Magnetic paste, circuit member, and method for manufacturing circuit member

Abstract

Provided is a magnetic paste to be used for filling a recess formed in a substrate for circuit members, the magnetic paste containing magnetic powder and a thermosetting component, wherein the volume-based particle size distribution of the magnetic powder has at least a first peak with a peak particle size of 0.5 to 6.0 µm, and a second peak with a peak particle size of 8.0 to 50.0 µm.

Description

Magnetic paste, circuit component, and method for manufacturing circuit component

[0001] The present disclosure relates to a magnetic paste, a circuit component, and a method for manufacturing a circuit component.

[0002] Materials containing metal powders with various physical properties are used depending on the characteristics required for industrial products. For example, magnetic materials containing magnetic powders are used in the fields of inductors, electromagnetic wave shields, bonded magnets, etc. In particular, there has been an increasing demand in recent years for materials containing magnetic powders and resins (see, for example, Patent Document 1).

[0003] JP 2014-127624 A

[0004] As a manufacturing method for circuit components, a method of filling recesses such as through holes (penetrating holes), blind holes, cavities, and trenches in a substrate with a paste-like magnetic material (magnetic paste) has been investigated. However, as circuit components become smaller, the size of the recesses to which the magnetic paste is applied has also become smaller, making it difficult to sufficiently fill the recesses with the magnetic paste. For the same reason, sudden temperature changes (thermal shock) during the manufacturing process and use have increasingly caused fine cracks to occur in the magnetic material (cured magnetic paste) filling the recesses. Therefore, it has become important that the cured magnetic paste is resistant to cracks.

[0005] Therefore, one aspect of the present disclosure aims to provide a magnetic paste that has excellent filling properties for recesses (e.g., through-holes, blind holes, cavities, and trenches) and can form a magnetic body that is less likely to crack within the recesses. Other aspects of the present disclosure aim to provide a circuit component obtained using the magnetic paste of the above aspect, and a method for manufacturing the same.

[0006] In some aspects, the present disclosure provides the following [1] to

[11] .

[0007] [1] A magnetic paste used to fill recesses provided in a substrate for circuit components, comprising a magnetic powder and a thermosetting component, wherein the volumetric particle size distribution of the magnetic powder has at least a first peak with a peak particle size of 0.5 to 6.0 μm and a second peak with a peak particle size of 8.0 to 50.0 μm.

[0008] [2] The magnetic paste according to [1], wherein the content of the magnetic powder is 70 mass % or more based on the total mass of nonvolatile matter in the magnetic paste.

[0009] [3] The magnetic paste according to [1] or [2], wherein the thermosetting component includes an epoxy group-containing compound and a curing agent.

[0010] [4] The magnetic paste according to [3], wherein the epoxy group-containing compound includes an epoxy group-containing compound that is liquid at 25°C.

[0011] [5] The magnetic paste according to [3] or [4], wherein the curing agent includes at least one selected from the group consisting of an amine-based curing agent and an imidazole-based curing agent.

[0012] [6] The magnetic paste according to any one of [3] to [5], wherein the curing agent includes a curing agent that is liquid at 25°C.

[0013] [7] The magnetic paste according to any one of [1] to [6], further containing a coupling agent.

[0014] [8] The magnetic paste according to any one of [1] to [7], which has a thermal weight loss rate of 5% or less when cured by heat treatment at 180°C.

[0015] [9] The magnetic paste according to any one of [1] to [8], having a viscosity at 25°C of 1 to 600 Pa·s.

[0016]

[10] A circuit component comprising a substrate and a magnetic body filling a recess provided in the substrate, wherein the magnetic body comprises a cured product of the magnetic paste according to any one of [1] to [9].

[0017]

[11] A method for manufacturing a circuit component, comprising: filling a recess provided in a substrate with the magnetic paste according to any one of [1] to [9]; and heating and hardening the magnetic paste.

[0018] According to one aspect of the present disclosure, it is possible to provide a magnetic paste that has excellent recess filling properties and is capable of forming a magnetic body that is less likely to crack in a through-hole. Furthermore, according to other aspects of the present disclosure, it is possible to provide a circuit component obtained using the magnetic paste of the above aspect and a method for manufacturing the same.

[0019] 1A to 1C are schematic cross-sectional views illustrating an example of a method for manufacturing a circuit member according to an embodiment of the present disclosure.

[0020] In this specification, a numerical range indicated using "to" indicates a range that includes the numerical values ​​written before and after "to" as the minimum and maximum values, respectively. Furthermore, unless specifically stated otherwise, the units of the numerical values ​​written before and after "to" are the same. In the numerical ranges described in stages in this specification, the upper or lower limit of a certain numerical range may be replaced with the upper or lower limit of a numerical range of another stage. Furthermore, in the numerical ranges described in this specification, the upper or lower limit of that numerical range may be replaced with a value shown in the examples. Furthermore, the upper and lower limits individually described can be arbitrarily combined. Furthermore, "A or B" may include either A or B, or may include both. Furthermore, unless otherwise specified, the materials exemplified below may be used alone or in combination of two or more. When multiple substances corresponding to each component are present in the paste, the content of each component in the paste means the total amount of the multiple substances present in the paste, unless otherwise specified.

[0021] Preferred embodiments of the present disclosure will be described below, but the present disclosure is not limited to the following embodiments.

[0022] One embodiment of the present disclosure is a magnetic paste used to fill recesses provided in a substrate for circuit components. The magnetic paste contains a magnetic powder and a thermosetting component, and the volume-based particle size distribution of the magnetic powder has at least a first peak with a peak particle size of 0.5 to 6.0 μm and a second peak with a peak particle size of 8.0 to 50.0 μm. Here, the volume-based particle size distribution of the magnetic powder is obtained by measuring the particle size distribution using a laser diffraction / scattering particle size distribution analyzer under the conditions described in the examples.

[0023] The magnetic paste has excellent filling properties (hereinafter simply referred to as "filling properties") for recesses such as through-holes (penetrating holes), blind holes, cavities, and trenches. Furthermore, the hardened product of the magnetic paste is less likely to crack. Therefore, the magnetic paste can satisfactorily fill recesses provided in a substrate for circuit components, and can form a magnetic body that is less likely to crack.

[0024] The fact that the volume-based particle size distribution of the magnetic powder has the first and second peaks means that the magnetic powder contains a group of particles having particle sizes near the first peak (a group of particles having particle sizes of about 0.5 to 6.0 μm) and a group of particles having particle sizes near the second peak (a group of particles having particle sizes of about 8.0 to 50.0 μm). Although the reason is not clear, it is presumed that the above effect is achieved by the magnetic paste containing magnetic powder that includes these two types of particle groups.

[0025] (Magnetic powder) The magnetic powder is an aggregate of magnetic particles. The magnetic particles contain at least a magnetic component. The magnetic particles may contain only one type of magnetic component, or may contain multiple types of magnetic components. The magnetic particles may consist of only the magnetic component, or may further contain components other than the magnetic component. The content of the magnetic component based on the total mass of the magnetic particles may be 20% by mass or more, and the content of the magnetic component based on the total mass of the magnetic powder may be 50% by mass or more.

[0026] The magnetic component includes, for example, a metal element. The metal element included in the magnetic component may be, for example, at least one selected from the group consisting of base metal elements, noble metal elements, transition metal elements, and rare earth elements. The metal element may be, for example, at least one selected from the group consisting of iron (Fe), copper (Cu), titanium (Ti), manganese (Mn), cobalt (Co), nickel (Ni), zinc (Zn), niobium (Nb), aluminum (Al), tin (Sn), chromium (Cr), barium (Ba), strontium (Sr), lead (Pb), silver (Ag), praseodymium (Pr), neodymium (Nd), samarium (Sm), and dysprosium (Dy).

[0027] The magnetic component may be a single metal element or an alloy composed of two or more metal elements. The alloy may include at least one selected from the group consisting of solid solutions, eutectics, and intermetallic compounds. The alloy may be, for example, an iron alloy such as an Fe—Cr alloy or an Fe—Ni—Cr alloy. It may also be a copper alloy such as a Cu—Sn alloy, a Cu—Sn—P alloy, a Cu—Ni alloy, or a Cu—Be alloy.

[0028] The magnetic component may be a metal compound containing the above metal element and an element other than the above metal element. Examples of the element other than the above metal element include at least one element selected from the group consisting of carbon (C), oxygen (O), beryllium (Be), phosphorus (P), boron (B), and silicon (Si). The metal compound may be, for example, a metal oxide such as iron oxide. The metal compound may also be a sintered body containing a metal oxide as a main component (for example, a sintered body obtained by mixing and sintering a metal oxide with a metal element such as cobalt, nickel, or manganese).

