Comparison of thermal decomposition and chemical reduction of particle-free silver ink for inkjet printing

Two current major methods (thermal decomposition of silver organic salts and chemical reduction of silver salts) to formulate a particle-free silver ink are compared. X-ray diffraction (XRD) and scanning electronics microscopy (SEM) are used to investigate the printed silver patterns from conductive inks made from those two methods. Both processes are shown to make silver with high purity from XRD results. SEM images indicate that chemical reduction can make denser silver film than thermal decomposition. Thermogravimetric analysis and Differential thermal analysis indicates that the silver film is formed at very low temperature compared with thermal decomposition. This phenomenon may be caused by volume shrinkage of silver precursor decomposition after thermal sintering. The resistivity of printed silver patterns made by chemical reduction is also lower than the silver patterns made by thermal decomposition because of less porosity. Also, our results show that a polymer additive can render the silver film more uniform and easier to be sintered.