Effects of different laser wavelengths on process performance and weld seam properties in copper processing for electric vehicle applications

Abstract

Modern battery and e-drive production requires the material bonding of copper enabling highest power densities to be transmitted and functional integration to be increased. Laser beam welding has become an established manufacturing technique in this sector in recent years due to its flexibility and reproducibility. Near infrared laser beam sources are often used for the copper welding applications, as these are broadly available and proven equipment from car body manufacturing. However, they reach their limits when processing highly reflective surfaces, as the low absorptivity of copper in this wavelength range can lead to unstable incoupling or back reflection issues. The use of visible laser radiation, which is available with brilliant beam quality and kW output power at 515 nm, is an appropriate strategy to overcome these challenges. Recent studies reported on altered energy coupling and changed defect formation. However, the question of a targeted application of a green or near infrared laser system in copper welding is rarely addressed in comparative analyses in literature.

In this work, an experimental comparison was performed using two disk lasers of 515 nm and 1030 nm wavelength with similar spot characteristics in order to investigate this topic from the perspective of both seam properties and efficiency. Experimental investigations are combined with analytical models, to reveal benefits of each wavelength in copper welding for a wide range of processing parameters. The results underscore the effectiveness of green laser radiation for heat conduction welding and small capillary aspect ratios. Additionally, observed wavelength-related differences in the seam properties affect the efficiency metrics.