Mixed Mode Interfacial Fracture Toughness Evaluation for Flip-Chip Assemblies and CSP Based on Fracture Mechanics Approaches

The increasing use of advanced electronic packages like Flip Chips and CSP under harsh environmental conditions, extreme temperatures is often a reason for damage, fatigue and failure of entire components and systems. Consequently, their thermo-mechanical reliability is one of the most important preconditions for adopting these technologies in industrial applications. To prevent chips from being exposed to the external environment integrated circuits are usually encapsulated into packages. As a result, a microelectronic package is basically a compound of several materials with quite different Young’s moduli and thermal expansion coefficients. Additionally, various kinds of inhomogeneity, residual stresses from several steps of the manufacturing process contribute to interface delaminations, chip cracking and fatigue of solder interconnects. This paper intends to describe the investigation of damage and interface delamination phenomena in micro components by numerical investigations by means of fracture mechanics concepts based on nonlinear FEA and experimental investigations. Consequently, the contribution shows the use of non-linear finite element simulations with respect to the nonlinear, temperature and rate dependent behavior of different materials used, the application of fracture mechanics concepts (energy release rate, integral fracture approaches, mode-mixity examinations) in combination with experimental investigations. For these purpose, bending specimens consisting of several materials interfaces widely used in FC ssemblies and CSP have been investigated in particular. In order to evaluate the different approaches used some results have been compared to micrographs from growing interface delaminations by using micro deformation measurements on the basis of a gray scale correlation method applied to micrographs, in particular. The methodology explained is a helpful basis for understanding and evaluating failure mechanisms especially of several polymer material interfaces as well as of solder joints in a more consistent manner. It should support further applications for raising the thermo-mechanical reliability of advanced electronic packages.