Research On The Effects Of Typical Solders On PbTe-Based Semiconductor Thermoelectric Generators

PbTe-based semiconductor thermoelectric generators convert thermal energy into electrical energy.It can improve energy utilization,reduce emissions and improve our living environment.The reliability of a PbTe device depends to a large extent on the quality of the joint between the thermoelectric material and the electrode,in particular the type and quality of the solder alloy and the welding technology applied.The connection of the joint will cause contact resistance and diffusion of elements.A reliable soldering method for analyzing lead and electrode is important for the application of PbTe-based devices.In this paper,p-type Na_0.02Pb_0.98Te and n-type PbTe_0.9988I_0.0012.0012 thermoelectric materials were first prepared.The ZT value of p-type Na_0.02Pb_0.98Te material reached1.7 at 500^oC,and the ZT value of the n-type PbTe_0.9988I_0.0012.0012 material reached 0.5 at450^oC.Sn₆₄Bi₃₅Ag₁ was used as a low-temperature solder to directly connect PbTe and Cu.and it was found that the weld interface had hole defects and the mechanical properties were poor.Weld nickel-plated PbTe thermoelectric materials by using different soldering temperatures for 1 min.Analyze the effect of welding temperature on the microstructure of the joint interface.The analysis results show that the welding temperature is higher than 220^oC,and cracks will occur at the interface.The higher the temperature,the more obvious the crack,and the excessive crack causes the solder to gradually chip and fall off.At a soldering temperature of160-190^o C,it is possible to bond p-type Na_0.02Pb_0.98Te and n-type PbTe_0.9988I_0.0012materials to Cu.The interface structure of the joint is Cu/Cu₆Sn₅/SnTe+Sn-Bi/Ni/NiTe/Na_0.02Pb_0.98Te and Cu/Cu₆Sn₅/SnTe+Sn-Bi/Ni/NiTe/PbTe_0.9988I_0.0012.Since the interface contact resistance is higher,the conversion efficiency and output power of the thermoelectric device are lower,and the interface contact resistance of 160-190°C welding is relatively small,which is suitable for the fabrication of the solder joint.When the PbTe and Cu are directly welded by the silver paste solder,the Ag element will diffuse and react with the thermoelectric material.When the silver paste solder is nickel-plated PbTe,the Ni layer blocks the diffusion of Ag,which can avoid the influence of Ag on Na_0.02Pb_0.98Te and PbTe_0.9988I_0.0012.The n-type and p-type thermoelectric materials are used to make a thermoelectric arm with a size of 2×2×1.78 mm³.When the temperature difference is 453.8^oC,the output power of the device is 3.021 W and the maximum conversion efficiency is 5.14%.