[0029] The magnetic component may be a soft magnetic component (e.g., a soft magnetic alloy) or a ferromagnetic component (e.g., a ferromagnetic alloy). The magnetic component may be, for example, at least one selected from the group consisting of an Fe—Si alloy, an Fe—Si—Al alloy (Sendust), an Fe—Ni alloy (Permalloy), an Fe—Cu—Ni alloy (Permalloy), an Fe—Co alloy (Permendur), an Fe—Cr—Si alloy (electromagnetic stainless steel), an Nd—Fe—B alloy (rare earth magnet), an Sm—Fe—N alloy (rare earth magnet), an Al—Ni—Co alloy (Alnico magnet), and a ferrite. The ferrite may be, for example, a spinel ferrite, a hexagonal ferrite, or a garnet ferrite.

[0030] The magnetic powder may contain at least one selected from the group consisting of Fe alone and Fe-based alloys, from the viewpoint of obtaining higher magnetic permeability. The Fe-based alloy may be, for example, at least one selected from the group consisting of Fe—Si-based alloys, Fe—Si—Al-based alloys, Fe—Ni-based alloys, Fe—Cu—Ni-based alloys, Fe—Co-based alloys, Fe—Cr—Si-based alloys, Fe—Si—B-based alloys, and Fe—Si—B—P—Nb—Cr-based alloys. The magnetic powder may contain Fe amorphous alloy powder, from the viewpoint of obtaining even higher magnetic permeability.

[0031] Amorphous Fe alloys are amorphous powders obtained by rapidly quenching a high-temperature melt of Fe, the primary component, together with other elements such as Si. These amorphous Fe alloy powders are also known as metallic glasses. Amorphous Fe alloy powders can be produced according to methods well known in the art. Commercially available products include those manufactured by Epson Atmix Corporation under the product names AW2-08 and KUAMET-6B2, those manufactured by Daido Steel Co., Ltd. under the product names DAPMS3, DAPMS7, DAPMSA10, DAPPB, DAPPC, DAPMKV49, DAP410L, DAP430L, and DAPHYB, and those manufactured by Kobe Steel, Ltd. under the product names MH45D, MH28D, MH25D, and MH20D. These amorphous Fe alloy powders may be used alone or in combination.

[0032] The entire or part of the surface of the magnetic powder may be coated with a surface treatment agent. The surface treatment agent may be, for example, an inorganic surface treatment agent such as an inorganic oxide, a phosphoric acid compound, a phosphate compound, or a silane coupling agent, an organic surface treatment agent such as montan wax, or a cured resin. The coupling agent described below may also be used as the surface treatment agent.

[0033] The magnetic powder (e.g., magnetic powder containing an Fe-based alloy) may have the entire or part of its surface coated with an insulating material. That is, the magnetic powder may include magnetic particles whose surfaces are coated with an insulating material (hereinafter referred to as "insulating-coated magnetic particles"). Examples of insulating materials include silica, titania, calcium phosphate, montan wax, and cured epoxy resins. The insulating-coated magnetic particles may be Fe amorphous alloy powder having an insulating coating. The thickness of the inorganic oxide coating that constitutes the insulating coating may be, for example, 1 to 100 nm.

[0034] Examples of insulating coated magnetic particles that can be used include "KUAMET9A4" (Fe-Si-B alloy, D50: 20 μm, with insulating coating) manufactured by Epson Atmix Corporation and "SAP-2C" (Fe-Si-B-P-Nb-Cr alloy, D50: 2.2 μm, with insulating coating) manufactured by Shinto Kogyo Co., Ltd. These insulating coated magnetic particles may be used in combination with magnetic particles that do not have an insulating coating, such as soft ferrite powder "BSN-125" (Ni-Zn alloy, D50: 10 μm, without insulating coating) manufactured by Toda Kogyo Co., Ltd.

[0035] The shape of the magnetic particles is not particularly limited. The magnetic particles may be, for example, spherical, ellipsoidal, flat, plate-like, rod-like, or needle-like. From the viewpoint of further improving the filling of recesses, the shape of the magnetic particles may be spherical. Here, "spherical" means that the average aspect ratio, which is the ratio of the major axis to the minor axis (major axis / minor axis) of the magnetic particles measured by the method described below, is 1.0 to 4.0. In this specification, the average aspect ratio is calculated by determining the ratio of the major axis to the minor axis (major axis / minor axis) for each of 100 randomly selected magnetic particles and averaging the aspect ratios obtained. The major axis of a magnetic particle refers to the distance between two planes that circumscribe the magnetic particle and are parallel to each other, selected so that the distance between them is maximized. The minor axis of a magnetic particle refers to the distance between two planes that circumscribe the magnetic particle and are parallel to each other, selected so that the distance between them is minimized. From the viewpoint of improving the fluidity and embeddability of the magnetic paste and the dense packing of the magnetic particles, the aspect ratio is preferably 1.0 to 3.0, more preferably 1.0 to 2.0, and even more preferably 1.0 to 1.5.

[0036] The volume-based particle size distribution of the magnetic powder has the first peak and the second peak.

[0037] The first peak may be the smallest peak particle size among the peaks present in the volume-based particle size distribution of the magnetic powder. The peak particle size of the first peak is 0.5 μm or more, but may be 1.0 μm or more or 1.5 μm or more from the viewpoint of improving the magnetic permeability, dispersibility, oxidation resistance, and dense packing of the particles, as well as the paste viscosity. The peak particle size of the first peak is 6.0 μm or less, but may be 5.0 μm or less or 4.0 μm or less from the viewpoint of improving the dense packing of the particles and the flatness of the cured product, and from the viewpoint of suppressing magnetic loss.

[0038] The second peak may be the peak with the largest peak particle size among the peaks present in the volume-based particle size distribution of the magnetic powder. The peak particle size of the second peak is 8.0 μm or more, but from the viewpoint of improving the magnetic permeability of the particles, the paste viscosity, and the thermal expansion coefficient of the cured product, it may be 10.0 μm or more or 15.0 μm or more. The peak particle size of the second peak is 50.0 μm or less, but from the viewpoint of suppressing magnetic loss of the particles and improving the printability of the paste, the filling ability of recesses, and the flatness of the cured product, it may be 40.0 μm or less or 30.0 μm or less.

[0039] The peak intensity ratio of the first peak to the second peak, i.e., the ratio of the peak intensity of the second peak to the peak intensity of the first peak (peak intensity of the second peak / peak intensity of the first peak), may be 2.0 or more, 2.5 or more, or 3.0 or more, from the viewpoint of improving the dense packing of the particles, the paste viscosity, and the magnetic permeability and thermal expansion coefficient of the cured product. The peak intensity ratio of the first peak to the second peak may be 20.0 or less, 15.0 or less, or 10.0 or less, from the viewpoint of improving the dense packing of the particles, the paste viscosity, and the magnetic permeability and thermal expansion coefficient of the cured product. From these viewpoints, the peak intensity ratio of the first peak to the second peak may be 2.0 to 20.0, 2.5 to 15.0, or 3.0 to 10.0.

[0040] The volumetric particle size distribution of the magnetic powder may have peaks other than the first and second peaks, but from the viewpoint of improving the dense packing of the particles, it is preferable that the volumetric particle size distribution of the magnetic powder has no other peaks. Here, "no other peaks" in the volumetric particle size distribution of the magnetic powder means that, when the intensity of the peak with the greater intensity of the first and second peaks is taken as 1, there is no peak with a peak intensity of 0.3 or more.

[0041] Magnetic powder D １０ , D ５０ and D ９０ may be 0.5 to 6.0 μm, 9.0 to 24.0 μm, and 24.0 to 50.0 μm, respectively. １０D means the particle size when the cumulative volume from the smallest particle size side in the volume-based particle size distribution of the magnetic powder is 10% of the total magnetic powder (10% cumulative particle size on a volume basis of the magnetic powder). ５０ D means the particle size when the cumulative volume from the smallest particle size side in the volume-based particle size distribution of the magnetic powder is 50% of the total magnetic powder (50% cumulative particle size on a volume basis of the magnetic powder). ９０ This means the particle size when the cumulative volume from the smallest particle size side in the volume-based particle size distribution of the magnetic powder is 90% of the total magnetic powder (90% cumulative particle size based on volume of the magnetic powder).

