As more and more clamshell phones come into market, the FPCs are more and more used.
The price of adhesiveless FPC is much higher than the adhesive FPC. However it is superior to FPC in the aspects of flexibility, boning force of copper and the base material, and the flatness of soldering pad. Therefore generally it only is used in the occasion of high demand, such as COF (chip on flex, to mount exposed chips on FPC has high requirement of the soldering pad flatness).
Because the FPC is mainly used at the occasion of bending, if the design or technique is not proper, defaults such as micro-crack, snap of the welding point will be easy to arise. I will introduce the structure of FPC and its special requirements on design and technique.