Interfacial reaction between the thermopile materials and eutectic Sn-based solders

The indium-based solders and bismuth-based solders are commonly employed in soldering the thermopile. Since the wettability between bismuth telluride materials and low melting point alloy solders is poor, a nickel layer was employed on the surface of thermoelectric materials. In this study, in the atmospheric environment, the eutectic Sn-Bi and Sn-In solders spreaded on the p-type thermoelectric respectively without using soldering flux, the corresponding interfacial microstructures were indentified. The interfacial reaction is more sufficient under 300 °C when comparing to that under 250 °C. In addition, a thin nickel layer was deposited on the thermoelectric unit by vapor deposition facility. However, a thin Ni-plated layer on thermoelectric materials might induce severe formation of cracks.