JP2006290720A - Aluminum nitride powder, method for producing the same, and use thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To produce an aluminum nitride powder which is turned into a sintered compact even at a temperature of ≤1,600°C, thus preparing an aluminum nitride sintered compact having high density, high thermal conductivity and being suitable for a substrate material. <P>SOLUTION: The aluminum nitride powder is produced by using a vapor-phase reaction apparatus 1. Ammonia gas is introduced through a feeding tube 6 into a reactor 3 which is kept heating at a temperature of 300-500°C by a heating band 2 while being regulated by a flow regulator 4. At the same time, nitrogen gas containing an organic aluminum compound is fed through a feeding tube 7 while being regulated by a flow regulator 5 to obtain an aluminum nitride-agglomerate powder A. The obtained powder is subjected to heat treatment at a temperature of 1,100-1,500°C in a reducing gas atmosphere and/or an inert gas atmosphere to obtain an aluminum nitride-agglomerate powder B. The powder B is subjected to mechanical treatment to obtain the objective aluminum nitride powder which has a primary particle diameter of ≤0.06 μm and a ratio of a secondary particle diameter to the primary one of ≤10, and is sinterable at a temperature of ≤1,600°C. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an aluminum nitride powder and a manufacturing method thereof, and an aluminum nitride sintered body and a manufacturing method thereof.

  In recent years, with the high integration and high output of electronic materials, there is an increasing need for a high heat dissipation (high thermal conductivity) substrate that replaces the alumina substrate used so far. Under such circumstances, a sintered body obtained by adding a sintering aid such as beryllia to silicon carbide, aluminum nitride, etc. and sintering is said to be a material meeting the above needs. In particular, an aluminum nitride sintered body has been attracting the most attention as a highly thermally conductive substrate material because it has characteristics such as low toxicity and high insulation.

  The aluminum nitride sintered body is usually produced by sintering aluminum nitride powder. The physical and chemical properties of the raw material aluminum nitride powder affect the properties (density, thermal conductivity, etc.) that are very important in using the obtained sintered body as a high thermal conductive substrate material. is there. Therefore, various researches have been made on the production method of aluminum nitride powder as a raw material of the sintered body, and various methods have been proposed.

  For example, the method of heating metal aluminum in nitrogen or ammonia atmosphere is mentioned. However, in this method, since the aluminum nitride powder is obtained as a large particle having a large solidification, it cannot be used as it is as a raw material for sintering. Moreover, since the consolidation is remarkably advanced, mechanical crushing is also difficult.

  Moreover, the method of mixing alumina powder and carbon powder, and heating in nitrogen or ammonia atmosphere is mentioned. However, in this method, the particle size and impurity content of the alumina powder, which is the raw material, have a great influence on the characteristics of the aluminum nitride powder produced, so it is essential to use alumina powder with high purity and fine particle size. Incurs an increase in cost.

  Moreover, the method of heat-processing the reaction product of an organoaluminum compound and amines is mentioned. However, in this method, carbon tends to remain in the obtained aluminum nitride powder, and the carbon adversely affects the properties of the finally obtained sintered body.

  Further, there is a method in which aluminum chloride and / or aluminum bromide gas and ammonia gas are reacted in a gas phase. However, in this method, a hydrogen halide gas is generated as a by-product, which corrodes the manufacturing apparatus and requires a processing apparatus for discharging the gas out of the reaction system.

  Furthermore, after mixing an organoaluminum compound such as trialkylaluminum and dialkylaluminum monohydride and ammonia gas at 200 ° C. or less, a gas phase reaction is performed at 600 to 1300 ° C. to produce aluminum nitride powder (for example, , See Patent Document 1).

  However, the aluminum nitride powder obtained by the above-described manufacturing method including the method described in Patent Document 1 has the inherently difficult sintering property of a substance called amylnium nitride, and a firing temperature of about 2000 ° C. is required. Therefore, there is a disadvantage that a special firing furnace is required, manufacturing equipment becomes expensive, and the amount of energy used for manufacturing increases.

For this reason, a method of adding a sintering aid is generally employed for sintering aluminum nitride. This method utilizes the fact that the melting point of the composite oxide of the component and the aluminum contained in the sintering aid is lower than the melting point of aluminum nitride (2000 ° C. or higher). That is, the composite oxide of the sintering aid and aluminum produced during firing melts to form a liquid phase, and mass transfer (sintering phenomenon) proceeds through this liquid phase. Therefore, for example, when Y ₂ O ₃ is used as a sintering aid, 1780 ° C., which is the melting point of the composite oxide of yttrium and aluminum, becomes the lower limit of the sintering temperature.

