Coil structure and method for manufacturing same, multilayer substrate circuit using coil structure, magnetic element, and resin-equipped

Abstract

The invention provides a coil structure, a multilayer circuit board and a magnetic element which can realize excellent withstand voltage characteristics and low capacitance between coils without using glass cloth. The coil structure (C) has coil patterns (21, 22, 23), which are flat-plate-shaped conductors wound on a plane, and an insulating material (1) that insulates the coil patterns (21, 22, 23) from each other. The coil patterns 21, 22, 23 and the insulating material 1 are alternately laminated. The insulating material (1) is a cured product of an insulating resin composition that does not contain a glass cloth. The multilayer circuit board P includes a coil structure C. The magnetic element D is configured by laminating a coil structure C and a multilayer circuit board P in multiple layers and mounting a core 4 to the coil structure C and the multilayer circuit board P.

Description

Technical Field

[0001] This invention relates to a coil structure used in magnetic components such as transformers constructed from stacked coils, and a method for manufacturing the same, as well as a multilayer substrate circuit using the coil structure. Furthermore, this invention relates to a magnetic component employing these coil structures or multilayer substrate circuits, and a coil structure using resin-coated copper foil. Background Technology

[0002] For example, as shown in Patent Document 1, since then, thin transformers used in switching power supplies and the like have been known to be obtained by stacking printed coils. The printed coils are as follows:

[0003] (1) Using a cloth containing glass fibers (called glass cloth) as the base material,

[0004] (2) An epoxy resin is impregnated in a substrate and cured to form a substrate.

[0005] (3) A spiral planar coil is formed on the surface and back of the substrate by printing or pasting.

[0006] (4) Apply heat-resistant resin to the surface of the planar coil to ensure its insulation.

[0007] Existing technical documents

[0008] Patent documents

[0009] Patent Document 1: Japanese Patent Application Publication No. 9-326316 Summary of the Invention

[0010] The problem that the invention aims to solve

[0011] However, the existing technology uses a substrate (generally called a prepreg) formed by impregnating epoxy resin in glass cloth and curing it. Therefore, if the existing magnetic components are simply made thinner, the following problems exist: due to insufficient insulation between layers or increased parasitic capacitance, they cannot be used for high-capacity applications, high-voltage applications, high-frequency applications, etc.

[0012] This invention is proposed to address the problems of the prior art as described above. The object of this invention is to provide a coil structure, multilayer circuit board, and magnetic element that achieves excellent voltage withstand characteristics and low electrostatic capacitance between coils without using glass cloth.

[0013] Technical means to solve the problem

[0014] The coil structure of the present invention is characterized in that,

[0015] It comprises a flat conductive body wound on a plane and an insulating material that insulates the conductive bodies from each other.

[0016] The conductor and the insulating material are alternately stacked.

[0017] The insulating material is a cured form of an insulating resin composition that does not contain glass cloth.

[0018] In this invention, the following structure may be adopted.

[0019] (1) The insulating resin composition has a withstand voltage of 100kV / mm or higher and a dielectric constant of 4.0 or lower.

[0020] (2) The insulating resin composition has adhesive properties.

[0021] (3) The insulating resin composition comprises epoxy resin.

[0022] (4) The insulating resin composition comprises at least one of polyamide resin, polyimide resin and polyamide-imide resin.

[0023] (5) The insulating resin composition comprises: (a1) a liquid epoxy resin, (a2) a solid epoxy resin with a softening point of less than 125°C, (b) an aromatic diamine compound having benzoate groups and polymethylene groups in the main chain, (c) a solvent-soluble polyimide resin with a Tg of more than 200°C and a weight average molecular weight Mw of less than 50,000, and (d) a phenoxy resin with a Tg of more than 130°C.

[0024] When the total amount of the liquid epoxy resin (a1), the solid epoxy resin (a2), and the aromatic diamine compound (b) is set to 100 parts by weight, the total amount of the solvent-soluble polyimide resin (c) and the phenoxy resin (d) is 15 parts by weight or more and 150 parts by weight or less.

[0025] (6) The insulating resin composition is a polyimide derived from (A) acid dianhydride and (B) diamine, wherein the (A) acid dianhydride comprises (A1) acid dianhydride having ester bonds, and wherein the (B) diamine is (B1) dimeric diamine with a molar number of 0.3 or more when the total number of all diamines is set to 1.0.

[0026] (7) The insulating resin composition is a polyimide derived from (A) acid dianhydride and (B) diamine, wherein the (B) diamine has (B1) a diamine with a fluorene backbone and (B2) a dimeric diamine.

[0027] The following structures are also included in this invention.

[0028] (1) A coil structure formed by multilayering a resin-coated copper foil on one side of a copper foil in which the insulating resin composition is formed.

[0029] (2) A multilayer circuit board, including the coil structure.

[0030] (3) In the multilayer circuit board, a shielding layer is provided in the outermost or middle layer.

[0031] (4) A magnetic element, which is formed by mounting the core on the multilayer circuit board.

[0032] (5) A magnetic element is formed by stacking and mounting a plurality of the multilayer circuit boards.

[0033] (6) A magnetic element is formed by stacking the coil structure and the multilayer circuit board in multiple layers and mounting the core.

[0034] (7) A magnetic element, wherein the operating frequency is 500kHz to 1MHz.

[0035] (8) A resin-coated copper foil for a coil structure, wherein an insulating resin composition is formed on one side of the copper foil, characterized in that a resin layer containing the insulating resin composition or an insulating resin composition different from the insulating resin composition is formed on the surface of the insulating resin composition of the resin-coated copper foil in a semi-cured state, and a protective film is laminated on the surface of the resin layer in the semi-cured state.

[0036] (9) A resin-coated copper foil for a coil structure, characterized in that a resin layer containing the insulating resin composition in a semi-cured state is formed on one side of the copper foil, and a protective film is laminated on the surface of the resin layer in the semi-cured state.

[0037] (10) A method for manufacturing a coil structure, characterized in that a resin-coated copper foil is laminated in such a way that the semi-cured resin layer is in contact with the copper foil while the protective film has been peeled off.

[0038] The effects of the invention

[0039] According to the present invention, since the insulating material between the coils comprises a hardened insulating resin composition without glass cloth, it is possible to provide a coil structure, multilayer circuit board, magnetic element, and resin-coated copper foil for the coil structure that can achieve high voltage resistance and low dielectric constant based on the insulating resin composition, resulting in high capacity / high frequency / thinness. Attached Figure Description

[0040] [ Figure 1 [Illustration 1] shows the basic structure of the magnetic element of the present invention. (a) is a top view of the coil structure, (b) is a perspective view of the coil structure with the core installed, and (c) is a cross-sectional view along line A-A' of (b).

[0041] [ Figure 2 ] indicates Figure 1 Cross-sectional views of each step in the manufacturing process of magnetic components.

