Curable resin composition

Abstract

This invention provides a curable resin composition suitable for use as a paste for coating or filling printed wiring boards with high degrees of freedom in wiring formation. It can form a deviation-free coating and yield a cured product with a stable and high relative magnetic permeability over time. This invention is a curable resin composition characterized by comprising a thermosetting resin, a curing agent, magnetic powder, and a diluent, wherein the thermosetting resin has a 5% weight reduction temperature based on thermogravimetric analysis greater than 180°C, and the diluent has a 5% weight reduction temperature based on thermogravimetric analysis of 50°C or higher and 180°C or lower.

Description

Technical Field

[0001] This invention relates to curable resin compositions, and to curable resin compositions that can be used as fillers for through holes and recesses in printed wiring boards. Background Technology

[0002] With the increasing demands for miniaturization and higher functionality in electronic devices in recent years, the field of wiring boards also requires further multi-layering and high-density designs. For example, wiring boards that mount multiple circuit components such as power circuits, high-frequency circuits, and digital circuits on a single substrate have been proposed.

[0003] In a substrate with multiple circuit elements mounted on it, noise generated by each circuit element affects adjacent circuit elements. Therefore, it is necessary to mount the circuit elements at fixed intervals or to place shielding between them. Consequently, it is difficult to miniaturize and increase the density of substrates with multiple circuit elements mounted on them.

[0004] To address the aforementioned issues, for example, Patent Document 1 proposes that by providing a magnetic layer between each substrate in a multilayer wiring board or filling vias with magnetic material, noise can be reduced in a compact and low-cost manner, even when multiple circuit elements are mounted on a multilayer board. Furthermore, Patent Document 2 proposes that in a multilayer wiring board, through-holes or vias are filled with a conductive paste containing magnetic filler to achieve interlayer electrical connections.

[0005] On the other hand, with the increasing functionality of printed circuit boards, frequency characteristics are improved by removing excess portions of the coating on the walls of vias and through-holes that are not related to interlayer conductivity. For example, Patent Document 3 proposes a printed circuit board having holes formed by drilling vias and through-holes to the middle using a method called back-drilling.

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent Document 1: Japanese Patent Application Publication No. 2017-017175;

[0009] Patent Document 2: Japanese Patent Application Publication No. 2001-203463;

[0010] Patent document 3: Japanese Patent Publication No. 2007-509487. Summary of the Invention

[0011] The problem the invention aims to solve

[0012] In high-frequency inductors, a high Q value is required as a characteristic. The Q value can be improved by increasing the relative permeability (μ') of the insulating layer constituting the high-frequency inductor. Therefore, materials capable of increasing the relative permeability of the insulating layer are needed. Furthermore, with the miniaturization and high density of components, the requirements for coating formation and filling of small diameters and narrow gaps are increasing, leading to higher demands for paste-like magnetic materials.

[0013] To address the above requirements, it is believed that simply increasing the content of magnetic powder in the paste-like magnetic material to achieve a relative permeability close to that of a bulk magnetic material is sufficient. However, a high content of magnetic powder makes it difficult to form a coating film without deviation. In particular, in paste-like magnetic materials with a large amount of magnetic powder, the viscosity tends to change over time, making it difficult to form a coating film without deviation. Furthermore, after the coating film is formed, the relative permeability also changes over time, making it difficult to form a coating film with a fixed and stable relative permeability.

[0014] Therefore, the object of the present invention is to provide a curable resin composition that is suitable for use as a paste for coating or filling printed wiring boards with a high degree of freedom in wiring formation, capable of forming a coating film without deviation, and obtaining a cured product with a stable and high relative magnetic permeability over time.

[0015] means for solving problems

[0016] The inventors investigated the reasons why it is difficult to form a uniform coating in paste-like magnetic materials and why the relative permeability changes over time. The results showed that the components in paste-like magnetic materials volatilize to a certain degree above a fixed level even at room temperature, thus causing the viscosity to change over time and making it difficult to form a uniform coating. Furthermore, it was clarified that the volatilization of certain components over time after coating formation also leads to changes in relative permeability. This invention is based on this understanding. Therefore, the main points of this invention are as follows.

[0017] [1] A curable resin composition, characterized in that it is a curable resin composition comprising a thermosetting resin, a curing agent, magnetic powder and a diluent.

[0018] The thermosetting resin has a 5% weight loss temperature based on thermogravimetric analysis of greater than 180°C.

[0019] The 5% weight reduction temperature of the diluted component, based on thermogravimetric analysis, is above 50°C and below 180°C.

[0020] [2] The curable resin composition as described in [1], wherein the curable resin composition contains less than 30% by mass of the diluent relative to the total amount of the thermosetting resin and the diluent.

[0021] [3] The curable resin composition as described in [1], wherein the thermosetting resin is in liquid state.

[0022] [4] The curable resin composition as described in [1], wherein the thermosetting resin comprises an epoxy resin with a viscosity of less than 1 Pa·s.

[0023] [5] The curable resin composition as described in [4], wherein the epoxy resin comprises 35% by mass or more relative to the total amount of the thermosetting resin.

[0024] [6] The curable resin composition as described in [1], wherein the curable resin composition is used as a filler for through holes or recesses of a printed wiring board.

