無電解銅めっき浴におけるＰｄ（ＩＩ）およびＳｎ（ＩＶ）イオンの作用機構

Abstract

Electroless copper deposition has been widely used in the manufacture of printed circuit boards with plated through-holes. Intrinsic contaminants originating from the mixed PdCl2/SnCl2 catalyst may be present in the plating bath. In this study, the effects of Pd2+ and Sn4+ ions on the rate of copper deposition and the mechanical properties of the copper films were investigated. An excess of PdCl2 makes the bath unstable, leading to a reduction in the apparent deposition rate, but the appropriate amount of Pd2+ ions not only decreases lattice strain but also improves the elongation of the copper films. In the presence of both Pd2+ and Sn4+ ions, internal stress in the copper films was reduced, and the elongation of copper films was significantly improved by synergism between the two different ion species. Electrochemical analysis of electroless copper deposition elucidates that the presence of Pd2+ and Sn4+ ions not only decreases the amount of the methylene glycol anion adsorbed on the electrode surface but also prevents the inclusion of hydrogen into electroless copper films.