Characterization of Flip Chip Bump Failure Mode by using High Frequency 230MHz MP and CP4 Transducer

Acoustic Micro Imaging has been used over the past decade as a successful nondestructive technique to detect discontinuities within materials and interconnects. This paper focused on the capability of this nondestructive tool in detecting defect bumps by using high frequency 230 MHz MP and CP4 transducer. Characterization work was done on both the transducer and it was found that the MP acoustic image was able to give a clearer indication of defect bumps than CP4 but has edge effect limitation. The CP4 acoustic image however was able to give a clear assessment of the edge bumps but was unable to highlight the defect bump clearly. Therefore in this study, defect bumps identification was established between CP4 and MP acoustic image to have full capability for assessing the bumps integrity. All the suspected defect bumps identified from acoustic image was then verified with physical cross sectioning and followed by standard optical scoped and scanning electron microscopy (SEM) to inspect the failing interfaces. These results demonstrate the capabilities of micro imaging as a nondestructive tool to capture defect bumps in early stages of assembly. This application also helps failure analysis to eliminate the need to destruct the unit for physical cross sectioning and reduce analysis cycle time.