Thermosetting resin composition, cured product of the same, and printed wiring board containing cured product

Abstract

To provide a thermosetting resin composition applied to a complicated metal structure such as a lead frame, which gives a cured product having satisfactory storage stability, and satisfactory electrical insulation properties and high thermal conductivity even after curing, and a cured product of the thermosetting resin composition, and a printed wiring board having the cured product.SOLUTION: The present invention relates to a thermosetting resin composition containing epoxy resin (A), phenoxy resin (B), phenol resin (C), curing catalyst (D), filler (E), and solvent (F), where the epoxy resin (A) contains epoxy resin having viscosity at 25°C of 200 dPa s or less, and the filler (E) contains boron nitride, a cured product thereof, and a printed wiring board having the cured product.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a thermosetting resin composition, a cured product, and a printed wiring board including the cured product.

Background Art

[0002] In electronic components such as power devices, transistors, thyristors, and CPUs, it is necessary to efficiently remove heat generated during use. Therefore, a heat dissipation material containing inorganic particles having thermal conductivity and a resin has been conventionally used.

[0003] In recent years, miniaturization and thinning of semiconductor devices mounted on substrates have been required. In order to meet this requirement, a so-called QFN (Quad Flat Non-lead Package) type semiconductor device has been proposed, which seals a lead frame and a semiconductor element mounted on its mounting surface with a sealing resin and exposes a part of the lead on the back side. With further miniaturization and thinning of semiconductor devices mounted on substrates, the shape of the lead frame has become more complex.

[0004] It has been proposed to promote miniaturization and high efficiency of semiconductor devices mounted on substrates by using a heat dissipation material as the above-mentioned sealing resin. When using a heat dissipation material as the sealing resin, it is necessary to achieve both electrical insulation and thermal conductivity. As general heat dissipation materials used in semiconductor devices, many reports have been made on those obtained by molding a thermosetting resin composition into a sheet shape and then curing the obtained sheet (for example, Patent Documents 1 to 3, etc.).

[0005] In recent years, the demand for substrates mounted with power semiconductors such as in-vehicle LED headlamps, MOSFETs (Metal-Oxide-Semiconductor Field Effect Transistors), and IGBTs (Insulated Gate Bipolar Transistors) for air conditioners has been increasing. Along with this, various reports have been made on metal base substrates that take further heat dissipation measures, that is, substrates obtained by bonding a metal substrate such as aluminum or copper and a heat dissipation material.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0007] The inventor searched for a heat dissipation material that can be directly applied and sealed to a complex metal structure such as a lead frame instead of a conventional heat dissipation sheet as the heat dissipation material. As a result, it was found that when directly applying and sealing to a metal structure using a conventional thermosetting resin composition for sheet shape, it is difficult to maintain both electrical insulation and thermal conductivity in the cured product. Furthermore, it was found that storage stability is also required in order to be able to directly apply to a metal structure.

[0008] Therefore, when the inventor examined various thermosetting resin compositions, it was found that by using a predetermined thermosetting resin composition, the storage stability is good, and even when directly applied to a metal structure, the cured product can achieve both good electrical insulation and high thermal conductivity.

[0009] Therefore, an object of the present invention is to provide a thermosetting resin composition that has good storage stability and gives a cured product having good electrical insulation and high thermal conductivity even after curing. Another object of the present invention is to provide a cured product of the thermosetting resin composition and a printed wiring board having the cured product.

Means for Solving the Problems

[0010] As a result of intensive studies, the inventors have found that a thermosetting resin composition containing an epoxy resin, a phenoxy resin, a phenol resin, a curing catalyst, a filler, and a solvent, wherein the epoxy resin contains an epoxy resin having a viscosity at 25°C of 200 dPa·s or less, and the filler contains boron nitride, can solve the above problems. Based on such findings, further studies were conducted to complete the present invention.

[0011] That is, the present invention provides the following thermosetting resin composition, its cured product, and a printed wiring board containing the cured product. Item 1. A thermosetting resin composition containing an epoxy resin (A), a phenoxy resin (B), a phenol resin (C), a curing catalyst (D), a filler (E), and a solvent (F), wherein the epoxy resin (A) contains an epoxy resin having a viscosity at 25°C of 200 dPa·s or less, and the filler (E) contains boron nitride. Item 2. The thermosetting resin composition according to Item 1, wherein the viscosity of the thermosetting resin composition at 25°C is 10 to 500 dPa·s. Item 3. The thermosetting resin composition according to Item 1 or 2, wherein the solvent (F) contains cyclic ketones. Item 4. The thermosetting resin composition according to any one of Items 1 to 3, wherein the boron nitride is an aggregated powder of boron nitride. Item 5. The thermosetting resin composition according to Item 4, wherein the aggregated powder of boron nitride is secondary aggregated particles obtained by aggregating primary particles of boron nitride. Item 6. A cured product obtained by curing the thermosetting resin composition according to any one of Items 1 to 5. Item 7. A method for producing the cured product according to Item 6, the method comprising a step of curing the thermosetting resin composition according to any one of Items 1 to 5. Item 8. A printed wiring board having a metal structure and the cured product according to Item 6, wherein a portion including the metal structure is sealed with the cured product. Item 9. A method for producing the printed wiring board according to Item 8, the method comprising a step of applying and curing the thermosetting resin composition according to any one of Items 1 to 5 to a portion including the metal structure.

Advantages of the Invention

[0012] Even when the thermosetting resin composition of the present invention is applied to a site where a complex metal structure such as a lead frame is mounted, it has appropriate fluidity (viscosity), and thus has good filling properties (good embedding properties into uneven portions). Further, the fluidity (viscosity) of the thermosetting resin composition is stably maintained even after long-term storage, that is, it has excellent storage stability.

