Silver Nanoparticles Stabilized by Nitrocellulose as Low Conversion Temperature Precursors for Inkjet-Printed Electronic Circuits

Liquid-based inkjet printing is considered as a constructive (rather than destructuve) low-cost technique for printed circuit board fabrication. A convenient way of depositing silver films and lines using inkjet technology is to generate silver nanoparticles (AgNP) that can be dispersed and stabilized in solutions, processed into desired patterns and subsequently annealed. To avoid the aggregation of AgNPs, polymers are usually preferred due to their better stabilization of AgNPs and good adhesion to substrates, but high conversion temperatures and incompatibility are the major drawbacks. Since low molecular-weight nitrocellulose decomposes at a relatively low temperature and possesses good adhesion properties to many substrates, it has been selected to stabilize AgNPs in methanol solutions with 3-aminopropanol as a co-stabilizer. These colloidal solutions were found to be very stable, with no evidence of aggregation over a period of 12 months, and displayed properties (viscosity, surface tension) compatible with inkjet printing technologies. The main advantages of using nitrocellulose are its property to stabilize AgNPs and its low converison temperature (degradation at 135oC, annealing temperature at 190oC). Films annealed on both glass and polyimide substrates showed identical overall properties (thickness, homogeneity, conductivity), demonstrating clearly the potential of nitrocellulosestabilized AgNPs for inkjet printing of electronic circuits.