Approaching the Practical Conductivity Limits of Aerosol Jet Printed Silver

TL;DR

This paper demonstrates aerosol jet printing of high-density silver traces with near-bulk conductivity at low temperatures, using a reactive ink and a predictive model to approach the practical conductivity limits of printed metals.

Contribution

It introduces a novel aerosol jet printing method with reactive ink, achieving high-density, high-conductivity silver traces at low temperature, supported by a microstructure-based transport model.

Findings

Achieved 93% density silver traces with near-bulk conductivity.

Validated electrical performance up to 20 GHz for printed RF components.

Developed a predictive model linking microstructure to conductivity.

Abstract

Previous efforts to directly write conductive metals have been narrowly focused on nanoparticle ink suspensions that require aggressive sintering (>200 {\deg}C) and result in low-density, small-grained agglomerates with electrical conductivities <25% of bulk metal. Here, we demonstrate aerosol jet printing of a reactive ink solution and characterize high-density (93%) printed silver traces having near-bulk conductivity and grain sizes greater than the electron mean free path, while only requiring a low-temperature (80 {\deg}C) treatment. We have developed a predictive electronic transport model which correlates the microstructure to the measured conductivity and identifies a strategy to approach the practical conductivity limit for printed metals. Our analysis of how grain boundaries and tortuosity contribute to electrical resistivity provides insight into the basic materials science that governs how an ink formulator or process developer might approach improving the conductivity. Transmission line measurements validate that electrical properties are preserved up to 20 GHz, which demonstrates the utility of this technique for printed RF components. This work reveals a new method of producing robust printed electronics that retain the advantages of rapid prototyping and three-dimensional fabrication while achieving the performance necessary for success within the aerospace and communications industries.