Manufacturing method of molded body

Abstract

To provide a manufacturing method of a molded body that can improve the voltage resistance of the molded body and suppress the occurrence of leakage current.SOLUTION: A manufacturing method of a molded body includes a step of molding a compound containing a resin and a magnetic powder by compression molding or transfer molding using a release film to obtain a molded body.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a molded body and a method for manufacturing a semiconductor device. [Background technology]

[0002] 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, encapsulants, electromagnetic wave shields (EMI shields), bonded magnets, etc. (See Patent Document 1 below). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-13803 Summary of the Invention [Problem to be solved by the invention]

[0004] When an industrial product is manufactured from a compound, the compound is adhered to a metal member and then cured to produce a molded body. If the manufactured industrial product is an inductor or other industrial product, the molded body may be required to have voltage resistance. Furthermore, if the molded body becomes a resistor before dielectric breakdown occurs and leakage current occurs in an industrial product such as an inductor, the circuit efficiency of the inductor product may decrease, potentially resulting in deterioration of product characteristics. Furthermore, Joule heat generated by the leakage current may pose a risk of causing the coil to ignite. Therefore, the molded body may be required to be able to suppress leakage current generation.

[0005] In view of the above circumstances, the present invention aims to provide a method for manufacturing a molded body and a method for manufacturing a semiconductor device that can improve the voltage resistance of the molded body and suppress the occurrence of leakage current. [Means for solving the problem]

[0006] A method for producing a molded article according to one aspect of the present invention includes a step of compressively molding a compound containing a resin and a magnetic powder using a release film to obtain a molded article.

[0007] A method for producing a molded article according to another aspect of the present invention includes a step of transferring a compound containing a resin and a magnetic powder using a release film to obtain a molded article.

[0008] A method for manufacturing a semiconductor device according to one aspect of the present invention is a method for manufacturing a semiconductor device comprising an inductor element and a molded body that encapsulates the inductor element, and includes a step of forming the molded body by a method for manufacturing the molded body. [Effects of the Invention]

[0009] According to the present invention, there are provided a method for manufacturing a molded body and a method for manufacturing a semiconductor device that can improve the voltage resistance of the molded body and suppress the occurrence of leakage current. [Brief explanation of the drawings]

[0010] [Figure 1] 1A to 1C are cross-sectional views schematically illustrating a method for manufacturing a molded body according to the present embodiment. [Figure 2] 1A to 1C are cross-sectional views schematically illustrating a method for manufacturing a molded body according to the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] Preferred embodiments of the present invention will be described below, but the present invention is not limited to the following embodiments.

[0012] In this specification, a numerical range indicated using "to" indicates a range that includes the numerical values ​​before and after "to" as the minimum and maximum values, respectively. In numerical ranges described in stages in this specification, the upper or lower limit of a numerical range in a certain stage may be replaced with the upper or lower limit of a numerical range in another stage. Furthermore, in numerical ranges described in this specification, the upper or lower limit of that numerical range may be replaced with a value shown in the examples. When referring to the amount of each component in a composition in this specification, if the composition contains multiple substances corresponding to each component, the total amount of those multiple substances present in the composition is meant, unless otherwise specified.

[0013] [Method of manufacturing molded body] The method for producing a molded article according to this embodiment includes a step of molding a compound containing a resin and a magnetic powder by compression molding or transfer molding using a release film to obtain a molded article.

[0014] The compound used in the above manufacturing method includes a resin and a magnetic powder. The compound may include a resin composition containing a resin and a magnetic powder. The resin composition may contain at least one resin selected from the group consisting of epoxy resins and phenolic resins. The resin composition may contain an epoxy resin and a curing agent. In the compound, the magnetic powder and the resin composition are mixed. The resin composition may further contain other components such as a coupling agent, a curing accelerator, a release agent, and additives. The resin composition may include a resin, a curing agent, a coupling agent, a curing accelerator, a release agent, and additives, and may be the remaining components (non-volatile components) excluding the organic solvent and the magnetic powder. The additives are the remaining components of the resin composition excluding the resin, the release agent, the curing agent, the curing accelerator, and the coupling agent. Examples of additives include flame retardants, lubricants, etc. The compound may be a powder (compound powder).

[0015] The compound may comprise a magnetic powder and a resin composition adhered to the surface of each magnetic particle constituting the magnetic powder. The resin composition may cover the entire surface of the magnetic particle, or may cover only a portion of the surface of the magnetic particle. The compound may comprise an uncured resin composition and a magnetic powder. The compound may comprise a semi-cured resin composition (e.g., a B-stage resin composition) and a magnetic powder. The compound may comprise both an uncured resin composition and a semi-cured resin composition. The compound may consist of a magnetic powder and a resin composition.

