Compound, molded body, cured product of compound, magnetic core, and coil component

Abstract

Provided is a compound that suppresses cracks in cured products of the compound. The compound includes a metal powder and a resin composition. The metal powder is a soft magnetic material. The resin composition includes an epoxy resin and a curing agent. The curing agent includes a first biphenyl aralkyl–type phenol resin and a second biphenyl aralkyl–type phenol resin that have different hydroxyl equivalent weights. The hydroxyl equivalent weight of the first biphenyl aralkyl–type phenol resin is lower than the hydroxyl equivalent weight of the second biphenyl aralkyl–type phenol resin. The resin composition contains 66.8–72.3 parts by mass of the first biphenyl aralkyl–type phenol resin and the second biphenyl aralkyl–type phenol resin per 100 parts by mass of the epoxy resin.

Description

Compounds, molded products, cured compound products, magnetic cores, and coil components

[0001] This disclosure relates to compounds, molded articles, cured products of compounds, magnetic cores, and coil components.

[0002] Compounds containing soft magnetic metal powder and electrically insulating resin compositions (such as thermosetting resins) are used as raw materials for various industrial products. (See Patent Documents 1 and 2 below.) For example, compounds are used as raw materials for inductors, reactors, transformers, motor stators, motor yokes, power modules, thyristor valves, noise filters (EMI filters), choke coils, and solenoid cores. Compounds are also used as encapsulants for electronic equipment such as semiconductors or electronic circuit boards.

[0003] Japanese Patent Publication No. 2023-18448 Japanese Patent Publication No. 2022-162463

[0004] For example, coil components such as inductors contain a magnetic core made of a hardened compound, with the magnetic core positioned inside the coil and the coil sealed within the hardened compound. Cracks that occur in the hardened compound within a coil component reduce the performance of the coil component (e.g., inductance value). For example, stress generated in the hardened compound during the reflow process of a coil component causes cracks in the hardened compound. The vaporization of moisture in the coil component during the reflow process also causes cracks in the hardened compound. The larger the volume of the coil within the coil component, the more likely cracks are to occur in the hardened compound. Suppression of cracks in the hardened compound is required not only for coil components but also for various industrial products that use compounds as raw materials.

[0005] One aspect of this disclosure is to provide a compound that suppresses cracking in the cured product of the compound, a molded article containing the compound, a cured product of the compound, a magnetic core containing the cured product of the compound, and a coil component containing the cured product of the compound.

[0006] For example, one aspect of the present disclosure relates to a compound as described in any one of the following [1] to [5], a molded article as described in [6], a cured product of the compound as described in [7], a magnetic core as described in [8], and a coil component as described in [9] or

[10] .

[0007] [1] A compound comprising a metal powder and a resin composition, wherein the metal powder is a soft magnetic material, the resin composition comprises an epoxy resin and a curing agent, the curing agent comprises a first biphenyl aralkyl type phenolic resin and a second biphenyl aralkyl type phenolic resin that differ in hydroxyl group equivalents, the hydroxyl group equivalent of the first biphenyl aralkyl type phenolic resin is smaller than the hydroxyl group equivalent of the second biphenyl aralkyl type phenolic resin, and the mass ratio of the first biphenyl aralkyl type phenolic resin and the second biphenyl aralkyl type phenolic resin to 100 parts by mass of the epoxy resin is 66.8 parts by mass or more and 72.3 parts by mass or less.

[0008] [2] The compound according to [1], wherein the hydroxyl group equivalent of the first biphenylaralkyl type phenol resin is 164 g / mol or more and 168 g / mol or less, and the hydroxyl group equivalent of the second biphenylaralkyl type phenol resin is 197 g / mol or more and 205 g / mol or less.

[0009] [3] The epoxy resin is the compound according to [1] or [2], comprising a polyaromatic ring epoxy resin.

[0010] [4] The compound according to any one of [1] to [3], wherein the resin composition comprises a curing accelerator, and the curing accelerator comprises one or more imidazoles.

[0011] [5] A compound described in any one of [1] to [4], which is the raw material for the magnetic core.

[0012] [6] A molded article comprising the compound described in any one of [1] to [5].

[0013] [7] A cured compound according to any one of [1] to [5].

[0014] [8] A magnetic core containing the cured material described in [7].

[0015] A coil component comprising the magnetic core described in [9] [8] and a coil, wherein the magnetic core is disposed inside the coil.

[0016] A coil component comprising the cured product described in

[10] [7] and a coil, wherein the coil is sealed within the cured product.

[0017] According to one aspect of this disclosure, a compound for suppressing cracks in the cured product of a compound is provided, a molded article containing the compound, a cured product of the compound, a magnetic core containing the cured product of the compound, and a coil component containing the cured product of the compound are provided.

[0018] Figure 1 is a schematic perspective view of a specific example of a coil component (inductor). Figure 2 is a schematic cross-sectional view of the coil component shown in Figure 1, and the cross-section shown in Figure 2 includes the central axis of the coil and crosses the pair of terminal electrodes that the coil component has.

[0019] Preferred embodiments of the present disclosure will be described below with reference to the drawings. In the drawings, equivalent components are denoted by equivalent reference numerals. The present disclosure is not limited to the embodiments described below. In the present disclosure, relative permeability means both the relative permeability of the compound and the relative permeability of the cured product of the compound (e.g., the magnetic core).

[0020] (Overview of Compound, Molded Article, Cured Compound, Magnetic Core, and Coil Part) The compound according to this embodiment comprises a metal powder and a resin composition. The compound may be solid at room temperature (e.g., 20 ± 15°C). For example, the compound may be a powder or tablet at room temperature. The metal powder and resin composition in the compound may be mixed. In other words, the compound may be rephrased as a mixture containing the metal powder and the resin composition. The compound may consist only of the metal powder and the resin composition. The compound may further contain other components in addition to the metal powder and the resin composition. For example, the compound may be a paste further containing an organic solvent in addition to the metal powder and the resin composition.

[0021] Metal powder consists of multiple metal particles. Metal powder is a soft magnetic material. Metal powder can also be described as a metal filler.

[0022] The resin composition comprises an epoxy resin and a curing agent. The epoxy resin is a thermosetting resin. The resin composition may also be described as a thermosetting binder (adhesive). The curing agent contains a first biphenyl aralkyl type phenolic resin and a second biphenyl aralkyl type phenolic resin, which differ in hydroxyl group equivalent (unit: g / mol). In other words, the first biphenyl aralkyl type phenolic resin and the second biphenyl aralkyl type phenolic resin cure the resin composition upon heating. For example, the epoxy groups (glycidyl groups) in the epoxy resin react with the hydroxyl groups contained in the first biphenyl aralkyl type phenolic resin and the second biphenyl aralkyl type phenolic resin, respectively, upon heating of the resin composition. As a result, multiple epoxy resin molecules are crosslinked by multiple first biphenyl aralkyl type phenolic resin molecules and multiple second biphenyl aralkyl type phenolic resin molecules. In other words, multiple crosslinked structures are formed between multiple epoxy resin molecules via multiple curing agent molecules, and the resin composition is cured. The compound may contain either or both of the following: an uncured resin composition (an uncured resin composition) and a semi-cured resin composition (a semi-cured resin composition, i.e., a B-stage resin composition).

