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t e s t i ng. Cr o s s - s e c t io n a n a ly si s
provides further information about the
resulting shape of the adhesive and its
dependence on the process parameters.
In Table 1, the variations under
a nalysis a re g iven. T he st a ndby
temperature of the wafer was kept
constant at 50°C. The main parameters
under analysis are the chip temperature
and the bonding pressure. After pick-
up, a delay of 10s is applied so that
the die is able to reach a homogeneous
t e m p e r a t u r e d i s t r i b ut i o n . T h e
temperature set points under analysis
are 160°C, 180°C, 200°C, 220°C Figure 6: Resulting damage in the adhesive layer after shear testing (shear direction from top to bottom).
and 240°C. For each temperature, a
bonding force of 0.6N, 1.0N, 1.4N, 1.8N
and 2.2N is applied. For the second
layout, fewer set points were analyzed
(1.0N, 3.0N and 5.0N). The chips were
shear tested before and after curing of
the adhesive material. A total number
of five shear tests were performed for
each set point.

Results
First, the influence of temperature
and applied force were analyzed.
Figure 3 shows the results before Figure 7: Cross-section images of the resulting adhesive layer shape after curing: a) 2.2N, 180ºC; b) 2.2N,
200ºC; c) 2.2N, 220ºC.
curing the adhesive material. Error
bars represent minimum and maximum T h e r e s i d u e i s s t i l l i n
shear values. The results clearly show contact with the silicon die
that a die temperature of only 160°C after testing.
leads to a significant decrease in shear To achieve good bond
strength. Furthermore, it can be seen quality, the covering of
that increasing the applied bonding t he e dge s of t he d ie is
force results in an increased shear another important factor to
strength. A temperature of 240°C leads be considered. Therefore,
to the highest shear values, but the cross-sectional images were
increased thermal load could likely taken in order to analyze
damage the die. the impact of the parameter
The shear values after curing are variation on the resulting
shown in Figure 4. The bond strength s h a p e of t h e a d h e sive.
seems to be less impacted by the Figure 7 shows the result for
variation in the process parameters. a constant force of 2.2N and
The influence of the applied force is a variation in temperature.
not as significant as in the previous I t c a n c l e a r l y b e s e e n Figure 8: Resulting die shear strength for varying adhesive layer
analysis before curing. Only for the that higher temperatures thicknesses after curing.
lowest temperature of 180°C could a are causing the die to be results. A slight trend towards lower
clear dependency on the applied force covered by the adhesive much better, shear values for thinner adhesive
be seen. however, the thickness of the remaining layers is evident, but the temperature
A direct comparison of the values layer underneath the silicon die is variation still proves to be more
before and after curing is shown in decreasing accordingly. Depending on significant. Furthermore, an alternative
Figure 5 where one can see the increase the application, this decrease needs adhesive design has been used. Instead
in shear strength before and after to be considered when choosing the of using the frame structure, the entire
curing. In order to better analyze the process parameters. face area of the die is in contact with
failure criterion, the resulting fracture Another question under analysis is the adhesive material. Figure 9 shows
has to be evaluated. Figure 6 shows a the influence of the adhesive thickness the results for a variation of applied
representative result. The damage is on the resulting shear strength of the force and temperature. Additionally,
occurring within the adhesive material. bond. Figure 8 shows the gathered the cross-sectional image of a silicon

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