An improved unified creep‐plasticity constitutive model for viscoplastic solder materials of electronic packaging subjected to high-strain-rate impact loadings

With the increasing demand for reliability in electronic packaging under extreme dynamic loading environments, accurate characterization of solder joint deformation behavior has become critical for optimizing structural design and enhancing product durability. This paper addresses this imperative by focusing on the deformation mechanisms and constitutive modeling challenges of solder joints under high-strain-rate conditions. Traditional metallic material models are unable to adequately capture the complex thermo-mechanical responses of solders, highlighting the need for advanced constitutive frameworks. By integrating split Hopkinson pressure bar (SHPB) experimental data with a unified creep-plasticity theory, an improved constitutive model is developed that incorporates the strengths of the Johnson-Cook formulation while addressing its limitations in temperature-dependent behavior. Experimental validation utilizes Pb37Sn63 solder specimens tested at temperatures of 25°C, 60°C, and 100°C under strain rates up to 5500 s⁻¹, enabling quantitative analysis of coupled temperature-strain rate effects on stress-strain behavior. The proposed model demonstrates exceptional accuracy in predicting solder deformation across extreme thermo-mechanical conditions. Following rigorous parameter calibration through SHPB test replication via user-defined material subroutines in finite element simulations, the model exhibits high predictive fidelity. Implementation in package-level structural simulations further reveals critical dynamic mechanical response characteristics under impact loading, confirming its efficacy in enhancing reliability analysis for electronics packaging design.