The phase evolution as well as microstructural change of thin film Au/Sn reaction couple was investigated at room temperature with respect to 1.0 × 104 A/cm2 of current stressing. Transmission electron microscopy (TEM) equipped with nano beam electron diffraction (NBED) and energy dispersive X-ray spectrometer (EDS) revealed the fully conversion of Sn layer into AuSn and Au5Sn IMCs after deposition. The rapid phase transformation of Au5Sn to Au and AuSn, regardless of direction of electron flow, was evidenced by TEM during short time of current stressing. The electron impingement induced lattice strain of Au5Sn higher than the offset yield limit was anticipated through in-situ XRD investigation. The lattice adjustment of Au5Sn to AuSn due to escape of Au from Au5Sn crystal was responsible for the phase transformation. The polarity migration of produced Au atoms from Au5Sn crystal to the anode gave rise to the numerous nano voids formation at the original Au5Sn/Au interface with forward electric current and dilution of Sn in Au layer with reverse current stressing.
All Science Journal Classification (ASJC) codes
- Mechanics of Materials
- Mechanical Engineering
- Metals and Alloys
- Materials Chemistry