<p>Nano-Ag sintering is widely used as a power chip bonding technology in power electronic devices due to its ability to achieve “low-temperature bonding and high-temperature performance.” However, sintered silver joints are prone to degradation or failure during prolonged high-temperature service. Current research on the degradation mechanisms of these joints primarily focuses on interfacial oxidation caused by oxygen, while the effects of microstructural evolution and internal pore dynamics on joint performance remain insufficiently explored. This study investigated the structural evolution of sintered silver during high-temperature aging and examined the associated degradation mechanisms. It was found that pores within the sintered silver layer undergo Ostwald ripening at elevated temperatures. Additionally, pore expansion and increased aspect ratios resulted from the decomposition of residual organic matter and gas formation. Pores located near the edge regions were particularly susceptible to growth and sharpening, leading to stress concentration that facilitated crack initiation and propagation. Furthermore, oxygen was observed to penetrate the nickel oxide interfacial layer during aging, resulting in delamination between the nickel and silver layers. The combined effects of crack development and nickel layer oxidation ultimately reduced the mechanical integrity of the joints.</p>