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Incomplete Solder Joint
Incomplete solder fillets are caused by poor hole to lead ratio, steep conveyor angles, excessive wave temperature and contamination on the edge of the pads. The example shown is as a result of burring on the copper pads. During either drilling or punching the copper on the surface of the board has been deflected in some areas making soldering difficult. The same thing can occur if resin is smeared onto the edge of the pads.