JPH05147910A - Aluminum nitride-based powder and its production - Google Patents

Abstract

PURPOSE:To produce aluminum nitride-based powder suitable for compacting by a doctor blade method. CONSTITUTION:This aluminum nitride-based powder has 1.5-5mum main particle diameter, <=15wt.% content of fine particle having <1mum particle diameter and <=3.5m<2>/g BET specific surface area, gives a green compact having >=1.65g/cm<3> density and contains 0.5-10wt.% (expressed in terms of oxide) lanthanoid and 70-500ppm (expressed in terms of element) sulfur.

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 suitable for forming by a doctor blade method and a method for producing the same.

[0002]

2. Description of the Related Art Aluminum nitride has a high thermal conductivity, which is several times to a dozen times higher than that of alumina, so that it is excellent in heat dissipation, has high electrical insulation, and has a thermal expansion coefficient close to that of a silicon chip. .. For this reason, semiconductor chip mounting circuit board materials that are becoming faster, more powerful, more multifunctional, and larger,
It is attracting attention as a packaging material.

The aluminum nitride powder used for these materials must have good sinterability. Therefore, aluminum nitride fine powder has been developed to obtain this good sinterability. Further, since the sintered body obtained from the aluminum nitride powder exhibits high thermal conductivity, it has been highly purified.

Substrates and IC packages, which are actual industrial products, are formed into a sheet by the doctor blade method in most cases, and become a product through a sintering process. However, since conventional aluminum nitride powders place importance on sinterability and the thermal conductivity of the sintered body, it is difficult to say that they are suitable powders for the doctor blade method. Has been desired.

[0005]

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

In order to perform molding by the doctor blade method, aluminum nitride powder is dispersed in a liquid dispersion medium to prepare a slurry. At this time, a dispersant, a binder, a plasticizer, a sintering aid and the like are added.

The mixture thus obtained is dispersed by a ball mill, an ultrasonic dispersion method or the like to obtain a slurry in which the aluminum nitride powder is uniformly dispersed. The slurry is formed into a sheet on a carrier film by a doctor blade device and dried to a thickness of 20 μm to 2 μm.
A sheet-shaped molded product in the range of mm is obtained.

[0008] Here, the problem of cracking often occurs during molding by the doctor blade method. When the sheet-shaped slurry is solidified by evaporating the dispersion medium to obtain a sheet-shaped molded body, cracks often occur in the drying step, which causes a problem. It is considered that the dispersion medium evaporates at the time of drying to cause volume contraction, which causes tensile stress to act on the sheet-shaped molded product to cause cracking.

When the sheet-shaped compact is sintered, it is necessary to remove the binder and the like added for molding before firing before the main firing in the sintering step. In the step of removing the binder and the like, it is required that the removal be easy and the residual carbon content be as small as possible.

The sheet-shaped molded body becomes a dense sintered body through a sintering process, and the shrinkage ratio at this time has a great influence on the accuracy of the product. That is, if the density of the compact is high, the shrinkage during sintering is small, and a product with good dimensional accuracy can be obtained. Therefore, it is desired to develop an aluminum nitride powder capable of obtaining a high compact density.

As described above, many properties are required for the aluminum nitride powder suitable for doctor blade molding, but no conventional aluminum nitride powder satisfying all of these conditions has been obtained yet. ..

[0012]

In view of the above circumstances, the inventors of the present invention have conducted studies on an aluminum nitride powder which is preferably used for doctor blade molding, and as a result, the presence of sulfur improves sinterability, In particular, it has been found that an aluminum nitride powder suitable for doctor blade molding can be obtained by allowing a lanthanoid group metal compound and sulfur to coexist in a raw material for a nitriding reaction, thereby completing the present invention.

