Curable resin composition, resin sheet, composite sheet, heat dissipation member

Abstract

The objective is to provide a curable resin composition that can achieve both heat dissipation and desmear resistance. [Solution] A curable resin composition comprising a resin and a thermally conductive filler, wherein the content of the thermally conductive filler is 50% by volume or more and 80% by volume or less based on the total amount of the curable resin composition, and the thermally conductive filler comprises aluminum nitride filler whose surface is coated with an inorganic film.

Description

Technical Field

[0001] The present invention relates to a curable resin composition, a resin sheet made of the composition, a composite sheet laminated on the resin sheet, and a heat dissipation member including the resin sheet or the composite sheet.

Background Art

[0002] Resin compositions and resin sheets having thermal conductivity are widely used as heat dissipation materials, and various types have been proposed in the past. For example, Patent Document 1 discloses a resin composition including a first filler containing α-alumina, a second filler containing a nitride filler, and a thermosetting resin having a mesogenic group in the molecule. In the resin composition of Patent Document 1, the content of the first filler is 0.1% to 10% by volume in the total volume, the content of the second filler is 55% to 85% by volume in the total volume, and it is shown that both the first and second fillers have a predetermined average particle diameter.

[0003] Patent Document 2 discloses a resin composition including a first filler containing α-alumina and having a peak in the range of 1 nm or more and less than 500 nm in the particle size distribution measured by laser diffraction method, a second filler having a peak in the range of 1 to 100 μm in the particle size distribution, and a mesogenic group-containing thermosetting resin. Patent Document 2 further discloses that the second filler contains a nitride filler and the content of the second filler is 55% to 85% by volume in the total volume of the total solid content.

[0004] Patent Document 3 discloses an epoxy resin composition including, in addition to an epoxy resin monomer having a predetermined structure, a first filler having a predetermined average particle diameter and containing α-alumina particles, and a first filler having a predetermined average particle diameter and containing at least one selected from boron nitride particles and aluminum nitride particles.

[0005] Furthermore, various thermally conductive fillers have been proposed to be incorporated into resin compositions or resin sheets in order to improve heat dissipation. For example, Patent Document 4 discloses a highly thermally conductive composite particle comprising aluminum nitride particles and an organic coating layer containing an organic compound having mesogenic groups chemically bonded to the surface of the aluminum nitride particles, wherein the organic compound having mesogenic groups has a predetermined molecular structure.

[0006] Patent Document 5 discloses an invention relating to an epoxy resin composition comprising an epoxy resin, a curing agent, a curing catalyst, and a filler. Patent Document 5 also discloses that the filler includes aluminum nitride filler, that the average particle size of the aluminum nitride filler is 10.0 μm or less, that the uranium content of the aluminum nitride filler is 20 ppb or less, and that the blending ratio of aluminum nitride filler to the total amount of filler is 70% by mass or more.

[0007] Patent Document 6 discloses an epoxy resin composition containing an epoxy resin, a curing agent, and an inorganic filler. Furthermore, Patent Document 6 discloses that the inorganic filler contains coarse aluminum nitride particles and fine alumina particles, and that the content of coarse aluminum nitride particles relative to the total sum of the coarse aluminum nitride particles and fine alumina particles is 60-80% by volume.

[0008] Patent Document 7 discloses composite particles having aluminum nitride particles, a first coating layer containing α-alumina, and a second coating layer containing an organic substance which is a reaction product of aluminum nitride and a compound that selectively reacts with aluminum nitride. Patent Document 7 further discloses that the first coating layer covers at least a portion of the surface of the aluminum nitride particles, and the second coating layer covers the area of ​​the surface of the aluminum nitride particles other than the first coating layer.

[0009] Patent Document 8 discloses aluminum oxide-coated inorganic particles having a particle size of 500 μm or less, having a core portion mainly composed of inorganic material and a coating portion made of aluminum oxide that densely covers the core portion.

[0010] Patent Document 9 discloses a thermally conductive substrate characterized by comprising an aluminum nitride sintered body and a coating layer formed on the surface of the aluminum nitride sintered body, the coating layer being substantially made of aluminum phosphate and having a surface roughness of 2 μm or less.

[0011] Patent Document 10 discloses a highly thermally conductive composite particle comprising aluminum nitride particles and an organic coating layer containing an organic compound having mesogenic groups chemically bonded to the surface of the aluminum nitride particles, wherein the organic compound having mesogenic groups has a predetermined molecular structure. [Prior art documents] [Patent Documents]

[0012] [Patent Document 1] Patent No. 6132041 [Patent Document 2] Patent No. 6102744 [Patent Document 3] Patent No. 6171310 [Patent Document 4] Patent No. 5392178 [Patent Document 5] International Publication No. 2023 / 089878 [Patent Document 6] Patent No. 6074447 [Patent Document 7] Japanese Patent Publication No. 2012-176886 [Patent Document 8] Japanese Patent Publication No. 2017-14074 [Patent Document 9] Patent No. 3679815 [Patent Document 10] Patent No. 5392178 [Overview of the project] [Problems that the invention aims to solve]

[0013] In recent years, with the miniaturization and increased performance of electrical equipment, component-embedded substrates (SUBS) that incorporate various components within the substrate have been attracting attention. In component-embedded substrates, heat can be generated from the embedded components, requiring heat dissipation materials that contain a large amount of heat dissipation filler in the resin. Furthermore, in component-embedded substrates, the shorter distances between wiring markers necessitate smaller filler particle sizes, and with the expected increase in heat generation from semiconductor chips and other components in the future, the need for high heat dissipation when using small-particle fillers is becoming increasingly important. Currently, alumina fillers are mainly used as heat dissipation fillers, but aluminum nitride is attracting attention as a promising filler from the perspective of heat dissipation.

[0014] However, aluminum nitride has poor stability, and during desmear treatment, which involves using a strongly alkaline chemical solution to process vias on a substrate, the aluminum nitride decomposes. This can lead to poor heat dissipation of the heat dissipation material and cause the vias to collapse during processing, making it difficult to process vias as intended.

[0015] Patent documents 1 to 10 do not envision imparting desmear resistance to heat dissipation materials or the resin compositions that are their raw materials, and no measures are taken to that end.

[0016] Therefore, the object of the present invention is to provide a curable resin composition that can achieve both heat dissipation and desmear resistance. [Means for solving the problem]

[0017] As a result of diligent research, the present inventors have found that the above problem can be solved by including aluminum nitride filler, whose surface is coated with an inorganic film, as the thermal conductive filler in a curable resin composition containing a resin and a thermal conductive filler, while keeping the content of the thermal conductive filler within a predetermined range. In other words, the present invention provides the following [1] to

[11] .

[0018] [1] A curable resin composition containing a resin and a thermally conductive filler, wherein the content of the thermally conductive filler is 50% by volume or more and 80% by volume or less in 100% by volume of the curable resin composition, and the thermally conductive filler includes an aluminum nitride filler whose surface is coated with an inorganic film. [2] The curable resin composition according to [1], wherein the inorganic film contains a metal oxide or a phosphoric acid-based inorganic substance. [3] The curable resin composition according to [1] or [2], wherein the film thickness of the inorganic film determined by the following measurement method is 2 nm or more and 100 nm or less. (Measurement method) Among the aluminum nitride fillers contained in the curable resin composition, a cross-sectional image of one particle is observed, the average value of the thickness of the coating film at any 10 points is calculated, and the average value is taken as the film thickness. [4] The curable resin composition according to any one of [1] to [3], wherein the average particle diameter of the thermally conductive filler is 1 μm or more and 5 μm or less. [5] The curable resin composition according to any one of [1] to [4], wherein the content of the aluminum nitride filler is 50% by volume or more based on the total amount of the thermally conductive filler. [6] The curable resin composition according to any one of [1] to [5], wherein the resin is a thermosetting resin. [7] The curable resin composition according to [6], wherein the thermosetting resin is an epoxy resin. [8] A resin sheet comprising the curable resin composition according to any one of [1] to [7]. [9] The resin sheet according to [8], wherein the thickness of the resin sheet is 20 μm or less.

