JP7639712B2 - Compound, molded body, and cured product of compound - Google Patents

Description

The present invention relates to a compound, a molded body, and a cured product of the compound.

Compounds containing metal powder and resin compositions are used as raw materials for a variety of industrial products depending on the physical properties of the metal powder. For example, compounds are used as raw materials for inductors, sealing materials, electromagnetic shields (EMI shields), bonded magnets, etc. (see Patent Document 1 below).

JP 2014-13803 A

When manufacturing industrial products from a compound, a molded body is produced by bonding the compound to a metal component and curing the compound, and then the molded body is heated. In the process of heating the molded body, cracks are likely to form in the molded body due to the difference in thermal expansion coefficient between the cured compound and the metal component, steam explosions inside the package, etc. Therefore, it is necessary to improve the reflow resistance of the molded body.

The present invention has been made in consideration of the above circumstances, and aims to provide a compound capable of forming a molded body having excellent reflow resistance, a molded body using the same, and a cured product of the compound.

A compound according to one aspect of the present invention comprises a metal powder and a resin composition containing an epoxy resin and a phenolic resin, the epoxy resin comprising a first epoxy resin having a biphenylene aralkyl skeleton and a second epoxy resin having an epoxy equivalent smaller than that of the first epoxy resin, the phenolic resin comprising a first phenolic resin having a biphenylene aralkyl skeleton and a second phenolic resin having a hydroxyl equivalent smaller than that of the first phenolic resin, and the metal powder content is 90% by mass or more and less than 100% by mass.

A molded body according to one aspect of the present invention comprises the above-mentioned compound.

A cured product of a compound according to one aspect of the present invention is a cured product of a compound comprising a metal powder and a resin composition containing an epoxy resin and a phenol resin, the metal powder content being 90 mass % or more and less than 100 mass %, the bending strength at 250°C being 4.6 MPa or more, the bending modulus at 250°C being less than 1.0 GPa, and the value obtained by dividing the bending strength by the bending modulus being 9.5 x ^10-3 or more.

The present invention provides a compound capable of forming a molded body having excellent reflow resistance, a molded body using the compound, and a cured product of the compound.

The following describes preferred embodiments of the present invention. However, the present invention is not limited to the following embodiments.

[Compound]
The compound according to the present embodiment includes a metal powder and a resin composition containing an epoxy resin and a phenolic resin. The metal powder may contain at least one selected from the group consisting of a simple metal, an alloy, an amorphous powder, and a metal compound. The resin composition may further contain other components in addition to the epoxy resin and the phenolic resin. The resin composition may further contain a curing accelerator, a release agent, an additive, and the like. The resin composition may be a component that may include an epoxy resin, a phenolic resin, a curing accelerator, a release agent, and an additive, and may be the remaining component (non-volatile component) excluding an organic solvent and a metal powder. The additive is the remaining component of the resin composition excluding a resin, a release agent, a curing agent, and a curing accelerator. The additive is, for example, a coupling agent, a flame retardant, a lubricant, and the like. The compound may be a powder (compound powder).

The compound may comprise a metal powder and a resin composition attached to the surface of each metal particle constituting the metal powder. The resin composition may cover the entire surface of the particle, or may cover only a portion of the surface of the particle. The compound may comprise an uncured resin composition and a metal powder. The compound may comprise a semi-cured product of the resin composition (e.g., a B-stage resin composition) and a metal powder. The compound may comprise both an uncured resin composition and a semi-cured product of the resin composition. The compound may be composed of a metal powder and a resin composition.

The metal powder content in the compound is 90% by mass or more and less than 100% by mass with respect to the mass of the entire compound. If the metal powder content is high, it becomes difficult to ensure the releasability of the molded body, and workability tends to be poor. From the viewpoint of the magnetic properties of the molded body, the metal powder content is preferably 92% by mass or more, more preferably 94% by mass or more, even more preferably 95% by mass or more, and particularly preferably 96% by mass or more. The upper limit of the metal powder content may be 99% by mass or less, 98% by mass or less, or 97.5% by mass or less.

(Resin composition)
The resin composition according to the present embodiment contains a specific epoxy resin as a thermosetting resin, and thereby the flowability, storage stability, and moldability of the compound can be improved. The epoxy resin includes a first epoxy resin having a biphenylene aralkyl skeleton and a second epoxy resin having an epoxy equivalent smaller than that of the first epoxy resin.

