Surfactant Effects in Cu-Sn Alloy Deposition

Abstract

Adsorption behavior of different polyethers (PE) on copper and tin was studied in combination with kinetic investigations. No pronounced effect of PE was detected in the Cu|Cu(II) system. In contrast, these substances show a high inhibition activity on the tin electrode. Halides enhance adsorption ability on copper electrode but suppress it on tin; this effect intensifies in the sequence: Cl − < Br − < I − . It is supposed that specifically adsorbed halides can act as species bridging the copper substrate with Cu(I)-polyether complexes, whereas the model of competitive adsorption is more suited for tin substrate. The inhibition degree of surfactants increases with the length of hydrocarbon chain. Underpotential deposition of Sn(II) is observed in the region of Cu(II) limiting current. The characteristic current minimum arises in the region where the free Sn phase becomes thermodynamically stable. Cl − ions broaden the range of current densities where yellow bronze can be obtained, but Br − ions show the opposite effect. Iodides retard the reduction of Cu(II) therefore tin prevails in the coatings. The deposits obtained present a mixture of pure copper, α-CuSn (fcc) phase and hcp phase of α-CuSn.

Electrodeposition of tin from a sulphate bath. An EQCM study

“…8 summarises the results obtained at −0.450 V, which is the potential at which the d.c. current is nearly zero. These results are similar to those reported in the literature for tin electroplating [4,24]. The Nyquist plots for both cases (Fig.…”

“…We added 1 mM hydroquinone (HQ) to maintain the stability of acid Sn(II) solutions [24]. Literature data shows that a small amount of HQ (≤1 mM) exerts no tangible effect on the results [25].…”

Electrodeposition of Cu-Sn alloys from a methanesulfonic acid electrolyte containing benzyl alcohol

“…This suggests that underpotential deposition (UPD) of Sn occurs at -0.26 V < E < -0.38 V, a common phenomenon during co-deposition of these two metals from acid electrolytes [41,47,17,15,14]. A sharp drop in current density is registered at E In = -0.38 V, which has been observed previously by Survila et al [17,15,48] during co-deposition of Cu and Sn from a sulphate-based electrolyte in the presence of polyethers (like the brightener used in the present work). These authors suggested that the adsorption of surface-active substances onto an unstable free tin phase deposited by an UPD mechanism accounted for this strong inhibition of the reduction process.…”

Effect of thiourea on electrocrystallization of Cu–Sn alloys from sulphate electrolytes

“…For several decades, highly toxic cyanide-based electrolytes were widely used for electrodeposition of copper-tin alloys [2,10]. Recently, sulphate [3,[11][12][13][14][15], pyrophosphate [16,17], methanesulfonic [9,[18][19][20][21], oxalic acid [22,23], and non-aqueous [1,24] electrolytes have been proposed. The use of mentioned compositions can significantly reduce the negative environmental impact.…”

“…Proposed compositions are based on salts of copper and tin and necessarily include special organic additives. Yellow bronzes containing up to 20 wt% of Sn have been obtained in sulphate electrolytes containing gelatin, [3] gluconic acid [11], polyethylene glycol [12], and benzaldehyde [13]. Thiourea (TU) is one of the most effective organic additives introduced into sulphate electrolytes of Cu and Cu-Sn plating because it increases cathodic polarization by chelating copper ions, imparts an appealing appearance, and assists in the deposition of fine crystalline coatings [20,[22][23][24].…”