Abstract: A method of forming solder bumps on a chip or wafer for flip-chip applications comprises the steps of providing a chip or wafer having a plurality of metal bonds pads which provide electrical connection to the chip or wafer, and applying a solder bump comprising pure tin or a tin alloy selected from tin-copper, tin-silver, tin-bismuth or tin-silver-copper by an electroplating technique, and melting the solder bumps by heating to a temperature above the bump melting point to effect reflow.

Abstract: A semiconductor wafer having solder bumps thereon for use in flip-chip bonded integrated circuits comprises a semiconductor substrate formed with metal bond pads at selected locations thereon, a metal electroplating buss layer or layers over the bond pads, a layer of solder-wettable under bump metal on the buss layer, a layer of barrier metal which overlies and encapsulates the solder-wettable metal, and a solder bump formed on the barrier metal.

Abstract: A method of fabrication of solder bumps on a semiconductor wafer provided with metal bond pads comprises the steps of: (a) applying a metal adhesion/barrier/electroplating buss layer or layers on at least the bond pads; (b) forming a layer of a resist in a predefined pattern defining openings therein over the bond pads; (c) applying a layer of solder-wettable under bump metal into the openings; (d) removing a volume of resist from the regions of the openings to create an opening between an edge of the layer of wettable metal and the resist; (e) applying a layer of a barrier metal over the layer of solder-wettable metal including the openings created at step (d) while encapsulates the layer of wettable metal; (f) fabricating a solder bump onto the layer of barrier metal; and (g) removing the resist material; and (h) removing any exposed adhesion/barrier layer.