[0025] The effects of the invention

[0026] According to the present invention, a curable resin composition comprising a thermosetting resin, a curing agent, and magnetic powder includes a thermosetting resin having a 5% weight reduction temperature greater than 180°C based on thermogravimetric analysis and a diluent having a 5% weight reduction temperature of 50°C or higher and 180°C or lower based on thermogravimetric analysis. This allows for the formation of a coating film without deviation, resulting in a curable resin composition that yields a cured product with a high relative permeability that is stable over time. Therefore, it is suitable for use as a paste that can be coated or filled onto printed wiring boards with a high degree of freedom in wiring formation. Furthermore, it is suitable for use as an insulating material for high-frequency inductors requiring high relative permeability in the 10MHz to 200MHz range. Detailed Implementation

[0027] <Curing Resin Composition>

[0028] The curable resin composition of the present invention comprises, as essential components, a thermosetting resin, a curing agent, magnetic powder, and a diluent. It should be noted that, in this specification, "liquid" refers to a fluid liquid or semi-liquid (paste) state at at least one temperature condition between 20°C and 40°C. The components are described in detail below.

[0029] [Thermosetting resins]

[0030] As a thermosetting resin included in the curable resin composition according to the present invention, any thermosetting compound can be used without particular limitation, provided that the 5% weight reduction temperature based on thermogravimetric analysis is greater than 180°C. The 5% weight reduction temperature is more preferably greater than 200°C. It should be noted that, in this specification, "5% weight reduction temperature based on thermogravimetric analysis" refers to the temperature at which the weight of the sample decreases by 5% relative to the weight of the sample before heating, when the sample is placed in an aluminum pan (non-airtight type) at a weight of 10 mg to 30 mg under atmospheric conditions and heated from 20°C to 500°C at a heating rate of 10°C / min. It should also be noted that, in the case of diluting the thermosetting resin with a solvent, the weight reduction temperature of the thermosetting resin monomer after removing the solvent is measured.

[0031] Examples of thermosetting resins include isocyanate compounds, terminal isocyanate compounds, amino resins, carbodiimide resins, cyclic carbonate compounds, epoxy resins, oxacyclobutane compounds, cyclic sulfide resins, urea-formaldehyde (urea) resins, melamine resins, and other resins containing triazine rings; unsaturated polyester resins; maleimide resins such as bismaleimide compounds; polyurethane resins; diallyl phthalate resins; benzoxazine resins; polyimide resins; polyamide-imide resins; benzocyclobutene resins; phenolic varnish-type cyanate resins; bisphenol A type cyanate resins; bisphenol E type cyanate resins; tetramethylbisphenol F type cyanate resins; and other bisphenol-type cyanate resins, as well as silicone resins and other commonly used resins. These can be used alone or in combination of two or more. Among them, epoxy resins are preferred.

[0032] As an epoxy resin, any epoxy resin having two or more epoxy groups in one molecule can be used without restriction. Examples include bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol E (AD) type epoxy resin, bisphenol S type epoxy resin, hydrogenated bisphenol A type epoxy resin, brominated bisphenol A type epoxy resin, bisphenol S type epoxy resin, and other epoxy resins with a bisphenol-type backbone; phenolic varnish type epoxy resin, cresol varnish type epoxy resin, bisphenol A phenolic varnish type epoxy resin, biphenyl type epoxy resin, naphthol type epoxy resin, naphthalene type epoxy resin, dicyclopentadiene type epoxy resin, triphenylmethane type epoxy resin, aliphatic chain epoxy resin, phosphorus-containing epoxy resin, anthracene type epoxy resin, norbornene type epoxy resin, adamantane type epoxy resin, fluorene type epoxy resin, aminophenol type epoxy resin, aminocresol type epoxy resin, and alkylphenol type epoxy resin, all of which can be used. One type of the above-mentioned epoxy resin can be used, or two or more types can be used in combination. Among them, bisphenol A type epoxy resin, bisphenol F type epoxy resin, and bisphenol E (AD) type epoxy resin are preferred. In addition, the epoxy resin with bisphenol type backbone can be any of liquid, semi-solid, or solid, but from the viewpoint of filling, liquid is preferred.

[0033] Both bisphenol A type epoxy resin and bisphenol F type epoxy resin are preferred. Examples of commercially available products include ZX-1059 (a mixture of bisphenol A and bisphenol F type epoxy resins) manufactured by Nippon Steel Chemical & Material Co., Ltd., jER 828, jER 834, jER 1001 (bisphenol A type epoxy resin), jER 807, jER 4004P (bisphenol F type epoxy resin) manufactured by Mitsubishi Chemical Co., Ltd., and R710 (bisphenol E type epoxy resin) manufactured by Air Water Inc.

[0034] Furthermore, the curable resin composition of the present invention can also include a multifunctional epoxy resin as a thermosetting resin. Examples of multifunctional epoxy resins include EP-3300E manufactured by ADEKA Co., Ltd., which is a hydroxybenzophenone-type liquid epoxy resin; jER 630 manufactured by Mitsubishi Chemical Corporation, which is an aminophenol-type liquid epoxy resin (p-aminophenol-type liquid epoxy resin); ELM-100 manufactured by Sumitomo Chemical Co., Ltd., which is an aminophenol-type liquid epoxy resin (p-aminophenol-type liquid epoxy resin); jER 604 manufactured by Mitsubishi Chemical Corporation, which is a glycidylamine-type epoxy resin; Epotohto YH-434 manufactured by Nippon Steel Chemical Materials Co., Ltd.; Sumi-Epoxy ELM-120 manufactured by Sumitomo Chemical Industry Co., Ltd.; and DEN431 manufactured by Dow Chemical Company, which is a phenolic varnish-type epoxy resin. These multifunctional epoxy resins can be used in one or in combination of two or more.

[0035] In this invention, from the viewpoint of coating properties such as film-forming properties and printability of the curable resin composition, the thermosetting resin is preferably in a liquid state compared to a solid state. In particular, from the viewpoint of printability and filler properties, the viscosity of the thermosetting resin at 25°C is preferably 5 Pa·s or less, more preferably 3 Pa·s or less, and even more preferably 1 Pa·s or less.

[0036] The amount of the thermosetting resin described above is preferably 3% by mass or more and 25% by mass or less relative to the total amount of the composition, and more preferably 5% by mass or more and 15% by mass or less.