By including the first epoxy resin in the resin composition, the elastic modulus of the molded body formed from the compound can be reduced and reflow resistance can be improved. The epoxy equivalent of the first epoxy resin is preferably 240 g/eq or more and 300 g/eq or less, more preferably 250 g/eq or more and 290 g/eq or less, and even more preferably 260 g/eq or more and 280 g/eq or less.

The content of the first epoxy resin in the resin composition may be 20 to 80 mass%, 30 to 70 mass%, or 40 to 60 mass%, based on the total mass of the epoxy resin.

As a commercially available product of the first epoxy resin, for example, biphenylene aralkyl type epoxy resin (NC-3000 manufactured by Nippon Kayaku Co., Ltd.) may be used.

By including the second epoxy resin in the resin composition, the mechanical strength of the molded body is likely to be high. The epoxy equivalent of the second epoxy resin is preferably 130 g/eq or more and less than 240 g/eq, more preferably 140 g/eq or more and 230 g/eq or less, and even more preferably 150 g/eq or more and 220 g/eq or less.

The second epoxy resin may be, for example, a resin having two or more epoxy groups in one molecule, or a polyfunctional epoxy resin having three or more epoxy groups. The second epoxy resin may be, for example, a stilbene type epoxy resin, a diphenylmethane type epoxy resin, a sulfur atom-containing epoxy resin, a novolac type epoxy resin, a dicyclopentadiene type epoxy resin, a salicylaldehyde type epoxy resin, a copolymer type epoxy resin of naphthols and phenols, an epoxidized product of an aralkyl type phenolic resin, a bisphenol type epoxy resin, a biphenyl type epoxy resin, an epoxy resin containing a bisphenol skeleton, a glycidyl ether type epoxy resin of alcohols, a glycidyl ether type epoxy resin of a paraxylylene and/or metaxylylene modified phenolic resin, a glycidyl ether type epoxy resin of a terpene modified phenolic resin, or a glycidyl ether type epoxy resin of a terpene modified phenolic resin. and at least one selected from the group consisting of glycidyl 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 type epoxy resins, halogenated phenol novolac type epoxy resins, ortho-cresol novolac type epoxy resins, hydroquinone type epoxy resins, trimethylolpropane type epoxy resins, and linear aliphatic epoxy resins obtained by oxidizing an olefin bond with a peracid such as peracetic acid.

In terms of excellent fluidity, the second epoxy resin may be at least one selected from the group consisting of orthocresol novolac type epoxy resins, phenol novolac type epoxy resins, bisphenol type epoxy resins, epoxy resins having a bisphenol skeleton, salicylic aldehyde novolac type epoxy resins, and naphthol novolac type epoxy resins.

The second epoxy resin may be a crystalline epoxy resin. Although the molecular weight of the crystalline epoxy resin is relatively low, the crystalline epoxy resin has a relatively high melting point and excellent fluidity. The crystalline epoxy resin (highly crystalline epoxy resin) may be, for example, at least one selected from the group consisting of hydroquinone type epoxy resin, bisphenol type epoxy resin, thioether type epoxy resin, and biphenyl type epoxy resin.

Commercially available crystalline epoxy resins include, for example, Epicron 860, Epicron 1050, Epicron 1055, Epicron 2050, Epicron 3050, Epicron 4050, Epicron 7050, Epicron HM-091, Epicron HM-101, Epicron N-730A, Epicron N-740, Epicron N-770, Epicron N-775, Epicron LON N-865, Epicron HP-4032D, Epicron HP-7200L, Epicron HP-7200, Epicron HP-7200H, Epicron HP-7200HH, Epicron HP-7200HHH, Epicron HP-4700, Epicron HP-4710, Epicron HP-4770, Epicron HP-5000, Epicron HP-6000, N50 0P-2, and N500P-10 (all product names manufactured by DIC Corporation); NC-3000, NC-3000-L, NC-3000-H, NC-3100, CER-3000-L, NC-2000-L, XD-1000, NC-7000-L, NC-7300-L, EPPN-501H, EPPN-501HY, EPPN-502H, EOCN-1020, EO CN-102S, EOCN-103S, EOCN-104S, CER-1020, EPPN-201, BREN-S, BREN-10S (all of which are trade names manufactured by Nippon Kayaku Co., Ltd.); and YX-4000, YX-4000H, YL4121H, and YX-8800 (all of which are trade names manufactured by Mitsubishi Chemical Corporation).

The resin composition according to the present embodiment contains a specific phenolic resin as a curing agent, which improves the fluidity, storage stability, and moldability of the compound. The phenolic resin includes a first phenolic resin having a biphenylene aralkyl skeleton and a second phenolic resin having a smaller hydroxyl equivalent than that of the first phenolic resin.

