The optimization of laser welding parameters for welding of Hilumin®-copper using Taguchi method in electric vehicle battery pack manufacturing

In the automotive industry, the increasing popularity of electric and hybrid vehicles requires an efficient and rapid joining process for the fabrication of electrical interconnects within battery packs. The selection of tab and busbar materials for these electrical interconnects is dependent upon a number of factors, including weldability, weight, electrical and thermal conductivity, and cost. The laser welding joining method has become the preferred technology in the automotive industry due to its high efficiency and relatively short cycle times. The present study investigates the feasibility of laser welding of copper to Hilumin® for cell-to-tab joints in Li-ion battery packs. The effects of welding parameters such as laser speed, laser power, and amplitude on the weld seam were examined, and the process parameters were optimized using the Taguchi method. Initially, copper and Hilumin® sheet materials were joined by laser welding. Subsequently, the electrical resistance of the welded samples was measured, followed by shear strength measurements using a tensile testing device. The optimizations conducted in this experimental study have enabled the determination of the laser welding parameters that achieve the lowest electrical resistance and the highest mechanical strength. The lowest values for electrical contact resistance and the highest mechanical strength values for battery interconnection joints were achieved when a parameters combination of 850 W laser power, 1.14 mm amplitude, and 6.4 m/min laser speed was employed. The application of the optimal parameter combination in the production of battery interconnection joints resulted in a maximum weld seam strength of 123.34 MPa and a minimum electrical contact resistance of 0.360 mΩ. The obtained results in this study, indicate that laser amplitude plays a crucial role in influencing weld seam geometry, microstructure, mechanical strength, and electrical contact resistance. Increasing the laser amplitude also increased the strength of weld connection.