High‐performance Cu–Cu interconnects attained through air sintering of oleylamine‐capped Cu nanoparticles for power electronics packaging

Abstract Cu nanoparticles exhibit excellent properties as high‐temperature‐resistant, conductive, heat‐dissipating, and connecting materials. However, their susceptibility to oxidation poses a major challenge to the production of high‐quality sintered bodies in the air, severely limiting their widespread adoption in power electronics packaging. This study presents a novel approach to the synthesis of Cu nanoparticles capped with oleylamine ligands. By employing a simple solvent‐cleaning process, effective control of the density of oleylamine ligands on particle surfaces was achieved, resulting in high‐performance Cu nanoparticles with both oxidation resistance and air‐sintering susceptibility. Moreover, through our research, the solvent‐cleaning mechanism was clarified, a model for the oleylamine ligand decomposition was developed, the air‐sintering behavior of Cu nanoparticles was analyzed, and the impacts of both the sintered bodies and interfaces on the sintering performance were explained. Additionally, Cu nanoparticles subjected to 5 cleaning rounds followed by sintering at 280 °C and 5 MPa in air were confirmed to be able to produce the highest shear strength (49.2 ± 3.51 MPa) and lowest resistivity (6.15 ± 0.32 μΩ·cm). Based on these results, flexible capacitive pressure sensors with Cu sintered electrodes were fabricated and demonstrated a stable pressure–capacitance response over the temperature range of 25–250 °C. These findings underscore the impressive robustness and durability of sintered structures and the potential for high‐temperature applications of oleylamine‐capped Cu nanoparticles. Our study provides reliable application demonstrations for the low‐cost manufacture of high‐performance power electronics packaging structures that can operate in high‐current–density, high‐heat‐flow‐density, high‐temperature, and high‐stress environments.