Abstract
Recently, electronics industry requires to increase circuit density with downsizing of equipment. Especially, Flexible Printed Circuit (FPC) is becoming an indispensable material. In this report, we show the applications of polyamic acid film to prepunched adhesiveless FPC and adhesiveless coverlay, these materials have excellent electrical and thermal characteristics. By using polyamic acid film, we can make holes to the film easily by punching, and we can laminate it with copper foil or adhesiveless FPC under mild (100°C) conditions. Further polyamic acid film becomes usual polyimide by curing. Except these developments, polyimide ink was applied to adhesiveless coverlay, but has poor flexibility. On the other hand our developed material has good flexibility because it contains no filler. Adhesiveless FPC with via hole was also required. But the difficulty in making via hole by etching method is another problem in ordinary adhesiveless FPC that shows excellent chemical resistivity. Then we successfully developed punching method utilizing polyamic acid as the base or coverlay film.
