Metrology and Characterization of Electrically Conductive Filaments (ECF) for Fused Deposition Modeling (FDM).

Abstract

Current electronics manufacturing is composed of several processes, usually with a high energy, space and knowledge footprint costs to produce a working product. The product is assembled from subcomponents such as the PCB, case and peripherals among others. Each of them requires several steps and multiple machines to be produced. Electronics boards require PCB routers, components mounting, and a soldering oven. The case and mounting require molding or CNC equipment, components such as bolts and nuts, and an assortment of assembly tools (such as screwdriver and pliers). Most of this equipment consumes a significant amount of energy to operate. This situation makes the production of electronics devices a centralized endeavor, where only certain locations around the world supply the global demand. In recent years, small volume and fast delivery of electronics has become available for small demand. Still, the amount of equipment and energy required to operate those production systems is excessive. In some cases, like the arctic or deeps space stations, or prolonged underwater missions, access to these locations presents a significant challenge. In these cases, a spare part may not be available and its on-time delivery may be impossible. Additive Manufacturing (AM) technology offers a potential solution to at least some of these challenges. Technologies such as Fusion Deposition Modeling (FDM) , where shapes are built layer by layer using different polymers, can build, with just one machine, high complex geometries with materials that can withstand high temperatures and be chemical-resistant. In recent years, FDM machines can use Electrically Conductive Filaments (ECF) to make the integration of electronics features such as electric traces, antennas, heat sinks, resistors and touch buttons, possible within the process of manufacturing the device itself. While the machine uses a regular polymer to print the case and support structures, the printing machine switches to a conductive filament to add electric paths and interface buttons that are completed by a rubber material that is also 3D printed using the same machine. After the printing is finished, adding the battery, screen and other components becomes easy by using the connectors and terminals already set in place by the printing process. The whole building and assembly process is reduced in terms of tooling, personnel and expertise required. Fewer tools and less equipment to operate can also reduce the risk of injury and supply of spare parts on-demand. If raw stock materials are impossible to produce in-situ, remote locations would still need to supply them. Nevertheless, in this case, it is more flexible to manufacture what is needed, instead of waiting for components and spare parts. Several types of ECF materials are available in the market that have different resistivity properties. In order to use these materials in real scenarios, we need to understand their principal characteristics. The goal of this dissertation is to characterize these new composite materials for proper use and understand their limitations. The characterization of the electric resistivity of the material and the resistance of printed specimens is the focus of this research.