Resin film, resin-coated copper foil, multilayer wiring substrate, coil structure, and magnetic device

Abstract

The present invention relates to a resin film (100) having a core layer (2) and adhesive resin layers (1) provided on both surfaces of the core layer (2), the adhesive resin layers (1) being formed of an adhesive resin composition containing an epoxy resin, the cured product of the adhesive resin composition having an insulation breakdown strength of 300 kV / mm or more, and the core layer (2) being formed of a polyimide film, the polyimide film having an insulation breakdown strength of 300 kV / mm or more.

Description

Technical Field

[0001] This invention relates to resin films, resin-coated copper foils, multilayer wiring substrates, coil structures, and magnetic devices. Background Technology

[0002] Thin transformers, as a type of magnetic device, are described in, for example, in Patent Document 1. These thin transformers consist of a printed coil, a core made of magnetic material, and a pedestal with terminals for mounting the printed coil and the core. A key feature of this thin transformer is that the exposed surface of the conductors of the printed coil is covered with a heat-resistant resin.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 9-326316 Summary of the Invention

[0006] The problem the invention aims to solve

[0007] However, in recent years, magnetic devices have required the ability to carry larger currents at higher voltages. Furthermore, conventional prepregs (glass cloth substrate / epoxy resin) as the heat-resistant resin layer cannot meet both the requirements for sufficient thinness and sufficient voltage withstand capability. In addition, conventional prepregs suffer from high dielectric constants.

[0008] The purpose of this invention is to provide a resin film with excellent voltage resistance and low dielectric constant, which enables the thinning of the insulating layer, as well as a resin-coated copper foil, a multilayer wiring substrate, a coil structure, and a magnetic device using the resin film.

[0009] Problem Solving Methods

[0010] According to the present invention, resin films, resin-coated copper foils, multilayer wiring substrates, coil structures, and magnetic devices can be provided as shown below.

[0011] [1] A resin film comprising a core layer and adhesive resin layers respectively disposed on both sides of the core layer.

[0012] The aforementioned adhesive resin layer is formed from an adhesive resin composition containing epoxy resin.

[0013] The cured adhesive resin composition described above has an insulation breakdown strength of 300 kV / mm or higher.

[0014] The core layer described above is formed of a polyimide film.

[0015] The insulation breakdown strength of the aforementioned polyimide film is above 300kV / mm.

[0016] [2] According to the resin film of [1], the ratio of the thickness of the adhesive resin layer to the thickness of the core layer is more than 1 / 2 and less than 4.

[0017] [3] A copper foil with resin, comprising the resin film described in [1] or [2] and a copper foil laminated on the resin film.

[0018] [4] A multilayer wiring substrate having an insulating layer formed using the resin film described in [1] or [2].

[0019] [5] A coil structure having an insulating layer formed using the resin film described in [1] or [2].

[0020] [6] A magnetic device having an insulating layer formed using the resin film described in [1] or [2].

[0021] According to one aspect of the present invention, a resin film with excellent voltage resistance and low dielectric constant, capable of achieving thin insulation layer, and a resin-coated copper foil, multilayer wiring substrate, coil structure, and magnetic device using the resin film can be provided. Attached Figure Description

[0022] Figure 1 This is a schematic diagram illustrating the resin film according to the first embodiment of the present invention.

[0023] Figure 2A This is an explanatory diagram illustrating an example of a method for manufacturing a resin film according to the first embodiment of the present invention.

[0024] Figure 2B This is an explanatory diagram illustrating an example of a method for manufacturing a resin film according to the first embodiment of the present invention.

[0025] Figure 2C This is an explanatory diagram illustrating an example of a method for manufacturing a resin film according to the first embodiment of the present invention.

[0026] Figure 3A This is an explanatory diagram illustrating an example of a method for manufacturing a resin-coated copper foil according to a first embodiment of the present invention.

[0027] Figure 3B This is an explanatory diagram illustrating an example of a method for manufacturing a resin-coated copper foil according to a first embodiment of the present invention.

[0028] Figure 4A This is an explanatory diagram illustrating an example of a method for manufacturing a multilayer wiring substrate according to a first embodiment of the present invention.

[0029] Figure 4BThis is an explanatory diagram illustrating an example of a method for manufacturing a multilayer wiring substrate according to a first embodiment of the present invention.

