JP7261027B2 - Aluminum nitride filler for silicone resin - Google Patents

Description

TECHNICAL FIELD The present invention relates to a novel aluminum nitride filler for silicone resins comprising sintered aluminum nitride granules. Specifically, a silicone resin that can effectively prevent the platinum catalyst from inhibiting curing even when the silicone resin is highly filled while maintaining the high thermal conductivity of the particles that make up the aluminum nitride sintered granules. It provides an aluminum nitride filler for.

In recent years, with the increase in power density of semiconductor devices, materials used in the above devices are required to have higher heat dissipation properties. Such materials include a group of materials called thermal interface materials, and their use is expanding rapidly. A thermal interface material is a material for reducing the thermal resistance of a path through which heat generated from a semiconductor element is released to a heat sink or a housing, and various forms such as sheet, gel, and grease are used. A thermal interface material is generally a composite material in which a resin such as an epoxy resin or a silicone resin is filled with a thermally conductive filler. Among them, sheet moldings using a silicone resin as the resin are excellent in handleability and adhesion and are in high demand.

On the other hand, fillers such as alumina (aluminum oxide), boron nitride, aluminum nitride, and silicon nitride are used as fillers to be filled in the resin. Among them, aluminum nitride has high thermal conductivity without anisotropy. At the same time, it has a high insulation resistance, and the demand for it as a filler for the purpose of heat dissipation is increasing.

When filling aluminum nitride fillers into silicone resins, aluminum nitride particles having a large particle size and having a long heat conduction distance per unit particle have been required. Sintered aluminum nitride granules, which are obtained by molding aluminum nitride fine powder into a spherical shape and sintering the spherical shape, are preferably used as such large-grain aluminum nitride.

The aluminum nitride sintered granules are also commercially available and used as thermally conductive fillers. Epoxy resins are mainly used as resins to which the fillers are added, but examples of adding them to silicone resins are also known (see Patent Documents 1 and 2).

However, when the aluminum nitride sintered granules are used as a filler and highly filled into a silicone resin, insufficient curing of the silicone resin occurs. It has been clarified by the studies of the present inventors that the thermal conductivity of the sheet does not improve depending on the filling amount, and the performance varies between sheets or within the sheet. became.

JP-A-4-174910 JP 2017-210518 A

Accordingly, an object of the present invention is to provide an aluminum nitride filler for silicone resin that uses sintered aluminum nitride particles, which does not cause poor curing or variation in the physical properties of the cured product even when the silicone resin is highly filled, and has high thermal conductivity. To provide an aluminum nitride filler for silicone resins capable of exhibiting

The inventors of the present invention conducted intensive studies in order to solve the above problems, and as a result, the aluminum nitride sintered granules have a small specific surface area due to their large particle size, and compared with conventional powders of 1 to several μm. However, unexpectedly, a large amount of amino groups or imino groups are present on the surface of the particles, and the amino groups present on the surface of such particles act as curing catalysts for silicone resins. It was found that curing inhibition occurs due to poisoning of the platinum-based catalyst. As a result of repeated investigations into means for removing problematic groups such as amino groups and suppressing their subsequent generation, it was found that Al—O bonds were present on the surfaces of the particles constituting the aluminum nitride sintered granules. It is extremely effective, and furthermore, in aluminum nitride sintered particles, by controlling the peak intensity ratio of the Al-O bond peak and the Al-N bond inside the particles to a specific range, platinum catalyst-based silicone resin Even if it is filled in a predetermined amount or more, it does not cause poor curing or a decrease in thermal conductivity caused by poor curing, and the thermal conductivity of the aluminum nitride powder itself can be maintained sufficiently high, which is high as an aluminum nitride filler for silicone resin. It was discovered that performance was exhibited, and the present invention was completed.

That is, according to the present invention, the average particle diameter (D50) is composed of aluminum nitride sintered granules of 5 to 100 μm , and the spectrum obtained by X-ray photoelectron spectroscopy-X-ray excitation Auger electron spectroscopy is measured. The intensity ratio ((PAl-O) / (PAl-N)) between the Al-O bond peak (PAl-O) and the Al-N bond peak (PAl-N) inside the particle is 0.3 to 1 There is provided an aluminum nitride filler for silicone resins characterized by exhibiting a value of .2.

The aluminum nitride filler for silicone resin of the present invention preferably has an average particle size (D50) of 5 to 100 μm.

