Abstract: A cooling mechanism for power semiconductors comprises a metallic evaporator (1) filled with a heat-carrying fluid and designed to be brought into close contact with one face of a smeiconductor (2); at least one condenser constituted by a tube (5) whose inner wall bears a capillary structure, and which is closed at one end and extended at the other end by a conduit (7) of insulating material; and an envelope (8) enclosing the tube (5) and attached at the upper part of the conduit (7) so as to create a chamber (11) for the circulation of a cooling fluid, with the conduit (7) being connected to the evaporator (1) by an elastic piece (14). The pressure inside the assembly constituted by the evaporator (1), the condenser(s) (5) and the conduit (7) is lower than atmospheric pressure, and cooling is effected by an evaporation-condensation cycle.