JPS62143806A - Aluminum nitride powder and production thereof - Google Patents

Abstract

PURPOSE:Crude aluminum nitride powder resulting from direct nitridation is stirred in a nonaqueous solvent of a specific pH and dried in vacuum to produce an aluminum nitride powder of less impurity content, large bulk density and high formability. CONSTITUTION:Crude aluminum nitride powder which has been produced by the direct nitridation of metallic aluminum is treated with a nonaqueous solvent of less than 4pH under stirring. Then, the powder is filtered and the resultant cake of aluminum nitride is dried under vacuum. The resultant aluminum nitride contains less than 1.5wt% of oxygen and less than 300ppm of iron and has more than 0.3 bulk density. The nonaqueous solvent is e.g., glacial acetic acid, acetonitrile or chloroform. The treatment operation is carried out at least at room temperature and the time is preferably at least 1hr.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an aluminum nitride powder with few impurities and excellent moldability, and a method for producing the same.

[Conventional technology]

Aluminum nitride (hereinafter referred to as AtN) such as a highly thermally conductive substrate
That's what it means. ] AtN powder used as a raw material for the molded body is one produced by the At203M original method (hereinafter referred to as the reduction method) (Japanese Patent Application Laid-open No. 59-207814), and one produced by the metal aluminum true nitriding method (hereinafter referred to as the direct method). It is known that it is manufactured by the nitriding method. AtN powder produced by the reduction method has the advantage of being highly pure with little impurities such as oxygen and iron, but has the disadvantage of being bulky and difficult to mold into compacts. -10,000, AtN by direct nitriding method
Powder has the advantage of being small in bulk and easy to mold, but it has a cation content of 2000 to 3000 p, especially among impurities.
There are many drawbacks such as pm.

[Problem that the invention seeks to solve]

The present invention solves the drawbacks of the prior art, and its purpose is to provide an AtN powder that has the same amount of impurities as AtN powder produced by a reduction method, has a large bulk specific gravity, and has excellent moldability. It's about doing.

[Means to solve the problem]

That is, the first invention of the present invention is an aluminum nitride powder characterized in that the content of oxygen and iron is 1.5 or less and 300 ppm or less, respectively, and the bulk specific gravity is 0.3 or more, The second invention is [raw material aluminum nitride powder k produced by the U nitriding method], stirred in a non-aqueous solvent with a pH of 4 or less, filtered, and dried the cake-like aluminum nitride under vacuum e%- This is a method for producing aluminum nitride powder according to a first aspect of the invention.

Hereinafter, the content of the present invention will be described in detail as a first aspect of the invention. The AtN powder of the present invention is produced by direct nitride, for example, and contains less than 1.5 g of oxygen and iron as an impurity. It contains 3.00 ppm or less. The oxygen content is 1.5% by weight, and the iron content is 300% by weight.
If it exceeds ppm, the thermal conductivity of the molded product such as a substrate will deteriorate, which is not preferable.

Next, the AtN powder of the present invention has a bulk specific gravity of 0.3 or more, preferably 0.5 or more. If the bulk specific gravity is less than 0.3, compaction will be poor during molding and the density of the green will not increase. The AtN powder having a high bulk specific gravity as used in the present invention is characterized by having a fractured surface on the surface, as illustrated in FIG. It is something that will be done.

Further, the particle size of the powder according to the present invention is preferably 6 μm or less in terms of average particle diameter, and if it exceeds 3 μm,
As with the case where the content of oxygen or iron increases, the thermal conductivity of the molded body tends to deteriorate.

Next, the second uninvented invention will be explained.

The raw material AtN powder used in this invention is produced by a direct nitriding method. A specific example is one manufactured according to Japanese Patent Application No. 59-38940 filed by the present applicant. The uN powder produced by the direct nitriding method has a larger bulk specific gravity than that produced by the reduction method, so it has excellent moldability and is inexpensive. In the present invention, the impurities are reduced by the following procedure.

Regarding iron among the cations contained in the raw AtN powder, the mineral composition may be cementite, hematite, magnetite, or alpha iron, but it is advantageous to contain alpha iron, which has the greatest removal effect. be. Further, in the case of powder containing cations other than iron such as calcium, magnesium, aluminum, silicon, etc. in an amount of 5000 ppm or more, it is advantageous to use a particle size of 3 μm or less in view of the removal effect. The reason for this is that the reaction can be promoted by exposing the entire boundary phase in which iron-based minerals are concentrated on the surface of the raw material AtN powder particles. Next, the above AtN powder'fr is stirred in a non-aqueous solvent having a pH of 4 or less.

Examples of the non-aqueous solvent include glacial acetic acid, acetonitrile, chloroform, etc., and the concentration thereof is a hydrogen ion concentration of 4 or less per day. In a solvent in which - exceeds 4, it takes time to remove the cations, and in some cases, less than half of the removable iron-form minerals can be removed.

Regarding the processing conditions, it is preferable that the temperature is at least room temperature and the time is at least 1 hour. If the temperature is lower than room temperature and the treatment time is less than 1 hour, the removal of cations tends to be insufficient, as in the case of the above concentration.

