Patterning Processes for Flexible Electronics

Patterning functional materials is one of the key technologies to enable flexible electronics. In almost every flexible electronic device, individual materials and layers need to be patterned. Moreover, the importance of patterning is probably second only to materials properties in fabricated flexible functional devices. Frequently, patterning is one of the limiting factors in device performance. Flexible electronics depends upon the ability to construct layers of materials having precisely defined architectures and relationships on flexible supports. These structures require the ability to either deposit (additive) or remove (subtractive) materials in a locally controlled fashion (patterning). There are many techniques that have been used to accomplish the patterning of materials on flexible supports. In general, these patterning techniques have either been derived or adapted from conventional electronics processing, from printing processes, or from a hybrid of both. The appropriate choice of patterning technique will depend upon many considerations, including feature size, area of coverage, throughput, registration, environment, position in the overall device structure, and material considerations. Many, if not most device structures will require the use of multiple different patterning techniques. The purpose of this paper is to review the major patterning techniques that have been used for flexible electronics, and to discuss the unique features, advantages, and disadvantages of each. The focus will be on large area, high throughput, additive deposition techniques that can be performed in ambient conditions.