Cracks in the 3D-printed conductive traces of silver nanoparticle ink

Printing conductive traces of sinterable metallic nanoparticle (NP) based inks is one of the key components of 3D additively manufactured (printed) electronic circuits. In this study, we employ 3D Aerosol Jet Printing (AJP) to print conductive traces of silver NP based ink and provide insights into the risk of cohesive longitudinal cracking inside the printed and sintered traces. This was investigated for a wide range of carrier and sheath gas flow rates, which implies a wide range of particle deposition rates and velocities. These cracks appear for both single and double pass traces that are several microns in height and hundreds of microns in width. We examine different sources of stress that could be the potential driver for the cracking and infer that the most likely source is the classical capillary-pressure-driven crack formation mechanism for the evaporating NP-based thin films. Most importantly, this hypothesis raises the possibility of crack formation at some locations of the NP-based conductive traces printed using an extremely popular recent technique for printed electronics, AJP.