An FE-Investigation of the State of Stress and Fracture Mechanics Properties of Intermetallic Compounds

This paper focuses on a finite element analysis of the state of stress and strain within an intermetallic layer at the interface of a lead-free solder joint. The magnitude and sign of the stresses and strains (tensile vs. compressive) is discussed as a function of various parameters, such as the thermo-mechanical properties of the materials constituting the joint, the geometry of the intermetallic phase (stress concentrations), and its potential change in volume during its creation. Moreover the stresses and strains are used to calculate stored energies in order to obtain an estimate for the energy release rates and related fracture mechanics properties of the intermetallics, as a function of the various parameters mentioned before. The findings of this paper can be used to develop guidelines that indicate which materials and geometry parameters to change in order to optimize the interfacial quality from the (theoretical) viewpoint of mechanics