JP2005082460A - Aluminum nitride grain, method of manufacturing the same and utilization - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an aluminum nitride (AlN) grain capable of being sintered into aluminum nitride sintered powder and a aluminum nitride sintered compact at a remarkably low temperature compared to a conventional method and a method of manufacturing the same. <P>SOLUTION: The aluminum nitride grain is prepared by incorporating a colloidal silica dispersion in aluminum nitride powder and the content of silicon dioxide originating in colloidal silica is 1-10 wt.% to aluminum nitride powder. The method of manufacturing aluminum nitride is carried out by spray-drying slurry containing the colloidal silica dispersion and the aluminum nitride powder. The aluminum nitride powder is obtained by firing the aluminum nitride grain and the aluminum nitride sintered compact is obtained by molding the aluminum nitride grain with a dry press and firing. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an aluminum nitride granule, an aluminum nitride sintered powder obtained therefrom, a method for producing an aluminum nitride sintered body by a dry press method, and an application.

  A ceramic substrate or a heat-dissipating resin sheet is used for the heat generation of the LSI IC chip, and an alumina substrate or a heat-dissipating sheet containing alumina is used.

  However, with the recent dramatic increase in LSI integration, the amount of heat generated by the IC chip increases, and the conventionally used alumina is insufficient in heat characteristics, and heat dissipation is reaching its limit.

  On the other hand, aluminum nitride powder has high thermal conductivity and high insulation, and has attracted attention as a raw material for aluminum nitride sintered powder and sintered bodies that are extremely useful as electronic materials such as packaging materials.

The method for producing an aluminum nitride sintered body includes a method in which an aluminum nitride powder is granulated into granules in the presence of an organic component such as a binding aid, and then molded by a dry press method to obtain a press-molded body, followed by firing. Known (for example, see Patent Documents 1 and 2). The melting temperature of aluminum nitride is a very high temperature of 2200 ° C. under a pressure of 0.4 Mpa and is a hardly sinterable material. Therefore, for sintering, a metal selected from the group consisting of alkaline earth metals, lanthanum group metals, and yttrium or the metal compound is used as a sintering aid (see, for example, Patent Document 3).
Japanese Patent Laid-Open No. 5-270810 Japanese Patent Laid-Open No. 9-2879 Japanese Patent No. 2826023

  However, since these methods sinter at a high temperature of 1600 ° C. or higher when sintering, a special furnace is required in a non-oxygen atmosphere, resulting in high costs. There is a big difference in the price.

  Accordingly, an object of the present invention is to provide granules in which aluminum nitride as a raw material is sintered at a low temperature in order to produce aluminum nitride sintered powder and a sintered body at low cost.

  As a result of intensive studies to solve the above problems, the present inventors have obtained a product obtained by using colloidal silica dispersion liquid and granules obtained by uniformly dispersing ultrafine silicon dioxide in aluminum nitride powder. The inventors have found that the object is achieved and have completed the present invention.

That is, the present invention
(1) Aluminum nitride granules characterized in that colloidal silica dispersion is contained in aluminum nitride, and the content of silicon dioxide derived from colloidal silica is 1 to 10% by weight with respect to aluminum nitride.
(2) Aluminum nitride sintered powder obtained by firing the aluminum nitride granules described in (1).
(3) An aluminum nitride sintered body obtained by molding and firing the aluminum nitride granules according to (1) by a dry press.
(4) The method for producing aluminum nitride granules according to (1), wherein an aluminum nitride powder slurry containing a colloidal silica dispersion is slurried with an organic solvent, and the slurry is dried with a spray dryer.
(5) The aluminum nitride sintered powder according to (2), wherein the firing temperature is 400 to 1500 ° C.
(6) The aluminum nitride sintered body according to (3), wherein the firing temperature is 400 to 1500 ° C.
(7) A filler for a heat-dissipating resin comprising the aluminum nitride sintered powder according to (2).
(8) A heat-dissipating resin sheet comprising the heat-dissipating resin filler of (7).
(9) The present invention relates to a heat dissipating ceramic substrate material comprising the aluminum nitride sintered body according to (3).

