Resin films, resin-coated copper foil, multilayer wiring boards, coil structures, and magnetic devices

Abstract

To provide a resin film with a low dielectric constant. [Solution] A resin film 100 comprising a core layer 2 and adhesive resin layers 1 provided on both sides of the core layer 2, wherein the adhesive resin layer 1 is made of a first adhesive resin composition containing polyamic acid which is a polyaddition reaction product of (A) an acid dianhydride and (B) a diamine, or a second adhesive resin composition containing an epoxy resin, wherein the polyamic acid in the first adhesive resin composition contains (B1) dimeramine in a molar ratio of 0.2 or more relative to the total diamine components, the dielectric breakdown strength of the cured product of the second adhesive resin composition is 300 kV / mm or more, and the core layer 2 is made of a polyimide film containing polyimide obtained by imidizing the polyamic acid in the first adhesive resin composition.

Description

Technical Field

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[0001] The present invention relates to a resin film, a copper foil with resin, a multilayer wiring board, a coil structure, and a magnetic device.

Background Art

[0002] As a thin transformer which is one of magnetic devices, for example, Patent Document 1 describes a thin transformer including a printed coil and a core made of a magnetic material, and a terminal base on which the printed coil and the core are mounted. This thin transformer is characterized in that the surface on which the conductor of the printed coil is exposed is covered with a heat-resistant resin.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in recent years, magnetic devices are required to handle higher voltages and larger currents. When using a conventional prepreg (glass cloth base / epoxy resin) as the heat-resistant resin layer, it has not been possible to satisfy both sufficient thinness and sufficient withstand voltage. Furthermore, the conventional prepreg has a problem of high dielectric constant.

[0005] An object of the present invention is to provide a resin film having a low dielectric constant, and a copper foil with resin, a multilayer wiring board, a coil structure, and a magnetic device using the same.

Means for Solving the Problems

[0006] According to the present invention, there are provided a resin film, a copper foil with resin, a multilayer wiring board, a coil structure, and a magnetic device as described below. [1] A resin film comprising a core layer and adhesive resin layers provided on both sides of the core layer, The adhesive resin layer consists of a first adhesive resin composition containing polyamic acid, which is a polyaddition reaction product of (A) an acidic dianhydride and (B) a diamine, or a second adhesive resin composition containing an epoxy resin. The polyamic acid in the first adhesive resin composition contains (B1) dimeramine in a molar ratio of 0.2 or more relative to the total diamine components. The dielectric breakdown strength of the cured product of the second adhesive resin composition is 300 kV / mm or more. The core layer consists of a polyimide film containing a polyimide obtained by imidizing the polyamic acid in the first adhesive resin composition. Resin film. [2] In the resin film described in [1], The (A) acidic dianhydride has the structure shown in the following formula (1): Resin film.

[0007] [ka]

[0008] (In formula (1), Ar represents a substituted or unsubstituted arylene group.) [3] In the resin film described in [1] or [2], The (B) diamine includes (B2) aromatic diamine, Resin film. [4] In any of the resin films described in [1] to [3], The ratio of the thickness of the adhesive resin layer to the thickness of the core layer is 1 / 2 or more and 4 or less. Resin film. [5] A resin film according to any one of [1] to [4] and a copper foil laminated on the resin film, Copper foil coated with resin. [6] An insulating layer formed using the resin film according to any one of [1] to [4], Multi-layer wiring board. [7] An insulating layer formed using the resin film according to any one of [1] to [4], Coil structure. [8] An insulating layer formed using the resin film according to any one of [1] to [4], Magnetic device.

Effect of the Invention

[0009] According to one aspect of the present invention, a resin film having a low dielectric constant, and a copper foil with resin, a multi-layer wiring board, a coil structure, and a magnetic device using the same can be provided.

Brief Description of the Drawings

[0010] [Figure 1] It is a schematic diagram showing a resin film according to a first embodiment of the present invention. [Figure 2] It is an explanatory diagram showing an example of a manufacturing method of a resin film according to a first embodiment of the present invention. <000008]1>It is an explanatory diagram showing an example of a manufacturing method of a copper foil with resin according to a first embodiment of the present invention. [Figure 4] It is an explanatory diagram showing an example of a manufacturing method of a multi-layer wiring board according to a first embodiment of the present invention. [Figure 5] It is an explanatory diagram showing an example of a manufacturing method of a multi-layer wiring board according to a second embodiment of the present invention. [Figure 6] It is an explanatory diagram showing an example of a manufacturing method of a multi-layer wiring board according to a third embodiment of the present invention. [Figure 7] It is a schematic diagram showing a magnetic device according to a fourth embodiment of the present invention. [Figure 8] It is a cross-sectional view showing the VIII-VIII cross-section of FIG. 7.

Mode for Carrying Out the Invention

[0011] [First Embodiment] The present invention will be described below with reference to embodiments, based on the drawings. The present invention is not limited to the embodiments. Note that some parts of the drawings have been enlarged or reduced in size for the purpose of facilitating explanation.

[0012] (Resin film) As shown in Figure 1, the resin film 100 according to this embodiment comprises a core layer 2, an adhesive resin layer 1, and a release film layer 3. The adhesive resin layer 1 is provided on both sides of the core layer 2. The release film layer 3 is provided on top of the adhesive resin layer 1. When using the resin film 100, the release film layer 3 is peeled off from the adhesive resin layer 1 before use. The adhesive resin layer 1 consists of a first adhesive resin composition containing polyamic acid, which is a polyaddition reaction product of (A) an acidic dianhydride and (B) a diamine, or a second adhesive resin composition containing an epoxy resin. Furthermore, the polyamic acid in the first adhesive resin composition must contain (B1) dimeramine in a molar ratio of 0.2 or more relative to the total diamine components. In addition, the dielectric breakdown strength of the cured product of the second adhesive resin composition must be 300 kV / mm or more. Furthermore, the core layer 2 must consist of a polyimide film containing a polyimide obtained by imidizing the polyamic acid in the first adhesive resin composition. The reason why the resin film 100 according to this embodiment has a low dielectric constant is as follows. In other words, the resin film 100 comprises a core layer 2 made of a polyimide film containing a polyimide obtained by imidizing polyamic acid in the first adhesive resin composition, which has a low dielectric constant. Furthermore, the cured product of the adhesive resin layer 1 has a low dielectric constant. In addition, the adhesive resin layer 1 contains epoxy resin or a polyamic acid solution and has sufficient adhesive properties, so a multilayer wiring board 300 (see Figure 4) can be manufactured using this resin film 100.

