Magnetic paste

Abstract

To provide, e.g., a magnetic paste that can yield a cured product that is excellent in mechanical strength and reduced in viscosity in spite of containing magnetic powder.SOLUTION: A magnetic paste comprises (A) magnetic powder, (B) epoxy resin, (C) a dispersant, and (D) a curing agent, where the component (C) has a polyester skeleton represented by the general formula (1) in the figure. (In general formula (1), each R independently represents a divalent hydrocarbon group having 2 to 10 carbon atoms, and n represents an integer of 2 to 1000.)SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a magnetic paste, a resin composition, and a cured product, a circuit board, and an inductor component using the magnetic paste or the resin composition. [Background technology]

[0002] In recent years, with the demand for smaller and thinner electronic devices, there has been a demand for smaller circuit boards used in electronic devices and higher wiring density. Known examples of such circuit boards are those formed by filling through holes with a paste material.

[0003] For example, Patent Document 1 describes a filled resin containing magnetic particles such as iron oxide (III) or cobalt iron oxide as a resin for filling through holes in a circuit board for an inductor component. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-197624 Summary of the Invention [Problem to be solved by the invention]

[0005] One possible way to increase the relative permeability of a cured magnetic paste, such as the filled resin in Patent Document 1, is to include a magnetic powder in the filled resin. However, including a magnetic powder in the magnetic paste increases the viscosity of the magnetic paste, which can lead to poor printability. In particular, when a paste containing a large amount of magnetic powder is used, such as the filled resin described in Patent Document 1, the viscosity of the paste increases significantly, further impairing printability.

[0006] The present invention has been made in view of the above circumstances, and aims to provide a magnetic paste and a resin composition that can give a cured product with high relative magnetic permeability and excellent printability, as well as cured products, circuit boards, and inductor components that use the magnetic paste or resin composition. [Means for solving the problem]

[0007] As a result of intensive research to achieve the above object, the inventors discovered that by using a magnetic paste containing a dispersant having a polyester skeleton, it is possible to lower the viscosity of the paste, improving printability, while also improving the relative permeability of the cured product, and thus completed the present invention.

[0008] That is, the present invention includes the following. [1] (A) Magnetic powder, (B) epoxy resin, (C) a dispersant, and (D) a hardener, A magnetic paste in which component (C) has a polyester skeleton represented by the following general formula (1): [ka] (In general formula (1), each R independently represents a divalent hydrocarbon group having 2 to 10 carbon atoms, and n represents an integer of 2 to 1000.) [2] The magnetic paste according to [1], wherein the content of component (C) is 0.1% by mass or more and 5% by mass or less, when the non-volatile components in the magnetic paste are taken as 100% by mass. [3] A magnetic paste according to [1] or [2], wherein component (A) comprises (A-1) a magnetic powder having an average particle size of 1 μm or more, and (A-2) a magnetic powder having an average particle size of less than 1 μm. [4] A magnetic paste according to any one of [1] to [3], wherein component (A) comprises (A-1) a magnetic powder having an average particle size of 1 μm or more and 10 μm or less, and (A-2) a magnetic powder having an average particle size of 0.005 μm or more and less than 1 μm. [5] The magnetic paste according to any one of [1] to [4], wherein component (A) is at least one selected from iron oxide powder and iron alloy metal powder. [6] The magnetic paste according to any one of [1] to [5], wherein component (A) contains iron oxide powder, and the iron oxide powder contains ferrite containing at least one selected from Ni, Cu, Mn, and Zn. [7] The magnetic paste according to any one of [1] to [6], wherein the content of component (A) is 70% by mass or more and 98% by mass or less, when the non-volatile components in the magnetic paste are taken as 100% by mass. [8] The magnetic paste according to any one of [1] to [7], which is for filling through-holes. [9] A cured product of the magnetic paste according to any one of [1] to [8].

[10] A circuit board comprising a substrate having through-holes and a cured product of the magnetic paste according to any one of [1] to [8] filled in the through-holes.

[11] (A) Magnetic powder, (B) epoxy resin, (C) a dispersant, and (D) a curing agent, A resin composition, wherein component (C) has a polyester skeleton represented by the following general formula (1): [ka] (In general formula (1), each R independently represents a divalent hydrocarbon group having 2 to 10 carbon atoms, and n represents an integer of 2 to 1000.)

[12] A cured product of the resin composition described in

[11] .

[13] A circuit board comprising a substrate having through-holes, and a cured product of the resin composition according to

[12] filled in the through-holes.

[14] An inductor component comprising the circuit board according to

[10] or

[13] . [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a magnetic paste and a resin composition that can give a cured product with a high relative dielectric constant and excellent printability, as well as a cured product, a circuit board, and an inductor component that use the magnetic paste or the resin composition. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic cross-sectional view of a core substrate as an example of a method for manufacturing a circuit board according to a first embodiment. [Figure 2] FIG. 2 is a schematic cross-sectional view of a core substrate in which through holes are formed, as an example of the method for manufacturing the circuit board according to the first embodiment. [Figure 3] FIG. 3 is a schematic cross-sectional view showing the state of a core substrate in which a plating layer has been formed in a through-hole as an example of the method for manufacturing a circuit board according to the first embodiment. [Figure 4] FIG. 4 is a schematic cross-sectional view showing a core substrate in which magnetic paste has been filled into through-holes as an example of the method for manufacturing the circuit board according to the first embodiment. [Figure 5] FIG. 5 is a schematic cross-sectional view showing the state of the core substrate after the magnetic paste filled therein has been thermally cured, as an example of the method for manufacturing the circuit board according to the first embodiment. [Figure 6] FIG. 6 is a schematic cross-sectional view showing the state of the core substrate after polishing the cured product as an example of the method for manufacturing the circuit board according to the first embodiment. [Figure 7] FIG. 7 is a schematic cross-sectional view showing the state of a core substrate with a conductor layer formed on the polished surface as an example of the method for manufacturing the circuit board of the first embodiment. [Figure 8] FIG. 8 is a schematic cross-sectional view showing the state of a core substrate on which a patterned conductor layer is formed as an example of the method for manufacturing a circuit board according to the first embodiment. [Figure 9] FIG. 9 is a schematic cross-sectional view illustrating step (A) included in an example of the method for manufacturing the circuit board according to the second embodiment. [Figure 10]FIG. 10 is a schematic cross-sectional view illustrating step (A) included in an example of the method for manufacturing the circuit board according to the second embodiment. [Figure 11] FIG. 11 is a schematic cross-sectional view illustrating step (B) included in an example of the method for manufacturing the circuit board according to the second embodiment. [Figure 12] FIG. 12 is a schematic cross-sectional view illustrating step (D) included in an example of the method for manufacturing the circuit board according to the second embodiment. [Figure 13] FIG. 13 is a schematic plan view of an inductor component including a circuit board obtained by the circuit board manufacturing method according to the second embodiment, as an example, viewed from one side in the thickness direction. [Figure 14] FIG. 14 is a schematic diagram showing a cut end surface of an inductor component including a circuit board obtained by the method for manufacturing a circuit board according to the second embodiment, cut at the position indicated by the dashed line II-II as an example. [Figure 15] FIG. 15 is a schematic plan view illustrating the configuration of a first conductor layer in an inductor component including a circuit board obtained by the method for manufacturing a circuit board according to the second embodiment, as an example. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that each drawing merely shows the shape, size, and arrangement of components in a schematic manner to the extent that the invention can be understood. The present invention is not limited by the following description, and each component can be modified as appropriate. In the drawings used in the following description, similar components are denoted by the same reference numerals, and redundant explanations may be omitted. Furthermore, the configuration according to the embodiments of the present invention may not necessarily be manufactured or used in the arrangement shown in the drawings.

[0012] [Magnetic paste] The magnetic paste of the present invention is a magnetic paste containing (A) magnetic powder, (B) epoxy resin, (C) dispersant, and (D) curing agent, and the component (C) has a polyester skeleton represented by the following general formula (1). [ka] (In general formula (1), each R independently represents a hydrocarbon group having 2 to 10 carbon atoms, and n represents an integer of 2 to 1000.)

[0013] In the present invention, by including the dispersant (C), the viscosity of the magnetic paste is reduced, resulting in excellent printability. Furthermore, it is usually possible to improve the mechanical strength of the cured product. Furthermore, the cured product of the magnetic paste usually has improved relative permeability and reduced magnetic loss in the frequency range of 10 to 200 MHz.

[0014] The magnetic paste may further contain (E) other additives as needed. Each component contained in the magnetic paste of the present invention will be described in detail below.

[0015] <(A) Magnetic powder> The magnetic paste contains (A) magnetic powder as component (A). The (A) magnetic powder may be used alone or in combination of two or more. Examples of the (A) magnetic powder include pure iron powder; Mg-Zn ferrite, Fe-Mn ferrite, Mn-Zn ferrite, Mn-Mg ferrite, Cu-Zn ferrite, Mg-Mn-Sr ferrite, Ni-Zn ferrite, Ba-Zn ferrite, Ba-Mg ferrite, Ba-Ni ferrite, Ba-Co ferrite, Ba-Ni-Co ferrite, Y ferrite, iron oxide powder (III), triiron tetroxide, etc. Examples of suitable iron oxide powders include iron alloy metal powders such as Fe-Si alloy powder, Fe-Si-Al alloy powder, Fe-Cr alloy powder, Fe-Cr-Si alloy powder, Fe-Ni-Cr alloy powder, Fe-Cr-Al alloy powder, Fe-Ni alloy powder, Fe-Ni-Mo alloy powder, Fe-Ni-Mo-Cu alloy powder, Fe-Co alloy powder, and Fe-Ni-Co alloy powder; and amorphous alloys such as Co-based amorphous alloys.

[0016] Among these, the magnetic powder (A) is preferably at least one selected from iron oxide powder and iron alloy metal powder. The iron oxide powder preferably contains ferrite containing at least one selected from Ni, Cu, Mn, and Zn, and more preferably ferrite containing Mn. Furthermore, the iron alloy metal powder preferably contains iron alloy metal powder containing at least one selected from Si, Cr, Al, Ni, and Co.

[0017] (A) As the magnetic powder, commercially available magnetic powders can be used. Specific examples of commercially available magnetic powders that can be used include "M05S" and "M001" manufactured by Powdertech Co., Ltd.; "PST-S" manufactured by Sanyo Special Steel Co., Ltd.; "AW2-08", "AW2-08PF20F", "AW2-08PF10F", "AW2-08PF3F", "Fe-3.5Si-4.5CrPF20F", "Fe-50NiPF20F", and "Fe-80Ni-4MoPF20F" manufactured by Epson Atmix Corporation; and "LD-M", "LD-MH", "KNI-106", "KNI-106GSM", "KNI-106GS", and "KNI- 109", "KNI-109GSM", "KNI-109GS"; Toda Kogyo Co., Ltd.'s "KNS-415", "BSF-547", "BSF-029", "BSN-125", "BSN-125", "BSN-714", "BSN-828", "S-1281", "S-1641", "S-1651", "S-1470", "S-1511", "S-2430"; Japan Metals and Chemical Industries, Ltd.'s "JR09P2"; CIK Nanotech Co., Ltd.'s "Nanotek"; Kinseimatec Co., Ltd.'s "JEMK-S" and "JEMK-H"; and Aldrich's "Yttrium iron oxide". The (A) magnetic powder may be used alone, but from the viewpoint of obtaining the effects of the present invention more significantly, it is preferable to use two or more types in combination.

[0018] (A) The magnetic powder is preferably spherical. The aspect ratio (the value obtained by dividing the length of the major axis of the magnetic powder by the length of the minor axis) is preferably 2 or less, more preferably 1.5 or less, and even more preferably 1.2 or less. In general, magnetic powders that are flat rather than spherical tend to improve the relative magnetic permeability. However, the use of spherical magnetic powders is particularly preferred from the viewpoints of reducing magnetic loss and obtaining a paste with a desirable viscosity.

[0019] From the viewpoint of improving relative magnetic permeability, the average particle size of the (A) magnetic powder is preferably 0.01 μm or more, more preferably 0.5 μm or more, and even more preferably 1 μm or more. It is also preferably 10 μm or less, more preferably 9 μm or less, and even more preferably 8 μm or less. When two or more types of (A) magnetic powder are used in combination, the average particle size of the entire (A) component should be within this range.

[0020] The average particle size of magnetic powder can be measured by a laser diffraction / scattering method based on Mie scattering theory. Specifically, a particle size distribution of the magnetic powder is created on a volume basis using a laser diffraction / scattering particle size distribution analyzer, and the median diameter is used as the average particle size. A preferable measurement sample is magnetic powder dispersed in water using ultrasonic waves. Examples of laser diffraction / scattering particle size distribution analyzers that can be used include the LA-500 manufactured by Horiba Ltd. and the SALD-2200 manufactured by Shimadzu Corporation.

[0021] (A) The specific surface area of ​​the magnetic powder is preferably 0.05 m from the viewpoint of improving the relative magnetic permeability. 2 / g or more, more preferably 0.1m 2 / g or more, more preferably 0.3m 2 / g or more. 2 / g or less, more preferably 8m 2 / g or less, more preferably 5m 2 / g or less. The specific surface area of ​​the (A) magnetic powder can be measured by the BET method. When two or more types of (A) magnetic powder are used in combination, it is sufficient that the specific surface area of ​​the entire (A) component is within this range.

