Page 46 - Chip Scale Review Sep Oct_2022-digital

As seen in Table 1a, the static uniformity
was notably worse than the dynamic
uniformity. However, this can be explained
by the size of the probe card. As this is
smaller than the chuck itself, there is a
smaller shielding effect from the probe
card. To verify this, the static and dynamic
test was performed on another prober
where the probe card is of similar size to the
chuck. Table 1b shows that this increased
shielding effect significantly impacts the
uniformity measurements in the static
case, which are now closer in value to the
dynamic measurements.
A wafer and a single sensor solution do not
vary widely in terms of performance when
it comes to uniformity measurements. The
hot spots and cold spots are generally found
in the same area. There is, however, a small
deviation in the maximum sensor values,
which amounts to 0.070°C when using the
GUM standard to calculate. As seen in the
previous tables, the uniformity data from
the static and dynamic measurements are
similar, but our tool offers an advantage
when used with the engineering prober from
Supplier A. Still, the measurement wafer
offers faster test times, as it can measure
many points at once, while the ProbeSense™
has longer soaking times and is, therefore,
more time-consuming when shifting
between different temperatures.
Summary
As temperature testing shifts from final
test to wafer probing, it is crucial to have
highly accurate tools that can perform
measurements that reflect the probing
conditions. Sensor devices for electronics,
automotive, and industry components have
strict temperature requirements, which puts
accuracy in the spotlight. It is not enough
to only focus on the thermal chuck system
when taking on these ever-increasing
requirements – continuous improvements
to and reassessments of the calibration tool
and method are also necessary to better the
overall accuracy.

Acknowledgments
For specific information on the
performance data described in this article,
please contact the lead author.

Biographies
Klemens Reitinger is the CTO at ERS electronic GmbH, Munich, Germany. He holds a Master’s degree in
Mechanical Engineering from the U. of Applied Science in Vienna, Austria. Over the course of 30 years, he has
invented and developed several temperature management solutions for wafer probing, including the thermal
chuck family, AirCool®. Email: kreitinger@ers-gmbh.de

Bengt Haunerland is Head of Software and Electronics, at ERS electronic GmbH, Munich, Germany. He has
a Master’s degree in Electronics Engineering from Simon Fraser U., Canada.

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