[0030] Figure 4C This is an explanatory diagram illustrating an example of a method for manufacturing a multilayer wiring substrate according to a first embodiment of the present invention.

[0031] Figure 4D This is an explanatory diagram illustrating an example of a method for manufacturing a multilayer wiring substrate according to a first embodiment of the present invention.

[0032] Figure 5A This is an explanatory diagram illustrating an example of a method for manufacturing a multilayer wiring substrate according to a second embodiment of the present invention.

[0033] Figure 5B This is an explanatory diagram illustrating an example of a method for manufacturing a multilayer wiring substrate according to a second embodiment of the present invention.

[0034] Figure 5C This is an explanatory diagram illustrating an example of a method for manufacturing a multilayer wiring substrate according to a second embodiment of the present invention.

[0035] Figure 6A This is an explanatory diagram illustrating an example of a method for manufacturing a multilayer wiring substrate according to a third embodiment of the present invention.

[0036] Figure 6B This is an explanatory diagram illustrating an example of a method for manufacturing a multilayer wiring substrate according to a third embodiment of the present invention.

[0037] Figure 6C This is an explanatory diagram illustrating an example of a method for manufacturing a multilayer wiring substrate according to a third embodiment of the present invention.

[0038] Figure 6D This is an explanatory diagram illustrating an example of a method for manufacturing a multilayer wiring substrate according to a third embodiment of the present invention.

[0039] Figure 7 This is a schematic diagram illustrating a magnetic device according to a fourth embodiment of the present invention.

[0040] Figure 8 It is shown Figure 7 A cross-sectional view of section VIII-VIII.

[0041] Symbol Explanation

[0042] 1. Adhesive resin layer

[0043] 1a···Cure the resin layer

[0044] 1b··· Coated film

[0045] 2···Core layer

[0046] 3. Peel off the film layer

[0047] 4··· Copper Foil

[0048] 41··· Wiring

[0049] 5···Core

[0050] 100··· Resin film

[0051] 200··· Copper foil with resin

[0052] 300, 300A, 300B... Multilayer wiring boards

[0053] 400··· Magnetic Devices Detailed Implementation

[0054] [First Implementation Method]

[0055] The present invention will now be described with reference to the accompanying drawings, using examples of embodiments. The present invention is not limited to the embodiments described herein. It should be noted that some parts in the accompanying drawings are enlarged or reduced for ease of explanation.

[0056] (Resin film)

[0057] like Figure 1 As shown, the resin film 100 of this embodiment includes a core layer 2, an adhesive resin layer 1, and a release film layer 3. The adhesive resin layer 1 is disposed on both sides of the core layer 2. The release film layer 3 is disposed on 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 for use.

[0058] Furthermore, the adhesive resin layer 1 is formed from an adhesive resin composition containing epoxy resin. Additionally, the cured adhesive resin composition requires an insulation breakdown strength of 300 kV / mm or higher.

[0059] Furthermore, the core layer 2 is formed of a polyimide film. Additionally, the insulation breakdown strength of this polyimide film needs to be above 300 kV / mm.

[0060] The reasons why the resin film 100 of this embodiment has excellent voltage resistance and low dielectric constant, and can achieve thinning of the insulating layer, are as follows.

[0061] That is, the resin film 100 has a core layer 2 formed of a polyimide film with low dielectric constant and high dielectric breakdown strength. Furthermore, the cured adhesive resin layer 1 also has high dielectric breakdown strength. Therefore, it exhibits excellent voltage resistance and a low dielectric constant. In addition, the adhesive resin layer 1 contains epoxy resin, which has sufficient adhesiveness, thus the resin film 100 can be used to fabricate a multilayer wiring substrate 300 (see reference). Figures 4A-4D Furthermore, the resin film 100 has high insulation breakdown strength, so it can maintain voltage resistance even when the film thickness is thin, thus enabling thin-film production.

[0062] (Adhesive resin layer)

[0063] The adhesive resin layer 1 is a layer formed from an adhesive resin composition containing epoxy resin. The cured adhesive resin composition needs to have an insulation breakdown strength of 300 kV / mm or higher. If this insulation breakdown strength is less than the aforementioned lower limit, the voltage withstand capability of the resin film 100 is insufficient, and since a film thickness must be ensured for voltage withstand capability, it is difficult to achieve a thinner profile. From the same viewpoint, the insulation breakdown strength of the cured adhesive resin composition is preferably 320 kV / mm or higher, more preferably 340 kV / mm or higher.

