A modeling approach for predicting the effects of dielectric moisture absorption on the electrical performance of passive structures

In this paper a modeling approach for predicting the electrical behavior of nonresonant and resonant structures under the influence of the absorption of moisture into the dielectric is presented. The paper focuses on the encapsulation materials used for printed circuit boards (PCBs) as a case study. For the investigated cases, analytical modeling shows that the loss of electrical insulation resulting from moisture absorption has minimal effects on the losses in transmission lines (TMLs), which would only cause system failure when combined with other aging effects. However, potential cases are discussed where the loss of electrical insulation could be significantly increased. Full-wave modeling shows that moisture absorption can cause the detuning of passive components, specifically antennas and impedance-controlled TMLs, that can have significant effects on system performance. Antenna resonance frequencies shift by up to 3-5%.