[0013] The cured product obtained by curing the thermosetting resin composition has characteristics of having good insulation properties and high thermal conductivity because it has few voids. Generally, when voids are generated in the cured product, air is contained inside the coating film and the resin layer becomes thin, so it is difficult to obtain a cured product having good electrical insulation properties and high thermal conductivity. Further, the generation of voids is mainly due to the fluidity of the thermosetting resin composition (liquid varnish). For example, if the fluidity is too low, voids are likely to be generated, while if the fluidity is too high, it tends to be difficult to adjust the film thickness of the resin layer. Since the thermosetting resin composition of the present invention has stable and appropriate fluidity, the generation of voids after application can be suppressed, and a cured product having good insulation properties and high thermal conductivity can be obtained. Therefore, when the cured product is used as a sealing material for directly sealing a metal structure on a substrate, heat generated from a heat-generating component such as a semiconductor chip can be more effectively released to the outside while ensuring insulation properties. In addition, the cured product has excellent adhesion to metals such as aluminum and copper, and since boron nitride is used as a filler, its hardness does not become too high, it has good abrasiveness, and it is also excellent in acid resistance and alkali resistance.

[0014] The cured product can be easily formed by applying, drying, and vacuum pressing the thermosetting resin composition onto a metal structure on a substrate.

Embodiments for Carrying Out the Invention

[0015] Hereinafter, the thermosetting resin composition, cured product, and printed wiring board including the cured product according to the present embodiment will be described.

[0016] 1. Thermosetting resin composition The thermosetting resin composition of the present invention is applied to a site where a metal structure such as a lead frame or a circuit on a metal base substrate is mounted, cured, and used to seal the metal structure. The composition has appropriate fluidity (viscosity) and retains its fluidity (viscosity) even after long-term storage. It also has good filling properties (good embedding properties into uneven portions). Its cured product has good insulation properties and high thermal conductivity, and has the characteristic of having few voids even when applied to a complex metal structure. In this specification, the metal base substrate means a substrate of an electronic circuit having at least an electrical insulating layer on a metal substrate with good thermal conductivity such as aluminum, copper, or iron so as to efficiently dissipate heat generated from electronic components, and having a metal foil or the like on the electrical insulating layer.

[0017] The thermosetting resin composition of the present invention contains an epoxy resin (A), a phenoxy resin (B), a phenol resin (C), a curing catalyst (D), a filler (E), and a solvent (F), wherein the epoxy resin (A) contains an epoxy resin having a viscosity at 25°C of 200 dPa·s or less, and the filler (E) contains boron nitride.

[0018] The thermosetting resin composition is usually a liquid composition, and its viscosity at 25°C is preferably 10 to 500 dPa·s, more preferably 30 to 300 dPa·s, and particularly preferably 40 to 250 dPa·s from the viewpoint of ease of filling and holding in a metal structure (lead frame, circuit, etc.) having a shape with many irregularities on the substrate. The thermosetting resin composition may hereinafter also be referred to as a "liquid varnish".

[0019] [Epoxy resin (A)] The thermosetting resin composition of the present invention contains an epoxy resin (A). The epoxy resin (A) contributes to the heat resistance, adhesion to the metal structure, insulation, etc. of the cured product. The epoxy resin (A) is characterized by containing an epoxy resin that is liquid at normal temperature (25°C), that is, an epoxy resin having a viscosity at 25°C of 200 dPa·s or less (hereinafter also referred to as a "liquid epoxy resin").

[0020] By including a liquid epoxy resin in the epoxy resin (A), the viscosity of the composition can be reduced without adding an excessive amount of solvent as compared with the case of containing only an epoxy resin that is solid at normal temperature. Further, the viscosity of the liquid epoxy resin at 25°C is preferably 1 to 200 dPa·s, more preferably 5 to 100 dPa·s, and particularly preferably 15 to 50 dPa·s from the viewpoints of filling property, handleability, etc.

[0021] Examples of the epoxy resin (A) contained in the thermosetting resin composition of the present invention include dicyclopentadiene type epoxy resin, naphthalene skeleton type epoxy resin, bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol AF type epoxy resin, bisphenol S type epoxy resin, glycidyl ester type epoxy resin having an aromatic structure, glycidyl amine type epoxy resin having an aromatic structure, phenol novolac type epoxy resin, alicyclic epoxy resin having an ester skeleton having an aromatic structure, cyclohexanedimethanol type epoxy resin having an aromatic structure, epoxy resin having a butadiene structure having an aromatic structure, cresol novolac type epoxy resin, alicyclic epoxy resin, amine type epoxy resins such as tetraglycidylaminodiphenylmethane, tetraglycidylmethylxylylenediamine, triglycidyl para-aminophenol, diglycidylaniline, and diglycidyl orthotoluidine, but are not limited thereto. These may be used alone or in combination of two or more.

[0022] The epoxy resin (A) contains a liquid epoxy resin at room temperature (25°C) among the epoxy resins listed above. The content of the liquid epoxy resin in the epoxy resin (A) is usually 10% by mass or more, preferably 10 to 100% by mass, more preferably 20 to 70% by mass, and particularly preferably 20 to 60% by mass. When the content is within this range, it is suitable because the fluidity of the liquid varnish can be ensured while improving the solder heat resistance and the adhesion between the metal and the resin composition.