[0013] (adhesive resin layer) The adhesive resin layer 1 is a layer made of either a first adhesive resin composition or a second adhesive resin composition.

[0014] (First adhesive resin composition) The first adhesive resin composition used in this embodiment is an adhesive resin composition containing polyamic acid, which is a polyaddition reaction product of (A) an acidic dianhydride and (B) a diamine. The polyamic acid in this first adhesive resin composition must contain (B1) dimeramine in a molar ratio of 0.2 or more relative to the total diamine components. That is, the polyimide formed using the polyamic acid used in this embodiment has an ester skeleton and a dimer skeleton, and low water absorption can be achieved due to the ester skeleton. Furthermore, low dielectric properties are exhibited due to the dimer skeleton, and by including a certain amount of dimeramine as a diamine component, the dielectric constant and dielectric loss tangent can be further reduced, thereby achieving the desired low dielectric properties. In addition, the presence of a dimer skeleton in the polyimide improves heat resistance, and a polyimide with excellent heat decomposition resistance can be formed.

[0015] (Component A) The polyamic acid used in this embodiment uses (A) an acid dianhydride as one of its raw materials. Any known acid dianhydride can be used as appropriate. Examples of acid dianhydride components include 3,3',4,4'-biphenyltetracarboxylic acid dianhydride, pyromellitic acid dianhydride, 4,4'-(hexafluoroisopropylidene)diphthalic acid anhydride, and ester-type acid dianhydrides having an ester bond in the molecule. Furthermore, in this embodiment, it is preferable that the acid dianhydride component has structural units derived from ester-type acid dianhydrides having ester bonds in the molecule. By having structural units derived from ester-type acid dianhydrides in the polyamic acid, low water absorption can be imparted to the resulting polyimide. The acid dianhydride has two acid anhydride groups in one molecule, and is preferably a tetracarboxylic dianhydride, and more preferably an aromatic tetracarboxylic dianhydride. There may be one or more ester bonds in the molecule, preferably one to three, and more preferably one or two. The acid dianhydride may be used alone, or two or more may be used in combination.

[0016] Such acidic dianhydrides preferably have the structure shown in the following formula (1). In formula (1), Ar represents a substituted or unsubstituted arylene group, and a substituted arylene group means that the hydrogen atoms of an unsubstituted arylene group are substituted by any substituent. The number of carbon atoms in the substituted or unsubstituted arylene group (excluding the number of carbon atoms of the substituent) is preferably 6 or more and 20 or less, and more preferably 6 or more and 12 or less.

[0017] [ka]

[0018] In formula (1), examples of unsubstituted arylene groups in Ar include o-phenylene, m-phenylene, p-phenylene, 2,6-naphthylene, and 4,4'-biphenylylene. Among these, p-phenylene, 2,6-naphthylene, or 4,4'-biphenylylene are preferred.

[0019] Examples of substituents on the substituted arylene group include C1-C8 alkyl groups, halogen atoms (fluorine, chlorine, bromine, or iodine atoms), and halogenated alkyl groups in which the hydrogen atoms of the alkyl group are substituted with the halogen atoms. Among these substituents, C1-C8 alkyl groups are preferred, and methyl groups are more preferred. The number of substituents may be one or two or more. If there are two or more substituents, they may be the same or different. Specific examples of substituted arylene groups include the 2,2',3,3',5,5'-hexamethyl-4,4'-biphenylylene group.

[0020] Preferred examples of acid dianhydrides represented by formula (1) include the compound represented by formula (1-1) below, and the compound represented by formula (1-2) below (TAHQ), with the compound represented by formula (1-2) below (TMPBP-TME) being more preferred.

[0021] [ka]

[0022] ((B) component) The polyamic acid used in this embodiment uses (B) diamine as one of its raw materials. Any known diamine can be used as appropriate. The polyamic acid has structural units derived from diamine as a diamine component, and one of the diamine components has structural units derived from (B1) dimer amine. Here, dimer amine refers to an aliphatic diamine in which two terminal carboxylic acid groups (-COOH) of a cyclic or acyclic dimer acid obtained as a dimer of an unsaturated fatty acid are substituted with primary aminomethyl groups (-CH2-NH2) or amino groups (-NH2). By having structural units derived from dimer amine in the polyamic acid, low dielectric properties can be imparted to the resulting polyimide. (B1) dimer amine may be used alone, or two or more may be used in combination.

[0023] Dimer acids are dibasic acids obtained by the intermolecular polymerization reaction of unsaturated fatty acids. Aliphatic diamines derived from dimer acids are obtained by polymerizing unsaturated fatty acids such as oleic acid, linoleic acid, or linolenic acid to form dimer acids, reducing them, and then aminating them. Such dimer amines are preferably diamine compounds obtained by substituting the terminal carboxylic acid group of a dibasic acid compound having 18 to 54 carbon atoms, preferably 22 to 44 carbon atoms, with a primary aminomethyl group or an amino group.

[0024] Commercially available dimeramines include "Versamin® 551" and "Versamin® 552" from Cognics Japan, and "PRIAMINE® 1073," "PRIAMINE® 1074," and "PRIAMINE® 1075" from Croda Japan.

[0025] Furthermore, the polyamic acid used in this embodiment contains (B1) dimeramine in a molar ratio of 0.2 or more relative to the total diamine components. By including dimeramine in a specific molar ratio or higher relative to the total diamine, the resulting polyimide can be given a lower dielectric constant and a lower dielectric loss tangent. The molar ratio of (B1) dimeramine to the total diamine components is preferably 0.3 or higher, and more preferably 0.4 or higher.

[0026] The polyamic acid used in this embodiment preferably contains (B2) aromatic diamine as another diamine component. Examples of (B2) aromatic diamines include p-phenylenediamine (PDA), m-phenylenediamine, 4,4'-oxydianiline (ODA), 3,3'-bistrifluoromethyl-4,4'-diaminobiphenyl (TFMB), 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenylmethane, 3,3'-dimethyl-4,4'-diaminodiphenylmethane, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 1,2-bis(anilino)ethane, diaminodiphenylsulfone, Examples include diaminobenzanilide, diaminobenzoate, diaminodiphenyl sulfide, 2,2-bis(p-aminophenyl)propane, 2,2-bis(p-aminophenyl)hexafluoropropane, 1,5-diaminonaphthalene, diaminotoluene, diaminobenzotrifluoride, 1,4-bis(p-aminophenoxy)benzene, 4,4'-bis(p-aminophenoxy)biphenyl, diaminoanthraquinone, and 4,4'-bis(3-aminophenoxyphenyl)diphenylsulfone. Among these aromatic diamines, PDA, ODA, or TFMB are preferred, with ODA being more preferred. (B2) Aromatic diamines may be used alone or in combination of two or more.

