Abstract: Micromachined z-axis vibrating rate gyroscopes we design are fabricated by the dissolved wafer process (DWP). Residual stresses are developed in mechanical parts of gyroscopes due to the fabrication process. The effect of residual stresses on the natural frequencies of the drive mode and sense mode is theoretically analyzed. Then, the FE model of the z-axis gyroscope is built to simulate the relation of the frequencies and residual stress by model analysis. The simulation results and experiments demonstrate that the outer flexure beams fabricated by DWP are subjected to tensile force, and the tensile stress value is about 20~30 Mpa. The methods of the residual stress relief are presented and an improved z-axis gyroscope is designed. The experiment results of the improved z-axis gyroscope demonstrate that the performance of the gyroscopes with serpentine beams and stress relief slots will greatly improve.

Key words: Mechanical sensitivity, Residual stresses, Serpentine beam, Stress relief slot