Kwanhum Park

Snapping microswitches with adjustable acceleration threshold

Abstract This paper presents the design, fabrication and testing of prestressed bimorph microbeams for applications to tunable acceleration switches. The prestressed bimorph beams are buckled due to the residual stress difference between two dissimilar films, thereby generating initial beam deflections upon fabrication. Necessary and sufficient conditions for snapping action of the deflected bimorph beam have been derived from snap-through buckling analysis. A set of SiO 2 /p + -silicon bimorph beams has been designed and fabricated in three different lengths, 800, 900 and 1000 μm. The electrostatic snap-through voltage for each microbeam has been measured as 32, 56.3 and 76.5 V, respectively. Micromechanical properties of beam materials have been measured from on-chip test structures. It is demonstrated that the three different microswitches with a 7 μg proof-mass can be applicable to acceleration switches, where threshold acceleration levels can be adjustable within the ranges 0–14, 0–35 and 0–47 g , respectively, under inter-electrode bias voltages of 0–76 V.

A skew-symmetric cantilever accelerometer for automotive airbag applications

Abstract A piezoresistive cantilever-beam microaccelerometer has been designed, fabricated and tested with a hybrid airbag electronic control unit for automobile crash detection. A skew-symmetric accelerometer has been proposed and the associated fabrication process has been developed. A simultaneous etching process for beam-thickness control, fillet-rounding formation and corner compensation is discussed. The microfabricated device shows a flat response with a resonance frequency of 2.07 kHz and a sensitivity of 65 μV g −1 V −1 . A sensitivity of 67 mV g −1 has been measured from the assembled unit with a non-linearity of 4%. The present skew-symmetric design and associated fabrication methods provide effective means for improving the robustness and reliability, as well as the transverse sensitivity of cantilever-beam accelerators.

Design, Fabricaiton and Testing of a Piezoresistive Cantilever-Beam Microaccelerometer for Automotive Airbag Applications

A self-diagnostic, air-damped, piezoresitive, cantilever-beam microaccelerometer has been designed, fabricated and tested for applications to automotive electronic airbag systems. A skew-symmetric proof-mass has been designed for self-diagnostic capability and zero transverse sensitivity. Two kinds of multi-step anisotropic etching processes are developed for beam thickness control and fillet-rounding formation, UV-curing paste has been used for sillicon-to-glass bounding. The resonant frequency of 2.07kHz has been measured from the fabricated devices. The sensitivity of 195 /g is obtained with a nonlinearity of 4% over 50g ranges. Flat amplitude response and frequency-proportional phase response have been obserbed, It is shown that the design and fabricaiton methods developed in the present study yield a simple, practical and effective mean for improving the performance, reliability as well as the reproducibility of the accelerometers.

A self-diagnostic airbag accelerometer with skew-symmetric proof-mass

This paper describes the design, fabrication and testing of a piezoresistive cantilever-beam microaccelerometer for automobile airbag applications. Fabricated devices show a resonant frequency of 2.07kHz, a sensitivity of 65pVIglV with a nonlinearity of 4% over f50g ranges. Flat amplitude response and frequency-proportional phase response indicate that 70% of critical damping level has been accurately achieved in the fabricatcd devices. Novel aspects of this work include: a skewsymmetric proof-mass design for self-diagnostic capability and zero transverse sensitivity; a multi-step anisotropic etching process for beam thickness control and fillet-rounding formation; the use of UV-curing paste for silicon-to-glass bonding. It is shown that the new aspects of this work are used to yield a simple, practical and effective mean for improving the performance, reliability, robusmess, process simplicity as well as the reproducibility of the accelerometers.

Design Fabrication and Testing of a Microswitch Using Snap-through Buckling Phenomenon

A snapping-beam microswitch has been designed, fabricated and tested. From a design analysis, necessary and sufficient conditions for a snap-through switching fouction have been derived for a clamped shallow beam. The necessary condition has resulted in a geometric relation, in which the ratio of beam thickness to initial beam deflection plays a key role in the snapping ability. The sufficient condition for the snapping action has been obtained as a function of the inertia force due to applied acceleration, and the electrostatic force, adjustable by an inter-electrode voltage. For experimental investigations, a set of microbeams of silicon dioxide/silicon bimorphs have been fabricated. Geometric size and mechanical behavior of each material film have been measured from on-chip test structures. Estimated and measured characteristics of the fabricated devices are compared.