Thermosetting resin composition, dry film, cured product, and printed wiring board

Abstract

[Problem] To provide a thermosetting resin composition capable of forming a cured product having high thermal conductivity and having high laminability to a substrate. [Solution] The thermosetting resin composition is obtained by blending an epoxy resin, a thermally conductive filler, and a polyalkylene glycol derivative, and the thermally conductive filler is substantially free from magnetic particles.

Description

Thermosetting resin composition, dry film, cured product, and printed wiring board

[0001] The present invention relates to a thermosetting resin composition, and particularly to a thermosetting resin composition suitably used for forming a highly thermally conductive insulating layer. Further, the present invention also relates to a dry film having a resin layer made of the thermosetting resin composition, a cured product of the thermosetting resin composition or the resin layer of the dry film, and a printed wiring board including the cured product.

[0002] In recent years, the demand for miniaturization and high performance of electronic devices has been increasing. Along with this, the density and functionality of semiconductor chips mounted thereon have been advancing, and miniaturization and high density have also been required for printed wiring boards on which semiconductor chips are mounted. As a result, recently, heat dissipation measures in semiconductor chips and printed wiring boards have been emphasized, and heat dissipation characteristics (heat dissipativity) have become a major issue.

[0003] By the way, inorganic materials such as inorganic fillers generally have a higher thermal conductivity than organic materials such as resins. Therefore, generally, an insulating layer formed by curing a resin composition containing only an organic material such as a resin has higher thermal conductivity than an insulating layer formed by curing a resin composition containing an inorganic material, and in a semiconductor chip or a printed wiring board provided with such an insulating layer, the generated heat can be dissipated more efficiently.

[0004] To improve the thermal conductivity of the insulating layer formed by curing a resin composition, it is common to use a thermally conductive filler, particularly among inorganic materials. Conventionally, the thermal conductivity of the insulating layer has been efficiently improved by increasing the content of the thermally conductive filler in the resin composition. However, when the content of thermally conductive filler is increased to the extent that sufficient thermal conductivity is achieved, the frequency of contact between inorganic fillers increases, making them prone to aggregation. As a result, the fluidity of the resin composition decreases significantly, impairing the surface smoothness when the resin composition is made into a sheet or film, and potentially resulting in insufficient adhesion when bonding the sheet or film resin composition to a substrate. Consequently, the laminating properties of the resin composition to the substrate decrease, leading to the problem of the resin composition easily peeling off the substrate. In particular, from the perspective of thinning resin compositions, which is required in recent years, such a decrease in laminating properties becomes more pronounced when inorganic fillers with small average particle size or large specific surface area are included in the resin composition.

[0005] To solve these problems, Patent Document 1 proposes a technique to improve the laminating properties of a resin composition by incorporating a polyimide resin into the resin composition, thereby suppressing the increase in the melt viscosity of the resin composition.

[0006] Japanese Patent Publication No. 2018-184595

[0007] However, the demands on electronic devices are diversifying, and consequently, the needs for semiconductor chips, printed circuit boards, and the insulating layers that constitute them are also diversifying. Therefore, providing resin compositions that can form cured products with high thermal conductivity and have high lamination properties to substrates remains an ongoing technical challenge in order to meet these diverse needs.

[0008] Therefore, the present invention aims to provide a thermosetting resin composition that can form a cured product having high thermal conductivity and has high lamination properties to a substrate. Furthermore, another object of the present invention is to provide a dry film having a resin layer made of such a thermosetting resin composition, a cured product of the thermosetting resin composition or the resin layer of the dry film, and a printed circuit board comprising the cured product.

[0009] As a result of diligent research, the inventors have found that the above-mentioned problems can be solved by blending an epoxy resin, a thermally conductive filler, and a polyalkylene glycol derivative into a thermosetting resin composition, and by making the thermally conductive filler substantially free of magnetic particles. The present invention is based on this finding. In other words, the gist of the present invention is as follows.

[0010] [1] A thermosetting resin composition comprising an epoxy resin, a thermally conductive filler, and a polyalkylene glycol derivative, wherein the thermally conductive filler substantially does not contain magnetic particles. [2] The thermosetting resin composition according to [1], wherein the thermally conductive filler comprises at least one selected from the group consisting of aluminum oxide, aluminum nitride, boron nitride, and silicon carbide. [3] The thermosetting resin composition according to [1] or [2], wherein the thermally conductive filler comprises a thermally conductive filler that has not been surface-treated with an organic compound. [4] The thermosetting resin composition according to any one of [1] to [3], wherein the content of the thermally conductive filler is such that the mass of the thermally conductive filler is 80% by mass or more relative to the total mass of non-volatile components of the thermosetting resin composition. [5] The thermosetting resin composition according to any one of [1] to [4] for forming an interlayer insulating layer. [6] A dry film having a first film and a resin layer formed on at least one surface of the first film, the resin layer being made of a thermosetting resin composition according to any one of [1] to [5]. [7] A cured product obtained by curing the thermosetting resin composition according to any one of [1] to [5] or the resin layer of the dry film according to [6]. [8] A printed circuit board comprising the cured product according to [7].

