JPS61272243A - Production of prepreg for printed circuit board - Google Patents

Abstract

PURPOSE:To obtain the titled prepreg having improved drillability, dielectric characteristics, etc., by compounding an epoxy resin containing a silicone- modified epoxy resin with a polyfunctional phenol, a cure accelerator and a coupling agent, and impregnating and drying the obtained varnish in a substrate. CONSTITUTION:The objective prepreg can be produced by compounding (A) an epoxy resin containing 1-100wt% silicone-modified epoxy resin produced by reacting (i) 100pts.(wt.) of a bisphenol-A epoxy resin, (ii) 40-80pts. of tetrabromobisphenol A and (iii) 0.1-30pts. of a methoxy-containing silicone intermediate of formula (R is methyl, phenyl or methoxy; n is 0-3), etc., with (B) a polyfunctional phenol, (C) a cure accelerator, preferably an imidazole compound having masked imino group and (D) a coupling agent, preferably a silane coupling agent, impregnating the resultant varnish in a substrate and drying the varnish at 80-200 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for producing prepreg for printed wiring boards.

[Conventional technology]

As the density of printed wiring boards increases, the number of layers and through holes become smaller, and materials for printed wiring boards with good drillability are required. In terms of drilling workability, the occurrence of smear significantly impairs the through-hole reliability by interfering with the conduction between the inner layer circuit copper and the through-hole plating copper. Printed wiring board manufacturers use a smear removal process to remove smear, but it uses concentrated sulfuric acid, hydrofluoric acid, etc., which poses safety issues, and can also roughen the inner walls of through holes, reducing reliability. Become. The cause of smear is said to be that resin softened by the frictional heat during drilling attaches to the cross section of the inner layer circuit copper due to the drilling. Although softening of the resin can be prevented by using a cured resin with a high Tg, the hardness of the resin also increases.
Various problems arise. Another way to reduce the occurrence of smear is to reduce the frictional heat generated during drilling. That is, this is a method of suppressing the generation of frictional heat and preventing softening of the resin by reducing the friction of the resin.

Additionally, the currently used glass cloth-epoxy laminate has excellent moisture resistance and heat resistance, but has a high dielectric constant.
It cannot cope with the miniaturization of printed wiring boards due to the reduction in pattern width and pattern spacing associated with higher density printed wiring boards, higher signal speeds, and higher frequencies. One way to lower the dielectric constant is to use quartz glass for the glass cloth, but it has problems such as being expensive and being extremely hard, which causes severe wear on drills.

[Problem that the invention seeks to solve]

The present invention relates to a method for producing prepreg for printed wiring boards, which aims to improve the drillability and dielectric properties of conventional multilayer materials.

[Means for solving problems]

The method for producing prepreg for printed wiring boards of the present invention includes (a)
1 to 1 silicone-modified epoxy resin obtained by reacting bisphenol A type epoxy resin, tetrabromobisphenol A, and a methoxy group-containing silicone intermediate.
After impregnating a base material such as glass cloth or glass nonwoven fabric with a fest containing 00% by weight of epoxy resin, (b) polyfunctional phenol, (c) curing accelerator, and (d) coupling agent as essential components, drying. It is characterized by

The present invention will be explained in detail below.

The epoxy resin of component (a) contains 1 to 100% by weight of a silicone-modified epoxy resin obtained by reacting a bisphenol A type epoxy resin, tetrabromobisphenol A, and a methoxy group-containing silicone intermediate as an essential component.

As the bisphenol A type epoxy resin, one having few hydroxyl groups is preferable, and one having a hydroxyl value of O to 0.08 is preferable. If the hydroxyl value is higher than that, the obtained silicone-modified epoxy resin will have a high molecular weight and will give a non-uniform cured product.

The hydroxyl value is the reciprocal of the hydroxyl equivalent multiplied by 100, and the hydroxyl equivalent is determined by the acetyl chloride method.

