An apparatus includes a laminate and a lid. The laminate generally includes a dielectric layer between a first conductive layer and a second conductive layer. The first conductive layer may include a probe configured to transfer a radio-frequency signal in a millimeter-wave band. The second conductive layer may be configured to provide a continuous ground plane parallel to the probe and separated from the probe by the dielectric layer. A plurality of channels may be (a) formed into a side of the second conductive layer opposite the dielectric layer, (b) formed to a depth less than a thickness of the second conductive layer, and (c) sized to permit gasses formed while securing the laminate to a substrate to escape from between the laminate and the substrate. The lid may be in contact with the first conductive layer.