Pulse plating of matt tin: effect on properties

The present work was conceived as an investigation on the effects of pulse plating on the microstructure of matt tin coatings from a proprietary acidic methanesulphonate bath. The effects of pulse plating on current efficiency, surface roughness, grain size and orientation of tin deposits were investigated as a function of the duty cycle and the pulse frequency. The impact of pulse plating on the microstructure emerged clearly from the results gathered in this work, though the effect size was relatively limited. The average grain size was found to increase with increasing duty cycle, while the opposite tendency was noticed with increasing frequency. The grain structure, i.e. the cross-section microstructure of the tin deposits, was not influenced to any appreciable degree by pulsed current deposition, remaining columnar irrespective of the pulse plating parameters within our operating range. Grain orientation of direct current as well as high duty cycle pulse plated deposits is a strong (110) texture; this turned out to weaken as either the duty cycle or the frequency was reduced. A relatively stronger impact of pulse plating was that on surface morphology, where surface roughness of pulse plated deposits is reduced with decreasing duty cycle or frequency.