Preparation of polyimide bond-linked covalent organic frameworks as resin-compatible nanofillers for copper clad laminates with improved thermal and electrical performances

Copper clad laminates (CCLs) with low dielectric constants and dielectric losses are preferred for high-frequency and high-speed printed circuit boards (PCBs). However, the dielectric interlayer of CCLs with improved thermal and electrical performances still requires further exploration. Single component such as polymers or ceramics can hardly meet the developing needs of advanced CCLs. Thus, incorporation of functional nanofillers with polymer resins has been considered as an effective solution. However, chemical or physical modifications are generally conducted for the nanofillers, which is harmful and complex for the fabrication of CCLs. In this work, crystalline polyimide bond-linked covalent organic frameworks (PI-COFs) nanoparticles (NPs) with porous structures have been prepared. Due to the organic nature and preferable particles size, PI-COFs NPs show improved compatibility with epoxy resin (ER). Decreased viscosity, increased settle ability, and improved film-forming capability can be achieved with suitable additive amount of PI-COFs NPs. Due to their high thermal stability and intrinsic low dielectric property, the PI-COFs have been introduced as nanofillers for CCLs. The thermal decomposition temperatures ( T d ) and glass transition temperatures ( T g ) can be improved, while the thermal conductivities show a decreased trend. A lowered dielectric constant of 5.52 with a dielectric loss of 0.00328 can be achieved at 1 MHz for 10 wt% PI-COFs filled CCLs. Higher electrical conductivities and Q factors can be obtained with the addition of PI-COFs NPs. Moreover, the PI-COFs-filled CCLs show improved signal integrity (SI) performances with reduced resonance peaks of insertion loss (IL, S 21 ) and reduced return loss (RL, S 11 ) values. The power integrity (PI) performances of PI-COFs-filled CCLs show reduced filtering effects due to the decreased dielectric properties. Considering the diversity of chemical compositions and porous structures of COFs, their application as resin-compatible nanofillers may provide a new avenue toward advanced high-frequency and high-speed CCLs. Graphical Abstract