Study on the meso-mechanical characteristics of SAC0307-xCe micro-solder joints

With the size of Lead-free solder joint decreasing, the reliability of solder joint is particularly prominent, which the mechanical properties of solder joint are critical to its reliability. Meso-mechanical properties and creep behavior of the SAC0307-xCe/Cu micro-solder joints were studied by Berkovich nanoindentation tests with different loading rates at room temperature. The load-depth curves were rate dependent. As the rate increased, the creep depth was increased at same hold time. The Young´s modulus of SAC0307-xCe/Cu solder joints are 46.9±0.9 GPa, 50.3±1.0 GPa, 51.4±0.8 GPa and 52.5±1.1 GPa, respectively, and indention hardness are 151.37±3.25 N/mm2, 152.85±2.96 N/mm2, 156.79±3.06 N/mm2, and 167.33±3.58 N/mm2, respectively. It can be seen that Young´s modulus and indention hardness increase with the increasing of Ce content. The strain rate sensitivity of creep m was fitted linearly by analysis of Anti-Physics of indentation hardness Hcr and strain rate έ_cr of creep. The stress index of creep n was calculated. The m values are 0.3944, 0.3229, 0.2029, 0.1233 respeetively and the n values are 2.5355, 3.0969, 4.9285, 8.1103 respeetively on SAC0307-xCe/Cu micro-solder joints, with the increasing of Ce content, the creep resistance property of SAC0307-xCe solder joints has changed much, m decreased and n increased. Results shows that adding trace amounts of Ce elements into low-Ag solder have notable effort to improve the meso-mechanical properties and creep resistance, Ce element will play an important role in providing better electronic interconnections.