Silver-coated Copper Powders Research Articles

Preparation and sintering properties in air of silver-coated copper powders and pastes

In this paper, uniform and well dispersed silver-coated copper powders were prepared by replacing reaction at first. The structure and properties of the bimetallic powders were investigated by XRD, SEM and TGA. It was found that anti-oxidization of the silver-coated copper powders increased with the increase of the silver content slightly and a dense coating surface was observed at Ag content of 53.9 wt%. Furthermore, the pastes with relatively low silver content which were prepared from silver-coated copper powders, displayed high conductivity similar to pure silver even after sintering in air. And their sintering properties were also investigated at different temperature in air atmosphere. The film exhibits good electrical properties at sintering temperature between 800 and 900 °C. When the paste from silver-coated copper powder with Ag content of 53.9 wt% was printed on Al2O3 substrate and sintered at 800 °C in air, the sheet resistance of the film is 0.036 Ω/□ only.

Preparation and Performance of Silver Coated Copper Powder

Different parameters are used to characterize the conductivity of copper powder with silver plating. Ethanediamine（C2H8N2） is employed to adjust the pH value of plating solution (solution A), and chelate Cu2+ generated by side reaction, forming sound five-membered ring structure with Cu2+, thus preventing the formation of Cu(NH3)42+ which can avoid adsorption of Cu(NH3)42+ on the surface of copper powder. In this way silver-plated copper powder with conductivity equal to fine silver powder can be obtained, the effects of dosage of C2H8N2 and Tollens' reagent concentration on performance of silver-plated copper powder have also been investigated. The result shows that dosage of C2H8N2 has significant effects on electrical conductivity of silver-plated copper powder. The dosage of C2H8N2 should ensure that pH value of control solution A maintains 9.0~10.0. The concentration of Tollens' reagent should make sure that the generated silver-plated copper powder is most even and continuous and tightness when silver particles in form of heterogeneous nucleation is surrounded on the surface of copper powder, , and the optimum concentration is 0.09mol/L. The conductivity of silver-plated copper powder made by Tollens' reagent with 0.09mol/L concentration is optimal, which is 3.9×10-4Ω•cm,when adjusting the pH value of solution A to 9.5 by C2H8N2 control.

Fabrication and performance of silver coated copper powder

Electroless silver coating on copper powder and its effects on oxidation resistance were investigated by varying the fabrication parameters. Using acetylacetone (C5H8O2) as chelating reagent, silver-coated copper powder was fabricated by displacement reaction method. In the process, acetylacetone forms chelating compound with Cu 2+, which prevent the formation of [Cu (NH3)4]2+. Therefore, Ag + can be reduced continully and deposited on the surface of copper particles. As-coated copper particles were characterized using x-ray diffraction (XRD), scanning electron microscopy (SEM) and x-ray energy dispersive spectroscopy (EDS). The oxidation resistance of silver coated copper powder was investigated by gravimetric method. It was found that a fairly continuous silver layer was formed on the surface of copper powder by the electroless type of substitution plating. When the silver content reached 10 wt. %, silver was homogeneously distributed around the copper particles and few free silver particles were detected. The results showed that the silver coated copper powder with the best oxidation resistance was prepared at 40°C and the C5H8O2/AgNO3 molar ratio was 1:1.

Synthesis and Characterization of Silver-Coated Copper Powder Layer

This paper presents the process of preparing spherical silver-coated copper powder with a silver content of 30-50%, using chemical reduction and by adjusting the silver-coating process. By means of SEM, XRD, grain size analyser, digital ohmmeter and differential thermal analyser, the surface topology, structure and conductivity of silver-coated copper powder and raw copper powder are characterised. The results show that the spherical silver-coated copper powder has superior compact surface, complete coverage, a coated layer reaching a thickness of 336nm and excellent conductivity and anti-oxidation property.

Preparation of silver-coated copper powder and its oxidation resistance research

Electroless silver coating on copper powder and its effects on oxidation resistance were investigated. In general, silver-coated copper powder is prepared by an electroless type of substitution plating making use of the substitution reaction between copper and silver. However, [Cu (NH3)4]2+ is produced during the electroless plating process and absorbed onto the surface of the copper particles, which prevent substitution reactions proceeding. In the new electroless plating process, RE-608 copper-specific extractant was used as chelating reagent to formed chelate compound with Cu2+ and the chelate compound was extracted to organic phase, which confirmed substitution reaction to be proceeding. As-coated copper particles were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). When the silver content reached 6.86wt.%, silver was homogeneously distributed around the copper particles and few free silver particles were detected. The results indicated that the properties of oxidation resistance were improved with increasing the dosage of RE-608 copper-specific extractant and reaction time, and with decreasing AgNO3 concentration. It was also found that the optimum reaction temperature was 80°C.

