Effect of Electric Current on Constitutive Behaviour and Microstructure of SAC305 Solder Joint

As the traditional lead-containing solders were banned for consumer electronics by RoHS laws, lead-free solders are widely adopted in the electronics packaging industry. The Sn3.0Ag-0.5Cu (wt%, SAC305) solder material is one of the most commonly used die-attach solders. But the reliability of SAC305 solder joints under complex working conditions still requires to be carefully investigated. In this paper, the uniaxial tensile behavior of solder joint specimens with a diameter of 1.0 mm was investigated subjected to the strain rate of $10^{-4} \mathrm{s}^{-1}$ under electric current density ranging from 1000 A/cm2 to 4000 A/cm2. In order to reveal the current stress effect under the mechanical-electrical coupled loadings, the uniaxial tensile properties of SAC305 solder joint specimens were measured by a multi-field loading system. In addition, the microstructure of the tensile specimens is observed by a scanning electron microscope. It was found that fracture mode changed from ductile fracture to the combination of brittle and ductile fracture when the current density raised from 1000A/cm2 to 2000A/cm2. And the fracture was more likely to happen near the interface when the current density is higher.