[10] A composite sheet in which a release film is laminated on at least one surface of the resin sheet according to [8] or [9].

[11] A heat dissipation member including the resin sheet according to [8] or [9], or the composite sheet according to

[10] .

Advantages of the Invention

[0019] According to the present invention, it is possible to provide a curable resin composition that can achieve both heat dissipation and desmear resistance. [Brief explanation of the drawing]

[0020] [Figure 1] This is a schematic cross-sectional view illustrating an example of a semiconductor chip package. [Figure 2] This is a schematic diagram showing the process of laminating a resin sheet onto a copper plate in the evaluation of embedding properties. [Modes for carrying out the invention]

[0021] [Curable resin composition] The curable resin composition of the present invention comprises a resin and a thermally conductive filler, and the content of the thermally conductive filler, expressed as a volume-based filling rate (volume filling rate), is 50% by volume or more and 80% by volume or less of 100% by volume of the curable resin composition. If the content of the thermally conductive filler is less than 50% by volume, it becomes difficult to impart heat dissipation properties to the curable resin composition. In addition, components other than the thermally conductive filler become more susceptible to decomposition during desmear treatment, reducing desmear resistance. Furthermore, if the content of the thermally conductive filler exceeds 80% by volume, even if the aluminum nitride particles are coated with an inorganic film, decomposition of the aluminum nitride particles occurs beyond a certain point, worsening desmear resistance. Based on the above, the content of the thermally conductive filler is preferably 50% to 75% by volume, and more preferably 50.2% to 70% by volume, based on the total amount of the curable resin composition.

[0022] The curable resin composition of the present invention contains aluminum nitride filler (hereinafter also simply referred to as "aluminum nitride filler") whose surface is coated with an inorganic film, as a thermally conductive filler. By including aluminum nitride filler, excellent heat dissipation can be provided, and by coating the surface of the aluminum nitride particles with an inorganic film, the stability of the aluminum nitride particles can be improved, and excellent desmear resistance can be provided.

[0023] The average particle size of the aluminum nitride filler is preferably 0.3 μm to 20 μm, more preferably 0.5 μm to 15 μm, even more preferably 0.8 μm to 10 μm, and even more preferably 1 μm to 5 μm. When the average particle size of the aluminum nitride filler is above the lower limit, it becomes easier to impart excellent heat dissipation properties to the curable resin composition. Furthermore, when the average particle size of the aluminum nitride filler is below the upper limit, it becomes easier to form a thin film when forming the curable resin composition into a sheet, making it suitable for use in applications such as circuit boards and component-embedded substrates. In addition, it improves embedding properties in confined spaces, making it more suitable for use in applications such as component-embedded substrates.

[0024] The average particle size mentioned above refers to the average particle size of the aluminum nitride filler contained in the curable resin composition. Furthermore, the average particle size of aluminum nitride filler is the average particle size obtained by averaging the particle sizes based on volume, and can be determined, for example, by measuring the particle size distribution using laser diffraction. As a measuring device, for example, the "Laser Diffraction Particle Size Distribution Analyzer" manufactured by Horiba, Ltd. can be used. For the calculation method of the average particle size, the particle size when the cumulative volume is 50% (d50) can be used as the average particle size. The same applies to the average particle size of other thermally conductive fillers described later.

[0025] The shape of the aluminum nitride filler is not particularly limited and can be, for example, polyhedral, irregular, plate-like, or spherical. Irregular shapes include crushed shapes obtained by crushing crystalline particles.

[0026] The inorganic film coating the aluminum nitride filler (hereinafter also referred to as the "coating film") preferably contains a metal oxide or a phosphoric acid-based inorganic substance. Including a metal oxide or a phosphoric acid-based inorganic substance makes it easier to impart excellent desmear resistance. Note that metal oxides also include metalloid oxides such as silicon oxide. The metal oxides are not particularly limited, but examples include magnesium oxide, titanium oxide, iron oxide, silicon oxide such as silica, aluminum oxide such as alumina, and zirconium oxide. Among these, titanium oxide, silicon oxide, and aluminum oxide are preferred.

[0027] When forming a coating film composed of metal oxides, it is preferable to deposit the film on the surface of the constituent aluminum nitride particles using methods such as chemical vapor deposition (CVD), atomic layer deposition (ALD), electrodeposition, sputtering, or sol-gel deposition. Among these methods, the sol-gel deposition method is preferred from the viewpoint of facilitating the uniform deposition of the coating film. The sol-gel method involves attaching a treatment agent, which includes, for example, an alkoxy compound containing Si, Al, Ti, and Zr, a curing agent as needed, and a catalyst, to the surface of aluminum nitride particles, and then forming a coating film composed of silica, alumina, titania, and zirconia by hydrolysis, dehydration condensation, etc. In this case, more specifically, the aluminum nitride particles are pre-immersed in a treatment agent containing a curing agent, stirred for a predetermined time as needed, then a precursor of a predetermined alkoxy compound is added to the treatment agent, and stirred for a predetermined time as needed, thereby attaching the treatment agent containing the precursor of the alkoxy compound to the aluminum nitride particles, and then undergoing hydrolysis, dehydration condensation, etc. Commercially available products may be used as the treatment agent, for example, the "Protector S" series from Okuno Pharmaceutical Co., Ltd., "Aluminum Isopropoxide" from Fujifilm Wako Pure Chemical Industries, Ltd., "Orgatic TA series" from Matsumoto Fine Chemical Co., Ltd., and "Orgatic ZA series" from Matsumoto Fine Chemical Co., Ltd. can be used.

[0028] When forming a coating film composed of phosphoric acid-based inorganic materials, it is preferable to form the film by baking phosphoric acid-based glass, as described above, from the viewpoint of facilitating uniform film formation. Wet treatment may be performed after baking. Specifically, the phosphate-based glass coating is obtained by mixing a predetermined amount of water, sodium hydrogen phosphate, and an 85% aqueous phosphoric acid solution, impregnating aluminum nitride particles into the mixture, and then firing it in air at 1300°C for 3 hours to obtain a phosphate-based glass film on the surface of the aluminum nitride particles.

[0029] The coating film may be formed from the above-mentioned metal oxides or phosphoric acid-based inorganic substances. Typically, the coating film may be mainly composed of compounds selected from the group consisting of the above-mentioned metal oxides and phosphoric acid-based inorganic substances. "Main component" means that the content of at least one of the metal oxides and phosphoric acid-based inorganic substances is, for example, 50% by mass or more, preferably 70% by mass or more, and more preferably 90% by mass or more and 100% by mass or less of the total coating film.

[0030] The thickness of the coating film covering the aluminum nitride filler is preferably 1 nm to 150 nm, more preferably 2 nm to 100 nm, and even more preferably 15 nm to 80 nm. If the film thickness is above the lower limit, it becomes easier to impart excellent desmear resistance to the curable resin composition. If the film thickness is below the upper limit, it becomes easier to impart excellent heat dissipation to the curable resin composition.

