Toshiba Corp has developed a four-layer circuit board just 0.38mm thick and promises samples next month and November and volume in October 1989: when used as the basis of a static random access memory board, it can carry up to six 1M-bit statics; Toshiba says the breakthrough to four from two layers was achieved by use of a central epoxy resin board, with only adhesive sticking it to the copper interconnections on either side.
TOSHIBA DEVELOPS FOUR-LAYER CIRCUIT BOARD
