Effects of Bi2O3/B2O3 Ratio in Lead-Free Glass on Sintering Behavior and Thick-Film Performance of Gold Conductor Pastes

High-reliability thick-film gold conductor pastes serve as core functional materials for high-end electronic packaging. Traditional lead-containing glass binders suffer from environmental toxicity, restricting their large-scale green applications. Herein, a series of Bi2O3–B2O3–TeO2 lead-free glasses with tunable Bi2O3/B2O3 ratios was prepared to explore the regulation of glass composition in the intrinsic structure, thermal behavior and sintering performance of gold thick films. The Bi2O3/B2O3 ratio strongly influences melt flow: excessive Bi2O3 induces local segregation of the glass phase, while surplus B2O3 weakens wettability and pore-filling capacity. Optimized A3 glass achieves synergy between glass flow and sintering kinetics of gold particles. The resulting P3 film has porosity of 3.12%, sheet resistance of 2.92 mΩ/sq and interfacial adhesion of 3.78 N/mm2. Its sheet resistance variations remain merely +0.96% and −1.02% after two refiring cycles, delivering good conductivity, strong interfacial bonding and stable electrical behavior upon refiring. This work offers experimental support for compositional design of lead-free glass binders for gold conductor pastes.