A fracture mechanics analysis of electronic packages

A fracture mechanics approach is used to investigate the delamination of electronic packages during the solder reflow process. A two-dimensional analytical fracture model is developed and provides a closed form solution for the energy release rate as a function of loading and geometry. Finite element analysis is used to determine the crack driving force in a generic electronic package. A comparison between the two results gives an indication as to the accuracy of the analytical model. The finite element model is used to calculate the magnitude of the mode I and mode II stress intensity factors as a function of package geometry. The fracture characteristics of two silica filled epoxy resins are investigated. The fracture characterizing parameter at room temperature is the critical stress intensity factor. The effects of temperature and moisture content on the fracture toughness of the compounds are examined. The validity of using the stress intensity as the fracture governing parameter in the silica filled molding compounds at elevated temperatures is investigated. A comparison between the numerically calculated crack driving force and the experimentally measured fracture toughness is presented as a criteria for predicting package cracking.