Thermo-visco-plastic constitutive model for lead-containing and lead-free solders subjected to monotonic and cyclic loadings

Structural reliability issues attract more and more attentions with the rapid development of electronic packaging industry. As the most venerable part of electronic packaging structure, the mechanical reliability of solder joints is greatly relevant to the system reliability of electronic products. The mechanical properties of solder materials have to be reasonably evaluated if numerical simulations are preferred compared with experimental studies. In the present study, a thermo-visco-plastic constitutive model is proposed for both lead-containing and lead-free solders under monotonic and cyclic loading conditions. Due to a simple formulation form and only a few parameters, the proposed thermo-visco-plastic constitutive model can be implemented into finite element software at minor effort and the determination of parameters can be achieved conveniently by regression to experimental data. The validations against experimental data show that the proposed model is capable of well simulating the tensile behavior of various solder materials at different strain rates and working temperatures. In addition, the required parameters in the proposed model are proved to be well defined as good changing patterns are achieved by revealing the intrinsic characteristic properties of solder material under various conditions.