Magnetic paste

Abstract

An object of the present invention is to provide a magnetic paste capable of obtaining a cured product with improved stain removal tolerance and improved adhesion between a magnetic layer and a conductor layer, a circuit board, an inductor board, and a method for manufacturing a circuit board using the magnetic paste. A solution to the present invention is a magnetic paste comprising: (A) magnetic powder, (B) an epoxy resin, (C) a reactive diluent, and (D) a curing agent, wherein the component (C) comprises a trifunctional or higher reactive diluent.

Description

Technical Field

[0001] The present invention relates to a magnetic paste, a circuit board, an inductor board obtained using the magnetic paste, and a method for manufacturing a circuit board. Background Art

[0002] Due to the recent demand for miniaturization and thinning of electronic devices, the demand for miniaturization and thinning of printed wiring boards and inductor components (coils) mounted on printed wiring boards has also been increasing. When an inductor component is mounted as a chip component, there is a limit to the thinning of the printed wiring board. Therefore, it is considered to form a magnetic layer on a printed substrate by using an adhesive film containing a magnetic material in a resin composition layer, thereby forming an inductor in the inner layer of the printed wiring board (see, for example, Patent Document 1).

[0003] Prior Art Documents

[0004] Patent Documents

[0005] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2015-187260. Summary of the Invention

[0006] Technical Problem to be Solved by the Invention

[0007] When the present inventors performed a wet desmear treatment when forming a conductor layer on a magnetic layer using a magnetic paste, or when performing a wet desmear treatment to remove contamination generated by grinding the magnetic layer, it was found that due to the peeling and dissolution of the resin component caused by the oxidizing agent solution, the roughening shape of the surface of the magnetic layer deteriorated (i.e., the desmear tolerance was poor). As a result, even when attempting to form a conductor layer such as a plating layer on the magnetic layer, there is a tendency for the conductor layer to expand and the adhesion between the magnetic layer and the conductor layer to decrease.

[0008] The present invention has been completed in view of the above circumstances, and an object thereof is to provide a magnetic paste capable of obtaining a cured product with improved desmear tolerance and adhesion between a magnetic layer and a conductor layer, a circuit board, an inductor board obtained using the magnetic paste, and a method for manufacturing a circuit board.

[0009] Technical Solution for Solving the Technical Problem

[0010] The present inventors have intensively studied and found that by making the magnetic paste contain a trifunctional or higher functional reactive diluent as a reactive diluent, the desmear tolerance and the adhesion between the magnetic layer and the conductor layer are improved, and thus the present invention has been completed.

[0011] That is, the present invention includes the following;

[0012] [1] A magnetic paste, comprising:

[0013] (A) magnetic powder

[0014] (B) epoxy resin

[0015] (C) reactive diluent, and

[0016] (D) curing agent

[0017] wherein the component (C) includes a polyfunctional reactive diluent with three or more functional groups;

[0018] [2] The magnetic paste according to [1], wherein when the non-volatile components in the magnetic paste are set to 100% by mass, the content of the polyfunctional reactive diluent with three or more functional groups is 0.5% by mass or more and 10% by mass or less;

[0019] [3] The magnetic paste according to [1] or [2], wherein when all the components (C) are set to 100% by mass, the content of the polyfunctional reactive diluent with three or more functional groups is 20% by mass or more;

[0020] [4] The magnetic paste according to any one of [1] to [3], wherein the component (A) is a soft magnetic powder;

[0021] [5] The magnetic paste according to any one of [1] to [4], wherein the component (A) is an iron oxide powder;

[0022] [6] The magnetic paste according to [5], wherein the iron oxide powder is a ferrite containing at least one element selected from Ni, Cu, Mn, and Zn;

[0023] [7] The magnetic paste according to any one of [1] to [6], wherein the component (A) is at least one selected from Fe-Mn ferrites and Fe-Mn-Zn ferrites;

[0024] [8] The magnetic paste according to any one of [1] to [7], wherein when the non-volatile components in the magnetic paste are set to 100% by mass, the content of the component (A) is 60% by mass or more;

[0025] [9] The magnetic paste according to any one of [1] to [8], which is used for filling through-holes;

[0026]

[10] A circuit board, comprising a substrate in which through-holes are filled with a cured product of the magnetic paste according to any one of [1] to [9];

[0027]

[11] An inductor substrate, comprising the circuit board according to

[10] ;

[0028]

[12] A method for manufacturing a circuit board, wherein the method includes:

[0029] (1) A step of filling a magnetic paste into a through-hole and thermally curing the magnetic paste to obtain a cured product;

[0030] (2) A step of grinding the surface of the cured product;

[0031] (3) A step of performing a decontamination treatment on the ground surface of the cured product; and

[0032] (4) A step of forming a conductor layer on the ground surface of the cured product;

[0033] The magnetic paste is the magnetic paste described in any one of [1] to [9].

[0034] Effects of the Invention

[0035] According to the present invention, it is possible to provide: a magnetic paste capable of obtaining a cured product with improved decontamination tolerance and adhesion between the magnetic layer and the conductor layer, a circuit board, an inductor substrate, and a method for manufacturing a circuit board obtained by using the magnetic paste. Description of the Drawings

[0036] Figure 1 is a schematic cross-sectional view of a core substrate as an example;

[0037] Figure 2 is a schematic cross-sectional view of a core substrate having through-holes formed therein as an example;

[0038] Figure 3 is a schematic cross-sectional view showing a state of filling a magnetic paste into a through-hole as an example;

[0039] Figure 4 is a schematic cross-sectional view showing a state of a cured product of a magnetic paste obtained by thermally curing the filled magnetic paste as an example;

[0040] Figure 5 is a schematic cross-sectional view showing a state after grinding a cured product of a magnetic paste as an example. Detailed Embodiments

[0041] Hereinafter, embodiments of the present invention will be described with reference to the drawings. It should be noted that each drawing only briefly shows the shapes, sizes, and arrangements of the constituent elements to the extent that the invention can be understood. The present invention is not limited to the following embodiments, and each constituent element can be appropriately changed. In addition, the configurations described in the embodiments of the present invention are not necessarily limited to being manufactured or used in the configurations illustrated in the drawings.

[0042] [Magnetic Paste]

[0043] The magnetic paste of the present invention contains (A) magnetic powder, (B) epoxy resin, (C) reactive diluent, and (D) curing agent, and the component (C) contains a trifunctional or higher reactive diluent.

[0044] In the present invention, by containing a trifunctional or higher reactive diluent as the component (C), the stain removal tolerance of the magnetic layer can be improved. Since the stain removal tolerance of the magnetic layer is improved, the adhesion between the magnetic layer and the conductor layer can be improved. In addition, the cured product of the magnetic paste can generally improve the relative magnetic permeability and magnetic loss at a frequency of 10 to 200 MHz.

[0045] The magnetic paste may further contain (E) dispersant and (F) other additives as required. Hereinafter, each component contained in the magnetic paste of the present invention will be described in detail.

[0046] <(A) Magnetic powder>

[0047] The magnetic paste may contain (A) magnetic powder as the component (A). By making the magnetic paste contain (A) magnetic powder, the relative magnetic permeability of its cured product can be improved. The (A) magnetic powder can be used alone or in combination of two or more.

[0048] As the (A) magnetic powder, it can be either a soft magnetic powder or a hard magnetic powder. From the viewpoint of significantly obtaining the effects of the present invention, a soft magnetic powder is preferably used.

[0049] Examples of the (A) magnetic powder include: Fe-Mn ferrites, Fe-Mn-Zn ferrites, Mg-Zn ferrites, Mn-Zn ferrites, Mn-Mg ferrites, Cu-Zn ferrites, Mg-Mn-Sr ferrites, Ni-Zn ferrites, Ba-Zn ferrites, Ba-Mg ferrites, Ba-Ni ferrites, Ba-Co ferrites, Ba-Ni-Co ferrites, Y ferrites, iron oxide powders such as iron oxide powder (III) and magnetite; pure iron powders; iron alloy powders such as Fe-Si alloy powders, Fe-Si-Al alloy powders, Fe-Cr alloy powders, Fe-Cr-Si alloy powders, Fe-Ni-Cr alloy powders, Fe-Cr-Al alloy powders, Fe-Ni alloy powders, Fe-Ni-Mo alloy powders, Fe-Ni-Mo-Cu alloy powders, Fe-Co alloy powders, or Fe-Ni-Co alloy powders; amorphous alloy powders such as Co-based amorphous, etc.

[0050] Among them, as the (A) magnetic powder, it is preferably at least one selected from iron oxide powder and ferroalloy-based metal powder. As the iron oxide powder, it preferably contains: ferrite containing at least one element selected from Ni, Cu, Mn, and Zn, and more preferably at least one selected from Fe-Mn-based ferrite and Fe-Mn-Zn-based ferrite. In addition, as the ferroalloy-based metal powder, it preferably contains: ferroalloy-based metal powder containing at least one element selected from Si, Cr, Al, Ni, and Co.

[0051] As the (A) magnetic powder, commercially available products can be used, and two or more kinds can be used in combination. Specific examples of the commercially available magnetic powders that can be used include: M series such as "M05S" manufactured by Powdertech Co., Ltd.; "MZ05" 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", "Fe-80Ni-4MoPF20F" manufactured by EPSON ATMIX Co., Ltd.; "LD-M", "LD-MH", "KNI-106", "KNI-106GSM", "KNI-106GS", "KNI-109", "KNI-109GSM", "KNI-109GS" manufactured by JFE Chemical Co., Ltd.; "KNS-415", "BSF-547", "BSF-029", "BSN-125", "BSN-714", "BSN-828", "S-1281", "S-1641", "S-1651", "S-1470", "S-1511", "S-2430" manufactured by Toda Kogyo Corporation; "JR09P2" manufactured by Nippon Heavy Chemical Industry Co., Ltd.; "Nanotek" manufactured by CIK NanoTek Corporation; "JEMK-S", "JEMK-H" manufactured by KINSEI MATEC Co., Ltd.; "Yttrium iron oxide" manufactured by ALDRICH Corporation, etc.

