The flexible circuit board is a highly reliable and excellent flexible printed circuit board made of polyimide or polyester film as the base material. Referred to as soft board or FPC, it has the characteristics of high wiring density, light weight and thin thickness.

The advantages of multi-layer circuit boards: high assembly density, small size, light weight, because of high-density assembly, the connection between components (including parts) is reduced, thereby increasing reliability; it can increase the wiring layer, and then increase the design flexibility; It can also form the impedance of the circuit, can form a certain high-speed transmission circuit, can set the circuit, electromagnetic shielding layer, and can also install a metal core layer to meet special thermal insulation and other functions and requirements; easy installation and high reliability.

Disadvantages of multi-layer pcb boards (unqualified): high cost, long cycle; high reliability inspection methods are required. Multilayer printed circuit is the product of electronic technology, multi-function, high speed, small volume and large capacity. With the development of electronic technology, especially the wide application of large-scale and ultra-large-scale integrated circuits, the rapid, high-precision, high-number change directions of the multilayer printed circuit with higher density appear fine lines.