[0023] The surface of some or all of the multiple metal particles constituting the metal powder may be covered with a resin composition. The compound may contain one or more metal particles that are not covered with a resin composition. The compound may contain one or more particles consisting solely of a resin composition. The compound may contain one or more composite particles (granules) consisting of one or more metal particles constituting the metal powder and a resin composition covering one or more metal particles. One composite particle may consist of multiple metal particles bound together via a resin composition.

[0024] The molded body according to this embodiment contains the above compound. The molded body according to this embodiment may consist only of the compound. The molded body may contain other members such as a coil in addition to the compound. The molded body may contain one or both of an uncured resin composition and a semi-cured resin composition. The cured product of the compound according to this embodiment contains the cured product of the resin composition (resin composition at the C stage). In the molded body containing the compound or the cured product of the compound, the resin composition or its cured product binds a plurality of metal particles to each other. Since the resin composition has electrical insulation properties, the resin composition or its cured product intervening between adjacent metal particles electrically insulates the plurality of metal particles. Further, the resin composition or its cured product intervening between adjacent metal particles suppresses the magnetic saturation of the compound or its cured product and suppresses the decrease in relative permeability.

[0025] For example, the compound may be a raw material for a coil component. For example, the coil component may contain a cured product of the compound and a coil. For example, the compound may be a raw material for a magnetic core (e.g., a dust core) contained in a coil component. That is, the magnetic core may contain a cured product of the compound. The magnetic core may consist only of the cured product of the compound. The structure of the coil component is not limited. For example, as shown in FIGS. 1 and 2, the coil component 1 (e.g., an inductor) may contain a cured product 2 of the compound and a coil 5, the coil 5 may be sealed in the cured product 2 of the compound, and a magnetic core 2dc containing the cured product 2 of the compound may be disposed inside the coil 5. The coil component

[0026] 1 may further include a pair of terminal electrodes 3, one terminal electrode 3 may be disposed on one end face of the coil component 1, and the other terminal electrode 3 may be installed on the other end face of the coil component 1. One end (lead-out portion 5a) of the coil 5 may be connected to one terminal electrode 3, and the other end (lead-out portion 5b) of the coil 5 may be connected to the other terminal electrode 3.

[0026] The hydroxyl group equivalent of the first biphenyl aralkyl type phenol resin is smaller than that of the second biphenyl aralkyl type phenol resin. The second biphenyl aralkyl type phenol resin, which has a relatively large hydroxyl group equivalent, reduces the density of the crosslinked structure in the cured compound. In other words, the second biphenyl aralkyl type phenol resin, which has a relatively small number of hydroxyl groups per molecule, reduces the density of the crosslinked structure in the cured compound. This reduction in the density of the crosslinked structure lowers the elastic modulus of the cured compound. This reduction in elastic modulus suppresses the stress generated in the cured compound. This stress suppression suppresses cracking in the cured compound. However, if the compound contains only the second biphenyl aralkyl type phenol resin as the curing agent, the number of hydroxyl groups (functional groups that react with epoxy resin) in the curing agent is insufficient, and the density of the crosslinked structure in the cured compound is too low. Cured products with excessively low crosslink density are too soft and do not easily possess the sufficient hardness and mechanical strength required for industrial products such as coil components. However, the compound according to this disclosure contains not only a second biphenyl aralkyl type phenolic resin but also a first biphenyl aralkyl type phenolic resin as a curing agent. Since the hydroxyl group equivalent of the first biphenyl aralkyl type phenolic resin is smaller than that of the second biphenyl aralkyl type phenolic resin, the first biphenyl aralkyl type phenolic resin appropriately compensates for the number of hydroxyl groups contained in the curing agent. As a result, excessive reduction in the density of the crosslink structure is suppressed, and the hardness and mechanical strength of the cured compound are appropriately increased. The inventors also surmise that the biphenyl aralkyl structures of both the first and second biphenyl aralkyl type phenolic resins contribute to the suppression of cracks in the cured compound. The compound according to this disclosure makes it possible to reduce the elastic modulus of the cured compound at high temperatures and to suppress cracking in the cured compound at high temperatures. For example, high temperature may be 230°C or higher and 270°C or lower.

[0027] The mass ratio (Rp) of the first biphenyl aralkyl type phenol resin and the second biphenyl aralkyl type phenol resin to 100 parts by mass of the epoxy resin is 66.8 parts by mass or more and 72.3 parts by mass or less. In other words, the mass of the epoxy resin is represented as me (unit: gram), the mass of the first biphenyl aralkyl type phenol resin is represented as m1 (unit: gram), the mass of the second biphenyl aralkyl type phenol resin is represented as m2 (unit: gram), Rp is defined as { (m1 + m2) / me} × 100, and is 66.8 parts by mass or more and 72.3 parts by mass or less. According to the research of the inventors, when Rp is 66.8 parts by mass or more and 72.3 parts by mass or less, cracks in the cured product of the compound are likely to be suppressed. When Rp is less than 66.8 parts by mass, it is difficult to reduce the elastic modulus of the cured product of the compound, and it is difficult to suppress cracks in the cured product of the compound. Since cracks in the cured product of the compound are likely to be suppressed and the hardness and mechanical strength of the cured product of the compound are likely to moderately increase, the ratio of the mass (m1) of the first biphenyl aralkyl type phenol resin to 100 parts by mass of the epoxy resin (that is, (m1 / me) × 100) may be 21.5 parts by mass or more and 47.1 parts by mass or less. Since cracks in the cured product of the compound are likely to be suppressed and the hardness and mechanical strength of the cured product of the compound are likely to moderately increase, the ratio of the mass (m2) of the second biphenyl aralkyl type phenol resin to 100 parts by mass of the epoxy resin (that is, (m2 / me) × 100) may be 20.7 parts by mass or more and 48.1 parts by mass or less.

[0028] Since cracks in the cured product of the compound are likely to be suppressed and the hardness and mechanical strength of the cured product of the compound are likely to moderately increase, the hydroxyl equivalent of the first biphenyl aralkyl type phenol resin may be 164 g / mol or more and 168 g / mol or less. Since cracks in the cured product of the compound are likely to be suppressed and the hardness and mechanical strength of the cured product of the compound are likely to moderately increase, the hydroxyl equivalent of the second biphenyl aralkyl type phenol resin may be 197 g / mol or more and 205 g / mol or less.

