Damage and fracture evaluation in microelectronic assemblies by FEA and experimental investigations

Abstract

Thermomechanical reliability of electronic packaging such as flip chip and chip scale packaging is most important for adoption of these technologies in industrial applications. However, various kinds of inhomogeneities, localized stresses and thermal mismatch between several components lead to interface delaminations, chip cracking and solder interconnect fatigue. Nonlinear finite element simulations which respect the nonlinear, temperature and rate dependent behaviour of different materials used (metals, polymeric and solder materials) and experimental investigations have been used for failure analysis. The development and application of failure models (e.g. thermal fatigue, lifetime prediction by Coffin-Manson type equations, integral fracture mechanics approaches such as J-, J/spl circ/-, and /spl Delta/T*-integral, and evaluation of critical regions) is explained. The influence of the scatter of some model parameters is investigated by probabilistic failure concepts. Additionally, simulation of damage growth in solder interconnects by an automatic adaptive finite element technique is performed using inherent local damage models to validate crack and damage models used. Consequently, some results have been compared to micrographs from damaged interconnects and to strain measurement results obtained by the microDAC measurement method. The application of those combined investigations should help further understanding of failure mechanisms especially in solder joints, and should support further applications for enhancing the thermomechanical reliability of advanced electronic assemblies.