Combined Laser Beam Braze-Welding Process for Fluxless Al-Cu Connections

A combined laser beam welding and brazing process for Al-Cu connections in overlap configuration is investigated. Aluminium and copper for electric and electronic application is used for experiments without surface treatment or activation, e.g. by flux. Although Al and Cu have been considered as “not weldable”, the possibility of a thermal joining process, i.e., the weld-brazing, was proved. The inevitable formation of intermetallic compounds at the interfacial region was reduced to less than 4 µm. Shear strength up to 51 MPa was achieved. A detailed fracture analysis has shown that the copper-rich intermetallic phase is the metallurgical weakest point due to the distinctive brittleness, even though the Al-rich Cu-phase is several times thicker.