Further, the aluminum nitride filler for silicone resin of the present invention preferably has a change width of 0.5 or less after being immersed in 50 times the mass of water at 30° C. for 4 hours.
In addition, it is particularly preferable that the pH value after the immersion is 7 or less.

Since the aluminum nitride filler for silicone resins of the present invention can effectively prevent curing inhibition of silicone resins, it can be used alone or in combination with other fillers, as shown in the examples below. There is no curing failure of the resin even in a system where the total filler content is 60% by volume or more, especially 80% by volume or more, in a platinum catalyst-based silicone resin, and the quality of the cured silicone resin is not uniform. It is possible to stably produce silicone resin moldings.

In addition, the aluminum nitride filler for silicone resin of the present invention has a specific amount of Al—O bonds on the surface of the sintered aluminum nitride particles within the above range, so that the surface is densified and the water resistance is further improved. Also, it exhibits a secondary effect such as improved compatibility with a surface treatment agent used as necessary, such as a silane coupling agent.

The aluminum nitride filler for silicone resin of the present invention is composed of aluminum nitride sintered granules. The aluminum nitride sintered granules are generally aggregates of particles (sintered particles) formed by sintering aluminum nitride crystal grains having an average particle size of about 0.1 to 2 μm. Moreover, those having an average particle diameter (D50) of 5 to 100 μm, particularly 20 to 80 μm are preferably used.

The most important feature of the aluminum nitride filler for silicone resin of the present invention, which is composed of the aluminum nitride sintered granules, is that the spectrum obtained by measuring the particle surface by X-ray photoelectron spectroscopy-X-ray excitation Auger electron spectroscopy The intensity ratio ((P _Al-O )/(P _Al-N )) of the Al—O bond peak (P _Al—O ) on the surface and the Al—N bond peak (P _Al—N ) inside the particle is It is to show a value of 0.3 to 1.2, preferably 0.3 to 1.0.

That is, when the strength ratio ((P _Al—O )/(P _Al—N )) of the aluminum nitride sintered granules is less than 0.3, it becomes difficult to prevent the curing inhibition of the silicone resin, resulting in poor curing. In addition, even if cured, there is variation in performance among the molded articles obtained. On the other hand, when the strength ratio ((P _Al—O )/(P _Al—N )) exceeds 1.2, the thermal conductivity of the aluminum nitride particles is reduced, and even if the silicone resin is highly filled, It becomes difficult to impart high thermal conductivity to the formed body.

The aluminum nitride filler for silicone resin of the present invention has a strength ratio ((P _Al-O )/(P _Al-N )) by adjusting the Al—O bond amount on the particle surface of the aluminum nitride sintered granules constituting it. is within the above range, even when the silicone resin is highly filled, it is possible to effectively prevent inhibition of curing of the silicone resin and stably obtain a molded product with no variation in performance, and the molded product It is also possible to give high thermal conductivity to.

Incidentally, the strength ratio ((P _Al—O )/(P _Al—N )) of commercially available aluminum nitride sintered granules is about 0.1 to 0.2. When the resin is filled in a large amount, there is a concern that the curing failure described above may occur, or that the performance of the obtained molded article may vary even if it is cured.

In the present invention, the intensity ratio (P _Al—O )/(P _Al—N ) will be described in detail in Examples, but X-ray Auger Electron Spectroscopy (X-ray Auger Electron Spectroscopy: hereinafter referred to as “XAES ”) is a value obtained using the peak intensity of the spectrum obtained by By using this method, X-ray photoelectron spectroscopy (hereinafter also referred to as "XPS") is difficult to measure, even for fillers with different particle sizes and shapes, the same It is possible to reliably measure the Al—O bond peak (P _Al—O ) on the particle surface under these conditions.

The measurement of the Al—O bond peak (P _Al—O ) on the particle surface and the Al—N bond peak (P _Al—N ) inside the particle by XAES is as described in the measurement method of Examples described later. It is not the measured value of individual aluminum nitride particles, but the average value of aluminum nitride sintered granules that constitute the aluminum nitride filler for silicone resin, which is performed for multiple aluminum nitride particles existing in a certain area. be.

The aluminum nitride filler for silicone resin of the present invention exhibits extremely excellent water resistance such that the width of change after immersion in 50 times the mass of water at 30 ° C. for 4 hours is 0.5 or less, particularly 0.3 or less. It is more preferable that the surface is densified, and such a property is also one of the features.
In addition, it is particularly preferable that the pH value after the immersion is 7 or less.

