HEAT SENSITIVE ELECTRICAL RELAY DEVICE

An electrical relay device comprises a first substrate of thermal insulative material mounted on a suitable heat conductive support, a heater film deposited on such first substrate, first electrical contacts mounted on the first substrate and connected to the heater film for connecting the heater film to a source of control voltage, a second substrate having a mass smaller than the first ssubstrate mounted on top of the heater film, a thin film of a sensing material showing a large change of impedance at a critical temperature deposited over the second substrate, and second electrical contacts on the second substrate and connected to the film of sensing material for connecting it to the terminals of a controlled circuit. The material of the second substrate is selected so as to optimize the sensing material properties or the relay performance properties.