[0064] The adhesive resin layer 1 can be formed by coating an adhesive resin composition with a coating liquid and then drying it. Alternatively, the adhesive resin composition can be heat-treated to form a B-stage.

[0065] The coating liquid used for the adhesive resin composition needs to contain epoxy resin, preferably epoxy resin, aromatic amine curing agent, and solvent-soluble polyimide resin. By performing a B-stage modification on this adhesive resin composition, an adhesive resin layer 1 with sufficient flowability and adhesion can be obtained.

[0066] In addition, the coating liquid used for adhesive resin compositions may contain fillers, curing accelerators, flame retardants, and solvents as needed.

[0067] Any epoxy resin containing two or more glycidyl groups can be used. Suitable epoxy resins include bisphenol A type epoxy resin, bisphenol F type epoxy resin, phenolic varnish type epoxy resin, biphenyl type epoxy resin, naphthalene type epoxy resin, and dicyclopentadiene type epoxy resin. These can be used individually or in combination.

[0068] Aromatic amine curing agents are not particularly limited as long as they possess aromatic groups and amino groups and can promote the curing of epoxy resins under light irradiation. Examples of aromatic groups include phenyl, biphenyl, and fluorene groups. Examples of aromatic amine curing agents include 4,4'-diaminodiphenyl sulfone, 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, trimethylene bis(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 can be used individually or in combination.

[0069] When the molar amount of epoxy resin is set to 1, the amount of aromatic amine curing agent is preferably 0.2 moles or more and 1.5 moles or less. When the amount is above the lower limit mentioned above, there is a tendency to easily obtain an appropriate coefficient of thermal expansion. On the other hand, when the amount is below the upper limit mentioned above, there is a tendency to easily obtain an appropriate Tg and coefficient of thermal expansion.

[0070] Solvent-soluble polyimide resin refers to a polyimide resin for which the solvent used in the manufacture of the adhesive resin composition of this embodiment is soluble. Resins exhibiting high Tg, low coefficient of thermal expansion, excellent film properties, low dielectric constant, and low dielectric loss tangent are suitable as solvent-soluble polyimide resins. Examples of solvent-soluble polyimide resins include fully imidized soluble polyimide resins obtained by reacting diaminotrimethylphenylindane with benzophenone tetracarboxylic dianhydride. This compound can improve adhesive strength without the need for the combined use of other tackifiers.

[0071] The number average molecular weight (Mn) of the solvent-soluble polyimide resin is not particularly limited, but is preferably 10,000 or more and 50,000 or less, and particularly preferably 12,000 or more and 20,000 or less.

[0072] When the total amount of epoxy resin and aromatic amine curing agent is set to 100 parts by mass, the amount of solvent-soluble polyimide resin is preferably 10 parts by mass or more and 100 parts by mass or less, particularly preferably 15 parts by mass or more and 100 parts by mass or less. When the amount is above the lower limit mentioned above, there is a tendency to easily obtain improved adhesive strength and flexibility. In addition, when the amount is below the upper limit mentioned above, there is a tendency to ensure the tensile strength of the film.

[0073] Examples of fillers include silica, alumina, aluminum hydroxide, and magnesium hydroxide. These can be used individually or in combination.

[0074] Examples of curing accelerators include imidazoles. These can be used alone or in combination.

[0075] Examples of flame retardants include condensed phosphate esters, phosphazenes, polyphosphates, and HCA (9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide) derivatives. These can be used individually or in combination.

[0076] Examples of solvents include NMP (N-methylpyrrolidone), diethylene glycol monomethyl ether acetate, cyclohexanone, and MEK (methyl ethyl ketone). These can be used individually or in combination.

[0077] The thickness of the adhesive resin layer 1 varies depending on the copper thickness of the wiring substrate to which it is bonded, and is not particularly limited. For example, when the copper thickness of the wiring substrate is 25 μm, the thickness of the adhesive resin layer 1 is preferably 5 μm or more and 100 μm or less, more preferably 10 μm or more and 70 μm or less, even more preferably 15 μm or more and 50 μm or less, and particularly preferably 20 μm or more and 30 μm or less. When the thickness is below the above upper limit, the thickness of the resin film 100 can be made thinner. When the thickness is above the above lower limit, the adhesion of the resin film 100 can be improved.

