Figure 9 HDD with conventional wiringFigure 10 Head suspension with conventional wiringFigure 11 A flexible circuit sample with new wireless suspensions66HDD is determined by the magnetic head suspension module (Figures 9 and 10), and this is our second case to study. In the past, HDDs used thin fluorine-insulated wires for magnetic head wiring, and its assembly work largely relied on manual labor but slowly, we witnessed problems in the skyrocketing manufacturing costs and the demands for faster and faster re-sponse speeds even in HDD. To tackle these issues, the idea of replacing the head suspension wiring with a flexible circuit was upheld, which became mainstream in the industry (Figure 11). However, the specifications were quite different from other general flexible circuits all in all even though it is a high-density circuit, there are only 4 or 5 wires despite the fact that the base material had to be extremely soft for the minute movements of the magnetic head. Furthermore, the conductors must be joined by metal-to-metal welding, and some of the circuit con-ductors must have a flying lead structure so as to improve the reliability of the connection,HDD suspensions are extremely small components but still, the annual demand was expected to reach one billion sets since all disks require two sets of modules. A high-hope envi-ronment was created for this business to grow with more than 10 corporates with their exclusive methods started a fierce technological development competition, including HDD manu-facturers, flexible circuit manufacturers, and parts manufactur-ers. Material manufacturers didn’t create their business format, they just joined in as material suppliers for other participating manufacturers. The market thus got various materials involved. Some manufacturers eventually dropped out for different rea-sons, and three dominating methods were slowly formulated. In the HDD industry, on the other hand, the idea that the circuit configuration of the head suspension needs to be a two-layer configuration with via holes for enhancement emerged. People also started to believe it was time to bring in a new material.This is the end of our lovely story. It would be wonderful if you could understand a bit more about PI films from another angle. This is the last series from Mr. Numakura. I would like to ex-press my respect and gratitude for his contribution.59. Other devicesThere is a huge number of applications for PI films besides the captioned ones. Especially in the emerging fields of flex-ible electronics and medical electronics with roaring demand soon, we might be stunned by breakthrough technologies and innovative usages in the near future. That is quite possible that we will get another chance to look into them together soon.
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