WO2023132317A1

WO2023132317A1 - Curable resin composition

Info

Publication number: WO2023132317A1
Application number: PCT/JP2022/048510
Authority: WO
Inventors: 智崇野口; 康代金沢; 千夏高橋
Original assignee: 太陽ホールディングス株式会社
Priority date: 2022-01-07
Filing date: 2022-12-28
Publication date: 2023-07-13
Also published as: TW202342636A

Abstract

Provided is a curable resin composition which has very low CTE and is excellent in terms of heat resistance and crack resistance and of filling property and adhesiveness to copper platings. This curable resin composition comprises (A) epoxy resins, (B) an epoxy resin hardener, and (C) an inorganic filler, wherein the epoxy resins (A) comprise at least three epoxy resins differing in the number of functional groups or in molecular skeletal structure, the three epoxy resins at least including an epoxy resin containing up to two functional groups and an epoxy resin including four or more aromatic rings.

Description

Curable resin composition

The present invention relates to a curable resin composition, and more particularly to a curable resin composition that can be suitably used as a filling material for filling through holes such as through holes and recesses in printed wiring boards.

With the miniaturization and sophistication of electronic devices, there is a demand for finer printed wiring board patterns, smaller mounting areas, and higher density component mounting. For this reason, double-sided boards with through-holes for forming interlayer connections for electrically connecting different wiring layers, insulating layers and conductor circuits are sequentially formed on a core material, and via holes and the like are used. A multi-layer substrate such as a build-up wiring board in which layers are connected and multi-layered is used.

In such a printed wiring board, recesses between conductor circuits on the surface, and holes such as through holes and via holes having wiring layers formed on the inner wall surfaces are filled with a thermosetting resin filler. is common. As the thermosetting resin filler, a thermosetting resin filler containing an epoxy resin as a thermosetting resin component, an epoxy resin curing agent, and an inorganic filler is generally used.

In addition, the heat resistance of printed wiring boards has been improved and the CTE (coefficient of thermal expansion) has been reduced, and along with this, thermosetting resin fillers are also required to have heat resistance and a low CTE. For example, the temperature at which electronic elements are mounted on a package substrate can reach as high as 250°C. There is a need for curable resin fillers. For example, Patent Document 1 proposes a curable resin composition capable of forming a hole insulating layer having excellent crack resistance, adhesion, insulation reliability, heat resistance, moisture resistance, PCT resistance, and the like.

JP 2009-269994 A

In recent years, in package substrates such as IC substrates, there has been a tendency for the thickness of substrates to increase due to multilayering, the length of through holes to increase, and the diameter of holes to decrease. Therefore, there is a growing demand for fillers that are more excellent in filling properties (printability) than ever before. Although the heat resistance and CTE can be reduced by increasing the blending ratio of the inorganic filler, there is a tendency for the fillability (printability) to deteriorate, and it can be said that these are in a trade-off relationship.

Accordingly, an object of the present invention is to provide a curable resin composition that is excellent in heat resistance, low CTE and crack resistance, as well as excellent filling properties and adhesion to copper plating.

The inventors focused on epoxy resins and found that the above problems can be solved by combining multiple types of epoxy resins with different functional groups. The present invention is based on such findings. That is, the gist of the present invention is as follows.

[1] (A) an epoxy resin;
(B) an epoxy resin curing agent;
(C) an inorganic filler;
A curable resin composition comprising
The (A) epoxy resin contains at least three epoxy resins having different numbers of functional groups or different molecular skeleton structures,
The three types of epoxy resins include at least an epoxy resin having a functional group number of 2 or less and an epoxy resin having a functional group number of 4 or more and an aromatic ring.
A curable resin composition characterized by:
[2] The curable resin composition according to [1], wherein the epoxy resin having 4 or more functional groups is liquid at room temperature.
[3] The curable resin composition according to [1] or [2], wherein (A) the epoxy resin further contains an epoxy resin having 3 functional groups.
[4] The curable resin composition according to [3], wherein the (C) inorganic filler is contained in an amount of 10 to 90% by mass based on the total solid content of the curable composition.
[5] The curable resin composition according to any one of [1] to [4], wherein the inorganic filler (C) contains silica.
[6] The curable resin composition according to any one of [1] to [5], which is used as a filler for through holes or recesses in printed wiring boards.

According to the present invention, by using a combination of three or more epoxy resins with different numbers of functional groups and molecular skeleton structures, heat resistance, low CTE, and crack resistance are excellent, as well as filling properties and adhesion to copper plating. An excellent curable resin composition can be realized.

<Curable resin composition>
The curable resin composition of the present invention contains (A) an epoxy resin, (B) an epoxy resin curing agent, and (C) an inorganic filler as essential components. In the present specification, the term "liquid" means a fluid state or a semi-liquid state (paste state). Each component will be described in detail below.

[Epoxy resin]
The curable resin composition according to the present invention contains at least three types of epoxy resins having different numbers of functional groups or different molecular skeleton structures as epoxy resins which are curable components. In this specification, the number of functional groups means an epoxy group (glycidyl group), and the molecular skeleton structure means a compound obtained by substituting a hydrogen atom for the epoxy group.

