Thermally conductive resin material

Abstract

This thermally conductive resin material (10) includes a resin (11) and a particulate filler (12) that is dispersed in the resin (11). A graph that represents the particle size distribution of the filler (12) of the thermally conductive resin material (10) has a first peak, a second peak, and a third peak. The first peak is at at least 20 μm but no more than 80 μm, the second peak is at at least 1 μm but no more than 10 μm, and the third peak is at at least 0.1 μm but less than 1 μm. The filler (12) includes first particles (21) that have a particle size of at least 10 μm, second particles (22) that have a particle size of at least 1 μm but less than 10 μm, and third particles (23) that have a particle size of at least 0.1 μm but less than 1 μm. The average circularity of a random sample of 30 of the third particles (23) that have a circle equivalent diameter of less than 1 μm is no more than 0.7.

Description

Thermally conductive resin materials

[0001] This invention relates to a thermally conductive resin material in which a filler containing alumina particles is dispersed in a resin. This application claims priority to Japanese Patent Application No. 2024-055594 filed on March 29, 2024, and Japanese Patent Application No. 2024-056768 filed on March 29, 2024, the contents of which are incorporated herein by reference.

[0002] In recent years, the amount of heat generated by electrical components has been increasing along with the advances in the performance of personal computers and smartphones and the development of electric vehicles and fuel cell vehicles. For example, lithium-ion batteries for automobiles generate a large amount of heat because they output a large amount of power continuously for a long period of time, and this large amount of generated heat must be efficiently dissipated to the outside. For this reason, thermally conductive resin materials with excellent thermal conductivity are sometimes used as heat dissipation materials for electrical components such as lithium-ion batteries and IC chips.

[0003] Conventionally, thermally conductive resin materials include those in which a thermally conductive filler having excellent thermal conductivity is dispersed in a resin material having excellent moldability. ２ O ３ Inorganic materials such as silicon dioxide (SiO2) particles and silicon carbide (SiC) particles are known.

[0004] For example, Patent Document 1 discloses a thermally conductive sheet that uses a mixture of two sizes of silicon carbide particles as a thermally conductive filler: silicon carbide particles with an average particle size of 50 μm to 100 μm and silicon carbide particles with an average particle size of 10 μm or less.

[0005] Patent Document 2 discloses a thermally conductive material that uses alumina particles and two sizes of silicon carbide particles (large and small) as thermally conductive fillers. The large silicon carbide particles have an average particle size of 50 to 100 μm, and the small silicon carbide particles have an average particle size of 5 to 10 μm.

[0006] Furthermore, Patent Document 3 discloses a composition containing, as a thermally conductive filler, three types of filler components with different average particle sizes, namely, a filler component (A1) with an average particle size of 0.1 to 2 μm, a filler component (A2) with an average particle size of 2 to 20 μm, and a filler component (A3) with an average particle size of 20 to 100 μm, and examples of the filler components include alumina such as aluminum oxide, zinc oxide, and aluminum nitride.

[0007] JP 2001-139733 A JP 2003-197833 A International Publication No. 2011 / 125636

[0008] However, in Patent Documents 1 to 3, filler particles with a relatively uniform particle size and high circularity were used as the smallest particle size filler among fillers with multiple particle sizes, which resulted in high material costs and made it difficult to increase thermal conductivity because the particles tended to make point contact rather than surface contact.

[0009] The present invention has been made in view of the above-mentioned circumstances, and has an object to provide a thermally conductive resin material that is low in cost and has excellent thermal conductivity.

[0010] In order to solve the above problems, a thermally conductive resin material according to one embodiment of the present invention proposes the following means: (1) A thermally conductive resin material according to a first aspect of the present invention is a thermally conductive resin material having a resin and a particulate filler dispersed in the resin, wherein a graph showing the particle size distribution of the filler has a first peak, a second peak, and a third peak, the first peak being 20 μm or more and 80 μm or less, the second peak being 1 μm or more and 10 μm or less, and the third peak being 0.1 μm or more and less than 1 μm, the filler including first particles having a particle size of 10 μm or more, second particles having a particle size of 1 μm or more and less than 10 μm, and third particles having a particle size of 0.1 μm or more and less than 1 μm, and the average circularity obtained by measuring 30 particles having a circle-equivalent diameter of less than 1 μm randomly selected from the third particles is 0.7 or less.

