Consequences of insufficient spacing between components for surface mount assembly

With the rapid push towards high-density electronics, designers and producers have to be more vigilant to keep up with the finer pitches and reduced PCB real estate of new designs. Ignorance towards component spacing is a recipe for high defect rates, repair difficulty, and overall poor reliability.

This short article highlights the consequences of insufficient spacing between components that should be noted by all PCB designers.

1. On the bottom side of the PCB, if the pins are too close to a nearby through-hole, short circuits may occur, destroying the PCB.
2. If mounting holes and pads are too close or if there is no solder resist between through-holes and pads, defects may occur during the wave soldering process and result in solder bridges.
3. When the spacing between through-holes and surface mount pads is too small, it can result in insufficient solder wetting, cold solder joints, tombstoning, and other defects. The reason is that solder paste could flow out of the through-hole, resulting in insufficient solder for the surface mount pad.
4. When through-holes are placed too close together, there is a risk of solder bridging especially when repairing.
5. For vias-in-pads without filling, solder paste melts and flows into the hole during reflow, resulting in a lack of solder on the component pads, thus forming dry joints. The leaked solder may even cause short circuits in some designs.
6. If the annular ring of vias and BGA pads are too close together, and the via is not covered with solder mask, this could cause solder bridges even if a solder dam exists.
7. If through-holes on the capacitor pad are missing the solder mask, less solder will be available for component pins, affecting the reliability of the joint.
8. If a via is placed on a solder pad which is subsequently sealed with solder mask, it will be blocked and will be difficult to fix.

HQ Electronics' HQDFM DFA analysis software capabilities can help identify clearance violations to improve assembly reliability in advance. Manufacturing and assembly-oriented product design is the key to product development with lower development costs, shorter development cycles, and higher product quality.
HQ NextPCB is a professional PCB manufacturer with PCB assembly capabilities. Looking for assistance with your design? Write to us at support@nextpcb.com.