Next, the stirred AtN powder is filtered by the usual Nutsche method, etc., but as a filtration washing liquid, a non-aqueous solvent such as Rhae, the above-mentioned ice vinegar, etc., or acetone, an alcohol without dissolving the AtN powder is used. Use a non-aqueous solvent that does not react with

The cake-like AtN obtained by filtering and washing is dried at a temperature of around 100°C, but it is preferable to dry it under vacuum. The reason for this is to prevent gold oxidation of AtN as much as possible during drying. The sufficiently dried AtN powder is cooled to room temperature and taken out as a product.

As explained above, the method according to the present invention uses AtN powder produced by the direct nitriding method, which is inexpensive and has excellent formability, as a raw material, and prevents the oxidation of AtN while reducing the amount of iron-containing cations.
It is unique in that it produces tN powder, but in addition, since it is treated with a non-aqueous solvent, the particle surface is coated with lipophilic groups, so when producing a compact, it is difficult to sinter. Mixing with a binder or the like is advantageous and also leads to stabilization of the particle surface.

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to Examples.

Example 1 Commercially available AtN powder 20 manufactured by the direct nitriding method shown in the table
200 d of acetonitrile-hydrogen chloride non-aqueous solvent adjusted to a hydrogen ion concentration of 10-1 mol/t (pH 1)
The mixture was placed in a polyethylene container containing 100 ml of water, and the acid treatment was carried out while stirring at room temperature for 1 hour. Next, the filtered and washed solution was filtered and washed using a Nutsche apparatus using A7Tone. Thereafter, the cake was dried in a vacuum dryer (manufactured by Toyo Seisakusho Co., Ltd., product name: VAOUMDRY).
The product was dried at 00 mHg x 100'C for a day and a night to obtain a product AtN powder. Magnification of the obtained AtN powder: 60
A micrograph of 00 is shown in FIG.

Next, this powder 2.0, Ft-graphite dice (15
11I) using a high-frequency heating furnace at a pressure of 100 KL.
Pressure sintering was performed at I/cm2 at a temperature of 2000°C for 2 hours in a nitrogen gas atmosphere of 1 atm to obtain an AtN sintered body. This AtN
After grinding and polishing the sintered body, its physical properties were measured. The results are shown in the table along with the analysis results of the AtN powder.

Example 2 The same procedure as in Example 1 was conducted except that the hydrogen ion concentration of the acetonitrile-hydrogen chloride nonaqueous solvent was set to 10-r5 mol/l (pH 3). The results are shown in the table.

Comparative Examples 1 to 3 The same procedure as in Example 1 was carried out except that the hydrogen ion concentration of the acetonitrile-hydrogen chloride nonaqueous solvent was set to 'tlO-5 mol/t (pH 5) (Comparative Example 1).

The same test was carried out using the commercially available AtN powder produced by the direct conversion method used in Example 1 (Comparative Example 2) The commercially available AtN powder produced by the λ reduction method (its magnification was 100%).

(A micrograph of which is shown in FIG. 2) was used as it was and tested in the same manner (Comparative Example 3).

The above results are shown in the table.

The measured values listed in the table were measured by the following method.

(1) Average particle diameter (μm)...Fisher's FS
According to SS method.

(2 oxygen (weight%)...r, Boo Co. To -136
Based on type oxygen analyzer.

(3) Iron (ppm): Based on alkali melting-absorption photometry.

(4) Bulk specific gravity (!j/α3)...Choyo Mikufour Co., Ltd.
Powder tester.

(5) Relative value of green density (correspondence): value obtained by dividing the bulk density of the green molded body by the true specific gravity (3, 20) of AtH.

(6) Relative value of thermal conductivity (%): Relative value to the thermal conductivity of the sintered body when AtN powder produced by the reduction method is used.

〔Effect of the invention〕

According to the first aspect of the present invention, it is possible to obtain A4N powder with a small amount of impurities and excellent moldability.

According to the second invention of the present invention, the AtN powder of the first invention can be easily produced by acid-treating the inexpensive AtN powder produced by the direct nitriding method.

[Brief explanation of drawings]

Figure 1 shows AtN powder according to the present invention (Example 1) at a magnification of 6.
000, and Figure 2 shows the commercially available AtN produced by the reduction method.
It is a micrograph of the powder (Comparative Example 3) at a magnification of i oooc+. Patent Applicant: Denki Kagaku Kogyo Co., Ltd. Procedural Amendment (Method) March 5, 1985 Commissioner of the Patent Office Michibe Uga 1, Indication of the Case 1985 Patent Application No. 283092 2, Name of the Invention Nitriding Aluminum powder and its manufacturing method 3, relationship with the amended case Patent applicant ■100 Address 1-4-1 Yurakucho, Chiyoda-ku, Tokyo 1986
February 25, 2019 (shipment date) Page 10, lines 13 to 16 of the specification are revised as follows.

Claims (2)

[Claims] (1) An aluminum nitride powder having an oxygen and iron content of 1.5% by weight or less and 300ppm or less, respectively, and a bulk specific gravity of 0.3 or more. (2) Oxygen, which is characterized by stirring the raw material aluminum nitride powder produced by the metal aluminum direct nitriding method in a non-aqueous solvent with a pH of 4 or less, filtering it, and drying the cake-like aluminum nitride under vacuum. and a method for producing aluminum nitride powder having an iron content of 1.5% by weight or less and 300ppm or less, respectively, and a bulk specific gravity of 0.3 or more.