Suitability of a 2 kw 515 nm Continous Wave Laser for Deep Penetration Welding of Copper

With advancing electromobility the demands regarding electrically conductive copper connections are increasing. In order to withstand the critical conditions in an electric traction motor the connections have to be stable and of high quality. Welding is a possible method to produce material bonded joints that, while fulfilling the requirements regarding electrical conductivity and mechanical stability, also allow for an increased integration density and reduced construction space by substituting screw connections. Especially laser welding offers a flexible, fully automatable approach while only needing single-sided optical access to the welding spot. While being an established industrial process, the joining of copper via laser-welding is still classified as difficult. The high thermal conductivity and low absorptivity of copper for infrared wavelength is challenging for a stable welding processes and sensitive to different material properties like material thickness, oxidation and roughness. Green wavelengths have significantly higher absorption rates at room temperature and are less sensitive to absorption-dependent material properties. The advantages are clearly visible in heat conduction welding applications. If these advantages are also applicable to a deep penetration welding process is investigated in this paper. The results are compared with weld seams produced by state-of-the-art industrial infrared lasers.