Fine Pattern Evolution on Metal Sheets Using Electrolytic Photochemical Machining

Abstract

Stainless steel sheets were electrolytically etched to fabricate fine patterns on them. They were masked with a negative photoresist stencil and etched in an NaNO₃ solution as a function of applied voltage (4-12V), electrode gap (5-40mm), and pattern width (25-1000μm). The etch factor exceeded 1.5 was obtained, showing that electrolytic photoetching was anisotropic. For wider grooves exceeding 200μm, the etch factor increased with increasing applied voltage. The electrode gap had no effect on the etch factor. To form perforations on sheets, a convex edge profile was developed when sheet breakthrough occurred. After certain overetching, however, a straight-edge profile was developed, because current concentrated on convex edges. For etching 50μm-thick stainless steel sheets at an applied voltage of 8V, overetching of about 80s was required to obtain a straight-edge profile. During overetching, etched groove width increased linearly with etching time at a rate of about 1μm/s for 8V etching, independent of pattern width. We applied this technique to realize masks for vacuum evaporation in fabricating electrode patterns for a quartz crystal microbalance and a microthermocouple pattern.