Pressing multilayer circuit board without creasing copper@ foil - separating packets of layers for lamination between sheets of steel undergoing comparable thermal expansion

摘要

Circuit boards are mfd. by hot-pressing of packets of internal layers (1) alternating with prepreg layers (3), each packet being overlaid and underlaid with Cu foils (2) and sepd. from its neighbours in the stack by steel sheets (4). Conventional steel having an expansion coefft. of 10 ppm/dec.C when heated to the lamination temp. (180 deg.C) creases the foil. An increase to 16 ppm/deg.C comparable with the coefft. of the Cu, eliminates this differential expansion problem. ADVANTAGE - Prod. quality and yield are improved with temporally and spatially uniform thermal expansion of steel sepn. sheets and Cu foils.