Oxidation resistance mechanism of copper wire regulated by nano-palladium coating

• Published in: Applied surface science 2025-01, Vol.680, p.161425, Article 161425
• Main Authors: Li, Shaolin, Su, Hui, Song, Kexing, Zhou, Yanjun, Cao, Jun, Xiao, Lili, Cao, Fei, Ge, Chenyang, Li, Jiyuan
• Format: Article
• Language: English
• Subjects: Amorphous; Bonding interface; Clearances; Diffusion; Oxidation resistance; Palladium-coated copper wire
• ISSN: 0169-4332
• DOI: 10.1016/j.apsusc.2024.161425

The multi-level distortion nanotwins in the palladium coating have excellent stability, which can reduce the stress difference of the palladium-copper bonding interface, thereby reducing the driving force of the outward diffusion of copper atoms, thereby improving the oxidation resistance of palladium-coated copper wires. [Display omitted] •The relationship between palladium coating thickness and clearances was proposed.•The nanocrystalline and amorphous band inhibit the diffusion of copper into palladium.•Nanotwins reduce the diffusion driving force by strain difference of interface.•The oxidation resistance mechanism based on the crystallographic characteristics. The microstructure characteristics of palladium coating are the key to the oxidation resistance of palladium-coated copper wire. In this paper, the microstructure characteristics of palladium coating thickness, nanocrystalline size and amorphous band width were controlled by adjusting the process parameters of micro-area coating. The relationship between microstructure characteristics of palladium coating and oxidation resistance was studied. The results show that the wire has good oxidation resistance when the deposition temperature is 400℃ and the copper wire/mold clearances are 2.5 μm. The surface of the copper wire has a palladium coating with a thickness of 74 nm, and the palladium particles are composed of amorphous encapsulated nanocrystals. The relationship between the thickness of palladium coating and the copper wire/mould clearances is y=0.012x+44, and the increase of palladium coating thickness can inhibit the migration of copper ions. The increase in the size of the nanocrystalline and the width of the amorphous band has a certain inhibitory effect on the lattice or grain boundary diffusion of copper to the palladium coating. The multi-stage distorted nanotwins in the amorphous palladium coating can reduce the strain difference at the palladium-copper bonding interface, reduce the diffusion driving force of copper outward, and thus improve the oxidation resistance of palladium-coated copper wires.