By including the first phenolic resin in the resin composition, the elastic modulus of the molded body can be reduced and reflow resistance can be improved. The hydroxyl equivalent of the first phenolic resin is preferably 140 g/eq or more and 230 g/eq or less, more preferably 150 g/eq or more and 220 g/eq or less, and even more preferably 160 g/eq or more and 210 g/eq or less.

The content of the first phenolic resin in the resin composition may be 20 to 80 parts by mass, 30 to 70 parts by mass, or 40 to 60 parts by mass per 100 parts by mass of the epoxy resin.

Commercially available biphenylene aralkyl type phenolic resins may be, for example, MEHC-7851SS, MEHC-7841-4S, etc. manufactured by Meiwa Kasei Co., Ltd.

By including the second phenolic resin in the resin composition, the mechanical strength of the molded body tends to be high. The hydroxyl equivalent of the second phenoxy resin is preferably 80 g/eq or more and less than 140 g/eq, more preferably 90 g/eq or more and 130 g/eq or less, and even more preferably 100 g/eq or more and 120 g/eq or less.

The second phenolic resin may be at least one selected from the group consisting of, for example, aralkyl-type phenolic resin, dicyclopentadiene-type phenolic resin, salicylaldehyde-type phenolic resin, novolac-type phenolic resin, copolymerized phenolic resin of benzaldehyde-type phenol and aralkyl-type phenol, paraxylylene- and/or metaxylylene-modified phenolic resin, melamine-modified phenolic resin, terpene-modified phenolic resin, dicyclopentadiene-type naphthol resin, cyclopentadiene-modified phenolic resin, polycyclic aromatic ring-modified phenolic resin, and triphenylmethane-type phenolic resin. Commercially available products of the second phenolic resin may be, for example, HE910-09 manufactured by Air Water Inc., HP-850N manufactured by Hitachi Chemical Co., Ltd., etc.

The ratio of active groups (phenolic OH groups) in the curing agent that react with the epoxy groups in the epoxy resin may be preferably 0.5 to 1.5 equivalents, more preferably 0.6 to 1.4 equivalents, and even more preferably 0.7 to 1.2 equivalents per equivalent of epoxy groups in the epoxy resin. When the ratio of active groups in the curing agent is within the above range, the fluidity of the compound is likely to be improved.

The curing accelerator is not limited to any particular composition, so long as it reacts with the epoxy resin to promote curing of the epoxy resin. The curing accelerator may be, for example, a phosphorus-based curing accelerator, an imidazole-based curing accelerator, or a urea-based curing accelerator. By containing a curing accelerator in the resin composition, the moldability and releasability of the compound can be improved. In addition, by containing a curing accelerator in the resin composition, the mechanical strength of a molded body (e.g., an electronic component) produced using the compound is improved, and the storage stability of the compound in a high-temperature and high-humidity environment is improved.

Examples of phosphorus-based curing accelerators include phosphine compounds and phosphonium salt compounds.

As a commercially available imidazole curing accelerator, for example, at least one selected from the group consisting of 2MZ-H, C11Z, C17Z, 1,2DMZ, 2E4MZ, 2PZ-PW, 2P4MZ, 1B2MZ, 1B2PZ, 2MZ-CN, C11Z-CN, 2E4MZ-CN, 2PZ-CN, C11Z-CNS, 2P4MHZ, TPZ, and SFZ (all of which are product names manufactured by Shikoku Chemical Industry Co., Ltd.) may be used.

The urea-based curing accelerator is not particularly limited as long as it is a curing accelerator having a urea group, but from the viewpoint of improving storage stability, an alkylurea-based curing accelerator having an alkylurea group is preferable. Examples of alkylurea-based curing accelerators having an alkylurea group include aromatic alkylureas and aliphatic alkylureas. Examples of commercially available alkylurea-based curing accelerators include U-CAT3512T (product name, manufactured by San-Apro Co., Ltd., aromatic dimethylurea) and U-CAT3513N (product name, manufactured by San-Apro Co., Ltd., aliphatic dimethylurea). Among these, aromatic alkylureas are preferable because they have a moderately low cleavage temperature and are easy to efficiently cure the compound.