That is, the present invention has a central particle size of 1.5 to 5
The content of fine particles with a particle size of 1 μm or less is 15 wt% or less, the BET specific surface area is 3.5 m ² / g or less, the green compact density is 1.65 g / cm ³ or more, and the lanthanoid group element is converted to an oxide. Aluminum nitride powder characterized by containing 0.5 to 10% by weight and 70 to 500 ppm of sulfur as an elemental sulfur, and alumina powder and carbon powder were mixed, and the mixture was mixed with nitrogen. In a method for producing an aluminum nitride powder by firing in an atmosphere containing, and removing excess carbon powder after firing in an oxidizing atmosphere, a lanthanoid group metal in the mixture with respect to the produced aluminum nitride powder. The compound is contained in an amount of 0.5 to 10% by weight in terms of oxide, and sulfur is contained in the mixture in an amount of 0.1 to 1 with respect to 100 parts by weight of carbon.
It is intended to provide a method for producing an aluminum nitride powder characterized by containing parts by weight. Here, the lanthanoid group element refers to an element from lanthanum (La) having an atomic number of 57 to lutetium (Lu) having an atomic number of 71.

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

BET of the aluminum nitride powder of the present invention
The specific surface area is preferably 3.5 m ² / g or less, and 2.5 m ²
/ G or less is more preferable. BET specific surface area is 3.5m
If it is larger than ² / g, it is difficult to remove the binder, and the residual carbon content after the binder removal firing is increased. When the carbon content is high, the sintering is adversely affected and the density of the sintered body becomes low. The aluminum nitride powder having good binder removability needs to have a smaller BET specific surface area than the particle diameter.

The aluminum nitride powder of the present invention preferably contains fine particles having a particle diameter of 1 μm or less in an amount of 15% by weight or less. If the content of the fine particles exceeds 15% by weight, the binder removability becomes poor.

The aluminum nitride powder of the present invention preferably has a green compact density of 1.65 g / cm ³ or more, and 1.70 g.
/ Cm ³ or more is more preferable. When the green compact density of the aluminum nitride powder used for doctor blade molding is lower than 1.65 g / cm ³ , a large number of aggregated particles cannot be obtained and a sufficiently high compact density cannot be obtained. Here, the green compact density is the density of a molded product that is molded into pellets using a mold at a pressure of 1000 kg / cm ² .

In order to obtain a dense sintered body having a high thermal conductivity, the lanthanoid group element, which is a sintering aid, must be uniformly contained in the aluminum nitride powder.
By adding the lanthanoid group metal compound before the nitriding reaction, grain growth is promoted by the effect as a sintering aid during the nitriding reaction, and a desired aluminum nitride powder can be obtained. Here, the content of the lanthanoid group element is preferably 0.5 to 10% by weight in terms of oxide when sintering. It is more preferably in the range of 1 to 5% by weight.

When the content of the lanthanoid group element is less than 0.5% by weight in terms of oxide, the effect as a sintering aid is small and the effect of grain growth cannot be expected. In addition, the density of the sintered body and the thermal conductivity decrease. If it exceeds 10% by weight, the grain growth tends to proceed too much and the agglomerated grains tend to increase. Furthermore, it is not preferable because it causes a decrease in the density and the thermal conductivity of the sintered body.

It is necessary that the aluminum nitride powder containing the lanthanoid group element as a sintering aid further contains 70 to 500 ppm of sulfur as a sulfur element. Since the aluminum nitride powder of the present invention has a relatively large center particle size of 1.5 to 5 μm, if it does not contain sulfur, it has excellent formability but causes a problem in sinterability. Therefore, in the present invention, it was found that the coexistence of sulfur, which has an auxiliary action of a sintering aid, improves the sinterability by a synergistic effect with the lanthanoid group element.

When the sulfur content of the aluminum nitride powder is less than 70 ppm as the elemental sulfur, no sufficient effect of sintering is observed, and when it is more than 500 ppm, the sintered body is prepared. This is not preferable because the amount of residual sulfur increases and the electrical properties of the sintered body such as insulation and dielectric loss deteriorate.

