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ELECTRONIC DEVICE FAILURE ANALYSIS | VOLUME 18 NO. 1
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intermetallic compound (IMC) was clearly visible. These
are indicated as “Voids (B)” in Fig. 4(b).
ANALYSIS OF XY-PLANE SLICES
Figure 5 shows XY-plane tomographic images of the
solder joints of the packages without TCT (Fig. 5a to c)
and with TCT (Fig. 5d to f). The images were extracted at
three different Z-heights:
• Figures 5(a) and (d), at level I (shown by arrow I in Fig.
4), are slice views of the copper pillar and IMC interface.
• Figures 5(b) and (e), at level II (shown by arrow II in Fig.
4), are slice views of the IMC layer.
• Figures 5(c) and (f), at level III (shown by arrow III in Fig.
4), are slice views at the level of the shrinkage voids.
Comparison of the two level-I views (Fig. 5a and d)
shows that the copper pillar and IMC interface changed
significantly with TCT treatment: although only small
voids are observed prior to TCT, numerous large voids
appear after TCT. At level II, very few voids were detected
in the IMC layer either before or after TCT. At level III,
numerous shrinkage voids and entrapped filler particles
from the preapplied underfill are observed. In addition,
the authors were able to observe the 3-D distribution of
filler in the underfill, as well as gaps between the copper
pillar and the adhesive. (continued on page 18)
Fig. 4 Tomographic images of the XZ- and YZ-planes in the center of the copper pillar. (a) Before TCT. (b) After TCT (–55 °C/125 °C,
30 min/30 min, 1000 cycles)
(a)
(b)