A circuit board is a basic device used to connect and support electronic components. It is usually made of conductive material on an insulating substrate with a series of printed circuits on it. The electronic components can be welded or inserted into the circuit board to achieve the functions of the electronic device,

Commonly used substrate materials include glass fiber reinforced plastic (FR-4), polyimide (PI) and so on. The conductive material is generally copper, and the thickness is usually expressed by the weight of copper per unit area, such as the thickness of 1 ounce copper, which is composed of wires, resistors, capacitors, inductors and other components.