Delineation of Parametric Controls on LTCC-Based Eddy Current Sensor Exposed to High Temperature

Abstract

The investigation is focused on the parametric evaluation of a microfabricated multilayer planar (MLP) coil exposed to high temperature (HT) (\ge 600 °C). It can potentially be used as eddy current (EC) sensor for in situ structural health monitoring (SHM) of critical engineering components. A detailed analysis of various contributing factors that affect the performance of the MLP coil is discussed. The coil is microfabricated on a ceramic substrate (DuPont L951 green tape) using the state-of-the-art low-temperature co-fired-ceramic (LTCC) technique. The stacked layer configuration (30 layers) soars the performance of the coil in terms of sensitivity and robustness. Emphasis is given on the performance both for dynamic and prolonged static thermal exposure. Delineation of electrical parameters, particularly the series inductance ( $L_{S}$ ) of the sensor, is found to be stable ( $\sim 130~\mu \text{H}$ ± 3%) up to 600 °C; beyond which up to 800 °C, there is a decreasing trend ( $\sim 70~\mu \text{H}$ ± 3%). Also, the sensor shows stable and consistent behavior with a nominal deviation of ±1% during prolonged thermal exposure. These findings throw light on the application of the MLP coil for in situ SHM of critical engineering components exposed to HT.