The soldering reaction and interfacial microstructure formed between liquid Sn-Zn-Ag solder and Cu at the early stage of soldering at 250 °C for 15 s were studied primarily with the aid of transmission electron microscope (TEM). To achieve the early stage reaction information, the soldered specimens, 5 mm × 5 mm × 500 μm solder on 10 mm × 10 mm × 20 μm Cu, were rapidly quenched in liquid nitrogen after soldering. The results of TEM interfacial analysis show that a Cu-Zn reaction zone, consisting of β′-CuZn and γ-Cu5Zn8, formed near Cu while a Ag-Zn zone, consisting of γ-Ag5Zn8 and ∈-AgZn3, formed near solder. The innermost layer adjacent to the Cu substrate is an amorphous Cu-Zn diffusion region that contains dispersed β′-CuZn nanocrystalline cells. The β′-CuZn also precipitates in the γ-Ag5Zn8 and ∈-AgZn3 layer due to the supersaturation of Cu.
All Science Journal Classification (ASJC) codes
- Materials Science(all)
- Condensed Matter Physics
- Mechanics of Materials
- Mechanical Engineering