A pad array semiconductor device (35) includes a thermal conductor (28) integrated into a circuitized substrate (14). A semiconductor die (12) is mounted on the substrate overlying the thermal conductor to establish a thermal path away from the die. The thermal conductor may also be covered or surrounded by a metallized area (37, 39), which together may serve as a ground plane in the device. Preferably one or more terminals (26) are attached to the thermal conductor for improved thermal and electrical performance. One method of integrating the thermal conductor in the substrate is to position a metal plug into an opening 30 of the substrate. The plug is then compressed or otherwise plastically deformed to fill the opening and create a substantially planar substrate surface.