The shape of the aluminum nitride sintered granules constituting the aluminum nitride filler for silicone resin of the present invention is not particularly limited, but is preferably as spherical as possible in consideration of fluidity. Specifically, it is preferable that the degree of circularity is 0.8 or more, particularly 0.9 or more.

The aluminum nitride filler for silicone resins of the present invention has a remarkable effect on silicone resins that use platinum-based curing catalysts. Known silicone resins, including commercially available ones, can be used without particular limitation.

In addition, the aluminum nitride filler for silicone resin of the present invention can be filled into the silicone resin alone, but it can also be blended into the silicone resin as a mixed filler in which other fillers are used together. In particular, the aluminum nitride filler for silicone resin of the present invention, which is used as a large-particle-size filler, is preferably used in combination with a small-particle-size filler because its filling rate can be improved.

A fine powder filler having an average particle size of less than 5 μm, preferably 1 to 3 μm, is suitable as the small particle size filler. Furthermore, submicron fillers may be used together in order to achieve higher filling. The material of the filler is not particularly limited, and may be aluminum nitride, aluminum oxide, silicon nitride, boron nitride, silicon oxide, etc., but aluminum nitride is preferably used. Among aluminum nitrides, in particular, reduced aluminum nitride nitride nitride obtained by the reduction nitriding method requires a decarburization step to remove carbon used as a reducing agent in the manufacturing process, and such an oxidation treatment reduces the strength ratio (( The value of P _Al-O )/(P _Al-N )) satisfies the range of the aluminum nitride filler for silicone resin of the present invention in many cases, and is preferably used. Of course, even if the fine powder filler is aluminum nitride obtained by another method, for example, a direct nitriding method, the strength ratio ((P _Al—O )/(P _Al—N )) value can be changed by the heat treatment described later. can be suitably used.

In the mixed filler, the aluminum nitride filler for silicone resin of the present invention is preferably used in a proportion of 60% by volume or more, particularly 70% by volume or more, based on the total filler.

In the present invention, the filling rate of the filler in the silicone resin is preferably 75% by volume or more, particularly about 80 to 85% by volume.

The method for producing the aluminum nitride filler for silicone resin of the present invention is not particularly limited. Aluminum nitride sintered granules obtained by firing at 1800 ° C. or commercially available aluminum nitride sintered granules are heat-treated in an atmosphere containing oxygen, and the strength ratio ((P _Al-O ) / (P _{Al −N} )) can be produced by adjusting the value to the above range.

Incidentally, the aluminum nitride sintered granules do not reach the above strength ratio (P _Al-O )/(P _Al-N ) only by natural oxidation by normal storage (storage at room temperature) without the above heat treatment.

As for the conditions for producing the sintered granules, that is, detailed conditions for granulation and sintering, known methods are employed without particular limitations. As a representative method, it is preferable to use aluminum nitride fine powder having an average particle size of about 0.5 to 2 μm. A sintering aid such as yttrium or calcium oxide is blended at a ratio of 1 to 5 parts by mass, and a binder resin is added as necessary, ketones such as acetone and methyl ethyl ketone, alcohols such as ethanol and propanol, and benzene. , A slurry obtained by mixing with a solvent such as an aromatic hydrocarbon such as toluene is formed into granules by a spray drying method, and the resulting granules are dried as necessary, followed by nitrogen gas or inert gas. A method of firing at a temperature of 1700 to 1800° C. for 1 to 8 hours in an atmosphere can be used.

In the above spray drying method, by appropriately adjusting conditions such as slurry concentration, slurry viscosity, spray nozzle diameter, etc., drying gas amount, slurry supply amount, etc., the average particle size of the sintered granules after firing The diameter (D50) is preferably 5-100 μm, particularly 10-80 μm.

In addition, although the optimum heat treatment conditions for the aluminum nitride sintered granules differ slightly depending on the particle size, the dew point is -20°C or less, preferably -30°C or less, -50°C or more in an air atmosphere, 400°C to 1000°C. , preferably at a temperature of 800 to 900 ° C., the time for the strength ratio ((P _Al-O )/(P _Al-N )) of the aluminum nitride sintered granules after heat treatment to be within the above range, specifically , 1 to 10 hours, preferably 2 to 8 hours. The adjustment of the dew point is important, and if the dew point is higher than −20° C., the oxidation progresses rapidly, making it difficult to adjust the strength ratio ((P _Al—O )/(P _Al—N )). Become.