It has also been reported that the firing temperature of aluminum nitride can be lowered to 1600 ° C. by using LiO ₂ —Y ₂ O ₃ —CaO as a sintering aid (see, for example, Non-Patent Document 1). However, depending on the use of the obtained sintered body, the kind of sintering aid may be limited. Even if a sintering aid is not used or the sintering aid is used, the chemical species is kept within a narrow range. If the sintering temperature can be lowered without limitation, the range of application suitability of the aluminum nitride sintered body is widened, and thus such a technique is desired.

In addition, a material obtained by adding yttrium fluoride (YF ₃ ), which is a low melting point sintering aid, to aluminum nitride ultrafine particles having an average particle size of 0.06 μm converted from a specific surface area at 1500 ° C. in a nitrogen atmosphere. A method of sintering has been proposed (see, for example, Patent Document 2). However, yttrium fluoride is rarely used industrially because it damages the firing furnace during sintering. In addition to yttrium fluoride, alkali metal compounds (such as LiO ₂ ) and fluorides (NaF) are known as auxiliary agents for sintering such aluminum nitride at low temperatures, but the former causes corrosion of electrical wiring. The latter, like yttrium fluoride, is not suitable for industrial use because it damages the firing furnace during sintering.

  On the other hand, those skilled in the art can naturally conceive of reducing the particle diameter in order to increase the sinterability of the inorganic particles. Certainly, the smaller the particle size, the higher the sinterability. On the other hand, the cohesive force increases, so it was difficult to produce an aluminum nitride powder having a primary particle size of submicron or less and little aggregation.

  In view of such a problem, an aluminum nitride coarse powder having an average particle diameter of 1 to 20 μm, an oxygen content of 2% by weight or less, and a metal impurity content excluding aluminum of 0.1% by weight or less is obtained by using a pulverization medium and the It is characterized by dry crushing in a non-oxidizing atmosphere using a crusher in which the part in contact with the coarse powder is formed of one or more selected from high-purity alumina, high-purity aluminum nitride and synthetic resin There has been proposed a method for producing an aluminum nitride powder in which the average particle diameter of primary particles is smaller than 1 μm and can be a sintered body at a firing temperature of 1600 to 1700 ° C. (see, for example, Patent Document 3). However, Patent Document 3 does not specifically describe the characteristics such as the density and thermal conductivity of the aluminum nitride sintered body, and it is unclear whether the sintered body can actually be used suitably as a substrate material. is there. In addition, the crusher used here is very special and expensive, and cannot cope with mass production on an industrial scale.

  As described above, an aluminum nitride sintered body can be obtained even at 1600 ° C. at the laboratory level. However, in order to mass-produce a practical aluminum nitride sintered body on an industrial scale, the prior art requires firing at least about 1800 ° C. Temperature is needed. However, the use of a special firing furnace (an electric furnace such as a carbon resistance furnace) is essential for firing at 1800 ° C., which raises the manufacturing cost of the aluminum nitride sintered body and lowers the production efficiency. Accordingly, there is a demand for an aluminum nitride powder that has sufficient sinterability even in a temperature range below 1600 ° C., which does not require a special firing furnace, and can produce an aluminum nitride sintered body at an industrial scale at low cost.

Japanese Unexamined Patent Publication No. 63-60102 JP-A-6-211577 Japanese Examined Patent Publication No. 6-15404 Ceramics Magazine (32) No. 6 (1997), published by the Ceramic Society of Japan

  An object of the present invention is to provide an aluminum nitride powder suitable for the production of a high-density, high thermal conductivity aluminum nitride sintered body, a method for producing the same, and a method for producing an aluminum nitride sintered body using the aluminum nitride powder. It is.

  As a result of intensive studies to solve the above problems, the present inventor succeeded in obtaining an aluminum nitride powder that can be a sintered body even at a firing temperature of 1600 ° C. or lower, and completed the present invention.

  The present invention is characterized in that the primary particle diameter is 0.06 μm or less, and the ratio of the secondary particle diameter to the primary particle diameter (secondary particle diameter / primary particle diameter) is 10 or less. It is a powder.

  Furthermore, the aluminum nitride powder of the present invention has a primary particle diameter of 0.012 μm to 0.06 μm (0.012 μm or more and 0.06 μm or less), and a ratio between the secondary particle diameter and the primary particle diameter (secondary The particle size / primary particle size is 1 to 10 (1 or more and 10 or less).

  Furthermore, the aluminum nitride powder of the present invention becomes a sintered body having a density of 98% or more of the theoretical density by sintering under normal pressure and at a temperature of 1400 to 1600 ° C. (1400 ° C. or higher and lower than 1600 ° C.). It is characterized by.