Characterizations of Plating Structures and Electromagnetic Shielding Properties of the Micron-Sized Flaky Silver-Coated Copper Powder

A new kind of the micron-sized flaky silver-coated copper powder was prepared by electroless silver plating in this paper. Its plating structures were characterized by XRD, SEM and EDS. And a new kind of the electromagnetic shielding composite coatings containing 60 wt% the micron-sized flaky silver-coated copper powders and 40 wt% epoxy resin was prepared. Its electromagnetic shielding properties were analyzed by coaxial transmission line equipment. The study results show the micron-sized flaky silver-coated copper powders are composed of 91.35 wt% Cu and 8.65 wt% Ag and have high width-thickness ratio and crystal structure characteristics. In the frequency range of 0.3-1000 MHz, the shielding effectiveness of the coatings is up to 70.15-77.46 dB and increased an average of 22.18 dB compared with the coatings containing 60 wt% micron-sized flaky copper powders when the coating layer thickness is 300 μm. It is seen that the electroless silver plating method effectively improves the inoxidizability, conductivity and electromagnetic shielding properties of copper powders.

Novel Preparation of Silver-Coated Copper in Aqueous Solution

Hollow and solid spherical silver-coated copper powders with size of 1μm were facilely prepared by the reduction of silver nitrate in the polyvinyl pyrrolidone (PVP) dispersed copper hydrosol solution at room temperature in the presence of hydrazine hydrate. Scanning electron microscopy and X-ray diffraction were conducted to investigate the formation process of silver-coated copper core-shell particles. The results showed that the absorption and deposition of the Ag nuclei initially occurred at the active sites on the core surfaces as seeds which urged the further deposition of silver species to form sprinkled-structure core-shell particles. During the growth of the silver shell, the dissolution of copper core would result in the formation of hollow spherical particles, while the hydrazine hydrate would help to generate the solid spherical silver-coated copper powders.

Electro magnetic interference shielding characteristic of silver coated copper powder

The present investigation deals with the synthesis of silver coated copper powder for potential application as filler material in conductive polymers for electro magnetic interference (EMI) shielding. Copper powders were obtained by the reaction of cuprous oxide and, hydrazine in a mixed solvent (H2O:ethanol) at various reaction conditions. The cuprous oxide powder was produced by the reaction of CuSO4, NaOH and D-glucose. The synthesized copper powder was silver coated by its reaction with (NH4)2SO4, C4H4O6KNa and AgNO3. The prepared powders were characterized by XRD, SEM, TGA and XPS. The coaxial transmission line method was used to measure the EMI shielding effectiveness of the powders. The silver coated copper powders exhibited an improved oxidation resistance and higher EMI shielding effectiveness as compared to the uncoated copper powders.

Production of Silver Coated Copper Powders by Electroless Plating Method

Copper powders with very dense, uniform silver coating layer were prepared by electroless plating method in aqueous system at room temperature. Silver-copper composite powders were obtained by strictly controlling the activation and complexing process variables such as NH4OH/(NH4)2SO4 molar ratio, tartrate concentration, and feeding rate of silver ion solution. The mechanism of composite powders formation and their characteristics were discussed. It is noted that completely cleansing the oxide layers and protecting the copper particles surface from hydrolysis are key factors to obtain high quality Ag-Cu composite powders.

Effects of oxidation and particle shape on critical volume fractions of silver‐coated copper powders in conductive adhesives for microelectronic applications

AbstractThe effects of oxidation and particle shape on critical volume fractions of silver‐coated copper powders in conductive adhesives are investigated. Silver‐coated copper powders with spherical and flake‐shaped particles were oxidized at temperatures of 30°C, 175°C and 240°C for two hours and dispersed in an epoxy matrix. As silver‐coated copper powders are oxidized at 30°C and 175°C, the critical volume fractions of the conductive adhesives are slightly affected by oxidation and particle shape at these temperatures. As the oxidation temperature approaches 240°C, the critical volume fractions of the conductive adhesives are strongly affected by oxidation temperature and particle shape, owing to the formation of oxides such as Cu2O on the surface of silver‐coated copper powder—Cu diffuses from the interior to the surface of silver‐coated copper powder and reacts with the oxygen in the air. Silver‐coated copper powder with flake‐shaped particles shows lower critical volume fractions in conductive adhesives than silver‐coated copper powder with spherically shaped particles. Polym. Eng. Sci. 44:2075–2082, 2004. © 2004 Society of Plastics Engineers.