Tailored absorptivity: Increasing the laser weldability of copper through surface structuring

Abstract

To increase the capability to weld copper using laser radiation, Direct Laser Interference Patterning is used for producing different surface textures with increased optical absorptivity. Depending on the depth of the produced patterns, the absorptivity of copper for a laser wavelength of 1070 nm was almost trebled from 4%, corresponding to a polished flat reference surface, to 11.3%. The last value equals the absorptivity of liquid copper, which permitted to obtain a temporally homogenous temperature distribution during the welding process, independently of the material temperature as well as material phase. Corresponding welding trials showed an increased stability and a continuous weld seam cross section using fiber lasers in the infrared.