[0052] (A) The magnetic powder is preferably spherical. The value obtained by dividing the major axis length of the magnetic powder by the minor axis length (aspect ratio) is preferably 2 or less, more preferably 1.5 or less, and even more preferably 1.2 or less. Generally, when the magnetic powder is in a non-spherical flat shape, it is easier to increase the relative magnetic permeability. However, especially when using spherical magnetic powder, the magnetic loss can usually be reduced, and a magnetic paste with a preferred viscosity can be obtained, which is preferred from this perspective.

[0053] From the viewpoint of increasing the relative magnetic permeability, the average particle diameter of the (A) magnetic powder preferably is 0.01 μm or more, more preferably 0.5 μm or more, and still more preferably 1 μm or more. Further, it preferably is 10 μm or less, more preferably 9 μm or less, and still more preferably 8 μm or less.

[0054] The average particle diameter of the (A) 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 can be prepared on a volume basis by a laser diffraction scattering type particle size distribution measuring device, and the median diameter thereof can be measured as the average particle diameter. As the measurement sample, a sample obtained by dispersing the magnetic powder in water by ultrasonic waves is preferably used. As the laser diffraction scattering type particle size distribution measuring device, “LA-500” manufactured by Horiba, Ltd., “SALD-2200” manufactured by Shimadzu Corporation, etc. can be used.

[0055] From the viewpoint of increasing the relative magnetic permeability, the specific surface area of the (A) magnetic powder preferably is 0.05 m 2 / g or more, more preferably 0.1 m 2 / g or more, and still more preferably 0.3 m 2 / g or more. Further, it preferably is 10 m 2 / g or less, more preferably 8 m 2 / g or less, and still more preferably 5 m 2 / g or less. The specific surface area of the (A) magnetic powder can be measured by the BET method.

[0056] Regarding the (A) magnetic powder, from the viewpoint of adjusting the viscosity of the magnetic paste and further improving the moisture resistance and dispersibility, surface treatment can be performed with a surface treatment agent. Examples of the surface treatment agent include vinyl silane coupling agents, (meth)acrylic acid coupling agents, fluorosilane coupling agents, amino silane coupling agents, epoxy group silane coupling agents, mercapto silane coupling agents, silane coupling agents, alkoxysilanes, organosilazane compounds, titanate coupling agents, etc. The surface treatment agent can be used alone as 1 type, or two or more types can be used in any combination.

[0057] Examples of commercially available surface treatment agents include, for example, "KBM-1003" (vinyltriethoxysilane) manufactured by Shin-Etsu Chemical Co., Ltd., "KBM-503" (3-methacryloxypropyltriethoxysilane) manufactured by Shin-Etsu Chemical Co., Ltd., "KBM-403" (3-glycidoxypropyltrimethoxysilane) manufactured by Shin-Etsu Chemical Co., Ltd., "KBM-803" (3-mercaptopropyltrimethoxysilane) manufactured by Shin-Etsu Chemical Co., Ltd., "KBE-903" (3-aminopropyltriethoxysilane) manufactured by Shin-Etsu Chemical Co., Ltd., "KBM-573" (N-phenyl-3-aminopropyltrimethoxysilane) manufactured by Shin-Etsu Chemical Co., Ltd., "SZ-31" (hexamethyldisilazane) manufactured by Shin-Etsu Chemical Co., Ltd., "KBM-103" (phenyltrimethoxysilane) manufactured by Shin-Etsu Chemical Co., Ltd., "KBM-4803" (long-chain epoxy type silane coupling agent) manufactured by Shin-Etsu Chemical Co., Ltd., "KBM-7103" (3,3,3-trifluoropropyltrimethoxysilane) manufactured by Shin-Etsu Chemical Co., Ltd., etc.

[0058] From the viewpoint of improving the dispersibility of (A) magnetic powder, the degree of surface treatment with a surface treatment agent is preferably within a specified range. Specifically, 100 parts by mass of (A) magnetic powder is preferably surface-treated with 0.01 to 5 parts by mass of a surface treatment agent, more preferably surface-treated with 0.05 to 3 parts by mass of a surface treatment agent, and even more preferably surface-treated with 0.1 to 2 parts by mass of a surface treatment agent.

[0059] From the viewpoint of improving the relative magnetic permeability and reducing the loss factor, when the non-volatile components in the magnetic paste are 100% by volume, the content (volume%) of (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. In addition, it is preferably 85% by volume or less, more preferably 80% by volume or less, and even more preferably 70% by volume or less.

[0060] From the viewpoint of improving the relative magnetic permeability and reducing the loss factor, when the non-volatile components in the magnetic paste are 100% by mass, the content (mass%) of (A) magnetic powder is preferably 60% by mass or more, more preferably 70% by mass or more, and even more preferably 75% by mass or more. In addition, it is preferably 98% by mass or less, more preferably 95% by mass or less, and even more preferably 90% by mass or less.

[0061] It should be noted that in the present invention, unless otherwise specified, the content of each component in the magnetic paste is the value when the non-volatile components in the magnetic paste are 100% by mass.

[0062] <(B) Epoxy resin>

[0063] The magnetic paste contains (B) an epoxy resin. However, the component (B) does not include components belonging to (C) reactive diluents. The component (B) can be used alone as one kind, or two or more kinds can be used in combination.

[0064] Examples of the (B) epoxy resin include, for example: bisphenol A type epoxy resin; bisphenol F type epoxy resin; bisphenol S type epoxy resin; bisphenol AF type epoxy resin; dicyclopentadiene type epoxy resin; triphenol type epoxy resin; phenol novolac type epoxy resin; tert-butyl-catechol type epoxy resin; naphthol novolac type epoxy resin, naphthalene type epoxy resin, naphthol type epoxy resin, anthracene type epoxy resin and other epoxy resins having a condensed ring structure; glycidylamine type epoxy resin; glycidyl ester type epoxy resin; cresol novolac type epoxy resin; biphenyl type epoxy resin; linear aliphatic epoxy resin; epoxy resin having a butadiene structure; alicyclic epoxy resin; heterocyclic type epoxy resin; epoxy resin containing a spiro ring; cyclohexanedimethanol type epoxy resin; trimethylol type epoxy resin; tetraphenylethane type epoxy resin; a resin obtained by monodispensing (single dispersion) core-shell rubber particles in an epoxy resin, etc. The (B) epoxy resin can be used alone as one kind, or two or more kinds can be used in combination. The (B) epoxy resin is preferably one or more selected from a resin obtained by monodispensing core-shell rubber particles in an epoxy resin, bisphenol A type epoxy resin, and bisphenol F type epoxy resin.

[0065] The (B) epoxy resin preferably includes an epoxy resin having two or more epoxy groups in one molecule. In addition, the (B) epoxy resin preferably has an aromatic structure, and in the case of using two or more epoxy resins, it is better that at least one has an aromatic structure. The aromatic structure refers to a chemical structure generally defined as aromatic, and also includes polycyclic aromatics and aromatic heterocycles. With respect to 100% by mass of the non-volatile components of the epoxy resin, the proportion of the epoxy resin having two or more epoxy groups in one molecule is preferably 50% by mass or more, more preferably 60% by mass or more, and particularly preferably 70% by mass or more.

[0066] The epoxy resin includes an epoxy resin that is liquid at 25°C (hereinafter sometimes referred to as "liquid epoxy resin") and an epoxy resin that is solid at 25°C (hereinafter sometimes referred to as "solid epoxy resin"). For the magnetic paste, as the (B) epoxy resin, it may contain only the liquid epoxy resin, or may contain only the solid epoxy resin. From the viewpoint of reducing the viscosity of the magnetic paste and improving the filling property in the through holes, it is preferably to contain only the liquid epoxy resin.

[0067] As the liquid epoxy resin, bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol AF type epoxy resin, naphthalene type epoxy resin, glycidyl ester type epoxy resin, glycidyl amine type epoxy resin, phenol novolac type epoxy resin, alicyclic epoxy resin having an ester skeleton, cyclohexanedimethanol type epoxy resin, and epoxy resin having a butadiene structure are preferably used, and glycidyl amine type epoxy resin, bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol AF type epoxy resin, and naphthalene type epoxy resin are more preferably used. Specific examples of the liquid epoxy resin include: "HP4032", "HP4032D", "HP4032SS" (naphthalene type epoxy resin) manufactured by DIC Corporation; "828US", "jER828EL" (bisphenol A type epoxy resin), "jER807" (bisphenol F type epoxy resin), "jER152" (phenol novolac type epoxy resin) manufactured by Mitsubishi Chemical Corporation; "630", "630LSD" (glycidyl amine type epoxy resin) manufactured by Mitsubishi Chemical Corporation; "ZX1059" (a mixture of bisphenol A type epoxy resin and bisphenol F type epoxy resin) manufactured by NIPPON STEEL Chemical & Material Co., Ltd.; "EX-721" (glycidyl ester type epoxy resin) manufactured by Nagase ChemteX Corporation; "PB-3600" (epoxy resin having a butadiene structure); "MX-153" (bisphenol A type epoxy resin containing an organic filler having a core-shell structure) manufactured by Kaneka Corporation, etc. They may be used alone or in combination of two or more.

