Quality control of printed electronics using terahertz radiation

Abstract

Graphic printing and electronics production are two high volume manufacturing technologies. Their combination brings a new fabrication technique and unique form of electronic applications. Printable electronics (PE) is a new advanced manufacturing technology that enables lower-cost fabrication for large-volume production of electronic devices. PE is a promising, environmentally friendly alternative route to produce display or energy products at a low cost and with new possibilities like flexible devices. One of the main challenges of this new technology is to scale it up to the industrial level. For the successful industrialization of this technology, reliability, and repeatability in both equipment and processes should be provided using efficient quality control. Currently, quality control is assessed manually or using well-developed laboratory techniques, which could be destructive or more time-consuming. To apply these methods in a production line, the specific conditions such as an appropriate illumination, a particular direction, a specific speed production, or even a cleanroom environment must be considered. These severely restrict the value of PE as an industrial manufacturing technique and requires developing an efficient in-line characterization technique to control the quality of fabrication process. This work focuses on studying and developing terahertz time-domain spectroscopy (THz-TDS) as a characterization tool for the quality control of printed process. During the last decade, THz-TDS has received a lot of attention due to its contactless, non-destructive, high-resolution, non-invasive abilities for quality control. In non-destructive testing of materials, quality control is often based on sampling the condition of a production line. To ensure THz light interacts with the printed conductive materials, we introduced a simple strategy using THz metamaterials as a printing quality control bar (QCB). To prove our idea, we printed QCBs using two types of printing techniques, which demonstrates the potential of using continuous roll to roll printing to manufacture functional printed devices. Our work employs QCBs in the same way that a test pattern is indispensable for quality control using offset color printing. In offset printing, the printed area of the control structure is around a 1 cm2. Our concept is quite similar. In the framework of this thesis, two types of metamaterials have been designed and studied for the tracking of printing quality : geometrical variation and conductivity. Implementation of metamaterials as a quality control structure is one of the possible solutions for an in-line and in-situ process monitoring in industrial production environments and a route to closed-loop control the quality.

Date	25 Jun 2021
Original language	American English
Awarding Institution	École de technologie supérieure
Supervisor	François Blanchard (Supervisor) & Ricardo J. Zednik (Co-supervisor)