Microbeams under Mechanical Shock and Electrostatic Actuation Accounting for the Effects of Circuit Board and Package Motion

Suny At Binghamton, Binghamton NY

Investigators

Abstract

The aim of the proposed research is to push the frontiers of micro-electro-mechanical systems (MEMS) development by exploring the little understood complex interaction between mechanical shock, nonlinear electrostatic forces, and the motion of the package and printed circuit board (PCB) in MEMS devices. Because of their small size and high functionality, MEMS devices can offer cost, manufacturability, and reliability advantages over traditional sensors and actuators systems. However, a critical issue limiting the commercialization of MEMS is their performance when subjected to mechanical shock. In addition, a crucial criterion for the growth of MEMS is their performance and survivability when dropped on hard surfaces; this is especially true for portable and handheld devices. Such an impact can induce bending motion in the PCB carrying the MEMS device. This motion can be transmitted to a microstructure leading to either its collapse or to a false function, such as by giving wrong measurements in the case of MEMS sensors. Also, shock loads in MEMS can induce stiction and related short circuit problems. This project will model, characterize, and test microbeams under combined shock/drop loads and nonlinear electrostatic forces and accounting for the PCB and packaging motion. Two commonly used MEMS microbeam configurations will be focused on: clamped-clamped and clamped-free microbeams. Reduced-order models based on the nonlinear Euler-Bernoulli beam model will be used for the theoretical investigation. Our theoretical results will be verified by characterizing and testing micromachined silicon beams under various levels of electrostatic actuation and mechanical shock loads. This research will help explain many of the failures reported in the literature, and will allow designers to avoid them and design improved and more reliable MEMS devices. This effort will reveal significant information about the effect of mechanical shock on the common, but rarely understood, dynamic pull-in phenomenon. In addition, the results of this research will improve the reliability and commercial viability of many microbeam-based MEMS sensors and actuators, which are used in a wide spectrum of applications in our everyday life, such as in automobiles. The results will also be used to investigate the feasibility of a new technology of smart tunable microswitches triggered by acceleration. The tunable nature of these switches allows for tailoring of the device for various triggering needs and may lead to future applications and products currently unforeseen. This research will train two graduate students on the modeling, simulation, characterization, and testing of MEMS microstructures. Knowledge from this research will support the development of a new course on the Dynamics of MEMS. Also, this project will train undergraduate minority students over the duration of the project to expose them to this new area of research and encourage them to attend graduate school.