The Failure Mechanisms of Micro‐Scale Cantilevers Under Shock and Vibration Stimuli

Abstract

Recent advances in micro-electro-mechanical system (MEMS) fabrication technology have resulted in proliferation of micro-scale mechanical devices, some of which are applied in environments with severe levels of shock. The objective of this paper was to investigate the use of experimental and numerical methods in quantifying the behaviour of representative MEMS devices subject to high-g impact stimuli. Micro-cantilevers were analysed under vibration and shock on a modified Hopkinson pressure bar and vibration table to determine the mechanical properties of single crystal silicon (SCS). The characteristic dimensions of the beams were of 100 lm in height/ width with beam lengths ranging from 5 to 7 mm. The experimental approach allowed non-invasive in situ monitoring of the micro-cantilevers upon impact through accelerometry and high-speed imaging. An investigation of the shock response of micro-cantilever beams indicates that orientation plays a significant role in their sensitivity to shock because of the planarity of the fabrication technique. Scanning electron microscopy identified octahedral cleavage of SCS as the dominant failure mechanism of the micro-cantilevers. Finite element analysis in conjunction with in situ high-speed imaging proved to be a viable non-invasive inverse technique to determine the loci and amplitude of tensile stress within generic micro-scale devices.

The response of a micro-electro-mechanical system (MEMS) cantilever-paddle gas sensor to mechanical shock loads

“…Hence, they are required to be tested under mechanical shock to ensure their survivability in various hostile environments. Several works have been published studying the reliability of MEMS devices under mechanical shock: They attempted on investigating experimentally the effect of shock loads on several MEMS devices such as sensors (Baselta at al., 2003;Sundaram et al, 2011), resonators (Kazinczi et al, 2002;Kurth et al, 2008), accelerometers (Ghaffarian et al, 2002;Currano et al, 2008;, Ghisi et al, 2008Walter, 2008;Wang and Li, 2010), microcantilever switches (Robinson et al, 1987;Fang et al, 2004;Sheehy et al, 2009), converters, magnetometers, microphones, and gyroscopes (Yee et al, 2002, Nouira et al, 2007Yang et al, 2010;Vahdat et al, 2011). Other groups attempting to control MEMS devices under variable loadings (Shin et al, 2009;Alsaleem and Younis, 2010), whereas others used the combined effect of shock impulse with electrostatic loading to suggest a MEMS shock/acceleration threshold sensor (Frobenius et al, 1972;Loke et al, 1991;Man et al, 1994;Go et al, 1996;Noetzel et al, 1996;Tonnesen et al, 1997;Wycisk et al, 2000;Selvakumar, 2001;Matsunaga and Esashi, 2002;McNamara and Gianchandani, 2004;Jia et al, 2007;Guo et al, 2011).…”

Fatigue of 1 μm-scale gold by vibration with reduced resonant frequency

“…Although monotonic tension tests have been developed for micro-components [8][9][10][11][12][13][14], additional improvements are necessary for the fatigue testing. In order to avoid this issue, bending tests have been widely used [14][15][16][17][18][19], and the lowcycle fatigue behavior of small component has been successfully investigated using a cantilever specimen [20,21]. However, since the load is applied by tip contact, it is difficult to extend this methodology to the fatigue testing with high-cycle loading (Difficulty 2).…”

Modeling the Structural-Thermal-Electrical Coupling in an Electrostatically Actuated MEMS Switch and Its Impact on the Switch Stability

“…Nevertheless, those structures can face several unwanted conditions while in use. They can stick to their lower electrodes or substrate due to several factors such as humidity due to large capillary forces [1][2][3][4][5][6][7][8][9][10][11], variation of its surrounding temperature, or some initial disturbances, such as mechanical shocks [12][13][14][15]. For example, humidity induces large capillary forces that a beam may undergo before it sticks to the substrate.…”