Influence of spike current in different shaped waveforms on the surface finish of nickel electroforms

This paper studies the effects of ramp-down spike-shaped waveform on the surface finish of nickel electroforms in pulse current electroforming. Experimental results show that the quality of the electroforms, in terms of surface roughness improvement, influenced by the types of waveform is of the order of ramp-down and triangular both with spike > rectangular with spike > ramp-down and triangular both with relaxation time > rectangular. The results show that at the same cathodic peak current density, pulse period and a fixed electro-deposition time or electro-deposition thickness, the surface roughness can be reduced by as much as 2-3 times when a ramp-down spike was used in the cases of triangular, rectangular and ramp-down waveforms. The best surface finish was obtained a ramp-down spike in a ramp-down waveform was used. These results are supported by the theoretical predictions and the study of the surface morphology of the electroforms by scanning electron microscopy.