An object of the present invention is to provide a cooler for cooling both
sides (top and bottom surfaces) of a semiconductor device, wherein the
variation of pressing force on flat cooling tubes holding a semiconductor
device is reduced, thereby uniformly dissipating the heat generated by
the semiconductor device. When the holding plates press the flat cooling
tubes and semiconductor modules by tightening the nut, the dimensional
tolerances in the stacking direction are absorbed by the deformable
portions in the inlet and outlet headers. A spacer may be employed inside
the flat cooling tubes in order to suppress the deformation of the flat
cooling tubes along the stacking direction.