Research On Micro Thermal MEMS Flow Sensor Based On Polymide And Silicon Substrate

The detection and control of fluids is essential in industrial production and daily life.Instruments and methods for flow rate measurement are widely used in food,chemical and pharmaceutical fields.Thermal flow sensors are widely studied and used because of their large working range and simple working principle.In recent years,the development of medical devices,chemical analysis and other industries and the requirements for the measurement and control of related solutions and liquids are getting higher and higher.Traditional thermal flowmeter devices often have problems such as low precision and large volume,and thermal MEMS flow.The sensor has extremely high measurement accuracy,miniaturization and low processing cost,which makes it have high application value and research significance.In this paper,the design and processing of two micro-thermal flow sensors based on flexible substrate and rigid substrate are studied.The process parameters of heat treatment process and alloying process are optimized to improve the performance of the sensor.Based on the working principle of the thermal flow sensor,the one-dimensional thermal differential equation and boundary conditions are established.The analytical results of the mathematical model are used to describe the working characteristics of the thermal flow sensor.Based on COMSOL simulation software,a simulation model was established for two-component thermal resistance and three-component thermopile flow sensors,and the influence of key size parameters on sensor performance was studied.A nickel film of a two-component thermal flow sensor was fabricated on a polyimide substrate and a heating element and thermopiles of a three-element thermal flow sensor are fabricated on a silicon substrate using a micromachining process.The process of heat treatment and alloying of the completed thermal flow sensor is optimized.For the different heat treatment and alloying process parameters,relatively good heat treatment and alloying process parameters were obtained from the experimental data.The control circuit was used to test the two flow sensors.The performance of the thermal resistance flow sensor was tested.The thermostatic reactor flow sensing input constant voltage power supply was used to verify the successful fabrication and signal output of the thermopile.The mathematical model and simulation model are used to study the influence of the key size parameters of the micro MEMS thermal flowmeter on the performance.The simulation results give a better combination of parameters.According to the experimental results,the heat treatment process can be maintained at 350 ?for two hours.Achieving good performance of the nickel metal film and an alloying process at 450 ° C for two hours enables the doped polysilicon heater and the thermopile to meet the design requirements;the flexible substrate thermal resistance type flow sensor signal energy produced by the test It has a near linear relationship in the working range and verifies the signal output of the fabricated thermopile.