[0037] Furthermore, as the aforementioned thermosetting resin with a 5% weight reduction temperature greater than 180°C based on thermogravimetric analysis, it is preferable to contain an epoxy resin with a viscosity of 1 Pa·s or less at 25°C. By containing such a low-viscosity epoxy resin, it is possible to achieve high filling of magnetic powders and other fillers, and the viscosity of the curing resin composition can be reduced. Therefore, printability is improved, and when applied to printed wiring boards, the freedom of wiring formation can be increased. It should be noted that in this specification, viscosity refers to the viscosity measured according to JIS Z 8803:2011, section 10, "Method for determining viscosity using a cone-plate rotational viscometer." Specifically, a cone-plate viscometer (TVE-33H, manufactured by Toki Sangyo Co., Ltd.) is used. For liquids with a viscosity less than 10 Pa·s, a 3°×R14 cone rotor is used; for pastes with a viscosity of 10–300 Pa·s, a 3°×R9.7 cone rotor is used. The values ​​are measured at 25°C, 5.0 rpm, and 30 seconds.

[0038] The amount of epoxy resin with a viscosity of 1 Pa·s or less is preferably 35% by mass or more, more preferably 60% by mass or more, relative to the total amount of thermosetting resin with a temperature greater than 180°C and a weight reduction of 5% based on thermogravimetric analysis.

[0039] [Dilution ingredients]

[0040] The curable resin composition according to the present invention comprises a diluent having a 5% weight reduction temperature of 50°C or higher and 180°C or lower based on thermogravimetric analysis. By including this diluent, a coating film without deviation can be formed, resulting in a curable resin composition that yields a cured product with a high relative magnetic permeability that is stable over time. The reason for this is not necessarily certain, but is speculated as follows: That is, the curable resin composition contains the aforementioned thermosetting resin with a 5% weight reduction temperature greater than 180°C based on thermogravimetric analysis and a diluent having a 5% weight reduction temperature of 50°C or higher and 180°C or lower based on thermogravimetric analysis. Therefore, at room temperature conditions such as when forming a coating film, the components in the curable resin composition are less likely to volatilize, thus suppressing rapid changes in viscosity over time. As a result, the coatability (printability) of the curable resin composition is improved, and a coating film with a consistent thickness without deviation is easily formed. Furthermore, the viscosity change is minimal after the coating is formed until the curable resin composition cures, thus suppressing the agglomeration or precipitation of magnetic powder. Therefore, it is believed that a cured product with a stable relative permeability that does not decrease over time can be obtained. Further, it is believed that during the curing of the resin composition (i.e., upon heating), most of the diluents evaporate and shrink, increasing the proportion of magnetic powder per unit volume in the cured product and thus improving the relative permeability. However, the above-described mechanism is ultimately only speculative and not necessarily limited to this.

[0041] From the viewpoint of coating uniformity and relative magnetic permeability, the 5% weight reduction temperature of the diluent based on thermogravimetric analysis is preferably 60°C or higher and 160°C or lower, more preferably 70°C or higher and 150°C or lower, and even more preferably 80°C or higher and 140°C or lower.

[0042] As diluents with a 5% weight reduction temperature of 50°C to 180°C based on thermogravimetric analysis, examples include alicyclic epoxy resins such as LDO and low molecular weight glycidyl ether type epoxy resins, such as butyl glycidyl ether, ethylhexyl glycidyl ether, and allyl glycidyl ether. Additionally, organic solvents such as ketones, aromatic hydrocarbons, glycol ethers, glycol ether acetates, esters, alcohols, aliphatic hydrocarbons, and petroleum-based solvents can also be used. These diluents can be used alone or as a mixture of two or more.

[0043] The aforementioned diluents do not necessarily need to completely evaporate during the curing of the thermosetting resin composition; a portion can function as a component in the curing reaction along with the thermosetting resin. For example, when using alicyclic epoxy resins such as LDO as diluents, curing shrinkage increases, thus significantly improving the relative magnetic permeability of the cured product. Furthermore, by using compounds with the same reactive functional groups as those found in the thermosetting resin as diluents, the affinity with the thermosetting resin is increased, suppressing viscosity changes in the cured resin composition and facilitating the formation of a uniform coating. For instance, when the thermosetting resin is an epoxy resin, using LDO, dipropylene glycol methyl ether, or diethylene glycol monoethyl ether acetate as diluents results in high affinity with the resin components and improved film formation over time.

[0044] The amount of the diluent is preferably 30% by mass or less relative to the total amount of thermosetting resin and diluent, and more preferably 5 to 20% by mass from the viewpoint of the stability of relative magnetic permeability over time and film formation properties.

[0045] [Curing agent]

[0046] The curable resin composition according to the present invention comprises a curing agent for curing the above-described thermosetting resin. As the curing agent, known curing agents commonly used for curing thermosetting resins can be used, such as amines, imidazoles, polyfunctional phenols, acid anhydrides, isocyanates, and polymers containing their functional groups; multiple of these may be used as needed. As amines, dicyandiamide, diaminodiphenylmethane, etc., are examples. As imidazoles, alkyl-substituted imidazoles, benzimidazoles, etc., are examples. Additionally, imidazole compounds may also be imidazole latent curing agents such as imidazole adducts. As polyfunctional phenols, hydroquinone, resorcinol, bisphenol A, and their halogen compounds are examples; further, phenolic varnishes, cresol resins, etc., as condensates of these phenols with aldehydes, are examples. As acid anhydrides, phthalic anhydride, hexahydrophthalic anhydride, methylnadic anhydride, benzophenone tetracarboxylic anhydride, etc., are examples. As isocyanates, there are toluene diisocyanate, isophorone diisocyanate, etc., and substances obtained by blocking the isocyanate with phenols or the like can also be used. These curing agents can be used alone or in combination of two or more.

