Preparation And Property Research Of Ag-Cu Composite Powders

Silver powder is one of the most common used materials in electronic industry, but the cost is too much due to its high price. Copper powder can be in place of silver powder while its oxidation-resist property is weakly. Many researchers pay much attention to Ag-Cu composite powders on account of their fine capability and low price.The method of electro-less plating silver on copper powders(5-6μm) was used to prepare Ag-Cu composite powders in this paper. The organic protectors on the surface of copper powders were removed by pretreatment firstly and the copper powders were not floating on the water any more. [Ag(NH3)2]+ were reduced by glucose to silvers which were deposited on the surface of copper powders. We have studied that the phase, size, surface content of silver, structure of silver coating were relative to the technical parameter of the dosage of AgNO3, plating times, activation, temperature of heat treatment. It was found that the phase of Ag-Cu composite powders were mainly silver and copper.Along with the dosage increase of AgNO3, the intensity of X-ray diffraction peak of silver strengthened compared with copper. The number of copper atom with high activity was decreased by increasing of plating times which could avoid the formation of Cu2O.Activation has influence upon the size of Ag-Cu composite powders. The size is the range of 6-10μm by silver plating after activation, while the range of 8-20μm by silver plating directly. Silver coating was mainly formed by small silver grain accumulating on the surface of copper powders. The nano- particle of silver can be melted by heat treatment to form the continuous silver coating.Flake like powders, with the size around 20μm, were prepared by spherical powders using ball milling. The surface of the sample(plating before milling), with little small silver grains on the copper, was smooth and the silver coating was continuous. And there are many silver grains on the surface of the Ag-Cu sample(milling before plating) with coarse and loose silver coating.Oxidation-resist property of Ag-Cu composite powders was measured by TG analytical method. The original oxidation temperature of Ag-Cu composite powders was higher than copper powders and the oxidation-resist property would be enhanced with increasing of AgNO3 dosage. With the same dosage of AgNO3, increasing the plating times, activation and heat treatment after plating were enhance the oxidation-resist property of Ag-Cu composite powders at a certain extent. Proper load-age and strong concentration of [Ag(NH3)2]+ can also enhance the oxidation-resist property of Ag-Cu composite powders. In the end, conductive property of electrically conductive adhesives(ECAs) prepared by Ag-Cu composite powders and resin was measured by four-probe method. That the volume resistivity of ECAs can reach 10-3 amount distinction indicated the conductive property of Ag-Cu composite powders were excellent. The capacitances were prepared by spreading the Ag-Cu slurry on the two sides of the ceramics, and their current surge resist ability would reach 10000A.