Preparation And Properties Of Polyimide-based Thermal Elements

With the development of technology, thin-film thermocouple sensors has been used in many fields of life. This paper is the research of temperature sensor based on polyimide and put forward the structure design and principle. It uses the ANSYS to analyze the design of the sensor, discusses polyimide substrate thickness, thermal conductivity, the structure of metal electrodes, the thickness of the thermal properties of the sensor has what kind of influences on thermoelectric performance to get the best design method.This paper used the method of electron beam evaporation to realize the preparation of thermocouple on polyimide substrate. To ensured these films have good continuous surface, no cracks, we used scanning electron microscope to guarantee the smoothness of the polyimide substrate, nickel film and copper film. On this basis, we measured the thickness of copper film and nickel film by steps instrument to make sure the thickness is 120 nm. Then we used E-type standard thermocouple with I grade precision to standardize the Cu/Ni thin film thermocouple based on polyimide and used Origin 8software to process the data and get the fitting line. Experimental results proved that the measurement value of thermocouple sensor based on polyimide and the ideal value were basically identical. Meanwhile we discussed the linearity, hysteresis, repeatability and sensitivity of thermal sensor based on polyimide further. It was concluded that this sensor has high linearity, small hysteresis, high repeatability, high sensitivity, so the sensor can be used to measure the temperature. In this paper, we use the sensor to text the temperature of battery and make sure that the testing process will not affect the normal work of the battery.After that we tested the performance of lithium battery to ensure the encapsulationprocess does not affect the normal work of the battery. Finally, the paper introduced the measurement and circuit design of thermal sensor based on polyimide, we used bridge compensation method to realize the cold junction compensation of thermocouple. The bridge compensation method is based on the voltage produced by the unbalanced bridge.We chose 89C51 as the microprocessor, ICL7109 as A/D converter, OP07 chip as operational amplifier, 555 chip as the timer, realize the signal amplification,transformation and display.