A metallic adhesion layer is formed on a last level metal plate exposed in an opening of a passivation layer. A Ni—Cu alloy in which the weight percentage of Ni is from about 50% to about 70% is deposited by sputtering onto the metallic adhesion layer to form an underbump metallic layer. Optionally, a wetting layer comprising Cu or Au may be deposited by sputtering. A C4 ball is applied to a surface of the underbump metallic layer comprising the Ni—Cu alloy or the wetting layer for C4 processing. The sputter deposition of the Ni—Cu alloy offers economic advantages relative to known methods in the art since the Ni—Cu alloy in the composition of the present invention is non-magnetic and easy to sputter, and the consumption of the inventive Ni—Cu alloy is limited during C4 processing.