Resin composition, dry film, and cured product

Abstract

The present invention provides a resin composition, a dry film, and a cured product that possess magnetic properties while ensuring insulation reliability and suppressing bleeding and warping after curing. [Solution] The resin composition comprises a solid epoxy resin having a weight-average molecular weight of 20,000 or more and an epoxy equivalent of 2,500 to 9,000, a liquid epoxy resin, and a magnetic filler. It contains an epoxy curing agent.

Description

[Technical Field]

[0001] The present invention relates to a resin composition, a dry film, and a cured product. [Background Art]

[0002] Along with the recent reduction in size and thickness of electronic devices, demands for smaller and thinner printed wiring boards and inductor components mounted on printed wiring boards have been increasing. For this reason, for inductor components, there are demands for thinner substrates (core materials), and even inductor components with a coreless structure.

[0003] In such inductor components, since the substrate is thin, if warpage occurs when the component is formed on the substrate and cured, it becomes difficult to form the component. Additionally, in order to improve the performance of inductors, the number of coil turns is sometimes increased, which shortens the distance between coiled circuits. Consequently, the magnetic materials used are required to satisfy both insulation reliability and magnetic properties. A technique of incorporating a magnetic filler into a resin composition to impart magnetic properties is known (for example, Patent Document 1). [Prior Art Literature] [Patent Literature]

[0004] [Patent Document 1] Japanese Unexamined Patent Publication No. 2016-172790 [Summary of the Invention] [Problems to be Solved by the Invention]

[0005] However, since magnetic fillers have low insulating properties, when a magnetic filler is incorporated into a resin composition, it becomes difficult to ensure the insulation reliability of the cured product. Further, when a thermoplastic resin having a relatively large molecular weight is used in the resin composition to maintain the strength and other properties of the cured product, warpage may occur after curing due to bleeding, a phenomenon in which a part of the resin composition oozes out from the coated surface, and uneven physical properties of the cured product.

[0006] Therefore, the present invention aims to provide a resin composition, a dry film, and a cured product that have magnetic properties while ensuring insulation reliability and suppressing bleeding and warping after curing. [Means for solving the problem]

[0007] One aspect of the present invention is a resin composition. The resin composition comprises a solid epoxy resin having a weight-average molecular weight of 20,000 or more and an epoxy equivalent of 2,500 to 9,000, a liquid epoxy resin, a magnetic filler, and an epoxy curing agent.

[0008] In the resin composition according to the above embodiment, it is preferable that the viscosity of the liquid epoxy resin is 10,000 mPa·s or less.

[0009] In the resin composition according to the above embodiment, it is preferable that the magnetic filler includes one or more selected from the group consisting of ferrite and alloy.

[0010] In the resin composition according to the above embodiment, it is preferable that the epoxy curing agent includes a phenolic curing agent.

[0011] Another aspect of the present invention is a dry film. This dry film is obtained by applying the resin composition of the above aspect to a first film.

[0012] Another aspect of the present invention is a cured product. The cured product is obtained using the resin composition of the above aspect or the dry film of the above aspect. [Effects of the Invention]

[0013] According to the present invention, a resin composition, a dry film, and a cured product are provided that have magnetic properties while ensuring insulation reliability and suppressing bleeding and warping after curing. [Modes for carrying out the invention]

[0014] In the present specification, where isomers exist for the compounds described, all possible isomers can be used in the present invention unless otherwise specified.

[0015] In the present specification, when the upper limit and lower limit of a numerical range are described separately, all combinations of each lower limit and each upper limit shall be deemed to be substantially described within a consistent range.

[0016] In the present specification, unless otherwise specified, various measurements are performed at an ambient temperature of room temperature (25°C).

[0017] In the present specification, the number average molecular weight and weight average molecular weight are measured by gel permeation chromatography (GPC) and converted using a calibration curve prepared with standard polystyrene.

[0018] In the present specification, solid content refers to components other than solvents (particularly organic solvents) among the components constituting the resin composition or each raw material, and is based on mass unless otherwise stated.

