Wafer-Level Vacuum Sealing by Coining of Wire Bonded Gold Bumps

This paper reports on the investigation of a novel room-temperature vacuum sealing method based on compressing wire bonded gold bumps which are placed to partially overlap the access ports into the cavity. The bump compression, which is done under vacuum, causes a material flow into the access ports, thereby hermetically sealing a vacuum inside the cavities. The sealed cavity pressure was measured by residual gas analysis to 8×10^-4 mbar two weeks after sealing. The residual gas content was found to be mainly argon, which indicates the source as outgassing inside the cavity and no measurable external leak. The seals are found to be mechanically robust and easily implemented by the use of standard commercial tools and processes.