IC device assemblies including a power delivery bus board that is mounted to a primary PCB (i.e., motherboard) that further hosts a power-sink device and a power-source device. The bus board, as a secondary PCB, may be surface-mounted on a back side of the primary PCB opposite the power source and sink devices, which are mounted on the front side of the primary PCB. The bus board need only be dimensioned so as to bridge a length between first and second back-side regions of the primary PCB that are further coupled to a portion of the front-side pads employed by the power-sink device. The secondary PCB may be purpose-built for conveying power between the source and sink devices, and include, for example, short, wide traces, that may be formed from multiple heavyweight metallization layers.