The amount of the curing accelerator 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 property and fluidity of the resin composition when absorbing moisture, the amount of the curing accelerator may be preferably 0.1 parts by mass or more and 30 parts by mass or less, more preferably 1 part by mass or more and 15 parts by mass or less, per 100 parts by mass of the epoxy resin. The content of the curing accelerator is preferably 0.001 parts by mass or more and 5 parts by mass or less, per 100 parts by mass of the total mass of the epoxy resin and the phenolic resin. If the amount of the curing accelerator is less than 0.1 parts by mass, it is difficult to obtain a sufficient curing acceleration effect. If the amount of the curing accelerator is more than 30 parts by mass, the storage stability of the compound is likely to decrease. However, even if the amount and content of the curing accelerator are outside the above range, the effect of the present invention can be obtained.

The coupling agent improves the adhesion between the resin composition and the metal element-containing particles constituting the metal powder, and improves the flexibility and mechanical strength of the molded body formed from the compound. 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. 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, and vinyl silane. The resin composition may contain one type of coupling agent among the above, or may contain multiple types of coupling agents among the above.

The resin composition may contain a compound having a siloxane bond (siloxane compound) because this tends to reduce the molding shrinkage rate of the compound and to improve the heat resistance and voltage resistance of the molded body. A siloxane bond is a bond containing two silicon atoms (Si) and one oxygen atom (O), and may be represented as -Si-O-Si-. The compound having a siloxane bond may be a polysiloxane compound.

For the purpose of the environmental safety, recyclability, moldability, and low cost of the compound, the compound may contain a flame retardant. 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 resin composition may contain one of the above flame retardants, or may contain multiple of the above flame retardants.

When a molded body is formed from the compound using a mold, the resin composition may contain a wax. The wax increases the fluidity of the compound during molding (e.g., transfer molding) of the compound and also functions as a mold release agent. The wax may be at least one of a fatty acid such as a higher fatty acid and a fatty acid ester.

Waxes include, for example, fatty acids such as montanic acid, stearic acid, 12-oxystearic acid, and lauric acid, or esters thereof; fatty acid salts such as zinc stearate, calcium stearate, barium stearate, aluminum stearate, magnesium stearate, calcium laurate, zinc linoleate, calcium ricinoleate, and zinc 2-ethylhexanoate; stearic acid amide, oleic acid amide, erucic acid amide, behenic acid amide, palmitic acid amide, lauric acid amide, hydroxystearic acid amide, methylene bisstearic acid amide, ethylene bisstearic acid amide, ethylene bislauric acid amide, distearyl adipate amide, ethylene bisoleic acid amide, dioleyl adipate amide, N-stearyl stearic acid amide, fatty acid esters such as butyl stearate; alcohols such as ethylene glycol and stearyl alcohol; polyethers such as polyethylene glycol, polypropylene glycol, polytetramethylene glycol and modified products thereof; polysiloxanes such as silicone oil and silicone grease; fluorine compounds such as fluorine-based oil, fluorine-based grease and fluorine-containing resin powder; and waxes such as paraffin wax, polyethylene wax, amide wax, polypropylene wax, ester wax, carnauba wax, and microwax.

(Metal powder)
The metal powder (metal element-containing particle) may contain at least one selected from the group consisting of, for example, a metal element, an alloy, and a metal compound. The metal element-containing powder may be, for example, at least one selected from the group consisting of a metal element, an alloy, and a metal compound. The alloy may contain at least one selected from the group consisting of a solid solution, a eutectic, and an intermetallic compound. The alloy may be, for example, stainless steel (Fe-Cr alloy, Fe-Ni-Cr alloy, etc.). The metal compound may be, for example, an oxide such as ferrite. The metal powder may contain one type of metal element or multiple types of metal elements. The metal element contained in the metal powder may be, for example, a base metal element, a precious metal element, a transition metal element, or a rare earth element. The compound may contain one type of metal element-containing powder, or may contain multiple types of metal element-containing powders with different compositions.

The metal powder is not limited to the above composition. The metal element contained in the metal powder may be at least one selected from the group consisting of, for example, iron (Fe), copper (Cu), titanium (Ti), manganese (Mn), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), tin (Sn), chromium (Cr), niobium (Nb), barium (Ba), strontium (Sr), lead (Pb), silver (Ag), praseodymium (Pr), neodymium (Nd), samarium (Sm), and dysprosium (Dy). The metal powder may further contain elements other than the metal element. The metal powder may contain, for example, carbon (C), oxygen (O), beryllium (Be), phosphorus (P), sulfur (S), boron (B), or silicon (Si).

