Interfacial reactions between Ga and Cu-xNi (x=0, 2, 6, 10, 14) substrates and the strength of Cu-xNi/Ga/Cu-xNi joints

There is potential for using Ga and Ga-based alloys as low temperature bonding materials in electronic packaging. This study investigates the interfacial reactions between liquid Ga and Cu-xNi (x = 0, 2, 6, 10, 14 wt%) substrates at room temperature using Synchrotron X-ray powder diffraction and analytical scanning/transmission electron microscopy, and subsequently examines the lap shear strength of these joints. The concentration of Ni in the substrate has a strong effect on both the type of intermetallics that form and their rate of growth. Mechanisms of intermetallic growth and the strength of the joints fabricated with the Cu-xNi substrates are discussed along with the crystallography of the intermetallics and methods of joining.