| In recent years, flip-chip technology has migrated to systems using laminated substrates to create Direct Chip Attach (DCA) configurations. DCA configurations have many advantages over existing technologies, but are vulnerable to thermally induced strains and the resulting solder joint fatigue.; The analytical aspects of this study focuses on the development of a rigorous fully-coupled physically-consistent linear-elastic thermostructural model of a tri-layer structure. The imposition of force and moment balance on the structure and use of an axial and shear stiffness (or spring-constant like) representation of the compliant, middle layer makes it possible to accurately represent the stress and strain in the compliant layer of a tri-layer structure, operating between two thermal end states.; Use of the Coffin-Manson solder fatigue relation is extended to underfilled flip-chip and DCA configurations, where the solder is embedded in an elastomeric material. Application of this relation to underfilled direct chip attach configurations, using analytically- and numerically-derived solder strain results, reveals that the dramatic improvement in fatigue life of solder joints reported in the literature for underfilled configurations can be related to solder shear strain reduction.; The numerical tasks performed in this study serve to verify the analytical model and results, and shed considerable light on the thermostructural behavior of underfilled DCA packaging configuration.; Experimental measurements of failure loads for a thin layer of a die-attach or underfill material are performed for a large number of specimens. This is one of the first systematic studies to present load measurements for a die-attach or underfill material, under combined loading conditions. |