The metal powder may be a magnetic powder. The metal powder may be a soft magnetic alloy or a ferromagnetic alloy. The metal powder may be, for example, a magnetic powder consisting of at least one selected from the group consisting of Fe-Si alloys, Fe-Si-Al alloys (Sendust), Fe-Ni alloys (Permalloy), Fe-Cu-Ni alloys (Permalloy), Fe-Co alloys (Permendur), Fe-Cr-Si alloys (electromagnetic stainless steel), Nd-Fe-B alloys (rare earth magnets), Sm-Fe-N alloys (rare earth magnets), Al-Ni-Co alloys (Alnico magnets), and ferrites. The ferrite may be, for example, spinel ferrite, hexagonal ferrite, or garnet ferrite. The metal powder may be a copper alloy such as a Cu-Sn alloy, a Cu-Sn-P alloy, a Cu-Ni alloy, or a Cu-Be alloy. The metal powder may include one of the above elements and compositions, or may include more than one of the above elements and compositions.

The metal powder may be Fe alone. The metal powder may be an alloy containing iron (Fe-based alloy). The Fe-based alloy may be, for example, an Fe-Si-Cr-based alloy or an Nd-Fe-B-based alloy. The metal element-containing powder may be at least one of an amorphous iron powder and a carbonyl iron powder. When the metal powder contains at least one of Fe alone and an Fe-based alloy, it is easy to produce a compact having a high space factor and excellent magnetic properties from the compound. The metal powder may be an Fe amorphous alloy.

As a commercially available Fe amorphous alloy powder, for example, at least one selected from the group consisting of AW2-08, KUAMET-6B2 (all product names manufactured by Epson Atmix Corporation), DAP MS3, DAP MS7, DAP MSA10, DAP PB, DAP PC, DAP MKV49, DAP 410L, DAP 430L, DAP HYB series (all product names manufactured by Daido Steel Co., Ltd.), MH45D, MH28D, MH25D, and MH20D (all product names manufactured by Kobe Steel, Ltd.) may be used.

<Compound manufacturing method>
In the manufacture of the compound, the metal powder and the resin composition (each component constituting the resin composition) are mixed while being heated. For example, the metal powder and the resin composition may be kneaded with a kneader, roll, stirrer, etc. while being heated. By heating and mixing the metal powder and the resin composition, the resin composition adheres to a part or the whole of the surface of the metal element-containing particles constituting the metal powder to cover the metal element-containing particles, and a part or the whole of the epoxy resin in the resin composition becomes a semi-cured product. As a result, a compound is obtained. The compound may be obtained by further adding wax to the powder obtained by heating and mixing the metal powder and the resin composition. The resin composition and the wax may be mixed in advance.

In the kneading, the metal powder, the epoxy resin, the phenolic resin, the hardening accelerator, the siloxane compound, and the coupling agent may be kneaded in a tank. After the metal powder, the siloxane compound, and the coupling agent are put into the tank and mixed, the epoxy resin, the phenolic resin, and the hardening accelerator may be put into the tank and the raw materials in the tank may be kneaded. After the siloxane compound, the epoxy resin, the phenolic resin, and the coupling agent are kneaded in the tank, the hardening accelerator may be put into the tank and the raw materials in the tank may be further kneaded. A mixed powder (resin mixed powder) of the epoxy resin, the phenolic resin, and the hardening accelerator may be prepared in advance, and then the metal powder, the siloxane compound, and the coupling agent may be kneaded to prepare a metal mixed powder, and then the metal mixed powder and the above-mentioned resin mixed powder may be kneaded.

The kneading time depends on the type of kneading machine, the volume of the kneading machine, and the amount of compound produced, but is preferably 1 minute or more, more preferably 2 minutes or more, and even more preferably 3 minutes or more. The kneading time is preferably 20 minutes or less, more preferably 15 minutes or less, and even more preferably 10 minutes or less. If the kneading time is less than 1 minute, the kneading is insufficient, the moldability of the compound is impaired, and the degree of hardening of the compound varies. If the kneading time exceeds 20 minutes, for example, the hardening of the resin composition (e.g., epoxy resin and phenolic resin) progresses in the tank, and the fluidity and moldability of the compound are easily impaired. When the raw materials in the tank are kneaded with a kneader while being heated, the heating temperature may be, for example, a temperature at which a semi-cured product of the epoxy resin (epoxy resin in B stage) is generated and the generation of a hardened product of the epoxy resin (epoxy resin in C stage) is suppressed. The heating temperature may be a temperature lower than the activation temperature of the hardening accelerator. The heating temperature is, for example, preferably 50° C. or higher, more preferably 60° C. or higher, and even more preferably 70° C. or higher. The heating temperature is preferably 150° C. or lower, more preferably 120° C. or lower, and even more preferably 110° C. or lower. When the heating temperature is within the above range, the resin composition in the tank softens and is likely to coat the surfaces of the metal element-containing particles that constitute the metal powder, a semi-cured epoxy resin is likely to be produced, and complete curing of the epoxy resin during kneading is likely to be suppressed.

