JPH0524812A - Aluminum nitride powder and its production - Google Patents

Abstract

PURPOSE:To provide raw material powder of an aluminum nitride sintered compact having high thermal conductivity and light shielding properties and strength at the same time. CONSTITUTION:Aluminum nitride powder contains particles of a compound of at least one element selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Mo, W, Fe, Co, Ni, Cu, Ag, Au, Pt, Pd, B, Al, Si and Mg in aluminum nitride particles. In order to include the aforementioned compound particles in the aluminum nitride particles, the aluminum nitride particles are initially dispersed in an organic solvent containing an organic compound of the above- mentioned element dissolved therein and the organic solvent is then separated and recovered. Thereby, the objective aluminum nitride powder containing the compound particles of the aforementioned element in the aluminum nitride particles is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to aluminum nitride powder and a method for producing the same, and more particularly, aluminum nitride powder as a raw material powder for an aluminum nitride sintered body having high thermal conductivity, light-shielding properties and mechanical properties, and the production thereof. It is about the method.

[0002]

2. Description of the Related Art Recently, the technology of large-scale integrated circuit devices (LSI) has been remarkably improved, and the degree of integration has been remarkably improved. With this increase in integration and increase in processing speed,
Furthermore, as the size of the IC chip increases, the amount of heat generated per package on which the IC chip is mounted, that is, the heat generation density, increases rapidly. For this reason, the heat dissipation characteristics required for the substrate material used for the semiconductor device package and the like have become severe. In addition, the alumina (Al ₂ O ₃ ) sintered body that has been widely used as a substrate material for ICs has a low thermal conductivity and an insufficient heat dissipation property.
It is becoming difficult to cope with an increase in the amount of heat generated by the C chip.
An alternative to this alumina sintered body is beryllia (BeO), which has a high thermal conductivity, but beryllia has the drawback of being toxic and difficult to handle.

In addition, in the field of automobiles, in order to improve the engine efficiency, in order to improve the engine efficiency, not only the weight reduction of the vehicle body but also the weight reduction and the efficiency improvement of the engine system are pursued in order to protect the global environment. Particularly in a portion where high heat is generated, a material that is lightweight, has high heat resistance and high strength, and has high thermal conductivity is required. As such a material, a conventional metal material can no longer be used, and a ceramic material has been studied. However, no conventional ceramics have been found that can satisfy both strength and thermal conductivity at the same time.

On the other hand, aluminum nitride (AlN) originally has a high thermal conductivity and a high insulating property as a material, has no toxicity, and has abundant resources. From this, if the aluminum nitride sintered body can be obtained at a low cost, the above-mentioned required characteristics can be satisfied, and therefore many researches and developments have been made for a long time to put it into practical use.

Aluminum nitride (AlN) has a strong covalent bond, and it is difficult to densify aluminum alone. Therefore, a sintering aid is added in the sintering step.
For example, as disclosed in JP-A-60-71575, aluminum nitride is prepared by using a compound of one or more metals selected from the group consisting of alkaline earth metals, yttrium and lanthanum group metals as a sintering aid. The sintered body is densified.

On the other hand, research and development of aluminum nitride powder as a raw material powder for an aluminum nitride sintered body have also been conducted. As a raw material powder for obtaining an aluminum nitride sintered body having high thermal conductivity, various methods for obtaining high-purity aluminum nitride powder have been proposed. For example,
JP-A-59-50008 discloses that the average particle size is 2 μm.
Hereafter, an aluminum nitride powder having an oxygen content of 1.5% by weight or less and a cation impurity of 0.3% by weight or less has been proposed. This aluminum nitride powder is obtained by reducing high-purity alumina (Al ₂ O ₃ ) with carbon. Further, JP-A-62-17161 discloses a method for producing aluminum nitride powder by nitriding metallic aluminum. Furthermore, JP-A-63
No. 8206 discloses a method of obtaining an aluminum nitride powder by heating an aluminate of a guanidine compound in an inert gas or a reducing gas.

It is known that a high-purity aluminum nitride powder is produced by using the above method, and an aluminum nitride sintered body obtained by using the powder has a light-transmitting property and exhibits a high thermal conductivity. ing. On the other hand, when the aluminum nitride sintered body is used for an IC package or the like, there is a problem that the IC malfunctions due to the transmission of ultraviolet rays through the package.

