The Temperature-Dependent Phase Transformation and Microstructural Characterisation in In-Sn Solder Alloys
Jiye Zhou, Xin Fu Tan, Qinfen Gu, Stuart D. McDonald, Kazuhiro Nogita
Abstract
Abstract Indium-based solder alloys are considered candidates for the next generation of low-temperature solder materials, especially for superconducting joints because of the properties of the β -In 3 Sn phase. The temperature-dependent phase transformation and thermal expansion behaviour of two different solder compositions including In-35Sn (in wt.%) and In-25.6Sn have been characterised using an in situ synchrotron powder X-ray diffraction method. The c-axis of the β -In 3 Sn unit cell in the In-35Sn alloy exhibited a complex relationship with increasing temperature compared to the positive increasing trend in In-25.6Sn due to the temperature-dependent solubility of Sn in β -In 3 Sn and change in the volume fraction of phases commencing at 80°C. In situ heating scanning electron microscopy recorded a real-time melting-solidification microstructure variation and phase transition during annealing at 90°C that was further analysed using energy dispersive X-ray spectroscopy. The observations are discussed with respect to the lattice parameters of the γ -InSn 4 and β -In 3 Sn phases and the proportions and composition of both phases present within the alloys.