An open-air brazing method for manufacturing an assembly including at least one aluminum based tube having an internal surface and an external surface, applying an Aluminum Association 4XXX aluminum based filler material to at least a portion of the external surface of the tube, disposing at least one aluminum based component adjacent the filler material, and applying a modified aluminum brazing flux to a joint between the at least one tube and the at least one component to form a precursor assembly, said brazing flux comprising cesium fluoride, lithium fluoride, or their mixture added into a potassium fluoaluminate flux in an amount of at least about 1% by weight of the modified flux. The method further comprises joining the at least one tube and at least one component together in an open-air brazing furnace whereby the temperature is raised from about 450.degree. C. to about 600.degree. C. in about 15 to 20 seconds.