Pulse Periodic Reverse Plating--Possibilities for Electrodeposition of Metal Coatings with Improved Properties: Part 2

摘要

In Part 1 of this paper we discussed the cathodic and anodic processes that take place during pulse periodic reverse plating (PPRP) of metal coatings and found an appropriate way to combine the cathodic pulses of electrocrystallization with the anodic pulses of metal dissolution in order to obtain a positive commutative effect in respect to leveling and structural homogeneity. We established that at definite parameters of the forward current pulses and of the reverse voltage pulses, the leveling performance of the deposited metal coatings could be considerably improved in comparison to that of ones deposited by the unipolar pulse plating (UPP). The second part of our paper presents the results of porosity and internal stress measurements of bright copper, nickel, gold and palladium coatings deposited by PPRP and UPP. The comparative analysis of the results obtained demonstrates indisputably the advantages of pulse periodic reverse techniques to unipolar pulse plating in regards to the deposition of metal coatings with improved properties. Thus, at those parameters of PPRP corresponding to the maximal leveling, we can deposit high-quality metal coatings with reduced internal stresses and less porosity. We also offer a theoretical explanation of the process mechanisms in which the applied reverse (anodic) pulses in PPRP act as internal stress reliever and porosity reducer.