[0047] Among the aforementioned curing agents, amines and imidazoles are preferred from the viewpoints of adhesion to conductive and insulating parts, storage stability, and heat resistance. Preferably, the main components are adducts of aliphatic polyamines such as alkylene diamines with 2 to 6 carbon atoms, polyalkylene polyamines with 2 to 6 carbon atoms, and aliphatic polyamines containing aromatic rings with 8 to 15 carbon atoms; or adducts of alicyclic polyamines such as isophorone diamine and 1,3-bis(aminomethyl)cyclohexane; or mixtures of the above-mentioned aliphatic polyamine adducts and the above-mentioned alicyclic polyamine adducts.

[0048] As the addition compound of the aforementioned aliphatic polyamine, it is preferable to obtain a compound by reacting the aliphatic polyamine with an aryl glycidyl ether (especially phenyl glycidyl ether or tolyl glycidyl ether) or an alkyl glycidyl ether. Alternatively, as the addition compound of the aforementioned alicyclic polyamine, it is preferable to obtain a compound by reacting the alicyclic polyamine with n-butyl glycidyl ether, bisphenol A diglycidyl ether, etc.

[0049] Examples of aliphatic polyamines include alkylene diamines with 2 to 6 carbon atoms such as ethylenediamine and propylenediamine, polyalkylene polyamines with 2 to 6 carbon atoms such as diethylenetriamine and triethylenetriamine, and aliphatic polyamines containing aromatic rings with 8 to 15 carbon atoms such as xylylenediamine. Examples of commercially available modified aliphatic polyamines include, for instance, Fujicure FXE-1000 or Fujicure FXR-1020, Fujicure FXR-1030, Fujicure FXR-1080, Fujicure FXR-1090M2 (manufactured by T&K TOKA Co., Ltd.), Ancamine 2089K, Sunmide P-117, Sunmide X-4150, Ancamine 2422, Surwet R, Sunmide TX-3000, and Sunmide A-100 (manufactured by Evonik Japan Co., Ltd.).

[0050] Examples of alicyclic polyamines include isophorone diamine, 1,3-bis(aminomethyl)cyclohexane, bis(4-aminocyclohexyl)methane, norbornene diamine, 1,2-diaminocyclohexane, and laromin. Commercially available modified alicyclic polyamines include, for example, Ancamine 1618, Ancamine 2074, Ancamine 2596, Ancamine 2199, Sunmide IM-544, Sunmide I-544, Ancamine 2075, Ancamine 2280, Ancamine 1934, Ancamine 2228 (manufactured by Evonik Industries, Inc.), Daitocurar F-5197, Daitocurar B-1616 (manufactured by Daito Sangyo Co., Ltd.), Fujicure FXD-821, Fujicure 4233 (manufactured by T&K TOKA Co., Ltd.), jER Cure 113 (manufactured by Mitsubishi Chemical Corporation), and laromin C-260 (manufactured by BASF (Japan) Co., Ltd.). In addition, examples of polyamine-type curing agents include EH-5015S (manufactured by ADEKA Co., Ltd.).

[0051] As imidazoles, these refer to products of the reaction between epoxy resins and imidazoles. Examples include 2-methylimidazolium, 4-methyl-2-ethylimidazolium, 2-phenylimidazolium, 4-methyl-2-phenylimidazolium, 1-benzyl-2-methylimidazolium, 2-ethylimidazolium, 2-isopropylimidazolium, 1-cyanoethyl-2-methylimidazolium, 1-cyanoethyl-2-ethyl-4-methylimidazolium, and 1-cyanoethyl-2-undecylimidazolium. Commercially available imidazole compounds include, for example, imidazoles such as 2E4MZ, C11Z, C17Z, and 2PZ; azine compounds of imidazoles such as 2MZ-A and 2E4MZ-A; isocyanurates of imidazoles such as 2MZ-OK and 2PZ-OK; and hydroxymethyl forms of imidazoles such as 2PHZ and 2P4MHZ (all manufactured by Shikoku Chemical Industry Co., Ltd.). Commercially available imidazole-based latent curing agents include, for example, Cureduct P-0505 (manufactured by Shikoku Chemical Industry Co., Ltd.).

[0052] The amount of the curing agent described above, relative to the total amount of the composition, is preferably 0.4% by mass or more and 2.5% by mass or less when converted according to solid content.

[0053] [Magnetic Powder]

[0054] The curable resin composition according to the present invention contains magnetic powder. By containing magnetic powder, it is possible to suppress or even absorb noise electromagnetic waves in the nearby electromagnetic field. Therefore, even when multiple circuit elements are mounted, it can become a printed wiring board with excellent noise suppression and other characteristics. In addition, it is suitable as an insulating material for high-frequency inductors that require high relative permeability in the range of 1MHz to 200MHz.

[0055] As magnetic powders, they can be used without particular restrictions. Examples include spinel-type ferrites such as Mg-Zn, Mn-Zn, Mn-Mg, Cu-Zn, Mg-Mn-Sr, and Ni-Zn ferrites; hexagonal ferrites such as Ba-Zn, Ba-Mg, Ba-Ni, Ba-Co, and Ba-Ni-Co ferrites; and garnet-type ferrites such as Y-series ferrites. These are all non-conductive magnetic materials. Pure iron powder, Fe... Conductive magnetic materials such as Fe-based alloy powders, Ni powders, Fe-Ni-Mo alloy powders, Fe-Ni-Mo-Cu alloy powders, Fe-Co alloy powders, Fe-Ni-Co alloy powders, Fe-Cr alloy powders, Fe-Cr-Si alloy powders, Fe-Ni-Cr alloy powders, or Fe-Cr-Al alloy powders, as well as Fe alloys, Ni alloys, Fe-based amorphous materials, Co-based amorphous materials, and other amorphous alloys.