[0078] (Core layer)

[0079] The core layer 2 is a layer formed of a polyimide film. The dielectric breakdown strength of this polyimide film needs to be 300 kV / mm or higher. If this dielectric breakdown strength is less than the aforementioned lower limit, the voltage withstand capability of the resin film 100 is insufficient, and since a sufficient film thickness is required to ensure voltage withstand capability, it is difficult to achieve a thinner profile. From the same viewpoint, the dielectric breakdown strength of the core layer 2 is preferably 340 kV / mm or higher, more preferably 370 kV / mm or higher. This core layer 2 improves the voltage withstand capability of the resin film 100 and reduces its dielectric constant. Furthermore, the core layer 2 maintains voltage withstand capability even when thin, thus enabling the resin film 100 to be made thinner.

[0080] The thickness of the core layer 2 varies depending on the configuration of the wiring substrate to which it is bonded, and is not particularly limited. For example, the thickness of the core layer 2 is preferably 5 μm or more and 100 μm or less, more preferably 7 μm or more and 50 μm or less, and particularly preferably 10 μm or more and 30 μm or less. When the thickness is below the above upper limit, the thickness of the resin film 100 can be made thinner. When the thickness is above the above lower limit, the insulation of the resin film 100 can be improved.

[0081] From the viewpoint of balancing the various physical properties of the resin film 100, such as voltage resistance, dielectric constant and adhesion, 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.

[0082] (Peel off the film layer)

[0083] The release film layer 3 is a layer formed from the release film and disposed on 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 for use. Alternatively, a coating liquid for the adhesive resin composition can be applied to the release film layer 3 to form a film, and then subjected to B-stepping, thus easily forming the adhesive resin layer 1. It should be noted that the release film layer 3 is not mandatory. The release film layer 3 is a component provided as needed.

[0084] Examples of release films include polyethylene terephthalate (PET) films and polyethylene naphthalate (PET) films. The surface of the release film can be subjected to a demolding treatment.

[0085] (Method for manufacturing resin film)

[0086] The method for manufacturing the resin film 100 in this embodiment is not particularly limited. For example, Figures 2A-2C As shown, the resin film 100 can be manufactured by the following steps: a film-forming step in which a coating liquid for an adhesive resin composition is applied to a release film layer 3 to form a coated film 1b; a drying step in which the coated film 1b formed in the film-forming step is dried to form an adhesive resin layer 1, thereby obtaining an adhesive laminated film; and a lamination step in which the core layer 2 is sandwiched between two adhesive laminated films obtained in the drying step and laminated to obtain the resin film 100.

[0087] In the film-forming process, such as Figure 2A As shown, a coating liquid for an adhesive resin composition is applied to the release film layer 3 to form a film.

[0088] Examples of coating devices for adhesive resin compositions include rod coating machines, die coating machines, curtain coating machines, spray coating machines, roller coating machines, and screen printing machines.

[0089] The coating thickness of the adhesive resin composition is preferably adjusted in such a way that the thickness of the adhesive resin layer 1 falls within the range described above.

[0090] In the drying process, such as Figure 2B As shown, the coated film 1b formed in the film-forming process is dried to form an adhesive resin layer 1, resulting in an adhesive laminated film.

[0091] The drying temperature is preferably 100°C or higher and 160°C or lower, more preferably 105°C or higher and 155°C or lower, and particularly preferably 110°C or higher and 150°C or lower. When the temperature is within the above range, the adhesive resin composition can be appropriately B-stage oxidized.

[0092] The drying time is preferably 10 seconds or more and 600 seconds or less, more preferably 15 seconds or more and 500 seconds or less, and particularly preferably 30 seconds or more and 500 seconds or less. When the time is within the above range, the adhesive resin composition can be appropriately graded to B-stage.

[0093] In the lamination process, such as Figure 2C As shown, the core layer 2 is sandwiched between two adhesive laminated films obtained in the drying process and laminated to obtain resin film 100.

[0094] Here, the core layer 2 is sandwiched between two adhesive laminates such that the release film layer 3 of the adhesive laminate is on the outside. Since the adhesive resin layer 1 has adhesive properties, a resin film 100 can be obtained.

[0095] As a lamination process, vacuum pressure lamination, vacuum roller lamination, and roller lamination can be used.

[0096] As described above, the resin film 100 of this embodiment can be manufactured.

