Study on Laser Welding of Dissimilar Materials between Aluminum and Copper (Ⅰ) - Research Trend in Laser Welding Technology and Materials Testing Methods -

Abstract

In the rapidly changing automobile market, the important issues in assembling electric vehicles (EVs) can be summarized as weight reduction and battery safety. For the battery manufacturing technology, welding of dissimilar materials is crucial to assure the functionality and reliability of the battery systems installed in the recently developed EVs. This paper discusses research trends in laser welding technology for joining Al and Cu, which is currently applied for the joining process in the battery pack manufacturing. Laser welding of Al/Cu is well known to be very difficult owing to the formation of brittle intermetallic compounds as well as the low absorption rate of laser beam in both Al and Cu. Thus, the energy absorption rate, optimal energy density (beam size), welding heat input, beam modulation, and laser wavelength should be carefully optimized. The quality of dissimilar Al/Cu laser welding has been assessed by evaluating tensile and electrical properties. However, no standardized testing method exists for the laser welded materials. Therefore, standards must be urgently established for the mechanical and electrical evaluation of the laser welded materials. From the tear-down analysis of commercially produced battery modules in domestic EV, the quality of Al/Cu and Cu/Cu laser welds is critically assessed. For future research, the monitoring technology for reliable real-time laser welding should be developed for the mass-production of EV battery systems with better productivity and higher reliability.

A study on the mechanical and electrical performance of Al/Cu laser multi-seam welded joints

“…Upon observing the cross-sections of the weld joints, no cracks were observed, but porosity was detected at the interface on the Al side. It is assumed that the fast welding speed and solidification speed, characteristic of laser welding, prevented hydrogen emission, resulting in porosity at the interface [18]. Additionally, it was confirmed that the higher amount of upper sheet Al melting was due to the different melting points of the two base materials [16,17].…”