[0056] When insulation is required in the cured product of the curable resin composition according to the present invention, it is necessary to use non-conductive magnetic powder as the magnetic powder. Even if it is a conductive magnetic powder, it can be used by adjusting the proportion or by coating its surface with insulating inorganic or organic materials.

[0057] Furthermore, commercially available magnetic fillers can be used as the magnetic powder. Specific examples of commercially available magnetic fillers include "PST-S" manufactured by Sanyo Special Steel Co., Ltd., and Epson Atmix Co., Ltd. Atmix Corporation manufactures "AW2-08PF20F", "AW2-08PF10F", "AW2-08PF8F", "AW2-08PF3F", "Fe-3.5Si-4.5CrPF20F", "Fe-50NiPF20F", "Fe-80Ni-4MoPF20F", JFE Chemicals Co., Ltd. manufactures "LD-M", "LD-MH", "KNI-106", "KNI-106GSM", "KNI-106GS", "KNI-109", "KNI-109GSM", "KNI-109GS", Toda Kogyo Co., Ltd. manufactures "KNS-415", "BSF-547", "BSF-029", "BSN-125", "BSN-714", "BSN-828", and Nippon Heavy Chemical Industry Co., Ltd. manufactures "JR09P2", etc. A single magnetic material can be used, or two or more can be used in combination.

[0058] There are no particular restrictions on the shape of magnetic powders; examples include spherical, needle-like, plate-like, flake-like, hollow, irregular, hexagonal, cubic, and flake-like shapes.

[0059] Furthermore, considering the dispersibility of the magnetic filler, its filling ability in the pores, and the smoothness when forming a wiring layer in the pore-filled portion, the average particle size of these magnetic powders is suitable to be 0.1 μm to 25 μm, preferably in the range of 0.1 μm to 15 μm. It should be noted that the average particle size refers to the average primary particle size, and the average particle size (D50) can be determined by laser diffraction / scattering.

[0060] The magnetic powder is preferably contained in a proportion of 60 to 94% by mass relative to the total amount of the curable resin composition, more preferably in a proportion of 75 to 94% by mass, and even more preferably in a proportion of 85 to 94% by mass. By setting the content of the magnetic filler within the above range, it is possible to achieve a higher level of balance between properties such as noise suppression and the filling properties of the curable resin composition.

[0061] Furthermore, from the viewpoint of uniform dispersion in the curable resin composition, a dispersant may also be used. As a dispersant, phosphate esters, acrylic copolymers, polyamines, polyurethanes, polyesters, polyacrylates, and their phosphate and alkylammonium salts, etc., having acidic or basic groups or both, are preferably used. The above-mentioned dispersants can be used alone or in combination.

[0062] [Other ingredients]

[0063] The curable resin composition according to the present invention can be used in combination with the above-mentioned thermosetting resin to contain a photocurable resin. Examples of photocurable resins include those that can be cured via a free radical addition polymerization reaction using active energy lines. Specific examples of free radical addition polymerization reactive components having one or more vinyl unsaturated groups in their molecules include conventionally known polyester (meth)acrylates, polyether (meth)acrylates, urethane (meth)acrylates, carbonate (meth)acrylates, epoxy (meth)acrylates, etc. Specifically, examples include diacrylates of glycols such as ethylene glycol, methoxytetraethylene glycol, polyethylene glycol, and propylene glycol; acrylamides such as N,N-dimethylacrylamide, N-hydroxymethylacrylamide, and N,N-dimethylaminopropylacrylamide; alkyl aminoacrylates such as N,N-dimethylaminoacrylate and N,N-dimethylaminoacrylate; polyols such as hexanediol, trimethylolpropane, pentaerythritol, dipentaerythritol, and tri-hydroxyethyl isocyanurate, or their ethylene oxide adducts, propylene oxide adducts, or ε-caprolactone adducts; phenoxyacrylates, bisphenol A diacrylates, etc. Polyacrylates, including esters and their phenolic ethylene oxide adducts or propylene oxide adducts; polyacrylates of glycidyl ethers such as diglycidyl ether, triglycidyl ether, trimethylolpropane triglycidyl ether, and triglycidyl isocyanurate; and not limited to the above substances, examples include acrylates obtained by directly acrylate-esterifying polyether polyols, polycarbonate diols, hydroxyl-terminated polybutadiene, polyester polyols, etc., or by acrylate-esterifying diisocyanates with urethane, as well as melamine acrylates, and at least one of the various methacrylates corresponding to the aforementioned acrylates. It should be noted that in this specification, (meth)acrylate is a general term encompassing acrylates, methacrylates, and mixtures thereof, and the same applies to other similar expressions. The above-mentioned photocurable resin is preferably in liquid form.

[0064] Furthermore, when promoting a thermosetting reaction with an epoxy resin in the curable resin composition of the present invention, or when using the composition of the present invention as an alkali-developable curable resin composition, a carboxyl-containing resin is preferably used as the curable resin. The carboxyl-containing resin can be a carboxyl-containing photosensitive resin having vinyl unsaturated groups, and may or may not have an aromatic ring.

