Low-Melting-Point Alloy Nanoparticles toward Multifunctional Fillers for Rigid and Flexible Interconnects

Owing to advantages such as high conductivity and low processing temperature, electrically conductive adhesives (ECAs) are critical for low-temperature interconnections; however, the ECAs remain challenging due to the need for high silver content. Sn–In–Bi alloys have attracted considerable attention due to their low melting point characteristics and well-established industrial applicability. This study investigated the synthesis of Sn–In–Bi low-melting-point alloy (LMPA) particles using water as an environmentally friendly and safe solvent under various conditions, successfully producing LMPA particles with an average size of 307 nm. Further, antimony-doped tin oxide nanoparticles were incorporated into the ECAs with LMPA particles to construct a multifunctional composite system. This filler system can serve as a “bridge” to connect the silver flakes to significantly improve ECAs’ electrical and thermal conductivity by using low Ag content (50 wt %) and bring functional natures such as enhancing mechanical strength and infrared stealth performance in different polymer substrates (epoxy resin E44 and thermoplastic polyurethane (TPU)). Especially, the ECA with TPU matrix demonstrates excellent flexible tensile performance, maintaining tensile properties comparable to pure TPU even at filler contents up to 65 wt %, offering an effective solution for high-performance, multifunctional, low-temperature interconnect materials in complex environments.