[0016] (magnetic powder) The content of the magnetic powder in the compound may be 60% by mass or more and less than 100% by mass, based on the total mass of the compound. If the content of the magnetic powder is too 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 content of the magnetic powder in the compound may be 70% by mass or more, 80% by mass or more, 90% by mass or more, 92% by mass or more, 94% by mass or more, or 95% by mass or more. From the viewpoint of the fluidity of the compound, the upper limit of the content of the magnetic powder may be 99% by mass or less, 98% by mass or less, or 97.5% by mass or less. In this specification, the total mass of the compound means the total mass of components (non-volatile components) excluding volatile components such as organic solvents.

[0017] The magnetic powder is a magnetic particle having magnetism. The magnetic powder may contain, for example, at least one selected from the group consisting of a metal element, an alloy, and a metal compound. The magnetic 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 magnetic powder may contain one metal element or multiple metal elements. The metal element contained in the magnetic powder may be, for example, a base metal element, a noble metal element, a transition metal element, or a rare earth element. The compound may contain one magnetic powder, or multiple magnetic powders with different compositions.

[0018] The metal element contained in the magnetic powder may be at least one selected from the group consisting of 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 magnetic powder may further contain elements other than metal elements. The magnetic powder may also contain, for example, carbon (C), oxygen (O), beryllium (Be), phosphorus (P), sulfur (S), boron (B), or silicon (Si).

[0019] The magnetic powder may be a soft magnetic alloy or a ferromagnetic alloy. The magnetic powder may be, for example, a magnetic powder made of at least one material selected from the group consisting of an Fe-Si alloy, an Fe-Si-Al alloy (Sendust), an Fe-Ni alloy (Permalloy), an Fe-Cu-Ni alloy (Permalloy), an Fe-Co alloy (Permendur), an Fe-Cr-Si alloy (electromagnetic stainless steel), an Nd-Fe-B alloy (rare earth magnet), an Sm-Fe-N alloy (rare earth magnet), an Al-Ni-Co alloy (Alnico magnet), and a ferrite. The ferrite may be, for example, a spinel ferrite, a hexagonal ferrite, or a garnet ferrite. The magnetic powder may also be a copper alloy such as a Cu-Sn alloy, a Cu-Sn-P alloy, a Cu-Ni alloy, or a Cu-Be alloy.

[0020] The magnetic powder may be Fe alone. The magnetic powder may be an alloy containing iron (Fe-based alloy). The magnetic powder may contain at least one Fe-based alloy selected from the group consisting of Fe-based amorphous alloys and Fe-based crystalline alloys. The Fe-based alloy may be, for example, an Fe-Si-Cr-based alloy or an Nd-Fe-B-based alloy. The magnetic powder may be at least one of amorphous iron powder and carbonyl iron powder. When the magnetic powder contains at least one of Fe alone and an Fe-based alloy, it is easy to produce a compact with a high space factor and excellent magnetic properties from the compound. The magnetic powder may be an Fe-based amorphous alloy.

[0021] As a commercially available product of the Fe-based amorphous alloy powder, for example, at least one selected from the group consisting of AW2-08, KUAMET 6B2, KUAMET 9A4-II (all of which are trade names of Epson Atmix Corporation), DAP MS3, DAP MS7, DAP MSA10, DAP PB, DAP PC, DAP MKV49, DAP 410L, DAP 430L, DAP HYB series (all of which are trade names of Daido Steel Co., Ltd.), MH45D, MH28D, MH25D, and MH20D (all of which are trade names of Kobe Steel, Ltd.) may be used.

[0022] When a magnetic powder containing iron (iron-containing magnetic powder) is used as the magnetic powder, the iron content in the iron-containing magnetic powder may be 80% by mass or more, or may be 83 to 99% by mass, 84 to 97% by mass, 85 to 95% by mass, or 87 to 93% by mass. By using an iron-containing magnetic powder with an iron content within the above range, the compound can be more suitably used as a raw material for inductors, sealing materials, electromagnetic wave shields (EMI shields), bonded magnets, etc.

[0023] The shape of the individual metal particles constituting the magnetic powder is not particularly limited, but may be, for example, spherical, flat, prismatic, or acicular. The average particle size of the magnetic powder is not particularly limited, but may be, for example, 0.1 μm or more, 0.5 μm or more, or 1.0 μm or more, and 100 μm or less, 80 μm or less, or 50 μm or less. The average particle size can be measured, for example, using a particle size distribution analyzer. The compound may contain multiple types of magnetic powders with different average particle sizes. From the viewpoint of improving fluidity and magnetic properties, the magnetic powder preferably includes a first magnetic powder with an average particle size of 10 to 50 μm and a second magnetic powder with an average particle size of 0.1 to 10 μm. The average particle size of the first magnetic powder may be 11 to 45 μm, 15 to 40 μm, 18 to 35 μm, or 20 to 30 μm. The average particle size of the second magnetic powder may be 0.1 to 9 μm, 0.5 to 6 μm, 0.8 to 5 μm, or 1.0 to 4 μm.

