JPH0848797A - Production of prepreg - Google Patents

Abstract

PURPOSE:To prevent the air present in a fibrous base material from being enclosed and entrapped in a solvent and as a result remaining in the form of bubbles when the material is immersed in the solvent. CONSTITUTION:A fibrous base material 1 is immersed in a solvent 2, while one of its surfaces is kept from being submerged in the solvent, the material is then impregnated with a resin varnish 3, and the resin is dried to stage B.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a prepreg for a printed wiring board.

[0002]

2. Description of the Related Art Prepreg is a material for electrical laminates, in which a fibrous base material is impregnated with a thermosetting resin varnish and heated to remove volatile components and the thermosetting resin to a semi-cured state. Is.

A laminated board is manufactured by stacking several prepregs and heating and pressing them. The presence of air bubbles in the prepreg adversely affects the heat resistance and electrical properties of the laminate. Therefore, it is necessary to prevent bubbles in the prepreg.

If the prepreg is poorly impregnated with the thermosetting resin varnish, bubbles remain in the prepreg. Therefore, in order to improve the familiarity of the varnish with the fiber base material, a method has been proposed in which the fiber base material is immersed in a solvent to replace the air in the fiber base material with the solvent, and then the thermosetting resin varnish is impregnated. (See JP-A-63-99910).

[0005]

Problems to be Solved by the Invention JP-A-63-9991
According to the solvent substitution method disclosed in Japanese Patent Publication No. 0, when the fiber base material is rapidly immersed in the solvent, the air existing in the fiber base material is surrounded by the solvent and the escape area disappears and remains as bubbles. There was an occasion. The present invention provides a method in which air present in the fibrous base material is less likely to remain as bubbles.

[0006]

The present invention is directed to a fiber substrate 1
Is soaked in a solvent 2 so that one surface thereof does not sink, then impregnated with a resin varnish 3 and dried to B-stage the resin (see FIG. 1).

The fiber base material used in the present invention may be made of an organic material such as cellulose, an inorganic material such as glass, or a woven or non-woven fabric as the base material. As the solvent, methyl ethyl ketone, 2-methoxyethanol, toluene, dimethylformamide or the like can be used. As the resin varnish, an epoxy resin, an unsaturated polyester resin, or a phenol resin, which is usually used as a matrix of a laminate, is dissolved in a solvent.

In order to immerse the fiber base material 1 in the solvent 2 so that one surface of the fiber base material 1 does not sink, the fiber base material 1 is rolled by rolls 4 and 4 maintained in contact with the liquid surface of the solvent as shown in FIG. The base material may be sent.

Following the step of immersing the fiber base material in a solvent, it is impregnated with a resin varnish such as an epoxy resin. The resin varnish may be impregnated by a usual method, that is, by immersing the fiber base material in an impregnation tank. The time from the immersion in the solvent to the impregnation into the resin varnish varies depending on the solvent used, but is usually 40 seconds to 80 seconds. If it is shorter than 40 seconds, the solvent does not sufficiently penetrate into the base material, and the replacement with the bubbles in the base material is not sufficiently performed. If it is longer than 80 seconds, the solvent volatilizes before the base material is impregnated with the resin varnish, so that air is reintroduced into the base material and the effect of solvent substitution is lost.

[0010]

Since the solvent impregnated from one side of the fiber base material penetrates into the fiber base material from below, the air escapes without being wrapped in the solvent as the solvent penetrates. The solvent penetrates due to the surface tension even in the portion not immersed in the solvent.

[0011]

Example A glass cloth having a thickness of 0.2 mm was immersed in methyl ethyl ketone while being careful not to sink the upper surface as shown in FIG. Subsequently, an epoxy resin varnish having a resin content of 60% by weight was impregnated and dried to obtain a prepreg. At this time, the time until the fiber base material is separated from the solvent and immersed in the epoxy resin varnish is 30 seconds (Example 1), 60
It was changed to seconds (Example 2) and 90 seconds (Example 3).

Comparative Example 1 A glass cloth having a thickness of 0.2 mm was immersed in methyl ethyl ketone so as to completely sink it. Continuously, resin content 60% by weight
Was impregnated with the epoxy resin varnish and dried to obtain a prepreg. The time until the fiber base material was separated from the solvent and immersed in the epoxy resin varnish was set to 60 seconds.

Comparative Example 2 A prepreg was obtained by impregnating with a resin varnish without impregnating with a solvent and drying.

8 pieces of the obtained prepregs are stacked, and further,
Copper foil was laminated on both sides and heated and pressed at 170 ° C. and 2 MPa for 90 minutes to produce a double-sided copper-clad laminate.

Copper foil was etched from this laminated plate to remove the entire surface, and the appearance (mainly presence or absence of air bubbles (voids)) was visually inspected. Further, the same evaluation was made for each prepreg. The results are shown in Table 1.

[0016]

[Table 1] ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ Example 1 Example 2 Example 3 Comparative example 1 Comparative example 2 ─────────────────────────────── Prepreg ○ ◎ ○ ○ △ ────────────── ────────────────── Laminate ◎ ◎ ◎ ◎ ○ △ ────────────────────────── ────── Note) ◎: Very good, ○: Good, △: Slightly bad (with void) ━━━━━━━━━━━━━━━━━━━━━━━━━━ ━━━━━━

[0017]

EFFECTS OF THE INVENTION According to the present invention, the solvent permeates into the fiber base material so as to expel the air bubbles, so that the solvent permeates without leaving any bubbles in the fiber base material. Therefore, after that, when the resin varnish is impregnated, a prepreg containing no bubbles can be obtained, and the laminated plate produced using this prepreg also becomes an excellent laminated plate without voids.

[0018]

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing an example of an apparatus for carrying out the present invention.

[Explanation of symbols]

 1 Fiber substrate 2 Solvent 3 Resin varnish 4 Roll

Claims (1)

[Claims] 1. A method for producing a prepreg, which comprises immersing a fiber base material in a solvent so that one surface thereof does not sink, then impregnating it with a resin varnish, and drying the resin to B-stage the resin.