A basic flexible circuit(Flexible PCB) is made of a flexible polymer film laminated to a thin sheet of copper that is etched to produce a circuit pattern.
Patterns can be created on both sides of the film. Interconnections are achieved with plated through-holes, yielding almost unlimited adaptability between various component parts. A polymer overcoat is often added to insulate and environmentally seal the circuit.
Flexible circuits can also combine several single- or double-sided circuits with complex interconnections, shielding, and surface-mounted devices in a multi-layer design. These multi-layer designs can also be combined with rigid circuit boards to create a rigid/flex circuit capable of supporting devices as needed.
The most widely used polyimide film is KAPTON®, because of its high heat resistance, dimensional stability, dielectric strength, and flexural capability. The characteristics of this raw material help the flex circuit maintain a high degree of durability, and also help it survive hostile environments.