In situ synchrotron observation of the vapor capillary geometry in laser welding of copper with 1030 nm and 515 nm laser beam sources

Laser welding as a tool for manufacturing highly precise parts for electronic and electro mobility components is gaining worldwide importance. The precise control of energy input is one paramount challenge of welding highly reflective materials with high thermal conductivity such as copper and its alloys. Laser beam wavelengths in the visible range show an increase in absorptivity from < 5% (1030 nm) to >= 40% (515 nm) on copper at room temperature and open new options in material processing technologies. This paper presents the in situ observation of laser welding processes on Cu-ETP and CuSn6 with laser beam sources of 1030 nm and 515 nm wavelength using synchrotron radiation at DESY Petra 3 Beamline P07 EH4. The influence of laser power from 1 kW up to 4 kW and feed rates from 50 mm/s up to 500 mm/s on vapor capillary geometry and dynamics with same focal diameters is compared. For the investigations, a synchrotron beam of 2x2 mm(2) in size with a photon energy of 89 keV is used for investigation. The material samples are analyzed by means of material phase contrast method to show boundaries between solid, liquid, and gaseous material phases. It is found, that both welding processes show a different geometry of the vapor capillary. A different sensitivity to changes of the feed rate of the welding process is observed. The vapor capillary of the 1030 nm welding process tends to be more sensitive on feed rate changes while showing an overall better weld seam quality. When welding with 515 nm, comparatively higher feed rates lead to better welding results.