Design And Fbrication Of LTCC Pressure Sensor

The current low temperature co-fired ceramic(LTCC)pressure sensor is based on an embedded cavity design.The pressure sensitive film on the upper part of the cavity is susceptible to deformation during lamination or sintering.The size of the deformation increases as the width of the cavity increases and the thickness of the sensitive film decreases,affecting the sensitivity of the sensor.While,our design is based on a passive LC resonant circuit to achieve a pressure sensor without a cavity structure,which can not only improve the reliability of the sensor,but also open up new ideas in sensor design and other integrated devices.Based on the research development of pressure sensors,this paper especially introduces the capacitive pressure sensors for high temperature and biomedical environment,and related studies on the design,simulation,preparation and testing of LTCC pressure sensors.Firstly,the LTCC pressure sensor is designed based on electromechanical model.The model is divided into electromagnetic model for developing passive wireless telemetry and mechanical model for developing sensor pressure characteristics.After combining it,the sensor's resonant frequency and pressure are analyzed.The function of this analysis model facilitates parameter optimization during sensor design and simplifies the design process.Then through finite element simulation,the theoretical sensitivity of the sensor was obtained.Most articles focus on sensor optimization,and there are few researchers developing stable and accurate readout systems.In this paper,the wireless reading part based on the hollow transformer system is studied.By comparing the measurement methods,the return loss parameter is selected for measurement and the relationship between the parameters and the antenna is discussed.The fabrication of LTCC pressure senor with innovative structure by this paper is based on the cofireable technology between the two different materials,one is low temperature sintered dielectric ceramic and the other is low temperature sintered glass.On the condition of optimum process was founded for excellent cofireability for the two materials,our work are focused on how to prepare this sensor.The concrete process parameters and their influencing results were discussed in details,especially for the technology of materials casting,circuit printing,laminating and cofiring.The slurry is combined with solvents,binder,dispersant and plasticizer with the addition ratio 130:48:4:20:1.The pressure for isopressing is 30 MPa,the temperature is 52 centigrade.The cofirable temperature for the two materials is 875 centigrade.And finally the structure of fabricated sensor by this process was analyzed with no obvious delamination and warpage.The inductance of inductor and the capacity of capacitor embedded in the sensor are 0.28?H and 16.80 p F respectively,which are in well accordance with the simulated results.The sensor's sensitivity is approximately 847 Hz/MPa.To enlarge the application of this type of pressure sensors,a LTCC/PDMS based pressure sensor model that can work in a biological environment was also put forward for their biocompatible ability due to PDMS's low modulus of elasticity.