Types of Wave Solder Defects（类型的波焊接缺陷）.pdf

Types of Wave Solder Defects ßNon-Wetting ßIcycling ßDewetting ßBridging ßPin Holes ßExcess Solder ßWebbing ßDull/Grainy Joints ßWhite Haze ßCold/Disturbed ßSolder Balls Joints Non-Wetting ßRecognized by pull back of solder to expose the surface to be soldered Non-Wetting ß Possible Causes: ß Grease, oil or dirt on the pre-soldered surface ß Bleeding or misregistered soldered mask ß Low temperature solder ß Contaminated solder ß Surfaces too heavily oxidized for flux being used ß Contaminated flux ß Poor application of flux ß Remedy ß Investigate each possible cause and correct suspected discrepancies one at a time until solderability is restored Dewetting ßRecognized by metal wetting initially, then pulling back to form droplets of solder on the surface. Dewetting ßPossible Causes: ßContamination of surface by abrasives ßPoor plating ßPoor hot air solder leveling during PCB manufacture ßRemedy ßRestore solderability of the surface Pin Holes ßRecognized by small holes or eruptions in the solder fillet. Pin Holes ßPossible Causes: ßMoisture or plating solution in the PCB laminate ßInadequate preheat to evaporate flux solvent ßFlux has absorbed water ßPhysical blockage due to foreign body in hole ßTop of Plated Through Hole prematurely solidifying Pin Holes ßRemedy ßIncrease preheat to see if it eliminates problem ßPut in new flux to see if it eliminates problem ßIncrease topside preheat and/or solder