NODULATION OF ELECTRODEPOSITED COPPER IN THE PRESENCE OF THIOUREA

This paper considers the effect of thiourea concentration, temperature and current density on electrodeposited copper nodulation. Thiourea concentration was varied from 0 to 60 mg dm-3 in the range 30 to 60-degrees-C and at current densities of 21.5, 48.4, 75.3 and 129.2 mA cm-2 . Thiourea was found to initiate nodulation and this effect was always associated with a large increase in overpotential, i.e., > 100 mV. This phenomenon occurred only when the applied current density was greater than a critical current density, i(c). The critical current density was found to be insensitive to potential over a range of about 100 mV. Also, it decreased nonlinearly but smoothly with increase in thiourea concentration at a given temperature and increased similarly with temperature at a given thiourea concentration. Galvanostatic experiments were carried out to study this phenomenon and a qualitative explanation is given based on potentiodynamic measurements and suppositions as to the possible chemical reactions taking place at the cathode surface based on evidence in the literature.