PURPOSE: To produce the titled prepreg having excellent curability and resin- flowability, by impregnating a substrate with varnish contg. an epoxy resin, dicyandiamide and a specified imidazole.
CONSTITUTION: A substrate such as glass fiber is impregnated with varnish obtd. by dissolving an epoxy resin (A), 0.3W1.5 equivalents (per equivalent of component A) of dicyandiamide (B) and 0.001W0.005 equivalent (per equivalent of component A) of an imidazole (C) of the formula (wherein R1 is a 11W20C alkyl; R2 is H, a 1W5C alkyl) in an org. solvent such as methyl cellosolve, and dried to obtain a prepreg 2. One-side copper-clad outer layer sheets 3 are placed on both sides of a circuit-printed inner layer sheet 1 interposing said prepreg 2. The resulting structures 8 are put upon one another while putting a mirror plate 4 therebetween. The resulting composite is put 6 between hot platens 7 interposing tool plates 5 and cushioning materials 6 and heated under pressure.
YOKOZAWA SHIYUNYA
ODA TATSUYA
MIZUNO YUTAKA
