Fluorinated active ester strategy for epoxy composites with ultra-low dielectric and robust moisture-thermal stability

Epoxy-based composites with excellent dielectric, thermal and hydrophobic properties are highly desired in advanced electronic packaging, especially for achieving ultralow dielectric constant ( D k ) and dielectric loss ( D f ) in high-frequency and high-speed applications. Introducing low-polarity functional groups, such as symmetrical fluorine and active ester moieties, has been proven to be an effective method for reducing the D k and D f , respectively. Herein, a fluorinated active ester (HFBAAE) incorporating symmetric trifluoromethyl and active ester groups was designed and synthesized as a curing agent for epoxy composites. Ultralow D k of 2.67 and D f of 0.006 at 20 GHz are achieved for the HFBAAE cured SiO 2 /epoxy composites. Moreover, excellent dielectric stability under humid-thermal conditions is observed owing to the low water absorption (<0.7 wt%). Additionally, a high thermal decomposition temperature of 385 °C, a high glass transition temperature of 129 °C, and a low coefficient of thermal expansion of 33 ppm °C −1 are obtained. This fluorinated active ester curing agent offers a promising strategy for tailoring and enhancing the dielectric, thermal and moisture-resistance properties of the epoxy-based dielectric composites.