Guifu Ding

Design, simulation and fabrication of a novel contact-enhanced MEMS inertial switch with a movable contact point

A novel inertial switch based on a micro-electro-mechanical system (MEMS) was designed, which consists of three main parts: a proof mass as the movable electrode, a cross beam as the stationary electrode and a movable contact point to prolong the contact time. A MATLAB/Simulink model, which had been verified by comparison with ANSYS transient simulation, was built to simulate the dynamic response, based on which the contact-enhancing mechanism was confirmed and the dependence of threshold acceleration on the proof mass thickness was studied. The simulated dynamic responses under various accelerations exhibit satisfactory device behaviors: the switch-on time is prolonged under transient acceleration; the switch-on state is more continuous than the conventional design under long lasting acceleration. The inertial micro-switch was fabricated by multilayer electroplating technology and then tested by a drop hammer experiment. The test results indicate that the contact effect was improved significantly and a steady switch-on time of over 50 µs was observed under half-sine wave acceleration with 1 ms duration, in agreement with the dynamic simulation.

A MEMS Inertia Switch With Bridge-Type Elastic Fixed Electrode for Long Duration Contact

A multilayer structural inertia microswitch with a bridge-type elastic fixed electrode for long duration contact has been designed and fabricated based on surface micromachining technology. The microswitch mainly consists of a suspended thick proof mass as a movable electrode and two parallel elastic beams with holes as a fixed electrode. The proof mass is designed to be much thicker than attached snake spring section. As a new type of fixed electrode, the bridge-type elastic beams can effectively improve the contact of the microswitch. The packaged microswitch (3.2 times 2.1 times1.3 mm3) has been tested and characterized by a dropping hammer system. The response time and the contact time of the microswitch are about 0.25 ms and 12 mus, respectively, when 100 g acceleration is applied, which indicates a better contact effect than current reported switches. Dependence of the contact time on the thickness of the parallel beam under applied acceleration of 100 g has been discussed. The contact time increases as the thickness of the parallel elastic beam decreases. The test data have an agreement with dynamic finite element simulation results.

Design, simulation and characterization of an inertia micro-switch fabricated by non-silicon surface micromachining

A multilayer structural inertia micro-switch with conjoined snake springs has been designed and successfully fabricated based on non-silicon surface micromachining technology. The micro-switch consists mainly of a suspended thick proof mass as a movable electrode that is located above the supporting layer, and an elastic beam with holes as a fixed electrode that is some distance above the proof mass. The designed proof mass is much thicker than the conjoined snake spring section. This conformation benefits the improvement of its sensitivity and the contact effect, while protecting the switch against severe shock damage from intensive impact of the switch contacts. The fabricated prototype micro-switch has been tested and characterized. The result indicates that the response time and the contact time of the micro-switch are about 0.40 ms and 12 µs, respectively, when a 100g acceleration is applied, which shows relatively better sensitivity and contact effect. This result agrees with that of dynamics finite-element contact simulation about the designed micro-switch. Besides, no severe plastic deformation occurs to springs or elastic beams after over 10 000 dropping tests in the optical profiling characterization. The fabricated micro-switch shows satisfactory mechanical behavior.

Design and fabrication of a magnetic bi-stable electromagnetic MEMS relay

This paper describes the principles, design, fabrication and performance of a new type of electromagnetic bistable MEMS relay. The microdevice is operated by a wiggling microactuator, which is symmetrically assembled with two integrated planar windings and one permanent rotor in the form of sandwich with coaxial sustained gaps between each other. The micromachined rotor moves to-and-fro around the axis and operates the joined brush to open or close external circuit. This hybrid MEMS relay has been provided with fast response and latching function owing to the special design. The response time is about 0.3ms and the maximum load current is 2A.

Development of a Novel MEMS Inertial Switch With a Compliant Stationary Electrode

A novel microelecromechnical system (MEMS) inertial switch based on the surface micromachining technology was developed, which mainly consists of a proof mass as the movable electrode and a compliant stationary electrode above the proof mass, whose deformation during the contact process would enhance the contact effect and prolong the switch-on time. Based on the original design which had already realized the enhancing effect to some extent, the device structure was redesigned as a centrosymmetric structure with the stationary electrode changed from two bridge-type beams to one cross beam in order to reduce the off-axis sensitivity. More importantly, a contact point was installed on top of the proof mass, changing the effective contact area of the stationary electrode from its end to the center, which undergoes the largest deformation. Therefore, the contact effect would be improved further, which has been confirmed by the ANSYS transient simulation. This simulation combined with the Simulink dynamic simulation described the device behavior, which were in agreement with the drop hammer tests. The threshold acceleration of the redesigned inertial microswitch was around 70 g, and the tested switch-on time reached 30 mus, more satisfactory than the original design.