[0011] According to the present invention, it is possible to provide a thermosetting resin composition that can form a cured product having high thermal conductivity and has high laminating properties to a substrate. Furthermore, according to the present invention, it is possible to provide a dry film having a resin layer made of such a thermosetting resin composition, a cured product of the thermosetting resin composition or the resin layer of the dry film, and a printed circuit board equipped with the cured product.

[0012] [Thermosetting Resin Composition] According to one aspect of the present invention, a thermosetting resin composition (hereinafter also referred to as "the thermosetting resin composition of the present invention") is provided. The thermosetting resin composition of the present invention contains an epoxy resin, a thermally conductive filler, and a polyalkylene glycol derivative as essential components. By containing a polyalkylene glycol derivative, the thermosetting resin composition of the present invention has excellent laminating properties even when a large amount of inorganic filler with a relatively small average particle size or a relatively small specific surface area is blended to enhance the thermal conductivity of the cured product. Therefore, the thermosetting resin composition of the present invention can be suitably used, for example, for forming a highly thermally conductive insulating layer, particularly an interlayer insulating layer. The components of the thermosetting resin composition of the present invention will be described in detail below. Note that commercially available components may be used, or components that have been appropriately synthesized may be used.

[0013] (Epoxy Resin) The thermosetting resin composition of the present invention contains an epoxy resin as an essential component. The epoxy resin can be used without limitation as long as it has two or more epoxy groups in one molecule. For example, bisphenol type epoxy resins such as bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, bisphenol E type epoxy resin, bisphenol M type epoxy resin, bisphenol P type epoxy resin, bisphenol Z type epoxy resin, etc., novolac type epoxy resins such as bisphenol A novolac type epoxy resin, phenol novolac type epoxy resin, cresol novolac epoxy resin, etc., biphenyl type epoxy resin, biphenyl aralkyl type epoxy resin, arylalkylene type epoxy resin, Examples of epoxy resins include tetraphenyloleethane-type epoxy resins, naphthalene-type epoxy resins, anthracene-type epoxy resins, phenoxy-type epoxy resins, dicyclopentadiene-type epoxy resins, norbornene-type epoxy resins, adamantane-type epoxy resins, fluorene-type epoxy resins, glycidyl methacrylate copolymer epoxy resins, copolymer epoxy resins of cyclohexylmaleimide and glycidyl methacrylate, epoxy-modified polybutadiene rubber derivatives, CTBN-modified epoxy resins, and tris(2,3-epoxypropyl) isocyanurate. The above-mentioned epoxy resins may be used individually or in combination of two or more. Among these, from the viewpoint of optimizing the film-forming properties, breaking strength, thermal expansion coefficient, and storage modulus of the cured coating film, it is preferable to use bisphenol A-type epoxy resins, bisphenol F-type epoxy resins, phenoxy-type epoxy resins, and phenol novolac-type epoxy resins, more preferably to use three or more of these in combination, and particularly preferable to use all four of these in combination.

[0014] Epoxy resins can be used in liquid, semi-solid, or solid form, but liquid form is preferred from the viewpoint of fluidity and filler properties. Liquid form refers to a state where the resin is fluid at 20°C.

[0015] These epoxy resins having a bisphenol-type skeleton may be used individually or in combination of two or more types. However, from the viewpoint of achieving excellent filling properties and thus having a better effect on the properties after curing, it is preferable to use a combination of two or more epoxy resins selected from bisphenol A type epoxy resin, bisphenol F type epoxy resin, and bisphenol E (AD) type epoxy resin. Examples of commercially available products include ZX-1059 manufactured by Nippon Steel Chemical & Material Co., Ltd., jER® 828, jER® 834, jER® 1001 (bisphenol A type epoxy resin), jER® 807, jER® 4004P (bisphenol F type epoxy resin) manufactured by Mitsubishi Chemical Corporation, and R710 (bisphenol E type epoxy resin) manufactured by Air Water Inc.

[0016] Furthermore, the thermosetting resin composition of the present invention may also contain a polyfunctional epoxy resin. Examples of commercially available polyfunctional epoxy resins include EP-3300E, a hydroxybenzophenone-type liquid epoxy resin manufactured by ADEKA Corporation; jER® 630, a para-aminophenol-type liquid epoxy resin manufactured by Mitsubishi Chemical Corporation; ELM-100, a para-aminophenol-type liquid epoxy resin manufactured by Sumitomo Chemical Co., Ltd.; jER® 604, a glycidylamine-type epoxy resin manufactured by Mitsubishi Chemical Corporation; Epotote YH-434, a Nippon Steel Chemical & Material Corporation; SumiEpoxy® ELM-120, a glycidylamine-type epoxy resin manufactured by Sumitomo Chemical Co., Ltd.; DEN-431, a phenol novolac-type epoxy resin manufactured by Dow Chemical Company; and Celoxide 2021P, an alicyclic epoxy resin manufactured by Daicel Corporation. These polyfunctional epoxy resins may be used individually or in combination of two or more types.

[0017] The epoxy resin content in the thermosetting resin composition is not particularly limited as long as the effects of the present invention are achieved, and can be, for example, 5 to 20% by mass relative to the total mass of nonvolatile components of the thermosetting resin composition.

