High temperature Te-containing solder alloys

High-temperature solders are categorized to have a solidus temperature above 270 °C and a liquidus temperature below 350 °C. The conventional alloys mainly contain Pb, which is known to be environmentally hazardous. Several Pb-free alloys have been previously developed but are not suitable due to excessive reactivity (Zn-based alloys) or high cost (Au-based alloys). Alternatively, Te is not environmentally hazardous and is not listed in RoHS directive. To the best of our knowledge, Te-based alloys have never been proposed for high temperature solder applications. This presentation will showcase the advances of four lead-free solder compositions suitable for high temperature solder applications. The proposed alloys have eutectic temperatures ranging from 300 to 350 °C and according to thermodynamic calculations, are less reactive to oxygen when compared to conventional Pb-free solder elements such as Sn and Zn. Each alloy will be discussed in terms of CalPhad modeling, differential scanning calorimetry, microstructure and phase development during molten interactions with Cu.