[0023] As the liquid epoxy resin, commercially available products can be used. Specific examples thereof include, for example, jER828US, jER828EL (bisphenol A type epoxy resin), jER806, jER807 (bisphenol F type epoxy resin), jER152 (phenol novolac type epoxy resin), jER630, 630LSD (glycidylamine type epoxy resin) (manufactured by Mitsubishi Chemical Corporation); ZX1059 (a mixture of bisphenol A type epoxy resin and bisphenol F type epoxy resin), (manufactured by Nippon Steel Chemical & Material Co., Ltd.); EX-721 (glycidyl ester type epoxy resin) (manufactured by Nagase ChemteX Corporation); Celoxide 2021P (alicyclic epoxy resin having an ester skeleton) (manufactured by Daicel Corporation); and the like.

[0024] Among them, a mixture of bisphenol A type epoxy resin and bisphenol F type epoxy resin, and glycidylamine type epoxy resin (polyfunctional epoxy resin) are preferred.

[0025] The epoxy resin (A) may contain resins other than the above liquid epoxy resin (for example, solid epoxy resins) as long as the effects of the present invention are not impaired. As the solid epoxy resin, commercially available products can be used. Specific examples thereof include, for example, XD-1000 (dicyclopentadiene type epoxy resin) manufactured by Nippon Kayaku Co., Ltd., EXA4700 (tetrafunctional naphthalene type epoxy resin) manufactured by DIC Corporation, and NC-7000 (naphthalene skeleton-containing polyfunctional solid epoxy resin) manufactured by Nippon Kayaku Co., Ltd. Naphthalene type epoxy resins such as these; Epoxidized products of condensates of phenols and aromatic aldehydes having phenolic hydroxyl groups (trisphenol type epoxy resins) such as EPPN-502H (trisphenol epoxy resin) manufactured by Nippon Kayaku Co., Ltd.; Dicyclopentadiene aralkyl type epoxy resins such as Epiklon HP-7200H (dicyclopentadiene skeleton-containing polyfunctional solid epoxy resin) manufactured by DIC Corporation; Biphenyl aralkyl type epoxy resins such as NC-3000H (biphenyl skeleton-containing polyfunctional solid epoxy resin) manufactured by Nippon Kayaku Co., Ltd.; Novolak type epoxy resins such as Epiklon N660, Epiklon N690 manufactured by DIC Corporation, and EOCN-104S manufactured by Nippon Kayaku Co., Ltd.; Tris(2,3-epoxypropyl) isocyanurate such as TEPIC manufactured by Nissan Chemical Industries, Ltd., and the like. Among them, dicyclopentadiene type epoxy resins, naphthalene type epoxy resins, and epoxy resins having an aromatic structure are preferred.

[0026] From the viewpoints of heat resistance and adhesiveness, the epoxy equivalent (g / eq) of the epoxy resin (A) is usually about 100 to 1000, preferably about 200 to 800.

[0027] The content of the epoxy resin (A) in the thermosetting resin composition of the present invention is usually 5 to 25% by mass, preferably 5 to 20% by mass, more preferably 5 to 15% by mass, based on the total amount of the solid content in the thermosetting resin composition.

[0028] In this specification, "the solid content in the thermosetting resin composition" means the total of the components excluding the solvent (F) described later from the total amount of the thermosetting resin composition.

[0029] [Phenoxy resin (B)] The thermosetting resin composition of the present invention contains a phenoxy resin (B). The phenoxy resin (B) contributes to the adhesion of the cured product to the metal structure, insulation, etc.

[0030] Examples of the phenoxy resin (B) include the formula (1): [Chemical formula] (In the formula, X represents a direct bond, [Chemical formula] R represents -CH 3 , -CH 2 (CH 3 ), -CH(CH 3 ), 2 or -C(CH 3 ), 3 n is 0 to 20.) Compounds represented by the formula are exemplified. Specifically, phenoxy resins having one or more skeletons selected from the group consisting of bisphenol A skeleton, bisphenol F skeleton, bisphenol S skeleton, bisphenol acetophenone skeleton, novolak skeleton, biphenyl skeleton, fluorene skeleton, dicyclopentadiene skeleton, norbornene skeleton, naphthalene skeleton, anthracene skeleton, adamantane skeleton, terpene skeleton, and trimethylcyclohexane skeleton are exemplified. The phenoxy resin (B) may be used alone or in combination of two or more.

[0031] Among these, as the phenoxy resin (B) used in the present invention, those having a softening point of 60 to 90 °C are preferable because excessive flow during vacuum pressing can be suppressed when applied as a sealing material for a metal structure.

[0032] As the phenoxy resin (B), commercially available products can be used. Specific examples thereof include, for example, 1256, 4250, YX8100, YX6954, YL7500BH30, YX6954BH30, YX7553, YX7553BH30, YL7769BH30, YL6794, YL7213, YL7290, and YL7482 (manufactured by Mitsubishi Chemical Corporation); FX280, FX293 (manufactured by Nippon Steel Chemical & Material Co., Ltd.), and the like.

[0033] The content of the phenoxy resin (B) in the thermosetting resin composition of the present invention is usually 0.5 to 40% by mass, preferably 1 to 25% by mass, and more preferably 3 to 10% by mass with respect to the total amount of the solid content in the thermosetting resin composition.

[0034] [Phenolic resin (C)] The thermosetting resin composition of the present invention contains a phenolic resin (C). The phenolic resin (C) can also be referred to as a phenolic curing agent.

