JPH0431366A - Production of aluminum nitride-based powder - Google Patents

Abstract

PURPOSE:To obtain powder capable of providing a sintered compact having better thermal conductivity and corrosion resistance by adding a calcium compound to aluminum nitride powder in disintegration thereof in a method for adding the calcium compound to the aluminum nitride and producing the subject powder. CONSTITUTION:A calcium compound as a sintering assistant in an amount of 0.01-1wt.% expressed in terms of CaO is added to aluminum nitride powder to provide aluminum nitride-based powder. In the aforementioned method, the calcium compound is added in disintegrating the aluminum nitride. Thereby, the objective powder in which the calcium compound is homogeneously dispersed can be obtained. As a result, the above-mentioned powder can be used to readily afford a high-density sintered compact excellent in thermal conductivity with hardly any contained pores.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a method for producing aluminum nitride powder, which produces a sintered body having better thermal conductivity and corrosion resistance than conventional aluminum nitride powders. It is about how to obtain.

[Conventional technology]

Alumina has traditionally been widely used in highly reliable IC substrates or package materials. High integration of LSI etc.
As speed increases and power increases, the amount of heat generated from semiconductor chips increases, and the need to efficiently dissipate heat outside the system increases, creating a demand for materials with better thermal conductivity and better heat dissipation than alumina. has been done.

Aluminum nitride has high thermal conductivity and excellent electrical properties such as insulation resistance, dielectric strength, dielectric constant, and mechanical properties such as strength, and is attracting attention as an IC substrate and package material with excellent heat dissipation. .

To obtain an aluminum nitride sintered body with excellent thermal conductivity,
It is necessary to shape the aluminum nitride powder and sinter it densely.

[Problem to be solved by the invention]

Since aluminum nitride is difficult to sinter under pressure alone, oxides such as CaO1YzOs are conventionally added as sintering aids during pressureless sintering, and the reaction between these aids and the Al2O3 of the aluminum nitride surface layer is stimulated. A liquid-phase sintering method has been used that utilizes sintering to achieve densification.

Among sintering aids, Y2O is particularly known as an excellent aid because it has the effect of trapping impurity oxygen and increasing thermal conductivity in addition to densification. In addition, in order to obtain a dense sintered body with high thermal conductivity by pressureless sintering, a high temperature of 1800°C or higher is required when Y,03 is added. Or JP-A-63
As disclosed in Japanese Patent No. 190761, CaO having a low melting point is added and mixed to aluminum nitride powder during sintering, and Y, 0. A method has been proposed that can be used in combination with but,
In this case, the relative density is 98.5 at a sintering temperature of 1800℃ or less.
% or more dense aluminum nitride sintered body has been obtained, but its thermal conductivity is about 150 W/mK.

The object of the present invention is to combine calcium compounds and Y! This method aims to improve the relative density, which could not be achieved by the conventional addition method of adding and mixing 03 at the same time, and manufactures aluminum nitride powder from which an aluminum nitride sintered body with high thermal conductivity and excellent corrosion resistance can be obtained. The purpose is to provide a method.

[Means to solve the problem]

That is, in the present invention, a calcium compound is added to aluminum nitride powder as a sintering aid.
A method for producing aluminum nitride powder by adding 0.01 to 1% by weight in terms of O, wherein a calcium compound is added at the time of crushing the aluminum nitride powder. This is what we provide.

According to the present invention, calcium compounds and Y are used as sintering aids.
Compared to the conventional case of adding and mixing 2O3 at the same time, it is possible to obtain aluminum nitride powder that yields an aluminum nitride sintered body with high density (high thermal conductivity) and excellent corrosion resistance.

In pressureless sintering of aluminum nitride, CaO or Y,03 added as a sintering aid reacts with Altos on the surface layer of aluminum nitride to form CaAl+O+ and Y2Al5O.
It is believed that densification progresses through a liquid phase such as 12.

Since YaAisO□2 solidifies at the edges and corners where multiple particles meet while trapping oxygen, the solid solution of oxygen into the aluminum nitride grains is suppressed, and this oxygen trapping effect achieves high thermal conductivity. .

However, CaA1. Since O+ is a glass phase and inhibits high thermal conductivity, it is preferable that the amount of O+ is small and the phase thickness is thin.

The present inventors added a calcium compound during crushing of the aluminum nitride powder, thereby uniformly coating the surface of the aluminum nitride powder with the calcium compound, and then Y, 0. When sintered with the addition of sintering aids such as
A liquid phase composition is quickly generated due to the effect of the low melting point calcium compound, so it exhibits easy sintering properties, and the thickness of the generated grain boundary composition is thinner, resulting in higher density, higher thermal conductivity, and corrosion resistance than before. The inventors have discovered that an aluminum nitride sintered body with excellent properties can be obtained, and have completed the present invention.

