thermal conductivity is significantly reduced.

These impurities can crush aluminum nitride coarse particles,
When mixing sintering additives, they are often mixed from a grinding/mixing container. For example, if aluminum nitride coarse powder lIc1i and an alcoholic dispersion medium are placed in a commercially available aluminum oxide pot mill (volume 3 J) and ground for 100 hours, oxidation occurs. A sintered body containing 2 to 3 qb of aluminum and using such a raw material usually has a thermal conductivity of only about 40 W/m.

[Purpose of the invention]

The present invention aims to provide an aluminum nitride raw material powder containing a small amount of impurities in order to obtain an aluminum nitride sintered body having high thermal conductivity.

[Summary of the invention]

The present invention provides a method for producing aluminum nitride powder, which includes a step of crushing and pulverizing coarse aluminum nitride powder to be crushed (by collision and friction with a layer mainly composed of aluminum nitride constituting at least the inner surface of a crusher). A method for producing aluminum nitride powder, characterized by:

This method is applicable to all production of aluminum nitride and ram powder by pulverization, and the layer mainly composed of aluminum nitride is formed by a sintered body or by a sputtering method.

Note that the crusher used in the present invention is a ball mill,
Vibration mill, Gyre crusher, gyratory
Examples include compression crushers such as crushers and roll crushers, impact crushers such as mark crushers, jet mills, and impeller breakers. For pot mills with relatively simple inner shapes, if the entire pot and pole are made of sintered aluminum nitride, the life of the pot will be longer and the contamination of the joints will be reduced.

In addition, in the case of a large plate using a vibrating mill, etc., the same effect can be obtained by closely adhering tiles made of aluminum nitride sintered body to the inner surface of the plate. However, sufficient care must be taken to prevent impurities from entering the joint.

In addition, if the inner surface is complex in shape and the device is large, such as a jet mill, aluminum nitride can be coated with a G-type or the like.

It is preferable that the layer mainly composed of aluminum nitride does not contain any impurities, but the total amount of other cationic impurities should be 10% by weight or less for oxygen, 1% by weight or less for silicon, 1% by weight or less for iron, and 2% by weight or less for iron. If the weight is less than -, it is practically applicable. The impurities here do not include constituent elements of additives intentionally included in the layer mainly composed of aluminum nitride. This is particularly true when additives added to facilitate the formation of a layer mainly composed of aluminum nitride (for example, by pressureless sintering) can act as an aid when sintering the powder to be ground. This is because there is no problem even if it is contained in large amounts.

The reason why the amount of impurities is limited to the above range is that within the above range, by selecting the amount of pulverization and the pulverization conditions, the amount of impurities can be kept within a range that has no practical effect.

〔Effect of the invention〕

By using the method of the present invention, it is possible to reduce the amount of impurities mixed into the nitride powder during the pulverization process. For example, three hot aluminum nitride balls with a diameter of 20 mm are placed in a hot pressed aluminum nitride pot with a capacity of 3.871 mm.
4 filled with commercially available aluminum nitride powder (average particle size 5 μm)
When 1# is crushed for 100 hours with an alcohol-based dispersion medium, compared to a similar alumina pot, the amount of mixed oxygen (including the oxidation of aluminum nitride itself) increases by 1/4 of that of alumina, such as x, Fe, st+ca9m, etc. The increase is 0.0
It was less than 1% f h .

When alumina pot pulverized powder and aluminum nitride pot pulverized powder were pot-pressed at 1800°C, both were completely densified, but the former had a thermal conductivity of 46 W/m;
k, while in the latter it was 73W/m≦
Furthermore, based on this, when additives such as Y2O3 are added and sintered using the method shown in Japanese Patent Application No. 58-233938, 100
A high thermal conductivity of W/m, k or more was achieved.

[Embodiments of the invention]

Example 1 Commercially available aluminum nitride powder (average particle size 5 μm) was ground with an aluminum oxide ball mill to obtain an average particle size of 1.5 μm.
Powder of μm was made, filled into a hot press mold made of carbon, and sintered at 1800℃ for 2 hours at a pressure of 300℃/cd, inner diameter 18α x outer diameter 21α x length 15c.
A cylindrical sintered body of IIL is obtained. In the same way, diameter 21c
A pot made of aluminum nitride sintered body was manufactured by making and combining disks with an IIL thickness of 10I31L.

