Effect of Soldering Temperature on the Performance of Cu/Zn Foil + Cu Powder/Cu High-Temperature Joints

This study uses T2 copper as the substrate and selects 10 μm Zn foil and 1-3 μm Cu powder as the filler material. Through a hot pressing process, the Cu/Zn foil + Cu powder/Cu joints were successfully fabricated by applying a pressure of 8 MPa and maintaining the temperature for 5 minutes within the range of 220 °C to 300 °C. A systematic investigation was conducted to examine how varying soldering temperatures influence the solder structure, interface morphology, mechanical properties, and fracture characteristics. The results indicate that at low temperatures of 220 °C and 240 °C, the joint interface formed poorly, with shear strengths of 8.09 MPa and 12.7 MPa, respectively. Significant porosity defects were observed in the soldered area, primarily due to the oxidation of Zn particles during the soldering process, leading to a high oxygen concentration in the soldering region. As the soldering temperature reached 260 °C, the oxidation of Zn was effectively minimized, leading to a notable decrease in the oxygen content within the soldering region. The increase in solder density boosted the joint's shear strength by 126.77 % as the temperature rose from 240 °C to 260 °C. Further increasing the soldering temperature to 280 °C and 300 °C resulted in stable improvement in joint quality, reduced porosity defects, and continuous increase in shear strength. EDS analysis and line scan data revealed that at high temperatures, a continuous layer of Cu5Zn8 intermetallic compound formed at the Cu-Zn interface, strengthening the mechanical properties of the joint.