[0011] (2) Aspect 2 of the present invention is a thermally conductive resin material according to aspect 1, wherein, when the total volume of the filler is 100 volume %, the filler contains the second particles in a proportion of 9 volume % or more and 33 volume % or less, the third particles in a proportion of 4 volume % or more and 28 volume % or less, and the remainder is the first particles.

[0012] (3) Aspect 3 of the present invention is the thermally conductive resin material of aspect 1 or 2, wherein the resin contains a silicone resin and a silane coupling agent.

[0013] (4) A fourth aspect of the present invention is the thermally conductive resin material of the third aspect, wherein the thermally conductive resin material contains the filler in a ratio of 2,500 parts by mass or less per 100 parts by mass of the resin.

[0014] (5) A fifth aspect of the present invention is the thermally conductive resin material according to any one of the first to fourth aspects, wherein the filler is alumina particles.

[0015] According to an aspect of the present invention, it is possible to provide a thermally conductive resin material having excellent thermal conductivity at low cost. In addition, when the average circularity of the third particles is lower, the contact area between the particles is increased, the thermal resistance is reduced, and a higher thermal conductivity is obtained.

[0016] 1 is a schematic diagram showing a thermally conductive resin material according to one embodiment of the present invention; FIG. 2 is a graph showing the particle size distribution of a filler; FIG. 3 is a graph showing the particle size distribution of DAM45, one of the three types of alumina particles used in an example of the present invention; FIG. 4 is a graph showing the particle size distribution of DAM05, one of the three types of alumina particles used in an example of the present invention; FIG. 5 is a SEM photograph of AES-11C, one of the three types of third particles (small particles); FIG. 6 is a SEM photograph of AA-03F, one of the three types of third particles (small particles); FIG. 7 is a SEM photograph of AA-05, one of the three types of third particles (small particles).

[0017] A thermally conductive resin material according to one embodiment of the present invention will be described below. The following embodiment is specifically described to provide a better understanding of the gist of the invention, and does not limit the present invention unless otherwise specified. Furthermore, the drawings used in the following description may show enlarged essential parts for the sake of clarity, and the dimensional proportions of the components may not necessarily be the same as those in reality.

[0018] (Thermal Conductive Resin Material) Fig. 1 is a schematic diagram showing a thermally conductive resin material according to one embodiment of the present invention. The thermally conductive resin material 10 of this embodiment has a resin 11 and particulate filler 12 dispersed in the resin 11. The resin 11 may be selected depending on the intended use of the thermally conductive resin material, and examples thereof include silicone resin and urethane resin.

[0019] Silicone resins are polymeric compounds with a main skeleton formed by siloxane bonds. Silicone resins include modified silicone resins into which various organic groups have been introduced. Examples of modified silicone resins include polyimide-modified silicone resins, polyester-modified silicone resins, urethane-modified silicone resins, acrylic-modified silicone resins, olefin-modified silicone resins, ether-modified silicone resins, alcohol-modified silicone resins, fluorine-modified silicone resins, amino-modified silicone resins, mercapto-modified silicone resins, and carboxy-modified silicone resins.

[0020] Examples of the urethane resin include polyol-type urethane resin and polyester-type urethane resin.

[0021] The resin 11 constituting the thermally conductive resin material 10 of this embodiment preferably further contains a silane coupling agent. The silane coupling agent can be selected from aminosilanes, mercaptosilanes, vinylsilanes, epoxysilanes, methacrylsilanes, and the like, depending on the type of resin 11. By including such a silane coupling agent, the hardness of the thermally conductive resin material 10 can be adjusted. The amount of the silane coupling agent per 100 parts by mass of the resin 11 (the total of the silicone resin, urethane resin, and silane coupling agent) is preferably 70 parts by mass or less.

[0022] The particulate filler 12 is dispersed in the resin 11 as described above to enhance thermal conductivity. The constituent material of the filler 12 is not particularly limited, but when used for heat dissipation purposes in a battery, inorganic materials having insulating properties and high thermal conductivity, such as alumina (aluminum oxide) particles, silicon carbide particles, zinc oxide particles, aluminum nitride particles, boron nitride particles, etc., can be used. In this embodiment, alumina particles are used as the filler 12.

