Qualification of the Assembly Process of Flip-Chip BGA Packages ...

Texas Tech University, Nivetha Shivan, May 2012
between the die and the bump due to diffusion. The ultrasound signals capture this
density difference as white halos around the bumps in the images. Figure 6.3 shows the
CSAM image of the white halos around the bumps.
Figure 6.3: CSAM Image Showing White Halos around Solder Bumps
� Darkened bumps
These are suspected as cracks in the bumps. The dark bumps could have been formed as a
result of interference of the ultrasonic waves between the interface and the cracked bumps.
Cross section of the bumps was done. Figure 6.4 shows CSAM image of the dark bumps.
Figure 6.5 shows the SEM image of one of the dark bumps.
Figure 6.4: CSAM Image Showing Dark Bumps
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