In-line Wideband RF MEMS Switch Integrated on PCB Using BCB Planarization

In this paper, the design, fabrication, and characterization of a wideband cantilever RF-MEMS coplanar line switch with metal-to-metal contact are presented. Printed circuit board (PCB) processing techniques and benzocyclobutene (BCB) as planarization material were used to integrate the RFMEMS switch to a microwave-friendly substrate. The proposed fabrication process was developed at low-temperature (< 210 C) and combines layers of BCB, photoresist and copper. The process is relatively simple, comparatively inexpensive, and it implies a wide usage of BCB as planarization material to reduce the surface roughness of the cantilever beam, enabling a high repeatability of the fabricated MEMS switches. This low-cost fabrication process was used to develop a switch with low actuation voltage, and acceptable levels of insertion loss and isolation in the frequency band from DC to 20 GHz. The fabricated switch demonstrated isolation higher than 13.1 dB and insertion loss lower than 0.63 dB in the frequency range from DC up to 12 GHz. In frequencies from 12 to 20 GHz, the insertion loss is lower than 1.16 dB and the isolation is higher than 9.6 dB. The pull-in voltage was 30 V with measured commutation time of 425 s. This RF-MEMS switch is suitable to be monolithically integrated with printed circuits on flexible microwave-friendly substrates.