Flexible and even stretchable electronic devices are showing more and more growth in interest in the field of printed electronics. Various kinds of material classes, like conducting, semi-conducting and insulating materials are used to manufacture multilayer devices, such as transistors and capacitors. One of the key components is the conductive layer, in the easiest way a resistor or contacts for diverse connections. Within the last years these metallic layers, e.g. silver copper or gold, were optimized regarding their morphological and electrical performance. On main step next to the printing process is the post-treatment, which forms in printed electronics a solid conductive structure out of the liquid printed films. New methods of selective sintering, using for example infrared (IR) radiation, microwaves or intense pulsed light (IPL) open the opportunity to form conductive metallic layers on even temperature instable substrates like polymeric foils. However, these post-treatment methodologies require detailed studies to obtain optimal results regarding the performance without damaging the base-substrates. For this purpose this research includes a detailed study on the novel method of IPL sintering technology. Various nanoparticle silver inks are inkjet printed on thin Poly(ethylene terephthalate) [PET] foil and post-treated with intense pulsed light to form conductive metal layers. It is shown, how to adjust the IPL flashing parameters depending on the silver ink to achieve highest conductivities without defects in the printed silver layers and the PET substrates.