[0022] From the viewpoint of improving the relative magnetic permeability, (A) the magnetic powder preferably contains (A-1) magnetic powder having an average particle size of 1 μm or more and (A-2) magnetic powder having an average particle size of less than 1 μm.

[0023] The average particle size of the magnetic powder (A-1) with an average particle size of 1 μm or more is 1 μm or more, preferably 1.2 μm or more, and more preferably 1.5 μm or more. The upper limit of the average particle size of component (A-1) is preferably 10 μm or less, more preferably 9 μm or less, and even more preferably 8 μm or less. The average particle size of component (A-1) can be measured by the method described above.

[0024] The specific surface area of ​​component (A-1) is preferably 0.01 m 2 / g or more, more preferably 0.05m 2 / g or more, more preferably 0.1m 2 / g or more. 2 / g or less, more preferably 1.5m 2 / g or less, more preferably 1m 2 The specific surface area of ​​the component (A-1) can be measured by the method described above.

[0025] The average particle size of the magnetic powder (A-2) having an average particle size of less than 1 μm is less than 1 μm, preferably 0.8 μm or less, and more preferably 0.5 μm or less. The lower limit of the average particle size of component (A-2) is preferably 0.005 μm or more, more preferably 0.01 μm or more, and even more preferably 0.02 μm or more. The average particle size of component (A-2) can be measured by the method described above.

[0026] The specific surface area of ​​component (A-2) is preferably 1 m 2 / g or more, more preferably 2m 2 / g or more, more preferably 3m 2 / g or more. 2 / g or less, more preferably 400m 2 / g or less, more preferably 300m 2 The specific surface area of ​​the component (A-2) can be measured by the method described above.

[0027] A preferred embodiment of component (A) preferably includes (A-1) a magnetic powder having an average particle size of 1 μm or more and 10 μm or less, and (A-2) a magnetic powder having an average particle size of 0.005 μm or more and less than 1 μm, more preferably includes (A-1) a magnetic powder having an average particle size of 1.2 μm or more and 9 μm or less, and (A-2) a magnetic powder having an average particle size of 0.01 μm or more and less than 0.8 μm, and even more preferably includes (A-1) a magnetic powder having an average particle size of 1.5 μm or more and 8 μm or less, and (A-2) a magnetic powder having an average particle size of 0.02 μm or more and less than 0.5 μm.

[0028] From the viewpoint of improving the relative magnetic permeability and reducing the loss factor, the content (volume %) of the (A) magnetic powder is preferably 40% by volume or more, more preferably 50% by volume or more, and even more preferably 60% by volume or more, when the nonvolatile components in the magnetic paste are taken as 100% by volume, and is also preferably 85% by volume or less, more preferably 80% by volume or less, and even more preferably 70% by volume or less.

[0029] From the viewpoint of improving the relative magnetic permeability and reducing the loss factor, the content (mass %) of the (A) magnetic powder is preferably 70 mass % or more, more preferably 75 mass % or more, and even more preferably 80 mass % or more, when the nonvolatile components in the magnetic paste are taken as 100 mass %, and is also preferably 98 mass % or less, more preferably 95 mass % or less, and even more preferably 90 mass % or less. In the present invention, the content of each component in the magnetic paste is a value when the non-volatile components in the magnetic paste are taken as 100 mass %, unless otherwise specified.

[0030] When component (A) includes components (A-1) and (A-2), the content (mass %) of component (A-1) is preferably 65 mass % or more, more preferably 70 mass % or more, based on 100 mass % of the nonvolatile components in the magnetic paste, from the viewpoint of improving the relative permeability and reducing the loss factor, and is preferably 98 mass % or less, more preferably 95 mass % or less, and even more preferably 90 mass % or less.

[0031] When component (A) includes components (A-1) and (A-2), the content (mass %) of component (A-2) is preferably 5 mass % or more, more preferably 10 mass % or more, and even more preferably 15 mass % or more, based on 100 mass % of the nonvolatile components in the magnetic paste, from the viewpoint of improving the relative permeability and reducing the loss factor. Also, it is preferably 98 mass % or less, more preferably 95 mass % or less, and even more preferably 90 mass % or less.

[0032] When the content of component (A-1) when the nonvolatile components in the magnetic paste are taken as 100% by mass is a1, and the content of component (A-2) when the nonvolatile components in the magnetic paste are taken as 100% by mass is a2, a1 / a2 is preferably 10 or less, more preferably 8 or less, and even more preferably 5 or less, and is preferably 1 or more, more preferably 2 or more, and even more preferably 3 or more. By adjusting the content of component (A) so that a1 / a2 falls within this range, it is possible to obtain the desired effects of the present invention more significantly.

[0033] <(B) Epoxy resin> The magnetic paste contains, as component (B), an epoxy resin (B). Examples of the epoxy resin (B) include bisphenol A epoxy resins, bisphenol F epoxy resins, bisphenol S epoxy resins, bisphenol AF epoxy resins, dicyclopentadiene epoxy resins, trisphenol epoxy resins, phenol novolac epoxy resins, tert-butyl-catechol epoxy resins, epoxy resins having a condensed ring structure such as naphthol novolac epoxy resins, naphthalene epoxy resins, naphthol epoxy resins, and anthracene epoxy resins, glycidylamine epoxy resins, glycidyl ester epoxy resins, cresol novolac epoxy resins, biphenyl epoxy resins, linear aliphatic epoxy resins, epoxy resins having a butadiene structure, alicyclic epoxy resins, heterocyclic epoxy resins, spiro ring-containing epoxy resins, cyclohexanedimethanol epoxy resins, trimethylol epoxy resins, tetraphenylethane epoxy resins, and alicyclic diglycidyl ether epoxy resins. The epoxy resins may be used singly or in combination of two or more. (B) The epoxy resin is preferably at least one selected from the group consisting of alicyclic diglycidyl ether epoxy resins, bisphenol A epoxy resins, and bisphenol F epoxy resins.

[0034] The (B) epoxy resin preferably contains an epoxy resin having two or more epoxy groups per molecule. The (B) epoxy resin preferably has an aromatic structure, and when two or more epoxy resins are used, it is more preferable that at least one of them has an aromatic structure. The aromatic structure is a chemical structure generally defined as aromatic, and also includes polycyclic aromatics and aromatic heterocycles. The proportion of the epoxy resin having two or more epoxy groups per molecule is preferably 50% by mass or more, more preferably 60% by mass or more, and particularly preferably 70% by mass or more, based on 100% by mass of the nonvolatile components of the epoxy resin.

[0035] Epoxy resins include epoxy resins that are liquid at a temperature of 25°C (hereinafter sometimes referred to as "liquid epoxy resins") and epoxy resins that are solid at a temperature of 25°C (hereinafter sometimes referred to as "solid epoxy resins"). The magnetic paste may contain only liquid epoxy resin as the (B) epoxy resin, only solid epoxy resin, or a combination of liquid epoxy resin and solid epoxy resin, but from the viewpoint of reducing the viscosity of the magnetic paste, it is preferable that the magnetic paste contains a liquid epoxy resin.

[0036] Preferred liquid epoxy resins include glycirol-type epoxy resins, bisphenol A-type epoxy resins, bisphenol F-type epoxy resins, bisphenol AF-type epoxy resins, naphthalene-type epoxy resins, glycidyl ester-type epoxy resins, glycidyl amine-type epoxy resins, phenol novolac-type epoxy resins, alicyclic epoxy resins having an ester skeleton, cyclohexanedimethanol-type epoxy resins, alicyclic diglycidyl ether-type epoxy resins, alicyclic glycidyl ether-type epoxy resins, alicyclic glycidyl ether-type epoxy resins, and epoxy resins having a butadiene structure, and more preferred are bisphenol A-type epoxy resins, bisphenol F-type epoxy resins, alicyclic diglycidyl ether-type epoxy resins, and alicyclic glycidyl ether-type epoxy resins. Specific examples of liquid epoxy resins include "HP4032", "HP4032D", and "HP4032SS" (naphthalene type epoxy resins) manufactured by DIC Corporation; "828US", "jER828EL" (bisphenol A type epoxy resin), "jER807" (bisphenol F type epoxy resin), and "jER152" (phenol novolac type epoxy resin) manufactured by Mitsubishi Chemical Corporation; "630" and "630LSD" manufactured by Mitsubishi Chemical Corporation; "ED-523T" (glycirol type epoxy resin (ADEKA glycirol)), "EP-3980S" (glycidylamine type epoxy resin), and "EP-4088S" ( dicyclopentadiene-type epoxy resins); "ZX1059" (a mixture of bisphenol A-type epoxy resin and bisphenol F-type epoxy resin), "EX-201" (alicyclic glycidyl ether-type epoxy resin), "ZX1658" and "ZX1658GS" (alicyclic diglycidyl ether-type epoxy resin) manufactured by Nippon Steel Chemical & Material Co., Ltd.; "EX-721" (glycidyl ester-type epoxy resin) manufactured by Nagase ChemteX Corporation; "Celloxide 2021P" (alicyclic epoxy resin having an ester skeleton) and "PB-3600" (epoxy resin having a butadiene structure) manufactured by Daicel Corporation. These may be used alone or in combination of two or more.

[0037] As the solid epoxy resin, naphthalene-type tetrafunctional epoxy resin, cresol novolac-type epoxy resin, dicyclopentadiene-type epoxy resin, trisphenol-type epoxy resin, naphthol-type epoxy resin, biphenyl-type epoxy resin, naphthylene ether-type epoxy resin, anthracene-type epoxy resin, bisphenol A-type epoxy resin, and tetraphenylethane-type epoxy resin are preferred, and naphthalene-type tetrafunctional epoxy resin, naphthol-type epoxy resin, and biphenyl-type epoxy resin are more preferred. Specific examples of solid epoxy resins include "HP4032H" (naphthalene-type epoxy resin), "HP-4700", "HP-4710" (naphthalene-type tetrafunctional epoxy resin), "N-690" (cresol novolac-type epoxy resin), "N-695" (cresol novolac-type epoxy resin), "HP-7200", "HP-7200HH", "HP-7200H" (dicyclopentadiene-type epoxy resin), "EXA-7311", "EXA-7311-G3", "EXA-7311-G4", "EXA-7311-G4S", and "HP6000" (naphthylene ether-type epoxy resin), manufactured by DIC Corporation; and "EPPN-502H" (trisphenol-type epoxy resin), "NC7000L" (naphthol novolac-type epoxy resin), "NC3000H", and "NC30 00, "NC3000L," and "NC3100" (biphenyl-type epoxy resins); "ESN475V" (naphthalene-type epoxy resin) and "ESN485" (naphthol novolac-type epoxy resin) manufactured by Nippon Steel Chemical & Material Co., Ltd.; "YX4000H," "YL6121" (biphenyl-type epoxy resin), "YX4000HK" (bixylenol-type epoxy resin), and "YX8800" (anthracene-type epoxy resin) manufactured by Mitsubishi Chemical Corporation; "PG-100" and "CG-500" manufactured by Osaka Gas Chemicals Co., Ltd.; "YL7760" (bisphenol AF-type epoxy resin), "YL7800" (fluorene-type epoxy resin), "jER1010" (solid bisphenol A-type epoxy resin), and "jER1031S" (tetraphenylethane-type epoxy resin) manufactured by Mitsubishi Chemical Corporation. These may be used alone or in combination of two or more.

[0038] When a liquid epoxy resin and a solid epoxy resin are used in combination as the (B) epoxy resin, the ratio thereof (liquid epoxy resin:solid epoxy resin) is preferably in the range of 1:0.1 to 1:4 by mass. By setting the ratio of the liquid epoxy resin to the solid epoxy resin in this range, effects such as the ability to obtain a cured product with sufficient breaking strength can be obtained. From the viewpoint of the above effects, the ratio of the liquid epoxy resin to the solid epoxy resin (liquid epoxy resin:solid epoxy resin) is more preferably in the range of 1:0.3 to 1:3.5 by mass, even more preferably in the range of 1:0.6 to 1:3, and particularly preferably in the range of 1:0.8 to 1:2.5.

[0039] From the viewpoint of obtaining a magnetic layer exhibiting good mechanical strength, the content of (B) epoxy resin is preferably 1% by mass or more, more preferably 3% by mass or more, even more preferably 5% by mass or more, or even 10% by mass or more, when the nonvolatile components in the magnetic paste are taken as 100% by mass. The upper limit of the epoxy resin content is not particularly limited as long as the effects of the present invention are achieved, but is preferably 30% by mass or less, more preferably 25% by mass or less, and even more preferably 20% by mass or less.

[0040] The content (vol %) of (B) epoxy resin is preferably 1% by volume or more, more preferably 3% by volume or more, and even more preferably 5% by volume or more, assuming that the nonvolatile components in the magnetic paste are 100% by volume. The upper limit is not particularly limited as long as the effects of the present invention are achieved, but is preferably 25% by volume or less, more preferably 20% by volume or less, and even more preferably 15% by volume or less.

