Copper-tin electrodeposition from an acid solution containing EDTA added

An acid Cu-Sn deposition bath was developed, containing EDTA (disodium ethylenediaminetetraacetate) to sequester the copper(II) and tin(II) ions, forming stable complexes in solution at pH 3.4. Voltammetric studies showed that the onset of Cu-Sn codeposition started with reduction of [CuEDTA](2-) and [Sn(H2O)(6)](2+) at potential more negative than -0.90 V (first region of deposition). The reduction of [SnEDTA](2-) complexes occurs at potential more negative than -1.20 V (second region of deposition), leading to Cu-Sn alloys with a higher tin content. The hydrogen evolution reaction (HER) occurs in all range of potential parallel to the Cu-Sn deposition. No nucleation loop was observed in the voltammetric curves for Cu-Sn deposition due to HER. Cu-Sn voltammetric deposition at various sweep rates indicated that the deposition process may be controlled by mass transport and charge transfer in both regions. The Sn content in the potentiostatic Cu-Sn (Ed) change, from similar to 27.0 wt.% to similar to 60.0 wt.%, for a constant composition of deposition bath. Cu-Sn deposit containing 43.6 wt.% Sn was obtained from the acid EDTA bath investigated herein. The color of the deposits was reddish (similar to 27.0 wt.% Sn) and grayish (similar to 32.0 wt.% -similar to 60.0 wt.% Sn). Scanning electron microscopy images showed that the deposits produced at -1.03 V and -1.30 V, for both deposition charge densities (q(d)), 2.55 C cm(-2) and 8.47 C cm(-2), were composed of cauliflower-like particles, which increased with qd, and that the deposits obtained at -1.30 V were more compact than those formed at -1.03 V, for both qd, being this, the main difference between these two types of deposits. X-ray patterns of the deposits formed at E-d = -1.03 V, with either q(d), using non-grazing incidence, indicated the presence of hcp-CuSn and Cu3Sn phases. However, for E-d = -1.30 V were identified the Cu6Sn5 and Cu10Sn3 phases for q(d) = 2.55 C cm(-2) and only Cu6Sn5 phase for q(d) = 8.47 C cm(-2). (C) 2013 Elsevier B.V. All rights reserved.