Bridging is the unwanted formation of a conductive path of solder between conductors. When bridging occurs, the primary process setup areas to check are:

• Conveyor speed too slow or other incorrect solder wave settings.
• Time over preheat is too long, causing the flux to be burned off.
• Dwell time too long, causing the flux to burn off before exiting the wave.
• Topside board temp too low.
• Not enough flux applied, or flux activity is too low.

Other things to look for in the process include:

• Preheat too high or low.
• Solder wave height too low or high, or uneven.
• Conveyor speed too slow or fast.
• Board not seated properly.
• Board pallet too hot.
• Contaminated flux.
• Contaminated solder.
• Solder temp too low.
• Flux-specific gravity too low.
• Flux applied unevenly.
• Flux not making contact.
• Excess flux blow-off.

Other causes to look for with the assembly include:

• Board contamination.
• Component lead length too long.
• Component contamination.
• Improper board handling.
  

Other causes to look for with the bare board include:

• Board oxidized.
• Defective mask material.
• Board contamination.
  

Other causes to look for with the design include:

• Poor pallet design.
• Internal ground plane.
• Component orientation.
• Lead-to-hole ratio too large.
• Weight distribution.

Paul Lotosky is global director - customer technical support at Cookson Electronics (cooksonelectronics.com; plotosky@cooksonelectronics.com.

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