WO2019017451A1

WO2019017451A1 - Aluminum nitride powder and production method therefor

Info

Publication number: WO2019017451A1
Application number: PCT/JP2018/027177
Authority: WO
Inventors: 橋詰　良樹; 祥子鈴木; 健男杉田
Original assignee: 東洋アルミニウム株式会社
Priority date: 2017-07-21
Filing date: 2018-07-19
Publication date: 2019-01-24
Also published as: JP6921671B2; JP2019019045A

Abstract

Provided is an aluminum nitride powder which is less likely to aggregate in a sintering step even without using boron nitride as a raw material. This aluminum nitride powder contains oxygen and a rare-earth element, and is characterized in that the aluminum nitride powder has an apparent density of 3.2 g/cm3 or higher, the contained amount of the oxygen is 0.01-1 mass% with respect to 100 mass% of the aluminum nitride powder, and the mass ratio (MR/MO) of the contained amount (MR) of the rare-earth element to the contained amount (MO) of the oxygen is 0.1-1.5.

Description

Aluminum nitride powder and method for producing the same

The present invention relates to an aluminum nitride-based powder and a method for producing the same.

Conventionally, aluminum nitride raw material powder is granulated and sintered to a high thermal conductivity resin used for cooling of electronic components with large heat generation such as power semiconductors, LEDs, high frequency devices, etc., and aluminum nitride based powder as a sintered body It is done to mix.

For example, Patent Document 1 discloses a method of obtaining a spherical powder having an average particle diameter of 10 μm or more by granulating an aluminum nitride raw material powder and sintering it in an inert gas atmosphere. In this method, there is a problem that the powders are fused and aggregated in the sintering step, and it is difficult to obtain a powder having a spherical shape and a good filling property even if the aggregate is crushed. Although it is also disclosed in the same document that the aggregation of the powder can be prevented by reducing the addition amount of the sintering aid, the high density and high thermal conductivity can be achieved simply by reducing the addition amount of the sintering aid. It is difficult to obtain an aluminum nitride-based powder.

Patent Document 2 discloses a method of obtaining an aluminum nitride-based powder obtained by granulating and sintering an aluminum nitride raw material powder, and adjusting the degreasing temperature to maintain the strength of the degreased body and maintain the shape of the powder. It is disclosed. However, even in this method, there is a problem of agglomeration, and agglomeration of the powder occurs in the sintering step, and it is necessary to grind it later, so it is difficult to obtain spherical powder of uniform particle size.

Patent Document 3 also discloses a method of obtaining an aluminum nitride-based powder having a small particle diameter by granulating and sintering an aluminum nitride raw material powder. However, even with this method, it is difficult to obtain spherical powder of uniform particle size because powder aggregation is likely to occur and it is necessary to grind it later.

On the other hand, Patent Document 4 and Patent Document 5 disclose a method in which boron nitride powder is added to raw material powder and sintered in order to overcome the problem of the aggregation of the aluminum nitride-based powder described above. However, such methods require the boron nitride powder to be separated later and can not be completely separated. As a result, when the aluminum nitride powder is blended with the high thermal conductivity resin, there arises a problem that the viscosity of the resin becomes excessively higher than the appropriate viscosity.

Further, Patent Document 6 discloses a spherical aluminum nitride-based powder excellent in filling property by mixing aluminum nitride raw material granules and a small amount of boron nitride powder without using a dispersion medium such as balls and then sintering. Methods of making are described. However, in the case of manufacturing by such a method, there is a problem that the granules are easily broken in the step of mixing the aluminum nitride raw material granules. There is also a problem that the resin viscosity becomes too high when the aluminum nitride powder is blended with the high thermal conductivity resin as described above.

On the other hand, in Patent Document 7, an alkaline earth metal compound and carbon are added to an aluminous material, and reduction nitriding is performed to produce spherical aluminum nitride powder having an average particle diameter of 3 to 30 μm and an oxygen content of 1% or less. Methods are disclosed. In this method, since alumina is used as the starting material, the reaction requires a long time, and the subsequent decarburization treatment also requires time. In addition, it is difficult to produce a powder having a large particle size exceeding 30 μm.

