Insulating resin composition

Abstract

This insulating resin composition includes a thermosetting resin and an insulating filler, in which D30, D50, and D100 in the particle size distribution of the insulating filler satisfy (D100 - D30) / D50 ≦ 1.5.

Description

Insulating resin composition Cross-reference of related applications

[0001] This application claims priority under Japanese Patent Application No. 2025-050079, which is incorporated into the description of this application by reference.

[0002] This invention relates to an insulating resin composition.

[0003] Conventionally, insulating resin compositions have been used to form fillers for sealing holes such as through-holes and via holes in circuit boards such as multilayer substrates. Such fillers can remove air from the holes, which can cause corrosion of the plating. Furthermore, in build-up substrates, it is important to fill the holes with fillers to prevent indentations caused by the holes from occurring in the layers placed on top of the holes.

[0004] This type of insulating resin composition typically includes an insulating filler along with a thermosetting resin to relieve stress caused by curing shrinkage of the thermosetting resin and to adjust the coefficient of thermal expansion. Furthermore, Patent Document 1 states that, from the viewpoint of filling holes, it is preferable that the average particle size of the insulating filler be 15 μm or less, and in the examples, silica with an average particle size of 1.6 μm is used.

[0005] Japanese Patent Application Publication No. 2013-216865

[0006] Incidentally, in recent years, with the miniaturization of substrates, the diameter of holes such as through-holes has also been designed to be smaller. Furthermore, in glass substrates, vias with a diameter of 100 μm or less may be formed. Even in substrates with such small-diameter holes, cracks may occur in the filler material of the holes due to heat during reflow soldering. When the inventors investigated this problem, they found that it is effective to further improve the filling ability of the holes and prevent the generation of voids in the filler material after curing.

[0007] In view of the above circumstances, the object of the present invention is to provide an insulating resin composition that can densely fill the holes in a substrate with an insulating filler.

[0008] An insulating resin composition used for filling holes in circuit boards, comprising a thermosetting resin and an insulating filler, wherein the particle size distribution of the insulating filler satisfies (D100-D30) / D50 ≤ 1.5.

[0009] According to the present invention, it is possible to provide an insulating resin composition that can densely fill the holes in a substrate with an insulating filler.

[0010] This is a schematic cross-sectional view of a glass substrate according to one embodiment, showing a state in which a hardened conductive paste has formed in the hole.

[0011] An example of an insulating resin composition according to an embodiment of the present invention will be described with reference to its use in filling holes in a glass substrate that serves as a circuit board.

[0012] As shown in Figure 1, the glass substrate B according to this embodiment is provided with at least one of the holes H, namely through-holes and via holes. The via holes may be IVH or BVH. The hole diameter of the hole H is, for example, 20 μm to 150 μm. The hole diameter of the hole H may be 20 μm to 100 μm, or 20 μm to 50 μm.

[0013] The insulating resin composition of this embodiment is filled into the hole H by a printing method such as screen printing, and then cured to form an insulating filler in the hole H. The insulating resin composition of this embodiment is a thermosetting resin composition that hardens with heat, and forms a filler, which is its cured product C, in the hole H. Among substrates, glass substrates have excellent heat resistance. Therefore, in the manufacturing process of circuit boards using glass substrates, heat treatments that take advantage of the heat resistance of the glass substrate may be considered. It is preferable that the thermosetting resin composition is configured to improve the heat resistance of the filler as much as possible so that the filler in the hole does not impair the advantage based on the heat resistance of the glass substrate.

[0014] The insulating resin composition of this embodiment comprises an epoxy resin as a thermosetting resin, a curing agent that promotes the curing reaction of the epoxy resin, and an insulating filler.

[0015] As the epoxy resin, for example, aromatic epoxy resins having a benzene skeleton or a naphthalene skeleton are preferred. Examples of the aromatic epoxy resins include bisphenol type epoxy resins such as bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, bisphenol AF type epoxy resin, bisphenol Z type epoxy resin, and bisphenol fluorene type epoxy resin, as well as diphenyl sulfide type epoxy resin, diphenyl ether type epoxy resin, naphthalene type epoxy resin, hydroquinone type epoxy resin, resorcinol type epoxy resin, phenol novolac type epoxy resin, cresol novolac type epoxy resin, alkyl novolac type epoxy resin, styrene-phenol novolac type epoxy resin, bisphenol novolac type epoxy resin, naphthol novolac type epoxy resin, phenol aralkyl type epoxy resin, α-naphthol aralkyl type epoxy resin, β-naphthol aralkyl type epoxy resin, naphthalenediol aralkyl type epoxy resin, biphenyl aralkylphenol type epoxy resin, biphenyl type epoxy resin, and triphenylmethane type epoxy resin.

