| Microelectronics research and manufacturing have been thriving over the past forty years. From the structural point of view, this means that more and more layers of different materials are stacked into a confined space from which more and more heat is generated. This trend raises concerns about electronic packaging reliability in general and about out-of-plane displacement (warpage) in particular. Warpage results from coefficient of thermal expansion (CTE) mismatch, as well as other material, geometry, and process factors. It may cause delamination, mis-registration, solder joint shortening/opening, and die crack.; In this research, warpage of printed wiring board assemblies (PWBAs) is studied by both experimental and modeling efforts. A projection moire measurement system, suitable for measuring warpage of surfaces with components, such as PWBAs, is developed to be used both on-line under simulated thermal processes and off-line. As a complementary experimental approach, an existing shadow moire system is improved by implementing a calibration scheme and adding more digital image processing capabilities. Due to material and geometry complexity, finite element analysis (FEA) is used to model PWBA warpage. A comprehensive assembly-level finite element model is built adopting the methodology of modularization, parameterization, and model reduction. The modeling results are validated by moire experimental results.; Based on experimental and validated modeling results, a parametric study is conducted to identify material, geometry, and process effects on PWBA warpage. Once influential parameters are identified, an electronic packaging design can be optimized to enhance the overall reliability of a PWBA. Besides the parametric study, structural topology optimization is conducted to optimize component layout so that a minimum warped assembly can be achieved.; This thesis presents a comprehensive approach to study thermomechanical reliability in electronic packaging. Experimentation, thermomechanical modeling, parametric study, and structural optimization are interwoven to study PWBA warpage. This study substantially enhanced the knowledge on thermomechanical reliability in PWBAs. |
