Optimization of silver paste printed passive UHF RFID tags

Passive UHF (Ultra High Frequency) RFID (Radio Frequency Identification) is a promising technology for products tracking in logistics or routing packages in supply chain. Usually, the UHF RFID antenna is made by etched copper, or aluminum. These etching process introduce chemical wastes during the etching process. Recently, printing silver paste becomes popular due to its environmental friendly manufacturing process. However, there are two drawbacks on printed silver paste RFID antenna. One is low conductivity compared to metal and the other is the high material cost. In this paper, we exam the effects of printing thickness on the performance of UHF RFID tags and summarize the optimized thickness for different read range requirements. A commercial conductive silver paste is printed on PET film as RFID tag antennas. Both finite element simulations and experiments are conducted to evaluate the effects of printed thickness. The simulation results presents that the 10 um thick RFID antenna exhibits relatively good radiation efficiency. The results indicate that 10 um thick RFID tag antenna presents the minimum turn-on power of 18 dBm to 22 dBm which is enough for most applications. The simulation and measurement results present that thinner printed silver paste RFID tag antenna is a potential solution for low cost UHF RFID tags. The cost of these tags could be lower than current etched Al/Cu RFID tags because of material saving.