Detectability of Penetration based on Weld Pool Geometry and Process Emission Spectrum in Laser Welding of Copper

Laser welding is a promising joining process for welding of copper interconnections. A key criterion of weld quality is the penetration depth. This paper presents the investigation of the change of weld pool contour and process emission spectrum of copper due change of penetration. Bead-on-plate welds with varying work piece thickness were monitored online with illuminated imaging of the weld pool and spectrometry. During full-penetration a 50% elongation of the weld pool in the welding direction was observed. The results indicate that weld pool contour is a viable quantity to detect full-penetration.