[0031] The thickness of the coating film can be measured by observing a cross-sectional image of a single particle of aluminum nitride filler contained in the curable resin composition and taking the average thickness of the coating film at any 10 points as the film thickness. Furthermore, the film thickness of the coating film can be adjusted by appropriately selecting the processing conditions when forming the coating film. For example, when forming the coating film by the sol-gel method, the film thickness can be adjusted by appropriately setting the concentration of the alkoxy compound precursor and curing agent in the processing agent. In addition, in CVD, ALD, sputtering, and electrodeposition methods, the film thickness can be adjusted by appropriately setting the amount of metal oxides and phosphoric acid-based inorganic substances attached to the surface of the aluminum nitride particles.

[0032] The aluminum nitride filler content, expressed as a volume-based filling rate, is preferably 35% by volume or more, more preferably 50% by volume or more, even more preferably 60% by volume or more, and even more preferably 65% ​​by volume or more, based on the total amount of thermal conductive filler. Setting the aluminum nitride filler content above the above lower limit makes it easier to impart excellent heat dissipation properties to the curable resin composition. The upper limit of the aluminum nitride filler content is not particularly limited, and it may be 100% by volume or less based on the total amount of thermal conductive filler. However, when used in combination with other thermal conductive fillers described later, for example, it may be 95% by volume or less, preferably 85% by volume or less, and more preferably 80% by volume or less.

[0033] The aluminum nitride filler content, expressed by mass, is preferably 20% by mass or more, more preferably 30% by mass or more, and even more preferably 40% by mass or more, based on the total amount of thermal conductive fillers. By setting the aluminum nitride filler content above the above lower limit, it becomes easier to impart excellent desmear resistance to the curable resin composition. The upper limit of the aluminum nitride filler content is not particularly limited, and it is sufficient if it is 100% by mass or less based on the total amount of thermal conductive fillers. However, when used in combination with other thermal conductive fillers described later, for example, it may be 90% by mass or less, preferably 80% by mass or less, and more preferably 75% by mass or less.

[0034] (Other thermally conductive fillers) The curable resin composition of the present invention may also contain thermally conductive fillers other than the aluminum nitride filler described above (hereinafter also referred to as "other thermally conductive fillers"). Specifically, examples include carbides, nitrides other than aluminum nitride filler, oxides, hydroxides, and carbon-based materials. From the viewpoint of improving thermal conductivity, the thermal conductivity of the other thermally conductive fillers is preferably 8 W / (m·K) or higher, more preferably 15 W / (m·K) or higher, and even more preferably 25 W / (m·K) or higher. The thermal conductivity can be measured, for example, on a cross-section of inorganic particles cut with a cross-section polisher using a thermal microscope manufactured by Bethel Co., Ltd., by the periodic heating thermoreflectance method.

[0035] Examples of carbides include silicon carbide, boron carbide, aluminum carbide, titanium carbide, and tungsten carbide. Examples of nitrides include silicon nitride, boron nitride, gallium nitride, chromium nitride, tungsten nitride, magnesium nitride, molybdenum nitride, and lithium nitride. Examples of oxides include zinc oxide, iron oxide, boehmite, aluminum oxide such as alumina, magnesium oxide, titanium oxide, cerium oxide, zirconium oxide, and silicon oxide (silica). Examples of hydroxides include metal hydroxides such as aluminum hydroxide, calcium hydroxide, and magnesium hydroxide. Examples of carbon-based materials include diamond, carbon black, graphite, graphene, fullerene, carbon nanotubes, and carbon nanofibers. Of the above, oxides are preferred, and alumina is more preferred. Furthermore, other thermally conductive fillers may be included individually or in combination of two or more types.

[0036] The average particle size of the other thermally conductive fillers is not particularly limited, but may be, for example, 0.05 μm or more and 20 μm or less, preferably 0.1 μm or more and 15 μm or less, and more preferably 0.2 μm or more and 10 μm or less. If the average particle size is above the lower limit, it becomes easier to impart excellent heat dissipation properties to the curable resin composition. If the average particle size is below the upper limit, it becomes easier to form a thin film when forming the curable resin composition into a sheet, making it suitable for use in applications such as circuit boards and component-embedded substrates. Furthermore, it improves embedding properties in confined spaces, making it suitable for use in applications such as component-embedded substrates.

[0037] Among the other thermally conductive fillers mentioned above, oxides are preferred, and alumina is more preferred. The alumina content is not particularly limited, but when expressed as a volume-based packing density (volume packing density), it is preferably 65 vol% or less, more preferably 50 vol% or less, and even more preferably 40 vol% or less. By keeping the content of other thermally conductive fillers below the above upper limit, it is possible to include a certain amount of the aluminum nitride filler, making it easier to achieve both heat dissipation and desmear resistance. Furthermore, the content of other thermally conductive fillers is not particularly limited, but for example, it may be 2 vol% or more, preferably 10 vol% or more, and more preferably 15 vol% or more.

[0038] The average particle size of the thermally conductive filler contained in the curable resin composition is preferably 0.3 μm to 20 μm, more preferably 0.5 μm to 10 μm, and even more preferably 1 μm to 5 μm. When the average particle size is above the lower limit, it becomes easier to impart excellent heat dissipation properties to the curable resin composition. Furthermore, when the average particle size is below the upper limit, it becomes easier to form a thin film when the curable resin composition is made into a sheet, making it suitable for use in applications such as circuit boards and component-embedded substrates. In addition, it becomes easier to embed in narrow spaces, making it suitable for use in applications such as component-embedded substrates. The average particle size of the thermally conductive filler referred to here is the average particle size of the entire thermally conductive filler contained in the curable resin composition.

[0039] The shape of the thermally conductive filler is not particularly limited and can be, for example, multifaceted, irregular, plate-like, needle-like, fibrous, or tubular. The polyhedron shape may be, for example, an octahedron, a truncated octahedron, or a cube. Polyhedron-shaped thermal conductive fillers are also known as as-grown particles, and are crystalline particles whose shape at the time of synthesis is maintained without being crushed. Irregular shapes include crushed shapes obtained by crushing crystalline particles.

[0040] The total content of the thermally conductive filler in the curable resin composition, expressed by mass, is preferably 300 parts by mass or more and 3000 parts by mass or less per 100 parts by mass of resin, more preferably 400 parts by mass or more and 2700 parts by mass or less, and even more preferably 500 parts by mass or more and 2500 parts by mass or less.

[0041] (resin) The resin included in the curable resin composition of the present invention is preferably a curable resin, and more preferably a thermosetting resin. Examples of thermosetting resins include amino resins such as urea resins and melamine resins, phenolic resins, acrylic resins, thermosetting urethane resins, epoxy resins, silicone resins, phenoxy resins, thermosetting polyimide resins, amino alkyd resins, benzoxazine resins, and bismaleimide resins. Among these, epoxy resins are preferred.

[0042] Examples of epoxy resins include compounds containing two or more epoxy groups in their molecules. Epoxy resins with a weight-average molecular weight of, for example, less than 10,000, preferably 5,000 or less. The weight-average molecular weight is the weight-average molecular weight in polystyrene terms, measured by gel permeation chromatography (GPC). For GPC measurements, tetrahydrofuran is preferably used as the eluent. However, for low molecular weights of 1000 or less, the weight-average molecular weight can be calculated from the structural formula. Furthermore, in curable resin compositions, epoxy resins may react during curing; however, the weight-average molecular weight refers to the weight-average molecular weight of the epoxy resin before curing.

