Patent ID: 8136240

Claim:
A method comprising the steps of: providing a substrate having a plurality of insulator layers and a plurality of internal conductive traces, wherein a plurality of through-holes extend completely through the substrate from a first surface of the substrate to a second surface of the substrate, wherein a first one of the through-holes passes through a first and a second of the internal conductive traces, and wherein the second internal conductive trace lies deeper within the substrate with respect to the substrate's first surface than does the first internal conductive trace; plating a first conductive via onto the first through-hole so that the first conductive via extends from the substrate's first surface to and terminates substantially at the first internal conductive trace; plating a second conductive via onto the first through-hole so that the second conductive via extends from the substrate's second surface to and terminates substantially at the second internal conductive trace; providing a plated-through-hole (PTH) plug in the first through-hole, wherein the PTH plug extends from a first end thereof at or adjacent to the first internal conductive trace to a second end thereof at or adjacent to the second internal conductive trace; providing a seed photoresist on portions of the substrate's first and second surfaces, wherein the seed photoresist has open regions in the vicinity of the first through-hole, and wherein the open regions of the seed photoresist expose a portion of the substrate's first surface adjacent the first through-hole, a portion of the first through-hole extending from the substrate's first surface to the first internal conductive trace, the first end of the PTH plug, a portion of the substrate's second surface adjacent the first through-hole, a portion of the first through-hole extending from the substrate's second surface to the second internal conductive trace, and the second end of the PTH plug; applying seed material to the seed photoresist, the exposed portions of the substrate's first and second surfaces, the exposed portions of the first through-hole, and the exposed first and second ends of the PTH plug; stripping the PTH plug and the seed photoresist so that the seed material remains substantially only at a portion of the substrate's first surface adjacent the first through-hole, a portion of the first through-hole extending from the substrate's first surface to the first internal conductive trace, a portion of the substrate's second surface adjacent the first through-hole, and a portion of the first through-hole extending from the substrate's second surface to the second internal conductive trace.