Process Capability of Aerosol-Jet Additive Processes for Long-Runs Up to 10-Hours

Abstract

Traditionally, printed circuit assemblies have been fabricated through a combination of imaging and plating-based subtractive processes involving the use of photo-exposure followed by baths for plating and etching in order to form the necessary circuitry on rigid and flexible laminates. The emergence of a number of additive technologies presents an opportunity for the development of processes for manufacturing of flexible substrates by utilizing mainstream additive processes. Aerosol-jet printing is capable of printing lines and spaces below 10 μm in width. The aerosol-jet system also supports a wide variety of materials, including nanoparticle inks, screen-printing pastes, conductive polymers, insulators, adhesives, and biological matter. The adoption of additive manufacturing for high-volume commercial fabrication requires an understanding of the print consistency and electrical mechanical properties. Little literature that addresses the effect of varying sintering time and temperature on the shear strength and resistivity of the printed lines exists. In this study, the effect of process parameters on the resultant line consistency and mechanical and electrical properties has been studied. Print process parameters studied include sheath rate, mass flow rate, nozzle size, substrate temperature, and chiller temperature. Properties include resistance and shear load to failure of the printed electrical line as a function of varying sintering time and temperature. The aerosol-jet machine has been used to print interconnects. Printed samples have been exposed to different sintering times and temperatures. The resistance and shear load to failure of the printed lines have been measured. The underlying physics of the resultant trend was then investigated using elemental analysis and scanning electron microscopy. The effect of line consistency drift over prolonged runtimes has been measured for up to 10 h of runtime. The printing process efficiency has been gaged as a function of the process capability index (Cpk) and process capability ratio (Cp). Printed samples were studied offline utilizing optical profilometry in order to analyze the consistency within the line width, height, and resistance, and shear load to study the variance in electrical and mechanical properties over time.