[0042] [ Figure 3 [Illustration 1] shows a first embodiment of the magnetic element of the present invention. (a) is a perspective view and (b) is a cross-sectional view along line B-B' of (a).

[0043] [ Figure 4 Figure 1 is a diagram showing a second embodiment of the magnetic element of the present invention. (a) is a perspective view and (b) is a cross-sectional view along line C-C' of (a).

[0044] [ Figure 5 Figure 1 is a diagram showing a third embodiment of the magnetic element of the present invention. (a) is a perspective view and (b) is a cross-sectional view along line D-D' of (a).

[0045] [ Figure 6 Figure 1 is a diagram showing a fourth embodiment of the magnetic element of the present invention. (a) is a perspective view and (b) is a cross-sectional view along line E-E' of (a).

[0046] [ Figure 7 Figure 1 is a diagram showing the fifth embodiment of the magnetic element of the present invention. (a) is a perspective view and (b) is a cross-sectional view along line B-B' of (a).

[0047] [ Figure 8 Figure 1 is a diagram showing the sixth embodiment of the magnetic element of the present invention. (a) is a perspective view and (b) is a cross-sectional view along line B-B' of (a).

[0048] [ Figure 9 [Illustration 1] is a cross-sectional view schematically illustrating the manufacturing method of the resin-coated copper foil according to the seventh embodiment.

[0049] [ Figure 10 [ ] is a cross-sectional view schematically illustrating the manufacturing method of the resin-coated copper foil according to the eighth embodiment.

[0050] [ Figure 11 [ ] is a cross-sectional view schematically illustrating the manufacturing method of the resin-coated copper foil according to the ninth embodiment. Detailed Implementation

[0051] [1. Basic Structure of Magnetic Components]

[0052] (1) Overall structure

[0053] Figure 1The figures illustrate a basic embodiment of the magnetic element D of the present invention. (a) is a top view of the coil structure, (b) is a perspective view showing the core mounted in the coil structure, and (c) is a cross-sectional view along line A-A' of (b). In this embodiment, the magnetic element D assumes a multilayer transformer. Therefore, within the insulating material 1, which is a hardened material containing an insulating resin composition, conductors comprising primary-side coil patterns 21, 22, and 23 are embedded at predetermined intervals. Furthermore, each coil pattern 21, 22, and 23 is insulated from the insulating material 1.

[0054] In this embodiment, the insulating material 1 is a cuboid with an opening 10 in the center. Primary coil patterns 21, 22, and 23 are embedded in a rectangular spiral shape surrounding the opening 10. The ends of each coil pattern 21, 22, and 23 are connected to external terminals via wires (not shown). A core 4 containing magnetic elements D is mounted around the insulating material 1. This core 4, generally referred to as the E-core, has left and right feet 41 and 42 arranged around the insulating material 1, upper and lower yokes 43 and 44, and a central foot 45 that connects the upper and lower yokes 43 and 44 through the opening 10. The core 4 contains a magnetic material, forming a magnetic circuit for the flow of magnetic flux generated by each coil pattern 21, 22, and 23. The core 4 can be a pressed powder core, a ferrite core, a laminated steel plate, or a metal composite core. A metal composite core is a magnetic material formed by mixing magnetic powder with resin and then hardening the resin.

[0055] (2) Manufacturing method

[0056] like Figure 2 As shown, the magnetic element D is composed of multiple layers of coil structure C, on which coil pattern 2a is formed on the surface of insulating material 1a with a specified thickness.

[0057] (2-1) Forming an insulating layer on the surface of the copper foil

[0058] To manufacture each coil structure C, firstly, as... Figure 2 As shown in (a), an insulating material (referred to as varnish) 1a, dispersed or dissolved in a solvent, is coated onto the surface of a copper foil 3a of a specified thickness (e.g., 18 μm, 25 μm, 35 μm). In this case, the coating thickness of the insulating material 1a is adjusted so that the thickness of the insulating material 1a after solvent evaporation is a desired value (e.g., 25 μm). Subsequently, pre-drying is performed at approximately 100°C to 120°C, thereby evaporating the solvent. In this state, since the insulating resin composition is not completely cured, the surface of the resin is adhesive; therefore, in cases of storage or transport, the surface of the insulating material 1a is coated with a protective film made of polypropylene.

[0059] (2-2) Thermal curing of insulating materials

[0060] After the single-sided laminate of insulating material 1a on copper foil 3a, as Figure 2 As shown in (b), a new copper foil 3b is laminated on the side of the insulating material 1a opposite to the copper foil 3a (the exposed side of the insulating material 1a). In this case, the new copper foil 3b is tightly fixed to the surface of the insulating material 1a by the adhesiveness of the insulating material 1a. In this state, the insulating material 1a with copper foil 3a and copper foil 3b laminated on both sides is placed in a vacuum press and heated / pressurized, for example, at 180°C for 120 minutes, 1 MPa, and a vacuum degree of 5 torr, thereby thermosetting the insulating material 1a.

[0061] In a coil structure C that uses only one layer of coil pattern, such as a coil for contactless power supply or an antenna for a radio frequency (RF) tag, an insulating material 1a is coated on a single-sided copper foil 3a and then directly heated and hardened after pre-drying.

[0062] (2-3) Formation of coil patterns

[0063] For the laminate of the hardened insulating material 1a taken from the vacuum press and the copper foils 3a and 3b, coil patterns 2a and 2b are formed by etching the copper foils 3a and 3b on both sides. Known techniques, such as those used in the manufacture of coil structures based on glass cloth, can be appropriately employed as the etching process. Figure 2 As shown in (c), by performing an etching process, the unwanted parts of copper foil 3a and copper foil 3b are removed, thereby obtaining a coil structure C with coil patterns 2a and 2b formed on both sides of the hardened insulating material 1a.

[0064] (2-4) Coil pattern and multilayer insulation

[0065] To obtain a multilayer circuit board P by stacking the coil structure C constructed as described above, the following procedure is performed. That is, in step (2-3), after forming coil patterns 2a and 2b on both sides, two new sheets are prepared. Figure 2 (a) Copper foil 3a with insulating material 1a, so that the surface after the protective film is peeled off is... Figure 2 (c) The coil patterns 2a and 2b overlap. In this manner, when obtaining... Figure 2 After the three-layer insulating material 1a is stacked as in step (d), the three-layer insulating material 1a is placed in a vacuum press for heating / pressurization, just like in step (2-2), thereby heat-curing the newly stacked insulating material 1a.

[0066] In addition, Figure 2 In the diagram, since insulating material 1a or copper foil 3a and copper foil 3b are schematically represented, gaps are exposed between coil patterns 2a and 2b formed by etching. Since the pre-dried insulating material 1a is flexible, the gaps are filled by the insulating material 1a when it is pressurized using a vacuum press.

