Effect of pulsed reverse current on the structure and hardness of copper deposits obtained from acidic electrolytes containing organic additives

Abstract

The effect of pulsed reverse current on the grain size, surface topography and hardness of copper deposits from an acidic electrolyte has been studied using a cathodic pulse time of 10 ms, an anodic pulse time of 0.5 ms, an anodic/cathodic current density ratio of 3:1 and an average current density of 3 A dm −2. Using these fixed conditions, the grain size and hardness of deposits obtained with various organic additive combinations were compared with those obtained by the use of direct current. It was found that in an additive-free electrolyte, the use of pulsed current increased the grain size of the deposits by an order of magnitude and reduced the deposit hardness. The addition of polyether molecules to the electrolyte was found to have a gain-refining effect with both direct and pulsed reverse current although the grain size obtained with pulsed reverse current was more uniform than that obtained with direct current. The addition of sulphopropyl sulphides to an electrolyte containing polyethers was found to produce grain growth with direct current, but grain refinement with pulsed reverse current, thus suggesting a different adsorption mechanism. A correlation was found between deposit hardness and grain size in all cases.