The present invention will be explained in detail below.

The method of manufacturing the aluminum nitride powder used in the present invention is not particularly limited, but a fine powder with high purity is preferable.

Further, it is preferable to use a powder having a center particle size of 4.0 μm or less.

In particular, in order to achieve densification at a temperature of 1800° C. or lower, it is preferable to use a fine powder with a center particle size of 2.5 μm or lower.

Calcium compounds used as sintering aids include:
oxides, hydroxides, carbonates, sulfates, nitrates, acetates,
Oxalates, halides, sulfides, higher fatty acid salts, etc. can be used.

Calcium may be any substance as long as it is a compound, but preferably a compound that does not contain water of crystallization.

For example, CaO1Ca(OH)2, CaC0a, CaS
O4・2HzO1Ca(NO3)!・4HzO1Ca
(CHaCoo)2, Ca(COO)2”H2O, Ca
F2, CaS, Ca[CH3(CH2)+5COO]
2 etc. are used.

In addition, the finer the particle size of these compounds, the more preferable they are. In particular, when using compounds that do not dissolve or are difficult to dissolve in the solvent used when mixing with aluminum nitride powder, the center particle size is usually 5.0 μm or less. It is preferable to use a fine powder of .

The amount of these calcium compounds added is preferably in the range of 0.01 to 1% by weight in terms of CaO based on the aluminum nitride powder.

If the amount is less than 0.601% by weight, the effect of the present invention cannot be obtained, while if it is more than 1% by weight, a dense sintered body can be obtained but a high thermal conductivity cannot be obtained, so it is not preferable to deviate from this range. More preferably, the amount is in the range of 0.02 to 0.7% by weight based on the aluminum nitride powder.

The mixture of aluminum nitride powder and calcium compound is
A method is used in which aluminum nitride powder is added at the same time as it is crushed. As a device for crushing, commonly used devices such as a ball mill, a vibrating ball mill, an attritor, and a jet mill can be used, but a ball mill is preferable in terms of simplicity.

The crushing time is preferably in the range of 0.5 to 3 hours, and can be appropriately selected depending on the central particle size of the aluminum nitride powder used, within a range that can achieve crushing of aggregates and uniform dispersion of the calcium compound.

The thus obtained aluminum nitride powder in which the calcium compound is uniformly dispersed can be mixed with a sintering aid such as Y2O by dry mixing or wet mixing using a non-aqueous solvent such as alcohol. However, it is usually preferable to use wet mixing using a non-aqueous solvent.

During wet mixing, to facilitate the next forming process,
A binder such as polyvinyl butyral, polyvinyl alcohol, or polyacrylic acid ester is usually added.

In addition to binders, various dispersants, plasticizers,
Wetting agents and the like are also added.

As the mixing device, commonly used devices such as a ball mill and a mixer can be used.

Further, the mixture is dried and granulated, and is prepared into raw material forms of various properties such as granules, clay, or slurry depending on the molding method in the next step.

As a molding method, a known method such as a dry method such as a uniaxial press or a rubber press, or a wet method such as a doctor blade method or an extrusion method can be used. Further, there is no problem in using a hot press method in which molding and sintering are performed simultaneously.

The obtained molded body is usually stored in a container called a sagger and sintered. Graphite, boron nitride, aluminum nitride, alumina, etc. can be used as the material, and it is preferable to use a sagger made of graphite, boron nitride, or aluminum nitride for high-temperature sintering of 1700° C. or higher. It is also possible to use a powder bed method in which the compact is embedded in powder whose main component is aluminum nitride and sintered.

Sintering must be performed in a non-oxidizing atmosphere to prevent oxidation of aluminum nitride during sintering. As the non-oxidizing atmosphere, nitrogen, argon, a mixed gas of nitrogen and hydrogen, a mixed gas of nitrogen and argon, etc. can be used, but a nitrogen gas atmosphere is most preferable in terms of manufacturing cost and ease of handling the apparatus.

The sintering temperature can be in the range of 1,500 to 2,000°C, but is preferably in the range of 1,550 to 1,850°C.

The heating rate is not particularly limited, but is usually 1 to 5.
It is in the range of °C/min.

The holding time at the sintering temperature is in the range of 2 to 20 hours, and the density of the aluminum nitride sintered body is required to be 3.1 g/aI or more. Even if the density of the sintered body is less than 3.1 g/c+d, the sintered body appears dense in appearance, but the sintered body contains many pores, and as a result, the sintered body does not have high thermal conductivity.

