Evaluating the Registration of Mirror-Image Photoresist Stencils
July 1981
For the production of photoctched metal parts, by etching
through an adherent photographic stencil, the minimum size of
hole that can be made and the control of hole size are both
limited by undercut. A valuable method of improving the
perfonnance is to coat both sides of the metal with photoresist,
and expose between a registered pair of mirror-image masks. By
the time the etchant has perforated the metal sheet, it will only
have been necessary to etch for half the depth required by singlesided
etching, and the effect of undercut will be correspondingly
reduced.
Acritical factor influencing the quality obtainable by doublesided
etching is the precise registration of the mirror-image
masks.
D.M. Allen, D.F. Horne, and G.W.W. Stevens,
Cranfield Institute of Technology