Thermosetting resin composition, cured product, and printed wiring board

Abstract

This thermosetting resin composition contains (A) a cyanate ester compound, (B) a phenolic resin, (C) another curable resin as an optional component, (D) a metal catalyst, and (E) another curing catalyst as an optional component. If the total amount of the component (A), the component (B), and the component (C) is taken as 100 parts by mass, the amount of the component (A) is 80-99 parts by mass, the amount of the component (B) is 1-15 parts by mass, and the amount of the component (C) is 0-10 parts by mass. The amount of the component (E) is 1 part by mass or less relative to a total of 100 parts by mass of the component (A), the component (B), and the component (C).

Description

Thermosetting resin composition, cured product, and printed wiring board

[0001] The present invention relates to a thermosetting resin composition, and a cured product and a printed wiring board obtained using the same.

[0002] In recent years, communication devices using printed wiring boards have become much faster. To achieve low-loss and low-latency communication, it is desirable to use materials for printed wiring boards with low dielectric constants and low dielectric loss tangents.

[0003] Under these circumstances, a lower dielectric constant and a lower dielectric loss tangent are also desired for hole-filling compositions and step-filling compositions for printed wiring boards. Here, the hole-filling composition is a resin composition used to fill through-holes or bottomed via structures in printed wiring boards. The step-filling composition is a resin composition used to fill steps that occur on the surface of a printed wiring board or on the surface of each layer during the manufacturing process. Hereinafter, the dielectric constant and the dielectric loss tangent are referred to as "dielectric properties," and a decrease in these values ​​is referred to as "improved dielectric properties," and low values ​​are referred to as "good dielectric properties."

[0004] Generally, compositions based on epoxy resins are known as hole-filling compositions. Although attempts have been made to improve the dielectric properties of compositions based on epoxy resins, further improvements in the dielectric properties are required.

[0005] On the other hand, cyanate ester compounds are known to produce cured products with good dielectric properties and are used as inner layer materials and insulating materials, but when used as materials for filling holes in printed wiring boards, the filling properties of cyanate ester compounds alone are considered to be poor.

[0006] In recent years, thermosetting resin fillers with high heat resistance have been developed by adding a cyanate ester compound to an epoxy resin (see Patent Documents 1 and 2). When a cyanate ester compound is added to an epoxy resin, the heat resistance is improved. However, according to the inventors' investigations, the dielectric properties of the epoxy resin are similar to those of the epoxy resin, leaving room for improvement. In addition, it has been confirmed that when a cured product of a combination of an epoxy resin and a cyanate ester compound is heated to 300°C or higher, voids form within the cured product, causing volume expansion.

[0007] International Publication No. 2016 / 117237 Japanese Patent Application Laid-Open No. 2013-216865

[0008] The present invention has been made in view of the above, and an object of the present invention is to provide a thermosetting resin composition that has excellent filling properties into through-holes and bottomed via structures of printed wiring boards, steps on the surface of substrates, etc., and that produces a cured product having excellent dielectric properties and heat resistance.

[0009] Patent Document 1 describes a thermosetting resin composition containing a bisphenol E epoxy resin, a curing agent or curing accelerator, and a filler, in which a phenolic resin and a cyanate ester resin are used as curing agents, and a metal catalyst is used as a curing accelerator. However, Patent Document 1 describes a high ratio of epoxy resin and does not describe the combined use of a cyanate ester resin, a phenolic resin, and a metal catalyst. Furthermore, Patent Document 2 describes the combined use of an epoxy resin, a cyanate compound, and a metal curing accelerator, but does not describe the combined use of a cyanate ester compound, a phenolic resin, and a metal catalyst.

