Synergistic effects of added bivalent aqua cobalt ion, bivalent aqua iron ion and aqueous sulfurous acid on a graphite anode during electrodeposition of copper from a sulfate bath

The individual as well as the synergistic effect of depolarisers, such as H2SO3 (aq) and/or Fe2+ (aq) and/or Co2+ (aq) on copper electrodeposition has been studied. A comparison is made of their relative effects on anode potential, cell potential, current efficiency (CE), power consumption and deposit quality. Linear sweep voltammetry (LSV) has been used to study the cathodic and the anodic behaviours of the depolarisers during electrodeposition of copper. The lowest value in anode potential is observed in the presence of H2SO3 and Fe2+ (aq) together. The presence of either added Fe2+ (aq) or added Co2+ (aq) or both together polarises the cathode deposition potential of copper; the extent of polarisation is more prominent in the presence of only Fe2+ (aq). In contrast, the cathode deposition potential of copper is depolarised in the presence of H2SO3 in the electrolyte; the depolarisation increases when Fe2+ (aq) is added to the electrolyte containing sulfurous acid. X-ray diffraction data show the change in the relative growth on the preferred orientations of cathode copper deposits in the absence and the presence of H2SO3 (aq) and/or Fe2+ (aq) and/or Co2+ (aq) in the electrolyte solution. Scanning electron microscopy (SEM) results establish different surface morphology of the copper samples deposited in the presence of H2SO3/Fe2+ (aq)/Co2+ (aq)/Fe2+ (aq)+Co2+ (aq)/H2SO3+Fe2+ (aq)/H2SO3+Co2+ (aq)/H2SO3+Fe2+ (aq)+Co2+ (aq) in the electrolyte solution.