Heat-pipe cooled power semiconductor device assembly having integral semiconductor device evaporating surface unit

Claim 1

A high pressure-interface-free heat-pipe cooled power semiconductor device assembly comprising a pressure-interface free integral power semiconductor deviceevaporating surface unit including a power semiconductor device consisting of a body of semiconductor material defined by first and second flat parallel major surfaces, first and second thin cup-like members having outer bottom surfaces respectively bonded to the first and second flat parallel surfaces of the body of semiconductor material so that the power semiconductor device-cup like member unit is pressure-interface-free, said cup-like members fabricated of a good electrically and thermally conductive material, and creepage path lengthening means formed along outer side wall portions of said cup-like members for increasing the creepage path across said power semiconductor device, said power semiconductor device defined as developing a thermal density of at least 100 watts per square inch of surface area, a first long nonwicked gravity-return heat pipe having an open evaporator section end closed by and connected to said first cup-like member along the side wall portion thereof by high pressure-free means, an inner bottom surface of said first cuplike member functioning as an evaporating surface in the evaporator section end of said first heat pipe, said first nonwicked gravity-return heat pipe 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 integral power semiconductor device-evaporating surface unit further including means bonded only along the inner bottom surface of said first cup-like member for enhancing the evaporating surface thereof to thereby increase the rate of heat transfer from the first cup-like member to a liquid coolant in said first heat pipe which becomes vaporized, the close spacing between the evaporating surface and heat-emitting power semiconductor device due to the thinness of said first cup-like member and lack of any pressure interfaces in the integral power semiconductor device-evaporating surface unit substantially decreasing the steady-state thermal resistance as well as improving the transient response of the heat-pipe cooled power semiconductor device assembly to obtain improved single-sided vaporization cooling of the device superior to that obtained with conventional finned heat sink or wicked heat pipe assemblies.