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

• Cu6Sn5 and Cu3Sn micro-beams were prepared by FIB for cantilever bending test using a nanoindentation system.
• The correlation between IMCs crystalline structures and the fracture characteristics of Cu6Sn5 and Cu3Sn was proposed.
• Finite element analysis was conducted to clarify the fracture modes of Cu6Sn5 and Cu3Sn under micro-cantilever bending.
• The fracture strength of Cu6Sn5 and Cu3Sn were estimated based on simulation and micro-mechanical test.

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.

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