What Is The Minimum Pitch You Can Wave Solder a PCB?

Al Wright - PCB Field Applications Engineer
Written by Al Wright - PCB Field Applications Engineer
Posted on August 7, 2014 at 2:46 PM

Wave soldering, the process of attaching electronic components to the printed circuit board (PCB), becomes increasingly difficult as pitch decreases. With the appropriate controls, it is still possible to get a good result with pitches as low as 0.5mm (.0197"). Wave soldering defects can occur in pitches below 0.5mm, so we recommend this as the minimum pitch to wave solder a PCB.

During the circuit board design stage, you need to pay close attention to component orientation and placement, and consider the following:

  • Use shorter lead lengths whenever possible.
  • Add solder thief pads to the PCB artwork, to allow excess solder to flow away from connectors so they will be less likely to bridge.
  • Control machine parameters such as temperature, immersion depth, and back flow according to manufacturer recommendations.
  • Use appropriate amounts of flux.
Illustration of Solder Thief Pad

Illustration of Solder Thief Pad in a Printed Circuit Board

Conclusion

Wave soldering printed circuit boards with SMT pitches below 0.5mm is not recommended. Pad size vs. pitch becomes so small that most bare PCB manufacturers are unable to guarantee adhesion of solder mask dams between pins. When no dams are present, solder is able to flow freely across the circuit board surface, and can form bridges between adjacent pins. The resulting short circuits force the assembler to rework the PCBA before it can be used.


Topics: Printed Circuit Boards


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