Incorporation of π-conjugated Molecular Wires into Anisotropic Conductive Adhesive for High-performance Interconnection Applications

Due to restricted contact area and poor interfacial bonding between anisotropic conductive adhesive (ACAs) and metal bond pads, ACA joints have lower electrical conductivity and poorer current carrying capability than solders. Interfacial property between ACA and metal bond pads is the key to improve the electrical properties of the resulting ACA joints. In this study, we have investigated the electrical properties of ACA joints using submicron-sized (˜500 nm in diameter) silver (Ag) particle as conductive filler with the effect of π-conjugated molecular wires (MWs). The ACAs with submicron-sized Ag particles have higher current carrying capability (˜3400 mA) than those with Ag nanoparticles (˜2500 mA) and micro-sized Au-coated polymer particles (˜2000 mA). More importantly, by construction of π-conjugated molecular wire junctions between conductive particles and an integrated circuit (IC)/substrate, the electrical conductivity has increased by one order of magnitude and the current carrying capability of ACAs has improved by 600 mA. The crucial factors that govern the improved electrical properties are discussed based on the study of alignments and thermal stability of molecules on the submicron-sized Ag particle surface with Surface-enhanced Raman Spectroscopy (SERS), providing a fundamental understanding of the conduction mechanism in ACA joints and guidelines for the formulation of high-performance ACAs in electronic packaging industry.