Vibrations can weaken the solder joint.

Rough or disturbed solder is a solder fillet that solidified while one or both metals to be joined were vibrating. The result is a weak, non-uniform metallic structure with many micro-cracks.

Primary process setup areas to check:

• Check conveyor for vibration or “jerky motion.”
• Removal of the board prior to the solder solidifying.

Other things to look for in the process:

• Solder temperature too low.    
• Conveyor speed high.    
• Solder wave height low.    
• Conveyor vibration.    
• Solder wave uneven.    
• Early removal of board.
• Solder contaminated.    
• Board not seated right.    
• Excessive solder dross.    
• Flux applied unevenly.

Things to look for with the board design:

• Poor pallet design. 

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