[0019] 1. Resin Composition The resin composition of the present embodiment contains a solid epoxy resin, a liquid epoxy resin, a magnetic filler, and an epoxy curing agent. Further, the resin composition may contain other components within a range that does not impair the effects of the present invention. Each component is described below.

[0020] 1-1. Solid Epoxy Resin A solid epoxy resin is an epoxy resin that is solid, i.e., in a solid state, at room temperature (25°C). The solid epoxy resin includes a solid epoxy resin having a weight average molecular weight of 20,000 or more and an epoxy equivalent of 2,500 to 9,000.

[0021] The weight average molecular weight of the solid epoxy resin is 20,000 or more, preferably 25,000 or more, 30,000 or more, 35,000 or more, etc., and preferably 100,000 or less, 95,000 or less, 90,000 or less, etc.

[0022] The epoxy equivalent of said solid epoxy resin is 2,500 or more, preferably 2,800 or more, 3,000 or more, 3,500 or more, etc., and preferably 8,500 or less, 8,000 or less, 7,800 or less, etc.

[0023] By setting the weight average molecular weight and epoxy equivalent of said solid epoxy resin within the above ranges, bleeding can be suppressed while maintaining insulation reliability through combination with a liquid epoxy resin described later.

[0024] Examples of the type of said solid epoxy resin include bisphenol A type epoxy resins, bisphenol F type epoxy resins, phenol novolac epoxy resins, cresol novolac epoxy resins, triphenylmethane type epoxy resins, dicyclopentadiene type epoxy resins, phenol aralkyl epoxy resins, biphenol aralkyl epoxy resins, trisphenol type epoxy resins, and the like. These may be used alone in one kind, or may be used in combination of two or more kinds.

[0025] Commercially available products can be used as said solid epoxy resin, and there is no particular limitation as long as the weight average molecular weight and epoxy equivalent are within the ranges described above. For example, as bisphenol A type epoxy resins, jER1256 (manufactured by Mitsubishi Chemical Corporation, weight average molecular weight: 50,000, epoxy equivalent: 7,700), jER1010 (manufactured by Mitsubishi Chemical Corporation, weight average molecular weight: 38,000, epoxy equivalent: 3,700) and the like are preferable.

[0026] As described above, the resin composition of the present embodiment contains a solid epoxy resin having a weight average molecular weight of 20,000 or more and an epoxy equivalent of 2,500 to 9,000, but may further contain other solid epoxy resins whose weight average molecular weight and epoxy equivalent are outside the ranges described above.

[0027] The content of solid epoxy resin having a weight-average molecular weight of 20,000 or more and an epoxy equivalent of 2,500 to 9,000 is preferably 10 to 80% by mass, and more preferably 20 to 60% by mass, when the total amount of all solid epoxy resins and liquid epoxy resins contained in the composition is 100% by mass.

[0028] The ratio of the solid content of a solid epoxy resin having a weight-average molecular weight of 20,000 or more and an epoxy equivalent of 2,500 to 9,000 to the solid content of the liquid epoxy resin described later is preferably 0.1 to 2.5, and more preferably 0.5 to 2.0.

[0029] 1-2. Liquid epoxy resin Liquid epoxy resins are fluid at room temperature (25°C), and more specifically, they have a viscosity in the range of 100 to 20,000 mPa·s at 25°C. In this respect, liquid epoxy resins are distinguished from the solid epoxy resins mentioned above.

[0030] The viscosity of the liquid epoxy resin is preferably 10,000 mPa·s or less, 8,000 mPa·s or less, 5,000 mPa·s or less, 3,000 mPa·s or less, 1,500 mPa·s or less, etc. By setting the viscosity of the liquid epoxy resin within the above range, warping of the resin composition after curing can be suppressed.

[0031] The viscosity of the resin in this invention is measured as follows. Specifically, in accordance with JIS-Z8803:2011, item 10 "Method for measuring viscosity using a cone-plate type rotational viscometer", a cone-plate type rotational viscometer (cone-plate type) (manufactured by Toki Sangyo Co., Ltd., TVE-33H) was used, and the 30-second value measured under conditions of 25°C and a rotation speed of 5 rpm was taken as the viscosity. For resins with a viscosity of 1,000 mPa·s or more, a cone-plate type rotational viscometer with a rotor of 3° × R9.7 was used, and for resins with a viscosity of less than 1,000 mPa·s, a rotor of 1°34' × R24 was used.