[0018] The thermosetting resin composition of the present invention may contain thermosetting components other than the epoxy resin described above. Examples of such thermosetting components include well-known and commonly used ones such as isocyanate compounds, blocked isocyanate compounds, amino resins, maleimide compounds, benzoxazine resins, carbodiimide resins, cyclocarbonate compounds, oxetane compounds, and episulfide resins.

[0019] (Curing Agent) The thermosetting resin composition of the present invention may contain a curing agent for curing the thermosetting resin. As the curing agent, known curing agents commonly used for curing thermosetting resins, particularly the epoxy resins described above, can be used. Examples of such curing agents include compounds having curable groups such as amino groups, carboxyl groups, acid anhydride groups, phenolic hydroxyl groups, thiol groups, and active ester groups. More specifically, examples include amide curing agents, amine curing agents, phenolic curing agents, imidazole curing agents, acid anhydride curing agents, and active ester curing agents. The curing agent may be used alone or in combination of two or more. Preferably, imidazole curing agents and phenolic curing agents are used, and particularly preferably, they are used in combination.

[0020] Specific curing agents include, for example, imidazole derivatives such as imidazole, 2-methylimidazole, 2-ethylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 4-phenylimidazole, 1-cyanoethyl-2-phenylimidazole, and 1-(2-cyanoethyl)-2-ethyl-4-methylimidazole; phenol derivatives such as bisphenol A, bisphenol F, phenol novolac resin, cresol novolac resin, and p-xylene novolac resin; amine compounds such as dicyandiamide, benzyldimethylamine, 4-(dimethylamino)-N,N-dimethylbenzylamine, 4-methoxy-N,N-dimethylbenzylamine, and 4-methyl-N,N-dimethylbenzylamine; hydrazine compounds such as adipic acid dihydrazide and sebacate dihydrazide; and phosphorus compounds such as triphenylphosphine. Furthermore, commercially available examples include 2MZ-A, 2MZ-OK, 2PHZ, 2P4BHZ, and 2P4MHZ (all trade names for imidazole compounds) manufactured by Shikoku Chemicals, Inc., HF-4M (trade name for phenol compound) manufactured by Meiwa Chemicals, Inc., and U-CAT 3513N (trade name for dimethylamine compound), DBU, DBN, and U-CAT SA 102 (all bicyclic amidine compounds and their salts) manufactured by Sunapro Co., Ltd. The curing agent is not limited to these, and any thermosetting catalyst for epoxy resin or oxetane compound, or any agent that promotes the reaction between at least one of an epoxy group and an oxetanyl group and a carboxyl group may be used, and can be used alone or in combination of two or more. Furthermore, S-triazine derivatives such as guanamine, acetoguanamine, benzoguanamine, melamine, 2,4-diamino-6-methacryloyloxyethyl-S-triazine, 2-vinyl-2,4-diamino-S-triazine, 2-vinyl-4,6-diamino-S-triazine isocyanuric acid adduct, and 2,4-diamino-6-methacryloyloxyethyl-S-triazine isocyanuric acid adduct can also be used, and preferably these compounds that also function as adhesion imparters are used in combination with a thermosetting catalyst.

[0021] (Thermal Conductivity Filler) The thermosetting resin composition of the present invention contains a thermal conductivity filler. Any particles capable of conducting heat can be used as the thermal conductivity filler without particular limitations. By incorporating a thermal conductivity filler into the thermosetting resin composition, it is expected that the thermal conductivity of the thermosetting resin composition will be improved. The thermal conductivity filler may be used alone or in combination of two or more types. By including a thermal conductivity filler in the thermosetting resin composition, the thermal conductivity efficiency of the thermosetting resin composition can be improved and the specific gravity can be adjusted.

[0022] The thermally conductive filler is substantially free of magnetic particles. That is, in this embodiment, the thermally conductive filler used in the thermosetting resin composition of the present invention is a thermally conductive filler that substantially contains magnetic powder. Specifically, "substantially free of magnetic particles" in the thermally conductive filler means that the amount of magnetic particles is 1% by mass or less, preferably 0.5% by mass or less, and more preferably 0% by mass, relative to the thermally conductive filler contained in the thermosetting resin composition. By substantially free of magnetic particles in the thermally conductive filler, the electrical insulation properties of the thermosetting resin composition can be improved.

[0023] The type of thermally conductive filler is not particularly limited as long as the effects of the present invention are achieved, but examples include aluminum oxide (alumina), aluminum nitride, boron nitride, silicon nitride, silicon carbide, magnesium oxide, zinc oxide, and diamond. Preferably, aluminum oxide, aluminum nitride, boron nitride, and silicon carbide are used as thermally conductive fillers, and aluminum oxide is particularly preferred. In particular, by using spherical aluminum oxide, the increase in viscosity of the thermosetting resin composition when high-filling can be suppressed. Furthermore, the thermally conductive filler may or may not be surface-treated. Therefore, it is particularly preferable to use aluminum oxide that has not been surface-treated with an organic compound as the thermally conductive filler. Examples of commercially available aluminum oxides include Denka Spherical Alumina DAW-01, DAW-03, and ASFP-20 manufactured by Denka Co., Ltd.

