Crack and Flow Rate Effect Analysis: Aerosol Jet Printed Silver Traces

There is an increasing trend of 3D printed functional materials, which led to the printing of materials and parts including dielectrics and passives, specifically resistors, capacitors, inductors, and others. With the rise of interest and accessibility to 3D printing technology, multiple published or ongoing studies are using this novel technology and materials. However, the underlying mechanisms have yet to be fully understood. Only a few parametric experimental studies have observed the inherent defects and long-term duration of AJ printed silver parts.

A research group at CALCE, led by Prof. Abhijit Dasgupta, has been conducting the parametric studies on printing parameters that are effective in the reliability in the AJ printed part delivered. Their findings regarding the influence of carrier (CGFR) and sheath gas flow rates (SGFR) were summarized in two articles: "Effects of Gas Flow Rates on Quality of Aerosol Jet Printed Traces with Nanoparticle Conducting Ink" and "Cracks in the 3D-Printed Conductive Traces of Silver Nanoparticle Ink". In these studies, commercial DOWA silver ink was printed on dielectric layer-coated FR4 substrates, and serpentine patterns were designed for the parametric study, as seen in Fig. 1.

The mechanisms of driven force were analyzed based on the understanding of nano-particle based films and explorations on pre-sintering and post-sintered state (the two possible cracking formation stress source). Many parameters were considered in this research: agglomeration, evaporation-driven capillary pressure, print geometry, print parameters, sintering profiles, conductor ink NP properties, and solvent content, chemistry, and volatilization. Fig. 2 presents an example of cross-section SEM for crack visualizations and FEA analysis for maximum in-plane principal stresses of printed traces.

The result from the parametric experiments considering flow rate effects indicates an increasing trend of effective electrical conductivity with increasing CGFR, and lower print speed or additional passes were suggested when the deposition rate was low. For the crack study, both long-term durable and traces with early life failures were observed in experiments.

For more information on this research, contact Prof. Abhijit Dasgupta and Prof. Siddhartha Das.

Referenced Publications:

N. Dalal, Y. Gu, G. Chen, D. R. Hines, A. Dasgupta, and S. Das, “Effects of Gas Flow Rates on Quality of Aerosol Jet Printed Traces with Nanoparticle Conducting Ink.” ASME Journal of Electronic Packaging, July, 2019.
N. Dalal, Y. Gu, D. R. Hines, A. Dasgupta, and S. Das, “Cracks in the 3D-Printed Conductive Traces of Silver Nanoparticle Ink.” Journal of Micromechanics and Microengineering, 29, 097001 (2019).

Published March 24, 2020