A load frame has an open region exposing a surface of an electronic component. A heat sink is disposed on the load frame and has a surface in thermal contact with the surface of the electronic component. A non-influencing fastener is disposed within a bore in the heat sink and threaded into the load frame for securing the heat sink to the load frame. The non-influencing fastener includes a screw with a head; a tapered ring disposed below the head of the screw and having a tapered lower peripheral surface; a sealing ring engaging the tapered lower peripheral surface of the tapered ring; and a load washer disposed between the sealing ring and the load frame. Compression of the rings by turning of the screw into the load frame causes the sealing ring to expand against the bore of the heatsink. Preferably, the sealing ring has a curved outer surface.