A surface temperature limit detector using nematic liquid crystals with an application to microcircuits

Abstract

A novel technique has been developed permitting the detection of surface temperatures in excess of a well defined threshold value within the range 25-300 degrees C. The technique utilizes the change in optical state of a thin film of liquid nematogen at a critical temperature and can be used for any smooth horizontal surface to which a thin film of liquid nematogen can be applied and which can be uniformly illuminated with polarized light. The technique has been applied to microcircuits where the temperature sensitivity and spatial resolution have been demonstrated to be better than 0.5 degrees C and 5 mu m respectively.