A new method of current density control during the pulse plating process

During metal deposition, the current density employed has a significant effect on the electrodeposition rate, the composition of the deposits, the throwing power, the filling capability and the surface morphology. Our investigations have shown that the value of current density used for metal deposition under changes of deposition area is adjustable by means of overpotential control and that provides the properties required for the plating deposit. It is possible to estimate the value of the overpotential by using a measuring electrode and to change it by the changing plating pulse width. The method of overpotential estimation depends on the ratio between the rate of overpotential change during the plating pulse and the width of the plating pulse. A constant current density for metal deposition yields a constant electrodeposition rate and the required metal deposit weight or average thickness can be provided with high accuracy. A system for current density control based on the above described method was designed and tested in a gold pulse plating process.