Impact of Silver Ink Material Properties on Performance of NFC Antennae Printed on Flexible Substrates
Over the recent past, the technology of flexible printed electronics has gained significant traction as it promises lower manufacturing costs, reduced weight, higher efficiency, and allows integration of electronics into other structures. Apart from the substrates, the building of these flexible electronic circuits requires a number of functional materials (inks) such as conductive inks, dielectric inks, resistive inks, etc. There are quite a few ink deposition techniques, but screen-printing is one of the most reliable and cost-effective application methods for flexible printed circuits/antennae. Of the several components/parts that can be produced by printing a combination of these functional inks on suitable substrates, RF/NFC antennae can be easily printed and integrated into a circuit design. In this work, we report a study of three conductive silver inks, including their uses and limitations of printing an antenna for near field communication (NFC) applications. The first part of the study presents a detailed DOE to understand the screen printability and limits of the process window for each ink. One of the key attributes of an antenna is its quality factor (Q-factor). In addition to the design of an inductor coil and the capacitances of the chip and other parts, the resistance of the printed traces is a key factor. The inherent electrical conductivity of the ink and limits of its printability determine the range of resistance that can be achieved. The second part of the study will present a comparative study of the three silver inks; their impact on antenna performance and the limitations that the material properties of the inks pose to the size and design of an antenna.