[0029] For example, the first biphenyl aralkyl type phenol resin may be represented by the following Chemical Formula 1.

[0030] In Chemical Formula 1, R １ , R ２ , R ３ , R ４ , and R ５ each may independently be a monovalent organic group having 1 to 6 or 1 to 3 carbon atoms. For example, R １ , R ２ , R ３ , R ４ , and R ５ in Chemical Formula 1 may each be one organic group selected from the group consisting of a methyl group, an ethyl group, an n-propyl group, an n-butyl group, a pentyl group, a hexyl group, an isopropyl group, an isobutyl group, and a t-butyl group. In Chemical Formula 1, each of x1, x2, and x, may independently be an integer of 0 or more and 4 or less. In Chemical Formula 1, each of x4 and x5 may independently be an integer of 0 or more and 3 or less. In Chemical Formula 1, n1 may be an integer of 1 or more and 10 or less. In Chemical Formula 1, n2 may be an integer of 1 or more and 10 or less.

[0031] For example, the second biphenyl aralkyl type phenol resin may be represented by the following Chemical Formula 2.

[0032] In Chemical Formula 2, R Ａ , R Ｂ , R Ｃ , R Ｄ , R Ｆ , and R Ｇ each may independently be a monovalent organic group having 1 to 6 or 1 to 3 carbon atoms. For example, R Ａ , R) Ｂ , R Ｃ , R Ｄ , R Ｆ , and R ＧEach may be one organic group selected from the group consisting of methyl group, ethyl group, n-propyl group, n-butyl group, pentyl group, hexyl group, isopropyl group, isobutyl group, and t-butyl group. Each of y1, y2, y3, y5, y6, and y7 in chemical formula 2 may be an integer between 0 and 4, inclusive. y4 in chemical formula 2 may be an integer between 0 and 3, inclusive. n in chemical formula 2 may be any positive integer.

[0033] The content of metal powder in the compound is not particularly limited. For example, the content of metal powder in the compound may be 90% by mass or more but less than 100% by mass, 92.0% by mass or more but 98.0% by mass or less, 93.0% by mass or more but 98.0% by mass or less, or 94.0% by mass or more but 98.0% by mass or less. The content of resin composition in the compound is also not particularly limited. For example, the content of resin composition in the compound may be greater than 0% by mass and 10% by mass or less, 2.0% by mass or more but 8.0% by mass or less, 2.0% by mass or more but 7.0% by mass or less, or 2.0% by mass or more but 6.0% by mass or less. The higher the content of metal powder in the compound, the higher the relative permeability. In other words, the lower the content of resin composition in the compound, the higher the relative permeability. The lower the content of metal powder in the compound, the more easily the compound flows, and the higher the mechanical strength of the cured compound. In other words, the higher the resin composition content in the compound, the more fluid the compound becomes, and the higher the mechanical strength of the cured compound.

[0034] For example, the respective contents of the metal powder and resin composition in the compound may be determined by the following method based on the specific gravity of the compound, metal powder, and resin composition. Specific gravity (unit: none) may be the ratio of the density of the compound, metal powder, and resin composition to the density of a standard substance (e.g., the density of water at 4°C). For example, the specific gravity of the compound, metal powder, and resin composition may be measured by a general method based on Archimedes' principle (e.g., the water displacement method). The specific gravity of the metal powder and resin composition may be measured in advance before the compound is manufactured. The compound may be separated into metal powder and resin composition (organic matter dissolved in the organic solvent) using an inert organic solvent that does not react with the metal powder and resin composition, and the specific gravity of the separated metal powder and resin composition may be measured. The specific gravity of the metal powder is S Ｍ It may be expressed as follows. The content of metal powder in the compound may be expressed as α mass%. The specific gravity of the resin composition is S Ｒ It may be expressed as follows. The content of the resin composition in the compound may be expressed as (100-α) mass%. Specific gravity S of the compound Ｃ This can be expressed by the following formula 1. Based on the following formula 1, each measured specific gravity (S Ｍ , S Ｒ , and S Ｃ The metal powder content α in the compound can be calculated from the above. Ｃ = [(S Ｍ ×α) + {S Ｒ ×(100-α)}] / 100 (1)

[0035] (Specific example of metal powder) For example, the average particle size or D50 (median diameter) of the metal powder (multiple metal particles) may be 0.1 μm or more and 45 μm or less.

[0036] The metal powder (multiple metal particles) may contain multiple types of metal powders with different particle sizes. For example, the metal powder may contain a first soft magnetic powder (multiple first soft magnetic particles) and a second soft magnetic powder (multiple second soft magnetic particles), and the particle size of the first soft magnetic powder may be larger than that of the second soft magnetic powder. For example, the average particle size of the first soft magnetic powder may be larger than the average particle size of the second soft magnetic powder. For example, the D50 (median diameter) of the first soft magnetic powder may be larger than that of the second soft magnetic powder. For example, the D90 of the first soft magnetic powder may be larger than that of the second soft magnetic powder. If the compound contains only first soft magnetic powder with a large particle size as the metal powder, gaps are easily formed between multiple adjacent first soft magnetic particles, making it difficult to increase the packing density of the metal powder in the compound. On the other hand, when the compound contains a first soft magnetic powder and a second soft magnetic powder as metal powder, the second soft magnetic particles, which are smaller than the first soft magnetic particles, fill the gaps between the multiple first soft magnetic particles, increasing the packing density of the metal powder in the compound. In other words, the specific gravity of the compound increases because the compound contains a first soft magnetic powder and a second soft magnetic powder with different particle sizes. As a result, the relative permeability improves. Furthermore, as the packing density of the metal powder in the compound increases, the cured compound becomes denser, improving the relative permeability and mechanical strength of the cured compound. For example, the average particle size or D50 of the first soft magnetic powder may be 11 μm or more and 45 μm or less. For example, the average particle size or D50 of the second soft magnetic powder may be 0.1 μm or more and 9.0 μm or less. When the average particle size or D50 of the first soft magnetic powder is within the above range, and the average particle size or D50 of the second soft magnetic powder is within the above range, the filling density of the metal powder in the compound tends to increase, and the relative permeability and mechanical strength tend to increase.

[0037] The mass of the first soft magnetic powder may be expressed as M1, and the mass of the second soft magnetic powder may be expressed as M2. M1 / (M1+M2) may be between 0.70 and 0.95, and M2 / (M1+M2) may be between 0.05 and 0.30. When M1 / (M1+M2) and M2 / (M1+M2) are within the above ranges, the second soft magnetic particles, which are smaller than the first soft magnetic particles, are more likely to fill the gaps between multiple first soft magnetic particles, and the filling rate of the metal powder in the compound (specific gravity of the compound) tends to increase. As a result, the relative permeability and mechanical strength tend to increase.

