What filler metal is used for copper-to-copper joints?

The BCuP series is the appropriate choice for copper-to-copper joints primarily because it consists of brazing alloys that contain phosphorus and other elements specifically formulated for effective bonding of copper. These fillers provide excellent fluidity and wetting properties, which help in forming strong, ductile joints without excessive oxidation. The phosphorus not only enhances the flow of the filler metal into the joint but also acts as a fluxing agent to minimize oxide formation on the copper surfaces during the brazing process, which can impede proper adhesion.

The other series of filler metals mentioned do not have the same suitability for copper joints. For instance, the BCuA series is better suited for joints that involve aluminum or brass, while the BCuZ series differs in composition and is typically used for zinc-containing metals. The BCuW series is primarily designed for welding rather than brazing, making it less appropriate for this specific application of joining copper. Thus, the BCuP series is the most effective and widely recommended for brazing copper joints due to its tailored properties and compatibility with copper materials.