Abstract: The reliability problems caused by the segregation of Bi element limit the application of Sn-Bi-Ag alloy solder in electronic packaging.Microalloying is an effective method to improve the reliability.It is of great significance to study the effect of trace element addition on the structure and morphology of Sn-Bi-Ag solder interfacial layer. Using the method of accelerated aging, the interface layer structure and morphology of SnBi36Ag0.5Sbx(x=0.3, 0.7, 1.0, 1.5, 2.0)solder alloy were studied under the condition of isothermal aging, high and low temperature impact and high and low temperature cycle. The results show that the thickness of the interface layer increases gradually with the extension of isothermal aging time and reaches its peak at 2000 h. The interface layer is divided into two regions:intersecting regions with rich Bi and non-intersecting regions.The interface layer of the intersection regions is thicker, and there is a"rich Bi layer".Because of the complex phase composition in the intersection region, most of the cracks are generated in the region. Sb element can inhibit the formation of interfacial layer cracks.The results of high and low temperature cycling show that the thickness of interfacial layer increases with the increase of Sb element.