18 March 2016 High-power CW and long-pulse lasers in the green wavelength regime for copper welding
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Abstract
We report on industrial high-power lasers in the green wavelength regime. By means of a thin disk oscillator and a resonator-internal nonlinear crystal for second harmonic generation we are able to extract up to 8 kW pulse power in the few-millisecond range at a wavelength of 515 nm with a duty cycle of 10%. Careful shaping and stabilization of the polarization and spectral properties leads to a high optical-to-optical efficiency larger than 55%. The beam parameter product is designed and measured to be below 5 mm·mrad which allows the transport by a fiber with a 100 μm core diameter. The fiber and beam guidance optics are adapted to the green wavelength, enabling low transmission losses and stable operation. Application tests show that this laser is perfectly suited for copper welding due to the superior absorption of the green wavelength compared to IR, which allows us to produce weld spots with an unprecedented reproducibility in diameter and welding depth. With an optimized set of parameters we could achieve a splatter-free welding process of copper, which is crucial for welding electronic components. Furthermore, the surface condition does not influence the welding process when the green wavelength is used, which allows to skip any expensive preprocessing steps like tin-coating. With minor changes we could operate the laser in cw mode and achieved up to 1.7 kW of cw power at 515 nm with a beam parameter product of 2.5 mm·mrad. These parameters make the laser perfectly suitable for additional applications such as selective laser melting of copper.
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Sebastian Pricking, Sebastian Pricking, Rudolf Huber, Rudolf Huber, Konrad Klausmann, Konrad Klausmann, Elke Kaiser, Elke Kaiser, Christian Stolzenburg, Christian Stolzenburg, Alexander Killi, Alexander Killi, "High-power CW and long-pulse lasers in the green wavelength regime for copper welding", Proc. SPIE 9741, High-Power Laser Materials Processing: Lasers, Beam Delivery, Diagnostics, and Applications V, 97410G (18 March 2016); doi: 10.1117/12.2213293; https://doi.org/10.1117/12.2213293
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