Damage Characterization and its Incorporation into the Constitutive Model for Several Solders in Electronic Packaging

A materials science based damage metric is presented for solders in electronic packaging. The damage metric characterizes the damage state when solders are subjected to cyclic thermal strain due to mismatch of the coefficient of thermal expansion (CTE). The damage metric is derived through a micromechanics approach, and its relationship to the damage parameters is assumed to follow power law. A unified creep and plasticity constitutive model with damage incorporation showed reasonable agreement with the experimental results for two solders under a one-dimensional strain controlled fatigue test.