As a countermeasure, various studies have been attempted for obtaining a colored aluminum nitride sintered body. The inventors of the present application, by adding a transition metal element to the high-purity aluminum nitride powder obtained by the above method in JP-A-2-124772, sinter aluminum nitride having high thermal conductivity and light-shielding properties. It shows that the body can be obtained. According to this publication, a method is used in which oxides, nitrides, etc. of transition metals are added to and mixed with aluminum nitride powder, followed by sintering.

[0009]

However, when the aluminum nitride powder and the compound powder of the oxide or nitride of the transition metal are mixed, the compound powder of the transition metal has a particle size of about 1 μm, Coarse grain and non-uniform distribution. Therefore, the desired light-shielding property could not be obtained in the aluminum nitride sintered body obtained by sintering the mixed powder. Further, since the compound of the transition metal is unevenly distributed, there is a problem that the withstand voltage of the aluminum nitride sintered body is lowered. further,
In order to increase the thermal conductivity, there is a problem in that, when the particles are sintered in a high temperature region for a long time, grain growth is accompanied, and the bending strength is lowered.

Therefore, an object of the present invention is to provide an aluminum nitride powder as a raw material powder for an aluminum nitride sintered body, which is capable of simultaneously satisfying high thermal conductivity, light shielding property and strength, and a method for producing the same. That is.

[0011]

The aluminum nitride powder according to the present invention comprises aluminum nitride particles with Ti, Z
r, Hf, V, Nb, Ta, Mo, W, Fe, Co, N
It contains compound particles of at least one element selected from the group consisting of i, Cu, Ag, Au, Pt, Pd, B, Al, Si and Mg. Preferably, the aluminum nitride particles have an average particle size of 2.0 μm or less. The content of the above elements is preferably 0.01% by weight or more and 30% by weight or less.

According to the method for producing an aluminum nitride powder according to one aspect of the present invention, Ti, Zr, Hf,
V, Nb, Ta, Mo, W, Fe, Co, Ni, Cu,
Aluminum nitride powder is dispersed in an organic solvent in which an organic compound of at least one element selected from the group consisting of Ag, Au, Pt, Pd, B, Al, Si and Mg is dissolved. By separating and recovering this organic solvent, aluminum nitride powder in which compound particles of the above elements are contained in aluminum nitride particles can be obtained. Preferably, this step is performed by heating in an atmosphere containing nitrogen gas in a temperature range equal to or lower than the sintering temperature.

[0013]

The function of the aluminum nitride powder in the present invention is to first nitrid metal aluminum, alumina (Al ₂ O ₃ )
It is obtained by a method such as the reduction nitriding of the above, heating of an aluminate of a guanidine compound, or the like. At least 1 selected from the group consisting of the above elements is added to each particle of this aluminum nitride powder.
Synthesized to contain compound particles of seed elements.

The method for synthesizing the aluminum nitride powder is not particularly limited, but an aluminum nitride sintered body having a high thermal conductivity can be obtained when the nitriding reaction rate (the number of atoms of bonded N to Al atoms) is as high as possible. Therefore, aluminum nitride having a high nitriding reaction rate is used. It is preferable to use one having a bonding rate of N to Al of 95% or more. The aluminum nitride particles preferably have a fine particle size, and particularly preferably have an average particle size of 2 μm or less.
More preferably, the average particle size is 1 μm or less. The particle size of aluminum nitride is measured by the centrifugal sedimentation method.

Impurities contained in aluminum nitride are small.
It is preferable not to. However, regarding transition metal elements
Must be a solid solution in the aluminum nitride lattice.
For example, even if it is contained up to about 1% by weight, aluminum nitride
Does not cause any deterioration of the characteristics. Raw material
Metallic aluminum and alumina (Al
₂O ₃), A transition metal compound is added to the guanidine compound, etc.
Nitriding containing transition metal compound particles by adding
Aluminum particles can be synthesized. At this time
Elements other than transition metals, especially in the aluminum nitride lattice
Add a small amount of elements (oxygen, carbon, silicon, etc.) that form a solid solution with
Comb and aluminum nitride powder synthesis conditions can be optimized.
And are required. Odor of aluminum nitride powder
The content of the above elements is 0.01 to 30% by weight.
Is preferred. The existence form of the compound of the above element is nitrogen.
Compound particles of the above elements on the surface of the aluminum fluoride particles
It may be dispersed. The content of the above elements is 0.01 weight
%, Use the synthesized aluminum nitride powder
To the light-shielding property of the aluminum nitride sintered body obtained by
Is small. Further, the content of the above elements exceeds 30% by weight.
And obtained using the synthesized aluminum nitride powder
The thermal conductivity of the obtained aluminum nitride sintered body is lowered.

