Integrated microrelays: concept and initial results

The addition of an arc suppression circuit to a microrelay (made by micromachining technology) minimizes arcing during switching and results in an increase in the relay service life. To demonstrate the concept and benefits of the integrated relay, an arc suppression circuit was designed and built with off-the-shelf components. In the demonstration, the microrelay was connected to a power transistor in parallel. The function of the power transistor is to carry the load current for a very short time during the make and break switching operations to prevent arc erosion of the microrelay contacts. The arc suppression circuit also provides a lower voltage difference, 2.5 V instead of 12 V, for the relay immediately before making and immediately after breaking the relay contact. Our results showed that the microrelays were protected from the transients accompanying each switching. Using an arc suppression circuit to protect different structured microrelays to switch resistor loads of 0.35 A and 1 A, the number of operation cycles increases substantially. The initial results are encouraging. However, the durability shown in these tests is not sufficient to meet automotive specifications. We believe that the durability can be improved by incorporating better packaging techniques to more efficiently dissipate the heat generated at the contact and to minimize contact material oxidation. Using special contact material to reduce the contact resistance of the microrelay can also improve its durability.