  The aluminum nitride granules of the present invention are suitable as a raw material for producing aluminum nitride sintered powder and aluminum nitride sintered body.

  That is, by using the aluminum nitride granule of the present invention, sintering at a lower temperature was possible as compared with the prior art. In addition, when producing sintered powder for heat-dissipating resin fillers used in the semiconductor field and aluminum nitride sintered bodies used for heat-dissipating ceramic substrates, discoloration of the sintered body and generation of micropores are eliminated. Thus, it becomes possible to produce an aluminum nitride sintered body with good yield.

  Therefore, the aluminum nitride granule of the present invention is an extremely useful raw material for producing an aluminum nitride sintered powder and an aluminum nitride sintered body industrially efficiently and at low cost.

  Hereinafter, the present invention will be described in detail.

  A first aspect of the present invention is an aluminum nitride granule comprising at least aluminum nitride and colloidal silica, wherein the content of silicon dioxide derived from colloidal silica is 1 to 10% by weight based on aluminum nitride.

  The aluminum nitride powder (hereinafter sometimes abbreviated as “AlN”) used in the present invention is not different depending on the production method, and a commonly used aluminum nitride powder can be used. For example, aluminum nitride powder produced by an alkylaluminum method in which alkylaluminum and ammonia are reacted and then heated, an alumina reduction method in which a mixture of alumina and carbon is heated in nitrogen, a direct nitridation method in which aluminum and nitrogen are reacted, etc. Either can be used suitably.

  In the AlN granule of the present invention, it is important to uniformly disperse ultrafine silicon dioxide on the surface of the AlN crystal, and therefore, a colloidal silica dispersion is used.

The colloidal silica dispersion is a liquid in which ultrafine silicon dioxide of 10 to 20 μm is dispersed in water, which is represented by the general formula SiO ₂ · xH ₂ 0. These are generally commercially available, and are usually contained in the solution in an amount of about 10 to 30% by weight based on SiO ₂ . Further, sodium added as a stabilizer (for example, trade name: Snowtex 30, manufactured by Nissan Chemical Industries, Ltd.) can be used without any problem.

  In the present invention, the colloidal silica serves to bond the particles of AlN, and the bonding between the particles is achieved by condensation of the fine colloidal silica in a certain temperature range.

The amount of colloidal silica is from 1 to 10 wt% in terms of SiO ₂ with respect to AlN powder, is preferably optionally in the range of 3 to 8 wt% used.

  When the amount of colloidal silica used is 1% by weight or more, the effect as a binder is exhibited, which is preferable. That is, firing is preferable because the bonds between the particles are sufficient and the primary particles are not dispersed. Further, the content of 10% by weight or less is preferable because the condensation is sufficient and the original heat transfer performance of AlN is not lost.

  The shape of the aluminum nitride granule of the present invention is not limited at all, and may be any shape, but a spherical shape or a shape close to it is preferable due to the production method. Further, the high-density aluminum nitride granules having few voids are more preferably spherical, and for example, those having a sphericity of 0.9 or more determined from the ratio of the minor axis to the major axis are preferred.

  The size of the granules is preferably 10 to 200 μm in terms of average particle size in the case of sintered powder for fillers, and 10 μm to 8 mm in terms of average particle size in the case of sintered bodies for substrates. As a method of measuring the size of the granule, it can be measured by dry sieving, light transmission centrifugal sedimentation, SEM photography or the like.

  The aluminum nitride granulation of the present invention is not particularly limited, and can be obtained by various methods.

  One method is to use a bread granulator. The open type pan (dish) can be adjusted in rotation speed and tilt angle. Put the aluminum nitride powder into this pan and rotate it to spray the liquid containing colloidal silica dispersion on the aluminum nitride powder with a sprayer. Can be obtained.