[0065] When the curable resin composition of the present invention contains a photocurable resin, it is preferable to add a photopolymerization initiator. Examples of such photopolymerization initiators include, for example, benzoin compounds and their alkyl ethers such as benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, and benzyl methyl ketal; acetophenones such as 2,2-dimethoxy-2-phenylacetophenone, 2-hydroxy-2-methyl-1-phenylpropane-1-one, diethoxyacetophenone, 2,2-diethoxy-2-phenylacetophenone, 1,1-dichloroacetophenone, 1-hydroxycyclohexylphenyl ketone, and 2-methyl-1-[4-(methylthio)phenyl]-2-morpholino-propane-1-one; and methylanthraquinone, 2-ethylanthraquinone, and 2-tert-butyl acetophenone. Anthraquinones, such as anthraquinones, 1-chloroanthraquinones, and 2-pentylanthraquinones; thioxanthones, such as 2,4-diethylthioxanthones, 2-chlorothioxanthones, 2,4-dichlorothioxanthones, 2-methylthioxanthones, and 2,4-diisopropylthioxanthones; ketals, such as acetophenone dimethyl ketal and benzyl dimethyl ketal; and benzophenones, such as benzophenone and 4,4-dimethylaminobenzophenone. These can be used alone or in combination of two or more, and further, can be used in combination with tertiary amines such as triethanolamine and methyldiethanolamine; and benzoic acid derivatives such as 2-dimethylaminoethylbenzoic acid and ethyl 4-dimethylaminobenzoate, as well as photopolymerization initiators.

[0066] Furthermore, the curable resin composition according to the present invention may also contain fillers other than the aforementioned magnetic powder, to mitigate stress caused by curing shrinkage of the composition or to adjust the coefficient of linear expansion, without impairing the effects of the present invention. There are no particular limitations on the fillers used; conventionally known fillers can be used, such as silica, barium sulfate, calcium carbonate, silicon nitride, aluminum nitride, boron nitride, aluminum oxide, magnesium oxide, aluminum hydroxide, magnesium hydroxide, mica, talc, etc. One of these fillers may be used alone, or two or more may be used in combination.

[0067] Among these fillers, calcium carbonate, silica, barium sulfate, and alumina, which have excellent low hygroscopicity and low volume expansion, are preferred, with silica and calcium carbonate being more preferred. Silica can be amorphous, crystalline, or a mixture thereof. Amorphous (fused) silica is particularly preferred. Calcium carbonate can be natural heavy calcium carbonate or synthetic precipitated calcium carbonate.

[0068] Thixotropic properties can be imparted by adding fillers treated with fatty acids or amorphous fillers such as organic bentonite and talc to the curable resin composition according to the present invention.

[0069] Alternatively, a silane-based coupling agent may be included in the curable resin composition of the present invention. By incorporating a silane-based coupling agent, the adhesion between the aforementioned magnetic powder, filler, and thermosetting resin can be improved, and the formation of cracks in the cured product can be suppressed.

[0070] The curable resin composition according to the present invention may also be combined with other oxazine compounds having an oxazine ring, obtained by reacting phenolic compounds, formalin, and primary amines as needed. By containing oxazine compounds, after the curable resin composition filling the holes of the printed wiring board is cured, electroless plating can be performed on the cured product, and the cured product can be easily roughened using an aqueous solution of potassium permanganate, etc., thereby improving the peel strength with the plating layer.

[0071] Alternatively, known colorants such as phthalocyanine blue, phthalocyanine green, diazo yellow, titanium dioxide, carbon black, and naphthalene black may be added to the curable resin composition according to the present invention.

[0072] In addition, known heat-inhibiting agents such as hydroquinone, hydroquinone monomethyl ether, tert-butylcatechol, pyrogallol, and phenothiazine can be added to impart storage stability during storage. Known thickeners and thixotropic agents such as clay, kaolin, organobentonite, and montmorillonite can be added to adjust viscosity. Furthermore, known additives such as silicone-based, fluorine-based, and polymer-based defoamers, leveling agents, imidazole-based, thiazole-based, triazole-based, and silane coupling agents can be used. In particular, when using organobentonite, the portion exposed from the pore surface easily forms a protruding state that is easy to grind and remove, exhibiting excellent abrasiveness, and is therefore preferred.

[0073] Considering coatability (printability), the viscosity of the curable resin composition according to the present invention is preferably 5 to 250 Pa·s, more preferably 7 to 200 Pa·s, and even more preferably 10 to 150 Pa·s. The viscosity of the curable resin composition can be adjusted by the amount of diluent components with a 5% weight reduction temperature of 50°C or higher and 180°C or lower based on thermogravimetric analysis, the type of thermosetting resin component with a 5% weight reduction temperature of greater than 180°C based on thermogravimetric analysis, or their amount.

[0074] <Uses of Curing Resin Compositions>

[0075] The above-described curable resin composition can be widely and generally used, preferably for forming a cured film on a printed wiring board, more preferably for forming a permanent protective film, and even more preferably for use as a solder resist, interlayer insulation layer, cover layer, or filler (material) for filling holes. Among these uses, it is particularly preferred as a filler for filling holes, specifically for filling through holes and recesses in printed wiring boards.

[0076] When the above-described curable resin composition is used as a filler for filling holes, the filler can be applied to, for example, the holes or recesses with bottoms of a multilayer printed circuit board using known patterning methods such as screen printing, roller coating, die coating, and vacuum printing. The inner diameter of the hole filled with the curable resin composition is preferably 0.05 to 0.8 mm, and the depth is preferably 0.4 to 10 mm. Similarly, the inner diameter of the recess filled with the curable resin composition is preferably 0.1 mm or more, and the depth is preferably 0.8 mm or less. In this case, it is preferable to completely fill the hole or recess with the curable resin composition such that it slightly protrudes from the hole or recess.

[0077] By heating a multilayer printed wiring board with holes or recesses filled with a liquid-curable resin composition at, for example, 80–160°C for about 30–180 minutes, the curable resin composition is cured to form a cured product. From the viewpoint that unwanted portions exposed on the substrate surface after filling the holes in the cured product can be easily removed by physical grinding, the curing of the curable resin composition can be carried out in two stages. That is, the curable resin composition can be pre-cured at a lower temperature, and then the main curing (final curing) is performed. As pre-curing conditions, heating at 80–110°C for about 30–180 minutes is preferred. The hardness of the pre-cured product is low, so unwanted portions exposed on the substrate surface can be easily removed by physical grinding, and a flat surface can be formed. Then, heating is performed for main curing. As main curing conditions, heating at 130–180°C for about 30–180 minutes is preferred.

