Wave soldering is a mass soldering process for electronic assemblies. It can be broken down into 4 phases – fluxing, preheating, soldering and cooling. For the soldering process, the printed circuit board is carried over a flowing wave, which contacts the full underside of the board and in doing so, assures complete wetting. The contact length of the board with the wave crest is between 20 and 40 mm. At all locations on the underside of the board, where there is no solder mask, solder joints are formed.