Development Of An Electro-thermal-driven MEMS Relay

Micro-electro-mechanical systems (i.e., MEMS) are integrated systems of microelectronics (IC), micro-actuator and, in most cases, micro-sensors. MEMS and related technologies make it possible the miniaturization and integration of optical, electronic, magnetic and thermal functional devices, and they have enabled successful demonstration of novel sensors, actuators, and systems in many diverse application areas.MEMS relay is a type of micro-relay produced by a combination of micro-fabrication techniques and relay technology. Micro-relays are used in various industries for a wide variety of applications, like information processing, communication etc, as a basic mechanical and electronic component. Compared with the traditional electric-mechanical relay, which based on mechanical manipulation and contact conduction, and solid-state relay, which based on non-contact semiconductor device, MEMS relay have some advantages: small volume, high linearity, low consumption, high insulation degree and compatibility etc. Micro-relay can be divided into three categories by driven model: electrostatic, electromagnetic, electro-thermal micro-switches and micro-relays. Electro-thermal micro-relays have some advantages of low driven force, large output force, simple structure and processing overweighing those of the electrostatic micro-relays and electromagnetic micro-relays.This paper introduces a novel electro-thermal-driven MEMS relay, mainly contains thermal-driven arm, amplifying arm, SU8 insulation block, contact head and input-and-output channel of signal. The whole structure is based on the principle of leverage, showing as a "T"-type structure. The U-shaped actuator can increases the output force without raising the resistance of the actuator and total consumption of the device; and the leverage-based amplifying beam can also magnify the small thermal-expansion stretch into relatively bigger offset. The micro-relay has a big course. Meanwhile, SU8 supports block are introduced to reinforce the structure of the thermal-driven arm and SU8 insulation block is used to isolate controlling signals and transmitting signals. Besides, Finite element Ansys10.0 is employed as an assistance of analysis and structural designing.The non-silicon MEMS fabrication process was used to produce the micro-relay and the related micromachining technology is studied and the proper method and parameters for the fabrication of micro-relay are selected. The process uses sputtering, spinning photoresist, lithography, electroplating, corrosion etc, with sputtered Cr/Cu film as seed layer of metal plating, with electroplated Cu as the control lines and the sacrificial layer material, with electroplated Ni as structural material of micro-relay, with negative resist technology to produce a SU8 insulation block, with positive photoresist materials for corrosion protection and etching Cu sacrificial layer using wet etching technology to form Cu Suspended beam, and finally with exposure method to remove protective layer. After integrating process, MEMS relay prototypes were successfully fabricated. Testing was took out on the self-made testing platform and the results showed that the resistance of the actuator, the driving voltage, responding time (ton) and recovering time (toff )are 2?, 0.5V, 11ms and 1ms respectively.