Study on reaction behavior of Sn37Pb/Ni- <i>x</i> Cu solid-liquid interface and mechanical properties of soldered joints

Purpose This study aims to reveals the metallurgical reaction mechanism at the interface between Sn37Pb solder and Ni- x Cu alloy substrates, as well as to explain the reasons for the elevated shear performance of Sn37Pb/Ni-xCu joints, the metallurgical reaction mechanism at the interface between Sn37Pb solder and Ni- x Cu alloy substrates was investigated to find a solution to the problem. This study further reveals the reasons for the elevated shear performance of Sn37Pb/Ni- x Cu joints. Design/methodology/approach The growth behavior of intermetallic compounds (IMCs) at the soldered Sn37Pb/Ni- x Cu ( x = 0, 20, 40, 60, 80 and 100 Wt.%) solid–liquid interface was investigated using electron probe microanalyzer and electron backscatter diffraction, the shear performance of the joints was conducted using a shear tester (MFM1200), following the JESD22-B117 shear testing standard. Findings The results indicated that as the Cu content increased in the Ni- x Cu alloy, the interfacial reactant in the Sn37Pb/Ni- x Cu joints transitioned from the (Ni,Cu) 3 Sn 4 phase ( x = 20 Wt.%) to the (Cu,Ni) 6 Sn 5 phase ( x = 80 Wt.%), effectively circumventing the formation of brittle Cu 3 Sn and Kirkendall voids. It was observed that the thickness of the IMCs layer increased significantly at the Ni matrix with 80 Wt.% Cu. Correspondingly, the (Cu,Ni) 6 Sn 5 grains exhibited a rod-like morphology characterized by [0001] orientation. Notably, this microstructural feature, functioning as a precipitation-strengthening mechanism, markedly enhanced the shear strength to 23.11 MPa. Originality/value The findings of this research could provide valuable theoretical insights into the composition design of microbumps on encapsulated substrates.