JPH0759625B2 - Epoxy resin composition for printed wiring board - Google Patents

Description

TECHNICAL FIELD The present invention relates to an epoxy resin composition for wiring boards, which is excellent in insulating properties, particularly in suppressing metal migration.

[Conventional technology]

With the miniaturization and high performance of electronic devices, the printed wiring boards mounted therein are becoming higher in density by increasing the number of layers, reducing the diameter of through holes, and reducing the hole spacing. For this reason, the demand for electric insulation characteristics of printed wiring boards, which has not been a serious problem until now, has become strict.

Epoxy resins have hitherto been widely used as insulating materials for printed wiring boards. However, with the increase in the density, there has been a problem that a printed wiring board using an epoxy resin is apt to cause insulation failure or conduction breakdown due to metal migration.

The metal migration is a phenomenon in which a metal forming wirings, circuit patterns, electrodes, or the like on or in an insulating material migrates on or in the insulating material due to the action of a potential difference in a high humidity environment.

Also, dicyandiamide, which has been conventionally used as a curing agent for epoxy resins, has poor compatibility with epoxy resins and, when used as a prepreg, dicyandiamide is likely to precipitate, and printed wiring boards produced by this curing system have a softening temperature. For example, the smear that resin adheres to the inner layer circuit copper is likely to occur during drilling, and the long-term heat resistance in air is also poor.

An epoxy resin cured with a polyfunctional phenol resin is a resin system that solves these problems. Compared with the dicyandiamide curing system, the printed wiring board produced by this curing system has less than half the generation of smear, and the long-term heat resistance in air is more than doubled.

However, there is a concern that metal migration will occur in any of the curing systems, and particularly in the dicyandiamide curing system, metal migration is likely to occur because of high hygroscopicity.

[Problems to be Solved by the Invention]

As a resin excellent in migration prevention, a triazine resin can be mentioned, but it has drawbacks such as a large curing shrinkage at the time of molding, a low adhesive property, and a hardness and brittleness. Further, in the method of adding a triazine compound as an anti-migration agent to an epoxy resin as disclosed in JP-B-61-233013, it is difficult to uniformly disperse the triazine compound, resulting in large variations in characteristics.

The present invention has been made in view of the above circumstances, and provides an epoxy resin composition which, when applied to a material for a printed wiring board, provides excellent electrical insulating properties.

[Means for Solving the Problems]

That is, the epoxy resin composition of the present invention comprises (a) an epoxy resin, (b) a polyfunctional phenolic resin, (c) a curing accelerator, and (d) butylated hydroxyanisole, 2,6-di-t-
Butyl-4-ethylphenol, 2,2'-methylene-bis (4-methyl-6-t-butylphenol), 4,4 '
-Thiobis- (3-methyl-6-t-butylphenol), 4,4'-butylidenebis (3-methyl-6-t-)
Butylphenol), 1,1,3-tris (2-methyl-4)
Hydroxy-5-t-butylphenyl) butane, 1,3,5
-Trimethyl-2,4,6-tris (3,5-di-t-butyl-
Among the hindered phenolic antioxidants selected from the group of 4-hydroxybenzyl) benzene and tetrakis- [methylene-3- (3 ', 5'-di-t-butyl-4'-hydroxyphenylpropionate] methane Any one or more, or any one or more of dilauryl thiodipropionate and distearyl thiodipropionate sulfur organic compound type antioxidant.

Is included as an essential component.

The present invention will be described in detail below.

The epoxy resin (a) may be any polyfunctional one, such as bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, phenol novolac type epoxy resin, cresol novolac type epoxy resin. Resin, bisphenol A novolac type epoxy resin, bisphenol F
Novolac type epoxy resin, alicyclic epoxy resin, glycidyl ester type epoxy resin, glycidyl amine type epoxy resin, hydantoin type epoxy resin, isocyanurate type epoxy resin, aliphatic chain epoxy resin and their halides, hydrogenated products, etc. However, any molecular weight may be used, and it is possible to use several kinds in combination.

The polyfunctional phenol resin (b) is not particularly limited as long as it has two or more functional groups in one molecule and reacts with an epoxy resin, and examples thereof include bisphenol A, bisphenol F, polyvinylphenol, or phenol, There are novolac resins such as cresol, alkylphenol, catechol, bisphenol A and bisphenol F, and halides of these phenol resins. These phenol resins may be used in combination of several kinds. From the viewpoint of drilling workability, it is preferable that the amount of the phenolic hydroxyl group is 0.5 to 1.5 equivalents relative to the epoxy group.