[0043] Examples of epoxy resins include epoxy resins containing a styrene skeleton, resorcinol-type epoxy resins, bisphenol A-type epoxy resins, bisphenol F-type epoxy resins, bisphenol S-type epoxy resins, phenol novolac-type epoxy resins, biphenol-type epoxy resins, phenoxy-type epoxy resins, naphthalene-type epoxy resins, phenylene ether-type epoxy resins, fluorene-type epoxy resins, phenol aralkyl-type epoxy resins, naphthol aralkyl-type epoxy resins, dicyclopentadiene-type epoxy resins, anthracene-type epoxy resins, biphenyl-type epoxy resins, and other epoxy resins having a mesogenic skeleton, epoxy resins having an adamantane skeleton, epoxy resins having a tricyclodecane skeleton, and epoxy resins having a triazine core as their skeleton, as well as glycidylamine-type epoxy resins. Among those described above, at least one selected from bisphenol A type epoxy resin, bisphenol F type epoxy resin, dicyclopentadiene type epoxy resin, and epoxy resin having a mesogenic skeleton is preferred. More preferably, at least one selected from bisphenol A type epoxy resin, bisphenol F type epoxy resin, and dicyclopentadiene type epoxy resin is preferred.

[0044] The epoxy equivalent of the epoxy resin is not particularly limited, but is, for example, 100 g / eq or more and 1000 g / eq or less. Preferably, the epoxy equivalent of the epoxy resin is 120 g / eq or more, more preferably 140 g / eq or more, and also preferably 500 g / eq or less, more preferably 400 g / eq or less. The epoxy equivalent can be measured, for example, according to the method specified in JIS K 7236.

[0045] Furthermore, the resin content is, for example, 20% by mass or more and 90% by mass or less, preferably 30% by mass or more and 85% by mass or less, more preferably 35% by mass or more and 80% by mass or less, and even more preferably 40% by mass or more and 75% by mass or less, relative to the total amount of components of the curable resin composition excluding the thermal conductive filler.

[0046] As the resin, a polymer with a weight-average molecular weight of, for example, 10,000 or more may be used. Using a polymer makes it easier to improve the sheet properties of the curable resin composition. The polymer may be a thermosetting resin or a resin other than a thermosetting resin, but a thermosetting resin is preferred. Furthermore, the polymer may have functional groups such as epoxy groups and hydroxyl groups. The polymer is preferably used in combination with a thermosetting resin (hereinafter also referred to as "resin (A)") having a weight-average molecular weight of, for example, less than 10,000, and is particularly preferably used in combination with an epoxy resin as resin (A). The weight-average molecular weight of resin (A) is preferably 5,000 or less.

[0047] Specific examples of polymers include phenoxy resin, polyester resin, polyether resin, polyamide resin, polyamide-imide resin, polyimide resin, polyvinyl butyral resin, polyvinyl formaldehyde resin, polyhydroxypolyether resin, polystyrene resin, polycarbonate resin, butadiene resin, acrylonitrile-butadiene copolymer, acrylonitrile-butadiene-styrene resin, and styrene-butadiene copolymer. Among these, phenoxy resin is preferred. Examples of phenoxy resins include phenoxy resins having skeletons such as bisphenol A skeleton, bisphenol F skeleton, bisphenol S skeleton, bisphenolacetophenone skeleton, novolac skeleton, biphenyl skeleton, fluorene skeleton, dicyclopentadiene skeleton, norbornene skeleton, naphthalene skeleton, anthracene skeleton, adamantane skeleton, terpene skeleton, trimethylcyclohexane skeleton, and imide skeleton. Phenoxy resins may or may not have epoxy groups.

[0048] Examples of commercially available phenoxy resins include "YP-50S", "YP55", "YP70" (all manufactured by Nippon Steel Chemical & Material Co., Ltd.), "JER1256", "JER4250", "JER4275", "YX6954BH30", "YX6954BH30", "YX7553", "YX7553BH30", "YL7769BH30", "YL6794", "YL7213", "YL7290", "YL7891BH30", and "YL7482" (all manufactured by Mitsubishi Chemical Corporation).

[0049] The weight-average molecular weight of the polymer is not particularly limited, but is preferably 20,000 or more, more preferably 35,000 or more, preferably 100,000 or less, more preferably 80,000 or less, and even more preferably 70,000 or less.

[0050] The content of resin (A) is, for example, 20% by mass or more and 80% by mass or less, preferably 30% by mass or more and 75% by mass or less, more preferably 35% by mass or more and 70% by mass or less, and even more preferably 40% by mass or more and 65% by mass or less, based on the total amount of components of the curable resin composition excluding the thermal conductive filler.

[0051] The curable resin composition of the present invention is preferably used in combination with resin (A) when a polymer is used. When resin (A) and polymer are used together, the mass ratio of resin (A) to polymer is not particularly limited, but is, for example, 0.1 or more and 10 or less, preferably 0.2 or more and 8 or less, more preferably 0.3 or more and 7 or less, and even more preferably 0.2 or more and 8 or less. Resin (A) and polymer may be used individually or in combination of two or more types.

[0052] (Hardening agent) The curable resin composition of the present invention may optionally contain a curing agent. The curing agent is preferably included together with the thermosetting resin, and more preferably together with the epoxy resin. As for the curing agent, for example, when the curable resin composition contains an epoxy resin, it is preferable to include at least one selected from a curing agent having a triazine skeleton, a cyanate ester curing agent, a diamine curing agent, a phenol curing agent, an amine curing agent, an acid anhydride curing agent, a mercaptan curing agent, and an imidazole curing agent. In particular, it is more preferable to include at least one selected from a curing agent having a triazine skeleton, a cyanate ester curing agent, a diamine curing agent, and an acid anhydride curing agent. Using these as curing agents makes it easier to impart excellent heat dissipation properties to the curable resin composition.

[0053] <Curing agent with a triazine skeleton> Examples of curing agents having a triazine skeleton include phenol compounds, amine compounds, thiol compounds, imidazole compounds, and phosphine compounds, among which phenol compounds having a triazine skeleton are preferred. Furthermore, among curing agents having a triazine skeleton, compounds having an aminotriazine skeleton are more preferred. Curing agents having a triazine skeleton tend to have improved heat dissipation due to the increased alignment provided by the triazine skeleton. Examples of phenol compounds having a triazine skeleton include novolac-type phenol compounds, and more specifically, novolac-type phenol resins modified with melamine, benzoguanamine, etc. Examples of phenol compounds having a triazine skeleton include "Phenolite® LA-7052", "Phenolite® LA-7054", "Phenolite® LA-7751", "Phenolite® LA-1356", and "Phenolite® LA-3018-50P" (all manufactured by DIC Corporation). The curing agent having a triazine skeleton may be used alone or in combination of two or more types.

[0054] <Cyanate ester-based hardening agent> Cyanate ester curing agents are compounds containing a cyanate ester group (-OCN). Some of the cyanate ester group trimerizes during curing, forming a triazine skeleton. This creates a highly aligned molecular structure with the resin after curing, improving heat dissipation. Furthermore, from the viewpoint of improving curability, it is preferable that the cyanate ester curing agent has two or more cyanate ester groups in one molecule. From the viewpoint of improving heat dissipation by increasing the arrangement of the molecular structure and lowering the melting point, it is preferable that the cyanate ester curing agent has two to three cyanate ester groups in one molecule, and more preferably two.

