An extension of the omega method to primary and tertiary creep of lead-free solders

A close examination of creep curves for Sn-based solders shows that steady-state creep is an ill-defined stage and that primary and tertiary creeps are both significant. In order to account for these effects in solder constitutive models, this paper presents a phenomenological model that predicts entire creep curves for Sn-based solders. The proposed constitutive model is an extension of the omega method by Prager (2000) for tertiary creep of steel alloys to primary and tertiary creep of Sn-based solders. The new creep modeling approach is of use for stress/strain and reliability analysis of lead-free solder joints.