Ink tankConnector electrode arrayInk tankInk ventFlying leadPiezo pumpOrifice chipBase filmGang bondingPiezo pump chipDimpled flexDimpled electrode arrayDimple connectionDimpled flexFigure 6 A flexible circuit sample for small to medium LCD driver modules in cell phonesFigure 8 The implementation of the IJ printer piezo Figure 7 Disposable ink tank for IJ printerpump chipThe first one is the disposable ink cartridges in computer inkjet (IJ) color printers. In the beginning, computer manufac-turers used their proprietary methods for IJ printers, so the production was unsystematic before HP (Hewlett-Packard, the USA) integrated the technology into the disposable ink car-tridge system, and today it is commonly thought that more than half of the printers produced globally have attained the technology license from HP. In the electronics industry with rapid changes stemming from technological innovations, this is definitely a rare case in which the basic structure and mate-rials both remain unchanged. 3M, the American electronic material manufacturer, and DuPont, the PI film manufacturer DuPont were the main con-tributors to the development and commercialization of HP’s disposable ink cartridges. Through MEMS technologies, HP has developed a disposable orifice chip that utilizes piezo ma-terial to eject ink from little pores. HP has also attained great help from 3M with extensive know-how and experience in tape circuit technologies and electronic materials to develop imple-mentation and wiring methods. 3M decided to use single-sid-ed, high-density flexible circuits as the main part of the wiring, a flying lead structure for some of the conductors, and to im-plement the orifice chip with gang bonding (Figures 7 and 8). The layer structure of the flexible circuit was the same as TAB, but the shape of the device hole required high dimensional accuracy. Thus, the adopted base material was Kapton E, and the hole drilling was done by photolithography and chemical etching. The CCL used was sputtered and electroplated inter-nally at 3M.Here, the solubility of Kapton E in a strongly alkaline aque-ous solution was fully utilized. At that time, 3M had integrat-ed control over everything from CCL to circuit processing; it also established a successful method to do sputtering nickel as a seed layer to be used as a delicate mask for the Kapton etch. Du Pont contributed to the development of the technol-ogy by offering Kapton E etching technology. The reward was not small indeed. After all, since most printers consume these disposable ink cartridges, the consumption amount of PI film was expected to soar with the estimated annual consumption reaching one million square meters, which made it an attrac-tive way out for Kapton E with no significant usage at the time.6557. Disposable cartridges for IJ printersAs the final topic of our lovely PI film story, let’s take a deeper look at two solid examples of how highly dimensional-stable PI films have revolutionized wiring technologies for electronic products.58. HDD wireless suspensionHard disk drives (HDD) remained a significant mnemonic device in computers although its demands dropped rapid-ly upon the appearance of flash memory. The capacity and storage density of HDDs have been increasing year by year these days, and the capacity of HDDs as external memory for computers far exceeds 1 terabyte. The functionality of the
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