Via-in-Pad Design Can Weaken Solder Joints, Requires Careful Manufacturing

Placing vias directly on SMD pads can cause solder to drain into the hole during reflow, weakening the joint. This is especially problematic for small components, potentially causing failures like tombstoning or intermittent connections. While sometimes necessary for dense designs like BGAs or thermal management, the recommended solution is to use vias that are filled and capped. This specialized process adds cost and must be explicitly specified to the fabricator. Designers are advised to avoid open vias in pads for small passives and to treat via-in-pad as a manufacturing decision, not just a layout technique.