In the present invention, at least two of these three types of epoxy resins are an epoxy resin with a functional group number of 2 or less and an epoxy resin with a functional group number of 4 or more and an aromatic ring. In a curable resin composition mainly containing an epoxy resin as a curable component, an epoxy resin having a functional group number of 2 or less, an epoxy resin having a functional group number of 4 or more and an aromatic ring, and an epoxy having a different molecular skeleton structure from these two types By including a resin or an epoxy resin having a functional group of 3, it is possible to obtain a curable resin composition that is excellent not only in heat resistance, low CTE, and crack resistance, but also in filling properties and adhesion to copper plating. Although the reason for this is not clear, the inclusion of an epoxy resin having a polyfunctional aromatic ring with a number of functional groups of 4 or more increases the cross-linking density of the cured product, thereby improving the heat resistance of the cured product and improving the CTE. decreases. Therefore, unlike the conventional curable resin composition, it is not necessary to add a large amount of inorganic filler, so that the printability is improved and the filling property is improved. In addition, it can be inferred that the volume shrinkage at the time of curing is suppressed, the crack resistance is improved, and etching is facilitated in the desmear process, and as a result, the adhesion to the copper plating is improved due to the unevenness of the surface. On the other hand, when only the polyfunctional epoxy resin of 4 or more is contained, the water absorption rate due to the amine during etching becomes too high, so that the adhesion to the copper plating rather deteriorates. In addition, when only epoxy resins having 2 or 3 functional groups are used, the volume shrinkage increases, so that cracks tend to occur during curing, and the CTE is not lowered sufficiently.

<Epoxy resin having 2 or less functional groups>
Among epoxy resins having a functional group number of 2 or less, epoxy resins having a functional group number of 2 (hereinafter also referred to as bifunctional epoxy resins) include, for example, bisphenol A diglycidyl ether type epoxy resin and bisphenol F diglycidyl ether type epoxy resin. Resin, bisphenol E type epoxy resin, bisphenol S diglycidyl ether type epoxy resin, resorcin diglycidyl ether type epoxy resin, hydroquinone diglycidyl ether type epoxy resin, terephthalic acid diglycidyl ester type epoxy resin, bisphenoxyethanolfluorenediglycidyl ether type epoxy resin resins, bisphenol fluorenediglycidyl ether type epoxy resins, biscresol fluorenediglycidyl ether type epoxy resins, novolak glycidyl ether type epoxy resins, epoxy resins having an aromatic skeleton such as hexahydrophthalic acid glycidyl ester, cyclohexanedimethanol diglycidyl ether , butanediol diglycidyl ether, hexahydrophthalic acid diglycidyl ester, and other epoxy resins having an aliphatic skeleton, but are not limited to these.

Epoxy resins having one functional group (hereinafter also referred to as monofunctional epoxy resins) include aliphatic skeletons having 6 to 36 carbon atoms, such as alkyl glycidyl ethers, alkenyl glycidyl ethers, alkyl glycidyl esters, and alkenyl glycidyl esters. and epoxy resins having an aromatic skeleton such as phenylglycidyl ether and phenylglycidyl ester, but are not limited thereto. The chain length of alkyl is usually about 6-18.

The above epoxy resins having a functional group number of 2 or less may be used alone, or two or more epoxy resins may be used in combination. Therefore, it preferably contains an epoxy resin having two functional groups.

From the viewpoint of crack resistance and adhesion of copper plating, the above-described epoxy resin having a functional group number of 2 or less is preferably contained in an amount of 5 to 70 parts by mass when the total solid content of the epoxy resin is 100 parts by mass. It is more preferable to contain up to 50 parts by mass.

<Epoxy resin having an aromatic ring with 4 or more functional groups>
Among epoxy resins having an aromatic ring with a functional number of 4 or more, epoxy resins having an aromatic ring with a functional number of 4 (hereinafter also referred to as tetrafunctional epoxy resin) include bisphenol A type epoxy resins and bisphenol F type epoxy resins. resin, bisphenol AF type epoxy resin, naphthalene type epoxy resin, glycidyl ester type epoxy resin, glycidylamine type epoxy resin, phenol novolac type epoxy resin, metaxylenediamine type epoxy resin, etc. Liquid epoxy resin at room temperature, bixylenol type Epoxy that is solid at room temperature such as epoxy resin, cresol novolac type epoxy resin, trisphenol type epoxy resin, naphthol type epoxy resin, biphenyl type epoxy resin, naphthylene ether type epoxy resin, anthracene type epoxy resin, tetraphenylethane type epoxy resin, etc. Examples include, but are not limited to, resins.

As the epoxy resin having an aromatic ring with 5 functional groups (hereinafter also referred to as pentafunctional epoxy resin), 2,4,6-tris[(4-hydroxyphenyl)methyl]-1,3-benzenediol type epoxy Resin etc. are mentioned.

Examples of the epoxy resin having an aromatic ring with 6 or more functional groups (hereinafter also referred to as a hexafunctional or higher epoxy resin) include 2,3,6,7,10,11-hexaglycidyloxytriphenylene and the like. However, it is not limited to these.

The epoxy resin having an aromatic ring with a functional number of 4 or more may be used alone, or two or more epoxy resins may be used in combination. In the present invention, a tetrafunctional epoxy resin is used. preferably. Among tetrafunctional epoxy resins, tetrafunctional epoxy resins that are liquid at room temperature are preferred from the viewpoint of the balance between filling properties (printability) and crack resistance. Among the tetrafunctional epoxy resins that are liquid at room temperature, meta-xylene diamine type epoxy resins and the like can be preferably used from the viewpoint of heat resistance.