[0023] The filler 12 has a trimodal particle size distribution including a first peak P1, a second peak P2, and a third peak P3, as shown in the particle size distribution graph shown in FIG. 2 (the vertical axis represents the volume-based frequency (%) and the horizontal axis represents the particle size (μm)). In this embodiment, the particle size distribution is a particle size distribution graph in which the vertical axis represents the volume-based frequency (%) and the horizontal axis represents the particle size (μm). The particle size distribution of the particles constituting the filler 12 was measured using a laser diffraction / scattering particle size distribution measuring device (MT3300EXII: manufactured by Microtrac Bell Co., Ltd.). The first peak P1 is located in the range of 20 μm to 80 μm, the second peak P2 is located in the range of 1 μm to 10 μm, and the third peak P3 is located in the range of 0.1 μm to less than 1 μm. For example, the first peak P1 being located in the range of 20 μm to 80 μm means that the particle size at the apex of the first peak P1 is in the range of 20 μm to 80 μm.

[0024] The filler 12 contains alumina particles of three different size ranges: first particles (large particles) 21 having a particle size of 10 μm or more, second particles (medium particles) 22 having a particle size of 1 μm or more but less than 10 μm, and third particles (small particles) 23 having a particle size of 0.1 μm or more but less than 1 μm. Note that the particle size referred to here refers to the diameter in the case of spherical particles, and the largest cross-sectional diameter in the case of oval-spherical particles or polygonal particles.

[0025] The particle size (D50) of the first particles (large particles) 21 is preferably 20 μm or more and 100 μm or less, more preferably 25 μm or more and 80 μm or less, and even more preferably 30 μm or more and 60 μm or less. The particle size (D50) of the second particles (medium particles) 22 is preferably 2 μm or more and 20 μm or less, more preferably 3 μm or more and 15 μm or less, and even more preferably 4 μm or more and 10 μm or less. The particle size (D50) of the third particles (small particles) 23 is preferably 0.1 μm or more and 2 μm or less, more preferably 0.2 μm or more and 1 μm or less, and even more preferably 0.3 μm or more and 0.8 μm or less. As an example, the particle size (D50) of the first particles (large particles) 21 is 41.2 μm, the particle size (D50) of the second particles (medium particles) 22 is 5.3 μm, and the particle size (D50) of the third particles (small particles) 23 is 0.43 μm. The particle size (D50) of the first particles (large particles) 21 is the median diameter (D50) when the amount (volume) of the first particles (large particles) 21 is 100%. Similarly, the particle size (D50) of the second particles (medium particles) 22 is the median diameter (D50) when the amount (volume) of the second particles (medium particles) 22 is 100%, and the particle size (D50) of the third particles (small particles) 23 is the median diameter (D50) when the amount (volume) of the third particles (small particles) 23 is 100%. The median diameter (D50) is the particle diameter at which the cumulative volume frequency of particles is 50% in a volume-based particle size distribution. As will be described later, the filler 12 is produced by mixing first particles (large particles) 21, second particles (medium particles) 22, and third particles (small particles) 23. The particle diameters (D50) of the first particles (large particles) 21, the second particles (medium particles) 22, and the third particles (small particles) 23 can also be referred to as the particle diameters (D50) of the respective particles before mixing.

[0026] Furthermore, among the third particles (small particles) 23, 30 particles having an equivalent circle diameter (ECD) of less than 1 μm are randomly selected and measured, and the average circularity obtained is 0.7 or less. The average circularity of the third particles is preferably 0.65 or less, and more preferably 0.63 or less. The lower limit of the average circularity of the third particles is preferably 0.50 or more. Note that the equivalent circle diameter in this embodiment may be the projected area diameter, i.e., the diameter of a circle having the same area as the projected area of ​​the particle (Heywood diameter).

