JPH0760921B2 - Prepreg for printed wiring board - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention has a low occurrence rate of smear during drilling in a printed wiring board, is excellent in heat resistance and moisture resistance, and is excellent in storage stability. The present invention relates to a good prepreg for printed wiring boards.

(Prior Art) In recent years, glass epoxy copper clad laminates used for printed wiring boards of electronic devices have been used not only in industrial equipment such as computers, communication equipment and industrial measuring equipment, but also in televisions, video recorders, audio equipment, etc. Utilization for consumer equipment is also increasing, and its production volume is increasing rapidly. Along with this, the required characteristics of glass-epoxy copper-clad laminates have also diversified, and it has become impossible to satisfy the conventional heat resistance level. In particular, the speeding up of drills when drilling printed wiring boards has caused problems such as smear that occurs when the temperature inside the holes rises and blistering that occurs when soldering due to moisture absorption after processing. It was

Generally, an epoxy resin composition used for a glass epoxy copper clad laminate is prepared by blending a bisphenol A type epoxy resin or tetrabromobisphenol A type epoxy resin with a curing agent such as amine and acid anhydride and a small amount of a curing accelerator. It was done. In this case, in order to improve heat resistance, a method of blending a novolac type epoxy resin is used. However, the average number of phenol nuclei of the novolac type epoxy resin used conventionally is as large as 9 to 10, and the reaction with the curing agent is quicker than that of the bisphenol A type epoxy resin or the tetrabromobisphenol A type epoxy resin. Therefore, an epoxy resin composition containing this, particularly a flame-retardant one, is easily gelled partially, the storage stability of the prepreg is poor, and it becomes difficult to control the press molding conditions. There is a drawback that the compounding amount cannot be increased.

As a method of improving this drawback, it is possible to react a novolac type epoxy resin having an average number of nuclei of 2.3 to 10, a bisphenol A type epoxy resin and tetrabromobisphenol A with JP-A 61-188413 and JP-A 62-188413. -64821 publication. However, when a novolac type epoxy resin (a) having an average number of nuclides of 7 to 10 is reacted, the viscosity of the resin composition becomes high, so that the impregnation property into the prepreg is significantly reduced, and (b) is not preferable. ) When a compound having an average number of nuclides of 2.3 to 6.9 is reacted, there is a drawback that the heat resistance of the resin composition is poor.

(Problems to be solved by the invention) The present invention has been made in order to solve the above-mentioned drawbacks, and is free from smear and blisters during drilling, excellent in heat resistance, moisture resistance and moldability, and prepreg. An object of the present invention is to provide a prepreg for flame-retardant printed wiring boards, which has good storage stability.

[Structure of the Invention] (Means for Solving the Problems) As a result of intensive studies aimed at achieving the above-mentioned objects, the present inventors have made trinuclear novolac type epoxy and tetranuclear novolak type epoxy as main components. It was found that the above object can be achieved by using a low molecular weight novolac type epoxy resin containing 30% by weight or more as the above, and the present invention has been completed.

That is, the present invention contains (A) bisphenol A type epoxy resin, (B) tetrabromopisphenol A and (C) trinuclear novolak type epoxy and tetranuclear novolak type epoxy as main components in an amount of 30% by weight or more. A prepreg for a printed wiring board, characterized in that a base material is impregnated and dried with an epoxy resin composition obtained by reacting a novolac type epoxy resin.

Hereinafter, the present invention will be described in detail.

As the (A) bisphenol A type epoxy resin used in the present invention, an epoxy resin obtained by reacting bisphenol A with epichlorohydrin can be used, and any of liquid to solid resins can be used. Among these, a liquid epoxy resin containing as a main component a reaction product of one molecule of bisphenol A and two molecules of epichlorohydrin can be preferably used.

The (B) tetrabromobisphenol A used in the present invention may be any one commonly used, and is not particularly limited for the present invention.

The novolak-type epoxy resin (C) used in the present invention is a low-molecular-weight epoxy resin having a novolak phenolic nucleus mainly composed of a trinuclear body and a tetranuclear body. The content of novolac type epoxy is
It is 30% by weight or more based on the component (C). Particularly preferably, the average number of nuclides is as small as possible and the dinuclear component is 10 or less.
It is less than or equal to weight%. As the nuclide of these resins,
Examples thereof include phenol novolac type epoxy resin and cresol novolac type epoxy resin, which can be used alone or in combination of two or more kinds.

1 to 5 are liquid chromatograph charts of cresol novolac type epoxy resin. 1 and 2 are liquid chromatograph charts of the low molecular weight novolac type epoxy resin used in the present invention. That is,
The resin in FIG. 1 has the most trinuclear component, and the content of the trinuclear and tetranuclear novolac type epoxy in the component (C) is 55% by weight calculated from the chart of the liquid chromatograph. And has a melting point of 42 ° C. Although the average number of nuclei is small and the melting point is as low as 42 ° C, the number of dinuclears is small. In the resin shown in FIG. 2, tetranuclear is the most component (content of trinuclear and tetranuclear is 40% by weight), the average number of nuclei is relatively small, and the melting point is 60 ° C. There are few. Further, the resin containing the trinuclear body as the most component shown in FIG. 1 and the resin containing the tetranuclear body as the most component shown in FIG. 2 are mixed at an arbitrary ratio to form the trinuclear body and the tetranuclear body. A resin containing 30% by weight or more as a main component can be used.