Further, Japanese Patent Application Laid-Open Publication No. 2008-112566 manufactures spherical aluminum nitride powder having a particle diameter of 10 to 200 μm, which contains aluminum oxynitride as a core, by two-stage firing of alumina granules in an atmosphere containing carbon monoxide and nitrogen. A method is disclosed. In this method, solid solution oxygen tends to remain in the aluminum nitride crystal, and as a result, there is a problem that the thermal conductivity as the filler material is lowered. Also, the relative density of the powder particles obtained is as low as 95% or less, and it is difficult to achieve 99% or more.

Japan Japanese Patent Laid-Open No. 3-295863 Japan Patent Publication 2003-267708 Japan Patent Publication 2006-206393 Japan JP-A-4-124006 Japan JP-A-11-269302 Japan JP 2017-036183 gazette Japan JP 2012-056774 Japan Patent Publication No. 2016-037438

In view of the above-mentioned circumstances, an object of the present invention is to provide an aluminum nitride-based powder which is less likely to cause aggregation in a sintering process without using boron nitride as a raw material.

As a result of intensive studies to achieve the above object, the present inventors have made it possible to obtain an aluminum nitride-based powder containing a rare earth element and oxygen at a predetermined ratio and further having an apparent density of at least a predetermined value. It has been found that the occurrence of aggregation in the sintering process can be suppressed without using boron. The present inventors have conducted further studies based on such findings, and have completed the present invention.

That is, the present invention provides the following aluminum nitride-based powder.
Item 1.
Aluminum nitride powder containing oxygen and rare earth elements,
The apparent density of the aluminum nitride powder is 3.2 g / cm ³ or more,
The content of the oxygen is 0.01 to 1% by mass in 100% by mass of the aluminum nitride-based powder,
Aluminum nitride powder characterized in that a mass ratio (M _R / M _{O 2} ) of the content (M _R ) of the rare earth element to the content (M _{O 2} ) of the oxygen is 0.1 to 1.5. .
Item 2.
The aluminum nitride-based powder according to Item 1, wherein the rare earth element is yttrium.
Item 3.
Furthermore, the nitriding according to item 1 or 2, wherein the alkaline earth metal element is contained in an amount of 0.01 to 0.05 parts by mass with respect to 100 parts by mass of components other than the alkaline earth metal element contained in the aluminum nitride powder. Aluminum-based powder.
Item 4.
The aluminum nitride-based powder particles in the aluminum nitride-based powder are
A first phase component which is an aluminum nitride crystal grain,
And comprising a second phase component which is a composite metal oxide,
95% or more of the entire second phase component has a longest diameter of 1 μm or less,
The aluminum nitride-based powder according to any one of Items 1 to 3.
Item 5.
The composite metal oxide is
The aluminum nitride-based powder according to Item 4, which is a composite metal oxide containing at least aluminum and a rare earth.
Item 6.
(1) A step of mixing an aluminum nitride raw material powder containing 0.01 to 3% by mass of oxygen and having an average particle diameter of 2 μm or less, a rare earth compound powder, an organic binder, and a solvent to form a slurry The slurry obtained in step 1 is granulated and dried to obtain a granulated product; and (3) the granulated material obtained in step 2 is degreased to a temperature of 1700 to 1900 ° C. in a reducing atmosphere. Step 3 of sintering at temperature conditions
A method for producing an aluminum nitride-based powder, comprising:
Item 7.
Item 7. The production method according to Item 6, wherein the alkaline earth metal compound powder is further mixed and slurried in the step 1.

The aluminum nitride-based powder of the present invention is less likely to cause aggregation in the sintering step without using boron nitride as a raw material.

The external appearance photograph of the aluminum nitride type powder of Example 1. FIG. 2 is a cross-sectional photograph of the aluminum nitride-based powder particles of Example 1. Sectional photograph of aluminum nitride type powder particles of comparative example 1.

Aluminum Nitride-Based Powder The aluminum nitride-based powder of the present invention is an aluminum nitride-based powder containing oxygen and a rare earth element, and the apparent density of the aluminum nitride-based powder is 3.2 g / cm ³ or more. The amount is 0.01 to 1% by mass in 100% by mass of the aluminum nitride-based powder, and the mass ratio (M _R / of the content of the rare earth element (M _R ) to the content of the oxygen (M _O ) M _{O 2} ) is characterized by being 0.1 to 1.5.

The aluminum nitride-based powder in the present specification means an aggregate of aluminum nitride-based powder particles obtained by granulating and sintering an aluminum nitride raw material powder to obtain a sintered body. Such an aluminum nitride-based powder can be suitably used, for example, as a filler for resin products that require high thermal conductivity.