[0016] Furthermore, the aromatic epoxy resin may be an aniline-type epoxy resin, a diaminodiphenylmethane-type epoxy resin, a metaxylenediamine-type epoxy resin, or the like. Among these, a polyfunctional glycidylamine-type epoxy resin, such as an aniline-type epoxy resin having two or more glycidylamino groups, like 4,4'-methylenebis(N,N-diglycidylaniline) or N,N-diglycidyl-4-glycidyloxyaniline, is preferred, and a polyfunctional aminophenol-type epoxy resin is more preferred.

[0017] The thermosetting resin preferably contains two or more of the aromatic epoxy resins. For example, the thermosetting resin preferably contains the bisphenol-type epoxy resin and the aniline-type epoxy resin. The bisphenol-type epoxy resin exhibits relatively high steric hindrance to the nucleophile in the curing reaction, thus preventing the crosslinking density of the filler from becoming too high and contributing to the suppression of cracks caused by increased internal stress in the filler. On the other hand, the polyfunctional aniline-type epoxy resin acts to improve the crosslinking density of the filler, contributing to improved heat resistance and mechanical strength of the filler. Therefore, a thermosetting resin containing both of these can improve crack suppression, heat resistance, and mechanical strength of the filler in a balanced manner. From the viewpoint of obtaining a balanced performance derived from each epoxy resin, the ratio of the bisphenol-type epoxy resin content to the aniline-type epoxy resin content is preferably 0.8:1 to 1.2:1.

[0018] The epoxy equivalent of the epoxy resin is preferably 80 g / eq or more and 200 g / eq or less. More specifically, the epoxy equivalents of the bisphenol-type epoxy resin and the aniline-type epoxy resin are preferably 80 g / eq or more and 200 g / eq or less. This improves the crosslinking density of the filler and enhances its heat resistance. It can also improve the mechanical strength of the filler.

[0019] The ratio of the aromatic epoxy resin to the total mass of the thermosetting resin is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more. The thermosetting resin may consist substantially of only the aromatic epoxy resin.

[0020] The thermosetting resin preferably includes a liquid epoxy resin that is liquid at room temperature (25°C). The ratio of the liquid epoxy resin to the total mass of the thermosetting resin is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more. The thermosetting resin may consist substantially of only the liquid epoxy resin.

[0021] The thermosetting resin preferably contains a liquid epoxy resin that is liquid at room temperature (25°C). The thermosetting resin may also contain a liquid epoxy resin as a reactive diluent. Examples of the reactive diluent include monofunctional diluents having C4-C18 alkyl groups, such as butyl glycidyl ether and 2-ethylhexyl glycidyl ether, and polyfunctional diluents having C4-C18 alkylene groups, such as 1,6-hexanediol diglycidyl ether. Such reactive diluents suppress the increase in viscosity of the insulating resin composition and facilitate the flow of the insulating resin composition into the pores. On the other hand, considering that reactive diluents may reduce the heat resistance of the filler, it is preferable that the thermosetting resin does not contain the reactive diluent.

[0022] The ratio of the liquid epoxy resin to the total mass of the thermosetting resin is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more. The thermosetting resin may consist substantially of only the liquid epoxy resin.

[0023] As the curing agent, high-temperature curing types such as imidazole-based curing agents and phenol-based curing agents are preferred.

[0024] Examples of the imidazole-based curing agents include alkyl-containing imidazoles such as 1-methylimidazole (1MZ), 2-methylimidazole (2MZ), 2-undecylimidazole (C11Z), 2-heptadecylimidazole (C17Z), 1,2-dimethylimidazole (1,2DMZ), 2-ethyl-4-methylimidazole (2E4MZ), 2-phenyl-4-methylimidazole (2P4MZ), and 1- Aryl group-containing imidazoles such as 2-methylimidazole (1B2MZ) and 2-phenylimidazole (2PZ), 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine (2MZ-A), 2,4-diamino-6-(2'-undecylimidazolyl)-ethyl-s-triazine (C11Z-A), 2,4-diamino-6-[2'-ethyl-4-methylimidazolyl-(1') Triazine ring-containing imidazoles such as 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine isocyanuric acid adduct (2MAOK-PW), 1-cyanoethyl-2-methylimidazole (2MZ-CN), 1-cyanoethyl-2-ethyl-4-methylimidazole (2E4MZ-CN), and 1-cyanoethyl-2-undecylimidazole Examples of cyano group-containing imidazoles include zole (C11Z-CN), 1-cyanoethyl-2-phenylimidazole (2PZ-CN), 1-cyanoethyl-2-ethyl-4-methylimidazolium trimellitate (2E4MZCNS), 1-cyanoethyl-2-undecylimidazolium trimellitate (C11ZCNS), and 1-cyanoethyl-2-phenylimidazole trimellitate (2PZCNS-PW). Furthermore, the imidazole-based curing agent may be 2-phenylimidazole isocyanuric acid adduct, 2-methylimidazole isocyanuric acid adduct, 2-phenyl-4,5-dihydroxymethylimidazole (2PHZ-PW), 2-phenyl-4-methyl-5-hydroxymethylimidazole (2P4MHZ), 1-cyanoethyl-2-phenyl-4,5-di(2-cyanoethoxy)methylimidazole, etc.