[0027] The average circularity (average roundness) was measured by analyzing powder particles photographed at 500x magnification using an SEM (SU8230, manufactured by Hitachi High-Tech Corporation) using image analysis software Fiji (ImageJ, with 'Batteries Included'). The circularity (roundness) of a particle was calculated by the following formula: 4π × (projected area of ​​particle) / (length of particle contour). ２ is the value of

[0028] Regarding the mixing ratio of each particle constituting the filler 12, for example, when the total amount of the filler 12 is taken as 100% by volume, the mixing ratio of the second particles 22 is 9% by volume or more and 33% by volume or less, the mixing ratio of the third particles 23 is 4% by volume or more and 28% by volume or less, and the first particles 21 may be the remainder excluding the second particles 22 and the third particles 23. The mixing ratio of the second particles 22 is preferably 14% by volume or more and 33% by volume or less, and more preferably 20% by volume or more and 33% by volume or less. The mixing ratio of the third particles 23 is preferably 7% by volume or more and 18% by volume or less, and more preferably 9% by volume or more and 17% by volume or less.

[0029] In the thermally conductive resin material 10 of this embodiment, as described above, the alumina particles constituting the filler 12 are composed of first particles (large particles) 21, second particles (medium particles) 22, and third particles (small particles) 23, each of which has a different particle size range, and the particle size distribution is trimodal. Therefore, the second particles (medium particles) 22 and the third particles (small particles) 23 can be inserted between the first particles (large particles) 21, and the third particles (small particles) 23 can be inserted between the second particles (medium particles) 22. This allows the amount of filler 12 added to the resin 11 to be increased, thereby improving thermal conductivity compared to when a filler of one type of particle size range is used.

[0030] Furthermore, by using particles with an average circularity of 0.7 or less as the third particles (small particles) 23, the contact area between adjacent particles increases compared to when spherical particles are used, thereby reducing thermal resistance and improving thermal conductivity.

[0031] Furthermore, when a silicone resin is used as the resin 11 as in this embodiment, the thermally conductive resin material 10 may be formulated so that it contains 2500 parts by mass or less of the filler 12 per 100 parts by mass of the resin 11 (the total of the silicone resin, the urethane resin, and the silane coupling agent). The amount of the filler 12 is preferably 1000 parts by mass or more and 2500 parts by mass or less, and more preferably 1200 parts by mass or more and 2500 parts by mass or less.

[0032] By adjusting the blending amount of filler relative to resin 11 within an appropriate range, the Asker C hardness of thermally conductive resin material 10 can be reduced, and thermally conductive resin material 10 can be provided in close contact with an object to which it is applied, even if the object has a curved or uneven surface. For example, the Asker C hardness of thermally conductive resin material 10 is measured using a durometer (Asker Rubber Hardness Tester Type C, manufactured by Kobunshi Keiki Co., Ltd.) in accordance with JIS K 7312, and this Asker C hardness may be 90 or less, preferably 80 or less, more preferably 75 or less, more preferably 70 or less, and more preferably 30 or less. The lower limit of the Asker C hardness is preferably 0 or more.

[0033] As described above, according to the thermally conductive resin material 10 of this embodiment, by using as the filler 12 the first particles (large particles) 21, the second particles (medium particles) 22, and the third particles (small particles) 23, which have a trimodal particle size distribution and three different particle size ranges, the amount of filler 12 added to the resin 11 can be increased, and a thermally conductive resin material with improved thermal conductivity can be realized compared to when a filler made up of particles of one or two different particle size ranges is used.

[0034] Furthermore, by using particles with an average circularity of 0.7 or less for the third particles (small particles) 23, the contact area between adjacent particles can be increased. For example, when spherical particles are used, adjacent particles will be in contact with each other in a manner that is close to point contact. However, by using third particles (small particles) 23 with an average circularity of 0.7 or less, as in this embodiment, the area of ​​surface contact between adjacent particles increases, thereby reducing thermal resistance and achieving a thermally conductive resin material with improved thermal conductivity. The thermal conductivity of the thermally conductive resin material 10 of this embodiment is preferably 4.3 W / m·K or more, more preferably 5.0 W / m·K or more, and even more preferably 5.5 W / m·K or more.

[0035] (Method for manufacturing thermally conductive resin material) When manufacturing the thermally conductive resin material of this embodiment, first, the first particles (large particles) 21 having a particle size of 10 μm or more, the second particles (medium particles) 22 having a particle size of 1 μm or more and less than 10 μm, and the third particles (small particles) 23 having a particle size of 0.1 μm or more and less than 1 μm, which constitute the filler 12, are mixed in advance (filler mixing process).

