Power modulation to stabilize laser welding of copper

Due to its high electric and thermal conductivity, copper has a wide range of applications. Many of those require an efficient and reliable welding process most preferably performed with laser beams. The low absorptivity of copper at a wavelength of 1 μm together with its high heat conductivity however make remote laser welding of copper a challenging task. With the currently commercially available lasers, welds with penetration depths of several millimeters in copper can only be achieved at comparatively low welding speeds (v < 10 m/min), which, however, leads to numerous defects such as melt ejections and pores. In this paper, we discuss the approach of laser power modulation to stabilize the welding of copper. It is demonstrated that the modulation of the laser power with the appropriate parameters significantly improves the weld quality. The influence of the average power, the modulation amplitude, welding speed, focal diameter, and modulation frequency on the welding quality is discussed.