A fluorine-free siloxane material with low dielectric loss in gigahertz frequencies for high-speed electronic devices

<h2>Summary</h2> Dielectrics with low dielectric loss in gigahertz (GHz) frequencies are essential for achieving reliable high-speed electronic devices. However, currently used dielectrics are inadequate for widespread industrial applications due to environmental regulations on fluorine content, insufficient dielectric properties, or limited environmental stability. Here, we present a fluorine-free dielectric with siloxane structures that exhibit an extremely low dielectric loss (≤0.00245) across frequencies from 2.5 to 50 GHz, along with high environmental robustness, via the incorporation of phenyl groups into siloxane networks. Through various experiments and theoretical calculations, we confirmed that the incorporation of phenyl groups enhances structural rigidity and suppresses the high-frequency dielectric response; the inorganic-like siloxane structures with phenyl groups ensure stable dielectric properties under high temperature or humidity. Using our dielectric, we demonstrate a highly reliable microstrip line with extremely low signal loss and excellent signal integrity during GHz signal transmission, which validates its remarkable potential as a distinguished dielectric for high-speed electronic devices.