In the present invention, water, a dispersant, a binder and an alumina powder are uniformly dispersed by a known method to obtain an alumina slurry, to which a lanthanoid group compound is added. Next, the carbon powder and sulfur or a compound containing sulfur is added in an amount of 0.1 to 100 parts by weight of carbon.
-1 part by weight was added to form a uniform mixture, which was dried to prepare a nitriding reaction raw material. The nitriding reaction raw material was fired in an atmosphere containing nitrogen, and after firing, excess carbon powder was fired and removed in an oxidizing atmosphere to obtain an aluminum nitride powder.

Here, generally known methods can be used for addition, mixing, drying, firing and the like.

For example, in order to uniformly add the dysprosium compound to the alumina powder, the alumina powder is dispersed in water at a pH of 8 or more to prepare a slurry, in which an aqueous solution of dysprosium nitrate and an alkaline solution are prepared. The solution and dysprosium hydroxide are simultaneously deposited while dropping the solution so that the pH does not drop below 8, and then
This is a method in which carbon powder is added to an alumina slurry in which dysprosium hydroxide is deposited, mixed, and then dried to obtain a raw material for a nitriding reaction. The same method can be used when another lanthanoid group metal compound is used instead of the dysprosium compound.

As the dispersant, ammonium polycarboxylate or a surfactant can be used.

As the binder, polyethylene glycol or polyvinyl alcohol can be used.

As the alumina powder, one having a purity of 99.0% by weight or more and an average particle diameter of 0.2 to 4 μm is used.

The carbon powder has an average particle size of 10
Use those with a thickness of μm or less. Usually, acetylene black or furnace black can be used.

When the carbon powder contains sulfur, the carbon powder can be used as it is.
Sulfur content is 0.1 per 100 parts by weight of carbon powder
When using carbon powder in an amount of less than or equal to parts by weight, sulfur alone or a compound containing sulfur is added so that 0.1 to 1 part by weight of sulfur is contained in the mixture with respect to 100 parts by weight of carbon powder. It is necessary to

As the sulfur-containing compound, sulfates such as aluminum sulfate and ammonium sulfate, and sulfides such as calcium sulfide and zinc sulfide can be used.

As the lanthanoid group metal compound, oxides, nitrates, sulfates, formates and the like can be used.

The raw material for nitriding reaction thus obtained is fired in a nitrogen atmosphere to carry out a nitriding reaction, whereby an aluminum nitride powder suitable for doctor blade molding can be obtained. At this time, the nitrogen flow rate and the firing temperature affect the nitriding reaction. When the nitrogen flow rate is 2 m ³ or more per hour for 1 kg of the nitriding reaction raw material, the aluminum nitride powder of the present invention may not be obtained. Nitrogen flow rate is 0.05m
When it is ³ or less, the nitriding reaction does not proceed sufficiently, and the central part of the alumina powder particles may remain unreacted, which is not preferable.

The nitriding reaction is generally carried out in the temperature range of 1500 to 1800 ° C, more preferably 1550 to 17 ° C.
The temperature range is 00 ° C. At 1500 ° C or lower, the central part of the alumina powder particles may remain unreacted,
If the temperature is 1800 ° C. or higher, the sintering of the aluminum nitride particles proceeds, the number of aggregated particles increases, the particle size distribution becomes broad, and the green compact density is greatly reduced, which is not preferable.

[0034]

INDUSTRIAL APPLICABILITY The aluminum nitride powder of the present invention is less likely to cause cracking during drying of a sheet-shaped compact obtained by doctor blade molding, and a compact having a high density can be obtained. It is useful.

