Fabrication And Performance Of Wireless Passive Pressure/Temperature Sensor Based On LTCC Technology

Passive wireless sensors can detect and transmit signals without the need of wires and power supply.The long service life and simple maintenance are important for future sensor development.Among them,the inductor-capacitor(LC)sensor based on the principle of electromagnetic coupling has become one of the most widely studied passive wireless sensors because of its advantages such as simple process,flexible carrier,and low cost.Low Temperature Co-fired Ceramics(LTCC)has the advantages of high melting point,high wear resistance and corrosion resistance inherent in inorganic materials such as ceramics and glass,and is an ideal carrier for sensors used in harsh environments.Based on the above background,the main research contents of this paper are as follows:1.Firstly,an LC pressure sensor based on plate cavity capacitor and planar spiral inductor was designed.Based on the membrane deformation theory,the ANSYS simulation was performed on the sensor model to optimize the sensor structure.Sensitive membranes of 3,5,7 and 9 layers(156 ?m,260 ?m,364 ?m,468 ?m)were prepared.2.The pressure sensor was prepared using a self-manufactured low Young's modulus(65 GPa)LTCC materials.A three-step lamination process was used without any sacrificial material.Through coordinated control of lamination pressure,temperature,and time,the cavity structure with no obvious deformation was obtained.3.The influence of pressure and temperature on the performance of LC resonant pressure sensor was studied.The results indicated that the sensitivity of the pressure sensor decreased and the detection range increased with the increasing of the sensing membrane thickness.Sensors with a sensing membrane thickness of 148 ?m have a sensitivity of up to 3.76 kHz/kPa,while sensors with a sensing membrane thickness of 432 ?m have a high detection range of up to 2660 kPa.At the same time,the temperature variation will cause a slight drift in the resonant frequency of the sensor.4.An LC temperature sensor based on interdigital capacitance and inductance coil is designed.The temperature signal is sensed through a change in the dielectric constant of the dielectric material and the change of the resistance of the electrode material.A device with an initial resonance frequency of ~60 MHz was obtained,and a preliminary high-temperature test of the device was performed.The experimental results show that the temperature sensitivity is-3.84 kHz/?,0.13% dB/?.5.A dual LC antenna passive wireless pressure and temperature integrated sensor that can simultaneously sense pressure and temperature is designed and prepared.The change of the reflection loss S11 with the temperature of the reaction environment and the change of the resonant frequency of the sensor with the pressure are detected.The experimental results show that the pressure/temperature integrated sensor has a sensitivity of 1.16 kHz/kPa,and the sensitivity with temperature changes is 0.062% dB/? within the range of 0-840 kPa and 50-500 ?.