Moreover, it is desirable that the materials of the apparatus and jigs used for the heat treatment are metals with low hygroscopicity or dense ceramics. If the material of the equipment used for the heat treatment is highly hygroscopic, such as brick, the absorbed moisture becomes an oxidation source, making it difficult to control the strength ratio ((P _Al—O )/(P _Al—N )). Become.

In the above heat treatment, a more preferable embodiment is an embodiment in which the aluminum nitride sintered granules are previously evacuated to 20 Pa or less, preferably 10 Pa or less before the heat treatment. According to the above-described mode, moisture and the like present between the particles of the sintered granules can be eliminated, and a dense Al—O bonding layer can be formed on the particle surfaces by subsequent oxidation treatment. In addition, after the heat treatment, the mode of recovering from the heating furnace when the temperature of the aluminum nitride sintered granules reaches 100 ° C. or less is preferable because it can prevent the Al-O bonding layer from being deteriorated by the action of moisture in the atmosphere. .

When the aluminum nitride filler for silicone resin of the present invention is used in combination with finely powdered aluminum nitride, the strength ratio ((P _Al—O )/(P _Al—N )) of the finely powdered aluminum nitride is within the scope of the present invention. Although it is preferable that there is, the adjustment is performed separately from the adjustment by the heat treatment of the aluminum nitride sintered granules, and the strength ratio ((P _Al—O )/(P _Al—N )) is prevented from becoming too high, and the strength ratio can be reliably adjusted.

In the aluminum nitride filler for silicone resin of the present invention, the aluminum nitride powder may be treated with a surface treatment agent in order to improve compatibility with the resin. In addition, the use of a surface treatment agent can further suppress the influence of the amino group on the surface of the aluminum nitride sintered particles, but its addition is not essential, and even without the use of a surface treatment agent, the silicone resin can be used. Curing can be done satisfactorily.

As the surface treatment agent, known agents can be used without particular limitation. Typical examples include alkylsilanes (methyltrimethoxysilane, dimethyldimethoxysilane, phenyltrimethoxysilane, , trifluoropropyltrimethoxysilane, phenyltriethoxysilane, hexyltrimethoxysilane, octyltriethoxysilane, decyltrimethoxysilane), silazanes (tetramethylsilazane, hexamethyldisilazane), cyclic siloxanes (tetramethylcyclotetra siloxane, octamethylcyclotetrasiloxane, hexamethylcyclotrisiloxane) and the like. It is preferable to limit the amount of the surface treatment agent to be used to about 0.01 to 2 parts by mass with respect to 100 parts by mass of the aluminum nitride powder. As for the treatment method, known methods can be used without any particular limitation, and the treatment may be carried out either wet or dry.

EXAMPLES The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples.

In the examples and comparative examples, each measuring method was carried out by the method shown below.

1) Average particle diameter It was determined by laser diffraction using MICROTRACK-HRA manufactured by Nikkiso. An aluminum nitride filler was added to a solution of 90 ml of water and a 5% aqueous solution of sodium pyrophosphate, and dispersed with a homogenizer at an output of 200 mA for 3 minutes. The average particle size was determined from the D50 of the method described above. In addition, D50 here is a volume distribution value.

2) Circularity 20,000 particles were measured using a Malvern Morphologi G3.
The circularity is calculated by using the area S and the perimeter L of the particle measured from the image obtained by the image analysis, and the circularity is 4πS/L2.

3) Intensity ratio (P _Al-O )/(P _Al-N )
The intensity ratio (P _Al-O )/(P _Al-N ) was measured using the apparatus and conditions shown below, and the peak intensity (P _Al-O ) at an Auger electron energy of 1386.7 eV and the peak intensity at 1388.5 eV ( P _Al—N ) ratio was determined.

・Apparatus: X-ray photoelectron spectrometer ESCA5701ci/MC manufactured by ULVAC-Phi, Inc.
・X-ray source: Mg-Kα ray 14.0 kV-25.7 mA
・Degree of vacuum: 5.0×10-7 Pa
・Aperture diameter (analysis area): Φ800 μm
- Photoelectron extraction angle: 45 deg.
• Neutralization gun: A neutralization gun was used to mitigate the effect of sample charging on the XPS-XAES spectral shape.

Charge correction: By adjusting the carbon C1s peak of the measured spectrum to 284.6 eV, the peak shift due to charging was corrected.

