A Flexible Printed Circuit Board (PCB) is a board that can be bent to conform to a desired shape during its application. The board can be bent or twisted without damaging the circuit. The substrate material used to build the PCB is responsible for its flexibility. Polyamide, PEEK (Polyether ether ketone) or a transparent conductive polyester film are common substrates used to make flexible PCBs.

The layers of a Flex PCB are more or less the same as a Rigid PCB, with the addition of an overlay, or coverlay i.e. a lamination process used to encapsulate and protect the external circuitry of a flex circuit. This is similar to the solder mask layer in a rigid PCB. The coverlay film is a polyimide film which is coated with a thermoset adhesive. It protects the flexible circuit from damage. The coverlay is optional, but most flexible PCBs do use this.

The fabrication of flexible PCBs does cost more than rigid PCBs, however they have a number of advantages in certain applications and thus the cost can be justified. For example, they can replace bulky wiring in Satellites where space and weight are the main constraints for the designers. They are also in LED Strips, consumer electronics and a number of other applications.

Other advantages of flexible Printed circuit boards are that they are lighter than rigid boards and have improved resistance to vibrations and movement so are often used in transportation applications.

Click here to see a list of PCB Manufacturers who manufacturer flexible boards.