[0067] Figure 2 (a) The copper foil 3a with insulating material 1a is obtained by forming an insulating resin composition on one side of the copper foil, and is called a so-called resin-bearing copper foil. In this embodiment, a semi-cured insulating resin composition layer (resin layer) is formed on the copper foil, and the thickness of the copper foil and the resin layer is not particularly limited. For example, when the thickness of the copper foil is 35 μm, the thickness of the resin layer is preferably 5 μm or more and 200 μm or less, more preferably 10 μm or more and 150 μm or less. If the thickness is below the upper limit, the thickness of the layer structure can be thinner. If the thickness is above the lower limit, the withstand voltage can be improved. The resin layer here can also be multi-layered. For example, by forming a resin layer on the copper foil in advance and forming a resin layer again on its cured surface after curing, the withstand voltage can be improved. In addition, the resin layers after multi-layering can be different insulating resin compositions.

[0068] The semi-cured resin surface with resin copper foil is laminated with a protective film to prevent dust and other contaminants from adhering to the surface of the resin layer and to improve operability.

[0069] Materials used for protective films include, for example, polyethylene, polypropylene, polyvinyl chloride and other polyolefins, polyethylene terephthalate (PET), polyethylene naphthalate (PEN) and other polyesters, polycarbonate, polyimide, etc.

[0070] (2-5) Formation of coil patterns

[0071] After the newly laminated insulating material 1a is hardened, the copper foil 3a exposed on both sides is etched, as follows: Figure 2 As shown in (e), coil patterns 2c and 2d are made.

[0072] (2-6) Fabrication of multilayer circuit boards

[0073] Hereinafter, by repeating the aforementioned steps, and by embedding the primary-side coil pattern 21, the primary-side coil pattern 22, and the secondary-side coil pattern 23, which constitute the coil patterns 2a to 2d of each coil structure, at predetermined intervals inside the block insulating material 1 obtained by stacking and integrating the insulating materials 1a constituting each coil structure, the following results are achieved: Figure 2As shown in (f), a multilayer circuit board P is constructed as a whole and formed into a block shape. By mounting the core 4 onto the multilayer circuit board P, the magnetic element D of this embodiment can be obtained. Furthermore, when the outermost coil pattern of the multilayer circuit board P is coated with an insulating material, after the outermost coil pattern is formed in step (2-5), the insulating material 1a is coated on its surface, and pre-drying and heat curing are performed.

[0074] (3) Insulating materials

[0075] As the insulating material in the above embodiment, an insulating resin composition without glass cloth is used. That is, the prepreg is formed by impregnating resin with glass cloth, therefore, it is unavoidable that the physical properties of the glass cloth will lead to a decrease in withstand voltage characteristics and an increase in capacitance between coil patterns. Therefore, in this embodiment, a cured form of an insulating resin composition without glass cloth is used as the insulating material. In particular, the insulating resin composition without glass cloth is preferably one with a withstand voltage of 100 kV / mm or more and a dielectric constant of 4.0 or less. In addition, the insulating resin composition preferably has adhesion in its state before thermal curing.

[0076] (3-1) Specific examples of insulating resin compositions

[0077] The insulating resin composition constituting the insulating material is preferably an insulating resin composition with high voltage withstand characteristics and low electrostatic capacitance when a coil pattern is formed on both sides of the insulating material to form a magnetic element. For example, it may include at least one thermosetting resin selected from the group consisting of epoxy resin, phenolic resin, cyanate ester resin, melamine resin, amino resin, imide resin, and amide-imide resin. When the thermosetting resin includes epoxy resin, the epoxy resin may include, for example, at least one resin selected from the group consisting of polyfunctional epoxy resin, bisphenol type epoxy resin, phenolic varnish type epoxy resin, and biphenyl type epoxy resin.

[0078] The insulating resin composition may also contain at least one component selected from the group consisting of fillers, curing agents, and curing accelerators. Fillers may include, for example, at least one selected from the group consisting of silica, aluminum hydroxide, magnesium hydroxide, calcium carbonate, talc, and alumina. Curing agents may include, for example, at least one selected from the group consisting of phenolic curing agents and dicyandiamine curing agents. Curing accelerators may include, for example, at least one selected from the group consisting of imidazoles, phenolic compounds, amines, and organophosphorus compounds. For example, polyimide resins, epoxy resins, etc., may be used.

[0079] The insulating resin composition may further include inorganic fillers, flame retardants, and additives as needed. To improve the heat resistance or flame retardancy, low expansion rate, and thermal conductivity of the cured insulating resin composition, various materials, including known materials, can be used as inorganic fillers. Specifically, examples of inorganic fillers include silica, alumina, talc, aluminum hydroxide, magnesium hydroxide, titanium dioxide, mica, aluminum borate, barium sulfate, and calcium carbonate. Only one of these inorganic fillers may be used, or two or more may be used in combination. Furthermore, inorganic fillers may be used directly, or they may be obtained by surface treatment with epoxy silane or amino silane type silane coupling agents, depending on the intended purpose.

[0080] Examples of flame retardants include phosphorus-based and halogen-based flame retardants. Specific examples of phosphorus-based flame retardants include phosphate esters such as condensed phosphate esters and cyclic phosphate esters, phosphononitrile compounds such as cyclic phosphazene compounds, and phosphonate salts such as aluminum dialkylphosphonates. Examples of halogen-based flame retardants include brominated flame retardants. Furthermore, from a halogen-free perspective, phosphorus-based flame retardants are preferred. The illustrated flame retardants can be used alone or in combination.

[0081] Examples of additives include silicone-based defoamers and acrylate-based defoamers, heat stabilizers, antistatic agents, ultraviolet absorbers, dyes or pigments, lubricants, and dispersants such as wetting and dispersing agents. Only one of these additives may be used, or two or more may be used in combination.

[0082] (3-2) Preferred insulating resin composition

[0083] In this embodiment, the preferred insulating material is a resin composition of materials A to D as shown below.

[0084] (a) Material A, Material D

[0085] An insulating resin composition comprising: (a1) a liquid epoxy resin,

[0086] (a2) Solid epoxy resin with a softening point below 125℃

[0087] (b) Aromatic diamine compounds having benzoate groups and polymethylene groups in the main chain;

[0088] (c) Solvent-soluble polyimide resins with a Tg above 200℃ and a weight-average molecular weight (Mw) below 50,000.

[0089] (d) Phenoxy resins with a Tg of 130℃ or higher.

[0090] When the total amount of the liquid epoxy resin (a1), the solid epoxy resin (a2), and the aromatic diamine compound (b) is set to 100 parts by weight, the total amount of the solvent-soluble polyimide resin (c) and the phenoxy resin (d) is 15 parts by weight or more and 150 parts by weight or less.

[0091] Material A can achieve a certain degree of flexibility and thin-film insulation, has durability and excellent processing characteristics, and has high insulation properties. Therefore, it reduces the capacitance between coil patterns and has excellent voltage withstand characteristics.