[0010] The present invention includes the following embodiments. [1] A thermosetting resin composition comprising (A) a cyanate ester compound, (B) a phenolic resin, (C) an optional curable resin other than component (A) and component (B), (D) a metal catalyst, and (E) an optional curing catalyst other than component (D), wherein, based on 100 parts by mass of the total of components (A), (B), and (C), the amount of component (A) is 80 to 99 parts by mass, the amount of component (B) is 1 to 15 parts by mass, and the amount of component (C) is 0 to 10 parts by mass, and the amount of component (E) is 1 part by mass or less per 100 parts by mass of the total of components (A), (B), and (C). [2] The thermosetting resin composition according to [1], wherein component (A) comprises a cyanate ester compound that is liquid at room temperature. [3] The thermosetting resin composition according to [1] or [2], further comprising (F) a filler. [4] The thermosetting resin composition according to any one of [1] to [3], wherein the amount of the (D) component is 0.001 to 1 part by mass per 100 parts by mass of the total amount of the (A), (B), and (C) components. [5] The thermosetting resin composition according to any one of [1] to [4], which is a composition for filling holes in printed wiring boards. [6] The thermosetting resin composition according to any one of [1] to [4], which is a composition for filling gaps in printed wiring boards. [7] A cured product obtained by curing the thermosetting resin composition according to any one of [1] to [6]. [8] A printed wiring board comprising the cured product according to [7].

[0011] The thermosetting resin composition according to the present invention has good filling properties for holes and steps in printed wiring boards, and also gives a cured product having excellent heat resistance and dielectric properties, making it possible to provide a printed wiring board having excellent heat resistance and dielectric properties.

[0012] Hereinafter, the embodiments of the present invention will be described in more detail.

[0013] The thermosetting resin composition according to the present embodiment includes (A) a cyanate ester compound, (B) a phenolic resin, (C) another curable resin as an optional component, (D) a metal catalyst, and (E) a curing catalyst other than the component (D) as an optional component.

[0014] [(A) Cyanate Ester Compound] The cyanate ester compound as component (A) is a compound having a cyanate group (—OCN). As the cyanate ester compound, a compound having two or more cyanate groups per molecule is preferably used. Specific examples include those obtained by reacting a cyanogen halide with a bisphenol or a phenolic resin such as phenol novolac.

[0015] Specific examples of cyanate ester compounds include bifunctional cyanate ester compounds such as bis(4-cyanatophenyl)methane (i.e., bisphenol F dicyanate), bis(4-cyanatophenyl)ethane (i.e., bisphenol E dicyanate), and 2,2-bis(4-cyanatophenyl)propane (i.e., bisphenol A dicyanate), as well as prepolymers obtained by prepolymerizing these compounds as monomers. Other examples include polyfunctional cyanate resins obtained by reacting a phenolic resin with a cyanogen halide, such as alkylphenol novolac cyanate ester resins, such as phenol novolac cyanate ester resins and cresol novolac cyanate ester resins, and dicyclopentadiene cyanate ester resins. These compounds may be used alone or in combination of two or more.

[0016] Examples of commercially available cyanate ester compounds include bisphenol A dicyanate "Cytester TA" manufactured by Mitsubishi Gas Chemical Co., Inc., and bisphenol E dicyanate "Cytester P-201" manufactured by Mitsubishi Gas Chemical Co., Inc., and examples of prepolymers include "TA-100," "TA-1000," and "TA-1500" manufactured by Mitsubishi Gas Chemical Co., Inc.

[0017] The thermosetting resin composition contains a cyanate ester compound (A) as a curable resin as a main component. Therefore, in order to make the thermosetting resin composition liquid at room temperature, it is preferable to include a cyanate ester compound that is liquid at room temperature. That is, the component (A) preferably contains a cyanate ester compound that is liquid at room temperature. The component (A) may contain a cyanate ester compound that is liquid at room temperature in combination with a cyanate ester compound that is solid at room temperature. For example, out of 100% by mass of the component (A), the cyanate ester compound that is liquid at room temperature preferably accounts for 50% by mass or more, more preferably 60% by mass or more, more preferably 75% by mass or more, and even more preferably 90% by mass or more. When a cyanate ester compound that is solid at room temperature is used, crystals of the solid cyanate ester compound may precipitate during long-term storage, impairing storage stability. Therefore, it is preferable that the component (A) consists solely of a cyanate ester compound that is liquid at room temperature.

[0018] In this specification, "liquid at room temperature" means that the substance has fluidity in a solvent-free state at 25°C. "Solid at room temperature" means that the substance does not have fluidity in a solvent-free state at 25°C. The presence or absence of fluidity can be determined by conducting an experiment in accordance with the liquid state confirmation method described in Appendix 2 of Fire and Disaster Management Agency's ...