  In addition, the present invention is obtained by a synthesis step in which an organoaluminum compound and ammonia are subjected to a gas phase reaction at a temperature of 300 ° C. to 600 ° C. (300 ° C. or more and 600 ° C. or less) to obtain an aluminum nitride aggregated powder A, and the synthesis step. Aluminum nitride agglomerated powder A in a reducing gas atmosphere and / or inert gas atmosphere at a temperature of 1100 ° C. to 1500 ° C. (1100 ° C. or higher and 1500 ° C. or lower) for 1 to 6 hours (1 hour or longer and 6 hours or shorter) A method of producing an aluminum nitride powder, comprising: a crystallization step of heat-treating to obtain an aluminum nitride aggregated powder B; and a mechanical treatment step of subjecting the aluminum nitride aggregated powder B obtained in the crystallization step to a mechanical treatment It is.

Furthermore, the method for producing an aluminum nitride powder of the present invention is characterized in that the specific surface area value of the aluminum nitride aggregated powder B obtained in the crystallization step is 5 m ² / g or more.

  Furthermore, the method for producing an aluminum nitride powder of the present invention is characterized in that in the mechanical treatment step, the aluminum nitride aggregated powder B is subjected to a wet mill crushing process using a small-diameter ball media of 3 mmφ or less.

  Furthermore, the method for producing an aluminum nitride powder according to the present invention is characterized in that in the mechanical treatment step, a sintering aid is added to and mixed with the aggregated powder B before or after the aluminum nitride aggregated powder B is mechanically treated. And

  The present invention also provides an aluminum nitride sintered body characterized by firing at least one selected from the above-mentioned aluminum nitride powder or at least one selected from the above-mentioned aluminum nitride powder and other aluminum nitride powder. It is a manufacturing method.

  Furthermore, the method for producing an aluminum nitride sintered body of the present invention is characterized in that the firing temperature is 1400 to 1600 ° C. (1400 ° C. or higher and 1600 ° C. or lower).

  According to the present invention, a sintered body of aluminum nitride can be obtained without using a sintering aid by firing at a temperature 100 to 200 ° C. lower than 1600 ° C. which is the lowest firing temperature of conventional aluminum nitride. An aluminum nitride powder is obtained. Therefore, it is not necessary to use a special electric furnace such as a carbon resistance furnace, and the amount of energy required for firing aluminum nitride can be reduced, so that a sintered body of aluminum nitride can be manufactured very advantageously industrially. Furthermore, the obtained aluminum nitride sintered body can be used very suitably as, for example, a substrate material.

[Aluminum nitride powder]
The aluminum nitride powder of the present invention has a primary particle size of 0.06 μm or less, preferably 0.012 μm to 0.06 μm. When the primary particle diameter exceeds 0.06 μm, the sinterable temperature may exceed 1600 ° C. Here, the primary particle diameter is a value calculated according to the following formula (1) from the BET specific surface area value of the aluminum nitride powder of the present invention. The BET specific surface area value is measured by a gas adsorption method. Specifically, it is a value measured using, for example, a flow-type specific surface area measuring device (Flow Soap II 2300 type, manufactured by Shimadzu Corporation). In addition, the BET specific surface area value of the aluminum nitride powder of the present invention can be analyzed and measured with high accuracy not only by the measuring apparatus but also by other various measuring methods. Incidentally, the aluminum nitride powder of the present invention, BET specific surface area of ^{30 m} 2 / g or more, preferably 30 to 150 m ² / g. The primary particle diameter is also referred to as “specific surface area converted particle diameter”.
Primary particle diameter (μm) = 6 ÷ [specific surface area value (m ² /g)]÷3.26 (1)

  The aluminum nitride powder of the present invention has a ratio of secondary particle diameter to primary particle diameter (secondary particle diameter / primary particle diameter) of 10 or less, preferably 1-10. When this ratio exceeds 10, low temperature sinterability may be impaired, and a temperature exceeding 1600 ° C. may be required for sintering. Here, the secondary particle diameter (μm) is measured by a laser diffraction method. Specifically, it is a value measured using, for example, a laser diffraction method powder measuring machine (trade name: SALDA2000, manufactured by Shimadzu Corporation).

  Aluminum nitride having such characteristics becomes a sintered body having a density of 98% or more of the theoretical density by sintering at normal pressure and at a temperature of 1400 to 1600 ° C.