It was measured.

Tetrabromobisphenol A is used to impart flame retardancy to epoxy resins, and the amount of bisphenol A
It is preferably 40 to 80 parts by weight based on 100 parts by weight of the mold epoxy resin. If it is less than 40 parts by weight, sufficient flame retardancy cannot be obtained, and if it is more than 80 parts by weight, the silicone-modified epoxy resin will have a high molecular weight.

The methoxy group-containing silicone intermediate is RR or its condensation polymer, and has a methoxy group equivalent of 50 to 30.
0 is used. If the methoxy group equivalent is larger than this, the silicone-modified epoxy resin will have a high molecular weight,
Gives an unevenly cured product. If it is smaller than this, the reaction will not proceed sufficiently due to steric hindrance, and unreacted methoxy groups will remain, resulting in decreased moisture resistance and heat resistance. The silicone intermediate is used in an amount of 0.1 to 30 parts by weight per 100 parts by weight of bisphenol A epoxy resin, but if it is less than this, it will have no effect on drillability, and if it is more than this, unreacted methoxy groups will remain. .

When these compounds are reacted, tertiary amines, quaternary ammonium salts, imidazole, alkali metal hydroxides, halogenated phosphonium salts, sulfonium salts, tertiary phosphines, organic titanate compounds, organic zirconium compounds are used as catalysts. etc. may also be used. Examples of tertiary amines include benzyldimethylamine, triethanolamine, and pyridine. Examples of quaternary ammonium salts include benzyltrimethylammonium hydroxide, benzyltrimethylammonium chloride, tetramethylammonium bromide, tetramethylammonium chloride, tetraethylammonium bromide, tetraethylammonium chloride, and N-cetylpyridinium chloride. As imidazole, 2
- Methylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 1-cyanoethyl-2-phenylimidazole, and the like. Examples of alkali metal hydroxides include sodium hydroxide, potassium hydroxide, and lithium hydroxide. Examples of the halogenated phosphonium salts include ethyltriphenylphosphonium bromide, tetraphenylphosphonium chloride, tetrabutylphosphonium chloride, and methyltriphenylphosphonium iodide. Examples of sulfonium salts include triphenylsulfonium chloride, benzyldimethylsulfonium chloride, and dimethylpropylsulfonium bromide. Examples of tertiary phosphine include triphenylphosphine and tributylphosphine. Organic titanate compounds include tetrapropyl titanate, tetrabutyl titanate, isopropyl triisostearoyl titanate, isopropyl tridecylbenzenesulfonyl titanate, isopropyl tolyl (dioctyl pyrophosphate) titanate, tetraisopropyl bis (dioctyl phosphite) titanate, tetraoctyl bis ( ditridecyl phosphite) titanate, tetra(2,2-diallyloxymethyl-1-butyl) bis(di-tridecyl) phosphite titanate, bis(dioctyl pyrophosphate) oxyacetate titanate, bis(dioctyl pyrophosphate) ethylene titanate, Examples include tetraisopropyl titanate, tetraoctyl titanate, and tetrastearyl titanate. Examples of organic zirconium compounds include zirconium acetate, tetrakis(acetylacetonate)zirconium, di-normalpropoxy-acetylacetonyl-stearyloxyzirconium, stearylzirconium, acetylacetonatezirconium,
Examples include hydroxyzirconium tolyl (acetylacetonate).

These catalysts are mixed with bisphenol A type epoxy resin 10
0! 0. OO1 to 0,605 parts by weight is used, but if it is less than that, there is no catalytic effect, and if it is more than that, it acts as an impurity in the resin and affects the electrical properties of the cured product.

The temperature for the synthesis reaction of silicone-modified epoxy resin is 10
0 to 200°C is preferred. When the temperature is lower than 100°C, the reaction is slow and takes 10 hours or more. When the temperature is higher than 200°C, the catalytic effect is lost and tetrabromobisphenol A begins to decompose.

