Smart RFID label printed on PET substrate with CMOS sensors

The present work shows the fabrication of a printed RFID label using large-area printing processes, such as roto-screen and stencil printing, and the integration with advanced assembly methods of CMOS-based humidity and temperature sensors. The fabrication of the antenna and the PCB on flexible plastic substrates (i.e. polyethylene terephthalate - PET) was performed by means of roto-screen printing in combination with flash photonic sintering. This allows a high thermal transfer to the printed material, which is necessary for its sintering, while preserving the delicate polymeric substrate. Cost-effective and low temperature methods are also developed for the assembling of the components onto polymeric substrates. The electrical interconnections were stencil-printed with isotropic conductive adhesives by using laser-ablated stencil masks on polymer foils. Additionally, the label incorporates an RF remotely rechargeable thin film battery which is used for data logging. Finally, the roto-screen printing of copper oxide patterns and their reduction to copper by means of a Xenon flash photonic process is presented.