Research On Degradation And Failure Characteristics Of MEMS Gyroscope Under Environmental Stresses

In recent years,MEMS gyroscope has become a new research field and MEMS gyroscope reliability has become a hot issue with the development of microelectronics technology.This thesis focuses on the research of the degradation and failure characteristics of MEMS gyroscope under different environmental stresses such as temperature,vibration and shock.The main contents are as follows:This thesis studies the degradation characteristics of gyroscopes under temperature stress.(1)The degradation characteristics of gyroscope performance parameters at 125? are studied.Experimental results show that high temperature aging leads to a decrease in the vacuum of the gyroscope,leading to the degradation of gyroscopes' key performance,such as quality factor,bias,angle random walk,bias stability and scale factor.(2)The degradation characteristics of driving Q at 125? are studied.It is found that the driving Q is reduced by the power function with aging time increasing.And the quality factor degradation theory model is established.(3)The aging characteristics of driving resonant frequency at 85? are studied.The experimental results show that the degradation of the driving resonant frequency is relatively slow.(4)A thermal cycle experiment is carried out at-55?~25?.The experimental results show that the stress is not effective enough to cause fatigue cracks in the gyroscope,which leads to failure of gyroscope.This thesis studies the failure behavior of gyroscope under vibration stress.The frequency range of one-dimensional random vibration is 50~2000Hz,and the resonant frequency of the gyroscope is about 8KHz.The experimental results show that gyroscope does not fail.Then,the experiment of comprehensive stress is designed,with the frequency of the three axis random vibration ranging from 0~10KHz and the temperature at 80?.The experimental results show that the mechanical structure of the gyroscope is not damaged,but the gold wire is off.This thesis studies the failure behavior of gyroscope under shock stress.The shock experiments with 1942 g and 8397 g are carried out,and the shock different Q value gyroscopes are also carried out with 8686 g.The experimental results show that the response of the gyroscope increases with the shock load amplitude and the Q value increasing,both leading to easier failure of the cantilever beam.In summary,the main effect of temperature stress on vacuum packaging MEMS gyroscopes is that the decrease in vacuum leads to a decrease in performance,while vibrations and shock mainly lead to structural fractures,including fracture of bonding wire and fracture of MEMS structures.And for the same shock load,it is more likely to cause the structure to fail with higher vacuum.