[0042] Magnetic powder D １０ When the D of the magnetic powder is 0.5 μm or more, the fluidity of the magnetic paste tends to improve, and the filling property tends to improve. １０ The D of the magnetic powder may be 1.0 μm or more or 1.5 μm or more. １０ When the D of the magnetic powder is 6.0 μm or less, the magnetic particles in the magnetic paste are densely filled into the recesses, which tends to further suppress the occurrence of cracks. １０ may be 5.0 μm or less or 4.5 μm or less.

[0043] Magnetic powder D ５０ When the D of the magnetic powder is 9.0 μm or more, the fluidity of the magnetic paste tends to be improved and the filling property tends to be improved. ５０ The D of the magnetic powder may be 11.0 μm or more or 13.0 μm or more. ５０ When the D of the magnetic powder is 24.0 μm or less, the magnetic particles in the magnetic paste are densely filled into the recesses, which tends to further suppress the occurrence of cracks. ５０ may be 22.0 μm or less or 20.0 μm or less.

[0044] Magnetic powder D ９０ When the D of the magnetic powder is 24.0 μm or more, the fluidity of the magnetic paste tends to be improved and the filling property tends to be improved. ９０ The D of the magnetic powder may be 25.0 μm or more or 26.0 μm or more. ９０When the D of the magnetic powder is 50.0 μm or less, the magnetic particles in the magnetic paste are densely filled into the recesses, which tends to further suppress the occurrence of cracks. ９０ may be 48.0 μm or less or 46.0 μm or less.

[0045] Magnetic powders having the above particle size distribution can be obtained, for example, by atomization or liquid-phase synthesis. The particle size distribution of the magnetic powder produced by the above method can be adjusted using, for example, a pulverizer, ball mill, bead mill, air classifier, wet sifter, or sieve. The method of adjusting the desired particle size distribution using a classifier, sieve, or the like maintains the spherical particle shape compared to methods of adjusting the particle size distribution by applying force to the particles, such as a pulverizer or ball mill, thereby improving the fluidity of the magnetic paste. Furthermore, since structural defects and crystal distortions at the interface caused by pulverization do not occur, the magnetic permeability is less likely to decrease.

[0046] A magnetic powder having the above-mentioned flow distribution can also be obtained by combining a first magnetic powder having a peak at 0.5 to 6.0 μm in its volume-based particle size distribution with a second magnetic powder having a peak at 8.0 to 50.0 μm in its volume-based particle size distribution.

[0047] The first magnetic powder is D ５０ It is preferable to use a magnetic powder having a particle size (50% cumulative particle size in the particle size distribution on a volume basis) of 0.5 to 6.0 μm. ５０ may be 1.0 to 5.0 μm or 1.5 to 4.5 μm.

[0048] The second magnetic powder is D ５０ It is preferable to use a magnetic powder having a particle size (50% cumulative particle size in the particle size distribution on a volume basis) of 8.0 to 50.0 μm. ５０ may be 10.0 to 40.0 μm or 12.0 to 30.0 μm.

[0049] The amount of the first magnetic powder may be 5.0% by mass or more, 8.0% by mass or more, or 10.0% by mass or more, based on the total mass of the magnetic powder in the magnetic paste, from the viewpoint of improving the dense packing of the particles. The amount of the first magnetic powder may be 30.0% by mass or less, 28.0% by mass or less, or 25.0% by mass or less, based on the total mass of the magnetic powder in the magnetic paste, from the viewpoint of improving the dense packing of the particles, the paste viscosity, and the magnetic permeability and thermal expansion coefficient of the cured product. From these viewpoints, the amount of the first magnetic powder may be 5.0 to 30.0% by mass, 8.0 to 28.0% by mass, or 10.0 to 25.0% by mass, based on the total mass of the magnetic powder in the magnetic paste.

[0050] The amount of the second magnetic powder may be 70.0% by mass or more, 72.0% by mass or more, or 75.0% by mass or more, based on the total mass of the magnetic powder in the magnetic paste, from the viewpoint of improving the dense packing of the particles, the paste viscosity, and the magnetic permeability and thermal expansion coefficient of the cured product. The amount of the second magnetic powder may be 95.0% by mass or less, 92.0% by mass or less, or 90.0% by mass or less, based on the total mass of the magnetic powder in the magnetic paste, from the viewpoint of improving the dense packing of the particles. From these viewpoints, the amount of the second magnetic powder may be 70.0 to 95.0% by mass, 72.0 to 92.0% by mass, or 75.0 to 90.0% by mass, based on the total mass of the magnetic powder in the magnetic paste.

[0051] The volume ratio of the first magnetic powder to the total volume of the first magnetic powder and the second magnetic powder ("volume of the first magnetic powder" / "total volume of the first magnetic powder and the second magnetic powder") may be 0.05 or more, 0.08 or more, or 0.1 or more, from the viewpoint of improving the dense packing of the particles, the paste viscosity, and the magnetic permeability and thermal expansion coefficient of the cured product. The volume ratio of the first magnetic powder to the total volume of the first magnetic powder and the second magnetic powder may be 0.3 or less, 0.28 or less, or 0.25 or less, from the viewpoint of improving the dense packing of the particles, the paste viscosity, and the magnetic permeability and thermal expansion coefficient of the cured product. From these viewpoints, the volume ratio of the first magnetic powder to the total volume of the first magnetic powder and the second magnetic powder may be 0.05 to 0.30, 0.08 to 0.28, or 0.10 to 0.25.

[0052] The content of the magnetic powder may be 70% by mass or more, 75% by mass or more, or 80% by mass or more, based on the total mass of nonvolatile matter in the magnetic paste, from the viewpoint of obtaining a magnetic material that is less susceptible to cracking and from the viewpoint of obtaining high magnetic permeability. Using only particles having a particle size near the first peak results in a large increase in viscosity with increasing particle amount, making it difficult to increase the amount of magnetic powder. However, by using a combination of particles having a particle size near the first peak and particles having a particle size near the second peak, the increase in viscosity with increasing particle amount can be suppressed, allowing the magnetic powder to be blended into the magnetic paste at a high concentration. From the viewpoint of improving filling properties, the content of the magnetic powder may be 97% by mass or less, 96% by mass or less, 95% by mass or less, or 93% by mass or less, based on the total mass of nonvolatile matter in the magnetic paste. From these viewpoints, the content of the magnetic powder may be 70 to 97 mass%, 75 to 96 mass%, 75 to 95 mass%, 80 to 95 mass%, or 80 to 93 mass% based on the total mass of the nonvolatile content in the magnetic paste. Here, the nonvolatile content in the magnetic paste refers to the components contained in the magnetic paste other than the volatile components. The volatile components refer to components that show a mass loss of 10 mass% or more when heated at 180°C for 60 minutes and components with a boiling point of 300°C or less.

[0053] (Thermosetting Component) The thermosetting component includes, for example, a thermosetting compound. The thermosetting component may further include a curing agent for the thermosetting compound, and may further include a curing accelerator.

[0054] [Thermosetting Compound] The thermosetting compound is a compound that cures by heat treatment alone or by reacting with a curing agent. The thermosetting compound may be a monomer, or may be a compound (oligomer or polymer) having structural units formed by polymerization of a monomer, which is generally called a thermosetting resin.

[0055] The thermosetting compound preferably contains a compound having one or more epoxy groups in the molecule (hereinafter referred to as an "epoxy group-containing compound"). The epoxy group-containing compound may be in the form of a monomer, or an oligomer or polymer having structural units formed by polymerization of the monomer. The epoxy group-containing compound is preferably used in combination with a curing agent described below.

[0056] An example of an epoxy group-containing compound is an oligomer or polymer having two or more epoxy groups in the molecule, which is generally known as an epoxy resin. Another example of an epoxy group-containing compound is a compound having one or more epoxy groups in the molecule but not containing a structural unit formed by polymerization (hereinafter referred to as an "epoxy compound"). Such epoxy compounds are generally known as reactive diluents. The epoxy group-containing compound preferably includes at least one selected from the group consisting of an epoxy resin and an epoxy compound.

