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|Benchmarking different Types of Thick-Film Pressure Sensors|
|Keywords: thick-film, ceramic, pressure sensor|
|Thick-film technology is one of the appropriate technologies for manufacturing sensors and transducers. This paper is focused on pressure sensors where the sensing elements are made with thick-film technology. Typical thick-film pressure sensors are designed as a capsule consisting of a circular edge-clamped ceramic based diaphragm, which bend under applied pressure. In general the displacement of diaphragm is dependant on a construction and mechanical properties of the materials. The sensing materials, electrodes and interconnecting lines are deposited onto the diaphragm by screen-printing technique and than sintered at 850°C. The diaphragm is usually based on alumina. However, sensing elements made on some other diaphragms / substrates would exhibit some improved characteristics, e.g. higher mechanical (flexural) strength and/or lower Young modulus. In the paper three different types of thick-film pressure sensors on alumina and LTCC substrates will be presented and compared. The first type is piezoresistive pressure sensor with four thick-film resistors, which are screen-printed and fired onto the diaphragm. Each thick-film resistor acts as a strain gauge that is capable of translating a strain into an electrical signal. The working principle is piezoresistivity – the property of resistor materials to change their resistivity under strain. The second type is capacitive pressure sensor, which is based on changes of capacitor values between two electrodes. One electrode is fixed and other is movable and their displacement depends on applied pressure. The third type is the piezoelectric resonant pressure sensor, which is based on shifting of resonant frequency of the diaphragm. The thick-film piezoelectric actuator structure on the diaphragm generates the vibration of diaphragm in the resonant frequency mode. This resonant frequency shifts due to a static deflection of diaphragm caused by an applied pressure.|
|Darko Belavic, Head of HIPOT R&D Group
Jozef Stefan Institute