  As a method for obtaining granules close to a true sphere, there is a method using a spray dryer. Since a granule can be obtained by drying a slurry containing a colloidal silica dispersion and aluminum nitride powder with a spray dryer, this is a preferred method in the present invention.

  A spray dryer is a method of sending hot gas from the side of a cylindrical tube, making slurry from the upper part into a mist with a sprayer, evaporating solvent and moisture in the gas phase, and forming aggregates. The hot air that accumulates in the lower part and contains moisture has a structure that discharges to the outside through a cyclone and a bag filter.

  Examples of the sprayer include those in which slurry is put into a high-pressure state by a pump and sprayed by a high-pressure dispersion nozzle, and sprayers that rotate a low-pressure nozzle called an atomizer at high speed, etc. However, either can be used.

  The fog state varies depending on the slurry concentration, the spray nozzle, and the rotation speed of the atomizer. The higher the slurry concentration, the larger the particle size, and the larger the nozzle diameter, the larger the particle size. Also, the higher the rotational speed of the atomizer, the smaller the particle size.

By spraying the slurry from the top of this spray dryer, the solvent and moisture are evaporated in the gas phase part, and fine SiO ₂ particles are uniformly attached to the surface of the AlN particles, and the aggregates form spherical granules. Falls to the bottom of the tube.

  As for the spray dryer used by this invention, the range whose hot gas blown to a pipe body is 150-400 degreeC is preferable, More preferably, 200-300 degreeC is suitable. When the temperature of the hot air is less than 150 ° C., the solvent and moisture may not evaporate sufficiently. On the other hand, when the temperature of the hot air exceeds 400 ° C., the particle diameters of the granules are not uniform, which tends to be undesirable.

  When supplying to a spray dryer, if the slurry concentration is not uniform, the variation in the particle size of the resulting granule increases, so it is desirable to supply it to the spray dryer at a uniform concentration.

The aluminum nitride granules of the present invention do not particularly require a sintering aid other than the colloidal silica dispersion, but may be used in combination. Examples of sintering aids that can be added other than the colloidal silica dispersion include calcium oxide, calcium phosphate, strontium oxide, yttrium oxide, lanthanum oxide, and calcium aluminate. When these are used, the same amount or less than the same amount of colloidal silica (in terms of SiO ₂ ) is sufficient.

  Moreover, it is preferable that an organic solvent is further added to the slurry.

  As the organic solvent, a water-soluble organic solvent is preferably used because it does not inhibit the dispersibility of the colloidal silica dispersion, and examples thereof include methanol, ethanol, isopropanol, acetone, and the like. However, since the colloidal silica dispersion contains a lot of water, AlN may be hydrolyzed in a short time even if an organic solvent is used. Therefore, a slurry in which AlN is dispersed in an organic solvent and a colloidal silica dispersion are prepared in advance, and are mixed and fed within a short residence time using a mixing tank with a stirrer or a line mixer, and supplied to a spray dryer. It is preferable to do. This residence time is preferably within 30 seconds, more preferably within 15 seconds.

Further, an aqueous solution containing a phosphoric acid compound can also be used to suppress hydrolysis of AlN. Examples of the phosphoric acid compound used include orthophosphoric acid, metaphosphoric acid, pyrophosphoric acid, and polyphosphoric acid. The concentration of the phosphoric acid aqueous solution is preferably 0.3 to ₂ % by weight, more preferably 0.5 to 1% by weight in terms of P ₂ O ₅ . When the concentration of the phosphoric acid aqueous solution is 0.3 weight or more in terms of P ₂ O ₅ , desired water resistance in the slurry state can be obtained, and there is less possibility of hydrolysis in a short time. Further, the content of 2% by weight or less in terms of P ₂ O ₅ is preferable without impairing the thermal conductivity that is the original characteristic of the AlN granules.

