1,721,646 research outputs found
Design of Experiment based Factorial Design and Response Surface Methodology for MEMS Optim
No full texthis paper presents the application of the design of experiments technique based factorial designs and response surface methodology (RSM) for optimization of MEMS devices. The RSM methodology is used to optimize the geometric parameters of the symmetric toggle RF MEMS switch to minimize the switch pull-in voltage. Fractional factorial based Plackett–Burman screening design is developed and the corresponding pull-in voltage is obtained, through finite element method (FEM) based simulations, for different combinations of the dimensional parameters. Analysis of variance is performed to distinguish the most significant parameters affecting the output response. The significant parameters, obtained using Plackett–Burman screening design, are further investigated using second order Box–Behnken design to obtain the optimal levels of the significant parameters and analyze their interactions. Regression analysis is carried out to check the adequacy of the Box–Behnkan based response surface model for predicting the output response. The effect of the significant parameters and their interactions on the pull-in voltage is analyzed through model based 3D surface and contour plots. The optimal levels of the parameters for a pull-in voltage ≤15 V, with compact device dimensions, are determined and verified through FEM simulations. A comparison is made for the results obtained through RSM with the analytical results presented in the literature. This showed a close agreement, verifying the practicability of this approach for the optimization of MEMS devices
Design optimization of RF-MEMS switch considering thermally induced residual stress and process uncertainties
No full textThis paper presents the Design of Experiments (DOE) based parametric design optimization of the Symmetric Toggle RF-MEMS Switch (STS) for minimizing the actuation voltage considering the fabrication process uncertainties and thermally induced residual stress. Initially, three-dimensional (3D) non-linear Finite Element Method (FEM) models are developed and the formation of residual stress during the plasma etching step of the microfabrication process is explained using the Bauschinger effect. The pull-in voltage values and the switch profiles obtained after the thermal loading-unloading cycle in the FEM models are compared with the experimental values and optical profile measurements which showed a close agreement. A DOE based Dual Response Surface Methodology (DRSM) is implemented to identify the significant design parameters affecting the STS switch pull-in voltage in the presence of thermally induced residual stress. Two separate response surface empirical models are developed; one for the mean pull-in voltage and other for variation in the pull-in voltage due to microfabrication process tolerances. The developed response surface models are optimized simultaneously using the desirability function approach. The optimal levels of the design parameters that result in minimum pull-in voltage with increased insensitivity to process uncertainties are obtained using the direct search algorithm
Modeling and experimental verification of thermally induced residual stress in RF-MEMS
No full textElectrostatically actuated radio frequency microelectromechanical systems (RF-MEMS) generally consist of microcantilevers and clamped-clamped microbeams. The presence of residual stress in these microstructures affects the static and dynamic behavior of the device. In this study, nonlinear finite element method (FEM) modeling and the experimental validation of residual stress induced in the clamped-clamped microbeams and the symmetric toggle RF-MEMS switch (STS) is presented. The formation of residual stress due to plastic deformation during the thermal loading-unloading cycle in the plasma etching step of the microfabrication process is explained and modeled using the Bauschinger effect. The difference between the designed and the measured natural frequency and pull-in voltage values for the clamped-clamped microbeams is explained by the presence of the nonhomogenous tensile residual stress. For the STS switch specimens, three-dimensional (3D) FEM models are developed and the initial deflection at zero bias voltage, observed during the optical profile measurements, is explained by the residual stress developed during the plasma etching step. The simulated residual stress due to the plastic deformation is included in the STS models to obtain the switch pull-in voltage. At the end of the simulation process, a good correspondence is obtained between the FEM model results and the experimental measurements for both the clamped-clamped microbeams and the STS switch specimens
Design and FEM modeling of notch effect in gold microbeams
No full textThis paper presents the design and modeling of the MEMS mechanical fatigue in the presence of stress raising notches. FEM models are realized to study the effect of notch geometric parameters on the stress concentration factor of the gold specimen subjected to tensile loading. Test structures with three different specimens, i.e. without notch, with single notch and with a double notch are modeled considering fabrication process constraints. Maximum axial stresses produced in the specimens and the corresponding stress concentration factors for the notched specimens are obtained using FEM modeling
Effect of creep in RF MEMS static and dynamic behavior
No full textThis paper presents the experimental characterization of the creep effect in electrostatically actuated gold microstructures. The tested specimens follow the typical configuration of the microbridge based radio frequency microelectromechanical systems switches and varactors. Initially, the plastic creep strain accumulation with time is measured for the specimens with different geometric dimensions and at different actuation voltages and temperatures. To avoid the size and cumulative heating effects, three specimens with the same geometric dimensions, actuation voltages and constant temperatures are tested. The test results allowed decoupling the permanent plastic strains due to the creep effect and reversible anelastic strains due to the viscoelastic behavior. The pull-in voltage and natural frequency values measured before and after the creep tests are compared, revealing the mechanical stiffness decrease caused by creep
Creep in MEMS
No full textThe study of creep in MEMS is crucial for their lifetime prediction and reliability evaluation. The experimental approaches used in macromechanics can be extended to the microscale if their effectiveness is proved by dedicated experiments. This goal may provide more general validity of creep effects prediction in MEMS, instead of spotted experiments on single devices like those ones reported in most of the work presented in literature. The demonstration of the validity of some established creep models and experimental methodologies also in the micromechanics is the goal of this paper
Experimental investigations of creep in gold RF-MEMS microstructuresSmart Sensors, Actuators, and MEMS VII; and Cyber Physical Systems
No full textLifetime prediction and reliability evaluation of micro-electro-mechanical systems (MEMS) are influenced by permanent
deformations caused by plastic strain induced by creep. Creep in microstructures becomes critical in those applications
where permanent loads persist for long times and thermal heating induces temperature increasing respect to the ambient.
Main goal of this paper is to investigate the creep mechanism in RF-MEMS microstructures by means of experiments.
This is done firstly through the detection of permanent deformation of specimens and, then, by measuring the variation
of electro-mechanical parameters (resonance frequency, pull-in voltage) that provide indirect evaluation of mechanical
stiffness alteration from creep. To prevent the errors caused be cumulative heating of samples and dimensional
tolerances, three specimens with the same nominal geometry have been tested per each combination of actuation voltage
and temperature. Results demonstrated the presence of plastic deformation due to creep, combined with a component of
reversible strain linked to the viscoelastic behavior of the material
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