[0027] The molar ratio of diamine to acidic dianhydride [(B) / (A)] is not particularly limited, but is preferably 0.90 to 1.10, more preferably 0.95 to 1.05, even more preferably 0.97 to 1.03, and particularly preferably 0.98 to 1.02.

[0028] ((C) component) The polyamic acid used in this embodiment can be synthesized by known general methods. For example, a polyamic acid composition (polyamic acid solution) can be obtained by reacting (A) an acidic dianhydride and (B) a diamine in (C) an organic solvent. The organic solvent used for polymerization of polyamic acid is not particularly limited as long as it can dissolve the acidic dianhydride and diamine as monomer components and also dissolve the polyamic acid produced by the polyaddition reaction. Examples of such organic solvents include urea-based solvents such as tetramethylurea and N,N-dimethylethylurea; sulfone-based solvents such as dimethyl sulfoxide, diphenyl sulfone, and tetramethyl sulfone; amide-based solvents such as N,N-dimethylacetamide, N,N-dimethylformamide, N,N-diethylacetamide, N-methyl-2-pyrrolidone, and hexamethylphosphate triamide; ester-based solvents such as γ-butyrolactone; alkyl halide-based solvents such as chloroform and methylene chloride; aromatic hydrocarbon-based solvents such as benzene and toluene; phenol-based solvents such as phenol and cresol; ketone-based solvents such as cyclopentanone; and ether-based solvents such as tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, dimethyl ether, diethyl ether, and p-cresol methyl ether. These organic solvents may be used individually or in combination of two or more. From the viewpoint of enhancing the solubility and reactivity of polyamic acids, the organic solvent is preferably selected from the group consisting of amide solvents, ketone solvents, ester solvents, and ether solvents, with amide solvents such as N,N-dimethylacetamide, N,N-dimethylformamide, N,N-diethylacetamide, and N-methyl-2-pyrrolidone being more preferred.

[0029] The molecular weight of polyamic acid can be adjusted by adjusting the molar ratio of the total number of moles of the acidic dianhydride component to the total number of moles of the diamine component. The molecular weight (weight-average molecular weight) of polyamic acid is not particularly limited, but from the viewpoint of solubility in organic solvents, it is more preferable to be between 10,000 and 100,000. The weight-average molecular weight of polyamic acid can be determined, for example, from the value converted to standard polystyrene by gel filtration chromatography (GPC) measurement.

[0030] The synthesis of polyamic acids by the polyaddition reaction of acidic dianhydrides and diamines is preferably carried out in an inert atmosphere such as argon or nitrogen. In an inert atmosphere, the polyaddition reaction proceeds by dissolving the acidic dianhydride and diamine in an organic solvent and mixing them. The order of addition of the acidic dianhydride and diamine is not particularly limited. For example, the diamine may be dissolved in an organic solvent or dispersed in a slurry to form a diamine solution, and the acidic dianhydride may be added to the diamine solution. The acidic dianhydride and diamine may be added directly to the organic solvent in a solid state, or they may be added separately dissolved in an organic solvent or dispersed in a slurry.

[0031] The temperature conditions for the polyaddition reaction are not particularly limited, but from the viewpoint of suppressing the decrease in molecular weight of the polyamic acid due to depolymerization, the reaction temperature is preferably 100°C or lower, and from the viewpoint of allowing the polyaddition reaction to proceed appropriately, the reaction temperature is more preferably 20°C to 80°C. The reaction time can be arbitrarily set within the range of 1 hour to 72 hours, and if necessary, it may be left overnight at room temperature.

[0032] When preparing the polyamic acid composition used in this embodiment, the viscosity of the solution is preferably 500 mPa·s or higher from the viewpoint of film-forming properties. Furthermore, the concentration of polyamic acid in the polyamic acid composition used in this embodiment is preferably 10% by mass or higher, more preferably 15% by mass or higher, and even more preferably 25% by mass or higher. In particular, if the concentration of polyamic acid is 15% by mass or higher, the productivity of forming a polyimide coating film using polyamic acid can be increased. Furthermore, the upper limit of the concentration of polyamic acid is preferably 50% by mass or lower, and even more preferably 30% by mass or lower, from the viewpoint of sufficiently dissolving the polyamic acid in the organic solvent.

[0033] To impart processing properties or various functionalities to polyamic acid and polyimides formed using said polyamic acid, various organic or inorganic low-molecular-weight or high-molecular-weight compounds may be blended into the polyamic acid composition. For example, the polyamic acid composition may contain solvent-soluble polyimide resin, flame retardants, dyes, surfactants, leveling agents, plasticizers, fine particles, sensitizers, or silane coupling agents. The fine particles may be either organic or inorganic, and may have a porous or hollow structure. Furthermore, after polyimidization of the polyamic acid, some of the amino groups may be maleimidized.

[0034] (Second adhesive resin composition) The second adhesive resin composition used in this embodiment is an adhesive resin composition containing an epoxy resin. The dielectric breakdown strength of the cured product of this second adhesive resin composition must be 300 kV / mm or higher. If this dielectric breakdown strength is below the lower limit, the dielectric strength of the resin film 100 will be insufficient, and it will be difficult to make it thin because it will be necessary to ensure sufficient film thickness for dielectric strength. From a similar viewpoint, the dielectric breakdown strength of the cured product of the adhesive resin composition is preferably 320 kV / mm or higher, and more preferably 340 kV / mm or higher. The adhesive resin layer 1 may be formed by applying a coating solution for the second adhesive resin composition and drying it. Alternatively, the second adhesive resin composition may be B-staged by heat. The coating solution for the second adhesive resin composition must contain an epoxy resin, and preferably contains an epoxy resin, an aromatic amine-based curing agent, and a solvent-soluble polyimide resin. By B-stage this second adhesive resin composition, an adhesive resin layer 1 with sufficient fluidity and adhesion can be obtained. Furthermore, the coating liquid for the second adhesive resin composition may contain fillers, curing accelerators, flame retardants, and solvents as needed.

