The Synthesis and Characteristic of Micro-particle Silver Used for Conductive-paste
|Keywords||liquid chemical reduction method silver powders ascorbic acid gum Arabic growth mechanism|
In this experiment, the micron-size silver powders used for conductive-paste were prepared by Liquid Chemical Reduction Method with silver nitrate as precursor.The obtained powders were able to meet the requirements of the conductive paste by optimizing the reaction conditions to control the silver particle’s morphology, size, size distribution, loose density, tap density and other properties. Scanning electronic microscope(SEM) was used to characterize the morphology of silver powders, the structure was analyzed by X-ray Diffraction(XRD), and the particle size distribution was analyzed by centrifugal sedimentation method. In addition, the possible the experimental system’s growth mechanism of the silver powders was also discussed. The optimal parameter is that ascorbic acid was used as reductant, gum Arabic was used as dispersant, mole ratio of oxidant to reductant is 1:2, AgNO3 concentration is 0.083 mol/L, gum Arabic is 0.04 g(wt%=0.02%), pH value of the solution is 1.0 adjusted by hydrogen nitrate, mixed with symmetric way., The ultimate product would be cubic silver、good crystallize and well dispersed, the mean particle size would be 1.5μm to 2.1μm, the loose density would be 1.5 g/cm3,the tap density would be 3.5 g/cm3,and the productivity would be 98.47%.The study indicated, in the process of preparing silver powders by liquid chemical reduction method with ascorbic acid as reductant and gum Arabic as dispersant, the concentration ratio of dispersant and reagent and the solution’s pH value were the crucial influencing factors of silver particle’s morphology, size and size distributing; and the mean silver particle size decreased with the increase of the usage of the dispersant and silver particle can get bigger in the low pH value of the solution. In addition, the proportion ratio of oxidant to reductant, the mixing way and other factors also affect the silver particle’s morphology. But the silver particle’s size can hardly be affected by the AgNO3 concentration.