[0057] Examples of the epoxy resin include biphenyl-type epoxy resins, stilbene-type epoxy resins, diphenylmethane-type epoxy resins, sulfur-containing epoxy resins, novolac-type epoxy resins, dicyclopentadiene-type epoxy resins, salicylaldehyde-type epoxy resins, naphthol- and phenol-copolymerized epoxy resins, epoxidized aralkyl-type phenolic resins, bisphenol-type epoxy resins, glycidyl ether-type epoxy resins of alcohols, glycidyl ether-type epoxy resins of paraxylylene- and / or metaxylylene-modified phenolic resins, and glycidyl ether-type epoxy resins of terpene-modified phenolic resins. The epoxy resin may be at least one selected from the group consisting of diol ether-type epoxy resins, cyclopentadiene-type epoxy resins, glycidyl ether-type epoxy resins of polycyclic aromatic ring-modified phenolic resins, glycidyl ether-type epoxy resins of naphthalene ring-containing phenolic resins, glycidyl ester-type epoxy resins, glycidyl or methylglycidyl-type epoxy resins, alicyclic epoxy resins, halogenated phenol novolac-type epoxy resins, hydroquinone-type epoxy resins, trimethylolpropane-type epoxy resins, and linear aliphatic epoxy resins obtained by oxidizing olefin bonds with a peracid such as peracetic acid. The epoxy resin may be in the form of liquid, semi-solid, or solid, or may be a mixture of these.

[0058] The molecular weight of the epoxy compound is preferably 100 or more, more preferably 150 or more, and even more preferably 200 or more. When an epoxy compound having a molecular weight of 100 or more is used, volatilization before reaction with a curing agent can be suppressed by setting appropriate curing conditions. In addition, a low molecular weight reduces the distance between crosslinking points after reaction, making the cured product more susceptible to cracking, which is a problem. On the other hand, the molecular weight of the epoxy compound is preferably 700 or less, more preferably 500 or less, and even more preferably 300 or less. When an epoxy compound having a molecular weight of 700 or less is used, an appropriate viscosity can be easily obtained as a diluent.

[0059] In one embodiment, the molecular weight of the epoxy compound is preferably in the range of 100 to 700, more preferably in the range of 150 to 500, and even more preferably in the range of 200 to 300. When an epoxy compound having a molecular weight in this range is used, it becomes easier to adjust the viscosity of the magnetic paste. Unlike components such as organic solvents that volatilize when heated, epoxy compounds harden when heated and are incorporated into the cured product. Therefore, the epoxy compound contributes to adjusting the viscosity of the magnetic paste and contributes to suppressing deterioration in the properties of the cured product.

[0060] The epoxy compound may contain one or more epoxy groups in the molecule, and may be, for example, at least one selected from the group consisting of n-butyl glycidyl ether, versatate glycidyl ether, styrene oxide, ethylhexyl glycidyl ether, phenyl glycidyl ether, butylphenyl glycidyl ether, 1,6-hexanediol diglycidyl ether, neopentyl glycol diglycidyl ether, diethylene glycol diglycidyl ether, and trimethylolpropane triglycidyl ether.

[0061] The epoxy compound is preferably sufficiently purified to have a low content of ionic impurities. For example, the epoxy compound preferably has ionic impurities such as free Na ions and free Cl ions of 500 ppm or less.

[0062] The epoxy equivalent of the epoxy group-containing compound is preferably 80 g / eq to 350 g / eq, more preferably 100 g / eq to 300 g / eq, and even more preferably 120 g / eq to 250 g / eq. When the epoxy equivalent is within the above range, the viscosity of the epoxy group-containing compound itself is low, making it easy to adjust the viscosity of the magnetic paste. The epoxy equivalent of the epoxy group-containing compound can be measured according to JIS K 7236. Note that when the thermosetting compound contains multiple types of epoxy group-containing compounds, the epoxy equivalent measured for a mixture of all of the epoxy group-containing compounds may be within the above range.

[0063] The epoxy group-containing compound preferably includes an epoxy group-containing compound that is liquid at 25°C. In this specification, "liquid at 25°C" means that the viscosity of the epoxy group-containing compound at 25°C is 200 Pa s or less. The viscosity is a value measured using an E-type viscometer under the following conditions: temperature: 25°C, rotor: SPP, rotation speed: 2.5 rpm. As the E-type viscometer, for example, a TV-33 viscometer manufactured by Toki Sangyo Co., Ltd. can be used.

[0064] When an epoxy group-containing compound that is liquid at 25°C is used, the amount of volatile components, such as organic solvents, typically used to achieve fluidity can be significantly reduced, improving the filling of recesses. Furthermore, voids in the magnetic paste after thermal curing can be suppressed. It is also possible to create a magnetic paste that does not contain organic solvents. Furthermore, the magnetic powder content can be easily increased while maintaining appropriate fluidity as a magnetic paste. From these perspectives, the viscosity of the epoxy group-containing compound is preferably 100 Pa·s or less, more preferably 50 Pa·s or less, and even more preferably 10 Pa·s or less. The viscosity of the epoxy group-containing compound may be greater than 0 Pa·s, but may be 0.001 Pa·s or greater, or 0.01 Pa·s or greater.

[0065] Among the epoxy group-containing compounds, the viscosity of the epoxy compound is preferably lower than that of the liquid epoxy resin from the viewpoint of adjusting the viscosity of the magnetic paste. The viscosity of the epoxy compound is preferably 1 Pa s or less, more preferably 0.5 Pa s or less, and even more preferably 0.1 Pa s or less. The viscosity of the epoxy compound may be greater than 0 Pa s, 0.001 Pa s or more, or 0.01 Pa s or more.

[0066] The epoxy group-containing compound that is liquid at 25°C may contain at least one selected from the group consisting of an epoxy resin that is liquid at 25°C (hereinafter referred to as a "liquid epoxy resin") and an epoxy compound that is liquid at 25°C. The content of the liquid epoxy resin is preferably 50% by mass or more, more preferably 70% by mass or more, and even more preferably 90% by mass or more, based on the total mass of the epoxy group-containing compound, and may even be 100% by mass. However, the content of the liquid epoxy resin is not limited to the above range.

[0067] The liquid epoxy resin may contain at least one liquid epoxy resin selected from, for example, bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol AD ​​type epoxy resin, bisphenol S type epoxy resin, naphthalenediol type epoxy resin, hydrogenated bisphenol A type epoxy resin, and aminoglycidyl ether type epoxy resin. Among these, it is preferable to use at least one liquid bisphenol A type epoxy resin, liquid bisphenol F type epoxy resin, and liquid aminoglycidyl ether type epoxy resin.

[0068] Liquid epoxy group-containing compounds can also be obtained as commercially available products. Examples of commercially available products include liquid bisphenol A epoxy resin and liquid bisphenol F epoxy resin sold by Nippon Steel Chemical Co., Ltd. For example, a liquid bisphenol F epoxy resin with the product name "YDF-8170C" (epoxy equivalent: 165, viscosity: 1,000 to 1,500 mPa·s) can be suitably used. Examples of epoxy compounds include the ADEKA GLYCIROL (product name) series manufactured by ADEKA Corporation. For example, a product with the product name "ADEKA GLYCIROL ED-503G" (epoxy equivalent: 135, viscosity: 15 mPa·s) can be suitably used.

[0069] The thermosetting compound may contain a thermosetting resin such as a phenolic resin, an acrylic resin, a polyimide resin, or a polyamide-imide resin instead of or in addition to the epoxy group-containing compound. When a phenolic resin is used in addition to the epoxy group-containing compound, the phenolic resin can also function as a curing agent for the epoxy group-containing compound. In this case, the phenolic resin is considered to be a curing agent rather than a thermosetting compound.

[0070] [Curing Agent] The curing agent can be a known curing agent corresponding to the thermosetting compound. For example, when the thermosetting compound is an epoxy group-containing compound, a compound that reacts with the epoxy group of the epoxy group-containing compound to form a cured product can be used. Specific examples of curing agents for epoxy group-containing compounds include phenol-based curing agents, acid anhydride-based curing agents, amine-based curing agents, imidazole-based curing agents, and imidazoline-based curing agents.

[0071] Curing agents are classified into those that cure epoxy resins in a temperature range from low temperature to room temperature (e.g., 0 to 30°C) and heat-curing curing agents that cure epoxy resins upon heating. Examples of curing agents that cure epoxy resins in a temperature range from low temperature to room temperature include aliphatic polyamines, polyaminoamides, and polymercaptans. Examples of heat-curing curing agents include aromatic polyamines, acid anhydrides, phenolic novolac resins, and dicyandiamide (DICY). From the perspective of reducing the coefficient of thermal expansion and further suppressing cracking at temperatures during the manufacturing process, use, storage, and the like, it is preferable for the curing agent to contain a heat-curing curing agent. Resin systems that cure in a temperature range from low temperature to room temperature tend to have low glass transition temperatures of the cured resin, while resin systems that cure by heating to temperatures higher than room temperature tend to have high glass transition temperatures of the cured resin, which tend to be higher than the temperatures during the manufacturing process, use, storage, and the like. One possible cause of cracking is thermal expansion of the cured resin. However, the coefficient of thermal expansion of the cured resin is sufficiently small at temperatures lower than the glass transition temperature. Therefore, in resin systems that are cured by heating to temperatures higher than room temperature, cracking at temperatures during the manufacturing process, use, storage, etc. tends to be further suppressed.

