Thermally conductive resin composition, cured material, thermally conductive member and electronic device

Abstract

To provide a thermally conductive resin composition that develops high thermal conductivity and excellent endurance, a cured material of the thermally conductive resin composition, a thermally conductive member containing the cured material, and an electronic device with the thermally conductive member and a heat dissipation member.SOLUTION: A thermally conductive resin composition comprises an epoxy resin and thermally conductive powders, wherein the thermally conductive powders include aluminum nitride having a silicon-containing oxide coating on the surface and other thermally conductive powders, the content of the epoxy resin is 1% by mass or more and 20% by mass or less based on the total amount of the thermally conductive resin composition, the content of the thermally conductive powders is 80% by mass or more and 99% by mass or less based on the total amount of the thermally conductive resin composition, the content of the aluminum nitride having the silicon-containing oxide coating on the surface is 10% by mass or more and 70% by mass or less based on the total amount of the thermally conductive resin composition, and the content of the other thermally conductive powders is 10% by mass or more and 89% by mass or less based on the total amount of the thermally conductive resin composition.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a thermally conductive resin composition, a cured product, a thermally conductive member, and an electronic device. [Background technology]

[0002] In recent years, with the advancement in performance and miniaturization of electronic devices and components, the amount of heat generated from heat sources in electronic devices and other devices has increased, and methods for efficiently dissipating heat have been actively researched. In order to efficiently dissipate heat from a heat source to a heat sink, the thermally conductive material interposed between them is required to have high thermal conductivity and also to have insulating properties. Such thermally conductive materials are generally thermally conductive resin compositions in which a matrix such as a resin is filled with a powder that imparts thermal conductivity.

[0003] As a thermally conductive material, Patent Document 1 discloses a resin composition containing a filler including alumina particles and boron nitride particles, an elastomer having a specific weight-average molecular weight, and a curable resin. Also, Patent Document 2 discloses an example of a resin composition containing an epoxy resin, boron nitride particles, and alumina particles. Here, particularly high thermal conductivity is required in the case of thermal conductive materials used to counter heat generation in, for example, power modules that generate a very large amount of heat. However, the resin compositions described in Patent Documents 1 and 2 only achieve a thermal conductivity of 12 W / m K or less, leaving room for further improvement.

[0004] Under these circumstances, Patent Document 3 discloses a thermally conductive sheet for semiconductor modules, which includes an epoxy resin layer made of an epoxy composition containing a specific epoxy monomer, a specific phenolic curing agent, and boron nitride particles or aluminum nitride particles, with the boron nitride particles or aluminum nitride particles contained in the form of aggregated particles. Some of the thermally conductive sheets disclosed in Patent Document 3 have high thermal conductivities of 14 W / m K or more. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 5907171 [Patent Document 2] Japanese Patent Application Publication No. 2019-150997 [Patent Document 3] Patent No. 6276576 Summary of the Invention [Problem to be solved by the invention]

[0006] In the case of thermal conductive materials used to counter heat generation in power modules and the like, high thermal conductivity is particularly required, as well as durability such as heat resistance and moisture resistance. However, according to the studies of the present inventors, it was found that the thermal conductive sheet described in Patent Document 3 has high thermal conductivity but insufficient durability.

[0007] The present invention has been made to solve the above-mentioned problems, and aims to provide a thermally conductive resin composition that exhibits high thermal conductivity and excellent durability, to provide a cured product of the thermally conductive resin composition, to provide a thermally conductive member containing the cured product, and to provide an electronic device that has the thermally conductive member and a heat dissipation member. [Means for solving the problem]

[0008] As a result of extensive research into solving the above problems, the present inventors have found that the above problems can be solved by the following invention.

[0009] The present invention includes the following [1] to

[11] . [1] A thermally conductive resin composition comprising an epoxy resin and a thermally conductive powder, the thermally conductive powder includes aluminum nitride having a silicon-containing oxide coating on its surface and other thermally conductive powders; the content of the epoxy resin is 1% by mass or more and 20% by mass or less with respect to the total amount of the thermally conductive resin composition, A thermally conductive resin composition, wherein the content of the thermally conductive powder is 80% by mass or more and 99% by mass or less, based on the total amount of the thermally conductive resin composition, the content of the aluminum nitride having a silicon-containing oxide coating on its surface is 10% by mass or more and 70% by mass or less, based on the total amount of the thermally conductive resin composition, and the content of the other thermally conductive powder is 10% by mass or more and 89% by mass or less, based on the total amount of the thermally conductive resin composition. [2] The thermally conductive resin composition according to [1] above, wherein the aluminum nitride having a silicon-containing oxide coating on its surface has a coverage of 70% or more and 100% or less as determined by low-energy ion scattering analysis. [3] The thermally conductive resin composition according to [1] or [2] above, wherein the epoxy resin comprises at least one selected from the group consisting of triphenylmethane-type epoxy resins and bisphenol-type epoxy resins. [4] The thermally conductive resin composition according to any one of the above [1] to [3], wherein the other thermally conductive powder contains a metal oxide. [5] The thermally conductive resin composition according to [4] above, wherein the metal oxide comprises alumina. [6] The thermally conductive resin composition according to any one of the above [1] to [5], which is used for heat dissipation in a power module. [7] A cured product of the thermally conductive resin composition according to any one of [1] to [6] above. [8] The cured product according to [7] above, which has a thermal conductivity of 14 W / m·K or more and exhibits a decrease in thermal conductivity of less than 10% after 168 hours in a pressure cooker test at 120°C, 2 atm (0.2 MPa), and 100% relative humidity. [9] A thermally conductive member comprising the cured product according to [7] or [8] above.

[10] The thermal conductive member according to [9] above, which is used for heat dissipation of a power module.

[11] An electronic device comprising the thermal conduction member according to [9] or

[10] above and a heat dissipation member. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a thermally conductive resin composition that exhibits high thermal conductivity and excellent durability. It is also possible to provide a cured product of the thermally conductive resin composition that has high thermal conductivity and excellent durability. Furthermore, it is also possible to provide a thermally conductive member that includes the cured product, and an electronic device that includes the thermally conductive member and a heat dissipation member. The thermally conductive resin composition of the present invention can achieve a thermal conductivity of 14 W / m·K or more, and also exhibits excellent durability. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, the present invention will be described in detail with reference to an embodiment. <Thermal conductive resin composition> One embodiment of the present invention is a thermally conductive resin composition comprising an epoxy resin and a thermally conductive powder, the thermally conductive powder includes aluminum nitride having a silicon-containing oxide coating on its surface and other thermally conductive powders (i.e., thermally conductive powders other than aluminum nitride having a silicon-containing oxide coating on its surface); the content of the epoxy resin is 1% by mass or more and 20% by mass or less with respect to the total amount of the thermally conductive resin composition, The thermally conductive resin composition has a thermally conductive powder content of 80% by mass or more and 99% by mass or less, based on the total amount of the thermally conductive resin composition, a content of aluminum nitride having a silicon-containing oxide coating on its surface of 10% by mass or more and 70% by mass or less, based on the total amount of the thermally conductive resin composition, and a content of the other thermally conductive powder of 10% by mass or more and 89% by mass or less, based on the total amount of the thermally conductive resin composition. The thermally conductive resin composition of the present embodiment exhibits high thermal conductivity and excellent durability, and therefore, a cured product of the thermally conductive resin composition has high thermal conductivity and excellent durability. Hereinafter, each component that may be contained in the thermally conductive resin composition of this embodiment will be described in detail.

