JPH04317402A - Aluminum nitride power and its production - Google Patents

Abstract

PURPOSE:To provide an aluminum nitride power suitable for forming by doctor blade method and the producing method thereof. CONSTITUTION:This aluminum nitride power features in that it has 1.5-5mum median particle size, contains fine particles of <=1mum particle size by <=15wt.%, <=3.5m<2>/g BET specific surface area, >=1.65g/cm<3> density of a compacted body, 0.5-5wt.% yttrium in terms of yttrim oxide, 70-500ppm sulfur in terms of sulfur atom. The producing method of the aluminum nitride powder features in processes of mixing alumina powder and carbon powder, adding yttrium compd. by 0.5-5wt.% in terms of yttrium to the aluminum nitride powder to be produced, and further adding sulfur by 0.1-1 pts.wt. to 100 pts.wt. of carbon to the mixture.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum nitride powder particularly suitable for forming by a doctor blade method and a method for producing the same.

0002

2. Description of the Related Art As integrated circuits are becoming increasingly faster and more highly integrated, the accompanying increase in the amount of heat generated per unit area of elements has become a major problem. To ensure the normal operation of devices, substrate materials and IC packaging materials with good heat dissipation are required, and aluminum nitride not only has high thermal conductivity, but also has high insulation properties and a coefficient of thermal expansion close to that of silicon. It is attracting attention as a material for substrates and IC packages.

Conventional aluminum nitride powder used for these materials has good sinterability, and the purpose is for the obtained sintered body to exhibit high thermal conductivity. has been developed up to. In many cases, substrates and IC packages, which are actual industrial products, are formed into sheets by the doctor blade method, and are made into products through a sintering process. However, since conventional aluminum nitride powder places emphasis on sinterability and thermal conductivity of the sintered body, it is difficult to say that it is a powder suitable for the doctor blade method, and it is desirable to develop aluminum nitride powder with better formability. It has become rare.

0004

SUMMARY OF THE INVENTION An object of the present invention is to provide an aluminum nitride powder suitable for forming by the doctor blade method and a method for producing the same.

[0005] In order to perform molding by the doctor blade method, it is necessary to disperse aluminum nitride powder in a liquid dispersion medium to prepare a slurry. At this time, a dispersant, binder, and plasticizer are added, and if necessary, a sintering aid is added.

The mixture thus obtained is processed by a ball mill or ultrasonic dispersion method to obtain a slurry in which aluminum nitride powder is uniformly dispersed. The slurry is placed in a doctor blade device, formed into a sheet on a carrier film, and dried to a thickness typically 20 μm.
A sheet-like molded product having a size ranging from m to 2 mm is obtained.

[0007] During molding using the doctor blade method, cracking problems often occur. When a dispersion medium is evaporated from a slurry formed into a sheet on a carrier film to form a solid, and a sheet-like molded product is obtained by peeling the slurry from the carrier film, cracks often occur during the drying process, causing problems. It is thought that volumetric shrinkage occurs due to evaporation of the dispersion medium during drying, and this causes tensile stress to act on the sheet-like molded product, causing cracks to occur.

[0008] Furthermore, the removability of the binder from the sheet-shaped molded product becomes a problem. Binder etc. added for molding,
It is necessary to remove the binder by firing before starting the main firing of the sintering process, and during this binder removal process, it is required that the binder be easily removed and that the residual carbon content be as low as possible.

[0009] The sheet-like molded body becomes a dense sintered body through a sintering process, and the shrinkage rate at this time has a great effect on the precision of the product. That is, if the density of the compact is high, the shrinkage during sintering will be small and a product with good dimensional accuracy will be obtained. Therefore, an aluminum nitride powder that can provide a high compact density is desired.

[0010] As described above, aluminum nitride powder suitable for doctor blade forming is required to have many properties, but no conventional aluminum nitride powder that satisfies all of these conditions has yet been obtained. do not have.

[0011]

[Means for Solving the Problems] In view of the above circumstances, the present inventors investigated aluminum nitride powder suitable for use in doctor blade forming and found that the presence of sulfur improves sinterability. In particular, the present invention was completed based on the discovery that an aluminum nitride powder particularly suitable for doctor blade forming can be obtained by including an yttrium compound and sulfur in the raw material for the nitriding reaction.