[0024] (Resin composition) The resin composition functions as a binder for the magnetic particles that make up the magnetic powder, imparting mechanical strength to a molded body formed from the compound. For example, when the compound is molded under high pressure using a mold, the resin composition contained in the compound fills between the magnetic particles and binds the particles together. By curing the resin composition in the molded body, the cured resin composition more firmly binds the magnetic particles together, improving the mechanical strength of the molded body.

[0025] The resin composition according to this embodiment may contain an epoxy resin as a thermosetting resin. When the resin composition contains an epoxy resin, the fluidity of the compound can be improved. The epoxy resin may be, for example, a resin having two or more epoxy groups in one molecule. The type of epoxy resin is not particularly limited and can be selected depending on the desired properties of the resin composition.

[0026] Examples of epoxy resins include biphenyl-type epoxy resins, stilbene-type epoxy resins, diphenylmethane-type epoxy resins, sulfur-containing epoxy resins, novolac-type epoxy resins, dicyclopentadiene-type epoxy resins, salicylaldehyde-type epoxy resins, naphthol- and phenol-copolymerized epoxy resins, epoxidized aralkyl-type phenolic resins, bisphenol-type epoxy resins, epoxy resins containing a bisphenol skeleton, glycidyl ether-type epoxy resins of alcohols, glycidyl ether-type epoxy resins of paraxylylene and / or metaxylylene-modified phenolic resins, and terpene-modified phenolic resins. Examples of epoxy resins include glycidyl ether type epoxy resins of phenol 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 type 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 a peracid such as peracetic acid.

[0027] In terms of fluidity, the epoxy resin may include at least one selected from the group consisting of biphenyl-type epoxy resins, orthocresol novolac-type epoxy resins, phenol novolac-type epoxy resins, bisphenol-type epoxy resins, epoxy resins having a bisphenol skeleton, salicylaldehyde novolac-type epoxy resins, and naphthol novolac-type epoxy resins.

[0028] In terms of mechanical strength, the epoxy resin may contain at least one selected from the group consisting of biphenylene aralkyl epoxy resins and orthocresol novolac epoxy resins.

[0029] The epoxy resin may be a crystalline epoxy resin. Although the molecular weight of a 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 contain, for example, at least one selected from the group consisting of hydroquinone-type epoxy resins, bisphenol-type epoxy resins, thioether-type epoxy resins, and biphenyl-type epoxy resins.

[0030] 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 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, and Epicron HP-6000, N500P-2, and N500P-10 (all product names manufactured by DIC Corporation); NC-3000, NC-3000-L, NC-3000-H, NC-310 0, CER-3000-L, NC-2000-L, XD-1000, NC-7000-L, NC-7300-L, EPPN-501H, EPPN-501HY, EPPN-50 2H, EOCN-1020, EOCN-102S, EOCN-103S, EOCN-104S, CER-1020, EPPN-201, BREN-S, and BREN-10S (all of which are trade names manufactured by Nippon Kayaku Co., Ltd.); YX-4000, YX-4000H, YL4121H, and YX-8800 (all of which are trade names manufactured by Mitsubishi Chemical Corporation).

[0031] The resin composition may contain one type of epoxy resin from the above. The resin composition may contain two or more types of epoxy resins from the above. Among the above epoxy resins, the resin composition may contain an epoxy resin containing a biphenyl skeleton, an orthocresol novolac epoxy resin, or a multifunctional epoxy resin containing two or more epoxy groups.

[0032] Curing agents are classified into those that cure epoxy resins at temperatures ranging from low to room temperature, and heat-curing curing agents that cure epoxy resins upon heating. Examples of curing agents that cure epoxy resins at temperatures ranging from low to room temperature include aliphatic polyamines, polyaminoamides, and polymercaptans. Examples of heat-curing curing agents include aromatic polyamines, acid anhydrides, phenol novolac resins, and dicyandiamide (DICY). The type of curing agent is not particularly limited and can be selected depending on the desired properties of the composition.

[0033] When a curing agent that cures an epoxy resin in the range from low temperature to room temperature is used, the glass transition point of the cured epoxy resin tends to be low and the cured epoxy resin tends to be soft. As a result, a molded article formed from the compound also tends to be soft. On the other hand, from the viewpoint of improving the heat resistance of the molded article, the curing agent may preferably be a heat-curing type curing agent, more preferably a phenolic resin, and even more preferably a phenolic novolac resin. In particular, by using a phenolic novolac resin as the curing agent, it is easy to obtain a cured epoxy resin with a high glass transition point. As a result, it is easy to improve the heat resistance and mechanical strength of the molded article.