[0012] [1. Epoxy Resin] The epoxy resin has electrical insulating properties and also has the function of increasing adhesion to the metal substrate. The epoxy resin may be any compound having two or more epoxy groups per molecule, and any epoxy resin known to date may be appropriately selected and used. Examples of epoxy resins include triphenylmethane-type epoxy resins, bisphenol-type epoxy resins, glycidyl ethers of polycarboxylic acids, and epoxy resins obtained by epoxidation of cyclohexane derivatives. One epoxy resin may be used alone, or two or more may be used in combination. Among these, from the viewpoints of heat resistance and ease of handling, it is preferable that the epoxy resin contains at least one selected from the group consisting of triphenylmethane-type epoxy resins and bisphenol-type epoxy resins. Examples of the bisphenol-type epoxy resin include bisphenol A-type epoxy resins and bisphenol F-type epoxy resins. It is also preferable to use a combination of bisphenol A-type epoxy resins and bisphenol F-type epoxy resins in order to lower the softening point of the epoxy resin.

[0013] The content of the epoxy resin is 1% by mass or more and 20% by mass or less, preferably 1% by mass or more and 10% by mass or less, more preferably 1.5% by mass or more and 7.0% by mass or less, and even more preferably 2.0% by mass or more and 5.0% by mass or less, based on the total amount of the thermally conductive resin composition of this embodiment. When the content of the epoxy resin is 1% by mass or more based on the total amount of the thermally conductive resin composition, the thermally conductive powder can be thoroughly mixed with the epoxy resin. Furthermore, when the content of the epoxy resin is 20% by mass or less based on the total amount of the thermally conductive resin composition, high thermal conductivity can be maintained.

[0014] [2. Thermally conductive powder] Thermally conductive powders are powders that have the function of transferring heat generated from electronic components or the like to the outside of the system (for example, to a heat dissipation member). Examples of thermally conductive powders include metals, metal nitrides, metal oxides, metal carbides, and metal hydroxides. One type of thermally conductive powder may be used alone, or two or more types may be used in combination. From the viewpoints of thermal conductivity and insulation, metal nitrides and metal oxides are preferred as thermally conductive powders, and it is particularly preferred to use a powder containing both a metal nitride and a metal oxide. However, in this embodiment, from the viewpoints of thermal conductivity and durability, as well as high fillability in epoxy resin, the thermally conductive powder contains aluminum nitride having a silicon-containing oxide coating on its surface (hereinafter, sometimes referred to as "silicon-containing oxide-coated aluminum nitride", which is a type of metal nitride). The thermally conductive powder further contains another thermally conductive powder, and as described above, it is preferable that the other thermally conductive powder contains the metal oxide. As described above, the other thermally conductive powder may be a metal, a metal nitride, a metal oxide, a metal carbide, a metal hydroxide, etc., but it is assumed that the other thermally conductive powder is not the silicon-containing oxide-coated aluminum nitride.

[0015] As described above, in this embodiment, the thermally conductive powder contains aluminum nitride coated with a silicon-containing oxide, but may further contain a metal nitride other than aluminum nitride coated with a silicon-containing oxide, such as boron nitride, aluminum nitride (excluding aluminum nitride coated with a silicon-containing oxide), and silicon nitride. From the viewpoint of achieving a thermal conductivity of 14 W / m·K or more and high durability, a preferred embodiment is one in which the thermally conductive powder contains aluminum nitride coated with a silicon-containing oxide and a metal oxide. The silicon-containing oxide coated aluminum nitride will be described in detail below, and the metal oxide will be described later.

[0016] (2-1. Aluminum nitride with a silicon-containing oxide coating on its surface) As the aluminum nitride, which is the raw material for the silicon-containing oxide-coated aluminum nitride, known products such as commercially available products can be used. Aluminum nitride may be obtained by any manufacturing method. For example, aluminum nitride obtained by a "direct nitriding method" in which metallic aluminum powder is directly reacted with nitrogen or ammonia, or a "reducing nitriding method" in which alumina is heated in a nitrogen or ammonia atmosphere while being reduced by carbon, and a nitriding reaction is simultaneously carried out, can be used. The shape of the silicon-containing oxide coated aluminum nitride is not particularly limited, but examples thereof include amorphous (crushed), spherical, elliptical, and plate-like (scale-like) shapes.

[0017] The silicon-containing oxide coated aluminum nitride has a silicon-containing oxide coating on its surface, which significantly contributes to improving the durability of the cured product of the thermally conductive resin composition. This is presumably because the "moisture resistance" of the cured product of the thermally conductive resin composition is improved. Commercially available silicon-containing oxide coated aluminum nitride products can also be used. Since aluminum nitride itself has excellent thermal conductivity, aluminum nitride having a silicon-containing oxide coating on its surface (hereinafter also referred to as silicon-containing oxide-coated aluminum nitride) also has excellent thermal conductivity. Examples of the "silicon-containing oxide" that forms the silicon-containing oxide coating include silica and oxides containing silicon and aluminum.

[0018] The silicon-containing oxide coating may cover a portion or the entire surface of the aluminum nitride. Hereinafter, the percentage of the aluminum nitride surface that is covered by the silicon-containing oxide coating will be referred to as the "coverage." This coverage can be determined by low-energy ion scattering (LEIS) analysis. LEIS analysis is a measurement method that uses an ion source and a rare gas as a probe. LEIS analysis uses rare gas with an energy of several keV as incident ions, and is an evaluation method that enables composition analysis of the outermost surface (Reference: The TRC News 201610-04 (October 2016)). In the silicon-containing oxide-coated aluminum nitride, the coverage determined by LEIS analysis is not particularly limited, but is preferably 70% to 100%, more preferably 70% to 95%, even more preferably 72% to 90%, and particularly preferably 74% to 85%. When the coverage is 70% to 100%, the durability is further improved. Furthermore, when the coverage is 95% or less, high thermal conductivity can be maintained.

[0019] The coverage (%) of the silicon-containing oxide film (SiO2) covering the surface of aluminum nitride can be calculated using the following formula after LEIS analysis. (S Al (AlN)-S Al (AlN+SiO2)) / S Al (AlN) x 100 In the above formula, S Al (AlN) is the area of ​​the Al peak of aluminum nitride, and S Al (AlN+SiO2) is the area of ​​the Al peak of aluminum nitride coated with silicon-containing oxide. The area of ​​the Al peak can be determined by LEIS analysis.

