Curable resin composition, cured product, and printed wiring board

Abstract

[Problem] To provide a curable resin composition from which a cured product having excellent insulation reliability can be formed and which has a suppressed amount of emission of halogen-containing substances during combustion. [Solution] This curable resin composition comprises an epoxy resin, an epoxy resin curing agent, and a filler, wherein a filler containing at least one selected from the group consisting of magnesium carbonate, magnesium oxide, hydrotalcite, and aluminum hydroxide is used as the filler.

Description

[Technical Field]

[0001] The present invention relates to a curable resin composition, particularly a curable resin composition suitable for use in filling holes in printed wiring boards or filling gaps between circuits to achieve smoothing. The present invention also relates to a cured product of the curable resin composition and a printed wiring board comprising the cured product, particularly a printed wiring board smoothed by the cured product. [Background technology]

[0002] With the recent trend toward miniaturization and high performance of electronic devices, there is an increasing need for finer patterns on printed wiring boards, smaller mounting areas, and higher density component mounting. Therefore, multilayer printed wiring boards are being used, such as double-sided boards with through-holes (i.e., through holes) that form interlayer connections for electrically connecting different wiring layers, and build-up wiring boards in which insulating layers and conductor circuits are sequentially formed on a core substrate and then interconnected by via holes or the like. In such printed wiring boards, gaps (recesses) between conductor circuits on the surface and holes such as through holes and via holes with wiring layers formed on the inner wall surfaces are typically filled with a curable resin filler to smooth them (e.g., Patent Documents 1 to 3). The curable resin filler typically comprises a thermosetting resin composition containing an epoxy resin as a curable resin component, an epoxy resin curing agent, and an inorganic filler (e.g., Patent Document 4).

[0003] In the manufacture of electronic devices, halogen-containing compounds, including resin materials, are widely used. Because such halogen-containing compounds generate harmful gases when burned, various efforts, including legal restrictions, have been made to suppress the generation of harmful gases.

[0004] Epoxy resins, which are used as the main component of thermosetting resin compositions, generally contain a large amount of chlorine because epichlorohydrin, a raw material typically used in their synthesis, contains a large amount of chlorine. In the manufacture of electronic devices, epoxy resins are almost always used in a chlorine-containing state. Therefore, when a thermosetting resin filler containing such an epoxy resin is burned, harmful gases containing a large amount of chlorine are released, causing a significant environmental burden. To solve this problem, it has been considered to reduce the chlorine content by cleaning (purifying) the epoxy resin or by using an epoxy resin synthesized without using epichlorohydrin. However, these methods require significant time and economic costs, making them unrealistic.

[0005] In addition, brominated epoxy resins are sometimes used as thermosetting resin fillers. Furthermore, colorants, particularly pigments, used in thermosetting resin fillers may contain bromine. When such thermosetting resin fillers containing brominated epoxy resins or colorants containing bromine are burned, harmful gases containing bromine are released, which poses a significant environmental burden, similar to the above-mentioned thermosetting resin fillers containing chlorine-containing epoxy resins. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-15909 [Patent Document 2] Japanese Patent Application Laid-Open No. 2007-49106 [Patent Document 3] Japanese Patent Application Laid-Open No. 2004-75967 [Patent Document 4] Japanese Patent Application Laid-Open No. 2013-76002 Summary of the Invention [Problem to be solved by the invention]

[0007] Therefore, an object of the present invention is to provide a curable resin composition that suppresses the release of halogen-containing substances during combustion. Another object of the present invention is to provide a cured product obtained by curing the curable resin composition, and a printed wiring board including the cured product. [Means for solving the problem]

[0008] The present inventors have discovered that the amount of halogen-containing substances released during combustion can be reduced by using a specific component as a filler in a curable resin composition containing an epoxy resin, an epoxy resin curing agent, and a filler. The present invention is based on this discovery. Specifically, the gist of the present invention is as follows.

[0009] [1] Epoxy resin, an epoxy resin hardener, and Filler A curable resin composition comprising: the filler comprises at least one selected from the group consisting of magnesium carbonate, magnesium oxide, hydrotalcite, and aluminum hydroxide, A curable resin composition characterized in that the amount of halogen measured by a quartz tube combustion method is 100 to 1000 ppm. [2] The curable resin composition according to [1], wherein the total content of the filler is 50 to 300 parts by mass relative to 100 parts by mass of the epoxy resin. [3] The curable resin composition according to [1] or [2], wherein the total content of the magnesium carbonate, magnesium oxide, hydrotalcite, and aluminum hydroxide is 10 to 250 parts by mass per 100 parts by mass of the epoxy resin. [4] The curable resin composition according to any one of [1] to [3], wherein the total content of the magnesium carbonate, magnesium oxide, hydrotalcite, and aluminum hydroxide is 4 to 100 mass% relative to the total content of the filler. [5] The curable resin composition according to any one of [1] to [4], wherein the epoxy resin comprises an epoxy resin having a tertiary amine. [6] The curable resin composition according to any one of [1] to [5], wherein the content of the epoxy resin is 10 to 60 parts by mass per 100 parts by mass of the curable resin composition. [7] The curable resin composition according to any one of [1] to [6], which has a viscosity of 200 to 1000 dPa·s when rotated at 25°C and 5 rpm for 30 seconds. [8] The curable resin composition according to any one of [1] to [7], which is used to plug holes in a printed wiring board or fill gaps between circuits in a printed wiring board. [9] A cured product of the curable resin composition according to any one of [1] to [8].

