  In printed electronics, conductive traces are often produced by printing inks
of silver nanoparticles dispersed in solvents. A sintering process is usually
needed to make the printed inks conductive by removing the organic dispersants
and allowing metal-to-metal contacts among nanoparticles for atomic diffusion
and neck formation. It has been challenging to sinter silver nanoparticle inks
in a thermal oven at a temperature < 150 C to avoid thermal damage to the
plastic substrate while achieving desired conductivity. This work presents a
simple yet effective way to sinter a silver nanoparticle ink below 120 C (even
at 80 C) by exposing the printed ink to water vapor in the oven. The results
consistently show a significant reduction of line resistivity for the samples
sintered in a moist oven compared to those sintered in a dry oven. Hence,
solvent vapor-assisted sintering of metal nanoparticle inks can become an
enabling approach to broaden product range of printed electronics.