Similarly, 200 aluminum nitride balls with a diameter of 20 m+31 were manufactured.

This was filled with 1 kg of commercially available A/N powder and 1/1 of butanol, and pulverized for 100 hours. This powder was plated to have an average particle size of 12 μm.

This powder was filled into a carbon hot press mold and sintered at 1800° under a pressure of 0,400 J/d for 1 hour. Cut out a 7X7X3- sample from the sintered body and use laser 7
．． Thermal conductivity was measured by the 7tsussier method.

Furthermore, the constituent phases were fixed by powder X-ray diffraction.

Example 2 Aluminum nitride and 3% by weight of yttrium oxide were mixed and pulverized in an alumina pot in the same manner as in Example-1, and 7x1% of paraffin was added and granulated.
It was made into a plate shape of ctLX 15cRx l cIIL.

This was heated in nitrogen gas at 700°C to degrease it, and then sintered in nitrogen gas at 1800°C for 2 hours under normal pressure. A plate made of fired aluminum nitride was attached to the inner surface of a pot of a vibrating mill having an internal volume of 301 mm using a Teflon adhesive.

Further, aluminum nitride pellets measuring 8 mm in diameter and 10 mm in height were prepared using the same pressureless sintering method and filled into the pot described above. A pot was filled with 10 kg of commercially available aluminum nitride powder and butanol, and pulverized for 20 hours. This powder had an average particle size of 1.0 μm. This powder was sintered and evaluated in the same manner as in Example 1.

Comparative Example 1 An aluminum nitride sintered body was produced using commercially available A/N powder under the same sintering conditions as in Example 1, and the same evaluation as in Example 1 was performed.

Comparative Example 2 An aluminum nitride sintered body was produced and evaluated in the same manner as in Example 1 except that commercially available alumina bottles (3, 34) and balls were used.

These results are shown in Table 1. It can be seen that when an aluminum nitride pot is used, it has the same crushing performance as a commercially available alumina pot, and the contamination of impurities is extremely low.

In addition, it can be seen that correspondingly, oxynitride (AION), which is a constituent phase that inhibits heat conduction, is not generated and the thermal conductivity is greatly improved.

Below is a blank space Example 3 3% yttrium oxide was mixed with the aluminum nitride powder prepared in Example 1 and Comparative Example 2, and the mixture was granulated, degreased, and sintered in the same manner as in Example 1. Example 3 and Comparative Example 3 It was evaluated as follows. As a result, Example 3 showed a high thermal conductivity of 107 W/m,k, while Comparative Example 3 showed a high thermal conductivity of 70 W/m,k.
I fell in love with K.

All of them have high thermal conductivity, but the aluminum nitride pot has greatly improved its effectiveness.

Example 4 Mo was shaped along the inner surface of a small experimental jet mill.
The film was formed and a coating layer of aluminum nitride made of IJcIs NHa-based G was provided on the surface. The coating condition is AlC1a/NHa ratio lX10-'
The temperature is 1200°0. Film thickness is 0.5 B/50
HR is Ruru.

Using this, the commercially available aluminum nitride powder of Comparative Example 1 was pulverized to obtain powder with a maximum particle size of 1.5 μm.

The amount of oxygen impurities in this powder was 1,951.

This powder was hot-breath sintered under the same conditions as in Example 1, resulting in a thermal conductivity of 65 W/m.

Claims (1)

[Claims] 1) In a method for producing aluminum nitride powder, coarse aluminum nitride powder to be crushed is crushed and pulverized by collision and friction with a layer mainly composed of aluminum nitride that constitutes at least the inner surface of a crusher. A method for producing aluminum nitride powder, characterized by comprising the steps. 2) The layer mainly composed of aluminum nitride contains as impurities 10% by weight or less of oxygen, 1% by weight or less of silicon, 1% by weight or less of iron, and 2% by weight or less of cationic impurities. A method for producing aluminum nitride powder according to claim 1.