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.