Effects of Ag addition on solid–state interfacial reactions between Sn–Ag–Cu solder and Cu substrate

Low–Ag–content Sn–Ag–Cu (SAC) solders have attracted much recent attention in electronic packaging for their low cost. To reasonably reduce the Ag content in Pb–free solders, a deep understanding of the basic influence of Ag on the SAC solder/Cu substrate interfacial reaction is essential. Previous...

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Bibliographic Details
Published in:Materials characterization 2017-02, Vol.124, p.250-259
Main Authors: Yang, Ming, Ko, Yong-Ho, Bang, Junghwan, Kim, Taek-Soo, Lee, Chang-Woo, Li, Mingyu
Format: Article
Language:English
Subjects:
AGING
ATOMS
CONCENTRATION RATIO
COPPER
CRYSTAL GROWTH
CRYSTALLOGRAPHY
CRYSTALS
DIFFUSION
Diffusion kinetics
INTERFACES
INTERMETALLIC COMPOUNDS
KINETICS
Low–Ag–content solder
MATERIALS SCIENCE
Pb–free solder
SILVER
SILVER ADDITIONS
SOLDERING
Solid–state reaction
SUBSTRATES
THICKNESS
TIN
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Summary:Low–Ag–content Sn–Ag–Cu (SAC) solders have attracted much recent attention in electronic packaging for their low cost. To reasonably reduce the Ag content in Pb–free solders, a deep understanding of the basic influence of Ag on the SAC solder/Cu substrate interfacial reaction is essential. Previous studies have discussed the influence of Ag on the interfacial intermetallic compound (IMC) thickness. However, because IMC growth is the joint result of multiple factors, such characterizations do not reveal the actual role of Ag. In this study, changes in interfacial IMCs after Ag introduction were systemically and quantitatively characterized in terms of coarsening behaviors, orientation evolution, and growth kinetics. The results show that Ag in the solder alloy affects the coarsening behavior, accelerates the orientation concentration, and inhibits the growth of interfacial IMCs during solid–state aging. The inhibition mechanism was quantitatively discussed considering the individual diffusion behaviors of Cu and Sn atoms, revealing that Ag inhibits interfacial IMC growth primarily by slowing the diffusion of Cu atoms through the interface. •Role of Ag in IMC formation during Sn–Ag–Cu soldering was investigated.•Ag affects coarsening, crystallographic orientation, and IMC growth.•Diffusion pathways of Sn and Cu are affected differently by Ag.•Ag slows Cu diffusion to inhibit IMC growth at solder/substrate interface.
ISSN:1044-5803
1873-4189
DOI:10.1016/j.matchar.2017.01.004