Autogenous Laser welding of copper to aluminium

This work investigates laser joining of copper sheets to aluminium in overlap configuration. Dissimilar Cu-Al connections are widely used in the electrical and electronics applications e.g. battery and solar panels.Joining these materials is a very critical assembly process. The laser welding from the aluminium surface to copper (Al-Cu) is well described in the literature .But there is no data concerning the laser seam welding from the copper side to join with aluminium i.e Cu-Al.The selection of aluminium surface to irradiate is mainly because of poor absorption of copper to laser in IR region.But high intensities of about 100 MW/cm2 allow for initial vaporization of copper surface.Once the keyhole is generated, absorption of laser light is improved.Thereby high power lasers allow for successful penetration of copper surface to produce a joint with aluminium.
The main objective is to investigate the approach of dissimilar laser welding starting from the copper surface to aluminium.The effect of process parameters on the shear force, microstructure and weld pool dimensions are studied.An experimental design is realized to see the effect of laser irradiation of copper surface (Cu-Al) in contrast to aluminium surface(Al-Cu). The selection of aluminium or copper surface is mainly dependent on the laser power.With the high power disk laser the possibility of joining from the copper side was evident and results of joining copper to aluminium and aluminium to copper are comparable.Therefore welding from a highly reflective surface to achive a comparable shear strength is demonstrated.