: Scheel, W.; Wittke, K.; Nowottnick, M.; Ulzhofer, H.-G.

Abstract
The reflow soldering process, which has growing requirements for the purity of electronic components, is applied frequently with nitrogen as a protection gas. The nitrogen reduces the amount of oxygen in the atmosphere and leads to lower use of flux and activators. This common nitrogen technology is connected with high gas consumption, and for this reason, it is also expensive. The newly developed auto-protection gas soldering (APG soldering) works with a low boiling point liquid. This liquid is vaporized in the soldering machine. The resulting vapor displaces the air and is used as a protective atmosphere. In a convection soldering machine, the vapor is overheated up to the soldering temperature, and is also used as a carrier gas for the convection heating. In the cooling zone of soldering machines, the vapor condenses and can be transferred back as a liquid. It is therefore possible to work with a nearly closed circulation and with low consumption of auto-protection gas. Another advantage is the very good heat transition of the vapor in comparison to a dry gas. This allows smaller temperature differences on the boards during the soldering process.