Lehrstuhl für Fertigungstechnologie, Universität Erlangen-Nürnberg

Closed loop control for laser micro welding in electronics

Datum: 11.02.2002



  • Prof. Dr.-Ing. M. Geiger
  • Prof. Dr.-Ing. F.-W. Bach, Universität Hannover

The demand for miniaturised spot welds especially of copper and its highly conductive alloys is rising fast in electronics production. The realisation of such weld situations is, in most cases, even with optimised parameters, hard to implement. Thus an effective process control for rejecting defective goods is needed in the case of a low added value; for a high added value a closed loop real time control helps to prevent rejects. For the methods of real time process control for intrinsic transient processes a lack of knowledge has to be stated. Therefore defined problems inside this topic are investigated. At first, a setup is built that allows a real time pulse power control via a digital signal processor to test different control algorithms. A multi-sensor-setup is used to detect process states in experiments concerning a control of the interaction position and a pulse power control in real time. The examination of the process emissions uses analysis in the time domain with feature extraction, different signal transformations, heuristic criteria and a statistical model to correlate signals with process states or weld quality. The miniaturisation of the interaction zone is likewise examined theoretically and practically in its impact on the process stability. For the geometry fillet weld experiments are carried out that proof a detectability of selected parameter deviations. The whole work offers results which enable, in several cases, a direct implementation and a better knowledge about the process and its control.