  As a method for mixing the phosphoric acid aqueous solution, for example, it is preferable to first disperse AlN powder in water to which a phosphoric acid compound has been added, mix the slurry, and then add colloidal silica. It should be noted that the organic solvent and the phosphoric acid aqueous solution can be used together as a matter of course.

  The concentration of the slurry for dispersing the AlN powder and colloidal silica dispersion in an organic solvent or / and phosphoric acid aqueous solution differs depending on the performance and capacity of the spray dryer, but the total weight of silicon dioxide in the AlN powder and colloidal silica is usually In (A), water is added so that the slurry concentration is 10 to 50% by weight according to the following formula (1).

Slurry concentration (%) = 100 × A / A + (organic solvent or / and phosphoric acid aqueous solution) (1)
When using an organic solvent, it is preferable to use an explosion-proof device for the spray dryer and use nitrogen gas as the hot gas blown to the tube. Moreover, it is important that the supply amount of the slurry is equal to or less than the evaporation amount of the solvent and water displayed in the specifications of the spray dryer.

  Next, a method for producing a sintered powder that uses the AlN granule of the present invention and is useful as a filler for a heat-dissipating resin will be described.

  In particular, the coagulable granule used as a film for a semiconductor is spherical and has a diameter of 10 to 200 [mu] m, preferably 20 to 100 [mu] m. The aluminum nitride granules are preferably spherical, and for example, those having a sphericity of 0.9 or more determined from the ratio of the minor axis to the major axis are preferred. As a method of measuring the size of the granule, it can be measured by dry sieving, light transmission centrifugal sedimentation, SEM photography or the like.

Further, in the sintered powder of the present invention, the volume specific gravity of the aluminum nitride granule is in the range of 0.5 to 1.3 g / cm ³ in order to obtain a sintered body at a high density with few internal voids. It is preferable that it is in the range of 0.7 to 1.1 g / cm ³ . As a method for adjusting the particle diameter, an arbitrary particle diameter can be obtained depending on the operating conditions of the spray dryer described above.

The AlN granules are heated and sintered in a firing furnace. As described above, fine SiO ₂ particles are uniformly deposited on the surface of the AlN particles, and the aggregates form spherical granules. By applying heat to the granules, the SiO _{2 on the} surface of the AlN fine particles condenses to firmly condense the bonds between the particles. As the firing furnace, a high temperature furnace such as an electric furnace or a high frequency furnace is used.

The firing temperature is preferably a temperature at which the fine SiO ₂ is condensed, that is, a range of 400 to 1500 ° C., more preferably 500 to 1200 ° C., and still more preferably 600 to 800 ° C. When the temperature is 400 ° C. or higher, sufficient condensation is achieved, and the fracture strength of the granules described later can be reached. Moreover, the strength of the sintered powder of AlN does not improve even when fired at a temperature exceeding 1500 ° C., and not only energy is lost, but also a special furnace such as a siliconit furnace or a high-frequency furnace is required, resulting in high cost. .

  Further, when the atmosphere in the furnace during firing exceeds 800 ° C., it is a non-oxidizing atmosphere, and nitrogen gas is generally employed. The container can be an alumina crucible or an alumina / silica magnetic crucible.

  The firing time varies depending on the firing temperature and the amount of colloidal silica used, but after achieving an arbitrary temperature, the firing is usually carried out for about 1 to 30 hours.

  After firing, the obtained granular AlN sintered powder becomes a product as it is, but if some granules are fused together, they can be dispersed using a jet mill or fused using a sieve. It is preferable to treat by a method such as removing the granulated particles.

  In the present invention, the average particle diameter was photographed with a scanning electron microscope at a magnification of 100, the diameter of 100 photographed particles was measured, and the average value was taken as the average particle diameter.

  The sintered state between the AlN granule particles can be evaluated by observing the denseness of the granule surface with an electron microscope, but can also be easily evaluated by the fracture strength and bulk density.

