Apparatus for effecting heat transfer from power semiconductors

Abstract

A magnetic resonance imaging system includes a main magnetic field generator ( ) which produces a temporally constant magnetic field through an examination region ( ). A gradient coil assembly ( ) powered by a gradient field amplifier ( ) produces gradient fields orthogonal to the main magnetic field. The gradient field amplifier ( ) includes a heat sink ( ) for dissipating the thermal energy of at least one power semiconductor device ( ) having a first surface opposite a thermally conductive surface ( ). The thermally conductive surface ( ) is in contact with the heat sink ( ) for transferring the thermal energy. A rigid plate clamp assembly ( ) is affixed to the heat sink ( ) and the semiconductor device ( ) is disposed therebetween. A resiliently deformable spring ( ) is positioned between a first surface of the semiconductor package ( ) and the plate clamp ( ) maintaining positive pressure between the thermally conductive surface ( ) and the heat sink ( ). The resilient deformable spring ( ) has an inner ring ( ) in contact with the rigid plate assembly ( ) and an outer ring ( ) angled from the inner ring in contact with the first surface of the semiconductor package ( ). Preferably, a plurality of semiconductor devices are provided each utilizing a deformable spring to ensure thermal contact between each semiconductor power device and the heat sink.