・Measurement parameters: for high energy resolution (Multiplex Scan)
Pass Energy/eV: 11.75, ΔV/V Interval: 0.05, Interval Time/ms: 50
4) Thermal conductivity of molded article The thermal conductivity of the silicone resin molded article was measured by the hot disk method using TPS2500S manufactured by Kyoto Electronics Industry Co., Ltd. Samples were prepared with N=20 and investigated for variation.

5) Curing state of the molded body Using a durometer TYPE-E (GS-721G) made by Teclock, two sheets of silicone resin molded bodies with a thickness of 6 mm are stacked and the rate of change immediately after the start of measurement and 15 seconds after the start (strength immediately after measurement- Hardness after 15 seconds)×100/strength immediately after measurement.

6) Aluminum nitride powder/sintered particles-1
Alumina balls with a diameter of 15 mm are placed in a nylon ball mill with an internal volume of 20 L, and then 100 parts by weight of AlN powder (H grade manufactured by Tokuyama) and 3 parts by weight of yttrium oxide as a sintering aid (manufactured by Nippon Yttrium). and a dispersant and a solvent were added and mixed for 14 hours to obtain a slurry. Granules of different sizes were prepared by spray-drying the mixed slurry and adjusting the rotation speed of the atomizer. The granules were sintered at 1750° C. for 5 hours in a nitrogen atmosphere to produce aluminum nitride sintered granules (sintered granules-1 and sintered granules-2).

Two types of commercially available sintered granules were also obtained (sintered granules-3 and sintered granules-4).

The average particle size, circularity, and strength ratio ((P _Al—O )/(P _Al—N ) ratio) of the aluminum nitride sintered granules are shown below.

・ Sintered granules-1 D50: 28 μm, circularity: 0.94, strength ratio: 0.24
・Sintered granules-2 D50: 81 μm, circularity: 0.94, strength ratio: 0.22
・ Sintered granules-3 D50: 30 μm, circularity: 0.92, strength ratio: 0.15
・ Sintered granules-4 D50: 33 μm, circularity: 0.95, strength ratio: 0.21

7) Silicone resin As the silicone resin, a two-liquid addition reaction type silicone resin mediated by the following Pt catalyst was used.

・Silicone resin-1: CY52-276A, B manufactured by Toray Dow Corning
・ Silicone resin-2: KE-1013A, B manufactured by Shin-Etsu Chemical Co., Ltd.
Example 1
The sintered granules-1 were charged into a furnace with a muffle made of SUS310 so that the thickness was 20 mm, the pressure in the furnace was set to 20 Pa, and then air with a dew point of -20 ° C. was introduced to return to normal pressure. ° C. x 3 hours to obtain an aluminum nitride filler for silicone resin composed of aluminum nitride sintered granules with (P _Al-O )/(P _Al-N ) adjusted to 0.34.

The aluminum nitride filler for silicone resin had an initial pH of 6.5 after being immersed in 50 times the mass of water at 30° C. for 4 hours, and the pH change range was 0.5.

This aluminum nitride filler for silicone resin and an aluminum nitride powder having a D50 of 0.8 μm and obtained by a reductive nitriding method (strength ratio: 0.56) were mixed at a volume ratio of 8:2 to prepare a mixed filler, This mixed filler was added to silicone resin 1 so that the filling rate was 83% by volume. The silicone resin is blended by kneading for 15 minutes using Labo Plastomill manufactured by Toyo Seiki Seisakusho. (manufactured by NICHIAS CORPORATION) and a SUS plate, and hot-pressed at 1 ton at 80° C. for 1 hour to obtain a sheet body with a thickness of 6 mm.

The obtained sheet body was a good cured body with no transfer of resin to Naflon (trade name: manufactured by Nichias Co., Ltd.) sheet. The thermal conductivity measured by the hot disk method was 10.6 W/m·K, and the variation at N=20 was 0.1 W/m·K. In addition, the change in intensity for 15 seconds was 6% on the durometer.

Example 2
Sintered granules-3 were used, and the (P _Al—O )/(P _Al—N ) ratio was 0.0 in the same manner as in Example 1, except that the heat treatment temperature and time were changed to 800° C. for 5 hours. An aluminum nitride filler for silicone resin was obtained, which consisted of aluminum nitride sintered granules adjusted to 57%.

The aluminum nitride filler for silicone resin had an initial pH of 6.4 after being immersed in 50 times the mass of water at 30° C. for 4 hours, and the pH change was 0.1.

The obtained aluminum nitride filler for silicone resin was treated in the same manner as in Example 1 to obtain a sheet having a thickness of 6 mm.

