JP2000169605A - Prepreg sheet for laminated board and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a prepreg sheet for a laminated board generating slight void in a lamination forming and slight flowing out of a resin. SOLUTION: This prepreg sheet for a laminated board is obtained by impregnating a base material with a resin varnish. The resin varnish is composed of a resin component comprising an epoxy resin, a hardener and a hardening accelerator, an inorganic filler component and a solvent component as essential components and has >=360 s hardening time at 170 deg.C based on 50 wt.% of the solvent component, and a resin flowing out at 170 deg.C after heating and drying is <=5%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a prepreg sheet for use in laminating or laminating laminates, and more particularly, to reduce the resin flow when laminating by heating and pressing.
The present invention also relates to a prepreg sheet with less generation of voids and a method for producing the same.

[0002]

2. Description of the Related Art A laminated plate can be obtained by laminating a suitable number of prepreg sheets, and heating and pressurizing the prepreg sheets to integrally form the prepreg sheets. Also, a copper foil-clad laminate used for printed wiring boards, etc., is formed by laminating a suitable number of prepreg sheets and copper foil on one or both sides thereof, and heating and pressing this laminated structure to form an integral body,
A single-sided or double-sided copper foil-clad laminate can be obtained.
Furthermore, a laminated board containing an inner layer circuit, which is an intermediate product of a multilayer printed wiring board, is a circuit board formed by forming a desired circuit pattern on a copper foil of a single-sided or double-sided copper foil-laminated laminate by means of chemical etching or the like. One or both sides of the prepreg sheet for bonding is laminated, copper foil or another circuit board or copper foil-clad laminate is further laminated thereon, and the laminated structure is heated and pressed to form an integrated body It can be obtained by molding. A concave portion for mounting an electronic component is often formed on the laminate containing an inner layer circuit for the multilayer printed wiring board. Using a prepreg sheet or another circuit board or a copper foil-clad laminate, which has been previously subjected to through-hole processing to form recesses for mounting electronic components, using a prepreg sheet, Molding of a recess for mounting a component is also performed. When forming a concave portion for mounting electronic components at the same time as forming a laminate by applying heat and pressure to the laminate, especially when forming a concave portion for mounting electronic components when the resin flow of the prepreg sheet is small, the laminated plate with an inner layer circuit is formed. Voids are easily generated inside and / or on the surface of the plate,
Also, if the resin flow is increased in order to suppress the generation of voids, the resin flows out into the recesses for mounting electronic components and the recesses for mounting electronic components cannot be formed in a desired shape and state. The appropriate range of resin flow with less resin flow to the recess for
There is a problem. In order to solve such a problem, the inventors have intensively studied to reduce the change width of the melt viscosity when the prepreg sheet is heated and melt-softened in response to the change in the degree of reaction of the prepreg sheet in the B-stage. In doing so, the present invention was accomplished.

[0003]

Means for Solving the Problems The prepreg sheet for a laminate according to the first invention is intended to solve the above problems.
A prepreg sheet for a laminate, in which a base material is impregnated with a resin varnish and heated and dried, wherein the resin varnish comprises an epoxy resin, a resin component including a curing agent and a curing accelerator, an inorganic filler component, and a solvent component. Essential component, solvent component 50
Curing time at 170 ° C. based on weight% is 36
It is a resin varnish of 0 seconds or more, and the resin flow at 170 ° C. after heating and drying is 5% or less. The method for producing a prepreg sheet for a laminate according to the second invention comprises, as essential components, a resin component comprising an epoxy resin, a curing agent and a curing accelerator, an inorganic filler component and a solvent component, and a solvent component of 50 wt. %, And impregnated with a resin varnish having a curing time at 170 ° C. of 360 seconds or more at 170 ° C., and drying by heating until the resin flow at 170 ° C. after drying becomes 5% or less. Is what you do.

[0004] The resin varnish used in the present invention comprises, as essential components, a resin component comprising an epoxy resin, a curing agent and a curing accelerator, an inorganic filler component and a solvent component which are impregnated into a base material. The curing time at 170 ° C. must be 360 seconds or more based on the above, and the resin flow at 170 ° C. after heating and drying must be 5% or less. The solid content of the resin varnish is not limited, but is preferably 40 to 60% by weight in terms of impregnation and workability.

