Rapid curing of printed pattern by UV irradiation and enhanced electrical conductivity in the flexible pattern consisting of Cu@Ag particles by successive photonic sintering

A paste containing Ag-coated Cu (Cu@Ag) particles with an average size of 350 nm underwent sequential UV and multiple Xe light exposures, resulting in a conductive layer with remarkable electrical conductivity and flexibility. The low-temperature process was enhanced by incorporating a hybrid photoinitiator into the binder formulation, enabling thorough curing of the paste. This prevented thermal degradation in the low-heat-resistant substrate and minimized stress at the layer/substrate interface. The oligomer-based binder formulation aimed to enhance layer adhesion and improve the mechanical bending performance of the conductive layer/substrate component. The resulting layer exhibited an impressive electrical resistivity of 3.5 × 10⁻⁶ Ω·cm, coupled with sufficient bending properties achieved through three rounds of light sintering post UV curing. In contrast to conventional thermal methods, prone to Ag shell dewetting and Cu oxidation in Cu@Ag filler, the described sequential process avoided Ag dewetting, out-diffusion of core Cu, and subsequent Cu oxidation. This is attributed to the low-temperature nature of the processes and the accelerated sintering achieved through post Xe light irradiation between Cu@Ag particles. Therefore, the UV curing-photonic sintering process proves highly suitable for comprehensive applications of Cu@Ag particle-based conductive paste.