As a method for synthesizing aluminum nitride powder, for example, when the element contained in the aluminum nitride particles is titanium (Ti), organic titanate (tetraisoprooxytitanium or the like) is used in an organic solvent such as ethanol, benzene or toluene. A method of precipitating titanium compound particles on the surface portion of the aluminum nitride particles by dispersing the raw material aluminum nitride powder in the dissolved and hydrolyzed solution is adopted. Further, a method of coating the surface of the aluminum nitride particles with the particles of the compound of the above element by drying the aluminum nitride powder dispersed in the organic solvent by using a spray drying method or the like is adopted. According to these methods, the particles of the compound of the above element can be dispersed extremely uniformly in the aluminum nitride particles, or the surface of the aluminum nitride particles can be uniformly coated with the particles of the compound of the above element. Even if the content of the above element is about 0.01% by weight, the particles of the compound of the above element can be uniformly dispersed in the aluminum nitride particles, or the surfaces of the aluminum nitride particles can be uniformly coated. Furthermore, after drying, the particles of the compound of the above element can be uniformly dispersed in the aluminum nitride particles by heating the powder in a temperature range equal to or lower than the sintering temperature in an atmosphere containing nitrogen gas.

The aluminum nitride powder of the present invention can be densified by a known method after adding a sintering aid, followed by molding and sintering. The aluminum nitride sintered body obtained thereby has high thermal conductivity, light-shielding properties, and mechanical strength.

[0018]

【Example】

Example 1 An aluminum nitride powder was prepared by using the direct nitriding method.
This aluminum nitride powder has an average particle size of 0.8 μm, an oxygen content of 1.5% by weight, a carbon content of 0.02% by weight, a silicon content of 0.008% by weight, and other impurity contents of 0. It was 0.005% by weight or less. This aluminum nitride powder was used as a raw material, sufficiently dispersed in ethanol in which a transition metal alkoxide was dissolved, and then dried by a spray dryer. As a result, an aluminum nitride powder containing particles of the transition metal compound was obtained. The types of transition metals include Ti, Zr, Hf, V, Nb,
An aluminum nitride powder containing particles of a compound of each element was prepared for each of Ta, Fe, Co, Ni, and Cu. The content of each element was 0.2 to 1.0% by weight.

The aluminum nitride powder thus synthesized was mixed with 1.0% by weight of Y ₂ O ₃ powder and 10% by weight of P.
VB was mixed in a toluene solvent, formed into a sheet, and punched into a size of 50 mm × 50 mm square.
An aluminum nitride sintered body was obtained by sintering each molded body at a temperature of 1800 ° C. in a nitrogen gas atmosphere for 5 hours.

The absorption coefficient, thermoelectric conductivity and bending strength of each aluminum nitride sintered body were measured. In any aluminum nitride sintered body containing a compound of a transition metal, the absorption coefficient is 60 cm ⁻¹ (wavelength 5 μm) or more, and the thermal conductivity is 100.
W / mK or more, bending strength was 40 kg / mm ² or more, and fracture toughness value (KIC) was 3.5 MN / m ^3/2 or more. Example 2 An aluminum nitride powder was prepared as a raw material powder by using a reduction nitriding method of alumina (Al ₂ O ₃ ). This aluminum nitride powder has an average particle size of 1.0 μm, an oxygen content of 1.2% by weight, a carbon content of 0.03% by weight, a silicon content of 0.005% by weight, and a titanium content of 0.3. The content of other impurities was 0.005% by weight or less. This aluminum nitride powder was dispersed in an isopropanol solvent in which a transition metal alkoxide was dissolved. After that, the pH of the solution was adjusted to 4 to 8 at 50 ° C. Hydrolysis was performed by dropping water into this solution. As a result, the transition metal oxide particles could be dispersed on the surface of the aluminum nitride particles. As the transition metal element, Ti, Zr,
Each of V and Cr was used. The content of the transition metal oxide in the aluminum nitride particles was 1.0 to 3.0% by weight. After recovering the used organic solvent by filtration, the powder was dried.

