WAVE SOLDERING USING INERT GAS TO PROTECT PRETINNED AND SOLDERED SURFACES OF RELATIVELY FLAT WORKPIECES

摘要

Relatively flat workpieces, such as printed circuit boards, are pretinned and soldered using the wave solder technique in which molten solder is forced upwardly through a nozzle to form a standing wave of molten solder which is gently curved in a direction parallel to the work travel direction. A flat workpiece is moved in the work travel direction with its undersurface in contact with the standing wave and, as its forward end emerges from the wave, it defines, with the surface of the wave, a space. Inert gas under pressure is supplied to this space to exclude air from the solder coated undersurface of the workpiece to inhibit oxidation thereof. The disclosure apparatus includes a nozzle for forming a one-sided standing wave, and a second nozzle is positioned above and extends in the same direction as the solder wave-forming nozzle. The second nozzle is supplied with the inert gas under pressure to be discharged over the surface of the standing wave of solder, with the inert gas flowing over the undersurface of the workpiece and exiting at the side edges thereof.