[0032] The epoxy equivalent of the liquid epoxy resin is preferably 100 or more, 150 or more, 170 or more, and preferably 800 or less, 700 or less, 500 or less.

[0033] Liquid epoxy resins preferably have a flexible skeleton. Having a flexible skeleton in the liquid epoxy resin helps to suppress warping after curing.

[0034] The flexible skeleton is not particularly limited as long as it is a structure that imparts flexibility to the main chain or side chains of the epoxy resin. Specifically, examples include aliphatic structures having linear or branched C1-C20 alkyl chains, ether bonds, aliphatic cyclic structures such as cyclohexane, and polyol skeletons. These structures enhance flexibility by improving the mobility of the molecular chains.

[0035] The type of liquid epoxy resin is not particularly limited, and known types can be used. Examples include liquid bisphenol A type epoxy resin, liquid bisphenol F type epoxy resin, liquid phenol novolac type epoxy resin, liquid bisphenol AD ​​type epoxy resin, liquid naphthalene type epoxy resin, liquid glycidyl ester type epoxy resin, liquid glycidyl ether type epoxy resin, liquid glycidylamine type epoxy resin, liquid heterocyclic epoxy resin, liquid diarylsulfone type epoxy resin, and modified liquids thereof. These may be used individually or in combination of two or more types.

[0036] The solid content of the liquid epoxy resin is preferably 5 to 80% by mass, and more preferably 10 to 60% by mass, when the total mass of all solid epoxy resins and liquid epoxy resins contained in the resin composition is considered to be 100% by mass.

[0037] 1-3. Magnetic fillers Magnetic fillers are used to ensure the magnetic properties of the cured product. The magnetic filler is not particularly limited, and known types can be used. Preferably, the magnetic filler includes one or more types selected from the group consisting of ferrite and alloys.

[0038] More specifically, Fe-Mn ferrite, Fe-Mn-Zn ferrite, Mg-Zn ferrite, Mn-Zn ferrite, Mn-Mg ferrite, Cu-Zn ferrite, Mg-Mn-Sr ferrite, Ni-Zn ferrite, Ba-Zn ferrite, Ba-Mg ferrite, Ba-Ni ferrite, Ba-Co ferrite, Ba-Ni-Co ferrite, Y ferrite, iron(III) oxide powder, triiron tetroxide, etc. Examples include iron oxide powder; pure iron powder; iron alloy metal powders such as Fe-Si alloy powder, Fe-Si-Al alloy powder, Fe-Cr alloy powder, Fe-Cr-Si alloy powder, Fe-Ni-Cr alloy powder, Fe-Cr-Al alloy powder, Fe-Ni alloy powder, Fe-Ni-Mo alloy powder, Fe-Ni-Mo-Cu alloy powder, Fe-Co alloy powder, or Fe-Ni-Co alloy powder; and amorphous alloys such as Co-based amorphous alloys.

[0039] The shape of the magnetic filler is not particularly limited as long as it does not impair the effects of the present invention. Examples include spherical, needle-shaped, plate-shaped, flake-shaped, hollow, irregularly shaped, hexagonal, cubic, and thin flake shapes. Among the above, a spherical shape is preferred from the viewpoint of high packing and high dispersibility.

[0040] From the viewpoint of improving the dispersibility of the magnetic filler, its ability to fill the gaps in the circuit, and its magnetic properties, the average particle size of the magnetic filler is preferably in the range of 0.1 μm to 25 μm, and more preferably in the range of 0.1 μm to 5 μm.

[0041] The average particle size of the magnetic filler is the median particle size D50 (volume-based), measured by a laser diffraction particle size distribution analyzer.

[0042] The magnetic filler may be surface-treated. Examples of surface treatment agents include vinylsilane coupling agents, (meth)acrylic coupling agents, fluorine-containing silane coupling agents, aminosilane coupling agents, epoxysilane coupling agents, mercaptosilane coupling agents, silane coupling agents, alkoxysilanes, organosilazane compounds, and titanate coupling agents. One type of surface treatment agent may be used alone, or two or more types may be used in any combination.