[0019] The amount of component (A) contained in the thermosetting resin composition is 80 to 99 parts by mass, preferably 82 to 97 parts by mass, and more preferably 85 to 95 parts by mass, based on 100 parts by mass of the total amount of components (A), (B), and (C) that are curable resins. By ensuring that the amount of cyanate ester compound (A) is 80 parts by mass or more per 100 parts by mass of the total amount of curable resins, deterioration in heat resistance and dielectric properties can be suppressed.

[0020] [(B) Phenolic Resin] The phenolic resin as component (B) is a compound having one or more phenolic hydroxyl groups per molecule, and is obtained by polymerizing phenols and aldehydes. Examples of phenolic resins include phenol novolac resin, alkylphenol novolac resin, trisphenolmethane resin, dicyclopentadiene-type phenolic resin, naphthol resin, phenol naphthol resin, and cresol naphthol resin. These may be used alone or in combination of two or more.

[0021] The phenolic resin of component (B) may be a copolymer of the above phenolic resin with another resin, such as a rosin phenolic resin, a terpene phenolic resin, or a camphene phenolic resin.

[0022] Examples of commercially available phenolic resins include "MEH-7000" manufactured by UBE Corporation (formerly Meiwa Kasei Co., Ltd.), which is a phenolic resin that is solid at room temperature. Also, "MEH-8000H" manufactured by UBE Corporation (formerly Meiwa Kasei Co., Ltd.), which is a phenolic resin that is liquid at room temperature, is an example. Furthermore, examples of copolymers with other resins include "YS Resin CP" and "YS Polystar K125" manufactured by Yasuhara Chemical Co., Ltd.

[0023] As with the above-mentioned component (A), the component (B) is preferably liquid at room temperature. That is, the component (B) preferably contains a phenolic resin that is liquid at room temperature. For example, of 100% by mass of the component (B), the phenolic resin that is liquid at room temperature is preferably 50% by mass or more, more preferably 60% by mass or more, more preferably 75% by mass or more, and even more preferably 90% by mass or more, and may even be 100% by mass.

[0024] The amount of component (B) contained in the thermosetting resin composition is 1 to 15 parts by mass, preferably 2.5 to 12 parts by mass, and more preferably 5 to 10 parts by mass, based on 100 parts by mass of the total amount of components (A), (B), and (C) that are curable resins. By keeping the amount of phenolic resin (B) 15 parts by mass or less per 100 parts by mass of the total amount of curable resin, it is possible to suppress volume changes before and after curing and the generation of voids during curing.

[0025] [(C) Other Curable Resins] The thermosetting resin composition according to this embodiment may or may not contain a curable resin other than the components (A) and (B) as an optional component. Examples of such (C) other curable resins include epoxy resins, benzoxazine resins, and oxetane compounds. These may be used alone or in combination of two or more.

[0026] Specific examples of epoxy resins include phenolic epoxy resins such as bisphenol A type epoxy resin, bisphenol E type epoxy resin, bisphenol S type epoxy resin, bisphenol F type epoxy resin, phenol novolac type epoxy resin, and cresol novolac type epoxy resin; and amine type epoxy resins such as tetraglycidylaminodiphenylmethane, tetraglycidylmeta-xylylenediamine, triglycidylmeta-aminophenol, triglycidylpara-aminophenol, diglycidylaniline, and diglycidylorthotoluidine.

[0027] Specific examples of benzoxazine resins include Fa-type benzoxazine resins such as bisphenol A-type benzoxazine compounds and bisphenol F-type benzoxazine compounds, and Pd-type benzoxazine resins such as diaminodiphenylmethane-type benzoxazine compounds.

[0028] The oxetane compound is not particularly limited as long as it has one or more oxetane rings, and examples thereof include 3-ethyl-3-hydroxymethyloxetane, 3-ethyl-3-(phenoxymethyl)oxetane, 1,4-bis{[(3-ethyl-3-oxetanyl)methoxy]methyl}benzene, bis(3-ethyl-3-oxetanylmethyl)ether, etc. Commercially available products may also be used as such compounds, and examples thereof include "Aron Oxetane (registered trademark) OXT-121" and "Aron Oxetane (registered trademark) OXT-221" manufactured by Toagosei Co., Ltd.