[Method for producing aluminum nitride powder]
The aluminum nitride powder of the present invention includes, for example, a synthesis step in which an organoaluminum compound and ammonia are reacted in a gas phase at a temperature of 300 to 600 ° C. to obtain an aluminum nitride agglomerated powder A, and an aluminum nitride agglomerated powder obtained in the synthesis step A crystallization process in which A is heat-treated in a reducing gas atmosphere and / or an inert gas atmosphere at a temperature of 1100 to 1500 ° C. for 1 to 6 hours to obtain aluminum nitride agglomerated powder B, and nitridation obtained in the crystallization process The aluminum agglomerated powder B can be manufactured by a manufacturing method including a mechanical processing step of performing a mechanical processing.

(Synthesis process)
The synthesis step is a step of obtaining aluminum nitride agglomerated powder A by using an organoaluminum compound and ammonia as raw materials and performing a gas phase reaction at 300 to 600 ° C.

  The organoaluminum compound can be used without particular limitation as long as it can exhibit a gaseous state or a liquid state. Among them, trialkylaluminum and dialkylaluminum halides are preferable. More specifically, for example, trimethylaluminum, triethylaluminum, triisobutylaluminum, dimethylaluminum halide, diethylaluminum halide, diisobutylaluminum halide and the like can be mentioned. An organoaluminum compound can be used individually by 1 type, or can use 2 or more types together. These organoaluminum compounds are supplied to the reaction system in gaseous or liquid form. When supplying in a liquid state, the stability of the reaction may be impaired due to the latent heat of vaporization of the compound, so it is preferable to supply in a gaseous state. Examples of the method for supplying in a gaseous state include a method in which an organoaluminum compound is vaporized by heating, a method in which the organoaluminum compound is supplied accompanied with a non-oxidizing gas such as nitrogen, hydrogen, argon, and helium.

  Ammonia can also be supplied to the reaction system in liquid or gaseous form, but is preferably supplied in gaseous form for the same reason as described above.

  The use ratio of the organoaluminum compound and ammonia is not particularly limited, and preferably within the range of 1 mol or more of ammonia with respect to 1 mol of the organoaluminum compound while considering the particle diameter of the obtained aluminum nitride aggregated powder A. What is necessary is just to select suitably.

  When the reaction temperature between the organoaluminum compound and ammonia is less than 300 ° C., the unreacted organoaluminum compound remains in the aluminum nitride aggregated powder A, which may adversely affect the physical properties of the finally obtained sintered body. Moreover, when it exceeds 600 degreeC, the alkyl group derived from an organoaluminum compound will graphitize and may have a bad influence on the physical property of the sintered compact finally obtained.

  As the reactor used for the gas phase reaction in the synthesis step, a known gas phase reaction vessel can be used, and examples thereof include a vertical tubular reactor and a horizontal tubular reactor.

(Crystallization process)
In the crystallization step, the aluminum nitride aggregated powder A obtained in the synthesis step is heat-treated at a temperature of 1100 ° C. to 1500 ° C. for 1 to 6 hours in a reducing gas atmosphere and / or an inert gas atmosphere. This is a step of obtaining B.

  As the reducing gas atmosphere and the inert gas atmosphere, known ones can be used, and among them, an atmosphere in which aluminum nitride is not substantially oxidized is preferable. Specific examples of such an atmosphere include ammonia, hydrogen, carbon monoxide, nitrogen, argon, helium, and the like. These atmospheres can be used alone or in combination of two or more. Here, the “atmosphere that does not substantially oxidize aluminum nitride” means that even if the aluminum nitride aggregated powder A is oxidized, the degree of oxidation is the final product of sintered aluminum nitride. It means an atmosphere that does not adversely affect the physical properties of the body.

  The heat treatment temperature determines the primary particle diameter of the aluminum nitride agglomerated powder B obtained by the heat treatment, and it is preferable to perform the heat treatment at a temperature as low as possible, but the carbon of the aluminum nitride agglomerated powder A obtained by vapor phase synthesis is used. It is necessary to strike a balance with the secondary effect of removing Therefore, in this invention, heat processing temperature shall be 1100-1500 degreeC.

  Also, the heat treatment time is a factor that determines the primary particle size, and when the heat treatment is performed for a long time, the primary particle size becomes too large. When the heat treatment temperature is 1100 to 1500 ° C., aluminum nitride agglomerated powder B having a preferable primary particle size can be obtained by firing for 1 to 6 hours.

The aluminum nitride aggregated powder obtained by the heat treatment preferably has a specific surface area value of 5 m ² / g or more. This eliminates the need for excessive pulverization energy in order to keep the primary particle diameter after mechanical treatment within a suitable range.