[0072] Among the curing agents, from the viewpoint of reducing the viscosity of the magnetic paste, it is preferable to use a curing agent that is liquid at 25° C. As the liquid curing agent, for example, at least one selected from the group consisting of amine-based curing agents such as aliphatic or aromatic polyamines and aliphatic or aromatic amines, polymercaptans, acid anhydrides, and imidazole-based curing agents can be used.

[0073] As long as the increase in viscosity of the magnetic paste can be suppressed, a solid curing agent at 25°C may be used, or a liquid curing agent and a solid curing agent may be used in combination. Examples of solid curing agents that can be used include dicyandiamide, tertiary amines, imidazole-based curing agents, and imidazoline-based curing agents. The solid curing agents exemplified above are polyfunctional or act catalytically, so they can function sufficiently even in small amounts.

[0074] The curing agent preferably includes at least one selected from the group consisting of an amine-based curing agent, an imidazole-based curing agent, and an imidazoline-based curing agent. The curing agent more preferably includes at least one selected from the group consisting of an amine-based curing agent and an imidazole-based curing agent. The curing agent further preferably includes at least an amine-based curing agent.

[0075] Amine-based curing agents (more specifically, tertiary amines), imidazole-based curing agents, and imidazoline-based curing agents can also be used as curing accelerators in combination with other curing agents.

[0076] The amine curing agent may be a compound having at least two amino groups in the molecule, and includes at least one selected from the group consisting of an aliphatic amine and an aromatic amine.

[0077] The aliphatic amine may be a compound having a linear or cyclic structure, and examples thereof include diethylenetriamine, triethylenetetramine, n-propylamine, 2-hydroxyethylaminopropylamine, cyclohexylamine, methylcyclohexylamine, isophoronediamine, 4,4′-diamino-dicyclohexylmethane, and diazabicycloundecene.

[0078] The aromatic amine may be a compound in which an amino group is substituted on an aromatic compound, and is particularly preferably a compound having a structure in which a hydrogen atom on a benzene ring is substituted with an amino group. Examples thereof include benzyldimethylamine, trisdimethylaminomethylphenol, metaphenylenediamine, benzyldimethylamine, 4,4'-diaminodiphenylmethane, 2-methylaniline, diaminodiphenylsulfone, polyamidoamine, an amine compound represented by the following formula (1), and an amine compound represented by the following formula (2).

[0079] When an amine-based curing agent is used, it tends to be easier to adjust the viscosity and the amount of weight loss due to heat. In particular, when an aromatic amine is used, it tends to be easier to adjust the viscosity and the rate of weight loss due to heat.

[0080] The imidazole curing agent is a compound having an imidazole skeleton, and may be an imidazole compound in which hydrogen atoms in the molecule are substituted with substituents. The imidazole curing agent may also be a compound having an imidazole skeleton, such as an alkyl group-substituted imidazole. Examples of imidazole curing agents include imidazole, 2-methylimidazole, 2-ethylimidazole, and 2-isopropylimidazole. As a commercially available product, "Curezol 2E4MZ" (2-ethyl-4-methylimidazole) manufactured by Shikoku Chemicals Corporation can be suitably used.

[0081] The imidazoline curing agent is a compound having an imidazoline skeleton, and may be an imidazoline compound in which hydrogen atoms in the molecule are substituted with a substituent. It may be a compound having an imidazoline skeleton, such as an alkyl group-substituted imidazoline. Examples of imidazoline curing agents include imidazoline, 2-methylimidazoline, and 2-ethylimidazoline.

[0082] From the viewpoints of compatibility with liquid epoxy resins and storage stability, it is preferable that the curing agent contains at least an aromatic amine. The aromatic ring of the aromatic amine may have a substituent other than an amino group. The aromatic ring of the aromatic amine may have, for example, an alkyl group having 1 to 5 carbon atoms, or an alkyl group having 1 or 3 carbon atoms. The number of aromatic rings in the aromatic amine may be one or two or more. When the number of aromatic rings is two or more, the aromatic rings may be bonded to each other by a single bond or via a linking group such as an alkylene group.

[0083] From the viewpoint of the viscosity of the magnetic paste, the curing agent preferably contains a liquid aromatic amine. As the liquid aromatic amine, for example, at least one selected from the group consisting of a compound represented by the following formula (1) and a compound represented by the following formula (2) can be used. A compound in which the methyl group in the compound represented by formula (2) is replaced with an ethyl group can also be used. Among them, the compound represented by formula (1) can be preferably used.

[0084]

[0085]

[0086] Liquid aromatic amines that can be used as curing agents are also available as commercially available products, such as "Grade: jER Cure WA" (a compound represented by formula (1), 2,6-diamino-3,5-diethyltoluene) manufactured by Mitsubishi Chemical Corporation and "Kayahard AA" (3,3'-diethyl-4,4'-diaminodiphenylmethane) manufactured by Nippon Kayaku Co., Ltd.

[0087] When at least one of the aromatic amines and imidazole-based compounds is used as the curing agent, a cured product with a lower CTE tends to be obtained more easily compared to cured products obtained when other curing agents are used. From this perspective, the curing agent preferably includes at least one selected from the group consisting of 2,6-diamino-3,5-diethyltoluene, 3,3'-dimethyl (or diethyl)-4,4'-diaminodiphenylmethane, and 2-ethyl-4-methylimidazole.

[0088] The content of the curing agent in the magnetic paste is not particularly limited and can be set in consideration of the ratio between the equivalent number of epoxy groups in the epoxy group-containing compound, such as the epoxy resin, and the equivalent number of active groups in the curing agent. For example, the ratio of the curing agent to 1 equivalent of the epoxy groups in the epoxy group-containing compound is preferably 0.5 to 1.5 equivalents, more preferably 0.9 to 1.4 equivalents, and even more preferably 1.0 to 1.2 equivalents.

[0089] When the ratio of active groups in the curing agent is 0.5 equivalents or more, the amount of OH groups per unit mass of the epoxy resin after heat curing is reduced, thereby preventing a decrease in the curing rate of the epoxy resin. Furthermore, a decrease in the glass transition temperature of the resulting cured product and a decrease in the elastic modulus of the cured product can be prevented. Furthermore, a decrease in the insulating reliability of the cured product due to unreacted resin components in the binder resin can be prevented. On the other hand, when the ratio of active groups in the curing agent is 1.5 equivalents or less, the mechanical strength of the cured product formed from the magnetic paste can be further increased. Furthermore, a decrease in the insulating properties of the cured product due to unreacted curing agent can be prevented. However, in the above embodiment, the ratio of active groups in the curing agent is not limited, and the effects of the present disclosure can be obtained even if the ratio is outside the above range.

[0090] [Curing Accelerator] The curing accelerator is not limited to any compound capable of accelerating the curing reaction between a thermosetting compound and a curing agent (e.g., the curing reaction between an epoxy group-containing compound and a curing agent). Examples of curing accelerators include tertiary amines, imidazole-based curing accelerators, imidazoline-based curing accelerators, and phosphorus compounds. The compounds previously exemplified as imidazole-based curing agents and imidazoline-based curing accelerators may be used as imidazole-based curing accelerators and imidazoline-based curing accelerators. Among liquid curing agents, when a liquid acid anhydride is used, it is preferable to use a curing accelerator in combination. The magnetic paste may contain one or more curing accelerators. The use of a curing accelerator improves the mechanical strength of the cured product of the magnetic paste and easily lowers the curing temperature of the magnetic paste.

[0091] The amount of the curing accelerator to be blended is not particularly limited as long as it is an amount that can achieve a curing acceleration effect. However, from the viewpoint of improving the curing properties and fluidity of the magnetic paste when absorbing moisture, the amount of the curing accelerator to be blended is preferably 0.001 parts by mass or more per 100 parts by mass of the thermosetting compound and the curing agent combined. The amount of the curing accelerator to be blended is more preferably 0.01 parts by mass or more, and even more preferably 0.1 parts by mass or more. The amount of the curing accelerator to be blended is preferably 5 parts by mass or less, more preferably 4 parts by mass or less, and even more preferably 3 parts by mass or less per 100 parts by mass of the thermosetting compound and the curing agent combined.

