10 Fundamentals of Bonding Technology and Process Materials …
301
Fig. 10.47 Comparison of
edge and center micro-bump
die interconnect height using
DOE1 bonding conditions
[18]
Center
Edge
~42u
~40u
40um
42um
Fig. 10.46. For example, the peak temperature was 305 °C and melting detection was
5 μm.
The results of this task shifted the failure mode to solder opens. Namely, this
DOE, designed to decouple the thermal and mechanical parameters, accomplished
the primary objective by finding the upper limit of the thermal process not resulting
in solder bridges. Based on these findings, the second DOE investigated the primary
mechanical parameter, displacement of bond head in z-axis to avoid open failures
by travelling further deeper. For all four legs of the DOE there were solder opens
as shown in Table 10.8, which implies that the thermal process window is stable
enough not to result in short failures and mechanical process window is independent
of thermal process parameters because no short failures were observed at even higher
temperature and longer peak. From this build, cross sectioning of the micro-bump
solder interconnects was done and it was found that there was a slight bow of the die
as shown in Fig. 10.47. Figure 10.47 shows the edge micro-bump die solder joints
having a height of 40 μm and the center die solder joints having a height of 42 μm.
It is believed that this bow is due to a temperature gradient across the micro-bump
die that results in an uneven gap height.
DOE2 selected upper limits of the thermal process window identified in DOE1,
which do not induce short failures, to guarantee stable solder interconnection. The
mechanical process condition required solder melting detection, to eliminate solder
opens are described in Table 10.9. In order to prevent total or insufficient collapse
of the molten solders, there is a z-displacement setting on the TCB tool to control
the amount of z-displacement of the head. Recall that this amount of controlled zdisplacement after solder reflow terms the “melt detection.” This is a tool parameter,
sensitive to yield and the parameter, mainly depends on equipment’s characteristics.
Here the major variable was to control the melting detection height ranging from 6
to 10 μm. From this work, the electrical testing confirmed no solder opens and no
shorts when using a melt setting height of 10 μm.
301
Fig. 10.47 Comparison of
edge and center micro-bump
die interconnect height using
DOE1 bonding conditions
[18]
Center
Edge
~42u
~40u
40um
42um
Fig. 10.46. For example, the peak temperature was 305 °C and melting detection was
5 μm.
The results of this task shifted the failure mode to solder opens. Namely, this
DOE, designed to decouple the thermal and mechanical parameters, accomplished
the primary objective by finding the upper limit of the thermal process not resulting
in solder bridges. Based on these findings, the second DOE investigated the primary
mechanical parameter, displacement of bond head in z-axis to avoid open failures
by travelling further deeper. For all four legs of the DOE there were solder opens
as shown in Table 10.8, which implies that the thermal process window is stable
enough not to result in short failures and mechanical process window is independent
of thermal process parameters because no short failures were observed at even higher
temperature and longer peak. From this build, cross sectioning of the micro-bump
solder interconnects was done and it was found that there was a slight bow of the die
as shown in Fig. 10.47. Figure 10.47 shows the edge micro-bump die solder joints
having a height of 40 μm and the center die solder joints having a height of 42 μm.
It is believed that this bow is due to a temperature gradient across the micro-bump
die that results in an uneven gap height.
DOE2 selected upper limits of the thermal process window identified in DOE1,
which do not induce short failures, to guarantee stable solder interconnection. The
mechanical process condition required solder melting detection, to eliminate solder
opens are described in Table 10.9. In order to prevent total or insufficient collapse
of the molten solders, there is a z-displacement setting on the TCB tool to control
the amount of z-displacement of the head. Recall that this amount of controlled zdisplacement after solder reflow terms the “melt detection.” This is a tool parameter,
sensitive to yield and the parameter, mainly depends on equipment’s characteristics.
Here the major variable was to control the melting detection height ranging from 6
to 10 μm. From this work, the electrical testing confirmed no solder opens and no
shorts when using a melt setting height of 10 μm.