(Mechanical processing process)
In the mechanical treatment process, in order to control the dispersibility of the finally obtained aluminum nitride powder, the aluminum nitride agglomerated powder B obtained in the crystallization process is subjected to crushing treatment, and the secondary particle diameter of the aluminum nitride particles produced And the ratio of the primary particle diameter to 10 or less.

  Further, this process has a secondary role of reducing powder aggregation and improving moldability and sinterability.

  Here, for the crushing treatment of the aluminum nitride agglomerated powder B, a crusher conventionally used for crushing inorganic powders can be used, and among them, a wet mill crusher using a small-diameter ball medium of 3 mmφ, preferably 1 mmφ. Is preferred. Moreover, it is preferable to perform the crushing treatment in an inert gas atmosphere so that the oxidation of aluminum nitride does not substantially occur during the crushing. The crushing conditions are appropriately selected according to the characteristics of the aluminum nitride agglomerated powder B, the type of crusher, and the like. When performing the wet crushing treatment, those commonly used in this field can be used as the dispersion medium, and examples thereof include ethanol, isopropanol, and toluene. In the case of wet crushing treatment, the treatment time is not particularly limited, but is preferably about 30 to 300 minutes, more preferably about 45 to 120 minutes.

In this step, a known sintering aid for producing an aluminum nitride sintered body, such as Y ₂ O ₃ , can be added before or after the crushing treatment of the aluminum nitride aggregated powder B. The addition amount is not particularly limited and can be appropriately selected from a wide range according to the particle size distribution or average particle size, purity, physical properties, etc. of the aluminum nitride obtained after the pulverization treatment, but is preferably based on 100 parts by weight of the aluminum nitride aggregated powder B And 0.1 to 10 parts by weight. As a result, not only a decrease in the sinterable temperature but also grain growth of the sintered body is promoted, and as a result, an effect of improving the thermal conductivity of the sintered body is obtained.

  In this step, when wet crushing is performed, a slurry of aluminum nitride powder is obtained. The slurry can be used as it is for the production of a sintered body, or the aluminum nitride powder can be separated from the slurry, dried and used for the production of a sintered body.

  If the aluminum nitride powder obtained in this step is used, an aluminum nitride sintered body that can be suitably used as a substrate material can be obtained at a firing temperature lower than 1600 ° C. without adding a sintering aid.

  The aluminum nitride powder of the present invention exhibits good dispersibility. For example, even when a sintering aid is used in combination, intimate mixing with the sintering aid can be achieved, which has a positive effect on the finally obtained sintered body. Can be given.

  In the present invention, the reason why the aluminum nitride powder having such sinterability is obtained is not sufficiently clear, but is considered as follows. In the present invention, an aluminum nitride powder having a fine primary particle size, a very low degree of aggregation, and a high surface energy is obtained by sequentially performing a gas phase reaction, crystallization, and crushing treatment between an organoaluminum compound and ammonia. It is estimated that It is estimated that the surface energy of the powder pulverized by reducing the particle diameter to the limit is high. In addition, since there are few internal pores in the agglomerates that tend to remain in the sintering process, it is thought that there was no residual pores in the final stage of sintering, and as a result, without using a sintering aid. It is considered that sintering can be performed at a temperature of 1600 ° C. or lower.

(Sintered aluminum nitride)
The aluminum nitride sintered body of the present invention has a density of 98% or more with respect to the theoretical density, and has physical properties such as high density and high thermal conductivity.

  The aluminum nitride sintered body of the present invention is, for example, the aluminum nitride powder of the present invention obtained above or the aluminum nitride powder of the present invention and other aluminum nitride powders (hereinafter referred to as “aluminum nitride powder for sintered body”). Can be obtained by firing at 1400 to 1600 ° C., preferably in an inert atmosphere.

  When the aluminum nitride powder of the present invention and the aluminum nitride powder for a sintered body are used in combination, the aluminum nitride powder of the present invention also exhibits a function as a sintering accelerator. The aluminum nitride powder for the sintered body is not particularly limited, and those manufactured by a known method such as a direct nitridation method or a reduction nitridation method can be used, but sintering characteristics (sinterability at low temperature) can be obtained. In view of improvement of the physical properties (particularly thermal conductivity) of the sintered body, an aluminum nitride powder having an average particle diameter of 1 to 5 μm and an oxygen content of 2% by weight or less is preferable. Here, the amount of the aluminum nitride powder of the present invention used is not particularly limited, and its specific surface area value, ratio (secondary particle diameter / primary particle diameter), particle size distribution or secondary particle diameter, purity, firing temperature, firing time, etc. May be appropriately selected from a wide range according to the various conditions, but preferably 0.1 to 50 parts by weight, more preferably 0.1 to 5 parts by weight with respect to 100 parts by weight of the aluminum nitride powder for a sintered body. is there. Of course, more aluminum nitride powder of the present invention may be used than aluminum nitride powder for sintered bodies.