[0036] There is no particular limitation on the order in which these first particles 21, second particles 22, and third particles 23 are mixed. For example, the first particles 21, second particles 22, and third particles 23 may be mixed simultaneously, or the third particles 23 may be mixed with a mixture of the first particles 21 and the second particles 22. Such a filler mixing step may be performed by dry mixing or wet mixing, and the mixing method is not particularly limited.

[0037] The mixing ratio of each particle constituting the filler 12 may be, for example, when the total amount of the filler 12 is taken as 100 volume %, such that the second particles 22 are 9 volume % or more and 33 volume % or less, the third particles 23 are 4 volume % or more and 28 volume % or less, and the first particles 21 are the volume % remaining excluding the second particles 22 and the third particles 23. An example of the mixing ratio is first particles 21:70 volume %, second particles 22:20 volume %, and third particles 23:10 volume %.

[0038] Next, the filler 12 is kneaded into the resin 11 (kneading step). As an example, 2000 parts by mass of the filler 12, which is a mixture of three types of particles having different particle diameter ranges as described above, is added with 100 parts by mass of silicone resin as the resin 11, and the mixture is kneaded.

[0039] As the kneading method, various kneading methods can be applied, for example, a method of kneading using a machine such as a vacuum degassing mixer, extrusion, a kneading roll, a kneader, a Banbury mixer, etc. Kneading using a vacuum degassing mixer is particularly preferred from the viewpoints of workability and reduction of entrapped air.

[0040] The thermally conductive resin material 10 of this embodiment is obtained through the steps described above. The thermally conductive resin material 10 thus obtained can be molded into a predetermined shape by, for example, a coater, a calendar roll, extrusion, a press, or the like. For example, when molding using a calendar roll, a film-like thermally conductive resin material 10 can be obtained that can be easily formed into heat-generating parts of electronic devices and the like.

[0041] Although the embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit (requirements) of the invention. These embodiments and their modifications are included within the scope and spirit (requirements) of the invention, as well as within the scope of the invention and its equivalents as set forth in the claims.

[0042] The thermally conductive resin material of the present invention was actually manufactured, and its properties were investigated. [1] Filler The following three types of alumina particles were used as fillers in the present invention examples: (Large particles) fused alumina (DAM45: manufactured by Denka Co., Ltd.), with a volume-based average particle diameter (D50) of 41.2 μm; (Medium particles) fused alumina (DAM05: manufactured by Denka Co., Ltd.), with a volume-based average particle diameter (D50) of 5.3 μm; (Small particles) fused alumina (AES-11C: manufactured by Sumitomo Chemical Co., Ltd.), with a volume-based average particle diameter (D50) of 0.43 μm. As fillers for comparative examples, the following two types of alumina particles were used instead of the small particles used in the present invention examples: (Small particles) Sumicorundum (registered trademark) (AA-03F: manufactured by Sumitomo Chemical Co., Ltd.), with a volume-based average particle diameter (D50) of 0.26 μm. (Small particles) Sumicorundum (registered trademark) (AA-05: manufactured by Sumitomo Chemical Co., Ltd.), volume-based average particle size (D50) is 0.58 μm.

[0043] Of the alumina particles described above, graphs of particle size distributions of DAM45, DAM05, and AES-11C used in the present invention examples are shown in Figures 3A to 3C. The particle size distribution after mixing these three types of alumina particles to form a filler is as shown in Figure 2 above. Note that Figure 2 is a graph after taking into account the blending ratio of each alumina particle. In detail, the graph of Figure 2 was calculated by adding up the particle size distributions of the three types of alumina particles, taking into account the blending ratios of the three types of alumina particles. As shown in Figure 2, the filler in the present invention example exhibited a trimodal particle size distribution containing three peaks.

[0044] Furthermore, among the alumina particles described above, the average circularity of AES-11C was 0.624, the average circularity of AA-03F was 0.734, and the average circularity of AA-05 was 0.763. SEM images of the shapes of these three types of small particles are shown in Figures 4A to 4C. As shown in Figures 4A to 4C, most of the particles in AA-05 were circular or nearly circular, while in AES-11C, there were few particles that were nearly circular, and many polygonal particles were observed.

