Advanced Process-Property Characterization of Additively Printed Flexible Hybrid Electronics (FHE)
Type of DegreePhD Dissertation
MetadataShow full item record
Printed Electronics (PE) is a constant evolving and growing technology that shows a tremendous potential for the future of electronics. Advancements in PE processes demonstrates its viability to fabricate electronic circuits simply by deposition of functional materials (conducting, semi-conducting, insulating), resulting in fewer number of process steps and cost-effective as compared to conventional photolithography. On one hand, conventional way of fabrication consists of multiple steps, including photoresist deposition, thin film vapor deposition, etching, masking, while on the other hand, PE consists of material deposition followed by post-treatment to activate the ink functionality. Furthermore, PE has provided pathways for flexible, stretchable electronics, as well as deposition on irregular surfaces, that are beyond the capabilities of conventional technology. PE also provides economic benefits compared with conventional due to reduced material wastage and its ability to readily scale to large-area production with much higher throughput via roll-to-roll techniques. With all the benefits and cost-effective advantages, PE proves to be an attractive technique for its integration in the electronics manufacturing lines to fulfill the ever-increasing demand of smaller, flexible, and more complex circuits required in new upcoming novel applications. In this study, state-of-art printing technologies are utilized to develop process-property relationships that are often neglected, kept proprietary, or not reported. The strict demand from PE industry necessities uniform, smooth, and fine features with high resolution that is comparable, if not greater, to conventional techniques and with properties close to the bulk material. With printing technologies and their complex mechanisms, there are various process parameters that work together to provide the required print with very fine resolution. Effect of these parameters on the printed features, along with the properties of the material, are investigated. The printing techniques consists of direct-write technology that consists of non-contact deposition. These include Aerosol Jet and Inkjet to deposit functional materials on a flexible substrate. Apart from these, screen-printing, that is another additive technology, a contact deposition, is also utilized to understand the process-property relationships. Using the process-property relationships, various applications of printed electronics are developed including printed sensors, multi-layer substrates with additively printed “donut” micro-vias, functional circuits. Surface Mount Devices (SMD) interconnections are also achieved with commercial-off-the-shelf (COTS) discrete components on additively printed metal pads. With each of the printing technique, detailed investigation is provided involving the steps taken involving pre-print, during the print, and post-print for fine feature definitions. Considering the printing mechanism is different for each, process parameters are quantified and their effect on physical, electrical, and mechanical properties of the material are presented. Various materials and different types consisting of both, conductive and insulating, are utilized and compared with each other in terms of feature definition and process parameters. Additionally, much time is spent initially to optimize the parameters based on the user definition. To that end, statistical modeling is utilized to develop regression models for help in prediction of certain features such as printed line width, electrical property, and other physical characteristics. Sustainability is another important aspect of printed electronics where the carbon footprint of printed materials should be minimal. To implement this, water-based printing inks are used and benchmarked against the inks containing volatile solvents such as ethanol, ethers that are harmful for the environment and should be avoided.