A polymer foil non-contact IR temperature sensor with a thermoresistor integrated on the back of a vertically configured thermopile

A very thin non-contact IR temperature sensor has been fabricated in a polymer foil. A thermoresistor was placed in the isothermal back-layer of a vertical configured IR-sensor. The IR-sensor is a thermopile consisting of through-the-foil thermocouple legs in a flexible polyimide foil, and the integration of a thermoresistor to one of its surfaces enables use of the sensor for non-contact temperature measurements. The size of the sensor is 3 mm × 3 mm and the thickness is less than 0.2 mm. The sensor can easily be surface mounted to printed circuit boards. An ion track technique followed by lithographically controlled electroplating of nanowires and thin film deposited interconnects are used to fabricate the infrared sensor. The thin film nickel thermoresistor was fabricated using evaporation. Layers of Parylene C was used for electric insulation and protection to improve environmental stability. In the temperature range of 20–55 °C, the thermoresistor shows good linearity. Some initial decrease in resistance was seen at 105 °C whereafter the resistance stabilized. The IR temperature sensor was characterized, and for temperatures near room temperature a simple linear equation using the voltage response and temperature of the thermoresistor as the only input parameters was curve fitted to the experimental data. The difference between the measured and the calculated object temperature is less than 0.5 °C using a confidence level of 95%.