[0092] (b) Material B

[0093] A polyimide, wherein the polyimide is derived from (A) acid dianhydride and (B) diamine, wherein

[0094] The (A) acid dianhydride comprises (A1) an acid anhydride having an ester bond.

[0095] In the (B) diamine, when the total number of moles of all diamines is set to 1.0, a mole count of 0.3 or more constitutes (B1) dimeric diamine.

[0096] While general polyimides possess excellent heat resistance and mechanical properties, their high dielectric constant leads to a large capacitance. A high dielectric constant results in a large capacitance, which can cause heat generation and malfunctions in high-speed communication (high-frequency) applications. Furthermore, the high water absorption rate of polyimides is also a challenge. Material B, possessing a dimer backbone + ester backbone, exhibits both a low dielectric constant and low water absorption rate.

[0097] (c) Material C

[0098] A polyimide, derived from (A) acid dianhydride and (B) diamine, characterized in that,

[0099] The (B) diamine has (B1) a diamine with a fluorene skeleton and (B2) a dimeric diamine.

[0100] According to material C, by introducing a fluorene backbone and a dimer backbone into the diamine component, the concentration of imide groups can be reduced, thereby lowering the overall polarity of the molecule and achieving a low dielectric constant. Furthermore, it exhibits excellent mechanical strength, and high relative dielectric constant and dielectric tangent values ​​can be obtained.

[0101] (4) Coil structure

[0102] like Figure 1As shown, the magnetic element in this embodiment is formed by forming multiple coil patterns 21, 22, and 23 inside the insulating material 1 and mounting a core 4 thereon. However, the present invention is not limited to magnetic elements with a core. For example, the present invention also includes coil structures having a flat conductive body wound on a plane and an insulating material insulating the conductive bodies from each other, with the conductive bodies and the insulating material alternately stacked, and without a core. In addition, it also includes multilayer circuit boards formed by stacking multiple such coil structures without using a core. As an example, the operating frequency of the magnetic element is preferably in the range of 500 kHz to 1 MHz, which is suitable for power transformers, etc., and this embodiment can also be applied to coil structures used in circuits with higher frequency bands.

[0103] In addition to using coil patterns obtained by etching copper foil, copper plates of a certain thickness or rod-shaped or wire-shaped conductors used as busbars can also be used as raw materials for coils. In the case of such rigid conductors, coil structures can also be formed by coating the conductor with an insulating material containing an insulating resin composition or by covering it with an insulating tape or sheet and then heating and hardening it.

[0104] (5) Multilayer circuit board

[0105] A multilayer circuit board is constructed by stacking multiple coil structures or by combining the coil structures with other circuit boards. The multilayer circuit board also includes a structure formed by stacking multiple substrates with coil patterns formed on the coil structures, which are part of a circuit board containing wiring patterns. Furthermore, the multilayer circuit board can not only stack the same coil structure, but also stack multiple different types of coil structures described in the embodiments of this specification, or combine and stack existing coil structures using glass cloth with coil structures without glass cloth based on this embodiment.

[0106] [2. First Implementation Method]

[0107] like Figure 3 As shown, the magnetic element in the first embodiment uses a multilayer circuit board formed by stacking coil structures, and its basic structure is similar to... Figure 1 The same applies. In this embodiment, a primary-side coil pattern 21, a primary-side coil pattern 22, and a secondary-side coil pattern 23 are embedded in the interior of the insulating material 1 at predetermined intervals to maintain insulation. Connectors 5 for connecting the primary-side coil pattern 21, the primary-side coil pattern 22, and the secondary-side coil pattern 23 to external devices are provided at both ends of the insulating material 1.

[0108] In this embodiment, the magnetic element has multiple coil patterns built into the interior of a multilayer circuit board, thus achieving a structure that enhances miniaturization and thinning, for example, suitable for power supplies with a capacity of approximately 30W or less.

[0109] Power semiconductor drive power supply

[0110] Large household appliances and air conditioner controls

[0111] Used for power adapters, etc.

[0112] In addition, it also has the effect of being integrated with peripheral circuit components by being made into a multilayer substrate.

[0113] [3. Second Implementation]

[0114] like Figure 4 As shown, the magnetic element in the second embodiment is formed by stacking multilayer circuit boards P1, P2, and P3, which include coil structures. That is, in this embodiment, primary-side coil patterns 21, 22, and 23 are respectively formed by different multilayer circuit boards P1, P2, and P3, and these multilayer circuit boards P1, P2, and P3 are stacked together to form a magnetic element D.

[0115] The magnetic element of this embodiment has the effect of reducing current density and thus increasing power by stacking multiple multilayer circuit boards P1, P2, and P3. Furthermore, when the number of coil patterns increases, the insulating material 1 at the center is repeatedly subjected to heat-hardening treatment each time a coil structure is stacked. In this embodiment, in cases where thermal degradation may occur due to varying heating methods, the number of heat-hardening treatments applied to the insulating material 1 can be reduced by manufacturing each multilayer circuit board P1, P2, and P3 separately, thus eliminating the effects of thermal degradation. Additionally, it has the advantage that when the number of coil turns is changed according to the ratings, capacitance, or other requirements of the magnetic element D, this can be addressed simply by changing the stacked multilayer circuit boards P1, P2, and P3.

[0116] The magnetic element in this embodiment is suitable, for example, for a power supply capacity of about 300W or less.

[0117] Power supplies for industrial equipment

[0118] Power supply for actuators

[0119] Servo amplifier power supply

[0120] Battery charger

[0121] • Used for applications such as light-emitting diode (LED) lighting power supplies.

[0122] [4. Third Implementation Method]

[0123] like Figure 5 As shown, the magnetic element in the third embodiment is formed by stacking a multilayer circuit board P including a coil pattern 23 on the secondary side and a copper plate 6 cut into a quadrilateral shape, and a primary side coil structure C1 and coil structure C2 connected in a coil shape. Around the copper plate 6 of the primary side coil structures C1 and C2, an insulating material 1 of the same thermosetting composition as the insulating material 1 of the multilayer circuit board P is formed. As a method for forming the insulating material 1 on the surface of the copper plate 6, coating, tape, or sheet coating, etc., can be used. Alternatively, the copper plate 6 formed in a coil shape can be placed in a mold, the insulating material 1 can be injected, and after pre-drying, it can be heat-cured using a vacuum press or the like.

[0124] In this embodiment, by using coil structures C1 and C2, which include a conductor with a copper plate 6 having a larger cross-sectional area compared to an etched coil pattern, as the secondary side, the current density can be further reduced, thereby increasing power. Furthermore, by combining a multilayer circuit board P using copper foil 3 with coil structures C1 and C2 using copper plate 6, for example, when using a magnetic element D as a power transformer, the conductor cross-sectional area or insulation thickness of the combined coil structures C1 and C2 can be easily changed according to the required power capacity, input / output voltage, etc., resulting in excellent versatility.

[0125] The magnetic element in this embodiment is suitable for power supplies with a capacity of approximately 1kW or less.

