Copper electroplating has been widely used for the metallization process of the inner conducting lines in printed circuit boards (PCBs). Short plating process time, which means that the electrochemical deposition is operated at a high current density is always expected because of high yield consideration. However, it is difficult to fill a microvia using copper electroplating at a high current density. The microvias of PCBs have to be fully filled by copper electroplating without void, and the organic plating additives have to overcome breakdown (i.e., electrochemical oxidation) on anode. In this work, we find out a formula employing polyethylene glycol (PEG) as the suppressor can fill the microvias within 20 minutes. The filling performance was assessed through the cross-sections of the filled microvias using optical microscope (OM). Both cyclic voltammetry (CV) and linear sweep voltammetry (LCV) were carried out to explain the fast filling mechanism.

Keywords: High speed copper filling, Microvia, Printed circuit board, Polyethylene glycol.

References

1. W. P. Dow, M. Y. Yen, S. Z. Liao, Y. D. Chiu and H. C. Huang, Electrochim. Acta, 53, 8228 (2008).