[0043] The magnetic filler content is preferably 40 to 85% by mass, and more preferably 50 to 85% by mass, when the total mass of the solid content of the resin composition is taken as 100% by mass.

[0044] 1-4. Epoxy curing agent The epoxy curing agent is added to cure the solid epoxy resin and liquid epoxy resin described above by a crosslinking reaction. The epoxy curing agent is not particularly limited, and known ones can be used. Examples include phenolic curing agents, polyamine curing agents, polyamide curing agents, acid anhydride curing agents, imidazole curing agents, thiol curing agents, catechol curing agents, photocuring curing agents, and diamine curing agents. These may be used individually or in combination of two or more.

[0045] Among the epoxy curing agents mentioned above, it is preferable to include a phenolic curing agent or an imidazole curing agent from the viewpoint of ensuring insulation reliability, and it is more preferable to include a phenolic curing agent.

[0046] The phenolic curing agent is not particularly limited, and conventionally known ones such as phenol novolac resins, alkylphenol novolac resins, bisphenol A novolac resins, dicyclopentadiene type phenolic resins, Xylok type phenolic resins, terpene-modified phenolic resins, cresol / naphthol resins, polyvinylphenols, phenol / naphthol resins, α-naphthol skeleton-containing phenolic resins, triazine skeleton-containing cresol novolac resins, biphenyl aralkyl type phenolic resins, and Xylok type phenol novolac resins can be used.

[0047] The imidazole-based curing agent is not particularly limited, and examples include 2-methylimidazole, 4-methyl-2-ethylimidazole, 2-phenylimidazole, 4-methyl-2-phenylimidazole, 1-benzyl-2-methylimidazole, 2-ethylimidazole, 2-isopropylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, and 1-cyanoethyl-2-undecylimidazole.

[0048] The epoxy curing agent content, calculated on a solid content basis, is preferably 1 to 100% by mass, and more preferably 4 to 50% by mass, when the total amount of all solid epoxy resins and liquid epoxy resins contained in the resin composition is taken as 100% by mass.

[0049] 1-5. Other ingredients Other components include additives such as crosslinking agents, crosslinking aids, defoaming agents, rust inhibitors, catalysts (reaction catalysts for epoxy resins, thermosetting catalysts), antioxidants, leveling agents, inorganic fillers such as silica, sensitizers, adhesion aids, surfactants, plasticizers, flame retardants, cellulose nanofibers, dispersants, and adhesion enhancers, provided they do not impede the effects of the present invention.

[0050] Other components may include organic solvents. Examples of organic solvents include ketones such as acetone, methyl ethyl ketone, and cyclohexanone; acetic acid esters such as ethyl acetate, butyl acetate, cellosolve acetate, propylene glycol monomethyl ether acetate, and carbitol acetate; cellosolves such as cellosolve and butyl cellosolve, and carbitols such as carbitol and butyl carbitol; aromatic hydrocarbons such as toluene and xylene; and other organic solvents such as dimethylformamide and dimethylacetamide.

[0051] The other ingredients may be used individually or in combination of two or more.

[0052] The total content of other components (excluding organic solvents) in the resin composition may be 1% by mass or more, 5% by mass or more, or 10% by mass or more, and may be 40% by mass or less, 30% by mass or less, or 20% by mass or less, based on the total mass of the solids in the resin composition.

[0053] The resin composition of this embodiment can be manufactured, for example, by mixing the above-mentioned components simultaneously or sequentially and kneading them appropriately using conventionally known methods. Each component may be prepared in advance as a solution or dispersion before mixing.

[0054] 2. Uses / Methods of Use of Resin Compositions The following describes the uses and applications of the resin composition, specifically dry films made using the resin composition and cured products obtained using the resin composition.

[0055] 2-1. Dry film The dry film has a resin layer obtained by applying the resin composition of this embodiment to at least one surface of a first film (carrier film) and then drying it. The dry film is used by laminating the resin layer so that it is in contact with a substrate.