As the curing accelerator of (c), an imidazole compound, an organic phosphorus compound, a tertiary amine, a quaternary ammonium salt, or the like is used, and an imidazole compound in which an imino group is masked with acrylonitrile, isocyanate, melamine acrylate, or the like. By using, it is possible to obtain a prepreg having a storage stability that is at least twice that of the conventional one.

Examples of the imidazole compound used here include imidazole, 2-ethylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-undecylimidazole, 1-benzyl-2-methylimidazole, and 2-heptadecylimidazole. , 4,5-diphenylimidazole, 2-methylimidazoline, 2-phenylimidazoline, 2-undecylimidazoline, 2
-Heptadecyl imidazoline, 2-isopropyl imidazole, 2,4-dimethyl imidazole, 2-phenyl-
4-methylimidazole, 2-ethylimidazoline, 2
-Isopropylimidazoline, 2,4-dimethylimidazoline, 2-phenyl-4-methylimidazoline and the like, as the masking agent, acrylonitrile, phenylene diisocyanate, triene diisocyanate, naphthalene diisocyanate, hexamemethylene diisocyanate, methylene bisphenyl isocyanate, Melamine acrylate and the like.

Several kinds of these curing accelerators may be used in combination, and the compounding amount is preferably 0.01 to 5 parts by weight with respect to 100 parts by weight of the epoxy resin. If it is less than 0.01 parts by weight, the promoting effect is small,
If it is more than 5 parts by weight, the storage stability becomes poor.

The antioxidant of (d) uses at least one of a hindered phenol-based antioxidant and a sulfur organic compound-based antioxidant, but when a hindered phenol-based antioxidant is used, other properties such as drill workability are deteriorated. It is possible to improve the electric insulation characteristics without performing the above. As the hindered phenolic antioxidant, butylated hydroxyanisole, 2,
6-di-t-butyl-4-ethylphenol, a monophenol system, 2,2'-methylene-bis- (4-methyl-6-t-butylphenol), 4,4'-thiobis-
(3-methyl-6-t-butylphenol), 4,4'-
Butylidene bis (3-methyl-6-t-butylphenol), a bisphenol system and 1,1,3-tris (2-
Methyl-4-hydroxy-5-butylphenyl) butane, 1,3,5-trimethyl-2,4,6-tris (3,5-di-t
-Butyl-4-hydroxybenzyl) benzene, tetrakis- [methylene-3- (3 ', 5'-di-t-butyl-
4'-hydroxyphenyl) propionate] methane is a polymeric phenolic system.

Examples of the sulfur organic compound-based antioxidant include dilauryl thiodipropionate and distearyl thiodipropionate.

Several kinds of these antioxidants may be used in combination, and the compounding amount is preferably 0.1 to 20 parts by weight with respect to 100 parts by weight of the epoxy resin. When the amount is 0.1 parts by weight or less, the insulating property is not improved, and when the amount is 20 parts by weight or more, the insulating property tends to decrease.

The epoxy resin composition according to the present invention is used in various forms, but a solvent is often used when coating and impregnating a substrate. These solvents include acetone, methyl ethyl ketone, toluene, xylene, methyl isobutyl ketone, ethyl acetate, ethylene glycol monomethyl ether, N, N-dimethylformamide, N, N-dimethylacetamide, methanol and ethanol. You may mix and use it.

The varnish obtained by blending the above (a), (b), (c), and (d) is impregnated into a base material such as glass cloth, non-woven glass cloth or paper, cloth having a component other than glass, and dried in a drying oven. At 80-200
A prepreg for a printed wiring board is obtained by drying in the range of ° C. The prepreg is used for producing a printed wiring board or a metal-clad laminate (hereinafter referred to as MCL) by heating and pressing at 150 to 190 ° C. and 20 to 80 kgf / cm ² .

The drying here means removing the solvent when the solvent is used, and making the fluidity disappear at room temperature when the solvent is not used.

〔Example〕

 The present invention will be further described below based on examples.

Example 1 Brominated bisphenol A type epoxy resin (epoxy equivalent
530) 100 parts by weight Phenol novolac resin (hydroxyl equivalent 106) 20 parts by weight 2-Ethyl-4-methylimidazole masked with hexamethylene diisocyanate 0.5 parts by weight 4,4'-butylidene bis (3-methyl-6-t-butylphenol) 0.5 parts by weight The above compound was dissolved in methyl ethyl ketone to give a nonvolatile content of 70%.
% Varnish was prepared.