[0020] (Method for forming silicon-containing oxide film) There are no particular limitations on the method for forming a silicon-containing oxide coating on the surface of aluminum nitride, and examples include a method comprising a first step of covering the surface of aluminum nitride with a siloxane compound containing a structural unit represented by the following formula (1), and a second step of heating the aluminum nitride covered with the siloxane compound at a temperature preferably between 300°C and 800°C.

[0021] [ka] (In formula (1), R is an alkyl group having 1 to 4 carbon atoms.)

[0022] In formula (1), R is an alkyl group having 1 to 4 carbon atoms, that is, a methyl group, an ethyl group, a propyl group, or a butyl group, preferably a methyl group, an ethyl group, an isopropyl group, or a t-butyl group, and more preferably a methyl group.

[0023] The siloxane compound is preferably an oligomer or polymer containing a structural unit represented by formula (1). In this specification, an oligomer refers to a compound having a weight-average molecular weight of 2,000 or less, and a polymer refers to a compound having a weight-average molecular weight of more than 2,000. The siloxane compound may be linear, branched, or cyclic. From the viewpoint of facilitating the formation of a silicon-containing oxide coating film with a uniform thickness, the weight-average molecular weight of the siloxane compound is preferably 100 to 2,000, more preferably 150 to 1,000, and even more preferably 180 to 500. In this specification, the weight-average molecular weight is a polystyrene-equivalent value measured by gel permeation chromatography (GPC).

[0024] As the siloxane compound, at least one selected from the group consisting of siloxane compounds represented by the following formula (2) and siloxane compounds represented by the following formula (3) is preferably used.

[0025] [ka] (In formula (2), R 1 and R 2 are each independently a hydrogen atom or a methyl group, and R 1 and R 2 At least one of the groups is a hydrogen atom. m is an integer of 0 to 10, preferably 1 to 5, and more preferably 1.

[0026] [ka] (In formula (3), n is an integer of 3 to 6, preferably 3 to 5, and more preferably 4.)

[0027] As the siloxane compound, a cyclic hydrogen siloxane oligomer in which n is 4 in the formula (3) is particularly preferred from the viewpoint of ease of forming a good silicon-containing oxide coating.

[0028] In the first step, the surface of the aluminum nitride is covered with a siloxane compound containing the structure represented by formula (1). In the first step, the method is not particularly limited as long as the surface of the aluminum nitride can be covered with a siloxane compound containing the structure represented by formula (1). Examples of the method for the first step include a dry mixing method in which a typical powder mixer is used to add the siloxane compound by spraying while stirring the raw material aluminum nitride, and then dry mixing to coat the aluminum nitride. Examples of the powder mixer include a Henschel mixer (manufactured by Nippon Coke & Engineering Co., Ltd.), a container-rotating V-blender, a container-rotating double-cone blender, a ribbon blender with mixing blades, a screw blender, a sealed rotary kiln, and stirring with a stirrer in a sealed container using a magnetic coupling. The temperature conditions are not particularly limited, but are preferably 10°C or higher and 200°C or lower, more preferably 20°C or higher and 150°C or lower, and even more preferably 40°C or higher and 100°C or lower.

[0029] Alternatively, a gas-phase adsorption method can be used, in which the vapor of the siloxane compound alone or a mixed gas of the siloxane compound vapor and an inert gas such as nitrogen gas is deposited or evaporated onto the surface of stationary aluminum nitride. The temperature conditions are not particularly limited, but are preferably 10°C to 200°C, more preferably 20°C to 150°C, and even more preferably 40°C to 100°C. In the gas-phase adsorption method, the system may be pressurized or depressurized as necessary. The apparatus that can be used in this case is preferably a sealed system that allows easy replacement of the gas within the system, such as a glass container, a desiccator, or a CVD (Chemical Vapor Deposition) apparatus.

[0030] The amount of the siloxane compound used in the first step is not particularly limited. In the aluminum nitride coated with the siloxane compound obtained in the first step, the amount of the siloxane compound coated is determined to be in proportion to the BET specific surface area (m 2 / g) to calculate the surface area of ​​1m 2 The coating amount of the siloxane compound is preferably 0.1 mg or more and 1.0 mg or less, more preferably 0.2 mg or more and 0.8 mg or less, and even more preferably 0.3 mg or more and 0.6 mg or less, per 1000 particles. When the coating amount of the siloxane compound is within the above range, aluminum nitride having a silicon-containing oxide coating with a uniform thickness can be obtained. The BET specific surface area (m 2 / g) to calculate the surface area of ​​1m 2 The coating amount of the siloxane compound per unit area was calculated by dividing the mass difference of the aluminum nitride before and after coating with the siloxane compound by the BET specific surface area (m 2 Surface area (m2) calculated from 2 ) can be found by dividing by

[0031] In the second step, the aluminum nitride coated with the siloxane compound obtained in the first step is heated at a temperature of preferably 300°C or higher and 800°C or lower. This allows a silicon-containing oxide coating to be formed on the surface of the aluminum nitride. The heating temperature is more preferably 400°C or higher and 800°C or lower, and even more preferably 500°C or higher and 800°C or lower.

[0032] The heating time is preferably 30 minutes to 6 hours, more preferably 45 minutes to 4 hours, and even more preferably 1 hour to 2 hours, from the viewpoint of ensuring sufficient reaction time and efficiently forming a good silicon-containing oxide coating. The heat treatment is preferably carried out in an atmosphere containing oxygen gas, for example, in the atmosphere (air).

[0033] After the heat treatment in the second step, the aluminum nitride particles coated with silicon-containing oxide may be partially fused together. In such cases, the aluminum nitride particles may be crushed using a general crusher such as a roller mill, hammer mill, jet mill, or ball mill to obtain aluminum nitride coated with silicon-containing oxide that is free from adhesion or aggregation.

[0034] Furthermore, after the second step is completed, the first step and the second step may be carried out in order. That is, the process of carrying out the first step and the second step in order may be repeated.

[0035] (2-2. Metal oxides) Examples of the metal oxide include zinc oxide, alumina, magnesium oxide, silicon dioxide, and iron oxide. Among these, alumina is preferred because it has high thermal conductivity, is available in a variety of particle sizes, and has a high degree of freedom in combination with metal nitrides. In other words, the metal oxide preferably includes alumina. The alumina is preferably α-alumina (α-Al2O3). In addition to α-alumina, γ-alumina, θ-alumina, δ-alumina, etc. may be included. The shape of the alumina is not particularly limited, but examples include amorphous (crushed), spherical, rounded, polyhedral, etc.

