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Raised strips were introduced into the micromachined acceleration switch to avoid the stiction between the mass and the substrate. The system spring constant of the switch with serpentine springs was calculated. The influence of the introduced anti-stiction raised strips on squeeze-film damping of the switch was analyzed closed-form using reasonable boundary conditions. Based on the calculated systems parameters, a Simulink model was constructed to simulate the dynamic properties of the switch under different types of shock acceleration. It is indicated that the dynamic responses (threshold acceleration and response time) were almost not affected by those raised strips which are instead beneficial to reduce the oscillation of the moving mass and improve the yield of the switch. Dependence of dynamic properties on the distance between two electrodes, thickness of the mass and spring constant has also been simulated. The drop hammer experiment was conducted to characterize dynamic properties of the fabricated and packaged acceleration switch. Test threshold acceleration and response time are, respectively, about 41 g and 0.7 ms when the half-sine wave shock was applied, which are in accordance with simulated ones. The package strength of the switch was also evaluated and corresponding critical shear stress for failure is about 22 MPa.
Components, Packaging and Manufacturing Technology, IEEE Transactions on (Volume:1 , Issue: 8 )
Date of Publication: Aug. 2011