Enhancing conductivity of silver-based conductive adhesives via biomass-derived aldehydes: Interfacial modification and network densification

Abstract

Electrically conductive adhesive (ECA) is a low-temperature bonding material that can replace toxic Sn-Pb solder. However, the electrical properties of ECA are severely deteriorated by insulating organic lubricants (e.g., oleic acid, stearic acid) on the surface of Ag flakes. Current methods for surface modification often rely on non-renewable or environmentally-concerning chemicals. This work proposes a sustainable and effective approach by utilizing biomass-derived aldehydes, such as hydroxymethylfurfural (HMF), for the interfacial modification of Ag flakes and concurrent densification of epoxy matrix. The resulting ECA achieved a minimum bulk resistivity of 2.49 × 10⁻⁵ Ω cm at an optimal HMF loading of 0.3 wt% (relative to Ag), achieving ∼26.5 % of decline, compared with that of untreated reference (3.38 × 10⁻⁵ Ω cm). Comprehensive characterizations (XPS, FT-IR) revealed that HMF was oxidized by oxygen during curing and generated carboxylic acid groups. These carboxyl groups participate in co-curing reactions with the epoxy matrix and enhanced the conductive network. The strategy also applied to other biomass-derived molecules, such as 2,5-furandicarboxylic acid (FDCA). This study provides a novel, green methodology that bridges the gap between high conductivity and sustainable material design in ECA.