[0029] The amount of component (C) contained in the thermosetting resin composition is 0 to 10 parts by mass, preferably 0 to 8 parts by mass, and more preferably 0 to 5 parts by mass, based on 100 parts by mass of the total amount of components (A), (B), and (C) that are curable resins. By keeping the amount of other curable resin (C) 10 parts by mass or less per 100 parts by mass of the total amount of curable resins, it is possible to suppress a decrease in heat resistance and / or dielectric properties.

[0030] [(D) Metal Catalyst] The metal catalyst as component (D) is a curing catalyst that promotes the thermosetting reaction of the thermosetting resin composition. Examples of the metal catalyst include organometallic complexes and / or organometallic salts, such as organometallic complexes and / or organometallic salts of metals such as cobalt, copper, zinc, iron, nickel, manganese, and tin.

[0031] Specific examples of organometallic complexes (i.e., metal complex catalysts) include organic cobalt complexes such as bis(2,4-pentanedionato)cobalt, tris(2,4-pentanedionato)cobalt, and phthalocyanine cobalt; organic copper complexes such as bis(2,4-pentanedionato)copper and phthalocyanine copper; organic zinc complexes such as bis(2,4-pentanedionato)zinc and phthalocyanine zinc; organic iron complexes such as tris(2,4-pentanedionato)iron and phthalocyanine iron; organic nickel complexes such as nickel(II) acetylacetonate and phthalocyanine nickel; and organic manganese complexes such as manganese(II) acetylacetonate and phthalocyanine manganese. These may be used alone or in combination of two or more.

[0032] Specific examples of the organic metal salt include zinc 2-ethylhexanoate, tin 2-ethylhexanoate, zinc naphthenate, cobalt naphthenate, tin stearate, zinc stearate, etc. Any of these may be used alone or in combination of two or more.

[0033] In a preferred embodiment, the metal catalyst is preferably a metal complex catalyst, more preferably an organocobalt complex and / or an organocopper complex. For example, the metal catalyst is preferably at least one selected from the group consisting of bis(2,4-pentanedionato)cobalt, tris(2,4-pentanedionato)cobalt, phthalocyanine cobalt, bis(2,4-pentanedionato)copper, and phthalocyanine copper.

[0034] The amount of component (D) contained in the thermosetting resin composition is not particularly limited, but is preferably 0.001 to 1 part by mass, more preferably 0.005 to 0.7 parts by mass, even more preferably 0.007 to 0.5 parts by mass, and may be 0.01 to 0.25 parts by mass, per 100 parts by mass of the total amount of components (A), (B), and (C). Adding a metal catalyst within these ranges can reduce the curing temperature of the thermosetting resin composition. Note that metal catalysts vary in their degree of curing and equivalent weight per mass. Therefore, while it is possible to add the component outside the above range, it is preferable to use the component within the above range from the viewpoint of storage stability.

[0035] [(E) Curing catalyst other than the component (D)] The thermosetting resin composition according to the present embodiment may or may not contain a curing catalyst other than the component (D) as an optional component. The other curing catalyst (D) is not particularly limited, but examples thereof include imidazole-based curing catalysts and amine-based curing catalysts.

[0036] The imidazole curing catalyst is not particularly limited, and examples thereof include 2-methylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine, etc. Any of these may be used alone, or two or more may be used in combination.

[0037] The amine curing catalyst is not particularly limited, and examples thereof include trialkylamines such as triethylamine and tributylamine, amine compounds such as 4-dimethylaminopyridine, benzyldimethylamine, 2,4,6-tris(dimethylaminomethyl)phenol and 1,8-diazabicyclo(5,4,0)-undecene (abbreviation: DBU), amine adduct compounds, etc. These may be used alone or in combination of two or more.

[0038] The amount of component (E) contained in the thermosetting resin composition is 1 part by mass or less (i.e., 0 to 1 part by mass) per 100 parts by mass of the total amount of components (A), (B), and (C). This prevents deterioration of filling ability and heat resistance. The amount of component (E) is preferably 0 to 0.7 parts by mass, more preferably 0 to 0.5 parts by mass, and even more preferably 0 to 0.2 parts by mass.