[0035] Any epoxy resin having two or more glycidyl groups can be used. Suitable epoxy resins include bisphenol A type epoxy resin, bisphenol F type epoxy resin, novolacphenol type epoxy resin, biphenyl type epoxy resin, naphthalene type epoxy resin, and dicyclopentadiene type epoxy resin. These may be used individually or in combination of two or more types.

[0036] Aromatic amine curing agents are not particularly limited as long as they have an aromatic group and an amino group and have the effect of accelerating the curing of epoxy resins when irradiated with light. Examples of aromatic groups include phenyl groups, biphenyl groups, and fluorenyl groups. Examples of aromatic amine curing agents include polytetramethylene oxide-di-p-aminobenzoate, 4,4'-diaminodiphenylsulfone, 4,4'-bis(4-aminophenoxy)biphenyl, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, bis[4-(4-aminophenoxy)phenyl]sulfone, 1,3-bis(4-aminophenoxy)benzene, 1,4-bis(4-aminophenoxy)benzene, trimethylenebis( Examples include 4-aminobenzoate, 3,3'-dimethyl-4,4'-diaminobiphenyl, 2,2'-dimethyl-4,4'-diaminobiphenyl, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, bis[4-(3-aminophenoxy)phenyl]sulfone, 9,9'-bis(4-aminophenyl)fluorene, and 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane. These may be used individually or in combination of two or more.

[0037] When the number of moles of epoxy resin is set to 1, the amount of aromatic amine-based curing agent used is preferably between 0.2 moles and 1.5 moles. If the amount used is above the lower limit, it tends to be easier to obtain appropriate toughness and chemical resistance. On the other hand, if the amount used is below the upper limit, it tends to be easier to obtain appropriate Tg and thermal expansion coefficient.

[0038] A solvent-soluble polyimide resin is a polyimide resin that is soluble in the solvent used in the production of the second adhesive resin composition used in this embodiment. Preferred solvent-soluble polyimide resins have high Tg, low thermal expansion coefficient, excellent film properties, low dielectric constant, and low dielectric loss tangent. Examples of solvent-soluble polyimide resins include fully imidized soluble polyimide resins obtained by reacting diaminotrimethylphenylindan with benzophenonetetracarboxylic acid 2-anhydride. This compound can improve adhesive strength without the need for other adhesion-imparting agents. The number-average molecular weight (Mn) of the solvent-soluble polyimide resin is not particularly limited, but is preferably between 10,000 and 50,000, and particularly preferably between 12,000 and 20,000.

[0039] When the total amount of epoxy resin and aromatic amine-based curing agent is 100 parts by mass, the amount of solvent-soluble polyimide resin blended is preferably 10 parts by mass or more and 100 parts by mass or less, and particularly preferably 15 parts by mass or more and 100 parts by mass or less. If the blending amount is above the lower limit, it tends to be easier to obtain an improvement in adhesive strength and flexibility. Also, if the blending amount is below the upper limit, it tends to be possible to ensure the breaking strength of the film.

[0040] Examples of fillers include silica, alumina, aluminum hydroxide, and magnesium hydroxide. These may be used individually or in combination of two or more. Examples of curing accelerators include imidazoles. These may be used individually or in combination of two or more. Examples of flame retardants include condensed phosphate esters, phosphazenes, polyphosphates, and HCA (9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide) derivatives. These may be used individually or in combination of two or more. Examples of solvents include NMP (N-methylpyrrolidone), diethylene glycol monomethyl ether acetate, cyclohexanone, and MEK (methyl ethyl ketone). These may be used individually or in combination of two or more.

[0041] The thickness of the adhesive resin layer 1 varies according to the copper thickness of the wiring board to be bonded, and is not particularly limited. For example, if the copper thickness of the wiring board is 25 μm, the thickness of the adhesive resin layer 1 is preferably 5 μm to 100 μm, more preferably 10 μm to 70 μm, even more preferably 15 μm to 50 μm, and particularly preferably 20 μm to 30 μm. If the thickness is below the upper limit, the thickness of the resin film 100 can be made thinner. If the thickness is above the lower limit, the adhesion of the resin film 100 can be improved.

[0042] (Core layer) The core layer 2 must be a layer made of a polyimide film containing a polyimide obtained by imidizing the polyamic acid in the first adhesive resin composition. The method for converting polyamic acid to polyimide is not particularly limited, but polyimide can be produced by dehydrating and cyclizing (imidizing) the polyamic acid obtained as described above. The dehydration and cyclization (imidization) method can be a known method such as thermal imidization, which involves dehydration and cyclization by heating, or chemical imidization, which involves chemical cyclization using a known dehydration and cyclization catalyst.

[0043] In the case of thermal imidation, the heating temperature is preferably 120°C to 350°C, and more preferably 150°C to 250°C. The heating time is preferably 3 minutes to 3 hours, and more preferably 5 minutes to 2 hours. In the case of chemical imidation, for example, pyridine, triethylamine, or acetic anhydride can be used as the dehydration and ring-closing catalyst. In this case, the reaction temperature can be selected from any temperature between 20°C and 180°C, but it is preferably 150°C or lower. The reaction time is also preferably 1 hour to 3 hours. Imidation may be carried out in air, under reduced pressure, or in an inert gas such as nitrogen, but in order to obtain a highly transparent polyimide film, it is preferable to carry it out under reduced pressure or in an inert gas such as nitrogen.

[0044] The molecular weight (weight-average molecular weight) of the polyimide is not particularly limited, but it is preferably between 10,000 and 100,000 from the viewpoint of low dielectric properties, solubility in organic solvents, and film-forming properties of the resulting polyimide. The weight-average molecular weight of the polyimide can be determined, for example, from the value converted to standard polystyrene by gel filtration chromatography (GPC) measurement.

[0045] The polyimide film used in this embodiment includes the polyimide obtained as described above. The method for producing such a polyimide film is not particularly limited, and examples include coating the above-mentioned polyamic acid composition in a film-like manner onto a substrate (for example, a plastic film made of a resin such as polyethylene, polypropylene, urethane, polyester, polyethylene terephthalate (PET), or polycarbonate, a glass plate, a stainless steel plate, a copper plate including thin copper foil, or an aluminum plate), then drying and heating to remove the solvent and dehydrate and cyclize (imidize), or dissolving the polyimide obtained by converting polyamic acid to polyimide in an organic solvent, coating the polyimide solution in a film-like manner onto the substrate, and then drying and removing the solvent. The method of coating onto the substrate is not particularly limited, and conventionally known coating methods can be applied.

