Enhancing process stability in infrared laser micro welding of copper using frequency converted short prepulses

We combine a frequency converted nanosecond laser pulse (prepulse) with a millisecond IR laser pulse improving reliability in copper spot welding significantly: The coefficient of variance of the spot weld diameter is decreased to 2% and the weld probability is increased to 100% in a wide parameter range. Additionally, when using the prepulse, the required IR pulse power can be reduced by more than 30% while the energy contribution of the prepulse (mJ-range) is negligible compared to the energy of the welding pulse (J-range). The prepulsing is carried out with a prototype of a small and robust laser module.