[0038] The average particle size, D50, and D90 of the metal powder may be calculated from the particle size distribution based on the volume, number, or mass of the metal particles constituting the metal powder. The average particle size, D50, and D90 of the first soft magnetic powder may be calculated from the particle size distribution based on the volume, number, or mass of the first soft magnetic particles constituting the first soft magnetic powder. The average particle size, D50, and D90 of the second soft magnetic powder may be calculated from the particle size distribution based on the number, volume, or mass of the second soft magnetic particles constituting the second soft magnetic powder. Each particle size distribution may be measured by a laser diffraction particle size distribution analyzer. Each particle size distribution may also be calculated based on the measurement of the volume or mass of each particle classified by one or more sieves having a predetermined mesh size. The shapes of the metal powder (metal particles), the first soft magnetic particles, and the second soft magnetic particles are not particularly limited. For example, the shapes of the metal powder (metal particles), the first soft magnetic particles, and the second soft magnetic particles may be spherical, nearly spherical, flattened, or needle-shaped.

[0039] As long as the metal powder is a soft magnetic material, the composition of the metal powder (each of the multiple metal particles) is not particularly limited. For example, the metal powder may contain iron. In addition to iron, the metal powder may further contain at least one metal element selected from the group consisting of base metal elements, noble metal elements, transition metal elements, and rare earth elements. For example, the metal element other than iron contained in the metal powder may be at least one element selected from the group consisting of cobalt (Co), nickel (Ni), copper (Cu), titanium (Ti), manganese (Mn), zinc (Zn), aluminum (Al), tin (Sn), arsenic (As), antimony (Sb), chromium (Cr), beryllium (Be), barium (Ba), strontium (Sr), lead (Pb), bismuth (Bi), silver (Ag), niobium (Nb), hafnium (Hf), zirconium (Zr), tantalum (Ta), molybdenum (Mo), tungsten (W), and vanadium (V). The metal powder may contain nonmetallic elements in addition to metallic elements. For example, the nonmetallic element contained in the metal powder may be at least one element selected from the group consisting of boron (B), carbon (C), nitrogen (N), oxygen (O), silicon (Si), phosphorus (P), and sulfur (S). For example, when the metal powder (e.g., the first soft magnetic powder) contains Cr, oxidation of the metal powder is easily suppressed, the metal powder is less prone to rusting, and the decrease in relative permeability is easily suppressed.

[0040] The metal powder may contain at least one metal from among pure iron and iron-containing alloys (iron-based alloys). The metal powder may consist only of pure iron. The metal powder may consist only of iron-based alloys. The metal powder may consist only of pure iron and iron-based alloys. For example, the pure iron may be carbonyl iron powder. Carbonyl iron powder is Fe(CO) ５ This is a perfectly spherical pure iron powder obtained by the reduction (thermal decomposition) of (iron pentacarbonyl). For example, the iron-based alloy contained in the metal powder may be at least one alloy selected from the group consisting of Fe-Cr-Si alloys, Fe-Cr alloys, Fe-Si alloys, Fe-Si-Al alloys, Fe-Ni alloys, Fe-Cu-Ni alloys, Fe-Co alloys, and Fe-Ni-Cr alloys. The iron or iron-based alloy contained in the metal powder may be crystalline or amorphous. The metal powder may contain metal nanocrystals.

[0041] Some or all of the multiple metal particles constituting the metal powder may be covered with an insulating coating. Some or all of the surface of each metal particle may be covered with an insulating coating. Covering the metal powder with an insulating coating improves the electrical insulation of the compound. If the insulating coating contains glass, the surface of the insulating coating tends to become smoother, and friction between multiple metal particles tends to be suppressed. As a result, aggregation (blocking) of the compound tends to be suppressed, and the fluidity of the compound tends to be improved. Some or all of the surface of the insulating coating may be covered with a resin composition.

[0042] For example, insulating coatings include glass, phosphoric acid (phosphate), silica (SiO ２ ), iron oxide (Fe ２ O ３ ), and chromium oxide (Cr ２ O ３ The insulating coating may contain at least one component selected from the group consisting of ) ). For example, in addition to silicon (Si), the glass may contain at least one element selected from the group consisting of oxygen (O), boron (B), sodium (Na), and aluminum (Al). For example, the glass may contain at least one component from silicate glass (silicate), phosphatesilicate glass (phosphate), and borosilicate glass (borosilicate). The composition of the insulating coating may be measured by at least one analytical method from photoelectron spectroscopy (XPS) and energy-dispersive X-ray analysis (EDX). The insulating coating may be formed by a wet method using an alkoxysilane solution, etc., or by a dry method such as mechanofusion. For example, the thickness of the insulating coating may be 10 nm or more and 200 nm or less. The thickness of the insulating coating may be measured in the cross-section of the metal particles by transmission electron microscopy (TEM) and EDX.

[0043] The compound may further contain a non-metallic filler in addition to the metal powder. For example, the compound may contain silica (SiO₂) as the non-metallic filler. ２ It may contain a filler (particulate filler) consisting of the following:

[0044] (Specific Examples of Resin Compositions) The resin composition may be the remaining portion (non-volatile component) of the compound excluding the metal powder. As described above, the resin composition includes at least an epoxy resin and a curing agent. The curing agent includes at least a first biphenyl aralkyl type phenolic resin and a second biphenyl aralkyl type phenolic resin. The epoxy resin may be the main component of the resin composition. In other words, the epoxy resin content (unit: mass%) of all components constituting the resin composition may be the maximum. In addition to the epoxy resin and curing agent, the resin composition may further include at least one component selected from the group consisting of a curing accelerator (curing catalyst), a coupling agent, a wax (release agent), and a flame retardant. Specific examples of each component are as follows.

[0045] The resin composition may further contain a thermosetting resin other than the epoxy resin. For example, the thermosetting resin other than the epoxy resin may be at least one resin selected from the group consisting of phenolic resins, bismaleimide resins, polyimide resins, and polyamideimide resins. In addition to thermosetting resins such as epoxy resins, the resin composition may further contain other resins (e.g., thermoplastic resins). For example, the resin composition may further contain at least one other resin selected from the group consisting of polyphenylene sulfide resins, acrylic resins, methacrylic resins, polyethylene, polypropylene, polystyrene, polyvinyl chloride, polyethylene terephthalate, and silicone resins.

