Patent ID: 6878259

Claim:
A method for depositing a smooth layer of a metal onto a microrough substrate comprising immersing, as an electrode, an electrically conductive substrate having a microrough surface in an electroplating bath containing ions of a metal to be deposited onto said surface, said plating bath being substantially devoid of levelers, immersing a counter electrode in said plating bath passing an electric current between said electrodes, wherein said electric current is a modulated reversing electric current comprising pulses that are cathodic with respect to said substrate and pulses that are anodic with respect to said substrate, said cathodic pulses have a duty cycle less than about 50% and said anodic pulses have a duty cycle greater than about 50%, the charge transfer ratio of said cathodic pulses to said anodic pulses is greater than one, and the frequency of said pulses ranges from about 10 Hertz to about 5000 Hertz.