With the diversification and miniaturization of applications, Shenzhen FPC used in electronic equipment requires both high-density circuits and high performance in the sense of quality. Recent changes in circuit density of FPC soft boards in Shenzhen. The single side circuit with conductor pitch less than 30um can be formed by using the subtraction method, and the double side circuit with conductor pitch less than 51um has also been applied. The conducting hole diameter between the conductor layers connecting double-sided circuits or multilayer circuits is also getting smaller and smaller. Now the holes with the conducting hole diameter below 100um have reached the mass production scale.
Based on the position of manufacturing technology, the possible manufacturing range of high-density circuits. According to the circuit pitch and through hole diameter, high-density circuits can be roughly divided into three types: (1) traditional FPC; (2) High density FPC; (3) Ultra high density FPC.
In the traditional reduction method, Shenzhen FPC with 150 um pitch and 15 um through hole diameter has been mass produced. Due to the improvement of materials or processing devices, the line pitch of 30um can be processed even in the subtraction method. In addition, due to the introduction of processes such as CO2 laser or chemical etching method, the mass production and processing of through holes with 50um aperture can be realized. Most high-density Shenzhen FPCs in mass production now use these technologies to process.
However, if the pitch is less than 25um and the diameter of the through hole is less than 50um, it is difficult to improve the qualification rate even if the traditional technology is improved, and new processes or new materials must be introduced. There are various processing methods proposed at present, but the half addition method using electroforming (sputtering) technology is the most applicable method. Not only the basic process is different, but also the materials and auxiliary materials used are different.
On the other hand, the progress of FPC bonding technology in Shenzhen requires FPC to have higher reliability. With the high density of circuits, the performance of FPC requires diversification and high performance, which largely depends on circuit processing technology or materials used.