[0034] The phenolic resin may include at least one selected from the group consisting of aralkyl phenolic resins, dicyclopentadiene phenolic resins, salicylaldehyde phenolic resins, novolac phenolic resins, copolymerized phenolic resins of benzaldehyde phenols and aralkyl phenols, paraxylylene and / or metaxylylene-modified phenolic resins, melamine-modified phenolic resins, terpene-modified phenolic resins, dicyclopentadiene naphthol resins, cyclopentadiene-modified phenolic resins, polycyclic aromatic ring-modified phenolic resins, biphenyl phenolic resins, and triphenylmethane phenolic resins. The phenolic resin may also be a copolymer composed of two or more of the above. Examples of commercially available phenolic resins include Tamanol 758 manufactured by Arakawa Chemical Industries, Ltd. and HP-850N manufactured by Showa Denko Materials Co., Ltd.

[0035] The phenol novolac resin may be, for example, 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 include, for example, 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 include, for example, at least one selected from the group consisting of α-naphthol, β-naphthol, and dihydroxynaphthalene. The aldehydes constituting the phenol novolac resin may include, for example, at least one selected from the group consisting of formaldehyde, acetaldehyde, propionaldehyde, benzaldehyde, and salicylaldehyde.

[0036] The curing agent may be, for example, a compound having two phenolic hydroxyl groups in one molecule. The compound having two phenolic hydroxyl groups in one molecule may include, for example, at least one selected from the group consisting of resorcinol, catechol, bisphenol A, bisphenol F, and substituted or unsubstituted biphenols.

[0037] The resin composition may contain one type of phenolic resin from among the above. The resin composition may comprise multiple types of phenolic resins from among the above. The resin composition may contain one type of curing agent from among the above. The resin composition may contain multiple types of curing agents from among the above.

[0038] The ratio of active groups (phenolic OH groups) in the curing agent that react with 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. If the ratio of active groups in the curing agent is less than 0.5 equivalents, it is difficult to obtain a sufficient elastic modulus of the resulting cured product. On the other hand, if the ratio of active groups in the curing agent exceeds 1.5 equivalents, the mechanical strength of a molded article formed from the compound after curing tends to decrease. However, the effects of the present invention can be obtained even if the ratio of active groups in the curing agent is outside the above range.

[0039] The resin composition may further contain a curing accelerator (catalyst) to improve the moldability and demoldability of the compound. When the resin composition contains a curing accelerator, the mechanical strength of a molded product (e.g., electronic component) produced using the compound is improved, and the storage stability of the compound under high-temperature and high-humidity environments is improved. The curing accelerator is not limited, as long as it is a composition that reacts with an epoxy resin to promote the 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.

[0040] Examples of the phosphorus-based curing accelerator include phosphine compounds and phosphonium salt compounds.

[0041] Commercially available imidazole curing accelerators include, for example, 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 trade names manufactured by Shikoku Chemicals Corporation).

[0042] 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 preferred. 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 (trade name, manufactured by San-Apro Co., Ltd., aromatic dimethylurea) and U-CAT3513N (trade name, manufactured by San-Apro Co., Ltd., aliphatic dimethylurea). Among these, aromatic alkylureas are preferred because they have a moderately low cleavage temperature and can easily cure the compound efficiently.

[0043] The amount of the curing accelerator to be added is not particularly limited as long as it is an amount that can achieve a curing acceleration effect. From the viewpoint of improving the curability and fluidity of the resin composition when absorbing moisture, the amount of the curing accelerator to be added may be 0.1 parts by mass or more and 20 parts by mass or less, 1 part by mass or more and 15 parts by mass or less, or 2 parts by mass or more and 10 parts by mass or less, relative to 100 parts by mass of the epoxy resin. When the amount of the curing accelerator to be added is 0.1 parts by mass or more, a sufficient curing acceleration effect is easily obtained. When the amount of the curing accelerator to be added is 20 parts by mass or less, the storage stability of the compound is less likely to decrease.

[0044] The resin composition may further contain a coupling agent. The coupling agent improves adhesion between the resin composition and the metal-element-containing particles that make up the magnetic powder, thereby improving the flexibility and mechanical strength of a molded body (such as an inductor) 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 epoxysilane compounds, mercaptosilane compounds, aminosilane compounds, alkylsilane compounds, acrylicsilane compounds, methacrylicsilane compounds, ureidosilane compounds, acid anhydride-based silane compounds, and vinylsilane compounds. The compound may contain one or more of the above coupling agents.

[0045] The content of the coupling agent in the compound according to this embodiment may be preferably 0.05 to 0.70% by mass, more preferably 0.10 to 0.60% by mass, and even more preferably 0.12 to 0.50% by mass, based on the total mass of the compound. When the content of the coupling agent is equal to or greater than the lower limit, the flexibility and mechanical strength of the molded article are likely to be improved. When the content of the coupling agent is equal to or less than the upper limit, blocking of the compound is unlikely to occur. However, even when the content of the coupling agent is outside the above range, the effects of the present invention can be obtained.