From the viewpoint of heat resistance and low CTE, the above-mentioned epoxy resin having an aromatic ring with 4 or more functional groups is preferably contained in an amount of 5 to 50 parts by mass when the total solid content of the epoxy resin is 100 parts by mass. It is more preferable to contain up to 40 parts by mass.

The blending ratio of the epoxy resin having a functional group number of 2 or less and the epoxy resin having a functional group number of 4 or more and having an aromatic ring is preferably 90:10 to 10:90, preferably 90:10 to 20 in terms of solid content. :80, more preferably 90:10 to 40:60.

<Other epoxy resins>
The curable resin composition according to the present invention contains an epoxy resin other than the two types of epoxy resins described above. Here, the term "epoxy resin other than two types of epoxy resins" refers to two types of epoxy resins, namely an epoxy resin having a functional group number of 2 or less and an epoxy resin having a functional group number of 4 or more and an aromatic ring. Epoxy resins that have the same number of functional groups as epoxy resins but have different molecular skeleton structures, or epoxy resins that have an arbitrary molecular skeleton structure and have three functional groups (hereinafter also referred to as trifunctional epoxy resins). do. In the present invention, the epoxy resin preferably contains one or more difunctional epoxy resins, one or more tetrafunctional aromatic ring-containing epoxy resins, and one or more trifunctional epoxy resins.

Examples of trifunctional epoxy resins include, but are not limited to, triazine skeleton-containing epoxy resins, aminophenol-type epoxy resins, aminocresol-type epoxy resins, triphenylglycidyl ether methane-type epoxy resins, and the like. Only one of these trifunctional epoxy resins may be used, or two or more epoxy resins may be used in combination.

When a trifunctional epoxy resin is included as the epoxy resin, the blending ratio is 10 to 50 parts by mass when the total solid content of the epoxy resin is 100 parts by mass, from the viewpoint of printability and heat resistance. Preferably, it is contained in an amount of 20 to 40 parts by mass.

When an epoxy with a functional group number of 3 is included, the blending amount of the epoxy resin with a functional group number of 2 or less, the epoxy resin with a functional group number of 3, and the epoxy resin with a functional group number of 4 or more and an aromatic ring is 80 to 80 in terms of solid content. It is preferably 10:10-45:10-45, more preferably 70-10:15-45:15-45.

In addition, an epoxy resin having no aromatic ring and having a functional group number of 4 or more may be included. Examples of these epoxy resins include alicyclic epoxy resins having an ester skeleton, cyclohexane-type epoxy resins, cyclohexanedimethanol-type epoxy resins, epoxy resins having a butadiene structure, dicyclopentadiene-type epoxy resins, and dipentaerythritol hexaglycidyl. ether, sorbitol hexaglycidyl ether and the like.

The total solid content of the epoxy resin is preferably 5 to 70 parts by mass, more preferably 10 to 60 parts by mass, based on the total solid content of the curable resin composition.

In addition, considering the coating film-forming properties of the curable resin composition, that is, the coating properties such as printability, the epoxy resin used in the present invention is preferably liquid rather than solid. In particular, the viscosity of the epoxy resin is preferably 20 Pa·s or less, more preferably 10 Pa·s or less, and even more preferably 5 Pa·s or less. In addition, the viscosity here is JIS K8803: 25 using a cone-plate viscometer (manufactured by Toki Sangyo Co., Ltd., TV-33H) in accordance with the viscosity measurement method using a 10 cone-plate rotation viscometer of 2011. It refers to the viscosity measured at ±1°C, 5 rpm, 30 seconds value.

[(B) Epoxy resin curing agent]
(B) The epoxy resin curing agent can be used without any particular limitation as long as it has the effect of accelerating the curing reaction of the epoxy resin. There are polymers containing functional groups, and more than one of these may be used if desired. Amines include dicyandiamide, diaminodiphenylmethane, and the like. Examples of imidazoles include alkyl-substituted imidazoles and benzimidazoles. The imidazole compound may also be an imidazole latent curing agent such as an imidazole adduct. Examples of polyfunctional phenols include hydroquinone, resorcinol, bisphenol A and their halogen compounds, and condensates of these with aldehydes such as novolak and resole resins. Acid anhydrides include phthalic anhydride, hexahydrophthalic anhydride, methylnadic anhydride, benzophenonetetracarboxylic acid and the like. Isocyanates include tolylene diisocyanate, isophorone diisocyanate, and the like, and these isocyanates may be used after being masked with phenols or the like. One type of these curing agents may be used alone, or two or more types may be used in combination.

Among the curing agents described above, amines and imidazoles can be preferably used from the viewpoint of adhesion to the conductive portion and the insulating portion, storage stability, and heat resistance. 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, or isophoronediamine, 1,3-bis Preferably, the main component is an alicyclic polyamine adduct compound such as (aminomethyl)cyclohexane, or a mixture of the above aliphatic polyamine adduct compound and the above alicyclic polyamine adduct compound.

As the adduct compound of the aliphatic polyamine, those obtained by subjecting the aliphatic polyamine to addition reaction with aryl glycidyl ether (especially phenyl glycidyl ether or tolyl glycidyl ether) or alkyl glycidyl ether are preferable. Moreover, as the adduct compound of the alicyclic polyamine, those obtained by subjecting the alicyclic polyamine to addition reaction with n-butyl glycidyl ether, bisphenol A diglycidyl ether or the like are preferable.