[0035] Examples of the phenolic resin (C) include novolak-type phenolic resins such as phenolic novolak resin, cresol novolak resin, naphthol novolak resin, aminotriazine novolak resin, novolak resin, and triphenylmethane-type phenolic novolak resin; modified phenolic resins such as terpene-modified phenolic resin and dicyclopentadiene-modified phenolic resin; aralkyl-type resins such as phenolic aralkyl resin having a phenylene skeleton and / or a biphenylene skeleton and naphthol aralkyl resin having a phenylene skeleton and / or a biphenylene skeleton; bisphenol compounds such as bisphenol A and bisphenol F; resol-type phenolic resins, and the like. These may be used alone or in combination of two or more. Among these, from the viewpoints of improving the glass transition temperature and reducing the linear expansion coefficient, novolak-type phenolic resin or resol-type phenolic resin is preferable.

[0036] The content of the phenolic resin (C) in the thermosetting resin composition of the present invention is usually 0.5 to 40% by mass, preferably 1 to 25% by mass, and more preferably 1 to 5% by mass with respect to the total amount of the solid content in the thermosetting resin composition.

[0037] [Curing catalyst (D)] The thermosetting resin composition of the present invention contains a curing catalyst (D). The curing catalyst (D) is used to adjust the curing rate of the thermosetting resin composition of the present invention and can also be called a curing accelerator.

[0038] Examples of the curing catalyst (D) include organic phosphine compounds such as TPP, TPP-K, TPP-S, and TPTP-S (manufactured by Kitakyo Chemical Industry Co., Ltd.); imidazole compounds such as Curezol 2MZ, 2E4MZ, 2PZ, 1B2PZ, Cl1Z, Cl1Z-CN, Cl1Z-CNS, Cl1Z-A, 2MZ-OK, 2MA-OK, and 2PHZ (manufactured by Shikoku Chemicals Corporation); amine adduct compounds such as Novacure (manufactured by Asahi Kasei Corporation) and Fujicure (manufactured by T&K Toka Corporation); amine compounds such as 1,8-diazabicyclo[5,4,0]undecene-7, 4-dimethylaminopyridine, benzyldimethylamine, 2,4,6-tris(dimethylaminomethyl)phenol, and 4-dimethylaminopyridine; and organometallic complexes or organometallic salts of cobalt, copper, zinc, iron, nickel, manganese, tin, etc. These may be used alone or in combination of two or more.

[0039] As the curing catalyst (D), an imidazole compound is preferable in terms of excellent adhesion to the metal structure. Specific examples of particularly preferable imidazole compounds include imidazole compounds, 2-ethyl-4-methylimidazole, 2-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, bis(2-ethyl-4-methyl-imidazole), 2-phenyl-4-methyl-5-hydroxymethylimidazole, 2-phenyl-4,5-dihydroxymethylimidazole, triazine-added imidazole, etc., and they can be used alone or in combination of two or more.

[0040] The content of the curing catalyst (D) in the thermosetting resin composition of the present invention is usually 0.01 to 1% by mass, preferably 0.05 to 0.5% by mass, based on the total amount of the solid content in the thermosetting resin composition.

[0041] [Filler (E)] Since the thermosetting resin composition of the present invention is used for sealing a metal structure, its cured product needs to have electrical insulation and good thermal conductivity. Therefore, the thermosetting resin composition of the present invention contains a filler (E) capable of exhibiting thermal conductivity, and the filler (E) contains boron nitride (BN).

[0042] The thermal conductivity of the filler (E) is preferably 10 W / m·K or more. The boron nitride contained in the filler (E) is preferably secondary aggregated particles formed by aggregating primary particles of boron nitride. The secondary particles have a thermal conductivity of 10 W / m·K or more. Examples of such secondary aggregated particles of boron nitride include those formed by aggregating primary particles of boron nitride and those formed by aggregating and sintering primary particles of boron nitride.

[0043] Boron nitride has a layered structure similar to graphite and has thermal anisotropy. Although there is a difference in thermal conductivity of several times to several tens of times between the plane direction and the thickness direction of the crystal of this boron nitride (it has anisotropic thermal conductivity), the secondary aggregated particles formed by aggregating primary particles of boron nitride have isotropic thermal conductivity because the primary particles are aggregated in all directions.

[0044] The average particle diameter (d50) of the primary particles constituting the secondary aggregated particles is preferably 15 μm or less, more preferably 0.1 to 8 μm. The average particle diameter (d50) of the secondary aggregated particles is preferably 10 to 180 μm, more preferably 10 to 130 μm, and even more preferably 15 to 80 μm.

[0045] The shape of the secondary agglomerated particles is not limited to spherical, and may be other shapes such as scaly. However, in the case of shapes other than spherical, the average particle size means the length of the long side in that shape. When manufacturing the thermosetting resin composition, it is preferable for it to be spherical because the blending amount of the secondary agglomerated particles can be increased while ensuring the fluidity of the thermosetting resin composition.

[0046] Preferred secondary agglomerated particles can be produced according to known methods. Specifically, primary particles of scaly boron nitride can be calcined and crushed, or primary particles of scaly boron nitride can be aggregated by known methods such as spray drying and then calcined and sintered (grain growth). The calcination temperature is not particularly limited, but is generally 2,000 °C.

[0047] From the viewpoint of further improving the thermal conductivity in the cured product for sealing the metal structure, the filler (E) of the thermosetting resin composition of the present invention essentially contains boron nitride. The content of boron nitride in the filler (E) is usually preferably 40% by mass or more, more preferably 50% by mass or more, and particularly preferably 55% by mass or more.

[0048] The filler (E) preferably contains boron nitride (particularly, secondary agglomerated particles of boron nitride), and may contain other fillers common in the art in addition to the above boron nitride as long as the effects of the present invention are not impaired. Such other fillers are not particularly limited, and examples include fused silica (SiO 2 ), crystalline silica (SiO 2 ), aluminum oxide (Al 2 O 3 ), aluminum nitride (AlN), silicon carbide (SiC), silicon nitride (Si 3 N 4 ), etc. These fillers may be used alone or in combination of two or more. Among these, from the viewpoint of further improving the thermal conductivity, aluminum oxide (Al 2 O 3 ), aluminum nitride (AlN), silicon nitride (Si 3 N 4) is preferred. The average particle diameter (d50) of these fillers is usually 0.01 to 100 μm, preferably 0.1 to 80 μm, and more preferably 1 to 70 μm.