[0055] Cyanate ester curing agents preferably have a skeleton containing an aromatic ring, and more preferably a skeleton containing a phenyl ring. Having a skeleton containing an aromatic ring improves the alignment after curing and makes it easier to further improve heat dissipation after curing. Furthermore, it is preferable that the cyanate ester group of the cyanate ester curing agent is directly bonded to the aromatic ring, and more preferably directly bonded to the phenyl ring. Direct bonding of the cyanate ester group to the aromatic ring makes it easier to increase the reactivity of the cyanate ester group, and facilitates trimerization and curing upon heating.

[0056] The cyanate ester curing agent preferably has a molecular weight of 500 or less. A molecular weight of 500 or less facilitates the curing reaction with the resin, making it easier to obtain a curable resin composition with excellent heat dissipation. Furthermore, the melting point of the cyanate ester curing agent tends to be below a certain level, improving the sheet properties of the curable resin composition and making it easier to prevent cracking when, for example, it is wound into a roll. The molecular weight of the cyanate ester curing agent is more preferably 400 or less, and even more preferably 320 or less. The molecular weight of the cyanate ester curing agent is not particularly limited, but for example, it may be 150 or more, or 200 or more.

[0057] Examples of cyanate ester curing agents include bisphenol-type cyanate esters. Bisphenol-type cyanate esters preferably have a bisphenol skeleton and a structure in which one cyanate ester group is directly bonded to each phenyl group of the bisphenol skeleton. Examples of bisphenol-type cyanate ester resins include bisphenol A-type cyanate ester resin, bisphenol E-type cyanate ester resin, and bisphenol F-type cyanate ester resin, among which bisphenol E-type cyanate ester resin is preferred. Furthermore, the cyanate ester curing agent may be a trimer of part or all of the above-mentioned bisphenol-type cyanate ester (trimerized cyanate ester), but monomeric bisphenol-type cyanate esters are preferred from the viewpoint of being able to lower the molecular weight and melting point. The cyanate ester-based curing agent may be used alone or in combination of two or more types. Commercially available cyanate ester curing agents may be used, such as "P-201" and "TA" from Mitsubishi Gas Chemical Company, and "BA-230S," "BA-3000S," "BTP-1000S," and "BTP-6020S" from Lonza Japan.

[0058] <Diamine-based curing agent> Examples of diamine-based curing agents include compounds having two amino groups. Here, the amino groups can be either primary or secondary amino groups, but primary amino groups are preferred from the viewpoint of reactivity. Therefore, it is preferable for amine-based curing agents to have two primary amino groups. Furthermore, as diamine-based curing agents, aromatic compounds or alicyclic compounds can be used from the viewpoint of improving arrangement and thus improving thermal conductivity, and aromatic compounds are preferred from the viewpoint of reactivity and further improving arrangement and thus improving thermal conductivity. Examples of aromatic compounds include aromatic compounds having an aromatic ring, preferably a phenyl group, in the molecule. Specifically, these may be aromatic amines in which an amino group is directly bonded to the aromatic ring, such as m-phenylenediamine, p-phenylenediamine, torylene-2,4-diamine, torylene-2,6-diamine, mesitylene-2,4-diamine, mesitylene-2,6-diamine, 3,5-diethyltrylene-2,4-diamine, 3,5-diethyltrylene-2,6-diamine, biphenylenediamine, 4,4-diaminodiphenylmethane, 2,5-naphthylenediamine, and 2,6-naphthylenediamine, or amines in which an amino group is not directly bonded to the aromatic ring, such as m-xylylenediamine, p-xylylenediamine, and reaction products of m-xylylenediamine and styrene. Among these, aromatic amines in which the amino group is directly bonded to the aromatic ring are more preferred from the viewpoint of reactivity. Examples of alicyclic compounds include alicyclic polyamines such as 1,3-bis(aminomethyl)cyclohexane, 1,4-bis(aminomethyl)cyclohexane, cyclohexanediamine, methylcyclohexanediamine, isophoronediamine, and 4,4'-methylenebis(N-sec-butylcyclohexaneamine). The diamine-based curing agent may be used alone or in combination of two or more types.

[0059] The molecular weight of the diamine curing agent is preferably 500 or less, more preferably 300 or less, and even more preferably 250 or less. By keeping the molecular weight of the diamine curing agent below the above upper limit, the amount of curing agent present is reduced, and consequently the amount of resin present is increased, making it easier to obtain a curable resin composition with excellent heat dissipation properties. The molecular weight of the diamine curing agent is not particularly limited, but for example, it may be 100 or more, preferably 150 or more, and more preferably 170 or more.

[0060] <Acid anhydride curing agent> Examples of acid anhydride-based curing agents include phthalic anhydride, hexahydrophthalic anhydride, 4-methylhexahydrophthalic anhydride, tetrahydrophthalic anhydride, 4-methyltetrahydrophthalic anhydride, and tetrabromophthalic anhydride. Acid anhydride-based curing agents may be used individually or in combination of two or more types.

[0061] The curing agent content is preferably 10 to 150 parts by mass, more preferably 15 to 120 parts by mass, and even more preferably 20 to 110 parts by mass, per 100 parts by mass of resin. If the curing agent content is above the lower limit, the curing reaction with the resin proceeds sufficiently, making it easier to obtain a curable resin composition with excellent sheetability. If the curing agent content is below the upper limit, the curing reaction with the resin can proceed without excessive curing agent content, making it easier to suppress curing agent bleed-out and other issues. As a result, by increasing the amount of resin present, it becomes easier to obtain a curable resin composition with excellent heat dissipation.

[0062] When a curable resin composition contains an epoxy resin and a curing agent, the ratio of the equivalent amount of the curing agent to the equivalent amount of the epoxy resin (equivalent amount of curing agent / equivalent amount of epoxy resin) is not particularly limited, but is, for example, 0.3 or more and 2 or less, preferably 0.4 or more and 1.5 or less, and more preferably 0.5 or more and 1.2 or less.

[0063] (Curing accelerator) The curable resin composition of the present invention may contain a curing accelerator. The curability of the curable resin composition can be enhanced by including a curing accelerator. The curing accelerator is not particularly limited and examples include imidazole-based curing accelerators, organophosphine-based curing accelerators, and tertiary amine-based curing accelerators. Among these, it is preferable to use at least one selected from imidazole-based curing accelerators and organophosphine-based curing accelerators.

[0064] Examples of imidazole-based curing accelerators include 1-cyanoethyl-2-phenylimidazole, in which the 1-position of imidazole is protected with a cyanoethyl group, and imidazole-based curing accelerators whose basicity is protected with isocyanuric acid. Examples of commercially available products include 2MA-OK, 2MZ, 2MZ-P, 2PZ, 2PZ-PW, 2P4MZ, C11Z-CNS, 2PZ-CN, 2PZ-CNS, 2PZCNS-PW, 2MZ-A, 2MZA-PW, C11Z-A, 2E4MZ-A, 2MAOK-PW, 2PZ-OK, 2MZ-OK, 2PHZ, 2PHZ-PW, 2P4MHZ, 2P4MHZ-PW, 2E4MZ·BIS, VT, VT-OK, MAVT, and MAVT-OK (all manufactured by Shikoku Chemicals Co., Ltd.).

[0065] Examples of organic phosphine-based curing accelerators include triphenylphosphine, tetraphenylphosphonium tetra-p-tolylborate, tetraphenylphosphonium tetraphenylborate, tri-tert-butylphosphonium tetraphenylborate, (4-methylphenyl)triphenylphosphonium thiocyanate, tetraphenylphosphonium thiocyanate, butyltriphenylphosphonium thiocyanate, and triphenylphosphinetriphenylborane. Examples of commercially available products include TPP, TPP-MK, TPP-K, TTBuP-K, TPP-SCN, and TPP-S (all manufactured by Hokko Chemical Industry Co., Ltd.).

