Interfacial Reaction and Shear Properties of Laser-Soldered Sn3.0Ag0.5Cu/Ni-P Microbumps

Laser welding has garnered significant attention in the field of microbump interconnections due to its advantages such as localized heating, rapid processing, flux-free operation, and ease of automation. A comparative study was conducted on the effects of laser welding and reflow welding processes, as well as the number of reflows, on the microstructure and shear properties of microbumps. The results indicate that the interfacial (Cu,Ni)₆Sn₅ intermetallic compound (IMC) layer in laser-soldered microbumps is relatively thin and exhibits a loose particulate morphology. With increasing laser energy, the IMC layer slightly thickens, and after multiple reflows, it transforms into dense short rod-shaped structures. Reflow-soldered microbumps initially feature a thicker and needle-like IMC layer, which evolves into irregular blocky or elongated rod-shaped structures following multiple reflows. The morphology of the IMC is closely related to its solid-solution Ni content, with a critical range of 7.02 at.%–10.13 at.% Ni content marking the transition from particulate to rod-like formations. Shear performance tests demonstrate that, both in the initial state and after multiple reflows, laser-soldered microbumps (particularly those fabricated at 7.5 mJ energy) consistently exhibit higher average shear forces compared to reflow-soldered microbumps, highlighting their superior interfacial reliability