That is, the present invention has a central particle size of 1.5 to 5.
μm, the content of fine particles with a particle size of 1 μm or less is 15% by weight or less,
BET specific surface area is 3.5m2/g or less, 1000kg
The green compact density is 1.65 when a pressure of /cm2 is applied.
g/cm3 or more, an aluminum nitride powder characterized by containing 0.5 to 5% by weight of yttrium in terms of yttrium oxide, and 70 to 500 ppm of sulfur as elemental sulfur, and alumina powder and carbon. In the method for producing aluminum nitride powder, the mixture is mixed with powder, the mixture is fired in a nitrogen-containing atmosphere, and after the firing, surplus carbon powder is removed by firing in an oxidizing atmosphere. The compound is contained in an amount of 0.5 to 5% by weight based on the aluminum nitride powder produced in terms of yttrium oxide, and the mixture contains sulfur in an amount of 0.1 to 1% by weight per 100 parts by weight of carbon. Provided is a method for producing aluminum nitride powder, characterized in that aluminum nitride powder contains a certain amount of aluminum nitride powder.

The present invention will be explained in detail below. The center particle size of the aluminum nitride powder of the present invention ranges from 1.5 to 5.
It is μm, more preferably 2 to 3 μm. If the center particle size is less than 1.5 μm, cracks are likely to occur during drying of the sheet-shaped molded body by the doctor blade method, while if the center particle size exceeds 5 μm, sintering becomes difficult.

BET of aluminum nitride powder of the present invention
The specific surface area is preferably 3.5 m2/g or less, more preferably 2.5 m2/g or less. If the BET specific surface area is larger than 3.5 m2/g, it will be difficult to remove the binder and the residual carbon content after binder removal firing will increase. If the carbon content increases, it will have a negative effect on sintering, and the density of the sintered body will decrease. For aluminum nitride powder to have good binder removability, it is necessary that the BET specific surface area is small compared to the particle size. A small BET specific surface area for the same particle size means that there are fewer agglomerated particles and the primary particle shape is spherical, and it means that there are fewer irregularities on the particle surface, so it is adsorbed to the concavities on the particle surface. It is thought that the amount of binder that is difficult to remove is small.

The aluminum nitride powder of the present invention preferably has a content of fine particles having a particle size of 1 μm or less of 15% by weight or less. If a large amount of fine particles are contained, the binder removability will not be good, so it is particularly desirable that the content of fine particles with a particle size of 1 μm or less be small. It is difficult to remove the binder from a sheet-shaped compact made using aluminum nitride powder containing more than 15% by weight of fine particles with a particle size of 1 μm or less, and the residual carbon content after binder removal firing is low. will increase.

The aluminum nitride powder of the present invention preferably has a compact density of 1.65 g/cm 3 or more, more preferably 1.70 g/cm 3 or more. If the green compact density of the aluminum nitride powder used in doctor blade molding is lower than 1.65 g/cm3, there will be many agglomerated particles, making it impossible to obtain a sufficiently high green compact density. Here, the compact density is 1000 kg/cm2
This refers to the density of pellets formed into pellets using a mold at a pressure of

Furthermore, in the aluminum nitride powder,
In order to obtain a dense sintered body with high thermal conductivity, yttrium, which is a sintering aid, must be uniformly contained. The content of yttrium is preferably in the range of 0.5 to 5% by weight in terms of yttrium oxide. Yttrium content converted to yttrium oxide is 0.5
If it is less than % by weight, the effect as a sintering aid is low, leading to a decrease in the density and thermal conductivity of the sintered body.

The aluminum nitride powder of the present invention containing yttrium as a sintering aid must further contain 70 to 500 ppm of sulfur as elemental sulfur. The aluminum nitride powder of the present invention has a relatively large center particle size of 1.5 to 5 μm, so if it does not contain sulfur, it may have problems with sinterability even if it has excellent formability. was there. Therefore, in the present invention, although the mechanism of action is not clear, it has been found that by incorporating sulfur, which has an auxiliary action as a sintering aid, sinterability is improved due to a synergistic effect with yttrium. Ta. If the sulfur content is less than 70 ppm as a sulfur element relative to the aluminum nitride powder, sufficient effects will not be observed, and if it is more than 500 ppm, the amount of sulfur remaining in the sintered body will decrease when the sintered body is produced. This is not preferable because the electrical properties of the sintered body, such as insulation and dielectric loss, tend to deteriorate.

