Development of a Novel Isotropic Conductive Adhesive Filled with Silver Nanowires

Abstract

As an alternative to lead-bearing solder, isotropic conductive adhesives (ICA) have been utilized for many years in microelectronic packaging. ICAs filled with conductive particles generally show high initial contact resistance, unstable contact resistance, and inferior impact strength. In this study, silver nitrate (AgNO3) is used as a precursor, N, N-dimethylformamide (DMF) as a solvent and reducing agent for preparing silver (Ag) nanowires in the nanoporous templates formed by the controlled hydrolysis and condensation of butyl titanate (Ti(OC4H9)4). Fundamental material characterizations including X-ray diffraction (XRD), transmission electron microscopy (TEM), and scanning electron microscopy (SEM) are conducted on these Ag nanowires. A novel ICA is developed by using Ag nanowires as conductive fillers. Electrical and mechanical properties are investigated and compared with that of conventional ICA filled with micrometer-sized Ag particles or nanometer-sized Ag particles, the average diameter of these Ag particles is about 1 mm and 100 nm, respectively. It is found that at a lower filler content, the ICA filled with Ag nanowires exhibited lower bulk resistivity and higher shear strength than ICA filled with micrometer-sized Ag particles or nanometer-sized Ag particles. Possible conductive mechanism of the new ICA is analyzed.