| The LC wireless passive pressure sensor,which has a simple structure and low cost,is the most potential of the resonant wireless passive pressure sensor and it has a broad application prospect.At present,such sensors are made of ceramic materials,the pressure sensitive film is thick and the capacitance gap is wide of this kind which has brought some difficulties to achieve pressure sensor with high sensitivity and small size.In addition,the connection between the capacitive plates of the LC wireless passive pressure sensor mostly relies on the through-hole interconnect process or alignment of the connection in the bonding surface through the preparation of the connection point.The process of the two methods is more complex,and the alignment precision is high,and it is prone to thermal mismatch at high temperature.In this paper,an double capacitance wireless passive pressure sensor based on MEMS technology is proposed.The electrical interconnection of resonant structure is realized by double capacitance structure.The main research work is as follows:(1)The dual capacitance model of double capacitance wireless passive pressure sensor is proposed,and its coupling mechanism is analyzed,and the electrical model and detection model were established.The ininfluence of the parameters of the coupling system on the signal read is analyzed to solve the problem that the signal read for the sensor is susceptible to temperature,coupling distance and so on.Combined with the design theory of inductor on the plane,the design of inductance coil is finished.Through the electric coupling simulation of the double capacitance structure,the overall size of the sensor is determined,and the design index of the sensor performance is determined.(2)The preparation process of the sensor is determined according to the size of the sensor structure determined by the theoretical analysis and simulation.A sensitive device with size of 11.2mm×11.2mm×1.5mm was prepared by MEMS process such as photolithography,secondary oxidation mask,silicon wet etching,magnetron sputtering electrode deposition,chemical electroforming and anodic bonding.The gluing and exposure parameters of photoresist castings with a thickness of more than 40?m were optimized and finally,the thickness of 42?m cast film was prepared by using the secondary coating method of 500r/min + 800r/min and the exposure parameters of 35mW/cm2 and 250s.The effects of different electroforming modes on the quality of electroformed coils and the effect of current density on the electroforming rate were studied.A large thickness copper inductor with a width of 47.9?m,a spacing of 33.1?m and a thickness of 32.1?m was prepared.(3)The inductance of the cast inductance coil with a value of 3.5436?H was measured and the caLculated parasitic capacitance of the inductor on the glass is 10.714pF.The sensor test platform was built and the frequency response characteristics of the sensing elements were measured.The test shows that The sensitivity of the sensor is about 52.8kHz/kPa,the maximum full scale linear fitting error is 4.18%,the hysteresis error is 1%.and the maximum coupling distance is 6mm.In the atmospheric environment,the temperature drift is 2.7kHz/?,and the temperature drift of the sensitivity is 0.027kHz/(kPa·?)... |
PDF Full Text Request