A compliant structure is provided on a semiconductor wafer. The compliant structure includes cavities. The compliant structure and the wafer seal the cavities during process steps used to form conductive elements on the compliant structure. After processing, vents are opened to connect the cavities to the exterior of the assembly. The vents may be formed by severing the wafer and compliant structure to form individual units, so that the severance planes intersect channels or other voids communicating with the cavities. Alternatively, the vents may be formed by forming holes in the compliant structure, or by opening bores extending through the wafer.