Thermoplastic based system-in-package for RFID application

The embedding of ultrathin components in printed circuit boards has evolved into a production technology which is used worldwide. Many recent projects have shown the wide range of applications which include RF circuits and power electronics. The scope of this paper is to show the potential of using thermoplastic material, e.g. Polycarbonate, instead of FR4 by demonstrating the realization of a complex multifunctional security device. The basic technologies are similar to conventional flex manufacturing with only a few modifications due to the properties of the polymer. In the first step, copper foils are laminated onto the polymer foil and structured. Subsequently ultrathin chips (30..150 μm) and thin passive components (150 μm) can be assembled either face up or face down. Face up assembly requires interconnection by vias similar to Chip in Polymer technology. Face down assembly using adhesive technologies leads to a complete functional inlay. Then the next layers are laminated and structured. Vias are filled by electroplating. This process flow allows the production of simple RFID modules but also complex multilayer devices. As an example a contactless security device with 4 chips, a sensor array and an OLED-display is shown. The final assemblies are as thin as standard smart cards and mechanically flexible. First reliability results for thermomechanical, climate and mechanical tests are shown. FEM modelling and simulation results have been achieved for the embedded thin chips so that the stress distribution can be determined and compared to the experimental results.