[0049] As the other fillers mentioned above, aluminum oxide (alumina) is preferred, and spherical alumina is more preferred. The content of fillers other than boron nitride in filler (E) is usually 5 to 50% by mass, and more preferably 5 to 45% by mass.

[0050] Filler (E) can contain a coupling agent from the viewpoint of improving the adhesive strength at the interface between the filler and the resin. The coupling agent is not particularly limited, and examples include silane-based coupling agents such as γ-glycidoxypropyltrimethoxysilane, N-β(aminoethyl)γ-aminopropyltriethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, and γ-mercaptopropyltrimethoxysilane. These coupling agents may be used alone or in combination of two or more.

[0051] The compounding amount of the coupling agent is preferably usually 0.2 to 5 parts by mass with respect to 100 parts by mass of filler (E).

[0052] It is preferable to use filler (E) by mixing two or more fillers having different average particle diameters. In this case, the types of fillers may be the same or different. By including both a filler with a large average particle diameter and a filler with a small average particle diameter, the viscosity of the thermosetting resin composition decreases and the fluidity improves. In particular, the thermosetting resin composition of the present invention has stable high fluidity even when the concentrations of components (A) to (E) are maintained at relatively high concentrations (when the content of solvent (F) is reduced), so that the composition can be filled into the metal structure without gaps, and the generation of voids during curing can be suppressed. Also, since the dispersibility of the filler in the thermosetting resin composition is improved, it becomes possible to fill the cured product with the filler homogeneously and densely, which contributes to the improvement of thermal conductivity as a result.

[0053] Examples of combinations of two or more fillers with different average particle diameters include, for example, a combination of boron nitride having an average particle diameter of 25 to 45 μm (particularly, secondary agglomerated particles of boron nitride) and alumina having an average particle diameter of 3 to 15 μm (particularly, spherical alumina).

[0054] In this specification, the average particle diameter is a value measured by a laser diffraction / scattering method based on the Mie scattering theory. Specifically, a particle size distribution of the inorganic filler can be created on a volume basis by a laser diffraction / scattering type particle size distribution measuring device, and the median diameter (d50) thereof can be used as the average particle diameter. As the measurement sample, a dispersion of the filler (E) in water by ultrasonic waves can preferably be used. Further, as the laser diffraction / scattering type particle size distribution measuring device, for example, LA-500 (manufactured by Horiba, Ltd.), SALD2200 (manufactured by Shimadzu Corporation), etc. can be used.

[0055] The filler (E) is contained in the thermosetting resin composition of the present invention in an amount such that the cured product of the thermosetting resin composition of the present invention exhibits a function as an electrically insulating material (sealing material) having thermal conductivity, and the thermal conductivity of the cured product is 3 W / m·K or more, further 5 W / m·K or more, further 8 W / m·K or more, and still further 10 W / m·K or more.

[0056] As the filler (E), commercially available products can be used. Examples of boron nitride agglomerated powder include, for example, HP-40MF100 (D50: 36 μm, specific surface area: 1.8 m 2 / g), HP-40J2 (D50: 16 μm, specific surface area: 3.2 m 2 / g) (both manufactured by JFE Minerals Co., Ltd.), etc. Examples of spherical boron nitride include, for example, PTX-60 (D50: 55 to 65 μm) (manufactured by Momentive), etc. Examples of flaky boron nitride include, for example, UHP-2 (D50: 11 μm, BET specific surface area: 3 to 5 m 2 / g) (manufactured by Resonac Co., Ltd.), etc. Examples of spherical alumina include, for example, DAW-03 (D50: 4.9 μm, specific surface area: 0.5 m 2Examples thereof include ASFP-20 (both manufactured by Denka Co., Ltd.).

[0057] The content of the filler (E) in the thermosetting resin composition of the present invention is usually 50 to 90% by mass, preferably 60 to 90% by mass, and more preferably 70 to 90% by mass with respect to the total amount of the solid content in the thermosetting resin composition.

[0058] [Solvent (F)] The thermosetting resin composition of the present invention contains a solvent (F). The solvent (F) is used to dissolve or disperse the components (A) to (E) and other components as necessary, and to adjust the viscosity to a suitable level for coating the thermosetting resin composition of the present invention on a metal structure such as a lead frame or a metal base substrate.

[0059] As the solvent (F), for example, an organic solvent can be used. There is no particular limitation as long as it is a known organic solvent. For example, ketones, aromatic hydrocarbons, glycol ethers, glycol ether acetates, esters, alcohols, aliphatic hydrocarbons, petroleum solvents, etc. can be mentioned. More specifically, 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 monoethyl ether, dipropylene glycol diethyl ether, and triethylene glycol monoethyl ether; esters such as ethyl acetate, butyl acetate, dipropylene glycol methyl ether acetate, propylene glycol methyl ether acetate, propylene glycol ethyl ether acetate, and propylene glycol butyl ether acetate; alcohols such as ethanol, propanol, ethylene glycol, and propylene glycol; aliphatic hydrocarbons such as octane and decane; petroleum solvents such as petroleum ether, petroleum naphtha, hydrogenated petroleum naphtha, and solvent naphtha. Such organic solvents may be used alone or as a mixture of two or more.