The apparent density of the aluminum nitride powder is 3.2 g / cm ³ or more. When the apparent density of the aluminum nitride-based powder is less than 3.2 g / cm ³ , sufficient sinterability can not be obtained when sintering at the time of production. Moreover, sufficient thermal conductivity can not be provided to the resin obtained by using the manufactured aluminum nitride type powder as a filler. On the other hand, the upper limit of the apparent density of the aluminum nitride powder is not particularly limited, but is preferably 3.32 g / cm ³ from the viewpoint of the theoretical density of the composite of aluminum nitride and rare earth oxide.

In the present specification, the apparent density means the volume obtained by removing the gap volume between the powder from the volume of the container when the powder is packed in a container of a fixed volume (however, the volume of the void existing inside the powder is (Not excluded) means the density of the powder mass in the container divided. Apparent density can be measured by a known method, for example, can be measured by the Archimedes method.

Oxygen and Rare Earth Element The aluminum nitride powder of the present invention contains oxygen and a rare earth element. The content of oxygen in the aluminum nitride-based powder is 0.01 to 1% by mass, and more preferably 0.5 to 1% by mass, with respect to 100% by mass of the aluminum nitride-based powder. More preferably, it is 1% by mass. If the content of oxygen is less than 0.01% by mass, there is a problem that the apparent density of the aluminum nitride powder is reduced. On the other hand, if the content of oxygen exceeds 1% by mass, the amount of liquid phase generation increases in the sintering step at the time of aluminum nitride-based powder production, and there is a problem that aggregation of aluminum nitride-based powder particles tends to occur. . At the same time, the amount of oxygen in the aluminum nitride crystal grains is increased, so that excellent thermal conductivity can not be obtained.

The content of oxygen in the aluminum nitride powder can be measured by quantitative analysis using, for example, an oxygen / nitrogen analyzer EMGA 920 manufactured by Horiba, Ltd. using an inert gas melting / non-dispersive infrared absorption method. it can.

Examples of the rare earth element include known rare earth elements. Such rare earth elements include one or more selected from the group consisting of yttrium (Y), lanthanum (La), neodymium (Nd), gadolinium (Gd), samarium (Sm), dysprosium (Dy), and europium (Eu). There may be mentioned, but not limited thereto. Among them, yttrium has excellent properties as a sintering aid, and aluminum nitride powder particles having high density and high thermal conductivity can be obtained.

The content of the rare earth element in the aluminum nitride powder is preferably 0.1 to 1.8% by mass, and preferably 0.3 to 1.5% by mass, from the viewpoint of thermal conductivity and aggregation prevention. Is more preferred. The content of the rare earth element in the aluminum nitride-based powder is determined by subjecting the sample to microwave heating in a sulfuric acid / nitric acid solution using an ICP emission spectrophotometer (for example, iCAP6100 manufactured by ThermoFisher Scientific Co., Ltd.) and ICP emission spectral analysis It can measure by doing.

The mass ratio (M _R / M _O ) of the content (M _R ) of the rare earth element to the content (M _O ) of oxygen in the aluminum nitride powder is 0.1 to 1.5, and 0.2 to More preferably, it is 1.3. If the mass ratio (M _R / M 2 _{O 3} ) is less than 0.1, the density of the aluminum nitride-based powder particles is lowered. On the other hand, if it exceeds 1.5, the aluminum nitride-based powder particles are bound to each other by the liquid phase generated in the sintering process, causing a problem of aggregation, and the density of the powder particles also decreases when the sintering temperature is low. . As described above, by setting the mass ratio (M _R / M 2 _{O 3} ) within the above numerical range, the aggregation of the aluminum nitride-based powder can be suppressed. As a result, it is not necessary to add boron nitride to prevent aggregation of the aluminum nitride-based powder, and the process of manufacturing the aluminum nitride-based powder can be simplified.

Alkaline Earth Metal Element The aluminum nitride-based powder of the present invention may further contain an alkaline earth metal element. By containing an alkaline earth metal element, it is possible to obtain a dense (without an air gap inside) aluminum nitride-based powder at a lower sintering temperature. As such an alkaline earth metal, one or more selected from the group consisting of beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba) and radium (Ra) may be mentioned. Of course, it is not limited to these. Among them, calcium is preferable because it can impart high thermal conductivity to the aluminum nitride powder.

