4 GPa and Poisson’s ratio of 0.22, is used [23].As shown in Figure 2, four strain gauges (R2, R1, R5, and R6) along the x-axis and four more strain gauges (R4, R3, R7, and R8) along the y-axis are arranged as pairs under the four force-transfer columns. The resistance of the strain gauges is changed symmetrically as they are physically deformed according to the applied direction of external force. Put simply, to measure the direction and magnitude of the applied external force, just four strain gauges (R1, R3, R5, and R7) inside of the contact plate are needed. The direction and magnitude of applied force could therefore be measured by combination of either increasing or decreasing the output resistance.Figure 2.Schematic representation of the configuration of the resistor and interconnects.
Eight strain gauges are candidates for quarter-bridge or moment-compensation circuit. Four strain gauges (R1, R3, R5, and R7) were used to measure applied normal and 2D tangential …2.2. Superposition Principle of Vector ForceForc
Radio frequency microelectromechanical (RF MEMS) switches have been drawing a lot of research interest in the past two decades, due to their several advantages such as high isolation, low insertion loss, zero power consumption and high linearity [1]. RF MEMS devices can offer attractive alternatives in switching networks, portable wireless systems, phased arrays and so on [2]. On the other hand, the reliability of RF MEMS switches is a major concern for long term applications. There have been a number of reports in this area, including both experimental measurements [3�C6] and computational simulations [7,8].
Generally, for capacitive switches, the lifetime is affected by the charging effects in the dielectric layer, and for ohmic-contact switches, the reliability is limited by the metal contacts.Compared to bulk metals, the microscopic contact behavior remains an important still not fully understood topic. In micro-contacts, surface morphology has to be taken into consideration. The reliability and RF performance are closely related to the physical contact made between the prominent asperities at the contact surfaces. Load cycling tests have been performed for RF MEMS switches [3,9�C12], to investigate the degradation mechanism of the metal contacts under different testing conditions.
Meanwhile, the behavior of microscopic contacts during a single load test has been intensively studied, with the electrical contact resistance Rc as an Anacetrapib important parameter to understand the contact behavior [13�C16]. It was found that the relation between Rc and contact force can be divided into three regions, as shown in Figure 1.Figure 1.Schematic plot of contact resistance Rcversus contact force during contact making. Region I: unstable region; Region II: gradual reduction of Rc; Region III: negligible reduction of Rc.