A Strategy for Organic Vehicle Design Enabling High-Performance Conductive Pastes for Flexible Electronics

The rapid advancement of flexible electronics has imposed stricter performance requirements on conductive pastes, particularly in terms of electrical conductivity, mechanical flexibility, and process compatibility. This study addresses the lack of a systematic framework for selecting organic vehicles tailored to the specific needs of flexible substrates in electronic device fabrication and proposes an optimization strategy. By integrating gradient solvent design, a polyurethane–acrylic resin composite binder system, and functional additive modulation, we achieved targeted control over multiple performance metrics of the conductive paste. Experiments demonstrated that a gradient solvent system composed of butyl acetate (BAC) and diethylene glycol butylether acetate (DBAC) (18:53.5) effectively suppressed the coffee-ring effect and improved the curing behavior. The composite binder of polyurethane and acrylic resin (10:5) provided a balance between flexibility and interfacial adhesion, resulting in a resistance change of less than 7.71% after 30 cycles of 180° bending. The incorporation of 4 wt % polyamide wax and 2 wt % anionic dispersant TDO further reduced the resistivity to (4.30 ± 1.41) × 10–4 Ω·cm and improved printing resolution. The optimized conductive paste was successfully screen printed on polyimide substrates, forming continuous circuits with a minimum line width of 0.2 mm. The printed patterns exhibited excellent conductivity [ρ < (3.06 ± 0.08) × 10–4 Ω·cm], bending stability (ΔR/R0 < 1.82), and strong adhesion (5B level) and were successfully implemented in flexible circuit prototypes. This systematic optimization strategy overcomes the limitations of traditional one-variable approaches, offering a pathway for the rational design of high-performance conductive pastes and contributing to the industrial advancement of flexible electronic devices.