Device for clamping a printed circuit board module in a mounting groove of a cold plate, comprising: an elongated housing made of metal, the cross-section of which having the shape of a horizontal U, wherein the back of the U forms the back wall, the U limbs form the lateral walls (42, 43) and the front side is substantially open; a pressure piece made of metal mounted between the lateral walls (42, 43) of the housing so as to be transversely displaceable relative to a longitudinal axis of the housing and having a flat clamping surface at the front side, said surface extending parallel to the back wall of the housing; a drive mechanism, which is inserted in the space between the back wall of the housing and the pressure piece and which pushes the pressure piece forward through the open front side of the housing at least so far that the pressure piece protrudes beyond the parallel lateral walls (42, 43) of the housing and the clamping surface thereof can be seated against an opposing wall of the mounting groove; wherein the pressure piece has the shape of an elongated rectangular cuboid the cross-section of which is matched to the cross-section of the housing and is made of solid steel; the pressure piece is slideably mounted between the lateral walls (42, 43) of the housing thereby producing a large-surface-contact between the housing and the pressure piece; wherein the drive mechanism comprises a number of wedge elements (49, 50, 51) which are arranged in a row on a threaded shaft, the axis of the threaded shaft being parallel to the back wall of the housing, wherein the wedge elements (49, 50, 51) are pulled together by a rotation of the threaded shaft and give way laterally at least to some degree, whereby at least one wedge element is pressed against the inner side of the pressure piece and pushes the same forward, and at least one other wedge element is pressed against the back wall of the housing to generate counterpressure. an elongated housing made of metal, the cross-section of which having the shape of a horizontal U, wherein the back of the U forms the back wall, the U limbs form the lateral walls (42, 43) and the front side is substantially open; a pressure piece made of metal mounted between the lateral walls (42, 43) of the housing so as to be transversely displaceable relative to a longitudinal axis of the housing and having a flat clamping surface at the front side, said surface extending parallel to the back wall of the housing; a drive mechanism, which is inserted in the space between the back wall of the housing and the pressure piece and which pushes the pressure piece forward through the open front side of the housing at least so far that the pressure piece protrudes beyond the parallel lateral walls (42, 43) of the housing and the clamping surface thereof can be seated against an opposing wall of the mounting groove; wherein the pressure piece has the shape of an elongated rectangular cuboid the cross-section of which is matched to the cross-section of the housing and is made of solid steel; the pressure piece is slideably mounted between the lateral walls (42, 43) of the housing thereby producing a large-surface-contact between the housing and the pressure piece; wherein the drive mechanism comprises a number of wedge elements (49, 50, 51) which are arranged in a row on a threaded shaft, the axis of the threaded shaft being parallel to the back wall of the housing, wherein the wedge elements (49, 50, 51) are pulled together by a rotation of the threaded shaft and give way laterally at least to some degree, whereby at least one wedge element is pressed against the inner side of the pressure piece and pushes the same forward, and at least one other wedge element is pressed against the back wall of the housing to generate counterpressure.