Date of Graduation
5-2025
Document Type
Dissertation
Degree Name
Doctor of Philosophy in Engineering (PhD)
Degree Level
Graduate
Department
Mechanical Engineering
Advisor/Mentor
Huitink, David
Committee Member
Millett, Paul C.
Second Committee Member
Ware, Morgan E.
Third Committee Member
Meng, Xiangbo
Keywords
Reliability; Solder Joints; Wire Bonds
Abstract
Continued development of high-density electronics has maintained use of solder sphere and wire bond interconnects due to their versatility. Current densities through and temperatures at or close in proximity to these interconnect structures have risen in electronic packages as power density demands have increased over time. In some cases, this trend has forced manufacturers to begin utilizing higher-temperature-capable materials with less well-established reliability estimates or rely on existing packaging strategies (with less redundancy due to continued package size reduction demands) which have not been well-qualified in these elevated stress environments. In this work, laboratory experiments with associated data analysis in concert with analytical modeling have been utilized to better inform material selection in next generation electronic systems and highlight that multiple failure modes can occur in these interconnect structures depending on the magnitudes of the stressors acting on them. Specifically, eutectic gold-tin (80Au20Sn) solder spheres have been examined as a candidate for next generation systems (due to their high melting point compared to conventional solders) through a series of electromigration and combined electromigration and mechanical stress tests. Combined stress testing better represents the use environments of these solder spheres, where ambient temperature and current density are elevated while coefficient of thermal expansion related deformation is simultaneously taking place at soldered regions. To qualify the results from AuSn testing, direct comparisons have been made against eutectic lead-tin (37Pb63Sn) and a common tin-silver-copper (SAC) alloy, SAC305 (96.5Sn3Ag0.5Cu), illustrating that simple selection of solder based on higher melting temperatures may not necessarily be a solution for operating a system at elevated temperatures. A focused examination on the performance of aluminum wire bonds under varied ambient temperature and current density pairs has also been conducted, highlighting that wire bond ampacity is limited by the baseline energy state associated with device and environment temperatures and that the individual contributions of current density and ambient temperature dictate the ultimate failure mode of a given wire bond. Additionally, work has been completed to examine wire bonds under high-density stressors equipped with electrically conductive or insulating coatings in an effort to combat ionic migration resulting from prolonged high power operation, demonstrating that all potential solutions for combating degradation should be subjected to rigorous qualification testing.
Citation
Vinson, W. (2025). Interconnect Selection Tradeoffs at Thermal-Electric Failure Regions in High-Density Electronics. Graduate Theses and Dissertations Retrieved from https://scholarworks.uark.edu/etd/5725
