A High Aspect Ratio Microfabricated Reed Switch Capable of Hot Switching

This paper describes the design and performance characteristics of a new type of small magnetically operated reed switch based on high-aspect ratio microfabrication. The new technology combines the advantages of conventional reed switches - such as high power hot switching capability - with the economies of scale achievable using semiconductor fabrication techniques. We describe the scaling laws that govern the contact closure forces that are generated as the physical size of the switch is decreased below 2 mm³, and discuss the optimum contact geometries for maximizing the magnetic flux in the contact gap. We show how the contact force magnitudes vary with respect to the applied magnetic field, and we quantify the influence of those forces on power switching capability and contact life. We also compare the performance attributes of the new switch with other types of MEMS switches based on planar rather than high aspect ratio technology. Contact life test data based on Weibull statistics at hot switched loads up to 50mW are presented. Potential applications for the switch include sensors, microrelays, and portable medical devices where a combination of zero power operation, very small size, and hot-switching capability is required.