Effect of Convection-Dependent Adsorption of Additives on Microvia Filling in an Acidic Copper Plating Solution

Microvia filling of a printed circuit board by acidic copper electroplating was performed to evaluate whether the filling performance of an acidic copper plating solution could be quantified and monitored. The acidic copper plating solution was composed of polyethylene glycol, chloride ions, bis(3-sulfopropyl) disulfide and Alcian Blue. The electrochemical methodology for quantifying the filling performance of the copper plating solution is based on the adsorption and mass transfer of chloride ions. The potential difference that was obtained from galvanostatic measurements at two different rotating speeds of a copper working electrode was confirmed to be an effective indicator of filling performance. A larger potential difference reflected better filling performance. The individual contribution of each additive in the potential difference was explored in detail. The leveler and chloride ion concentrations dominated the potential difference, i.e., the filling performance. When the potential difference was larger than a critical value, i.e., 11 mV, the filling performance was higher than 80%.