Impregnation it does the production mannered

摘要

PURPOSE: To reduce the generation of a crack at the time of perforating processing by interrupting heating and pressing before the curing of a thermosetting resin is completed and performing perforation processing before further heating the thermosetting resin to complete the curing thereof. CONSTITUTION: A cresol novolac type epoxy resin for a laminated sheet being a thermosetting resin and a cresol novolac resin are dissolved in a methyl ethyl ketone solvent and 2-ethyl-4-methylimidazole is added to the resulting soln. as a curing accelerator to prepare varnish. Glass cloth (MIL standards: 2116) is impregnated with the varnish thus prepared and dried to obtain a prepreg. Eight prepregs 8 are superposed one upon another and copper foils are arranged to both outsides of them and pressed under pressure to obtain a double-side copper clad laminated sheet. The glass transition temp. of this laminated sheet is set to 70-85% of a perfectly cured state. After perforating processing is applied to the laminated sheet by a drill, this laminated sheet is further heated by a dryer to complete the curing of the thermosetting resin to obtain a perforated laminated sheet having desired glass transition temp.