Rate dependent constitutive relations based on Anand model for 92.5Pb5Sn2.5Ag solder

A rate dependent constitutive model, the Anand model, was applied to repres ent the inelastic deformation behavior for a Pb-rich solder 92.5Pb5Sn2.5Ag used in electronic packaging and surface mount technology. This rate depend ent model is a unified viscoplastic constitutive model using an internal st ate variable, the deformation resistance, to describe the averaged isotropi c resistance to macroscopic plastic flow, In order to obtain the acquired d ata for the fitting of the material parameters of this unified model for 92 .5Pb5Sn2.5Ag solder, a series of experiments of constant strain rate test a nd constant load creep test were conducted under isothermal conditions at d ifferent temperatures ranged from -65 degrees C to 250 degrees C, A procedu re for the determination of material parameters was proposed in this paper. Model simulations and verifications revealed that there are good agreement s between model predictions and experimental data. Moreover, some discussio ns on using this rate dependent model in the finite element simulation of s tress/strain responses of solder joints under thermal fatigue loading were presented.