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

The characteristics of the powder were measured by the following devices and methods. [Content of central particle size and fine particles having particle size of 1 μm or less]: SEDIGRAPH E50 manufactured by Micromeritics Co., Ltd.
00 3 g of aluminum nitride powder was added to 0.5% by weight n-butanol solution 4 of Ceramo D-18 manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.
It was dispersed by measuring with 0 g of ultrasonic waves for 10 minutes and measured. About alumina powder, 3g alumina powder
Was measured by dispersing it in 47 g of a 0.01% by weight aqueous solution of sodium hexametaphosphate by ultrasonic treatment for 10 minutes. [BET specific surface area]: Micromeritics BET specific surface area measuring device Flowsorb 11 2300 type [Oxygen amount]: Horiba, Ltd. oxygen nitrogen analysis device in ceramics EMGA-2800 Standard sample is Nihon Ceramics Association nitriding Silicon powder R-005 was used. [Dense powder density]: Using a uniaxial molding die for a diameter of 20 mm, 3 g of aluminum nitride powder without adding a binder or the like to 1000
A pressure of kg / cm ² was applied to form a pellet, and the density was calculated from the size and weight. [Sulfur content in carbon powder and aluminum nitride powder]: Fluorescent X-ray analyzer PW1480 manufactured by Philips
The sulfur content in carbon powder containing about 2500 ppm of sulfur was determined by wet chemical analysis and used as a standard sample for fluorescent X-ray analysis. Further, the sulfur content was calculated from the pure intensity of the Kα ray of sulfur by proportional calculation.

[0037]

【Example】

 Example 1 Neugen EA manufactured by Daiichi Kogyo Seiyaku Co., Ltd. was added to 1900 g of water.
8.3 g of -137, SN-D manufactured by San Nopco Co., Ltd.
7.5 g of ISPERSANT 5468, Wako Pure Chemical Industries
Polyethylene glycol (average molecular weight 10
(00) was dissolved in 29.4 g, and the central particle size was 0.4 μm.
BET specific surface area is 8.2m²Na / g ₂O content is
0.21 wt% alumina powder made by Sumitomo Chemical Co., Ltd.
Add 2000 g of powder (purity 99.7% by weight) for 30 minutes
Alumina slurry is obtained by dispersing by ultrasonic treatment during
It was 80g of concentrated nitric acid, 120g of water, Japanese yttrium stock
Dissolve company-produced dysprosium oxide
What was made into an aqueous solution of rosium was dropped into the alumina slurry.
did. The amount of dysprosium oxide added depends on the amount of nitriding
This corresponds to 3% by weight based on the aluminum powder. nitric acid
Concentrated ammonia water is added at the same time as the dysprosium aqueous solution is dropped.
, To adjust the pH to around 9.5, and
SN-DISPERSANT 5468 also 82.5g at the same time
Was added dropwise to suppress the increase in viscosity. Concentrated ammonia water is about 75
g was required. In addition, 10.1 g of aluminum sulfate (sulfur
Content is 0.30 parts by weight per 100 parts by weight of carbon powder
Part) dissolved in 100 g of water was added. in this way
Dysprosium hydroxide precipitated alumina slurry obtained by
Lee and 100 parts by weight of carbon powder have a sulfur content of
Carbon powder up to 0.0005 parts by weight (acetylene
Rack) 941g and vertical made by Fuji Sangyo Co., Ltd.
The resulting mixture was mixed for 20 minutes using a granulator.
The mixture is dried at 120 ° C. for 15 hours to obtain a nitriding reaction raw material.
Got 400 g of the raw material for nitriding reaction is made of graphite
The tray is charged to a thickness of 15 mm and the nitrogen flow rate is set.
Is 0.38 m / kg / hour for nitriding reaction raw material³of
Nitriding is performed by firing at 1590 ° C for 8 hours in a nitrogen stream.
It was The temperature rising rate was 2.6 ° C./min. After nitriding reaction, air
Bake at 700 ℃ for 2 hours to remove excess carbon powder
Then, the aluminum nitride powder was obtained. The obtained nitride
The properties of the luminium-based powder are shown in Tables 1 and 2.

