Dewetting behavior of Ag in Ag-coated Cu particle with thick Ag shell

With the aim of application as either a conductive filler or a sinter-bonding material with enhanced antioxidation properties, Ag-coated Cu (Cu@Ag) particles with thick Ag shells were fabricated and heated at 220 degrees C for 10 min in air to observe the dewetting behavior of the thick Ag shell. The fabricated Cu@Ag particles were spherical with the average size of 2 mu m, and the Ag shell was 250-400 nm in thickness, comprising a mixed Ag-Cu layer and a dense Ag layer. As the heat-treatment time increased, the Cu@Ag particles were aggregated by forming numerous Ag nodules covering the surface of the particle. Dewetting in the thick Ag shell occurred from 4 min and only in the outer layer of the Ag shell even after 10 min of heat-treatment. In addition, the thickness of the dewetting layer and the mixed Ag-Cu layer were increased because the outward diffusion of Cu and Ag were increased proportionally with the time. However, because the dense Ag layer remained even after the dewetting of the Ag shell and the formation of the mixed Ag-Cu layer, the Cu@Ag particles were not oxidized after heating at 220 degrees C for 10 min in air.