Methods for monitoring metal ion concentrations in plating baths

摘要

A rotating disk electrode system operates at constant speed in a solution whose metal ion concentration is held constant at multiple concentrations within a range of concentration. The current at the working electrode (16) is recorded, while the potential at the working electrode is swept by potential source (20) at a predetermined rate for each of the concentration values. The diffusion limiting current is determined by recorder (24) for each of the concentration values. Then the rotating disk electrode system is operated continuously in a metal plating bath (12) whose metal ion concentration can vary. A voltage applied to the working electrode produces a current at the electrode whose magnitude is compared to the values of the previous calibration to determine the current metal ion concentration. Alternatively, a rotating disk electrode system is operated over a range of speeds in a solution whose ion concentration is held constant over a range of concentration. Current at the working electrode is measured for a given electric potential applied to the working electrode. In this way, a calibration relationship between the current at the electrode and the range of metal ion concentrations is established which can be used with current measured in the plating bath under the same conditions as those that established the calibration curve to predict the concentration of the bath. ;