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 fats having 8 to 15 carbon atoms such as xylylenediamine. group polyamines. Examples of commercially available modified aliphatic polyamines include Fujicure FXE-1000, Fujicure FXR-1020, Fujicure FXR-1030, Fujicure FXR-1080, Fujicure FXR-1090M2 (manufactured by T&K TOKA Co., Ltd.), Ancamine 2089K, and Sunmide P. -117, Sunmide X-4150, Ancamine 2422, Serwet R, Sunmide TX-3000, Sunmide A-100 (manufactured by Evonik Japan Co., Ltd.) and the like.

Examples of alicyclic polyamines include isophoronediamine, 1,3-bis(aminomethyl)cyclohexane, bis(4-aminocyclohexyl)methane, norbornenediamine, 1,2-diaminocyclohexane, and lalomine. 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, and Ancamine 2228 (Evonik Japan Co., Ltd.). ), Daito Clar F-5197, Daito Clar B-1616 (manufactured by Daito Sangyo Co., Ltd.), Fuji Cure FXD-821, Fuji Cure 4233 (manufactured by T&K Toka Co., Ltd.), JER Cure 113 (manufactured by Mitsubishi Chemical Corporation), Lalomin C -260 (manufactured by BASF Japan Ltd.) and the like. In addition, EH-5015S (manufactured by ADEKA Co., Ltd.) and the like can be mentioned as a polyamine-type curing agent.

Examples of imidazoles include reaction products of epoxy resin and imidazole. For example, 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 and the like. Examples of commercially available imidazole compounds include imidazoles such as 2E4MZ, C11Z, C17Z, and 2PZ, imidazole AZINE compounds such as 2MZ-A and 2E4MZ-A, and imidazoles such as 2MZ-OK and 2PZ-OK. and imidazole hydroxymethyl compounds such as isocyanurate of 2PHZ and 2P4MHZ (all of which are manufactured by Shikoku Kasei Kogyo Co., Ltd.). Examples of commercially available imidazole-type latent curing agents include Cure Duct P-0505 (manufactured by Shikoku Kasei Kogyo Co., Ltd.).

The amount of the above curing agent is preferably 1 to 100 parts by mass, more preferably 2 to 30 parts by mass, when the total solid content of the epoxy resin (A) is 100 parts by mass. It is more preferably 3 to 20 parts by mass. In particular, when the amount of (B) the epoxy resin curing agent is 3 parts by mass or more, the pre-curing speed of the resin composition generally does not slow down, and as a result, the composition in the deep part of the hole is sufficiently cured, resulting in the occurrence of cracks. It is preferable because it can prevent In addition, when the amount of the (B) epoxy resin curing agent is 50 parts by mass or less, the storage stability is improved, and generally the pre-curing speed of the resin composition does not become too fast, making it difficult for voids to remain in the cured product. Therefore, it is preferable.

[(C) inorganic filler]
(C) The inorganic filler includes an inorganic filler for stress relaxation due to curing shrinkage of the filler and adjustment of the coefficient of linear expansion. As the inorganic filler, known inorganic fillers used in ordinary resin compositions can be used. Specifically, non-metals such as silica, barium sulfate, calcium carbonate, silicon nitride, aluminum nitride, boron nitride, alumina, magnesium oxide, aluminum hydroxide, magnesium hydroxide, titanium oxide, mica, talc, and organic bentonite. Examples include fillers and metal fillers such as copper, gold, silver, palladium, silicon, alloys, and ferrite. One type of these inorganic fillers may be used alone, or two or more types may be used in combination.

Among these inorganic fillers, calcium carbonate, silica, barium sulfate, and aluminum oxide, which are excellent in low hygroscopicity and low volume expansion, are preferably used, and silica is more preferably used. Silica may be amorphous, crystalline, or a mixture thereof. Amorphous (fused) silica is particularly preferred.

The shape of the inorganic filler is not particularly limited, and includes spherical, needle-like, plate-like, scale-like, hollow, irregular, hexagonal, cubic, and flaky shapes. A spherical shape is preferable from the point of view.

The average particle size of these inorganic fillers is preferably 0.1 μm to 25 μm, preferably 0.1 μm to 25 μm, taking into account the dispersibility of the inorganic filler, the ability to fill holes, and the smoothness when a wiring layer is formed in the filled portion. A range of 0.1 μm to 15 μm is suitable. More preferably, it is 1 μm to 10 μm. The average particle size means the average primary particle size, and the average particle size (D50) can be measured by a laser diffraction/scattering method.

The blending ratio of the inorganic filler is 10% with respect to the total solid content of the curable resin composition, from the viewpoint of achieving both the thermal expansion coefficient, polishability, and adhesiveness of the cured product, as well as printability and hole-filling properties. It is preferably up to 90% by mass, more preferably 20 to 80% by mass, and particularly preferably 40 to 75% by mass.

[Other ingredients]
The curable resin composition of the present invention may contain, as a curable component, a curable resin other than the epoxy resins described above, such as isocyanate compounds, blocked isocyanate compounds, amino resins, carbodiimide resins, cyclocarbonate compounds, Oxetane compounds, episulfide resins, urea resins, resins with triazine rings such as melamine resins, unsaturated polyester resins, maleimide resins such as bismaleimide compounds, polyurethane resins, diallyl phthalate resins, benzoxazine resins, polyimide resins, polyamides Imide resin, benzocyclobutene resin, novolac type cyanate resin, bisphenol A type cyanate resin, bisphenol E type cyanate resin, cyanate ester resin such as bisphenol type cyanate resin such as tetramethylbisphenol F type cyanate resin, silicone resin etc. things are mentioned. These can be used alone or in combination of two or more.

