The accurate electromagnetic modeling of the power distribution network at the board level is critical for today's digital applications. In this work, we propose a modular approach for board power distribution network design. The proposed approach relies on the decomposition of the board metallization layers into parallel-plate polygons and the various geometric discontinuities introduced by vias, slots and splits in metallization planes, and the edges of the board. Electromagnetic models for the various segments are generated a-priori and are brought together in a physically consistent manner to yield a compact model for the board that lends itself to an expedient numerical solution toward the generation of a SPICE-compatible, broadband, frequency-dependent multi-port network. Numerical studies are presented that validate the proposed methodology and demonstrate its attributes.