[0126] Power supplies for industrial equipment

[0127] Power supply for actuators

[0128] Servo amplifier power supply

[0129] Battery charger

[0130] • For applications such as server power supplies.

[0131] [5. Fourth Implementation Method]

[0132] like Figure 6As shown, in the fourth embodiment, a coil structure C3 containing a conductor of copper plate 6 is used instead of the multilayer circuit board P of the third embodiment as the primary coil. That is, for the secondary-side coil structures C1 and C2, the same as in the third embodiment, a square copper plate 6 is used, which is punched into a coil shape. For the primary-side coil structure C3, a flat winding is used as the copper plate 6. Regarding the insulating material 1 formed around the copper plate 6, the same insulating material formed around the copper plate 6 in the third embodiment can be used. In this case, the characteristics of the magnetic element, such as the cross-sectional shape, cross-sectional area, and number of turns of the copper plate 6 required as the conductor, can be changed for the secondary-side coil structures C1 and C2 and the primary-side coil structure C3.

[0133] In this embodiment, by using a conductor comprising a copper plate 6 in all coil structures C1, C2, and C3, the current density can be further reduced, thereby increasing the power. Therefore, it is suitable, for example, for power supplies with a capacity of approximately 1 kW or less.

[0134] Power supplies for industrial equipment

[0135] Battery charger

[0136] • For applications such as server power supplies.

[0137] [6. Fifth Implementation Method]

[0138] like Figure 7 As shown, the magnetic element in the fifth embodiment is formed by disposing a shielding layer S on the outermost layer of a multilayer circuit board P. As the shielding layer S, the following can be used:

[0139] Sheet materials in which soft magnetic powder is dispersed in resin.

[0140] • Sheet materials in which carbon powder is dispersed in resin

[0141] • Sheet material obtained by coating a metal layer with resin.

[0142] According to this fifth embodiment, leakage flux generated from the coil can be suppressed from leaking out of the outermost layer.

[0143] [7. Sixth Implementation Method]

[0144] like Figure 8 As shown, the magnetic element in the sixth embodiment is formed by disposing a shielding layer S in the middle layer of a multilayer circuit board P. The shielding layer S described in the fifth embodiment can be used.

[0145] According to this sixth embodiment, the coupling degree between the primary coil and the secondary coil can be adjusted.

[0146] [Example]

[0147] Regarding Examples 1 to 6 of the present invention, compared with Comparative Examples 1 and 2 which used prepreg as insulating material, the effects of each item related to capacitance (1MHz), withstand voltage, low leakage, and total thickness were confirmed.

[0148] (1) Comparison Example 1

[0149] The coil structure is made by stacking three layers of 100μm thick prepreg (glass cloth substrate epoxy resin substrate R-1766 / R-1661 sold by Panasonic Industry Co., Ltd.) as insulation material, and forming coil patterns with a thickness of 25μm on both sides.

[0150] • Dielectric constant of the insulating material (1MHz): 4.7

[0151] Withstand voltage 64kV / mm

[0152] • Insulation material thickness 100μm × 3 = 300μm

[0153] • Coil pattern thickness 25μm × 2 = 50μm

[0154] Total thickness 350μm

[0155] • Pattern spacing 300μm

[0156] (2) Comparison Example 2

[0157] The coil structure was fabricated by using a 100μm thick prepreg (glass cloth substrate epoxy resin substrate R-1766 / R-1661 sold by Panasonic Corporation) as the insulating material, with a coil pattern of 25μm thickness on both sides thereof.

[0158] • Dielectric constant of the insulating material (1MHz): 4.7

[0159] Withstand voltage 64kV / mm

[0160] • Insulation material thickness 100μm × 1 = 100μm

[0161] • Coil pattern thickness 25μm × 2 = 50μm

[0162] Total thickness 150μm

[0163] • Pattern spacing 100μm

[0164] (3) Example 1 Polyimide + Material A

[0165] A coil structure having a coil pattern formed on a flexible substrate material (single-sided copper clad laminate R-F770 sold by Panasonic Industry Co., Ltd.) with a thickness of 25 μm as an insulating material, and a coil structure having a coil pattern formed on one side of material A described below, are stacked with the coil pattern on the outside.

[0166] (3-1) Polyimide (R-F770)

[0167] • Dielectric constant of the insulating material (1MHz): 3.2

[0168] Withstand voltage 276kV / mm

[0169] • Insulation material thickness 25μm

[0170] • Coil pattern thickness 25μm

[0171] (3-2) Specific examples of material A

[0172] The preparation comprises 98 parts by weight of bisphenol A type epoxy resin Epiclon 850-S (manufactured by DIC, epoxy equivalent 188), 147 parts by weight of dicyclopentadiene type epoxy resin HP-7200H (manufactured by DIC, epoxy equivalent 283, softening point 83℃), 126 parts by weight of elastomer 250P (polytetramethylene oxide-di-para-aminobenzoate) (manufactured by Ihara Chemical, melting point 60℃), 100 parts by weight of soluble polyimide resin Q-VR-X0163 (manufactured by PI Technology Research Institute, Tg 246℃, resin solids content 20% by weight), and 303 parts by weight of phenoxy resin ERF-001M30 (manufactured by Nippon Steel Chemical Co., Ltd., Tg 246℃, resin solids content 20% by weight), and Tg 246℃. A resin varnish with a resin solid content of 40% by weight was prepared by mixing 18 parts by weight of HCA (146°C, 30% by weight of resin solids content). The resin varnish prepared in this manner was applied to a copper foil forming a coil pattern, pre-baked at 120°C for 10 minutes, and then heat-cured at 180°C for 120 minutes to obtain material A1 as a cured epoxy resin.

[0173] • Dielectric constant of the insulating material (1MHz): 3.1

[0174] Withstand voltage 229kV / mm

[0175] • Insulation material thickness 25μm

[0176] • Coil pattern thickness 25μm

[0177] (3-3) Overall thickness and inter-pattern spacing of (polyimide + material A)

[0178] Total thickness 100μm

[0179] • Pattern spacing 50μm

[0180] (4) Example 2 Polyimide + Material B

[0181] The coil structure of Example 1, which has a coil pattern formed on a single-sided copper-clad laminate (R-F770) using polyimide, and the coil structure of the same type, which has a coil pattern formed on a single side of material B described below, are laminated with the coil pattern on the outside.

