Factors Influencing the Line Consistency of Commonly Used Geometries for Additively Printed Electronics

Abstract

3D printing functional devices onto flexible and conformal substrates is rapidly gaining importance in several industries. The ability to deposit nanoparticles using Aerosol Jet technology brings up a lot of advantages which conventional methods cannot achieve. Aerosol Jet Printing (AJP) technology requires control of number of process parameters such as sheath flow rate, carrier gas rate to transport the aerosol mist onto a substrate. There are two ways to obtain the aerosol formation: Ultrasonic Atomizer (UA), which creates the mist by ultrasonic waves and can only be used for inks with viscosity ranging from l-5cP, and another is from a Pneumatic Atomizer (PA), which smashes the ink on the wall of the jar, thus creating the aerosol. PA can be used for a much wider range of ink viscosity i.e. 1-1000cP. Much work has been demonstrated in the research community regarding the AJP, test protocols in refinement of the inks, but if AJP is to be used at large scale production, a print consistency study needs to be performed on the lines printed. In this paper, the influence of the geometry of silver lines on a flexible substrate is studied with the aim of creating high quality and conductive lines. In the study, a silver-based ink is utilized to study the line consistency in different geometry of lines printed through state-of-art Optomec AJ-300 printer. Because of the high viscosity of the ink used, PA is used to atomize the ink. Different types of geometry including zig-zag lines, straight lines, and horse-shoe pattern are used to study the effect on the conductivity measurements and the physical properties. Process parameters have been optimized by varying the mass flow rate of the ink, and the sheath gas flow rate to achieve the highest conductivity of the printed line. The printed lines are later analyzed for a shear load to failure to study the geometry effect. SEM analysis is also performed to understand the line consistency in more depth.