Preparation And Performance Of Thermal Resistance Thin Film Heat Flow Sensor

Heat flow exists everywhere in real life all the time.In some important occasions,such as the outer surface of high-speed aircraft and various high-speed propulsion engines,real-time monitoring of heat flow changes is important for equipment safety and active thermal protection design.significance.The traditional heat flow sensor is not suitable for these important occasions due to its large size,great influence on the measured environment and slow response.Based on the above problems,a thermal resistance thin film heat flow sensor is designed and fabricated in this paper.It has the advantages of small size,fast response,little impact on the measured environment,high sensitivity,and long service life.It can be well used in these occasions.In order to make the heat flow sensor achieve a sensitivity better than 0.01μV/(W/m~2),temperature resistance of more than 1200°C,response time of less than 0.1s,and the volume is less than 13mm×13mm×1mm the requirements,around the design,development,packaging and testing of thermal resistance thin film sensors,this paper mainly carried out the following work.(1)Overall scheme design of heat flow sensor.The overall structure of the thermal resistance thin film heat flow sensor is designed according to Fourier’s law.In order to increase the upper temperature limit of the heat flow sensor,the base material of the sensor is alumina ceramic.In order to solve the problem of small output voltage and low sensitivity of the heat flow sensor,multiple groups of thermocouples are designed to form a thermocouple in series,and the thermopile is used as the core of the temperature difference detection of the heat flow sensor,and the number of thermocouples in the thermocouple is increased as much as possible in the limited space.Using silica as a thermal resistance material,with its smaller coefficient of thermal resistance,to provide a large temperature difference,thereby increasing the output of the thermopile,and the silicon dioxide thermal resistance layer is designed as a step type,which can make the hot and cold nodes of the thermocouple in the same plane.(2)Preparation and encapsulation of heat flow sensors.The physical development of the heat flow sensor Using the micro-nano manufacturing process,235 sets of platinum-rhodium-platinum thermocouple combination thermopiles were prepared by photolithography development and sputtering stripping.The line width is 45um,the thickness is 0.5μm,and the length is 0.5μm.is 0.75mm.Through the sputtering and wet corrosion process,the silica thermal resistance layer step was prepared above the thermopile,with a thickness of 5μm.The platinum wire is used as the signal output line of the sensor,and the high temperature silver paste is used to bond the platinum wire and the sensor.(3)Study of the output characteristics of heat flow sensors.In order to study the performance of the prepared heat flow sensor,the sensor performance calibration equipment is designed and built.The calibration equipment adopts the principle of comparison method,and changes the heat flow by adjusting the output of the heating equipment,so as to realize the performance test and calibration of the sensor under different heat flow environments.The actual measured sensitivity of the sensor is 0.0129μV/(w/m~2),the response time is 78ms,the temperature resistance exceeds 1238℃,and the repeatability and consistency are good,which meet the design requirements.