Meaning
Distortion of a laser beam’s profile caused by temperature-induced refractive index gradients within the focusing optics. Thermal lensing degrades the precision of high-power laser welds on cell tabs and busbars. The effect occurs when high-power laser welding heats up the protective glass cover and focusing lenses.
Welding Failure
Loss of focus leads to a wider laser beam spot with lower power density at the workpiece surface. This reduction in power density can cause incomplete weld penetration or cold weld joints. These weak joints can fail under the mechanical stress and vibration experienced during vehicle operation.
Diagnostic Approach
Real-time weld monitoring systems and periodic laser beam profiling measure these focal shifts on the assembly line. Sourcing contracts for laser welding equipment require specific lens materials and cooling systems to minimize this thermal effect. Using quartz optics and active nitrogen cooling helps to stabilize the focal spot.
Production Optimization
Maintaining a clean lens cover prevents spatter and dust from absorbing laser energy and initiating the thermal distortion. Sourcing specifications require automated cover glass changing systems to ensure consistent weld quality over high-volume production runs. This preventive measure reduces scrap rates and maintains high line yield.
It also minimizes the need for manual inspection of weld joints.
