JP2722533B2 - Aluminum nitride powder and method for producing the same - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to an aluminum nitride powder excellent in formability and sinterability and a method for producing the same.

[Problems to be solved by conventional technology and invention]

Alumina has been used for IC package and substrate materials.However, with high integration, high speed, and high output of LSI etc., the need to efficiently release the heat of the chip to the outside of the system has increased. Also, a material having good heat conductivity and excellent heat dissipation is demanded.

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

Examples of the method for producing aluminum nitride powder include (1) a direct nitriding method in which metallic aluminum powder is heated and nitrided in an atmosphere containing nitrogen, and (2) a mixture of alumina or alumina hydrate and carbon in an atmosphere containing nitrogen. There are known two typical reduction nitriding methods in which heating is carried out at a temperature. The aluminum nitride powder obtained by the former method is a powder having a large tap density and easy to be formed, but contains a relatively large amount of cationic impurities such as iron, and is not always satisfactory for obtaining a sintered body having high thermal conductivity. is not. Therefore, as a powder for obtaining a high thermal conductive substrate, an aluminum nitride powder having a low content of cationic impurities synthesized by a reduction nitriding method is considered to be promising, but has a drawback that the tap density is small and the formability is poor. doing.

In addition, aluminum nitride powder has a problem that it is easily hydrolyzed and requires care in storage and handling. Further, the surface of the aluminum nitride powder is usually oxidized or hydrolyzed and covered with an extremely thin oxide film layer, and a sintered body having high thermal conductivity cannot be obtained by sintering under normal pressure. Accordingly, a sintered body having high thermal conductivity is usually obtained by adding aluminum nitride powder to a compound such as calcium carbonate, strontium carbonate, yttrium oxide and sintering. However, in this method, the surface characteristics of the aluminum nitride powder and these additive compounds do not always match,
There is a problem that it is not easy to uniformly mix and disperse the additive compound.

Further, aluminum nitride powder has a high bulk and a small tap density, it is difficult to disperse in a solvent, and it is difficult to obtain a high compact density at the time of compaction, so that the shrinkage ratio at the time of sintering is large, and the dimensional accuracy is good. There is a problem that it is difficult to obtain a sintered body. In addition, if the mixing and dispersion of the aluminum nitride powder and the additive powder are insufficient and the uniformity is poor, sintering is difficult to proceed uniformly, resulting in uneven shrinkage during sintering and warpage of the sintered body. And anisotropy of shrinkage easily occur.

An object of the present invention is to solve these problems of the conventional aluminum nitride powder, and has a small amount of cationic impurities, a high tap density, excellent hydrolysis resistance, and excellent moldability. An object of the present invention is to provide an easily sinterable aluminum nitride powder having an oily surface and a method for producing the same by a reduction nitriding method.

[Means for solving the problem]

That is, the present invention relates to oxygen obtained by the reduction nitriding method 2.
Aluminum nitride powder containing 0 wt% or less, iron 80 ppm or less, silicon 150 ppm or less, and titanium 30 ppm or less is sintering aid 0.01-10 wt% and dispersant having a lipophilic group 0.05-2.
It has a lipophilic surface obtained by dry contact treatment with 0% by weight in dry air or dry nitrogen gas, and has a tap density of
An object of the present invention is to provide an aluminum nitride powder of 1.0 g / cm ³ or more.

Further, the present invention relates to a method of producing a steel sheet by using 2.0% by weight or less of oxygen, 80 ppm or less of iron, 150 ppm or less of silicon,
pm or less aluminum nitride powder containing sintering aid 0.01
The present invention provides a method for producing an aluminum nitride-based powder, comprising subjecting a dry contact treatment in dry air or dry nitrogen gas to 0.05 to 2.0% by weight of a dispersant having a lipophilic group in an amount of 0.05 to 2.0% by weight.

Hereinafter, the aluminum nitride powder of the present invention will be described in detail.

The production method of the aluminum nitride powder is not particularly limited, but a powder obtained by a reduction nitridation method is preferable. Further, in order to stably obtain a sintered body having a higher thermal conductivity, a powder containing no more than a certain limit of impurities is required. Specifically, oxygen 2.0% by weight or less, iron 100ppm or less, silicon 200ppm or less, and It is desirable to control titanium to 50 ppm or less.

The lipophilicity of the aluminum nitride powder is given by attaching a lipophilic group to its surface. The details of the method of attaching the lipophilic group to the surface of the aluminum nitride powder will be described later, but the wet or dry contact treatment of the aluminum nitride powder with 0.01 to 10% by weight of a sintering aid and a dispersant having a lipophilic group is performed. Can be provided. By providing a lipophilic group on the surface, the water resistance and hydrolysis resistance of the aluminum nitride powder are significantly improved.