〔Effect of the invention〕

In the aluminum nitride powder obtained by the method of the present invention, calcium compounds are uniformly dispersed, and by using this powder, it is possible to easily obtain a sintered body with high density and excellent thermal conductivity, which contains almost no pores. can. It is useful as a powder for producing a sintered body having better thermal conductivity and corrosion resistance than conventional powders.

〔Example〕

EXAMPLES Hereinafter, the present invention will be specifically explained with reference to Examples, but the present invention is not limited thereto.

The various physical properties were measured using the following method and apparatus.

(Oxygen content) Method: Coin pulse heating - Infrared absorption spectrometer + LECO TC-436 model (metal impurities) Method: ICP luminescence emission spectroscopy chamber: (Kikki Shimadzu Cantlet GQM-75 (
Particle size distribution) Method/Sedigraph device: (Sedigraph 5000ET manufactured by Kikki Shimadzu Corporation (
Sintered compact density) Method: Archimedes method Apparatus: (Solid specific gravity measuring device (thermal conductivity) manufactured by Kiki Shimadzu Corporation Method: Laser flash method Device: TC-7000 type manufactured by Shinku Riko ■ (corrosion resistance) Method = 10% by weight NaOH aqueous solution Inside 24hr and 4
Evaluation Examples 1 to 2 Based on weight change after immersion at room temperature for 8 hours Oxygen content was 1.1% and iron was 10ppI11
A powder containing 60 ppm of silicon, 16 ppm of titanium, and having a center particle size of 2.1 μm was used.

In addition, CaC03 (Shiraishika CCR manufactured by Shiroishi Calcium ■) was used as a calcium compound.

300g of the above aluminum nitride powder and CaCO30,2
7 g (equivalent to 0.05% by weight of aluminum nitride powder in terms of CaO) and 3 g of methanol were placed in a polyethylene pot of 51 along with alumina balls of diameter 15, and crushed at a rotation speed of 40 rpm for 3 hours. I did it.

20 g of the aluminum nitride powder with a center particle size of 1.4 μm thus obtained and 0.6 g of Y2O3 (Nippon Yttrium Co., Ltd.) as a sintering agent were placed in a 250 ml polyethylene pot, and 25 g of n-butanol was added. Acrylic binder (Sanyo Chemical Co., Ltd. CB-1) 1.0g
was added, and wet ball mill mixing was performed for 4 hours at a rotation speed of 60 rpm using a nylon coated ball with a 15+nmφ iron core.

After drying the obtained slurry, it was lightly crushed in an agate mortar to prepare a powder for sintering. 150% of this sintering powder
After press forming at 0 kg/cJ, the green compact was buried in a mixed powder of aluminum nitride and boron nitride, and sintered under normal pressure at 1750° C. and 1800° C. for 5 hours in a nitrogen atmosphere. Table 1 shows the sintered density and thermal conductivity of the obtained sintered body.

Table-1 Sintering temperature Sintering density Thermal conductivity Example 1 1750°C: 3.28g/c+1
205W/mK Example 2 1800℃ 3.29g
/co? 219 W/mK Furthermore, as a result of evaluating the corrosion resistance of the sintered body at 1800° C., the weight loss rate after 24 hours was 2.9% and after 48 hours it was 4.3%.

Comparative Examples 1 to 2 Aluminum nitride powder 2 was obtained by a reduction nitriding method of alumina with an oxygen content of 1.3% and an iron content of 10 ppm.
, contains 60 ppm silicon, 6 ppm titanium,
Powder with a center particle size of 1.4 μm was used.

20g of the above aluminum nitride powder and Y as a sintering aid.
, 0. 0.6g and 0.018g CaC0 (
0.0 in terms of CaO for aluminum nitride powder
A slurry was prepared and sintered in the same manner as in Example 1. Table 2 shows the sintered density and thermal conductivity of the obtained sintered body.

Table-2 Sintering temperature Sintering density Thermal conductivity comparative example 1 1750°C3, 27g/cffl
186W/mK Comparative Example 2 18008C3, 28g/
c/ 195W/mK Also, the corrosion resistance evaluation result of the sintered body at 1800℃ shows that the weight loss rate after 24 hours is 3
．． 9%, and 8.2% after 48 hours.

Claims (1)

[Claims] Calcium compound is added to aluminum nitride powder as a sintering aid, calculated as CaO to aluminum nitride.
1. A method for producing aluminum nitride powder, which comprises adding a calcium compound at the time of crushing the aluminum nitride powder.