Low Dielectric Polyimide/Fluorinated Ethylene Propylene (PI/FEP) Nanocomposite Film for High‐Frequency Flexible Circuit Board Application

Abstract

AbstractThe low dielectric polymer films have drawn great attention to the application as the dielectric insulating materials in high‐frequency circuit boards, while the weak adhesion to the copper foils and the poor processability resulted from the fluorinated or rigid structures limited their high‐frequency application. In this work, the low dielectric and high adhesive polyimide/fluorinated ethylene propylene (PI/FEP) nanocomposite film for high‐frequency flexible circuit board application is developed. It is indicated that the fluorocarbon surfactants can significantly improve the dispersion of FEP in PI substrate, and thus, the PI/FEP nanocomposite film exhibits excellent mechanical properties, including the tensile strength increases to 46.6 MPa and the elongation at the break increases to 13.7%. Importantly, at the high‐frequency of 10 GHz, the 60 wt% FEP filled PI nanocomposite film displays an ultralow dielectric loss (0.006) and a reduced dielectric constant (2.69). In addition, the high‐frequency flexible circuit board with the PI/FEP film as the dielectric insulating layer has a high peel strength of 0.75 N mm−1, indicating this PI/FEP nanocomposite film can meet the requirements of the high‐frequency flexible circuit board application.