Bio-based benzoxazine electrically conductive adhesives for sustainable and epoxy-free hybrid printed electronics

Electrically conductive adhesives (ECAs) are critical for the assembly of surface-mounted devices in printed and hybrid electronics; however, conventional epoxy-based systems are associated with toxicity and limited working life. In this work, we present a benzoxazine-based anisotropic conductive adhesive (ACA) derived from a bio-based diphenolic acid benzoxazine (DPA-Bz) copolymerized with 1,12-diaminododecane (DIADO), combined with environmentally preferable metallic fillers. The developed system enables reduced curing temperatures (~ 150°C) compared to conventional benzoxazines, improving compatibility with temperature-sensitive substrates. From an electrical standpoint, the optimized Cu-based ACA exhibits low contact resistance and clear anisotropic conductivity with electrical performance comparable to a commercial epoxy-based adhesive. Furthermore, the ACA maintains stable electrical behavior under accelerated aging (85°C / 85% RH) and thermal shock testing, indicating robust reliability under environmental stress. Finally, life cycle assessment reveals a reduced global warming potential (5.48 kg CO₂/kg) compared to a reference Ni-based adhesive (6.27 kg CO₂/kg), with further reduction potential through solvent-free formulations and increased recycled copper content. The presented benzoxazine-based ACA achieves comparable electrical and mechanical performance to commercial systems while delivering improved environmental performance and reduced toxicity, highlighting its potential as a sustainable alternative for next-generation electronic assembly and opening the path towards greener electronics.