Are copper-to-copper joints allowed to be made using a copper-phosphorus brazing filler metal without flux?

Copper-to-copper joints can indeed be made using a copper-phosphorus brazing filler metal without the need for flux. This is due to the inherent properties of the copper-phosphorus alloy, which contains phosphorus that acts as a fluxing agent. Phosphorus helps to clean the surfaces of the copper during the heating process, thereby promoting better bonding and flow of the brazing material.

The ability to join copper without flux simplifies the brazing process, as it reduces the number of materials required and minimizes preparation time. This method is particularly useful in applications where flux residues may be problematic, such as in plumbing and refrigeration Systems.

For clarity, while other methods of joining copper, such as with traditional silver solder or when using other types of filler metals, may require the use of flux to ensure a reliable joint, the specifics of using copper-phosphorus filler create a unique scenario where it is not necessary. This allows for a cleaner result, avoiding potential issues that can arise from residual flux.