[10] A printed wiring board comprising the cured product according to [9]. [Effects of the Invention]

[0010] According to the present invention, it is possible to realize a curable resin composition that suppresses the amount of halogen-containing substances released upon combustion. Furthermore, it is possible to realize a cured product that suppresses the amount of halogen-containing substances released upon combustion using the curable resin composition, and a printed wiring board including the cured product. DETAILED DESCRIPTION OF THE INVENTION

[0011] [Curable resin composition] The curable resin composition of the present invention contains an epoxy resin, an epoxy resin curing agent, and a filler as essential components. The curable resin composition of the present invention can be used to form a solder resist layer on a printed wiring board, as an interlayer insulating material, and as a hole-filling material, and is particularly suitable for use as a hole-filling material for filling holes such as through-holes and via holes on a printed wiring board, and gaps (recesses) between circuits, and as a filler for the gaps between circuits on a printed wiring board. The curable resin composition of the present invention can suppress the amount of halogen-containing substances released during combustion by using a specific component as a filler.

[0012] Conventionally, epoxy resins have mainly been synthesized using epichlorohydrin, and because epichlorohydrin contains chlorine atoms, the synthesized epoxy resin contains a large amount of chlorine derived from epichlorohydrin. Therefore, when such an epoxy resin is used in the production of a curable resin composition, a large amount of chlorine will inevitably be contained in the curable resin composition unless the epoxy resin is subjected to a treatment such as washing (purification) or the like.

[0013] In addition, in the production of a curable resin composition, a brominated epoxy resin or a component containing bromine may be used as the epoxy resin. In particular, colorants such as pigments often contain bromine. When such a brominated epoxy resin or a component containing bromine is used in the production of a curable resin composition, bromine will be contained in the curable resin composition.

[0014] Therefore, when a cured product of such a halogen-containing curable resin composition is burned, compounds containing the halogen, i.e., halogen-containing substances, are released as components of the gas generated by the combustion of the cured product. Many halogen-containing substances are harmful, including elemental halogens such as chlorine and bromine, hydrogen halides such as hydrogen chloride, and organic halogen compounds such as dioxins and brominated dioxins (brominated dioxins). Many of these halogen-containing substances are defined as harmful substances or pollutants under various environmental standards. Therefore, in curable resin compositions produced using the halogen-containing components described above, the large amounts of halogen-containing substances released when the curable resin composition is burned presents an inseparable problem.

[0015] The reason why the use of a specific component as a filler in a curable resin composition produced using a halogen-containing component reduces the amount of halogen-containing substances released during combustion of the cured product as described above is unclear, but can be inferred as follows. That is, it is believed that the specific filler used in the present invention retains liberable anions within the filler. Therefore, it is believed that the halogen in the halogen-containing component contained in the curable resin composition is liberated to become a halide ion, and the halide ion is exchanged or substituted with the anion retained in the filler, thereby forming a chemical or physical bond between the halogen and the filler (e.g., the metal species constituting the filler). This retains the halide ion in the filler, and as a result, it is believed that the amount of halogen-containing substances released during combustion of a cured product of the curable resin composition is reduced.

[0016] The curable resin composition of the present invention has a halogen content of 100 to 1,000 ppm, preferably 100 to 700 ppm, and more preferably 100 to 650 ppm, as measured by a quartz tube combustion method. In this specification, halogen refers to chlorine and bromine. Furthermore, in this specification, the terms "amount" and "content" refer to the total amount of chlorine and bromine, respectively. For example, "amount of halogen of 100 to 1,000 ppm" means that the total amount of chlorine and bromine is in the range of 100 to 1,000 ppm. While there are currently no regulations regarding "halogen-free" in environmental laws and regulations, for example, standards set by the Japan Electronics Packaging and Circuits Association (JPCA) and the International Electrotechnical Commission (IEC) allow copper-clad laminates used in electrical and electronic devices to be labeled "halogen-free" if the chlorine and bromine contents are each 900 ppm or less and the total chlorine and bromine content is 1,500 ppm or less. The curable resin composition of the present invention has a total halogen (chlorine and bromine) content of 1000 ppm or less as measured by the quartz tube combustion method. Therefore, if the chlorine and bromine contents are both 900 ppm or less, the composition can be used to produce "halogen-free" cured products and printed wiring boards. Therefore, it is preferable that the chlorine and bromine contents of the curable resin composition of the present invention are both 900 ppm or less. On the other hand, since the lower the halogen content in the curable resin composition, the greater the reactivity of the curable resin composition. Therefore, if the halogen content in the curable resin composition is too low, the viscosity of the curable resin composition tends to be excessively high, causing problems during use. Therefore, if the halogen content in the curable resin composition of the present invention is 100 ppm or more as measured by the quartz tube combustion method, such problems can be avoided.