[0019] Also, due to the sulfur content,
It was found that the color unevenness that was commonly seen in sintered bodies was less likely to occur. It is presumed that this is due to the synergistic effect with yttrium, which improves sinterability and increases the density of the sintered body, thereby eliminating color unevenness. Although color unevenness does not directly affect the physical properties of the sintered body, the occurrence of color unevenness is undesirable because it reduces the value as a product.

In the method for producing aluminum nitride powder of the present invention, an yttrium compound, which is a sintering aid for aluminum nitride powder, is added before the nitriding reaction, and grain growth is caused by the effect of the sintering aid during the nitriding reaction. The purpose is to obtain aluminum nitride powder by drying. The amount of yttrium added must be appropriate both during the nitriding reaction and during the sintering of the produced aluminum nitride powder. If the amount of yttrium added is less than 0.5% by weight (calculated as yttrium oxide) of the aluminum nitride powder to be produced, no effect on grain growth can be expected, but if it is more than 5% by weight, grain growth will progress too much. Agglomerated particles tend to increase. Therefore, the amount of yttrium added is preferably 0.5 to 5% by weight in terms of yttrium oxide based on the aluminum nitride powder to be produced.

In the present invention, it is necessary to uniformly mix raw material alumina powder, carbon powder, and yttrium compound. In particular, in order to uniformly add the yttrium compound to the raw material alumina powder, for example, the alumina powder is dispersed in water at a pH of 8 or higher to create a slurry, and an aqueous yttrium nitrate solution is added into the slurry at a pH of 8 or lower. A method was adopted in which an alkaline liquid was added dropwise at the same time to prevent deterioration, causing it to precipitate as yttrium hydroxide. Carbon powder was added to the alumina slurry from which yttrium hydroxide had precipitated, and the mixture was dried and used as a raw material for the nitriding reaction. can.

The sulfur content contained in the carbon powder used at this time has a significant influence on the properties of the aluminum nitride powder produced. Although the mechanism by which sulfur affects the properties of aluminum nitride powder is not clear, sulfur is present in a mixture of alumina powder and carbon powder, which are raw materials, in an amount of 0.2% per 100 parts by weight of carbon powder. 1
It has been found that by containing up to 1 part by weight of sulfur, an aluminum nitride powder suitable for use in doctor blade molding can be obtained.

[0023] If the carbon powder contains sulfur, the carbon powder can be used as is, but the sulfur content is 0.1 parts by weight or less per 100 parts by weight of the carbon powder. When using carbon powder, add simple sulfur or a substance containing sulfur so that the mixture contains 0.1 to 1 part by weight of sulfur per 100 parts by weight of carbon powder. It is necessary.

[0024] The raw material for nitriding reaction obtained in this manner is fired in a nitrogen atmosphere to perform a nitriding reaction, thereby obtaining an aluminum nitride powder suitable for forming a doctor blade. At this time, the nitrogen flow rate and firing temperature affect the nitriding reaction. If the nitrogen flow rate is 2 m3 or more per hour per kg of raw material for nitriding reaction, the aluminum nitride powder of the present invention may not be obtained, although the mechanism is unclear. If the nitrogen flow rate is less than 0.05 m3, the nitriding reaction may not proceed sufficiently, and the center of the alumina powder particles may remain unreacted.

[0025] The nitriding reaction is generally carried out at a temperature range of 1500 to 1800°C, more preferably 1550 to 17°C.
The temperature range is 00°C. At temperatures below 1500°C, the center of the alumina powder particles may remain unreacted.
At temperatures above 1800°C, sintering of the aluminum nitride particles progresses, the number of aggregates increases, the particle size distribution becomes broad, and the green compact density decreases significantly.