[0039] [Filler (F)] The thermosetting resin composition according to this embodiment may further contain a filler (F). By blending a filler, it is possible to improve the curing properties. The filler is not particularly limited, and may be a commonly known inorganic filler or an organic filler. From the viewpoint of heat resistance, an inorganic filler is desirable, but an organic filler may also be used in consideration of the elastic modulus of the cured product and the use temperature. Furthermore, an inorganic filler and an organic filler may also be used in combination.

[0040] Specific examples of inorganic fillers include silica, titanium oxide, kaolin clay, talc, calcium carbonate, copper, boron nitride, and aluminum nitride. These may be used alone or in combination of two or more.

[0041] As the organic filler, various resin fillers can be used, for example, polymer particles such as polymethyl methacrylate particles, polyurethane particles, and PEEK (polyether ether ketone) particles. These may be used alone or in combination of two or more.

[0042] The shape of the filler is not particularly limited, and examples thereof include spherical, needle-like, plate-like, scale-like, hollow, irregular, hexagonal, cubic, and flaky shapes.

[0043] The amount of component (F) contained in the thermosetting resin composition is not particularly limited, and is preferably 10 to 300 parts by mass, more preferably 20 to 200 parts by mass, and even more preferably 30 to 100 parts by mass, per 100 parts by mass of the total amount of components (A), (B), and (C).

[0044] [(G) Other Components] In addition to the components (A) to (F), the thermosetting resin composition according to this embodiment may contain additives such as solvents, dispersants, thickeners, anti-settling agents, antifoaming agents, flame retardants, adhesion promoters, and colorants, as needed.

[0045] The solvent may be a volatile substance that does not affect the curing reaction and hardly remains in the cured product. Specific examples of the solvent include butyl carbitol, butyl carbitol acetate, butyl triglycol, and butyl cellosolve. These may be used alone or in combination of two or more.

[0046] The amount of solvent contained in the thermosetting resin composition is not particularly limited. For example, in the case of applications for filling gaps in printed wiring boards, the amount is preferably 0 to 10 parts by mass, more preferably 0 to 5 parts by mass, per 100 parts by mass of the total amount of components (A), (B), and (C). In the case of applications for filling holes in printed wiring boards, it is preferable not to include a solvent, but depending on the thickness of the board to be filled, 0 to 5 parts by mass of the solvent may be included per 100 parts by mass of the total amount of components (A), (B), and (C).

[0047] The thermosetting resin composition according to this embodiment is preferably liquid at room temperature, since it is suitably used for applications such as filling recesses and through holes in printed wiring boards.

[0048] The thermosetting resin composition according to this embodiment is suitable for use in the production of a printed wiring board (preferably a multilayer printed wiring board). Specifically, the thermosetting resin composition is suitable for use as a hole-filling composition or a step-filling composition in a printed wiring board.

[0049] When used as a hole-filling composition for printed wiring boards, the thermosetting resin composition is used to fill through-holes or holes with bottomed via structures in printed wiring boards. The filling method in this case is not particularly limited, and can be performed by any known method. For example, the thermosetting resin composition can be filled into holes such as via holes or through-holes in printed wiring boards using screen printing, roll coating, die coating, etc. Next, the substrate is preferably preheated. For example, the substrate is heated at a temperature of 100°C or less for 15 to 90 minutes. The thermosetting resin composition is then cured, for example, by heating at about 120 to 200°C for about 30 to 100 minutes. Next, unnecessary portions of the cured thermosetting resin composition that protrude from the substrate surface can be removed by physical polishing to obtain a flat surface.

[0050] When used as a step-filling composition for printed wiring boards, the thermosetting resin composition is used to fill steps on the surface of a printed wiring board or on the surface of each layer during the manufacturing process of a multilayer printed wiring board. Examples of steps include grooves between copper wiring formed by wiring formation by etching. In this case, the step-filling composition is also referred to as a groove-filling composition. The method for filling the steps in this case is not particularly limited, and can be performed by any known method. For example, the thermosetting resin composition can be filled into the steps on the surface of a printed wiring board using a screen printing method, a roll coating method, a die coating method, or the like. Next, the substrate is preferably preheated. For example, the substrate is heated at a temperature of 100°C or less for 15 to 90 minutes. The thermosetting resin composition is then cured, for example, by heating at about 120 to 200°C for about 30 to 100 minutes. The surface may then be physically polished to remove any unnecessary cured material remaining on the copper wiring, resulting in a flat surface.