In addition, to the curable resin composition of the present invention, a filler treated with a fatty acid or an amorphous filler such as organic bentonite or talc can be added to impart thixotropy.

The above fatty acid has the general formula: (R ¹ COO) _n —R ² (substituent R ¹ is a hydrocarbon having 5 or more carbon atoms, substituent R ² is hydrogen, a metal alkoxide, or a metal, and n is 1 to 4) can be used. The fatty acid can exhibit the effect of imparting thixotropy when the substituent R ¹ has 5 or more carbon atoms. More preferably, n is 7 or more.

The fatty acid may be an unsaturated fatty acid that has a double bond or triple bond in the carbon chain, or a saturated fatty acid that does not contain them. For example, stearic acid (the number of carbon atoms and the number of unsaturated bonds and the numbers in parentheses are represented by their positions. 18: 0), hexanoic acid (6: 0), oleic acid (18: 1 (9)), icosane acid (20:0), docosanoic acid (22:0), melissic acid (30:0) and the like. The substituent R1 of these fatty acids preferably has 5 to 30 carbon atoms. More preferably, it has 5 to 20 carbon atoms. Also, for example, a skeleton having a coupling agent-based structure and a long (having 5 or more carbon atoms) aliphatic chain, such as a metal alkoxide in which the substituent R2 is a titanate-based substituent capped with an alkoxyl group. There may be. For example, the product name KR-TTS (manufactured by Ajinomoto Fine-Techno Co., Inc.) can be used. In addition, metallic soaps such as aluminum stearate and barium stearate (each manufactured by Kawamura Kasei Co., Ltd.) can be used. Other metal soap elements include Ca, Zn, Li, Mg and Na.

When the curable resin composition of the present invention contains a fatty acid, the blending ratio of the fatty acid is 0.1 to 2 parts by mass with respect to 100 parts by mass of the inorganic filler from the viewpoint of thixotropy, embedding, antifoaming, etc. Proportion is appropriate.

The fatty acid may be incorporated by using an inorganic filler that has been surface-treated with a fatty acid in advance, making it possible to more effectively impart thixotropy to the curable resin composition. In this case, the blending ratio of the fatty acid can be lower than when the untreated filler is used. It is preferably 1 to 1 part by mass.

In addition, the curable resin composition of the present invention may contain a silane coupling agent. By adding a silane-based coupling agent, it is possible to improve the adhesion between the inorganic filler and the epoxy resin and suppress the occurrence of cracks in the cured product.

Examples of silane-based coupling agents include epoxysilane, vinylsilane, imidazolesilane, mercaptosilane, methacryloxysilane, aminosilane, styrylsilane, isocyanatesilane, sulfidesilane, and ureidosilane. Also, the silane coupling agent may be blended by using an inorganic filler that has been surface-treated with a silane coupling agent in advance.

When the curable resin composition of the present invention contains a silane coupling agent, the mixing ratio of the silane coupling agent is 100% of the inorganic filler from the viewpoint of achieving both adhesion and defoaming properties between the inorganic filler and the epoxy resin. It is preferably 0.05 to 2.5 parts by weight per part by weight.

The curable resin composition of the present invention may optionally contain an oxazine compound having an oxazine ring obtained by reacting a phenol compound, formalin and a primary amine. By containing an oxazine compound, after curing the curable resin composition filled in the holes of the printed wiring board, when electroless plating is performed on the formed cured product, curing with an aqueous solution of potassium permanganate or the like is avoided. It facilitates the roughening of the material and improves the peel strength of the plating.

In addition, known colorants such as phthalocyanine blue, phthalocyanine green, disazo yellow, titanium oxide, carbon black, and naphthalene black, which are used in ordinary screen printing resist inks, may be added.

In addition, known thermal polymerization inhibitors such as hydroquinone, hydroquinone monomethyl ether, tert-butyl catechol, pyrogallol, and phenothiazine for imparting storage stability during storage, and clay, kaolin, and the like for viscosity adjustment. Known thickeners and thixotropic agents such as organic bentonite and montmorillonite can be added. In addition, known additives such as silicone-based, fluorine-based, polymer-based antifoaming agents, leveling agents, imidazole-based, thiazole-based, triazole-based, silane coupling agents, and other adhesive agents are added. be able to. In particular, when organic bentonite is used, the portion protruding from the surface of the hole portion is easily formed into a protruding state that is easy to polish and remove, and is excellent in polishability, which is preferable. In addition, known and commonly used colorants such as phthalocyanine blue, phthalocyanine green, iodine green, disazo yellow, crystal violet, titanium oxide, carbon black, naphthalene black, etc., can also be blended.

In the curable resin composition of the present invention, when a liquid epoxy resin is mainly included as the epoxy resin, it is not always necessary to use a diluent solvent, but voids are generated in order to adjust the viscosity of the curable resin composition. A diluent solvent may be added to the extent that it does not

Diluent solvents include ketones such as methyl ethyl ketone and cyclohexanone; aromatic hydrocarbons such as toluene, xylene and tetramethylbenzene; methyl cellosolve, butyl cellosolve, methyl carbitol, butyl carbitol, propylene glycol monomethyl ether, dipropylene glycol mono Glycol ethers such as ethyl ether and triethylene glycol monoethyl ether; Esters such as ethyl acetate, butyl acetate, and acetic esters of the above glycol ethers; Alcohols such as ethanol, propanol, ethylene glycol and propylene glycol; Octane , aliphatic hydrocarbons such as decane; and petroleum solvents such as petroleum ether, petroleum naphtha, hydrogenated petroleum naphtha, and solvent naphtha.

