Solid state intermetallic compound layer growth between Sn-8Zn-3Bi solder and bare copper substrate

The growth kinetics of the intermetallic compound layer formed between Sn-8Zn-3Bi solder and a bare Cu substrate by solid-state isothermal aging were examined at temperatures between 343 and 423 K for periods ranging from 0 to 100 days. A quantitative analysis was performed of the intermetallic compound layer thickness as a function of the aging time and aging temperature. For the identification of the intermetallic compounds, both Energy Dispersive X-ray and X-Ray Diffraction were employed.The experimental results showed that the γ -Cu5Zn8 intermetallic compound was observed at the interface between the solder and the bare copper substrate. Additionally, the thickness of the γ -Cu5Zn8 intermetallic compound increased with increasing aging temperature and aging time. The layer growth of the intermetallic compound in the Cu/Zn couple follow a parabolic law within a given temperature range. As a whole, because the value of the time exponent (n) is approximately equal to 0.5, the layer growth of the intermetallic compound was mainly controlled by the diffusion mechanism in the temperature range studied. The apparent activation energy of the γ -Cu5Zn8 intermetallic compound was 61.19 kJmol.

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