Western Michigan University ScholarWorks at WMU Dissertations Graduate College 12-2014 Printing Functional Electronic Circuits and Components Ahmed Tausif Aijazi Western Michigan University, [email protected] Follow this and additional works at: https://scholarworks.wmich.edu/dissertations Part of the Chemical Engineering Commons, Engineering Science and Materials Commons, and the Materials Science and Engineering Commons Recommended Citation Aijazi, Ahmed Tausif, "Printing Functional Electronic Circuits and Components" (2014). Dissertations. 364. https://scholarworks.wmich.edu/dissertations/364 This Dissertation-Open Access is brought to you for free and open access by the Graduate College at ScholarWorks at WMU. It has been accepted for inclusion in Dissertations by an authorized administrator of ScholarWorks at WMU. For more information, please contact [email protected]. PRINTING FUNCTIONAL ELECTRONIC CIRCUITS AND COMPONENTS by Ahmed Tausif Aijazi A dissertation submitted to the Graduate College in partial fulfillment of the requirements for the degree of Doctor of Philosophy Chemical and Paper Engineering Western Michigan University December 2014 Doctoral committee: Margaret Joyce, PhD (Chair) Paul Dan Fleming, PhD Alexandra Pekarovicova, PhD Bradley Bazuin, PhD PRINTING FUNCTIONAL ELECTRONIC CIRCUITS AND COMPONENTS Ahmed Tausif Aijazi, Ph.D. Western Michigan University, 2014 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 . Copyright by Ahmed Tausif Aijazi 2014 O LORD! INCREASE ME IN KNOWLEDGE ACKNOWLEDGMENTS This thesis is the culmination of three years research conducted for my doctor of philosophy degree within the Department of Chemical and Paper Engineering, Western Michigan University (WMU). It has been an extremely good experience to work at WMU with all the people of this department. I would like to express my sincere gratitude to my erudite supervisor and examiner Dr. Margaret Joyce. Her lectures and discussions assisted me at every stage, from inception to completion. It was really enjoyable and motivating to have so much confidence in me and my work. Working together with her has been really productive and rewarding. Her guidance and supervision has opened so many new ventures for me to explore. Also, I would also like to thank my parents, back home, for providing a ‘listening ear’. I now realize that all those Skype calls might have been ‘one way conversations’ in which I was so full of all my own experiences and I might forgot about them and also not to forget, my dear wife whom I would like to thank, first for her patience and secondly for all the care and support she has given me during the course of my PhD studies. Furthermore I would like to emphasize the nice time I had with all my multicultural and multinational classmates. I really enjoyed spending time with them, sharing experiences, having delicious dinners, going to parties and all other fun stuff we had together. Thank you all! Ahmed Tausif Aijazi ii TABLE OF CONTENTS ACKNOWLEDGMENTS ............................................................................................ ii LIST OF FIGURES ..................................................................................................... vi 1 - INTRODUCTION ................................................................................................... 1 2 - BACKGROUND AND OVERVIEW ..................................................................... 5 2.1 - Printing for the manufacture of electronics ...................................................... 6 2.2 - Available Printing Technologies .................................................................... 10 2.2.1 - Non-Impact Printing ................................................................................ 10 2.2.2 – Impact Printing ........................................................................................ 12 2.3 - Gravure process for printed electronics .......................................................... 17 2.3.1 - Basic Principles of Gravure Printing ....................................................... 17 2.3.2 - Gravure Cylinder Engraving ................................................................... 19 2.3.3 - Substrates for Gravure Printing ............................................................... 22 2.3.4 - Functional Inks for Gravure Printing ....................................................... 23 2.3.5 - Challenges in Printing of Electronics ...................................................... 29 2.4 – Current status and recent advancements in printed electronics using direct gravure ........................................................................................................... 32 3 - PROBLEM STATEMENT AND OBJECTIVES ................................................. 35 3.1 – Tasks .............................................................................................................. 36 3.1.1 – Determination of limitations to the high yield gravure printing of sub 50micron lines ......................................................................................... 36 3.1.2 – Passive components ................................................................................ 36 3.1.3 – Active components .................................................................................. 37 iii Table of Contents—continued 4 - LIMITATIONS OF HIGH YIELD SUB 50µM GRAVURE PRINTING ............ 38 4.1 – Introduction .................................................................................................... 38 4.2 – Experimental .................................................................................................. 39 4.2.1 – Cylinder design ....................................................................................... 40 4.2.2 – Challenges in Rasterization ..................................................................... 41 4.2.3 – Pattern engraving .................................................................................... 42 4.2.4 - Metallic inks ............................................................................................ 45 4.3 – Results and discussion ................................................................................... 47 4.3.1 – Inks: Nano Ag vs Ag Precursor .............................................................. 47 4.3.2 – Blade types and configurations ............................................................... 48 4.3.3 – Cell Spacing A vs. D ............................................................................... 51 4.3.5 – 9 µm and 18 µm lines ............................................................................. 52 4.3.4 – K-Proofer prints ...................................................................................... 53 4.4 – Conclusion .................................................................................................. 55 5 - SCREEN