[0041] The epoxy equivalent of the (B) epoxy resin is preferably 50 g / eq to 5000 g / eq, more preferably 50 g / eq to 3000 g / eq, even more preferably 80 g / eq to 2000 g / eq, and even more preferably 110 g / eq to 1000 g / eq. This range ensures sufficient crosslink density in the cured product, resulting in a magnetic layer with low surface roughness. The epoxy equivalent can be measured according to JIS K7236 and is the mass of the resin containing one equivalent of epoxy groups.

[0042] The weight-average molecular weight of the (B) epoxy resin is preferably 100 to 5000, more preferably 250 to 3000, and even more preferably 400 to 1500. Here, the weight-average molecular weight of the epoxy resin is a weight-average molecular weight in terms of polystyrene measured by gel permeation chromatography (GPC).

[0043] <(C) Dispersant> The magnetic paste contains, as component (C), a dispersant having a polyester skeleton represented by the following general formula (1). [ka] (In general formula (1), each R independently represents a divalent hydrocarbon group having 2 to 10 carbon atoms, and n represents an integer of 2 to 1000.)

[0044] As mentioned above, the greater the content of (A) magnetic powder, the higher the viscosity of the magnetic paste, and the lower the mechanical strength of the cured product of the magnetic paste. In the present invention, the magnetic paste contains component (C) as a dispersant, so the viscosity can be lowered compared to a paste that does not contain component (C) (i.e., a paste that has the same composition as the magnetic paste except for not containing component (C)). Therefore, even if the content of (A) magnetic powder is high, the increase in viscosity of the magnetic paste can be suppressed, and the mechanical strength of the cured product of the magnetic paste can be improved.

[0045] The component (C) has a polyester skeleton represented by general formula (1). [ka] (In general formula (1), each R independently represents a divalent hydrocarbon group having 2 to 10 carbon atoms, and n represents an integer of 2 to 1000.)

[0046] R in general formula (1) represents a divalent hydrocarbon group having 2 to 10 carbon atoms. The hydrocarbon group has 2 or more carbon atoms, preferably 3 or more, and more preferably 4 or more. The upper limit of the number of carbon atoms is 10 or less, preferably 8 or less, and more preferably 6 or less. The hydrocarbon group may be linear, branched, or cyclic, with linear and branched hydrocarbon groups being preferred. Examples of the hydrocarbon group include aliphatic hydrocarbon groups and aromatic hydrocarbon groups, with aliphatic hydrocarbon groups being preferred. Specific examples of the hydrocarbon group include alkylene groups, alkenylene groups, alkynylene groups, and arylene groups. Of these, alkylene groups are preferred as the hydrocarbon group from the viewpoint of significantly achieving the effects of the present invention.

[0047] Examples of alkylene groups include ethylene, propylene, butylene, pentylene, hexylene, heptylene, octylene, nonylene, and decylene groups. Examples of alkenylene groups include ethenylene, propenylene, butenylene, pentenylene, hexenylene, heptenylene, octenylene, nonenylene, and decenylene groups. Examples of alkynylene groups include ethynylene, propynylene, butynylene, pentynylene, hexynylene, heptynylene, octynylene, nonenylene, and decynylene groups. Examples of arylene groups include phenylene and naphthylene groups. Among these, butylene and pentylene groups are preferred as R.

[0048] The divalent hydrocarbon group represented by R in the general formula (1) may or may not have a substituent. The substituent is not particularly limited, and examples thereof include a halogen atom, -OH, -OC 1-6An alkyl group, -N(C 1-10 alkyl group)2, C 1-10 alkyl group, C 6-10 aryl group, -NH2, -CN, -C(O)O-C 1-10 alkyl group, -COOH, -C(O)H, -NO2 and the like. Here, the term "C p-q "(p and q are positive integers and satisfy p < q.) represents that the number of carbon atoms of the organic group described immediately after this term is p to q. For example, the expression "C 1-10 alkyl group" indicates an alkyl group having 1 to 10 carbon atoms. These substituents may be bonded to each other to form a ring, and the ring structure includes spiro rings and fused rings.

[0049] The above-mentioned substituents may further have a substituent (hereinafter sometimes referred to as a "secondary substituent"). As the secondary substituent, the same ones as the above-mentioned substituents may be used unless otherwise specified.

[0050] In the general formula (1), n represents an integer of 2 to 1000. n is 2 or more, preferably 5 or more, more preferably 10 or more. The upper limit is 1000 or less, preferably 500 or less, more preferably 100 or less, 50 or less.

[0051] (Component (C) may contain any skeleton in addition to the polyester skeleton represented by the general formula (1) as long as it does not inhibit the effects of the present invention. Examples of any skeleton include a polyester skeleton in which R in the general formula (1) is a divalent hydrocarbon group having 1 or 11 or more carbon atoms (n is the same as in formula (1)), and a polyallylamine skeleton. For example, the terminals of the polyester skeleton are not particularly limited.

[0052] Examples of the terminal of component (C) include a residue of a carboxylic acid, a hydroxy group, a hydrogen atom, and the like, which will be described later.

[0053] The component (C) having a polyester skeleton represented by the general formula (1) can be produced, for example, by reacting a lactone and a carboxylic acid represented by the general formula (2). [ka] (In general formula (2), R 2 is the same as R in general formula (1).

[0054] Examples of lactones represented by general formula (2) include ε-caprolactone, β-propiolactone, γ-butyrolactone, δ-valerolactone, β-methyl-δ-valerolactone, 4-methylcaprolactone, and 2-methylcaprolactone.

[0055] The carboxylic acid may be one that functions as an initiator for ring-opening polymerization of the lactone represented by general formula (2). Examples of such carboxylic acids include hydroxycarboxylic acids such as ricinoleic acid, ricinoleic acid, 9- and 10-hydroxystearic acid, castor oil fatty acid, hydrogenated castor oil fatty acid, lactic acid, 12-hydroxystearic acid, and glycolic acid; dodecanoic acid, and stearic acid. Among these, hydroxycarboxylic acids are preferred from the viewpoint of achieving significant effects of the present invention.

[0056] The reaction temperature is preferably 120 to 220° C., more preferably 160 to 210° C. The reaction time is preferably 0.5 to 72 hours. When the reaction is carried out under a nitrogen stream, a polyester with a high degree of polymerization can be obtained.

[0057] In addition, the reaction may be carried out in the presence of a polymerization catalyst or a polymerization initiator, if necessary, in order to control the reaction.

[0058] Examples of the polymerization catalyst include quaternary ammonium salts such as tetramethylammonium chloride, tetrabutylammonium chloride, tetramethylammonium bromide, tetrabutylammonium bromide, tetramethylammonium iodide, tetrabutylammonium iodide, benzyltrimethylammonium chloride, benzyltrimethylammonium bromide, and benzyltrimethylammonium iodide; tetramethylphosphonium chloride, tetrabutylphosphonium chloride, tetramethylphosphonium bromide, tetrabutylphosphonium bromide, tetramethylphosphonium iodide, tetrabutylphosphonium iodide, and benzyltrimethylammonium iodide; Examples of suitable phosphonium compounds include quaternary phosphonium salts such as methylphosphonium chloride, benzyltrimethylphosphonium bromide, benzyltrimethylphosphonium iodide, tetraphenylphosphonium chloride, tetraphenylphosphonium bromide, and tetraphenylphosphonium iodide; phosphorus compounds such as triphenylphosphine; organic carboxylates such as potassium acetate, sodium acetate, potassium benzoate, and sodium benzoate; alkali metal alcoholates such as sodium alcoholate and potassium alcoholate; tertiary amines; organic tin compounds; organic aluminum compounds; organic titanate compounds such as tetrabutyl titanate; and zinc compounds such as zinc chloride.

[0059] Examples of the polymerization initiator include aliphatic monocarboxylic acids such as acetic acid, propionic acid, caprylic acid, nonanoic acid, capric acid, octylic acid, lauric acid, myristic acid, palmitic acid, stearic acid, isononanoic acid, and arachic acid; and aromatic monocarboxylic acids such as benzoic acid and p-butylbenzoic acid.

[0060] In producing component (C), in addition to the lactone and carboxylic acid represented by general formula (2), any other monomer may be used, as long as it does not impair the effects of the present invention. Examples of such optional monomers include polyallylamine. For example, when polyallylamine is used as the optional monomer, component (C) containing a polyallylamine skeleton in addition to the polyester skeleton represented by general formula (1) can be produced. The reaction temperature and reaction time are the same as those used in producing component (C) having a polyester skeleton represented by general formula (1).

[0061] Polyallylamine can be obtained by polymerizing allylamine in the presence of a polymerization initiator and / or a chain transfer catalyst.

[0062] The polymerization initiator is not particularly limited, and examples thereof include ketone peroxides such as methyl ethyl ketone, diacyl peroxides such as benzoyl peroxide, peroxydicarbonates such as diisopropyl peroxydicarbonate, peroxyketals such as 1,1-bis(t-butylperoxy)cyclohexane, hydroperoxides such as t-butyl hydroperoxide, peroxyesters such as t-butyl peroxypivalate, and also azobisisobutyronitrile, hydrogen peroxide, and ferrous salts. Furthermore, the polymerization initiators described in JP-B-2-14364 may also be used. These may be used alone or in combination of two or more.

[0063] The chain transfer catalyst is not particularly limited, and examples thereof include alkyl mercaptans such as lauryl mercaptan, thiocarboxylic acids such as mercaptoacetic acid, 2-mercaptopropionic acid, and 3-mercaptopropionic acid, and thiocarboxylic acid esters such as butyl thioglycolate and 2-ethylhexyl thioglycolate. These may be used alone or in combination of two or more.

[0064] The weight-average molecular weight of polyallylamine is preferably 150 to 100,000, and more preferably 600 to 20,000. When the weight-average molecular weight is 150 or more, the adsorptive power to particles of component (A) and the like is improved, improving particle dispersibility, while when the weight-average molecular weight is 100,000 or less, particle aggregation can be suppressed, improving particle dispersibility. Note that polyallylamine of any weight-average molecular weight may be produced using the method described in JP-B-2-14364.

[0065] Commercially available polyallylamine products can be used, such as "PAA-01," "PAA-03," "PAA-05," "PAA-08," "PAA-15," "PAA-15C," and "PAA-25," manufactured by Nittobo Medical Co., Ltd.

[0066] The pH of component (C) in the present invention can usually be 4 or more and less than 7. The pH can be measured by an indicator method. Specifically, the pH can be measured by immersing a measurement sample (22°C) with a dispersant concentration of 0.1 g / mL, prepared by dissolving the dispersant in acetone, into a pH test paper. The pH test paper can be one that can measure pH in the acidic range (for example, one with a measurement range of pH 0.0 to 14.0, pH 1.0 to 14.0, or pH 0.5 to 5.0), such as the pH test paper "pH Test Paper pH 1-14" (pH measurement range pH 1.0 to 14.0) manufactured by AS ONE Corporation.

[0067] From the viewpoint of achieving the remarkable effects of the present invention, the acid value of component (C) is preferably 1 mgKOH / g or more, more preferably 3 mgKOH / g or more, even more preferably 5 mgKOH / g, and is preferably 30 mgKOH / g or less, more preferably 25 mgKOH / g or less, even more preferably 20 mgKOH / g or less. The acid value can be measured by neutralization titration.

[0068] When component (C) is a dispersant reacted with polyallylamine, the amine value is, from the viewpoint of significantly obtaining the effects of the present invention, preferably 1 mgKOH / g or more, more preferably 5 mgKOH / g or more, even more preferably 10 mgKOH / g or more, and preferably 45 mgKOH / g or less, more preferably 40 mgKOH / g or less, even more preferably 35 mgKOH / g or less. The amine value can be measured by neutralization titration.

[0069] From the viewpoint of significantly achieving the effects of the present invention, the weight average molecular weight of component (C) is preferably at least 2000, more preferably at least 3000, even more preferably at least 5000, and is preferably at most 50000, more preferably at most 40000, even more preferably at most 30000. The weight average molecular weight is a polystyrene-equivalent weight molecular weight measured by gel permeation chromatography (GPC).

[0070] In order to significantly exert the effects of the present invention, the content of component (C) is preferably 0.1% by mass or more, more preferably 0.3% by mass or more, and even more preferably 0.5% by mass or more, when the non-volatile components in the magnetic paste are taken as 100% by mass, and the upper limit is preferably 5% by mass or less, more preferably 4% by mass or less, and even more preferably 3% by mass or less.

[0071] When the mass of component (C) when the nonvolatile components in the magnetic paste are taken as 100% by mass is taken as C1, and the mass of magnetic powder (A) when the nonvolatile components in the magnetic paste are taken as 100% by mass is taken as A1, (C1 / A1) x 100 is preferably 0.1 or more, more preferably 0.3 or more, even more preferably 0.5 or more, and is preferably 10 or less, more preferably 5 or less, and even more preferably 1 or less. By adjusting the masses of component (A) and (C) so that (C1 / A1) x 100 is within this range, it is possible to obtain the desired effects of the present invention more significantly.

[0072] <(D) Curing agent> The magnetic paste contains a (D) curing agent. The (D) curing agent includes an epoxy resin curing agent that has the function of curing the (B) epoxy resin, and a curing accelerator that has the function of accelerating the curing rate of the (B) epoxy resin. The magnetic paste preferably contains an epoxy resin curing agent as the (D) curing agent. The (D) curing agent may contain a curing accelerator together with the epoxy resin curing agent. The curing accelerator is usually used in combination with the epoxy resin curing agent.

