Fully Flexible, Polymer based Microwave Devices Part I: Materials, Fabrication Technique, and Application to Transmission Lines

Abstract

To achieve fully flexible microwave devices, we investigated flexible polymers in terms of chemical, mechanical, and electrical properties. Moreover, the fabrication techniques for polymer-based microwave devices have been developed to address chemical adhesion and demolding issues. Finally, based on formulated criteria, we have developed recipes for low-loss (0.001), low-Dk (1.73) flexible dielectric materials and applied them to the microstrip and CPW transmission lines. The microstrip and CPW lines' transmission loss is as low as 0.065 and 0.034 dB/cm at 2.5 GHz, respectively. The effects of various materials on microwave performance have been analyzed, from which we show acceptable limits for fully flexible microwave devices in S and L bands. The proposed molding process allows us to step out from 2D PCB designs and build 3D structures or hybrid PCB-3D components with a certain freedom in material properties. Additionally, the new material exhibits unique mechanical properties, which extends the material application to other fields. This work demonstrates that polymer-based flexible microwave electronics can have a competitive performance compared to rigid PCB technology. Additionally, it has been found that the polymer-based devices have significant performance improvements at elevated temperatures, which can be exploited in a high-temperature application.