Fabrication and testing of RF-MEMS switches using PCB techniques

In this paper some design considerations and process development for fabricating RF MEMS switches on microwave laminate printed circuit boards (PCBs) are presented. PCB MEMS is a new technology, in which RF MEMS devices can be fabricated on any substrate, and can be monolithically integrated with other elements on the same substrate offering adaptability and reconfigurbility features to the communication systems. This work describes an alternative technique to improve manufacturing for fabrication of RF-MEMS switches on PCB. The integrated process uses metal as part of the sacrificial layer and the isotropic profile (undercut) of the wet etching to help on the bridge release. The mechanical characteristic and theory of operation of capacitive membrane switches is detailed. Pull-in voltage is in the range of 30-40 V. In the OFF state (up-position), the insertion loss is less than 0.3-0.4 dB up to 6 GHz. In the ON state (down-position), the isolation value is about 16 dB at 6 GHz and increases to 34 dB at 18 GHz.