[0045] Using the above-described alumina particles, large particles, medium particles, and small particles were mixed in the ratios (volume %) shown in Table 1 below to form respective fillers. Then, 1600 parts by mass of each filler was mixed with 100 parts by mass of a resin containing 50 parts by mass of a silicone resin (KE-1051J: manufactured by Shin-Etsu Chemical Co., Ltd.) and 50 parts by mass of a silane coupling agent (KBM3103C: manufactured by Shin-Etsu Chemical Co., Ltd.). The filler and resin were mixed using a rotary / revolution vacuum mixer (Thinky Mixer ARV-310, manufactured by Thinky Corporation) while degassing to produce a thermally conductive resin material. The resulting thermally conductive resin material was molded into a predetermined shape. The silicone resin (KE-1051J) is a two-component curing resin that cures at room temperature by mixing two components (component A and component B). However, the curing rate increases when heated. Therefore, heating may be used to obtain a desired curing rate (curing time).

[0046] In this manner, samples of Inventive Examples 1 to 17 and Comparative Examples 1 and 2 were prepared. These samples were then used to measure thermal conductivity and Asker C hardness. Thermal conductivity was measured using a thermal conductivity measuring device (IE-1237, manufactured by Iwasaki Tsushinki Co., Ltd.) by a steady-state method in accordance with ASTM D5470. Additionally, Asker C hardness was measured using a durometer (Asker Rubber Hardness Tester Type C, manufactured by Kobunshi Keiki Co., Ltd.) in accordance with JIS K 7312.

[0047] Table 1 shows the compounding ratio (volume %) of each particle constituting the filler of each sample of Inventive Examples 1 to 17 and Comparative Examples 1 and 2, as well as the measurement results of Asker C hardness and thermal conductivity.

[0048]

[0049] According to the results shown in Table 1, even when small particles with low average circularity (AES-11C) were used, as in Examples 1 to 17 of the present invention, the thermal conductivity was at least 4.4 (W / mK) and at most 5.8 (W / mK), and on average, almost the same thermal conductivity was obtained as compared to the thermal conductivity of Comparative Examples 1 and 2, which used small particles with high average circularity (AA-03F, AA-05).

[0050] AA-03F and AA-05 are alpha alumina crystal particles manufactured using a special manufacturing method such as the hydrolysis of aluminum alkoxide, but by using AES-11C, a low-cost fused alumina, instead of high-cost alumina particles such as AA-03F or AA-05, it has been confirmed that a low-cost thermally conductive resin material can be realized without significantly reducing thermal conductivity.For reference, if the general market price of AES-11C is taken as 1, then AA-03F and AA-05 are around 10.

[0051] When the thermally conductive resin material of this embodiment is applied to an IC chip, a lithium ion battery, or the like, it can quickly conduct the large amount of heat generated in the heat-generating portion toward a heat dissipation member, etc. Therefore, the thermally conductive resin material of this embodiment is suitably applied as a heat dissipation member for electrical components such as an IC chip or a lithium ion battery.

[0052] REFERENCE SIGNS LIST 10... Thermally conductive resin material 11... Resin 12... Filler 21... First particles (large particles) 22... Second particles (medium particles) 23... Third particles (small particles)

Claims

1. A thermally conductive resin material having a resin and a particulate filler dispersed in the resin, wherein a graph showing the particle size distribution of the filler has a first peak, a second peak, and a third peak, the first peak being 20 μm or more and 80 μm or less, the second peak being 1 μm or more and 10 μm or less, and the third peak being 0.1 μm or more and less than 1 μm, the filler including first particles having a particle size of 10 μm or more, second particles having a particle size of 1 μm or more and less than 10 μm, and third particles having a particle size of 0.1 μm or more and less than 1 μm, and wherein the average circularity obtained by measuring 30 particles having a circle-equivalent diameter of less than 1 μm among the third particles is 0.7 or less.

2. A thermally conductive resin material as described in claim 1, wherein, when the total amount of the filler is 100% by volume, the filler contains the second particles in a proportion of 9% by volume or more and 33% by volume or less, the third particles in a proportion of 4% by volume or more and 28% by volume or less, and the remainder being the first particles.

3. The thermally conductive resin material according to claim 1 or 2, wherein the resin contains a silicone resin and a silane coupling agent.

4. A thermally conductive resin material according to claim 3, wherein the thermally conductive resin material contains 2,500 parts by mass or less of the filler per 100 parts by mass of the resin.

5. The thermally conductive resin material according to claim 1 or 2, wherein the filler is alumina particles.

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