AC Impedance and Coulostatic Studies on Electrochemical Detection of 2‐Mercaptobenzothiazole in a Copper Electroless Plating Bath

A concentration evaluation method for 2‐mercaptobenzothiazole, which is a common additive in copper electroless plating baths, was demonstrated. This method consists of measuring polarization resistance values for a platinum electrode on which no copper deposition occurs at a predetermined immersion time. The reaction proceeding on the platinum electrode in this case was analyzed by the coulostatic method and ac impedance measurements using coulostatic pulse perturbation combined with an FFT spectrum analyzer. It was revealed that formaldehyde oxidation by dissolved oxygen is a predominant reaction, and that 2‐MBT inhibits this reaction markedly by adsorption with low coverage, leading to an increase in polarization resistance values.