[0046] The resin composition may contain a compound having a siloxane bond (siloxane compound) as an additive, since this tends to reduce the molding shrinkage of the compound and improve the heat resistance and voltage resistance of the molded article. The siloxane bond is a bond containing two silicon atoms (Si) and one oxygen atom (O), and may be represented by -Si-O-Si-. The compound having a siloxane bond may be a polysiloxane compound.

[0047] When a molded article 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 (compression molding or 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.

[0048] Examples of waxes include fatty acids such as montanic acid, stearic acid, 12-hydroxystearic acid, and lauric acid, and 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-ethylhexoate; and fatty acid salts such as 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, and 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 microcrystalline wax.

[0049] The compound may contain a flame retardant to improve the environmental safety, recyclability, moldability, and low cost of the compound. 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 or more of the above flame retardants.

[0050] When preparing the compound, the magnetic powder and the resin composition (each component constituting the resin composition) are mixed while being heated. For example, the magnetic powder and the resin composition may be kneaded using a kneader, roll, agitator, or the like while being heated. By heating and mixing the magnetic powder and the resin composition, the resin composition adheres to part or all of the surface of the metal element-containing particles constituting the magnetic powder, coating the metal element-containing particles, and part or all of the resin in the resin composition becomes semi-cured. As a result, the compound is obtained. The compound may also be obtained by further adding wax to the powder obtained by heating and mixing the magnetic powder and the resin composition. The resin composition and wax may be mixed in advance.

[0051] In the kneading process, the magnetic powder, resin, curing agent, curing accelerator, and coupling agent may be kneaded in a tank. After the magnetic powder and coupling agent are charged into the tank and mixed, the resin, curing agent, and curing accelerator may be charged into the tank and the raw materials in the tank may be kneaded. After the resin, curing agent, and coupling agent are kneaded in the tank, the curing accelerator may be charged into the tank and the raw materials in the tank may be further kneaded. A mixed powder of resin, curing agent, and curing accelerator (resin mixed powder) may be prepared in advance, and the magnetic powder and coupling agent may be kneaded to prepare a metal mixed powder, and then the metal mixed powder and resin mixed powder may be kneaded.

[0052] The kneading time varies depending on the type of kneading machine, the capacity of the kneading machine, and the amount of compound produced, but is preferably, for example, 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 will be insufficient, the moldability of the compound will be impaired, and the degree of cure of the compound will vary. If the kneading time exceeds 20 minutes, for example, the resin composition (e.g., epoxy resin and phenolic resin) will harden rapidly in the tank, which will likely impair the fluidity and moldability of the compound.

[0053] When the raw materials in the tank are heated and kneaded in a kneader, the heating temperature may be, for example, a temperature at which a semi-cured resin (B-stage resin) is produced and the production of a cured resin (C-stage resin) is suppressed. The heating temperature may be lower than the activation temperature of the curing 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 tends to coat the surfaces of the metal element-containing particles that make up the magnetic powder, making it easier to produce a semi-cured resin and suppressing complete curing of the resin during kneading.

[0054] The method for producing a molded body according to this embodiment includes a step of molding the above-described compound by compression molding or transfer molding using a release film to obtain a molded body. By molding the above-described compound using a release film, the voltage resistance of the resulting molded body can be improved and leakage current generation can be suppressed. It was previously unknown and unexpected that the use of a release film not only improves the releasability of the molded body but also improves the voltage resistance and leakage current suppression of the molded body. The reason for this effect is unclear, but it is thought to be because the surface condition of the molded body changes when a release film is used. For example, it is presumed that when a release film is used, the magnetic powder is less likely to be exposed on the surface of the molded body, thereby improving the voltage resistance and leakage current suppression.

[0055] The release film used in the method for producing a molded article according to this embodiment may have a support substrate and a release layer formed on the support substrate.

[0056] In the method for producing a molded article according to this embodiment, the release film is adhered to the mold, and therefore the release film is required to have excellent conformability to the shape of the mold. By using a resin with excellent stretchability as the supporting substrate for the release film, the conformability to the mold can be further improved.

[0057] From the viewpoint of heat resistance, the supporting substrate preferably has a melting point equal to or higher than the molding temperature (for example, 100 to 200° C.) Furthermore, in order to prevent the release film from being torn when attached to the mold and during molding, and to prevent the molded article from being wrinkled after molding, it is advisable to select the supporting substrate taking into consideration the elastic modulus and elongation at high temperatures.

[0058] The supporting substrate may be a commercially available resin film that has not been subjected to a release treatment. The resin component constituting the resin film may be at least one selected from the group consisting of polyester resin, polyimide resin, polyolefin resin, and fluorine-containing resin. From the viewpoint of heat resistance and elastic modulus at high temperatures, the resin component constituting the resin film is preferably a polyester resin. Examples of polyester resins include polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, copolymers thereof, and modified resins thereof. The supporting substrate is preferably a polyester film obtained by molding a polyester resin into a sheet, and more preferably a biaxially stretched polyester film from the viewpoint of mold conformability.

