The liquid/solid (L/S) interface of dissimilar metals is critical to the microstructure, mechanical strength, and structural integrity of interconnects in many important applications such as electronics, automotive, aeronautics, and astronautics, and therefore has drawn increasing research interests. To design preferential microstructure and optimize mechanical properties of the interconnects, it is crucial to understand the formation and growth mechanisms of diversified structures at the L/S interface during interconnecting. In situ synchrotron radiation or tube-generated X-ray radiography and tomography technologies make it possible to observe the evolution of the L/S interface directly and therefore have greatly propelled the research in this field. Here, we review the recent progress in understanding the L/S interface behaviors using advanced in situ X-ray imaging techniques with a particular focus on the following two issues: (1) interface behaviors in the solder joints for microelectronic packaging including the intermetallic compounds (IMCs) during reflow, Sn dendrites, and IMCs during solidification and reflow porosities and (2) growth characteristics and morphological transition of IMCs in the interconnect of dissimilar metals at high temperature. Furthermore, the main achievements and future research perspectives in terms of metallurgical bonding mechanisms under complex conditions with improved X-ray sources and detectors are remarked and discussed.

在许多重要应用（例如电子，汽车，航空和航天）中，异种金属的液/固（L / S）界面对于互连的微观结构，机械强度和结构完整性至关重要，因此吸引了越来越多的研究兴趣。为了设计优先的微观结构并优化互连的机械性能，至关重要的是要了解互连期间L / S界面处多样化结构的形成和生长机理。原位同步加速器辐射或电子管产生的X射线摄影和断层摄影技术使直接观察L / S界面的演化成为可能，因此极大地推动了该领域的研究。在这里，我们回顾了使用先进的原位X射线成像技术了解L / S界面行为的最新进展，特别关注以下两个问题：（1）微电子封装（包括金属间化合物）的焊点中的界面行为（IMC）的回流，锡枝晶和凝固和回流孔隙中的IMC，以及（2）高温下异种金属互连中IMC的生长特性和形态转变。此外，