A Cost-Effective Method for Extracting the Complex Permittivity of Inner Layer Dielectric PCB Materials

This paper presents a new cost-effective method to deduce the dielectric properties of substrate materials, which are used in inner layers of low cost printed circuit boards (PCBs). Two different on board structures are applied to estimate the desired complex permittivity in two different ways. On the one hand, a T-resonator based on substrate integrated waveguide technology (SIW) is used, on the other hand a stripline, whereby both are a combination of the outer layer laminate and the underlying prepreg. At first, the scattering parameters of both dielectric structures are measured with a vector network analyzer (VNA). The structures are then simulated with the finite integral method (FI) with all dielectric materials substituted by air. Afterwards, a second simulation with the dielectric constant (DK) of the known dielectric material is necessary. Next, the real part of the complex permittivity is calculated. Finally, the dissipation factor (DF) is calculated.