[0036] (2-3. Properties of thermally conductive powder) The particle size at 50% cumulative volume in the particle size distribution of the thermally conductive powder measured by the laser diffraction scattering method (hereinafter referred to as D50) is preferably 0.1 μm or more and 200 μm or less, more preferably 0.5 μm or more and 100 μm or less, and even more preferably 1.0 μm or more and 50 μm or less, from the viewpoints of adjusting the thickness of the thermally conductive material and of ease of handling when kneading the thermally conductive powder into a liquid resin. The D50 of the thermally conductive powder can be measured using a particle size distribution analyzer, and specifically, is measured by the method described in the examples. In particular, the D50 of alumina is not particularly limited, but is preferably 0.1 μm or more and 40 μm or less, more preferably 0.1 μm or more and 30 μm or less, and even more preferably 0.5 μm or more and 20 μm or less. In particular, the D50 of the silicon-containing oxide coated aluminum nitride is not particularly limited, but is preferably 0.2 μm or more and 200 μm or less, more preferably 10 μm or more and 100 μm or less, even more preferably more than 30 μm and 100 μm or less, particularly preferably 40 μm or more and 100 μm or less, and most preferably 40 μm or more and 80 μm or less, and may be 40 μm or more and 60 μm or less.

[0037] The specific surface area of ​​the thermally conductive powder is preferably 0.01 m from the viewpoint of high packing of the thermally conductive powder. 2 / g or more 10m 2 / g or less, more preferably 0.02m 2 / g or more 9m 2 / g or less, more preferably 0.03m 2 / g or more 8m 2 / g or less. In particular, the specific surface area of ​​alumina is not particularly limited, but is preferably 0.05 m 2 / g or more 10m 2 / g or less, more preferably 0.08m 2 / g or more 9m 2 / g or less, more preferably 0.1m 2 / g or more 8m 2 / g or less. In particular, the specific surface area of ​​the silicon-containing oxide coated aluminum nitride is not particularly limited, but is preferably 0.01 m 2 / g or more 0.3m 2 / g or less, more preferably 0.02m 2 / g or more 0.25m 2 / g or less, more preferably 0.03m 2 / g or more 0.2m 2 / g or less, particularly preferably 0.05m 2 / g or more 0.15m 2 / g or less. In this specification, the specific surface area is determined by the BET method (hereinafter referred to as the BET specific surface area), and is measured by the nitrogen adsorption BET single-point method using a gas flow method. The evaluation device that can be used is the "Macsorb (registered trademark) HM model-1210" (manufactured by Mountec Co., Ltd.). Incidentally, the resin compositions described in Patent Documents 1 and 2 do not achieve a high thermal conductivity of 14 W / m K or more, and this is presumably because the boron nitride particles used in Patent Documents 1 and 2 have a large specific surface area, and therefore the boron nitride particles cannot be densely packed to a degree that would achieve a thermal conductivity of 14 W / m K or more. Therefore, from the perspective of achieving a thermal conductivity of 14 W / m K or more, the specific surface area of ​​the thermally conductive powder used in this embodiment is preferably within the above range.

[0038] The thermally conductive powder may be a mixture of two or more types with different particle sizes (D50). For example, by combining alumina with a small particle size (e.g., alumina with a D50 of 0.1 μm to 30 μm) and aluminum nitride coated with a silicon-containing oxide with a larger particle size than alumina (e.g., aluminum nitride coated with a silicon-containing oxide with a D50 of more than 30 μm and 100 μm or less), the amount of the thermally conductive powder loaded in the thermally conductive resin composition can be increased, thereby increasing the thermal conductivity of the thermally conductive resin composition. From the same viewpoint, two or more aluminas with different D50 may be used in combination, or three to seven aluminas with different D50 may be used in combination, or three to five aluminas with different D50 may be used in combination. It is also preferable to use one or more silicon-containing oxide-coated aluminum nitrides in combination with two or more aluminas with different D50.

[0039] When two or more aluminas with different D50s are used in combination as the thermally conductive powder, it is preferable that the thermally conductive powder contains an alumina with a D50 of 0.1 μm or more and 2 μm or less (hereinafter referred to as "alumina I") and an alumina with a D50 of more than 2 μm and 30 μm or less (hereinafter referred to as "alumina II"). In this case, the mass ratio of alumina I to alumina II (alumina I / alumina II) is not particularly limited, but is preferably 10 / 90 to 60 / 40, more preferably 20 / 80 to 50 / 50, and even more preferably 30 / 70 to 45 / 55, from the viewpoint of increasing the loading of the thermally conductive powder in the thermally conductive resin composition. It is also preferable that the thermally conductive powder contains alumina I, alumina having a D50 of more than 2 μm and not more than 10 μm (hereinafter referred to as "alumina IIa"), and alumina having a D50 of more than 10 μm and not more than 30 μm (hereinafter referred to as "alumina IIb"). In this case, the mass ratio of alumina IIa to alumina IIb (alumina IIa / alumina IIb) is not particularly limited, but from the viewpoint of increasing the loading amount of the thermally conductive powder in the thermally conductive resin composition, it is preferably 40 / 60 to 90 / 10, more preferably 50 / 50 to 80 / 20, even more preferably 55 / 45 to 75 / 25, and particularly preferably 60 / 40 to 70 / 30. The mass ratio of alumina I to the total amount of alumina IIa and alumina IIb (which corresponds to the amount of alumina II) is as described above for alumina I / alumina II.

[0040] (2-4.Content) In the thermally conductive resin composition of this embodiment, the content of the silicon-containing oxide-coated aluminum nitride is 10% by mass or more and 70% by mass or less, preferably 20% by mass or more and 60% by mass or less, more preferably 30% by mass or more and 60% by mass or less, and even more preferably 40% by mass or more and 50% by mass or less, based on the total amount of the thermally conductive resin composition. When the content of the silicon-containing oxide-coated aluminum nitride is 10% by mass or more, based on the total amount of the thermally conductive resin composition, high thermal conductivity and excellent durability can be exhibited. Furthermore, when the content of the silicon-containing oxide-coated aluminum nitride is 70% by mass or less, based on the total amount of the thermally conductive resin composition, the silicon-containing oxide-coated aluminum nitride can be sufficiently filled into the epoxy resin. In the thermally conductive resin composition of this embodiment, the content of the other thermally conductive powder corresponds to the total amount of the thermally conductive powder minus the content of the silicon-containing oxide-coated aluminum nitride. Specifically, the content of the other thermally conductive powder is 10% by mass or more and 89% by mass or less, preferably 20% by mass or more and 79% by mass or less, more preferably 20% by mass or more and 69% by mass or less, and even more preferably 30% by mass or more and 59% by mass or less, based on the total amount of the thermally conductive resin composition. When the content of the other thermally conductive powder is 10% by mass or more, the fillability of the thermally conductive powder into the epoxy resin is excellent. When the content is 89% by mass or less, high thermal conductivity and excellent durability can be achieved.