[0024] The thermal conductivity of the thermally conductive filler is preferably 10 W / m·K or higher, and more preferably 20 W / m·K or higher.

[0025] The thermally conductive filler may or may not have electrical insulating properties.

[0026] In a preferred embodiment, the thermally conductive filler is a filler having a thermal conductivity of 10 W / m·K or higher and also having electrical insulating properties.

[0027] The particle size of the thermal conductive filler is not particularly limited as long as the effects of the present invention are achieved, but its average particle size (d50) is preferably 0.01 to 30 μm, more preferably 0.01 to 20 μm. The average particle size (d50) of the thermal conductive filler refers to the average particle size including not only the particle size of primary particles but also the particle size of secondary particles (aggregates). An average particle size (d50) of 0.01 μm or more suppresses excessive viscosity of the thermosetting resin composition, resulting in high dispersibility and high coatability to the coated object. On the other hand, an average particle size of 30 μm or less reduces the likelihood of particles emerging from the coating film and results in a sufficiently slow sedimentation rate, thus providing high storage stability. The average particle size (d50) of the thermal conductive filler can be measured by laser diffraction using a Microtrac MT3300EXII manufactured by Nikkiso Co., Ltd.

[0028] The thermally conductive filler may be a combination of two or more average particle sizes having a particle size distribution that results in a close-packed structure when compounded into the thermosetting resin composition. In a thermosetting-focused composition, the close-packed structure of the thermally conductive filler increases the packing efficiency, which can further improve the storage stability of the thermosetting resin composition and the thermal conductivity of the cured product.

[0029] The content of the thermally conductive filler in the thermosetting resin composition is not particularly limited as long as the effects of the present invention are achieved, and can be appropriately set according to the type of thermally conductive filler and the various properties of the thermally conductive filler as described above. The content of the thermally conductive filler is preferably 80% by mass or more, more preferably 85% by mass or more, and even more preferably 90% by mass or more, based on the total mass of the nonvolatile components of the thermosetting resin composition. By setting the content of the thermally conductive filler to 80% by mass or more based on the total mass of the nonvolatile components of the thermosetting resin composition, the cured product can have sufficient thermal conductivity. Alternatively, the content of the thermally conductive filler is preferably 60% to 80% by volume, more preferably 65% ​​to 75% by volume, based on the total volume of the nonvolatile components of the thermosetting resin composition.

[0030] (Polyalkylene glycol derivative) The thermosetting resin composition of the present invention contains a polyalkylene glycol derivative. Generally, in thermosetting resin compositions, the higher the filler content, the worse the laminating properties become. By containing a polyalkylene glycol derivative, the thermosetting resin composition of the present invention allows for good dispersion of thermally conductive fillers, suppresses the increase in viscosity, and improves fluidity compared to thermosetting resin compositions that do not contain a polyalkylene glycol derivative, thus exhibiting good laminating properties to the substrate.

[0031] Polyalkylene glycol derivatives are not particularly limited as long as they are compounds derived from polyalkylene glycols. Examples include polyoxyalkylene alkyl ethers such as polyoxyalkylene monoalkyl ethers and polyoxyalkylenedialkyl ethers, polyoxyalkylene alkenyl ethers such as polyoxyalkylene monoalkenyl ethers and polyoxyalkylenedialkenyl ethers, polyoxyalkylene aryl ethers such as polyoxyalkylene monoaryl ethers and polyoxyalkylenediaryl ethers, polyoxyalkylene alkylphenyl ethers, polyoxyalkylene glycol fatty acid esters such as polyoxyalkylene glycol monofatty acid esters and polyoxyalkylene glycol difatty acid esters, polyoxyalkylene sorbitan fatty acid esters, polyoxyalkylene alkylamines, and polyoxyalkylenediamines.

[0032] Examples of alkyl ethers in polyalkylene glycol derivatives include lower alkyl ethers such as methyl ether and ethyl ether, and higher alkyl ethers such as lauryl ether and stearyl ether. Examples of alkenyl ethers in polyalkylene glycol derivatives include vinyl ether, allyl ether, and oleyl ether. Examples of fatty acid esters in polyalkylene glycol derivatives include saturated fatty acid esters such as acetate ester and stearic acid ester, and unsaturated fatty acid esters such as (meth)acrylic acid ester and oleic acid ester.

[0033] Polyalkylene glycol derivatives may be incorporated into thermosetting resin compositions as polyalkylene glycol derivatives themselves, or as a composition containing polyalkylene glycol derivatives. Examples of compositions containing polyalkylene glycol derivatives include dispersants.

[0034] The dispersant containing the polyalkylene glycol derivative may have an acidic functional group and may be acidic. The dispersant containing the polyalkylene glycol derivative preferably contains a carboxyl group as an adsorption group for the filler. Furthermore, from the viewpoint of fluidity when laminating the thermosetting resin composition of the present invention onto a substrate, the molecular weight of the polyalkylene glycol derivative is preferably 10,000 or less, more preferably 1,000 or less. On the other hand, the molecular weight of the polyalkylene glycol derivative is not particularly limited, but can be, for example, 100 or more. The dispersant containing the polyalkylene glycol derivative may be used alone or in combination of two or more types. Examples of commercially available dispersants containing polyalkylene glycol derivatives include C-2091I, C-2093I, C-2095I, etc., of the S-Ream® C series manufactured by NOF Corporation.

