Chip Scale Review - January February 2020

13 Chip Scale Review January • February • 2020 [] life failure. For solder fatigue, the driving force does not reduce, but remains constant and eventually causes an end- of-life failure. F o r e v a l u a t i n g t h e fatigue modes on the RF pe r for ma nce, t he pha s e shift on the RF transmission Ф(S21) was analyzed. For fatigue levels up to 90%, the phase shift stays within the specified limit considering RDL, UBM, and solder ball fatigue separately. Thermal simulation shows that the thermal balls on the silicon chip area are very effective and dissipate almost 70% of the generated heat. For assessing several different use cases with a different level of fatigue for each ball position across the package ball out, thermal simulation shows that, for example, assuming 50% degradation on average for all thermal balls, an increase in RTH of up to about 30% is seen. Acknowledgment This article is based on a presentation a t t h e I n t e r n a t i on a l Wa f e r L e ve l 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. 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 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. Figure 11: Various use cases 1-4 with different fatigue levels of the balls showing an assessment of the thermal behavior of the package. Figure 10: Thermal simulation results for various use cases as shown in Figure 11 for a power consumption of about 3.3W.