Ag Fractal Dendrite With Nano-size Branch Structure And Its Electrically Conductive Composites

Nano-materials have been drawing widespread attention recently due to its unique chemical,magnetic,mechanical,electrical and optical properties.The sintering temperature of Nano-metal is much lower than the original melting point of the bulk metal and which has been applied to microelectronics packaging areas such as electrically conductive adhesives.The unique properties of nano-materials are not only related to the size of the material itself,but also closely related to its dimension,especially the three-dimensional nano-materials,such as the Fractal dendrite structure,which has become a hot topic in recent years.Here we demonstrate a controllable synthesis of fractal Ag micro-dendrites with nano-size branch structure by simple chemical reduction method.The increase of the concentration of reactant and the unique selective adsorption effect of hydroxylamine is the key factor in the formation of the dendrite structure.It is found that the 0.06mol/L of silver nitrate is the best concentration to form dendrite structure.we are able to obtain FDs with various fractal structures and sizes when the molar ratio of hydroxylamine to silver nitrate is 1:1,1:4,1:8 respectively.It is also found that the prepared FDs has unique low temperature sintering characteristic which can start sintering at a temperature below 80?.When used it as the fillers for isotropically electrically conductive adhesive,the unique three-dimensional fractal geometrical configuration and low-temperature sintering characteristic render the Ag micro dendrites with an ultra-low electrical percolation threshold and excellent electrical conductivity and reliability.the experimentally observed volume resistivity of the FD are 4.73×10^-3?·cm with the filler loading of 10 wt% and 2.59×10^-5?·cm with the filler loading of 70 wt%.Moreover the variation of volume resistivity of the FD can be maintained below 20% after being aged in the high temperature and high humidity test for 1000 h.This study also expect that the FD of silver has great potential application prospects as a new type of conductive material.