[0035] The content of polyalkylene glycol derivatives in the thermosetting resin composition is not particularly limited as long as the effects of the present invention are achieved, but the lower limit of the content per 100 parts by mass of thermal conductive filler is preferably 0.01 parts by mass, more preferably 0.03 parts by mass, and even more preferably 0.05 parts by mass. On the other hand, the upper limit of the content per 100 parts by mass of thermal conductive filler is preferably 10 parts by mass, more preferably 5 parts by mass, and even more preferably 2 parts by mass. Furthermore, the range of content per 100 parts by mass of thermal conductive filler is preferably 0.01 to 10 parts by mass, more preferably 0.03 to 5 parts by mass, and even more preferably 0.05 to 2 parts by mass.

[0036] In one embodiment, when a polyalkylene glycol derivative is incorporated into a thermosetting resin composition as a composition containing the polyalkylene glycol derivative (e.g., a dispersant), the content of such a composition containing the polyalkylene glycol derivative in the thermosetting resin composition can be appropriately set according to the amount of polyalkylene glycol derivative contained in the composition containing the polyalkylene glycol derivative. For example, when S-Ream® C-2091I, a dispersant containing a polyalkylene glycol derivative manufactured by NOF Corporation, is incorporated into the thermosetting resin composition as the polyalkylene glycol derivative, the amount of the dispersant incorporated into the thermosetting resin composition is preferably 0.1 to 10 parts by mass, more preferably 0.3 to 5 parts by mass, and even more preferably 0.5 to 2 parts by mass, per 100 parts by mass of the thermally conductive filler.

[0037] (Solvent) The thermosetting resin composition of the present invention may contain a solvent for purposes such as preparing the composition or adjusting the viscosity when applying it to a substrate or film. As solvents, for example, ketones such as methyl ethyl ketone and cyclohexanone; aromatic hydrocarbons such as toluene, xylene, and tetramethylbenzene; glycol ethers such as cellosolve, methyl cellosolve, butyl cellosolve, carbitol, methyl carbitol, butyl carbitol, propylene glycol monomethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol diethyl ether, diethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, and tripropylene glycol monomethyl ether; esters such as ethyl acetate, butyl acetate, butyl lactate, cellosolve acetate, butyl cellosolve acetate, carbitol acetate, butyl carbitol acetate, propylene glycol monomethyl ether acetate, dipropylene glycol monomethyl ether acetate, and propylene carbonate; aliphatic hydrocarbons such as octane and decane; and petroleum-based solvents such as petroleum ether, petroleum naphtha, and solvent naphtha can be used. The solvent may be used individually or in combination of two or more types.

[0038] The solvent can be dried by evaporation using a hot air circulation drying oven, an IR oven, a hot plate, a convection oven, etc. (using a heat source equipped with a steam-heated air heating method, either by bringing the hot air inside the dryer into countercurrent contact or by blowing it onto the support from a nozzle).

[0039] The thermosetting resin composition of the present invention can be dissolved (diluted) in a solvent and made into a varnish by conventionally known methods. The amount of solvent to be blended when the thermosetting resin composition of the present invention is made into a varnish is not particularly limited and can be appropriately determined, for example, taking into account sheet processability. Specifically, it is preferable to blend the solvent so that the viscosity of the resulting varnish is 500 mPa·s to 10,000 MPa·s.

[0040] (Other Additives) The thermosetting resin composition of the present invention may further contain, as needed, components such as dispersants, surface modifiers, photoinitiators, cyanate compounds, elastomers, mercapto compounds, urethane catalysts, thixonating agents, adhesion promoters, block copolymers, chain transfer agents, polymerization inhibitors, copper damage inhibitors, antioxidants, rust inhibitors, thickeners such as organic bentonite and montmorillonite, defoamers and leveling agents such as silicone-based, fluorine-based, and polymer-based agents, silane coupling agents such as imidazole-based, thiazole-based, and triazole-based agents, and flame retardants such as phosphinates, phosphate ester derivatives, and phosphazene compounds. These can be those known in the field of electronic materials.

[0041] The thermosetting resin composition of the present invention may be used in liquid form or as a dry film as described later. When used in liquid form, it may be a one-component or two-component or more-component composition.

[0042] [Dry Film] The thermosetting resin composition of the present invention can also be in the form of a dry film comprising a first film and a resin layer made of the thermosetting resin composition formed on the first film. That is, according to another aspect of the present invention, a dry film comprising a resin layer made of the thermosetting resin composition of the present invention (hereinafter also referred to as "the dry film of the present invention") is provided.

