Parylene as thin flexible 3-D packaging enabler for biomedical implants

In this paper, the novel use of Parylene for implantable biomedical microsystems packaging is presented. Parylene is an excellent candidate material to be used for implantable and clinically usable miniature devices due to its biocompatibility, flexibility, near-hermeticity, and high-density integration capability in a small form factor. Here, we propose a novel all-Parylene packaging technique where Parylene is used as a package substrate, an isolation layer, a capacitor insulator, and a sealing layer. Fully-integrated embedded passive devices, transmission lines, and surface mount components on a thin-film multilayer Parylene substrate are described. Metal-insulator-metal capacitors are implemented on Parylene and their DC and RF properties are characterized. Further, high-density 3-D trench capacitors are developed on Parylene for the first time. By integrating embedded capacitors and antenna with surface mount diodes, a rectifier module is implemented. Wireless powering onto the Parylene package is demonstrated as a proof-of-concept for the implant package to be powered by external environment. The authors believe that the all-Parylene packaging method described here can be widely applied to other miniature implant applications.