[0046] <Epoxy Resins and Curing Agents> Epoxy resins include biphenyl-type epoxy resins, stilbene-type epoxy resins, diphenylmethane-type epoxy resins, sulfur atom-containing epoxy resins, novolac-type epoxy resins, dicyclopentadiene-type epoxy resins, salicylaldehyde-type epoxy resins, copolymer epoxy resins of naphthols and phenols, epoxidized aralkyl-type phenol resins, bisphenol-type epoxy resins, glycidyl ether-type epoxy resins of alcohols, glycidyl ether-type epoxy resins of paraxylylene-modified phenol resins and / or metaxylylene-modified phenol resins, and glycidyl ether-type epoxy resins of terpene-modified phenol resins. The resin may be at least one resin selected from the group consisting of cyanoacrylate resins, cyclopentadiene-type epoxy resins, glycidyl ether-type epoxy resins of polycyclic aromatic ring-modified phenol resins, glycidyl ether-type epoxy resins of naphthalene ring-containing phenol resins, glycidyl ester-type epoxy resins, glycidyl-type or methylglycidyl-type epoxy resins, alicyclic epoxy resins, halogenated phenol novolac-type epoxy resins, orthocresol novolac-type epoxy resins, hydroquinone-type epoxy resins, trimethylolpropane-type epoxy resins, and linear aliphatic epoxy resins obtained by oxidizing olefin bonds with peracids such as peracetic acid.

[0047] At least some of the epoxy resins may be naphthalene-type epoxy resins having a naphthalene structure. Naphthalene-type epoxy resins are solid at room temperature. When the compound contains a naphthalene-type epoxy resin, the product manufactured from the compound (cured compound) tends to have high mechanical strength at both room temperature and high temperatures. The naphthalene-type epoxy resin may be at least one resin selected from the group consisting of naphthalene diepoxy compounds, naphthylene ether-type epoxy resins, naphthalene novolac-type epoxy resins, methylene-bonded dimers of naphthalene diepoxy compounds, and methylene-bonded compounds of naphthalene monoepoxy compounds and naphthalene diepoxy compounds. The epoxy resin may also include a bifunctional epoxy resin. For example, the bifunctional epoxy resin may be at least one resin from among α-naphthol-type epoxy resins and β-naphthol-type epoxy resins.

[0048] The epoxy resin may contain at least one of the trifunctional epoxy resins and tetrafunctional epoxy resins. The naphthalene-type epoxy resin described above may be at least one of the trifunctional epoxy resins and tetrafunctional epoxy resins. A trifunctional epoxy resin is an epoxy resin composed of structural units having three epoxy groups. A tetrafunctional epoxy resin is an epoxy resin composed of structural units having four epoxy groups. When the epoxy resin contains at least one of the trifunctional epoxy resins and tetrafunctional epoxy resins, the epoxy resins are crosslinked three-dimensionally during the thermal curing process of the compound, forming a strong crosslinked network. As a result, the movement of the epoxy resin in the cured compound is easily suppressed at high temperatures. In other words, the glass transition temperatures of the trifunctional epoxy resins and tetrafunctional epoxy resins are higher than those of the difunctional epoxy resin. Therefore, when the epoxy resin contains at least one of the trifunctional epoxy resins and tetrafunctional epoxy resins, the cured compound tends to have high mechanical strength at high temperatures.

[0049] For example, the epoxy resin may include a polyaromatic epoxy resin. Among the various types of epoxy resins, polyaromatic epoxy resins have a relatively large molecular weight, and therefore their epoxy equivalent (unit: g / mol) is relatively large. Consequently, polyaromatic epoxy resins in a compound tend to moderately reduce the density of the crosslinked structure in the cured compound. As a result, the elastic modulus of the cured compound tends to decrease, stress generated in the cured compound is easily suppressed, and cracks in the cured compound are easily suppressed. For example, the polyaromatic epoxy resin may be one or more epoxy resins selected from the group consisting of biphenylaralkyl type epoxy resins and trifunctional epoxy resins that are derivatives of 1-[α-methyl-α-(4-hydroxyphenyl)ethyl]-4-[α,α-bis(4-hydroxyphenyl)ethyl]benzene.

[0050] The compound may contain one of the epoxy resins listed above. The compound may contain multiple types of epoxy resins listed above.

[0051] As described above, the curing agent comprises a first biphenyl aralkyl type phenol resin and a second biphenyl aralkyl type phenol resin. The curing agent may consist only of the first biphenyl aralkyl type phenol resin and the second biphenyl aralkyl type phenol resin. In addition to the first biphenyl aralkyl type phenol resin and the second biphenyl aralkyl type phenol resin, the curing agent may further contain one or more other curing agents.

[0052] Curing agents are classified into two types: those that cure epoxy resins in a low temperature to room temperature range, and heat-curing curing agents that cure epoxy resins upon heating. For example, curing agents that cure epoxy resins in a low temperature to room temperature range include aliphatic polyamines, polyaminoamides, and polymercaptans. For example, heat-curing curing agents include aromatic polyamines, acid anhydrides, phenolic resins, phenol novolac resins, and dicyandiamide (DICY). From the viewpoint of improving the heat resistance (mechanical strength at high temperatures) of the cured compound, the curing agent may preferably be a heat-curing curing agent, more preferably a phenolic resin, and even more preferably a phenol novolac resin.

[0053] For example, phenol resins other than the first biphenylaralkyl type phenol resin and the second biphenylaralkyl type phenol resin may be at least one resin selected from the group consisting of aralkyl type phenol resins, dicyclopentadiene type phenol resins, salicylaldehyde type phenol resins, novolac type phenol resins, copolymer phenol resins of benzaldehyde type phenol and aralkyl type phenol, paraxylylene and / or metaxylylene modified phenol resins, melamine modified phenol resins, terpene modified phenol resins, dicyclopentadiene type naphthol resins, cyclopentadiene modified phenol resins, polycyclic aromatic ring modified phenol resins, biphenyl type phenol resins, and triphenylmethane type phenol resins. The phenol resin may also be a copolymer composed of two or more of the above phenol resins.

[0054] The phenol novolac resin may be a resin obtained by condensing or co-condensing phenols and / or naphthols with aldehydes under an acidic catalyst. The phenols constituting the phenol novolac resin may be at least one selected from the group consisting of phenol, cresol, xylenol, resorcinol, catechol, bisphenol A, bisphenol F, phenylphenol, and aminophenol. The naphthols constituting the phenol novolac resin may be at least one selected from the group consisting of α-naphthol, β-naphthol, and dihydroxynaphthalene. The aldehydes constituting the phenol novolac resin may be at least one selected from the group consisting of formaldehyde, acetaldehyde, propionaldehyde, benzaldehyde, and salicylaldehyde.

[0055] The curing agent may be a compound having two phenolic hydroxyl groups in one molecule. For example, the compound having two phenolic hydroxyl groups in one molecule may be at least one compound selected from the group consisting of resorcinol, catechol, bisphenol A, bisphenol F, and substituted or unsubstituted biphenols.

