3D flexible Fan-Out Wafer-Level Packaging for Wearable Devices

This paper presents a 3D flexible Fan-Out Wafer-Level Packaging (FOWLP) approach to enhance the integration density, safety, and reliability of wearable devices. Within this structure, the Li-ion battery and wireless charging module are positioned on the backside of the wearable device, while the data acquisition and processing module is powered by Through-Glass Vias (TGVs) on the front. This study examined the conditions and rates of plasma dry etching of Polydimethylsiloxane (PDMS), revealing an etching rate of up to 0.49
$\mu \mathrm{m}$
/min. The minimum etchable pattern size of 150
$\mu \mathrm{m}$
is achieved. Furthermore, a bending test was conducted with a 2mm bending radius for 1000 cycles, which revealed only a 7% change in resistance of the 40
$\mu \mathrm{m}$
pitch Cu interconnects. The findings of this work provide a foundation for further development in integrating flexible hybrid electronics in the z-direction.