Abstract
Measurements of limiting current densities at copper plating in acidified copper sulfate and copper fluoborate baths were conducted with a Hull Cell and a rotational electrode method. In the same cocentration of copper and an acid, the limiting current densities showed the same order of magnitude for copper sulfate solution and for copper fluoborate solutions. The diffusion coefficient of CuSO4 calculated from the Levich equation had the same value as the calculated diffusion coefficient of Cu(BF4)2. These suggest that the reason why copper fluoborate bath is used for high speed copper plating is due not to the difference in diffusion coefficients of Cu(BF4)2 and CuSO4 but to the higher copper concentrations obtained in the fluoborate bath. The paterns of “burnt” on a Hull Cell panel under unagitated conditions were explained in terms of the distribution of current densities over the panel in natural convection of the plating solution caused by electrolysis.
