An enhanced mechanism is disclosed for via stub
elimination in printed wiring boards (PWBs) and other substrates. In one embodiment, the substrate includes a plurality of insulator
layers and internal conductive traces. First and second through-holes extend completely through the substrate and respectively pass through first and second ones of the internal conductive traces, which are at different depths within the substrate. Photolithographic techniques are used to generate plated-through-hole (PTH) plugs of controlled, variable depth in the through-holes before first and second conductive vias are respectively plated onto the first and second through-holes. The depth of these PTH plugs is controlled (e.g., using a
photomask and / or variable
laser power) to prevent the first and second conductive vias from extending substantially beyond the first and second internal conductive traces, respectively, and thereby prevent via stubs from being formed in the first place. This advantageously eliminates the costly and
time consuming process of via stub backdrilling.