The Research On Encapsulation Of Micro-machined Gyroscopes

The encapsulation of micro-machined gyroscopes is one of the main factors which are related to their applications. Through the research and analysis of the development status of micro-mechanical gyroscopes and encapsulation at home and abroad, we launch the research on the vacuum encapsulation of Z-axis micro-mechanical tuning fork gyroscope, which is designed by Peking University, and the test and analysis of its performance.In the thesis, there is an analysis of the structure and working principle of the Micro-machined gyroscopes, and is a discussion about the related theories that vacuum encapsulation can improve their sensitivity and reduce the damping error. Through the combination of the theorized research and experimental analysis, we also choose the vacuum cold welding technology, and confirm the approximate inverse ratio relationship between the quality factor Q of drive and the atmospheric pressure in the encapsulation cavity, and provide a method that may test the vacuum in the MEMS encapsulation.In consideration of the effects of the encapsulation effect on device performance, we make simulation analysis and experiment on the effects, which adhesive glue, Young's modulus of base materials and devices, thermal expansion coefficient and other aspects may produce on the resonant frequency of the gyro, and make the encapsulation effect the least with the encapsulation method of plastic 1 and ceramic substrates. Also, through the analysis on the encapsulation thermal stress of the device, we know that the thermal resistance of the dispersed air bubbles to the device is the least,and raise a patch method that produces dispersed air bubbles. In addition, the test on the performance of the encapsulated MEMS gyroscope is done, the atmospheric pressure in the encapsulation cavity is 600Pa, driving resonant frequency is 9065.32Hz, Q is 432.27, scale factor is 2.61mv/deg/s, nonlinearity is 0.424 %, asymmetry is 0.545%, bias is13.04deg / s.