Over the past 50 years, electronics manufacturing industry has undergone revolutionary changes, which have provided consumers with a plethora of electronic products. The increase in functionality of electronic products and decrease in cost due to continuous miniaturization and lower manufacturing costs have evolved over time. As electronics manufacturing technology becomes more advanced, reliability of electronic products and devices have become more of a concern. Thermomechanical reliability in electronics is studied in this research. Thermomechanical failures are failures due to temperature loading conditions electronic products and devices experience during manufacturing and service. The thermomechanical issue studied in this research is the effect of convective solder reflow on the warpage of packaged electronic devices, bare boards and chip packages. A convective reflow-projection moir warpage measurement system is designed and implemented in this research. The system is the first available system capable of measuring warpage of printed wiring boards (PWBs) with and without electronic components during simulated convective reflow process. A finite element prediction tool is also developed to predict the warpage of PWBs populated with plastic ball grid array (PBGA) packages. The developed warpage measurement system as well as the developed finite element model is used to study various PWB assembly (PWBA) configurations during simulated convective reflow processes.

Out-of-plane displacement (warpage) is one of the major thermomechanical reliability concerns for board-level electronic packaging. Printed wiring board (PWB) and component warpage results from CTE mismatch among the materials that make up the PWB assembly (PWBA). Warpage occurring during surface-mount assembly reflow processes and normal operations may cause serious reliability problems. In this research, a convective reflow and projection moire warpage measurement system was developed. The system is the first real-time, non-contact, and full-field measurement system capable of measuring PWB/PWBA/chip package warpage with the projection moire technique during different thermal reflow processes. In order to accurately simulate the reflow process and to achieve the ideal heating rate, a convective heating system was designed and integrated with the projection moire system. An advanced feedback controller was implemented to obtain the optimum heating responses. The developed system has the advantages of simulating different types of reflow processes, and reducing the temperature gradients through the PWBA thickness to ensure that the projection moire system can provide more accurate measurements. Automatic package detection and segmentation algorithms were developed for the projection moire system. The algorithms are used for automatic segmentation of the PWB and assembled packages so that the warpage of the PWB and chip packages can be determined individually. The effect of initial PWB warpage on the fatigue reliability of solder bumps on board assemblies was investigated using finite element modeling (FEM) and the projection moire system. The 3-D models of PWBAs with varying board warpage were used to estimate the solder bump fatigue life for different chip packages mounted on PWBs. The simulation results were validated and correlated with the experimental results obtained using the projection moire system and accelerated thermal cycling tests. Design of experiments and an advanced prediction model were generated to predict solder bump fatigue life based on the initial PWB warpage, package dimensions and locations, and solder bump materials. This study led to a better understanding of the correlation between PWB warpage and solder bump thermomechanical reliability on board assemblies.