[0026] The content of the present invention will be specifically explained below with reference to examples, but the present invention is not limited to the following examples. The characteristics of the powder were measured using the following apparatus and method. Center particle size and content of fine particles with a particle size of 1 μm or less: 3 g of Sedigraph E5000 aluminum nitride powder manufactured by Micromeritics was added to a 0.5% n-butanol solution of Ceramo D-18 manufactured by Daiichi Kogyo Seiyaku Co., Ltd. 40
g was treated with ultrasonic waves for 10 minutes to disperse the particles. For alumina powder, add 3 g of alumina powder to 4 ml of a 0.01 wt% aqueous solution of sodium hexametaphosphate.
Measurements were made by dispersing 7g of the sample by treating it with ultrasonic waves for 10 minutes. BET specific surface area: Micromeritics BET specific surface area measuring device Flowsorb 11 Model 2300 Oxygen amount: Ceramic oxygen nitrogen analyzer EMGA-2800 manufactured by Horiba, Ltd. Standard sample is silicon nitride powder R- manufactured by Japan Ceramics Association 005 was used. Green density: Using a uniaxial molding die with a diameter of 20 mm,
3 g of aluminum nitride powder was molded into a pellet by applying a pressure of 1000 kg/cm2 without adding a binder or the like, and the density was calculated from the dimensions and weight. Carbon content: LECO carbon analyzer WR-
112 Standard sample is LECO steel standard sample Sulfur content in carbon powder and aluminum nitride powder: Phillips X-ray fluorescence analyzer P
The sulfur content in carbon powder containing about 2500 ppm of W1480 type sulfur was determined by wet chemical analysis, and was used as a standard sample for fluorescent X-ray analysis. Further, the sulfur content was calculated by proportional calculation from the pure intensity of the Kα rays of sulfur.

[0027]

【Example】

Example 1 Add Neugen EA- manufactured by Daiichi Kogyo Seiyaku Co., Ltd. to 1500 g of water.
8.3g of 137, SN-DIS manufactured by San Nopco Co., Ltd.
Dissolve 7.5g of PERSANT5468 and 29.4g of polyethylene glycol #1000, and the center particle size is 0.
．． Na2 with a BET specific surface area of 8.2 m2 /g at 4 μm
2000g of alumina powder with O content of 0.21% by weight
was added and dispersed by ultrasonication for 30 minutes. 497 ml of an aqueous yttrium nitrate solution manufactured by Nippon Yttrium Co., Ltd. was added dropwise into the alumina slurry produced. Y in 1000ml of yttrium nitrate aqueous solution
It was adjusted to contain 100g of 2O3. The amount of the yttrium nitrate aqueous solution dropped corresponds to 3% by weight in terms of yttrium oxide based on the produced aluminum nitride powder. Concentrated ammonia water was added dropwise at the same time as the yttrium nitrate aqueous solution was added, and the pH was adjusted to around 9.5.
82.5g of the solution was also dropped at the same time to suppress the increase in viscosity. Approximately 75 g of concentrated ammonia water was required. The thus obtained yttrium hydroxide-precipitated alumina slurry and carbon powder (sulfur content is 0.0% per 100 parts by weight of carbon powder).
26 parts by weight) were mixed for 20 minutes using a vertical granulator manufactured by Fuji Sangyo Co., Ltd., and the resulting mixture was dried at 120° C. for 15 hours to obtain a raw material for nitriding reaction. 400 g of the raw material for the nitriding reaction was placed on a graphite tray to a thickness of 15 mm, and fired at 1660° C. for 8 hours in a nitrogen stream to perform the nitriding reaction. The temperature increase/decrease rate was 2.6°C/min. After the nitriding reaction, the product was fired in air at 700° C. for 2 hours to remove excess carbon powder and obtain aluminum nitride powder. Table 1 shows the properties of the obtained aluminum nitride powder. Further, the oxygen content of the obtained aluminum nitride powder was 1.57% by weight.

Example 2 Aluminum nitride powder was prepared in the same manner as in Example 1 except that carbon powder with a sulfur content of 0.25 parts by weight was used for 100 parts by weight of carbon powder. I got it. Table 1 shows the properties of the obtained aluminum nitride powder.

Example 3 Aluminum nitride powder was prepared in the same manner as in Example 1 except that carbon powder with a sulfur content of 0.32 parts by weight was used for 100 parts by weight of carbon powder. I got it. Table 1 shows the properties of the obtained aluminum nitride powder.

Example 4 Aluminum nitride powder was prepared in the same manner as in Example 1 except that carbon powder with a sulfur content of 0.17 parts by weight was used for 100 parts by weight of carbon powder. I got it. Table 1 shows the properties of the obtained aluminum nitride powder.

