In this paper, we present a novel thermal and electrical power-management solution for high-density electronic appliances, (such as a Microserver), that can handle a volumetric power density of up to 1350 W/dm3. The Microserver consists of a multitude of smart-phone-sized compute-node boards placed in vertical position with a pitch of 7.6 mm on a backplane board that fits into a 19x2U rack unit. In this approach, a passive cooling element, called heat spreader, is thermally attached to each processor chip of the compute node board; the heat is transferred to the sides, which are thermally in contact with an active liquid-cooled heat sink. This solution keeps the electronic components below 85°C, even when they are cooled with a 45°C hot fluid. The heat spreader and the heat sink contain also the electrical connections for the main electrical power delivery at 12 V which eases the strain on the backplane board and the plugs.