Example 2 Instead of 4,4′-butylidene bis (3-methyl-6-t-butylphenol) in Example 1, 1,1,3-tris (2-methyl-4-hydroxy-5-t-butylphenyl) was used. ) 0.5 parts by weight of butane was blended.

Example 3 Instead of 4,4'-butylidene bis (3-methyl-6-t-butylphenol) in Example 1, tetrakis [methylene-3- (3 ', 5'-di-t-butyl-4'-] was used.
0.5 parts by weight of hydroxyphenyl) propionate] methane was blended.

Example 4 Instead of 4,4′-butylidene bis (3-methyl-6-t-butylphenol) in Example 1, 0.5 part by weight of dilaurylthiopropionate was blended.

Example 5 In place of 4,4′-butylidene bis (3-methyl-6-t-butylphenol) in Example 1, 0.25 parts by weight of 4,4′-butylidene bis (3-methyl-6-t-butylphenol) was used. , Dilauryl thiopropionate
0.25 part by weight was compounded.

Comparative Example 1 The 4,4′-butylidene bis (3-methyl-6-t-butylphenol) in Example 1 was not added.

Comparative Example 2 4 parts by weight of dicyandiamide was blended in place of the phenol novolac resin in Comparative Example 1, and ethylene glycol monomethyl ether was further added as a solvent.

A glass cloth having a thickness of 0.2 mm was impregnated with the varnishes obtained in Examples 1 to 5 and Comparative Examples 1 and 2, and then heated at 140 ° C. for 5 to 10 minutes to obtain a prepreg.

18 μm on each side of the 8 prepregs thus obtained
A thick copper foil was placed, and a double-sided copper-clad laminate was produced under the press conditions of 170 ° C., 90 minutes, and 50 kg / cm ² . Circuit processing was performed on this MCL and a migration test was performed. Through hole drilling was performed using a 0.9 mm diameter drill under the conditions of a rotational speed of 60,000 rpm and a feed rate of 1,800 mm / min.

The hole wall spacing was 350 μm, and the insulation resistance of 400 holes (200 holes between through holes) of each sample was measured with time. The test conditions were 100 V applied in an atmosphere of 85 ° C./90% RH, and the number of days until conduction breakdown occurred between the through holes was measured. The insulation resistance was measured at 100V / 1min.

Solder heat resistance test is conducted at 260 ℃ for MCL with double-sided etching.
After 20 seconds of immersion in the solder, the appearance was visually evaluated, and those without blisters were OK and those with blisters were NG.

The gel time of the prepreg was measured at 160 ° C, and the storage stability of the prepreg was evaluated by measuring the gel time of the prepreg immediately after coating and the prepreg after storage at 20 ° C / 40% RH for 60 days. The results are shown in Table 1.

Examples 1 to 5 in which the antioxidant was blended did not cause conductive breakdown even after 60 days, and exhibited higher insulating properties than Comparative Examples 1 and 2. In particular, Examples 1, 2, 3, and 5 using the hindered phenol-based antioxidant showed a tendency that the insulation resistance value on the 60th day was also high.

[Effects of the Invention] As is clear from the above description, the epoxy resin composition of the present invention suppresses the occurrence of metal migration when applied to the material of a printed wiring board as compared with the prior art, and has an excellent electrical insulating property. It is what makes me.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP 61-200156 (JP, A) JP 61-272244 (JP, A) JP 62-161820 (JP, A) JP 62- 161817 (JP, A) JP-A-2-86149 (JP, A)

Claims (1)

[Claims] 1. An epoxy resin composition for a printed wiring board, which comprises the following (a), (b), (c) and (d) as essential components. (A) Epoxy resin (b) Polyfunctional phenolic resin (c) Curing accelerator (d) Butylated hydroxyanisole, 2,6-di-t-
Butyl-4-ethylphenol, 2,2'-methylene-bis (4-methyl-6-t-butylphenol), 4,4 '
-Thiobis- (3-methyl-6-t-butylphenol), 4,4'-butylidenebis (3-methyl-6-t-)
Butylphenol), 1,1,3-tris (2-methyl-4)
Hydroxy-5-t-butylphenyl) butane, 1,3,5
-Trimethyl-2,4,6-tris (3,5-di-t-butyl-
Among the hindered phenolic antioxidants selected from the group of 4-hydroxybenzyl) benzene and tetrakis- [methylene-3- (3 ', 5'-di-t-butyl-4'-hydroxyphenylpropionate] methane Any one or more, or any one or more of dilauryl thiodipropionate and distearyl thiodipropionate sulfur organic compound type antioxidant.