[0097] (Copper foil with resin)

[0098] The resin-coated copper foil 200 of this embodiment includes the resin film 100 of this embodiment described above, and the copper foil 4 laminated on the resin film 100.

[0099] For example, Figure 3A and Figure 3B As shown, the resin-coated copper foil 200 can be manufactured by the following steps: a release film removal step, in which the release film layer 3 is removed from the resin film 100; and a lamination step, in which the copper foil 4 is laminated onto the resin film 100 with the release film layer 3 removed on one side, to obtain the resin-coated copper foil 200.

[0100] In the stripping membrane removal process, such as Figure 3A As shown, the release film layer 3 on one side is removed from the resin film 100.

[0101] The release film layer 3 is a layer used to protect the adhesive resin layer 1 before use, and is removed by peeling it off from the adhesive resin layer 1.

[0102] In the lamination process, such as Figure 3B As shown, copper foil 4 is laminated onto a resin film 100 with the release film layer 3 removed on one side to obtain a copper foil 200 with resin.

[0103] The adhesive resin layer 1 of the resin film 100, with the release film layer 3 removed from one side, is exposed. Then, the exposed adhesive resin layer 1 is positioned in contact with the rough surface of the copper foil 4, and lamination is performed. The lamination is as described above. Because the adhesive resin layer 1 has adhesive properties, a copper foil 200 with resin can be obtained.

[0104] (Multilayer wiring substrate)

[0105] The multilayer wiring substrate 300 of this embodiment has an insulating layer formed using the resin film 100 of this embodiment described above.

[0106] For example, Figures 4A-4D As shown, the multilayer wiring substrate 300 can be manufactured by comprising the following steps: a release film removal step, in which release film layers 3 on both sides of the resin film 100 are removed; a lamination step, in which the resin film 100 with the release film layers 3 removed is sandwiched between two copper foils 4 to obtain a copper-clad laminate; a thermosetting step, in which the adhesive resin layer 1 of the copper-clad laminate obtained in the lamination step is thermoset to obtain a copper-clad laminate substrate; and an etching step, in which the copper foils 4 of the copper-clad laminate substrate are etched in a manner that forms wiring 41 of a given pattern to obtain the multilayer wiring substrate 300.

[0107] In the stripping membrane removal process, such as Figure 4A As shown, the release film layers 3 on both sides are removed from the resin film 100.

[0108] In the lamination process, such as Figure 4B As shown, a copper-clad laminate is obtained by sandwiching a resin film 100 with the stripping film layer 3 removed between two copper foils 4.

[0109] The copper foil 4 preferably has one rough side. In addition, the two copper foils 4 are preferably arranged such that the rough sides of the two copper foils 4 face each other.

[0110] Here, a resin film 100 with the release film layer 3 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.

[0111] In the thermosetting process, such as Figure 4C As shown, 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 is thermoset to become a cured resin layer 1a formed from the cured product of the adhesive composition.

[0112] Examples of thermosetting processes include heat pressing and heat treatment. It should be noted that thermosetting can be a single-stage process or a process involving two or more stages.

[0113] The temperature for thermosetting is preferably above 130°C and below 200°C, and more preferably above 150°C and below 190°C.

[0114] The pressure for thermosetting is preferably 0.1 MPa or higher and 10 MPa or lower, and particularly preferably 0.5 MPa or higher and 4 MPa or lower.

[0115] The heat curing time is preferably 0.5 hours or more and 4 hours or less, and particularly preferably 1 hour or more and 3 hours or less.

[0116] In the etching process, such as Figure 4D As shown, the copper foil 4 of the copper-clad laminate is etched in a manner that forms a given pattern of wiring 41 to obtain a multilayer wiring substrate 300.

[0117] To form the wiring 41 of a given pattern, a photoresist can be used, for example. Specifically, a photoresist is applied to form a pattern on the copper foil 4, and then an etching process is performed, thereby forming the wiring 41 of the given pattern.

[0118] As described above, the multilayer wiring substrate 300 of this embodiment can be fabricated. The multilayer wiring substrate 300 is a wiring substrate with a two-layer structure having two layers of wiring 41.

[0119] [Second Implementation]

[0120] Next, a second embodiment of the present invention will be described based on the accompanying drawings. It should be noted that descriptions of configurations identical to those in the first embodiment will be omitted.

