A process for producing a copper lead frame tape in which the individual fingers of the lead frame are provided with gold plated bumps. A copper foil is provided with dry film photoresist on both sides and is initially processed to provide openings in one side of the resist for electroforming of the end products directly on the copper foil. Further processing produces openings on the other resist side in locations other than opposite the first resist side bumps whereby a following chemical milling of the exposed opposite side copper yields a plurality of fingers, each consisting of an integral bump/copper foil arrangement. The electroforming step is made possible by a novel double-cell electroplating method in which a relatively high-impedance ion path connects the two cells. Bump heights of as much as 0.0013 inch or greater are produced by the disclosed process, with uniformly excellent quality.

Electroformed and chemical milled bumped tape process

A method of chemical machining utilizing selective plating techniques to form a metal component from sheet metal sheets, in which each sheet is degreased, rinsed in deionized water, and thoroughly dried, then is coated with a positive photoresist. The photoresist is cured, and then the image of the component to be formed is photographically applied to either side of the sheet utilizing photomasks, the photographically exposed photoresist is removed from the sheet, and the sheet etched to provide the basic component configuration. Selective plating is effected by further photographically exposing the photoresist of the sheet that overlies the portions of the sheet to be plated, by utilizing photomasks delineating the areas to be plated, after which the freshly exposed photoresist is removed, the sheet baked to better condition the resist for plating, and then suitably electroplating the areas of the sheet metal thus exposed. After plating, the completed component is soaked in acetone to remove the resist.

Burlingame George G

Papers

Process of etching and electroplating printed circuits