[0060] Among these, from the viewpoint of good drying property and effective suppression of filler sedimentation, ketones such as methyl ethyl ketone and cyclohexanone are preferred, and cyclic ketones such as cyclohexanone are more preferred.

[0061] The content of the solvent (F) in the thermosetting resin composition of the present invention is not particularly limited. For example, the solvent can be contained so as to be within the preferred viscosity range of the thermosetting resin composition at 25°C.

[0062] Since the thermosetting resin composition of the present invention contains the epoxy resin (A) as a liquid epoxy resin having a predetermined viscosity, the fluidity during high-pressure pressing is good, and voids can be suppressed.

[0063] [Other components] The thermosetting resin composition of the present invention can further contain a wetting dispersant, a silane coupling agent, an antioxidant, an antifoaming agent (leveling agent), etc.

[0064] The wetting dispersant is used to improve the dispersibility of the filler (E) in the thermosetting resin composition. Examples of the wetting dispersant include copolymers containing acid groups, pigment-affinity block copolymers, phosphate ester compounds, polyether phosphate ester compounds, fatty acid ester compounds, alkylene oxide copolymers, modified polyether polymers, fatty acid derivatives, urethane polymers, etc. Examples of commercially available products include ANTI-TERRA-U, ANTI-TERRA-U100, ANTI-TERRA-204, ANTI-TERRA-205, DISPERBYK-101, DISPERBYK-102, DISPERBYK-103, DISPERBYK-106, DISPERBYK-108, DISPERBYK-109, DISPERBYK-110, DISPERBYK-111, DISPERBYK-112, DISPERBYK-116, DISPERBYK-130, DISPERBYK-140, DISPERBYK-142, DISPERBYK-145, DISPERBYK-161, DISPERBYK-162, DISPERBYK-163, DISPERBYK-164, DISPERBYK-166, DISPERBYK-167, DISPERBYK-168, DISPERBYK-170, DISPERBYK-171, DISPERBYK-174, DISPERBYK-180, DISPERBYK-182, DISPERBYK-183, DISPERBYK-185, DISPERBYK-184, DISPERBYK-2000, DISPERBYK-2001, DISPERBYK-2009, DISPERBYK-2020, DISPERBYK-2025, DISPERBYK-2050, DISPERBYK-2070, DISPERBYK-2096, DISPERBYK-2150, BYK-P104, BYK-P104S, BYKP105, BYK-9076, BYK-9077, BYK-220S, BYK-1160, BYK-1165, BYK-W903, BYK-W908, BYK-W909, BYK-W940, BYK-W961, BYK-W966, BYK-W969, BYK-W972, BYK-W974, BYK-W980, BYK-W985, BYK-W995, BYK-W996, BYK-W9010, BYK-W9011,BYK-W9012 (manufactured by BYK-Chemie Japan Co., Ltd. as mentioned above), Disparlon 2150, Disparlon 1210, Disparlon KS-860, Disparlon KS-873N, Disparlon 7004, Disparlon 1830, Disparlon 1860, Disparlon 1850, Disparlon DA-400N, Disparlon PW-36, Disparlon DA-703-50 (manufactured by Kusumoto Chemicals, Ltd. as mentioned above), Floren G-450, Floren G-600, Floren G-820, Floren G-700, Floren DOPA-44, Floren DOPA-17 (manufactured by Kyoeisha Chemical Co., Ltd.) and the like can be mentioned. When the thermosetting resin composition contains a wetting dispersant, the content of the wetting dispersant in the thermosetting resin composition is usually 0.1 to 10 parts by mass, preferably 0.1 to 5 parts by mass, based on 100 parts by mass of the filler (E).

[0065] The defoaming agent (leveling agent) can be used to prevent deterioration of surface smoothness and deterioration of insulation and thermal conductivity due to voids. Examples of the defoaming agent (leveling agent) include silicone-based defoaming agents and non-silicone-based defoaming agents which are defoaming polymer solutions. Commercially available products of silicone-based defoaming agents include BYK (registered trademark)-063, BYK-065, BYK-066N, BYK-067A, BYK-077 (manufactured by BYK-Chemie Japan Co., Ltd. as mentioned above), KS-66 (manufactured by Shin-Etsu Chemical Co., Ltd.) and the like. When the thermosetting resin composition contains a defoaming agent (leveling agent), the content of the defoaming agent (leveling agent) in the thermosetting resin composition is 0.01 to 5.0 parts by mass based on 100 parts by mass of the solid content of the thermosetting resin composition excluding the filler.

[0066] [Preparation of Thermosetting Resin Composition] The thermosetting resin composition (liquid varnish) of the present invention can be prepared by mixing the above components (A) to (F) and other components as required. Specifically, each component is mixed and stirred using a centrifugal defoaming stirrer or the like until it becomes uniform. Further, in order to suppress the generation of voids in the cured product, it is recommended to go through a defoaming process such as standing defoaming and vacuum defoaming before coating.

[0067] 2. Formation of cured product The thermosetting resin composition of the present invention is applied (applied) to a site where a metal structure such as a lead frame or a circuit on a metal base substrate is mounted, dried, and cured to form a cured product that seals the metal structure.

[0068] The metal constituting the metal structure is not particularly limited, and aluminum, iron, copper, stainless steel, magnesium, silicon, and alloys thereof can be used.

[0069] Hereinafter, as a typical example, the case where the thermosetting resin composition of the present invention is applied to a metal base substrate having a metal structure will be cited to explain the method for producing a cured product. Here, the metal base substrate means a substrate including a metal plate, a resin layer, and a metal foil.

