Circuit substrate and method for forming bumps on the circuit substrate

Abstract

A circuit substrate for use in manufacturing integrated circuit devices by the strip-support method in connection with a semiconductor element having conductive pads. The circuit substrate includes a base layer, a conductive circuit layer supported on the base layer for mechanically and electrically coupling to the conductive pads of a semiconductor device. The conductive circuit layer includes a plurality of finger leads with a bump at the end of each finger lead for mechanically and electrically coupling to one of the conductive pads. The coupling surface of each bump has a roughness in a range between 5 and 20 microns. The inherent roughness of the bumps can be augmented by plating the bumps with nickel and gold. A method for forming bumps on the conductive layer of a circuit substrate for attachment of the circuit substrate to conductive pads of a semiconductor element is also provided. The method includes coating a front and a back surface of the conductive layer with photo-resists. Then the photo-resists on both surfaces of the conductive layer are patterned by simultaneous exposure and development. Next, both surfaces of the conductive layer are half-etched. Then, one of the surfaces of the conductive layer is coated with a protective resist and the other surface of the conductive layer is etched. Finally, the photo-resist and protective resist are removed.