Nonwicked heat-pipe cooled power semiconductor device assembly having enhanced evaporated surface heat pipes

Claim 1

A heat-pipe cooled power semiconductor device assembly comprising a power semiconductor device including a body of semiconductor material defined by first and second flat parallel major surfaces, and first and second support plates having first major surfaces forming interfaces with the first and second flat parallel surfaces of the body of semiconductor material, said support plates fabricated of an electrically conductive high strength material having a coefficient of thermal expansion substantially equal to that of the semiconductor material, said first support plate bonded to said body of semiconductor material along the first surface thereof, said second support plate not being bonded to said body of semiconductor material but merely in pressure contact therewith to prevent damage to the body of semiconductor material due to stresses that would be induced by the thermal expansions of both support plates and body of semiconductor material when the semi-conductor device is operating under normal conditions if both support plates and body of semiconductor material were bonded together to form an integral body, said power semiconductor device defined as developing a thermal density of at least 100 watts per square inch of surface area, first and second relatively thin pressure plates fabricated of a thermally conductive material and having first major surfaces respectively in pressure contact with second major surfaces of said first and second support plates, said pressure plates are each of thickness in the range of 100 to 300 mils, means for clamping said first and second pressure plates together to obtain a pressure in the order of 2,000 lbs. per square inch against said semiconductor device and for providing easy removal of said power semiconductor device from the assembly, means for connecting a pair of electrical conductors to said pressure plates for supplying electrical power to said power semiconductor device, a first long nonwicked gravity-return heat pipe having an open evaporator section end enclosed by and connected to a second major surface of said first pressure plate which functions as an evaporating surface of the first heat pipe in close proximity to the heat-emitting power semiconductor device for decreasing the steady-state thermal resistance as well as decreasing transient temperature rise for long term heat overloads to obtain improved vaporization cooling of the device superior to that obtained with conventional finned heat sinks or with wicked heat pipes, a second long nonwicked gravity-return heat pipe having an open evaporator section end enclosed by and connected to a second major surface of said second pressure plate which functions as an evaporating surface of the second heat pipe in close proximity to the semiconductor device to obtain improved double-sided vaporization cooling of the device, means connected only along the second major surfaces of said pressure plates for enhancing the evaporation surfaces thereof and thereby increasing the rate of heat transfer from the pressure plates to a liquid coolant in the heat pipes which is vaporized, said first and second nonwicked gravity-return heat pipes each comprise an enclosed elongated hollow chamber having an evaporator section at a first end thereof defined by said pressure plates and a condenser section at a second end thereof remote from the first end, a two-phase fluid coolant cOntained within each said chamber, the liquid state of the fluid coolant having sufficient volume to cause immersion of at least the heated portion of the evaporation surface enhancing means in the liquid coolant, and at least a substantial portion of each of said first and second heat pipes being oriented at an angle greater than 0* with respect to the horizontal.