In situ tensile tests on Sn-3.5Ag lead-free solder were performed with different rates of 10 μm/s and 300 μm/s at − 198 °C liquid nitrogen temperature. Microstructure evolution and deformation behavior of Sn-3.5Ag solder were observed by optical metallographic microscopy. The morphological influence of the second-phase particles Ag₃Sn on fracture behaviors was investigated by scanning electron microscopy. The results showed that plastic deformation occurred at the low tensile rate, while no fracture toughness was observed at the high tensile rate. Several fracture modes were observed, including intergranular fracture and transgranular fracture. The morphology and distribution of the second-phase particles had a significant impact on the fracture behavior of solder. The long rod-shaped second-phase particles perpendicular to the tensile direction were difficult to fracture, while the parallel second-phase particles were broken into segments. The smaller second-phase particles barely deformed, and the voids nearby provided a favorable pathway for fracture.

在− 198 °C 液氮温度下，以 10 μm /s 和 300  μm /s的不同速率对 Sn-3.5Ag 无铅焊料进行原位拉伸测试 。通过光学金相显微镜观察Sn-3.5Ag焊料的显微组织演变和变形行为。第二相颗粒Ag _{3的形貌影响}通过扫描电子显微镜研究了 Sn 对断裂行为的影响。结果表明，低拉伸速率时发生塑性变形，而高拉伸速率时未观察到断裂韧性。观察到几种断裂模式，包括沿晶断裂和穿晶断裂。第二相颗粒的形貌和分布对焊料的断裂行为有显着影响。垂直于拉伸方向的长棒状第二相颗粒难以断裂，而平行的第二相颗粒则破碎成段。较小的第二相颗粒几乎不变形，附近的空隙为断裂提供了有利的途径。