[0051] The cured product according to this embodiment is obtained by curing the thermosetting resin composition. The printed wiring board according to this embodiment includes the cured product. Preferably, the printed wiring board includes the cured product obtained by using the thermosetting resin composition as a hole-filling composition to fill through holes and / or via holes. Alternatively, the printed wiring board preferably includes the cured product obtained by using the thermosetting resin composition as a step-filling composition to fill steps on the substrate surface.

[0052] Examples of the present invention will be described below, but the present invention is not limited to these examples.

[0053] Each component was mixed according to the formulation (parts by mass) shown in Tables 1 and 2 below to prepare a thermosetting resin composition that was liquid at room temperature. Details of each component are as follows.

[0054] [Component (A)] Cyanate ester 1: a prepolymer prepolymerized using bisphenol A dicyanate as a monomer, liquid at room temperature, "Cytester TA-100" manufactured by Mitsubishi Gas Chemical Co., Ltd. Cyanate ester 2: bisphenol E dicyanate, liquid at room temperature, "Cytester P-201" manufactured by Mitsubishi Gas Chemical Co., Ltd. Cyanate ester 3: bisphenol A dicyanate, solid at room temperature, "Cytester TA" manufactured by Mitsubishi Gas Chemical Co., Ltd.

[0055] [Component (B)] Phenolic resin 1: Liquid at room temperature, "MEH-8000H" manufactured by UBE Corporation Phenolic resin 2: Solid at room temperature, "MEH-7000" manufactured by UBE Corporation

[0056] [Component (C)] Epoxy resin 1: Liquid at room temperature, "jER630" manufactured by Mitsubishi Chemical Corporation Oxetane compound 1: Liquid at room temperature, "Aron Oxetane OXT-121" manufactured by Toagosei Co., Ltd.

[0057] [(D) Component] ・Co(acac) ３ : Tris(2,4-pentanedionato)cobalt Co phthalocyanine: Cobalt phthalocyanine Cu phthalocyanine: Copper phthalocyanine

[0058] [Component (E)] 2MZA: imidazole curing catalyst, "2MZA" manufactured by Shikoku Chemicals Corporation PN-H: amine adduct curing catalyst, "Amicure PN-H" manufactured by Ajinomoto Fine-Techno Co., Ltd.

[0059] [Component (F)] Silica: "SD-5SDC" manufactured by Denka Co., Ltd.

[0060] The resulting thermosetting resin composition was evaluated for filling ability, heat resistance, and dielectric properties, and the results are shown in Tables 1 and 2. The evaluation methods were as follows.

[0061] [Filling] A glass epoxy laminate was prepared as a fillability evaluation substrate by forming 30 grooves, each 30 mm long, 0.4 mm wide, and 0.4 mm deep, spaced 0.4 mm apart. A thermosetting resin composition was filled into the fillability evaluation substrate. A metal squeegee was used to fill the grooves until the substrate surface was smooth. The filled substrate was then heated at 80°C for 30 minutes in a hot air oven, and then further heated at 180°C for 1 hour in a hot air oven to cure the composition, producing a fillability evaluation sample. The appearance and cross-section of each groove in the fillability evaluation sample were observed using an optical microscope to observe any abnormalities in each groove. The fillability was evaluated according to the following evaluation criteria. An abnormality refers to an abnormal condition such as voids, bulging of the top surface, surface irregularities, or resin bleeding. A: 30 out of 30 grooves were free of abnormalities. B: 27 to 29 out of 30 grooves were free of abnormalities. C: 26 or less grooves out of 30 were normal.

[0062] [Preparation of Bulk Body] A silicone resin mold having a groove 135 mm long, 13 mm wide, and 2 mm deep was prepared. The groove of this mold was filled with a thermosetting resin composition. The composition was then heated in a hot air drying oven at 80°C for 30 minutes, and then further heated in a hot air drying oven at 180°C for 1 hour to harden the composition, yielding a bulk body as a cured product.

