A packaged semiconductor device includes a substrate, a heat-generating component positioned on a surface of the substrate, an enclosure at least partially surrounding the substrate and the heat-generating component, and a thermal interface material disposed between the heat-generating component and the enclosure. The enclosure includes a cover portion having a convexly curved surface configured to apply a pressure to the thermal interface material. The pressure may be substantially uniform over the area of the thermal interface material, or may be higher at a center of the thermal interface material than at a periphery of the thermal interface material.