Flexible circuits are designed for improving space utilization and product design flexibility, meeting the design needs of smaller and higher density installation, and also helping to reduce assembly process and enhance reliability. It is the only solution to meet the requirements of miniaturization and movement of electronic products.

A flexible circuit is to etch a copper circuit on the substrate of a polymer or to print a polymer thick film circuit. For the thin, light, compact and complex devices, its design solutions include a single - side conductive line to a complex multi-layer package. The total mass and volume of the flexible package is 70% less than that of the conventional wire harness method. A flexible circuit can also increase its strength by using an enhanced material or liner to gain additional mechanical stability.

Flexible circuits can be moved, bent, torsional, without damaging the wires, and can have different shapes and special packaging sizes. The only limitation is the volume space problem. Because it can withstand millions of dynamic bending, flexible circuits can be well applied to the continuous connection or regular movement of the internal connection system, and become a part of the final product function. Some products that require electrical signal / power supply move and some products with smaller shape coefficient / package size benefit from the flexible circuit.

The flexible circuit provides excellent electrical performance. The lower permittivity allows for fast transmission of electrical signals. Good thermal performance makes components easy to cool down. Higher glass transition temperature or melting point makes components run well at higher temperatures.

Due to the reduction of the hardware needed for internal connection, such as common solder joints, trunk lines, chassis lines and cables, flexible circuits can provide higher assembly reliability and output. Because the traditional hardware in the complex multiple systems is assembled, it is easy to have a higher component misplacement rate. With the emergence of quality engineering, a thin thin flexible system is designed to be assembled in only one way, thus eliminating human errors which are usually related to independent wiring engineering.

Early flexible circuits are mainly used in the fields of connection between small or thin electronic products and rigid pcb. In the late 1970s, it gradually applied to computers, digital cameras, inkjet printers, car audio, disc drivers (see Figure 10, 1) and hard disk drives. Open a 35mm camera and there are 9~14 different flexible circuits in it. The only way to reduce the volume is that the components are smaller, the lines are more precise, the pitch is closer, and the objects can be bent. Cardiac pacemakers, medical devices, video cameras, hearing aids, Laptops - almost all of the things used today have flexible circuits.