Synthesis of Silver Flakes and Their Application as Conductive Filler for Low-Curing-Temperature Silver Pastes

摘要

Silver microparticles have inspired much research interest due to their enhanced properties for use in optical, electric, catalytic, and magnetic applications. One such use is as electrically conductive filler for printed electronics. A manufacturing approach has been developed to prepare low-curing-temperature silver pastes. Firstly, silver flakes were synthesized directly by a one-step aqueous-phase reduction reaction, using silver nitrate as silver salt precursor and iron(II) sulfate heptahydrate as reducing agent. Various silver flake samples were synthesized by controlling experimental parameters such as the reaction temperature, surfactant concentration, and reducing agent concentration. The obtained silver powders were characterized by x-ray diffraction analysis, scanning electron microscopy, and dynamic light scattering measurements. The results revealed that the morphology of the silver powders was a plate-like structure with diameter of 1 mu m to 1.5 mu m and thickness of 30nm. The prepared silver flakes were then used directly without ball milling to prepare low-curing-temperature silver pastes. The bulk resistivity of a line screen-printed using silver paste containing 48wt.% (34 +/- 5vol.%) silver flakes and cured at 140 degrees C for 30 min in air was about (1.773 +/- 0.118)x10(-6) Omega m. More importantly, the prepared screen-printed patterns exhibited excellent durability in terms of peel strength and folding endurance.