[0068] As the solid epoxy resin, naphthalene-type tetrafunctional epoxy resins, cresol novolac epoxy resins, dicyclopentadiene-type epoxy resins, triphenol-type epoxy resins, naphthol-type epoxy resins, biphenyl-type epoxy resins, naphthyl ether-type epoxy resins, anthracene-type epoxy resins, bisphenol A-type epoxy resins, and tetraphenylethane-type epoxy resins are preferable, and naphthalene-type tetrafunctional epoxy resins, naphthol-type epoxy resins, and biphenyl-type epoxy resins are more preferable. Specific examples of the solid epoxy resin include: "HP4032H" (naphthalene-type epoxy resin), "HP-4700", "HP-4710" (naphthalene-type tetrafunctional epoxy resins), "N-690" (cresol novolac epoxy resin), "N-695" (cresol novolac epoxy resin), "HP-7200", "HP-7200HH", "HP-7200H" (dicyclopentadiene-type epoxy resins), "EXA-7311", "EXA-7311-G3", "EXA-7311-G4", "EXA-7311-G4S", "HP6000" (naphthyl ether-type epoxy resins) manufactured by DIC Corporation; "EPPN-502H" (triphenol-type epoxy resin), "NC7000L" (naphthol novolac epoxy resin), "NC3000H", "NC3000", "NC3000L", "NC3100" (biphenyl-type epoxy resins) manufactured by Nippon Kayaku Co., Ltd.; "ESN475V" (naphthalene-type epoxy resin), "ESN485" (naphthol novolac epoxy resin) manufactured by Nippon Steel Chemical & Material Co., Ltd.; "YX4000H", "YL6121" (biphenyl-type epoxy resins), "YX4000HK" (xylenol-type epoxy resin), "YX8800" (anthracene-type epoxy resin) manufactured by Mitsubishi Chemical Corporation; "PG-100", "CG-500" manufactured by Osaka Gas Chemical Co., Ltd., "YL7760" (bisphenol AF-type epoxy resin), "YL7800" (fluorene-type epoxy resin), "jER1010" (solid bisphenol A-type epoxy resin), "jER1031S" (tetraphenylethane-type epoxy resin), etc. manufactured by Mitsubishi Chemical Corporation. They may be used alone or in combination of two or more.

[0069] As the (B) epoxy resin, in the case of using a liquid epoxy resin and a solid epoxy resin, the ratio of their amounts (liquid epoxy resin: solid epoxy resin) is preferably in the range of 1:0.01 to 1:2 by mass. By setting the ratio of the liquid epoxy resin to the solid epoxy resin within such a range, effects such as obtaining a cured product having sufficient fracture strength can be achieved. 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 1:0.02 to 1:1 by mass, still more preferably in the range of 1:0.03 to 1:0.5 by mass, and particularly preferably in the range of 1:0.05 to 1:0.3 by mass.

[0070] From the viewpoint of obtaining a magnetic layer showing good mechanical strength, when the non-volatile components in the magnetic paste are set to 100% by mass, the content of the (B) epoxy resin is preferably 1% by mass or more, more preferably 5% by mass or more, still more preferably 10% by mass or more, preferably 30% by mass or less, more preferably 20% by mass or less, and still more preferably 15% by mass or less.

[0071] From the viewpoint of obtaining a magnetic layer showing good mechanical strength and insulation reliability, in the case where the non-volatile components in the magnetic paste are set to 100% by volume, the content (volume%) of the (B) epoxy resin is preferably 1% by volume or more, more preferably 3% by volume or more, still more preferably 5% by volume or more, preferably 30% by volume or less, more preferably 27% by volume or less, and still more preferably 25% by volume or less.

[0072] 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., still more preferably 60 g / eq. to 2000 g / eq., and even more preferably 70 g / eq. to 1000 g / eq. By setting it within this range, a magnetic layer with a sufficient crosslinking density of the cured product can be obtained. It should be noted that the epoxy equivalent can be measured according to JIS K7236 and is the mass of the resin containing 1 equivalent of epoxy groups.

[0073] The viscosity of the (B) epoxy resin is preferably 0.5 Pa･s or more, preferably 1000 Pa･s or less, more preferably 500 Pa･s or less, and still more preferably 100 Pa･s or less. Here, the viscosity of the epoxy resin is the value measured using an E-type viscometer at 25 ± 2°C.

[0074] (B) The weight-average molecular weight of the epoxy resin is preferably 100 or more, more preferably 250 or more, still more preferably 400 or more, preferably 5000 or less, more preferably 3000 or less, and still more preferably 1500 or less. Herein, the weight-average molecular weight of the epoxy resin is the weight-average molecular weight in terms of polystyrene measured by gel permeation chromatography (GPC).

[0075] <(C) Reactive diluent>

[0076] The magnetic paste contains (C) a reactive diluent. In the present invention, a trifunctional or higher-functional reactive diluent is included as the (C) component. Generally, the higher the content of the (A) magnetic powder in the magnetic paste, the more significant the decrease in stain removal tolerance and the decrease in the adhesion between the magnetic layer and the conductor layer, which are the problems of the present invention. In the magnetic paste of the present invention, by making the magnetic paste contain a trifunctional or higher-functional reactive diluent, even when the content of the (A) magnetic powder is high, a cured product with improved stain removal tolerance and adhesion between the magnetic layer and the conductor layer can be obtained. The (C) component can be used alone or in combination of two or more.

[0077] (C) The reactive diluent contains a trifunctional or higher-functional reactive diluent. The trifunctional or higher-functional reactive diluent is a reactive diluent having 3 or more reactive groups, preferably tetrafunctional or higher, more preferably pentafunctional or higher, preferably decafunctional or lower, more preferably octafunctional or lower, and still more preferably hexafunctional or lower.

[0078] Examples of the reactive group include, for example, an epoxy group, an acryloyl group, a methacryloyl group, an oxetanyl group, etc. Among them, as the reactive group, from the viewpoint of further decreasing the viscosity of the magnetic paste, an epoxy group is preferably used.

[0079] For the (C) reactive diluent, in addition to containing a trifunctional or higher-functional reactive diluent, it may further contain a difunctional or lower-functional reactive diluent as a reactive diluent having 2 or less of the above-mentioned reactive groups.

[0080] Regarding the content of the trifunctional or higher-functional reactive diluent, from the viewpoint of significantly obtaining the effects of the present invention, when the total amount of the (C) component is 100% by mass, it is preferably 20% by mass or more, more preferably 25% by mass or more, still more preferably 30% by mass or more, 35% by mass or more, preferably 100% by mass or less, more preferably 95% by mass or less, and still more preferably 90% by mass or less.

[0081] As a polyfunctional active diluent with three or more functional groups, commercially available products can be used. Specific examples of commercially available polyfunctional active diluents with three or more functional groups that can be used include "EX-321L" (aliphatic triglycidyl ether) manufactured by Nagase ChemteX Corporation, "PETG" (aliphatic tetraglycidyl ether) manufactured by Showa Denko K.K., and "ED-505" (aliphatic triglycidyl ether) manufactured by ADEKA Corporation. They can be used alone or in combination of two or more.

[0082] Regarding the content of the bifunctional or less active diluent, from the viewpoint of significantly obtaining the effects of the present invention, when the whole component (C) is set to 100% by mass, it is preferably 0% by mass or more, more preferably 5% by mass or more, still more preferably 10% by mass or more, preferably 80% by mass or less, more preferably 75% by mass or less, still more preferably 70% by mass or less, 65% by mass or less.

[0083] As the bifunctional or less active diluent, commercially available products can be used. Specific examples of commercially available bifunctional or less active diluents that can be used include: "EX-201" (cycloaliphatic glycidyl ether) manufactured by Nippon Steel Chemical & Materials Co., Ltd.; "EX-830", "EX-821" (ethylene glycol type epoxy resin); "EX-212" (hexanediol type epoxy resin); "ZX1658", "ZX1658GS" (liquid 1,4-glycidylcyclohexane); "EP-3980S" (glycidylamine type epoxy resin), "EP-4088S", "EP-4088L" (dicyclopentadiene type epoxy resin), ED-509S (tert-butylphenyl glycidyl ether) manufactured by ADEKA Corporation; X-22-163 (siloxane type epoxy resin) manufactured by Shin-Etsu Chemical Co., Ltd., etc. They can be used alone or in combination of two or more.

[0084] (C) The viscosity of the active diluent is preferably 0.001 Pa･s or more, more preferably 0.005 Pa･s or more, still more preferably 0.01 Pa･s or more. The upper limit is preferably less than 0.5 Pa･s. The viscosity of the active diluent can be measured by the same method as the viscosity of (B) epoxy resin.

[0085] When (C) the active diluent has a glycidyl group or an epoxy group, the epoxy equivalent of (C) the active diluent is preferably 50 g / eq. to 5000 g / eq., more preferably 50 g / eq. to 3000 g / eq., still more preferably 60 g / eq. to 2000 g / eq., and even more preferably 70 g / eq. to 1000 g / eq. By making it within this range, a magnetic layer with sufficient crosslinking density of the cured product can be obtained.

[0086] From the viewpoint of significantly obtaining the effects of the present invention, when the non-volatile components in the magnetic paste are set to 100% by mass, the content of the (C) reactive diluent is preferably 0.5% by mass or more, more preferably 1% by mass or more, still more preferably 3% by mass or more, preferably 10% by mass or less, more preferably 7% by mass or less, and still more preferably 5% by mass or less.

[0087] From the viewpoint of significantly obtaining the effects of the present invention, when the non-volatile components in the magnetic paste are set to 100% by mass, the content of the trifunctional or higher reactive diluent is preferably 0.5% by mass or more, more preferably 1% by mass or more, still more preferably 2% by mass or more, preferably 10% by mass or less, more preferably 7% by mass or less, and still more preferably 5% by mass or less.

[0088] From the viewpoint of significantly obtaining the effects of the present invention, when the non-volatile components in the magnetic paste are set to 100% by mass, the content of the bifunctional or lower reactive diluent is preferably 0% by mass or more, more preferably 0.1% by mass or more, still more preferably 0.3% by mass or more, preferably 3% by mass or less, more preferably 1.5% by mass or less, and still more preferably 1% by mass or less.