[0056] For example, the ratio of the hydroxyl group equivalent of the curing agent to the epoxy equivalent of the epoxy resin may be between 0.5 and 1.5. In other words, the ratio of the active group (phenolic OH group) in the curing agent that reacts with the epoxy groups in the epoxy resin may be between 0.5 and 1.5 equivalents per equivalent of epoxy groups in the epoxy resin.

[0057] <Curing Accelerator> The curing accelerator (curing catalyst) may be any composition that reacts with the epoxy resin to accelerate its curing, and is not limited to any other composition. For example, the curing accelerator may be a urea compound. The curing accelerator may also be an alkyl-substituted imidazole or an imidazole such as benzimidazole. The curing accelerator may also be a phosphorus-based curing accelerator. The compound may contain one type of curing accelerator. The compound may contain multiple types of curing accelerators.

[0058] The curing accelerator may contain one or more imidazoles for the reason that cracks in the cured compound are easily suppressed and the hardness and mechanical strength of the cured compound are easily increased to a moderate degree. For example, the one or more imidazoles may be one or more compounds selected from 2-ethyl-4-methylimidazole, 2-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole (4-methyl-2-phenylimidazole), 2-phenyl-4-methyl-5-hydroxymethylimidazole, 1-aminopropyl-2-methylimidazole, 1-cyanoethyl-2-undecylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, and 1-cyanoethyl-2-phenylimidazole.

[0059] The amount of curing accelerator added is not particularly limited. From the viewpoint of improving the curability and fluidity of the epoxy resin when it absorbs moisture, the amount of curing accelerator added may be 0.1 parts by mass or more and 30 parts by mass or less per 100 parts by mass of epoxy resin. The content of the curing accelerator may be 0.001 parts by mass or more and 5 parts by mass or less relative to the total mass of the epoxy resin and the curing agent (e.g., phenolic resin).

[0060] <Coupling Agent> The coupling agent may be a coupling agent that reacts with glycidyl groups present in a resin composition such as epoxy resin. The coupling agent improves the adhesion between the metal powder and the resin composition and improves the mechanical strength of the cured compound. The coupling agent that reacts with glycidyl groups may be a silane compound (silane coupling agent). For example, the silane coupling agent may be at least one coupling agent selected from the group consisting of epoxysilane, mercaptosilane, aminosilane, alkylsilane, ureidosilane, acid anhydride silane, methacrylicsilane, and vinylsilane. The compound may contain one of the above coupling agents. The compound may contain multiple types of the above coupling agents.

[0061] <Wax> The compound may contain wax. Wax may be rephrased as a lubricant or release agent. The inclusion of wax in the compound improves its fluidity and moldability, and improves its release properties. As a result, the accuracy of the shape and dimensions of the product manufactured from the compound (cured compound) is improved, and structural defects in the product are more easily suppressed. For example, the wax may be at least one compound from saturated fatty acids, saturated fatty acid salts, saturated fatty acid esters, and fatty acid amides. The wax may also be a synthetic wax. The compound may contain one of the above waxes. The compound may contain multiple types of the above waxes.

[0062] <Flame Retardants> The compound may contain flame retardants. For example, the flame retardant may be at least one compound selected from the group consisting of brominated 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 compound may contain one of the above flame retardants, or more of the above flame retardants.

[0063] (Method for manufacturing the compound) The method for manufacturing the compound includes the step of preparing a mixed powder containing a metal powder and a resin composition.

[0064] For example, a mixed powder may be obtained by kneading a metal powder and each component constituting a resin composition while heating. A lump of mixed powder (aggregated mixed powder) may be obtained by heating and kneading the metal powder and the resin composition, and the mixed powder may be obtained by grinding the lump of mixed powder.

[0065] For example, the means for mixing the metal powder and the resin composition may be a kneader, rolls, or a stirrer. By heating and mixing the metal powder and the resin composition, the resin composition may coat part or all of the surface of each metal particle constituting the metal powder. By heating and mixing the metal powder and the resin composition, part or all of the resin composition may become a semi-cured product.

[0066] The metal powder and all the components constituting the resin composition may be kneaded together. A mixture of metal powder and a coupling agent may be prepared in advance, and this mixture may be kneaded with the other components of the resin composition. A mixture of each component of the resin composition, excluding the curing accelerator, and the metal powder may be prepared in advance, and this mixture may be kneaded with the curing accelerator. A mixture of each component of the resin composition, excluding the wax, and the metal powder may be prepared in advance, and this mixture may be kneaded with the wax.

[0067] The mixing time depends on the type of mixing means, the volume of the mixing means, and the amount of compound to be produced. The mixing time is not limited. For example, the mixing time may be between 1 minute and 20 minutes. For example, the temperature of the metal powder and resin composition during mixing (heating temperature) may be below the thermosetting temperature of the thermosetting resin. The heating temperature may be a temperature at which a semi-cured product of the thermosetting resin (B-stage resin composition) is formed and the formation of a cured product of the thermosetting resin (C-stage resin composition) is suppressed. The heating temperature may be lower than the activation temperature of the curing accelerator. For example, the heating temperature may be between 50°C and 150°C.

[0068] The method for preparing the mixed powder is not limited to the method described above. For example, a mixture may be obtained by kneading a metal powder, a resin composition, and an organic solvent while heating, and the mixed powder may be obtained by drying (and grinding) the mixture. When the organic solvent in which the resin composition is dissolved comes into contact with the surface of the metal particles, the metal particles are easily covered with the resin composition. For similar reasons, a mixture may be obtained by mixing the metal powder and the resin composition in an organic solvent, and the mixed powder may be obtained by drying (and grinding) the mixture. For example, the organic solvent may be at least one solvent selected from the group consisting of acetone, methyl ethyl ketone (2-butanone), methyl isobutyl ketone (4-methyl-2-pentanone), benzene, toluene, xylene, and N-methyl-2-pyrrolidone (NMP).

[0069] The above mixed powder itself may be used as a compound. A compound with an adjusted particle size distribution may be obtained by grinding the mixed powder. A compound with an adjusted particle size distribution may be obtained by classifying the mixed powder using a sieve. The above mixed liquid itself (i.e., paste) may be used as a compound.

