In order to acquire the relevant creep characteristics such as stress exponent and activation energy, creep strain tests were conducted on Sn-3.5Ag and Sn-5Sb systems of solder alloys in the intermediate temperature regime from 353K to 453K corresponding to the homologous temperatures =0.715 0.917 and =0.699 0.897 for two alloys, respectively.It was found that an apparent creep-activation energy of both Sn-3.5Ag and Sn-5Sb solder alloys had a changing point at the =0.82 under the higher stress of 9.8MPa. At the lower stress of 4MPa, the change point was found only for Sn-5Sb alloy.Moreover, under the lower stress level(less than 6MPa), the stress exponent of the both solder alloys indicated n 1, while under the higher stress region (more than 9.8MPa), the stress exponent of the both solders showed n 7.Determining factors of creep deformation were discussed in relation with the temperature and stress regimes. It was considered that the deformation of the both solder alloys is dominated by the rate of the dislocation climb/dislocation glide at the higher temperature and stress regime.
The dissolution properties of Cu in molten Sn-Cu-Ni and Sn-Zn alloys were investigated and compared with those of Cu in SnAg -Cu alloys. In the Sn-Cu-Ni alloys with small amounts of Ni, the dissolution rate of Cu decreases with increasing Ni content when the Ni content is below 0.15 mass%. The dissolution rate is proportional to the difference between the saturated solute concentration in liquid (C s) and the solute concentration in liquid (C), (C s ϪC), which is estimated from the isothermal section of the Cu-Sn-Ni ternary phase diagram. In the Sn-Zn alloy, the Cu-Zn reaction layer forms at the solder/Cu interface. The layer prevents Cu dissolution and thus the dissolution rate of Cu is dramatically reduced.
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