Despite a large amount of research on transient liquid phase (TLP) bonding methods for high operating temperature Pb-free solder electric interconnections using Cu6Sn5 intermetallics (IMCs), two fundamental difficulties remain, namely, slow TLP process kinetics and uncontrolled void formation. Here we observe the TLP processes for rapid Cu6Sn5 growth using a recently developed technique via real-time synchrotron X-ray imaging. The technique enables in-situ characterization of the growth kinetics and real-time observation of the IMC evolution at the molten solder/solid substrate interfaces and the formation of voids and cracking during TLP bonding, which will contribute to the development of products suitable for high reliability and high-temperature applications, e.g., electric vehicles.
