Vacuum Packaging for High-Performance Low Cost MEMS Gyro Used in 6 Degree of Freedom Inertial Navigation System (DOF INS)

Abstract

Sensors in Motion Inc. is developing a navigation grade 6 DOF MEMS INS using its proprietary and patented technologies. The military is investing in INS and IMU technology which can answer its needs as well as provide the baseline for hundreds of other DOD and commercial applications which need a C-swap sensitive utility. SIM’s technology for MEMS gyros was conceived to address past problems associated with MEMS gyroscopes while leveraging the C-swap benefits of high volume, high yield batch fabrication, automated packaging, self-calibration, and thermal compensation. A key requirement for the MEMS Gyroscope is controlled vacuum-levels to obtain high Q devices. Gyro die are packaged using a multilayer package and getter system, which provides and maintains sealed vacuum cavities. Die are assembled into the LCC package using conventional assembly techniques and the package cavity is sealed using an SST 3150 high-vacuum sealing system. The SST system is used to activate a thin-film getter layer on the package lid before reflow of the solder seal. Resulting pressure levels have been determined by characterizing packaged but unlidded sensor die in a vacuum chamber. The package material, process flow and test results are summarized and reviewed. Tooling, process parameters, and test techniques are explained.