Improved and fast extraction of dielectric parameters of thin organic packaging materials using open-ended coaxial line technique

Abstract

In this work the open-ended coaxial line technique is analyzed and improved. A lumped equivalent model is proposed. The interaction between the probe, material under test (MUT) and the backing of the MUT is studied and the sample backing was found to have a strong effect over the measured results, especially over high frequencies. In This work we use an optimum dielectric backing for accurate extraction of the complex permittivity of thin packaging materials. A frequency dependent term was also included in the lumped circuit model to account for variations of the static capacitance with increasing frequency for a given coaxial line dimension. In addition, an error network was incorporated for convenient probe calibration. The validity and accuracy of the model is verified through numerical modeling and high frequency measurements. In addition the effects of the testing environment on the dielectric properties were also investigated for a few FR4 substrates over a broad frequency band and the results are reported here.