Abstract: A technique for cooling electrical bus structures is disclosed, in which a phase change heat spreader is thermally coupled to the bus. A continuous phase change cycle occurs within the heat spreader to draw heat from the bus during operation. The heat spreader may be planar, and extend over an area greater then the surface area of the bus to enhance cooling and to render the overall assembly more isothermal. The heat spreader may be placed near bus joints and circuits to remove heat caused by increased resistance at such locations.