Abstract: A plastically deformable lever is used to compress a flat spring against the upper surface of a power electronic device in mounting the device on a bus bar or heat sink. The lever preferably is integral with the bus bar or heat sink. The heat sink or bus bar has at least one mounting area onto which at least one power electronic device may be mounted. At least one spring is positionable against an upper surface of each power electronic device to be mounted on the heat sink or bus bar, and at least one plastically deformable element is positioned such that deformation bends a spring so as to cause the spring to exert pressure against the upper surface of at least one of the power electronic devices to bias same against the heat sink or bus bar.