[Use of curable resin composition]
The curable resin composition according to the present invention can be used widely and generally, but it is preferably used for forming a cured film of a printed wiring board, more preferably for forming a permanent protective film, and is used for soldering. More preferably, it is used as a resist, an interlayer insulating layer, a coverlay, or a filler (material) for filling holes. Among these uses, it is particularly preferable to use it as a filling material for filling holes, specifically, as a filling material for filling through holes such as through holes of printed wiring boards and recesses.

When the curable resin composition described above is used as a filling material for filling holes, the filling material is formed using a known patterning method such as a screen printing method, a roll coating method, a die coating method, and a vacuum printing method, for example, a multilayer printed wiring board. through-holes and recesses with bottoms. The inner diameter of the hole or recess to be filled with the curable resin composition is not particularly limited, but it is 0.05 to 0.8 mm for package substrates such as IC substrates, server substrates, vehicle-mounted substrates, and the like. and the depth is 0.4 to 10 mm. At this time, it is preferable that the curable resin composition is completely filled so as to protrude slightly from the holes and recesses.

Therefore, the curable resin composition of the present invention preferably has a viscosity at 25±1° C. in the range of 100 to 1000 dPa s, more preferably 200 to 800 dPa s, more preferably 200 to 600 dPa s. s is particularly preferred. With such a range, the holes can be easily filled, and the concave portions and the through holes can be satisfactorily filled without generating voids or the like. The viscosity here is based on JIS K8803: 2011 10 cone-plate type rotational viscometer viscosity measurement method, using a cone plate type viscometer (manufactured by Toki Sangyo Co., Ltd., TV-33H) It refers to the viscosity measured at 25°C, 5 rpm, 30 seconds value.

By heating the multilayer printed wiring board in which the holes and recesses are filled with the curable resin composition, for example, at 80 to 160 ° C. for about 30 to 180 minutes, the curable resin composition is cured and a cured product is formed. . The curing of the curable resin composition may be carried out in two stages from the viewpoint of easily removing unnecessary portions protruding from the surface of the substrate after filling the holes in the cured product by physical polishing. That is, the curable resin composition can be pre-cured at a lower temperature and then subjected to main curing (finish curing). Heating at 80 to 110° C. for about 30 to 180 minutes is preferable as the condition for pre-curing. Since the hardness of the pre-cured cured product is relatively low, the unnecessary portion protruding from the substrate surface can be easily removed by physical polishing, and the surface can be flattened. After that, it is heated to be fully cured. Heating at 130 to 180° C. for about 30 to 180 minutes is preferable as the condition for main curing.

For both pre-curing and main curing, a hot air circulation drying oven, IR oven, hot plate, convection oven, etc. (equipped with a steam air heating type heat source) is used to heat the dryer in the countercurrent direction. A contact method and a method of spraying onto the material to be cured from a nozzle) can be used. Among these, a hot air circulation drying furnace is particularly preferable. At this time, the cured product hardly expands or contracts due to its low expansibility, and the final cured product is excellent in dimensional stability, low hygroscopicity, adhesion, electrical insulation and the like. The hardness of the pre-cured product can be controlled by changing the heating time and heating temperature for pre-curing.

After curing the curable resin composition as described above, unnecessary portions of the cured product protruding from the surface of the printed wiring board are removed by a known physical polishing method, planarized, and then the wiring layer on the surface is removed. A predetermined circuit pattern is formed by patterning into a predetermined pattern. If necessary, the surface of the cured product may be roughened with an aqueous solution of potassium permanganate or the like, and then a wiring layer may be formed on the cured product by electroless plating or the like.

The present invention will now be described in more detail with reference to examples, but the present invention is not limited to these examples. In the following description, "parts" and "%" are based on mass unless otherwise specified.

<Preparation of curable resin composition>
Various components shown in Table 1 below were blended in proportions (parts by mass) shown in each table and mixed with a stirrer to prepare curable resin compositions of Examples 1 to 7 and Comparative Examples 1 to 6. .

Note that *1 to *9 in Table 1 represent the following components.
*1: Bifunctional bisphenol A type epoxy resin (Nippon Steel Chemical & Materials Co., Ltd., YD-127)
*2: Bifunctional biphenol F type epoxy resin (Nippon Steel Chemical & Materials Co., Ltd., YDF-170)
* 3: Trifunctional phenol type epoxy resin (manufactured by Mitsubishi Chemical Corporation, jER-630)
* 4: Tetrafunctional meta-xylene diamine type epoxy resin (Mitsubishi Gas Chemical Co., Ltd., TERTAD-X)
* 5: Tetrafunctional diallyl bisphenol A type epoxy resin (Showfree BATG manufactured by Showa Denko Karenz Co., Ltd.)
* 6: Tetrafunctional pentaerythritol tetraallyl ether type epoxy resin (Showfree PETG manufactured by Showa Denko Karens Co., Ltd.)
* 7: Tetrafunctional diaminodiphenylmethane type epoxy resin (manufactured by Mitsubishi Chemical Corporation, jER-604)
* 8: Pentafunctional siloxane skeleton epoxy resin (manufactured by Mitsubishi Chemical Corporation, YL-9028)
* 9: Imidazole-based curing agent (manufactured by Shikoku Kasei Co., Ltd., Curesol 2MZA-PW)
* 10: Imidazole-epoxy adduct type latent curing agent (Fujicure FXR-1121 manufactured by T&K TOKA Co., Ltd.)
*11: Fused silica (FB-7SDC manufactured by Denka Co., Ltd.)
*12: Heavy calcium carbonate (Maruo Calcium Co., Ltd., Super 4S)

