The most well-known and widely observed microstructural changes during aging are the coarsening of Ag3Sn and Cu6Sn5 intermetallic compounds (IMCs) present in the eutectic regions between β-Sn dendrites. In this investigation, Scanning Electron Microscopy (SEM) has been utilized to examine aging induced coarsening of IMCs occurring within lead free solders. Unlike many prior studies, fixed regions in the solder joint cross-sections were monitored throughout the aging process, rather than examining different samples and/or different regions after the various aging exposures. Sn-3.0Ag-0.5Cu (SAC305) lead free solder samples were formed with reflowed (RF) and water quenched (WQ) cooling profiles and resulting initial microstructures, and then polished microscopy cross-sections were prepared. Nanoindentation marks were added to the cross-sections at certain locations to facilitate locating the fixed regions of interest in subsequent microscopy observations. After preparation, the samples were then aged at T = 125 °C, and the microstructures were observed and recorded in the selected regions after various aging exposures using SEM. In addition, the coarsening of IMCs during aging has been quantitatively analyzed. Particularly, the aging induced changes in number of IMCs, total area of all IMCs, average particle area, and average particle diameter have been quantified for fixed regions in the samples.
- Electronic and Photonic Packaging Division
Investigation of Aging Induced Evolution of the Microstructure of SAC305 Lead Free Solder
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Fu, N, Wu, J, Ahmed, S, Suhling, JC, & Lall, P. "Investigation of Aging Induced Evolution of the Microstructure of SAC305 Lead Free Solder." Proceedings of the ASME 2017 International Technical Conference and Exhibition on Packaging and Integration of Electronic and Photonic Microsystems collocated with the ASME 2017 Conference on Information Storage and Processing Systems. ASME 2017 International Technical Conference and Exhibition on Packaging and Integration of Electronic and Photonic Microsystems. San Francisco, California, USA. August 29–September 1, 2017. V001T01A010. ASME. https://doi.org/10.1115/IPACK2017-74266
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