During firing, a sintering aid may or may not be used. By adding the sintering aid, the low-temperature sinterability, the thermal conductivity of the obtained sintered body, and the like are further improved. As the sintering aid, those commonly used in this field can be used, and examples include oxides, hydroxides and carbonates of rare earth elements and alkaline earth metals. Among these, Y ₂ O ₃ , CaO, CaCO ₃ , La ₂ O ₃ , La (OH) _{3 and the} like are preferable. The sintering aid can be used alone or in combination of two or more. The addition amount of the sintering aid is not particularly limited, and various conditions such as the ratio (secondary particle diameter / primary particle diameter), particle size distribution or secondary particle diameter, purity, firing temperature, firing time of the aluminum nitride powder of the present invention. Accordingly, it may be selected appropriately within a range not impairing the preferred physical properties of the obtained aluminum nitride sintered body.

  As described above, the baking is performed at a temperature of 1400 to 1600 ° C., and is preferably completed in about 3 to 10 hours. When the firing temperature is less than 1400 ° C., the density of the sintered body becomes too low and may not be suitably used as a substrate material. Of course, the sintered body of the present invention can be obtained even at a temperature exceeding 1600 ° C. However, as described above, considering the increase in cost in production on an industrial scale, firing at 1600 ° C. or lower is desirable. Further, the firing is preferably performed in an inert atmosphere. The inert atmosphere is not particularly limited, and examples thereof include nitrogen and argon.

  The aluminum nitride sintered body of the present invention thus obtained can be suitably used as a substrate material, for example. Furthermore, in addition to the substrate material, for example, it can be suitably used for applications such as semiconductor manufacturing apparatus members, insulators, and fillers.

  Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples. Here, the specific surface area was measured using a flow type specific surface area measuring apparatus (Flow Soap II 2300 type, manufactured by Shimadzu Corporation). The secondary particle diameter was measured with a laser diffraction measuring instrument (trade name: SALDA2000, manufactured by Shimadzu Corporation).

  In the following, the value of the primary particle size is a value obtained by rounding off the 4th decimal place of the calculated value, and the ratio of the secondary particle size to the primary particle size (hereinafter referred to as “aggregation degree”) is the decimal point of the calculated value. The value rounded off to the second place.

Example 1
Using the gas phase reaction apparatus 1 shown in FIG. 1, ammonia gas was introduced through the supply pipe 6 while adjusting with the flow rate controller 4 from the lower part of the reactor 3 heated and held at 500 ° C. by the heating zone 2. At the same time, triethylaluminum entrained in nitrogen gas was introduced through the supply pipe 7 while being controlled by the flow rate controller 5. By adjusting the flow rate of the flow rate controllers 4 and 5, the residence time in the reaction gas heating zone (reaction zone) was set to 2 seconds. The molar ratio of ammonia / triethylaluminum was 20.

Aggregated aluminum nitride powder A produced in the reaction zone was taken out together with unreacted gas from the upper part of the reactor 3, separated from the gas by the filter 8, and collected in the collector 9. The collected aluminum nitride agglomerated powder A was placed in a graphite crucible and heat treated at 1300 ° C. for 3 hours while flowing nitrogen gas in an electric furnace to obtain a white fine powder of aluminum nitride agglomerated powder B. The specific surface area of the powder was 10.2 m ² / g, and the oxygen content in the powder measured by an oxygen-nitrogen simultaneous analyzer (trade name: TC436, manufactured by LECO) was 1.1% by weight.

The aluminum nitride agglomerated powder B 100 g was wet-mixed for 1 hour using ethanol as a dispersion medium and using a ball mill (trade name: Super Apex Mill, manufactured by Kotobuki Giken Co., Ltd.) for pulverization treatment. As the crushing media, zirconia balls of 1 mmφ or less were used. The obtained slurry was dried to obtain aluminum nitride powder. The specific surface area of this powder was 70 m ² / g, and the primary particle size calculated from this was 0.026 μm. The secondary particle size was 0.2 μm, and the degree of aggregation was 7.7.

Using the aluminum nitride powder obtained above, it was molded into a 20 mmφ disc at a pressure of about 9.8 × 10 ⁷ Pa (1000 kg / cm ² ), and in a graphite furnace at 1500 ° C. in a nitrogen stream according to a conventional method. Baked for 3 hours. The obtained sintered body was ground to a diameter of 10 mm and a thickness of 3 mm, and the density was measured by the Archimedes method and the thermal conductivity was measured by the laser flash method. The density of the sintered body was 3.22 g / cm ³ , the ratio to the theoretical density was 98.8%, and the thermal conductivity was 75 W / mK.