[0017] The amount of halogen (chlorine and bromine) in a cured product of a curable resin composition using a quartz tube combustion method can be measured in accordance with IEC 62321-3-2, a standard established by the International Electrotechnical Commission (IEC). Specifically, the measurement can be performed according to the following procedure. First, 0.1 g of the curable resin composition to be measured is combusted using an automatic sample combustion device AQF-2100H manufactured by Nitto Seiko Analytech Co., Ltd., to collect the gas components. The collected gas components are then absorbed in an absorption liquid (hydrogen peroxide solution), and the chlorine and bromine contents of the resulting absorption liquid are quantified by ion chromatography using a Thermo Scientific Dionex ICS-1100 ion chromatograph system, a Thermo Scientific Dionex AERS 500 suppressor, and a Dionex IonPac AS12A column manufactured by Thermo Fisher Scientific.

[0018] Each component of the curable resin composition of the present invention will be described in detail below. (epoxy resin) The curable resin composition of the present invention contains an epoxy resin. Any known epoxy resin can be used as the epoxy resin. The epoxy resin may be monofunctional or polyfunctional.

[0019] Epoxy resins include epoxidized vegetable oils, bisphenol A epoxy resins, hydroquinone epoxy resins, bisphenol epoxy resins, thioether epoxy resins, brominated epoxy resins, novolac epoxy resins, phenol novolac epoxy resins, biphenol novolac epoxy resins, bisphenol F epoxy resins, hydrogenated bisphenol A epoxy resins, glycidylamine epoxy resins, hydantoin epoxy resins, alicyclic epoxy resins, trihydroxyphenylmethane epoxy resins, bixylenol or biphenol epoxy resins, or mixtures thereof. Examples of epoxy resins include, but are not limited to, epoxy resins such as epoxy resins of bisphenol S type, bisphenol A novolac type, tetraphenylolethane type, heterocyclic epoxy resins, diglycidyl phthalate resins, tetraglycidyl xylenoylethane resins, naphthalene group-containing epoxy resins, epoxy resins having a dicyclopentadiene skeleton, glycidyl methacrylate copolymer epoxy resins, cyclohexylmaleimide and glycidyl methacrylate copolymer epoxy resins, epoxy-modified polybutadiene rubber derivatives, CTBN-modified epoxy resins, and brominated epoxy resins. These epoxy resins may be used alone or in combination of two or more.

[0020] As the epoxy resin, preferably, an epoxy resin having a tertiary amine or an epoxy resin having a bisphenol skeleton is used. In this specification, an epoxy resin having a tertiary amine refers to an epoxy resin having two or more epoxy groups and one or more tertiary amine groups per molecule. These epoxy resins may be aliphatic or aromatic epoxy resins. From the viewpoints of heat resistance, electrical insulation, water absorption, and the like, aromatic epoxy resins are preferably used. Furthermore, these epoxy resins are used in a liquid state. In the present invention, "liquid" refers to a liquid state that is fluid at 20°C. When using the above-mentioned epoxy resins, particularly epoxy resins having a tertiary amine, the crosslink density increases when the curable resin composition is cured, resulting in sufficient curing and the production of a cured product with good heat resistance (high glass transition temperature Tg) and a linear expansion coefficient (low CTE). On the other hand, epoxy resins having a tertiary amine generally have a high chlorine content because many chlorine-containing raw materials are used in the synthesis process to impart functional groups to the molecule, which is problematic in terms of the increased amount of chlorine-containing substances released during combustion. In the present invention, by using a specific component as a filler, such problems can be solved while the above-mentioned advantages can be enjoyed, and therefore an epoxy resin having a tertiary amine is preferably used.

[0021] Examples of epoxy resins containing tertiary amines include N,N,N',N'-tetraglycidylaminodiphenylmethane, N,N,N',N'-tetraglycidyl-m-xylylenediamine, triglycidyl-p-aminophenol, N,N-diglycidylaniline, and N,N-diglycidyl-o-toluidine. Commercially available epoxy resins containing tertiary amines include jER (registered trademark) 630 (paraaminophenol-type epoxy resin) and jER (registered trademark) 604 (diaminodiphenylmethane-type epoxy) manufactured by Mitsubishi Chemical Corporation, ELM-100 (paraaminophenol-type epoxy resin) manufactured by Sumitomo Chemical Co., Ltd., GAN (diglycidylaniline) manufactured by Nippon Kayaku Co., Ltd., GOT (diglycidyl orthotoluidine) manufactured by Nippon Kayaku Co., Ltd., Sumiepoxy (registered trademark) ELM-434 manufactured by Sumitomo Chemical Co., Ltd., and TETRAD (registered trademark)-X manufactured by Mitsubishi Gas Chemical Company, Inc.