The synthetic aluminum nitride thus obtained
Um powder and Y₂O₃Mix powder with 1.0 wt%
After adding FA as a molding aid, the pressure is 1 ton / cm
²It was press molded with. The temperature of the obtained molded body is 1850 ° C.
Sintering was carried out for 2 hours in a nitrogen stream. Obtained in this way
For each aluminum nitride sintered body, thermal conductivity and bending
The strength and absorption coefficient were measured. Any of aluminum nitride
The sintered body also has a thermal conductivity of 130 W / mK or more and bending strength.
Degree is 45kg / mm²Above, for absorption wavelength of 5 μm
60 cm against light^-1That was all. Also, each transition metal
The element is divided into aluminum nitride particles as nitride particles.
It was recognized that it was scattered. Example 3 Alkyl aluminum to NH₃And N₂In a mixed gas with
By reacting, aluminum nitride as raw material powder
Um powder (gas phase synthetic powder) was prepared. Also, reduction nitriding
Reduced aluminum nitride powder as raw material powder by the method
Prepared. Aluminum nitride powder as vapor-phase synthetic powder
For the powder, the specific surface areas are 1.5, 3.
0, 5.0, 10.0, 20.0, 50.0, 100.
0 (m²/ G) was prepared. Reduced aluminum nitride
The specific surface area of the powders is 2.5,
3.5 (m²/ G) was prepared. In this way
For each prepared aluminum nitride powder, the imide decomposition method
Specific surface area of 12 m ²/ G of Si₃N_FourPowder
4.5 parts by weight and acetylene black 1 part by weight
While sonicating, mix in ethyl alcohol
did. Then, dry each mixed solution with nitrogen gas.
By heating to a temperature of 1500 ° C in an air stream, the average grain
Si with a diameter of 300 nm₃N_FourThe particles are aluminum nitride particles
An aluminum nitride powder dispersed in the child was obtained.

To the composite aluminum nitride powder thus obtained, 1.5 parts by weight of Y ₂ O ₃ and 0.4 parts by weight of CaO were added, and the mixture was molded. Sintered for hours. The transverse rupture strength and the thermal conductivity of each aluminum nitride sintered body thus obtained were measured. As a comparative example, an aluminum nitride powder containing no Si ₃ N ₄ was sintered. These measurement results are shown in Table 1.
Shown in. As is clear from Table 1, both the transverse rupture strength and the thermal conductivity of the aluminum nitride sintered body using the aluminum nitride powder of the present invention are excellent.

[0023]

[Table 1]

[0024]

As described above, according to the present invention, it is possible to provide the raw material powder of the aluminum nitride sintered body which can simultaneously satisfy the high thermal conductivity, the light shielding property and the strength.

Claims (5)

[Claims] 1. Aluminum nitride particles containing Ti, Zr, and H
f, V, Nb, Ta, Mo, W, Fe, Co, Ni, C
u, Ag, Au, Pt, Pd, B, Al, Si and M
An aluminum nitride powder containing compound particles of at least one element selected from the group consisting of g. 2. The aluminum nitride powder according to claim 1, wherein the average particle diameter of the aluminum nitride particles is 2.0 μm or less. 3. The aluminum nitride powder according to claim 1, wherein the content of the element is 0.01% by weight or more and 30% by weight or less. 4. Ti, Zr, Hf, V, Nb, Ta, M
o, W, Fe, Co, Ni, Cu, Ag, Au, Pt,
By dispersing aluminum nitride powder in an organic solvent in which an organic compound of at least one element selected from the group consisting of Pd, B, Al, Si and Mg is dissolved, and separating and recovering the organic solvent And a step of obtaining an aluminum nitride powder containing compound particles of the element in the aluminum nitride particles. 5. The step of obtaining an aluminum nitride powder containing the compound particles of the element in the aluminum nitride particles includes heating in an atmosphere containing nitrogen gas in a temperature range equal to or lower than a sintering temperature. 4. The method for producing the aluminum nitride powder according to item 4.