<Evaluation of Volume Shrinkage>
The density (D1) before curing and the density (D2) after curing were measured for the curable resin compositions of each example and comparative example. Measurements were carried out as follows.

(Density measurement before curing of curable resin composition)
After thoroughly defoaming each curable resin composition with a vacuum stirring and rotation-revolution stirrer, the density (D1) of the curable resin composition was measured by a pycnometer method using a 100 cm ³ capacity metal pycnometer ( Measured according to JIS K5600-2-4:2014).

(Density measurement after curing of curable resin composition)
Each curable resin composition is applied to the glossy side (copper foil) of GTS-MP foil (manufactured by Furukawa Circuit Foil Co., Ltd.) with an applicator so that the coating thickness before curing is 100 to 150 μm. Then, the curable resin composition was cured by heating at 150° C. for 60 minutes in a hot air circulating drying oven, and the obtained cured product was peeled off from the copper foil to obtain a sample for measurement. The density (D2) of the obtained sample was measured by an underwater substitution method (according to JIS K7112:1999).

(Calculation of volumetric shrinkage)
Using D1 and D2 measured as described above, the volumetric shrinkage defined by the following formula was calculated.
Volume shrinkage rate (%) = (D2-D1)/D2 x 100
The calculated volumetric shrinkage was as shown in Table 1 below.

<Evaluation of Ink Viscosity>
The viscosity at 25° C. was measured for each curable resin composition of Examples and Comparative Examples. That is, 0.2 ml of a sample is collected, and in accordance with JIS K8803: 2011 10, using a cone-plate viscometer (manufactured by Toki Sangyo Co., Ltd., TV-33H), 25 ° C., rotation speed 5 rpm, 30 seconds. The viscosity was measured at the value.

<Preparation of evaluation board>
Screen printing from one side of a glass epoxy substrate (thickness 1.6 mm with through-holes with conductor layers formed by panel plating/through-hole diameter 0.15 mm (after plating)/pitch 1 mm glass epoxy substrate) , the curable resin compositions of Examples and Comparative Examples were filled in the through-holes under the following printing conditions. After filling, the curable resin composition was cured by heating at 110° C. for 30 minutes and then heating at 150° C. for 60 minutes in a hot air circulating drying oven to obtain an evaluation substrate.
(Printing conditions)
Squeegee: squeegee thickness 20mm flat squeegee (hardness 70°)
Screen plate: PET150 mesh bias plate Printing pressure: 50 kg
Squeegee speed: 10mm/Sec
Squeegee angle: 95° (attack angle 5°)

<Evaluation of printability>
Using the substrate prepared in <Preparation of evaluation substrate>, the surface of the substrate on the side opposite to the printed surface was observed with an optical microscope to confirm the state of ink protruding from the through-holes. 5,000 through holes were observed to evaluate the printability. The evaluation criteria were as follows.
◎: The curable resin composition protrudes from all through-holes ○: 1 to 10 through-holes in which the curable resin composition does not protrude △: Through holes in which the curable resin composition does not protrude 11 to 100 holes were generated. ×: 101 or more through holes were generated in which the curable resin composition did not protrude. The evaluation results were as shown in Table 1 below.

<Evaluation of crack resistance>
Using the substrate produced in <Preparation of evaluation substrate>, a cross section passing through the center of the through hole in the substrate was cut with a precision cutting machine and polished, and the surface state of the cross section was observed with an optical microscope. 200 through holes were observed and evaluated for crack resistance. The evaluation criteria were as follows.
A: No cracks O: 1 to 2 cracks B: 2 to 20 cracks C: 21 or more cracks The evaluation results are shown in Table 1 below.

<Measurement of glass transition temperature (Tg) and coefficient of thermal expansion (CTE (α1))>
Each curable resin composition is applied to the glossy side (copper foil) of GTS-MP foil (manufactured by Furukawa Circuit Foil Co., Ltd.) with an applicator so that the coating thickness before curing is 100 to 150 μm. Then, the curable resin composition was cured by heating at 150° C. for 60 minutes in a hot air circulating drying oven. The obtained cured product was peeled off from the copper foil and cut into a measurement size (3 mm×16 mm) to obtain a sample for measurement.
The obtained measurement sample was subjected to TMA measurement using a thermomechanical analyzer (TMA Q400, manufactured by TA Instruments Japan Co., Ltd.). In the TMA measurement, a test load of 5 g was applied, and the temperature of the sample was increased from room temperature to 300°C at a heating rate of 10°C/min, and the measurement was continuously performed twice. The intersection point of two tangent lines with different coefficients of thermal expansion in the second time was defined as the glass transition temperature (Tg). Also, the coefficient of thermal expansion CTE (α1) in the region below the glass transition temperature was calculated.

