Lötbad

Lötbad, literally “solder bath” in German, is a reservoir containing molten solder used to join metals or to apply a tin coating. In electronics manufacturing, solder baths are used for dip soldering and as the source of solder in wave soldering. The bath typically contains tin-based alloys, historically lead-containing solders such as Sn-Pb 63/37, now increasingly replaced by lead-free alloys like SAC305. Flux is applied to improve wetting and prevent oxidation; some baths incorporate flux within the solder, while others rely on prefluxed parts. The bath is heated and maintained at temperatures above the alloy’s melting point, often in the range of roughly 180–230°C for lead-free solders.

Process-wise, dip soldering involves immersing components or boards into the molten solder to form joints, while wave soldering uses a controlled solder wave created by pumping solder through a nozzle. Lead-free systems typically require more careful temperature control and dwell times to ensure reliable joints and minimize defects such as solder bridging or tombstoning.

The Lötbad is also used in metal finishing to tin surfaces, such as tinning copper wires or tinplate steel. Maintenance includes skimming dross, filtration, and periodic chemistry adjustments to keep the alloy composition within specification. Safety considerations include handling molten metals, venting metal fumes, and proper disposal of lead-containing waste in accordance with environmental regulations.