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Open AccessArticle

Dynamic Observation of Interfacial IMC Evolution and Fracture Mechanism of Sn2.5Ag0.7Cu0.1RE/Cu Lead-Free Solder Joints during Isothermal Aging

by Di Zhao 1,2,3, Keke Zhang 1,2,*, Ning Ma 1,2, Shijie Li 1,2, Chenxiang Yin 1,2 and Fupeng Huo 4,5
1
School of Materials Science and Engineering, Henan University of Science and Technology, Luoyang 471023, China
2
Henan Province Key Laboratory of Nonferrous Metal Material Science and Processing Technology, Luoyang 471023, China
3
State Key Laboratory of Advanced Welding and Joining, Harbin Institute of Technology, Harbin 150001, China
4
Joining and Welding Research Institute, Osaka University, 11-1 Mihogaoka, Ibaraki, Osaka 567-0047, Japan
5
Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan
*
Author to whom correspondence should be addressed.
Materials 2020, 13(4), 831; https://doi.org/10.3390/ma13040831
Received: 10 January 2020 / Revised: 31 January 2020 / Accepted: 4 February 2020 / Published: 12 February 2020
Dynamic observation of the microstructure evolution of Sn2.5Ag0.7Cu0.1RE/Cu solder joints and the relationship between the interfacial intermetallic compound (IMC) and the mechanical properties of the solder joints were investigated during isothermal aging. The results showed that the original single scallop-type Cu6Sn5 IMC gradually evolved into a planar double-layer IMC consisting of Cu6Sn5 and Cu3Sn IMCs with isothermal aging. In particular, the Cu3Sn IMC grew towards the Cu substrate and the solder seam sides; growth toward the Cu substrate side was dominant during the isothermal aging process. The growth of Cu3Sn IMC depended on the accumulated time at a certain temperature, where the growth rate of Cu3Sn was higher than that of Cu6Sn5. Additionally, the growth of the interfacial IMC was mainly controlled by bulk diffusion mechanism, where the activation energies of Cu6Sn5 and Cu3Sn were 74.7 and 86.6 kJ/mol, respectively. The growth rate of Cu3Sn was slightly faster than that of Cu6Sn5 during isothermal aging. With increasing isothermal aging time, the shear strength of the solder joints decreased and showed a linear relationship with the thickness of Cu3Sn. The fracture mechanism of the solder joints changed from ductile fracture to brittle fracture, and the fracture pathway transferred from the solder seam to the interfacial IMC layer. View Full-Text
Keywords: Sn2.5Ag0.7Cu0.1RE/Cu soldering; dynamic observation; isothermal aging; intermetallic compound; growth kinetics; fracture mechanism Sn2.5Ag0.7Cu0.1RE/Cu soldering; dynamic observation; isothermal aging; intermetallic compound; growth kinetics; fracture mechanism
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MDPI and ACS Style

Zhao, D.; Zhang, K.; Ma, N.; Li, S.; Yin, C.; Huo, F. Dynamic Observation of Interfacial IMC Evolution and Fracture Mechanism of Sn2.5Ag0.7Cu0.1RE/Cu Lead-Free Solder Joints during Isothermal Aging. Materials 2020, 13, 831.

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