Study on the Cu Microstructure and Sn Supply Affecting the Interfacial Reaction of Cu/Sn Nanowires for Advanced Electronic Packaging

The interfacial reactions between Cu and Sn at the nanoscale, which is critical to the development of microbump (μ-bump) technology, require further understanding. Constructing the nanoscale interface for observing the interfacial behavior during reactions is a challenge. This study investigates the interfacial reactions within Cu/Sn composite nanoarrays fabricated through template electrodeposition to explore the growth process of intermetallic compounds (IMCs). The results reveal that polycrystalline Cu/Sn composite nanoarrays were successfully electroplated with varying Sn fractions, which regulated the growth of IMCs. Additionally, both polycrystalline copper/IMC and nanotwinned copper (nt-Cu)/IMC nanowires were analyzed to explore the effect of the Cu microstructure on IMC growth. Finally, full-IMC nanowires were prepared via high-temperature storage, where twins may act as vacancy sinks at this condition, preventing the formation of voids, which should hold great significance for guiding the preparation of full-IMC μ-bumps in transient liquid-phase (TLP) bonding. This work provides deeper insights into solder joint interface changes in electronic devices during operation.