FIG. 3, FIG. 4 and FIG. 5 are liquid chromatograph charts of the cresol novolac type epoxy resin used conventionally. The resin shown in FIG. 3 has the highest content of dinuclear components of 35% by weight (content of trinuclear and tetranuclear bodies of 28% by weight), has a low average number of nuclei and has a melting point of 40 ° C. It has a melting point equivalent to that of the resin used in FIG. However, when the resin of FIG. 3 is used, the resin composition is improved in impregnation property but inferior in heat resistance, whereas the resin of FIG. 1 of the present invention is improved in both impregnation property and heat resistance. The resin of FIG. 4 also has a considerable amount of dinuclear components as in the case of the resin of FIG. 3, but also has a large amount of pentanuclear components or more (content of trinuclear and tetranuclear 22% by weight). The average number of nuclei becomes large and the melting point becomes 60 ° C. The resin of FIG. 4 and the resin of FIG. 2 used in the present invention have the same melting point, but the resin of FIG. However, the impregnation property is poor. On the other hand, the resin of FIG. 2 of the present invention has a tetranuclear body as the most component and a small amount of dinuclear body, and by using this resin, both the heat resistance and the impregnation property can be improved.
The resin shown in FIG. 5 has a large content of pentanuclear components of 70% by weight or more (content of trinuclear and tetranuclear bodies of 15% by weight), and thus has a high melting point of 80 ° C. When this resin is used, Although the heat resistance is improved, the impregnation property is remarkably inferior.

The compounding ratio of the low molecular weight novolac type epoxy resin containing trinuclear and tetranuclear as main components is 5 to 40 relative to the resin composition.
It is desirable to formulate so as to contain the composition in a weight percentage. If the compounding ratio is less than 5% by weight, there is no effect of improving the characteristics.
If it exceeds 5% by weight, the reaction with the curing agent is accelerated and the gelation is apt to occur partially, and the viscosity of the reaction product is high and the impregnation property is deteriorated, which is not preferable.

The epoxy resin composition used in the present invention is obtained by reacting a bisphenol A type epoxy resin, tetrabromobisphenol A, a specific novolac type epoxy resin with an inorganic base such as NaOH or Na ₂ CO ₃ , an inorganic salt, a tertiary amine, The reaction can be performed in the presence of a quaternary ammonium salt, a quaternary phosphonium salt or the like. The epoxy resin composition used in the present invention contains each of the above-mentioned components as essential components, but other components can be blended within a range not deviating from the object of the present invention. The epoxy resin composition thus obtained is impregnated into a base material and dried to easily produce a prepreg. The substrate used here is not particularly limited and may be a commonly used one such as glass cloth or glass paper.

(Function) The present invention is excellent in heat resistance, moisture resistance, and moldability by using a low molecular weight novolac epoxy resin containing 30 wt% or more of a trinuclear and tetranuclear novolac epoxy as a main component. Thus, it is possible to manufacture a prepreg for a printed wiring board, which has good storage stability.

Trinuclear and tetranuclear are 30 in novolac type epoxy resin
If the main component is more than wt%, the average number of nuclides is reduced, the content of five or more nuclides is reduced and the impregnating property is improved, and the amount of dinuclear is less than 15 wt%. Therefore, the heat resistance can be improved. Further, in the reaction of the epoxy resin composition with the curing agent, the reaction rate can be reduced by reducing the presence of the pentanuclear compound or more, and the storage stability of the prepreg is improved when the prepreg is used. In addition, the press formability becomes stable.

(Examples) Next, the present invention will be described with reference to examples, but the present invention is not limited to these examples.

Example 1 In a four-necked flask equipped with a capacitor, 210 g of bisphenol A type epoxy resin (epoxy equivalent 189), tetrabromobisphenol A 130 g, and cresol novolac type epoxy resin containing 30% by weight or more of a trinuclear body as a main component (Fig. 1, Melting point
42 ℃) 60g, tetraethylammonium chloride 0.02g
And the inside of the flask was replaced with nitrogen. Then, after reacting at a temperature of 140 ° C. for 5 hours, 135 g of methyl ethyl ketone was added to prepare an epoxy resin composition solution having a resin solid content of 75% by weight, a viscosity of 4.2 poise (25 ° C.) epoxy equivalent of 410, and a bromine content of 19%. . Next, 11.2 g of cyiandiamide, 0.05 g of 2-ethyl-4-methylimidazole and acetone were added to prepare a varnish having a resin solid content of 65% by weight.