[0022] Examples of epoxy resins having a bisphenol skeleton include bisphenol A epoxy resins, bisphenol F epoxy resins, bisphenol E (AD) epoxy resins, and bisphenol S epoxy resins. From the viewpoints of the electrical insulation properties of the cured product of the curable resin composition and adhesion to conductive parts and insulating parts, bisphenol A epoxy resins, bisphenol F epoxy resins, and bisphenol E (AD) epoxy resins are preferably used. From the viewpoint of the filling properties of the curable resin composition, the epoxy resins having a bisphenol skeleton are preferably liquid. Note that the liquid state of the epoxy resins having a bisphenol skeleton is as described in the explanation of the epoxy resins having a tertiary amine. Commercially available epoxy resins having a bisphenol skeleton include, for example, jER (registered trademark) 828, jER (registered trademark) 834, and jER (registered trademark) 1001 (all bisphenol A-type epoxy resins), jER (registered trademark) 807, and jER (registered trademark) 4004P (all bisphenol F-type epoxy resins) manufactured by Mitsubishi Chemical Corporation, and R710 (bisphenol E-type epoxy resin) manufactured by Air Water Inc. One type of epoxy resin having a bisphenol skeleton may be used alone, or two or more types may be used in combination, but it is particularly preferred to use a combination of a bisphenol A-type epoxy resin and a bisphenol F-type epoxy resin.

[0023] The content of the epoxy resin in the curable resin composition is not particularly limited as long as the effects of the present invention are achieved, but it can be preferably 10 to 60 parts by mass, more preferably 25 to 50 parts by mass, calculated as solid content, per 100 parts by mass of the curable resin composition.

[0024] (epoxy resin hardener) The curable resin composition of the present invention contains an epoxy resin curing agent for curing the above-mentioned epoxy resin. As the epoxy resin curing agent, a known curing agent generally used for curing epoxy resins can be used. Examples of the epoxy resin curing agent include amines, imidazoles, polyfunctional phenols, acid anhydrides, isocyanates, and polymers containing these functional groups. The epoxy resin curing agent may be used alone or in combination of two or more.

[0025] Among the above-mentioned epoxy resin curing agents, amines and imidazoles are particularly preferred from the viewpoints of adhesion to conductive and insulating parts, storage stability, heat resistance, etc. Examples of amines include adduct compounds of aliphatic polyamines such as alkylenediamines having 2 to 6 carbon atoms, polyalkylenepolyamines having 2 to 6 carbon atoms, and aromatic ring-containing aliphatic polyamines having 8 to 15 carbon atoms, adduct compounds of alicyclic polyamines such as isophoronediamine and 1,3-bis(aminomethyl)cyclohexane, and those containing as the main component a mixture of the above-mentioned adduct compounds of the aliphatic polyamines and the above-mentioned adduct compounds of the alicyclic polyamines. In particular, curing agents containing as the main component an adduct compound of xylylenediamine or isophoronediamine are preferred.

[0026] The adduct compounds of the aliphatic polyamines are preferably those obtained by addition reaction of the aliphatic polyamines with aryl glycidyl ethers (particularly phenyl glycidyl ether or tolyl glycidyl ether) or alkyl glycidyl ethers, and the adduct compounds of the alicyclic polyamines are preferably those obtained by addition reaction of the alicyclic polyamines with n-butyl glycidyl ether, bisphenol A diglycidyl ether, or the like.

[0027] Examples of aliphatic polyamines include alkylenediamines having 2 to 6 carbon atoms, such as ethylenediamine and propylenediamine, polyalkylenepolyamines having 2 to 6 carbon atoms, such as diethylenetriamine and triethylenetriamine, and aromatic ring-containing aliphatic polyamines having 8 to 15 carbon atoms, such as xylylenediamine. Examples of commercially available modified aliphatic polyamines include FXE-1000, FXR-1020, Fujicure FXR-1030, Fujicure FXR-1080, and FXR-1090M2 manufactured by T&K TOKA Corporation, and Ankamine 2089K, Sanmaid P-117, Sanmaid X-4150, Ankamine 2422, Surwet R, Sanmaid TX-3000, and Sanmaid A-100 manufactured by Evonik Japan Co., Ltd.

[0028] Examples of alicyclic polyamines include isophoronediamine, 1,3-bis(aminomethyl)cyclohexane, bis(4-aminocyclohexyl)methane, norbornenediamine, 1,2-diaminocyclohexane, and laromine. Commercially available modified alicyclic polyamines include, for example, Ancamine 1618, Ancamine 2074, Ancamine 2596, Ancamine 2199, Sanmaid IM-544, Sanmaid I-544, Ancamine 2075, Ancamine 2280, Ancamine 1934, and Ancamine 2228, all manufactured by Evonik Japan Co., Ltd.; Daitoclar F-5197 and Daitoclar B-1616, all manufactured by Daito Sangyo Co., Ltd.; Fujicure FXD-821 and Fujicure 4233, all manufactured by T&K TOKA Corporation; jER (registered trademark) Cure 113, all manufactured by Mitsubishi Chemical Corporation; and Laromin C-260, all manufactured by BASF Japan Ltd.

