Fabrication
Via-in-Pad
In plain English
Putting the tiny layer-to-layer tunnel right inside the spot where a part sits, then filling it flat so it still solders cleanly — a space-saver for very crowded chips.
The technical version
Via-in-pad places a via directly within a surface-mount pad, essential for breaking out fine-pitch BGAs below roughly 0.5 mm pitch. To prevent solder wicking and voids, the via is copper-filled and planarized (capped) before finish. It trades higher process cost for maximum routing density.