[0073] -Epoxy resin hardener- Epoxy resin curing agents typically react with epoxy resins to harden the magnetic paste. Examples of epoxy resin curing agents include phenol-based epoxy resin curing agents, naphthol-based epoxy resin curing agents, active ester-based epoxy resin curing agents, acid anhydride-based epoxy resin curing agents, benzoxazine-based epoxy resin curing agents, cyanate ester-based epoxy resin curing agents, and imidazole-based epoxy resin curing agents. Acid anhydride-based epoxy resin curing agents and imidazole-based epoxy resin curing agents are preferred as epoxy resin curing agents from the viewpoint of reducing the viscosity of the magnetic paste, and imidazole-based epoxy resin curing agents are more preferred from the viewpoint of the mechanical strength of the resulting cured product. One type of epoxy resin curing agent may be used alone, or two or more types may be used in combination.

[0074] As the phenolic epoxy resin curing agent and naphthol epoxy resin curing agent, from the viewpoint of heat resistance and water resistance, a phenolic epoxy resin curing agent having a novolac structure or a naphthol epoxy resin curing agent having a novolac structure is preferred. As the phenolic epoxy resin curing agent, a nitrogen-containing phenolic epoxy resin curing agent is preferred, a triazine skeleton-containing phenolic epoxy resin curing agent is more preferred, and a triazine skeleton-containing phenolic novolac epoxy resin curing agent is even more preferred.

[0075] Specific examples of phenol-based epoxy resin curing agents and naphthol-based epoxy resin curing agents include "MEH-7700," "MEH-7810," and "MEH-7851" manufactured by Meiwa Chemical Industry Co., Ltd.; "NHN," "CBN," and "GPH" manufactured by Nippon Kayaku Co., Ltd.; "SN170," "SN180," "SN190," "SN475," "SN485," "SN495V," "SN375," and "SN395" manufactured by Nippon Steel & Sumikin Chemical Co., Ltd.; "TD-2090," "LA-7052," "LA-7054," "LA-1356," "LA-3018-50P," "EXB-9500," "HPC-9500," "KA-1160," "KA-1163," and "KA-1165" manufactured by DIC Corporation; and "GDP-6115L" and "GDP-6115H" manufactured by Gun-ei Chemical Co., Ltd.

[0076] The active ester-based epoxy resin curing agent is not particularly limited, but compounds having two or more highly reactive ester groups per molecule, such as phenol esters, thiophenol esters, N-hydroxyamine esters, and esters of heterocyclic hydroxy compounds, are generally preferred. The active ester-based epoxy resin curing agent is preferably one obtained by the condensation reaction of a carboxylic acid compound and / or a thiocarboxylic acid compound with a hydroxy compound and / or a thiol compound. From the viewpoint of improving heat resistance, active ester-based epoxy resin curing agents obtained from a carboxylic acid compound and a hydroxy compound are preferred, and active ester-based epoxy resin curing agents obtained from a carboxylic acid compound and a phenol compound and / or a naphthol compound are more preferred. Examples of carboxylic acid compounds include benzoic acid, acetic acid, succinic acid, maleic acid, itaconic acid, phthalic acid, isophthalic acid, terephthalic acid, and pyromellitic acid. Examples of phenol compounds or naphthol compounds include hydroquinone, resorcinol, bisphenol A, bisphenol F, bisphenol S, phenolphthalene, methylated bisphenol A, methylated bisphenol F, methylated bisphenol S, phenol, o-cresol, m-cresol, p-cresol, catechol, α-naphthol, β-naphthol, 1,5-dihydroxynaphthalene, 1,6-dihydroxynaphthalene, 2,6-dihydroxynaphthalene, dihydroxybenzophenone, trihydroxybenzophenone, tetrahydroxybenzophenone, phloroglucin, benzenetriol, dicyclopentadiene-type diphenol compounds, and phenol novolak. Here, "dicyclopentadiene-type diphenol compounds" refers to diphenol compounds obtained by condensing one dicyclopentadiene molecule with two phenol molecules.

[0077] Specifically, active ester-based epoxy resin curing agents containing a dicyclopentadiene-type diphenol structure, active ester-based epoxy resin curing agents containing a naphthalene structure, active ester-based epoxy resin curing agents containing an acetylated product of phenol novolac, and active ester-based epoxy resin curing agents containing a benzoylated product of phenol novolac are preferred. The "dicyclopentadiene-type diphenol structure" refers to a divalent structure consisting of phenylene-dicyclopentylene-phenylene.

[0078] Commercially available active ester epoxy resin curing agents include DIC Corporation's "EXB9451," "EXB9460," "EXB9460S," "HPC-8000-65T," "HPC-8000H-65™," and "EXB-8000L-65™," which are active ester epoxy resin curing agents containing a dicyclopentadiene-type diphenol structure; DIC Corporation's "EXB9416-70BK," which is an active ester compound containing a naphthalene structure; Mitsubishi Chemical Corporation's "DC808," which is an active ester epoxy resin curing agent containing an acetylated phenol novolac; Mitsubishi Chemical Corporation's "YLH1026," "YLH1030," and "YLH1048," which are active ester epoxy resin curing agents containing a benzoylated phenol novolac; and Mitsubishi Chemical Corporation's "DC808," which is an active ester epoxy resin curing agent that is an acetylated phenol novolac.

[0079] Acid anhydride-based epoxy resin curing agents include epoxy resin curing agents having one or more acid anhydride groups in one molecule. Specific examples of acid anhydride-based epoxy resin curing agents include phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, methylnadic anhydride, hydrogenated methylnadic anhydride, trialkyltetrahydrophthalic anhydride, dodecenyl succinic anhydride, 5-(2,5-dioxotetrahydro-3-furanyl)-3-methyl-3-cyclohexene-1,2-dicarboxylic anhydride, trimellitic anhydride, pyromellitic anhydride, benzophenone tetracarboxylic anhydride, methyl tetrahydrophthalic anhydride, methyl hexahydrophthalic anhydride, methyl hexahydrophthalic anhydride, methyl hexahydrophthalic anhydride, methyl hexahydrophthalic anhydride, trialkyltetrahydrophthalic anhydride, dodecenyl succinic anhydride, 5-(2,5-dioxotetrahydro-3-furanyl)-3-methyl-3-cyclohexene-1,2-dicarboxylic anhydride, trimellitic anhydride, pyromellitic anhydride, benzophenone tetracarboxylic anhydride, methyl hexahydrophthalic anhydride, methyl hexahydrophthalic anhydride, trialkyl tetrahydrophthalic anhydride, dodecenyl succinic anhydride, 5-(2,5-dioxotetrahydro-3-furanyl)-3-methyl-3-cyclohexene-1,2-dicarboxylic ... Examples of suitable anhydrides include carboxylic acid dianhydride, biphenyltetracarboxylic acid dianhydride, naphthalenetetracarboxylic acid dianhydride, oxydiphthalic dianhydride, 3,3'-4,4'-diphenylsulfonetetracarboxylic acid dianhydride, 1,3,3a,4,5,9b-hexahydro-5-(tetrahydro-2,5-dioxo-3-furanyl)-naphtho[1,2-C]furan-1,3-dione, ethylene glycol bis(anhydrotrimellitate), and polymeric anhydrides such as styrene-maleic acid resin, which is a copolymer of styrene and maleic acid.

[0080] Commercially available acid anhydride epoxy resin curing agents include "HNA-100" and "MH-700" manufactured by New Japan Chemical Co., Ltd.

[0081] Specific examples of benzoxazine-based epoxy resin curing agents include "HFB2006M" manufactured by Showa Polymer Co., Ltd., and "Pd" and "Fa" manufactured by Shikoku Chemical Industry Co., Ltd.

[0082] Examples of cyanate ester-based epoxy resin curing agents include bifunctional cyanate resins such as bisphenol A dicyanate, polyphenol cyanate, oligo(3-methylene-1,5-phenylene cyanate), 4,4'-methylenebis(2,6-dimethylphenyl cyanate), 4,4'-ethylidene diphenyl dicyanate, hexafluorobisphenol A dicyanate, 2,2-bis(4-cyanate)phenylpropane, 1,1-bis(4-cyanate phenylmethane), bis(4-cyanate-3,5-dimethylphenyl)methane, 1,3-bis(4-cyanate phenyl-1-(methylethylidene))benzene, bis(4-cyanate phenyl)thioether, and bis(4-cyanate phenyl)ether; multifunctional cyanate resins derived from phenol novolac and cresol novolac; and prepolymers in which these cyanate resins are partially converted to triazine. Specific examples of cyanate ester-based epoxy resin curing agents include "PT30" and "PT60" (both phenol novolac-type multifunctional cyanate ester resins) manufactured by Lonza Japan Co., Ltd., "BA230" and "BA230S75" (prepolymers in which part or all of bisphenol A dicyanate has been triazine-converted to form a trimer).

[0083] Examples of imidazole-based epoxy resin curing agents include 2-methylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 1,2-dimethylimidazole, 2-ethyl-4-methylimidazole, 1,2-dimethylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 1-benzyl-2-methylimidazole, and 1-benzyl-2-phenylimidazoline. 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 1-cyanoethyl-2-phenylimidazole, 1-cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2-phenylimidazolium trimellitate, 1-cyanoethyl-2-phenylimidazolium trimellitate, 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine, 2,4-Diamino-6-[2'-undecylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-ethyl-4'-methylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine isocyanuric acid adduct, 2-phenylimidazole isocyanuric acid adduct, 2-phenyl-4,5-dihydroxymethylimidazole, 2- Examples thereof include imidazole compounds such as phenyl-4-methyl-5-hydroxymethylimidazole, 2,3-dihydro-1H-pyrrolo[1,2-a]benzimidazole, 1-dodecyl-2-methyl-3-benzylimidazolium chloride, 2-methylimidazoline, and 2-phenylimidazoline, as well as adducts of imidazole compounds with epoxy resins, with 2-ethyl-4-methylimidazole and 1-benzyl-2-phenylimidazole being preferred.

[0084] As the imidazole-based epoxy resin curing agent, commercially available products may be used, such as "2MZA-PW" and "2PHZ-PW" manufactured by Shikoku Chemical Industry Co., Ltd., and "P200-H50" manufactured by Mitsubishi Chemical Corporation.

[0085] The ratio of the amount of epoxy resin to the amount of epoxy resin curing agent, expressed as the ratio of [total number of epoxy groups in the epoxy resin] to [total number of reactive groups in the epoxy resin curing agent], is preferably in the range of 1:0.2 to 1:2, more preferably in the range of 1:0.3 to 1:1.5, and even more preferably in the range of 1:0.4 to 1:1. Here, the reactive groups in the epoxy resin curing agent are active hydroxyl groups, active ester groups, etc., and vary depending on the type of epoxy resin curing agent. The total number of epoxy groups in the epoxy resin is the sum of the values ​​obtained by dividing the mass of the nonvolatile components of each epoxy resin by the epoxy equivalent weight for all epoxy resins, and the total number of reactive groups in the epoxy resin curing agent is the sum of the values ​​obtained by dividing the mass of the nonvolatile components of each epoxy resin curing agent by the reactive group equivalent weight for all epoxy resin curing agents. By maintaining the ratio of epoxy resin to epoxy resin curing agent within this range, the heat resistance of the cured product is further improved.

[0086] -Curing accelerator- The curing accelerator typically acts as a catalyst in the curing reaction of the epoxy resin, accelerating the curing reaction. Examples of the curing accelerator include amine-based curing accelerators, imidazole-based curing accelerators, phosphorus-based curing accelerators, guanidine-based curing accelerators, and metal-based curing accelerators. From the viewpoint of reducing the viscosity of the magnetic paste, amine-based curing accelerators, imidazole-based curing accelerators, and guanidine-based curing accelerators are preferred, and from the viewpoint of improving the mechanical strength of the resulting cured product, imidazole-based curing accelerators are more preferred. One type of curing accelerator may be used alone, or two or more types may be used in combination. The curing accelerator is generally used in combination with an epoxy resin curing agent.

[0087] Examples of the amine curing accelerator include trialkylamines such as triethylamine and tributylamine, 4-dimethylaminopyridine, benzyldimethylamine, 2,4,6-tris(dimethylaminomethyl)phenol, and 1,8-diazabicyclo(5,4,0)-undecene, with 4-dimethylaminopyridine and 1,8-diazabicyclo(5,4,0)-undecene being preferred.

[0088] As the amine-based curing accelerator, commercially available products may be used, such as "PN-50," "PN-23," and "MY-25" manufactured by Ajinomoto Fine-Techno Co., Ltd.

[0089] The imidazole-based curing accelerator is the same as the imidazole-based epoxy resin curing agent described above. When used in combination with other epoxy resin curing agents, the imidazole-based epoxy resin curing agent may function as a curing accelerator.

[0090] Examples of phosphorus-based curing accelerators include triphenylphosphine, phosphonium borate compounds, tetraphenylphosphonium tetraphenylborate, n-butylphosphonium tetraphenylborate, tetrabutylphosphonium decanoate, (4-methylphenyl)triphenylphosphonium thiocyanate, tetraphenylphosphonium thiocyanate, and butyltriphenylphosphonium thiocyanate, with triphenylphosphine and tetrabutylphosphonium decanoate being preferred.