[0070] (Methods for manufacturing molded articles, cured products, magnetic cores, and coil components) A molded article is obtained by molding the compound described above. By heat treatment of the molded article (thermosetting of the resin composition in the molded article), multiple metal particles are firmly bonded to each other by the cured resin composition, and a cured compound (e.g., a magnetic core) is obtained. For example, the method for molding the compound may be transfer molding, extrusion molding, or compression molding. Transfer molding is a type of injection molding. Transfer molding may be rephrased as pressure molding. Transfer molding may include the steps of heating the compound in a heating chamber to make it fluid, and supplying (pressure-injecting) the fluidized compound from the heating chamber into the mold through a casting runner. Depending on the industrial product (e.g., a coil component) to be manufactured using the compound, the dimensions and shape of the mold used for molding the compound may be selected. The heat treatment temperature of the molded body may be any temperature at which the resin composition in the molded body is sufficiently cured, and may be above the activation temperature of the curing accelerator. For example, the heat treatment temperature may be between 100°C and 300°C. For example, the heat treatment time may be between a few minutes and 10 hours. To suppress the oxidation of the metal powder in the molded body, the heat treatment of the molded body may be carried out under an inert atmosphere. A paste which is a mixture of the compound and an organic solvent may be used to manufacture a molded body containing the compound, a cured product of the compound, a magnetic core containing the cured product of the compound, and a coil component containing the cured product of the compound.

[0071] (Analysis Method) The composition of the compound used in the manufacture of the molded article and the cured product may be retrospectively analyzed by analyzing the samples obtained by crushing the molded article and the cured product, respectively. The sample may be dissolved in an organic solvent, and the metal powder may be separated from the resin composition dissolved in the organic solvent. The separated metal powder and resin composition may be analyzed individually. Even when the unused compound itself is analyzed directly, the separated metal powder and resin composition may be analyzed individually using the method described above. For example, metal powders may be analyzed and identified by one or more analytical methods selected from the group consisting of X-ray fluorescence analysis (XRF), inductively coupled plasma (ICP) emission spectroscopy, X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray spectroscopy (EDS or EDX), and mass spectrometry (MS). For example, each component constituting the resin composition may be analyzed and identified by one or more analytical methods selected from the group consisting of infrared spectroscopy (IR), nuclear magnetic resonance (NMR), gas chromatography (GC), high-performance liquid chromatography (HPLC), and mass spectrometry.

[0072] This disclosure is not necessarily limited to the embodiments described above. Various modifications to this disclosure are possible and are included in this disclosure, without departing from the spirit of this disclosure.

[0073] For example, industrial products manufactured using the compound are not limited to inductors. Specific industrial products manufactured using the compound may include reactors, transformers, motor stators, motor yokes, power modules, thyristor valves, noise filters (EMI filters), choke coils, and solenoid cores.

[0074] The compound, the molded article containing the compound, or the cured product of the compound may be a encapsulant (for example, an encapsulant for electronic components). The compound can possess both the electrical insulation properties required for encapsulants for electronic or electrical equipment and the soft magnetic properties (electromagnetic shielding ability) required for electromagnetic shielding materials. For example, the compound, the molded article containing the compound, or the cured product of the compound may be an encapsulant (underfill, etc.) for semiconductor packages such as IC packages and LSI packages.

[0075] The present disclosure will be illustrated in detail by the following examples and comparative examples. The present disclosure is not limited to the following examples.

[0076] [Components included in the resin composition] The "Resin 1" described below is NC-3000 manufactured by Nippon Kayaku Co., Ltd., and is a biphenyl aralkyl type epoxy resin.

[0077] The "Resin 2" described below is TECHMORE VG-3101L manufactured by Printec Co., Ltd., and is a trifunctional epoxy resin that is a derivative of 1-[α-methyl-α-(4-hydroxyphenyl)ethyl]-4-[α,α-bis(4-hydroxyphenyl)ethyl]benzene.

[0078] The "curing agent 1" described below was HE910 manufactured by Air Water Performance Chemical Co., Ltd., and was a triphenylmethane-type phenolic resin.

[0079] The "curing agent 2" described below was MEHC7841 manufactured by UBE Corporation (formerly Meiwa Chemicals Co., Ltd.). "Curing agent 2" is the first biphenyl aralkyl type phenolic resin represented by the above-mentioned chemical formula 1, and the hydroxyl group equivalent of "curing agent 2" was 167 g / mol.

[0080] The "curing agent 3" described below was MEHC7851 manufactured by UBE Corporation (formerly Meiwa Chemicals Co., Ltd.). "Curing agent 3" is a second biphenyl aralkyl type phenolic resin represented by the above-mentioned chemical formula 2, and the hydroxyl group equivalent of "curing agent 3" was 199 g / mol.

[0081] The "curing agent 4" described below was MEW-1800 manufactured by UBE Corporation (formerly Meiwa Chemicals Co., Ltd.), and was a phenol novolac resin.

[0082] The "curing accelerator" described below was 2P4MHZ-PW, manufactured by Shikoku Chemicals Co., Ltd., and was 2-phenyl-4-methyl-5-hydroxymethylimidazole.

[0083] The "coupling agent 1" described below was KBM-403 manufactured by Shin-Etsu Chemical Co., Ltd., and was 3-glycidoxypropyltrimethoxysilane.

[0084] The "coupling agent 2" described below was KBM-5803 manufactured by Shin-Etsu Chemical Co., Ltd., and was 8-methacryloxyoctyltrimethoxysilane.

[0085] The "release agent 1" described below was Licowax OP manufactured by Clariant Chemicals Co., Ltd., which was a montanic acid ester partially saponified with calcium hydroxide.

[0086] The "release agent 2" described below was zinc stearate.

[0087] [Components contained in the metal powder] A mixture consisting of powder 1 and powder 2 was used as the metal powder.

[0088] Powder 1 was 9A4-03 manufactured by Epson Atomics Corporation, and was a metal (soft magnetic material) composed of Fe, Si, and B. Powder 1 was amorphous. The cutoff diameter of powder 1 was 53 μm. In other words, particles with a particle size (maximum particle width) larger than 53 μm were removed from powder 1 by sieving. The average particle size of powder 1 was 23 μm. The content of powder 1 in the metal powder was 80% by mass.

[0089] Powder 2 was SAP-2 manufactured by Shinto Kogyo Co., Ltd., and was a metal (soft magnetic material) composed of Fe, Si, Cr, and B. Powder 2 was amorphous. The average particle size of powder 2 was 2.0 μm. The content of powder 2 in the metal powder was 20% by mass.

[0090] (Example 1) The resin composition of Example 1 was a mixture consisting of resins 1 and 2, curing agents 2 and 3, curing accelerators, coupling agents 1 and 2, and release agents 1 and 2. The mass ratios (in parts by mass) of resin 1, resin 2, curing agents 2 and 3, curing accelerators, coupling agents, and release agents 1 and 2 in the resin composition were adjusted to the values ​​shown in Table 1 below. Mtotal (in parts by mass) shown in Table 2 below is the sum of the mass ratios (in parts by mass) of curing agents 1 to 4 relative to 100 parts by mass of epoxy resin (resins 1 and 2). Mp (in parts by mass) shown in Table 2 below is the sum of the mass ratios (in parts by mass) of curing agents 2 and 3 (i.e., the first biphenyl aralkyl type phenolic resin and the second biphenyl aralkyl type phenolic resin) relative to 100 parts by mass of epoxy resin (resins 1 and 2).