[0005] The curing time of the resin varnish was such that 0.5 ml was sampled from a resin varnish having a solvent component of 50% by weight (corresponding to a solid component concentration of 50% by weight).
It is determined by placing the sample on a hot plate, stirring with a spatula, repeating tangential movement until the thread-like resin is cut, and measuring the time until the cut. The resin flow of the prepreg sheet is determined by measuring in accordance with 5.5 of JIS-C6521.

The solid content of the resin varnish is not limited, but is preferably 40 to 60% by weight in terms of impregnation and workability. The conditions for impregnating the base material with the resin varnish and heating and drying the resin varnish are not limited, but the temperature is in the range of about 120 to 220 ° C. and the time is about 1 hour.
It is in the range of ３０30 minutes and is determined from the point of 5% or less of resin flow.

In the prepreg sheet, the longer the curing time of the resin varnish impregnated in the base material, the smaller the range of change in the melt viscosity with respect to the resin flow when the prepreg resin is heated and melt-softened. In seconds, 6
If the time is longer than 00 seconds, the resin flows less, the curing time is longer, and the point of void removal can be improved. However, another problem occurs that the curing reaction requires a longer time and the production efficiency is reduced. I do. The longer the curing time of the resin varnish (360 seconds or more), in other words, the slower the curing speed of the resin varnish, the higher the melt viscosity of the prepreg resin and the more constant it is at the beginning of the curing reaction. This is probably because the two-dimensional (linear) reaction occurs preferentially over the three-dimensional reaction, and the ratio of the long-chain polymer state is high.

Examples of the substrate used in the present invention include, but are not limited to, cloth, nonwoven fabric, paper and the like using glass fiber, cellulose fiber, synthetic fiber and the like.

The epoxy resin used in the present invention includes:
Use a solid one. Although not limited, bisphenol A type epoxy resin, novolak type epoxy resin, trifunctional type epoxy resin, tetrafunctional type epoxy resin, bifel type epoxy resin, dicyclopentadiene type epoxy resin, etc. and modified epoxy resins thereof, Can be exemplified by these brominated and phosphinated resins, and one or more of these can be used in combination.

As the curing agent used in the present invention, a solid type curing agent is used. Examples include, but are not limited to, amines, acid anhydrides, polyamide resins, phenolic resins, imidazoles, and boron fluoride complex salts.

The curing accelerator used in the present invention includes, but is not limited to, imidazoles, tertiary amines, phosphines and the like.

The inorganic filler used in the present invention is preferably capable of imparting thixotropic properties to the viscous flow of the prepreg resin during melt softening, and has a particle size of 0.8 μm to 1.
Flat talc in the range of 2 μm is preferred,
When 0 parts are blended, the retention of uniform dispersion in the resin varnish,
In addition to being excellent in impregnating properties to the base material, thixotropic properties are exhibited when the prepreg resin is melt-softened.

Examples of the solvent used in the present invention include, but are not limited to, ketones such as acetone and MEK, alcohols, cellosolves, DMF, and aromatic hydrocarbons. Determined in consideration of properties, boiling point, toxicity, etc.

Hereinafter, the present invention will be described with reference to Examples and Comparative Examples.

