A LTCC low-loss inductive proximity sensor for harsh environments

Proximity and position measurements with eddy current sensors are limited by the quality factor of the sensing coils. By enlarging the conductor path cross section, the quality factor can be increased. On ceramic multilayer substrates such cross sections, which are considerably larger in comparison to screen printed thick films, can be manufactured with an embossing and filling procedure, which is integrated into the conventional fabrication process. The conductor path layout is molded into the unfired ceramic substrate prior to filling the trenches completely with the conducting paste, thus generating a large cross section. This technique is applied for the sensing coil of an eddy current sensor. The higher quality factor leads to a doubled sensitivity in comparison to conventionally screen printed sensors. Due to the thermal and chemical durability of the ceramic substrate, the coils can be directly applied in a variety of harsh environment conditions, such as in situ engine monitoring.