[0041] In the thermally conductive powder, the mass ratio of the silicon-containing oxide-coated aluminum nitride to the other thermally conductive powder [silicon-containing oxide-coated aluminum nitride / other thermally conductive powder] is not particularly limited, but from the viewpoint of improving the fillability of the thermally conductive powder in the epoxy resin, it is preferably 20 / 80 to 80 / 20, more preferably 30 / 70 to 70 / 30, even more preferably 40 / 60 to 60 / 40, and particularly preferably 45 / 55 to 55 / 45. When the other thermally conductive powder contains a metal oxide, the mass ratio of the silicon-containing oxide-coated aluminum nitride to the metal oxide [silicon-containing oxide-coated aluminum nitride / metal oxide] from the viewpoint of improving the fillability of the thermally conductive powder in the epoxy resin is preferably 20 / 80 to 80 / 20, more preferably 30 / 70 to 70 / 30, even more preferably 40 / 60 to 60 / 40, and particularly preferably 45 / 55 to 55 / 45. Furthermore, even when the metal oxide contains alumina, the mass ratio of the silicon-containing oxide-coated aluminum nitride to the alumina [silicon-containing oxide-coated aluminum nitride / alumina] is preferably 20 / 80 to 80 / 20, more preferably 30 / 70 to 70 / 30, even more preferably 40 / 60 to 60 / 40, and particularly preferably 45 / 55 to 55 / 45, from the viewpoint of improving the fillability of the thermally conductive powder into the epoxy resin.

[0042] In order to enhance thermal conductivity, the total content of the silicon-containing oxide-coated aluminum nitride and the metal oxide in the thermally conductive powder is preferably 90% by mass or more, more preferably 95% by mass or more, and particularly preferably 100% by mass, based on the total amount of the thermally conductive powder. The same applies when the metal oxide contains alumina.

[0043] The content of the thermally conductive powder (i.e., the total content of the silicon-containing oxide-coated aluminum nitride and other thermally conductive powders) is 80% by mass or more and 99% by mass or less, preferably 85% by mass or more and 98% by mass or less, more preferably 90% by mass or more and 97% by mass or less, even more preferably 92% by mass or more and 97% by mass or less, and most preferably 94% by mass or more and 97% by mass or less, based on the total amount of the thermally conductive resin composition of this embodiment. When the content of the thermally conductive powder is 80% by mass or more, thermal conductivity can be increased, and when it is 99% by mass or less, the thermally conductive powder can be kneaded with a liquid resin.

[0044] [3. Hardener] The thermally conductive resin composition of this embodiment may contain a curing agent as needed. The curing agent is not particularly limited, and any known curing agent compatible with the epoxy resin may be used. Examples of the curing agent include phenol-based curing agents, amine-based curing agents, acid anhydride-based curing agents, isocyanate-based curing agents, polyaminoamide-based curing agents, and thiol-based curing agents. One type of curing agent may be used alone, or two or more types may be used in combination. Among these, a preferred embodiment is to use a phenolic curing agent as the curing agent, and more preferably to use a resorcinol novolac resin. The hydroxyl group equivalent of the phenolic curing agent is not particularly limited, but is preferably 20 to 200 g / eq, more preferably 30 to 150 g / eq, even more preferably 40 to 100 g / eq, and particularly preferably 45 to 80 g / eq.

[0045] When the thermally conductive resin composition of the present embodiment contains a curing agent, the content thereof is not particularly limited, but is preferably 5 parts by mass or more and 40 parts by mass or less, more preferably 10 parts by mass or more and 35 parts by mass or less, and even more preferably 15 parts by mass or more and 35 parts by mass or less, relative to 100 parts by mass of the epoxy resin.

[0046] The thermally conductive resin composition of the present embodiment may also contain a curing accelerator, a dispersant, a solvent, a discoloration inhibitor, a flexibility-imparting agent, an inorganic ion scavenger, a colorant, a viscosity adjuster, a reaction accelerator, and the like.

[0047] [4. Curing accelerator] Examples of the curing accelerator include imidazole compounds and derivatives thereof, organic phosphorus compounds, secondary amines, tertiary amines, and quaternary ammonium salts. One type of curing accelerator may be used alone, or two or more types may be used in combination. Among these, organic phosphorus compounds are preferred from the viewpoint of suppressing homopolymerization of the epoxy resin and facilitating the reaction between the epoxy resin and the curing agent.

[0048] When the thermally conductive resin composition of the present embodiment contains a curing accelerator, the content thereof is not particularly limited, but is preferably 0.1 parts by mass or more and 10 parts by mass or less, more preferably 0.3 parts by mass or more and 5 parts by mass or less, and even more preferably 0.5 parts by mass or more and 3 parts by mass or less, relative to 100 parts by mass of the epoxy resin.

[0049] [5. Dispersants] The thermally conductive resin composition of the present embodiment contains a dispersant, which improves the dispersion of the thermally conductive powder in the thermally conductive resin composition, thereby improving the performance of the thermally conductive resin composition and its cured product. The dispersant is not particularly limited, and examples thereof include elastomers, coupling agents, wetting dispersants, etc. One dispersant may be used alone, or two or more dispersants may be used in combination. Alternatively, an elastomer, a coupling agent, and a wetting dispersant may be used in combination. The elastomer, the coupling agent, and the wetting dispersant will be described below in order.

[0050] (5-1. Elastomer) The thermally conductive resin composition of this embodiment contains an elastomer, which reduces the viscosity of the thermally conductive resin composition. This reduces the increase in viscosity caused by the inclusion of a thermally conductive powder, improving the dispersion of the thermally conductive powder. As a result, the performance of the thermally conductive resin composition and its cured product can be improved, and the occurrence of voids can be reduced. Furthermore, the inclusion of an elastomer imparts flexibility to a coating film formed by applying a solvent-containing thermally conductive resin composition onto a film. The weight average molecular weight of the elastomer is not particularly limited, but from the viewpoint of compatibility with the curable resin, it is preferably from 10,000 to 100,000, more preferably from 10,000 to 50,000, and taking into consideration the dispersibility of the thermally conductive powder and ease of kneading, it is even more preferably from 10,000 to 30,000.

[0051] The elastomer preferably has at least one polarizable functional group. Here, the polarizable functional group (hereinafter also referred to as "polarizable group") refers to a functional group containing two or more types of atoms with different electronegativities and having a dipole moment. Examples of polarizable groups include carboxyl groups, ester groups, hydroxyl groups, carbonyl groups, amide groups, and imide groups. Among these, from the viewpoint of adsorption to the thermally conductive powder, the polarizable group is preferably at least one selected from the group consisting of carboxyl groups, ester groups, and hydroxyl groups. When an elastomer has a polarizable functional group, the polarizable functional group can form a hydrogen bond or electrostatic interaction with oxygen atoms on the surface of a thermally conductive powder (e.g., alumina). Therefore, an elastomer containing a polarizable functional group can efficiently adhere to the surface of the thermally conductive powder, efficiently coating at least a portion of the surface of the thermally conductive powder (e.g., alumina). Furthermore, the presence of the elastomer on at least a portion of the surface of the thermally conductive powder smoothes the surface of the thermally conductive powder and reduces the viscosity of the thermally conductive resin composition. Furthermore, the flexibility of a cured product formed using the thermally conductive resin composition is improved. Furthermore, the improved flexibility is thought to relieve stress and improve the adhesive strength between the cured product and a metal substrate. There are no particular restrictions on the content of polarizable groups contained in the elastomer. The content of structural units having polarizable groups in the resin constituting the elastomer is preferably 30 mol % or more, and more preferably 50 mol % or more. By keeping the polarizable group content within this range, the dispersibility of the thermally conductive powder is further improved.