[0091] Examples of guanidine-based curing accelerators include dicyandiamide, 1-methylguanidine, 1-ethylguanidine, 1-cyclohexylguanidine, 1-phenylguanidine, 1-(o-tolyl)guanidine, dimethylguanidine, diphenylguanidine, trimethylguanidine, tetramethylguanidine, pentamethylguanidine, 1,5,7-triazabicyclo[4.4.0]dec-5-ene, and 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene. Examples of suitable biguanide include 1-methylbiguanide, 1-ethylbiguanide, 1-n-butylbiguanide, 1-n-octadecylbiguanide, 1,1-dimethylbiguanide, 1,1-diethylbiguanide, 1-cyclohexylbiguanide, 1-allylbiguanide, 1-phenylbiguanide, and 1-(o-tolyl)biguanide. Of these, dicyandiamide and 1,5,7-triazabicyclo[4.4.0]dec-5-ene are preferred.

[0092] Examples of metal-based curing accelerators include organometallic complexes or organometallic salts of metals such as cobalt, copper, zinc, iron, nickel, manganese, and tin. Specific examples of organometallic complexes include organic cobalt complexes such as cobalt(II) acetylacetonate and cobalt(III) acetylacetonate, organic copper complexes such as copper(II) acetylacetonate, organic zinc complexes such as zinc(II) acetylacetonate, organic iron complexes such as iron(III) acetylacetonate, organic nickel complexes such as nickel(II) acetylacetonate, and organic manganese complexes such as manganese(II) acetylacetonate. Examples of organometallic salts include zinc octoate, tin octoate, zinc naphthenate, cobalt naphthenate, tin stearate, and zinc stearate.

[0093] The content of (D) curing agent, assuming the non-volatile components in the magnetic paste to be 100% by mass, is preferably 0.1% by mass or more, more preferably 0.3% by mass or more, and even more preferably 0.5% by mass or more, from the viewpoint of reducing the viscosity of the magnetic paste and improving the viscosity pot life, and the upper limit is preferably 5% by mass or less, more preferably 3% by mass or less, and even more preferably 1% by mass or less.

[0094] When the mass of the (D) curing agent when the nonvolatile components in the magnetic paste are taken as 100% by mass is D1, and the mass of the (C) dispersant when the nonvolatile components in the magnetic paste are taken as 100% by mass is C1, C1 / D1 is preferably 0.1 or more, more preferably 0.15 or more, even more preferably 0.2 or more, and is preferably 5 or less, more preferably 3 or less, and even more preferably 2.5 or less. By adjusting the masses of the (C) component and (D) so that C1 / D1 falls within this range, it is possible to obtain the desired effects of the present invention more significantly.

[0095] When the mass of the (A) magnetic powder when the nonvolatile components in the magnetic paste are 100% by mass is defined as A1, the mass of the (B) epoxy resin when the nonvolatile components in the magnetic paste are 100% by mass is defined as B1, the mass of the (C) dispersant when the nonvolatile components in the magnetic paste are 100% by mass is defined as C1, and the mass of the (D) curing agent when the nonvolatile components in the magnetic paste are 100% by mass is defined as D1, then (B1 + C1 + D1) / A1 is preferably 0.01 or more, more preferably 0.05 or more, and even more preferably 0.1 or more, and preferably 1 or less, more preferably 0.5 or less, and even more preferably 0.3 or less. By adjusting the masses of components (A) to (D) so that (B1 + C1 + D1) / A1 falls within this range, the desired effects of the present invention can be more significantly achieved.

[0096] When the mass of the (A) magnetic powder when the nonvolatile components in the magnetic paste are 100% by mass is defined as A1, the mass of the (C) dispersant when the nonvolatile components in the magnetic paste are 100% by mass is defined as C1, and the mass of the (D) curing agent when the nonvolatile components in the magnetic paste are 100% by mass is defined as D1, then ((C1+D1) / A1) x 100 is preferably 0.1 or more, more preferably 0.5 or more, and even more preferably 1 or more, and is preferably 10 or less, more preferably 5 or less, and even more preferably 3 or less. By adjusting the masses of the (A), (C), and (D) components so that ((C1+D1) / A1) x 100 is within this range, it is possible to obtain the desired effects of the present invention more significantly.

[0097] <(E) Other additives> The magnetic paste may further contain (E) other additives as needed, such as, for example, hardening retarders such as triethyl borate; inorganic fillers (excluding those corresponding to magnetic powder); thermoplastic resins; flame retardants; organic fillers; organometallic compounds such as organic copper compounds, organic zinc compounds, and organic cobalt compounds; and resin additives such as thickeners; antifoaming agents; leveling agents; adhesion promoters; and colorants.

[0098] The content of the organic solvent in the magnetic paste described above is preferably less than 1.0% by mass, more preferably 0.8% by mass or less, even more preferably 0.5% by mass or less, and particularly preferably 0.1% by mass or less, based on the total mass of the magnetic paste. There is no particular lower limit, but the content can be 0.001% by mass or more, or none at all. The magnetic paste can have a low viscosity even without containing an organic solvent. By using a small amount of organic solvent in the magnetic paste, the generation of voids due to the evaporation of the organic solvent can be suppressed.

[0099] <Magnetic paste manufacturing method> The magnetic paste can be produced, for example, by a method in which the ingredients are stirred using a stirring device such as a three-roll mixer or a rotary mixer.

[0100] <Physical properties of magnetic paste> The magnetic paste exhibits low viscosity, which provides excellent printability. The viscosity at 25°C is preferably less than 300 Pa·s, more preferably 250 Pa·s or less, and even more preferably 200 Pa·s or less, and is preferably 10 Pa·s or more, preferably 20 Pa·s or more, and more preferably 30 Pa·s or more. The viscosity can be measured, for example, using an E-type viscometer (RE-80U manufactured by Toki Sangyo Co., Ltd.), and details can be determined by the method described in the examples below.

[0101] A cured product obtained by heating a magnetic paste at 180°C for 90 minutes typically exhibits excellent mechanical strength (tensile strength at break). Therefore, the cured product provides a magnetic layer with excellent tensile strength at break. The tensile strength at break is preferably 50 MPa or more, more preferably 60 MPa or more, and even more preferably 70 MPa or more. There is no particular upper limit, but it can be 100 MPa or less. The tensile strength at break can be measured by the method described in the examples below.

[0102] A cured product obtained by heating the magnetic paste at 180°C for 90 minutes exhibits the characteristic of high relative magnetic permeability at a frequency of 100 MHz. Therefore, the cured product provides a magnetic layer with high relative magnetic permeability. The relative magnetic permeability of this cured product at a frequency of 100 MHz is preferably 1 or more, more preferably 3 or more, and even more preferably 7 or more. The upper limit is not particularly limited, but can be 20 or less. The relative magnetic permeability can be measured by the method described in the examples below.

[0103] A cured product obtained by heating a magnetic paste at 180°C for 90 minutes typically exhibits low magnetic loss at a frequency of 100 MHz. Therefore, the cured product provides a magnetic layer with low magnetic loss. The magnetic loss of this cured product at a frequency of 100 MHz is preferably 1 or less, more preferably 0.5 or less, and even more preferably 0.3 or less. The lower limit is not particularly limited, but may be 0.001 or more. Magnetic loss can be measured by the method described in the Examples below.

[0104] [Resin composition] The magnetic paste described above may be in a state other than a paste state, if necessary. For example, the magnetic paste may be in a state other than a paste state during storage or transportation. Thus, the resin composition of the present invention can be obtained in any state. Typically, this resin composition has the same structure, effects, and uses as the magnetic paste described above. Specifically, the resin composition may contain (A) magnetic powder, (B) epoxy resin, (C) dispersant, and (D) curing agent. This resin composition may be the same composition as the magnetic paste described above, except that it may be in a state other than a paste state.

[0105] [Cured product] The cured product of the present invention is obtained by curing the magnetic paste of the present invention. Also, the cured product of the present invention is obtained by curing the resin composition of the present invention. The curing conditions for the magnetic paste and the resin composition may be the conditions of step (2) described below. Furthermore, the magnetic paste and the resin composition may be preheated before being thermally cured, and heating may be performed multiple times, including preheating.

[0106] [Magnetic sheet] The magnetic sheet includes a support and a resin composition layer formed from a magnetic paste provided on the support. The magnetic sheet also includes a support and a resin composition layer formed from a resin composition provided on the support.

[0107] From the viewpoint of thinning, the thickness of the resin composition layer is preferably 250 μm or less, more preferably 200 μm or less, further preferably 150 μm or less, or 100 μm or less. The lower limit of the thickness of the resin composition layer is not particularly limited, but can usually be 5 μm or more.

[0108] Examples of the support include films made of plastic materials, metal foils, and release papers, with films made of plastic materials and metal foils being preferred.

[0109] When a film made of a plastic material is used as the support, examples of the plastic material include polyesters such as polyethylene terephthalate (hereinafter sometimes abbreviated as "PET") and polyethylene naphthalate (hereinafter sometimes abbreviated as "PEN"), polycarbonate (hereinafter sometimes abbreviated as "PC"), acrylics such as polymethyl methacrylate (PMMA), cyclic polyolefins, triacetyl cellulose (TAC), polyether sulfide (PES), polyether ketone, polyimide, etc. Among these, polyethylene terephthalate and polyethylene naphthalate are preferred, with inexpensive polyethylene terephthalate being particularly preferred.

[0110] When a metal foil is used as the support, examples of the metal foil include copper foil and aluminum foil, with copper foil being preferred. The copper foil may be a foil made of a single metal, copper, or an alloy of copper and another metal (e.g., tin, chromium, silver, magnesium, nickel, zirconium, silicon, titanium, etc.).

[0111] The surface of the support that is to be bonded to the resin composition layer may be subjected to a matte treatment or a corona treatment.

[0112] The support may also be a support with a release layer, which has a release layer on the surface that bonds to the resin composition layer. Examples of the release agent used in the release layer of the support with a release layer include one or more release agents selected from the group consisting of alkyd resins, polyolefin resins, urethane resins, and silicone resins. Commercially available products may also be used as the support with a release layer, including, for example, "SK-1," "AL-5," and "AL-7" manufactured by Lintec Corporation, "Lumirror T60" manufactured by Toray Industries, Inc., "Purex" manufactured by Teijin Limited, and "Uni-Peel" manufactured by Unitika Limited, which are PET films having a release layer primarily composed of an alkyd resin-based release agent.

[0113] The thickness of the support is not particularly limited, but is preferably in the range of 5 μm to 75 μm, more preferably 10 μm to 60 μm. When a support with a release layer is used, it is preferable that the thickness of the entire support with a release layer is in the above range.

[0114] The magnetic sheet can be produced, for example, by preparing a resin varnish by dissolving a magnetic paste in an organic solvent, applying this resin varnish to a support using a die coater or the like, and then drying it to form a resin composition layer. Note that the magnetic sheet can also be produced by applying the magnetic paste directly to a support using a die coater or the like to form a resin composition layer.

[0115] Examples of organic solvents include ketones such as acetone, methyl ethyl ketone (MEK), and cyclohexanone, acetate esters such as ethyl acetate, butyl acetate, cellosolve acetate, propylene glycol monomethyl ether acetate, and carbitol acetate, carbitols such as cellosolve and butyl carbitol, aromatic hydrocarbons such as toluene and xylene, and amide solvents such as dimethylformamide, dimethylacetamide (DMAc), and N-methylpyrrolidone. The organic solvents may be used alone or in combination of two or more.

[0116] Drying may be carried out by known methods such as heating or hot air blowing. Drying conditions are not particularly limited, but drying is carried out so that the content of organic solvent in the resin composition layer becomes 10% by mass or less, preferably 5% by mass or less. Although this varies depending on the boiling point of the organic solvent in the resin varnish, for example, when a resin varnish containing 30% by mass to 60% by mass of organic solvent is used, the resin composition layer can be formed by drying at 50°C to 150°C for 3 to 10 minutes.

[0117] In the magnetic sheet, a protective film conforming to the support can be further laminated on the surface of the resin composition layer that is not bonded to the support (i.e., the surface opposite the support). The thickness of the protective film is not particularly limited, but is, for example, 1 μm to 40 μm. By laminating the protective film, it is possible to prevent the adhesion of dust and the like to the surface of the resin composition layer and to prevent scratches. The magnetic sheet can be stored in a roll. When the magnetic sheet has a protective film, it can be used by peeling off the protective film.

[0118] [Circuit board and its manufacturing method] The circuit board of the first embodiment includes a substrate having through holes and a cured product of the magnetic paste of the present invention filled in the through holes. The circuit board of the second embodiment includes a magnetic layer formed from a cured product of the resin composition layer of the magnetic sheet. Hereinafter, first and second embodiments of the method for manufacturing a circuit board will be described. However, the method for manufacturing a circuit board according to the present invention is not limited to the first and second embodiments exemplified below.

