Study on Thermal Stability of Ag-Coated Cu Powders Fabricated By Electrochemical Methods

The conductive paste market is growing with many uses and development in solar cells, touch panels, and other display devices. Those conductive pastes contain the Ag powders as a metal filler to maintain its high electrical conductivity. Recently, as the price and consumption of Ag has been precipitously increased, there are many efforts to use alternative materials.

One of the ways to reduce the paste cost is adoption of core-shell structured metal fillers with putting the inexpensive Cu in the core. By coating the Ag on Cu powders, the low electrical resistance has been maintained even at higher temperatures in air. The key technique in this process is the way how to achieve uniform Ag coating on Cu, which prevents the Cu powders from oxidation and sustains its conductivity.

In our work, galvanic displacement reaction by being based on difference of potential and electroless plating method supplied the electrons from reducing agent are used to coat Ag on Cu powder. The Ag has been formed on Cu powders using electrochemical method that coats uniform metal thickness on material surfaces using those electrochemical methods.

We report Ag shell which has been coated various contents (silver 15wt.%, 30wt.%, 40wt.%) and  analyze thermal stability of the powders using FE-SEM (Field Emission Scanning Electron Microscope, JSM-7000F, JEOL, Japan), EDS (Energy Dispersive Spectroscopy, EDAX, U.S.A.), ICP-AES (Inductively Coupled Plasma-Atomic Emission Spectrometer, Optima-4300 DV, PerkinElmer, U.S.A.), XRD (X-ray Diffraction, D8 ADVANCE, Bruker corporation, Germany), and CP (Cross-section Polishing, IB-09020CP, JEOL, Japan).

Keywords: Core-shell, Silver-coated copper, Galvanic displacement reaction, Electroless plating method, Thermal stability