Abstract: Many housings for electronic devices require to be carefully sealed, as well as incorporate heat sinks for the electronic devices. Careful sealing has required expensive machined housing joints and, because electronic devices may be misaligned to the substrate, rounded heat sinks have been used, giving restricted contact areas and hence limited cooling. The invention employs a thermally conducting flexible membrane capable of being urged into thermal contact with the electronic device, for example by a evacuation of the housing, thereby permitting a simple hermetic seal as well as contact with the electronic device over a large area.