Fabrication of a Bi₂Te₃-Based Thermoelectric Module Using Tin Electroplating and Thermocompression Bonding

A method for directly bonding thermoelectric elements onto copper electrodes without applying a solder paste was developed in this study. A tin coating of thickness approximately 50 μm was deposited via electroplating onto the surface of a Bi₂Te₃-based thermoelectric element, which had a nickel diffusion barrier layer. The resulting structure was subsequently subjected to direct thermocompression bonding at 250 °C on a hotplate for 3 min at a pressure of 1.1 kPa. Scanning electron microscopy imaging confirmed that a strong and uniform bond was formed at the copper electrode-thermoelectric element interface, and the melted or solidified tin layer remained defect-free. The thermoelectric module fabricated using tin plating had an average bonding strength similar to that fabricated using soldering.