Ultrasonic inspection methods for defect detection and process control in roll-to-roll flexible electronics manufacturing

Abstract

Roll-to-roll flexible electronics manufacturing technologies require new sensing and measurement capabilities for defect detection and process control. This body of work investigates the use of ultrasound, specifically Lamb and longitudinal waves, as a sensing modality and measurement technique for thin film roll-to-roll manufacturing. A variety of custom wedges were designed and machined from multiple materials to test their suitability at launching ultrasonic Lamb waves along Polyethylene Terephthalate (PET) film. Using hydrogel wedges, the fundamental antisymmetric (Ao) Lamb wave mode was successfully propagated a distance of 2 cm. ABS wedges were found to initiate longitudinal waves, which were detected at a distance of 5 cm. InstronTM based extension-tensile experiments revealed that the longitudinal wave is affected by tension in the PET, exhibited by a general increase in attenuation and a decrease in wave speed during plastic deformation; such variation may have process control applications.