[0056] A dry film can be manufactured by uniformly applying a resin composition onto a first film using an appropriate method such as a blade coater, lip coater, comma coater, or film coater, and then drying it to form the aforementioned resin layer. Preferably, the dry film has a second film (protective film) laminated on top of the resin layer. The first film and the second film may be made of the same film material or different film materials.

[0057] The first film is one that serves to support the resin layer of the dry film, and when it is laminated onto a substrate by heating or other means so that the resin layer side of the dry film is in contact with the substrate, it refers to a film that is at least adhered to the resin layer.

[0058] The second film is provided on the side of the resin layer opposite the first film to the dry film, with the purpose of preventing dust and other debris from adhering to the surface of the resin layer and improving handling. When the second film is laminated onto the substrate by heating or other means so that the resin layer side of the dry film is in contact with it, it is peeled off from the resin layer before lamination.

[0059] The film materials for the first and second films can be any of those known to be used for dry films.

[0060] As the first film, for example, a thermoplastic film such as a polyester film like polyethylene terephthalate with a thickness of 2 to 150 μm is used.

[0061] As the second film, polyethylene film, polypropylene film, etc., can be used, but it is preferable that the adhesive strength to the resin layer is weaker than that of the first film.

[0062] The thickness of the resin layer on the first film is preferably 100 μm or less, and more preferably in the range of 5 to 50 μm.

[0063] 2-2.Cured product A cured product can be obtained using the resin composition of this embodiment, or a dry film having a resin layer obtained from the resin composition of this embodiment. The method for producing the cured product and its applications will be described below.

[0064] (Method of manufacturing a cured product) The following describes an example of a method for manufacturing the cured product related to this disclosure.

[0065] Step 1 involves applying a resin composition to the substrate and drying it to form a resin layer. When using 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.

[0066] Methods for applying the resin composition onto a substrate include conventional methods used for applying resin compositions, such as application using a spin coater, bar coater, blade coater, curtain coater, screen printing machine, spray application using a spray coater, and inkjet methods.

[0067] The dry film is preferably bonded to the substrate using a vacuum laminator or the like, under pressure and heat. By using such a vacuum laminator, even if the circuit-formed substrate has irregularities on its surface, 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.

[0068] Drying methods after coating the resin composition include air drying, heating and drying in an oven or on a hot plate, and vacuum drying. The drying conditions are not particularly limited and can be performed by natural drying, forced-air drying, or heating and drying at 60 to 130°C for 1 to 30 minutes.

[0069] There are no particular limitations on the substrate on which the resin layer is formed. Examples include printed circuit boards and flexible printed circuit boards with circuits pre-formed using copper, etc., copper-clad laminates using 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, metal substrates, glass substrates, ceramic substrates, wafers, etc. In addition, in the present invention, films such as polyimide film, polyethylene terephthalate film, and polyethylene naphthalate (PEN) film can also be used as substrates.

[0070] Step 2 involves heat curing the resin layer formed on the substrate. If a dry film is used, the first film is peeled off from the dry film before curing. The heating temperature is not particularly limited, but for example, it can be heated at 100-220°C for 30-120 minutes. The atmosphere (gas) at this time may be air, or an inert gas such as nitrogen or argon may be used.

[0071] Heat curing may be performed in two stages. That is, the curable resin composition can be pre-cured at a lower temperature, and then fully cured (final curing) can be performed. Pre-curing conditions are preferably heating at 80-120°C for about 30-120 minutes. After that, heating is performed to fully cure. Pre-curing conditions are preferably heating at 160-180°C for about 30-180 minutes.

[0072] (Uses of hardened material) The cured product of this embodiment can be used in various electronic components, including inductor components. While possessing magnetic properties, the cured product of this embodiment ensures insulation reliability and suppresses bleeding and warping after curing, thus enabling miniaturization and thinning of the aforementioned electronic components. [Examples]

[0073] <<Preparation of Resin Composition>> Using the raw materials listed below, resin compositions according to Examples 1-14 and Comparative Examples 1-5 were prepared to match the formulations shown in Tables 1 and 2. Tables 1 and 2 show the solid content (parts by mass) of each raw material.