[0052] The type of the elastomer is not particularly limited. Examples include silicone elastomers, nitrile elastomers, and acrylic elastomers. Among these, acrylic elastomers are preferred as the elastomer from the viewpoint of adhesion to the surface of the thermally conductive powder.

[0053] When the thermally conductive resin composition of this embodiment contains an elastomer, the content thereof is preferably 0.1 to 5% by mass, more preferably 0.2 to 2% by mass, and even more preferably 0.2 to 1.5% by mass, based on the total amount of the thermally conductive resin composition of this embodiment. When the elastomer content is 0.1% by mass or more, the dispersion of the thermally conductive powder in the thermally conductive resin composition can be improved, and when it is 5% by mass or less, the thermal conductivity of the thermally conductive resin composition and its cured product is not impaired.

[0054] (5-2. Coupling Agents) The thermally conductive resin composition of this embodiment contains a coupling agent, which improves the dispersion of the thermally conductive powder, thereby improving the performance of the thermally conductive resin composition and the cured product. Examples of the coupling agent include a silane-based coupling agent, a titanate-based coupling agent, and a silicone oligomer. When the thermally conductive resin composition of this embodiment contains a coupling agent, the content thereof is preferably 0.1 to 5 mass% of the total amount of the thermally conductive resin composition of this embodiment, more preferably 0.2 to 2 mass%, and even more preferably 0.2 to 1.5 mass%. When the content of the coupling agent is 0.1 mass% or more, the dispersion of the thermally conductive powder in the thermally conductive resin composition can be improved, and when it is 5 mass% or less, the thermal conductivity of the thermally conductive resin composition and its cured product is not impaired.

[0055] (5-3. Wetting and dispersing agents) The thermally conductive resin composition of the present embodiment contains a wetting dispersant, which improves the dispersion of the thermally conductive powder, thereby improving the performance of the thermally conductive resin composition and the cured product. Examples of wetting and dispersing agents include fluorine-based wetting and dispersing agents and silicone-based wetting and dispersing agents. One type of wetting and dispersing agent may be used alone, or two or more types may be used in combination. Commercially available wetting and dispersing agents may be used. When the thermally conductive resin composition of this embodiment contains a wetting dispersant, the content thereof is preferably 0.01% by mass or more and 3% by mass or less, more preferably 0.05% by mass or more and 2% by mass or less, and even more preferably 0.05% by mass or more and 1% by mass or less, relative to the total amount of the thermally conductive resin composition of this embodiment. When the content of the wetting dispersant is 0.01% by mass or more, the dispersion of the thermally conductive powder in the thermally conductive resin composition can be improved, and when it is 3% by mass or less, the thermal conductivity of the thermally conductive resin composition and its cured product is not impaired.

[0056] From the viewpoint of improving the performance of the thermally conductive resin composition and the cured product, the content (total content) of the dispersant in the thermally conductive resin composition of this embodiment is preferably 0.1 mass % or more and 5 mass % or less, more preferably 0.2 mass % or more and 3 mass % or less, and even more preferably 0.5 mass % or more and 2 mass % or less, relative to the total amount of the thermally conductive resin composition of this embodiment.

[0057] [6. Solvent] The thermally conductive resin composition of this embodiment may contain a solvent. The solvent may be used as a diluent or to dissolve a predetermined component. An example of a solvent used to dissolve a predetermined component is when, in preparing the thermally conductive resin composition of this embodiment, semi-solid or solid components such as an epoxy resin monomer, a curing agent, and a curing accelerator are dissolved in at least one solvent and then mixed. The solvent is not particularly limited as long as it does not inhibit the curing of the thermally conductive resin composition, and can be appropriately selected from commonly used solvents. Examples of the solvent include ketone-based organic solvents such as methyl ethyl ketone and cyclohexanone, and aromatic hydrocarbon-based organic solvents such as toluene and xylene. One type of solvent may be used alone, or two or more types may be used in combination. In the thermally conductive resin composition of this embodiment, the content of the solvent is not particularly limited, and can be appropriately selected depending on the degree of coatability of the thermally conductive resin composition.

[0058] In addition, known agents can be used as the discoloration inhibitor, the flexibility imparting agent, the inorganic ion scavenger, the colorant, the viscosity modifier, and the reaction accelerator.

[0059] (Method for preparing thermally conductive resin composition) The thermally conductive resin composition of this embodiment can be obtained by supplying the epoxy resin, the thermally conductive powder, and other components, which are blended as needed, all at once or in portions, to a dispersing / dissolving device, and mixing, dissolving, and kneading them while heating as needed. Examples of the dispersing / dissolving device include a grinder, a planetary mixer, a rotation / revolution mixer, a kneader, and a roll mill.

[0060] <Cured product> A cured product of the thermally conductive resin composition can be obtained by heating and curing the thermally conductive resin composition of this embodiment. In particular, a cured sheet of the thermally conductive resin composition can be obtained by applying the thermally conductive resin composition of this embodiment to a film, drying to remove the solvent, and then heating and curing. This cured sheet is one of the cured products described above. There are no particular restrictions on the heating temperature, but from the viewpoint of sufficient curing, it is preferably 150°C or higher and 200°C or lower, more preferably 155°C or higher and 200°C or lower, and even more preferably 160°C or higher and 180°C or lower. The heating and curing operation may be carried out in two or more stages. In this case, it is preferable to drive the curing reaction by heating at the highest temperature in the final stage. There are no particular restrictions on the thickness of the cured sheet, and it may be 100 μm or more and 400 μm or less, 150 μm or more and 400 μm or less, 150 μm or more and 300 μm or less, or 150 μm or more and 250 μm or less. The cured product may be in a B-stage state, i.e., a semi-cured state, but is preferably in a more cured C-stage state, as defined in JIS K6900 (1994).

