Dielectric Properties of Printed Circuit Board Insulations at Microwaves and Millimetre Waves

We measured the complex permittivities of various polymeric materials used as the insulation layers of PCBs from 1 MHz to 110 GHz using various measurement systems. The data obtained by different methods are in good agreement and the permittivities are almost constant at frequencies higher than 10 GHz. The experimental results reveal that the anisotropy in the complex permittivities of insulating materials for PCBs is large owing to the inhomogeneous internal structure. The experimental results also proved that the permittivity is strongly influenced by humidity. By introducing these experimental results, we encourage studies of high frequency characteristics in solid dielectrics and insulating materials in PCB industries.