Flexible printed circuits, also known as flexible printed circuit, are sometimes thought of as printed circuit boards (PCBs) that can be bent, when in reality there are significant differences between PCBs and flexible printed circuitin terms of circuit board design, manufacture, and functionality. A common mistake designers make is to design circuit board  using the same rules as PCBs. Flex circuits require unique setups and have their own set of design rules,
The word"print"is a bit of a misnomer, as many manufacturing processes today use photo-imaging or laser imaging as the pattern definition method rather than printing.
The number of material combinations that can be used in flexible printed circuits is almost endless. Current, capacitance, chemical and mechanical resistance, extreme temperatures and bending types are just some of the criteria that influence the selection of materials that best meet functional requirements.