Formation of uniform square‐shaped tunnel pit by electrochemical etching with an opened polyimide layer on aluminum foil

Uniform tunnel pits are fabricated with equally spaced intervals while avoiding excessive dissolution of an aluminum surface with a polyimide material as a mask layer. To increase the area S of capacitance C, uniform tunnel pits are made selectively to increase the aluminum surface area S into the vertical direction on Al foil. In this article, the relationship between the surface area and the etching tunnel is analyzed through selective electrochemical etching with patterning on aluminum foil, and the controllability of the etching tunnel is also studied. Copyright © 2012 John Wiley & Sons, Ltd.