[0182] (4-1) Polyimide

[0183] Same as Example 1

[0184] (4-2) Specific examples of material B

[0185] In a 1L four-necked separable flask including a stirrer, reflux condenser, and thermometer, 0.5g of 4,4-oxydiphenylamine, 4g of dimeric diamine (Croda Japan, PRIAMINE 1075), 6.2g of 2,2',3,3',5,5'-hexamethyl[1,1'-biphenyl]-4,4'-diyl=bis(1,3-dioxo-1,3-dihydro-2-benzofuran-5-carboxylic acid ester), and 32g of N-methyl-2-pyrrolidone were added. Nitrogen gas was purged into the reaction vessel at 0.1mL / sec, and the mixture was heated and stirred at 50°C for approximately 3.5 hours. After confirming that the salts had dissolved, the mixture was stirred at room temperature for 24 hours to synthesize polyamic acid, a precursor to polyimide. The polyamic acid itself is a solution and can be used directly as a varnish for coating copper foil. After the polyamic acid synthesized in the manner described is coated onto a copper foil forming a coil pattern, it is pre-baked at 120°C for 10 minutes, heat-cured at 150°C for 60 minutes, and then heat-cured at 180°C for 30 minutes, thereby achieving the closed-ring polymerization of the polyamic acid to obtain material B as a polyimide resin.

[0186] • Dielectric constant of the insulating material (1MHz): 2.65

[0187] Withstand voltage 308kV / mm

[0188] • Insulation material thickness 25μm

[0189] • Coil pattern thickness 25μm

[0190] (4-3) Overall thickness and spacing between patterns of (polyimide + material B)

[0191] Same as Example 1

[0192] (5) Example 3 Polyimide + Material C

[0193] The coil structure of Example 1, which has a coil pattern formed on a single-sided copper-clad laminate (R-F770) using polyimide, and the coil structure of the same type, which has a coil pattern formed on a single side of material C described below, are stacked with the coil pattern on the outside.

[0194] (5-1) Polyimide (R-F770)

[0195] Same as Example 1

[0196] (5-2) Material C

[0197] In a 1L four-necked separable flask including a stirrer, reflux condenser, and thermometer, 8.7g of 9,9-bis(4-aminophenyl)fluorene, 13.35g of dimeric diamine (Priamine 1075, Croda Japan), 10.9g of pyromellitic dianhydride, and 76.9g of N-methyl-2-pyrrolidone were added. Nitrogen gas was purged into the reaction vessel at 0.1mL / sec, and the mixture was heated and stirred at 50°C for approximately 3.5 hours. After confirming the salt dissolution, the mixture was stirred at room temperature for 24 hours to synthesize polyamic acid, a precursor to polyimide. Similar to Material B, the polyamic acid itself is a solution and can be used directly as a varnish for coating copper foil. The polyamic acid synthesized in the manner described is coated onto a copper foil forming a coil pattern, pre-baked at 120°C for 10 minutes, heat-cured at 150°C for 60 minutes, and then heat-cured at 180°C for 30 minutes, thereby achieving cyclic polymerization of the polyamic acid to obtain material C as a polyimide resin.

[0198] • Dielectric constant of the insulating material (1MHz): 2.7

[0199] Withstand voltage 333kV / mm

[0200] • Insulation material thickness 25μm

[0201] • Coil pattern thickness 25μm

[0202] (5-3) Overall thickness and spacing between patterns of (polyimide + material C)

[0203] Same as Example 1

[0204] (6) Example 4 Material A alone

[0205] A coil structure was fabricated using material A, on both sides of which coil patterns were formed, as the insulation material. The insulation thickness of material A was set to 50 μm, which was equal to the total thickness of the polyimide and material A in Example 1.

[0206] (7) Example 5 Material B alone

[0207] A coil structure was fabricated using material B, on both sides of which had coil patterns formed, as the insulation material. The insulation thickness of material B was set to 50 μm, which was equal to the total thickness of the polyimide and material A in Example 1.

[0208] (8) Example 6 Material C alone

[0209] A coil structure was fabricated using material C, on both sides of which coil patterns were formed, as the insulation material. The insulation thickness of material C was set to 50 μm, which was equal to the total thickness of the polyimide and material A in Example 1.

[0210] (9) Example 7

[0211] Figure 9 This schematically illustrates an example of a method for manufacturing resin-coated copper foil according to this embodiment.

[0212] (1) The resin varnish of material D is coated onto a copper foil Cu with a thickness of 18 μm using a die coating machine and dried at a temperature of 190°C to produce a resin-coated copper foil (A1) with a resin layer in a fully hardened state having a resin thickness of 51 μm.

[0213] (2) Next, the resin varnish of material A is applied to the resin-cured film of the resin-coated copper foil film and dried at 120°C to produce a resin-coated copper foil (A2) with a further laminated resin layer of 51 μm thickness in a semi-cured state. The volatile content is adjusted to 0.5 wt%.

[0214] (3) Subsequently, a PEN (polyethylene naphthalate) film as a protective film is laminated onto the semi-cured resin layer to produce a resin-coated copper foil (A3) for multilayering.

[0215] (4) During evaluation, the PEN, which serves as a protective film, is removed from the resin-coated copper foil (A3), and a copper foil Cu for conducting electricity is laminated onto the surface of the semi-cured resin material A to prepare an evaluation sample S. The evaluation sample corresponds to a single layer portion of the coil structure of this embodiment, which is formed by alternating layers of conductors and insulating materials, and the electrical characteristics obtained from the sample correspond to the electrical characteristics of the coil structure.

[0216] (5) Specific examples of material D

[0217] The preparation comprises 98 parts by weight of bisphenol A type epoxy resin Epiclon 850-S (manufactured by DIC, epoxy equivalent 188), 147 parts by weight of dicyclopentadiene type epoxy resin HP-7200H (manufactured by DIC, epoxy equivalent 283, softening point 83℃), 126 parts by weight of elastomer 250P (polytetramethylene oxide-di-para-aminobenzoate) (manufactured by Ihara Chemical, melting point 60℃), 100 parts by weight of soluble polyimide resin Q-VR-X0163 (manufactured by PI Technology Research Institute, Tg 246℃, resin solids content 20% by weight), and 303 parts by weight of phenoxy resin ERF-001M30 (manufactured by Nippon Steel Chemical Co., Ltd., Tg 246℃, resin solids content 20% by weight), and Tg 246℃. A resin varnish with a resin solids content of 40% by weight is prepared by mixing 146°C, 30% by weight of resin solids, 18 parts by weight of HCA, and 10 parts by weight of 2E4MZ (manufactured by Shikoku Chemical Industry Co., Ltd.).

[0218] • Dielectric constant of the insulating material (1MHz): 3.1

[0219] Withstand voltage 229kV / mm

[0220] • Insulation material thickness 25μm

[0221] (10) Example 8

[0222] Figure 10 An example of the method for manufacturing resin-coated copper foil in this embodiment is shown schematically. (1) A resin varnish of material B is applied to a 18 μm copper foil using a die coating machine and dried at a temperature of 190°C to manufacture a resin-coated copper foil (B1) with a fully cured resin layer having a resin thickness of 51 μm.

[0223] (2) Next, the resin varnish of material A is applied to the resin-cured film of the resin-coated copper foil film and dried at 120°C to produce a resin-coated copper foil (B2) with a further laminated 51 μm thick semi-cured resin layer. The volatile content is adjusted to 0.5 wt%.

