Abstract
Sn-based solder is widely used in the electronic packaging industry due to the toxicity of Pb. Among all Pb-free solder materials, SnAg alloy attracts much attention owing to its great flexibility, electromigration resistance and high mechanical strength. However, the formation Ag3Sn intermetallic compounds (IMC) should be carefully investigated, since the IMC is brittle and may coarsen during operation process, resulting in lowered creep resistance and poorer mechanical strength. When the microelectronic technology moves toward denser input/output arrays and higher power, a temperature gradient is easily established in the solder, therefore, how Ag3Sn IMCs response to a temperature gradient is of interest. In this study, we report the microstructural evolution of SnAg solder under a temperature gradient. The mechanism of particle-like Ag3Sn redistribution inside the bulk of Sn matrix will be discussed and the molar heat of transport (Q*) of Ag in Sn is calculated.