[0025] The phenolic curing agent is preferably a novolac-type phenolic resin such as a cresol novolac resin, a naphthol novolac resin, a naphthol-phenol cocondensed novolac resin, or a naphthol-cresol cocondensed novolac resin.

[0026] The content of the curing agent is preferably 1 to 20 parts by mass, more preferably 5 to 10 parts by mass, and even more preferably 8 to 10 parts by mass, per 100 parts by mass of the epoxy resin.

[0027] The insulating resin composition of this embodiment has a volume resistivity of the cured product at room temperature (25°C) of, for example, 1 × 10⁻⁶. １１ It is prepared to exhibit a volume resistivity of Ω·cm or greater. The volume resistivity of the cured product at room temperature (25°C) is 1 × 10⁻⁶. １２ It may be greater than or equal to Ω·cm, and 1 × 10 １３ It may be Ω·cm or more. Therefore, it is preferable to select an insulating filler used in the insulating resin composition that, for example, produces a cured product with the above-mentioned volume resistivity when blended in a ratio of 100 parts by mass per 100 parts by mass of bisphenol-type epoxy resin (for example, trade name "jER828").

[0028] Examples of materials constituting the insulating filler include inorganic oxides such as silicon oxide, aluminum oxide, zinc oxide, titanium oxide, and zirconium oxide; inorganic carbides such as silicon carbide; inorganic nitrides such as silicon nitride, aluminum nitride, boron nitride, gallium nitride, and titanium nitride; inorganic hydroxides such as aluminum hydroxide and magnesium hydroxide; inorganic carbonides such as calcium carbonate and magnesium carbonate; and minerals (such as clay minerals like talc, clay, mica, and smectite, as well as basalt and shirasu).

[0029] The insulating filler is preferably silica. The silica may be wet silica or dry silica. The wet silica may be sol-gel method silica or precipitation method silica. The dry silica may be fumed silica obtained by burning silicon tetrachloride in an oxyhydrogen flame, or deflagration method silica obtained by the VMC method (deflagration method). The silica may be hydrophilic silica not surface-treated with a silane coupling agent or the like, or may be surface-treated hydrophobic silica. Among these, sol-gel method silica that has not been surface-treated is preferable. This can suppress excessive thickening of the insulating resin composition, and is therefore preferable from the viewpoint of fillability into holes. The fact that silica is not surface-treated can be confirmed by the absence of a methylene stretching peak (3000 to 2840 cm －１ -1) as measured by FT-IR (KBr pellet method or ATR method).

[0030] The BET specific surface area of the silica is 25 m ２ / g or less, more preferably 20 m ２ / g or less, and even more preferably 15 m ２ / g or less. This makes it possible to obtain an insulating resin composition containing a high concentration of silica that can fill dense silica in holes while suppressing an increase in viscosity. The BET specific surface area of the silica is, for example, 2 m ２ / g or more, 3 m ２ / g or more, or 4 m ２ / g or more. The BET specific surface area can be determined from a nitrogen adsorption isotherm measured in accordance with the BET method.

[0031] The particles constituting the insulating filler are preferably spherical. Specifically, when the insulating filler is observed at magnification with an SEM or the like, and the maximum diameter and minimum diameter of 20 arbitrarily selected particles are measured, the average value of the sphericity obtained by (minimum diameter / maximum diameter) for the 20 particles is preferably 0.7 or more, more preferably 0.8 or more, and even more preferably 0.9 or more. This makes it easy for the insulating resin composition to flow into the holes while allowing high loading of the insulating filler in the insulating resin composition.