[0043] In the dry film of the present invention, the first film refers to a film that adheres to at least the resin layer when it is laminated and integrally formed by heating or the like so that one side is in contact with a base material such as a substrate and the side of the layer (resin layer) composed of the thermosetting resin composition formed on the dry film. The first film may be peeled off from the resin layer in the process after lamination. Particularly in the present invention, it is preferable to peel off from the resin layer in the process after curing. When forming the dry film, the thermosetting resin composition of the present invention is diluted with the above organic solvent and adjusted to an appropriate viscosity, and then uniformly coated on the first film with a comma coater, blade coater, lip coater, rod coater, squeeze coater, reverse coater, transfer roll coater, gravure coater, spray coater, etc. to a uniform thickness, and usually dried at a temperature of 50 to 130 ° C for 1 to 30 minutes to obtain a film. There is no particular limitation on the coating film thickness, but generally, it is appropriately selected in the range of 1 to 150 μm, preferably 5 to 60 μm, in terms of the film thickness after drying.

[0044] As the first film, any known film can be used without particular limitation. For example, polyester films such as polyethylene terephthalate and polyethylene naphthalate, polyimide films, polyamideimide films, polypropylene films, and polystyrene films made of thermoplastic resins can be preferably used. Among these, polyester films are preferable from the viewpoints of heat resistance, mechanical strength, and handling properties. Also, a laminate of these films can be used as the first film.

[0045] Further, from the viewpoint of improving mechanical strength, the thermoplastic resin film as described above is preferably a film stretched in a uniaxial direction or a biaxial direction.

[0046] The thickness of the first film is not particularly limited, but for example, it can be 5 μm to 150 μm.

[0047] After forming a resin layer of the thermosetting resin composition of the present invention on the first film, it is preferable to further laminate a peelable second film onto the surface of the resin layer for purposes such as preventing dust from adhering to the surface of the resin layer. The second film is one that is peeled off from the resin layer before lamination when integrally molding by lamination by heating or the like so that the substrate (such as a substrate) and the layer (resin layer) made of the thermosetting resin composition formed on the dry film are in contact. Examples of peelable second films include polyethylene film, polytetrafluoroethylene film, polypropylene film, and surface-treated paper. The adhesive force between the resin layer and the second film should be less than the adhesive force between the resin layer and the first film when the second film is peeled off.

[0048] The thickness of the second film is not particularly limited, but can be, for example, 5 μm to 150 μm.

[0049] Furthermore, the dry film may be prepared by forming a resin layer on the second film by applying and drying the thermosetting resin composition of the present invention, and then laminating the first film onto its surface. In other words, when producing the dry film in the present invention, either the first film or the second film may be used as the film on which the thermosetting resin composition of the present invention is applied.

[0050] [Cured Product] According to another aspect of the present invention, a cured product (hereinafter also referred to as "the cured product of the present invention") is provided, which is obtained by curing the thermosetting resin composition of the present invention or the resin layer of the dry film of the present invention. Since the cured product of the present invention has high thermal conductivity, it can be suitably used as a high thermal conductivity substrate material.

[0051] The conditions for curing the thermosetting resin composition or the resin layer of the dry film of the present invention are not particularly limited as long as they are general conditions used for curing resin compositions, and can be appropriately set according to the composition of the thermosetting resin composition, etc. Specifically, the thermosetting resin composition layer formed on a substrate can be cured by heating it at a temperature of 100 to 300°C for 1 to 120 minutes.

[0052] The thermal conductivity of the cured product of the present invention can be measured as follows. First, a substrate (18 μm thick copper foil) is prepared, and a dry film for evaluating thermal conductivity is brought into contact with the substrate using a vacuum diaphragm laminator. After creating a vacuum for 30 seconds, it is laminated under pressure of 0.5 MPa. The first film is peeled off from the dry film, and a new dry film of the same type is brought into contact with the surface of the dry film from which the first dry film was peeled off, and laminated using the same procedure as above. Next, the thermosetting resin composition is cured by heating at 100°C for 30 minutes and then at 180°C for another 30 minutes to form a cured product (insulating layer). Next, the first dry film and the substrate are peeled off from the insulating layer, and the thermal diffusivity of the obtained cured product is measured using an FTC-1 manufactured by ULVAC, Inc. under a load of 5 kgf / cm². ３ The thermal diffusivity (α), specific heat capacity (c), and density (ρ) of the cured material are measured using the periodic heating method. The specific heat capacity of the cured material is measured using a Perkin-Elmer differential scanning calorimetry (DSC) with a heating rate of 20°C / min, a helium gas flow rate of 20 ml / min, and a sample volume of 15 mg. The density of the cured material is measured at room temperature (25°C) using the water displacement method. Based on the measured thermal diffusivity (α), specific heat capacity (c), and density (ρ) of the cured material, the thermal conductivity (λ) of the cured material is calculated using the following formula: Thermal conductivity (λ) = Thermal diffusivity (α) × Specific heat capacity (c) × Density (ρ)

[0053] [Printed Wiring Board] According to another aspect of the present invention, a printed wiring board (hereinafter also referred to as "the printed wiring board of the present invention") is provided that comprises the cured product of the present invention as described above. That is, the printed wiring board of the present invention has a cured product obtained from the thermosetting resin composition of the present invention or from the resin layer of the dry film of the present invention. As a method for manufacturing the printed wiring board of the present invention, for example, the thermosetting resin composition of the present invention is adjusted to a viscosity suitable for the coating method using an organic solvent as described above, and applied to a substrate by a method such as dip coating, flow coating, roll coating, bar coating, screen printing, or curtain coating, and then the organic solvent contained in the composition is evaporated and dried (pre-dried) at a temperature of 60 to 100°C to form a tack-free resin layer. In the case of a dry film, the resin layer is formed on the substrate by laminating it onto the substrate using a laminator or the like so that the resin layer is in contact with the substrate.

