1. Field of the Invention
The present invention relates to an improvement to a semiconductor vapor-cooling apparatus which is suitable for use in a chopper or a DC-AC inverter used for controlling the speed of the main motor of a railroad.
2. Description of the Prior Art
Developments in the technology of vapor-cooling a semiconductor element have centered on its application to a chopper or DC-AC inverter which is used in a railroad train, and which requires a semiconductor element of a large capacity.
Known semiconductor vapor-cooling apparatuses include a cooling vessel containing a semiconductor stack and a liquid refrigerant such as Freon 113, as well as a condenser provided above the cooling vessel in such a manner that it communicates with this cooling vessel. The entire cooling vessel and the condenser are hermetically sealed from the atmosphere to constitute a sealed vessel. A typical example of this apparatus is disclosed in the specification of Japanese Patent Laid-Open No. 68662/1980.
One example of the semiconductor stack is disclosed in, for example, the specification of Japanese Patent Laid-Open No. 41734/1980. The semiconductor stack includes a semiconductor element, cooling members (heat-radiating plates) between which the semiconductor element is disposed, and wiring conductors between which the cooling members and semiconductor element are disposed. It is further proposed (in the specification of the above-mentioned Japanese Patent Laid-Open No. 41734/1980) that the surface of the cooling member is made to be porous or it roughened so as to increase the heat dissipation characteristics with respect to a liquid refrigerant, and that a plurality of pins are inserted so as to provide gaps between the cooling members and the wiring conductors.