What is a flexible printed circuit?

Flexible printed circuit is a printed circuit etched on a flexible laminate material. Mostly we see rigid printed circuit boards around e.g. a PC motherboard and cards in a PCI slot of PC. Flexible circuits were originally developed to replace bigger wire harnesses but now ae used extensively in small electronic devices like camera, media players and so on. These can be built with varying degree of flexibility and semi-rigid form based on design needs.

Originally only single sided flexible circuits were in use but with advances in technology, need for controlled impedance high speed interconnects and more miniaturization needs we now have a variety of flexible printed circuits including multi-layer ones and ones which are combined with rigid PCBs for achieving specific design needs.