[0078] In either pre-curing or primary curing, curing can be performed using a hot air circulating drying oven, an IR oven, a hot plate, a convection oven, or a device that uses a heat source with a steam-based air heating method to allow hot air to convect within the dryer, or by blowing air from a nozzle onto the object to be cured. A hot air circulating drying oven is particularly preferred. In this case, due to its low expansion, the cured material hardly expands or shrinks, resulting in a final cured product with good dimensional stability, low moisture absorption, excellent adhesion, and electrical insulation. It should be noted that the hardness of the pre-cured material can be controlled by changing the pre-curing heating time and temperature.

[0079] Furthermore, in this invention, the curable resin composition can be cured by irradiating it with an active energy line, as needed. When the curable resin composition contains a photocurable resin such as a carboxyl-containing photosensitive resin, for example, an ultraviolet exposure machine equipped with a high-pressure mercury lamp or a metal halide lamp can be used at approximately 500–2000 mJ / cm². 2The cumulative amount of light is used for exposure (light irradiation), and the exposed part (the part irradiated by light) is cured. Furthermore, for example, it can be heated to a temperature of about 100 to 180°C to thermally cure it (post-curing).

[0080] After the curable resin composition is cured as described above, unwanted portions of the cured material exposed from the surface of the printed wiring board are removed by a known physical polishing method, and the surface is planarized. The wiring layer on the surface is then patterned into a predetermined pattern to form a predetermined circuit pattern. It should be noted that, if necessary, the surface of the cured material can be roughened using a potassium permanganate aqueous solution or similar method, and then a wiring layer can be formed on the cured material using electroless plating or the like.

[0081] Example

[0082] The present invention will be further described in detail below with reference to specific embodiments, but the present invention is not limited to these embodiments. It should be noted that, unless otherwise stated, "parts" and "%" in the following text are all based on mass.

[0083] <Preparation of Curable Resin Compositions>

[0084] The various components shown in Table 1 below were mixed in the proportions (parts by weight) indicated in each table using a mixer to prepare the curable resin compositions of Examples 1-6 and Comparative Examples 1 and 2. It should be noted that the amount of magnetic powder in the tables was adjusted to be fixed by weight in each curable resin composition. Furthermore, the diluent content ratio in the tables indicates the content ratio (mass %) relative to the total amount of thermosetting resin and diluent, and the epoxy resin content ratio with a viscosity of 1 Pa·s or less indicates the content ratio (mass %) relative to the total amount of thermosetting resin with a 5% weight reduction temperature greater than 180°C based on thermogravimetric analysis. Additionally, the magnetic powder content ratio indicates the content ratio (mass %) relative to the total amount of the composition.

[0085] It should be noted that *1 to *9 in Table 1 represent the following components.

[0086] *1: Alicyclic epoxy resin (manufactured by Tomoe Kogyo Co., Ltd., LDO, 5% weight reduction temperature: 109.1℃)

[0087] *2: 1,6-Hexanediol diglycidyl ether (Mitsubishi Chemical Corporation, YED216D, 5% weight reduction temperature: 172.0℃)

[0088] *3: Dipropylene glycol methyl ether (manufactured by Dow Chemical Company, Japan, Dowanol DPM, 5% weight loss temperature: 78.5°C)

[0089] *4: Mixed solvent of ethanol, IPA, and NPA (manufactured by Amakozaki Chemical Co., Ltd., Alcohzol K, 5% weight reduction temperature based on thermogravimetric analysis: 23.4℃ (5% weight reduction temperature as mixed solvent))

[0090] *5: Triglycidylaminophenol type epoxy resin (manufactured by Mitsubishi Chemical Corporation, JER 630, viscosity: 0.5~1 Pa·s, liquid epoxy resin, 5% weight loss temperature: 250.6℃)

[0091] *6: A 50:50 mixture of bisphenol A type epoxy resin and bisphenol F type epoxy resin (Nippon Steel Chemical Materials Co., Ltd. ZX-1059, viscosity: 1.9~2.6 Pa·s, liquid epoxy resin, 5% weight loss temperature: 271.5℃)

[0092] *7: Amorphous alloy magnetic powder (manufactured by Epson Atmex, AW02-08PF8F, average particle size 5μm)

[0093] *8: Copolymer containing acid groups (manufactured by BYK Chemicals (Japan), DISPERBYK-111)

[0094] *9: Imidazole-type curing agent (manufactured by Shikoku Chemical Industry Co., Ltd., 2MZA-PW, mixture)

[0095] It should be noted that the 5% weight reduction temperature was measured using a differential calorimeter (TG / DTA6200, Hitachi High-Tech Co., Ltd.) under atmospheric conditions with a sample weight of 10–20 mg, an aluminum disk (non-airtight type), a heating rate of 10 °C / min, and a measurement temperature of 20–500 °C.

[0096] <Evaluation of printability>

[0097] The prepared curable resin compositions were screen-printed twice on a copper foil substrate (150mm × 95mm, 18μm thick) using an 80-mesh screen without adjusting the viscosity to form a coating film with a cured film thickness of 100μm. Next, the coating film was heat-treated twice at 150°C for 30 minutes each time in a hot air circulating drying oven (Daiwa Scientific Corporation DF610) to form a cured coating film.

[0098] For printability, confirm whether there is any deviation in the thickness of the cured coating (control film thickness). For film thickness, use a digital micrometer (manufactured by Mitutoyo Corporation, Japan) to measure five points at 15mm intervals within the cured coating, confirming the highest and lowest values. The evaluation criteria for printability are as follows.