[Molded body]
The molded body according to the present embodiment may include the above-mentioned compound. The molded body according to the present embodiment may include a cured product of the above-mentioned compound. The molded body may include at least one selected from the group consisting of an uncured resin composition, a semi-cured product of the resin composition (B-stage resin composition), and a cured product of the resin composition (C-stage resin composition). The molded body according to the present embodiment may be used as a sealant for electronic components or electronic circuit boards. According to the present embodiment, cracks in the molded body caused by the difference in thermal expansion coefficient between the metal member of the electronic component or electronic circuit board and the molded body (sealant) can be suppressed.

The cured product of the compound is a cured product of a resin composition containing a metal powder, an epoxy resin and a phenolic resin, and the content of the metal powder is 90% by mass or more and less than 100% by mass. The bending strength of the cured product at 250 ° C is 4.6 MPa or more, preferably 4.8 MPa or more, and more preferably 5.0 MPa or more, from the viewpoint of increasing the strength of the cured product. The upper limit of the bending strength is about 10 MPa. The bending modulus of the cured product at 250 ° C is less than 1.0 GPa, preferably 0.1 GPa or more and less than 1.0 GPa, more preferably 0.2 GPa or more and 0.8 GPa or less, even more preferably 0.3 GPa or more and 0.7 GPa or less, and particularly preferably 0.4 GPa or more and 0.68 GPa or less, from the viewpoint of imparting flexibility to the cured product. The value obtained by dividing the bending strength (MPa) at 250 ° C by the bending modulus (GPa) at 250 ° C can be used as an index of the reliability of the cured product. The index is preferably 9.5×10 ⁻³ or more, more preferably 10×10 ⁻³ or more, and even more preferably 10.5×10 ⁻³ or more. The upper limit of the index is not particularly limited, and may be, for example, 5×10 ⁻² or less.

<Method of manufacturing molded body>
The method for producing a molded body according to the present embodiment may include a step of pressurizing the compound in a mold. The method for producing a molded body may include a step of pressurizing the compound covering a part or the entire surface of the metal member in a mold. The method for producing a molded body may include only the step of pressurizing the compound in a mold, or may include other steps in addition to the step. The method for producing a molded body may include a first step, a second step, and a third step. Each step will be described in detail below.

In the first step, the compound is prepared using the method described above.

In the second step, the compound is pressed in a mold to obtain a molded body (B-stage molded body). In the second step, the compound covering a part or the entire surface of the metal component may be pressed in a mold to obtain a molded body (B-stage molded body). In the second step, a resin composition is filled between the individual metal element-containing particles that make up the metal element-containing powder. The resin composition then functions as a binding material (binder) to bind the metal element-containing particles together.

As the second step, transfer molding of the compound may be performed. In transfer molding, the compound may be pressurized at 5 MPa or more and 50 MPa or less. The higher the molding pressure, the easier it is to obtain a molded body with excellent mechanical strength. Considering the mass productivity of the molded body and the life of the mold, the molding pressure is preferably 8 MPa or more and 20 MPa or less. The density of the molded body formed by transfer molding may be preferably 75% or more and 86% or less, more preferably 80% or more and 86% or less, relative to the true density of the compound. When the density of the molded body is 75% or more and 86% or less, a molded body with excellent mechanical strength is easily obtained. In transfer molding, the second step and the third step may be performed together.

In the third step, the molded body is cured by heat treatment to obtain a molded body in the C stage. The temperature of the heat treatment may be any temperature at which the resin composition in the molded body is sufficiently cured. The temperature of the heat treatment may be preferably 100°C or more and 300°C or less, more preferably 110°C or more and 250°C or less. In order to suppress oxidation of the metal powder in the molded body, it is preferable to perform the heat treatment in an inert atmosphere. If the heat treatment temperature exceeds 300°C, the metal powder may be oxidized or the resin cured product may deteriorate due to the trace amount of oxygen inevitably contained in the heat treatment atmosphere. In order to sufficiently cure the resin composition while suppressing oxidation of the metal powder and deterioration of the resin cured product, the holding time of the heat treatment temperature may be preferably several minutes or more and 10 hours or less, more preferably 3 minutes or more and 8 hours or less.

