Method of stopping-off plating in electroplating baths

Abstract

Abstract A PROCESS FOR ELECTROPLATING A PLATE METAL FROM A BATH ONTO A CATHODE HAVING PREDETERMINED AREAS TO BE PLATED AND SELECTED AREAS TO BE STOPPED OFF WHICH COMPRISES PLACING AN AUXILIARY ELECTRODE ADJACENT TO SAID SELECTED AREAS, MAINTAINING SAID SELECTED AREAS ANODIC TO SAID AUXILIARY ELECTRODE AND SUBJECTING SAID CATHODE TO PLATING CURRENT DENSITY WHEREBY SAID METAL IS DEPOSITED ON THE SAID PREDETERMINED AREAS AND SAID SELECTED AREAS REMAIN STOPPED OFF, AND AN APPARATUS FOR ELECTROPLATING WHICH COMPRISES AN ELECTROPLATING BATH, AT LEAST ONE ANODE THEREIN, A CATHODE HAVING PREDETERMINED AREAS TO BE PLATED AND SELECTED AREAS TO BE STOPPED, OFF AN AUXILIARY ELECTRODE ADJACENT TO EACH OF THE SAID SELECTED AREAS OF SAID CATHODE, A MAIN POWER SUPPLY ESTABLISHING A POTENTIAL ACROSS THE ANODE AND THE CATHODE, AND MEANS FOR MAINTAINING SAID SELECTED AREAS ANODIC TO SAID AUXILIARY ELECTRODE. IN ONE EMBODIMENT, THE MEANS FOR MAINTAINING SAID SELECTEDAREAS ANODIC TO SAID AUXIALIARY ELECTRODE INCLUDES A POLARIZING POWER SUPPLY ESTABLISHING A POTENTIAL BETWEEN SELECTED AREAS OF THE CATHODE AND THE AUXILIARY ELECTRODE, THE POSITIVE TERMINAL OF THE POLARIZING POWER SUPPLY BEING JOINED TO THE NEGATIVE TERMINAL OF THE MAIN POWER SUPPLY. THE AUXILIARY ELECTRODE MAY CONTAIN A THIN COATING OF PLATINUM SUFFICIENT TO SUBSTANTIALLY INHIBIT ELECTROPLATING OF SAID AUXILIARY ELECTRODE.

Inventors

• 👤 Ram Dev Bedi

Bibliographic Details