[0029] Examples of imidazole compounds include 2-methylimidazole, 4-methyl-2-ethylimidazole, 2-phenylimidazole, 4-methyl-2-phenylimidazole, 1-benzyl-2-methylimidazole, 2-ethylimidazole, 2-isopropylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 1-cyanoethyl-2-undecylimidazole, etc. Commercially available imidazole compounds include imidazoles such as 2E4MZ, C11Z, C17Z, and 2PZ manufactured by Shikoku Chemical Industry Co., Ltd., imidazole AZINE compounds such as 2MZ-A and 2E4MZ-A, imidazole isocyanurates such as 2MZ-OK and 2PZ-OK, and imidazole hydroxymethyl compounds such as 2PHZ and 2P4MHZ. Furthermore, examples of commercially available imidazole-type latent curing agents include Cureduct P-0505 manufactured by Shikoku Chemicals Corporation.

[0030] The content of the epoxy resin curing agent in the curable resin composition is not particularly limited as long as the effects of the present invention are achieved, but it can be preferably 1 to 30 parts by mass, more preferably 4 to 20 parts by mass, per 100 parts by mass of the above-mentioned epoxy resin.

[0031] When imidazoles are used in combination with at least one of polyamines and imidazole-type latent curing agents, the content ratio of imidazoles to polyamines and imidazole-type latent curing agents is preferably 1:99 to 99:1 by mass, and more preferably 10:90 to 90:10.

[0032] (filler) The curable resin composition of the present invention contains a filler. The filler contains at least one selected from the group consisting of magnesium carbonate, magnesium oxide, hydrotalcite, and aluminum hydroxide. In the present invention, the term "hydrotalcite" is a concept that also encompasses so-called hydrotalcite-like compounds.

[0033] Hydrotalcite is a type of clay mineral that can be obtained naturally or artificially. It is a layered inorganic compound represented by the following general formula, which has a basic layer mainly composed of positively charged 1-X Al X (OH)2] X+ and an intermediate layer mainly composed of negatively charged [(CO3) X / 2 ·mH2O] X- : [Chemical formula] [In the formula, M 1 represents divalent metal cations such as Mg 2+ , Fe 2+ , Zn 2+ , Ca 2+ , Li 2+ , Ni 2+ , Co 2+ , Cu 2+ etc., M 2 represents trivalent metal cations such as Al 3+ , Fe 3+ , Mn 3+ etc., A n- represents n-valent anions such as CO3 2- , Cl - , NO 3- etc., X represents any number that satisfies 0 < X ≤ 0.33, m represents any number that satisfies 0 ≤ m.].

[0034] Specific examples of hydrotalcite include Indigirite Mg2Al2[(CO3)4(OH)2]·15H2O, Fe 2+ 4Al2[(OH) 12 CO3]·3H2O, Quintinite Mg4Al2(OH) 12 CO3·H2O, Manasseite Mg6Al2[(OH) 16 CO3]·4H2O, SjOegrenite Mg6Fe 3+ 2[(OH) 16 CO3]·4H2O, Zaccagnaite Zn4Al2(CO3)(OH)12 ·3H2O, Desautelsite Mg6Mn 3+ 2[(OH) 16 CO3]·4H2O, Hydrotalcite Mg6Al2[(OH) 16 CO3]·4H2O, Pyroaurite Mg6Fe 3+ 2[(OH) 16 CO3]·4H2O, Reevesite Ni6Fe 3+ 2[(OH) 16 CO3]·4H2O, Stichtite Mg6Cr2[(OH) 16 CO3]·4H2O, Takovite Ni6Al2[(OH) 16 Examples of commercially available hydrotalcites include Alcamizer (registered trademark), DHT-4A (registered trademark), Kyoward (registered trademark) 500, and Kyoward (registered trademark) 1000 manufactured by Kyowa Chemical Industry Co., Ltd., and HT-1, HT-7, and HT-P of the STABIACE (registered trademark) series manufactured by Sakai Chemical Industry Co., Ltd. Examples of hydrotalcites include those containing magnesium and aluminum as main components, i.e., the above-mentioned M 1 Mg 2+ and M 2 Al 3+ Hydrotalcite represented by the formula (I) is preferably used.

[0035] Commercially available magnesium carbonate products include, for example, GP-30 manufactured by Konoshima Chemical Co., Ltd. Commercially available magnesium oxide products include, for example, the SMO series manufactured by Sakai Chemical Industry Co., Ltd. and RF-50-FC manufactured by Ube Material Industries, Ltd. Commercially available aluminum hydroxide products include, for example, C-305 manufactured by Hayashi Kasei Co., Ltd., C-310 manufactured by Sumitomo Chemical Co., Ltd., and BF-013 manufactured by Nippon Light Metal Co., Ltd. The fillers including hydrotalcite are not limited to the commercially available products described above, and other commercially available products may be used, or appropriately prepared products may be used.