The content of the alkaline earth metal element is 0.01 to 0.05 parts by mass of the alkaline earth metal element with respect to 100 parts by mass of components other than the alkaline earth metal element contained in the aluminum nitride powder Is preferable, and 0.01 to 0.05 parts by mass is more preferable. By containing 0.01 mass part or more of alkaline-earth metal elements, the sintering temperature in the sintering process of aluminum nitride-type powder manufacture can be made low. Moreover, the thermal conductivity of the aluminum nitride type powder obtained can be improved by setting it as 0.08 mass part or less.

Aluminum Nitride-Based Powder Particles The aluminum nitride-based powder particles in the aluminum nitride-based powder preferably include a first phase component which is aluminum nitride crystal grains and a second phase component which is a composite metal oxide.

Here, in the second phase component, at least 95% of the total second phase component contained in the aluminum nitride-based powder is a grain boundary triple point of crystal grains constituting the first phase component (hereinafter simply referred to as a triple point) It is preferable to intersperse. That is, it is preferable that the second phase components do not exist continuously but are dotted at the triple points of the first phase components. When the second phase component is present in the form of a surface continuously in grain boundaries, the liquid phase easily exudes to the surface in the sintering step, and as a result, the aluminum nitride-based powder tends to aggregate. In other words, aggregation of the aluminum nitride-based powder can be suppressed by adopting a configuration in which 95% or more of the second phase component is present at the triple point of the first phase component.

As described above, 95% or more of the entire second phase component is 1 μm or less in longest diameter. When the longest diameter exceeds 1 μm, the second phase component may not be accommodated in the above-mentioned triple point, and may spread in a plane. The fact that 95% or more of the entire second phase component has a longest diameter of 1 μm or less means that the second phase is distributed in the matrix of the first phase component (dark part) by SEM observation of the cross section of the aluminum nitride powder by ion milling or the like. It can be calculated by measuring the size of the component (bright portion) and determining the ratio of the number of second phase components having a size of 1 μm or less of the longest diameter to the total number.

The composite metal oxide in the second phase component is preferably a composite metal oxide containing at least aluminum and a rare earth. Further, it may be a composite metal oxide containing aluminum, rare earths and alkaline earth metals. By having such a configuration, the melting point of the second phase component is lowered, and a high density aluminum nitride-based powder can be obtained even if the sintering step is performed at a low temperature.

In particular, yttrium is used as the rare earth element, and the mass ratio (M _R / M _O ) of the content of the rare earth element (M _R ) to the content of the oxygen (M _O ) is 0.1 to 1.5. The main component of the second phase component is yttrium aluminum garnet (Y ₃ Al ₅ O ₁₂ ) by producing the aluminum nitride-based powder. Since the main component of the second phase component is yttrium aluminum garnet (Y ₃ Al ₅ O ₁₂ ), the melting point of the second phase component is lowered, and a high-density aluminum nitride-based material is obtained even if a sintering step is performed at low temperatures. Powder can be obtained.

The shape of the aluminum nitride-based powder particles is not particularly limited, but particles having a sphericity of 0.9 or more are preferable. The average particle size is preferably 5 to 200 μm. When the average particle size exceeds 200 μm, there is a problem that the powder particles stick out when mixed with a resin and formed into a sheet or the like. Here, the sphericity of the aluminum nitride-based powder particles is determined by determining the area S and peripheral length L of the projected image of the individual particles using an image analysis device (for example, Mophorogi G3 manufactured by Malvern) for the projected image of the powder. By calculating 4πS / L ² and calculating the average value per unit number, the average particle size can be determined by using a general laser diffraction / scattering type particle size distribution measuring apparatus (eg, MT3300 manufactured by Nikkiso Co., Ltd.). It can be calculated by measuring the volume average particle size of the aluminum nitride-based powder ultrasonically dispersed in water to which (for example, Triton X-100 manufactured by Dow Chemical Co., Ltd.) is added.

The proportion of aluminum nitride powder particles having a particle diameter of 2 μm or less in 100 mass% of the aluminum nitride powder is desirably 0.01 to 10 mass%. If the amount is more than 10% by mass, the packing density when the aluminum nitride powder is compounded with the resin is low. In addition, since the viscosity when mixing the aluminum nitride powder and the resin becomes high, the filling amount can not be increased, and it becomes difficult to obtain a high thermal conductivity. As described above, the shape is preferably spherical particles having a sphericity of 0.9 or more in principle, but it may be adjusted to be flat or block depending on the application.

