Remote Laser Welding (RLW) of battery tab connectors presents a critical challenge: (1) weldability of dissimilar thin metal components; and, (2) in-process measurement of weld penetration depth as a vital indicator of the weld quality and safety, including electrical continuity, thermal conduction and joint strength. The paper addresses the above challenges challenges by (i) developing welding process parameters for Al-Cu thin foil lap joint (Al 1050 foil 450 μm and nickel plated Cu foil 300 μm) using novel Adjustable Ring Mode (ARM) laser; and, (ii) integrating Optical Coherence Tomography (OCT) with two measuring beams, targeting keyhole bottom and parts surface (TwinTec technology).

The methodology is underpinned by the “Keyhole Mapping” approach which helps to identify the optimal placement of the OCT beam position with considerations to both measurement accuracy and repeatability of the weld penetration depth. Findings indicated that welding with the ARM laser results in more stable process, reduces fluctuations of keyhole opening and, therefore, helps to improve the measurement accuracy by a factor of 50% (from average error of 0.22 mm to 0.11 mm). Results further identified that the feasible measurement window (corresponding to the highest measurement accuracy) of the OCT beam position is only 20 mm in length.