Methods for assembling a die-down array integrated circuit (IC) device packages with enhanced thermal, electrical, and input/output properties are presented. The method includes coupling a first surface of a substrate to a first surface of a heat spreader, mounting a first surface of an IC die to the first surface of the heat spreader within a central cavity of the substrate, coupling a plurality of bond pads on a second surface of the IC die to corresponding bond pads on a second surface of the substrate with a plurality of wire bonds, and coupling a first surface of an interposer to the second surface of said IC die. A central opening is open at the first surface of the substrate and the second surface of the substrate. The central opening overlaps the central cavity formed in the first surface of the heat spreader. A plurality of electrically conductive bumps on the second surface of the IC die are coupled to corresponding bond pads on the first surface of said interposer.