Method for Producing Aluminum Nitride-Based Powder The method for producing an aluminum nitride-based powder of the present invention is
(1) A step of mixing an aluminum nitride raw material powder containing 0.01 to 3% by mass of oxygen and having an average particle diameter of 2 μm or less, a rare earth compound powder, an organic binder, and a solvent to form a slurry The slurry obtained in step 1 is granulated and dried to obtain a granulated product; and (3) the granulated material obtained in step 2 is degreased to a temperature of 1700 to 1900 ° C. in a reducing atmosphere. And Sintering at a temperature condition.

Step 1
The aluminum nitride raw material powder used in step 1 contains 0.01 to 3% by mass of oxygen in 100% by mass of the aluminum nitride raw material powder. When the oxygen content exceeds 3% by mass, it is difficult to obtain an aluminum nitride-based powder having a high thermal conductivity.

In the aluminum nitride raw material powder, as long as the content of oxygen described above is contained, there is no particular limitation on the contained aspect. For example, an embodiment in which 2% by mass or more of oxygen is present as a surface oxide film (hydrated film) on the surface of aluminum nitride can be mentioned.

Moreover, as an aluminum nitride raw material powder used at the process 1, an average particle diameter of 2 micrometers or less is used. When the mean particle size exceeds 2 μm, it is difficult to obtain a compact aluminum nitride-based powder. The lower limit value of the average particle diameter of the aluminum nitride raw material powder is not particularly limited, but for example, 0.1 μm or more is preferable.

The aluminum nitride raw material powder is preferably added at a content of 20 to 60% by mass in 100% by mass of the slurry obtained in step 1 from the viewpoint of easiness of dispersion and easiness of granulation.

A wide variety of known rare earth compound powders can be used. Although there is no particular limitation, specifically, Y ₂ O ₃ , La ₂ O ₃ , Nd ₂ O ₃ , CeO ₂ , Dy ₂ O ₃ , Sm ₂ O ₃ , Sc ₂ O _{3 and the} like can be mentioned. These may be used alone or in combination of two or more. As the particle diameter, it is preferable to use one having an average particle diameter of 0.1 to 2 μm.

Further, from the viewpoint of facilitating sintering and making the thermal conductivity of the obtained aluminum nitride-based powder good, the amount of the rare earth compound powder added is 0.1 parts by mass with respect to 100 parts by mass of the aluminum nitride raw material powder. The amount is preferably 10 to 10 parts by mass, more preferably 0.1 to 5 parts by mass, and still more preferably 0.3 to 3 parts by mass.

As an organic binder, it is possible to use widely the well-known organic binder used for manufacture of aluminum nitride type powder. Specifically, acrylic resins, waxes, polyvinyl butyral resins, polyester resins and the like can be mentioned, and of course are not limited thereto. These may be used alone or in combination of two or more.

The addition amount of the organic binder may be appropriately adjusted according to the kind and addition amount of the aluminum nitride raw material powder and the rare earth compound powder to be used, for example, 0.5 to 10 parts by mass with respect to 100 parts by mass of the aluminum nitride raw material powder Is preferred.

As the solvent, it is possible to widely use known solvents used for producing aluminum nitride powders. Specific examples thereof include ester solvents, ketone solvents, aromatic solvents, ether solvents and the like, and of course are not limited thereto. These may be used alone or in combination of two or more.

The addition amount of the solvent may be appropriately adjusted according to the kind and addition amount of the aluminum nitride raw material powder and the rare earth compound powder used, for example, 50 to 300 parts by mass with respect to 100 parts by mass of the aluminum nitride raw material powder preferable.

Furthermore, alkaline earth metal compound powder may be added to make a slurry of step 1. Specific examples of the alkaline earth metal compound powder, BeO, mention may be made of MgO, _CaO, SrO, BaO, and CaC _{_2,} CaCO 3, CaCN _2, and the like. These may be used alone or in combination of two or more. As the particle diameter, it is preferable to use one having an average particle diameter of 0.1 to 2 μm.