The present invention will be explained in more detail below with reference to examples and comparative examples, but the present invention is not limited to these examples in any way.

Details of each component used in preparing the compounds of the examples and comparative examples are given below.
(First Epoxy Resin)
Biphenylene aralkyl type epoxy resin (trade name: NC-3000, manufactured by Nippon Kayaku Co., Ltd., epoxy equivalent: 275 g/eq)
(Second Epoxy Resin)
Multifunctional epoxy resin (product name: TECHMORE VG3101L, manufactured by Printec Co., Ltd., epoxy equivalent: 215 g/eq)
Triphenylmethane type multifunctional epoxy resin (EPPN-501HY manufactured by Nippon Kayaku Co., Ltd., epoxy equivalent: 169 g/eq)
Orthocresol novolac epoxy resin (manufactured by DIC Corporation under the trade name EPICLON N-500P-2, epoxy equivalent: 202 g/eq)

(First phenolic resin)
Biphenylene aralkyl type phenolic resin (product name: MEHC-7851SS, manufactured by Meiwa Kasei Co., Ltd., hydroxyl group equivalent: 202 g/eq)
Biphenylene aralkyl phenol resin (product name: MEHC-7841-4S, manufactured by Meiwa Kasei Co., Ltd., hydroxyl group equivalent: 166 g/eq)
(Second phenolic resin)
Triphenylmethane type phenolic resin (product name: HE910-09, manufactured by Air Water Inc., hydroxyl group equivalent: 101 g/eq)
Novolac phenolic resin (product name: HP-850N, manufactured by Hitachi Chemical Co., Ltd., hydroxyl group equivalent: 103 g/eq)

(Cure Accelerator)
Urea-based curing accelerator (product name: U-CAT 3512T, manufactured by San-Apro Co., Ltd.)
(Coupling Agent)
Methacryloxyoctyltrimethoxysilane (product name: KBM-5803, manufactured by Shin-Etsu Chemical Co., Ltd.)
3-Mercaptopropyltrimethoxysilane (trade name: KBM-803, manufactured by Shin-Etsu Chemical Co., Ltd.)
(Siloxane Compound)
Caprolactone-modified dimethyl silicone (product name: DBL-C32, manufactured by Gelest Corporation)
(Release Agent)
Zinc laurate (product name: Powder Base L, manufactured by NOF Corporation)
Partially saponified Montan acid ester wax (product name: LICOWAX OP, manufactured by Clariant Chemicals Co., Ltd.)

(Metal powder)
Amorphous iron powder (product name: 9A4-II, average particle size 24 μm, manufactured by Epson Atmix Corporation)
Amorphous iron powder (product name: AW2-08, average particle size 5.3 μm, manufactured by Epson Atmix Corporation)

[Preparation of Compound]
(Examples 1 to 3)
The epoxy resin, phenolic resin, curing accelerator, and release agent shown in Table 1 were charged into a plastic container in the amounts (unit: g) shown in the same table. These materials were mixed in the plastic container for 10 minutes to prepare a resin mixture. The resin mixture corresponds to all components of the resin composition except for the siloxane compound and the coupling agent.

The two types of amorphous iron powder shown in Table 1 were mixed uniformly for 5 minutes in a pressurized twin-axis kneader (manufactured by Nippon Spindle Manufacturing Co., Ltd., capacity 5 L) to prepare a metal powder. The coupling agent and siloxane compound shown in Table 1 were added to the metal powder in the twin-axis kneader. Next, the contents of the twin-axis kneader were heated to 90°C, and the contents of the twin-axis kneader were mixed for 10 minutes while maintaining that temperature. Next, the above resin mixture was added to the contents of the twin-axis kneader, and the contents were melted and kneaded for 15 minutes while maintaining the temperature of the contents at 120°C. The kneaded product obtained by the above melting and kneading was cooled to room temperature, and then crushed with a hammer until the kneaded product had a predetermined particle size. Note that the above "melting" means melting at least a part of the resin composition in the contents of the twin-axis kneader. The metal powder in the compound does not melt during the preparation process of the compound. The compounds of Examples 1 to 3 were prepared by the above method.

(Comparative Examples 1 to 5)
Compounds of Comparative Examples 1 to 5 were prepared in the same manner as in the Examples, except that the types and amounts of each component were changed as shown in Table 2.