[0089] When the content (mass%) of the trifunctional or higher reactive diluent when the non-volatile components in the magnetic paste are set to 100% by mass is set to C3, and the content (mass%) of the bifunctional or lower reactive diluent when the non-volatile components in the magnetic paste are set to 100% by mass is set to C2, as C2 / (C2 + C3), it is preferably 0 or more, more preferably 0.1 or more, still more preferably 0.2 or more, preferably 5 or less, more preferably 1 or less, and still more preferably 0.7 or less. By adjusting the contents of the trifunctional or higher reactive diluent and the bifunctional or lower reactive diluent so that C2 / (C2 + C3) is within the above range, the desired effects of the present invention can be obtained more significantly.

[0090] When the content (mass%) of the (C) reactive diluent when the non-volatile components in the magnetic paste are set to 100% by mass is set to C1, and the content (mass%) of the (B) epoxy resin when the non-volatile components in the magnetic paste are set to 100% by mass is set to B1, B1 / C1 is preferably 0.1 or more, more preferably 0.5 or more, still more preferably 1 or more, 3 or more, preferably 10 or less, more preferably 8 or less, and still more preferably 5 or less. By adjusting the contents of the (B) component and the (C) component so that B1 / C1 is within the above range, the desired effects of the present invention can be obtained more significantly.

[0091] In addition, B1 / C3 is preferably 1 or more, more preferably 2 or more, still more preferably 3 or more, preferably 20 or less, more preferably 10 or less, and still more preferably 8 or less. By adjusting the contents of component (B) and component (C) so that B1 / C3 is within the above-mentioned range, the desired effects of the present invention can be obtained more significantly.

[0092] <(D) Curing Agent>

[0093] The magnetic paste contains (D) a curing agent. The (D) curing agent includes: an epoxy resin curing agent having a function of curing (B) the epoxy resin, and a curing accelerator having a function of accelerating the curing rate of (B) the epoxy resin. The magnetic paste preferably contains either the epoxy resin curing agent or the curing accelerator as the (D) curing agent, and more preferably contains the curing accelerator.

[0094] (Epoxy Resin Curing Agent)

[0095] Examples of the epoxy resin curing agent include, for example: acid anhydride type epoxy resin curing agents, phenol type epoxy resin curing agents, naphthol type epoxy resin curing agents, active ester type epoxy resin curing agents, benzoxazine type epoxy resin curing agents, cyanate ester type epoxy resin curing agents, and amine type epoxy resin curing agents. From the viewpoint of reducing the viscosity of the magnetic paste, the acid anhydride type epoxy resin curing agent is preferably used. The epoxy resin curing agent can be used alone as one kind, or two or more kinds can be used in combination.

[0096] Examples of the acid anhydride type epoxy resin curing agent include epoxy resin curing agents having one or more acid anhydride groups in one molecule. Specific examples of the acid anhydride type epoxy resin curing agent include, for example: 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 dianhydride, biphenyltetracarboxylic dianhydride, naphthalenetetracarboxylic dianhydride, oxydiphthalic dianhydride, 3,3'-4,4'-diphenylsulfone tetracarboxylic 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(trimellitate), polymers such as styrene-maleic acid resin obtained by copolymerizing styrene and maleic acid, and the like.

[0097] Examples of commercially available acid anhydride type epoxy resin curing agents include "HNA-100", "MH-700", etc. manufactured by Shin Nippon Rika Co., Ltd.

[0098] As a phenol-based epoxy resin curing agent and a naphthol-based epoxy resin curing agent, from the viewpoints of heat resistance and water resistance, it is preferably a phenol-based epoxy resin curing agent having a novolac structure or a naphthol-based epoxy resin curing agent having a novolac structure. As the phenol-based epoxy resin curing agent, a nitrogen-containing phenol-based epoxy resin curing agent is preferable, a phenol-based epoxy resin curing agent having a triazine skeleton is more preferable, and a phenol novolac epoxy resin curing agent having a triazine skeleton is further more preferable.

[0099] Specific examples of the phenol-based epoxy resin curing agent and the naphthol-based epoxy resin curing agent include, for example, "MEH-7700", "MEH-7810", "MEH-8000" manufactured by Meiko Kasei Co., Ltd., "NHN", "CBN", "GPH" manufactured by Nippon Kayaku Co., Ltd., "SN170", "SN180", "SN190", "SN475", "SN485", "SN495V", "SN375", "SN395" manufactured by Nippon Steel Chemical & Material Co., Ltd., "TD-2090", "LA-7052", "LA-7054", "LA-1356", "LA-3018-50P", "EXB-9500", "HPC-9500", "KA-1160", "KA-1163", "KA-1165" manufactured by DIC Corporation, "GDP-6115L", "GDP-6115H", etc. manufactured by Gunei Chemical Industry Co., Ltd.

[0100] As the epoxy resin curing agent of the active ester type, there is no particular limitation. Generally, it is preferably a compound having two or more highly reactive ester groups in one molecule, such as phenol ester (phenolester) type, thiophenol ester type, N-hydroxyamine ester type, ester type of heterocyclic hydroxy compounds, etc. The epoxy resin curing agent of the active ester type is preferably a compound 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. Especially from the viewpoint of improving heat resistance, the epoxy resin curing agent of the active ester type obtained from a carboxylic acid compound and a hydroxy compound is preferred, and the epoxy resin curing agent of the active ester type obtained from a carboxylic acid compound and a phenol compound and / or a naphthol compound is more preferred. Examples of the carboxylic acid compound include benzoic acid, acetic acid, succinic acid, maleic acid, itaconic acid, phthalic acid, isophthalic acid, terephthalic acid, pyromellitic acid, etc. Examples of the phenol compound or naphthol compound include hydroquinone, resorcinol, bisphenol A, bisphenol F, bisphenol S, phenolphthalin, 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, phloroglucinol, pyrogallol, dicyclopentadiene type diphenol compound, phenol novolac resin, etc. Herein, the "dicyclopentadiene type diphenol compound" refers to a diphenol compound obtained by condensing two molecules of phenol with one molecule of dicyclopentadiene.

[0101] Specifically, it is preferably an epoxy resin curing agent of the active ester type containing a dicyclopentadiene type diphenol structure, an epoxy resin curing agent of the active ester type containing a naphthalene structure, an epoxy resin curing agent of the active ester type containing an acetylated product of phenol novolac, and an epoxy resin curing agent of the active ester type containing a benzoylated product of phenol novolac. The "dicyclopentadiene type diphenol structure" represents a divalent structure formed by phenylene-dicyclopentylene-phenylene.

[0102] As commercially available active ester epoxy resin curing agents, active ester epoxy resin curing agents containing a dicyclopentadiene-type diphenol structure include "EXB9451", "EXB9460", "EXB9460S", "HPC-8000-65T", "HPC-8000H-65TM", and "EXB-8000L-65TM" manufactured by DIC Corporation; active ester compounds containing a naphthalene structure include "EXB9416 -70BK"; active ester epoxy resin curing agents containing acetylated phenol novolacs include "DC808" manufactured by Mitsubishi Chemical Corporation; active ester epoxy resin curing agents containing benzoylated phenol novolacs include "YLH1026", "YLH1030" and "YLH1048" manufactured by Mitsubishi Chemical Corporation; active ester epoxy resin curing agents as acetylated phenol novolacs include "DC808" manufactured by Mitsubishi Chemical Corporation; and the like.

[0103] Specific examples of the benzoxazine-based epoxy resin curing agent include "HFB2006M" manufactured by Showa Highpolymer Co., Ltd. and "Pd" and "Fa" manufactured by Shikoku Chemicals Co., Ltd.

[0104] Examples of cyanate epoxy resin curing agents include difunctional cyanate resins such as bisphenol A dicyanate, polyphenol cyanate, oligo(3-methylene-1,5-phenylene cyanate), 4,4'-methylenebis(2,6-dimethylphenylcyanate), 4,4'-ethylenediphenyl dicyanate, hexafluorobisphenol A dicyanate, 2,2-bis(4-cyanate)phenylpropane, 1,1-bis(4-cyanatephenylmethane), bis(4-cyanate-3,5-dimethylphenyl)methane, 1,3-bis(4-cyanatephenyl-1-(methylethylene))benzene, bis(4-cyanatephenyl)sulfide, and bis(4-cyanatephenyl)ether; polyfunctional cyanate resins derived from phenol novolac resins and cresol novolac resins; and prepolymers obtained by triazinizing a portion of these cyanate resins. Specific examples of cyanate ester epoxy resin curing agents include "PT30" and "PT60" manufactured by Lonza Japan Co., Ltd. (both are phenol novolac-type multifunctional cyanate resins), "BA230", and "BA230S75" (prepolymers in which part or all of bisphenol A dicyanate is triazine-treated to form a trimer), etc.

[0105] Examples of the amine-based epoxy resin curing agent include epoxy resin curing agents having amines and having one or more active hydrogen atoms in one molecule. Specific examples of the amine-based epoxy resin curing agent include diethylenetriamine, triethylenetetramine, diaminodiphenylsulfone, and dicyandiamide.

[0106] Examples of commercially available amine-based epoxy resin curing agents include "DICY7" manufactured by Mitsubishi Chemical Corporation, etc.

[0107] The amount ratio of the epoxy resin to the epoxy resin curing agent, in terms of the ratio of [total number of epoxy groups in the epoxy resin]:[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 of the epoxy resin curing agent refer to active hydroxyl groups, active ester groups, etc., which vary depending on the type of the epoxy resin curing agent. In addition, the total number of epoxy groups in the epoxy resin is the value obtained by summing up the values obtained by dividing the mass of the non-volatile component of each epoxy resin by the epoxy equivalent for all epoxy resins, and the total number of reactive groups in the epoxy resin curing agent is the value obtained by summing up the values obtained by dividing the mass of the non-volatile component of each epoxy resin curing agent by the reactive group equivalent for all epoxy resin curing agents. By setting the amount ratio of the epoxy resin to the epoxy resin curing agent within such a range, the heat resistance when forming a cured product is further improved.

[0108] From the viewpoint of significantly obtaining the desired effects of the present invention, when the non-volatile component in the magnetic paste is set to 100% by mass, the content of the epoxy resin curing agent is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, and even more preferably 0.3% by mass or more. 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.