The synthesis reaction time may be any number of hours, but is preferably 2 to 5 hours. The end point of the reaction is confirmed by measuring the epoxy equivalent by the cetyltrimethylammonium bromide-perchloric acid method. If the measured epoxy equivalent is between 90% and 110% of the theoretically calculated value, it is considered as the end point. If it is less than 90%, there will be a large amount of unreacted substances, resulting in slow curing, and if it exceeds 110%, there will be a large amount of high molecular weight substances, which will deteriorate the appearance of the prepreg, which is not preferable.

During the synthesis reaction, inert gas substitution may or may not be performed.

Methanol, which is a reaction by-product, is removed from the system by distillation, and if necessary, by vacuum distillation.

The silicone-modified epoxy resin obtained as described above is used in an amount of 1 to 100% by weight. If it is less than 1% by weight, no improvement in drill workability will be observed.

There is no particular restriction on the type of epoxy resin used as a component other than silicone-modified epoxy resin, and examples include bisphenol A epoxy resin, bisphenol F epoxy resin, bisphenol S epoxy resin,
Phenol novolac type epoxy resin, cresol novolac type epoxy resin, bisphenol A novolac type epoxy resin, bisphenol F novolac type epoxy resin, alicyclic epoxy resin, glycidyl ester type epoxy resin, glycidylamine type epoxy resin, hydantoin type epoxy resin, isocyanate There are nurate-type epoxy resins, resorcinol-type epoxy resins, and their halides and hydrogenated products, and several types can be used in combination. Furthermore, there are no restrictions on the method or temperature for mixing these epoxy resins.

The polyfunctional phenol (b) may be of any type as long as it is polymerized with the epoxy resin, such as bisphenol A1 bisphenol F1 polyvinylphenol, or novolak resin such as phenol, cresol, alkylphenol catechol, bisphenol A1 bisphenol F, etc. and halides of these phenolic resins. Several types of these phenol resins can also be used in combination. The blending amount is preferably in the range of 0.5 to 1.5 equivalents of phenolic hydroxyl group to epoxy group from the viewpoint of drill workability.

As the curing accelerator (C), imidazole compounds, organic phosphorus compounds, tertiary amines, quaternary ammonium salts, etc. are used, but imidazole compounds whose imino groups are masked with acrylonitrile, isocyanate, melamine acrylate, etc. By using this method, it is possible to obtain a prepreg that has storage stability that is more than twice that of conventional prepregs.

The imidazole compounds used here include imidazole, 2-ethylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-undecylimidazole, 1-benzyl-2-methylimidazole, 2-heptadecylimidazole. , 4.5-diphenylimidazole, 2-methylimidacillin, 2-
Phenylimidacillin, 2-undecylimidacillin,
2-heptadecyl imidacilline, 2-isopropylimidazole, 2,4-dimethylimidazole, 2-phenyl-4-methylimidazole, 2-ethylimidacilline, 2-isopropylimidacilline, 2,4-dimethylimidacillin Examples of masking agents include acrylonitrile, phenylene diisocyanate, toluene diisocyanate, naphthalene diisocyanate, hexamethylene diisocyanate, methylene bisphenyl isocyanate, and melamine acrylate.

Several types of these curing accelerators may be used in combination, and the blending amount is preferably 0.01 to 5 parts by weight per 100 parts by weight of the epoxy resin. If it is less than 0.01 part by weight, the accelerating effect will be small, and if it is more than 5 parts by weight, drilling workability will be reduced.

The coupling agent (d) is necessary to improve the peeling strength of the copper foil, and silane coupling agents, titanate coupling agents, etc. are used, but silane coupling agents, titanate coupling agents, etc. Ring agents are preferred.

