Polyimide Film Micromachining by Wet-Etching Technology

Abstract

We have presented the characteristics of polyimide (PI) film wet-etching using the commercially available and most commonly used Kapton Upilex PI-film as the testing materials and a strong alkaline solution named TPE3000 (from Toray Engineering Co., Ltd., Japan) as the etchant. We have introduced the fabrication process of micro through-holes on the PI-film by wet-etching using two types of etching-mask materials, i.e. a photosensitive dry film and thin copper film. We have also developed thermal-type micro sensor device using densely arrayed micro heaters as the sensing elements. The sensing elements were resistors made of sputtered 200-nm-thick platinum film on the thin (50-μm-thick) flexible PI-film substrate. The electrical feed-through was arranged on the different sides of the substrate and interconnected to the micro heater elements via the wet-etched through-holes, inside walls of which were deposited with thin metal film by means of the electroless copper plating technology. The fabricated device was robust, flexible and can be attached to non-flat curved surface.