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life failure. For solder fatigue, Thermal simulation shows that the
the driving force does not thermal balls on the silicon chip area are
reduce, but remains constant very effective and dissipate almost 70% of
and eventually causes an end- the generated heat. For assessing several
of-life failure. different use cases with a different level
F or e v a l u at i n g t h e of fatigue for each ball position across
fatigue modes on the RF the package ball out, thermal simulation
performance, the phase shows that, for example, assuming 50%
shift on the RF transmission degradation on average for all thermal
Ф(S21) was analyzed. For balls, an increase in RTH of up to about
fatigue levels up to 90%, the 30% is seen.
phase shift stays within the
specified limit considering Acknowledgment
Figure 10: Thermal simulation results for various use cases as shown RDL, UBM, and solder ball This article is based on a presentation
in Figure 11 for a power consumption of about 3.3W. fatigue separately. at the Inter national Wafer Level
Packaging Conference (IWLPC) 2019.
References
1. J. Böck, M. Wojnowski, C. Wagner,
H. Knapp, W. Hartner, M. Treml,
et al., “Low-cost eWLB packaging
for automotive radar MMICs in the
76-81GHz range,” Inter. Jour. of
Microwave and Wireless Tech., 5(1),
pp. 25-34, 2013.
2. T. Meyer, G. Ofner, S. Bradl, M.
Brunnbauer, R. Hagen, “Embedded
wafer-level ball grid array (eWLB),”
Proc. 10th Elec. Packaging Tech.
Conf. (EPTC 2008), Singapore, 2008.
3. G. Haubner, W. Hartner, S. Pahlke,
M. Niessner, ”77GHz automotive
RADAR in eWLB package: from
consumer to automotive packaging,“
Microelectronics Rel., Vol. 64, pp.
699-704, 2016.
4. M. Niessner, G. Haubner, W. Hartner,
S. Pahlke, ”Controlling the solder
joint reliability of eWLB packages in
automotive radar application using
a design for reliability approach,“
Proc. of the ASME 2018 Inter. Tech.
Conf. and Exhibition on Packaging
and Integration of Elec. and Photonic
Microsystems InterPACK2018, 2018.
Figure 11: Various use cases 1-4 with different fatigue levels of the balls showing an assessment of the thermal
behavior of the package.

Biographies
Walter Hartner is Principal at Infineon Technologies AG, Regensburg Germany. His development focus is
in wafer-level package technologies for automotive radar applications. He holds a Master’s degree in Physics
from the Friedrich-Alexander U. of Erlangen, Germany and a PhD from the Technical U. of Aachen, Germany.
He has authored and co-authored more than 40 articles and he holds more than 60 patents in the field of
semiconductor frontend and backend technology. Email Walter.Hartner@infineon.com
Martin Niessner is a Senior Staff Engineer for mechanical simulation at Infineon Technologies AG, Munich
Germany. He received his MS and PhD degrees in Electrical Engineering from the Technical U. Munich, Germany.
Francesca Arcioni is a Staff Engineer for electrical simulation at Infineon Technologies AG, Munich Germany. She studied
electronic engineering and received her Master’s degree from the U. of Pavia, Italy.
Markus Fink is a Staff Engineer for thermal and thermomechanical simulation at Infineon Technologies, AG Regensburg, Germany.
He holds a Master’s degree in Microsystems Engineering from the Technical U. of Applied Sciences in Regensburg, Germany.

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