Flexible Printed Circuit Board, also known as "FPC flexible board", is a printed circuit made of flexible insulating substrate, offering many advantages that rigid printed circuit boards do not possess. For example, it can be freely bent, wound, folded, arranged according to spatial layout requirements, and moved and stretched arbitrarily in three-dimensional space, thereby achieving the integration of component assembly and wire connection. Using FPC flexible boards can reduce the volume of electronic products, meeting the needs of electronic products developing towards high density, miniaturization, and high reliability. Therefore, FPC flexible boards are widely used in fields or products such as aerospace, military, mobile communications, laptops, computer peripherals, PDAs, and digital cameras. FPC flexible boards also offer good heat dissipation and solderability, are easy to assemble, have relatively low comprehensive costs, and the combination of rigid and flexible design to some extent compensates for the slight deficiency of flexible substrates in component carrying capacity. Flexible printed circuit boards can be single-sided, double-sided, or multi-layered. The substrate used is mainly polyimide copper-clad laminate. This material has high heat resistance and good dimensional stability, and is pressed together with a cover film that provides both mechanical protection and good electrical insulation to form the final product. The surface and inner layer conductors of double-sided and multi-layer printed circuit boards achieve electrical connection between inner and outer layer circuits through metallization. The functions of flexible circuit boards can be divided into four types: lead lines, printed circuits, connectors, and multi-functional integrated systems, with applications covering computers, computer peripheral auxiliary systems, consumer appliances, and automobiles, among others. FPC flexible boards (1) can be freely bent, wound, folded, arranged according to spatial layout requirements, and moved and stretched arbitrarily in three-dimensional space, thereby achieving the integration of component assembly and wire connection; (2) using FPC can reduce the volume and weight of electronic products, meeting the needs of electronic products developing towards high density, miniaturization, and high reliability. Therefore, FPC flexible boards are widely used in fields or products such as aerospace, mobile communications, laptops, computer peripherals, PDAs, and digital cameras; (3) FPC flexible boards also offer good heat dissipation and solderability, are easy to assemble, have relatively low comprehensive costs, and the combination of rigid and flexible design to some extent compensates for the slight deficiency of flexible substrates in component carrying capacity. FPC flexible boards have many advantages such as space saving, weight reduction, and high flexibility, and the global demand for flexible circuit boards is increasing year by year. The characteristics of flexible circuit boards make them a replacement for rigid circuit boards and traditional wiring solutions in many situations, while also driving the development of many new fields. The fastest-growing part is the internal connection lines of computer hard disk drives (HDD), the second fastest-growing field is new integrated circuit packaging, and the market potential of flexible circuit technology in portable devices (such as mobile phones) is very large.