On the Feasibility of Fan-Out Wafer-Level Packaging of Capacitive Micromachined Ultrasound Transducers (CMUT) by Using Inkjet-Printed Redistribution Layers
by
Ali Roshanghias 1,*
, Marc Dreissigacker 2, Christina Scherf 3,4, Christian Bretthauer 5, Lukas Rauter 1, Johanna Zikulnig 1, Tanja Braun 2,6, Karl-F. Becker 2,6, Sven Rzepka 3,4 and Martin Schneider-Ramelow 2,6
Ali Roshanghias 1,*, Marc Dreissigacker 2, Christina Scherf 3,4, Christian Bretthauer 5, Lukas Rauter 1, Johanna Zikulnig 1, Tanja Braun 2,6, Karl-F. Becker 2,6, Sven Rzepka 3,4 and Martin Schneider-Ramelow 2,6
1
Silicon Austria Labs GmbH, Europastrasse 12, 9524 Villach, Austria
2
Microperipheric Center, Technical University Berlin, 13355 Berlin, Germany
3
Materials and Reliability of Microsystems, Chemnitz University of Technology, 09111 Chemnitz, Germany
4
Micro Material Center, Fraunhofer Institute for Electronic Nano Systems, 09126 Chemnitz, Germany
5
Infineon Technologies AG, 85579 Neubiberg, Germany
6
Fraunhofer-Institut für Zuverlässigkeit und Mikrointegration (IZM), 13355 Berlin, Germany
*
Author to whom correspondence should be addressed.
Micromachines 2020, 11(6), 564; https://doi.org/10.3390/mi11060564
Received: 4 May 2020 / Revised: 25 May 2020 / Accepted: 30 May 2020 / Published: 31 May 2020
(This article belongs to the Special Issue MEMS Packaging Technologies and 3D Integration)
Fan-out wafer-level packaging (FOWLP) is an interesting platform for Microelectromechanical systems (MEMS) sensor packaging. Employing FOWLP for MEMS sensor packaging has some unique challenges, while some originate merely from the fabrication of redistribution layers (RDL). For instance, it is crucial to protect the delicate structures and fragile membranes during RDL formation. Thus, additive manufacturing (AM) for RDL formation seems to be an auspicious approach, as those challenges are conquered by principle. In this study, by exploiting the benefits of AM, RDLs for fan-out packaging of capacitive micromachined ultrasound transducers (CMUT) were realized via drop-on-demand inkjet printing technology. The long-term reliability of the printed tracks was assessed via temperature cycling tests. The effects of multilayering and implementation of an insulating ramp on the reliability of the conductive tracks were identified. Packaging-induced stresses on CMUT dies were further investigated via laser-Doppler vibrometry (LDV) measurements and the corresponding resonance frequency shift. Conclusively, the bottlenecks of the inkjet-printed RDLs for FOWLP were discussed in detail.
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Keywords:
microelectromechanical systems (MEMS) packaging; inkjet printing; redistribution layers; capacitive micromachined ultrasound transducers (CMUT); fan-out wafer-level packaging (FOWLP)
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MDPI and ACS Style
Roshanghias, A.; Dreissigacker, M.; Scherf, C.; Bretthauer, C.; Rauter, L.; Zikulnig, J.; Braun, T.; Becker, K.-F.; Rzepka, S.; Schneider-Ramelow, M. On the Feasibility of Fan-Out Wafer-Level Packaging of Capacitive Micromachined Ultrasound Transducers (CMUT) by Using Inkjet-Printed Redistribution Layers. Micromachines 2020, 11, 564.
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