Microstructural evolution of a lead-free solder alloy Sn-Bi-Ag-Cu prepared by mechanical alloying during thermal shock and aging |
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| Authors: | M L Huang C M L Wu J K L Lai Y C Chan |
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| Affiliation: | (1) Dept. of Physics and Materials Science, City University of Hong Kong, Hong Kong;(2) Dept. of Electronic Engineering, City University of Hong Kong, Hong Kong |
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| Abstract: | In a previous study, a lead-free solder, Sn-6Bi-2Ag-0.5Cu, was developed by mechanical alloying. The alloy shows great potential
as a lead-free solder system. In the present work, the microstructural evolution during thermal shock and aging was examined.
In the as-soldered joints small bismuth (1 μm to 2 μm) and Ag3Sn (1 μm) particles were finely dispersed in a nearly pure tin matrix with a small amount of η-Cu6Sn5 phase in the bulk of solder. During thermal shock and aging microstructural evolution occurred with Cu-Sn intermetallic compound
(IMC) layer growth at interface, bismuth phase coarsening and Ag3Sn phase coarsening. The microstructure of the solder appeared to be stable at high temperature. The shear strength of the
present solder joint is higher than that of Sn-37Pb and Sn-3.5Ag solders. Shear failure occurred Cu-Sn IMC layer-solder interface
and in the bulk of solder. |
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| Keywords: | Lead-free solder Sn-Bi-Ag-Cu microstructural evolution shear strength thermal shock aging |
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