Example 2 In a four-necked flask equipped with a condenser, 150 g of bisphenol A type epoxy resin (epoxy equivalent 189), tetrabromobisphenol A 130 g, and cresol novolac type epoxy resin mainly composed of 30% by weight or more of a tetranuclear compound (Fig. 2, Melting point
60 ℃) 120g, tetraethylammonium chloride 0.02
The flask was charged with g and the inside of the flask was replaced with nitrogen. Then, after reacting at a temperature of 140 ° C for 5 hours, 135 g of methyl ethyl ketone was added to produce an epoxy resin composition solution having a resin solid content of 75% by weight, a viscosity of 5.2 poise (25 ° C), an epoxy equivalent of 420, and a bromine content of 19%. did. Next, 11.0 g of dicyandiamide, 0.05 g of 2-ethyl-4-methylimidazole and acetone were added to prepare a varnish having a resin solid content of 65% by weight.

Comparative Example 1 210 g of bisphenol A type epoxy resin (epoxy equivalent 189), tetrabromophenol A 130 g, cresol novolac type epoxy resin (Fig. 5, melting point 80 ° C) 60 g, tetraethylammonium chloride 0.02 g were placed in a four-necked flask with a condenser. The inside of the flask was replaced with nitrogen.
Then, after reacting at a temperature of 140 ° C. for 5 hours, 135 g of methyl ethyl ketone was added to prepare an epoxy resin composition solution having a resin solid content of 75% by weight, a viscosity of 9.2 poise (25 ° C.) epoxy equivalent of 430, and a bromine content of 19%. . Then dicyandiamide
11.2 g, 0.05 g of 2-ethyl-4-methylimidazole and acetone were added to prepare a varnish having a resin solid content of 65% by weight.

Comparative Example 2 210 g of bisphenol A type epoxy resin (epoxy equivalent 189), cresol novolac type epoxy resin (Fig. 3, melting point 42 ° C) 60 g, tetrabromobisphenol A 130 g, tetraethylammonium chloride 0.02 g were added to a four-necked flask with a condenser. The inside of the flask was replaced with nitrogen. Then, after reacting at a temperature of 140 ° C for 5 hours, 135 g of methyl ethyl ketone was added to the mixture to give a resin solid content of 75% by weight and a viscosity of
4.1 Poise (25 ° C) An epoxy resin composition having an epoxy equivalent of 420 and a bromine content of 19% was produced. Then dicyandiamide
11.2 g, 0.05 g of 2-ethyl-4-methylimidazole and acetone were added to prepare a varnish having a resin solid content of 65% by weight.

Using the varnishes prepared in Examples 1-2 and Comparative Examples 1-2, a 0.18 mm-thick glass substrate surface-treated with epoxysilane was impregnated and dried, and dried at a temperature of 160 ° C. to give a resin content of 4
A 3 wt% prepreg for a printed wiring board was manufactured.

Eight of these prepregs are piled up and the thickness is 18μ on both sides.
m copper foils on top of each other at a temperature of 170 ° C and a pressure of 40 kg / cm ²
A copper-clad laminate having a plate thickness of 1.6 mm was manufactured by integrally molding for 0 minutes under heat and pressure.

About these copper clad laminates, flame retardancy, glass transition point,
Solder heat resistance and measling resistance were measured, and the results are shown in Table 1.

In addition, the drill workability is 4 layers of circuit layer (copper foil thickness 18, 70, 7
0,18 μm), 3 circuit boards with a board thickness of 1.6 mm are stacked, drill diameter
0.9 mm, drill rotation speed 60,000 rpm, drill feed speed 2,100 m
The test was conducted at m / min, and the relationship between the number of holes drilled (horizontal axis) and the smear occurrence rate% (vertical axis) was determined and shown in FIG.

Then again, the storage stability of the prepreg is 30
It was stored at 40 ° C. for a day, and the change rate (%) of the curing time with respect to the initial curing time was determined and shown in FIG.

As can be seen from the results shown in Table 1, FIG. 6 and FIG. 7, the present invention was excellent in any test, and the effect of the present invention could be confirmed.

[Effects of the Invention] As is clear from the above description, the prepreg for a printed wiring board of the present invention has excellent heat resistance, can sufficiently cope with smear caused by high-speed drilling, and can be soldered by moisture absorption after processing a laminated board. There is no blister at the time. Further, it is easy to control the storage stability of the prepreg and the press molding conditions without partial gelation, and the moldability is excellent.

[Brief description of drawings]

FIGS. 1 and 2 are liquid chromatograph charts showing the composition of the novolac type epoxy resin in the present invention, and FIGS. 3 to 5 are liquid chromatograph charts showing the composition of the conventionally used novolak type epoxy resin. , Sixth
FIG. 7 is a graph showing the drill workability of the example of the present invention and the comparative example, and FIG. 7 is a graph showing the storage stability of the prepreg of the example of the present invention and the comparative example.

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Claims (1)

[Claims] 1. A novolak type resin containing (A) bisphenol A type epoxy resin, (B) tetrabromobisphenol A and (C) trinuclear novolac type epoxy and tetranuclear novolak type epoxy as main components in an amount of 30% by weight or more. A prepreg for a printed wiring board, comprising a base material impregnated and dried with an epoxy resin composition obtained by reacting an epoxy resin.