[0054] The substrates constituting the printed circuit board of the present invention include printed circuit boards with circuits pre-formed using copper or the like, flexible printed circuit boards, and materials such as paper phenol, paper epoxy, glass cloth epoxy, glass polyimide, glass cloth / nonwoven fabric epoxy, glass cloth / paper epoxy, synthetic fiber epoxy, fluororesin / polyethylene / polyphenylene ether, polyphenylene oxide / cyanate, etc., as well as copper-clad laminates for high-frequency circuits. Examples include copper-clad laminates of all grades (FR-4, etc.), metal substrates, polyimide films, polyethylene terephthalate films, polyethylene naphthalate (PEN) films, glass substrates, ceramic substrates, wafers, etc.

[0055] The bonding of the dry film to the resin layer on the substrate is preferably performed under pressure and heat using a vacuum laminator or the like. By using such a vacuum laminator, even if the surface of the circuit board is uneven when a circuit-formed substrate is used, the dry film adheres closely to the circuit board, preventing the inclusion of air bubbles and improving the ability to fill in depressions on the substrate surface. The pressure is preferably around 0.1 to 2.0 MPa, and the heating is preferably around 40 to 120°C.

[0056] The volatilization drying performed after forming the thermosetting resin composition layer of the present invention on the substrate can be carried out using a hot air circulation drying oven, an IR oven, a hot plate, a convection oven, etc. (a method in which hot air inside the dryer is brought into countercurrent contact using a heat source equipped with a steam-heated air heating method, or a method in which hot air is blown onto the support from a nozzle).

[0057] Next, a printed circuit board comprising a cured thermosetting resin composition can be obtained by heat-curing the thermosetting resin composition layer formed on the substrate. The heat curing of the thermosetting resin composition layer can be carried out, for example, by heating at temperatures of 80 to 200°C or 90 to 190°C for 10 to 60 minutes or 20 to 40 minutes, or more specifically, at 100°C for 30 minutes or at 180°C for 30 minutes.

[0058] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. In the examples, the numerical values ​​for each component all refer to parts by mass unless otherwise specified.

[0059] [Preparation of Thermosetting Resin Compositions] The components shown in Table 1 below were mixed in the amounts shown in the table, pre-mixed using a stirrer, and then kneaded using a three-roll mill to prepare the thermosetting resin compositions for Examples 1-2 and Comparative Examples 1-4. Details of each component in Table 1 are as follows. Epoxy resin 1: jER (registered trademark) 828 manufactured by Mitsubishi Chemical Corporation Epoxy resin 2: NC3000H-CA70 manufactured by Nippon Kayaku Co., Ltd. Epoxy resin 3: YX6954BH30 manufactured by Mitsubishi Chemical Corporation Thermal conductive filler 1: Denka spherical alumina DAW-03 manufactured by Denka Co., Ltd. Thermal conductive filler 2: Denka spherical alumina DAW-01 manufactured by Denka Co., Ltd. Polyalkylene glycol derivative: Esream (registered trademark) C-2093I manufactured by NOF Corporation Other component 1: Curing agent HF-4M H55 manufactured by Meiwa Kasei Co., Ltd. Other component 2: Polyacrylate-based surface modifier BYK-350 manufactured by BIC Chemie Japan Co., Ltd. Other component 3: Imidazole-based epoxy resin curing agent Curesol 2E4M manufactured by Shikoku Chemicals, Ltd. Furthermore, it has been confirmed from publicly available documents of NOF Corporation, the distributor of Esream® C-2093I, which was used as a polyalkylene glycol derivative, that its molecular weight is 1,000 or less.

[0060]

[0061] [Preparation of Varnish] 10 to 30 parts by mass of solvent (cyclohexanone, diethylene glycol monoethyl ether acetate) were added to 100 parts by mass of the nonvolatile component of each thermosetting resin composition of Examples 1 to 2 and Comparative Examples 1 to 4, mixed, and kneaded using a drilling machine and a three-roll mill.

[0062] [Preparation of Dry Films] Each of the thermosetting resin compositions contained in Examples 1-2 and Comparative Examples 1-4 was applied to a first film (polyethylene terephthalate film, thickness: 38 μm) using an applicator, and dried in a hot air circulating drying oven at 50-60°C for 10 minutes to prepare dry films. For the dry films used to evaluate lamination properties, the varnish was applied so that the film thickness after drying was 35 μm, and for the dry films used to evaluate thermal conductivity, the varnish was applied so that the film thickness after drying was 70-80 μm.