[0092] The content of the thermosetting component may be 3% by mass or more, 4% by mass or more, or 5% by mass or more, based on the total mass of nonvolatile components in the magnetic paste, from the viewpoint of improving the viscosity of the magnetic paste, the filling ability of recesses, and the adhesion of the cured product. The content of the thermosetting component may be 30% by mass or less, 25% by mass or less, or 20% by mass or less, based on the total mass of nonvolatile components in the magnetic paste, from the viewpoint of improving the magnetic permeability and thermal expansion coefficient of the cured product. From these viewpoints, the content of the thermosetting component may be 3 to 30% by mass, 4 to 25% by mass, or 5 to 20% by mass, based on the total mass of nonvolatile components in the magnetic paste.

[0093] (Other Components) The magnetic paste may further contain components (other components) other than the magnetic powder and the thermosetting component, such as a thermoplastic resin, a coupling agent, a flame retardant, a dispersant, a viscosity modifier, a lubricant, etc.

[0094] [Thermoplastic Resin] The thermoplastic resin may be, for example, at least one selected from the group consisting of acrylic resin, polyethylene, polypropylene, polystyrene, polyvinyl chloride, and polyethylene terephthalate. The content of the thermoplastic resin may be, for example, 0.01 to 1.0 mass% based on the total mass of the nonvolatile content in the magnetic paste.

[0095] [Coupling Agent] The coupling agent contributes to improving the dispersibility of the magnetic powder, improving the adhesion between the thermosetting component and the magnetic powder, and improving the adhesion to the substrate, flexibility, mechanical strength, etc. of the cured product obtained from the magnetic paste. Therefore, the use of a coupling agent tends to further improve the filling property and also tends to produce a magnetic material that is less likely to crack. The coupling agent may be, for example, at least one selected from the group consisting of silane-based compounds (silane coupling agents), titanium-based compounds, aluminum compounds (aluminum chelates), and aluminum / zirconium-based compounds. Among these, silane coupling agents are preferred from the viewpoint of easily achieving the above-mentioned effects.

[0096] The silane coupling agent has the formula: -SiR １ ｎ (OR ２ ) ３－ｎ It is an organic compound having a hydrolyzable silyl group represented by the formula: １ and R ２ each independently represents a hydrocarbon group, and n represents an integer of 0 to 2. １ and R ２ If there are multiple R １ and R ２ may be the same or different. The hydrocarbon group is, for example, an alkyl group having 1 to 20 carbon atoms.

[0097] In addition to the hydrolyzable silyl group, the silane coupling agent may further have a reactive functional group such as an epoxy group, a mercapto group, an acryloyl group, a methacryloyl group, a styryl group, a vinyl group, an acid anhydride group, or a ureido group, and / or an organic functional group such as an alkyl group or an aryl group.

[0098] The silane coupling agent may be, for example, at least one selected from the group consisting of epoxy silane, mercapto silane, amino silane, alkyl silane, ureido silane, acid anhydride silane, methacryl silane, styryl silane, and vinyl silane.

[0099] Specific examples of the silane coupling agent include N-phenyl-3-aminopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, octyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 8-methacryloxyoctyltrimethoxysilane, p-styryltrimethoxysilane, vinyltrimethoxysilane, and 7-octenyltrimethoxysilane.

[0100] From the viewpoints of adhesion and dispersibility, the content of the coupling agent may be 0.01% by mass or more, 0.05% by mass or more, or 0.1% by mass or more, based on the total mass of the nonvolatile content in the magnetic paste. From the viewpoint of magnetic permeability, the content of the coupling agent may be 1.0% by mass or less, 0.9% by mass or less, or 0.8% by mass or less, based on the total mass of the nonvolatile content in the magnetic paste. From these viewpoints, the content of the coupling agent may be 0.01 to 1.0% by mass, 0.05 to 0.9% by mass, or 0.1 to 0.8% by mass, based on the total mass of the nonvolatile content in the magnetic paste.

[0101] [Flame Retardant] The flame retardant contributes to the environmental safety, recyclability, and cost reduction of the magnetic paste. The flame retardant may be, for example, at least one selected from the group consisting of bromine-based flame retardants, phosphorus-based flame retardants, hydrated metal compound-based flame retardants, silicone-based flame retardants, nitrogen-containing compounds, hindered amine compounds, organometallic compounds, and aromatic engineering plastics. The content of the flame retardant may be, for example, 0.01 to 0.5 mass% based on the total mass of the nonvolatile content in the magnetic paste.

[0102] The magnetic paste may contain an organic solvent if necessary. The organic solvent is not particularly limited. For example, an organic solvent capable of dissolving the thermosetting component can be used. The organic solvent may be, for example, at least one selected from the group consisting of acetone, methyl ethyl ketone, methyl isobutyl ketone, benzene, toluene, carbitol acetate, butyl carbitol acetate, cyclohexanone, ethyl acetate, butyl acetate, toluene, and xylene. From the viewpoint of workability, it is preferable that the organic solvent be liquid at room temperature (25°C). From the viewpoint of workability, it is preferable that the boiling point of the organic solvent is 50°C or higher and 250°C or lower, and more preferably 50°C or higher and 160°C or lower.

[0103] On the other hand, if the magnetic paste contains an organic solvent, a drying process is required after filling the recesses with the magnetic paste, which creates an environmental burden due to volatile components. Furthermore, organic solvents with boiling points lower than the heating temperature during curing may rapidly volatilize upon heating, resulting in the formation of voids in the cured magnetic paste. Furthermore, organic solvents with boiling points higher than the heating temperature during curing may be less likely to volatilize upon heating and may remain in the paste, degrading the properties of the cured product. For example, the presence of voids in the cured product can lead to a decrease in properties such as mechanical strength and magnetic properties. Furthermore, particularly when organic solvents remain in the cured product, ionic components and the like in the cured product are more likely to migrate, which can lead to a decrease in insulation properties such as insulation resistance and insulation reliability.

[0104] From these viewpoints, if the magnetic paste contains an organic solvent, the content thereof is preferably 5% by mass or less, more preferably 3% by mass or less, and even more preferably 1% by mass or less, based on the total mass of the magnetic paste. Most preferably, the magnetic paste is substantially free of organic solvents. In this specification, "substantially free" means that no organic solvents have been intentionally added to the magnetic paste. Therefore, a magnetic paste that is substantially free of organic solvents may contain, for example, organic solvents that were used during the production of the resin and remained in the resin.

[0105] From the same viewpoint as above, it is preferable that the magnetic paste has a thermal weight loss rate of 5% or less when cured by heat treatment at 180°C. The thermal weight loss rate is more preferably 3% or less, and even more preferably 2% or less. The thermal weight loss rate is most preferably 0%. The thermal weight loss rate can be calculated from measurements using a thermogravimetric differential thermal analyzer (TG-DTA). When the thermal weight loss rate of the magnetic paste is 5% or less, it is possible to easily obtain a cured product that has excellent desired properties such as insulation.

[0106] The viscosity of the magnetic paste is preferably 1 Pa·s or more, more preferably 10 Pa·s or more, and even more preferably 100 Pa·s or more. Adjusting the viscosity to 1 Pa·s or more suppresses the settling of magnetic powder in the magnetic paste, and easily improves the decrease in filling ability over time after stirring the magnetic paste. The viscosity of the magnetic paste is preferably 600 Pa·s or less, more preferably 400 Pa·s or less, and even more preferably 200 Pa·s or less. Adjusting the viscosity to 600 Pa·s or less makes it easier for the magnetic paste to become fluid, making it easier to obtain better filling ability. From these perspectives, the viscosity of the magnetic paste may be 1 to 600 Pa·s, 10 to 400 Pa·s, or 100 to 200 Pa·s. The above viscosity is measured at 25°C using the method described in the examples.

[0107] The viscosity of the magnetic paste can be freely adjusted by the type and characteristics of the thermosetting component (e.g., the structure of the epoxy group-containing compound), as well as the combination and compounding ratio of each component used as the thermosetting component. The magnetic paste may contain additives such as a viscosity adjuster, a thixotropic agent, and a dispersion stabilizer.

[0108] The magnetic paste of the above embodiment can be prepared by, for example, uniformly stirring and kneading the magnetic powder, the thermosetting component, and other components (optional components) such as a silane coupling agent. The method of stirring and kneading is not particularly limited, and for example, a stirring blade, a rotary / revolution type stirring, a planetary mixer, a roll mill, a disk mill, or a ball mill can be used.

