Excessive Porosity in Laser Welding of Highly Reflective Metals? Multi-Wavelength Hybrid Welding Parameter Optimization

Industry Background: Process Bottlenecks in Copper-Aluminum Welding

In new energy vehicle power batteries and 3C electronics industries, demand for copper-aluminum dissimilar metal welding has surged. However, copper material exhibits reflectivity exceeding 95% for near-infrared lasers (1064nm), causing frequent issues including excessive porosity, severe spattering, and poor weld formation. One power battery manufacturer reported porosity rates of 8-12% in aluminum casing to copper tab welding, resulting in cell yield rates of only 87%—far below the industry standard of 95%.

Technical Principles of Dual-Wavelength Hybrid Welding

United Winner Laser's self-developed multi-wavelength coaxial hybrid welding head combines fiber laser (1070nm) with diode laser (915nm/940nm) through spatial beam combining. The shorter wavelength laser preheats to reduce material reflectivity, while the main welding laser achieves deep penetration keyhole effect, improving energy coupling efficiency to over 30%. Measured data shows copper welding spatter particle diameter reduced from 150-200μm in traditional processes to 20-30μm, with porosity controlled within 0.5%.

Critical Process Parameter Windows

For copper-aluminum overlap welding of 0.3-2.0mm thickness, recommended welding speeds are 200-300mm/s, laser power ratio (fiber:diode) of 7:3 to 8:2, and defocus of +2 to +4mm (positive defocus expands spot size, reducing power density). Shielding gas uses high-purity argon (≥99.999%), flow rate 15-25L/min, with side-blowing angle of 30-45° effectively suppressing plasma shielding effects.

Welding Quality Verification and Process Monitoring

United Winner Laser's integrated Real-time Weld Depth (RWD) detection system achieves micron-level precision in penetration online monitoring through optical coherence tomography. The system captures keyhole depth fluctuations at 10kHz sampling frequency, with AI algorithms real-time identifying precursors of pores and lack-of-fusion defects. One leading power battery customer reduced welding station defect escape rate from 3.2% to 0.15% after implementation.