[0061] (Thermal conductivity and durability of the cured product) The cured product of the thermally conductive resin composition of this embodiment has extremely high thermal conductivity, and can have a thermal conductivity of 14 W / m·K or more. The thermal conductivity of the cured product of the thermally conductive resin composition of this embodiment is preferably 15 to 20 W / m·K, and may be 15 to 18 W / m·K, 15 to 17 W / m·K, or 15 to 16 W / m·K. The thermal conductivity can be measured by the flash method in accordance with ISO 18755, and specifically, the value is measured by the method described in the examples. Furthermore, in a cured product of the thermally conductive resin composition of this embodiment, the rate of decrease in thermal conductivity after 168 hours in a pressure cooker test at 120°C, 2 atm (0.2 MPa), and 100% relative humidity [100 × (thermal conductivity before test − thermal conductivity after 168 hours) / (thermal conductivity before test)] is less than 10%, indicating excellent durability. The rate of decrease is preferably 8% or less, more preferably 5% or less, even more preferably 3% or less, and particularly preferably 2% or less.

[0062] Because the cured product of the thermally conductive resin composition of this embodiment has excellent thermal conductivity and durability, the thermally conductive resin composition of this embodiment and its cured product can be suitably used in heat-generating electronic components such as electronic devices, personal computers, automotive ECUs (Electronic Control Units), batteries, etc. More specifically, the thermally conductive resin composition of this embodiment is useful as a thermally conductive member such as a thermally conductive grease, sheet, or adhesive that is provided between a heat source and a heat dissipation member in an electronic device. In particular, considering its excellent durability, it is also useful as a heat dissipation material for power modules, which generally generate a large amount of heat.

[0063] <Thermal conductive materials and electronic devices> A thermally conductive member containing a cured product of the thermally conductive resin composition of this embodiment is also one aspect of this embodiment. By placing the heat dissipation member on a heat-generating electronic component via the heat conduction member of this embodiment, heat generated from the electronic component is efficiently dissipated to the outside through the heat conduction member and the heat dissipation member. The heat dissipation member is not particularly limited, but examples include (i) aluminum or copper fins, (ii) aluminum or copper blocks connected to a heat sink or heat pipe, (iii) aluminum or copper blocks with a cooling liquid circulated therein by a pump, (iv) Peltier elements, and (v) aluminum or copper blocks equipped with Peltier elements. The heat conduction member of this embodiment has high thermal conductivity and excellent heat resistance, and is therefore useful for heat dissipation in power modules. Furthermore, an electronic device having the heat conducting member and the heat dissipating member is also one of the present embodiments. Usually, the heat dissipating member is installed on the electronic device via the heat conducting member. [Example]

[0064] The present invention will now be described in detail with reference to examples, but the present invention is not limited to these examples in any way.

[0065] (Example 1 and Comparative Examples 1 and 2) (Preparation of Thermally Conductive Resin Composition) Each component was weighed into a polyethylene container in the blending amounts shown in Table 1, assuming a total epoxy resin content of 100 parts by mass, and then placed in a planetary centrifugal mixer (Thinky Corporation). Stirring and mixing was repeated three times at a rotational speed of 2,000 rpm for 20 seconds to obtain a thermally conductive resin composition for each example and comparative example. The blending amounts shown in Table 1 are blending amounts assuming that all solvent has been removed. Blank spaces in Table 1 indicate no blending. (Preparation of hardened sheet) The thermally conductive resin composition obtained above was applied to a release PET film (Panac Corporation, 75 μm thick) using a film coater (PI-1210, Tester Sangyo Co., Ltd.) to a thickness of 300 μm, and then dried at room temperature for 10 minutes and then in an oven at 100°C for 20 minutes to remove the solvent. After drying, the same release PET film as above was placed on the surface of the thermally conductive resin composition to sandwich the thermally conductive resin composition, and then heat-pressed at 150°C, 10 MPa, and 3 minutes using a heat press machine (H300-15, AS ONE Corporation) to obtain a B-stage (semi-cured) thermally conductive resin composition sheet. Next, the release PET films present on both sides were peeled off, and then both sides of the B-staged (semi-cured) thermally conductive resin composition sheet were sandwiched between copper foil (manufactured by Takumi Giken Co., Ltd., thickness 15 μm), and the sheet was heat-pressed at 165°C, 10 MPa, and 1 hour using the heat press. After that, the copper foil was peeled off to obtain a cured sheet (thickness 200 μm) of the thermally conductive resin composition in a C-staged state. The cured sheets thus obtained were evaluated according to the evaluation methods described below, and the results are shown in Table 1.

[0066] Here, the details of each component listed in Table 1 are as follows. <Epoxy resin> EPPN-502H: Triphenylmethane type epoxy resin, epoxy equivalent: 158 to 178 g / eq, manufactured by Nippon Kayaku Co., Ltd. Used as a cyclohexanone solution with a component concentration of 50% by mass. ZX-1059: Nippon Steel Chemical & Material Co., Ltd., a mixture of bisphenol F diglycidyl ether resin and bisphenol A diglycidyl ether resin, epoxy equivalent: 165g / eq

[0067] <Curing agent> Resorcinol novolak: manufactured by Showa Denko Materials Co., Ltd., hydroxyl group equivalent: 62 g / eq. Used as a cyclohexanone solution with a component concentration of 33 mass %. <Curing accelerator> Triphenylphosphine: manufactured by Kanto Chemical Co., Inc., used as a cyclohexanone solution with a component concentration of 16.7% by mass.

[0068] <Dispersant> Elastomer: Acrylic elastomer, manufactured by Showa Denko Materials Co., Ltd., weight average molecular weight: 24,000 Coupling agent: Silane coupling agent "KBM-573", N-phenyl-3-aminopropyltrimethoxysilane, manufactured by Shin-Etsu Chemical Co., Ltd. Wetting and dispersing agent: BYK-106, a salt of a polymer with an acid group, manufactured by BYK Japan Co., Ltd.

[0069] <Thermal conductive powder> (Silicon-containing oxide coated aluminum nitride) AlN5001: Showa Denko K.K., D50 = 45 μm, BET specific surface area = 0.09 m 2 / g, 75% coverage by LEIS analysis (aluminum nitride) FAN-f50-A1: Furukawa Denshi Co., Ltd., D50 = 42 μm, BET specific surface area = 0.08 m 2 / g, no silicon-containing oxide coating on the surface. (metal oxides) Alumina 1: ALUNABEAD (registered trademark) CB-A50S, manufactured by Showa Denko K.K., D50 = 50 μm, BET specific surface area = 0.10 m 2 / g Alumina 2: Sumicorundum (registered trademark) AA-18, manufactured by Sumitomo Chemical Co., Ltd., D50 = 20 μm, BET specific surface area = 0.15 m 2 / g Alumina 3: Sumicorundum (registered trademark) AA-5, manufactured by Sumitomo Chemical Co., Ltd., D50 = 6 μm, BET specific surface area = 0.28 m 2 / g Alumina 4: Sumicorundum (registered trademark) AA-3, manufactured by Sumitomo Chemical Co., Ltd., D50 = 3.7 μm, BET specific surface area = 0.48 m 2 / g Alumina 5: Sumicorundum (registered trademark) AA-04, manufactured by Sumitomo Chemical Co., Ltd., D50 = 0.5 μm, BET specific surface area = 4.10 m 2 / g

