Research on Reliability of Solder Layer in IGBT Module Packaging

Abstract

Sn-3.0Ag-0.5Cu (SAC305) and Pb-8Sn-2Ag are two common solders in IGBT module packaging. In this paper, the tensile tests of these two kinds of solders at strain rates of 2E-4/s, 4E-4/s, 1.2E-3/s, 2E-3/s and 4E-3/s were carried out at −40 °C, 25 °C and 150 °C. The physical properties and fracture characteristics of the two solders were compared. The Young's modulus and UTS (Ultimate Tensile Strength) of SAC305 solder were higher than those of Pb-8Sn-2Ag. In addition, the reliability of the IGBT module under thermal cycling conditions is simulated and analyzed based on the finite element software Abaqus. The results show that the stress distribution of the SAC305 solder layer is always higher than that of the Pb-8Sn-2Ag solder layer, but the equivalent creep strain is smaller than that of the Pb-8Sn-2Ag solder layer, which characterizes the solder layer in the process of long-term service, the SAC305 solder layer has a harsher stress environment than the Pb-8Sn-2Ag solder layer, but the lead-tin solder has poorer creep resistance. The IMC (Intermetallic Compound) layer between each solder layer and copper mainly plays a role in slowing down the creep, but has little effect on the stress distribution of solder layer. Finally, suggestions are made for the selection of IGBT solder.