[0074] <Solid epoxy resin (A)> Solid epoxy resin (A) is a solid epoxy resin having a weight-average molecular weight of 20,000 or more and an epoxy equivalent of 2,500 to 9,000. jER1256 (manufactured by Mitsubishi Chemical Corporation) (weight-average molecular weight: 50,000, epoxy equivalent: 7,700) jER1010 (manufactured by Mitsubishi Chemical Corporation) (weight-average molecular weight: 38,000, epoxy equivalent: 3,700) • jER1009 (manufactured by Mitsubishi Chemical Corporation) (weight-average molecular weight: 20,000, epoxy equivalent: 2,600)

[0075] <Other solid epoxy resins> Other solid epoxy resins are solid epoxy resins whose weight-average molecular weight and epoxy equivalent are outside the range of solid epoxy resin (A) described above. jER1004F (manufactured by Mitsubishi Chemical Corporation) (weight-average molecular weight: 6,200, epoxy equivalent: 930) • YX6954 (manufactured by Mitsubishi Chemical Corporation) (weight-average molecular weight: 38,000, epoxy equivalent: 12,000) • XD-1000 (manufactured by Nippon Kayaku Co., Ltd.) (weight-average molecular weight: 1,000, epoxy equivalent: 245-260)

[0076] <Liquid epoxy resin (B)> • EP-4040L (manufactured by ADEKA Corporation) (Viscosity: 220 mPa·s, Epoxy equivalent: 310) • AER-9000 (manufactured by Asahi Kasei Corporation) (viscosity: 1,200 mPa·s, epoxy equivalent: 350-400) jER828 (Mitsubishi Chemical Corporation) (Viscosity: 12,000 mPa·s, Epoxy equivalent: 184~194)

[0077] <Magnetic filler> • M03S (ferrite, manufactured by Powdertech Co., Ltd.) AW02-08 PF-3F (Amorphous alloy, manufactured by Epson Atomics Corporation)

[0078] <Epoxy curing agent> • HF4MH55 (manufactured by Meiwa Kasei Co., Ltd.) (phenol-based curing agent) • 2E4MZ (manufactured by Shikoku Chemicals Holdings Co., Ltd.) (imidazole-based curing agent) • 1BPZ (manufactured by Shikoku Chemicals Holdings Co., Ltd.) (imidazole-based curing agent)

[0079] <<Preparation of dry film>> The resin compositions of Examples 1-14 and Comparative Examples 1-5 were each appropriately diluted with cyclohexanone, and then applied to a carrier film (PET film; manufactured by Toyobo Co., Ltd., TN-200, 38 μm thick) using an applicator so that the resin layer thickness after drying was 80 μm. Next, the resin layer was dried in an IR drying oven at 100-110°C for 5-10 minutes so that the residual solvent in the resin layer was 0.5-2.0% by mass, thereby forming a resin layer on the carrier film.

[0080] <<Rating>> For each of the examples and comparative examples below, the resin compositions were evaluated for magnetic permeability, post-lamination bleeding, warping, and insulation reliability based on the following evaluation method. The evaluation results are shown in Tables 1 and 2.

[0081] <Measurement of magnetic permeability> The dry film obtained by the above method was attached to the glossy side of copper foil attached to an etch-out board using a vacuum laminator (Nikko Materials Co., Ltd., CVP-600) under the following conditions: vacuum pressure: 4 hPa, pressure: 0.4 MPa, temperature: 60°C, and lamination pressure time: 60 seconds. Next, a cured coating film was formed by heat treatment in a hot air circulation drying oven (Yamato Scientific Co., Ltd., DF610) at 100°C for 60 minutes, followed by 180°C for 30 minutes. After peeling off the carrier film, the cured coating film was peeled off the copper foil, and the peeled cured coating film was cut into strips with an outer diameter of 1 cm and an inner diameter of 3 cm to prepare evaluation test pieces. For each evaluation test piece obtained as described above, the relative permeability (μ') was measured at a temperature of 25°C and 100 MHz using an impedance analyzer (Keysight, E4291B).

