Silane-Assisted Surface Modification of Solder Bump Interfaces for Reliable Underfill Adhesion

Herein, an organosilane-assisted surface treatment is investigated to enhance the interfacial reliability of flip-chip package assemblies. Interfacial voids and insufficient adhesion between solder joints and epoxy underfill remain major reliability concerns in flip-chip packaging owing to insufficient wettability during underfill dispensing. To overcome the issue, three organosilanes with different functional groups, such as 3-aminopropyltriethoxysilane (APTES), 3-glycidoxypropyltrimethoxysilane (GPTMS), and phenyltriethoxysilane (PTES), are applied to the solder bump surfaces prior to underfill dispensing. After underfill dispensing and curing, the effects of silane functionality on interfacial defect formation are evaluated by polishing-assisted cross-sectional observation using optical microscopy and field-emission scanning electron microscopy. The untreated and APTES-treated assemblies show noticeable void formation at the solder and underfill interface, indicating relatively non-uniform underfill coverage. In contrast, the GPTMS- and PTES-treated assemblies exhibit more continuous interfacial coverage with suppressed void formation. These results suggest that the glycidyl- and phenyl-functionalized silanes provide higher compatibility compared with amine-functionalized silane. Overall, this study demonstrates that a simple organosilane-assisted surface modification can effectively improve underfill adhesion and interfacial reliability in flip-chip package assemblies.
- This work was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (RS-2022-NR070869).