Supercritical carbon dioxide foaming for ultra-low dielectric loss perfluorinated foam

Microelectronic is developing towards high frequency (GHz) and high speed (Gpbs), putting forward high re-quirements for low dielectric materials. The most efficient method for fabricating low dielectric materials is the incorporation of air into matrix via supercritical CO2 foaming. Herein, a low dielectric thermoplastic per -fluorinated polymer is selected to be the matrix and another low dielectric perfluorinated polymer which is capable to form in-situ nanofibrils is selected to regulate the matrix viscoelasticity. Supercritical CO2 foaming method is then applied to introduce a large amount of low dielectric air into nanofibrill modified perfluorinated polymer. Owing to supercritical CO2 as a residue-free foaming agent (residue impurities in matrix originated from foaming agent would increase dielectric loss significantly at GHz) and its strong interaction with per -fluorinated polymer (ensure large expansion ratio of the obtained foams to introduce a large amount of low dielectric air in matrix), the lowest dielectric loss of 0.00015 (among the existing polymeric materials) is then obtained by supercritical CO2 foaming of in-situ nanofibril modified perfluorinated polymer. Furthermore, the hydrophobic and oilphobic properties of the perfluorinated polymer were enhanced by supercritical CO2 foaming to form a cellular structure; simultaneously, the corrosion resistance to strong alkali and V0 flame retarding properties of the ultra-low dielectric foam were maintained resulted from the perfluorinated cell walls. There-fore, such superior comprehensive performance of this ultra-low dielectric perfluorinated foam made from su-percritical CO2 foaming enables it the best alternative for the next-generation high-frequency (GHz to THz) and high-speed (sub Tbps) signal transmission substrate in electronics.