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

Texas Tech University, Nivetha Shivan, May 2012
Figure 6.5: SEM Image Showing Bump Delamination from Die
It was seen from the SEM image that there was separation between the bump and the
passivation layer on the die. This is different from the hypothesis. Though there is no
crack inside the bump, there is separation of the bump from the die which is not good for
electrical continuity.
Thus, the suspected failures from the CSAM images were validated using the cross-
section technique. Out of the three anomalies, the dark bumps and white area in the
underfills are important as they could be real failures and it is necessary to validate them.
The major failure modes in the flip chip BGA was learnt from the phase I stress tests –
underfill and bump delamination.
6.1.1.2 Shadow Moiré Results
A total of eight units were used for this evaluation (two samples from each DOE). Table
6.2 shows the maximum warpage of the devices and the temperature at which the
maximum warpage occurred. Table 6.3 shows the measured warpage across
temperatures.
55