Research status of wafer level packaging for RF MEMS switches

Compared with traditional switches, RF MEMS switches are characterized by low power consumption, low insertion loss, high isolation, good linearity and high integration. However, the high cost of packaging process has great impact on the device performance among the RF MEMS processing. This paper overviews the research status of RF MEMS switch, such as the structural design, the wafer-level packaging. The review will focus on the wafer-level packaging of RF MEMS switch and the following conclusions are drawn by comparing the different methods of wafer level packaging: 1) The packaging of RF MEMS switches mainly adopts WLP methods, which are divided into two types, cap packaging and thin film packaging. Thin film packaging is more promising due to it presenting a lower temperature than cap packaging. 2) The low temperature bonding technology is used in the cap packaging for RF MEMS switch, and the cap packaging has gradually matured. 3) The sacrificial layer release technique is needed in the thin film packaging, and the contamination problem caused by clean technology in the packaging process still needs to be solved. 4) As cap materials or sealing ring materials, polymer is a low-temperature encapsulation material, which has great development potential. But, it is too sensitive to humidity, and it still need a deeper study. The reviews are presented to get a better understanding of the state of the art work done in the field RF-MEMS package for nearly past twenty years.