The materials that make up FPC flexible boards include an insulating film that forms the base layer of the circuit, and an adhesive that bonds the copper foil to the insulating layer. In multilayer designs, it is then bonded with the inner layers. They are also used as protective coverings to isolate the circuit from dust and moisture, and to reduce stress during bending, while the copper foil forms the conductive layer.

In some flexible circuits, rigid components made of aluminum or stainless steel are used. They can provide dimensional stability, offer physical support for the placement of components and conductors, and relieve stress. Adhesives bond the rigid components to the flexible circuit. Additionally, there is another material sometimes used in flexible circuits, which is the adhesive layer sheet. It is formed by coating adhesive on both sides of an insulating film. The adhesive layer sheet provides environmental protection and electrical insulation, and can replace a layer of film as well as support the ability to have multiple layers with fewer adhesive layers.