A Au-Si eutectic vacuum packaging process was evaluated using high sensitivity poly-Si Pirani vacuum sensors. Encapsulation of devices was achieved by bonding a silicon cap wafer to a device wafer using a Au-Si eutectic solder at above 390°C in a vacuum bonder. The Au-Si eutectic solder encircled the devices, providing an airtight seal. The Pirani gauges were encapsulated and tested over a period of several months in order to determine base pressures and leak/outgassing rates of the micro-cavities. Packaged devices without getters showed initial pressures from 2 to 12 Torr with initial leak/outgassing rates of −0.073 to 80 Torr/year. Using getters, pressures as low as 5 mTorr have been achieved with leak/outgassing rates of <10 mTorr/year. Trends in pressure over time seem to indicate outgassing (desorption of atoms from inside of the microcavity) as the primary mechanism for pressure change over time.
- Heat Transfer Division and Electronic and Photonic Packaging Division
Reliability and Characterization of Micro-Packages in a Wafer Level Au-Si Eutectic Vacuum Bonding Process
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Mitchell, JS, Lahiji, GR, & Najafi, K. "Reliability and Characterization of Micro-Packages in a Wafer Level Au-Si Eutectic Vacuum Bonding Process." Proceedings of the ASME 2005 Pacific Rim Technical Conference and Exhibition on Integration and Packaging of MEMS, NEMS, and Electronic Systems collocated with the ASME 2005 Heat Transfer Summer Conference. Advances in Electronic Packaging, Parts A, B, and C. San Francisco, California, USA. July 17–22, 2005. pp. 2041-2045. ASME. https://doi.org/10.1115/IPACK2005-73341
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