Furthermore, the tap density of the aluminum nitride powder is set at 1.0 g.
By setting the ratio to / cm ³ or more, a compact having a high compact density is easily obtained, and as a result, a shrinkage ratio during sintering is reduced, and a sintered body with good dimensional accuracy is easily obtained.

 Next, the production method of the present invention will be described in detail.

In the present invention, first, a mixture of alumina powder and carbon powder is reacted at 1500 to 1700 ° C. for 2 to 10 hours in an atmosphere containing nitrogen by a reduction nitridation method to synthesize aluminum nitride powder.

The raw material alumina powder includes those manufactured by the Bayer method, which are manufactured and sold in large quantities, and those having a center particle size of 5 μm or less, preferably 3 μm or less, manufactured by various methods, It is preferable to use alumina powder having a low content of metal impurities such as silicon and titanium which are difficult to volatilize during the reductive nitridation reaction.

Further, it is preferable to use a raw carbon powder having a purity as high as possible and a fine powder. More preferably, a carbon powder having a primary particle diameter of 1 μm or less and an ash content of 0.3% by weight or less is used. Examples of such carbon powder include acetylene black, channel black, furnace black and the like. Among them, acetylene black is preferable in terms of higher purity. If it is easy to disperse from the viewpoint of handling, it is advantageous to use a granular material granulated to 0.3 to 1.5 mm or a powdered material obtained by pressing.

As a method for mixing and dispersing the alumina powder and the carbon powder, a general method such as an ultrasonic dispersion method or various mixers such as a ball mill and a vertical granulator can be used. In addition, it is desirable to use components made of a material that does not allow metal impurities to be mixed in the components of the apparatus that come into direct contact with these raw materials. As such a material, it is desirable to use a synthetic resin such as polyethylene, nylon, urethane or the like, a natural or synthetic rubber, a material made of alumina or aluminum nitride, or a material lined or coated with these materials.

As a method for drying the mixture, ordinary industrial methods can be used.However, when the slurry viscosity during mixing is low and separation of alumina powder and carbon powder may occur during drying, spray drying, freeze drying, rotary It is preferable to use a method such as an evaporator. Further, if necessary, the particles can be granulated into particles having a size of about 20 μm to 3 mm together with mixing and drying, and the granulation has an advantage that subsequent handling becomes easier.

In order to easily complete the reductive nitridation reaction, carbon powder having a reaction equivalent or more to alumina powder is usually used.
The mixing ratio of the alumina powder and the carbon powder is preferably in the range of 3 to 10 in terms of the molar ratio of carbon / alumina. More preferably, the molar ratio of carbon / alumina is 3.2-7. When the molar ratio is less than 3, unreacted alumina remains, while when it is greater than 10, it becomes difficult to remove carbon in a subsequent step, and it is not economically preferable. Therefore, the reaction product obtained by the reduction nitriding reaction is usually a mixture of aluminum nitride powder and excess carbon powder, which is heated to 600 to 750 ° C in air or dry air to burn off excess carbon. To obtain aluminum nitride powder.

The aluminum nitride powder obtained in such a process is a powder containing a small amount of agglomerated particles and having a low tap density.

The present invention provides dry contact treatment by adding 0.01 to 10% by weight of a sintering aid to the aluminum nitride powder obtained by the above reduction nitridation reaction, and further adding 0.05 to 2.0% by weight of a dispersant having a lipophilic group. The sintering aid contains 0.5 to 10% by weight and has a lipophilic surface having a tap density of 1.0 g / cm ³
An object of the present invention is to provide a method for producing the above aluminum nitride powder.

The aluminum nitride powder used in the present invention is obtained by the above reductive nitridation reaction. From the viewpoint of obtaining a sintered body having higher thermal conductivity, oxygen 2.0% by weight or less, iron 80p
It is preferable to use an aluminum nitride powder containing pm or less, silicon 150 ppm or less, and titanium 30 ppm or less.

The sintering aid is not particularly limited as long as it is a compound proposed so far. Preferred sintering aids include one or more compounds selected from alkaline earth metal, yttrium and rare earth metal compounds. More preferred sintering aids include one or more compounds selected from calcium carbonate, strontium carbonate, and yttrium oxide. Its content is suitably in the range of 0.01 to 10% by weight. If the content is less than 0.01% by weight, the effect cannot be seen in improving the sinterability and the thermal conductivity of the sintered body. On the other hand, when the content is 10% by weight or more, even though improvement in sinterability is recognized, a large amount of these sintering aid components remain in the sintered body, and a sintered body with high thermal conductivity cannot be obtained. The particle size of the sintering aid is preferably 3 μm or less.

