The Effect of Some Addition Agents on the Kinetics of Copper Electrodeposition from a Sulfate Solution

The mechanism whereby certain organic addition agents modify the crystal growth of copper electrodeposits was studied with the aid of cathode polarization measurements and microscopic examination of the deposit. Thiourea and 1(−) cystine refine grain size and brighten the deposit. The effect is attributed to a degradation of the additive at the cathode surface with the formation of sulfide ions and precipitation of . The normal crystal growth habit is modified by the incorporation of copper sulfide into the deposit. Gelatin, a grain refiner and hardener, modifies crystal growth of copper electrodeposits by being adsorbed on growth sites thereby interfering with normal growth. Glycine, a "leveling" agent, affects cathode polarization only between about 0.1 and 1 ma/cm2. Additions of up to 0.1 g/l dextrin have no effect on the cathode polarization curve for copper plating.