Abstract: A method for chemically milling an etchable workpiece by exposure thereof to an etchant in order to mill selected etchant-active areas and thereby form a plurality of raised die elements separated and bounded by a plurality of recessed cavities is comprised of the steps of initially, partially etching the workpiece to form recessed die element precursors separated and bounded by recessed cavities, depositing a film of an etchant-resistant composition on the workpiece in at least selected ones of the recessed cavities, filling those selected cavities with an etchant-resistant filler and then subsequently processing the workpiece to form a die. The die is then completed by deposition of a film of a tribological composition, which may be the same as or different from the etchant-resistant composition, within those recessed cavities not theretofore bearing the etchant-resistant film.

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.

Abstract: A method for chemically milling an etchable workpiece by exposure thereof to an etchant in order to mill selected etchant-active areas and thereby form a plurality of raised die elements separated and bounded by a plurality of recessed cavities, which method is comprised of the steps of initially, partially etching the workpiece to form recessed die element precursors separated and bounded by recessed cavities, depositing a film of an etchant-resistant composition on the workpiece in at least selected ones of the recessed cavities, filling those selected cavities with an etchant-resistant filler and then subsequently processing the workpiece. In a highly preferred embodiment, the method comprises depositing a thin film of gold on the workpiece, removing the gold film from selected areas where active etching is to occur, and then filling the recessed cavities with an epoxy filler.

Abstract: A method for fabricating a precision fine-line die 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, is comprised of the steps of forming an etchant-resistant surface pattern of boundary grooves penetrating slightly into the working face of the etchable workpiece outwardly proximate and substantially conforming to the configuration of die element precursors, and then selectively etching the workpiece in regions outwardly bounded by the boundary grooves to undercut same and form recessed cavities outwardly proximate and substantially conforming to the complementary configuration of the die element precursors. The step of forming the boundary grooves is preferably a two stage procedure comprised of first chemical milling shallow grooves in the workpiece in the desired pattern and then loading these grooves with an etchant-resistant fill.

Abstract: A high precision die particularly adapted to form, from a relatively heavy foil sheet, a circuit board where the individual circuit elements and the spacing thereof are of relatively small dimensions. The die is made as follows. A working surface of a die block is covered with a first protective overlay having an enlarged pattern corresponding to the pattern of the die elements to be formed, but enlarged by a substantially uniform width dimension. The surface is then exposed to an etching solution to remove material from the exposed area. These two steps are repeated a second time with a pattern enlarged to a lesser degree, and again a third time to bring the die elements being formed from the die block within quite close tolerances to the original pattern. The die faces of the die elements are then etched to form knife edges on the die elements, in a plurality of etching steps using reduced protective overlay patterns.

Abstract: A high precision die particularly adapted to form from a relatively heavy foil sheet a circuit board where the individual circuit elements and the spacing thereof are of relatively small dimensions. The die is made as follows. A working surface of a die block is covered with a first protective overlay having an enlarged pattern corresponding to the pattern of the die elements to be formed, but enlarged by a substantially uniform width dimension. The surface is then exposed to an etching solution to remove material from the exposed areas. These two steps are repeated a second time with a pattern enlarged to a lesser degree, and again a third time to bring the die elements being formed from the die block within quite close tolerances to the original pattern. The die faces of the die elements are then etched to form knife edges on the die elements.

Abstract: A circuit board having through hole connections between circuit elements on opposite sides of the board. Each through hole has its end portions countersunk, with peripheral portions of the circuit element depressed into the countersink area. A layer of conductive material is plated in the wall of each hole, with the conductive material overlapping the circuit element material that is depressed into the countersink.In the method of the present invention, a resist coating is applied uniformly over both planar surfaces of a circuit board on which the circuit elements have already been formed. The portions of the circuit elements contacting the edge portions of the through holes in the board are mechanically depressed into the substrate to form the countersink areas. Thereafter a coating is applied, either by an electroless process or electrolytically to form the plated through hole connection.

Abstract: Stamping a sheet of conductive foil by means of a die of a predetermined pattern against a dielectric substrate to shear out foil sections and pressing them against the substrate while applying heat through said die to the sheared sections so as to bond the sections by means of a thermal curing adhesive to the substrate. The die has a plurality of individual die elements which shear out individual foil sections. Each die element has two lateral high pressure surfaces, a recessed middle portion and two transitional surface portions between the high pressure surfaces and the middle portion. The outer edges of each die element are shearing corners or edges, with the high pressure surfaces applying the shearing forces to the foil and substrate. In one embodiment the high pressure surfaces which produce the shearing forces against the foil sheet are substantially parallel to the foil sheet being engaged, and in another embodiment the high pressure surfaces are sloped at about 45.degree.