[0121] The multilayer wiring substrate 300A in this embodiment is as follows: Figure 5C As shown, it is a wiring substrate with a 4-layer structure having 4 layers of wiring 41.

[0122] For example, Figures 5A-5CAs shown, the multilayer wiring substrate 300A can be manufactured by the following steps: a release film removal step, in which two multilayer wiring substrates 300 and one resin film 100 are prepared, and the release film layer 3 is removed from the resin film 100; a lamination step, in which the resin film 100 with the release film layer 3 removed is sandwiched between the two multilayer wiring substrates 300 to obtain a wiring laminate; and a thermosetting step, in which the adhesive resin layer 1 of the wiring laminate obtained in the lamination step is thermoset to obtain the multilayer wiring substrate 300A.

[0123] In the stripping membrane removal process, such as Figure 5A As shown, prepare two multilayer wiring substrates 300 and one resin film 100, and remove the release film layer 3 from the resin film 100.

[0124] In the lamination process, such as Figure 5B As shown, a wiring laminate is obtained by sandwiching a resin film 100 with the release film layer 3 removed between two multilayer wiring substrates 300.

[0125] Here, a resin film 100 with the release film layer 3 removed is sandwiched between two multilayer wiring substrates 300 and laminated. The lamination is performed as described above. The adhesive resin layer 1 has adhesive properties, thus enabling the formation of a copper-clad laminate.

[0126] It should be noted that the thickness of the adhesive resin layer 1 is preferably greater than the thickness of the wiring 41 of the multilayer wiring substrate 300. With this configuration, the wiring 41 can be embedded in the adhesive resin layer 1.

[0127] In the thermosetting process, such as Figure 5C As shown, the adhesive resin layer 1 of the wiring laminate obtained in the lamination process is subjected to thermosetting treatment to obtain a multilayer wiring substrate 300A. The adhesive resin layer 1 becomes a cured resin layer 1a formed from the cured product of the adhesive composition through thermosetting treatment.

[0128] The thermosetting process is as described above.

[0129] As described above, the multilayer wiring substrate 300A of this embodiment can be manufactured. This multilayer wiring substrate 300A is a 4-layer wiring substrate having 4 layers of wiring 41. Furthermore, wiring substrates with an even number of layers (6 or more) can be manufactured using the manufacturing method of the multilayer wiring substrate 300A of this embodiment.

[0130] [Third Implementation Method]

[0131] Next, a third embodiment of the present invention will be described based on the accompanying drawings. It should be noted that descriptions of configurations identical to those in the first embodiment are omitted.

[0132] The multilayer wiring substrate 300B in this embodiment is as follows: Figure 6D As shown, it is a wiring substrate with a 3-layer structure and 3-layer wiring 41.

[0133] For example, Figures 6A-6D As shown, the multilayer wiring substrate 300B can be manufactured by the following steps: a release film removal step, in which a multilayer wiring substrate 300 and a copper foil 200 with resin are prepared, and the release film layer 3 is removed from the copper foil 200 with resin; a lamination step, in which the copper foil 200 with resin with the release film layer 3 removed is laminated onto the multilayer wiring substrate 300 to obtain a wiring laminate with copper foil; a thermosetting step, in which the adhesive resin layer 1 of the wiring laminate with copper foil obtained in the lamination step is thermoset to obtain a wiring laminate substrate with copper foil; and an etching step, in which the copper foil 4 of the wiring laminate substrate with copper foil is etched in a manner that forms wiring 41 of a given pattern to obtain the multilayer wiring substrate 300B.

[0134] In the stripping membrane removal process, such as Figure 6A As shown, a multilayer wiring substrate 300 and a copper foil 200 with resin are prepared, and the release film layer 3 is removed from the copper foil 200 with resin.

[0135] In the lamination process, such as Figure 6B As shown, a copper foil 200 with resin removed from the release film layer 3 is laminated onto a multilayer wiring substrate 300 to obtain a wiring laminate with copper foil.

[0136] The adhesive resin layer 1 of the copper foil 200 with resin, after the release film layer 3 has been removed, is exposed. Then, the exposed adhesive resin layer 1 is positioned in contact with the multilayer wiring substrate 300, and lamination is performed. The lamination is as described above. Because the adhesive resin layer 1 has adhesive properties, a wiring laminate with copper foil can be obtained.

