The soldering process of interconnecting crystalline silicon solar cells to form photovoltaic (PV) module is a keymanufacturing process. However, during the soldering process, stress is induced in the solar cell solder jointsand remains in the joint as residual stress after soldering. Furthermore, during the module service life time,thermo-mechanical degradation of the solder joints occurs due to thermal cycling of the joints which inducestress, creep strain and strain energy. The resultant effect of damage on the solder joint is premature failure,hence shortened fatigue life. This study seeks to determine accumulated thermo-mechanical damage and fatiguelife of solder interconnection in solar cell assembly under thermo-mechanical cycling conditions. In thisinvestigation,finite element modelling (FEM) and simulations are carried out in order to determine nonlineardegradation of SnAgCu solder joints. The degradation of the solder material is simulated using Garofalo-Arrhenius creep model. A three dimensional (3D) geometric model is subjected to six accelerated thermal cycles(ATCs) utilising IEC 61215 standard for photovoltaic panels. The results demonstrate that induced stress, strainand strain energy impacts the solder joints during operations. Furthermore, the larger the accumulated creepstrain and creep strain energy in the joints, the shorter the fatigue life. This indicates that creep strain and creepstrain energy in the solder joints significantly impacts the thermo-mechanical reliability of the assembly joints.Regions of solder joint with critical stress, strain and strain energy values including their distribution aredetermined. Analysis of results demonstrates that creep energy density is a better parameter than creep strain inpredicting interconnection fatigue life. The use of six ATCs yields significant data which enable betterunderstanding of the response of the solder joints to the induced loads. Moreover, information obtained fromthis study can be used for improved design and better-quality fabrication of solder interconnections in solar cellassembly for enhanced thermo-mechanical reliability
