Publication: Investigation of porous copper (cu) formation using electroplating and dealloying for cu-cu bonding
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Date
2024-08-01
Authors
Lum Jing Yan
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Abstract
Direct Cu-Cu bonding provide low bond strength, higher electrical resistance, inferior mechanical properties, and higher processing temperature and pressure compared to copper (NP-Cu). Nanoporous copper (NP-Cu) provides the potential of low cost, good electrical conductivity, thermal stability, and high-density connections for Cu-Cu bonding. The present study investigates the formation of porous copper (Cu) structure by varying the electroplating times (5, 10, 15, 20, 25, and 30 minutes) and dealloying times (6, 24 hours). The porous copper (Cu) was characterized by surface morphology, elemental analysis, phase analysis, electrical resistivity, and hardness using FE-SEM, EDX, XRD, 4-point probe, and Vickers hardness. The sample electroplated for 15 mins exhibited porous network structure, and EDX and XRD analysis confirmed the present of Cu only. In contrast, the sample electroplated for 5 mins showed fewer pores, while the sample electroplated for 30 minutes has a formation of intermetallic compound (Cu5Zn8) as confirmed by XRD analysis. The compound is difficult to dissolve. The sample electroplated for 30 mins has the highest sheet resistivity (1.532 Ω), while the sample plated for 15 minutes has the lowest sheet resistivity (1.213 Ω). The high hardness recorded for sample electroplated for 5 mins (99.8 Hv) and 30 mins (73.3 Hv). The sample with interconnected porous network has high hardness (68.2 Hv) than pure copper (64.8 Hv).