Novel surface micromachined membranes have been developed for wafer level packaging and polymer encapsulation. Laterally unconstrained electroforming allows small etch holes to be included in thick membranes whilst only requiring a thin, low stress, mould. These holes have been shown to have a sufficiently small aperture (<10 µm) and depth (17 µm) to block a high viscosity encapsulant (AZ4562 photoresist). However, they enable the low viscosity sacrificial release etchant (acetone) to pass through. Etch hole inclusion provides a rapid and clean release. In order to route interconnect to the membranes, side port flow channels have been developed which effectively block spin-on encapsulants from entering the protected cavity. The influence of the membranes on the RF performance of micromachined meander inductors is reported.