The effects of isothermal aging on sandwich structural of p- and n-TE/Ni/SBA/Cu joints

Thermoelectric materials are widely used as thermoelectric cooler in electronic devices. Bismuth telluride is considered as one of the candidates because of the good performance in room temperature. Besides, Sn-Bi solder paste has been employed to connect the electronic component and thermoelectric materials due to its low melting point. However, Te consumed rapidly because of the reaction between solder and bismuth telluride. The fast formation of intermetallic compound degraded the reliability of the joints. Thus, a Ni resistant layer plated by vacuum evaporation was introduced in current study to obstruct the formation of SnTe intermetallic compound and improve the mechanical stability and electrical properties of the joints. The results revealed that the resistance of p- or n-TE/SBA/Cu joints was stable and the shear strength of both them decreased during isothermal aging. There was no obvious SnTe intermetallic compound formed when introducing Ni layer. However, the p- or n-TE/Ni/SBA/Cu joints generated some defects such as cracks which grew larger during isothermal aging. With the increase of aging time, the resistance and shear strength increased and decreased, respectively. Besides, no obvious effect of introducing Ni layer between solder and thermoelectric materials on the mechanical property during aging process. It was suggested that the bonding strength of Ni layer may not strong enough through the vacuum evaporation method.