Double-sided heat-pipe cooled power semiconductor device assembly

Claim 1

A heat-pipe cooled power semiconductor device assembly comprising an integral power semiconductor device unit including a power seMiconductor device consisting of 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 semiconductor device is operating under normal conditions if both support plates and body of semiconductor material were bonded together, said integral power semiconductor device unit further including first and second cup-like members fabricated of a good thermally and electrically conductive material and having outer bottom surfaces respectively in pressure contact with second major surfaces of said first and second support plates, and creepage path lengthening means formed along side wall portions of said cup-like members for increasing the creepage path across said integral power semiconductor device unit, 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 having first major surfaces respectively in pressure contact with inner bottom surfaces of said first and second cup-like members, mean 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 integral power semiconductor device unit from the assembly, means for connecting a pair of electrical conductors to said assembly or 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 said first pressure plate along a side wall portion thereof, a second major surface of said first pressure plate functioning as a first 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 single-sided 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 said second pressure plate along a side wall portion thereof, a second major surface of said second pressure plate functioning as a second evaporating surface of the second heat pipe in close proximity to the heat-emitting power semiconductor device to obtain improved double-sided vaporization cooling of the device superior to that obtained with conventional finned heat sinks or with wicked heat pipes, said nonwicked heat pipes being substantially greater in length and having improved cooling characteristics than wicked heat pipes which are limited in length due to wick pumping losses, said first and second nonwicked gravity-return heat pipes comprise first and second enclosed elongated hollow chambers having evaporator sections at first ends thereof respectively defined by said first and second pressure plates and condenser sections at seconds ends thereof remote from the first ends, a two-phase fluid coolant contained within said chambers and being of sufficient volume in the liquid state to cause full immeRsion of at least the heated portion of the evaporation surface enhancing means in the liquid coolant, and means connected only along the second major surfaces of said first and second pressure plates for enhancing the evaporation surfaces thereof and thereby increasing the rate of heat transfer from the pressure plates to the liquid coolant in the heat pipes which is vaporized, said clamping means comprising a relatively large diameter threaded connection between said first and second heat pipes, said large diameter threaded connection comprising a first collar member joined to the outer surface of a side wall of said first heat pipe adjacent the first end thereof, said first collar being threaded along its outermost surface, a second collar member joined to the outer surface of a side wall of said second heat pipe adjacent the first end thereof, a rotatable sleeve member retained along the outer surface of the side wall of said second heat pipe and retained longitudinally therealong by said second collar member, said sleeve member having a projecting portion, and a U-shaped hollow cylindrical member having a first end portion threaded for mating with the threaded portion of said first collar member, and a second end portion bearing against an outermost side of the projecting portion of said sleeve member, said U-shaped hollow cylindrical member being rotatable in a first direction for applying pressure against said integral power semiconductor device unit, and rotatable in a second direction or easy removal of said integral power semiconductor device unit from the assembly, said large diameter threaded connection providing a high degree of self-alignment of said pressure plates and integral power semiconductor device unit.