Electrically Conductive Adhesive Interconnections on Additively Printed Substrates

In this paper, the assembly of passive components on additively printed metallization using additively dispensed conductive adhesive is studied. Additively printing technologies are being increasingly explored in the realm of electronics manufacturing. These have found their way in various aspects of manufacturing starting from achieving reliable traces to multi-layer circuits with micro-via, and now surface mount devices. Different technologies have their merits and demerits based on the conductive material properties, substrate, and the printer’s capability to incorporate multiple materials simultaneously. Previously, authors have shown how Aerosol Jet Printing (AJP) technology can be utilized to deposit very fine traces and realize multi-layer metallization with additively printed donutvias. To move on to the other aspect of electronics manufacturing, assembly of Surface Mount Devices (SMD) on a flexible substrate is being looked into using additive methods. For the assembly, having an additively printed pad along with a conductive adhesive appears to be a suitable path and an alternative to solder reflow process where components suffer high temperatures. However, certain process limitations come to light in this aspect. For example, instead of copper being used as a conducting material, silver is used due to its availability and ease in thermal curing as opposed to copper because of oxide formation. Another example could be the depositing of conductive adhesive. Since the adhesive is extremely viscous, printer should be able to incorporate high viscosity materials without any blockage issues every minute. In this work, authors have utilized two different printing technologies: InkJet and micro-dispensing, to characterize the assembly process of SMD components. InkJet technology is used to deposit the metal conductive pad, on top of which conductive adhesive is pneumatically dispensed. SMD components are placed using a semi-automatic pick-and-place machine. Different SMD discreet components are used such as resistors, capacitors, and inductors. Process studies on the two state-of-art printing technologies in achieving a fine quality print are developed. With this work, authors aim to characterize the printing processes of two materials, and also providing a viable method for the assembly of SMDs on a flexible substrate.