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On the feasibility of fan-out wafer-level packaging of capacitive micromachined ultrasound transducers (CMUT) by using inkjet-printed redistribution layers

: Roshanghias, A.; Dreissigacker, M.; Scherf, C.; Bretthauer, C.; Rauter, L.; Zikulnig, J.; Braun, T.; Becker, K.-F.; Rzepka, S.; Schneider-Ramelow, M.

Volltext ()

Micromachines 11 (2020), Nr.6, Art. 564, 13 S.
ISSN: 2072-666X
European Commission EC
H2020; 737487; SILENSE
Zeitschriftenaufsatz, Elektronische Publikation
Fraunhofer IZM ()
Fraunhofer ENAS ()

Fan-outwafer-levelpackaging(FOWLP)isaninterestingplatformforMicroelectromechanical 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) wererealizedviadrop-on-demandinkjet printingtechnology. The long-termreliability ofthe printed trackswasassessed viatemperature cyclingtests. The effectsofmultilayering andimplementationof 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.