The effect of the hot air levelling process on skip solder defects in the wave soldering process

It was observed that “no solder” or “skipped solder” defects occurred on a particular printed circuit board assembly product during wave soldering. Investigations were carried out to find out the cause of this defect and to recommend an optimal hot air level coating thickness. To evaluate whether thicker plating helps to produce better solderability, new printed circuit boards with an average plating thickness of 4.27 μm were sent for solderability testing. This increase in plating thickness resulted in no defects in the solderability test. This is in contrast to the current printed circuit board that had a no/skipped solder defect rate of 1,433 ppm due to the thinner plating thickness which was in the region of 2.26 μm. In summary, the investigations made have revealed imperfections in the pad plating, and it is recommended that a thicker or more even plating is achieved during the hot air levelling process at the printed circuit board manufacturing site so as to eliminate no/skipped solder defects that are induced by this printed circuit board deficiency.