[0046] The thickness of the polyimide film is not particularly limited and can be appropriately selected depending on the application. The thickness of the polyimide film can be easily controlled by appropriately adjusting the solid content concentration of each component in the polyamic acid composition, the coating thickness, and the viscosity. This core layer 2 improves the dielectric strength of the resin film 100 and lowers its dielectric constant. Furthermore, since this core layer 2 can maintain its dielectric strength even when thinned, it becomes possible to make the resin film 100 thinner.

[0047] The thickness of the core layer 2 varies depending on the configuration of the wiring board to be bonded and is not particularly limited. For example, the thickness of the core layer 2 is preferably 5 μm to 100 μm, more preferably 7 μm to 50 μm, and particularly preferably 10 μm to 30 μm. If the thickness is below the upper limit, the thickness of the resin film 100 can be made thinner. If the thickness is above the lower limit, the insulating properties of the resin film 100 can be improved.

[0048] From the viewpoint of balancing various physical properties of the resin film 100, such as dielectric strength, dielectric constant, and adhesiveness, the ratio of the thickness of the adhesive resin layer 1 to the thickness of the core layer 2 (thickness of adhesive resin layer 1 / thickness of core layer 2) is preferably 1 / 2 or more and 4 or less, more preferably 2 / 3 or more and 4 or less, even more preferably 1 or more and 3 or less, and particularly preferably 3 / 2 or more and 5 / 2 or less.

[0049] (Release film layer) The release film layer 3 is a layer made of release film provided on top of the adhesive resin layer 1. When using the resin film 100, the release film layer 3 can be peeled off from the adhesive resin layer 1 and used. Furthermore, the release film layer 3 can be coated with a coating liquid for the adhesive resin composition to form a film and create a B-stage, making it easy to form the adhesive resin layer 1. Note that the release film layer 3 is not necessarily required. The release film layer 3 is a component that is provided as needed. Examples of release films include polyethylene terephthalate film (PET film) and polyethylene naphthalate film. The surface of the release film may be treated with a mold release agent.

[0050] (Method of manufacturing resin film) The method for manufacturing the resin film 100 according to this embodiment is not particularly limited. The resin film 100 can be manufactured, for example, as shown in Figure 2, by a method comprising: a film-forming step of applying a coating liquid for an adhesive resin composition (a coating liquid containing either the first adhesive resin composition or the second adhesive resin composition described above) onto a release film layer 3 to form a coated film 1b; a drying step of drying the coated film 1b formed in the film-forming step to form an adhesive resin layer 1 and obtain an adhesive laminated film; and a lamination step of sandwiching a core layer 2 between the two adhesive laminated films obtained in the drying step and laminating them to obtain the resin film 100. In this embodiment, the case in which a second adhesive resin composition is used as the adhesive resin composition will be explained as an example.

[0051] In the film formation process, as shown in Figure 2(A), a coating liquid for the adhesive resin composition is applied to the release film layer 3 to form a film. Examples of coating equipment for adhesive resin compositions include bar coaters, die coaters, curtain coaters, spray coaters, roll coaters, and screen printing machines. The coating thickness of the adhesive resin composition is preferably adjusted so that the thickness of the adhesive resin layer 1 falls within the aforementioned range.

[0052] In the drying process, as shown in Figure 2(B), the coated film 1b formed in the film formation process is dried to form an adhesive resin layer 1, thereby obtaining an adhesive laminated film. The drying temperature is preferably 100°C to 160°C, more preferably 105°C to 155°C, and particularly preferably 110°C to 150°C. If the temperature is within this range, the adhesive resin composition can be appropriately B-staged. The drying time is preferably between 10 seconds and 600 seconds, more preferably between 15 seconds and 500 seconds, and particularly preferably between 30 seconds and 500 seconds. If this time is within the above range, the adhesive resin composition can be appropriately B-staged.

[0053] In the lamination process, as shown in Figure 2(C), the core layer 2 is sandwiched between two adhesive laminated films obtained in the drying process and laminated to obtain a resin film 100. Here, the core layer 2 is sandwiched between two adhesive laminated films, with the release film layer 3 of the adhesive laminated film facing outwards. Since the adhesive resin layer 1 has adhesive properties, a resin film 100 can be obtained. For lamination, vacuum pressure lamination, vacuum roll lamination, and roll lamination can be used. As described above, the resin film 100 according to this embodiment can be manufactured.

[0054] (Copper foil with resin coating) The resin-coated copper foil 200 according to this embodiment comprises the resin film 100 according to this embodiment described above and the copper foil 4 laminated on the resin film 100. The resin-coated copper foil 200 can be manufactured, for example, by a method comprising a release film removal step of removing the release film layer 3 from the resin film 100, as shown in Figure 3, and a lamination step of laminating the copper foil 4 onto the resin film 100 from which one of the release film layers 3 has been removed to obtain the resin-coated copper foil 200.

[0055] In the release film removal process, one of the release film layers 3 is removed from the resin film 100, as shown in Figure 3(A). The release film layer 3 is intended to protect the adhesive resin layer 1 until use, and can be removed by peeling it off the adhesive resin layer 1.

[0056] In the lamination process, as shown in Figure 3(B), a copper foil 4 is laminated onto a resin film 100 from which one of the release film layers 3 has been removed to obtain a resin-coated copper foil 200. When one of the release film layers 3 is removed from the resin film 100, the adhesive resin layer 1 is exposed. The exposed adhesive resin layer 1 is then positioned so that it is in contact with the matte surface of the copper foil 4, and laminated. The lamination is as described above. Since the adhesive resin layer 1 has adhesive properties, a resin-coated copper foil 200 can be obtained.

[0057] (Multilayer wiring board) The multilayer wiring board 300 according to this embodiment includes an insulating layer formed using the resin film 100 according to this embodiment described above. The multilayer wiring board 300 can be manufactured by a method comprising, for example, as shown in Figure 4, a release film removal step of removing both release film layers 3 from a resin film 100; a lamination step of sandwiching the resin film 100 from which the release film layers 3 have been removed between two copper foils 4 to obtain a copper-clad laminate; a thermosetting step of applying a thermosetting treatment to the adhesive resin layer 1 of the copper-clad laminate obtained in the lamination step to obtain a copper-clad laminated substrate; and an etching step of etching the copper foils 4 of the copper-clad laminated substrate so that wiring 41 of a predetermined pattern are formed to obtain a multilayer wiring board 300.