Examples of the dispersant having a lipophilic group include C ₁₀ -C ₁₈ higher fatty acids such as decanoic acid, dodecanoic acid and oleic acid, and salts thereof (where the salt of the acid is ammonium, Na, K, Mg, Ca, Sr, Al refers to salts of Y hereinafter the same):. decyl sulfate, C ₁₀ -C ₁₈ higher alcohol sulfate ester salts such as dodecylsulfate: alkyl group C ₁₀ -C _18, such as dodecylbenzenesulfonic acid,
An alkyl group having an aryl group of C ₆ or C ₁₂ , an alkylaryl sulfonate salt such as di-2-ethylhexyl sulfosuccinate; and an alkyl group having a C _{4 to} C ₁₂ dialkyl sulfosuccinate: an alkyl such as polyoxyethylene decyl ether sulfate group C ₁₀ -C _18, polyoxyethylene alkyl ether sulfate salts of ethylene oxide addition mole number 7-13:
Higher alcohols C ₁₀ -C ₁₈ polyoxyethylene decyl ether, polyoxyethylene higher alcohol ethers of ethylene oxide addition mole number 7-13: alkyl groups such as polyoxyethylene octylphenol ether C ₈
-C ₁₈ , polyoxyethylene alkyl phenol ether having ethylene oxide addition mole number of 7 to 13: sorbitan higher fatty acid ester of C ₁₀ -C ₁₈ higher fatty acid such as sorbitan decanate, sorbitan oleate: polyoxyethylene sorbitan decanate, polyoxyethylene C ₁₀ -C ₁₈ higher fatty acids such as sorbitan oleate, polyoxyethylene sorbitan higher fatty acid esters of ethylene oxide addition mole number 7-13: such as polyoxyethylene deca sulphonate
C ₁₀ -C ₁₈ higher fatty acids, ethylene oxide addition mole number 7
13 polyoxyethylene higher fatty acid esters of: dodecanoic acid glyceride, glyceride octadecanoic acid, glyceryl higher fatty acid ester of C ₁₀ -C ₁₈ higher fatty acids such as glyceride oleate: higher alkyl groups such as decyl amine acetate is C ₁₀ -C ₁₈ alkylamine acetates: alkyl polyoxyethylene decyl amine is C ₁₀ -C _18,
Polyoxyethylene alkylamine ethylene oxide addition mole number 7-13: phosphoric acid esters of C ₁₀ -C ₁₈ higher fatty acids such as lecithin: selected from acetoalkoxyaluminum diisopropylate group consisting organoaluminum coupling agent 1 Alternatively, two or more compounds can be used. These dispersants having a lipophilic group can be used as they are, or dissolved or dispersed in an appropriate solvent.

The addition amount varies depending on the surface area of the aluminum nitride powder used and the nature of the dispersant having a lipophilic group, but is suitably in the range of 0.05 to 2.0% by weight. Addition amount
If less than 0.05% by weight, almost no lipophilic effect is seen,
If the content is more than 2.0% by weight, the surface becomes sticky, which is not economically preferable.

As a method for imparting a lipophilic group, a dry contact treatment method in which a dispersant having a lipophilic group or a solution thereof is added to aluminum nitride powder and a sintering aid, and the mixture is mixed and ground by a ball mill or the like, may be selected. Appropriate. After dispersing the aluminum nitride powder and the sintering aid in a solution of the dispersant having a lipophilic group, the lipophilic group can be imparted by using a wet contact treatment method in which the lipophilic group is dried. It is necessary and not always economically appropriate, and it is difficult to obtain a powder having a large tap density. As the dry contact treatment method, other than a ball mill, an apparatus generally used for crushing and pulverizing a powder such as a vibration mill and a jet mill can be used. However, aluminum nitride powder is easily hydrolyzed and may be hydrolyzed in the course of dry contact treatment. Therefore, the operation of the dry contact treatment is preferably performed in dry air or dry nitrogen gas in the shortest possible time. Furthermore, depending on the material of the pulverizer and the pulverizing medium, contamination by metal impurities such as iron and silicon may occur. Therefore, it is preferable to use a material lined or coated with aluminum nitride, alumina, plastic, rubber, or the like. preferable.

