(Dr. Jianmin Qu, advisor)
"Moisture and Interfacial Adhesion in Microelectronic Assemblies"
Moisture poses a significant threat to the reliability of microelectronic assemblies and can be attributed as being one of the principal causes of many premature package failures. Since the vast majority of advanced underfills are epoxy based, they have the propensity to absorb moisture, which can lead to undesirable changes in stress and interfacial adhesion. To ensure the reliability and durability of the electronic packages, the effect of moisture must be understood. In addition to being a moisture sensitive property, the interfacial adhesion is also affected by the elastic mismatch, relative mode mixity, temperature, and the corresponding surface chemistry and topology of the adherends. Therefore, the study of the moisture effect on interfacial adhesion is inevitably a multidisciplinary effort.
In this proposed research, a systematic and multi-disciplinary study will be conducted to understand the fundamental science of moisture-induced degradation of interfacial adhesion of polymer/metal and polymer/ceramic interfaces. The research will be comprised of both experimental and modeling components of analysis. The experimental portion of this work will consist of evaluating the effect of moisture on both the elastic modulus of a commercially available no-flow underfill and its associated interfacial adhesion to copper, silicon, and silicon nitride. In addition, the recovery of both the elastic modulus and interfacial adhesion from moisture preconditioning will also be assessed. Last, the diffusion coefficient of the underfill will be experimentally determined for each respective level of moisture preconditioning. The modeling portion of this work will consist of developing a model to predict the loss of interfacial adhesion from moisture to reflect what was established from the experimental portion of this study. The model will be based on experimentally observed mechanical, physical, and chemical degradation mechanisms due to moisture near the interface.
It is anticipated that this research will result in a comprehensive understanding of the primary mechanisms responsible for the interfacial degradation due to the presence of moisture. The experimental results obtained through this research will provide definitive data for the electronics industry in their product design, failure analysis, and reliability modeling. The predictive model developed in this research will provide a useful tool for developing new adhesives, innovative surface treatment methods, and effective protection methodologies for enhancing interfacial adhesion.