When wave soldering boards populated with SMT components, these components can impede the laminar flow of the main wave. This is the reason for the occurrence of opens, that is, unsoldered joints on the SM device. To over come this and to safely process boards with SM devices, very dynamic press-solder waves are installed, whose main purpose is to wet the pads and the leads. Excessive solder that may be found on these wetted leads is afterwards removed again by the main wave. The terminology dual wave soldering refers to the fact that two solder nozzle / solder wave are used in this process.