First, the curing time of a varnish at 170 ° C. was adjusted to 380 seconds by the amount of the curing accelerator (c), comprising the following compositions (a ₁ ) to (e ₂ ). The epoxy resin varnish A was prepared by adjusting the solvent component to 50% by weight (this corresponds to a solid component of 50% by weight) depending on the amount of e ₂ ). _{(A 1)} an epoxy resin: Toto Kasei YDB-530 ............ 90 parts. _{(A 2)} epoxy resin: Toto Kasei YDCN-704 ......... 10 parts. (B) Curing agent: dicyandiamide ……………………………… 3 parts. (C) Curing accelerator: imidazole 2E4MZ (an amount that gives a varnish curing time of 380 seconds) Approx. 0.03 parts. (D) Filler: talc (average particle size: 1.0 μm) 20 parts. _{(E 1)} Solvent: methyl cellosolve .................................... 30 parts. (E ₂ ) Solvent: MEK (amount of varnish having a solid content of 50% by weight) ... appropriate amount. Next, the epoxy resin varnish A was impregnated and pre-dried into a 0.05 mm-thick glass cloth base material of WE-05E manufactured by Nitto Bosshi to prepare a prepreg sheet having a resin content of 65% by weight, and the prepreg sheet was dried at 150 ° C. In the above, the resin flow was adjusted to 0.1%, 1.2% by adjusting the drying time.
%, 3%, 4%, and 5% of prepreg sheets. Then, a separately prepared copper foil of a double-sided copper foil (thickness: 35 μm) -clad glass cloth base epoxy resin laminate (thickness: 0.5 mm) was provided with a bottom having a size of about 25 mm square of a recess for storing electronic components. On a circuit board on which a desired circuit pattern is formed by chemical etching, a prepreg sheet with a through-hole of about 25 mm square for storing electronic components is superimposed while aligning, and further over it The prepared single-sided copper foil (thickness: 18 μm) -clad glass cloth base epoxy resin laminate (thickness: 0.3 mm) with a through-hole of approximately 25 mm square for storing electronic components processed and superimposed while aligning With the combined structure, the resin flow is 0.1%, 1.0%, 2.0%,
Six types of combined components using 3.0%, 4.0%, and 5.0% prepreg sheets were obtained. These six types of combined components are set in a mold that heats and presses from above and below, and a pressure of 40 kgf / cm ² , a temperature of 150 ° C. for 30 minutes, and a temperature of 170 ° C., respectively, above and below the mold via ten pieces of kraft cushion paper. And heated and pressurized under the condition of 60 minutes to reduce the resin flow to 0.1%, 1.0%, 2.0% and 3.
Six types of double-sided copper foil-clad laminates having an inner layer circuit and having recesses for housing electronic components with a thickness of 0.8 mm corresponding to 0%, 4.0%, and 5.0% prepreg sheets were obtained. The occurrence of voids and the amount of resin exudation in the recesses of the double-sided copper foil-clad laminate containing the inner layer circuit having these six types of recesses for housing electronic components were examined. The results are shown in Table 1.

[0015]

[Comparative Example] In Examples, an average particle size of 1.6 was used as a filler.
The varnish curing time of the epoxy resin varnish can be adjusted by adjusting the amount of the curing accelerator (c) by using talc of μm.
Except for 0 second, the same procedure as in Example was carried out to obtain a double-sided copper foil-clad laminate containing an inner circuit having six kinds of recesses for accommodating electronic components, and the generation of voids and the amount of resin exudation were examined. The results are shown in Table 2.

[0016]

[Table 1]

[0017]

[Table 2]

[0018]

According to the present invention, it is possible to provide a prepreg sheet in which the generation of voids is small and the resin is less exuded when laminating and molding by heating and pressing, and a method for producing the same.

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Claims (3)

[Claims] 1. A prepreg sheet for a laminate in which a base material is impregnated with a resin varnish and heated and dried, wherein the resin varnish is a resin component comprising an epoxy resin, a curing agent and a curing accelerator, and an inorganic filler. Component and a solvent component as essential components, and 170 ° C. based on 50% by weight of the solvent component.
A resin varnish having a curing time of at least 360 seconds,
A prepreg sheet for a laminate, wherein the resin flow at 170 ° C. after the heating and drying is 5% or less. 2. The prepreg sheet for a laminated board according to claim 1, wherein the inorganic filler is talc having an average particle size of 0.8 μm to 1.2 μm. 3. A base material comprising a resin component comprising an epoxy resin, a curing agent and a curing accelerator, an inorganic filler component and a solvent component as essential components, and at 170 ° C. based on 50% by weight of the solvent component. A method for producing a prepreg sheet for a laminate, comprising impregnating a resin varnish having a curing time of 360 seconds or longer, and heating and drying the resin varnish until the resin flow at 170 ° C. after drying becomes 5% or less.