[0036] The filler may include, in addition to the above-mentioned magnesium carbonate, magnesium oxide, hydrotalcite, and aluminum hydroxide, other known fillers used in ordinary resin compositions, particularly inorganic fillers. Examples of such inorganic fillers include non-metallic fillers such as silica, barium sulfate, calcium carbonate, silicon nitride, aluminum nitride, boron nitride, alumina, magnesium hydroxide, titanium oxide, mica, talc, and organic bentonite, with silica and calcium carbonate being preferred. The other fillers may be used alone or in combination of two or more.

[0037] The shape of the filler is not particularly limited, and examples thereof include spherical, needle-like, plate-like, scaly, hollow, irregular, hexagonal, cubic, and flaky shapes. From the viewpoint of increasing the filler content, however, a spherical shape is preferred.

[0038] The average particle size of the filler is preferably 0.1 μm to 25 μm, more preferably 0.1 μm to 15 μm, and even more preferably 1 μm to 10 μm, taking into consideration the dispersibility of the filler, the ability to fill holes, and the smoothness when forming a wiring layer on the filled holes. Note that the "average particle size" of the filler means the average primary particle size, and the average particle size (D50) can be measured by a laser diffraction / scattering method.

[0039] The content of the filler in the curable resin composition is not particularly limited as long as the effects of the present invention are achieved, but the total content of magnesium carbonate, magnesium oxide, hydrotalcite, and aluminum hydroxide per 100 parts by mass of epoxy resin is not particularly limited as long as the effects of the present invention are achieved, and is adjusted to preferably 10 to 250 parts by mass, more preferably 10 to 150 parts by mass, and even more preferably 20 to 100 parts by mass per 100 parts by mass of epoxy resin. By adjusting the total amount of magnesium carbonate, magnesium oxide, hydrotalcite, and aluminum hydroxide relative to the epoxy resin within the above-mentioned range, the amount of halogen-containing substances released upon combustion of a cured product of the curable resin composition can be sufficiently suppressed, while the viscosity of the curable resin composition can be adjusted to a range suitable for use (e.g., application to a substrate, etc.). When the filler contains the other fillers described above, the filler content in the curable resin composition is adjusted so that the total amount of magnesium carbonate, magnesium oxide, hydrotalcite, and aluminum hydroxide is within the above-mentioned range, and the total amount of all fillers is preferably 50 to 300 parts by mass, more preferably 100 to 250 parts by mass, per 100 parts by mass of epoxy resin. By adjusting the filler content relative to the epoxy resin within the above-mentioned range, a composition with good printability suitable for filling holes in printed wiring boards and gaps between circuits can be obtained, and the cured product can achieve the good solder heat resistance required. In this specification, the term "filler content" refers to the total content of the magnesium carbonate, magnesium oxide, hydrotalcite, and aluminum hydroxide described above, plus the other fillers.

[0040] In the curable resin composition, the total content of magnesium carbonate, magnesium oxide, hydrotalcite, and aluminum hydroxide is not particularly limited as long as the effects of the present invention are achieved, but is preferably 4 to 100 mass%, more preferably 10 to 100 mass%, and even more preferably 20 to 100 mass%, relative to the total content of fillers. By adjusting the ratio of the total content of magnesium carbonate, magnesium oxide, hydrotalcite, and aluminum hydroxide relative to the total content of fillers to within the above-mentioned range, the amount of halogen-containing substances released during combustion of the curable resin composition can be suppressed and kept within the above-mentioned range.

[0041] (solvent) The curable resin composition of the present invention preferably does not contain a solvent. Generally, most solvents (dilution solvents) used to adjust the viscosity of a curable resin composition volatilize during curing of the curable resin composition. However, the volatilized solvent can cause voids to form in the cured product of the curable resin composition. For example, when the curable resin composition of the present invention is used as a filler, the presence of voids in the cured product of the curable resin composition may impair the properties required of the filler. From the viewpoint of avoiding such impairment of the properties of the cured product of the curable resin composition, the curable resin composition preferably does not contain a solvent.

[0042] (Other ingredients) The curable resin composition of the present invention may further contain, as necessary, components such as colorants, elastomers, mercapto compounds, urethanization catalysts, thixotropic agents, adhesion promoters, block copolymers, chain transfer agents, polymerization inhibitors, copper inhibitors, antioxidants, rust inhibitors, thickeners such as organic bentonite and montmorillonite, at least one of silicone-based, fluorine-based, and polymer-based antifoaming agents and leveling agents, imidazole-based, thiazole-based, and triazole-based silane coupling agents, and flame retardants such as phosphinates, phosphate ester derivatives, and phosphorus compounds such as phosphazene compounds. These may be known in the field of electronic materials.

