Polarity effect on interfacial reactions at soldered junctions of electrically stressed thermoelectric modules

摘要

Polarity-dependent interfacial reaction at soldered junctions of bismuth telluride based thermoelectric modules is reported. Using infrared thermal imaging system asymmetrical heating at various soldered junctions of thermoelectric modules under electrical stressing was directly observed. It is suggested that electromigration (EM) coupled with asymmetrical heating leads to preferential consumption of Ni barrier and formation of Ni_3Sn_4, SnTe, and SbSn compounds at the cathode junction of p-type element. By measuring the EM-induced Sn atomic flux, the product of diffusivity and effective charge number, DZ~*, was determined to be 10~(-8)-10~(-9) cm~2/s at 200 ℃.