Electrodeposition of Sn–In Alloys Involving Deep Eutectic Solvents

Tin–indium alloys represent attractive lead-free solder candidates. They show lower values of melting point than pure indium, so that they are investigated as materials with significant applications potential in the electronic industry. Electrodeposition is a very convenient route to prepare Sn–In alloys. The paper presents several experimental results regarding the electrodeposition of Sn–In alloy coatings involving deep eutectic solvents (DESs), namely using choline chloride-ethylene glycol eutectic mixtures. The influence of the main operating parameters on the Sn–In alloy composition and characteristics are presented. Adherent and uniform Sn–In alloy deposits containing 10–65 wt % In have been obtained on Cu substrates. The In content was found to increase as both the In:Sn molar concentration ratio of ionic species in the electrolyte and the applied temperature increased. The use of pulsed current allowed the use of higher current densities leading to slightly higher values of In content in the alloy deposit. X-ray diffraction (XRD) analysis revealed the presence of InSn4 and In3Sn phases in agreement with the phase diagram. According to thermogravimetric analysis (TGA) measurements, values of melting points in the range of 118.6 and 127.5 °C were obtained depending on the alloy composition. The solder joints’ behavior and alloy coatings corrosion performance were also discussed.

Wetting behavior and interfacial characteristic of eutectic In-Ag solders on Au thin films

Soldering electrical contacts to gold thin films is a matter of consideration due to high soldering temperature, restricted wetting, excessive scavenging and low strength offered by most of the common soldering alloys. Indium alloys offer certain benefits for gold soldering justifying their increased cost. In the present study, hypo-, hyper- and eutectic In-Ag solder were prepared and investigated for compositional and structural homogeneity, soldering temperature, contact angle, spreading factor, scavenging zone and scavenging phase (i.e. AuIn2). It was found that addition of silver (~3.5%) ameliorated the above mentioned characteristics for better control of soldering practice with gold thin films besides lowering the soldering temperature.

Wetting behavior and interfacial characteristic of eutectic In-Ag solders on Au thin films

Soldering electrical contacts to gold thin films is a matter of consideration due to high soldering temperature, restricted wetting, excessive scavenging and low strength offered by most of the common soldering alloys. Indium alloys offer certain benefits for gold soldering justifying their increased cost. In the present study, hypo-, hyper- and eutectic In-Ag solder were prepared and investigated for compositional and structural homogeneity, soldering temperature, contact angle, spreading factor, scavenging zone and scavenging phase (i.e. AuIn2). It was found that addition of silver (~3.5%) ameliorated the above mentioned characteristics for better control of soldering practice with gold thin films besides lowering the soldering temperature.