Call them blowholes or pin holes. Just don’t call them often.
Where the solder joint has a small, visible hole that penetrates from the surface of a solder connection between the conductive patterns on internal layers, external layers or both of a board is known as a solder void. This is typically due to moisture entrapment that, during the soldering process, outgassed from the joint.
Primary process setup areas to check:
- Topside or overall board temperature too low, entrapping moisture that is out-gassed at the wave.
- Entrapped fluid by component in through-hole.
- Chemical contaminants not removed during fabrication process.
- Contamination in the hole.
- Topside of the hole covered by component body or flashing.
Other conditions to look for in the process:
- Solder temp too high.
- Preheat too low.
- Insufficient flux blow-off.
- Solder temp too low.
- Contaminated flux.
- Board pallet too hot.
- Flux applied unevenly.
- Flux SP GR too low.
- Conveyor speed high.
- Solder wave height low.
- Flux SP GR too high.
- Conveyor speed low.
- Solder wave uneven.
- Flux not making contact.
- Board not seated properly.
Other conditions to look for with the assembly:
- Board contamination.
- Component contamination.
- Improper board handling.
Things to look for with fabrication:
- Board oxidized.
- Defective mask material.
- Board warped.
- Board contaminated.
- Moisture in the laminate.
- Poor plating in the hole.
- Mask in hole.
- Hole and pad misregistered.
- Misregistration of the mask.
Things to look for with the board design:
- Lead-to-hole ratio too large.
- Internal ground plane.
- Component orientation.
- Lead-to-hole ratio too small.
Paul Lotosky is global director - customer technical support at Cookson Electronics (cooksonelectronics.com) plotosky@cooksonelectronics.com.