[0137] In the thermosetting process, such as Figure 6C As shown, the adhesive resin layer 1 of the wiring laminate with copper foil obtained in the lamination process is subjected to a thermosetting treatment to obtain a wiring laminate substrate with copper foil. The adhesive resin layer 1 becomes a cured resin layer 1a formed from the cured product of the adhesive composition through the thermosetting treatment.

[0138] The thermosetting process is as described above.

[0139] In the etching process, such as Figure 6D As shown, the copper foil 4 of the wiring stack substrate with copper foil is etched in such a way as to form a wiring 41 with a given pattern to obtain a multilayer wiring substrate 300B.

[0140] Etching is performed as described above.

[0141] As described above, the multilayer wiring substrate 300B of this embodiment can be manufactured. This multilayer wiring substrate 300B is a wiring substrate with a 3-layer structure having 3 layers of wiring 41. Furthermore, wiring substrates with an odd number of layers (5 or more) can be manufactured using the manufacturing method of the multilayer wiring substrate 300B of this embodiment.

[0142] [Fourth Implementation Method]

[0143] Next, a fourth embodiment of the present invention will be described based on the accompanying drawings. It should be noted that descriptions of configurations identical to those in the first embodiment are omitted.

[0144] The coil structure and magnetic device of this embodiment have an insulating layer formed using the resin film 100 of this embodiment described above.

[0145] That is, the magnetic device 400 in this embodiment is as follows: Figure 7 and Figure 8 As shown, it has a multilayer wiring substrate 300A and a core 5.

[0146] The multilayer wiring substrate 300A has a coil-shaped wiring pattern 41 formed therein. Therefore, the multilayer wiring substrate 300A becomes the coil structure of this embodiment. It should be noted that the multilayer wiring substrate 300A has a hole in the center portion, and the core 5 is inserted into the hole.

[0147] For core 5, known cores can be used, such as ferrite magnets, powder cores, and laminated steel plates.

[0148] [Variations on the implementation method]

[0149] This invention is not limited to the embodiments described above. Modifications or improvements that achieve the purpose of this invention are also included in this invention.

[0150] For example, in the above embodiments, the multilayer wiring substrates 300, 300A, and 300B are wiring substrates 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 substrate may also be a wiring substrate with a layer structure having 5 or more layers.

[0151] Example

[0152] The present invention will now be described in further detail through examples and comparative examples, but the present invention is not limited to these examples in any way.

[0153] [Preparation Example 1]

[0154] A resin varnish with a resin solid content of 46% by weight was prepared by mixing a mixture comprising 453 parts by weight of bisphenol A type epoxy resin "Epiclon 850-S" (manufactured by DIC Corporation, epoxy equivalent: 188), 247 parts by weight of aromatic amine curing agent "BAPP" (manufactured by Wakayama Seika Kogyo Co., Ltd., 2,2-bis[4-(4-aminophenoxy)phenyl]propane), 1500 parts by weight of soluble polyimide resin "Q-VR-X0163" (manufactured by PI Technology Research Institute Co., Ltd., resin solids content 20% by weight), and 0.7 parts by weight of 2-ethyl-4-methylimidazolium.

[0155] [Example 1]

[0156] The resin varnish obtained in Preparation Example 1 was coated onto a release film (a PET film that had undergone a demolding treatment) and dried at 110°C for 300 seconds to produce a PET film with an adhesive resin layer. The thickness of the adhesive resin layer was 25 μm. Two sheets of this PET film with the adhesive resin layer were arranged with the adhesive resin layers facing each other, and a core layer (polyimide film, thickness: 12.5 μm) was sandwiched between them. The films were then laminated using a roller laminator at a peak actual temperature of 111°C and a roller speed of 0.35 m / min to produce a resin film.

[0157] [Example 2]

[0158] After removing the release film from one side of the resin film obtained in Example 1, a resin-coated copper foil was fabricated by laminating the rough surface of an electrolytic copper foil (thickness: 35 μm) onto the removed surface under conditions of a peak actual temperature of 111°C and a roller speed of 0.35 m / min.

[0159] [Example 3]

[0160] Two electrolytic copper foils (thickness: 35 μm) were prepared and arranged with their rough surfaces facing each other. Then, the release film on both sides of the resin film obtained in Example 1 was removed, and the film was sandwiched between the two electrolytic copper foils and subjected to hot pressing to fabricate a double-sided copper-clad laminate substrate. The hot pressing conditions were: the first stage was set at a temperature of 150°C and a pressure of 0.5 MPa for 30 minutes, and the second stage was set at a temperature of 190°C and a pressure of 2 MPa for 70 minutes.

