Zero TCR foil resistor ten fold improvement in temperature coefficient

Foil resistors have been the leading choice in precision and stability, since they were introduced in 1962. One of the important parameters influencing stability is the Temperature Coefficient of Resistance (TCR). Although the TCR of foil resistors is considered extremely low, this characteristic has been further refined over the years. The resistance change versus temperature is a nonlinear function, and it is extremely low to begin with. Therefore the key to improve further the temperature dependency was to find a way to linearize this function, or to reduce the non linear component first, and then reduce the slope (linear component) of resistance versus temperature (TCR) to zero or as close to zero as possible. This paper describes such a resistor. Its nominal TCR was reduced to -0.2 ppm/°C from -55°C to +25°C and +0.2 ppm/°C from +25°C to +125°C, this is a 5 fold TCR improvement over the best previous available foil resistor and a 10 fold improvement over standard foil resistors