In addition, from the viewpoint of facilitating sintering and making the thermal conductivity of the obtained aluminum nitride-based powder good, the addition amount of the alkaline earth metal compound powder is 0 with respect to 100 parts by mass of the aluminum nitride raw material powder. The content is preferably from 0.1 to 0.1 parts by mass, and more preferably from 0.01 to 0.08 parts by mass.

In addition, when the slurry is obtained in Step 1, a dispersing agent, a thixo agent, a plasticizer, an antifoaming agent, and the like may be further added as necessary.

The method for forming a slurry is not particularly limited, and examples thereof include a method of mixing the various materials described above and dispersing them using a ball mill, a bead mill, a stirrer or the like.

Step 2
In step 2, the slurry obtained in step 1 is granulated and dried. The method for granulation and drying is not particularly limited, and it is possible to adopt widely known methods. Specifically, methods such as spray drying and rolling granulation can be mentioned.

Step 3
In step 3, the granulated product obtained in step 2 is degreased and sintered under temperature conditions of 1700 to 1900 ° C. in a reducing atmosphere.

As a specific method of degreasing, for example, a method of heating to 400 to 600 ° C. in air or in an inert atmosphere is preferable. By this method, it is possible to effectively remove the resin component of the organic binder added in step 1, and the amount of remaining carbon derived from the organic binder in the resulting degreased body is 0. It can be reduced to 1 to 0.5% by mass. In addition, when the amount of residual carbon derived from the organic binder in the defatted body becomes 0.1% by mass or more, the defatted body of the granulated product obtained becomes difficult to be broken, and the amount of remaining carbon becomes 0.5% by mass or less Thereby, the density of the obtained aluminum nitride-based powder is sufficient.

Furthermore, the obtained degreased body is sintered at a temperature of 1700 to 1900 ° C. in a reducing atmosphere.

As a method of setting it as a reducing atmosphere, the method of setting it as a reducing nitrogen atmosphere can be mentioned, for example.

As a more specific embodiment for setting such a reducing nitrogen atmosphere, using a sintering furnace using a carbon-based material, it is possible to use materials other than carbon (BN, WC, Mo, SiC, Si ₃ N ₄ etc.) By surrounding granulated powder, the method of adjusting the amount of penetration of carbon vapor to a sintered compact can be mentioned.

As another specific embodiment for setting a reducing nitrogen atmosphere, there is also mentioned a method of forming a weakly reducing atmosphere by adding carbon or carbide or an organic substance to granulated powder and vaporizing carbon at the time of sintering. be able to. Here, the amount of carbon to be added is preferably 70 parts by mass or less with respect to 100 parts by mass of the oxygen content of the raw material aluminum nitride-based powder at the stage of the degreased body.

Moreover, the method of performing sintering in the mixed atmosphere of nitrogen and hydrocarbon can also be mentioned as another specific aspect for setting it as a reducing nitrogen atmosphere. By making the atmosphere reductive, preferably weakly reductive, the amount of oxygen contained in the sintered aluminum nitride powder can be reduced to 1% by mass or less, thereby preventing aggregation due to excessive liquid phase formation, and firing It is possible to increase the thermal conductivity of the sintered powder. Here, the hydrocarbon concentration in nitrogen is preferably 5% by volume or less.

In addition, when the sintering temperature is less than 1700 ° C., the density of the obtained aluminum nitride-based powder particles may be insufficient. On the other hand, when the sintering temperature exceeds 1900 ° C., the aluminum nitride-based powder particles are easily aggregated. In view of such circumstances, the sintering temperature is more preferably 1750 to 1850 ° C.

Although the embodiments of the present invention have been described above, the present invention is not limited to these examples, and it is needless to say that the present invention can be practiced in various forms without departing from the scope of the present invention.

Hereinafter, the embodiments of the present invention will be more specifically described based on examples, but the present invention is not limited to these.

(Examples 1 to 7 and Comparative Examples 1 to 5)
A slurry was produced by mixing in a ball mill for 24 hours with the composition of Table 1 below. Thereafter, the obtained slurry was granulated and dried by a spray dry method (apparatus: CDL 20 manufactured by Ogawara Kakohki Co., Ltd.) to obtain a granulated powder having a volume average particle size of 70 μm. The granulated powder was degreased at 400 ° C. in air for 1 hour, then filled in a carbon container equipped with a BN plate on the inner surface, and sintered in nitrogen for 3 hours. The apparent density of the obtained aluminum nitride powder was measured by the Archimedes method. Further, the amount of oxygen contained in the aluminum nitride powder was measured by an inert gas melting / non-dispersive infrared absorption oxygen nitrogen analyzer (manufactured by Horiba, Ltd., ENGA-920). The amount of yttrium contained in aluminum nitride was measured by microwave heating a sample in a sulfuric acid / nitric acid solution using an ICP (high frequency inductively coupled plasma) emission spectrophotometer (iCAP 6100 manufactured by Thermo Fisher Scientific) to measure the dissolved sample.

