Large area controllable ITO patterning using micro-EDM and electrochemical etching.

Transparent conducting films have been widely used in display devices such as flat panel displays, touchscreens, organic light-emitting diodes (OLEDs), and liquid-crystal displays. However, common techniques of patterning transparent conducting films, such as photolithography and laser patterning, are complex and require large investment. Therefore, research regarding fast and inexpensive patterning procedures for large area is still ongoing. In this study, a novel technique, which combines micro-electrical discharge machining (μ-EDM) with dynamic electrochemical etching, was applied to produce indium tin oxide (ITO) line patterns on glass substrates. Commercial tungsten (W) rods were used to fabricate microelectrodes by dynamic electrochemical etching and were subsequently used to create ITO line patterns by μ-EDM. A series of experiment was carried out to optimize the machining conditions such as gap voltage, cutting speed, and spindle speed. The criteria of this investigation were of the minimum difference between the tool diameter and the pattern width and the low waviness of the line edges. In addition, practical relations for each step were built to control machining process at high accuracy. By using these mathematical relations, the width of the resulting ITO line patterns can be predicted with an error of less than 4 %. Furthermore, the proposed technique proved that it can work well for long working distance. [ABSTRACT FROM AUTHOR]