<p>The microstructure evolution, properties, and lifetime of Sn2.5Ag0.7Cu0.1RE/Cu solder joints under ideal electromigration conditions were systematically investigated. The results show that intermetallic compounds (IMCs) at the anode and cathode interfaces exhibit asymmetric growth during electromigration. At the anode, the Cu₆Sn₅ IMC transforms from a thin scallop-like morphology into a thicker, flatter layered structure with dispersed granular Ag₃Sn particles, while a thin Cu₃Sn layer forms on the Cu substrate side. In contrast, the Cu₆Sn₅ IMC at the cathode gradually dissolves from its initial scallop-like morphology. The crystallographic orientation of β-Sn grains in the solder matrix plays a key role in IMC evolution. When the current density reaches or exceeds 0.7 × 10⁴ A/cm², the β-Sn grain orientation changes significantly. With increasing current density, the misorientation among β-Sn grains increases, resulting in more pronounced asymmetry in interfacial IMC growth. The median time to failure (MTTF) is used to evaluate the service life of the solder joints under electromigration. With prolonged current loading, micro-voids at the cathode coalesce and grow, leading to increased electrical resistance and decreased shear strength. Meanwhile, the fracture mode changes from ductile fracture with small equiaxed dimples to brittle quasi-cleavage fracture at the Cu₆Sn₅/Cu₃Sn interface.</p>