A pad is the copper feature, round, rectangular or custom-shaped, that a component terminal is soldered to, either on the surface or around a plated hole. Its size and shape control solder fillet formation, tombstoning risk and joint reliability. Pads are either copper-defined, with a mask opening larger than the copper, or soldermask-defined, where the mask overlaps the copper edge, a choice that matters most for BGAs.
Pads on the 0402s are too long, pull them in 0.1 mm or they'll keep standing up in reflow.
Also heard as
- land
- solder pad
Related terms
Footprint
Pattern of copper pads, outline and markings on a board that matches one component package.
Annular ring
Ring of pad copper left around a drilled hole, which must stay wide enough after the drill wanders.
Tombstoning
Defect where a small two-terminal chip stands up on one end during reflow, leaving the other end unsoldered.
Soldermask
Thin polymer coating over a board's copper that leaves pads exposed and keeps solder where it belongs.