[0109] <Circuit Component> Another embodiment of the present disclosure is a circuit component comprising a substrate and a magnetic body filling a recess provided in the substrate, the magnetic body including a cured product of the magnetic paste of the above embodiment. For example, the circuit component comprises a substrate having a through hole and the magnetic body filling the through hole. The recess may be a blind hole, a cavity, or a trench.

[0110] The circuit component of the embodiment may be, for example, an inductor, or an intermediate component for manufacturing an inductor.

[0111] <Method for Manufacturing Circuit Component> Another embodiment of the present disclosure is a method for manufacturing a circuit component, including the steps of filling a recess provided in a substrate with the magnetic paste of the above embodiment (for example, filling a through hole of a substrate having a through hole with the magnetic paste of the above embodiment), and heating and curing the magnetic paste. The recess may be a blind hole, a cavity, or a trench.

[0112] The above method can obtain the circuit component of the above embodiment. Furthermore, since the above method uses the magnetic paste of the above embodiment, the above method can obtain a circuit component in which the recesses are well filled with the magnetic material that is less likely to crack.

[0113] The circuit component and the manufacturing method thereof according to the above embodiment will be described in more detail below, taking a method of filling a through hole as an example, with reference to Figure 1. In the following description, the term "through hole" may be read as a recess, a blind hole, a cavity, or a trench.

[0114] 1 is a schematic cross-sectional view showing a method for manufacturing a circuit member 10 according to one embodiment. The method for manufacturing a circuit member 10 according to one embodiment includes at least a step of filling a through-hole 1 a of a substrate 1 with a magnetic paste 2 (hereinafter referred to as “step (1)”), and a step of heating and hardening the magnetic paste 2 (hereinafter referred to as “step (2)”).

[0115] [Step (1)] In step (1), a magnetic paste 2 is filled into the through holes 1a of a substrate 1 having the through holes 1a (see (a) of FIG. 1). The substrate 1 may be a substrate having a metal layer (e.g., a copper layer) on the surface of an insulating substrate such as a glass epoxy substrate, a metal substrate, a polyester substrate, a polyimide substrate, a BT resin substrate, or a thermosetting polyphenylene ether substrate. Although not shown, the metal layer may be a single layer or multiple layers. The metal layer may be formed on the inner wall of the through hole constituting the through hole 1a. The substrate 1 usually has multiple through holes 1a, but the number of through holes 1a is not particularly limited.

[0116] The filling of the magnetic paste 2 may be carried out by printing the magnetic paste by a known printing method (e.g., screen printing) using a squeegee, vacuum printing machine, etc., or by a method such as a roll coating method, an inkjet method, a dispensing method, etc. The filling may also be carried out by pressing a film coated with the magnetic paste onto a substrate having through holes using a vacuum press, vacuum lamination, etc.

[0117] In step (1), a substrate 1 that has been prepared in advance may be used, or a substrate 1 that has through-holes 1 a may be prepared by preparing a substrate that does not have through-holes 1 a and forming through-holes in the substrate by drilling, laser irradiation, plasma irradiation, etc. After the through-holes are formed, a metal layer can be formed on the inner walls of the through-holes by performing a roughening treatment (plasma treatment, wet treatment using a swelling liquid, an oxidizing agent, etc.) and a plating treatment.

[0118] [Step (2)] In step (2), the magnetic paste 2 is heated and cured. This forms a magnetic body 3 containing the cured magnetic paste, and a circuit member 10 is obtained (see FIG. 1(b)). The heating temperature is, for example, 80°C or higher, and may be 100 to 240°C, 120 to 220°C, or 140 to 200°C. The heating time may be, for example, 20 to 180 minutes, 30 to 150 minutes, or 60 to 120 minutes. The heating may be performed in multiple stages, including preheating. For example, preheating at 80°C for 60 minutes may be followed by heating at 200°C for 60 minutes. Heating is preferably performed so that the degree of curing of the magnetic paste is 80% or higher. The degree of curing after heating is more preferably 85% or higher, and more preferably 90% or higher. The degree of curing can be measured, for example, using a differential scanning calorimeter.

[0119] Although one embodiment of the method for manufacturing a circuit component has been described above, the method for manufacturing a circuit component of the present disclosure is not limited to the above method.

[0120] For example, in step (1), if a portion of the magnetic paste protrudes from the surface of the substrate 1, a step of removing the excess magnetic paste may be carried out. This step may be carried out after step (2). The removal method is not particularly limited, but the excess magnetic material may be removed, for example, by polishing the magnetic material 3 by buff polishing, belt polishing, or the like.

[0121] The method may further include, for example, a step of cleaning cutting residue adhering to the through-holes formed in the magnetic body 3 with water and / or air, a step of roughening the magnetic body 3 (desmearing step), a step of forming a conductor layer on the magnetic body 3, etc. The conductor layer can be formed, for example, by a method in which after electroless plating, a resist corresponding to the wiring pattern is formed, electrolytic copper plating is performed, and the resist is stripped and flash etching is performed.

[0122] The present disclosure will be described in more detail below using examples and comparative examples, but the present disclosure is not limited to the following examples.

[0123] Example 1 (Preparation of Thermosetting Component) 14.00 g of liquid epoxy resin "YDF-8170C" manufactured by Nippon Steel Chemical Co., Ltd., 6.00 g of liquid epoxy resin "ADEKA GLYCIROL ED-503G" manufactured by ADEKA Corporation, and 5.96 g of curing agent "jER Cure WA" (liquid aromatic amine) manufactured by Mitsubishi Chemical Corporation were weighed out. These were placed in a 250 ml ointment container as raw materials. All raw materials in the ointment container were stirred and kneaded using a planetary mixer to obtain a mixture of liquid epoxy resin (YDF-8170C and ADEKA GLYCIROL ED-503G) and curing agent (jER Cure WA). The planetary mixer used was an "ARE-500" manufactured by Thinky Corporation. The stirring and kneading was carried out for 1 minute with the revolution speed of the planetary mixer set to 2000 rpm. The mixture was stirred with a spoon, and then the revolution speed of the rotary and revolving mixer was set to 2000 rpm again, and the mixture was stirred and kneaded for 1 minute to obtain a thermosetting component A.

[0124] (Preparation of Magnetic Powder) 60.00 g of iron amorphous alloy powder "KUAMET 9A4" (Fe-Si-B alloy with insulating coating, D50: 20 μm) manufactured by Epson Atmix Corporation and 13.17 g of metallic glass magnetic powder "SAP-2C" (Fe-Si-B-P-Nb-Cr alloy with insulating coating, D50: 2.2 μm) manufactured by Shinto Kogyo Co., Ltd. were mixed to obtain magnetic powder A. The blending ratio was 81 vol % KUAMET 9A4 and 19 vol % SAP-2C.

[0125] The particle size distribution of the magnetic powder A on a volume basis was measured by the following method, and it was confirmed that the magnetic powder A had a first peak with a particle size of 2 μm and a second peak with a particle size of 20 μm. １０ is 2.4 μm, and D ５０ is 16.0 μm, and D ９０ was 35.0 μm.

[0126] [Method for measuring particle size distribution] Magnetic powder and cyclohexanone were weighed to prepare a magnetic powder dispersion of approximately 50% by mass. The prepared dispersion was dispersed for 90 seconds using an ultrasonic disperser, and then placed in a particle size distribution measuring device (LS 13 320 manufactured by Beckman Coulter, laser diffraction method) to measure the particle size distribution of the magnetic powder.

[0127] (Preparation of Magnetic Paste) 4.67 g of thermosetting component A, 73.17 g of magnetic powder A, and 0.22 g of silane coupling agent "KBM-573" manufactured by Shin-Etsu Silicones Co., Ltd. were weighed out. These were placed in a 50 ml ointment container as raw materials. The raw materials in the ointment container were stirred using a medicine spoon, and then stirred and kneaded using a rotary and revolutionary mixer (ARE-500) at a revolution speed of 2000 rpm for 45 seconds. Next, the raw materials in the ointment container were stirred using a medicine spoon, and then stirred using a rotary and revolutionary mixer at a revolution speed of 2000 rpm for 45 seconds. This process was repeated twice to obtain the magnetic paste of Example 1. The content of magnetic powder in the obtained magnetic paste was 94% by mass. The content of magnetic powder was calculated from m / (m+M), where "M" is the mass of non-volatile components (solids) other than the magnetic powder contained in the magnetic paste, and "m" is the mass of the magnetic powder.

