A copper electroplating process using a single organic additive was developed for filling through holes of printed circuit boards. The organic additive acted as an inhibitor of copper deposition in the presence of chloride ions and H2SO4. This copper electroplating formula resulted in center-up filling, which differs from the bottom-up filling exhibited by blind microvias. The inhibiting strength of the organic additive and the filling capability of the plating solution strongly depended on the concentration of H2SO4. The electrochemical behavior of the organic additive was characterized by electrochemical analyses and imaging of TH cross sections. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3511757] All rights reserved.