Surface Functionalization of Micrometer Silver Flakes for Fabricating High-Performance Electrically Conductive Adhesives

Silver (Ag) flakes are widely used as conductive fillers in the electrically conductive adhesives (ECAs). However, there are organic lubricants on the Ag surface such as oleic acid and stearic acid, a kind of surfactant commonly used in the production of Ag flakes, which will deteriorate the conductivity and mechanical properties of the ECAs. In this study, glutaric acid was used to remove the organic lubricants, which can increase the electrical conductivity and mechanical properties of the ECAs. FTIR, Raman, and XPS tests revealed that the glutaric acid was chemically adsorbed on the Ag surface by single-dentate coordination and then reacted with organic lubricants, explaining the action mechanism by which the glutaric acid enhanced the electrical and mechanical properties of the ECAs. In addition, the effects of glutaric acid on the thermal stability, bulk resistivity, shear strength, and viscosity of the ECAs were investigated. When the glutaric acid reached 0.12 wt %, the minimum bulk resistivity of the ECAs was 1.52 × 10–4 Ω·cm, the shear strength was 24.57 MPa, and the viscosity was 149 Pa·s. This provides a method for fabricating high-performance ECAs.