Influence of dispersants on the properties of flake silver powders by milling

Spherical silver powders prepared by the thermal decomposition of silver carbonate were used as the precursors to produce the flake silver powders by mechanical ball milling, adding stearic acid, oleic acid, ricinoleic acid, and caprylic acid as the dispersants. Scanning electron microscope (SEM), particle size distribution (PSD) statistics, apparent density tester, tap density tester, and four point probe instrument were used to study the microstructures, particle size distribution, apparent density, tap density, and conductivity of the flake silver powders. The results show that, the length of carbon chain in dispersant molecules affects the properties of flake silver powders. The flake silver powders in narrower particle size distribution with the apparent density of 1.0 g·cm^-3 and the tap density of 1.7 g·cm^-3 can be obtained by using oleic acid as the dispersant, and the sheet resistance of silver paste by low temperature curing in the Ag mass fraction of 50% can be below 10 mΩ·□^-1.