[0032] Furthermore, the insulating filler satisfies the condition (D100 - D30) / D50 ≤ 1.5 for D30, D50, and D100 in the particle size distribution. Since such an insulating filler has little variation in particle size in the particle size distribution, it is considered to be densely packed into the pores. The insulating resin composition of this embodiment is considered to be able to suppress the generation of voids in the filler caused by curing shrinkage of the thermosetting resin due to the insulating filler densely packed into the pores, and consequently, to suppress the expansion of the filler due to heat such as in the reflow process, which can cause defects such as cracks. The insulating filler may also satisfy 0.3 ≤ (D100 - D30) / D50 ≤ 1.5. In this specification, particle size distribution refers to the volume-based particle size distribution measured by the laser diffraction scattering particle size distribution measurement method, and D30, D50, and D100 each refer to the particle diameters at which the cumulative values ​​in the particle size distribution are 30%, 50%, and 100%, respectively.

[0033] The particle size distribution of the insulating filler, D100, is preferably 1.5 μm or less, and more preferably 1.0 μm or less. Such insulating filler can be more densely packed into fine holes in the glass substrate.

[0034] On the other hand, from the viewpoint of viscosity (fluidity) of the insulating resin composition, D30 in the particle size distribution of the insulating filler is preferably 0.05 μm or more, more preferably 0.10 μm or more, even more preferably 0.20 μm or more, and even more preferably 0.3 μm or more. Furthermore, D50 in the particle size distribution of the insulating filler is preferably 0.10 μm or more. This reduces the amount of particles with small particle sizes that can increase viscosity, resulting in an insulating resin composition with appropriate viscosity (fluidity) that allows it to flow into the holes.

[0035] The content of the insulating filler may be 100 parts by mass or more per 100 parts by mass of the thermosetting resin. The content of the insulating filler may be 110 parts by mass or more, or 120 parts by mass or more. For example, the content of the insulating filler may be 300 parts by mass or less, 200 parts by mass or less, or 150 parts by mass or less.

[0036] A content ratio of the silica relative to a total mass of the insulating filler is preferably 80% by mass or more, more preferably 90% by mass or more, and still more preferably 95% by mass or more. The insulating filler may be substantially constituted only of the silica.

[0037] The insulating resin composition may have a viscosity (2 rpm) of 500 dPa·s to 7200 dPa·s measured with a Brookfield viscometer (VISCOMETER TVB-10, manufactured by Toki Sangyo Co., Ltd.) under conditions of 25°C and 2 rpm. The viscosity (2 rpm) is preferably 700 dPa·s to 1500 dPa·s, and more preferably 700 dPa·s to 1000 dPa·s. Further, the viscosity (20 rpm) of the insulating resin composition is preferably 500 dPa·s to 2000 dPa·s, and more preferably 500 dPa·s to 1000 dPa·s.

[0038] It is preferable that the insulating resin composition contains a defoaming agent as an optional additive. Examples of the defoaming agent include those containing acrylic resins, vinyl ether resins, silicone resins, fluorine resins and modified resins thereof.

[0039] The insulating resin composition may contain other additives. For example, the insulating resin composition may contain a flame retardant, an antioxidant, a leveling agent, a rheology control agent, and the like.

[0040] It is preferable that the insulating resin composition does not contain a solvent. That is, the insulating resin composition is preferably solvent-free. This makes it possible to suppress the generation of voids due to volatilization of the solvent during thermosetting.

[0041] An example of how to use the insulating resin composition of this embodiment is as follows: First, the insulating resin composition is filled into the holes of the glass substrate by a screen printing method. Next, the insulating resin composition placed in the holes is cured at a first heating temperature to form a primary cured product. At this time, if the primary cured product protrudes from the surface of the substrate, the excess portion may be removed by polishing. Then, the primary cured product is fully cured at a second heating temperature higher than the first heating temperature to form the filler. At this time, if the filler protrudes from the surface of the substrate, the excess portion may be removed by polishing to flatten the substrate.

[0042] Although the embodiments described are illustrative, the insulating resin composition according to the present invention is not limited to the configuration of the above embodiments. Furthermore, the insulating resin composition according to the present invention is not limited by the above-described effects. The insulating resin composition according to the present invention can be modified in various ways without departing from the spirit of the present invention.

[0043] This disclosure includes the following: [1] An insulating resin composition used for filling holes in a circuit board, comprising a thermosetting resin and an insulating filler, wherein the particle size distribution of the insulating filler satisfies (D100-D30) / D50 ≤ 1.5.

[0044] [2] The insulating resin composition according to [1], wherein D100 in the particle size distribution of the insulating filler is 1.5 μm or less.

[0045] [3] The insulating resin composition according to [1] or [2], wherein D30 in the particle size distribution of the insulating filler is 0.1 μm or more.

[0046] [4] The insulating resin composition according to any one of [1] to [3] above, wherein the insulating filler contains silica, and the silica content is 100 to 300 parts by mass per 100 parts by mass of the thermosetting resin.

