Controlled atmosphere brazing is brazing in a dry, inert gas atmosphere. Mostly nitrogen is used. Argon and helium can also be used, but they are more expensive. The gas is introduced in the critical brazing section of the furnace and flows towards the entrance and exit. This prevents contamination of the atmosphere in the braze section. The process sequence of CAB depends on the type of HX being manufactured. For HX such as radiators and condensers, the most common process sequence is showed below. This is the preferred sequence as it minimizes handling of fluxed components and therefore flux drop-off:

• Core assembly
• Fixturing
• Degreasing/cleaning
• Fluxing:
  The appropriate flux is applied, usually by means of spray nozzles that ensure a homogenous distribution of the flux on the heat exchangers
• Blowing:
  Excessive flux is blown off the heat exchanger.
• Drying:
  The temperature is increased to around 250°C in order to dry the heat exchanger.
• Heating:
  The temperature of the heat exchanger moving through the heating section is raised uniformly to the target braze temperature (around 600°C)
• Brazing:
  The flux melts and dissolves the oxide film on the aluminium just prior to the filler metal melting and forming their joints.
• Cooling:
  Solidification of flux and filler metal occurs. The flux residue forms a thin, adherent film.

Due to relatively high investment costs and relative limited flexibility in running production, CAB is most suitable for large series numbers.