Fabrication and dielectric properties of BADCy/Ni0.5Ti0.5NbO4 composites for ultra-low-loss printed circuit board application

Ni0.5Ti0.5NbO4 was firstly reported as filler to adjust dielectric properties of polymer matrix composites for printed circuit board (PCB) application. In this study, the Ni0.5Ti0.5NbO4 filler was modified using γ-aminopropyl triethoxy silane (KH550). The effects of KH550 on particle lipophilicity and Bisphenol-A cyanate ester resin (BADCy) curing behavior were studied. BADCy/Ni0.5Ti0.5NbO4 composites were fabricated by the traditional casting method. The dielectric properties and moisture absorption of the composites were tested. Results show that most hydrophilic groups on the surface of Ni0.5Ti0.5NbO4 powder are replaced by lipophilic groups after modification, which results in the obvious improvement of Ni0.5Ti0.5NbO4 filler dispersion in BADCy. Beyond that, surface modification also greatly affects the curing behavior of BADCy resin. The BADCy/Ni0.5Ti0.5NbO4-KH550 composites exhibit excellent dielectric properties as well as low moisture absorption. Furthermore, the dielectric constant can be accurately predicted using Effective Medium Theory (EMT model) when the morphology factor is 0.1407.