Brazing is a joining process in which similar or dissimilar materials are joined together by melting a filler material between them. The assembly should be heated above the liquidus of the filler materials but below the solidus of the parent materials. Brazing and soldering are differentiated by the temperature of the process. Soldering process is performed at a temperature below 450°C whereas brazing is carried out at a temperature higher than 450°C
When the filler material reaches the brazing temperature, it wets the surfaces of the two materials to be joined, and then it flows by capillary action into any gap. To ensure wetting of the filler onto the parent materials, the surfaces have to be free from oxides or contaminants. A flux material can be used to prevent the formation of oxide on the faying surfaces. Alternatively, a controlled atmosphere on vacuum can be used to minimise or remove flux requirements.