[0082] <Breeding after lamination> The dry film obtained by the above method was cut to a size of 3 cm x 3 cm and attached to the copper of a copper-clad laminate treated with CZ8101 (manufactured by MEC Corporation) using a vacuum laminator (manufactured by Nikko Materials Co., Ltd., CVP-600) under the following conditions: vacuum pressure: 4 hPa, pressure: 0.4 MPa, temperature: 110°C, and lamination time: 60 seconds. Next, it was heat-pressed under atmospheric pressure at a temperature of 110°C, pressure of 0.5 MPa, and time: 60 seconds to obtain an evaluation substrate. The length of the bleed from the original size (3 cm x 3 cm) on each of the four sides of the evaluation substrate was measured using an optical microscope and evaluated according to the following criteria. (Evaluation Criteria) A: The average bleed of all four sides is less than 2mm. B: The average bleed of all four sides is between 2mm and 4mm. C: The average bleed of all four sides is between 4mm and 6mm. D: The average length of the bleed on all four sides is 6mm or more.

[0083] <curve> The dry film prepared using the above method was placed on the glossy surface of 35μm electrolytic copper foil (product name: FV-WS) manufactured by Furukawa Electric Co., Ltd., and laminated using a vacuum laminator (Nikko Materials Co., Ltd., CVP-600) under the following conditions: vacuum pressure: 4hPa, pressure: 0.4MPa, temperature: 60℃, and lamination time: 60 seconds. This copper foil was then heated in a hot air circulation drying oven (Yamato Scientific Co., Ltd., DF610) at 100℃ for 30 minutes, followed by 180℃ for 60 minutes to cure the resin layer. A 5cm x 5cm section was cut out, and the amount of warping on each of the four sides was measured and evaluated according to the following criteria. (Evaluation Criteria) A: The average curvature of all four sides is less than 2 mm. B: The average curvature of all four sides is 2mm or more and less than 4mm. C: Average curvature of all four sides is 4mm or more and less than 10mm. D: The average curvature of all four sides is 10mm or more.

[0084] <Insulation reliability> The dry film prepared by the above method was laminated onto a substrate with a Cu thickness of 18 μm and a circuit pattern with L / S = 13 μm / 12 μm formed on it, after acid treatment, in the same manner as the <warpage> evaluation described above. The resin was cured by heat treatment in a hot air circulation drying oven (Yamato Scientific Co., Ltd., DF610) at 100°C for 60 minutes, followed by 180°C for 30 minutes, and the carrier film was peeled off to obtain the evaluation substrate. In a highly accelerated life test apparatus (HAST apparatus, Hirayama Seisakusho Co., Ltd.) PC-R8D, the insulation resistance value was 10 under the conditions of 130 RH°C, 85 RH%, and applied voltage of 2 V. 6 The time it took for the reading to drop below Ω was measured. (Evaluation Criteria) A: Over 168 hours, resistance value 10 6 It remained above Ω. B: 96 hours or more but less than 168 hours, resistance value 10 6 It remained above Ω. C: 48 hours or more but less than 96 hours, resistance value 10 6 It remained above Ω. D: Resistance value is 10 for less than 48 hours 6 It became less than Ω

[0085] [Table 1]

[0086] [Table 2] [Industrial applicability]

[0087] The resin composition, dry film, and cured product of the present invention can be used in electronic components, including inductor components, because they possess magnetic properties while ensuring insulation reliability and suppressing bleeding and warping after curing.

Claims

1. A solid epoxy resin having a weight-average molecular weight of 20,000 or more and an epoxy equivalent of 2,500 to 9,000, Liquid epoxy resin and Magnetic filler and, Epoxy hardener and A resin composition containing the following:

2. The resin composition according to claim 1, wherein the viscosity of the liquid epoxy resin is 10,000 mPa·s or less.

3. The resin composition according to claim 1, wherein the magnetic filler comprises one or more selected from the group consisting of ferrite and alloy.

4. The resin composition according to claim 1, wherein the epoxy curing agent comprises a phenolic curing agent.

5. A dry film obtained by applying the resin composition according to claim 1 to a first film.

6. A cured product obtained using the resin composition according to claim 1 or the dry film according to claim 5.

Images