Microstructural evolution of intermetallic compounds between crystalline/amorphous Cobalt-Phosphorous coatings and lead-free solders

• DOI: 10.1016/j.jmrt.2022.06.035
• Publication Date: 2022-06-11T15:50:36Z
• Authors: Shuang Liu; Limin Ma; Cheng Zhen; Yishu Wang; Dan Li; Fu Guo
• Keywords: Ductility (Earth science); Nanocrystalline material; Brittleness; Ostwald ripening

In the advanced microelectronic packaging, Cu/Sn joints require high-quality diffusion barriers to inhibit Cu–Sn intermetallic compounds (IMCs) growth and improve interface brittleness. Cobalt-Phosphorous (Co–P) alloy coatings are ideal candidates due their good wettability, promising resistance low interfacial this work, microstructural evolution of IMCs between crystalline/amorphous Co–P lead-free solders during solid-state were systemically investigated. The microstructure, phase distribution, grain characteristics carefully characterized by SEM, EPMA, EBSD, TEM. It was found that consumption rate crystalline Co–P, 21.2 nm/h, significantly slower than amorphous 96.4 exhibited an excellent resistance, which attributed nanocrystalline structure P-rich layer performed for Sn Cu atoms. Compared with Ni, could better brittleness soft ductile Co–Sn (hardness 3.0 GPa) growing rapid Co, toughened Co–Sn–P attributing Sn. Kinetic analysis showed rate-controlling process jointly controlled reaction volume diffusion, effect is more pronounced in system, leads coarse grains beneficial softness ductility IMCs. Crystalline can be applied surface treatment die pads print-circuit-board according own characteristics, respectively.