Pin Hole & Blow Hole Soldering Defects and Remedies on PCB Solder Joint

Pin hole or blow hole defects are the same problem caused by the printed board outgassing during wave soldering. Pin hole and blow hole formation during wave soldering is generally associated with thickness of copper plating. Moisture in the board escapes through either thin copper plating or voids in the plating. The plating in the through hole should be a minimum of 25um to stop the moisture in the board turning to water vapor and gassing through the copper wall during wave soldering.

Pin Hole Blow Hole Defect during Wave Soldering

 

The term pin or blow hole are normally used to indicate the size of the hole, pin being small and blow hole being bigger. This size depends on the volume of water vapor that escapes at the point when solder solidifies.

What to Check During Wave Soldering if Pin Hole / Blow Hole / Outgassing Happens:

  1. Make sure the Topside temperature or overall board temperature is not too low. Low temperature can entrap moisture that is out-gassed during wave soldering.
  2. Ensure there is no Entrapped fluid / liquid by any thru-hole electronic component.
  3. Check all Chemical contaminants are removed thoroughly during PC fab.
  4. Ensure there is No Contamination in the hole.
  5. Make sure the Topside of the hole is NOT covered by component body or flashing
  6. Make sure the Solder temperature is neither too high nor too low.
  7. Is the Pre-heat too low?
  8. Make sure Flux SP GR is Not Too low.
  9. Ensure the Flux is not contaminated and Flux is applied evenly. Insufficient flux blow-off or uneven spray of flux can cause pin hole or blow hole defect.
  10. Make sure the Board pallet is Not too hot
  11.  Is the Conveyor speed high or too Low.
  12. Is the Board not seated properly on the conveyor belt?
  13. Check that Solder Wave Height is neither too high nor too low. Uneven solder wave can also cause pin hole and blow hole defects.
  14. The Board and all components should be handled properly and there is No contamination.
  15. Check if the Green Mask is not defective and the Board is not oxidized.

Other Reasons of Outgassing / Blow Hole / Pin Hole Defect:

  • Moisture in the laminate
  • Poor plating in the hole
  • Mask in hole
  • Lead-to-hole ratio mismatch
  • Internal ground plane
  • Component orientation too large

Solution and Precaution – How to Avoid Pin Hole Defect and Blow Hole Defect:

  • Improve the board quality with a minimum of 25um of copper plating.
  • Baking or Preheating the board takes the water out of the board.
  • Store PCB in Moisture Proof Cabinets.
  • Store Circuit Board in Moisture Proof ESD Bags.
  • Green Mask the Board when in Storage.

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