Parylene Interposer as Thin Flexible 3-D Packaging Enabler for Wireless Applications

This paper presents a novel, all-Parylene, thin, flexible 3-D packaging technology with an application demonstration of wireless powering. Parylene is utilized as a base substrate of a packaging interposer, and multilayer thin films are conformally stacked on the Parylene substrate. High-density (450 pF/mm²) metal-insulator-metal capacitors are implemented with an ultrathin (~47 nm) deposition of Parylene-N. The energy storage capabilities as well as RF characteristics are characterized. To demonstrate interposer applicability, an RF energy-harvesting study is performed by implementing a rectifier circuit on the Parylene interposer utilizing embedded capacitors of wide-ranging values and an antenna. Finally, substrate folding tests are performed to verify the applicability of the Parylene interposer in a flexible form factor without undergoing degradation in energy-harvesting capability. The thin-film flexible capacitors are demonstrated to not short-circuit even under the stress of folding the interposer.