〔The invention's effect〕

In the present invention, since the contact treatment is carried out with the dispersant in the presence of the aluminum nitride powder and the dry sintering aid, an aluminum nitride-based powder with good dispersion of the aluminum nitride powder and the sintering aid can be obtained.

Further, the aluminum nitride-based powder obtained in the present invention is an easily sinterable aluminum nitride-based powder having a lipophilic surface having a high tap density, containing almost no agglomerated particles, a high hydrolysis resistance, and excellent moldability, By using this, it is possible to reduce the shrinkage ratio during sintering, and it is possible to easily obtain a sintered body having high density and excellent thermal conductivity containing almost no pores,
It is useful as a raw material for producing an aluminum nitride sintered body having excellent thermal conductivity.

〔Example〕

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

Example 1 Purity 99.9%, center particle size 0.7 μm according to Cedigraph,
306g of 80% low soda alumina powder of 1% or less and ash content of 0.00
216 g of a 5% acetylene black 100% pressed product, and a nonionic surfactant composed of aluminum nitrate [Al (NO ₃ ) ₃ .9H ₂ O] 11.3 g, polyethylene glycol 5.2 g and polyoxyethylene alkyl phenyl ether 2600 g of ion-exchanged water, in which 15.1 g of Neugen EA137 manufactured by Industrial Chemicals Co., Ltd. were dissolved, was put into a polyethylene pot together with 600 nylon balls having a diameter of 15 mm, and 10 rpm was rotated at 40 rpm.
Wet mixing was performed for hours.

After drying the thus obtained mixed slurry in a dryer, 500 g of the mixed slurry was collected on a graphite tray,
The mixture was heated at 1580 ° C. for 7 hours while flowing a nitrogen gas at a speed of 200 cm / min. Using an electric furnace to perform a reductive nitridation reaction. Then, the reaction product was heated in dry air at 700 ° C. for 3 hours to burn off excess carbon to obtain aluminum nitride powder (a).

Table 1 shows the physical properties of this aluminum nitride powder.
This aluminum nitride powder was a high-purity fine powder having relatively few agglomerated particles.

The measurement of oxygen was performed by impulse heating-infrared absorption method (LECO TC-436 oxygen-nitrogen simultaneous analyzer), and the measurement of metal ions was performed by ICP emission spectroscopy (Cantlet GQM, Shimadzu Corporation)
-75), particle size distribution is measured by a Sedigraph (Micromeritic
The measurement of bulk density and tap density was carried out based on JIS H-1902. The same measurement was performed for each of the following Examples and Comparative Examples.

Next, 150 g of this powder, 2 g of calcium carbonate powder and 4.5 g of yttrium oxide powder as sintering aids were placed in a 2 polyethylene pot and placed in a 15 mm diameter alumina ball 2.
After adding 5 kg and 1.5 g of oleic acid as a dispersant having a lipophilic group, the inside of the pot was sufficiently replaced with dry air, and then a dry ball mill was performed at a rotation speed of 60 rpm for 3 hours. Table 2 shows the physical properties of the obtained powder. This powder was a fine powder having a sharp particle size distribution with almost no aggregated particles. Also, this powder did not adapt to water at all. Therefore, the hydrolyzability of the nonionic surfactant (Twin 60 manufactured by Hanoi Chemical Co., Ltd.) was investigated by dispersing it in an aqueous solution. The pH value of the aqueous solution was 6.1, even after immersion for 90 days. The hydrolysis resistance was remarkably improved without change.

A compact obtained by press-molding this powder at 1500 kg / cm ² was embedded in a mixed powder of aluminum nitride and boron nitride, and sintered at 1900 ° C. for 3 hours at normal pressure in a nitrogen atmosphere.
The relative density of the compact is as large as 58.5%, and the shrinkage during sintering is
The value was as small as 16%. The obtained sintered body had no pores, and its thermal conductivity was as high as 200 W / mK.

The measurement of the thermal conductivity was performed based on the laser flash method (Vacuum Riko TC-7000). The same applies to the measurements in the following Examples and Comparative Examples.

Example 2 As an alumina raw material, the purity was 99.7%, the central particle diameter was 0.6 μm,
A reduction nitridation reaction was carried out in the same manner as in Example 1 except that a normal alumina powder of 1% or less and 80% by a Bayer method was used to obtain a reaction product comprising an aluminum nitride powder and a carbon powder. Then, the reaction product was heated in dry air at 700 ° C. for 3 hours to burn off excess carbon to obtain aluminum nitride powder (b).

Table 1 shows the physical properties of this aluminum nitride powder.
This powder was a high-purity fine powder having relatively few agglomerated particles.