The obtained sheet body was a good cured body with no transfer of resin to Naflon (trade name: manufactured by Nichias Co., Ltd.) sheet. The thermal conductivity measured by the hot disk method was 7.3 W/m·K, and the variation at N=20 was 0.1 W/m·K. The hardness change in durometer for 15 seconds was 7%.

Example 3
Sintered granules-4 were used, and the (P _Al—O )/(P _Al—N ) ratio was 0.0 in the same manner as in Example 1, except that the heat treatment temperature and time were changed to 900° C. for 7 hours. An aluminum nitride filler for silicone resin was obtained, which consisted of aluminum nitride sintered granules adjusted to 78%.

The aluminum nitride filler for silicone resin had an initial pH of 6.5 after being immersed in 50 times the mass of water at 30° C. for 4 hours, and a pH change of 0.3.

The obtained aluminum nitride filler for silicone resin was treated in the same manner as in Example 1 to obtain a sheet having a thickness of 6 mm.

The obtained sheet body was a good cured body with no transfer of resin to Naflon (trade name: manufactured by Nichias Co., Ltd.) sheet. The thermal conductivity measured by the hot disk method was 10.4 W/m·K, and the variation at N=20 was 0.1 W/m·K. The hardness change in durometer for 15 seconds was 5%.

Example 4
Sintered granules-2 were used, and the (P _Al—O )/(P _Al—N ) ratio was 1.0 in the same manner as in Example 1, except that the heat treatment temperature and time were changed to 1000° C. for 5 hours. An aluminum nitride filler for a silicone resin was obtained, which consisted of aluminum nitride sintered granules adjusted to No. 2.

The aluminum nitride filler for silicone resin had an initial pH of 6.4 after being immersed in 50 times the weight of water at 30° C. for 4 hours, and the pH change range was 0.5.

The obtained aluminum nitride filler for silicone resin, the aluminum nitride filler for silicone resin obtained in Example 1, and the aluminum nitride powder obtained by the reduction nitriding method having a D50 of 0.8 μm used in Example 1 (the strength ratio: 0.56) were mixed at a volume ratio of 1:1:1 to prepare a mixed filler, and this mixed filler was added to silicone resin 1 so that the filling rate was 85% by volume. A sheet with a thickness of 6 mm was obtained in the same manner as in Example 1.

The obtained sheet body was a good cured body with no transfer of resin to Naflon (trade name: manufactured by Nichias Co., Ltd.) sheet. The thermal conductivity measured by the hot disk method was 12.4 W/m·K, and the variation at N=20 was 0.2 W/m·K. The hardness change in durometer for 15 seconds was 3%.

Comparative example 1
The sintered granules-1 were kneaded and hot-pressed in the same manner as in Example 1 except that the sintered granules-1 were not heat-treated (strength ratio: 0.24), but the silicone resin had an uncured portion and could not be formed into a sheet. I didn't.

Comparative example 2
The sintered granules-3 were kneaded and hot-pressed in the same manner as in Example 2 except that the sintered granules-3 were not heat-treated (strength ratio: 0.15), but the silicone resin had an uncured portion and could not be formed into a sheet. I didn't.

Comparative example 3
In Example 1, by changing the heat treatment conditions of sintered granules-1, the (P _Al—O )/(P _Al—N ) ratio was adjusted to 1.6 for silicone resin made of aluminum nitride sintered granules An aluminum nitride filler was obtained.

The obtained aluminum nitride filler for silicone resin was treated in the same manner as in Example 1 to obtain a sheet having a thickness of 6 mm.

When the thermal conductivity of the obtained sheet body was measured by the hot disk method, it was 9.7 W/m·K, which was nearly 10% lower than that of Example 1. It is presumed that the Al—O layer became thicker, resulting in the thermal resistance.

Claims (2)

The average particle size (D50) is made of aluminum nitride sintered granules containing a sintering agent with an average particle size (D50) of 5 to 100 μm, and is measured by X-ray photoelectron spectroscopy-X-ray excitation Auger electron spectroscopy. The intensity ratio ((PAl-O)/(PAl-N)) between the Al-O bond peak (PAl-O) and the Al-N bond peak (PAl-N) inside the particle is 0.3 to 1.0. An aluminum nitride filler for a silicone resin, characterized by showing a value of 2. 2. The aluminum nitride filler for silicone resin according to claim 1, wherein the change in pH after being immersed in 50 times the weight of water at 30[deg.] C. for 4 hours is 0.5 or less.