[0063] [Evaluation of Lamination Properties] A substrate (copper-clad laminate CCL-832NXA, thickness: 0.4 mm) was prepared, and as a pretreatment, surface roughening treatment was performed using MEC Etchbond (trademark) CZ-8101B manufactured by MEC Corporation. Next, using a two-chamber vacuum laminator CVP-600 manufactured by Nikko Materials Co., Ltd., each dry film for lamination property evaluation was applied to the substrate after surface roughening treatment at a temperature of 90°C and a pressure of 5 kgf / cm². ２ The lamination was performed under the following conditions: temperature 90°C, pressure 5 kgf / cm². ２ The material was hot-pressed under the specified conditions. Next, the thermosetting resin composition was cured by heating at 100°C for 30 minutes and then at 180°C for another 30 minutes to form an insulating layer. After curing, the first film was peeled off and the condition of the insulating layer was visually inspected. Based on the condition of the insulating layer after curing, the lamination properties of each thermosetting resin composition were evaluated according to the following evaluation criteria. The evaluation results are shown in Table 1. ○: The insulating layer is sufficiently adhered to the substrate and the surface condition of the insulating layer is excellent. ×: The insulating layer is not sufficiently adhered to the substrate and the surface condition of the insulating layer is poor, or the insulating layer has completely peeled off from the substrate.

[0064] [Measurement of Thermal Conductivity and Evaluation of Thermal Conductivity] A substrate (18 μm thick copper foil) was prepared, and a dry film for evaluating thermal conductivity was brought into contact with the substrate using a vacuum diaphragm laminator. After creating a vacuum for 30 seconds, it was laminated under pressure of 0.5 MPa. The first film was peeled off from the dry film, and a new dry film of the same type was brought into contact with the surface of the dry film from which the first dry film had been peeled off, and laminated using the same procedure as above. Next, the thermosetting resin composition was cured by heating at 100°C for 30 minutes and then at 180°C for another 30 minutes to form a cured product (insulating layer). Next, the first dry film and the substrate were peeled off from the insulating layer, and the thermal diffusivity of the obtained cured product was measured using an FTC-1 manufactured by ULVAC, Inc. under a load of 5 kgf / cm². ３ The thermal diffusivity (α), specific heat capacity (c), and density (ρ) of the cured material were measured using a periodic heating method. The specific heat capacity of the cured material was measured using a Perkin-Elmer differential scanning calorimetry (DSC) with a heating rate of 20°C / min, a helium gas flow rate of 20 ml / min, and a sample volume of 15 mg. The density of the cured material was measured at room temperature (25°C) using the water displacement method. Based on the measured thermal diffusivity (α), specific heat capacity (c), and density (ρ) of the cured material, the thermal conductivity (λ) was calculated using the following formula: Thermal conductivity (λ) = Thermal diffusivity (α) × Specific heat capacity (c) × Density (ρ)

[0065] Based on the obtained values, thermal conductivity was evaluated according to the following criteria. The values ​​for thermal conductivity and the evaluation results for thermal conductivity are shown in Table 1. ○: Thermal conductivity is 2.5 W / m·K or higher, indicating excellent thermal conductivity. △: Thermal conductivity is 2.0 W / m·K or higher and less than 2.5 W / m·K, indicating good thermal conductivity. ×: Thermal conductivity is less than 2.0 W / m·K, indicating insufficient thermal conductivity.

[0066] The results shown in Table 1 indicate that each of the thermosetting resin compositions in Examples 1 and 2 exhibits excellent lamination properties and excellent thermal conductivity of the cured product. In other words, each of the thermosetting resin compositions in these examples achieves both high lamination properties to the substrate and high thermal conductivity of the cured product. On the other hand, each of the thermosetting resin compositions in Comparative Examples 1 to 3 exhibits excellent thermal conductivity, but all have poor lamination properties. Furthermore, Comparative Example 4 exhibits excellent lamination properties but poor thermal conductivity. In other words, each of the thermosetting resin compositions in the comparative examples fails to achieve both high lamination properties to the substrate and high thermal conductivity of the cured product.

Claims

1. A thermosetting resin composition comprising an epoxy resin, a thermally conductive filler, and a polyalkylene glycol derivative, characterized in that the thermally conductive filler substantially does not contain magnetic particles.

2. The thermosetting resin composition according to claim 1, wherein the thermally conductive filler comprises at least one selected from the group consisting of aluminum oxide, aluminum nitride, boron nitride, and silicon carbide.

3. The thermosetting resin composition according to claim 1, wherein the thermal conductive filler includes a thermal conductive filler that has not been surface-treated with an organic compound.

4. The thermosetting resin composition according to claim 1, wherein the content of the thermally conductive filler is such that the mass of the thermally conductive filler is 80% by mass or more relative to the total mass of the nonvolatile components of the thermosetting resin composition.

5. The thermosetting resin composition according to claim 1, for forming an interlayer insulating layer.

6. A dry film having a first film and a resin layer formed on at least one surface of the first film, the resin layer being made of the thermosetting resin composition according to claim 1.

7. A cured product obtained by curing the resin layer of the thermosetting resin composition according to claim 1, or the dry film according to claim 6.

8. A printed circuit board comprising the cured product described in claim 7.

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