Artifact-Free Microstructures in the Interfacial Reaction between Eutectic In-48Sn and Cu Using Ion Milling

oleh: Fu-Ling Chang, Yu-Hsin Lin, Han-Tang Hung, Chen-Wei Kao, C. R. Kao

Format: Article
Diterbitkan: MDPI AG 2023-04-01

Deskripsi

Eutectic In-48Sn was considered a promising candidate for low-temperature solder due to its low melting point and excellent mechanical properties. Both Cu<sub>2</sub>(In,Sn) and Cu(In,Sn)<sub>2</sub> formation were observed at the In-48Sn/Cu interface after 160 °C soldering. However, traditional mechanical polishing produces many defects at the In-48Sn/Cu interface, which may affect the accuracy of interfacial reaction investigations. In this study, cryogenic broad Ar<sup>+</sup> beam ion milling was used to investigate the interfacial reaction between In-48Sn and Cu during soldering. The phase Cu<sub>6</sub>(Sn,In)<sub>5</sub> was confirmed as the only intermetallic compound formed during 150 °C soldering, while Cu(In,Sn)<sub>2</sub> formation was proven to be caused by room-temperature aging after soldering. Both the Cu<sub>6</sub>(Sn,In)<sub>5</sub> and Cu(In,Sn)<sub>2</sub> phases were confirmed by EPMA quantitative analysis and TEM selected area electron diffraction. The microstructure evolution and growth mechanism of Cu<sub>6</sub>(Sn,In)<sub>5</sub> during soldering were proposed. In addition, the Young’s modulus and hardness of Cu<sub>6</sub>(Sn,In)<sub>5</sub> were determined to be 119.04 ± 3.94 GPa and 6.28 ± 0.13 GPa, respectively, suggesting that the doping of In in Cu<sub>6</sub>(Sn,In)<sub>5</sub> has almost no effect on Young’s modulus and hardness.