This powder was subjected to dry contact treatment with a ball mill together with a sintering aid and a lipophilic group-containing dispersant in the same manner as in Example 1. Table 2 shows the physical properties of the obtained powder. This powder was a fine powder having a sharp particle size distribution with almost no aggregated particles. Further, this powder was not completely compatible with water, and was dispersed in an aqueous solution containing the same surfactant as in Example 1 to examine its hydrolyzability.
The value was not changed from the initial value of 5.9, and the hydrolysis resistance was remarkably improved.

When the obtained powder was molded and sintered in the same manner as in Example 1, the relative density of the molded body was as large as 59%, and the shrinkage during sintering was as small as 16%. The thermal conductivity of this sintered body showed a high value of 205 W / mK.

Comparative Example Purity 99.9%, center particle size 0.8 μm by Cedigraph,
306 g of low soda alumina powder of 78% or less with 1 μm or less and ash content of 0.00
216 g of a 5% acetylene black 100% pressed product, and a nonionic surfactant composed of aluminum nitrate [Al (NO ₃ ) ₃ .9H ₂ O] 11.3 g, polyethylene glycol 5.2 g and polyoxyethylene alkyl phenyl ether 2600 g of ion-exchanged water, in which 15.1 g of Neugen EA137 manufactured by Industrial Chemicals Co., Ltd. were dissolved, was put into a polyethylene pot together with 600 nylon balls having a diameter of 15 mm, and 10 rpm was rotated at 40 rpm.
Wet mixing was performed for hours.

After drying the thus obtained mixed slurry in a dryer, 500 g of the mixed slurry was collected on a graphite tray,
The mixture was heated at 1580 ° C. for 7 hours while flowing nitrogen gas at a rate of 200 cm / min. Using an electric furnace to perform a reductive nitridation reaction. Next, the reaction product was heated in dry air at 700 ° C. for 3 hours to burn off excess carbon to obtain aluminum nitride powder. Table 2 shows various physical properties of the aluminum nitride powder. This powder was a high-purity fine powder having some aggregated particles. Further, this powder was dispersed in an aqueous solution containing the same surfactant as in Example 1 and its hydrolyzability was examined. However, the pH value of the aqueous solution was 5.
It increased from 8 to 10.6 and hydrolysis was easy to occur.

When the obtained powder was molded and sintered in the same manner as in Example 1, the relative density of the molded body was 52%, and the shrinkage during sintering was as large as 20%. The thermal conductivity of the obtained sintered body was 75 W / mK.

Example 3 The aluminum nitride powders (a) and (b) obtained in Example 1 and Example 2 were combined with the sintering aid and the dispersant having a lipophilic group shown in Table 3 in Examples 1 and 2. Dry contact treatment was performed in the same manner.

All of the obtained aluminum nitride-based powders were lipophilic without being compatible with water. Table 3 shows various physical properties of the powder evaluated in the same manner as in Example 1.

Further, 100 g of the aluminum nitride-based powder thus obtained was mixed with an acrylic binder (CB-
1) 1 g was added to 100 ml of an n-butanol solution in which
After mixing and dispersing in a ball mill for 6 hours, dry and dry
Passed through a sieve. A compact obtained by press-molding this powder at 1500 kg / cm ² was embedded in a mixed powder of aluminum nitride and boron nitride, and sintered at 1850 ° C. for 3 hours at normal pressure in a nitrogen atmosphere. Table 3 also shows the properties of each of the compacts and the sintered compacts.

 ──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Hideaki Murakami 5-1 Sokai-cho, Niihama-shi, Ehime Sumitomo Chemical Co., Ltd. (56) References JP-A-63-225507 (JP, A) JP-A Sho 62-241814 (JP, A)

Claims (2)

(57) [Claims] 1. Oxygen 2.0% by weight obtained by a reduction nitriding method
Below, iron 80ppm or less, silicon 150ppm or less and titanium 30ppm
Aluminum nitride powder containing
10% by weight and a dispersant having a lipophilic group 0.05 to 2.0% by weight
Having a lipophilic surface and a tap density of 1.0 g / cm ³ obtained by dry contact treatment in dry air or dry nitrogen gas.
Aluminum nitride powder composed of the above 2. Oxygen 2.0% by weight obtained by a reduction nitriding method
Below, iron 80ppm or less, silicon 150ppm or less and titanium 30ppm
Aluminum nitride powder containing
10% by weight and a dispersant having a lipophilic group 0.05 to 2.0% by weight
For producing aluminum nitride-based powder by dry contact treatment with water and dry air or dry nitrogen gas