[0099] ○: The difference between the highest and lowest values ​​is less than 30 μm.

[0100] △: The difference between the highest and lowest values ​​is greater than 30 μm and less than 50 μm.

[0101] ×: The difference between the highest and lowest values ​​is greater than 50 μm

[0102] The evaluation results are shown in Table 1 below.

[0103] <Evaluation of printability stability over time>

[0104] To reproduce the actual coating formation process, 50g of each of the prepared curable resin compositions was temporarily placed in Hi-Resist BHR-150, which is an open system container. After standing at 25°C for 20 minutes, the mixture was coated onto the surface of a copper foil substrate without adjusting the viscosity, as described above, and then cured to form a cured coating.

[0105] The printability of the obtained cured coating was evaluated in the same manner as above. The evaluation criteria for printability are as follows.

[0106] ○: The difference between the highest and lowest values ​​is less than 30 μm.

[0107] △: The difference between the highest and lowest values ​​is greater than 30 μm and less than 50 μm.

[0108] ×: The difference between the highest and lowest values ​​is greater than 50 μm

[0109] The evaluation results are shown in Table 1 below.

[0110] <Evaluation of Magnetic Properties>

[0111] The prepared curable resin compositions were screen-printed onto the surface of copper foil attached to an etched plate without adjusting the viscosity to form a coating film with a cured film thickness of 150 μm. Next, a heat treatment at 150°C for 45 minutes was performed using a hot air circulating drying oven (Daiwa Scientific Corporation DF610) to form a cured coating film.

[0112] Next, the cured coating was peeled off from the copper foil, and the peeled cured coating was cut into rings with an outer diameter of 1.7 cm and an inner diameter of 0.5 cm to make evaluation test pieces.

[0113] The relative permeability (μ') of each evaluation test piece obtained as described above was measured at 25°C and 100MHz using a Keysight E4291B impedance analyzer. The measurement results are shown in Table 1 below.

[0114] <Evaluation of the stability of magnetic properties over time>

[0115] To reproduce the actual coating formation process, 50g of each prepared curable resin composition was temporarily placed in a Hi-Resist BHR-150 container, which is an open system. After standing at 25°C for 20 minutes, the same as above, the coating was applied to the copper foil surface attached to the etched plate without adjusting the viscosity, and then cured to form a cured coating.

[0116] Next, the cured coating was peeled off from the copper foil, and the peeled cured coating was cut into rings with an outer diameter of 1.7 cm and an inner diameter of 0.5 cm to prepare evaluation test pieces. The relative permeability was measured in the same manner as above. The evaluation criteria for the time-dependent stability of the magnetic properties are as follows.

[0117] 〇: The relative permeability did not decrease compared to the value measured in <Evaluation of Magnetic Properties>.

[0118] ×: The relative permeability is lower than the value measured in the <Evaluation of Magnetic Properties>.

[0119] The evaluation results are shown in Table 1 below. It should be noted that "-" in the table indicates that a cured coating could not be formed and the relative magnetic permeability could not be measured.

[0120] Table 1

[0121]

[0122] According to the evaluation results in Table 1, the curable resin compositions (Examples 1-6) of the present invention exhibit excellent stability of printability over time, and also excellent stability of relative magnetic permeability over time. Furthermore, compared to Comparative Example 2 without diluent components, the relative magnetic permeability is improved, resulting in superior magnetic properties.

[0123] On the other hand, it is known that for a curable resin composition (Comparative Example 1) containing a diluent component with a 5% weight reduction temperature of less than 50°C based on thermogravimetric analysis, when the composition is placed, some components in the composition also volatilize at room temperature, resulting in insufficient time-dependent stability of printability.

[0124] In addition, it is known that the curable resin composition without diluent (Comparative Example 2) has poor printability and a lower relative magnetic permeability compared to others.

[0125] <Evaluation of fillability>

[0126] The curable resin compositions used in Examples 1 to 6 were filled into the through-holes (inner diameter of 0.3 mm and depth of 3.2 mm) of a multilayer printed wiring substrate by screen printing. The substrate was placed upright against a support at an angle of 90° ± 10° relative to the mounting surface, and then cured by heat treatment at 150° for 30 minutes in a hot air circulating drying oven (manufactured by Daiwa Scientific Corporation DF610).

[0127] Next, using a substrate with the through holes filled with a cured material, the cross-section of the through holes after filling was observed by optical microscopy and electron microscopy to confirm whether cracks were generated and whether there was delamination (peeling).

[0128] As a result, no cracking or delamination (peeling) was observed when filling pores using the curable resin composition of any embodiment.

Claims

1. A curable resin composition comprising a thermosetting resin, a curing agent, magnetic powder, and a diluent, characterized in that, The thermosetting resin has a 5% weight loss temperature based on thermogravimetric analysis of greater than 180°C. The 5% weight reduction temperature of the diluted component, based on thermogravimetric analysis, is above 50°C and below 180°C. The diluent is an alicyclic epoxy resin or an organic solvent.

2. The curable resin composition of claim 1, wherein, The curing resin composition contains less than 30% by mass of the diluent relative to the total amount of the thermosetting resin and the diluent.

3. The curable resin composition according to claim 1, wherein, The thermosetting resin is in liquid form.

4. The curable resin composition of claim 1, wherein, The thermosetting resin includes an epoxy resin with a viscosity of less than 1 Pa·s.

5. The curable resin composition of claim 4, wherein, The epoxy resin comprises 35% by mass or more relative to the total amount of the thermosetting resin.

6. The curable resin composition of claim 1, wherein, The curable resin composition is used as a filler for through holes or recesses in a printed wiring board.

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