Electrically conductive adhesive with π-conjugated self-assembled molecular wire junctions for enhanced electrical and thermal properties

Anisotropic conductive adhesives/films (ACAs/ACFs) have been developed as a promising lead-free interconnect material in the electronic industry. However, due to the restricted contact area and poor interfacial bonding between ACAs and metal bond pads, the ACA joints have lower electrical conductivity and poorer current carrying capability than that of solders. In this study, we investigated the current carrying capability of submicron-sized (~500 nm) silver (Ag) particles in ACA. It was found that the submicron-sized Ag particles have higher current carrying capability (~3400 mA) than micro-sized Au-coated polymer particles (~2000 mA) and Ag nanoparticles (~2500 mA). More importantly, with the introduction of self-assembled monolayer (SAM) on a Ag particle surface, the electrical conductivity and current carrying capability of the ACAs could be significantly improved. By studying the adsorption behavior and thermal stability of the SAMs on submicron-sized Ag particles with ATR FT-IR, Raman spectroscopy and TGA, the crucial factors that govern the improved electrical properties were discussed.