With advancements in miniaturization and performance in advanced packaging technology, the diameter of Sn-based microbumps continues to shrink to the micrometer scale. Consequently, the current density passing through each solder bump increases exponentially as the radius reduces. This emphasizes the critical need to understand the behaviors and mechanisms of electromigration (EM) for the reliability evaluation and design of chip interconnects in integrated circuits. This study systematically summarizes and analyzes the physical nature, key influencing factors and research methods related to the electromigration of Sn-based microbumps. The EM characteristics during the solid-solid EM, including the “polarity effect”, “reverse polarity effect” and “two-phase separation” are reviewed. Similarly, the EM behaviors during the liquid-solid EM, including atomic migration, phase segregation and phase dissolution, are systematically reviewed. The EM lifetime assessment models and their modifications are evaluated. Furthermore, this study summarizes methods to improve the EM reliability of Sn-based microbumps and outlines prospective research direc