Deformation kinetics and recovery assisted microstructural evolution of SAC305 solder under simultaneous electrical and tensile loading

SAC305 solder interconnects operate under simultaneous electrical current, tensile stress and Joule heating, but the relationship among thermal response, deformation kinetics and microstructural evolution remains insufficiently quantified. Here, SAC305 dog bone specimens were tensile tested at current densities of 0, 100, 500 and 1000 A/cm² and initial strain rates of 1 × 10⁻², 1 × 10⁻³ and 5 × 10⁻⁴ s⁻¹. Zero current temperature dependent tensile tests were used to establish a thermal strength baseline. Increasing current density and decreasing strain rate reduced tensile strength. At 5 × 10⁻⁴ s⁻¹, the ultimate tensile strength decreased from about 17.5 MPa at 0 A/cm² to 13.5 MPa at 1000 A/cm². Electrically loaded specimens remained weaker than zero current specimens at comparable externally measured temperatures, indicating that the measured macroscopic thermal response cannot fully explain the strength reduction. A current augmented Garofalo type relation captured the apparent deformation kinetics, with the apparent stress exponent decreasing from about 8.2 to 4.6. Interrupted EBSD revealed suppressed LAGB accumulation, less continuous high KAM regions, weaker texture and a late stage HAGB rebound under 1000 A/cm², consistent with recovery assisted boundary rearrangement and possible continuous recrystallization. Fractography showed a transition from dimpled rupture to smoother terminal fracture morphology at the highest current density.