[0047] [5] The insulating resin composition according to [4] above, wherein the silica is sol-gel silica.

[0048] [6] The thermosetting resin comprises a liquid epoxy resin with an epoxy equivalent of 200 g / eq or less, as described in any of [1] to [5] above, the insulating resin composition.

[0049] [7] The thermosetting resin is an insulating resin composition according to [6], wherein the liquid epoxy resin includes an aminophenol-type epoxy resin and a bisphenol-type epoxy resin.

[0050] [8] The insulating resin composition according to any one of [1] to [7] above, wherein the circuit board is a glass substrate.

[0051] The present invention will be further described below with reference to examples, but the present invention is not limited thereto.

[0052] [Materials Used] Epoxy resin 1: Trifunctional glycidylamine type epoxy resin (aminophenol type epoxy resin, liquid, epoxy equivalent 90-106 g / eq) Epoxy resin 2: Bisphenol A type epoxy resin (liquid, epoxy equivalent 180-190 g / eq) Epoxy resin 3: Mixture of bisphenol A type epoxy resin and bisphenol F type epoxy resin (liquid, epoxy equivalent 160-170 g / eq) Epoxy resin 4: Alicyclic epoxy resin (liquid, epoxy equivalent 150-160 g / eq) Epoxy resin 5 (reactive diluent): C12-13 alkoxyglycidyl ether (epoxy equivalent 320 g / eq) Curing agent 1 (triazine-containing imidazole curing agent): 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine curing agent 2 (C11 alkyl group-containing imidazole curing agent): 2-undecylimidazole curing agent 3 (naphthol-phenol cocondensed novolac resin): Naphthol-cresol-formaldehyde polymer Antifoaming agent: Xylene solution of acrylic polymer Silica 1: Deflagration silica (D30: 0.4 μm, D50: 0.5 μm, D80: 0.7 μm, D100: 1.4 μm) Silica 2: Deflagration silica (D30: 0.25 μm, D50: 0.3 μm, D80: 0.5 μm, D100: 1.6 μm) Silica 3: Sol-gel silica (D30: 0.35 μm, D50: 0.4 μm, D80: 0.5 μm, D100: 0.6 μm, BET specific surface area: 7 m²) ２Silica 4 ( / g): Sol-gel silica (D30: 0.25 μm, D50: 0.3 μm, D80: 0.3 μm, D100: 0.4 μm, BET specific surface area: 11 m²) ２ Silica 5 (per g): Sol-gel silica (D30: 0.65 μm, D50: 0.7 μm, D80: 0.8 μm, D100: 1.0 μm, BET specific surface area: 4 m²) ２ Silica 6 (per g): Sol-gel silica (D30: 0.09 μm, D50: 0.1 μm, D80: 0.2 μm, D100: 0.3 μm, BET specific surface area: 24 m²) ２ / g)

[0053] [Manufacturing Example] After pre-mixing each component shown in Table 1 with a stirrer, the mixture was dispersed using a three-roll mill to produce an insulating resin composition.

[0054] [Evaluation 1: Via Filling Properties] After filling the vias using a screen plate, the paste was cured under specified curing conditions. The via cross-section was then observed to check for voids and cracks.

[0055] [Evaluation 2: Presence or absence of coarse particles in the via] The via cross-section was magnified and observed using SEM to confirm the presence or absence of coarse particles larger than 5 μm.

[0056]

Claims

1. An insulating resin composition used for filling holes in circuit boards, comprising a thermosetting resin and an insulating filler, wherein the particle size distribution of the insulating filler satisfies (D100-D30) / D50 ≤ 1.

5.

2. The insulating resin composition according to claim 1, wherein D100 in the particle size distribution of the insulating filler is 1.5 μm or less.

3. The insulating resin composition according to claim 2, wherein D30 in the particle size distribution of the insulating filler is 0.1 μm or more.

4. The insulating resin composition according to claim 1, wherein the insulating filler contains silica, and the silica content is 100 to 300 parts by mass per 100 parts by mass of the thermosetting resin.

5. The insulating resin composition according to claim 4, wherein the silica is sol-gel silica.

6. The insulating resin composition according to claim 1, wherein the thermosetting resin comprises a liquid epoxy resin with an epoxy equivalent of 200 g / eq or less.

7. The insulating resin composition according to claim 6, wherein the thermosetting resin comprises an aminophenol-type epoxy resin and a bisphenol-type epoxy resin as the liquid epoxy resin.

8. The insulating resin composition according to any one of claims 1 to 7, wherein the circuit board is a glass substrate.

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