Date of Award
Doctor of Philosophy
Chemical and Paper Engineering
Dr. Margaret Joyce
Dr. Paul Dan Fleming
Dr. Alexandra Pekarovicova
Dr. Bradley Bazuin
The purpose of this study was to investigate the challenges in printing reliable multilayer flexible circuits, devices and components. Gravure was used as the primary printing process for this work, but due to some limitations of gravure, other printing methods were also investigated. At first a systematic study was done to determine the optimum parameters for the gravure printing of sub 50 micron lines. Commercially available silver nanoparticle inks were printed on a lab scale gravure printer, Accupress®. The highest resolution line that was electrically conductive was 36μm wide. The 9μm, 18μm and 27μm lines were printed but were not repeatable, nor conductive. The failure of these lines to conduct was due to the excessive amount of blade pressure required to remove streaking. At such high pressures, ink was wiped-out from the cells reducing the volume of ink transfer. These problems were found to be associated with the design of the inking system on the Accupress which is a non-conventional design and does not represent commercial practice. The press was specifically designed for printed electronics applications.
After investigating the printing of fine lines, printing of passive components was studied. Due to the inability to attain sufficient electrical performance with gravure printing process, screen printing was used to fabricate inductive coils. Copper based ink was used to print the coils. Even though suitable curing was not achieved mathematically calculated results show a promising future of copper based inks. To extend the study to other passive components, capacitors were printed using silver based inks. The thickness and quality of two layers of conductive material separated by a thin layer of insulating film defines the performance of the final device. After successful printing of capacitors they were electrically characterized and yields were measured. Although this work was done with a limited material set, the trends discovered can be extended to other ink sets.
Next, organic light emitting diodes were printed using multiple printing methods to enable the benefits of each process. The biggest challenge was to form a uniform, pinhole free film. Polymers were dissolved in solvents and other additives to make them printable. To compare and verify the functionality of the OLED structure all layers were also spin coated. Improved performance of the printed device was observed compared to spin coated devices due to smoother and thinner emissive polymer layers. The printed polymer layers were flat and uniform over relatively large area suggesting the use of roll-to-roll manufacturing for thin film based OLEDs is possible .
Aijazi, Ahmed Tausif, "Printing Functional Electronic Circuits and Components" (2014). Dissertations. 364.