In Situ Rheoimpedance and Thermogravimetry–Differential Thermal Analysis of Copper-Based Conductive Inks for High-Oxidation-Resistant Performance

Thermal sintering is essential for forming continuous conductive pathways or electrodes after the deposition of metal-based conductive inks, particularly those containing metallic particles. The sintering process comprises several vital stages: solvent evaporation, degradation of organic stabilizers, particle sintering, and formation of conductive networks. However, accurately correlating these stages remains a significant challenge due to the complex and interrelated dynamics involved. In this study, we introduce in situ rheoimpedance approach combined with thermogravimetry-differential thermal (TG-DTA) analysis to achieve real-time monitoring of the sintering behavior of copper–nickel (Cu–Ni) mixed inks under nitrogen (N2) and air atmospheres. This method enables the simultaneous tracking of the electrical conductance, mechanical properties, and thermal behavior throughout the sintering process, providing unprecedented insights into the development of conductive pathways. Our analysis revealed that the sintering process occurs in three distinct stages, with oxidation becoming increasingly prominent at elevated temperatures in the air. Notably, the incorporation of Ni significantly enhances the oxidation resistance of Cu films during air sintering, resulting in higher conductivity under oxidative conditions compared to Cu-only inks. Furthermore, we demonstrated that the formation of conductive pathways aligns with critical electrical transitions during the sintering process, a correlation captured in real-time by using our combined measurement technique. These findings highlight not only the enhanced performance of Ni-modified Cu inks but also the potential of our in situ rheoimpedance-TG-DTA method as a powerful tool for optimizing sintering conditions and advancing the development of high-performance electronic components.