Example 5 8.3g of Neugen EA-137 was added to 1800g of water, SN
- Dissolve 7.5g of DISPERSANT 5468 and 29.4g of polyethylene glycol #1000, the center particle size is 0.4μm and the BET specific surface area is 8.2m2 /g
Alumina powder 2 with Na2O content of 0.21% by weight
Further, 4.71 g of sulfur powder (sulfur content: 0.50 parts by weight per 100 parts by weight of carbon powder) was added and dispersed by ultrasonic treatment for 30 minutes. 497 ml of the aqueous yttrium nitrate solution used in Example 1 was dropped into the alumina slurry produced. The amount of the yttrium nitrate aqueous solution to be applied corresponds to 3% by weight in terms of yttrium oxide based on the aluminum nitride powder to be produced. Concentrated ammonia water was added dropwise at the same time as the yttrium nitrate aqueous solution was added to adjust the pH to around 9.5.
．． 5g was added dropwise at the same time to suppress the increase in viscosity. Approximately 75 g of concentrated ammonia water was required. Carbon powder 10% was added to the thus obtained yttrium hydroxide precipitated alumina slurry.
Sulfur content is 0.0005 parts by weight or less per 0 parts by weight (
941 g of carbon powder (no sulfur content detected by fluorescent
The material was dried for several hours to obtain a raw material for nitriding reaction. Using the obtained raw material for nitriding reaction, nitriding reaction and removal of excess carbon powder were carried out in the same manner as in Example 1 to obtain aluminum nitride powder. Table 1 shows the properties of the obtained aluminum nitride powder.

Example 6 The same procedure as in Example 5 was carried out except that the amount of sulfur powder added was 3.76 g (sulfur content was 0.40 parts by weight per 100 parts by weight of carbon powder). An aluminum nitride powder was obtained. Table 1 shows the properties of the obtained aluminum nitride powder.

Example 7 The same procedure as in Example 5 was carried out except that the amount of sulfur powder added was 2.82 g (sulfur content was 0.30 parts by weight per 100 parts by weight of carbon powder). An aluminum nitride powder was obtained. Table 1 shows the properties of the obtained aluminum nitride powder.

Example 8 The same procedure as in Example 5 was carried out except that the amount of sulfur powder added was 1.88 g (sulfur content was 0.20 parts by weight per 100 parts by weight of carbon powder). An aluminum nitride powder was obtained. Table 1 shows the properties of the obtained aluminum nitride powder.

Example 9 In Example 5, instead of adding sulfur when preparing the alumina slurry, 14.3 g of zinc sulfide powder (sulfur content: 0.50 parts by weight per 100 parts by weight of carbon powder) was added. Then, in the same manner as in Example 5, aluminum nitride powder was obtained. Table 1 shows the properties of the obtained aluminum nitride powder.

Example 10 In Example 5, instead of adding sulfur when preparing the alumina slurry, 16.7 g of anhydrous aluminum sulfate powder was added.
(Sulfur content is 0.5 parts by weight per 100 parts by weight of carbon powder)
0 parts by weight) to obtain aluminum nitride powder in the same manner as in Example 5. Table 1 shows the properties of the obtained aluminum nitride powder.

Example 11 In Example 5, sulfur was not added during the preparation of the alumina slurry, and 10.6 g of calcium sulfide powder (the sulfur content was
0.50 parts by weight per 100 parts by weight of Bonn powder,
Aluminum nitride powder was obtained in the same manner as in Example 5. Incidentally, since calcium sulfide powder decomposes slowly in water, it was not added to the alumina slurry, but added to the carbon powder. Table 1 shows the properties of the obtained aluminum nitride powder. Further, the oxygen content of the obtained aluminum nitride powder was 1.47% by weight.

Example 12 The carbon powder used in Example 1 and the carbon powder used in Example 2 (sulfur content: 0.0005 parts by weight or less per 100 parts by weight of carbon powder) were mixed in a ratio of 1:1. By mixing, carbon powder having a sulfur content of 0.13 parts by weight based on 100 parts by weight of carbon powder was prepared, and aluminum nitride powder was obtained in the same manner as in Example 1. Table 1 shows the properties of the obtained aluminum nitride powder. Further, the oxygen content of the obtained aluminum nitride powder was 1.55% by weight.

