In situ study on growth behavior of interfacial bubbles and its effect on interfacial reaction during a soldering process

The growth behavior of interfacial bubbles and the effect of bubbles on interfacial reaction during a soldering process were in situ studied by the synchrotron radiation real-time imaging technology. It was found that the bubbles at the solid/liquid interface were heterogeneous nucleation. The heterogeneous nucleation energy of bubbles at the interface was one-tenth of the homogeneity nucleation energy at 250 °C. At the interface, each bubble grew into spherical finally and its volume increased with the rise of temperature. Annexations between adjacent bubbles occurred, during which the bigger bubbles moved toward the smaller ones. The bubbles at the solid/liquid interface affected the dissolution behavior of Cu substrate greatly, i.e., the closer to the bubble bottom the less the Cu dissolution was, since the less the solder and the easier the saturation were. Moreover, the effect of bubbles on the growth behavior of interfacial intermetallic compound (IMC) was also discussed.