The flotation process is used initially to ensure the integrity of the ceramic hollow spheres. To modify the ceramic hollow spheres and achieve excellent dispersion in tetrahydrofuran, KH560 was employed as the optimum coupling agent. By further optimizing the technological parameters, the ceramic hollow spheres are uniformly dispersed in the polytetrafluoroethylene mesh in the laminate, resulting in a variety of laminate qualities. The dielectric constant of the dielectric layer in the copper-clad laminate is less than 2, making it suitable for high-frequency and high-speed PCB applications.

Abstract

Ceramic hollow spheres and polytetrafluoroethylene (PTFE) resin are essential for the fabrication of ultra-low dielectric constant laminates for high-frequency printed circuit boards. The poor bonding between ceramic hollow spheres and PTFE is the fundamental obstacle to the homogeneity of the composite. In this work, the broken ceramic hollow spheres were first removed by flotation, and then the surface of the floated hollow spheres was modified using different silane coupling agents at various concentrations. By comprehensively considering the results of the orthogonal experiment, the optimal coupling agent is determined to be 3-(methacryloyloxy) propyltrimethoxysilane (KH560). The effect of KH560 content, ethanol/water volume ratio, and pH value on the dielectric constant, dielectric layer density, water absorption, and Z-axis thermal expansion coefficient of the parallel samples was investigated in detail. The optimum surface modification parameters are found to be 6 wt % KH560, an ethanol/water volume ratio of 9 : 1 and a pH of 4. Under optimum technological conditions, the fabricated composites exhibit superior properties with dielectric constant less than 2, indicating a potential application in high performance high frequency copper clad laminates.