Example 13 8.3 g of Neugen EA-137 and SN
- Dissolve 7.5g of DISPERSANT 5468 and 29.4g of polyethylene glycol #1000, the center particle size is 0.4μm and the BET specific surface area is 8.2m2 /g
Alumina powder 2 with Na2O content of 0.21% by weight
000g was added and dispersed by ultrasonication for 30 minutes. 162 ml of the aqueous yttrium nitrate solution used in Example 1 was dropped into the alumina slurry produced. The amount of the yttrium nitrate aqueous solution dropped is 1% by weight in terms of yttrium oxide based on the aluminum nitride powder to be produced.
corresponds to Concentrated ammonia water was added dropwise at the same time as the yttrium nitrate aqueous solution was added, and the pH was adjusted to around 9.5.
2.5g was added dropwise at the same time to suppress the increase in viscosity. Approximately 30 g of concentrated ammonia water was required. The thus obtained yttrium hydroxide precipitated alumina slurry and 941 g of the carbon powder used in Example 1 were mixed for 20 minutes using a vertical granulator, and the resulting mixture was
It was dried at 20° C. for 15 hours to obtain a raw material for nitriding reaction. Using the obtained raw material for nitriding reaction, nitriding reaction and removal of excess carbon powder were performed in the same manner as in Example 1 to obtain aluminum nitride powder. Table 1 shows the properties of the obtained aluminum nitride powder. Further, the oxygen content of the obtained aluminum nitride powder was 1.25% by weight.

Example 14 Using the aluminum nitride powder obtained in Example 1,
Aluminum nitride powder containing polyvinyl butyral as a binder and dioctyl phthalate as a plasticizer.
10 parts by weight and 5 parts by weight, respectively, were added to 0 parts by weight, and a mixture of toluene and ethanol at a weight ratio of 6:4 was used as a dispersion medium, and doctor blade molding was performed to obtain a 100 mm piece.
A sheet-like molded body with a width of 100 mm was produced. There was no cracking during drying of the sheet-shaped molded product, and the density of the molded product was 1.74 g/cm.
3, the moldability was good. This sheet-shaped molded product was fired in air at 500° C. for 30 minutes, and the residual carbon content was measured to be 0.096% by weight, indicating that the binder removability was good.

Example 15 The aluminum nitride powders obtained in Examples 1 to 13 were sintered. Dissolve 0.10 g of Ceramo D-18 manufactured by Daiichi Kogyo Seiyaku Co., Ltd. as a dispersant and 0.20 g of acrylic resin as a binder in 40 g of n-butanol, add 20 g of each aluminum nitride powder, and make 250 ml of polyethylene. The mixture was mixed in a ball mill for 4 hours using a wide mouth bottle and 40 plastic balls with an iron core each having a diameter of 15 mm, and then dried. The mixture was heated using a mold for 300 min.
The mixture was press-molded into a pellet having a diameter of 13 mm and a thickness of 10 mm at a pressure of kg/cm2, and further molded using a rubber press at a pressure of 1500 kg/cm2 to produce a molded product. The molded body was held at 1800° C. for 5 hours in a nitrogen atmosphere in a carbon double container to perform atmospheric pressure sintering. After measuring the density of the sintered body, the sintered body was cut and the occurrence of color unevenness was observed. The results are shown in Table 2.

Comparative Example 1 Aluminum nitride powder was obtained in the same manner as in Example 5 except that sulfur was not added. Table 1 shows the properties of the obtained aluminum nitride powder. Further, the oxygen content of the obtained aluminum nitride powder was 2.01% by weight.

Comparative Example 2 Sulfur content was 0.0 with respect to 100 parts by weight of carbon powder.
Aluminum nitride powder was obtained in the same manner as in Example 1 using 8 parts of carbon powder. Table 1 shows the properties of the obtained aluminum nitride powder. Further, the oxygen content of the obtained aluminum nitride powder was 1.56% by weight.

