Flexible circuit board, also known as "soft board", is a printed circuit made of flexible insulating substrate. Flexible circuits provide excellent electrical performance, can meet the design requirements of smaller and higher density installation, and also help to reduce assembly procedures and enhance reliability. Flexible circuit board is the only solution to meet the requirements of miniaturization and mobility of electronic products. It can be freely bent, wound and folded, and can withstand millions of times of dynamic bending without damaging the wire. It can be arranged arbitrarily according to the space layout requirements, and can move and expand freely in three-dimensional space, so as to achieve the integration of component assembly and wire connection; Flexible circuit boards can greatly reduce the volume and weight of electronic products, and are suitable for the development of electronic products in the direction of high density, miniaturization and high reliability.