(Example 2)
The aluminum nitride powder was sintered in the same manner as in Example 1 except that 3 parts by weight of Y ₂ O ₃ was added as a sintering aid to 100 parts by weight of the aluminum nitride powder after the ball milling. The density of the sintered body was 3.29 / cm ³ , the ratio to the theoretical density (value corrected for added Y ₂ O ₃ minutes) was 99.4%, and the thermal conductivity was 110 W / mK.

(Example 3)
The aluminum nitride powder of the present invention was prepared in the same manner as in Example 2 except that the heat treatment temperature of the aluminum nitride agglomerated powder A was 1400 ° C., and 0.5 mmφ zirconia balls were used as the crushing media in the crushing treatment by the ball mill. Synthesized.

The specific surface area of the aluminum nitride aggregated powder after the heat treatment was 8.2 m ² / g. Moreover, the specific surface area of the aluminum nitride powder of the present invention obtained after the crushing treatment was 33 m ² / g, and the primary particle diameter converted from this was 0.056 μm. The secondary particle size was 0.5 μm. From this, the degree of aggregation was 8.9. The density of the obtained sintered body was 3.25, and the ratio to the theoretical density was 98.2%. The thermal conductivity was 113 W / mk.

Example 4
The aluminum nitride powder of the present invention was synthesized in the same manner as in Example 2 except that 3 mmφ zirconia balls were used as the crushing media in the crushing treatment by the ball mill. The specific surface area of the aluminum nitride powder was 31 m ² / g, and the primary particle size calculated from this was 0.059 μm. The secondary particle diameter was 0.3 μm. From this, the degree of aggregation was 5.1. The density of the obtained sintered body was 3.26, and the ratio to the theoretical density was 98.5%. The thermal conductivity was 115 W / mk.

(Comparative Example 1)
An aluminum nitride powder was synthesized in the same manner as in Example 1 except that the heat treatment temperature of the aluminum nitride agglomerated powder A was 1700 ° C. This powder had a specific surface area of 3.0 m ² / g, and the primary particle size converted from this was 0.613 μm. The secondary particle diameter was 0.8 μm, and the degree of aggregation was 1.3. The oxygen content was 0.4% by weight. The density of the sintered body produced using this powder in the same manner as in Example 1 was 2.60 g / cm ³ , which was lower than the theoretical density (3.26).

(Comparative Example 2)
The aluminum nitride agglomerated powder B obtained in the same manner as in Example 1 was pulverized by a ball mill for 40 hours using a resin pot and an iron-cored nylon ball (10 mmφ) using ethanol as a dispersion medium. The specific surface area of the obtained crushed powder was 10.3 m ² / g, and the primary particle diameter converted from this was 0.179 μm. The secondary particle size was 1.2 μm and the degree of aggregation was 6.7. The density of the sintered body produced using this crushed powder in the same manner as in Example 1 was 2.73 g / cm ³ .

(Comparative Example 3)
An aluminum nitride powder was synthesized in the same manner as in Example 1 except that the heat treatment temperature of the aluminum nitride aggregated powder A was 850 ° C. This powder had a specific surface area of 68 m ² / g, and the primary particle size converted from this was 0.027 μm. The secondary particle size was 1.2 μm and the degree of aggregation was 44.4. The amount of oxygen was 1.3% by weight. The density of the sintered body produced using this powder in the same manner as in Example 1 was 2.85 g / cm ³ .

(Comparative Example 4)
Aluminum nitride agglomerated powder (specific surface area 30 m ² / g) and aluminum nitride powder were the same as in Example 1 except that the heat treatment temperature of aluminum nitride agglomerated powder A was 1050 ° C. and the wet crushing time was 15 minutes. Was synthesized. The obtained aluminum nitride powder had a specific surface area of 49 m ² / g, and the primary particle size calculated from this was 0.038 μm. The secondary particle size was 0.56 μm and the degree of aggregation was 14.7. The density of the sintered body produced using this powder was 2.94 g / cm ³ .

(Example 5)
[Preparation of sintered aluminum nitride powder]
Aluminum nitride powder (trade name: MAN-2, average particle size 1.8 μm, Mitsui Chemicals, Inc.
(Product made) To 100 g, 3.53 g of Y ₂ O ₃ and 2.0 g of CaO were added and mixed as a sintering aid to prepare an aluminum nitride powder for a sintered body.