Comparative Example 3 8.3g of Neugen EA-137 was added to 1800g of water, and SN
- Dissolve 7.5g of DISPERSANT 5468 and 29.4g of polyethylene glycol #1000, the center particle size is 0.4μm and the BET specific surface area is 8.2m2 /g
Alumina powder 2 with Na2O content of 0.21% by weight
000g and further added 4.71g of sulfur powder,
Dispersion was performed by ultrasonication for 30 minutes. The amount of sulfur added is 0.50 parts by weight per 100 parts by weight of carbon powder to be mixed later.
Corresponds to parts by weight. Yttrium nitrate was not added to the alumina slurry produced, and the sulfur content was 0.0005 parts by weight or less based on 100 parts by weight of the carbon powder used in Example 5 (no sulfur content was detected by fluorescent X-rays). car
The resulting mixture was mixed with 941 g of Bone powder using a vertical granulator for 20 minutes at 120°C.
It was dried for 5 hours to obtain a raw material for nitriding reaction. Using the obtained raw material for nitriding reaction, nitriding reaction and removal of excess carbon powder were performed in the same manner as in Example 1 to obtain aluminum nitride powder. Table 1 shows the properties of the obtained aluminum nitride powder. Further, the oxygen content of the obtained aluminum nitride powder was 1.10% by weight.

Comparative Example 4 8.3 g of Neugen EA-137 was added to 1800 g of water, and SN
- Dissolve 7.5g of DISPERSANT 5468 and 29.4g of polyethylene glycol #1000, the center particle size is 0.4μm and the BET specific surface area is 8.2m2 /g
Alumina powder 2 with Na2O content of 0.21% by weight
000g was added and dispersed by ultrasonication for 30 minutes. Yttrium nitrate was not added to the alumina slurry produced, and the sulfur content was 0.0005 parts by weight or less based on 100 parts by weight of the carbon powder used in Example 5 (no sulfur content was detected by fluorescent X-rays). 941g of carbon powder
and mixed for 20 minutes using a vertical granulator, and the resulting mixture was dried at 120°C for 15 hours.
A raw material for nitriding reaction was obtained. Using the obtained raw material for nitriding reaction, nitriding reaction and removal of excess carbon powder were performed in the same manner as in Example 1 to obtain aluminum nitride powder. Table 1 shows the properties of the obtained aluminum nitride powder. In addition, the amount of oxygen in the obtained aluminum nitride powder was 1.15% by weight.
Met.

Comparative Example 5 50 g of aluminum nitride powder obtained in Comparative Example 4 and 1 kg of alumina balls with a diameter of 15 mm were added to 1000 ml.
The mixture was placed in a wide-mouthed polyethylene bottle and subjected to dry ball milling for 6 hours. Table 1 shows the properties of the obtained aluminum nitride powder. Further, the oxygen content of the obtained aluminum nitride powder was 1.29% by weight.

Comparative Example 6 Using the aluminum nitride powder obtained in Comparative Example 5, doctor blade molding was performed in the same manner as in Example 14. During drying, cracks occurred at four locations per 50 cm of the sheet-like molded product with a width of 100 mm. The compact density was 1.80 g/cm3. This sheet-shaped molded product was fired in air at 500° C. for 30 minutes, and the residual carbon content was measured to be 0.136% by weight.

Comparative Example 7 A sintered body was produced in the same manner as in Example 15 using the aluminum nitride powder or aluminum nitride powder obtained in Comparative Examples 1 to 5. After measuring the density of the sintered body, the sintered body was cut and the occurrence of color unevenness was observed. The results are shown in Table 2.

[0049]

[Effects of the Invention] The aluminum nitride powder of the present invention is less prone to cracking during sheet drying, has a high density of compacts, provides sheets with excellent binder removability, and has excellent sinterability. It is particularly suitable for doctor blade molding, and is therefore extremely useful industrially.

[0050]

[0051]

Claims (2)

[Claims] Claim 1: The center particle size is 1.5 to 5 μm, the content of fine particles with a particle size of 1 μm or less is 15% by weight or less, and the BET specific surface area is 3
．． 5 m2 /g or less, the green compact density is 1.65 g/cm3 or more when applying a pressure of 1000 kg/cm2,
0.5 to 5 when converting yttrium to yttrium oxide
Contains 70-500pp of sulfur as elemental sulfur.
An aluminum nitride powder characterized by containing m. [Claim 2] Mixing alumina powder and carbon powder,
In the method for producing aluminum nitride powder, the mixture is fired in an atmosphere containing nitrogen, and excess carbon powder after firing is removed by firing in an oxidizing atmosphere. 0.5 to generated aluminum nitride powder
5% by weight of aluminum nitride powder, and 0.1 to 1 part by weight of sulfur per 100 parts by weight of carbon in the mixture.