Solder joint lifetime assessment of electronic devices

The continuum mechanical and constitutive description of eutectic tinÐlead (Ðsilver) solder is discussed with respect to the expected mean lifetime of solder joints of electronic devices under thermal cycling conditions, especially, the creep damage evolution in the joints. Since the mechanical loads are introduced into the model by thermal loads and due to the thermal expansion mismatch of di¤erent components, the solder joints are modelled by Þne meshes of non-linear triangular Þnite elements, whereas the remaining surrounding structure is modelled by linear beams, linear quadrilaterals and speciÞc compatibility elements. The strain-rate and temperature-dependent creep evolution and stressÐstrain relations of tinÐlead (Ðsilver) are presented in tensorial form. A hypothesis of the creep damage evolution is also o¤ered. Simulation results on the creep damage evolution in solder joints of quad ßat packs (QFP) with gull wing leads are discussed and compared with thermal cycling experiments