Pasty flux for soft soldering in electrical engineering and electrical appliance construction. Halogen-containing flux paste for soft soldering in electrical engineering, in electrical appliance construction and, to a limited extent, in electronics. The solder paste is very suitable for soldering or tinning work that has to be carried out under high soldering temperatures and long soldering times. The formation of soldering spigots is completely prevented by this flux. The flux residues are non-corrosive. Can 20g with screw cap.