Fine-line die and method of making same

Abstract

A method for fabricating a precision die having a line-and-space array by chemical milling the working face of an etchable workpiece to form a plurality of raised die elements separated and bounded by a plurality of cavities, including separating cavities and background cavities, is comprised of the steps of forming an etchant-resistant surface pattern of pockets penetrating slightly into the working face of the workpiece and at least partially overlapping and substantially conforming to the spatial disposition of a desired configuration for the die elements to be produced, and then selectively etching the workpiece in etchant-active regions intermediate and outwardly bounded by the pockets to undercut the same and form at least the conformation of the separating/background cavities within the working face. The step of forming the etchant-resistant pattern of pockets is preferably a two-stage procedure comprised of first chemical milling shallow pockets in the workpiece in the desired pattern and then loading those pockets with an etchant-resistant fill extending in an oversized pattern with respect to the surface width dimension of the die elements. The workpiece is selectively milled in the etchant-active regions to form cavity precursors having a surface width dimension approximately equal to the desired width for the spaces in the finished die; followed by selectively milling the regions intermediate those cavities to establish raised die elements conforming to the line array of the finished die.