High-speed non-contact sheet resistivity monitoring of printed electronics using inductive sensors

Abstract

An increase in the market growth of conductive inks for flexible and printed electronics is predicted to increase from $2.3 billion to $3.2 billion by 2025 (Savastano 2015 Printed Electronics Now). For quality and process control, in order to maintain output yield and reduce waste, it is critical that we are able to verify the electrical properties of printed electronics. This work explores a non-contact technique developed to measure the electrical properties of the printed structures during manufacture in a roll-to-roll process. Inductive sensors are used to measure the electrical response of electrically conductive printed samples. The impedance of the inductive sensors are affected by the eddy currents induced in the printed samples. Six sensor designs, each operating at a unique measurement frequency are discussed. The effect of the measurement frequency on the measurement of a variety of samples with varying values of sheet resistivity is investigated. For implementation into a roll-to-roll process, the system must operate at high speed, therefore a low-cost method to achieve this is introduced and demonstrated.