[0119] First Embodiment The circuit board of the first embodiment is manufactured, for example, by a manufacturing method including the following steps (1) and (2). Preferably, this manufacturing method further includes steps (3) and (4). In the first embodiment, it is preferable to form the magnetic layer using a magnetic paste. (1) A process of filling a through-hole in a substrate having the through-hole with a magnetic paste. (2) A step of thermally curing the magnetic paste to obtain a cured product. (3) A step of polishing the surface of the cured product or magnetic paste. (4) A step of forming a conductive layer on the polished surface of the cured product. The method for producing a circuit board of the present invention may be carried out in the order of steps (1) to (4), or step (2) may be carried out after step (3).

[0120] The above steps (1) to (4) for manufacturing the circuit board will be described in detail below.

[0121] <Process (1)> The step (1) may include the step of preparing a magnetic paste, as described above.

[0122] 1, the process may further include preparing a core substrate 10 including a support substrate 11, a first metal layer 12 made of a metal such as copper foil, and a second metal layer 13 provided on both surfaces of the support substrate 11. Examples of materials for the support substrate 11 include insulating substrates such as glass epoxy substrates, metal substrates, polyester substrates, polyimide substrates, BT resin substrates, and thermosetting polyphenylene ether substrates. Examples of materials for the first and second metal layers include copper foil with a carrier, and the materials for the conductor layers described below.

[0123] 2, the method may also include a step of forming through holes 14 in the core substrate 10. The through holes 14 can be formed, for example, by drilling, laser irradiation, plasma irradiation, etc. Specifically, the through holes 14 can be formed by drilling through the core substrate 10 using a drill or the like.

[0124] The through holes 14 can be formed using a commercially available drilling device, such as the "ND-1S211" manufactured by Hitachi Via Mechanics.

[0125] After forming the through holes 14 in the core substrate 10, the process may include a step of roughening the core substrate 10 and forming a plating layer 20 within the through holes 14, on the surface of the first metal layer 12, and on the surface of the second metal layer 13, as shown in an example in Figure 3.

[0126] The roughening treatment may be either a dry or wet roughening treatment. An example of the dry roughening treatment is plasma treatment. An example of the wet roughening treatment is a method in which a swelling treatment using a swelling liquid, a roughening treatment using an oxidizing agent, and a neutralization treatment using a neutralizing liquid are performed in this order.

[0127] The plating layer 20 is formed by a plating method, and the procedure for forming the plating layer 20 by a plating method is the same as that for forming the conductive layer in step (4) described later.

[0128] After preparing the core substrate 10 with the plating layer 20 formed in the through-holes 14, the magnetic paste 30a is filled into the through-holes 14, as shown in an example in Fig. 4. Examples of filling methods include filling the magnetic paste 30a into the through-holes 14 using a squeegee, filling the magnetic paste 30a using a cartridge, filling the magnetic paste 30a by mask printing, roll coating, inkjet printing, etc.

[0129] <Process (2)> In step (2), after filling the through-holes 14 with magnetic paste 30a, the magnetic paste 30a is thermally cured to form a hardened layer (magnetic layer) 30 in the through-holes 14, as shown in an example in FIG. 5. The thermal curing conditions for the magnetic paste 30a vary depending on the composition and type of the magnetic paste 30a, but the curing temperature is preferably 120°C or higher, more preferably 130°C or higher, and even more preferably 150°C or higher, and is preferably 240°C or lower, more preferably 220°C or lower, and even more preferably 200°C or lower. The curing time for the magnetic paste 30a is preferably 5 minutes or longer, more preferably 10 minutes or longer, and even more preferably 15 minutes or longer, and is preferably 120 minutes or shorter, more preferably 100 minutes or shorter, and even more preferably 90 minutes or shorter.

[0130] The degree of hardening of magnetic layer 30 in step (2) is preferably 80% or more, more preferably 85% or more, and even more preferably 90% or more. The degree of hardening can be measured using, for example, a differential scanning calorimeter.

[0131] Before thermally curing the magnetic paste 30a, the magnetic paste 30a may be subjected to a preheating treatment in which the magnetic paste 30a is heated at a temperature lower than the curing temperature. For example, prior to thermally curing the magnetic paste 30a, the magnetic paste 30a may be preheated at a temperature of typically 50°C or higher and lower than 120°C (preferably 60°C or higher and 110°C or lower, more preferably 70°C or higher and 100°C or lower) for typically 5 minutes or longer (preferably 5 minutes to 150 minutes, more preferably 15 minutes to 120 minutes).

[0132] <Process (3)> In step (3), as shown in an example in Figure 6, excess magnetic layer 30 protruding from or attached to core substrate 10 is removed by polishing to flatten the surface. As a polishing method, any method that can polish excess magnetic layer 30 protruding from or attached to core substrate 10 can be used. Examples of such polishing methods include buff polishing and belt polishing. An example of a commercially available buff polishing device is "NT-700IM" manufactured by Ishii Hyoki Co., Ltd.

[0133] From the viewpoint of improving plating adhesion, the arithmetic mean roughness (Ra) of the ground surface of the magnetic layer is preferably 300 nm or more, more preferably 350 nm or more, and even more preferably 400 nm or more. The upper limit is preferably 1000 nm or less, more preferably 900 nm or less, and even more preferably 800 nm or less. The surface roughness (Ra) can be measured, for example, using a non-contact surface roughness meter.

[0134] When step (3) is carried out after step (2), a heat treatment may be carried out after step (2) and before step (3) as necessary for the purpose of further increasing the degree of hardening of the magnetic layer. The temperature in the heat treatment may be in accordance with the above-mentioned hardening temperatures, and is preferably 120°C or higher, more preferably 130°C or higher, even more preferably 150°C or higher, and preferably 240°C or lower, more preferably 220°C or lower, and even more preferably 200°C or lower. The heat treatment time is preferably 5 minutes or longer, more preferably 10 minutes or longer, even more preferably 15 minutes or longer, and preferably 90 minutes or shorter, more preferably 70 minutes or shorter, and even more preferably 60 minutes or shorter.

[0135] Furthermore, when step (3) is performed before step (2), a preheating treatment may be performed before step (3), in which the magnetic paste is heated at a temperature lower than the hardening temperature. The temperature in the preheating treatment is preferably 100°C or higher, more preferably 110°C or higher, even more preferably 120°C or higher, and preferably 240°C or lower, more preferably 220°C or lower, even more preferably 200°C or lower. The heat treatment time is preferably 5 minutes or longer, more preferably 10 minutes or longer, even more preferably 15 minutes or longer, and preferably 90 minutes or shorter, more preferably 70 minutes or shorter, even more preferably 60 minutes or shorter.

[0136] <Process (4)> In step (4), as shown in FIG. 7, a conductor layer 40 is formed on the polished surface of the magnetic layer 30 and on the plating layer 20. After the conductor layer 40 is formed, a patterned conductor layer 41 may be formed by removing portions of the conductor layer 40, the first metal layer 12, the second metal layer 13, and the plating layer 20 by etching or other processes, as shown in FIG. 8. In the present invention, the cured product is polished in step (3), so a step of roughening the magnetic layer is not included. In FIG. 7, the conductor layer 40 is formed on both sides of the core substrate 10, but the conductor layer 40 may be formed on only one side of the core substrate 10.

[0137] Methods for forming the conductor layer include, for example, plating, sputtering, and vapor deposition, with plating being preferred. In a preferred embodiment, the surface of the cured product is plated using an appropriate method such as a semi-additive method or a full-additive method to form a patterned conductor layer having a desired wiring pattern. Examples of materials for the conductor layer include single metals such as gold, platinum, palladium, silver, copper, aluminum, cobalt, chromium, zinc, nickel, titanium, tungsten, iron, tin, and indium; and alloys of two or more metals selected from the group consisting of gold, platinum, palladium, silver, copper, aluminum, cobalt, chromium, zinc, nickel, titanium, tungsten, iron, tin, and indium. Among these, from the viewpoints of versatility, cost, ease of patterning, and the like, chromium, nickel, titanium, aluminum, zinc, gold, palladium, silver, or copper, or nickel-chromium alloys, copper-nickel alloys, and copper-titanium alloys are preferred. Chromium, nickel, titanium, aluminum, zinc, gold, palladium, silver, or copper, or nickel-chromium alloys are more preferred, and copper is even more preferred.

[0138] Here, an example of an embodiment in which a patterned conductor layer is formed on the polished surface of the cured product will be described in detail. A plating seed layer is formed on the polished surface of the cured product by electroless plating. Next, an electrolytic plating layer is formed on the formed plating seed layer by electrolytic plating, and if necessary, unnecessary plating seed layer is removed by a process such as etching, thereby forming a conductor layer having a desired wiring pattern. After forming the conductor layer, an annealing treatment may be performed as necessary for purposes such as improving the peel strength of the conductor layer. The annealing treatment can be performed, for example, by heating the circuit board at 150 to 200°C for 20 to 90 minutes.

[0139] From the viewpoint of thinning, the thickness of the patterned conductor layer is preferably 70 μm or less, more preferably 60 μm or less, even more preferably 50 μm or less, still more preferably 40 μm or less, particularly preferably 30 μm or less, 20 μm or less, 15 μm or less, or 10 μm or less. The lower limit is preferably 1 μm or more, more preferably 3 μm or more, and even more preferably 5 μm or more.

[0140] Second Embodiment The circuit board of the second embodiment includes a magnetic layer formed from a hardened magnetic paste. In the second embodiment, it is preferable to form the magnetic layer using a magnetic sheet. The second embodiment of the method for manufacturing the product substrate will be described below. Explanations of parts that overlap with the first embodiment will be omitted as appropriate.

[0141] The circuit board of the second embodiment is manufactured, for example, by a manufacturing method including the following step (A): Preferably, this manufacturing method further includes steps (B) to (D). (A) a step of laminating a magnetic sheet onto an inner layer substrate so that the resin composition layer is bonded to the inner layer substrate to form a magnetic layer; (B) a step of drilling holes in the magnetic layer; (C) polishing the surface of the magnetic layer; and (D) forming a conductive layer on the polished surface of the magnetic layer.

[0142] The above steps (A) to (D) for manufacturing a circuit board will be described in detail below.

[0143] <(A) Process> Step (A) is a step of laminating a magnetic sheet onto an inner layer substrate so that the resin composition layer is bonded to the inner layer substrate to form a magnetic layer. In one embodiment of step (A), the magnetic sheet is laminated onto the inner layer substrate so that the resin composition layer is bonded to the inner layer substrate, and the resin composition layer is thermally cured to form the magnetic layer.

[0144] In step (A), as shown in an example in Figure 9, a magnetic sheet 310 including a support 330 and a resin composition layer 320a provided on the support 330 is laminated onto an inner layer substrate 200 so that the resin composition layer 320a is bonded to the inner layer substrate 200.

[0145] The inner substrate 200 is an insulating substrate. Examples of materials for the inner substrate 200 include insulating base materials such as a glass epoxy substrate, a metal substrate, a polyester substrate, a polyimide substrate, a BT resin substrate, and a thermosetting polyphenylene ether substrate. The inner substrate 200 may be an inner circuit board having wiring and the like built into its thickness.

[0146] As shown in FIG. 9, the inner substrate 200 has a first conductor layer 420 provided on the first main surface 200a and an external terminal 240 provided on the second main surface 200b. The first conductor layer 420 may include multiple wirings. In the illustrated example, only the wirings constituting the coil-shaped conductive structure 400 of the inductor element are shown. The external terminal 240 is a terminal for electrically connecting to an external device or the like (not shown). The external terminal 240 can be configured as part of the conductor layer provided on the second main surface 200b.

[0147] The conductive material that can form the first conductive layer 420 and the external terminals 240 is the same as the material of the conductive layer explained in the section "<Step (4)>" of the first embodiment.

[0148] The first conductor layer 420 and the external terminal 240 may have a single-layer structure or a multi-layer structure in which two or more single metal layers or alloy layers made of different types of metals or alloys are stacked. The thickness of the first conductor layer 420 and the external terminal 240 is the same as that of the second conductor layer 440 described below.

[0149] The line (L) / space (S) ratio of the first conductor layer 420 and the external terminal 240 is not particularly limited, but from the viewpoint of reducing surface irregularities and obtaining a magnetic layer with excellent smoothness, it is usually 900 / 900 μm or less, preferably 700 / 700 μm or less, more preferably 500 / 500 μm or less, even more preferably 300 / 300 μm or less, and even more preferably 200 / 200 μm or less. The lower limit of the line / space ratio is not particularly limited, but from the viewpoint of improving the embedding of the resin composition layer in the spaces, it is preferably 1 / 1 μm or more.

[0150] The inner substrate 200 may have a plurality of through holes 220 that penetrate the inner substrate 200 from the first main surface 200a to the second main surface 200b. The through holes 220 are provided with internal through-hole wiring 220a. The internal through-hole wiring 220a electrically connects the first conductor layer 420 and the external terminal 240.

[0151] The resin composition layer 320a and the inner substrate 200 can be bonded, for example, by thermocompression bonding the magnetic sheet 310 to the inner substrate 200 from the support 330 side. Examples of a member for thermocompression bonding the magnetic sheet 310 to the inner substrate 200 (hereinafter also referred to as a "thermocompression bonding member") include a heated metal plate (such as a stainless steel (SUS) plate) or a metal roll (SUS roll). Note that rather than pressing the magnetic sheet 310 by directly contacting it with the thermocompression bonding member, it is preferable to press it via a sheet made of an elastic material such as heat-resistant rubber so that the magnetic sheet 310 can sufficiently conform to the irregularities on the surface of the inner substrate 200.