[0109] (Curing accelerator)

[0110] Examples of the curing accelerator include, for example, amine-based curing accelerators, imidazole-based curing accelerators, phosphorus-based curing accelerators, guanidine-based curing accelerators, metal-based curing accelerators, etc. The curing accelerator can be used alone as one kind, or two or more kinds can be used in combination.

[0111] Examples of the amine-based curing accelerator include, for example: trialkylamines such as triethylamine and tributylamine, 4-dimethylaminopyridine, benzyldimethylamine, 2,4,6-tris(dimethylaminomethyl)phenol, 1,8-diazabicyclo[5.4.0]undecene, etc., and preferably 4-dimethylaminopyridine and 1,8-diazabicyclo[5.4.0]undecene.

[0112] As the amine-based curing accelerator, commercially available products can be used, and examples include "MY-25" manufactured by Ajinomoto Fine-Techno Co., Ltd., etc.

[0113] Examples of imidazole-based curing accelerators include, for example: 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, 1-benzyl-2-phenylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 1-cyanoethyl-2-phenylimidazole, 1-cyanoethyl-2-undecylimidazolium 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-phenyl-4-methyl-5-hydroxymethylimidazole, 2,3-dihydro-1H-pyrrolo[1,2-a]benzimidazole, 1-dodecyl-2-methyl-3-benzylimidazolium chloride, 2-methylimidazoline, 2-phenylimidazoline and other imidazole compounds, and adducts of imidazole compounds and epoxy resins. Preferably, they are 2-ethyl-4-methylimidazole and 1-benzyl-2-phenylimidazole.

[0114] As imidazole-based curing accelerators, commercially available products can be used. Examples include "2MZA-PW" and "2PHZ-PW" manufactured by Shikoku Kasei Kogyo Co., Ltd., and "P200-H50" manufactured by Mitsubishi Chemical Corporation.

[0115] Examples of phosphorus-based curing accelerators include, for example: triphenylphosphine, phosphonium borate compounds, tetraphenylphosphonium tetraphenylborate, n-butylphosphonium tetraphenylborate, tetrabutylphosphonium caprate, (4-methylphenyl)triphenylphosphonium thiocyanate, tetraphenylphosphonium thiocyanate, butyltriphenylphosphonium thiocyanate, etc. Preferably, they are triphenylphosphine and tetrabutylphosphonium caprate.

[0116] 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, 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene, 1-methylbiguanide, 1-ethylbiguanide, 1-n-butylbiguanide, 1-n-octadecylbiguanide, 1,1-dimethylbiguanide, 1,1-diethylbiguanide, 1-cyclohexylbiguanide, 1-allylbiguanide, 1-phenylbiguanide, 1-(o-tolyl)biguanide, etc. Dicyandiamide and 1,5,7-triazabicyclo[4.4.0]dec-5-ene are preferred.

[0117] 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 organocobalt complexes such as cobalt(II) acetylacetonate and cobalt(III) acetylacetonate, organocopper complexes such as copper(II) acetylacetonate, organozinc complexes such as zinc(II) acetylacetonate, organoiron complexes such as iron(III) acetylacetonate, organonickel complexes such as nickel(II) acetylacetonate, and organomanganese complexes such as manganese(II) acetylacetonate. Examples of organometallic salts include zinc octoate, tin octoate, zinc naphthenate, cobalt naphthenate, tin stearate, zinc stearate, etc.

[0118] As the curing agent (D), from the viewpoint of obtaining the desired effects of the present invention, a curing accelerator is preferred, and at least one selected from amine-based curing accelerators and imidazole-based curing accelerators is more preferred, and an imidazole-based curing accelerator is even more preferred.

[0119] From the viewpoint of reducing the viscosity of the magnetic paste, when the non-volatile components in the magnetic paste are 100% by mass, the content of the curing accelerator is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, and even more preferably 0.3% by mass or more. 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.

[0120] From the viewpoint of significantly obtaining the desired effects of the present invention, when the non-volatile components in the magnetic paste are 100% by mass, the content of the curing agent (D) is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, and even more preferably 0.3% by mass or more. 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.

[0121] <(E) Dispersant>

[0122] The magnetic paste may further contain (E) a dispersant as an optional component.

[0123] As the (E) dispersant, examples thereof include: phosphate ester dispersants such as polyoxyethylene alkyl ether phosphate esters; anionic dispersants such as sodium dodecylbenzenesulfonate, sodium laurate, and ammonium salts of polyoxyethylene alkyl ether sulfates; nonionic dispersants such as organosiloxane dispersants, acetylene glycol, polyoxyethylene alkyl ethers, polyoxyethylene alkyl esters, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene alkyl phenyl ethers, polyoxyethylene alkyl amines, and polyoxyethylene alkyl amides. Among them, anionic dispersants are preferably used. The dispersant can be used alone or in combination of two or more kinds.

[0124] Commercially available products can be used as the phosphate ester dispersants. As commercially available products, for example, "RS-410", "RS-610", "RS-710", etc. of the "Phosphanol (フォスファノール)" series manufactured by Toho Chemical Industry Co., Ltd. can be cited.

[0125] As the organosiloxane dispersants, commercially available products such as "BYK347", "BYK348", etc. manufactured by BYK-Chemie can be cited.

[0126] As the polyalkylene oxide dispersants, commercially available products such as "AKM-0531", "AFB-1521", "SC-0505K", "SC-1015F", "SC-0708A", and "HKM-50A" of the "MALIALIM" series manufactured by NOF Corporation can be cited. The polyalkylene oxide dispersants refer to the general term for aggregating polyoxyethylene alkyl ethers, polyoxyethylene alkyl esters, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene alkyl phenyl ethers, polyoxyethylene alkyl amines, polyoxyethylene alkyl amides, etc.

[0127] As acetylene glycol, commercially available products such as "82", "104", "440", "465", "485", and "Olefin Y (オレフィンY)" of the "Surfynol" series manufactured by Air Products and Chemicals Inc. can be cited.

[0128] From the viewpoint of significantly exerting the effects of the present invention, when the non-volatile components in the magnetic paste are 100% by mass, the content of the (E) dispersant is preferably 0.1% by mass or more, more preferably 0.3% by mass or more, still more preferably 0.5% by mass or more, and the upper limit is preferably 5% by mass or less, more preferably 3% by mass or less, still more preferably 1% by mass or less.

[0129] <(F) Other additives>

[0130] For the magnetic paste, (F) other additives may be further included as needed. Examples of such other additives include: thermoplastic resins, curing retarders such as triethyl borate for improving storage stability, inorganic fillers (however, materials belonging to magnetic powders are excluded), flame retardants, organic fillers, organometallic compounds such as organic copper compounds, organic zinc compounds, and organic cobalt compounds, and resin additives such as thickeners, defoamers, leveling agents, adhesion-imparting agents, and colorants.

[0131] The content of the solvent contained in the above magnetic paste is preferably less than 1.0% by mass, more preferably 0.8% by mass or less, still more preferably 0.5% by mass or less, and particularly preferably 0.1% by mass or less, relative to the total mass of the magnetic paste. The lower limit is not particularly limited and is 0.001% by mass or more or it may be free of it. By making the content of the organic solvent within the above range, the generation of pores can be suppressed, and the processability and operability can also be excellent.

[0132] The viscosity of the magnetic paste is usually 20 Pa･s or more, preferably 25 Pa･s or more, more preferably 30 Pa･s or more or 50 Pa･s or more, and usually less than 200 Pa･s, preferably 180 Pa･s or less, more preferably 160 Pa･s or less. The viscosity can be measured by the same method as the viscosity of (B) epoxy resin.

[0133] <Manufacturing method of magnetic paste>

[0134] The magnetic paste can be manufactured, for example, by a method of stirring the blending components with a stirring device such as a three-roll mill or a rotary mixer. The mixing order of components (A) to (F) is arbitrary.

[0135] <Physical properties, etc. of magnetic paste>

[0136] The cured product of the magnetic paste does not expand even after a defouling treatment, and thus exhibits excellent coating adhesion to the coating. Therefore, the above cured product provides a magnetic layer with excellent peel strength from the coating. As the peel strength indicating the coating adhesion, it is preferably 0.1 kgf / cm or more, more preferably 0.15 kgf / cm or more, still more preferably 0.2 kgf / cm or more. The upper limit is not particularly limited and can be set to 1.0 kgf / cm or less, etc. The peel strength can be measured by the method described in the examples below.

[0137] The cured product of the magnetic paste generally exhibits the characteristic of having a high relative magnetic permeability at a frequency of 100 MHz. Therefore, the aforementioned cured product gives a magnetic layer with a high relative magnetic permeability. The relative magnetic permeability of the cured product at a frequency of 100 MHz is preferably 3 or more, more preferably 4 or more, and even more preferably 5 or more. In addition, the upper limit is not particularly limited and can be set to 20 or less, etc. The relative magnetic permeability can be measured by the method described in the following examples.

[0138] The cured product of the magnetic paste generally exhibits the characteristic of having a low magnetic loss at a frequency of 100 MHz. Therefore, the aforementioned cured product gives a magnetic layer with a low magnetic loss. The magnetic loss of the cured product at a frequency of 100 MHz is preferably 1 or less, more preferably 0.5 or less, and even more preferably 0.2 or less. The lower limit is not particularly limited and can be set to 0.001 or more, etc. The magnetic loss can be measured by the method described in the following examples.

[0139] The magnetic paste exhibits the characteristic of having a low viscosity. Therefore, the magnetic paste can be suitably used as: a magnetic paste for filling through-holes.

[0140] [Circuit board and method for manufacturing the same]

[0141] The circuit board includes a substrate in which the through-holes are filled with the cured product of the magnetic paste of the present invention. For the circuit board, since the magnetic paste of the present invention is used, the stain removal tolerance is excellent, and as a result, a magnetic layer having a desired shape can be obtained. In addition, the magnetic paste of the present invention has an appropriate viscosity, and thus the filling property for through-holes is excellent.

