Over Printing

Over printing is a term used in the Through-Hole Reflow / Pin-in-Paste technology. To fill the complete plated through hole with solder, large amounts of paste need to be printed on to the pads. The reason for this is that the metal content (i.e. the volume) of the paste is only by around 50%. Since the pad area is of a given size and usually not large enough for the total volume required, over printing, placing paste beyond the immediate pad area, is the chosen method. Overprinting, though, is critical, since the full amount of paste has to flow back during melting on to the pad. If the paste separates during the pull-back, solder balls remain.