A method including forming a copper pillar, electroplating a metal layer on a top surface and a sidewall of the copper pillar, and electroplating a metal cap above the top surface of the copper pillar in direct contact with the metal layer. The method further including forming an intermetallic by heating the metal layer and the copper pillar in a non-reducing environment, the intermetallic including elements of both the copper pillar and the metal layer, where molten solder will wet to the metal cap and will not wet to the intermetallic.