Defect : Solder balls

Process/machine infomation :

Board type – Double sided

Solderability protection – HASL

Flux carrier – Water

Preheat type – Forced Convection

Process solutions

• Conveyor speed too slow.

  a. Time over preheat too long causing flux to be burned off.

  b. Dwell time too long causing flux to be destroyed before exiting the wave.

• Conveyor speed too fast.

  a. Time over preheat not long enough to dry flux carrier.

• Flux not active enough or solids percentage too low.
• The use of nitrogen may increase solder balls.
• Not enough flux.
• Flux carrier is not being completely dried by the preheat.
• Too much flux.

Board and design solutions

• Lead length too long.
• Solder mask type or curing.

  a. Matte finish is preferred.