[0152] The temperature during thermocompression bonding is preferably in the range of 80°C to 160°C, more preferably 90°C to 140°C, and even more preferably 100°C to 120°C, the pressure during thermocompression bonding is preferably in the range of 0.098MPa to 1.77MPa, more preferably 0.29MPa to 1.47MPa, and the time during thermocompression bonding is preferably in the range of 20 seconds to 400 seconds, more preferably 30 seconds to 300 seconds. The bonding of the magnetic sheet and the inner layer substrate is preferably carried out under reduced pressure conditions of 26.7hPa or less.

[0153] The resin composition layer 320a of the magnetic sheet 310 can be bonded to the inner layer substrate 200 using a commercially available vacuum laminator. Examples of commercially available vacuum laminators include a vacuum pressure laminator manufactured by Meiki Seisakusho Co., Ltd. and a vacuum applicator manufactured by Nikko Materials Co., Ltd.

[0154] After bonding the magnetic sheet 310 and the inner layer substrate 200, the laminated magnetic sheet 310 may be smoothed under normal pressure (atmospheric pressure), for example, by pressing from the support side with a thermocompression member. The pressing conditions for the smoothing process may be the same as the thermocompression conditions for the lamination. The smoothing process may be performed using a commercially available laminator. Note that the lamination and smoothing processes may be performed consecutively using the commercially available vacuum laminator.

[0155] After the magnetic sheet is laminated on the inner substrate, the resin composition layer is thermally cured to form the magnetic layer. As shown in an example in Figure 10, the resin composition layer 320a bonded to the inner substrate 200 is thermally cured to form the first magnetic layer 320.

[0156] The thermal curing conditions for the resin composition layer 320a vary depending on the composition and type of the resin composition, but the curing temperature is preferably 120° C. or higher, more preferably 130° C. or higher, even more preferably 150° C. or higher, and preferably 240° C. or lower, more preferably 220° C. or lower, and even more preferably 200° C. or lower. The curing time for the resin composition layer 320a is preferably 5 minutes or longer, more preferably 10 minutes or longer, even more preferably 15 minutes or longer, and preferably 120 minutes or shorter, more preferably 100 minutes or shorter, and even more preferably 90 minutes or shorter.

[0157] The support 330 may be removed between the end of the thermal curing in step (A) and step (B), or may be peeled off after step (B).

[0158] <(B) Process> In step (B), as shown in FIG. 11 , the first magnetic layer 320 is drilled to form via holes 360. The via holes 360 serve as paths for electrically connecting the first conductor layer 420 to the second conductor layer 440 described below. The via holes 360 may be formed using, for example, a drill, a laser, plasma, or the like, depending on the composition of the resin composition used to form the magnetic layer. The dimensions and shape of the holes may be determined appropriately depending on the design of the printed wiring board.

[0159] <(C) Process> In step (C), the surface of the magnetic layer in which the via holes have been formed is polished. The polishing method in step (C) can be the same as that described in the section “<Step (3)>” of the first embodiment.

[0160] From the viewpoint of improving plating adhesion, the arithmetic mean roughness (Ra) of the ground surface of the magnetic layer is preferably 300 nm or more, more preferably 350 nm or more, and even more preferably 400 nm or more. The upper limit is preferably 1000 nm or less, more preferably 900 nm or less, and even more preferably 800 nm or less. The surface roughness (Ra) can be measured, for example, using a non-contact surface roughness meter.

[0161] <(D) Process> In step (D), a second conductor layer 440 is formed on the first magnetic layer 320, as shown in an example in FIG.

[0162] The conductive material that can be used to form the second conductive layer 440 is the same as the material for the conductive layer described in the section "<Step (4)>" of the first embodiment.

[0163] From the viewpoint of thinning, the thickness of the second conductor layer 440 is preferably 70 μm or less, more preferably 60 μm or less, even more preferably 50 μm or less, still more preferably 40 μm or less, particularly preferably 30 μm or less, 20 μm or less, 15 μm or less, or 10 μm or less. The lower limit is preferably 1 μm or more, more preferably 3 μm or more, and even more preferably 5 μm or more.

[0164] The second conductor layer 440 can be formed by plating. The second conductor layer 440 is preferably formed by a wet plating method such as a semi-additive method or a full-additive method including an electroless plating process, a mask pattern formation process, an electrolytic plating process, and a flash etching process. By forming the second conductor layer 440 using a wet plating method, it is possible to form the second conductor layer 440 including a desired wiring pattern. Note that this process also forms via-hole wiring 360a in the via hole 360.

[0165] The first conductor layer 420 and the second conductor layer 440 may be provided in a spiral shape, for example, as shown in Figures 13 to 15 described later. In one example, one end of the spiral wiring portion of the second conductor layer 440 on the central side is electrically connected to one end of the spiral wiring portion of the first conductor layer 420 on the central side by via-hole wiring 360a. The other end of the spiral wiring portion of the second conductor layer 440 on the outer periphery is electrically connected to land 420a of the first conductor layer 42 by via-hole wiring 360a. Therefore, the other end of the spiral wiring portion of the second conductor layer 440 on the outer periphery is electrically connected to external terminal 240 via via-hole wiring 360a, land 420a, and through-hole wiring 220a.

[0166] The coil-shaped conductive structure 400 is composed of a spiral wiring portion that is part of the first conductor layer 420, a spiral wiring portion that is part of the second conductor layer 440, and via-hole wiring 360a that electrically connects the spiral wiring portion of the first conductor layer 420 and the spiral wiring portion of the second conductor layer 440.

[0167] After step (D), a step of forming a magnetic layer on the conductor layer may be performed. More specifically, as shown in an example in Fig. 14, the second magnetic layer 340 is formed on the first magnetic layer 320 on which the second conductor layer 440 and the via-hole wiring 360a are formed. The second magnetic layer may be formed by the same steps as those already described.

[0168] [Inductor components] The inductor component includes the circuit board of the present invention. When such an inductor component includes a circuit board obtained by the circuit board manufacturing method of the first embodiment, it has an inductor pattern formed of a conductor around at least a portion of the periphery of the cured product of the magnetic paste. For example, the inductor component described in JP 2016-197624 A can be used.

[0169] Furthermore, when including a circuit board obtained by the circuit board manufacturing method of the second embodiment, the inductor substrate has a magnetic layer and a conductive structure at least partially embedded in the magnetic layer, and includes an inductor element formed by the conductive structure and a portion of the magnetic layer extending in the thickness direction of the magnetic layer and surrounded by the conductive structure. Fig. 13 is a schematic plan view of the inductor substrate incorporating the inductor element, as viewed from one side in the thickness direction. Fig. 14 is a schematic view showing a cut end surface of the inductor substrate cut at the position indicated by the dashed dotted line II-II in Fig. 13. Fig. 15 is a schematic plan view illustrating the configuration of a first conductor layer in the inductor substrate.

[0170] 13 and 14, the circuit board 100 is a build-up wiring board having multiple magnetic layers (first magnetic layer 320, second magnetic layer 340) and multiple conductor layers (first conductor layer 420, second conductor layer 440), i.e., having build-up magnetic layers and build-up conductor layers. The inductor substrate 100 also includes an inner layer substrate 200.

[0171] 14, the first magnetic layer 320 and the second magnetic layer 340 constitute the magnetic part 300, which can be seen as an integrated magnetic layer. Therefore, the coiled conductive structure 400 is provided so that at least a portion thereof is embedded in the magnetic part 300. That is, in the inductor substrate 100 of this embodiment, the inductor element is constituted by the coiled conductive structure 400 and a core portion that extends in the thickness direction of the magnetic part 300 and is a portion of the magnetic part 300 surrounded by the coiled conductive structure 400.

[0172] 15, the first conductor layer 420 includes a spiral wiring portion for constituting the coil-shaped conductive structure 400, and a rectangular land 420a electrically connected to the through-hole wiring 220a. In the illustrated example, the spiral wiring portion includes a straight portion, a bent portion that bends at a right angle, and a detour portion that detours around the land 420a. In the illustrated example, the spiral wiring portion of the first conductor layer 420 has an overall outline that is approximately rectangular, and has a shape that winds counterclockwise from the center toward the outside.

[0173] Similarly, a second conductor layer 440 is provided on the first magnetic layer 320. The second conductor layer 440 includes a spiral wiring portion for configuring the coil-shaped conductive structure 400. In Fig. 13 or 14, the spiral wiring portion includes a straight portion and a bent portion bent at a right angle. In Fig. 13 or 14, the spiral wiring portion of the second conductor layer 440 has an overall outline that is approximately rectangular, and has a shape that winds clockwise from the center toward the outside.

[0174] Such an inductor component can be used as a wiring board for mounting electronic components such as semiconductor chips, or as a (multilayer) printed wiring board using such a wiring board as an inner layer substrate.Furthermore, such a wiring board can be singulated and used as a chip inductor component, or as a surface-mounted printed wiring board.

[0175] Furthermore, various types of semiconductor devices can be manufactured using such a wiring board. Semiconductor devices including such wiring boards can be suitably used in electrical appliances (e.g., computers, mobile phones, digital cameras, televisions, etc.) and vehicles (e.g., motorcycles, automobiles, trains, ships, aircraft, etc.). [Example]

[0176] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. In the following description, "parts" and "%" representing amounts mean "parts by mass" and "% by mass", respectively, unless otherwise specified.

[0177] <Measurement of pH of dispersant (indicator method)> A measurement sample (22°C) with a dispersant concentration of 0.1 g / mL was prepared by dissolving the dispersant in acetone. A pH test paper was gently immersed in the solution and then removed to dry off excess water. The color of the wet part of the test paper was compared with the color sample, and the pH of each sample was determined to be the closest color.

[0178] <Synthesis Example 1: Synthesis of Dispersant 1> A reaction flask equipped with a thermometer, stirrer, nitrogen inlet, and reflux condenser was charged with 10.0 parts of 12-hydroxystearic acid (manufactured by Junsei Chemical Co., Ltd.) and 190 parts of ε-caprolactone (manufactured by Junsei Chemical Co., Ltd.). The mixture was heated to 160°C over 4 hours under a nitrogen stream, heated at 160°C for 2 hours, and then heated until the remaining amount of ε-caprolactone was 1% or less. The mixture was then cooled to room temperature. Hereinafter, this reaction liquid will be referred to as Dispersant 1. Dispersant 1 had a polyester skeleton represented by the general formula (1), in which R was an alkylene group containing 5 carbon atoms, a weight-average molecular weight of 23,000, and an acid value of 9.0 mgKOH / g. The pH measured by the indicator method was 5.

[0179] <Synthesis Example 2: Synthesis of Dispersant 2> A reaction flask equipped with a thermometer, stirrer, nitrogen inlet, and reflux condenser was charged with 10.0 parts of 12-hydroxystearic acid (Junsei Chemical Co., Ltd.) and 180 parts of δ-valerolactone (Tokyo Chemical Industry Co., Ltd.). The mixture was heated to 160°C over 4 hours under a nitrogen stream, heated at 160°C for 2 hours, and then heated until the remaining amount of δ-valerolactone was 1% or less. The mixture was then cooled to room temperature. This reaction liquid is hereinafter referred to as Dispersant 2. Dispersant 2 has a polyester skeleton in which R in the general formula (1) is an alkylene group having 4 carbon atoms, a weight-average molecular weight of 22,000, and an acid value of 8.9 mgKOH / g. The pH measured by the indicator method was 5.

[0180] <Synthesis Example 3: Synthesis of Dispersant 3> A mixture of 25.0 parts xylene and 70 parts 10% aqueous polyallylamine solution ("PAA-1LV" manufactured by Nitto Boseki Co., Ltd., number-average molecular weight approximately 3,000) was stirred at 160°C in a reaction flask equipped with a thermometer, a stirrer, a nitrogen inlet, and a reflux condenser. Water was distilled off using a separator, and while the xylene was returned to the reaction solution, 114.21 parts of the polyester dispersant obtained in Synthesis Example 1, heated to 160°C, was added and the reaction was carried out at 160°C for 2 hours. The mixture was further heated at 160°C for 4 hours, and the xylene was distilled off at 160°C to obtain Dispersion 3. Dispersant 3 has a polyester skeleton represented by the general formula (1), where R is an alkylene group having 5 carbon atoms, and had an amine value of 31.0 mgKOH / g and an acid value of 19.5 mgKOH / g. The amine value immediately after mixing was 312.6 mgKOH / g. The pH was 6 by the indicator method.

[0181] <Synthesis Example 4: Synthesis of Dispersant 4> A reaction flask equipped with a thermometer, a stirrer, a nitrogen inlet, a reflux condenser, and a water separator was charged with 30.0 parts of xylene (Junsei Chemical Co., Ltd.), 300.0 parts of 12-hydroxystearic acid (Junsei Chemical Co., Ltd.), and 0.1 parts of tetrabutyl titanate (Tokyo Chemical Industry Co., Ltd.), and the mixture was heated to 160°C over 4 hours under a nitrogen stream. The mixture was further heated at 160°C for 4 hours, and the xylene was distilled off at 160°C. Dispersant 4 had a polyester skeleton in which R in the general formula (1) was an alkylene group having 11 carbon atoms, and had a weight-average molecular weight of 6000. The acid value of Dispersant 4 was 23.0 mgKOH / g. The pH of Dispersant 4 measured by the indicator method was 5.

