Synthesis of Low-k Poly(ether ether ketone) Films and Surface Functionalization for Exceptional Copper Adhesive Properties

Developing low-dielectric metal-adhesive polymer substrates for next-generation high-frequency communications and miniaturized electronic devices remains challenging. In this study, poly(ether ether ketone)-based copolymers (TB x BP y -PEEK) were synthesized via nucleophilic aromatic substitution of two aromatic alcohols: tert -butylhydroquinone and 4,4′-(α-methylbenzylidene)bisphenol. Neat film-type specimens, fabricated via solution casting with chloroform, exhibited a low dielectric constant and loss of 2.49 and 5.84 × 10 –3, respectively, with a low water uptake of less than 0.5%. Furthermore, the films demonstrated excellent mechanical and thermal properties, achieving elastic moduli exceeding 0.884 GPa and initial decomposition temperatures exceeding 458.9 °C. Moreover, Cu-adhesive monomers glycidyl methacrylate and 3-(trimethoxysilyl)propyl methacrylate were successfully grafted onto the polymer surface by using the self-initiating property of the benzophenone moiety within the PEEK structure. The final Cu-polymer laminate displayed an outstanding peel strength of 11.45 N/m, more than double that of a commercially bonded sheet-laminated polyimide film.