Flexible Printed Circuit Board (FPC), also known as "FPC flexible board," is a printed circuit made from flexible insulating substrate materials, offering many advantages that rigid printed circuit boards do not possess. For example, it can be freely bent, wound, folded, and arranged according to spatial layout requirements, allowing movement and expansion in three-dimensional space, thereby achieving the integration of component assembly and wire connection. The use of FPC flexible boards can reduce the size of electronic products, meeting the needs of electronic products toward high density, miniaturization, and high reliability. As a result, 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, solderability, ease of assembly, and relatively low overall costs. The combination of rigid and flexible designs also compensates to some extent for the slight deficiency of flexible substrates in component load-bearing capacity. Flexible printed circuit boards can be categorized into single-sided, double-sided, and multi-layer boards. The primary substrate material used is polyimide copper-clad laminate. This material has high heat resistance and excellent dimensional stability, and it is combined with a cover film that provides mechanical protection and good electrical insulation through pressing to form the final product. For double-sided and multi-layer printed circuit boards, the surface and inner layer conductors are connected through metallization to achieve electrical connectivity between inner and outer layer circuits. The functions of flexible circuit boards can be divided into four types: lead lines, printed circuits, connectors, and integrated function systems. Their applications cover computers, computer peripheral auxiliary systems, consumer appliances, and automotive fields. FPC flexible boards (1) can be freely bent, wound, folded, and arranged according to spatial layout requirements, allowing movement and expansion in three-dimensional space, thereby achieving the integration of component assembly and wire connection; (2) the use of FPC can reduce the volume and weight of electronic products, meeting the needs of electronic products toward 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, solderability, ease of assembly, and relatively low overall costs. The combination of rigid and flexible designs also compensates to some extent for the slight deficiency of flexible substrates in component load-bearing capacity. FPC flexible boards offer numerous advantages, such as space savings, weight reduction, and high flexibility. Global demand for flexible circuit boards is increasing year by year. The characteristics of flexible circuit boards make them a substitute for rigid circuit boards and traditional wiring solutions in many scenarios, while also driving development in many new fields. The fastest-growing segment is internal connection lines for computer hard disk drives (HDDs), followed by new integrated circuit packaging. The market potential for flexible circuit technology in portable devices (such as mobile phones) is very significant.