Liquid crystal polymer for RF MEMS packaging

We have developed a Liquid Crystal Polymer (LCP) encapsulation technology for RF MEMS. The RF MEMS devices are flip-chip interconnected on 50 ohm microstrip transmission line on an alumina substrate. After flip-chip device transfer, LCP is used to encapsulate the device on the substrate. This approach is similar to glob-top encapsulation used for low-cost microelectronic packaging. The effectiveness of LCP (Vectra A950) sealing has been demonstrated by monitoring the moisture level inside the package under a 100% RH environment. In addition, the LCP's permeabilities to helium and nitrogen were measured through a standard membrane characterisation setup. These permeabilities were proven to be in the same level as those of borosilicate glasses used for hermetic sealing at room temperature. LCP is an excellent encapsulation material for hermetic or near-hermetic packaging of RF MEMS.