Study of Ga-21.5In-10Sn/Cu Liquid-Solid Interfacial Reaction and Reaction Barrier Layer

• Published in: 2024 25th International Conference on Electronic Packaging Technology (ICEPT) pp. 1 - 6
• Main Authors: Huang, Yaoxuan, Wang, Li, Ma, Haobo, Su, Xiaolin, Zhao, Ning, Ma, Haitao
• Format: Conference Proceeding
• Language: English
• Published: IEEE 07.08.2024
• Subjects: Conductivity; Flexible interconnects; Ga-21.5In-10Sn/Cu interface; Heating systems; Interficial reaction; Liquids; Nickel; Plating; Reaction barrier layer; Shape; Temperature
• ISSN: 2836-9734
• DOI: 10.1109/ICEPT63120.2024.10668493

Gallium-based liquid metal combines metallic conductivity and liquid mobility, and is the material of choice for wearable flexible electronics. However, flexible interconnect structures represented by Ga-21.5In-10Sn/Cu undergo spontaneous reactions at the liquid-solid interface, leading to interfacial instability, which reduces the reliability of the flexible devices and causes the failure of liquid-metal-based electronic devices. Therefore, it is necessary to inhibit the spontaneous interfacial reaction of Ga-21.5In-10Sn/Cu in order to improve its reliability. Ni, Ni-P and Ni-Co alloy coatings are difficult to react with Ga-21.5In-10Sn at room temperature and the preparation process is well established, so these three coatings are used as a reaction blocking layer between Ga-21.5In-10Sn and copper. The results show that, when heated at 50°C for 1h, the interfacial reaction between Ga-21.5In-10Sn and Cu occurs, and more brick intermetallic compounds CuGa2 are generated; However, there is no intermetallic compound with Ni-P/Cu, Ni/Cu, and Ni-Co/Cu, indicating that there is no interfacial reaction between Ga-21.5In-10Sn and the three coatings, and that the three coatings have a certain reaction blocking effect. Under the condition of 120°C and heating for 1 h, the integrity of the Ni-P coating is destroyed and intermetallic compounds are produced, losing the blocking effect on the interfacial reaction; on the other hand, the Ni and Ni-Co coatings still do not produce intermetallic compounds, which can obviously inhibit the interfacial reaction between Ga-21.5In-10Sn/Cu and improve the reliability of the flexible devices. The upper temperature limit of the pure Ni coating as a reaction barrier for Ga-21.5In-10Sn/Cu is as high as 200°C. At a higher temperature of 280°C, the Ni and Ni-Co coatings can be used to inhibit the reaction of Ga-21.5In-10Sn/Cu. At a higher temperature of 280°C for 1 h, Ni-Co as Ga-21.5In-10Sn/Cu reaction barrier still shows excellent chemical inertness. In addition, the Ni-P coating has poor electrical conductivity, while Co has higher electrical conductivity than Ni. Among these three types of barrier layers, the conductivity of Ni-Co is more favorable. Therefore, Ni-Co has better application prospects as a reactive barrier layer for liquid metal Ga-21.5In-10Sn.