[0070] The thermosetting resin composition is applied to the side of the metal base substrate where the metal wiring is provided. For the application, screen printing, dispenser coating, bar coater coating, etc. can be used. The application amount can be arbitrarily set, and for example, it can be appropriately adjusted so that the film thickness after drying on the substrate surface is 150 to 300 μm. Since the thermosetting resin composition of the present invention has good viscosity (fluidity) immediately after preparation and after storage for a certain period, it can be well filled into the gaps of a metal structure having a complex structure.

[0071] Next, the applied thermosetting resin composition is dried to remove the solvent. The drying conditions can be appropriately set according to the boiling point of the solvent. Usually, it is at 60 to 120 °C under normal pressure for about 10 to 60 minutes.

[0072] Next, the dried composition is heated and cured. In order to densely pack the filler in the cured product, usually, heat treatment is performed while applying pressure. Specifically, it can be heated at 80 to 200 °C for 30 minutes to 120 hours, and vacuum pressed while applying a pressure of about 0.5 to 20 MPa to cure (press cure) the composition. Thereby, a cured product (sealing film) is formed on the side of the metal base substrate where the metal wiring (metal foil, particularly copper foil) is provided.

[0073] In this way, electronic components, printed wiring boards, etc. in which the metal structure is sealed with a cured product can be obtained. Since there are no voids, voids, etc. between the cured product and the metal structure, and the filler is uniformly and highly densely dispersed in the cured product, it has excellent insulating properties and thermal conductivity. The surface of the press-cured cured product has a smooth surface. Since the cured product contains boron nitride having a relatively low hardness as a filler, it is easy to perform molding processing using polishing or the like.

[0074] The thermal conductivity of the obtained cured product is usually 4 W / m·K or more, preferably 7 W / m·K or more, and more preferably 10 W / m·K or more.

[0075] The film thickness of the cured product (film) formed on the substrate is usually 200 μm or less, preferably 100 to 150 μm.

Example

[0076] Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

[0077] 1. Thermosetting resin composition (1) Preparation of thermosetting resin composition The thermosetting resin compositions of Examples 1 to 6 and Comparative Examples 1 to 4 were each produced by mixing the respective components in the composition and ratio described in Table 1 below and stirring and defoaming for 8 minutes with a centrifugal defoaming stirrer. The numerical values in Table 1 mean "parts by mass" unless otherwise specified.

Table 1

[0078] (2) Evaluation of the thermosetting resin composition The following evaluations were performed on the obtained thermosetting resin compositions. The results are shown in Table 2.

[0079] <Measurement of viscosity (25 °C)> The viscosities of the thermosetting resin compositions of Examples 1 to 6 and Comparative Examples 1 to 4 were measured by the following method in accordance with the viscosity measurement method using a cone - plate type rotational viscometer (JIS - Z8803:2011). Using a cone - plate viscometer (manufactured by Toki Sangyo Co., Ltd., TY - 33, rotor 3°×R9.7), the 30 - second value at 25 °C and 5.0 rpm was measured. The measurement results are shown in Table 2.

[0080] <Storage stability of the liquid varnish> 120 mL of each of the thermosetting resin compositions of Examples 1 to 6 and Comparative Examples 1 to 4 was collected, placed in a container with a volume of 150 mL, and stored at 20 °C for 48 hours. Among the thermosetting resin compositions after storage, the thermosetting resin compositions in the surface layer part (5 mm from the liquid surface in the container) and the bottom layer part (5 mm from the bottom surface in the container) were sampled with a syringe and the viscosity was measured. When sampling the thermosetting resin composition after storage, sampling was performed without stirring the thermosetting resin composition. The viscosities of the thermosetting resin compositions in the surface layer part and the bottom layer part after storage at 20 °C for 48 hours were measured by the same method as <Measurement of Viscosity (25 °C)>, the viscosity difference between the surface layer part and the bottom layer part was calculated by the following formula, and evaluation was performed according to the following criteria. The evaluation results are shown in Table 2. Viscosity difference between surface layer part and bottom layer part [dPa·s] = Viscosity of thermosetting resin composition in surface layer part [dPa·s] - Viscosity of thermosetting resin composition in bottom layer part [dPa·s] (Evaluation Criteria) ◎: Viscosity difference between surface layer part and bottom layer part is less than 20 dPa·s ○: Viscosity difference between surface layer part and bottom layer part is 20 dPa·s or more and less than 30 dPa·s △: Viscosity difference between surface layer part and bottom layer part is 30 dPa·s or more and less than 35 dPa·s ×: Viscosity difference between surface layer part and bottom layer part is 35 dPa·s or more

[0081] 2. Formation of cured film on metal-based substrate Next, the liquid varnishes prepared in Examples 1 to 6 and Comparative Examples 1 to 4 were respectively applied to the electrical insulation layer of the metal base substrate to form a cured film.

[0082] (1) Preparation of metal base substrate Each of the thermosetting resin compositions of Examples 1 to 6 and Comparative Examples 1 to 4 was applied onto a copper foil (manufactured by Furukawa Electric Co., Ltd., F2WS) with a size of 190 mm × 150 mm and a thickness of 35 μm using a bar coater so that the film thickness after drying was 100 μm, and then heat-dried at 80 °C for 30 minutes using a hot air circulation drying furnace to obtain a thermosetting resin layer in a B-stage state (semi-cured state). Next, on an aluminum substrate with dimensions of 190 mm × 150 mm and a thickness of 1.0 mm (A1050 material specified in Table 2 of JIS H4160-1994), it was overlaid so that the thermosetting resin layer previously formed on the copper foil was in contact, and heated and pressed at 190 °C, 10 MPa for 60 minutes under vacuum pressing to cure, and metal base substrates each composed of three layers of an aluminum substrate, a cured product layer (= electrical insulation layer), and a copper foil were produced respectively.