Example 2 An alumina slurry was obtained in the same manner as in Example 1 except that 1600 g of water was used. 497 ml of an aqueous solution of lanthanum nitrate manufactured by Japan Yttrium Co., Ltd. in the alumina slurry
Was dripped. The lanthanum was adjusted so that 100 g of La ₂ O ₃ was contained in 1000 ml of the lanthanum nitrate aqueous solution. The amount of the lanthanum nitrate aqueous solution added dropwise corresponds to 3% by weight in terms of lanthanum oxide with respect to the produced aluminum nitride powder. Concentrated aqueous ammonia is added at the same time as the aqueous lanthanum nitrate solution is added to adjust the pH to around 9.5. Also, SN-DISPERSANT5468 is 8
2.5 g was added dropwise at the same time to suppress an increase in viscosity. Concentrated ammonia water required about 75 g. Further aluminum sulfate 1
A solution prepared by dissolving 0.1 g (a sulfur content of 0.30 part by weight with respect to 100 parts by weight of carbon powder) in 100 g of water was added. The lanthanum hydroxide-precipitated alumina slurry thus obtained and 941 g of carbon powder (acetylene black) having a sulfur content of 0.0005 parts by weight or less with respect to 100 parts by weight of carbon powder were used for 20 minutes using a vertical granulator. Mix and mix the resulting mixture to 120
It was dried at ℃ for 15 hours to obtain a nitriding reaction raw material. Using the obtained nitriding reaction raw material, a nitriding reaction and removal of excess carbon powder were performed in the same manner as in Example 1 to obtain an aluminum nitride powder. The characteristics of the obtained aluminum nitride powder are shown in Tables 1 and 2.

Reference Example 1 Using the aluminum nitride powder obtained in Example 1,
Triolein manufactured by Wako Pure Chemical Industries, Ltd. as a dispersant, polyvinyl butyral manufactured by Sekisui Chemical Co., Ltd. as a binder, and dioctyl phthalate manufactured by Wako Pure Chemical Industries, Ltd. as a plasticizer are aluminum nitride powders 1
2 parts by weight, 10 parts by weight, and 5 parts by weight were added to 100 parts by weight, and a mixture of toluene and ethanol in a weight ratio of 6: 4 was used as a dispersion medium, and doctor blade molding was performed to form a 100 mm wide sheet. A molded body was produced. There is no cracking when the sheet-shaped compact is dried, and the compact density is 1.
It was as high as 76 g / cm ³ .

Comparative Example 1 A raw material for nitriding reaction was obtained in the same manner as in Example 1 without adding aluminum sulfate. 400 g of the nitriding reaction raw material is placed on a graphite tray and has a thickness of 15 mm.
So that the nitrogen flow rate is 1 kg of raw material for nitriding reaction
A nitriding reaction was carried out by firing at 1660 ° C. for 8 hours in a nitrogen stream of 0.38 m ³ per hour. Temperature rising rate is 2.6
C / min. After the nitriding reaction, firing was performed in air at 700 ° C. for 2 hours to remove excess carbon powder to obtain aluminum nitride powder. The characteristics of the obtained aluminum nitride powder are shown in Tables 1 and 2.

