材料期刊网

The wetting property of (Sn-9Zn)-2Cu (wt pct) on Ni substrate and the evolution of interfacial microstructure in (Sn-9Zn)-2Cu/Ni joints during soldering as well as isothermal aging were studied. The wetting ability of eutectic Sn-9Zn solder on Ni substrate was markedly improved by adding 2 wt pct Cu into this solder alloy. Plate-like Cu5Zn8 intermetallic compounds (IMCs) were detected in (Sn-9Zn)-2Cu solder matrix. A continuous Ni₅Zn₂₁ IMC layer was formed at (Sn-9Zn)-2Cu/Ni interface after soldering. This IMC layer kept its type and integrality even after aging at 170°C for up to 1000 h. At the early aging stage (before 500 h), the IMC layer grew fast and its thickness followed a linear relationship with the square root of aging time. Thereafter, however, the thickness increased very slowly with longer aging time. When the joints were aged for 1000 h,
a new IMC phase, (Cu,Ni)₅Zn₈, was found in the matrix near the interface. The formation of (Cu,Ni)₅Zn₈ phase can be attributed to the di®usion of Ni atoms into the solder matrix from the substrate.