[0091] By kneading all the raw materials, consisting of the components of the resin composition and the metal powder, while heating, a compound (powder) consisting only of the metal powder and the resin composition was obtained. The maximum temperature of all the raw materials during kneading was 130°C. The content of the metal powder in the compound (unit: mass%) was adjusted to 96.2% by mass. In other words, the content of the resin composition in the compound was adjusted to 3.8% by mass.

[0092] <Measurement of Elastic Modulus and Bending Strength> A test specimen made of cured compound was obtained by transfer molding of the compound at 140°C and post-curing (heating at 180°C for 2 hours) following the transfer molding. The test specimen was a rectangular parallelepiped (rod). The pressure applied to the compound during transfer molding was 12.4 MPa. The dimensions of the test specimen were length L: 80 mm × width W: 10 mm × thickness t: 3.0 mm. A three-point support bending test was performed using the test specimen with an autograph equipped with a constant temperature bath. The autograph used was an AGS-500A manufactured by Shimadzu Corporation. The temperature of the constant temperature bath in which the test specimen was placed during the test was 200°C. In the bending test, one side of the test specimen (the side with dimensions L × W) was supported by two support points. A load was applied to the part of the other side of the test specimen located in the center between the two support points. The deflection (elongation) of the test specimen was continuously measured at each load as the load increased. The load at which the specimen broke, and the deflection of the specimen immediately before breakage, were also measured. The measurement conditions for the bending test were as follows: Distance Lv between the two support points: 64.0 ± 0.5 mm; Head speed: 2.0 ± 0.2 mm / min; Chart speed: 100 mm / min; Chart full scale: 490 N (50 kgf)

[0093] The bending strength σ (unit: MPa) was calculated based on the following formula A. The modulus of elasticity E (unit: GPa) was calculated based on the following formula B. σ = (3 × P × Lv) / (2 × W × t) ２ ) (A) E=[Lv ３ / (4 × W × t ３ )]×(F / Y) (B) In formula A, "P" is the load (unit: N) at which the test specimen broke. In formulas A and B, "Lv" is the distance (unit: mm) between the two support points that support the test specimen. In formulas A and B, "W" is the width (unit: mm) of the test specimen. In formulas A and B, "t" is the thickness (unit: mm) of the test specimen. In formula B, "F / Y" is the slope (unit: N / mm) of the straight portion of the load-deflection curve measured by the above test. The modulus of elasticity and bending strength of Example 1 are shown in Table 2 below.

[0094] (Measurement of crack occurrence rate) A coil with 5.5 turns was sealed in the compound by transfer molding of the compound at 140°C. Post-curing (heating at 180°C for 2 hours) following the transfer molding yielded 50 samples consisting of the cured compound with the coil inside. Each sample was a rectangular parallelepiped. The pressure applied to the compound during transfer molding was 6.9 MPa. The dimensions of each sample were: length: 5.2 mm × width: 5.2 mm × thickness: 2.0 mm.

[0095] The following MSL (Moisture Sensitivity Level) test was performed. In the MSL test, 50 of the above samples were left in a sealed container containing water vapor for 168 hours. The temperature inside the sealed container was 85°C, and the humidity inside the sealed container was 85% RH. After moisture absorption in the sealed container, each sample was reflow soldered. The peak temperature during reflow was 260°C. After reflow, the number of samples with cracks formed, X, was counted. However, no cracks were formed in any of the samples before moisture absorption. The crack occurrence rate Rcrack (unit: %) is defined as (X / 50) × 100. A low Rcrack is desirable. The Rcrack for Example 1 is shown in Table 2 below.

[0096] (Examples 2-5, Comparative Examples 1 and 2) The mass ratios (in parts by mass) of resins 1 and 2, curing agents 1-4, curing accelerators, coupling agents 1 and 2, and release agents 1 and 2 in the resin compositions of Examples 2-5 and Comparative Examples 1 and 2 were adjusted to the values ​​shown in Table 1 below. The total and Mp values ​​for Examples 2-5 and Comparative Examples 1 and 2 are shown in Table 2 below.

[0097] Except for the matters described above, compounds for Examples 2-5 and Comparative Examples 1 and 2 were prepared in the same manner as in Example 1. The elastic modulus, flexural strength, and Rcrack of Examples 2-5 and Comparative Examples 1 and 2 were measured in the same manner as in Example 1. The elastic modulus, flexural strength, and Rcrack of Examples 2-5 and Comparative Examples 1 and 2 are shown in Table 2 below.

[0098]

[0099]

[0100] For example, a compound relating to one aspect of this disclosure may be used as a raw material for coil components such as inductors.

[0101] 1... Coil component (inductor), 2... Hardened compound, 2dc... Magnetic core (e.g., compacted magnetic core), 3... Terminal electrode, 5... Coil, 5a, 5b... Coil lead-out sections.

Claims

1. A compound comprising a metal powder and a resin composition, wherein the metal powder is a soft magnetic material, the resin composition comprises an epoxy resin and a curing agent, the curing agent comprises a first biphenyl aralkyl type phenolic resin and a second biphenyl aralkyl type phenolic resin that differ in hydroxyl group equivalents, the hydroxyl group equivalent of the first biphenyl aralkyl type phenolic resin is smaller than the hydroxyl group equivalent of the second biphenyl aralkyl type phenolic resin, and the mass ratio of the first biphenyl aralkyl type phenolic resin and the second biphenyl aralkyl type phenolic resin to 100 parts by mass of the epoxy resin is 66.8 parts by mass or more and 72.3 parts by mass or less.

2. The compound according to claim 1, wherein the hydroxyl group equivalent of the first biphenylaralkyl type phenol resin is 164 g / mol or more and 168 g / mol or less, and the hydroxyl group equivalent of the second biphenylaralkyl type phenol resin is 197 g / mol or more and 205 g / mol or less.

3. The compound according to claim 1, wherein the epoxy resin comprises a polyaromatic ring epoxy resin.

4. The compound according to claim 1, wherein the resin composition comprises a curing accelerator, and the curing accelerator comprises one or more imidazoles.

5. The compound according to claim 1, which is a raw material for a magnetic core.

6. A molded article comprising the compound according to any one of claims 1 to 5.

7. A cured compound according to any one of claims 1 to 5.

8. A magnetic core comprising the cured product described in claim 7.

9. A coil component comprising a magnetic core as described in claim 8, and a coil, wherein the magnetic core is disposed inside the coil.

10. A coil component comprising the cured product described in claim 7, and a coil, wherein the coil is sealed within the cured product.

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