Electrical contact performance of MEMS acceleration switch fabricated by UV-LIGA technology

Abstract

telecommunication, radar, RF and defense systems, etc. (Li et al. 2012;Kim et al. 2012). In particular, MEMS acceleration switches can respond rapidly in specific applications without power consumption. For instance, Wang et al. (2013) developed a low-G horizontally-sensitive inertial micro-switch which switches on when an acceleration threshold is met. Fu et al. (2013) presented a novel MEMS inertial switch used for power management, which can be integrated with detection and control systems without power consumption. Deng et al. (2013) reported an inertial micro-switch based on nonlinear-spring shock stopper which can reduce contact bouncing. Ma (2013) and Kim et al. (2013) also designed several inertial switches which are capable to adjust the acceleration threshold.Electrical contact performance is one of three key parameters of the MEMS acceleration switch (The other two are response time and contact reliability respectively) (Zhou et al. 2013). Contact resistance plays a key role in electrical performance and depends on sample material, contact pressure, temperature, structure design, surface cleanliness, roughness and flatness (Zhou et al. 2013). Greenwood, et al. (1966 put forward a classic theory of elastic contact, which introduced an item named 'elastic contact hardness', a composite quantity depending on the material properties and surface topography. Li et al. (2012) presented an electrical contact resistance model and pointed out that the contact resistance is a function of contact load. Jensen et al. (2005) explored contact heating in the RF MEMS switch and demonstrated that it can reduce the contact resistance significantly. In addition, mechanical cycling would increase the contact resistance because of the insulating film on surface. Broue et al. (2010) proposed a new method to investigate the micro-scale contact mechanism and indicated that the material is a key issue of contact resistance. Jackson et al. (2012) presented the multipleAbstract This paper expanded a micro-contact resistance model to investigate the contact performance for a acceleration switch fabricated by UV-LIGA (Ultra-violet Lithographie, Galvanoformung and Abformung) technology. Based on the relationship between the contact radius a and electron mean free path λ, three different contact resistance models have been analyzed. The material properties (elastic modulus E, hardness H and Poisson's ratio v) and surface topographic parameters (asperity summit radius r, standard deviation of height distribution σ, and surface density of asperity) have been studied to evaluate the contact resistance-load characteristics. The results show that the theoretical prediction of contact resistance-load characteristics correlates well with the experimental results except there exists experimental discrepancy. The discrepancy between theoretical predictions and experimental results mainly is due to the contaminations, errors from assumptions, surface oxidation and external environmental conditions.

Recent Advancements in Inertial Micro-Switches

“…The results showed that the contact resistance was less than 5 Ω while the isolation resistance was more than 200 MΩ, and the maximum allowable current was up to 100 mA. Zhou et al [36] presented a micro-contact resistance model to investigate the contact performance of the latching switches. As seen in Figure 7, Currano et al [31] also designed a reset actuator driven by the current to unlatch the switch, although the device size was remarkably increased.…”

Quantitative measurement of contact area and electron transport across platinum nanocontacts for scanning probe microscopy and electrical nanodevices

“…More recently, a combined c-AFM and simulation investigation used the ballistic transport equation to describe electron transport through a conductive doped ultrananocrystalline diamond tip and a graphene sheet [16]. Further, various analytical models have been proposed to describe current flow through technologically relevant devices such as microelectromechanical systems switches [17][18][19][20][21][22][23][24][25][26]. These models describe microcontacts, which have inherent roughness, as an array of smaller point-contacts, each of which is described by the intermediate transport theory.…”

A 5 g Inertial Micro-Switch with Enhanced Threshold Accuracy Using Squeeze-Film Damping

“…The switches with a keep-close function can keep it closed after the acceleration event is over, thus improving the contact reliability. However, the keep-close function requires special constructions, such as the hook-shaped electrodes of the latching switches [ 6 , 7 , 8 ], the V-shaped beams of the bi-stable switches [ 9 , 10 ], and the valve-channel of the micro-fluidic switches [ 11 , 12 ], complicating the structure topology or working mechanism or fabrication method, thus reducing the threshold accuracy, as shown in Table 1 . The latching switch with a 50.59 g designed threshold value in Ref.…”