Crystallographic changes and mechanical Performances of SnAg2.4/Cu Pillars during thermal shocks in a large temperature range

Microelectronics can easily be destroyed under extreme temperature conditions. Smaller solder joints become the weak points and enhance the risk of microelectronics failures. Therefore, it is essential to study the reliability of high-density packaged micro-bumps under extreme temperature conditions. This study investigated the impact of thermal shock on micro-bumps reliability, focusing on the microstructural and crystalline changes at the interface. Additionally, ball shear tests were conducted to evaluate the mechanical properties and fracture behavior of the micro-bumps. The results indicated that with increasing thermal shock cycles, the Cu₃Sn thickness steadily increases, twins appeared in the Sn after 200 cycles, and the grain orientation was about 60°, with the primary twin system being {111} < 010>; furthermore, stress-induced led to grain orientation alignment and an increase in grain size, while the shear mechanical properties, microhardness, and modulus of micro-bumps decrease with the increasing number of thermal shock cycles.