Contamination or poor heat are likely culprits.

Grainy or dull solder is defined as a rough solder surface with small, gritty projections protruding through the top, or a non-shiny surface that shows no signs of chemical attack.

• Primary process setup areas to check:
• Impurities in the solder.
• Intermetallic compounds.
• Dross mixed into the solder.
• Insufficient heat.

Other things to look for in the process:

• Solder temperature too low.     
• Preheat too low.     
• Early removal of board.
• Solder contaminated.     
• Conveyor speed high.     
• Excessive solder dross.     
• Conveyor vibration.

Other things to look for with the assembly:

• Board contamination.    
• Component contamination.    
• Improper board handling.
• Component leads too short.

Thing to look for with the bare board:

• Board contamination.

Thing to look for with the board design:

• Board contamination.  CA

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