The production of polyimide film is basically two steps, the first step: synthesis of polyamide acid, step two: film-forming amine. The film-forming methods are mainly impregnated (or aluminum foil), flow casting method and cast drawing method (Biaxial oriented stretching method). The Pi film produced by the casting method can be used in a small amount of FCCL. La Rifa (biaxial directional method) production of films, performance has been significantly improved, but the process of complex production conditions, investment, high prices, can obtain high dimensional stability, low moisture absorption and other high-quality film products. The Polyimide films used in flexible CCL are the varieties made by this method.