Study of Diffusion Barrier for Solder/n-Type Bi2Te3 and Bonding Strength for p- and n-Type Thermoelectric Modules

This paper investigates the interfacial reaction between Sn and Sn3Ag0.5Cu (SAC305) solder on n -type Bi 2 Te 3 thermoelectric material. An electroless Ni-P layer successfully suppressed the formation of porous SnTe intermetallic compound at the interface. The formation of the layers between Bi 2 Te 3 and Ni-P indicates that Te is the dominant diffusing species. Shear tests were conducted on both Sn and SAC305 solder on n - and p -type Bi 2 Te 3 with and without a Ni-P barrier layer. Without a Ni-P layer, porous SnTe would result in a more brittle fracture. A comparison of joint strength for n - and p -type thermoelectric modules is evaluated by the shear test. Adding a diffusion barrier increases the mechanical strength by 19.4% in n -type and 74.0% in p -type thermoelectric modules.