[0058] In the release film removal process, both release film layers 3 are removed from the resin film 100, as shown in Figure 4(A).

[0059] In the lamination process, as shown in Figure 4(B), the resin film 100 from which the release film layer 3 has been removed is sandwiched between two copper foils 4 to obtain a copper-clad laminate. It is preferable that one side of the copper foil 4 is a matte surface. Furthermore, it is preferable that the two copper foils 4 be arranged so that their matte surfaces face each other. Here, the resin film 100 from which the release film layer 3 has been removed is sandwiched between two copper foils 4 and laminated. The lamination is as described above. Since the adhesive resin layer 1 has adhesive properties, a copper-clad laminate can be obtained.

[0060] In the thermosetting process, as shown in Figure 4(C), the adhesive resin layer 1 of the copper-clad laminate obtained in the lamination process is subjected to a thermosetting treatment to obtain a copper-clad laminate substrate. The adhesive resin layer 1 becomes a cured resin layer 1a, which is made up of cured adhesive composition, through the thermosetting treatment. Examples of thermosetting treatments include heat-pressing treatment and heat treatment. The thermosetting treatment may be a single-step process or a two-step or more-step process. The temperature for the thermosetting treatment is preferably between 130°C and 200°C, and particularly preferably between 150°C and 190°C. The pressure for the thermosetting treatment is preferably 0.1 MPa to 10 MPa, and particularly preferably 0.5 MPa to 4 MPa. The time for the heat curing treatment is preferably 0.5 hours or more and 4 hours or less, and particularly preferably 1 hour or more and 3 hours or less.

[0061] In the etching process, as shown in Figure 4(D), the copper foil 4 of the copper-clad laminate is etched so that wiring 41 of a predetermined pattern is formed, thereby obtaining a multilayer wiring board 300. To form the wiring 41 in a predetermined pattern, for example, an etching resist may be used. Specifically, the wiring 41 in a predetermined pattern can be formed by forming an etching resist pattern on the copper foil 4 and then performing an etching process.

[0062] As described above, the multilayer wiring board 300 according to this embodiment can be manufactured. This multilayer wiring board 300 is a two-layer wiring board having two layers of wiring 41.

[0063] [Second Embodiment] Next, a second embodiment of the present invention will be described with reference to the drawings. A description of the configuration similar to that of the first embodiment will be omitted. As shown in Figure 5(C), the multilayer wiring board 300A according to this embodiment is a wiring board with a four-layer structure having four layers of wiring 41. The multilayer wiring board 300A can be manufactured, for example, as shown in Figure 5, by a method comprising: preparing two multilayer wiring boards 300 and one resin film 100; a release film removal step of removing the release film layer 3 from the resin film 100; a lamination step of sandwiching the resin film 100 from which the release film layer 3 has been removed between the two multilayer wiring boards 300 to obtain a wiring laminate; and a thermosetting step of applying a thermosetting treatment to the adhesive resin layer 1 of the wiring laminate obtained in the lamination step to obtain the multilayer wiring board 300A.

[0064] In the release film removal process, as shown in Figure 5(A), two multilayer wiring boards 300 and one resin film 100 are prepared, and the release film layer 3 is removed from the resin film 100.

[0065] In the lamination process, as shown in Figure 5(B), the resin film 100 from which the release film layer 3 has been removed is sandwiched between two multilayer wiring substrates 300 to obtain a wiring laminate. Here, the resin film 100 from which the release film layer 3 has been removed is sandwiched between two multilayer wiring boards 300 and laminated. The lamination is as described above. Since the adhesive resin layer 1 has adhesive properties, a copper-clad laminate can be obtained. Furthermore, it is preferable that the thickness of the adhesive resin layer 1 is greater than the thickness of the wiring 41 of the multilayer wiring board 300. With such a configuration, the wiring 41 can be embedded in the adhesive resin layer 1.

[0066] In the thermosetting process, as shown in Figure 5(C), the adhesive resin layer 1 of the wiring laminate obtained in the lamination process is subjected to a thermosetting treatment to obtain a multilayer wiring board 300A. The adhesive resin layer 1 becomes a cured resin layer 1a, which is made up of cured adhesive composition, through the thermosetting treatment. The thermosetting treatment is as described above.

[0067] As described above, the multilayer wiring board 300A according to this embodiment can be manufactured. This multilayer wiring board 300A is a wiring board with a four-layer structure having four layers of wiring 41. Furthermore, wiring boards with an even number of layers, six or more, can be manufactured by applying the manufacturing method of the multilayer wiring board 300A according to this embodiment.

[0068] [Third Embodiment] Next, a third embodiment of the present invention will be described with reference to the drawings. Note that a description of the configuration similar to that of the first embodiment will be omitted. As shown in Figure 6(D), the multilayer wiring board 300B according to this embodiment is a wiring board with a three-layer structure having three layers of wiring 41. The multilayer wiring board 300B can be manufactured, for example, as shown in Figure 6, by a method comprising: preparing one multilayer wiring board 300 and one resin-coated copper foil 200; a release film removal step of removing the release film layer 3 from the resin-coated copper foil 200; a lamination step of laminating the resin-coated copper foil 200 from which the release film layer 3 has been removed onto the multilayer wiring board 300 to obtain a copper foil-coated wiring laminate; a thermosetting step of applying a thermosetting treatment to the adhesive resin layer 1 of the copper foil-coated wiring laminate obtained in the lamination step to obtain a copper foil-coated wiring laminate; and an etching step of etching the copper foil 4 of the copper foil-coated wiring laminate so that wiring 41 of a predetermined pattern is formed to obtain the multilayer wiring board 300B.

[0069] In the release film removal process, as shown in Figure 6(A), one multilayer wiring board 300 and one resin-coated copper foil 200 are prepared, and the release film layer 3 is removed from the resin-coated copper foil 200.

[0070] In the lamination process, as shown in Figure 6(B), the resin-coated copper foil 200 from which the release film layer 3 has been removed is laminated onto a multilayer wiring substrate 300 to obtain a copper foil-coated wiring laminate. After removing the release film layer 3 from the resin-coated copper foil 200, the adhesive resin layer 1 is exposed. The exposed adhesive resin layer 1 is then positioned so that it is in contact with the multilayer wiring board 300, and laminated. The lamination is carried out as described above. Since the adhesive resin layer 1 has adhesive properties, a copper foil-coated wiring laminate can be obtained.

