Surface modification of Cu electroplated layers for Cu-Sn transient liquid phase bonding

Transient liquid phase (TLP) bonding technology attracts great attention as it can produce a full intermetallic compound (IMC) bonding structure for high-temperature applications. In this study, the Cu-Sn TLP bonding is investigated based on the microstructural and mechanical analyses of a sandwiched structure of Cu/Sn-3.5 wt% Ag/Cu under thermal compression at 260 degrees C for 20 min. Electroplating is used to prepare the Cu base with various surface structures to investigate the topographical effect on the TLP bonding technology. The microstructural analysis indicates that two IMCs, Cu6Sn5 and Cu3Sn, are formed at the bonding interface. The shear strength test shows that the Cu base with a dome and step pyramid shaped surface structure benefits the TLP bonding and increases the shear strength as compared to common faceted Cu base. The improvement of shear strength is attributed to the riveting and interlocking effect of the Cu domes and pyramids which disadvantages the propagation of fracture.

Automated summary

In this study, Cu-Sn TLP bonding is investigated and two IMCs are formed at the bonding interface. Additionally, it is found that Cu bases with special topographical surface structures can improve the shear strength of TLP bonding.