Flexible printed circuit boards are used in many electronic products such as notebook and mobile phones because of its good physicochemical properties.The most attractive flexible substrate,polyimide (PI),has good thermal stability,chemical resistance,ease of processing and low dielectric constant.Nowadays,many dry processes have been applied for metal coating on PI,like sputtering and CVD.These nano-metallic particles serve as seed layers for following copper electroless deposition or electroplating.