Solder mask prevents bridging, but poor processes can undo that.

Solder on the mask can occur on solder resist, board surfaces, pallet surfaces and conveyor fingers.

Primary process setup areas to check:

• Poor flux application.
• Flux and resist incompatibility.
• Poor cure of the solder mask.
• Preheat temperature too high.
• Solder temperature too high. 

Paul Lotosky is global director – customer technical support at Cookson Electronics (cooksonelectronics.com); plotosky@cooksonelectronics.com. His column appears monthly.