The invention relates to a machine for wave soldering or tinning comprising a solder reservoir (9); means that can form at least one solder wave with a so-called laminar form (8b); a conveyor system (2) that can bring a piece (1) to be soldered or tinned into contact with said laminar wave; and means for injecting (12) a gas in the vicinity of the wave; characterized in that the said injection means includes an injector located in a position adjacent to and downstream from the wave and provided with a wall (17) facing the solder wave, wherein the wall of the injector has at least a first group (15) of openings positioned so as to provide a first gas jet directed toward the flat surface of the solder wave.