Abstract: A semiconductor device is carried in compressive contact relationship between two vapor cooling containers put in fluid communication with condensers disposed above them through connection tubes respectively. A condensible liquid coolant fully fills each container, and the associated connection tube and partly fills the mating condenser. One auxiliary tube is disposed within each connection tube and has a bent upper end opening in the associated condenser below the liquid surface of the coolant and a lower end opening in the associated cooling container connected thereto.

Abstract: A semiconductor device is immersed into a cooling medium in its liquid phase disposed in a vessel. The cooling medium changes to its vapor phase due to heat from the semiconductor device to enter a condenser located above the vessel. The cooling medium condensed in the condenser passes through a conduit connected to the lower portion of the vessel to be directly mixed with the liquid cooling medium within the vessel.