In addition, the detail regarding the material used in each Example and a comparative example is as Table 2. In addition, about the aluminum nitride raw material powder of Example 7 and Comparative Example 4, although it does not display in Table 2, when manufacturing Toyo Aluminum Co., Ltd. product JD, a particle size is adjusted by adjusting the grade of grinding. What was changed was used as an aluminum nitride raw material powder.

When the aluminum nitride powder of Example 1 was observed by a scanning electron microscope, it could be confirmed that the powder was composed of substantially spherical aluminum nitride powder particles as shown in FIG.

Similarly, when the cross section of the aluminum nitride-based powder particles of Example 1 was observed by grinding by ion milling, as shown in FIG. 2, the second phase was interposed between the crystal grains of aluminum nitride as the first phase component. It was confirmed that the component composite metal oxides were scattered, and the maximum diameter of 1 μm or less was 100%. On the other hand, when the cross section of the aluminum nitride-based powder particles of Comparative Example 1 was observed, it was confirmed that the number of second phase components having a longest diameter of 1 μm or less was 60% as shown in FIG.

Aggregation Evaluation Test The presence or absence of aggregation of the aluminum nitride-based powder of each Example and each Comparative Example was evaluated by measuring the particle size. Specifically, the particles were crushed into primary particles, and the particle size of the powder after crushing was measured by a laser diffraction method, and it was judged that no aggregation was observed when the volume average particle diameter was 80 μm or less.

Thermal conductivity evaluation test After mixing the aluminum nitride-based powder of each Example and each Comparative Example with a silicone resin (KE-1013 manufactured by Shin-Etsu Chemical Co., Ltd.) at 65% by volume and performing mixing stirring and defoaming, A sheet having a thickness of 3 mm was produced, and the thermal conductivity was measured by a thermal conductivity measuring device (TCi manufactured by C-THERMTECHNOLOGIES).

As shown in Table 3, it was confirmed that the aluminum nitride-based powder of each example had excellent thermal conductivity, and that no aggregation of particles was also observed.

Claims

Aluminum nitride powder containing oxygen and rare earth elements,
The apparent density of the aluminum nitride powder is 3.2 g / cm 3 or more,
The content of the oxygen is 0.01 to 1% by mass in 100% by mass of the aluminum nitride-based powder,
Aluminum nitride powder characterized in that a mass ratio (M R / M O 2 ) of the content (M R ) of the rare earth element to the content (M O 2 ) of the oxygen is 0.1 to 1.5. .
The aluminum nitride-based powder according to claim 1, wherein the rare earth element is yttrium.
The alkaline earth metal element according to claim 1 or 2, further comprising 0.01 to 0.05 parts by mass with respect to 100 parts by mass of components other than the alkaline earth metal element contained in the aluminum nitride-based powder. Aluminum nitride powder.
The aluminum nitride-based powder particles in the aluminum nitride-based powder are
A first phase component which is an aluminum nitride crystal grain,
And comprising a second phase component which is a composite metal oxide,
95% or more of the entire second phase component has a longest diameter of 1 μm or less,
The aluminum nitride-based powder according to any one of claims 1 to 3.
The composite metal oxide is
The aluminum nitride-based powder according to claim 4, which is a composite metal oxide containing at least aluminum and a rare earth.
(1) A step of mixing an aluminum nitride raw material powder containing 0.01 to 3% by mass of oxygen and having an average particle diameter of 2 μm or less, a rare earth compound powder, an organic binder, and a solvent to form a slurry The slurry obtained in step 1 is granulated and dried to obtain a granulated product; and (3) the granulated material obtained in step 2 is degreased to a temperature of 1700 to 1900 ° C. in a reducing atmosphere. Step 3 of sintering at temperature conditions
A method for producing an aluminum nitride-based powder, comprising:
7. The method according to claim 6, wherein alkaline earth metal compound powder is further mixed and slurried in the step 1.