Thermomechanical properties and performance of ceramic resonators for wireless pressure reading at high temperatures

Abstract

Thermomechanical properties and performance of ceramic resonators for wireless pressure reading in high temperatures. Micromechanics and Microengineering, 25(9) Abstract -This paper reports on the design, fabrication and thermomechanical study of ceramic LC resonators for wireless pressure reading, verified at room temperature, at 500 °C and at 1000 °C for pressures up to 2.5 bar. Five different devices were fabricated of high-temperature co-fired ceramics (HTCC) and characterized. Alumina green tape sheets were screen printed with platinum paste, micromachined, laminated and fired. The resulting samples were 21 x 19 mm 2 with different thicknesses. An embedded communicator part was integrated with either a passive backing part or with a pressure-sensing element, including an 80 µm thick and 6 mm diameter diaphragm. The study includes measuring thermally and mechanically induced resonance frequency shifts, and thermally induced deformations. For the pressure sensor device, contributions from changes in the relative permittivity and from expanding air, trapped in the cavity, were extracted. The devices exhibited thermomechanical robustness during heating, regardless of the thickness of the backing. The pressure sensitivity decreased with increasing temperature from 15 050 ppm/bar at room temperature to 2400 ppm/bar at 1000°C, due to the decreasing pressure difference between the external pressure and the air pressure inside the cavity. Journal of

Ceramic Pressure Sensor for High Temperatures – Investigation of the Effect of Metallization on Read Range

“…The components were then placed between plates of porous alumina in a high-temperature furnace (ECF 20/18, Entech, Sweden), and heated, fired and sintered as described in detail in [14]. During this, organic binders and solvents in the pastes are removed.…”

“…To reduce the resistance of the LC resonators and increase their quality factor and, potentially, their read range, in comparison with those of [14], two methods were employed: screen printing of two layers of ESL 5574-A paste on top of each other, and electroplating of silver on ESL 5571 platinum. (Detaching from the substrate, the ESL 5574-A was found incompatible with electroplating, and therefore excluded from this step.…”

“…The sample surface was electrochemically cleaned at 5 V for 5 minutes (ActiClean, Spa Plating, UK), followed by silver plating for 40 min (Silver tank plating solution, Spa Plating, UK), using a plating factor of 5 mA/cm 2 and aiming for a silver film thickness of 12 µm, which corresponds to the typical thickness of a screen printed conductor line. In addition to these double-metallized components, samples with single layers of ESL 5574-A, such as those presented in [14], and ESL 5571, were prepared as references.…”

“…In parallel with this, cavity resonators working at the same temperature have been developed and presented [13]. In 2015, a thermomechanical study on LC resonators fabricated from HTCC, including a demonstration of wireless reading of pressures up to 2.5 bar at 1000°C, was published [14].…”

“…For high-temperature environments, the resistance, being temperature dependent, can be assumed to influence the quality factor. In [10][11][12]14], capacitor plates on membranes provide a pressure-dependent capacitance, implying a function-based influence of the quality factor. As the geometry of the conducting patterns is relatively stable, mainly governed by the thermal expansion coefficient (CTE) of the substrate material, changes in quality factor due to elevated temperatures are determined by changes in dielectric constant and resistivity.…”