The fracture strength of the AlN sintered powder is preferably 5 kgf / mm ² or more. When the breaking strength is less than 5 kgf / mm ² , the granule collapses when kneaded with the resin, and as a result, the heat dissipation performance is lowered, which is not preferable. The fracture strength of the AlN sintered powder of the present invention was determined by measuring three granules having a particle size in the range of D × (1 ± 0.05), where D is the average particle size of the three granules used for measurement. Place it at the apex of a regular triangle with a side of 10 mm, apply a load gently from above, and measure the load when one or more of the three break. When the load is P and the breaking strength is S, the breaking strength can be calculated from the following equation (2). The measurement is repeated 10 times, and an 8-point average value excluding the lowest value and the highest value is used.
S = 2.8 × (P / 3) / (πD ² ) (2)
Further, the bulk density of the AlN sintered powder varies depending on the average particle diameter, but in the present invention, the one in the range of 0.9 to 1.6 g / cm ³ is preferable. The larger the amount of AlN added, the better, and the higher the bulk density, the more it can be added.

  The bulk density was measured by putting 50 g of ALN powder into a 100 ml graduated cylinder and tapping the bottom of the graduated cylinder lightly at a pace of 2 times / second from about 2 cm from the desk. The volume of the AlN powder can be read and the density can be calculated.

  In addition, since the AlN sintered powder is spherical, it has excellent fluidity, but if the particles are fused, the fluidity of the sintered powder decreases. Accordingly, as one of the indicators for measuring the fusion state, there is a method of measuring the angle of repose θ, and the smaller the value of this angle, the less the fusion of the sintered powder.

  The angle of repose θ is set at the center of a circular table with a diameter of 80 mm and the lower end of a glass funnel is set at a height of 80 mm, and the powder is dropped from the funnel until the powder falls off the table, forming a conical shape. Then, it can obtain | require by measuring the inclination angle (repose angle (theta)) toward the vertex.

  In the present invention, the repose angle θ of the AlN sintered powder is preferably 45 ° or less. When using as a filler of a heat radiating sheet, the better the fluidity, the better the dispersibility in the resin and the better the heat radiating performance.

  The AlN sintered powder of the present invention obtained by the method described above can be used for various purposes such as a film for semiconductors as a heat-dissipating resin composition by adding it as a filler to silicon resin or other resins.

  Next, a method for producing a sintered body that uses the granules and is useful as a heat-dissipating ceramic substrate will be described.

  The average particle size of the granules for producing the sintered body is arbitrarily selected according to the size and shape of the pressed body, but is usually 10 μm to 8 mm, preferably 20 μm to 4.0 mm, and more preferably 50 μm to An average particle size of 2.0 mm is preferred. When the average particle diameter exceeds 8 mm, the voids between individual granules are increased, and internal voids remain after sintering, and a good sintered body cannot be obtained. In addition, when the average particle size is less than 0.02 mm, it is not preferable because it becomes bulky due to electrostatic repulsion or the like, and the above disadvantages occur. The aluminum nitride granules are preferably spherical, and for example, those having a sphericity of 0.9 or more determined from the ratio of the minor axis to the major axis are preferred. As a method of measuring the size of the granule, it can be measured by dry sieving, light transmission centrifugal sedimentation, SEM photography or the like.

Further, in the sintered body of the present invention, the volume specific gravity of the aluminum nitride granules is in the range of 0.5 to 1.3 g / cm ³ in order to obtain a sintered body with a low density and high density. It is preferable that it is in the range of 0.7 to 1.1 g / cm ³ .

  The aluminum nitride sintered body of the present invention is obtained by molding and baking the above-described aluminum nitride granules of the present invention by a dry press.