[0043] The viscosity of the curable resin composition is not particularly limited as long as the effects of the present invention are achieved. However, the viscosity measured using a rotational viscometer, i.e., the viscosity measured at 25°C and 5 rpm for 30 seconds, is preferably 200 to 1000 dPa·s, and more preferably 200 to 800 dPa·s. Having the viscosity of the curable resin composition within the above-mentioned range allows for good shape retention (suppression of dripping) and embeddability of the curable resin composition. The viscosity of the curable resin composition can be measured using a cone-plate viscometer (e.g., TV-30 model manufactured by Toki Sangyo Co., Ltd., rotor 3° x R9.7) consisting of a cone rotor and plate as described in JIS Z 8803.

[0044] The curable resin composition of the present invention can be used to fill, for example, through-holes or gaps between circuits (recesses with bottoms) in multilayer printed wiring boards using known patterning methods such as screen printing or vacuum printing. Preferably, the curable resin composition of the present invention is filled so that the through-holes or gaps between circuits are flat (having a uniform height). By filling the curable resin composition in this manner, a cured product having a smooth surface can be formed on the printed wiring board after curing the curable resin composition. The curable resin composition is preferably filled completely, with a small amount of overflowing from the holes or recesses. The multilayer printed wiring board with the holes or recesses filled with the curable resin composition is heated, for example, at 80 to 160°C for about 30 to 180 minutes, to cure the curable resin composition and form a cured product. To prevent bubbles from forming during printing, the curing may be performed in two stages. That is, the curable resin composition may be pre-cured at a lower temperature, followed by main curing (finish curing). The pre-curing conditions are preferably heating at 80 to 110°C for about 30 to 90 minutes. Because the pre-cured product has a relatively low hardness, unnecessary portions protruding from the substrate surface can be easily removed by physical polishing, resulting in a smooth surface. The product is then heated for full curing. The pre-curing conditions are preferably heating at 130 to 160°C for about 30 to 180 minutes. The hardness of the pre-cured product can be controlled by changing the heating time and temperature for pre-curing.

[0045] After curing the curable resin composition as described above, if necessary, unnecessary portions of the cured product of the printed wiring board are removed by a known physical polishing method, smoothed, and then the wiring layer on the surface is patterned into a predetermined pattern to form a predetermined circuit pattern. Note that if necessary, the surface of the cured product may be roughened with an aqueous potassium permanganate solution or the like, and then a wiring layer may be formed on the cured product by electroless plating or the like. [Example]

[0046] 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 the examples, "parts" and "%" are all by mass unless otherwise specified.

[0047] [Preparation of Curable Resin Composition] The components shown in Table 1 below were mixed in the amounts shown in the table, pre-mixed using a mixer, and then kneaded using a three-roll mill to prepare the curable resin compositions of Examples 1 to 11 and Comparative Examples 1 to 4. Details of each component in Table 1 are as follows. In Table 1, all values ​​without units represent parts by mass. Epoxy resin 1 (epoxy resin having a tertiary amine): p-aminophenol-type liquid epoxy resin (jER (registered trademark) 630, manufactured by Mitsubishi Chemical Corporation) Epoxy resin 2 (epoxy resin with tertiary amine): N,N,N',N'-tetraglycidyl-m-xylenediamine Epoxy resin 3 (epoxy resin having a tertiary amine): p-aminophenol-type liquid epoxy resin (jER (registered trademark) 604, manufactured by Mitsubishi Chemical Corporation) Epoxy resin 4 (epoxy resin having a bisphenol skeleton): bisphenol A type epoxy resin (jER (registered trademark) 828, manufactured by Mitsubishi Chemical Corporation) Epoxy resin 5 (epoxy resin having a bisphenol skeleton): bisphenol F type epoxy resin (jER (registered trademark) 806H, manufactured by Mitsubishi Chemical Corporation) Epoxy resin curing agent: 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine (Curezol 2MZA-PW, manufactured by Shikoku Chemicals Corporation) Filler 1: Calcium carbonate Filler 2: Silica Filler 3: Synthetic hydrotalcite Filler 4: Aluminum hydroxide Filler 5: Magnesium oxide Filler 6: Magnesium carbonate Antifoaming agent: Silicone resin (KS-66, manufactured by Shin-Etsu Chemical Co., Ltd.)

[0048] [Table 1]

[0049] [Measurement of halogen content by quartz tube combustion method] The amounts of chlorine and bromine released when each of the curable resin compositions of the Examples and Comparative Examples was burned were measured according to the following procedure. First, 0.1 g of each curable resin composition was combusted using an AQF-2100H automatic sample combustion apparatus manufactured by Nitto Seiko Analytech Co., Ltd., and the gas components were collected. The collected gas components were then absorbed in an absorption solution (hydrogen peroxide solution), and the chlorine and bromine contents of the resulting absorption solution were quantified by ion chromatography using a Thermo Fisher Scientific Dionex ICS-1100 ion chromatograph system, a Thermo Fisher Scientific Dionex AERS 500 suppressor, and a Dionex IonPac AS12A column. The halogen content of each curable resin composition in the Examples and Comparative Examples was evaluated according to the following criteria. The measurement and evaluation results for the halogen content (total amount of chlorine and bromine) are shown in Table 1. ⊚: The amount of halogen is 500 ppm or less, and the amount of halogen-containing substances released is extremely well suppressed. ◯: The amount of halogen is more than 500 ppm and not more than 1000 ppm, and the amount of halogen-containing substances released is well suppressed. ×: The amount of halogen exceeds 1000 ppm, and the amount of halogen-containing substances released is not sufficiently suppressed.

