High conductivity of isotropic conductive adhesives filled with silver nanowires

As an alternative to lead-bearing solder, isotropic conductive adhesives (ICA) have been utilized for many years in microelectronic packaging. In this study, silver nitrate (AgNO3) as precursor, N-N-dimethylformamide (DMF) as solvent and reducing agent, preparing silver (Ag) nanowires in the nanoporous templates formed by the controlled hydrolysis and condensation of butyl titanate (Ti(OC4H9)(4)). The Ag nanowires were characterized by X-ray diffraction and transmission electron microscopy. An isotropic conductive adhesive (ICA) has been developed by adding Ag nanowires as conductive filler. Bulk resistivity and shear strength of the ICA are measured and compared with those of conventional ICA filled with micrometer-sized Ag particles (about 1 mu m) and nanometer-sized Ag particles (about 100 nm). It is found that the ICA filled with lower content of Ag nanowires exhibits lower bulk resistivity and higher shear strength than ICA filled with micrometer-sized Ag particles and nanometer-sized Ag particles. Possible conductive mechanisms of the ICA are discussed. (C) 2005 Elsevier Ltd. All rights reserved.