Kinetic transformation of nanofilamentary Au metal-metal composites

Abstract

Recovery and recrystallization of Au wire can degrade strength and alter conductivity properties during exposure to elevated temperature. Au Deformation Processed Metal-Metal Composites (Au DMMC's) are being developed for electronic applications requiring high conductivity and high strength. This paper discusses the relationships between microstructure, strength, and resistivity of Au DMMC's. Au DMMC samples were prepared by a powder metallurgy technique and processed into wire down to diameters as low as 120 μm. The extensive deformation reshaped the initially equi-axed powder into filaments that are 30 to 100 nm in diameter and 16 to 180 mm in length, which confers high strength. The high conductivity can be explained by electrons flowing parallel to the filamentary microstructure aligned with the wire axis. Au DMMCs were found to have good thermal stability compared to conventional cold-worked Au interconnection wires. Although these composites will revert to solid solutions if exposed to high temperatures for prolonged times, their relative stability is sufficient to allow them to maintain their two-phase microstructure during the anticipated lifetime temperature profiles of many products.