Water vapor assisted sintering of silver nanoparticle inks for printed electronics

TL;DR

This paper demonstrates a water vapor-assisted sintering method for silver nanoparticle inks that achieves high conductivity at temperatures below 120°C, enabling printed electronics on plastic substrates.

Contribution

It introduces a novel water vapor-assisted sintering process that significantly reduces resistivity at low temperatures, expanding the potential for flexible printed electronics.

Findings

Resistivity decreases significantly with water vapor sintering.

Effective sintering achieved at temperatures as low as 80°C.

Water vapor enhances nanoparticle neck formation and conductivity.

Abstract

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.