[0066] The above-mentioned curing accelerators may be used individually or in combination of two or more types. The curing accelerator content is, for example, 0.3 parts by mass or more and 7 parts by mass or less, preferably 0.5 parts by mass or more and 5 parts by mass or less, and more preferably 0.7 parts by mass or more and 3 parts by mass or less, based on 100 parts by mass of the total amount of resin and curing agent.

[0067] (Other ingredients) The curable resin composition of the present invention may also contain other additives besides the above-mentioned components, such as flame retardants, antioxidants, tackifiers, plasticizers, thixotropic agents, and colorants. Furthermore, the curable resin composition may contain solvents in its manufacturing process, but it is preferable that some of the added solvents remain in the curable resin composition.

[0068] The curable resin composition of the present invention may be uncured or in a semi-cured state. When the curable resin composition is in an uncured or semi-cured state, its adhesion to other components is enhanced, allowing it to adhere to other components with high adhesive strength.

[0069] (Thermal conductivity) The thermal conductivity of the curable resin composition is preferably 1.0 W / (m·K) or higher. A thermal conductivity of 1.0 W / (m·K) or higher ensures good heat dissipation. Furthermore, from the viewpoint of heat dissipation, the above thermal conductivity is more preferably 1.5 W / (m·K) or higher, and even more preferably 3.0 W / (m·K) or higher. As described above, increasing the thermal conductivity results in excellent heat dissipation, and when used as a circuit board or a component-embedded substrate, for example, heat generated by electronic components mounted on the circuit board or electronic components embedded inside the curable resin composition can be efficiently dissipated to the outside. Furthermore, there is no particular upper limit to the thermal conductivity of the curable resin composition, but practically it is, for example, around 30 W / (m·K). The thermal conductivity of the curable resin composition is best measured on the cured product obtained by curing the curable resin composition, and can be determined in detail as described in the examples below.

[0070] [Resin sheet] The present invention also provides a resin sheet made of the curable resin composition described above. The resin sheet may contain a resin and a thermally conductive filler, and in addition to these, it may also contain other additives such as the curing agent, curing accelerator, dispersant, flame retardant, antioxidant, tackifier, plasticizer, thixotropic agent, and colorant described above. The details of each component in the resin sheet are as described in the section on the curable resin composition, so these detailed explanations will be omitted here. However, regarding the content of each component, where the explanation was based on the total amount of the curable resin composition, the explanation for the resin sheet will be based on the total amount of the resin sheet.

[0071] (Thickness) The thickness of the resin sheet is preferably 20 μm or less, more preferably 15 μm or less, and even more preferably 10 μm or less. When the thickness of the resin sheet is below the above upper limit, it becomes easier to make thinner electronic devices to which the resin sheet is applied, such as circuit boards and semiconductor devices, and it becomes particularly suitable for use as a component-embedded substrate. Furthermore, from the viewpoint of ensuring a certain level of heat dissipation, the thickness of the resin sheet may be, for example, 1 μm or more, preferably 2 μm or more, and more preferably 3 μm or more.

[0072] [Composite Sheet] The resin sheet of the present invention may be used in a composite sheet. The composite sheet may be one in which a release film is laminated on at least one surface of the resin sheet. The release film should be peeled off from the resin sheet when the resin sheet is used.

[0073] A release film made of resin film is preferred as the release film. When using a release film made of resin film, examples of raw materials for the film include polyesters such as polyethylene terephthalate (hereinafter sometimes abbreviated as "PET") and polyethylene naphthalate (hereinafter sometimes abbreviated as "PEN"), polycarbonate (hereinafter sometimes abbreviated as "PC"), acrylics such as polymethyl methacrylate (PMMA), cyclic polyolefins, triacetylcellulose (TAC), polyether sulfide (PES), polyether ketones, and polyimides. Among these, polyethylene terephthalate and polyethylene naphthalate are preferred, and inexpensive polyethylene terephthalate is particularly preferred.

[0074] The thickness of the release film is not particularly limited, but for example, it is in the range of 1 to 80 μm, preferably in the range of 5 to 75 μm, and more preferably in the range of 10 to 60 μm.

[0075] (Methods for manufacturing resin sheets and composite sheets) Resin sheets can be obtained by molding a curable resin composition into a sheet. The curable resin composition can be obtained by mixing a resin and a thermally conductive filler, along with various additives such as dispersants, curing agents, curing accelerators, and other additives, which may be optionally added. Furthermore, the curable resin composition may be diluted with a diluent solvent, such as an organic solvent.

[0076] The method for forming a curable resin composition into a sheet is not particularly limited, but for example, the curable resin composition may be applied to a release film, laminated, etc., and dried by heating as needed to form a sheet. The term "sheet" or "sheet" refers to a thin, flat material with a relatively small thickness relative to its length and width, and includes materials formed in a film-like or layered manner on other components such as a release film. Furthermore, as explained above, a composite sheet can be obtained by forming a resin sheet on a release film. Furthermore, the curable resin composition (resin sheet) molded into a sheet may be uncured, but may be heated as needed to partially cure it to a B-stage state.

[0077] Examples of organic solvents used as diluents include ketones such as acetone, methyl ethyl ketone (MEK), and cyclohexanone; acetic acid esters such as ethyl acetate, butyl acetate, cellosolve acetate, propylene glycol monomethyl ether acetate, and carbitol acetate; carbitols such as cellosolve and butyl carbitol; aromatic hydrocarbons such as toluene and xylene; and amide solvents such as dimethylformamide, dimethylacetamide (DMAc), and N-methylpyrrolidone. Organic solvents may be used individually or in combination of two or more.

[0078] (How to use the resin sheet) The resin sheet is preferably cured and used as a cured product for various applications. The resin sheet is preferably laminated onto a metal base plate or other substrate, electronic components, or other adherends in the uncured or semi-cured state described above, and then cured to adhere to the adherends. Resin sheets or composite sheets can be used in various applications where heat dissipation is required. In other words, the present invention also provides a heat dissipation member comprising a resin sheet or composite sheet. In particular, it is preferably used as a heat dissipation member for electronic equipment, and more preferably for use in semiconductor devices.

[0079] More specifically, the resin sheet may be used as part of a circuit board or as a encapsulant for electronic components, such as semiconductor chips, to embed them inside. Of these uses, its use as an encapsulant is preferable. The circuit board is preferably a component-embedded board. Furthermore, the circuit board is preferably used in a semiconductor package. The semiconductor chip package includes a circuit board and a semiconductor chip mounted on the circuit board, and in the semiconductor chip package, the semiconductor chip is preferably sealed with the resin sheet of the present invention described above.

[0080] Figure 1 shows an example in which the resin sheet of the present invention is used in a semiconductor package. As shown in Figure 1, for example, a semiconductor chip package 100 comprises a semiconductor chip 110, a sealing layer 120 formed to cover the periphery of the semiconductor chip 110, and a resin layer 130 provided on the side of the semiconductor chip 110 opposite to the side covered by the sealing layer, wherein the sealing layer 120 is preferably formed from the resin sheet of the present invention. The resin layer 130 is preferably an insulating layer, and may be formed from known resin materials or curable resin compositions. In the semiconductor package 100, the resin layer 130 may be provided with a conductive layer 140 that is electrically connected to the semiconductor chip 110, a solder resist layer 150, and bumps 160 that are further connected to the conductive layer 140, as appropriate. However, the semiconductor chip package configuration shown in Figure 1 is just one example, and specific examples of semiconductor chip packages are not limited to the configuration shown in Figure 1.

