Sandwich-Layered Dielectric Film with Intrinsically Excellent Adhesion, Low Dielectric Constant, and Ultralow Dielectric Loss for a High-Frequency Flexible Printed Circuit

With the high-frequency development of high-speed communication electronic devices, excellently adhesive materials with low dielectric constant and ultralow dielectric loss have been highlighted. However, intrinsically strong adhesive materials (e.g., epoxy) with numerous polar functional groups disappointingly deteriorate their high-frequency dielectric properties. Herein, a double cross-linked network of maleic-anhydride polybutadiene–amino-terminated polyimide oligomers (MAPB-PIO) is synthesized, and then a novel sandwich-layered dielectric film (MAPB-PIO/polytetrafluoroethylene (PTFE)/MAPB-PIO) is prepared through double-sided coating. The MAPB-PIO/PTFE/MAPB-PIO film exhibits low dielectric constant (Dk = 1.9929) and ultralow dielectric loss (Df = 0.0012) at 10 GHz. Meanwhile, the interface peel strength reaches 0.912 N/mm. Additionally, the MAPB-PIO/PTFE/MAPB-PIO film is successfully applied to manufacture a flexible printed circuit board (PCB) and shows an outstanding high-frequency signal transmission capability; i.e., signal loss is 26.45 dB at 18 GHz, which is only 43% of the commercially available epoxy resin PCB. All results indicate that the flexible MAPB-PIO/PTFE/MAPB-PIO film is highly promising for applications in next-generation flexible electronics and radiofrequency devices, especially in the millimeter wave field.