[0142] For the circuit board, for example, the above-mentioned magnetic paste can be used and manufactured by a manufacturing method sequentially including the following steps (1) to (4):

[0143] (1) A step of filling a through-hole with a magnetic paste and thermally curing the magnetic paste to obtain a cured product;

[0144] (2) A step of grinding the surface of the cured product;

[0145] (3) A step of performing a stain removal treatment (roughening treatment) on the ground surface of the cured product;

[0146] (4) A step of forming a conductor layer on the ground surface of the cured product.

[0147] When performing step (1), a step of preparing the magnetic paste may be included. The magnetic paste is as described in the above description.

[0148] In addition, when performing step (1), as Figure 1As shown in one example, it may include a process of preparing a core substrate 10. Here, as the core substrate 10, a core substrate 10 having a support substrate 11 and first and second metal layers 12 and 13 formed of a metal such as copper foil on two surfaces of the support substrate 11 will be described as an example. 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.

[0149] In addition, as Figure 2 shown in one example, it may include a process of forming a through hole 14 in the core substrate 10. The through hole 14 can be formed, for example, by a drill, laser irradiation, plasma irradiation, etc. Specifically, a through hole can be formed in the core substrate 10 by using a drill or the like to form the through hole 14.

[0150] The formation of the through hole 14 can be carried out using a commercially available drill device. As a commercially available drill device, for example, "ND-1S211" manufactured by Hitachi High-Tech Corporation can be cited.

[0151] After the through hole 14 is formed in the core substrate 10, it may include a process of roughening the core substrate 10 and forming a plating layer on the inner surface of the through hole 14, the surface of the first metal layer 12, and the surface of the second metal layer 13.

[0152] As the aforementioned roughening treatment, either a dry or wet roughening treatment can be carried out. Examples of the dry roughening treatment include plasma treatment, etc. In addition, as an example of the wet roughening treatment, a method of sequentially performing a swelling treatment using a swelling liquid, a roughening treatment using an oxidizing agent, and a neutralization treatment using a neutralizing liquid can be cited.

[0153] The plating layer is formed by a plating method, and the steps of forming the plating layer by the plating method are the same as those for forming the conductor layer in process (4) described later.

[0154] After preparing the core substrate 10 in which the through hole 14 is formed, as Figure 3 shown in one example, the magnetic paste 20 is filled into the through hole 14. As a filling method, screen printing is usually carried out, and it can also be carried out by other methods, such as a method of filling the magnetic paste 20 via a dispenser, a method of filling the magnetic paste 20 into the through hole 14 via a squeegee, a method of filling the magnetic paste 20 via a cartridge, a method of filling the magnetic paste 20 by mask printing, a roll coating method, an inkjet method, etc.

[0155] After the magnetic paste 20 is filled into the through hole 14, the magnetic paste 20 is thermally cured, as Figure 4As shown in one example, a magnetic layer 20A is formed in the through hole 14. The thermal curing conditions of the magnetic paste 20 vary depending on the composition and type of the magnetic paste 20. The curing temperature is preferably 120°C or higher, more preferably 130°C or higher, still more preferably 150°C or higher, preferably 240°C or lower, more preferably 220°C or lower, and still more preferably 200°C or lower. The curing time of the magnetic paste 20 is preferably 5 minutes or longer, more preferably 10 minutes or longer, still more preferably 15 minutes or longer, preferably 120 minutes or shorter, more preferably 100 minutes or shorter, and still more preferably 90 minutes or shorter.

[0156] As the degree of curing of the magnetic layer 20A in step (1), it is preferably 80% or higher, more preferably 85% or higher, and still more preferably 90% or higher. Regarding the degree of curing, for example, a differential scanning calorimetry device can be used for measurement.

[0157] Before thermally curing the magnetic paste 20, a preheating treatment of heating the magnetic paste 20 at a temperature lower than the curing temperature can be performed. For example, before thermally curing the magnetic paste 20, the magnetic paste 20 is usually preheated at a temperature of 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 usually 5 minutes or longer (preferably 5 minutes to 150 minutes, more preferably 15 minutes to 120 minutes).

[0158] In step (2), as shown in one example Figure 5 the excess magnetic layer 20A protruding from or attached to the core substrate 10 is removed by grinding to perform planarization. As the grinding method, a method capable of grinding the excess magnetic layer 20A protruding from or attached to the core substrate 10 can be used. Examples of such grinding methods include polishing and belt grinding. Examples of commercially available polishing devices include "NT-700IM" manufactured by Ishii Koki Co., Ltd.

[0159] Regarding the arithmetic mean roughness (Ra) of the ground surface of the magnetic layer, from the viewpoint of forming the conductor layer, it is preferably 300 nm or higher, more preferably 350 nm or higher, and still more preferably 400 nm or higher. The upper limit is preferably 1000 nm or lower, more preferably 900 nm or lower, and still more preferably 800 nm or lower. The surface roughness (Ra) can be measured using a non-contact surface roughness meter, for example.

[0160] After process (2) and before process (4), for the purpose of further improving the degree of curing of the magnetic layer, etc., a heat treatment process can be carried out as required. The temperature in the heat treatment process can be carried out according to the above-mentioned curing temperature, preferably 120 °C or higher, more preferably 130 °C or higher, still more preferably 150 °C or higher, preferably 240 °C or lower, more preferably 220 °C or lower, still more preferably 200 °C or lower. The heat treatment time is preferably 5 minutes or longer, more preferably 10 minutes or longer, still more preferably 15 minutes or longer, preferably 90 minutes or shorter, more preferably 70 minutes or shorter, still more preferably 60 minutes or shorter.

[0161] In process (3), the polished surface of the magnetic layer 20A polished in process (2) is decontaminated. By carrying out process (3), contaminants generated in process (2) can be removed.

[0162] The steps and conditions of the roughening process are not particularly limited, and known steps and conditions commonly used in the manufacturing method of a multilayer printed wiring board can be adopted. As the roughening process, for example, the magnetic layer 20A can be roughened by sequentially performing a swelling treatment using a swelling liquid, a roughening treatment using an oxidizing agent, and a neutralization treatment using a neutralizing liquid.

[0163] The swelling liquid that can be used in the roughening process is not particularly limited, and examples include an alkali solution, a surfactant solution, etc., preferably an alkali solution. Regarding the alkali solution as the swelling liquid, sodium hydroxide solution and potassium hydroxide solution are more preferable. As commercially available swelling liquids, for example, "Swelling DipSecuriganth P" and "Swelling Dip Securiganth SBU" manufactured by Atotech Japan Co., Ltd. can be cited.

[0164] The swelling treatment using the swelling liquid is not particularly limited. For example, it can be carried out by immersing the core substrate 10 provided with the magnetic layer 20A in the swelling liquid at 30 °C to 90 °C for 1 minute to 20 minutes. From the viewpoint of controlling the swelling of the resin constituting the magnetic layer 20A at an appropriate level, it is preferable to immerse the magnetic layer 20A in the swelling liquid at 40 °C to 80 °C for 5 minutes to 15 minutes.

[0165] The oxidizing agent that can be used for the roughening treatment using an oxidizing agent is not particularly limited, and examples thereof include an alkaline permanganic acid solution obtained by dissolving potassium permanganate or sodium permanganate in an aqueous solution of sodium hydroxide. The roughening treatment using an oxidizing agent such as an alkaline permanganic acid solution is preferably carried out by immersing the magnetic layer 20A in the solution of the oxidizing agent heated to 60°C to 80°C for 10 minutes to 30 minutes. In addition, the concentration of the permanganate in the alkaline permanganic acid solution is preferably 5% by mass to 10% by mass. Examples of commercially available oxidizing agents include alkaline permanganic acid solutions such as "Concentrate Compact P" and "Dosing solution Securiganth P" manufactured by Atotech Japan Co., Ltd.

[0166] As the neutralizing liquid that can be used for the neutralization treatment, an acidic aqueous solution is preferably used. Examples of commercially available products include "Reduction solution Securiganth P" manufactured by Atotech Japan Co., Ltd. The neutralization treatment using the neutralizing liquid can be carried out by immersing the treated surface that has undergone the roughening treatment using the oxidizing agent solution in the neutralizing liquid at 30°C to 80°C for 5 minutes to 30 minutes. From the perspective of operability and the like, a method of immersing the magnetic layer 20A that has undergone the roughening treatment using the oxidizing agent solution in the neutralizing liquid at 40°C to 70°C for 5 minutes to 20 minutes is preferably used.

[0167] For the magnetic layer 20A, since it is formed of the cured product of the magnetic paste of the present invention having excellent stain removal tolerance, it exhibits the characteristic that even after the stain removal treatment, the arithmetic mean roughness (Ra) of the surface of the cured product is low. That is, a magnetic layer with excellent stain removal tolerance and excellent adhesion to the conductor layer is brought about. As the arithmetic mean roughness (Ra) of the magnetic layer 20A after the stain removal treatment, from the viewpoint of improving the adhesion to the plating layer, it is preferably 300 nm or more, more preferably 350 nm or more, and still more preferably 400 nm or more. The upper limit is preferably less than 1000 nm, more preferably 700 nm or less, and still more preferably 650 nm or less. The surface roughness (Ra) can be measured using, for example, a non-contact type surface roughness meter.

[0168] In step (4), a conductor layer is formed on the polished surface of the magnetic layer 20A. After forming the conductor layer as needed, a part of the conductor layer, the first metal layer 12, and the second metal layer 13 can be removed by etching or the like to form a patterned conductor layer.