[0050] [Printability evaluation] The printability of each of the curable resin compositions of the Examples and Comparative Examples was evaluated according to the following procedure. Each of the curable resin compositions of the Examples and Comparative Examples was filled into a 1 mm thick glass epoxy substrate, which had previously been formed with 500 μm diameter through holes by panel plating, using a screen printing method under the following printing conditions: The glass epoxy substrate filled with each curable resin composition was placed in a hot air circulating drying oven and held horizontally at 180°C for 1 hour to cure each curable resin composition, thereby obtaining each evaluation substrate. (Printing conditions) Squeegee: Squeegee thickness 20mm, hardness 70°, angled grinding: 23° Plate: PET100 mesh bias plate Printing pressure: 60kgf / cm 2 Squeegee speed: 5cm / sec Squeegee angle: 80°

[0051] For each evaluation board, the degree of filling of the cured product of the curable resin composition in the through-holes was visually observed, and the printability of each curable resin composition of the Examples and Comparative Examples was evaluated according to the following criteria. The evaluation results are shown in Table 1. ◎: Completely filled and hardened. ○: Not completely filled but sufficiently filled and hardened. ×: Difficult to fill.

[0052] [Evaluation of solder heat resistance] The solder heat resistance of each of the curable resin compositions of the Examples and Comparative Examples was evaluated according to the following procedure. First, the same evaluation substrates as those used in the polishability evaluation described above were prepared. The surface of each evaluation substrate, on which the curable resin composition had been applied, was physically polished using a single-axis polishing buff equivalent to #320 using a polishing machine. Next, after physical polishing, each evaluation substrate was immersed in a soldering solution at 288°C for 10 seconds three times and then allowed to cool to room temperature. Next, each evaluation substrate was cut at the through-holes, and the cross sections were observed with an optical microscope to count the number of cracks in 100 through-holes. Based on the number of cracks, the solder heat resistance of each curable resin composition in the Examples and Comparative Examples was evaluated according to the following criteria. The evaluation results are shown in Table 1. ○: 0 cracks. △: 1 to 5 cracks. ×: Six or more cracks.

[0053] The evaluation results shown in Table 1 reveal that the amount of halogen measured by the quartz tube combustion method for each of the curable resin compositions of the Examples was as low as 1000 ppm or less. The amount of halogen measured by the quartz tube combustion method is considered to be the amount of halogen derived from various halogen-containing substances released during combustion. Therefore, it can be said that the amount of halogen-containing substances released during combustion is suppressed for each of the curable resin compositions of the Examples. Furthermore, it can be seen that each of the curable resin compositions of the Examples exhibits good printability and good solder heat resistance, making it suitable for use in filling holes in printed wiring boards and smoothing gaps between circuits. On the other hand, it can be seen that the amount of halogen released during combustion for each of the curable resin compositions of the Comparative Examples was high, exceeding 1000 ppm. Therefore, it can be said that the amount of halogen-containing substances released during combustion is not sufficiently suppressed for each of the curable resin compositions of the Comparative Examples.

Claims

1. epoxy resin, an epoxy resin hardener, and Filler A curable resin composition comprising: the filler comprises hydrotalcite; the total content of the filler is 50 parts by mass or more and less than 250 parts by mass relative to 100 parts by mass of the epoxy resin, The content of the hydrotalcite is 4 to 100 mass% based on the total content of the filler, A curable resin composition characterized in that the amount of halogen measured by a quartz tube combustion method is 100 to 1000 ppm.

2. The curable resin composition according to claim 1, wherein the content of the hydrotalcite is 10 parts by mass or more and less than 250 parts by mass per 100 parts by mass of the epoxy resin.

3. The curable resin composition according to claim 1 or 2, wherein the epoxy resin comprises an epoxy resin having a tertiary amine.

4. 3. The curable resin composition according to claim 1, wherein the content of the epoxy resin is 10 to 60 parts by mass per 100 parts by mass of the curable resin composition.

5. 3. The curable resin composition according to claim 1, wherein the viscosity of the curable resin composition is 200 to 1000 dPa·s when rotated at 25° C. and a rotation speed of 5 rpm for 30 seconds.

6. The curable resin composition according to claim 1 or 2, which is used to plug holes in a printed wiring board or to fill gaps between circuits in a printed wiring board.

7. A cured product of the curable resin composition according to claim 1 or 2.

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

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