The flexible printed circuits are designed to save room and improve product design flexibility, which can satisfy the design need of smaller and higher density installation, in favor of decreasing mounting steps and improving reliability, and become the only solution for satisfying the miniaturization and flexibility of electronic products.
The flexible circuit boards are to etch the copper traces on the polymer base material, or to print polymer heavy layer circuit. In regard to thin, light, tightly and complicated structured components, their design scheme comprises from single sided conductive circuit to complex multilayer 3-D packing. The overall quality and volume of flexible packing decreases by 70% than using the traditional mega wire thread method. The flexible circuit can also increase its strength by using supporting material or lining board, so as to obtain extra mechanical stability.
The flexible circuits can be moved, bent, twisted, without ruining the traces. They are with different shapes and special packing dimensions. The only limit is the problem of room and volume. Due to being able to bear millions of dynamic bending, the flexible circuits can be well applied in the inner connection system of continuous movement or regular movement, becoming one part of the final product function. Some products demanding for smaller shape modulus/packing dimensions because of the movement of electrical signal/power all benefit from the flexible circuits.
The flexible circuit provides good electrical performance. Lower dielectric constant allows electrical signals to transmit quickly. Good thermal performance makes the assembly easy to cool. Higher glass transfer temperature or melting point makes the assembly work well at higher temperature.
Because the quantity of the hardware needed for inner connection is reduced, such as the welding pots、trunk lines, base board traces and cables usually used in traditional electric packing, the flexible circuits can provide with higher installation reliability and yield. When the traditional inner connection hardware comprised of many complicated systems is mounted, higher rate of assembly out of alignment happens easier. As the emergence of quality engineering, a very thin flexible system is designed to be mounted in only one way, so as to eliminate the human error related to independent wiring installation。
At early stage the flexible circuits are mainly applied in the fields such as the connection between the small or thin electronic products and rigid printed boards. In the end of 1970s, they were used in the electrical products such as computers, digital cameras, ink jet printers, car audio, CD-ROM and hard disk driver. Opening one 35mm camera, there are 9~14 different flexible circuits. The only way to decrease volume is smaller assembly, more precise lines, tighter spacing, and bendable objects. Heart maker, medical instruments, video camera, hearing aid, laptops, all most all the products we use comprise of flexible circuits today.