[0182] <Synthesis Example 5: Synthesis of Dispersant 5> A reaction flask equipped with a thermometer, stirrer, nitrogen inlet, reflux condenser, and water separator was charged with 30.0 parts of xylene (Junsei Chemical Co., Ltd.), 300.0 parts of 12-hydroxystearic acid (Junsei Chemical Co., Ltd.), and 0.1 parts of tetrabutyl titanate (Tokyo Chemical Industry Co., Ltd.). The mixture was heated to 160°C over 4 hours under a nitrogen stream. The mixture was further heated at 160°C for 4 hours (the acid value at this time was approximately 20 mgKOH / g), and the xylene was distilled off at 160°C. The mixture was then cooled to room temperature, and the water generated during the heating reaction was separated from the xylene in the distillate. The xylene was then returned to the reaction solution. This reaction solution is designated Polyester PE-1.

[0183] A mixture of 25.0 parts xylene and 70 parts 10% aqueous polyallylamine solution ("PAA-1LV" manufactured by Nitto Boseki Co., Ltd., number-average molecular weight approximately 3,000) was stirred at 160°C in a reaction flask equipped with a thermometer, a stirrer, a nitrogen inlet, a reflux condenser, and a water separator. Water was distilled off using a separator, and 2.5 parts of polyester PE-1 was added to the mixture while the xylene was returned to the reaction solution. The reaction was carried out at 160°C for 2 hours. The mixture was further heated at 160°C for 4 hours, and the xylene was distilled off at 160°C. Dispersant 5 had a polyester skeleton represented by the general formula (1), where R is an alkylene group containing 11 carbon atoms, and had an amine value of 38.5 mgKOH / g and an acid value of 23.5 mgKOH / g. The amine value of Dispersant 5 immediately after mixing was 317 mgKOH / g. The pH of Dispersant 5 measured by the indicator method was 6.

[0184] <Example 1: Preparation of magnetic paste 1> Magnetic paste 1 was prepared by mixing 3 parts by mass of epoxy resin ("ZX-1059", a mixture of bisphenol A type epoxy resin and bisphenol F type epoxy resin, manufactured by Nippon Steel Chemical & Material Co., Ltd.), 5 parts by mass of epoxy resin ("ZX-1658GS", a cyclic aliphatic diglycidyl ether, manufactured by Nippon Steel Chemical & Material Co., Ltd.), 10 parts by mass of epoxy resin ("EX-201", a cyclic aliphatic diglycidyl ether type epoxy resin, manufactured by Nagase ChemteX Corporation), 1 part by mass of dispersant 1, 1 part by mass of curing agent ("2MZA-PW", an imidazole-based epoxy resin curing agent, manufactured by Shikoku Chemicals Co., Ltd.), 120 parts by mass of magnetic powder ("M05S", an Fe-Mn ferrite, average particle size 3 μm, manufactured by Powder Tech Co., Ltd.), and 30 parts by mass of magnetic powder ("M001", an Fe-Mn ferrite, average particle size 0.2 μm, manufactured by Powder Tech Co., Ltd.).

[0185] Example 2: Preparation of magnetic paste 2 In Example 1, 1 part by mass of Dispersant 1 was changed to 1 part by mass of Dispersant 2. Magnetic paste 2 was prepared in the same manner as in Example 1 except for the above points.

[0186] Example 3: Preparation of magnetic paste 3 In Example 1, 1 part by mass of Dispersant 1 was changed to 1 part by mass of Dispersant 3. Magnetic paste 3 was prepared in the same manner as in Example 1 except for the above points.

[0187] <Comparative Example 1: Preparation of Magnetic Paste 4> In Example 1, 1 part by mass of Dispersant 1 was changed to 1 part by mass of Dispersant 4. Magnetic paste 4 was prepared in the same manner as in Example 1 except for the above points.

[0188] Comparative Example 2: Preparation of Magnetic Paste 5 In Example 1, 1 part by mass of Dispersant 1 was changed to 1 part by mass of Dispersant 5. Magnetic paste 5 was prepared in the same manner as in Example 1 except for the above points.

[0189] Comparative Example 3: Preparation of Magnetic Paste 6 In Example 1, the amount of magnetic powder ("M05S", Fe-Mn ferrite, average particle size 3 μm, manufactured by Powder Tech Co., Ltd.) was changed from 120 parts to 50 parts by mass, the amount of magnetic powder ("M001", Fe-Mn ferrite, average particle size 0.2 μm, manufactured by Powder Tech Co., Ltd.) was changed from 30 parts to 11 parts by mass, and 1 part by mass of Dispersant 1 was changed to 0.5 parts by mass of Dispersant 4. Magnetic Paste 6 was prepared in the same manner as in Example 1, except for the above changes.

[0190] Comparative Example 4: Preparation of Magnetic Paste 7 In Example 1, 1 part by mass of Dispersant 1 was changed to 1 part by mass of Dispersant ("SC-1015F", a dispersant without a polyester skeleton, manufactured by NOF Corporation, pH = 3 as measured by the indicator method). Magnetic paste 7 was prepared in the same manner as in Example 1, except for the above.

[0191] <Measurement of viscosity of magnetic paste> The temperature of magnetic pastes 1 to 7 was kept at 25±2°C, and the viscosity at 25°C was measured using an E-type viscometer (Toki Sangyo Co., Ltd. "RE-80U", 3° x R9.7 cone, rotation speed 5 rpm). The measured viscosity was also evaluated from the viewpoint of handling according to the following criteria. ○: Less than 300 Pa·s ×:300Pa·s or more

[0192] <Evaluation of printability> (1) Preparation of the support substrate A support substrate (700 μm thick, made of glass cloth impregnated with epoxy resin and cured) with multiple uniformly formed through-holes was prepared. The through-holes were cylindrical, with a diameter of 350 μm and a spacing of 100 μm between them.

[0193] (2) Prepare a mask The mask was a metal mask with a thickness of 100 μm and a hollow hole formed in a flat metal plate. The planar shape of the opening was a 20 mm square.

[0194] (3) Magnetic paste printing Using the mask, the magnetic paste was printed on the support substrate in the following manner (3-1) to (3-3). The printing was performed using a vacuum high-precision screen printer (LS-100VC manufactured by Newlong Seimitsu Kogyo Co., Ltd.).

[0195] (3-1) Installation process A mask was placed on one side of the support substrate such that each opening in the mask communicated with a plurality of through-holes in the support substrate.

[0196] (3-2) Supply process Thereafter, a magnetic paste was applied to the surface of the mask opposite to the support substrate.

[0197] (3-3) First printing process Then, a rubber squeegee ("SVFSQ" manufactured by Newlong Precision Industry Co., Ltd., 9 mm thick, rubber hardness 90 degrees) made of rubber as an elastic material was moved along the surface of the mask to print the magnetic paste. The squeegee's attack angle was 10°, the printing pressure was 4.4 MPa, and the printing speed was 5 mm / sec.

[0198] (4) Hardening of magnetic paste By the printing, a filled substrate including a support substrate and a resin composition layer was obtained. This filled substrate was heated at 130°C for 30 minutes. By this heating, the resin composition layer was thermally cured to form a filled layer, thereby obtaining a hole-filled substrate.

[0199] (5) Evaluation of printability The shape of the resulting filled-in substrate was measured using a laser microscope. From the measurement results, the printability of the magnetic paste was evaluated according to the following criteria. ◯: There is no through-hole on the back surface of the filled substrate that is recessed deeper than the supporting substrate. ×: On the back surface of the filled substrate, there is one or more through holes that are recessed further than the support substrate. Here, the "back surface of the filled substrate" refers to the surface of the support substrate opposite to the surface on which the mask is placed. The "through hole on the back surface of the filled substrate that is recessed further than the support substrate" refers to a through hole in which the filling layer filled in the through hole is recessed further than the back surface of the support substrate. In other words, the "through hole on the back surface of the filled substrate that is recessed further than the support substrate" refers to a through hole in which the position of the surface of the filling layer filled in the through hole opposite the mask is closer to the mask in the thickness direction than the back surface of the support substrate.

[0200] <Measurement of mechanical strength (tensile breaking strength)> A polyethylene terephthalate (PET) film ("PET501010" manufactured by Lintec Corporation, thickness 50 μm) treated with a silicone-based release agent was prepared as a support. Each of the magnetic pastes 1 to 7 was uniformly applied to the release surface of the PET film using a doctor blade so that the paste layer would be 100 μm thick after drying, yielding a magnetic sheet. The resulting magnetic sheet was heated at 180°C for 90 minutes to thermally cure the paste layer, and the support was peeled off to obtain a sheet-like cured product. The tensile breaking strength of the resulting sample was measured in accordance with JIS K7127. The measurement results were evaluated according to the following criteria. ○: Mechanical strength is 50 MPa or more ×: Mechanical strength less than 50 MPa

[0201] <Measurement of relative permeability and magnetic loss> A polyethylene terephthalate (PET) film (Lintec Corporation, "PET501010," 50 μm thick) treated with a silicone-based release agent was prepared as a support. Each of the magnetic pastes 1 to 7 was uniformly applied to the release surface of the PET film using a doctor blade so that the paste layer would be 100 μm thick after drying, yielding a magnetic sheet. The resulting magnetic sheet was heated at 180°C for 90 minutes to thermally cure the paste layer, and the support was peeled off to obtain a sheet-like cured product. The resulting cured product was cut into test pieces measuring 5 mm wide and 18 mm long to serve as evaluation samples. The relative permeability (μ') and magnetic loss (μ'') of these evaluation samples were measured using an Agilent Technologies (Agilent Technologies, "HP8362B") at a room temperature of 23°C using a 3-turn coil method at a measurement frequency of 100 MHz.

[0202] [Table 1] [Explanation of symbols]

[0203] 10 Core Board 11 Support substrate 12 1st metal layer 13 Second metal layer 14 through holes 20 plating layer 30a magnetic paste 30 Magnetic layer 40 Conductor Layer 41 Patterned conductor layer 100 Circuit Boards 200 inner layer board 200a 1st main surface 200b 2nd main surface 220 through hole 220a Through-hole wiring 240 External terminal 300 Magnetic part 310 Magnetic Sheet 320a Resin composition layer 320 First insulating layer 330 Support 340 Second insulating layer 360 Beer Hall 360a via hole wiring 400 Coil-shaped conductive structure 420 First conductor layer 420a Land 440 Second conductor layer

Claims

1. (A) magnetic powder, (B) Epoxy resin, (C) Dispersant, and (D) A magnetic paste containing a hardening agent, Component (C) has a polyester skeleton represented by the following general formula (1), (C) A magnetic paste in which the pH of component is between 4 and 7. 【Chemistry 1】 (In general formula (1), R independently represents a divalent hydrocarbon group having 2 to 10 carbon atoms, and n represents an integer from 2 to 1000.)

2. The magnetic paste according to Claim 1, wherein the content of component (C) is 0.1% by mass or more and 5% by mass or less, when the nonvolatile components in the magnetic paste are considered to be 100% by mass.

3. The magnetic paste according to claim 1 or 2, wherein component (A) comprises (A-1) magnetic powder with an average particle size of 1 μm or more, and (A-2) magnetic powder with an average particle size of less than 1 μm.

4. The magnetic paste according to any one of claims 1 to 3, wherein component (A) comprises (A-1) magnetic powder with an average particle size of 1 μm or more and 10 μm or less, and (A-2) magnetic powder with an average particle size of 0.005 μm or more and less than 1 μm.

5. The magnetic paste according to any one of claims 1 to 4, wherein component (A) is at least one selected from iron oxide powder and iron alloy-based metal powder.

6. The magnetic paste according to any one of claims 1 to 5, wherein component (A) comprises iron oxide powder, and the iron oxide powder comprises ferrite containing at least one selected from Ni, Cu, Mn, and Zn.

7. The magnetic paste according to any one of claims 1 to 6, wherein the content of component (A) is 70% by mass or more and 98% by mass or less, when the nonvolatile components in the magnetic paste are considered to be 100% by mass.

8. A magnetic paste according to any one of claims 1 to 7, for filling through holes.

9. A cured product of magnetic paste according to any one of claims 1 to 8.

10. A circuit board having a substrate having through holes, and a cured product of a magnetic paste according to any one of claims 1 to 8, which is filled into the through holes.

11. (A) magnetic powder; (B) Epoxy resin, (C) Dispersant, and (D) A resin composition comprising a curing agent, Component (C) has a polyester skeleton represented by the following general formula (1), A resin composition in which the pH of component (C) is 4 or higher and less than 7. 【Chemistry 2】 (In general formula (1), R independently represents a divalent hydrocarbon group having 2 to 10 carbon atoms, and n represents an integer from 2 to 1000.)

12. A cured product of the resin composition according to claim 11.

13. A circuit board having a substrate having through holes, and a cured product of the resin composition according to claim 12, which is filled into the through holes.

14. An inductor component including the circuit board according to claim 10 or 13.

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