| In this study, three-dimensional finite elements were employed to study interfacial cracking problems encountered in electronic packaging. The study consists of two main parts. Analysis of three-dimensional elastic interface cracks with curved crack fronts and modeling the materially non-linear behavior of solder balls in a semiconductor package with a neighboring elastic interfacial crack.; In the first part of the study, three-dimensional enriched finite elements were employed to solve interfacial semi-circular and quarter-circular corner cracks between silicon and epoxy. These problems were solved for both uniform tensile loading and thermal loading cases. The results showed that, especially for thermal loading problems, there is a strong mode mixity in the stress intensity factors both in terms of mode II and mode III. Also, for problems that involve curved crack fronts, it was concluded that the solution is sensitive to mesh refinement in the crack tip region.; In the second part of this study, the elastic-plastic behavior of solder balls and interaction effects with nearby cracks in a semiconductor package was investigated. Neglecting time dependent effects (creep, viscoplasticity), stress and fracture analyses were performed. Applying periodicity boundary conditions, a slice near the central region of a semiconductor device was considered. In the absence of a crack in the package, a so-called “processing model”, which contains three processing steps, was used to simulate the fabrication of a flip-chip package. The results from this model showed that stresses and strains are not constant along the “z” direction and that the outermost solder ball is most critical in terms of permanent damage. It was also concluded that corners of the fillet are subjected to high residual stresses and that crack initiation can take place in these regions.; Fracture calculations were also performed using the same device and material property specifications. Three differently shaped interfacial cracks near the fillet region were considered. The results from these calculations showed that plastic deformation, especially on the last solder ball, is affected by the presence of a crack in its vicinity and vice versa. It was observed that the plastic strains increase as the crack tip approaches the outermost solder ball. In studying the “L” shaped crack, it was concluded that inclusion of crack surface contact is critical for accurate determination of plastic strains and fracture parameters. (Abstract shortened by UMI.)... |
