Avoiding the formation of pores during laser welding of copper hairpins by dynamic beam shaping

Abstract

Any pores formed during laser welding of copper hairpins affect the structural integrity and the mechanical/electrical functionality of the joint. We report on investigations using synchrotron X-ray imaging techniques to observe the formation of the pores in the processing zone while welding. It was found that all pores are formed at the joint gap and that the small pores are distributed throughout the complete joint volume as a result of the melt flow induced by the movement of the laser beam. This insight has led to the development of a welding strategy that minimizes pore formation by avoiding the movement of the laser beam across the joint gap. This was achieved by rapid beam shaping based on coherent beam combining (CBC) technology.