[0169] Examples of the method for forming the conductor layer include, for example, plating methods, sputtering methods, evaporation plating methods, etc., among which the plating method is preferably used. In a preferred embodiment, plating is performed on the surface of the cured product by an appropriate method such as semi-additive method or full-additive method to form a patterned conductor layer having a desired wiring pattern. Examples of the material for the conductor layer include: single metals such as gold, platinum, palladium, silver, copper, aluminum, cobalt, chromium, zinc, nickel, titanium, tungsten, iron, tin, indium, etc.; alloys of two or more metals selected from gold, platinum, palladium, silver, copper, aluminum, cobalt, chromium, zinc, nickel, titanium, tungsten, iron, tin, and indium. Among them, from the viewpoints of versatility, cost, ease of patterning, etc., it is preferably to use chromium, nickel, titanium, aluminum, zinc, gold, palladium, silver or copper, or nickel-chromium alloy, copper-nickel alloy, copper-titanium alloy, and more preferably to use chromium, nickel, titanium, aluminum, zinc, gold, palladium, silver or copper, or nickel-chromium alloy, and even more preferably to use copper.

[0170] Here, an example of an embodiment of forming a patterned conductor layer on the ground surface of the cured product will be described in detail. An electroless plating seed layer is formed on the ground surface of the cured product by electroless plating. Then, an electroplated layer is formed on the formed electroless plating seed layer by electroplating. If necessary, the unnecessary electroless plating seed layer is removed by treatment such as etching, etc., and a conductor layer having a desired wiring pattern can be formed. After the conductor layer is formed, for the purpose of improving the peel strength of the conductor layer, etc., annealing treatment can be performed if necessary. The annealing treatment can be performed, for example, by heating the circuit board at 150 to 200 °C for 20 to 90 minutes.

[0171] After the conductor layer is formed, a mask pattern that exposes a part of the electroless plating seed layer is formed on the formed electroless plating seed layer corresponding to the desired wiring pattern. In this case, after an electroplated layer is formed on the exposed electroless plating seed layer by electroplating, the mask pattern is removed. Then, the unnecessary electroless plating seed layer is removed by treatment such as etching, etc., to form a patterned conductor layer having a desired wiring pattern.

[0172] 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.

[0173] [Inductor substrate]

[0174] The inductor substrate includes the circuit board of the present invention. Such an inductor substrate has an inductor pattern formed of a conductor at least in part around the cured product of the aforementioned magnetic paste. Such an inductor substrate can be applied to, for example, the inductor substrate described in Japanese Patent Laid-Open No. 2016-197624.

[0175] The inductor substrate can be used as a wiring board for mounting electronic components such as semiconductor chips, or as a (multi-layer) printed wiring board using the wiring board as an inner layer substrate. In addition, it can be used as a chip inductor component formed by singulating the wiring board, or as a printed wiring board on which the chip inductor component is surface-mounted.

[0176] In addition, the wiring board can be used to manufacture semiconductor devices in various forms. The semiconductor device including the wiring board can be suitably used for electrical products (such as computers, mobile phones, digital cameras, and televisions, etc.) and transportation means (such as motorcycles, automobiles, trams, ships, and aircraft, etc.). Examples

[0177] Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited to these examples. It should be noted that in the following description, unless otherwise specified, "parts" and "%" indicating amounts refer to "parts by mass" and "% by mass", respectively.

[0178] <Example 1>

[0179] 12 parts by mass of an 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 a core-shell dispersed epoxy resin (“MX-153”, a bisphenol A type epoxy resin containing an organic filler having a core-shell structure, the content of the organic filler is 33% by mass, the average particle size is 0.2 μm, manufactured by Kaneka Corporation), 5 parts by mass of a trifunctional or higher active diluent (“EX-321L”, an aliphatic triglycidyl ether, manufactured by Nagase ChemteX Corporation), 1 part by mass of a dispersant (“RS-710”, a phosphate ester dispersant, manufactured by Toho Chemical Co., Ltd.), 1 part by mass of a curing agent (“2MZA-PW”, an imidazole type curing accelerator, manufactured by Shikoku Kasei Co., Ltd.), and 120 parts by mass of a magnetic powder (“M05S”, an Fe-Mn type ferrite, the average particle size is 3 μm, manufactured by Powdertech Co., Ltd.) were mixed and uniformly dispersed with a three-roll mill to prepare magnetic paste 1.

[0180] <Example 2>

[0181] In Example 1,

[0182] The amount of the trifunctional or higher active diluent (“EX-321L”, an aliphatic triglycidyl ether, manufactured by Nagase ChemteX Corporation) was changed from 5 parts by mass to 4 parts by mass.

[0183] Furthermore, 1 part by mass of an active diluent having two or less functional groups (“ZX-1658GS”, cycloaliphatic diglycidyl ether, manufactured by Nippon Steel Chemical & Material Co., Ltd.) was used;

[0184] Except for the above matters, the operation was carried out in the same manner as in Example 1 to prepare Magnetic Paste 2.

[0185] <Example 3>

[0186] In Example 2,

[0187] the amount of the active diluent having two or less functional groups (“ZX-1658GS”, cycloaliphatic diglycidyl ether, manufactured by Nippon Steel Chemical & Material Co., Ltd.) was changed from 1 part by mass to 2 parts by mass,

[0188] and the amount of the active diluent having three or more functional groups (“EX-321L”, aliphatic triglycidyl ether, manufactured by Nagase ChemteX Corporation) was changed from 4 parts by mass to 3 parts by mass;

[0189] Except for the above matters, the operation was carried out in the same manner as in Example 2 to prepare Magnetic Paste 3.

[0190] <Example 4>

[0191] In Example 2,

[0192] the amount of the active diluent having two or less functional groups (“ZX-1658GS”, cycloaliphatic diglycidyl ether, manufactured by Nippon Steel Chemical & Material Co., Ltd.) was changed from 1 part by mass to 3 parts by mass,

[0193] and the amount of the active diluent having three or more functional groups (“EX-321L”, aliphatic triglycidyl ether, manufactured by Nagase ChemteX Corporation) was changed from 4 parts by mass to 2 parts by mass;

[0194] Except for the above matters, the operation was carried out in the same manner as in Example 2 to prepare Magnetic Paste 4.

[0195] <Example 5>

[0196] In Example 2,

[0197] the amount of the active diluent having two or less functional groups (“ZX-1658GS”, cycloaliphatic diglycidyl ether, manufactured by Nippon Steel Chemical & Material Co., Ltd.) was changed from 1 part by mass to 4 parts by mass,

[0198] and the amount of the active diluent having three or more functional groups (“EX-321L”, aliphatic triglycidyl ether, manufactured by Nagase ChemteX Corporation) was changed from 4 parts by mass to 1 part by mass;

[0199] Except for the above matters, the operation was carried out in the same manner as in Example 2 to prepare the magnetic paste 5.

[0200] <Example 6>

[0201] In Example 1,

[0202] 5 parts by mass of a trifunctional or higher active diluent ("EX-321L", an aliphatic triglycidyl ether, manufactured by Nagase ChemteX Corporation) was changed to 5 parts by mass of a trifunctional or higher active diluent ("PETG", a cycloaliphatic tetraglycidyl ether, manufactured by Showa Denko K.K.). Except for the above matters, the operation was carried out in the same manner as in Example 1 to prepare the magnetic paste 6.

[0203] <Example 7>

[0204] In Example 1,

[0205] The amount of the 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.) was changed from 12 parts by mass to 10 parts by mass,

[0206] The amount of the trifunctional or higher active diluent ("EX-321L", an aliphatic triglycidyl ether, manufactured by Nagase ChemteX Corporation) was changed from 5 parts by mass to 7 parts by mass;

[0207] Except for the above matters, the operation was carried out in the same manner as in Example 1 to prepare the magnetic paste 7.

[0208] <Example 8>

[0209] In Example 1,

[0210] The amount of the 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.) was changed from 12 parts by mass to 3 parts by mass,

[0211] The amount of the trifunctional or higher active diluent ("EX-321L", an aliphatic triglycidyl ether, manufactured by Nagase ChemteX Corporation) was changed from 5 parts by mass to 14 parts by mass;

[0212] Except for the above matters, the operation was carried out in the same manner as in Example 1 to prepare the magnetic paste 8.

[0213] <Comparative Example 1>

[0214] In Example 2,

[0215] Change the amount of the active diluent having two or less functional groups (“ZX-1658GS”, cycloaliphatic diglycidyl ether, manufactured by Nippon Steel Chemical & Material Co., Ltd.) from 1 part by mass to 5 parts by mass.

[0216] Do not use 4 parts by mass of the active diluent having three or more functional groups (“EX-321L”, aliphatic triglycidyl ether, manufactured by Nagase ChemteX Corporation);

[0217] Except for the above matters, perform the operation in the same manner as in Example 2 to prepare Magnetic Paste 9.

[0218] <Comparative Example 2>

[0219] In Example 6, change 5 parts by mass of the active diluent having three or more functional groups (“PETG”, cycloaliphatic tetraglycidyl ether, manufactured by Showa Denko K.K.) to 5 parts by mass of the active diluent having two or less functional groups (“EX-201L”, cycloaliphatic diglycidyl ether, manufactured by Nagase ChemteX Corporation). Except for the above matters, perform the operation in the same manner as in Example 6 to prepare Magnetic Paste 10.

[0220] <Measurement of relative magnetic permeability and magnetic loss>

[0221] As a support, prepare a polyethylene terephthalate (PET) film (Lintec Corporation's “PET501010”, thickness 50 μm) treated with a silicone-based mold release agent. On the release surface of the above PET film, uniformly coat the Magnetic Pastes 1 to 8 prepared in each Example and each Comparative Example with a doctor blade so that the thickness of the dried paste layer becomes 100 μm to obtain a resin sheet. By heating the obtained resin sheet at 190 °C for 90 minutes, thermally cure the paste layer, and by peeling off the support, obtain a sheet-like cured product. Cut the obtained cured product into test pieces with a width of 5 mm and a length of 18 mm as evaluation samples. For this evaluation sample, use Agilent Technologies (manufactured by Agilent Technologies, “HP8362B”), and using the 3-turn coil method, set the measurement frequency to 100 MHz, and measure the relative magnetic permeability (μ') and magnetic loss (μ'') at room temperature of 23 °C.