[0059] The thickness of the supporting substrate is not particularly limited, and is preferably 5 μm to 100 μm, more preferably 10 μm to 70 μm, and even more preferably 15 μm to 50 μm. When the thickness of the supporting substrate is 5 μm or more, the substrate tends to be easy to handle and less prone to wrinkles, while when the thickness is 100 μm or less, the substrate tends to be able to conform to the mold during molding, and thus the formation of wrinkles and the like in the formed molded article tends to be suppressed.

[0060] The release layer can be prepared, for example, by applying a release agent to a supporting substrate and drying the applied agent. The release agent is not particularly limited and can be appropriately selected from release agents used in the art.

[0061] Examples of the release agent include silicone-based release agents, fluorine-based release agents, polyolefin-based release agents, and alkyd resin-based release agents. The release agent is preferably a thermosetting type, since it can form a crosslinked structure in the release layer. A thermosetting release agent containing an aminoalkyd resin is preferred. Examples of commercially available release agents include those available from Showa Denko Materials Co., Ltd., under the trade names "Tesfine 303" and "Tesfine 314." A lubricant, an antistatic agent, etc. can also be added to the release agent as needed.

[0062] The thickness of the release layer is not particularly limited, but from the viewpoint of more sufficient release properties and suppression of wrinkles during molding, it is preferably 0.01 μm to 1 μm, more preferably 0.05 μm to 0.8 μm, and even more preferably 0.1 μm to 0.5 μm.

[0063] The surface of the support substrate that contacts the mold may be adjusted to facilitate release from the mold after molding. For example, the surface of the support substrate that contacts the mold may be subjected to a surface treatment such as a matte finish, or a new release layer may be provided in addition to the release layer. The material constituting the release layer is not particularly limited as long as it satisfies the heat resistance, releasability from the mold, etc. In this case, the thickness of the release layer is not particularly limited, but is preferably 0.01 μm to 1 μm. Furthermore, if necessary, a layer such as an anchoring improvement layer, an antistatic layer, or a colored layer may be provided between the release layer and the support substrate.

[0064] The release film preferably has an arithmetic mean roughness Ra of 0.1 to 20 μm and a maximum height Rz of 1 to 300 μm on the surface that comes into contact with the compound (for example, the surface of the release layer). By having the arithmetic mean roughness Ra and the maximum height Rz within the above ranges, the voltage resistance of the resulting molded article can be further improved, and the generation of leakage current can be further suppressed. From the viewpoint of more fully achieving the above effects, the arithmetic mean roughness Ra is more preferably 0.2 to 10 μm. From the same viewpoint, the maximum height Rz is more preferably 5 to 250 μm. In this specification, the arithmetic mean roughness Ra and the maximum height Rz refer to values ​​measured in accordance with JIS B0601-2001.

[0065] FIG. 1 is a cross-sectional view that schematically shows a method for manufacturing a molded body according to this embodiment. FIG. 1 shows a method for manufacturing a molded body by compression molding. As shown in FIG. 1(a), the mold used in the compression molding method is composed of a first mold 10 and a second mold 20. The second mold 20 is the portion where the inductor element 3 is placed and has a flat surface. The first mold 10 is the portion where the release film 1 is placed and has a recess.

[0066] First, as shown in FIG. 1(b), a release film is attached to the first mold 10 along the recess so that the support substrate of the release film is in contact with the first mold 10. The first mold 10 is provided with a suction mechanism (vacuum suction, etc.), and the release film is adsorbed and held by the first mold 10. Next, as shown in FIG. 1(c), the inductor element 3 is attached onto the second mold 20. The second mold 20 may be provided with a suction mechanism (vacuum suction, etc.), and the inductor element 3 may be adsorbed and held by the second mold 20.

[0067] Next, as shown in FIG. 1(d), compound 5 is placed on inductor element 3. Compound 5 is placed so as to face the recessed portion of first mold 10. Next, as shown in FIG. 1(e), first mold 10 and second mold 20 are brought together, and compound 5 is pressurized, compressed, and heated. As a result, compound 5 hardens into a shape that conforms to the recessed portion of first mold 10, forming molded body 7 and sealing inductor element 3. From the viewpoint of ease of operation, it is preferable that the mold temperature during compression molding be 100 to 200°C, the molding pressure be 0.5 to 20 MPa, and the molding time be 60 to 600 seconds.

