Board level solder joint life prediction of fine pitch large IC

This paper presents three dimensional finite element analysis of a FCBGA package. It consists of a large die with fine pitch mounted on a build up substrate. Life prediction analysis is carried out for the package subjected to thermal cycling. A creep constitutive relation is adopted for both eutectic (Pb37Sn63) and lead free (95.5Sn3.8Ag0.7Cu) solders. The focus is to predict the fatigue life of the 2nd level solder joint using Coffin-Manson model. The various effects including lid materials, window size and die thickness are investigated. In the perspective of the 2nd level solder joint reliability, our results showed that lead-free solder (95.5Sn3.8Ag0.7Cu) is more reliable than eutectic solder (Pb37Sn63), and the introduction of lid generally reduces the life cycle. Al as lid material is better than Cu, whereas AlSiC is the least favored. Studies also showed that thinner die favors better reliability for solder joints. Meanwhile the effect of lid window size is relatively minor and negligible.