| The intermetallic compound formation, growth reaction and microstructural changes as functions of aging time and temperatures were studied in the electrodeposited SnPb/Cu and SnPb/Ni/Cu system. Diffusivities in the SnPb/Cu were about one order less than those in the Sn/Cu system. Activation energies for the growth of the η phase(Cu_6Sn_5) were 10.44 and 15.97 ㎉/㏖ for the Sn80Pb20/Cu and the Sn60Pb40/Cu system, respectively. Those of the ε phase(Cu₃Sn) were 15.47 and 15.20 ㎉/㏖ respectively. Mostly, the T/T_m(homologous temperature) of the SnPb layer affected the growth rate of the η phase when the aging temperature was near to the melting temperature(T_m) of the SnPb alloy(>0.9T_m). Therefore the growth rate of the η phase depended on the composition of the SnPb. However, the ε phase which grows consuming the η phase did not depend on the composition. In the SnPb/Ni/Cu system, an unknown phase(name it as χ phase) was formed in addition to the stable Ni₃Sn₄phase. The χ phase grew fast toward the SnPb layer at the SnPb/Ni interface and developed as plate like shape. From the EDS analysis, the composition of χ phase was approximately Cu_7(NiSn₃)_(83). |
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