[0068] After the molded body 7 is formed, the first mold 10 is separated from the second mold 20, as shown in FIG. 1(f). The molded body 7 may then be heat-treated (post-cured) to sufficiently cure it. The heat treatment temperature may be any temperature at which the resin composition in the molded body is sufficiently cured. The heat treatment temperature may be preferably 100°C or higher and 300°C or lower, more preferably 110°C or higher and 250°C or lower. To prevent oxidation of the magnetic powder in the molded body 7, the heat treatment is preferably performed in an inert atmosphere. If the heat treatment temperature exceeds 300°C, the magnetic powder may be oxidized by trace amounts of oxygen inevitably contained in the heat treatment atmosphere, or the cured resin may deteriorate. To sufficiently cure the resin composition while preventing oxidation of the magnetic powder and deterioration of the cured resin, the heat treatment temperature may be maintained for a period of preferably several minutes to 10 hours, more preferably 3 minutes to 8 hours.

[0069] Through the above steps, the molded body 7 is formed, and a semiconductor device including the inductor element 3 and the molded body 7 that seals the inductor element is obtained.

[0070] The obtained molded article 7 may contain the above-mentioned compound. The molded article 7 may also contain a cured product of the above-mentioned compound. The molded article 7 may contain at least one selected from the group consisting of an uncured resin composition, a semi-cured product of a resin composition (a B-stage resin composition), and a cured product of a resin composition (a C-stage resin composition).

[0071] Although the preferred embodiments of the present invention have been described above, the present invention is not limited to the above embodiments.

[0072] Figure 1 shows a case where the inductor element 3 and compound 5 are placed on the flat surface of the second mold 20, but the positions of the first mold 10 and the second mold 20 in Figure 1 (c) can be reversed, with the first mold 10 placed below and the compound 5 placed in a recess on the release film 1 attached to the first mold 10 for molding.

[0073] Molded body 7 may be provided so as to completely cover the entire inductor element 3. In addition, inductor element 3 may be a silicon wafer, a substrate, a lead frame, a semiconductor package, or the like.

[0074] Although FIG. 1 shows a method for producing a molded article by compression molding, a molded article may also be produced by transfer molding.

[0075] FIG. 2 is a cross-sectional view schematically illustrating a method for producing a molded body according to this embodiment. FIG. 2 illustrates a method for producing a molded body by transfer molding. When producing a molded body by transfer molding, as shown in (a) to (c) of FIG. 2, a compound 5 is pressed into a cavity between a first mold 10, on which a release film 1 is disposed, and a second mold 20 using a plunger 30. Thereafter, as shown in (c) of FIG. 2, the compound 5 is cured to form a molded body 7, thereby obtaining a semiconductor device including an inductor element 3 and a molded body 7 that encapsulates the inductor element. From the viewpoint of ease of operation, the mold temperature during transfer molding is preferably 100 to 200°C, the molding pressure is preferably 0.5 to 20 MPa, and the molding time is preferably 60 to 600 seconds. Furthermore, to sufficiently harden the molded body 7, the molded body 7 may be heat-treated (post-cured) using a method similar to that used for compression molding. Production of a molded body by transfer molding is not limited to the embodiment shown in FIG. 2, and similar modifications to those used for compression molding may be made. [Example]

[0076] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples in any way.

[0077] Details of each component used in preparing the compounds of the Examples and Comparative Examples are given below.

[0078] <Resin composition> Epoxy resin 1 (biphenylene aralkyl type epoxy resin, product name: NC-3000 manufactured by Nippon Kayaku Co., Ltd., epoxy equivalent: 275 g / eq) Epoxy resin 2 (multifunctional epoxy resin, manufactured by Printec Co., Ltd. under the trade name TECHMORE VG-3101L, epoxy equivalent: 215 g / eq) Epoxy resin 3 (cresol novolac epoxy resin, product name: N500P-2, manufactured by DIC Corporation, epoxy equivalent: 200 g / eq)

[0079] Curing agent 1 (phenol novolac resin, product name: HF-3M, manufactured by Meiwa Kasei Co., Ltd., hydroxyl group equivalent: 107 g / eq) Curing agent 2 (biphenylene aralkyl phenolic resin, product name: MEHC7841-4S, manufactured by Meiwa Kasei Co., Ltd., hydroxyl group equivalent: 166 g / eq) Curing agent 3 (triphenylmethane type phenolic resin, product name: HE910-09, manufactured by Air Water Inc., hydroxyl group equivalent: 101 g / eq)

[0080] Curing accelerator (triphenylphosphine) Coupling agent (methacryloxyoctyltrimethoxysilane, product name: KBM-5803, manufactured by Shin-Etsu Chemical Co., Ltd.) Release agent (partially saponified Montan acid ester wax, Clariant Chemicals Co., Ltd., trade name: Licowax-OP)

[0081] <Magnetic powder> Magnetic powder 1 (amorphous iron powder, Epson Atmix Corporation, product name: 9A4-II, average particle size: 24 μm) Magnetic powder 2 (FeSiCr alloy powder, manufactured by Shinto Kogyo Co., Ltd., average particle size: 2.1 μm)

[0082] [Examples 1 to 6 and Comparative Examples 1 to 6] (Preparation of Compound) The epoxy resin, curing agent, curing accelerator, and release agent in the amounts (unit: g) shown in Tables 1 and 2 were placed in a plastic container. 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 coupling agent.