<Heat resistance evaluation>
The heat resistance was evaluated based on the glass transition temperature (Tg) measured as described above. The evaluation criteria were as follows.
⊙: Tg is 180°C or higher ◯: Tg is 170°C or higher and lower than 180°C Δ: Tg is 150°C or higher and lower than 170°C ×: Tg is lower than 150°C The evaluation results were as shown in Table 1 below.

<CTE evaluation>
The CTE was evaluated using the CTE (α1) measured as described above. The evaluation criteria were as follows.
◎: CTE (α1) is less than 20 ppm ○: CTE (α1) is 20 ppm or more and less than 30 ppm △: CTE (α1) is 30 ppm or more and less than 40 ppm ×: CTE (α1) is 40 ppm or more The evaluation results are shown in Table 1 below. It was true.

<Evaluation of adhesion with copper plating>
(Preparation of test substrate for adhesion evaluation)
A copper solid substrate (thickness 1.6 mm) was subjected to CZ treatment (manufactured by MEC Co., Ltd., CZ8101, etching amount 1.0 μm), and the curable resin composition of each example and comparative example was applied to the treated surface by screen printing. Solid printing was performed, and the curable resin composition was cured by heating in a hot air circulating drying oven at 110° C. for 30 minutes, followed by heating at 150° C. for 60 minutes. After that, the surface of the cured product was polished with a high-cut buff #320 to about 20 μm to obtain a resin laminated substrate.
The surface of the obtained laminated substrate was subjected to roughening treatment (*1), electroless copper plating treatment (*2), and electrolytic copper plating treatment (*3) in the following order. Then, an annealing treatment was performed at 180° C. for 60 minutes in a hot air circulating drying oven to obtain a test substrate for adhesion evaluation.

(roughening treatment (*1))
The resin laminated substrate obtained in the above (Preparation of test substrate for adhesion evaluation) was immersed in a commercially available wet permanganate desmear (Swelling Dip Securigant P, manufactured by Atotech Japan Co., Ltd.) at 60 ° C. for 5 minutes. After (swelling treatment), immersed in potassium permanganate (Concentrate Compact CP, manufactured by Atotech Japan Co., Ltd.) for 10 minutes at 80 ° C. (roughening treatment), then neutralizing solution (manufactured by Atotech Japan Co., Ltd., reduction Securigant P500) at 40° C. for 5 minutes (reduction treatment), and then dried at 100° C. for 30 minutes.

(Electroless plating treatment (*2))
Electroless copper plating (Thrucup PEA, manufactured by Uyemura & Co., Ltd.) was performed on the roughened resin laminated substrate. The thickness of the formed electroless copper plating layer was approximately 1 μm.

(Electrolytic copper plating treatment (*3))
After heating the resin laminated substrate on which the electroless copper plating layer is formed for 30 minutes at 150° C., copper sulfate electroplating is performed in the following steps to form an electroless copper plating layer with a thickness of 25 μm on the resin layer. bottom.

A cut of 10 mm in width and 60 mm in length was made in the copper plating layer of the test board obtained as described above (Preparation of test board for adhesion evaluation), and one end was peeled off and pinched with a gripper, Peel strength (N/cm ) was measured. The evaluation criteria for adhesion to copper plating were as follows.
◎: Peel strength is 5.0 or more ○: Peel strength is 4.0 or more and less than 5.0 △: Peel strength is 3.0 or more and less than 4.0 ×: Peel strength is less than 3.0 The evaluation results are shown in the table below. 1 as shown.

As is clear from the evaluation results in Table 1, curing containing at least three types of epoxy resins with different numbers of functional groups or different molecular skeleton structures, and containing an epoxy resin with a functionality of 2 or less and an epoxy resin with an aromatic ring of 4 or more functionality It can be seen that the flexible resin compositions (Examples 1 to 7) are excellent in heat resistance, low CTE and crack resistance, as well as excellent filling properties and adhesion to copper plating.
On the other hand, as the epoxy resin, a curable resin composition containing two types of epoxy resins but not containing three or more types of epoxy resins, or an epoxy resin containing three or more types of epoxy resins but having a tetrafunctional or more aromatic ring. It can be seen that the curable resin compositions that do not contain (Comparative Examples 1 to 6) cannot improve heat resistance, low CTE, crack resistance, heat resistance, filling properties, and adhesion to copper plating in a well-balanced manner. .

Claims

(A) an epoxy resin;
(B) an epoxy resin curing agent;
(C) an inorganic filler;
A curable resin composition comprising
The (A) epoxy resin contains at least three epoxy resins having different numbers of functional groups or different molecular skeleton structures,
The three types of epoxy resins include at least an epoxy resin having a functional group number of 2 or less and an epoxy resin having a functional group number of 4 or more and an aromatic ring.
A curable resin composition characterized by:
The curable resin composition according to claim 1, wherein the epoxy resin having an aromatic ring with 4 or more functional groups is liquid at room temperature.
The curable resin composition according to claim 1 or 2, wherein (A) the epoxy resin further contains an epoxy resin having 3 functional groups.
The curable resin composition according to claim 1 or 2, wherein (C) the inorganic filler is contained in an amount of 10 to 90% by mass based on the total solid content of the curable resin composition.
The curable resin composition according to claim 1 or 2, wherein the (C) inorganic filler contains silica.
The curable resin composition according to claim 1 or 2, which is used as a filler for through-holes or recesses in printed wiring boards.