For dry press, the aluminum nitride granules are filled in a mold and pressed, so-called pressure forming method, or the rubber mold is filled with granules, and so-called hydrostatic forming is performed by using fluid pressure. There are pressure molding methods using the former and the latter in combination, and these pressure molding methods are used to mold into an arbitrary shape. In general, a molding pressure of 0.3 to 2.0 t / cm ² is preferably employed.

The obtained aluminum nitride press body is fired to obtain a sintered body. The firing temperature is preferably a temperature at which the fine SiO ₂ is condensed, that is, a range of 400 to 1500 ° C., more preferably 500 to 1200 ° C., and still more preferably 600 to 1000 ° C. When the temperature is 400 ° C. or higher, sufficient condensation is achieved, and the fracture strength of the granules described later can be reached. Moreover, the strength of the sintered powder of AlN does not improve even when fired at a temperature exceeding 1500 ° C., and not only energy is lost, but also a special furnace such as a siliconit furnace or a high-frequency furnace is required, resulting in high cost. . As a firing atmosphere, when it exceeds 800 ° C., it is a non-oxidizing atmosphere, and nitrogen gas is generally employed.

  In this way, an aluminum nitride sintered body can be obtained efficiently and inexpensively by subjecting the aluminum nitride granules of the present invention to dry press molding and firing at a low temperature.

  The present invention will be specifically described with reference to examples and comparative examples.

The tube body 1 shown in FIG. 1 uses an explosion-proof spray dryer with 10 m ³ , the heater 12 sets the inlet temperature of hot nitrogen gas to 300 ° C., and the pressure inside the tube body is slightly reduced to −10 mmH ₂ O. Thus, the opening degree of the damper 14 of the exhaust system was adjusted.

When the temperature inside the tube was stabilized at 250 ° C., the rotation speed of the atomizer 3 was set to 8000 rotations. Next, 5 kg of AlN powder (manufactured by Mitsui Chemicals, Inc .: alkyl aluminum method) having a specific surface area of 2.2 m ² / g was added to 5 L of isopropyl alcohol to the slurry container 5 and stirred for 30 minutes. On the other hand, 830 g of a colloidal silica solution having a SiO ₂ content of 30 wt% (Nissan Chemical Industry Co., Ltd .: Snowtex 30) was placed in the container 7, and the AlN powder was 5 wt% in terms of SiO ₂ .

  The total amount of these two liquids was adjusted with a quantitative pump so as to be quantitatively fed in 1 hour and fed to the line mixer 9. The two liquids were mixed with the line mixer 9 and the residence time in the mixer was set to 15 seconds. Then, a fixed amount was supplied to the atomizer 3, and the entire amount was fed in 1 hour, followed by spray drying. Thereafter, the granules accumulated in the tube collector 2 were collected.

The granules were photographed with a scanning electron microscope (manufactured by JEOL: JSM-T330). The granules were porous spheres with an average particle size of 95 μm and a bulk density of 0.85 g / cm ³ . Further, the repose angle θ of the AlN powder was measured and found to be 32 °.

100 g of the granule obtained in Example 1 was put in an alumina crucible and baked at 600 ° C. for 3 hours in an electric furnace. The calcined granule was photographed with a scanning electron microscope (manufactured by JEOL: JSM-T330) in the same manner as in Example 1. The sintered powder had a dense spherical shape, an average particle diameter of 85 μm, and a bulk density of 1.22 g / cm ³ .

The AlN powder had an angle of repose θ of 32 ° and a breaking strength of 56 kgf / mm ² . The obtained AlN sintered powder was added to a silicon resin to form a heat-dissipating resin sheet, and its thermal conductivity was measured by a laser flash method to satisfy the desired performance of 21 W / m · k.

50 g of the granule obtained in Example 1 was put into a 5 cm × 5 cm × 4 cm mold and molded by applying a pressure of 1 t / cm ² with a press. After molding, firing was performed at 800 ° C. for 5 hours in an electric furnace in the atmosphere. The density of this sintered body was 3.22 g / cm ³ .

