Tensile deformation and microstructures of Sn–3.0Ag–0.5Cu solder joints: Effect of annealing temperature

The mechanical quality of solder joints plays an important role in determining the structural integrity of electronic interconnects. In this work, we study the annealing effects on the tensile deformation and microstructure of Sn-3.0Ag-0.5Cu (SAC305) solder joints. The annealing temperature is in a range of 75 °C to 230 °C, which covers both liquid and solid states of SAC305 solder material. There are three intermetallic compounds (IMCs) of Ag₃Sn, Cu₃Sn and Cu₆Sn₅ formed in the solder joints. The tensile strength of SAC305 solder joints decreases from 27.3 MPa to 18.9 MPa with the increase of the annealing temperature from 210 °C to 230 °C likely due to the decrease of the volume fractions of the IMC particles of Ag₃Sn and Cu₆Sn₅ and the dislocation density. The average sizes of the IMC particles of Ag₃Sn and Cu₃Sn in the solder joints annealed at a temperature higher than the melting temperature are greater than the corresponding ones in the solder joints annealed at a temperature below the melting temperature.