[Production of aluminum nitride sintered body]
To 100 g of the aluminum nitride powder for sintered body obtained above, 1.89 g of the aluminum nitride powder of the present invention obtained in Example 1 was added and mixed, and this mixture was mixed with about 9.8 × 10 ⁷ Pa (1000 kg / It was molded into a 20 mmφ disc with a pressure of cm ² ) and sintered in a graphite furnace at 1600 ° C. for 3 hours in a nitrogen stream. The obtained aluminum nitride sintered body was ground to a diameter of 10 mm and a thickness of 3 mm, and the density was measured by Archimedes method and the thermal conductivity was measured by laser flash method. The density of the sintered body was 3.28 g / cm ³ , and the thermal conductivity was 133 W / m · k.

(Example 6)
An aluminum nitride sintered body was obtained in the same manner as in Example 5 except that the addition amount of the aluminum nitride powder of the present invention was changed to 50 g. The sintered body was ground to a diameter of 10 mm and a thickness of 3 mm, and the density was measured by Archimedes method and the thermal conductivity was measured by laser flash method. The density of the sintered body was 3.28 g / cm ³ and the thermal conductivity was 87 W / m · k.

(Comparative Example 5)
An aluminum nitride sintered body was obtained in the same manner as in Example 5 except that 2.0 g of the aluminum nitride powder obtained in Comparative Example 2 was used instead of 1.89 g of the aluminum nitride powder of the present invention. This sintered body had a density of 2.73 g / cm ³ and a thermal conductivity of 52 W / m · k.

(Comparative Example 6)
An aluminum nitride sintered body was obtained in the same manner as in Example 5 except that 2.0 g of the aluminum nitride powder obtained in Comparative Example 3 was used instead of 1.89 g of the aluminum nitride powder of the present invention. This sintered body had a density of 2.85 g / cm ³ .

(Comparative Example 7)
An aluminum nitride sintered body was obtained in the same manner as in Example 5 except that only the aluminum nitride powder for sintered body of Example 5 was used. This sintered body had a density of 2.78 g / cm ³ and a thermal conductivity of 52 W / m · k.

It is a flowchart which shows roughly the structure of the gas phase reaction reaction apparatus used for manufacture of the aluminum nitride powder of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Gas phase reactor 2 Heating zone 3 Reactor 4,5 Flow controller 6,7 Supply pipe 8 Filter 9 Collector

Claims (9)

  An aluminum nitride powder having a primary particle size of 0.06 μm or less and a ratio of the secondary particle size to the primary particle size (secondary particle size / primary particle size) of 10 or less.   The primary particle diameter is 0.012 μm to 0.06 μm, and the ratio of the secondary particle diameter to the primary particle diameter (secondary particle diameter / primary particle diameter) is 1 to 10. 1. The aluminum nitride powder according to 1.   The aluminum nitride powder according to claim 1 or 2, wherein the sintered body has a density of 98% or more of the theoretical density by sintering at normal pressure and at a temperature of 1400 to 1600 ° C.   A synthesis step for obtaining an aluminum nitride agglomerated powder A by subjecting an organoaluminum compound and ammonia to a gas phase reaction at a temperature of 300 ° C. to 600 ° C., and an aluminum nitride agglomerated powder A obtained in the synthesis step in a reducing gas atmosphere and / or non-reducing gas. A crystallization process in which an aluminum nitride aggregated powder B is obtained by heat treatment in an active gas atmosphere at a temperature of 1100 ° C. to 1500 ° C. for 1 to 6 hours, and an aluminum nitride aggregated powder B obtained in the crystallization process is subjected to mechanical treatment. A method for producing an aluminum nitride powder, comprising a mechanical treatment step. The method for producing an aluminum nitride powder according to claim 4, wherein the specific surface area of the aluminum nitride agglomerated powder B obtained in the crystallization step is 5 m ² / g or more.   5. The method of producing aluminum nitride powder according to claim 4, wherein in the mechanical treatment step, the aluminum nitride aggregated powder B is subjected to a wet mill crushing process using a small-diameter ball medium of 3 mmφ or less.   5. The production of aluminum nitride powder according to claim 4, wherein in the mechanical treatment step, a sintering aid is added to and mixed with the aggregated powder B before or after the aluminum nitride aggregated powder B is mechanically treated. Method.   An aluminum nitride powder comprising firing at least one selected from the aluminum nitride powders of claims 1 to 3 or at least one selected from the aluminum nitride powders of claims 1 to 3 and another aluminum nitride powder. A method for producing a knot.   The method for producing an aluminum nitride sintered body according to claim 8, wherein the firing temperature is 1400 to 1600 ° C.

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