Dissimilar copper-aluminum joint processed by low-temperature nickel electroplating

This study proposed a low-temperature method to form joints between copper (Cu) and aluminum (Al) by electroplating nickel (Ni) at temperatures below 50 °C. Both the Cu/Ni and Al/Ni interfaces were characterized by transmission electron microscopy (TEM). The Cu/Ni interface was an approximately 60-nm-wide layer of an unlimited substitutional solid solution of Cu and Ni, whereas a 20-nm-wide layer of a BCC-structured AlNi intermetallic compound (IMC) was observed at the Al/Ni interface on the Ni side. The joined samples were heat-treated at 200 °C for durations of 5 h to 1000 h, and the joint strength did not degrade after isothermal aging. No further growth of the intermetallic compound was observed at the Al/Ni interface during the isothermal aging process.