Surface diffusion controlled reaction in small size microbumps

[Display omitted] •Head-shaped Cu-Sn solder joints with diameters about 10 μm, 20 μm, and 50 μm are reflowed.•Grain growth in the small size bumps has the faster growth rate.•In the 10 μm bumps, there is only one Cu6Sn5 grain after reflow.•The classic scallop-type grain growth model of Cu6Sn5 does n...

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Veröffentlicht in:Materials letters 2021-02, Vol.284, p.129036, Article 129036
Hauptverfasser: Liu, Yingxia, Shi, Xiuyu, Ren, Haoxiang, Cai, Jian, Zhao, Xiuchen, Tan, Chengwen, Tu, K.N.
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Sprache:eng
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Zusammenfassung:[Display omitted] •Head-shaped Cu-Sn solder joints with diameters about 10 μm, 20 μm, and 50 μm are reflowed.•Grain growth in the small size bumps has the faster growth rate.•In the 10 μm bumps, there is only one Cu6Sn5 grain after reflow.•The classic scallop-type grain growth model of Cu6Sn5 does not apply.•A surface diffusion-controlled model is proposed to explain the new kinetics. We made head-shaped Cu-Sn solder joints with diameters about 10 μm, 20 μm, and 50 μm and reflowed the samples at 240 °C, 260 °C, and 280 °C for 60 s to 600 s. In the 10 μm bumps, there is only one Cu6Sn5 grain after reflow, thus the classic model of scallop-type grain growth of Cu6Sn5 does not apply. Also, the grain growth in the small size bumps has the faster growth rate. We proposed a surface diffusion-controlled model to explain the new kinetics. According to our model, the diffusion activation energy is calculated to be QS = 0.18 ± 0.02 eV/atom and diffusion frequency factor to be DS0 = 5.65 × 10−3 cm2/s.
ISSN:0167-577X
1873-4979
DOI:10.1016/j.matlet.2020.129036