[0083] The magnetic powders in the amounts (unit: g) shown in Tables 1 and 2 were mixed in a pressure twin-screw kneader (manufactured by Nihon Spindle Manufacturing Co., Ltd., capacity: 5 L) for 5 minutes, and then the coupling agents shown in Tables 1 and 2 were added to the twin-screw kneader. The contents of the twin-screw kneader were then heated to 90°C and mixed for 10 minutes while maintaining that temperature. The resin mixture was then added to the contents of the twin-screw kneader, and the contents were melted and kneaded for 15 minutes while maintaining the temperature at 120°C. The kneaded product obtained by the above melting and kneading was cooled to room temperature and then pulverized with a hammer until it reached the specified particle size. Note that "melting" in the above means that at least a portion of the resin composition in the contents of the twin-screw kneader is melted. The magnetic powder in the compound does not melt during the compound preparation process. The compounds of the examples and comparative examples were prepared using the above methods. Tables 1 and 2 show the content of magnetic powder based on the total amount of the compound.

[0084] (Preparing the release film) The following release films 1 to 3 were prepared. The arithmetic mean roughness Ra and maximum height Rz are values ​​on the surface that comes into contact with the compound. Release film 1 (manufactured by AGC Inc., product name: Aflex, arithmetic mean roughness Ra: 14.2 μm, maximum height Rz: 128 μm, thickness: 50 μm, film composition: fluorine-based resin) Release film 2 (product name: RM-4100, manufactured by Showa Denko Materials Co., Ltd., arithmetic mean roughness Ra: 1.6 μm, maximum height Rz: 28.8 μm, thickness: 40 μm, film composition: PET resin) Release film 3 (product name: RM4200, manufactured by Showa Denko Materials Co., Ltd., arithmetic mean roughness Ra: 8.2 μm, maximum height Rz: 113 μm, thickness: 50 μm, film composition: PET resin)

[0085] (Production of molded body) As shown in FIG. 1(a), a first mold 10 having a recess and a second mold 20 having a flat surface for compression molding were prepared. In the example, as shown in FIG. 1(b), release films 1 to 3 were placed on the first mold 10 and fixed by vacuum so as to fit along the recess. In the comparative example, no release film was placed on the first mold 10. Next, compound 5 was placed on the second mold 20. Subsequently, the first mold 10 and the second mold 20 were clamped together, and compound 5 was molded and cured under conditions of a mold temperature of 175°C, a molding pressure of 12 MPa, and a molding time of 180 seconds to form a molded body 7. Thereafter, the first mold 10 was separated from the second mold 20, and post-curing was performed at 175°C for 5.5 hours to obtain a disk-shaped test piece having a diameter of 50 mm and a thickness of 2.0 mm.

[0086] [Evaluation of molded products] (voltage resistance) For the withstand voltage test, a stainless steel plate connected to a ground wire, a conductive rubber plate, a test specimen, and a 10 mm diameter stainless steel electrode connected to a high-voltage wire were placed on an insulating plate in this order. The high-voltage wire and ground wire were connected to the high-voltage output terminal and ground terminal of a high-voltage amplifier, respectively. The waveform output of a function generator was input to the high-voltage amplifier, and a test voltage was generated, increasing from 0 V to a maximum of 2000 V at a rate of 10 V per second, and applied to the test specimen. The voltage was read when the current passing through the test specimen exceeded 10 mA. Next, a stainless steel electrode was placed at a different position on the test specimen, and a voltage was similarly applied. The test was repeated seven times, and the average of the read voltages was taken as the withstand voltage (breakdown voltage: V / mm) of the test specimen. The above test was performed on two test specimens, and the average withstand voltage of the two specimens was calculated.

[0087] (Number of insulators (leakage current suppression)) To confirm the effect of suppressing the occurrence of leakage current, the following evaluation was carried out. That is, in the above-mentioned voltage resistance test, it was confirmed whether the leakage current value could be maintained at 0.25 mA or less until dielectric breakdown occurred. This confirmation was carried out for 14 test pieces, and the number and percentage of pieces that could maintain a leakage current value of 0.25 mA or less were calculated.

[0088] [Table 1]

[0089] [Table 2] [Explanation of symbols]

[0090] 1...release film, 3...inductor element, 5...compound, 7...molded body, 10...first mold, 20...second mold.

Claims

[Claim 1] A method for producing a molded body, comprising a step of compressively molding a compound containing a resin and a magnetic powder using a release film to obtain a molded body.

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