Publication: Investigation of the dealloying process for producing nanoporous copper structures in cu-cu interconnection bonding for advanced electronic packaging
Loading...
Date
2025-08-03
Authors
Charmaine, Lim Xin Chi
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
Achieving reliable Cu-Cu interconnection in advanced electronic packaging remains a major challenge due to limitations in conventional bonding techniques, prompting the need for innovative materials like nanoporous copper (NP-Cu). This study aims to fabricate NP-Cu using a dual-deposition method combining electroplating and dealloying with focus on parameters of dealloying. The process involves electroplated zinc coatings onto copper substrates, followed by heat treatment in muffle furnace at 150°C for 2 hours to promote zinc diffusion forming solid solution alloy. Subsequently, a dealloying process was conducted using hydrochloric and sulphuric acids at varying concentration (0.5 M, 3 M) and dealloying time (3, 6, 18, 24 hours) to form nanoporous structure. The coatings were characterized for morphology, elemental analysis, phases, pore sizes, electrical resistivity and hardness. The nanoporous pore size produced are in the range of 68.36-88.23 nm. The morphology of nanoporous copper (NP-Cu) is influenced by acid type, concentration, and dealloying duration. HCl, particularly at 3 M and shorter durations (3–6 hours), produced more uniform and interconnected porous structures, resulting in lower electrical resistivity (6.32 Ω/sq) and moderate hardness (up to 115.32 HV). In contrast, H₂SO₄ formed smaller pores with higher hardness (up to 157.46 HV) but lacked interconnectivity, as reflected by higher electrical resistivity (9.53 Ω/sq). At 24 hours, complete Zn removal occurred in all conditions, but HCl maintained better structural 16 connectivity but H₂SO₄ produced the largest pore size (88.23 nm) and low electrical resistivity (5.87 Ω/sq). Overall, dealloying with HCl at higher concentrations and shorter durations facilitated the formation of more uniform and interconnected nanoporous structures, exhibiting improved electrical conductivity. In contrast, H₂SO₄ typically produced finer but less interconnected pore networks, which corresponded to higher hardness and low electrical resistivity. These findings highlight the influence of acid types, concentration and dealloying duration in formation of nanoporous copper structure.