In-Package Characterization of Dielectrics Using Ring Resonators and Adaptive 3D EM-Simulations Around 77 GHz

A method to obtain the permittivity and gauge the loss tangent of packaging materials at frequencies around 77 GHz from a single package is presented in this paper. In-package ring resonators, calibrated with an integrated TRL standard, are measured and their results contrasted with adaptive 3D elec-tromagnetic simulations. By comparing the resonance frequency and peak bandwidth, the characteristics of the RDL separating dielectric and the mold compound were extracted, respectively. The results were validated in Infineons eWLB technology with a minimal deviation of 0.16%/14.28% in
$\epsilon_{\mathrm{r},\text{DIEL}}/\epsilon_{\mathrm{r},\text{Mold}}$
and 0% /11.11 % in
$\tan(\delta_{\mathrm{r},\text{DIEL}})/\tan(\delta_{\mathrm{r},\text{Mold}})$
over all samples. It was further used to deduce the attributes of Fraunhofers RDL-first technology. Under a-priori knowledge of the permittivity, this concept has also been shown feasible to estimate fluctuations in a given technology.