[0224] (3) Subsequently, a PEN (polyethylene naphthalate) film as a protective film is laminated onto the semi-cured resin layer to produce a resin-coated copper foil (B3) for multilayering.

[0225] (4) When evaluating, the PEN, which serves as a protective film, is removed from the resin-coated copper foil (B3), and an electric copper foil Cu is laminated on the surface of the semi-cured resin material A to prepare the evaluation sample S.

[0226] (11) Example 9

[0227] (1) The resin varnish of material B is coated onto a copper foil with a thickness of 18 μm using a die coating machine and dried at a temperature of 190°C to produce a resin-coated copper foil (C1) with a resin layer in a fully cured state having a resin thickness of 51 μm.

[0228] (2) Next, the resin varnish of material B is applied to the resin-cured film of the resin-coated copper foil film and dried at 120°C to produce a resin-coated copper foil (C2) with a further laminated 51 μm thick semi-cured resin layer. The volatile content is adjusted to 0.5 wt%.

[0229] (3) Subsequently, a PEN (polyethylene naphthalate) film as a protective film is laminated onto the semi-cured resin layer to produce a resin-coated copper foil (C3) for multilayering.

[0230] (4) When evaluating, the PEN, which serves as a protective film, is removed from the resin-coated copper foil (C3), and an electric current-carrying copper foil Cu is laminated on the surface of the semi-cured resin material B to prepare the evaluation sample S.

[0231] (12) Evaluation Methods

[0232] The evaluation of the comparative examples and embodiments was conducted using the methods described below.

[0233] (12-1) Capacitance

[0234] The capacitance is calculated using the following formula.

[0235] • Capacitance C = (Dielectric constant of insulating material × Dielectric constant of vacuum × Pattern area) / Distance between patterns

[0236] • Examples 1 to 3 are two capacitors with two different dielectrics. The capacitance is calculated using the above formula, and then the final capacitance is calculated using the following formula to calculate the combined capacitance when the two capacitors are connected in series.

[0237] 1 / C = 1 / C1 + 1 / C2

[0238] (12-2) Withstand voltage

[0239] The voltage withstand value per unit thickness of the insulating material is used as a basis, and then converted into the distance between patterns to calculate the voltage.

[0240] (12-3) Evaluation of low leakage (leakage flux)

[0241] Since the leakage flux from between patterns decreases inversely proportional to the distance between patterns, the evaluation is based on the distance between patterns.

[0242] • Set to × for values ​​exceeding 100μm

[0243] • Set the value to ○ when it is between 100μm and 50μm.

[0244] • Set to ◎ when the value is below 50μm

[0245] (12-4) Total Thickness

[0246] The thickness of the insulating material between the patterns and the thickness of the patterns sandwiching the insulating material are calculated.

[0247] (12-5) Determination Method

[0248] (1) Dielectric constant (1MHz)

[0249] The evaluation sample was 20 mm × 20 mm × 200 μm thick.

[0250] The manufacturer's name is KEYSIGHT (Germany).

[0251] Evaluation Device Name & Model: RF Impedance / Material Analyzer, 1.8GHz 4291B

[0252] The measurement was performed at 1 MHz.

[0253] (2) Withstand voltage (kV / mm)

[0254] Measurements were performed under the following conditions: the evaluation sample had a shape of 100 mm × 100 mm, the prepreg thickness of the comparative example was 100 μm, and the thickness of other materials was 25 μm.

[0255] Manufacturer Name: Measurement Technology Research Institute Co., Ltd.

[0256] Evaluation Device Name & Model: Ultra-high voltage withstand voltage tester, Model 7472

[0257] The measurement conditions were performed according to the Institute of Printed Circuits (IPC) TM-650TM2.5.7.

[0258] The evaluation results for Examples 1 to 6 are shown in Table 1 below.

[0259] [Table 1]

[0260]

[0261] The evaluation results for Examples 7 to 9 are shown in Table 2 below.

[0262] [Table 2]

[0263]

[0264] [13. Examination of the Examples]

[0265] (1) Capacitance

[0266] As can be seen from Comparative Examples 1 and 2, when the insulating material is the same, the capacitance is inversely proportional to the thickness of the insulating material (the distance between the coil patterns formed on both sides of the insulating material). Therefore, in order to reduce the capacitance, it is necessary to increase the thickness of the insulating material, but this makes it difficult to make the magnetic element thinner. In Examples 1 to 9, which do not use a prepreg, the element was made thinner with a total thickness of 100 μm. Compared with Comparative Example 2, where the insulating material thickness was 100 μm and the total thickness was 150 μm, the capacitance was reduced by about 2 / 3.

[0267] Even when comparing the embodiments with each other, compared to Embodiments 1 to 3, which laminated polyimide and materials A to C, Embodiments 4 to 6, which used materials A to C alone with a lower dielectric constant compared to polyimide, had the same insulating material thickness but lower capacitance. Therefore, it is considered that, as in Embodiments 1 to 3, in magnetic elements that laminated polyimide and any of materials A to C, a reduction in capacitance was achieved compared to magnetic elements using polyimide monomers of the same thickness.

[0268] According to Examples 4 to 6, among the three materials, materials B and C exhibit superior electrostatic capacitance, with material B showing a particularly significant effect. Even when combined with polyimide, materials B and C demonstrate better electrostatic capacitance than material A. This aspect is also confirmed by the following: in Examples 7 to 9, where materials A to B are combined and stacked in two layers, and especially in Examples 8 and 9, which include material B, and particularly in Example 8, where only two layers of material B are stacked, the electrostatic capacitance is significantly reduced.

[0269] (2) Withstand voltage

[0270] Compared to the prepreg, polyimide and materials A to C exhibit significantly superior voltage withstand properties. Therefore, Examples 1 to 9 demonstrate significantly superior voltage withstand properties compared to Comparative Examples 1 and 2. Polyimide, even as a monomer, exhibits excellent voltage withstand properties. By combining it with materials B or C, which have even higher voltage withstand properties, magnetic components with excellent voltage withstand properties, as shown in Examples 2 and 3, can be obtained. In particular, material C exhibits the best voltage withstand properties even compared to materials A and B.

[0271] Regarding material A, as shown in Examples 1 and 4, although its voltage resistance is lower than that of polyimide monomers if only voltage resistance is considered, it has excellent voltage resistance and low electrostatic capacitance compared to the prepregs of Comparative Examples 1 and 2. Therefore, it is more suitable than polyimide monomers for applications that correspond to the required voltage resistance and electrostatic capacitance.

[0272] It is clear that, considering the low electrostatic capacitance and such excellent voltage withstand characteristics, the coil structure and multilayer circuit board using material B, or the magnetic element having such a coil structure or multilayer circuit board, exhibit extremely superior characteristics in practical application.

