Micromechanics-based interfacial stress analysis and fracture in electronic packaging assemblies with heterogeneous underfill

The flip-chip assembly, which is composed of three main components, i.e. chip with C4 interconnects, underfill and substrate, undergoes thermal loading during the curing process and its operational life. This analysis is focused on delamination of the underfill from the passivation layer of a chip due to thermal loading by using a simple model involving a finite bi-material strip. The underfill is modeled as a composite material consisting of the polymer matrix and silica particles. The interfacial stresses are determined here for several particle arrangements, while the interfacial fracture is studied using a J-integral method. The interfacial stress analysis and the J-integral method give the same trends.