Micro-mechanical and fracture characteristics of Cu6Sn5 and Cu3Sn intermetallic compounds under micro-cantilever bending

This study focuses on the fracture characteristics of Cu₆Sn₅ and Cu₃Sn micro beams under micro-cantilever bending tests. These micro beams were fabricated by focused ion beam (FIB) from the Sn-rich solder joints aged at 175 °C for 1132.5 h, and then tested using a nanoindenter with a flat tip. Experimental results show that both Cu₆Sn₅ and Cu₃Sn micro beams underwent elastic deformation before their failure. From fractographic analysis, both cleavage fracture and intergranular fracture can be identified from the tested Cu₆Sn₅ micro beams, while only intergranular fracture was found in Cu₃Sn micro beams. Furthermore, based on the experimental results, finite element analysis was carried out to evaluate the tensile fracture strength and strain of Cu₆Sn₅ and Cu₃Sn micro beams. For Cu₆Sn, the tensile fracture strength was estimated to be 1.13 ± 0.04 Pa and the average tensile strain was 0.01. The tensile fracture strength and strain of Cu₃Sn were evaluated to be 2.15 ± 0.19 GPa and 0.016, respectively.