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Materials Science at Oregon State University

What can a Materials Scientist do in a world of Internet of everything (IoE): The impact and role of Grain orientation and Anisotropy of Sn in Sn-Ag-Cu interconnect reliability

Date: Thursday, Mar 10th
Presenter: Prof. Tae-Kyu Lee, Portland State University


Much of the earlier work on interconnect structure reliability was focused on consumer or communications applications but attention is now turning to high reliability products such as automotive, aerospace, telecommunication and medical devices, whether those are wearable or deep drilling, the end use conditions drastically expanded in the last few years. Failures in solder joints often occur at locations other than the most highly shear-strained regions due to the impact of the Sn anisotropy, reliability prediction is challenging. To gain physical understanding of this phenomenon, understanding of how elastic and plastic deformation anisotropy affect microstructural evolution during thermo-mechanical cycling or mechanical shock is necessary. The evolution of microstructures and properties is characterized statistically using optical and orientation imaging microscopy. In situ synchrotron x-ray measurements during thermal cycling are used to examine how crystal orientation and thermal cycling history change strain history. With time and thermal history, microstructural evolution occurs mostly from continuous recrystallization and particle coarsening that is unique to each joint, because of the specific interaction between local thermal and displacement boundary conditions and the strong anisotropic elastic, plastic, expansion, and diffusional properties of Sn crystals. Complications arising from electromigration and corrosion are also considered. This presentation will be focused on the anisotropic properties of Sn, the microstructure evolution, and identifying various factors impacting the interconnection and joint long-term reliability. Along with the scientific findings and mechanisms, a social aspect in the IoE era will be shared, based on experience gained from the fast moving Silicon-valley culture.

Tae-Kyu Lee is an associate professor in Portland State University. Before joining the Department of mechanical and materials engineering this year, he worked as a Senior Engineer in Cisco Component quality and technology (CQT) group, Packaging and Interconnect Technology Team located in San Jose, CA. He is working on board level interconnect reliability, next generation packaging technology, macro to micro joining technology and solder/welding joint material characterizations. Tae-Kyu received his Ph.D. degree in Materials Science and engineering from University of California, Berkeley on studies related to high temperature Superconducting Quantum Interference Device (SQUID) non-destructive evaluation and was a Postdoctoral fellow in Lawrence Berkeley National Laboratory before joining Cisco. He is actively involved in several industry consortia and as a lead organizer for the Lead free solder technology workshop, for the last five years, and serving as a Vice Chair in the Electronic Packaging and Interconnect Technology Committee in TMS. He is also serving as an associate editor in Journal of Electronic Materials.