  Further, when the thermal conductivity of the obtained molded body was measured by a laser flash method, it was 190 W / m · k, which satisfies the desired performance.

Colloidal silica solution (made by Nissan Chemical Industries, Ltd .: Snowtex 30) 170 g was added, except for using 1.02 wt.% With Si0 ₂ in terms of relative AlN powder, a granule by a spray dryer in the same manner as in Example 1 It was collected. The granules were photographed with a scanning electron microscope (manufactured by JEOL: JSM-T330). The granules were porous spheres with an average particle size of 93 μm and a bulk density of 1.00 g / cm ³ . The repose angle θ of this AlN powder was 32 °.

The granules obtained in Example 4 were fired in an electric furnace in the same manner as in Example 2, and then the granules were photographed with a scanning electron microscope (manufactured by JEOL: JSM-T330). The sintered powder had a dense spherical shape, an average particle size of 83 μm, and a bulk density of 1.15 g / cm ³ . Further, when the repose angle θ of this AlN powder was measured, it was 32 ° and the breaking strength was 36 kgf / mm ² . The obtained AlN sintered powder was added to a silicon resin to form a heat-dissipating resin sheet, and its thermal conductivity was measured by a laser flash method, and the desired performance of 19 W / m · k was satisfied.

The granules obtained in Example 4 were put in the same mold as in Example 3, press-molded, and fired at 800 ° C. for 5 hours in an electric furnace. The obtained molded body was cut, and the surface and the cross section were photographed with a scanning electron microscope (manufactured by JEOL: JSM-T330). The sintered body was dense and the density was 3.10 g / cm ³ . Further, when the thermal conductivity of the obtained molded body was measured by a laser flash method, the desired performance heat radiation characteristic of 186 W / m · k satisfied the desired performance.

Colloidal silica solution (made by Nissan Chemical Industries, Ltd .: Snowtex 30) 1600 g was added, except for using 9.6 wt.% In Si0 ₂ in terms of relative AlN powder, a granule by a spray dryer in the same manner as in Example 1 It was collected. The granules were photographed with a scanning electron microscope (manufactured by JEOL: JSM-T330). The granules were porous spheres with an average particle size of 96 μm and a bulk density of 1.07 g / cm ³ . The repose angle θ of this AlN powder was 31 °.

The granules obtained in Example 7 were fired in an electric furnace in the same manner as in Example 2, and then the granules were photographed with a scanning electron microscope (manufactured by JEOL: JSM-T330). The sintered powder had a dense spherical shape, an average particle diameter of 82 μm, and a bulk density of 1.20 g / cm ³ . Further, when the repose angle θ of this AlN powder was measured, it was 32 ° and the breaking strength was 64 kgf / mm ² . The obtained AlN sintered powder was added to a silicon resin to form a heat-dissipating resin sheet, and its thermal conductivity was measured by a laser flash method, which was 20 W / m · k and satisfied the desired performance.

The granules obtained in Example 7 were put in the same mold as in Example 3, press-molded, and fired at 900 ° C. for 10 hours in an electric furnace. The obtained molded body was cut, and the surface and the cross section were photographed with a scanning electron microscope (manufactured by JEOL: JSM-T330). The sintered body was dense and the density was 3.32 g / cm ³ . Further, when the thermal conductivity of the obtained molded body was measured by a laser flash method, the desired performance heat dissipation characteristic of 192 W / m · k satisfied the desired performance.

Using the same spray dryer as in Example 1, the inlet temperature of the hot air is set to 300 ° C. with the heater 12, and the exhaust system damper 15 is set so that the pressure inside the tube body is slightly reduced to −10 mmH ₂ O. The opening was adjusted.