[0128] (Viscosity Measurement) The viscosity of the obtained magnetic paste was measured using a TV-33 viscometer manufactured by Toki Sangyo Co., Ltd. under the conditions of a temperature of 25°C, a rotor of SPP, and a rotation speed of 2.5 rpm. The viscosity of the magnetic paste was in the range of 10 to 400 Pa s.

[0129] (Measurement of Thermal Weight Loss Rate) The thermal weight loss rate of the obtained magnetic paste was measured using a Hitachi High-Tech Science Corporation's "NEXTA STA200RV" differential scanning calorimeter (TG-DSC). Specifically, 15 mg of magnetic paste was heated from 25°C to 100°C at a rate of 10°C / min in a nitrogen atmosphere and held at 100°C for 1 hour. The temperature was then raised from 100°C to 180°C at a rate of 3°C / min, and the thermal weight loss after heating was measured while holding at 180°C for 1 hour. The thermal weight loss rate was calculated as the weight loss rate of the magnetic paste after heating at 180°C, with the weight of the magnetic paste (before heating) at 25°C as the reference (100%). The thermal weight loss rate can be used to evaluate the content of volatile components in the magnetic paste. The thermal weight loss rate of the magnetic paste was within the range of 0 to 1.0%.

[0130] Comparative Example 1 (Preparation of Magnetic Powder) As magnetic powder B, metallic glass magnetic powder "SAP-2C" (Fe-Si-B-P-Nb-Cr alloy with insulating coating, D50: 2.2 μm) manufactured by Shinto Kogyo Co., Ltd. was prepared. When the volumetric particle size distribution of magnetic powder B was measured in the same manner as in Example 1, only a first peak with a peak particle size of 2 μm was confirmed, and a second peak with a peak particle size of 8.0 to 50.0 μm was not confirmed. In addition, the D50 of magnetic powder B １０ is 1.1 μm, and D ９０ was 4.1 μm.

[0131] (Preparation of magnetic paste) 13.56 g of thermosetting component A, 80.00 g of magnetic powder B, and 0.24 g of silane coupling agent "KBM-573" manufactured by Shin-Etsu Silicones Co., Ltd. were weighed out. These were placed in a 50 ml ointment container as raw materials. The raw materials in the ointment container were stirred using a medicine spoon, and then stirred for 45 seconds using a rotary stirrer at a revolution speed of 2000 rpm. This process of stirring again with a medicine spoon and stirring for 45 seconds using a rotary stirrer at a revolution speed of 2000 rpm was repeated twice. Next, 0.28 g of Aerosil "RY200S" manufactured by Nippon Aerosil Co., Ltd. was added to impart thixotropy. The magnetic paste of Comparative Example 1 was obtained by repeating the process of stirring with a medicine spoon and stirring for 30 seconds using a rotary stirrer at a revolution speed of 2000 rpm twice. The content of magnetic powder in the obtained magnetic paste was 85% by mass.

[0132] <Evaluation 1: Filling Ability Evaluation> The magnetic pastes of Example 1 and Comparative Example 1 were filled into the through-holes by the following method, and the filling state was observed to evaluate the filling ability (through-hole filling ability). The results are shown in Table 1.

[0133] [Filling Method] A substrate for filling with magnetic paste was prepared by forming through holes of 0.35 mm diameter in copper-clad laminate A (MCL-E-700G(R), manufactured by Resonac Corporation, thickness 1.0 mm). Next, the magnetic paste was printed on the substrate using a vacuum printing machine, thereby filling the through holes of the substrate with the magnetic paste. Using an explosion-proof oven (DH610S, manufactured by Yamato Scientific Co., Ltd.), the substrate filled with the magnetic paste was heated at 100°C for 60 minutes in an atmospheric environment. Subsequently, the temperature was raised to 180°C, and the magnetic paste was cured by heating for 60 minutes. This resulted in a substrate (substrate sample A) filled with a magnetic material, which was the cured product of the magnetic paste.

[0134] [Observation Method] The substrate sample A obtained above was placed in epoxy resin (Epomount, manufactured by Refine Tech Co., Ltd.) and the epoxy resin was cured to obtain a cast sample. The cast sample was cut near the through-hole of substrate sample A using a Refine Saw (RCA-005, manufactured by Refine Tech Co., Ltd.). The cross section of the cut cast sample was polished with abrasive paper to expose the cross section of the through-hole, and the cross section of the through-hole was further smoothed with alumina powder to obtain an observation surface. The obtained observation surface was observed with a scanning electron microscope (SEM) (SU5000, manufactured by Hitachi High-Technologies Corporation).

[0135] [Evaluation Method] In the observation surface observed by the above observation method, the filling ratio (Sm / St) was calculated when the total area of ​​the through-hole cross section was St and the total area of ​​the magnetic material in the through-hole cross section was Sm, and the filling ratio was compared to evaluate the filling property. Specifically, the filling property was evaluated as good when it satisfied "A" or "B" in the following criteria. A: Filling ratio (Sm / St) is 0.95 or more B: Filling ratio (Sm / St) is 0.90 or more but less than 0.95 C: Filling ratio (Sm / St) is less than 0.90

[0136] <Evaluation 2: Crack Resistance Evaluation> Substrates (substrate samples B and C) filled with a magnetic material, which was a cured product of the magnetic paste, were obtained in the same manner as in the [Filling method] of Evaluation 1, except that copper-clad laminate B (manufactured by Resonac Corporation, MCL-E-795G, thickness 1.2 mm, in-plane CTE = 3.0 to 5.0) and copper-clad laminate C (manufactured by Resonac Corporation, MCL-E-795G(LH), thickness 1.2 mm, in-plane CTE = 0.5 to 3.0) were used instead of copper-clad laminate A.

[0137] A heat shock test was carried out on each of the substrate samples B and C obtained above. Specifically, the substrate samples were placed in a liquid bath thermal shock tester, and a process of exposing them to −65°C for 5 minutes and then to 150°C for 5 minutes was repeated 1000 times.

[0138] The filling state of the magnetic material in board samples B and C before (initial stage) the heat shock test and the filling state of the magnetic material in board samples B and C after the heat shock test (after repeating the above process 1000 times) were observed using the same method as the [Observation Method] in Evaluation 1. Crack resistance was evaluated based on the number of through-hole cross sections (number of defects) in which cracks had occurred in the magnetic material or peeling had occurred between the magnetic material and the through-hole, out of 16 through-hole cross sections present within the observation surface. Specifically, crack resistance was evaluated as good if it met the following criteria of "A" or "B". The results are shown in Table 1. A: 0 defects B: 1 to 5 defects C: 6 or more defects

[0139]

[0140] REFERENCE SIGNS LIST 1...substrate, 1a...through hole, 2...magnetic paste, 3...magnetic body, 10...circuit member

Claims

1. A magnetic paste used to fill recesses provided in a substrate for circuit components, comprising a magnetic powder and a thermosetting component, the magnetic powder having a volumetric particle size distribution with at least a first peak having a peak particle size of 0.5 to 6.0 μm and a second peak having a peak particle size of 8.0 to 50.0 μm.

2. The magnetic paste according to claim 1, wherein the content of said magnetic powder is 70 mass % or more based on the total mass of non-volatile matters in said magnetic paste.

3. The magnetic paste of claim 1, wherein the thermosetting component comprises an epoxy group-containing compound and a curing agent.

4. The magnetic paste according to claim 3, wherein the epoxy group-containing compound includes an epoxy group-containing compound that is liquid at 25°C.

5. The magnetic paste according to claim 3, wherein the hardener comprises at least one selected from the group consisting of amine-based hardeners and imidazole-based hardeners.

6. The magnetic paste of claim 3, wherein the hardener comprises a hardener that is liquid at 25°C.

7. The magnetic paste according to claim 1, further comprising a coupling agent.

8. The magnetic paste according to claim 1, which has a thermal weight loss rate of 5% or less when hardened by heat treatment at 180°C.

9. The magnetic paste according to claim 1, having a viscosity at 25° C. of 1 to 600 Pa·s.

10. A circuit component comprising a substrate and a magnetic body filling a recess provided in the substrate, the magnetic body comprising a hardened product of the magnetic paste according to any one of claims 1 to 9.

11. A method for manufacturing a circuit component, comprising the steps of: filling a recess provided in a substrate with the magnetic paste according to any one of claims 1 to 9; and heating and hardening the magnetic paste.

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