[0081] As described above, an example of a method for encapsulating electronic components such as semiconductor chips in a resin sheet using a resin sheet as a encapsulant is as follows. For example, the semiconductor chip package described above can be manufactured by the following method, but the method for manufacturing a semiconductor chip package is not limited to the following method. First, prepare an electronic component such as a semiconductor chip, or a fixing film to which the electronic component and substrate are fixed. The fixing film should have an adhesive layer on one side, and the electronic component or substrate should be fixed via this adhesive layer. Next, the resin sheet of the present invention is laminated onto one side of the fixing film, thereby embedding electronic components, or electronic components and a substrate, inside the resin sheet while laminating the resin sheet on top of the fixing film. The resin sheet, with electronic components, or electronic components and a substrate, embedded inside as described above, hardens upon heating, becoming a cured product. It is suitable for embedding electronic components such as semiconductor chips and using it as a component-embedded substrate. Furthermore, the resin sheet with the electronic components embedded inside, as described above, may be peeled off the fixing film as appropriate, and other components (for example, the resin layer described above) may be formed on the surface from which the fixing film was peeled off. The resin sheet may be cured after the fixing film is peeled off, or it may be cured on the fixing film. [Examples]

[0082] The present invention will be described in more detail below with reference to examples, but the present invention is not limited in any way by these examples.

[0083] [Film thickness of inorganic films in aluminum nitride fillers] The thickness of the inorganic film was measured according to the method described in the specification.

[0084] [Thermal conductivity] The resin sheets obtained in each example and comparative example were pressed in a vacuum press at 100°C for 1 hour while maintaining a pressure of 1 MPa, and then at 200°C for 1 hour. The thermal conductivity in the thickness direction of the cured material was measured using a laser flash thermal constant measuring device (NETZSCH "LFA447").

[0085] [Desmear resistance] The 170 μm thick resin sheets obtained in each example and comparative example were cured at 200°C for 2 hours to obtain cured resin sheets. The thickness of the obtained cured products was 170 μm. In the cured material obtained as described above, through holes with a diameter of 50 μm were drilled using a CO2 laser. The cured material, which had through holes drilled using the method described above, was subjected to desmear treatment using a 60 g / L permanganate solution and a 60 g / L sodium hydroxide solution at a treatment temperature of 85°C for 30 minutes. The desmear resistance was evaluated according to the following criteria. (Evaluation Criteria) ◎: The through-hole did not widen at all. ○: The increase in diameter of the through hole was between 0% and 30%. ×: The increase in the diameter of the through hole was 30% or more.

[0086] [Implantable] As shown in Figure 2, a 170 μm thick resin sheet 10, obtained by the procedure described in each example and comparative example, was laminated onto a 75 μm thick copper plate 12 having three φ10 μm through holes 11. Then, it was cured by pressing it in a vacuum press at 100°C for 1 hour and then at 200°C for 1 hour while maintaining a pressure of 1 MPa. The cross-section of the through-hole 11 after hardening was photographed using an optical microscope, and the resulting image was analyzed using a dispersion measurement system ("Luzex AP" manufactured by Nireco Corporation) to perform the evaluation shown below.

[0087] (Entering narrow spaces) The ability to enter confined spaces was evaluated based on the following evaluation criteria. ◎: Components of the resin sheet 10 flowed into all three through holes 11. ○: Components of the resin sheet 10 flowed into the two through holes 11. △: Components of the resin sheet 10 flowed into one of the through holes 11. ×: No components of the resin sheet 10 flowed into any of the through holes 11. *Here, "flowed into the through hole" means that the components of the resin sheet 10 flowed all the way down to the bottom of the through hole 11.

[0088] The components used in the examples and comparative examples are as follows:

[0089] (Thermal conductive filler) Alumina (1): "AO502", manufactured by Admatex Corporation Alumina (2): "AA03", manufactured by Sumitomo Chemical Co., Ltd. Alumina (3): "AA05", manufactured by Sumitomo Chemical Co., Ltd. Alumina (4): "AA1.5", manufactured by Sumitomo Chemical Co., Ltd. Alumina (5): "YC5", manufactured by Ginet.

[0090] Aluminum nitride (1): "HF-01D", manufactured by Tokuyama Corporation, no surface treatment. Aluminum nitride (2): "HF-01D", manufactured by Tokuyama Corporation, surface treated with sol-gel silica (indicated as "HF-01D_Treatment 1" in Tables 1-5) Aluminum nitride (3): "HF-01D", manufactured by Tokuyama Corporation, surface treated with sol-gel titania (indicated as "HF-01D_treatment 2" in Tables 1-5) Aluminum nitride (4): "HF-01D", manufactured by Tokuyama Corporation, surface treated with sol-gel alumina (indicated as "HF-01D_treatment 3" in Tables 1-5) Aluminum nitride (5): "HF-01D", manufactured by Tokuyama Corporation, surface treated with inorganic materials such as phosphate glass (indicated as "HF-01D_treatment 4" in Tables 1-5)

[0091] Aluminum nitride (6): "TFZ-N01P", manufactured by Toyo Aluminum Co., Ltd., no surface treatment. Aluminum nitride (7): "TFZ-N01P", manufactured by Toyo Aluminum Co., Ltd., surface treated with sol-gel silica (indicated as "TFZ-N01P_Treatment 1" in Tables 1-5) Aluminum nitride (8): "TFZ-N01P", manufactured by Toyo Aluminum Co., Ltd., surface treated with sol-gel titania (indicated as "TFZ-N01P_treatment 2" in Tables 1-5) Aluminum nitride (9): "TFZ-N01P", manufactured by Toyo Aluminum Co., Ltd., surface treated with sol-gel alumina (indicated as "TFZ-N01P_treatment 3" in Tables 1-5) Aluminum nitride (10): "TFZ-N01P", manufactured by Toyo Aluminum Co., Ltd., surface treated with inorganic materials such as phosphate glass (indicated as "TFZ-N01P_treatment 4" in Tables 1-5)

[0092] Aluminum nitride (11): "ALN020BF", manufactured by Thrutek, untreated. Aluminum Nitride (12): "ALN020SF", manufactured by Thrutek, surface treated with organic material. Aluminum nitride (13): "HF-01Da", manufactured by Tokuyama Corporation, surface treated with organic material. Aluminum nitride (14): "HF-10", manufactured by Tokuyama Corporation, surface treated with sol-gel silica (indicated as "HF-10_Treatment 1" in Tables 1-5)

[0093] (Epoxy resin) Epoxy resin (1): "JER828", manufactured by Mitsubishi Chemical Corporation, bisphenol A type epoxy resin, epoxy equivalent 189 g / eq Epoxy resin (2): "YL6121HA", manufactured by Mitsubishi Chemical Corporation, epoxy resin with a mesogenic skeleton, epoxy equivalent 165 g / eq Epoxy resin (3): "HP7200L", manufactured by DIC Corporation, dicyclopentadiene type epoxy resin, epoxy equivalent 247 g / eq

[0094] (Hardening agent) Hardener (1): Bisphenol A type cyanate ester resin, "P-201", manufactured by Mitsubishi Gas Chemical Company, equivalent weight 132 Hardener (2): Bisphenol A type cyanate ester resin, "TA", manufactured by Mitsubishi Gas Chemical Company, equivalent weight 139 Curing agent (3): Phenolic novolac resin having a triazine skeleton, "LA-1356", manufactured by DIC Corporation, equivalent weight 146 Hardener (4): "4,4-diaminodiphenylmethane", manufactured by TCI, equivalent weight 198 Hardener (5): Acid anhydride, "Ricacid MH-700", manufactured by Shin Nippon Rika Co., Ltd., equivalent weight 164

[0095] (polymer) "YP-50S", manufactured by Nippon Steel Chemical & Material Co., Ltd., molecular weight 50,000, phenoxy resin

[0096] (Curing accelerator) Curing accelerator (1): "2PHZ-PW", manufactured by Shikoku Chemicals Co., Ltd. Curing accelerator (2): "TPP-MK", manufactured by Hokko Chemical Co., Ltd.

