An embodiment bump structure includes a contact element formed on a substrate, a passivation layer overlying the substrate, the passivation layer having a passivation opening exposing the contact element a polyimide layer overlying the passivation layer, the polyimide layer having a polyimide opening exposing the contact element an under bump metallurgy (UMB) feature electrically coupled to the contact element, the under bump metallurgy feature having a UBM width, and a copper pillar on the under bump metallurgy feature, a distal end of the copper pillar having a pillar width, the UBM width greater than the pillar width.