Printing flexible Cu–Ni traces with high conductivity and high thermal stability by in-situ formed multiscale core–shell structures in inks

Abstract

Direct printing of flexible Cu traces is one of the most promising additive manufacturing technologies in advanced electronics because it is a cost-effective and environmentally friendly process. However, the low oxidation resistance of Cu is currently a critical issue for the preparation of high-performance metallic inks and the manufacturing of reliable printed traces. Herein, we propose a hybrid ink containing Cu/Ni complexes and Cu particles that can be directly printed onto polyimide substrates to generate high-performance Cu–Ni alloy traces by low-temperature preheating and intense pulsed-light irradiation. The nanoparticles in-situ formed by the decomposition of the complexes effectively bridge the interfaces among Cu particles, allowing the printed traces after subsequent intense pulsed-light irradiation to achieve a low resistivity of 29.4 μΩ·cm and excellent mechanical stability at a bending radius of 7 mm. Strikingly, the obtained Cu–Ni alloy traces achieve multiscale core–shell structures because of the heterogeneous nucleation and passivation of Ni, which enables the printed traces to maintain high conductivity and oxidation resistance even at 250 °C in the air, showing strong potential for use in advanced electronics manufacturing.