[0097] (Surface treatment agent) Surface treatment agent (1): "KBM403", manufactured by Shin-Etsu Chemical Co., Ltd., silane coupling agent Surface treatment agent (2): "KBM3063", manufactured by Shin-Etsu Chemical Co., Ltd., silane coupling agent Surface treatment agent (3): "DISPER BYK111", manufactured by BIC Chemie Japan Co., Ltd.

[0098] [Method for forming inorganic films] Aluminum nitride (2) was produced by forming an inorganic film on the surface of aluminum nitride (1) using the sol-gel method described below. (Sol-gel method) Aluminum nitride (1) was degreased by washing with Okuno Pharmaceutical Co., Ltd.'s "Ace Screen A-220" at 60°C for 5 minutes, followed by filtration, washing with water, washing with acetone, and drying at 80°C for 1 hour as a pretreatment. Then, a specified amount of Okuno Pharmaceutical Co., Ltd.'s silica coating agent "Protector PW-SB" (curing agent) was mixed and stirred, and then a specified amount of Okuno Pharmaceutical Co., Ltd.'s "Protector PW-SA" (main component) was added and stirred at room temperature for 6 hours. After stirring, the material was filtered, washed with water, washed with acetone, and dried at 80°C for 1 hour to obtain aluminum nitride (2).

[0099] Aluminum nitride (3) was manufactured using the same method as aluminum nitride (2), except that the silica coating agent was changed to Matsumoto Fine Chemical's titania coating agent "Orgatics TA series".

[0100] Aluminum nitride (4) was manufactured using the same method as aluminum nitride (2), except that the silica coating agent was changed to aluminum isopropoxide, an alumina coating agent manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.

[0101] Aluminum nitride (5) was manufactured by forming an inorganic film on the surface of aluminum nitride (1) by firing a phosphate-based glass, as shown below. (Phosphate-based glass firing) A predetermined amount of Na2HPO4·12H2O and Al2O3 were thoroughly mixed and ground in a glass mortar, an 85% H3PO4 aqueous solution was added, and water was added to adjust the viscosity. A predetermined amount of aluminum nitride (1) was impregnated into the resulting liquid treatment agent, and it was fired at 1300°C for 3 hours under a nitrogen atmosphere to bake a phosphoric acid-based glass onto the surface of the aluminum nitride (1).

[0102] Aluminum nitride (7) was manufactured using the same method as when aluminum nitride (2) was manufactured, except that aluminum nitride (1) was replaced with aluminum nitride (6).

[0103] Aluminum nitride (8) was manufactured using the same method as when aluminum nitride (3) was manufactured, except that aluminum nitride (1) was replaced with aluminum nitride (6).

[0104] Aluminum nitride (9) was manufactured using the same method as in the manufacture of aluminum nitride (4), except that aluminum nitride (1) was replaced with aluminum nitride (6).

[0105] Aluminum nitride (10) was manufactured using the same method as when aluminum nitride (5) was manufactured, except that aluminum nitride (1) was replaced with aluminum nitride (6).

[0106] Aluminum nitride (14) was manufactured using the same method as when aluminum nitride (2) was manufactured, except that aluminum nitride (1) was replaced with aluminum nitride (11).

[0107] [Example 1] Each component shown in Table 1, along with the solvent methyl ethyl ketone, was added to obtain a diluted resin composition with a solid content of 80% by mass. The obtained diluted resin composition was applied to a support made of a release PET sheet and dried at 90°C for 10 minutes to form a thin film of the resin composition on the release PET sheet, obtaining a resin sheet with a thickness of 170 μm.

[0108] [Examples 2-34, Comparative Examples 1-10] The procedure was carried out in the same manner as in Example 1, except that the formulation was changed as shown in Tables 1 to 5. In Comparative Examples 6 to 8, the aluminum nitride used was not coated with an inorganic film on its surface, but after mixing with each component, the surface treatment agent bonded to the surface of the aluminum nitride.

[0109] [Table 1]

[0110] [Table 2]

[0111] [Table 3]

[0112] [Table 4]

[0113] [Table 5] *In Tables 1-5, a "○" in the "Inorganic Surface Treatment of Aluminum Nitride Filler" column indicates that the aluminum nitride filler used was surface-treated with an inorganic substance. A "×" in the same column indicates that the aluminum nitride filler used was not surface-treated with an inorganic substance.

[0114] As is clear from the above results, the curable resin composition prepared in the examples contained aluminum nitride coated with an inorganic film on its surface, resulting in high thermal conductivity, excellent heat dissipation, and good desmear resistance. In contrast, the resin compositions prepared in Comparative Examples 1 to 3 used aluminum nitride that was not coated with an inorganic film on its surface, and therefore could not achieve good desmear resistance. The resin compositions prepared in Comparative Examples 4 and 5 used aluminum nitride that had been surface-treated with organic materials, and therefore could not achieve good desmear resistance. The resin compositions prepared in Comparative Examples 6 to 8 used aluminum nitride that had been surface-treated with a surface treatment agent incorporated into the composition, and therefore could not achieve good desmear resistance. The resin compositions prepared in Comparative Examples 9 and 10 had thermally conductive filler content outside the specified range, and therefore could not achieve good desmear resistance.

Claims

1. A curable resin composition comprising a resin and a thermally conductive filler, The content of the thermally conductive filler is 50% by volume or more and 80% by volume or less in 100% by volume of the curable resin composition. A curable resin composition comprising an aluminum nitride filler whose surface is coated with an inorganic film, wherein the thermally conductive filler is an aluminum nitride filler.

2. The curable resin composition according to claim 1, wherein the inorganic film comprises a metal oxide or a phosphoric acid-based inorganic substance.

3. The curable resin composition according to claim 1 or 2, wherein the thickness of the inorganic film determined by the measurement method described below is 2 nm or more and 100 nm or less. (Measurement method) The cross-sectional image of one particle of the aluminum nitride filler contained in the curable resin composition is observed, the average thickness of the inorganic film at any 10 points is calculated, and the average value is defined as the film thickness.

4. The curable resin composition according to claim 1 or 2, wherein the average particle size of the thermally conductive filler is 1 μm or more and 5 μm or less.

5. The curable resin composition according to claim 1 or 2, wherein the content of the aluminum nitride filler is 50% by volume or more based on the total amount of the thermally conductive filler.

6. The curable resin composition according to claim 1 or 2, wherein the resin is a thermosetting resin.

7. The curable resin composition according to claim 6, wherein the thermosetting resin is an epoxy resin.

8. A resin sheet comprising the curable resin composition according to claim 1 or 2.

9. The resin sheet according to claim 8, wherein the thickness of the resin sheet is 20 μm or less.

10. A composite sheet comprising a release film laminated on at least one surface of the resin sheet according to claim 8.

11. A heat dissipation member comprising a resin sheet according to claim 8, or a composite sheet according to claim 10.

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