Integration and Reliability Issues on MEMS-based Switch Matrices

In the last years MEMS technology has demonstrated to be a very attractive solution for the production of high performances RF switches. As such, it is an enabling technology for the development of high performances, high complexity and very compact switch matrices, able to cope with the ever increasing requirements in terms of capability, flexibility and connectivity of modern telecom payloads. In order to achieve this goal, integration and reliability issues linked to that technology and to that kind of units shall be extensively explored since R&D efforts have been until now mainly focused at the component level. In this frame Thales Alenia Space Italia is involved in several R&D programs aimed at the development and reliability investigation of RF MEMS based switch matrices. These include the ESA programs "Very Large Order Switch Matrices Using MEMS Technology" and "High Reliability MEMS Redundancy Switch", the development of a MEMS switch matrix unit to be included in Alphasat experimental payload, the development of in-house foundry capabilities for MEMS on ceramics and MEMS integrated on ISP (Integrated Substrate Package). This paper reports about the studies conducted in the frame of these activities and their main findings. One of the main challenges in manufacturing very compact, high order switching matrices is the need to route an high number of RF and DC signals in a small space while assuring an high isolation between channels and signal integrity on control lines. Integration and packaging thus play a key role. In the paper several switch matrix architectures are presented along with different integration and packaging solutions based on LTCC (Low Temperature Co-fired Ceramics) technology. A trade off analysis among size/weight, RF-performances, modularity, cost, complexity and reliability is performed. Integration of such equipments inside existing and next generation telecom payloads is addressed as well. RF-MEMS technology reliability is still an open point which has prevented until now its use on-board spacecrafts. In this paper different MEMS-based switching cells topologies and technologies are analyzed in terms of RF-performances, reliability and ease of integration. Their use as switching units inside complex switching networks is described, along with the related reliability and integration issues. Design solutions aimed at improving the switching cell long term reliability are addressed as well. Finally a tentative qualification plan for RF MEMS switch based units is presented.