[0222] <Measurement of peel strength>

[0223] As an inner layer substrate, prepare a substrate obtained by roughening the copper surface by etching 1 μm on both sides of a glass cloth base epoxy resin double-sided copper-clad laminate (copper foil thickness 18 μm, substrate thickness 0.3 mm, Panasonic Corporation's R5715ES) using a micro-etchant (Meg Chemical Co., Ltd.'s CZ8100).

[0224] On the above-mentioned inner substrate, the magnetic pastes 1 to 10 prepared in each example and each comparative example were uniformly coated using a doctor blade so that the thickness of the dried paste layer became 50 μm, and a paste layer was formed. The paste layer was heated at 130°C for 30 minutes and then at 150°C for 30 minutes, thereby performing thermal curing to form a cured product layer. After polishing the surface of the formed cured product layer, it was heated at 180°C for 30 minutes, thereby performing heat treatment.

[0225] The surface of the heat-treated cured product layer was immersed in Swelling Dip Securiganth P (a glycol ether-based, aqueous sodium hydroxide solution) containing diethylene glycol monobutyl ether manufactured by Atotech Japan Co., Ltd. as a swelling liquid at 60°C for 5 minutes. Then, it was immersed in Concentrate Compact P (an aqueous solution of KMnO4: 60 g / L, NaOH: 40 g / L) manufactured by Atotech Japan Co., Ltd. as a roughening liquid at 80°C for 5 minutes. Finally, it was immersed in Reduction solution Securiganth P (an aqueous sulfuric acid solution) manufactured by Atotech Japan Co., Ltd. as a neutralizing liquid at 40°C for 5 minutes. Then, it was dried at 40°C to obtain laminate A.

[0226] Laminate A was immersed in an electroless plating solution containing PdCl2 at 40°C for 5 minutes, and then immersed in an electroless copper plating solution at 25°C for 20 minutes. After annealing treatment by heating at 150°C for 30 minutes, a resist layer was formed. After pattern formation by etching, electrolytic copper plating was performed to form a conductor layer with a thickness of 25 μm. Then, annealing treatment was performed at 180°C for 60 minutes. This substrate was used as an evaluation substrate.

[0227] A notch was formed in a portion with a width of 10 mm and a length of 100 mm on the conductor layer of the evaluation substrate. One end was peeled off and clamped with a jig (TSE Co., Ltd., AUTOCOM type testing machine "AC-50C-SL"), and the load (kgf / cm) when peeled vertically at a speed of 50 mm / minute for 35 mm at room temperature was measured. The substrate on which the above measurement could be performed was evaluated as "○". In addition, a substrate in which the conductor layer after the electroless plating treatment of the evaluation substrate swelled and the peel strength could not be measured was evaluated as "×".

[0228] <Measurement of arithmetic mean roughness (Ra value)>

[0229] For the laminated board A, a non-contact surface roughness meter (WYKONT3300 manufactured by Veeco Instruments) was used. In the VSI mode with a 50-fold lens, the measurement range was set to 121 μm × 92 μm, and the Ra value was obtained from the resulting values. Regarding the Ra value, it was measured by finding the average of three randomly selected points and evaluated according to the following criteria;

[0230] ○: The Ra value is 700 nm or less

[0231] △: The Ra value is more than 700 nm and less than 1000 nm

[0232] ×: The Ra value is 1000 nm or more.

[0233] [Table 1]

[0234] 。

[0235] It can be seen that in Examples 1 to 8, due to excellent decontamination tolerance, even after decontamination treatment, the Ra value can be reduced. On the other hand, it can be seen that in Comparative Examples 1 to 2, since the decontamination tolerance is worse than that of Examples 1 to 8, the resin component in the magnetic layer falls off and dissolves due to decontamination treatment, and the Ra value becomes higher than that of Examples 1 to 8. In addition, it can be seen that in Examples 1 to 8, due to excellent decontamination tolerance, even if a conductor layer is formed after decontamination treatment, expansion in the conductor layer can be suppressed, and as a result, the peel strength between the magnetic layer and the conductor layer is increased.

[0236] It was confirmed that in Examples 1 to 8, even in the case of not containing the (E) component, although there are differences in degree, it also leads to the same results as the above examples.

[0237] Explanation of symbols

[0238] 10-core substrate

[0239] 11-supporting substrate

[0240] 12-first metal layer

[0241] 13-second metal layer

[0242] 14-through hole

[0243] 20-magnetic paste

[0244] 20A-magnetic layer.

Claims

1. A magnetic paste, comprising: (A) magnetic powder (B) epoxy resin (C) reactive diluent, and (D) curing agent Among them, (C) component contains a reactive diluent having trifunctional or more When the content (mass %) of the (C) reactive diluent when the non-volatile components in the magnetic paste are set to 100 mass % is set to C1, and the content (mass %) of the (B) epoxy resin when the non-volatile components in the magnetic paste are set to 100 mass % is set to B1, B1 / C1 is 0.1 or more and 5 or less.

2. The magnetic paste according to claim 1, wherein, When the non-volatile components in the magnetic paste are set to 100 mass %, the content of the reactive diluent having trifunctional or more is 0.5 mass % or more and 10 mass % or less.

3. The magnetic paste according to claim 1, wherein, When the non-volatile components in the magnetic paste are set to 100 mass %, the content of the reactive diluent having trifunctional or more is 2 mass % or more.

4. The magnetic paste according to claim 1, wherein, When the non-volatile components in the magnetic paste are set to 100 mass %, the content of the reactive diluent having trifunctional or more is 5 mass % or less.

5. The magnetic paste according to claim 1, wherein, When all of the (C) components are set to 100 mass %, the content of the reactive diluent having trifunctional or more is 20 mass % or more.

6. The magnetic paste according to claim 1, wherein, When all of the (C) components are set to 100 mass %, the content of the reactive diluent having trifunctional or more is 35 mass % or more.

7. The magnetic paste according to claim 1, wherein, When all of the (C) components are set to 100 mass %, the content of the reactive diluent having trifunctional or more is 100 mass % or less.

8. The magnetic paste according to claim 1, wherein, When all of the (C) components are set to 100 mass %, the content of the reactive diluent having trifunctional or more is 90 mass % or less.

9. The magnetic paste according to claim 1, wherein, (A) component is a soft magnetic powder.

10. The magnetic paste according to claim 1, wherein, (A) component is iron oxide powder.

11. The magnetic paste according to claim 10, wherein The iron oxide powder is a ferrite containing at least one element selected from Ni, Cu, Mn, and Zn.

12. The magnetic paste according to claim 1, wherein, (A) component is at least one selected from Fe-Mn ferrites and Fe-Mn-Zn ferrites.

13. The magnetic paste according to claim 1, wherein, When the non-volatile components in the magnetic paste are set to 100 mass %, the content of the (A) component is 60 mass % or more.

14. The magnetic paste according to claim 1, wherein, When the non-volatile components in the magnetic paste are set to 100 mass %, the content of the (A) component is 75 mass % or more.

15. The magnetic paste according to claim 1, wherein, When the non-volatile components in the magnetic paste are set to 100 mass %, the content of the (A) component is 98 mass % or less.

16. The magnetic paste according to claim 1, wherein, When the non-volatile components in the magnetic paste are set to 100 mass %, the content of the (A) component is 90 mass % or less.

17. The magnetic paste according to claim 1, wherein, When the non-volatile components in the magnetic paste are set to 100 mass %, the content of the (B) component is 1 mass % or more.

18. The magnetic paste according to claim 1, wherein, When the non-volatile components in the magnetic paste are set to 100 mass %, the content of the (B) component is 10 mass % or more.

19. The magnetic paste according to claim 1, wherein, When the non-volatile components in the magnetic paste are set to 100 mass %, the content of the (B) component is 30 mass % or less.

20. The magnetic paste according to claim 1, wherein, When the non-volatile components in the magnetic paste are set to 100 mass %, the content of the (B) component is 15 mass % or less.

21. The magnetic paste according to claim 1, wherein, When the non-volatile components in the magnetic paste are set to 100 mass %, the content of the (C) component is 0.5 mass % or more.

22. The magnetic paste according to claim 1, wherein, When the non-volatile components in the magnetic paste are set to 100 mass %, the content of the (C) component is 3 mass % or more.

23. The magnetic paste according to claim 1, wherein, When the non-volatile components in the magnetic paste are set to 100 mass %, the content of the (C) component is 10 mass % or less.

24. The magnetic paste according to claim 1, wherein, When the non-volatile components in the magnetic paste are set to 100% by mass, the content of component (C) is 5% by mass or less.

25. The magnetic paste according to claim 1, wherein, When the non-volatile components in the magnetic paste are set to 100% by mass, the content of component (D) is 0.1% by mass or more.

26. The magnetic paste according to claim 1, wherein, When the non-volatile components in the magnetic paste are set to 100% by mass, the content of component (D) is 0.3% by mass or more.

27. The magnetic paste according to claim 1, wherein, When the non-volatile components in the magnetic paste are set to 100% by mass, the content of component (D) is 5% by mass or less.

28. The magnetic paste according to claim 1, wherein, When the non-volatile components in the magnetic paste are set to 100% by mass, the content of component (D) is 1% by mass or less.

29. The magnetic paste according to claim 1, which is used for filling a through-hole.

30. A circuit board, which comprises a board in which a through-hole is filled with a cured product of the magnetic paste according to any one of claims 1 to 29.

31. An inductor board, which comprises the circuit board according to claim 30.

32. A method for manufacturing a circuit board, wherein, The method includes: (1) A step of filling a through-hole with a magnetic paste and thermally curing the magnetic paste to obtain a cured product; (2) A step of grinding the surface of the cured product; (3) A step of performing a defouling treatment on the ground surface of the cured product; and (4) A step of forming a conductor layer on the ground surface of the cured product, The magnetic paste is the magnetic paste according to any one of claims 1 to 29.

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