When the temperature inside the tube was stabilized at 250 ° C., the rotation speed of the atomizer 3 was set to 8000 rotations. Next, after putting 1 wt% orthophosphoric acid aqueous solution into the slurry tank 5 in terms of P ₂ O _{5, 5} kg of AlN powder having a specific surface area of 2.2 m ² / g (manufactured by Mitsui Chemicals, Inc .: alkyl aluminum method) is added and added 30 Stir for minutes. Next, 830 g of a colloidal silica solution having a SiO ₂ content of 30% by weight (manufactured by Nissan Chemical Industries, Ltd .: Snowtex 30) was added to 5% by weight in terms of SiO _{2 with} respect to the AlN powder, and further stirred for 10 minutes. 4, a fixed amount was supplied to the atomizer 3 via the line mixer 7, and the whole amount was fed in 1 hour to perform spray drying. Thereafter, the granules accumulated in the tube collector 2 were collected.

The granules were photographed with a scanning electron microscope (manufactured by JEOL: JSM-T330). The granules were porous spheres with an average particle size of 95 μm and a bulk density of 1.01 g / cm ³ . The repose angle θ of this AlN powder was 32 °.

The granules obtained in Example 10 were fired in an electric furnace in the same manner as in Example 2, and then the granules were photographed with a scanning electron microscope (manufactured by JEOL: JSM-T330). The sintered powder had a dense spherical shape, an average particle diameter of 90 μm, and a bulk density of 1.18 g / cm ³ . Further, when the repose angle θ of this AlN powder was measured, it was 32 ° and the breaking strength was 51 kgf / mm ² . The obtained AlN sintered powder was added to a silicon resin to form a heat-dissipating resin sheet, and its thermal conductivity was measured by a laser flash method to satisfy 22 W / m · k and desired performance.

The granules obtained in Example 4 were put in the same mold as in Example 3, press-molded, and fired at 800 ° C. for 5 hours in an electric furnace. The obtained molded body was cut, and the surface and the cross section were photographed with a scanning electron microscope (manufactured by JEOL: JSM-T330). The sintered body was dense and the density was 3.26 g / cm ³ . Further, when the thermal conductivity of the obtained molded body was measured by a laser flash method, the desired performance heat dissipation characteristic of 190 W / m · k satisfied the desired performance.

  The AlN granule of the present invention obtained by the method described above is added as a filler to a silicon resin or other resin, so that a resin film for heat dissipation can be used as a semiconductor film or a body temperature during pathology. It can be used for various purposes such as medical heat-dissipating sheets and cooling sheets for beverage cans.

Schematic diagram of spray dryer

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tube 2 Collector 3 Atomizer 4 Metering pump 5 Slurry container 6 Stirrer container 7 Container 8 Metering pump 9 Line mixer 10 Air inlet 11 Blower
12 Heater 13 Oil tank 14 Cyclone 15 Damper 16 Bag filter 17 Exhaust fan 18 Exhaust port 19 Air compressor

Claims (9)

An aluminum nitride granule comprising colloidal silica dispersion in aluminum nitride, wherein the content of silicon dioxide derived from colloidal silica is 1 to 10% by weight with respect to aluminum nitride. 2. An aluminum nitride sintered powder obtained by firing the aluminum nitride granules according to claim 1. 2. An aluminum nitride sintered body obtained by molding and firing the aluminum nitride granules according to claim 1 by a dry press. 2. The method for producing aluminum nitride granules according to claim 1, wherein the aluminum nitride powder containing the colloidal silica dispersion is slurried with an organic solvent, and the slurry is dried with a spray dryer. The aluminum nitride sintered powder according to claim 2, wherein the firing temperature is 400 to 1500 ° C. The aluminum nitride sintered body according to claim 3, wherein the firing temperature is 400 to 1500 ° C. A filler for heat-dissipating resin comprising the aluminum nitride sintered powder according to claim 2. A heat-dissipating resin sheet comprising the heat-dissipating resin filler according to claim 7. A heat dissipating ceramic substrate material comprising the aluminum nitride sintered body according to claim 3.

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