Comparative Example 2 Neugen EA-137 (8.3 g) and SN (SN) were added to 1800 g of water.
Dissolved 7.5 g of DISPERSANT 5468 and 29.4 g of polyethylene glycol (average molecular weight 1000), the central particle size was 0.4 μm and the BET specific surface area was 8.
2000 g of alumina powder having a Na ₂ O content of ₂ m ² / g and a content of Na ₂ O of 0.21% by weight was added, and further 4.71 g of sulfur powder was added.
It was added and dispersed by ultrasonic treatment for 30 minutes to obtain an alumina slurry. The amount of sulfur added corresponds to 0.50 parts by weight with respect to 100 parts by weight of carbon powder to be mixed later. 941 g of carbon powder (acetylene black) having a sulfur content of 0.0005 parts by weight or less based on 100 parts by weight of the alumina slurry and 100 parts by weight of the carbon powder without adding dysprosium nitrate or lanthanum nitrate to the alumina slurry.
Were mixed for 20 minutes using a vertical granulator, and the resulting mixture was dried at 120 ° C. for 15 hours to obtain a raw material for nitriding reaction. Using the obtained nitriding reaction raw material, a nitriding reaction and removal of excess carbon powder were performed in the same manner as in Comparative Example 1 to obtain an aluminum nitride powder. The characteristics of the obtained aluminum nitride powder are shown in Table 1 and Table 2.
Shown in.

Comparative Example 3 Neugen EA-137 (8.3 g) and SN (SN) were added to 1800 g of water.
Dissolved 7.5 g of DISPERSANT 5468 and 29.4 g of polyethylene glycol (average molecular weight 1000), the central particle size was 0.4 μm and the BET specific surface area was 8.
2000 g of alumina powder having a Na ₂ O content of 0.21 wt% at 2 m ² / g was added, and dysprosium nitrate or lanthanum nitrate was not added to the alumina slurry obtained by dispersing by ultrasonic treatment for 30 minutes, The content of sulfur is 0.1 with respect to 100 parts by weight of this alumina slurry and carbon powder.
941 g of carbon powder (acetylene black) of 0005 parts by weight or less was mixed for 20 minutes using a vertical granulator, and the resulting mixture was heated at 120 ° C. for 15 minutes.
It was dried for an hour to obtain a raw material for nitriding reaction. Using the obtained nitriding reaction raw material, a nitriding reaction and removal of excess carbon powder were performed in the same manner as in Comparative Example 1 to obtain an aluminum nitride powder. The characteristics of the obtained aluminum nitride powder are shown in Table 1. And shown in Table 2.

Comparative Example 4 50 g of aluminum nitride powder obtained in Comparative Example 3
And 1000 ml of 1 kg of 15 mmφ alumina ball
It was put in a polyethylene wide-mouthed bottle of No. 3, and ball-milled for 6 hours by a dry method. The characteristics of the obtained aluminum nitride powder are shown in Tables 1 and 2.

Comparative Reference Example 1 Using the aluminum nitride powder obtained in Comparative Example 1, doctor blade molding was performed in the same manner as in Reference Example 1. The compact density was as low as 1.63 g / cm ³ .

Comparative Reference Example 2 Using the aluminum nitride powder obtained in Comparative Example 4, doctor blade molding was performed in the same manner as in Reference Example 1. The density of the molded product was as high as 1.80 g / cm ³ , but the sheet-shaped molded product had four cracks per 50 cm of the sheet-shaped molded product having a width of 100 mm during drying.

[0046]

[Table 1]

[0047]

[Table 2]

Claims (2)

[Claims] 1. A central particle diameter of 1.5 to 5 μm, a content of fine particles having a particle diameter of 1 μm or less is 15% by weight or less, a BET specific surface area is 3.5 m ² / g or less, and a green compact density is 1.65 g. / Cm
³ or more, 0.5 in terms of lanthanoid group elements converted to oxides
10 to 10% by weight, and sulfur as elemental sulfur 70 to 50
Aluminum nitride powder characterized by containing 0 ppm. 2. Alumina powder and carbon powder are mixed,
In a method for producing an aluminum nitride powder by firing the mixture in an atmosphere containing nitrogen and firing and removing excess carbon powder in an oxidizing atmosphere, the mixture is added to the produced aluminum nitride powder. The lanthanoid group metal compound is converted into an oxide in an amount of 0.5 to 10
% By weight and contains sulfur in the mixture.
The method for producing an aluminum nitride powder according to claim 1, wherein 0.1 to 1 part by weight is contained with respect to 00 parts by weight.