[Compound evaluation]
The compounds obtained in the Examples and Comparative Examples were evaluated as follows. The results are shown in Tables 1 and 2.

(Liquidity)
The evaluation of fluidity was performed using a flow tester CFT-100 manufactured by Shimadzu Corporation. 7 g of the compound was molded to prepare a tablet. Using the tablet, the evaluation of fluidity was performed under the conditions of 130°C, preheating for 20 seconds, and a load of 100 kg. The plunger pushing distance (unit: mm) until the flow of the compound stopped was defined as the flow tester stroke, and the time until the flow of the compound stopped was measured as the flow time, which was used as an index of fluidity.

(Gel time)
The gel time of the compound was measured by the following method. Using a Curastometer (manufactured by JSR Trading Co., Ltd.), the gel time was measured under the conditions of a sample amount of 1.5 mL and 140° C. The time at which the torque on the obtained chart started to rise was taken as the gel time. The shorter the gel time, the higher the curability.

(Bending test)
The compound was transfer molded under the conditions of a mold temperature of 140° C., a molding pressure of 13.5 MPa, and a curing time of 360 seconds, and then post-cured at 180° C. for 2 hours to obtain a test specimen. The dimensions of the test specimen were 80 mm long x 10 mm wide x 3.0 mm thick.

A three-point support bending test was carried out on the test specimen at room temperature and 250°C using an autograph equipped with a thermostatic bath. The autograph used was an AGS-500A manufactured by Shimadzu Corporation. In the bending test, one side of the test specimen was supported by two supports. A load was applied to the center position between the two supports on the other side of the test specimen. The load at which the test specimen broke was measured. The measurement conditions for the bending test were as follows:
Distance between two fulcrums Lv: 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)

The bending strength σ (unit: MPa) was calculated based on the following formula (A). The bending modulus E (unit: GPa) was calculated based on the following formula (B). In the following formulas, "P" is the load (unit: N) when the test piece breaks. "Lv" is the distance between two supports (unit: mm). "W" is the width of the test piece (unit: mm). "t" is the thickness of the test piece (unit: mm). "F/Y" is the gradient of the straight line portion of the load-deflection curve (unit: N/mm).
σ=(3×P×Lv)/(2×W× ^t2 ) (A)
E=[ ^Lv3 /(4×W× ^t3 )]×(F/Y) (B)

(Reliability)
The value obtained by dividing the bending strength (MGa) at 250° C. by the bending modulus (GPa) at 250° C. was used as an index for evaluating reliability. A larger value indicates a better balance between strength and modulus.

(Reflow processing)
A copper metal member was sealed with a compound by transfer molding, and the compound was hardened to obtain a molded body. The molded body was subjected to a reflow treatment. The maximum heating temperature in the reflow treatment was 260°C. The heating time was 300 seconds. After the reflow treatment, the molded body was observed to check whether or not there was a crack in the molded body. "A" in the table means that no crack was formed in the molded body, and "B" means that a crack was formed in the molded body.

Claims (6)

The present invention comprises a metal powder and a resin composition containing an epoxy resin and a phenolic resin,
the epoxy resin comprises a first epoxy resin having a biphenylene aralkyl skeleton and a second epoxy resin having an epoxy equivalent smaller than that of the first epoxy resin,
the phenolic resin includes a first phenolic resin having a biphenylene aralkyl skeleton and a second phenolic resin having a hydroxyl group equivalent smaller than that of the first phenolic resin,
The compound , wherein the metal powder contains at least one of simple Fe and an Fe-based alloy, and the content of the metal powder is 90 mass % or more and less than 100 mass %. The compound according to claim 1, wherein the epoxy equivalent of the first epoxy resin is 240 g/eq or more and 300 g/eq or less. The compound according to claim 1 or 2, wherein the hydroxyl equivalent of the first phenolic resin is 140 g/eq or more and 230 g/eq or less. The compound according to any one of claims 1 to 3, wherein the content of the first epoxy resin is 20 to 80 mass% based on the total mass of the epoxy resin. A molded body comprising the compound according to any one of claims 1 to 4. A cured product of a compound comprising a metal powder and a resin composition containing an epoxy resin and a phenolic resin,
The metal powder contains at least one of Fe elemental element and Fe-based alloy, and the content of the metal powder is 90 mass% or more and less than 100 mass%,
A cured product of the compound has a flexural strength at 250° C. of 4.6 MPa or more, a flexural modulus at 250° C. of less than 1.0 GPa, and a value obtained by dividing the flexural strength by the flexural modulus is 9.5×10 ⁻³ or more.