Examples of the silane coupling agent include γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, T-glycidoxypropylmethyldimethoxysilane, N-β (aminoethyl)-r-aminopropyl Methoxysilane, T-mercaptopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, N-vinylbenzyl-δ-aminopropyltriethoxysilane, etc., and other epoxy Any substance may be used as long as it has a functional group that reacts with a phenolic hydroxyl group and a hydrolyzable alkoxy group.

Titanate coupling agents include isopropyl triisostearoyl titanate, isopropyl tridodecylbenzenesulfonyl titanate, isopropyl tris(dioctyl pyrophosphate) titanate, tetraisopropyl bis(dioctyl phosphite) titanate, tetraoctyl bis(ditridecyl phosphite) )
Titanate, tetra(2,2-diallyloxymethyl-
Examples include 1-butyl)bis(di-tridecyl)phosphite titanate, bis(dioctylpyrophosphate)oxyacetate titanate, and bis(dioctylpyrophosphate)ethylene titanate, and titanates with lower molecular weights may also be used.

The blending amount of these coupling agents is 1 epoxy resin.
0.00 parts by weight, preferably 0.1 to 5 parts by weight, and if it is less than this, there is no effect on the copper foil peeling strength,
If the amount is more than this, heat resistance and drill workability will deteriorate.

Solvents used in making the face include acetone, methyl ethyl ketone, toluene, xylene, methyl isobutyl ketone, ethyl acetate, ethylene glycol monomethyl ether, N,N-dimethylformamide, N,N-dimethylacetamide, methanol, ethanol, etc. Some of these may be used in combination.

Moreover, the above (a), (b), (c), and (d) are essential components, and it is also possible to mix other compounds.

After incorporating the fest obtained by blending the above (a), (b), (c), and (d) into a base material such as glass cloth or glass nonwoven fabric,
It is dried in a drying oven at a temperature of 80 to 200°C to obtain a prepreg for printed wiring boards. Prepreg is used to manufacture printed wiring boards or metal-clad laminates by heating and pressing.

〔Example〕

Examples of the present invention will be described below.

The epoxy resin used in the present invention was synthesized as follows.

Silicone epoxy Month L = Epoxy equivalent weight 175 Bisphenol A type epoxy resin 4300 g, Tetrabromobisphenol A
2650 g, KR9218 (trade name: manufactured by Shin-Etsu Chemical Co., Ltd., silicone intermediate with a methoxy group equivalent weight of 210) 4
20g, tetramethylammonium chloride 0.5
The mixture was mixed and stirred and kept at a temperature of 160°C for 2 hours. During that time, volatile components in the system were removed under reduced pressure. Epoxy equivalent weight 58
Silicone-modified epoxy resin A of No. 4 was obtained.

Silicone epoxy Item B: Bisphenol A type epoxy resin with epoxy equivalent weight 190 3600 g, tetrabromobisphenol A
2600g, KR213 (Product name: Shin-Etsu Chemical Co., Ltd.)
silicone intermediate with a methoxy group equivalent weight of 157”) 3
15g, tetrabutylphosphonium chloride 0.4
0 g were mixed and stirred and kept at a temperature of 130°C for 3 hours.

During that time, volatile components in the system were removed under reduced pressure. Epoxy equivalent
568 silicone-modified epoxy resin B was obtained.

Silicone Epoxy C: Bisphenol A type epoxy resin with epoxy equivalent weight 190 4300 g, tetrabromobisphenol A
2200g, KR217 (Product name: Shin-Etsu Chemical Co., Ltd.)
(silicone intermediate with methoxy group equivalent weight 263) 42
0g of tetrapropyl titanate and 1.0g of tetrapropyl titanate were mixed and stirred and kept at a temperature of 8.0°C for 1 hour. During that time, volatile components in the system were removed under reduced pressure. A silicone-modified epoxy resin C having an epoxy equivalent weight of 563 was obtained.