[0273] (3) Low leakage

[0274] Compared to Comparative Examples 1 and 2, all of Examples 1 to 9 exhibited excellent low leakage flux characteristics. In particular, despite the significant reduction in the distance between coil patterns to 50 μm and the decrease in the wall thickness of the insulating material, the reduction in leakage flux is beneficial for the use of various magnetic components.

[0275] (4) Total thickness

[0276] Compared to Comparative Examples 1 and 2, the total thickness of any of Examples 1 to 9 is significantly reduced. In particular, even when the insulating material is thinned to the same thickness as the coil pattern, the desired capacitance, withstand voltage, and low leakage can be achieved, thereby enabling miniaturization / thinning of the magnetic component.

[0277] [14. Other Implementation Methods]

[0278] This invention is not limited to the described embodiments. During implementation, the constituent components can be modified and embodied without departing from its spirit. Furthermore, various inventions can be formed through appropriate combinations of the multiple constituent components disclosed in the described embodiments. For example, several constituent components may be deleted from all the constituent components shown in the embodiments. Specifically, other embodiments as follows are also included.

[0279] (1) When constructing a coil structure, a multilayer circuit board, and magnetic elements, the insulating material used to insulate between conductors can be either a single type or, as shown in Examples 1 to 3, a combination of different types of insulating materials. Furthermore, by using a different type of insulating material for each coil structure and stacking multiple coil structures with different types of insulating materials, it is possible to construct a coil structure with thicker walls or to construct a multilayer circuit board and magnetic elements.

[0280] (2) The present invention is characterized by not using glass cloth, but is not limited to glass cloth. It is also not preferable to use other resin impregnation substrates impregnated with insulating resin compositions. That is, conventional resin impregnation substrates often have poor electrostatic capacitance and voltage withstand characteristics compared with the homogeneous layer of the insulating resin composition shown in this embodiment. If such a substrate is present in the insulating material, the desired electrical and magnetic properties cannot be obtained.

[0281] (3) As a conductor, etched coil patterns based on copper foil, coils made of copper plates, busbars, flat windings, etc., can be used. When using copper foil, the coil pattern can be pre-cut and overlapped with the surface of pre-dried or heat-cured insulation material, or uncured insulation material can be coated or sprayed onto the cut coil pattern. In the case of a rigid conductor, it can be immersed in liquid insulation material (impregnation treatment) and pre-dried and heat-cured after being pulled up.

[0282] (4) Regarding materials A to C, the composition is not limited to that described in the examples. If the range of materials shown in [1. Basic Structure of Magnetic Element] is used, superior performance can be expected compared to the polyimide described in the examples.

[0283] Explanation of icon numbers

[0284] D: Magnetic components

[0285] C, C1, C2, C3: Coil structure

[0286] P, P1, P2, P3: Multilayer circuit board

[0287] S: Shielding layer

[0288] 1, 1a: Insulating material

[0289] 10: Opening

[0290] 21, 22, 23, 2a, 2b: Coil patterns

[0291] 3, 3a, 3b: Copper foil

[0292] 4: Core

[0293] 41, 42: Feet

[0294] 43, 44: Magnetic yoke

[0295] 45: Center foot

[0296] 5: Connector

[0297] 6: Copper Coin

Claims

1. A coil structure, characterized in that, It comprises a flat conductive body wound on a plane and an insulating material that insulates the conductive bodies from each other. The conductor and the insulating material are alternately stacked. The insulating material is a cured form of an insulating resin composition that does not contain glass cloth.

2. The coil structure according to claim 1, characterized in that, The insulating resin composition has a withstand voltage of 100kV / mm or higher and a dielectric constant of 4.0 or lower.

3. The coil structure according to claim 1 or 2, characterized in that, The insulating resin composition has adhesive properties.

4. The coil structure according to claim 3, characterized in that, The insulating resin composition comprises epoxy resin.

5. The coil structure according to claim 3 or 4, characterized in that, The insulating resin composition comprises at least one of polyamide resin, polyimide resin, and polyamide-imide resin.

6. The coil structure according to claim 4 or 5, characterized in that, The insulating resin composition comprises: (a1) Liquid epoxy resin, (a2) Solid epoxy resin with a softening point below 125℃ (b) Aromatic diamine compounds having benzoate groups and polymethylene groups in the main chain; (c) Solvent-soluble polyimide resins with a Tg above 200℃ and a weight-average molecular weight (Mw) below 50,000. (d) Phenoxy resins with a Tg of 130℃ or higher. When the total amount of the liquid epoxy resin (a1), the solid epoxy resin (a2), and the aromatic diamine compound (b) is set to 100 parts by weight, the total amount of the solvent-soluble polyimide resin (c) and the phenoxy resin (d) is 15 parts by weight or more and 150 parts by weight or less.

7. The coil structure according to any one of claims 3 to 6, characterized in that, The insulating resin composition is a polyimide derived from (A) acid dianhydride and (B) diamine. The (A) anhydride comprises (A1) anhydrides having ester bonds. In the (B) diamine, when the total number of moles of all diamines is set to 1.0, a mole count of 0.3 or more constitutes (B1) dimeric diamine.

8. The coil structure according to any one of claims 3 to 6, characterized in that, The insulating resin composition is a polyimide derived from (A) acid dianhydride and (B) diamine. The (B) diamine has (B1) a diamine with a fluorene skeleton and (B2) a dimeric diamine.

9. The coil structure according to claim 1, which is formed by multilayering a resin-coated copper foil on one side of the copper foil in which the insulating resin composition is formed.

10. A multilayer circuit board comprising a coil structure as described in any one of claims 1 to 9.

11. The multilayer circuit board according to claim 10, wherein, A shielding layer is provided in the outermost or middle layer.

12. A magnetic element comprising mounting a core on a multilayer circuit board as described in claim 10 or 11.

13. A magnetic element comprising stacking and mounting a plurality of multilayer circuit boards as described in claim 10 or 11.

14. A magnetic element comprising stacking multiple layers of the coil structure as described in claim 1 and the multilayer circuit board as described in claim 10 or 11 and mounting a core thereon.

15. The magnetic element according to any one of claims 12 to 14, wherein, The operating frequency is 500kHz to 1MHz.

16. A resin-coated copper foil for a coil structure, characterized in that an insulating resin composition is formed on one side of the copper foil, and that... A semi-cured resin layer containing the insulating resin composition or an insulating resin composition different from the insulating resin composition is formed on the surface of the insulating resin composition with the resin copper foil, and a protective film is laminated on the surface of the semi-cured resin layer.

17. A type of coil structure using resin-coated copper foil, characterized in that, A resin layer containing the insulating resin composition in a semi-cured state is formed on one side of a copper foil, and a protective film is laminated onto the surface of the semi-cured resin layer.

18. A method for manufacturing a coil structure, characterized in that, The resin-coated copper foil as described in claim 16 or 17 is laminated in such a way that the semi-cured resin layer is in contact with the copper foil after the protective film has been peeled off.

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