The thermal management of the PCB based power electronics is a key element to ensure safe operating conditions and to meet lifetime, reliability and safety requirements. This is challenging for applications above 1 kW because the substrate material used in a PCB such as FR-4 has very low heat conducting properties. Hence, there is a limit on how much loss can be dissipated from the board and for that reason this approach has only been adopted in the industry for very low power applications. With the proposed multilevel topology, WBG devices, and innovative thermal management strategies it is possible to expand the PCB based power electronics approach to power ratings between 1kW and 10 kW. For instance, an improvement in the thermal resistance of the PCB can be obtained by soldering a discrete WBG device with a TO-263 package directly on a PCB with about one inch square copper area around the device which will act as a heat spreader. Then, a further substantial reduction in the thermal resistance of a PCB is possible by the application of electrical vias. In principle each via is a copper sleeve through the board or through a part of the board. Where, instead of using its electrical function, a via can also be used as a thermal conductor. In this work, the thermal analysis of the PCB and the effect of number of vias as well as the effect of filling the vias with a thermally conductive material has been studied. The design has been optimized for the number of vias and the modeling results have been verified with experimental tests.