[0063] [Heat Resistance] The bulk body was cut and polished to a length of 35 mm, width of 5 mm, and thickness of 1.5 mm to prepare a sample for evaluating heat resistance. The sample for evaluating heat resistance was heated at 300°C for 1 hour using a muffle furnace. After heating, it was allowed to cool to room temperature, and the appearance was visually observed. Subsequently, a cross-section was observed using an optical microscope. From the results of the visual observation and cross-section observation, the heat resistance was evaluated according to the following evaluation criteria. A: No distortion or deformation was observed by visual observation, and no abnormalities were observed by cross-section observation. B: No distortion or deformation was observed by visual observation, but minute voids were observed by cross-section observation. C: Distortion or deformation was observed by visual observation.

[0064] [Dielectric Properties] The bulk body was cut and polished to a length of 100 mm, width of 1.5 mm, and thickness of 1.5 mm, and then heated in a muffle furnace at 250°C for 1 hour to prepare a sample for measuring dielectric properties. The dielectric constant and dielectric loss tangent at a frequency of 1 GHz were measured for the sample for measuring dielectric properties by a cavity resonator method. Using the measured dielectric constant and dielectric loss tangent, an evaluation value was calculated according to the following formula (1), and the dielectric properties were evaluated according to the following evaluation criteria. Formula (1): (Evaluation value) = (Dielectric loss tangent) × √(Dielectric constant) A: Evaluation value is 0.015 or less B: Evaluation value is greater than 0.015 and less than 0.02 C: Evaluation value is greater than 0.02

[0065]

[0066]

[0067] As shown in Table 1, each example had excellent filling rate, heat resistance, and dielectric properties. In contrast, as shown in Table 2, Comparative Example 1, which contained an epoxy resin (C) as the main component, had poor dielectric properties. Comparative Example 2 was an example in which a cyanate ester compound (A), a phenolic resin (B), and a metal catalyst (D) were used in combination. However, Comparative Example 2 had a low content of the cyanate ester compound and a high content of the epoxy resin (C), resulting in poor filling and heat resistance. Comparative Example 3 was an example in which a cyanate ester compound (A), a phenolic resin (B), and a metal catalyst (D) were used in combination. However, Comparative Example 3 had a high content of the oxetane compound (C), resulting in poor filling and heat resistance.

[0068] Comparative Example 4 is an example in which the content of the phenolic resin (B) exceeded the upper limit, resulting in poor filling properties. Comparative Example 5 is an example in which an imidazole-based curing catalyst (E) was used instead of the metal catalyst (D), resulting in poor heat resistance. Comparative Example 6 is an example in which a metal catalyst (D) was used, but the content of the imidazole-based curing catalyst (E) exceeded the upper limit, resulting in poor heat resistance. Comparative Example 7 is an example in which an amine-based curing catalyst (E) was used instead of the metal catalyst (D), resulting in poor filling properties.

[0069] The various numerical ranges described in this specification can be arbitrarily combined with their respective upper and lower limit values, and all such combinations are considered to be preferred numerical ranges described in this specification. Furthermore, a numerical range described as "X to Y" means from X to Y.

Claims

1. A thermosetting resin composition comprising: (A) a cyanate ester compound; (B) a phenolic resin; (C) an optional curable resin other than the components (A) and (B); (D) a metal catalyst; and (E) an optional curing catalyst other than the component (D), wherein, relative to a total amount of the components (A), (B), and (C) being 100 parts by mass, the amount of the component (A) is 80 to 99 parts by mass, the amount of the component (B) is 1 to 15 parts by mass, and the amount of the component (C) is 0 to 10 parts by mass, and the amount of the component (E) is 1 part by mass or less relative to a total amount of 100 parts by mass of the components (A), (B), and (C).

2. The thermosetting resin composition according to claim 1, wherein the component (A) contains a cyanate ester compound that is liquid at room temperature.

3. The thermosetting resin composition according to claim 1 or 2, further comprising (F) a filler.

4. A thermosetting resin composition according to any one of claims 1 to 3, wherein the amount of the (D) component is 0.001 to 1 part by mass per 100 parts by mass of the total amount of the (A) component, the (B) component, and the (C) component.

5. The thermosetting resin composition according to any one of claims 1 to 4, which is a composition for filling holes in printed wiring boards.

6. The thermosetting resin composition according to any one of claims 1 to 4, which is a composition for filling gaps in printed wiring boards.

7. A cured product obtained by curing the thermosetting resin composition according to any one of claims 1 to 6.

8. A printed wiring board comprising the cured product according to claim 7.

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