Diffusion Soldering of Bi0.5Sb1.5Te3 Thermoelectric Material with Cu Electrode

For the production of thermoelectric modules, Bi0.5Sb1.5Te3 was sequentially electroplated with a 4-mu m Ni barrier layer and a 10-mu m Ag layer and then diffusion soldered with the Cu electrode, which was also electroplated with 4-mu m Ag and 4-mu m Sn layers. The Bi0.5Sb1.5Te3 and Ni interface with no sufficient chemical bonds resulted in a bonding strength lower than 3 MPa. Through the pre-coating of a 1-mu m Sn thin film on Bi0.5Sb1.5Te3 and heating at 250 A degrees C for 3 min before the electroplating of the Ni barrier layer, the bonding strengths of Bi0.5Sb1.5Te3/Cu assemblies increased to a maximal value of 10.7 MPa. The intermetallic compounds formed at various interfaces in the Bi0.5Sb1.5Te3/Cu modules after diffusion soldering at temperatures ranging from 250 to 325 A degrees C for 5-60 min and their growth kinetics was analyzed.