Formation of highly conductive copper films from oxide-based nanoparticle inks via intense pulsed light sintering

초록

Copper ink was formulated using oxide-encapsulated copper nanoparticles without additional surface modification to suppress further oxidation. The ink composition was systematically optimized by controlling the native oxide shell thickness, bimodal particle size distribution, wetting-dispersing agents, and solvent properties to enhance dispersion stability, printability, and sintering behavior. Screen-printed copper patterns were successfully fabricated on polyimide substrates and converted into dense metallic films via intense pulsed light (IPL) sintering under ambient conditions using a single-pulse irradiation (20 ms). A minimum electrical resistivity of 5 mu Omega center dot cm was achieved at an energy density of 8.5 J center dot cm- 2. Beyond electrical performance, the reliability of the IPL-sintered copper electrodes was systematically evaluated. The dense microstructure formed during IPL sintering provided excellent resistance against chemical exposure, as well as strong adhesion to polymer substrates. Accelerated environmental aging tests under 85 degrees C / 85% relative humidity and cyclic bending fatigue tests up to 200,000 cycles demonstrated superior electrical stability of the copper electrodes compared to silver nanoparticle-based counterparts processed under identical conditions. The enhanced environmental and mechanical reliability is attributed to strong particle-particle welding and robust interfacial bonding enabled by PVP-assisted in situ reduction during IPL sintering. These results highlight the potential of the proposed copper ink system for reliable, low-temperature fabrication of conductive electrodes in flexible and printed electronics.

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