[0161] It should be noted that a multilayer wiring substrate can be obtained by etching the copper foil of a double-sided copper-clad laminate substrate into a given pattern.

[0162] [Comparative Example 1]

[0163] Two electrolytic copper foils (thickness: 35μm) were prepared and arranged with their rough surfaces facing each other. Then, two prepregs (thickness: 100μm, Panasonic Industry's "R-1551") were prepared, overlapped, and sandwiched between the two electrolytic copper foils. A hot-pressing process was then performed to fabricate a double-sided copper-clad laminate. The hot-pressing conditions were: the first stage was at a set temperature of 130°C and a pressure of 1.0MPa for 30 minutes; the second stage was at a set temperature of 180°C and a pressure of 2.0MPa for 90 minutes.

[0164] [Comparative Example 2]

[0165] Except that the number of prepreg sheets used was set to 3, a double-sided copper-clad laminate substrate was obtained in the same manner as in Comparative Example 1.

[0166] [Evaluation of Multilayer Wiring Boards]

[0167] The multilayer wiring substrate was evaluated using the following methods (voltage withstand capability (insulation breakdown strength and insulation breakdown voltage of the insulating material), thickness, and relative permittivity). The results are shown in Table 1. Additionally, the layer composition of the insulating material in Example 3 and Comparative Examples 1-2 is shown in Table 1.

[0168] (1) Withstand voltage

[0169] The copper foil of the obtained double-sided copper-clad laminate was completely etched to serve as a sample of the insulating material. Additionally, the polyimide film used in the examples was used as a sample for the core layer. For the cured resin layer, the product obtained by curing the adhesive resin layer used in the examples under the same conditions as in Example 3 was used as a sample.

[0170] For the obtained sample, the voltage is increased at 0.5 kV / sec relative to the thickness direction of the sample under a given area. The voltage at which conduction occurs is measured using the "Ultra-High Voltage Withstand Voltage Tester 7472" manufactured by the Measurement Technology Research Institute Co., Ltd., and the insulation breakdown strength and insulation breakdown voltage are calculated.

[0171] (2) Thickness

[0172] The copper foil of the obtained double-sided copper-clad laminate was completely etched to obtain a sample. The thickness of the sample was measured using vernier calipers.

[0173] (3) Relative permittivity

[0174] All the copper foils on the obtained double-sided copper-clad laminate were etched, and then processed into a sample with a size of 20mm×20mm and a thickness of 200μm.

[0175] The relative permittivity of the obtained sample at 1 MHz was determined using a measuring device (KEYSIGHT RF Impedance / Material Analyzer, 1.8 GHz 4291B).

[0176]

[0177] The results shown in Table 1 clearly confirm that the voltage withstand capability, thickness, and relative permittivity of the multilayer wiring substrate (Example 3) of the present invention are excellent. In contrast, the insulation breakdown voltage of the multilayer wiring substrate using two prepreg sheets (Comparative Example 1) is 20kV, which is lower than the target of 21kV, and its relative permittivity is also high. Furthermore, the insulation material thickness of the multilayer wiring substrate using three prepreg sheets (Comparative Example 2) is 300μm, which is excessively thick, and its relative permittivity is also high.

[0178] Therefore, it has been confirmed that the resin film of the present invention has excellent voltage resistance and low dielectric constant, enabling the thinning of the insulating layer.

Claims

1. A resin film comprising a core layer and adhesive resin layers respectively disposed on both sides of the core layer, The adhesive resin layer is formed from an adhesive resin composition containing epoxy resin. The cured adhesive resin composition has an insulation breakdown strength of 300 kV / mm or higher. The core layer is formed of a polyimide film. The polyimide film has an insulation breakdown strength of 300kV / mm or higher.

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

3. A copper foil with resin, comprising the resin film as described in claim 1 or 2, and a copper foil laminated on the resin film.

4. A multilayer wiring substrate having an insulating layer formed using the resin film of claim 1 or 2.

5. A coil structure having an insulating layer formed using the resin film of claim 1 or 2.

6. A magnetic device comprising an insulating layer formed using the resin film of claim 1 or 2.

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