ANALYSIS OF ORGANIC PLATING ADDITIVES USING BORON-DOPED DIAMOND ELECTRODES

摘要

Boron-doped, diamond film electrodes were investigated as sensor electrodes for typical organic copper-plating additives. On diamond, oxidative peaks for dilute (ppm range) poly(alkylene glycol) (E_p=+2.05, +2.4V) and disodium (bis(3-sulfopropyl)) disulfide (E_p=+1.65, +2.1V) in excess CuSO_4/H_2SO_4 were observed. The peaks increased linearly with additive concentration. In contrast, on platinum, no peaks for glycol or disulfide oxidation or reduction could be observed. On diamond, CuSO_4/H_2SO_4 solutions of 4000 molecular weight poly(ethylene glycol) displayed higher peak currents than 10,000 molecular weight. Disulfide in H_2SO_4 displayed different oxidation peak potentials and heights than in CuSO_4/H_2SO_4 mixtures. In CuSO_4/H_2SO_4/HCl, the oxidative charge (E_p=+2.1, +2.3 V) and peak current (E_p=+2.1V) for glycol, disulfide, and 2-imidazolidinethione mixtures varied linearly, when varying one additive concentration and holding the others constant. The majority of charge transfer was from glycol oxidation, which was present in greater concentration. Selective glycol dilution should improve sensitivity for concentration changes of the less concentrated additives. Consequently, diamond electrodes are highly promising as sensor electrodes for plating bath additives.