Experimental investigation of heat transfer performance for a novel microchannel heat sink

We demonstrated a novel microchannel heat sink with a high local heat transfer efficiency contributed by a complicated microchannel system, which comprises parallel longitudinal microchannels etched in a silicon substrate and transverse microchannels electroplated on a copper heat spreader. The thermal boundary layer develops in transverse microchannels. Meanwhile, the heat transfer area is increased compared with the conventional microchannel heat sink only having parallel longitudinal microchannels. Both benefits yield high local heat transfer efficiency and enhance the overall heat transfer, which is attractive for the cooling of high heat flux electronic devices. Infrared tests show the temperature distribution in the test objects. The effects of flow rate and heat flux levels on heat transfer characteristics are presented. A uniform temperature distribution is obtained through the heating area. The reference temperatures decrease with the increasing flow rate from 0.64 ml min−1 to 6.79 ml min−1 for a constant heat flux of 10.4 W cm−2. A heat flux of 18.9 W cm−2 is attained at a flow rate of 6.79 ml min−1 for assuring the maximum temperature of the microchannel heat sink less than the maximum working temperature of electronic devices.

Fabrication and characterization of a multidirectional-sensitive contact-enhanced inertial microswitch with a electrophoretic flexible composite fixed electrode

A multidirectional-sensitive inertial microswitch with a polymer?metal composite fixed electrode has been designed and fabricated based on surface micromachining in this work. The microswitch mainly consists of a suspended proof mass as a movable electrode and a T-shaped structure on the substrate with maple leaf-like top and cantilevers around the central cylinder as vertical and lateral fixed electrodes. It can sense the applied shock accelerations from any radial direction in the xoy plane and z-axis. The new vertical composite fixed electrode of the switch is completed by electroplating and electrophoretic deposition, which can realize a flexible contact between the electrodes and reduce the bounces and prolong the contact time. As a result, the stability and reliability of the inertial switch could be greatly improved. The fabricated microswitches have been tested and characterized by a standard dropping hammer system. It is shown that the threshold acceleration of the prototype is generally uniform in different sensitive directions in the xoy plane and z-axis, which is about 70 g. The contact time of the microswitch with the composite fixed electrode is ?110 ?s in the vertical direction, which is longer than that (?65 ?s) without a polymer. The test data are in agreement with dynamic finite-element simulation results.

Design and analysis of the micromechanical structure for an electromagnetic bistable RF MEMS switch

A radio-frequency micro-electro-mechanical systems (RF MEMS) switch with two stable states based on electromagnetic actuation is presented. The switch has two stable positions due to the use of the permanent magnets, which will lead to a low power consumption of the device. The micromechanical structure of the switch is designed and analyzed by means of mechanics and electromagnetism. The results show that the 13-/spl mu/m displacement of the cantilever beam in the switch model with stiffening rib can be achieved with the force of 20/spl mu/N on the beam, and the natural frequency of the switch is about 5600Hz. Electromagnetic analysis reveals that the driving force of 20/spl mu/N can be obtained by magnetic interaction.

MEMS-based carbon nanotube and carbon nanofiber Cu micro special electric contact

Two new electrical contact materials, carbon nanotube (CNT) and carbon nanofiber (CNF), Cu-matrix composite films are prepared by composite electroplating. The microstructure, morphology and physical performance of Cu–CNT/CNF composite films were analyzed by a scanning electron microscope, a Vickers hardness tester and a semiconductor parameter analyzer. The scanning electron microscope images showed that the CNTs/CNFs were dispersed uniformly and combined well in the Cu matrix. Furthermore, the Cu–CNT/CNF composite films show relatively good physical properties, for example the hardnesses of Cu/CNT and Cu/CNF composite films are 156 HV and 207 HV, about 13.9% and 51.1% higher than that of the pure copper plating film (137 HV); the resistivities of CNT/CNF composite plating films are 2.656 × 10−6 Ω cm and 1.815 × 10−6 Ω cm, lower than those of other Cu-matrix composites such as CuW, 4.35 × 10−6 Ω cm, and CuMo, 3.571 × 10−6 Ω cm. In addition, CNT and CNF Cu micro special electric contacts have been designed and successfully fabricated by MEMS technology. The arc-erosion behavior of Cu/CNT and Cu/CNF contacts has been examined on an electric arc-erosion apparatus. The test result shows that the arc-erosion losses of Cu/CNT and Cu/CNF contacts are 2.7 mg and 3.0 mg, 22.9% and 14.3% lower than that of pure Cu (3.5 mg) under the same condition.

Development of a shock acceleration microswitch with enhanced-contact and low off-axis sensitivity

In the present work, microswitches with different shapes have been fabricated by low-cost and convenient multi-layer electroplating in order to develop a shock acceleration microswitch with enhanced-contact and low off-axis sensitivity. Modal analysis based on FEM shows that the three kinds of new designed microswitches have lower off-axis sensitivity than our previous device, i.e., type I. The packaged microswitches were tested by the drop hammer system. The generated half-sine-like shocking acceleration with amplitude of 80g, lager than the threshold, was applied to the microswitches. The test contact time of the microswitch IV is about 55µs, whose contact effect is much better than conventional. A shock acceleration microswitch IV with a movable contact point utilizes the double spring-mass system to realize an enhanced-contact effect and is considered as a better selection for long duration contact and relatively low off-axis sensitivity.