Modeling the effects of cycling of a localized heat source on the durability of a FCOC with defects

A nonlinear, finite element based, coupled-field, sequential thermal-structural analysis was conducted on a flip-chip on ceramic (FCOC) package with defects. The effect of cycling of a localized heat source on the underside of the package die was studied in order to explore the possible formation of hot spots in the package resulting from heat flow inhibiting defects due to imperfect thermal contacts at key interfacial locations. In addition, an energy partitioning model was used to evaluate the reliability of the solder joints under such accelerated thermal fatigue cycling loads. The effects of different peak heat flux values, and thermal boundary conditions were investigated within the bounds of a maximum allowable solder joint temperature indicative of failure. The thermal results clearly show pronounced temperature gradients that can be induced within the package due to localized power dissipation in the die, and clearly point to the need and significance of non-uniform thermal analyses of such packages. The associated structural results applied to the damage model show that creep continues to be the primary mechanism of failure in the FCOC package.