Direct writing of stable Cu–Ag-based conductive patterns for flexible electronics

Abstract

Cu–Ag-based highly conductive patterns were drawn directly on a flexible substrate using a roller pen filled with Cu–Ag NPs ink. The particle packing density is important for the pattern's conductivity. First, the addition of smaller Cu NPs (∼6.5 nm) between the larger Ag particles (∼16.5 nm) improves the particle packing density by filling the pores, which can help improve conductivity at lower temperatures. Furthermore, combination of temperature and stress by hot sintering & hot-pressure sintering makes the residual pore space decrease and improves the conductivity of the patterns. Finally, compared to bulk Cu wire (1.72 μΩ cm), the resistivity of the Cu–Ag patterns sintered at 160 °C is reduced to 6.2 ± 0.4 μΩ cm, which is acceptable for conductive patterns. Samples with a decorative logo drawn by the Cu–Ag NPs exhibited excellent conductive performance and mechanical integrity.