Realizing low-temperature air sintering of robust Cu-Cu joints through benzimidazole-coated in-situ Cu paste with protective encapsulation

With the rapid development of third-generation power semiconductor devices, there is an increasing demand for advanced interconnect materials. Copper nanoparticles have emerged as a promising alternative to their cost-effectiveness, superior durability, and electrical conductivity comparable to silver. However, the practical application of copper is hindered by its susceptibility to oxidation, which prevents low-temperature sintering in ambient air. This study introduces an innovative in situ preparation method for copper paste, where benzimidazole-coated copper particles are synthesized directly through a one-step process. This novel approach simultaneously integrates copper particle synthesis, in-situ benzimidazole coating, and paste formulation, thereby obtain oxidation-resistant and well-dispersed copper paste. The entire process is simple, efficient, environmentally friendly, and achieves a yield of up to 99 %. An encapsulation sintering method is further developed to protect the joint from oxidation during sintering via an epoxy sealing layer. The copper paste was successfully sintered in air at 220 °C, and exhibited remarkable performance, with a shear strength of 60.35 MPa and a low resistivity of 19.25 × 10 −8  Ω m. The method of this study effectively reduces the requirement for protective sintering atmospheres of copper nanoparticles, representing a substantial advancement for the power semiconductor industry.