[0071] In the thermosetting process, as shown in Figure 6(C), the adhesive resin layer 1 of the copper foil-equipped wiring laminate obtained in the lamination process is subjected to a thermosetting treatment to obtain a copper foil-equipped wiring laminate substrate. The adhesive resin layer 1 becomes a cured resin layer 1a, which is made up of cured adhesive composition, through the thermosetting treatment. The thermosetting treatment is as described above.

[0072] In the etching process, as shown in Figure 6(D), the copper foil 4 of the copper foil-equipped wiring laminate is etched so that wiring 41 of a predetermined pattern is formed to obtain a multilayer wiring substrate 300B. Etching is as described above.

[0073] As described above, the multilayer wiring board 300B according to this embodiment can be manufactured. This multilayer wiring board 300B is a three-layer wiring board having three layers of wiring 41. Furthermore, wiring boards with an odd number of layers (five or more) can be manufactured by applying the manufacturing method of the multilayer wiring board 300B according to this embodiment.

[0074] [Fourth Embodiment] Next, a fourth embodiment of the present invention will be described with reference to the drawings. Note that a description of a configuration similar to that of the first embodiment will be omitted. The coil structure and magnetic device according to this embodiment include an insulating layer formed using the resin film 100 according to this embodiment described above. In other words, the magnetic device 400 according to this embodiment comprises a multilayer wiring board 300A and a core 5, as shown in Figures 7 and 8. In the multilayer wiring board 300A, coil-shaped wiring patterns 41 are formed. Therefore, the multilayer wiring board 300A is a coil structure according to this embodiment. The multilayer wiring board 300A has a hole in its center, into which the core 5 is inserted. For core 5, known materials can be used, such as magnetic materials like ferrite, compacted magnetic cores, and laminated steel sheets.

[0075] [Variations of the Embodiment] The present invention is not limited to the embodiments described above, and any modifications or improvements that can achieve the objectives of the present invention are included in the present invention. For example, in the embodiments described above, the multilayer wiring boards 300, 300A, and 300B are wiring boards with a 2-layer to 4-layer structure having 2 to 4 layers of wiring 41, but are not limited to this. For example, the multilayer wiring board may be a wiring board with a layer structure having 5 or more layers. [Examples]

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

[0077] [Preparation Example 1] In a 1 L four-neck separable flask equipped with a stirrer, reflux condenser, and thermometer, 0.5 parts by mass of 4,4'-oxydianiline, 4 parts by mass of dimeramine (Croda Japan, PRIAMINE 1075), 6.2 parts by mass of 2,2',3,3',5,5'-hexamethyl[1,1'-biphenyl]-4,4'-diyl-bis(1,3-dioxo-1,3-dihydro-2-benzofuran-5-carboxylate) (TMPBP-TME), and 32 parts by mass of N-methyl-2-pyrrolidone were charged. The mixture was heated and stirred at 50°C for about 3.5 hours while blowing nitrogen into the reaction vessel at 0.1 mL / sec. After confirming salt dissolution, the mixture was stirred at room temperature for 24 hours to synthesize polyamic acid, a precursor of polyimide. Then, a varnish containing this polyamic acid was prepared.

[0078] [Preparation Example 2] 98 parts by mass of bisphenol A type epoxy resin "Epiclon 850-S" (manufactured by DIC Corporation, epoxy equivalent: 188), 147 parts by mass of dicyclopentadiene type epoxy resin "HP-7200H" (manufactured by DIC Corporation, epoxy equivalent: 283, softening point: 83°C), 126 parts by mass of aromatic amine-based curing agent "Elasmer 250P" (polytetramethylene oxide-di-p-aminobenzoate, manufactured by Ihara Chemical Co., Ltd.) A mixture consisting of 100 parts by mass of soluble polyimide resin "Q-VR-X0163" (manufactured by PI Technical Research Institute, Tg: 246°C, resin solids content: 20% by mass), 303 parts by mass of phenoxy resin "ERF-001M30" (manufactured by Nippon Steel Chemical & Material, Tg: 146°C, resin solids content: 30% by mass), and 18 parts by mass of flame retardant HCA was prepared to create a resin varnish with a resin solids content of 40% by mass.

[0079] [Example 1] The varnish containing polyamic acid obtained in Preparation Example 1 was applied to a release film (a PET film treated with a mold release agent), pre-baked at 120°C for 10 minutes to reach the B-stage state, peeled off the release film, placed on a Teflon® plate, and subjected to a heat-curing treatment at 150°C for 60 minutes, followed by a further heat-curing treatment at 180°C for 30 minutes. This caused the polyamic acid to undergo ring-closing polymerization, yielding an imide-based core film (thickness: 12.5 μm).

[0080] [Example 2] The resin varnish obtained in Preparation Example 2 was applied to a release film (a PET film treated with a mold release agent), pre-baked at 120°C for 10 minutes to reach the B-stage state, peeled off the release film, placed on a Teflon® plate, and subjected to a heat-curing treatment at 150°C for 60 minutes, followed by a further heat-curing treatment at 180°C for 30 minutes to obtain an epoxy core film (thickness: 12.5 μm).

[0081] [Example 1] A varnish containing polyamic acid obtained in Preparation Example 1 was applied to an 18 μm thick copper foil, and pre-baked at 120°C for 10 minutes to reach the B-stage state, thereby producing a copper foil with an adhesive resin layer. The thickness of the adhesive resin layer was 25 μm. Two of these copper foils with adhesive resin layers were placed with the adhesive resin layers facing each other, and the imide-based core film obtained in Preparation Example 1 was sandwiched between them. After lamination, a heat-curing treatment was performed at 150°C for 60 minutes, followed by a further heat-curing treatment at 180°C for 30 minutes. This resulted in the ring-closing polymerization of the polyamic acid and the formation of an imide-based cured resin layer, obtaining a double-sided copper-clad laminate substrate.

[0082] [Example 2] A double-sided copper-clad laminate substrate with an epoxy-cured resin layer was obtained in the same manner as in Example 1, except that the resin varnish obtained in Preparation Example 2 was used instead of the polyamic acid-containing varnish obtained in Preparation Example 1.

