A solder fatigue model for 63Sn/Pb solder has been developed bycombining nonlinear finite element modelling with thermal fatigue dataof assorted flip chip assemblies. The model characterizes the creepfatigue phenomena of the solder alloy by correlating the amount of creepstrain energy dissipated per thermal cycle with the characteristicWeibull life of the critical solder joint. It has been validated forvarious die sizes, bump geometries, board materials and thermalprofiles. Furthermore, the model has accurately predicted fatigue livesfor flip chip assemblies with and without underfill. The solder fatiguemodel has been utilized to investigate the reliability of flip chipjoints subjected to thermal cycling. In particular, a parametric studyhad been performed which shows how various flip chip design parameterswill affect solder joint fatigue. Finite element models have beendeveloped to analyze the effect of die size, die thickness, solder jointheight, cap diameter and underfill properties on solder fatigue. Forthis investigation, all analyses have been carried out for parts onceramic substrates. The results for underfilled parts show that whiledie size does not influence solder joint reliability, the effects ofunderfill CTE are very important. Non-underfilled parts aresignificantly influenced by die size, cap size and joint height
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