Monitoring the quality of copper deposition by statistical and frequency analyses of electrochemical noise

This study deals with, on a laboratory scale, the influence of additions of Gelatin and Thiourea on the quality of copper electrorefining in a sulphuric acid electrolyte bath. Results showed that the quality and, in particular, roughness of cathodic deposits could be monitored and analysed using Electrochemical Noise Measurements “ENM”. In addition, different characterization techniques such as profilometry, AFM, SEM, XRD and optical microscopy have been employed to evaluate the deposits. For an electrolyte containing 2 mg/L of Gelatine and 4 mg/L of Thiourea, frequency analysis showed that the highest value of power spectral intercept (Av) corresponded to the best characteristics of the deposit such as homogeneity, smoothness and grain size. Important oscillations in the potential-time curves during galvanostatic experiments have been also related to the presence of nodules.