[0070] <Methods for measuring the physical properties of the above components> The epoxy equivalent of the epoxy resin was measured by perchloric acid titration method in accordance with JIS K 7236 (2009). The hydroxyl equivalent of the curing agent was measured by acetyl chloride-potassium hydroxide titration. Specifically, the hydroxyl groups of the curing agent to be measured were acetylated with acetyl chloride in a pyridine solution, and the excess acetyl chloride was then decomposed with water to produce acetic acid, which was then titrated with a potassium hydroxide / methanol solution. The titration endpoint was determined by potentiometric titration. The weight-average molecular weight of the elastomer is a polystyrene-equivalent value measured by gel permeation chromatography (GPC). The measurement was performed using a Showa Denko K.K. product, Shodex (registered trademark) GPC System-21 (columns: KF-802, KF-803, KF-805). The measurement conditions were a column temperature of 40°C, tetrahydrofuran as the eluent, and an elution rate of 1 ml / min. The D50 of the thermally conductive powder was defined as the particle size at which the cumulative volume reached 50% in the particle size distribution measured using a laser diffraction particle size distribution analyzer (manufactured by Microtrack Bell, product name: MT3300EXII). The specific surface area of ​​the thermally conductive powder was measured by a BET specific surface area using a nitrogen adsorption BET single-point method using a gas flow method. The evaluation device used was a Macsorb (registered trademark) HM model-1210 (manufactured by Mountec Co., Ltd.).

[0071] [Evaluation method] (I) Thermal conductivity Samples of the cured sheets obtained in each example were prepared using the method described below, and the thermal diffusivities of the samples were measured at 25°C using a laser flash thermal diffusivity analyzer "LFA447 NanoFlash" (manufactured by NETZSCH) conforming to ISO 18755. Additionally, assuming simple additivity for each component, the theoretical specific heat of the cured sheet was calculated as a weighted average taking into account the blending amounts of each component. Furthermore, the density of samples cut into 10 mm x 10 mm from the cured sheets was measured using the Archimedes method. The thermal conductivity of the cured sheet was calculated by multiplying the thermal diffusivity by the theoretical specific heat and the density. The samples for measuring thermal diffusivity were prepared by cutting the cured sheets obtained in each example into 10 mm × 10 mm pieces, coating both sides with gold using an ion coater (IB-3, manufactured by Eiko Co., Ltd.), and then coating both sides with graphite. The theoretical specific heat of the cured sheet in each example was calculated using the theoretical specific heat of aluminum nitride as 0.73 J / g K, the theoretical specific heat of alumina as 0.83 J / g K, and the theoretical specific heat of the epoxy resin component including the curing agent as 1.80 J / g K. Other components were ignored due to their trace amounts.

[0072] (II) Decrease rate of thermal conductivity (durability) The cured sheet obtained in each example was cut into a size of 10 mm x 10 mm and placed in a pressure-resistant container, which was then sealed with 5.0 g of ion-exchanged water. The pressure-resistant container was then heated in an oven (120°C, 2 atm (0.2 MPa), 100% relative humidity) to perform a pressure cooker test (hereinafter referred to as "PCT"), and the thermal conductivity was measured according to the above-mentioned (I) Method for Measuring Thermal Conductivity. The thermal conductivity was measured three times: before PCT, 48 hours after PCT, and 168 hours after PCT. The rate of decrease in thermal conductivity (%) was calculated using the following formula and used as an index of durability. The smaller the rate of decrease in thermal conductivity, the better the durability. Reduction rate of thermal conductivity (%) = 100 × (thermal conductivity before PCT - thermal conductivity after PCT) / (thermal conductivity before PCT)

[0073] [Table 1]

[0074] Table 1 shows that the cured product obtained in Example 1 had a very high thermal conductivity of 14 W / m K or more, and the rate of decrease in thermal conductivity after 168 hours of PCT was less than 10%, indicating excellent durability. Note that in Example 1, the thermal conductivity after 168 hours of PCT is slightly higher than the thermal conductivity after 48 hours of PCT, but this is due to measurement error, and it can be considered that there is substantially no change in thermal conductivity between 48 hours of PCT and 168 hours of PCT. On the other hand, in Comparative Example 1, in which aluminum nitride without a silicon-containing oxide coating on its surface was used instead of silicon-containing oxide-coated aluminum nitride, the thermal conductivity before PCT was high, but the rate of decrease in thermal conductivity after PCT was significantly more than 10%, indicating poor durability. Furthermore, in Comparative Example 2, in which alumina 1 (D50 = 50 μm) was used instead of silicon-containing oxide-coated aluminum nitride, the thermal conductivity before PCT was insufficient at less than 14 W / m·K, and the rate of decrease in thermal conductivity after PCT was significantly more than 10%, indicating poor durability.

Claims

1. A thermally conductive resin composition comprising an epoxy resin and a thermally conductive powder, the thermally conductive powder includes aluminum nitride having a silicon-containing oxide coating on its surface and other thermally conductive powders; the content of the epoxy resin is 1% by mass or more and 20% by mass or less based on the total amount of the thermally conductive resin composition, A thermally conductive resin composition, wherein the content of the thermally conductive powder is 80% by mass or more and 99% by mass or less, based on the total amount of the thermally conductive resin composition, the content of the aluminum nitride having a silicon-containing oxide coating on its surface is 10% by mass or more and 70% by mass or less, based on the total amount of the thermally conductive resin composition, and the content of the other thermally conductive powder is 10% by mass or more and 89% by mass or less, based on the total amount of the thermally conductive resin composition.

2. 2. The thermally conductive resin composition according to claim 1, wherein the aluminum nitride having a silicon-containing oxide coating on its surface has a coverage of 70% or more and 100% or less as determined by low-energy ion scattering analysis.

3. 2. The thermally conductive resin composition according to claim 1, wherein the epoxy resin comprises at least one selected from the group consisting of triphenylmethane-type epoxy resins and bisphenol-type epoxy resins.

4. The thermally conductive resin composition according to claim 1 , wherein the other thermally conductive powder comprises a metal oxide.

5. The thermally conductive resin composition according to claim 4 , wherein the metal oxide comprises alumina.

6. The thermally conductive resin composition according to claim 1, which is used for heat dissipation in a power module.

7. A cured product of the thermally conductive resin composition according to any one of claims 1 to 6.

8. 8. The cured product according to claim 7, which has a thermal conductivity of 14 W / m K or more and a decrease in the thermal conductivity of less than 10% after 168 hours in a pressure cooker test at 120°C, 2 atm (0.2 MPa), and 100% relative humidity.

9. A thermally conductive member comprising the cured product according to claim 7 .

10. The heat conduction member according to claim 9, which is used for heat dissipation in a power module.

11. An electronic device comprising the heat conduction member according to claim 9 and a heat dissipation member.

Images