[0083] <Evaluation of Electrical Insulation> Samples with a circular pattern of 20 mm in diameter formed were produced respectively by immersing the copper foil of each metal base substrate produced as described above in a 30 - 40 wt% ferric chloride aqueous solution heated to 40 °C for 10 minutes for etching. Then, using a withstand voltage tester (manufactured by Kikusui Electronics, TOS5051A), the withstand voltage was measured. The withstand voltage measurement started from 1 kV in AC and increased the voltage at a rate of 25 V / second. The lowest voltage at which the sample suffered dielectric breakdown was taken as its withstand voltage, and the electrical insulation was evaluated. The measurement results of the withstand voltage and the evaluation results evaluated according to the following criteria are shown in Table 2. (Evaluation Criteria) ◎: 4 kV / 0.1 mm or more ○: 3 kV / 0.1 mm or more and less than 4 kV / 0.1 mm ×: Less than 3 kV / 0.1 mm

[0084] (2) Formation of Cured Product on Thick Copper Circuit Board As a pretreatment for a printed wiring board on which a circuit with a comb - tooth pattern with a copper thickness of 210 μm and L (line: wiring width) / S (space: interval width) = 100 μm / 100 μm was formed, an etching treatment equivalent to 0.5 μm was performed with CZ - 8101 treatment manufactured by Meck. Next, each of the curable resin compositions of the examples and comparative examples obtained above was applied onto the substrate by a bar coater so that the film thickness became 300 μm. The printed wiring boards coated with each curable resin composition were placed in a hot - air circulation drying furnace and heat - cured at 80 °C for 60 minutes to form a B - staged curable resin composition. Next, the above substrate was heated and pressed at 190 °C, 10 MPa for 60 minutes by vacuum pressing to be cured, and an evaluation substrate was produced.

[0085] <Evaluation of concavo-convex embedding property> The evaluation substrates of Examples 1 to 6 obtained as described above were cut and polished into a size of 2 cm × 2 cm with a precision cutting machine, and it was evaluated whether the resin composition could be filled (printed) without gaps at the bottom of the line and space. The evaluation was performed by observing cross-sections of 10 evaluation substrates with SEM (scanning electron microscope, JSM-7600F manufactured by JEOL Ltd.). For SEM, observation was carried out at an acceleration voltage of 30 kV, a measurement magnification of 500 times, and in a reflected electron composite image. The evaluation criteria are as follows. (Evaluation criteria) ○: No unfilled part ×: There is an unfilled part in one or more places

[0086] (3) Evaluation of cured film The formed cured film was evaluated for thermal conductivity. The results are shown in Table 2.

[0087] <Thermal conductivity> The liquid varnishes of Examples 1 to 6 and Comparative Examples 1 to 4 were applied to one side of a copper foil with a thickness of 35 μm using a bar coater, and then heated at 80 °C for 30 minutes using a hot air circulation drying oven to dry the solvent, and an electrical insulation layer which is a resin layer in a B-stage state (semi-cured state) with a thickness of 100 μm was produced respectively. Copper foils were overlaid on these electrical insulation layers formed on the copper foils, heated and pressed at 190 °C and 10 MPa for 60 minutes by vacuum pressing to be cured, and then the copper foils were peeled off to obtain film-like cured products. After blackening the cured products on the films with a graphite spray, the thermal diffusivity was evaluated using the xenon flash method (NETZSCH LFA447 nanoflash). The thermal conductivity was obtained from the product of the density measured by the Archimedes method and the specific heat measured by DSC (DSC manufactured by Perkin Elmer, Pyris1).

Table 2

[0088] From the results in Table 2, it was found that all of the liquid varnishes of Examples 1 to 6 were excellent in storage stability, and their cured products were also excellent in electrical insulation and thermal conductivity.

Industrial Applicability

[0089] Even when the thermosetting resin composition of the present invention is applied to a complex metal structure such as a lead frame, it has appropriate fluidity and can maintain it stably for a long period of time, and provides a cured product having good insulation and high thermal conductivity after curing. Therefore, it is useful as a sealing material for metal structures.

Claims

1. A thermosetting resin composition comprising an epoxy resin (A), a phenoxy resin (B), a phenolic resin (C), a curing catalyst (D), a filler (E), and a solvent (F), wherein the epoxy resin (A) comprises an epoxy resin having a viscosity at 25 °C of 200 dPa·s or less, and the filler (E) comprises boron nitride. A thermosetting resin composition.

2. The thermosetting resin composition according to claim 1, wherein the viscosity of the thermosetting resin composition at 25 °C is 10 to 500 dPa·s.

3. The thermosetting resin composition according to claim 1, wherein the solvent (F) comprises cyclic ketones.

4. The thermosetting resin composition according to claim 1, wherein the boron nitride is an aggregated powder of boron nitride.

5. The thermosetting resin composition according to claim 4, wherein the aggregated powder of boron nitride is secondary aggregated particles formed by aggregating primary particles of boron nitride.

6. A cured product obtained by curing the thermosetting resin composition according to any one of claims 1 to 5.

7. A method for producing the cured product according to claim 6, comprising a step of curing the thermosetting resin composition according to claim 1. A manufacturing method.

8. A printed wiring board having a metal base substrate having a metal structure and a cured product according to claim 6, wherein a portion containing the metal structure is sealed with the cured product. A printed wiring board.

9. A method for producing the printed wiring board according to claim 8, comprising a step of coating and curing the thermosetting resin composition according to claim 1 on a portion containing the metal structure on the metal base substrate. A manufacturing method.

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