Time-Lapse Imaging of Ag3Sn Thermal Coarsening in Sn-3Ag-0.5Cu Solder Joints
Jingwei Xian, S. Belyakov, C.M. Gourlay
Abstract
Abstract The coarsening of Ag 3 Sn particles occurs during the operation of joints and plays an important role in failure. Here, Ag 3 Sn coarsening is studied at 125°C in the eutectic regions of Sn-3Ag-0.5Cu/Cu solder joints by SEM-based time-lapse imaging. Using multi-step thresholding segmentation and image analysis, it is shown that coalescence of Ag 3 Sn particles is an important ripening process in addition to LSW-like Ostwald ripening. About 10% of the initial Ag 3 Sn particles coalesced during ageing, coalescence occurred uniformly across eutectic regions, and the scaled size distribution histograms contained large particles that can be best fit by the Takajo model of coalescence ripening. Similar macroscopic coarsening kinetics were measured between the surface and bulk Ag 3 Sn particles. Tracking of individual surface particles showed an interplay between the growth/shrinkage and coalescence of Ag 3 Sn.