[0083] [Example 3] A copper foil with an adhesive resin layer was fabricated by applying a varnish containing polyamic acid obtained in Preparation Example 1 to an 18 μm thick copper foil, pre-baking it at 120°C for 10 minutes to reach the B-stage state, and then applying the same varnish containing polyamic acid obtained in Preparation Example 1 to a release film (a PET film with a release treatment), pre-baking it at 120°C for 10 minutes to reach the B-stage state, and then applying the same varnish to a PET film with an adhesive resin layer. The thickness of the adhesive resin layer in each case was 25 μm. The copper foil with the adhesive resin layer and the PET film with the adhesive resin layer were placed with the adhesive resin layers facing each other, and the imide-based core film obtained in Fabrication Example 1 was sandwiched between them. Lamination was then performed to obtain a resin-coated copper foil. This resin-coated copper foil can be used to fabricate a multilayer wiring board.

[0084] [Example 4] A varnish containing polyamic acid obtained in Preparation Example 1 was applied to a copper foil on a release film (PET film with mold release treatment), pre-baked at 120°C for 10 minutes to reach the B-stage state, and a PET film with an adhesive resin layer was fabricated. The thickness of the adhesive resin layer was 25 μm. Two of these PET films with adhesive resin layers were placed with the adhesive resin layers facing each other, and the imide-based core film obtained in Fabrication Example 1 was sandwiched between them. Lamination was performed to obtain a resin film. This resin film can be used to fabricate a multilayer wiring board.

[0085] [Comparative Example 1] A double-sided copper-clad laminate substrate with an epoxy-cured resin layer was obtained in the same manner as in Example 2, except that the epoxy-based core film obtained in Example 2 was used instead of the imide-based core film obtained in Example 1.

[0086] [Comparative Example 2] A double-sided copper-clad laminate substrate with an epoxy-cured resin layer was obtained in the same manner as in Example 2, except that a commercially available polyimide film (Toray DuPont, Kapton®, thickness: 12.5 μm) was used instead of the imide-based core film obtained in Example 1.

[0087] [Comparative Example 3] Two sheets of electrolytic copper foil (thickness: 25 μm) were prepared and placed so that their matte surfaces faced each other. Then, two sheets of prepreg (thickness: 100 μm, "R-1551" manufactured by Panasonic Industries) were prepared, the two prepregs were stacked, sandwiched between the two sheets of electrolytic copper foil, and a double-sided copper-clad laminate substrate was fabricated by heat pressing. The heat pressing conditions were as follows: the first stage was 30 minutes at a set temperature of 130°C and a pressure of 1.0 MPa, and the second stage was 90 minutes at a set temperature of 180°C and a pressure of 2.0 MPa.

[0088] [Evaluation of multilayer wiring boards] The multilayer wiring boards were evaluated (withstand voltage (dielectric breakdown strength and dielectric breakdown voltage of the insulating material), thickness, and relative permittivity) using the following method. The results are shown in Table 1. The layer configuration of the insulating material in Examples 1 and 2, and Comparative Examples 1 to 3, is also shown in Table 1. (1) Dielectric Strength The copper foil of the obtained double-sided copper-clad laminate was entirely etched to obtain a sample of insulating material. For the core layer, the core film used in the example was used as the sample. For the cured resin layer, the adhesive resin layer used in the example was cured under the same conditions as in the example and used as the sample. For the obtained samples, the voltage was increased at 0.5 kV / sec in the thickness direction of the sample over a predetermined area. The conductive voltage was measured using the "Ultra-High Voltage Withstand Voltage Tester Model 7472" manufactured by Keisoku Gijutsu Kenkyusho Co., Ltd., and the dielectric breakdown strength and dielectric breakdown voltage were calculated. (2) Thickness The copper foil of the obtained double-sided copper-clad laminate was completely etched to obtain a sample. The thickness of this sample was measured using calipers. (3) Relative permittivity The copper foil of the obtained double-sided copper-clad laminate was completely etched, and then the sample was processed to a size of 20 mm x 20 mm and a thickness of 200 μm. The relative permittivity of the obtained samples at 1 MHz was measured using a measuring device (KEYSIGHT RF Impedance / Material Analyzer, 1.8 GHz 4291B).

[0089] [Table 1]

[0090] As is clear from the results shown in Table 1, the multilayer wiring boards according to the present invention (Examples 1 and 2) were confirmed to have good dielectric strength, thickness, and dielectric constant. In contrast, the multilayer wiring board using two prepregs (Comparative Example 3) had a dielectric breakdown voltage of 20kV, which was lower than the target of 21kV, and had a thicker insulating material and a higher dielectric constant. Furthermore, the multilayer wiring boards obtained in Comparative Examples 1 and 2 also had high dielectric constants. Therefore, it was confirmed that the resin film according to the present invention has a low dielectric constant. [Explanation of Symbols]

[0091] 1...Adhesive resin layer 1a…cured resin layer 1b...Coated film 2…Core Layer 3…Release film layer 4...Copper foil 41…Wiring 5... Core 100... Resin film 200... Copper foil with resin 300,300A,300B...Multilayer wiring board 400… Magnetic devices

Claims

1. A resin film comprising a core layer and adhesive resin layers provided on both sides of the core layer, The adhesive resin layer consists of a first adhesive resin composition containing a polyamic acid which is a polyaddition reaction product of (A) an acidic dianhydride and (B) a diamine, or a second adhesive resin composition containing an epoxy resin. The polyamic acid in the first adhesive resin composition contains (B1) dimeramine in a molar ratio of 0.2 or more relative to the total diamine components. The dielectric breakdown strength of the cured product of the second adhesive resin composition is 300 kV / mm or more. The core layer consists of a polyimide film containing a polyimide obtained by imidizing the polyamic acid in the first adhesive resin composition. Resin film.

2. In the resin film according to claim 1, The (A) acid dianhydride has the structure shown in the following formula (1): Resin film. 【Chemistry 1】 (In formula (1), Ar represents a substituted or unsubstituted arylene group.)

3. In the resin film according to claim 1 or claim 2, The (B) diamine includes (B2) aromatic diamine, Resin film.

4. In the resin film according to claim 1 or claim 2, The ratio of the thickness of the adhesive resin layer to the thickness of the core layer is 1 / 2 or more and 4 or less. Resin film.

5. A resin film according to claim 1 or claim 2, and a copper foil laminated on the resin film, Copper foil coated with resin.

6. The insulating layer is formed using the resin film described in claim 1 or claim 2. Multilayer wiring board.

7. The insulating layer is formed using the resin film described in claim 1 or claim 2. Coil structure.

8. The insulating layer is formed using the resin film described in claim 1 or claim 2. Magnetic device.

Images