Epoxy resin D: 4300 g of bisphenol A type epoxy resin with epoxy equivalent weight of 175, tetrabromobisphenol A 2
650g, tetramethylammonium chloride 0.
25 g were mixed and stirred and kept at a temperature of 160°C for 2 hours. During that time, volatile components in the system were removed under reduced pressure. An epoxy resin having an epoxy equivalent weight of 550 was obtained.

A festival was made using the epoxy resin obtained above according to the formulation shown in Table 1.

The varnishes of Examples 1 to 4 and Comparative Examples 1 and 2 above were added to 0.1
A thick glass cloth was impregnated and dried at 120° C. for 10 minutes to obtain a prepreg.

Using 15 sheets of the above prepreg and 6 sheets of copper foil with a thickness of 35 μm, a 6-layer printed wiring board was fabricated by heat-pressing molding at 170°C for 60 minutes, and the results showed drill workability, copper foil peeling strength, and solder heat resistance. The properties and storage stability of the prepreg were tested. Drill workability test was conducted using a 6N printed wiring board at a rotation speed of 60 kr.
pm, feed rate 3, 0 m/+++in, hole diameter 1.
Holes were punched up to 12,000 hits using two stacked sheets and the smear occurrence rate was measured.

The characteristics test results are shown in Table 2.

The measurement was performed according to JIS C-6481.

1) Smear incidence rate evaluation method Through-hole plating was applied to a drilled 6-layer wiring board, and the cut surface of the through-hole part was examined using a microscope for 5000 hours.
The connection portion between the inner layer copper of 20 holes and the through-hole plated copper near 10,000 hits was observed, and the smear occurrence rate was evaluated. The smear incidence rate for each connection point is
The ratio of the height of the generated smear to the connection height was calculated and averaged.

t. Copper Foil Peeling Strength Measuring Method A 10fi wide line was formed on the outer layer copper foil, and the peeling strength in the 90° direction of the line was measured at a peeling speed of 50 m/min.

' Inner layer copper peel strength measurement method The glossy surface of the inner layer copper foil was treated with copper oxide, and the peel strength between the copper oxide treated surface and the prepreg layer was measured under the same conditions as in 2).

4) Solder Heat Resistance After immersing in solder at 260° C. for 20 seconds, the appearance was visually evaluated, and those with no blisters were rated OK, and those with blisters were rated NG.

I Prepreg Gel Time The gel time at 160°C of the prepreg immediately after coating was taken as the initial value, and the gel time at 160°C of the prepreg after being stored for 60 days at a temperature of 20°C and a humidity of 40% was measured.

As shown in Margin Table 2 below, silicone-modified epoxy resin,
It can be seen that in Examples 1 to 4 using phenol resin, the smear occurrence rate is lower than in Comparative Example 2 using dicyandiamide. Comparative Example 1 did not use silicone-modified epoxy resin, so the smear occurrence rate was higher than in Examples 1 to 4.

In Examples 1 to 4, since a coupling agent was added and masked imidazole was used as an accelerator, the copper foil peeling strength and storage stability were good. Comparative Example 1 does not use a coupling agent or a masked imidazole, and therefore has poor peel strength and storage stability.

〔Effect of the invention〕

As described above, the prepreg for printed wiring boards of the present invention has improved drilling workability and copper foil peeling strength of multilayer wiring boards, as well as storage stability of the prepreg, as compared to the conventional technology.

Claims (1)

[Scope of Claims] 1. (a) An epoxy resin containing 1 to 100% by weight of a silicone-modified epoxy resin obtained by reacting a bisphenol A type epoxy resin, tetrabromobisphenol A, and a methoxy group-containing silicone intermediate, (b 1. A method for producing a prepreg for a printed wiring board, which comprises impregnating a base material with a varnish containing as essential components a) polyfunctional phenol, (c) a curing accelerator, and (d) a coupling agent, and then drying the varnish. 2. The method for producing a prepreg for a printed wiring board according to claim 1, wherein the curing accelerator is an imidazole compound with masked imino groups.