Soldering aluminium can be simple, but has a couple of critical areas that require strict process control. Tenacious aluminium oxide makes most soldering processes with conventional means difficult. In addition, care must be taken when choosing the metal mixture. Aluminium alloys, meters and temperature often show very varied soldering results. Before commencing an order, it must be carefully studied how aluminium accepts or rejects heat during soldering.
Soldering can be done with soft solder (Sn-based, low temperature) or hard solder (Zn-based, high temperature) and with appropriate fluxes that suit the processing temperatures. Soldering is by definition a low-temperature joining process. Therefore, less deformation of the component is expected with aluminium soldering than with soldering, welding or other melt bonding processes. Soldering temperatures of 225 to 490°C are way below the aluminium melting temperature of 661°C, although 490°C is above the glow point.
Different aluminium alloys have different solderability: 1xxx, 2xxx, 3xxx, 4xxx en 7xxx are easier to sold than alloys from the 6xxx-series. Due to their magnesium content, alloys from the 5xxx-series are most difficult to solder.
Due to the high thermal conductivity and reflectivity of aluminium, the heat source must be custom-made.