Pyrolytic Film Resistors: Carbon and Borocarbon

V I D E A L resistor would possess a resistance precisely adjusted to value and constant with time, temperature, voltage and frequency under all conditions of use in the application for which it is intended. Wirewound resistors, which early references to "resistance helices" suggest were the first to be employed, approach the ideal in a n u m b e r of respects. T h e advent, however, of applications requiring resistors with high values of resistance, of smaller size, and of greater stability over augmented ranges in operating conditions soon m a d e the realization of the ideal more difficult. Moreover, despite great progress in the development of resistance alloys and in the drawing of fine wires from them, the growth of the communications and electronics industries necessitated the development of resistors smaller and cheaper than can be produced from wire and possessing different characteristics. Non-metallic resistive materials were accordingly introduced, even though some of these possess electrical and mechanical properties which are comparatively less stable. T h e industries now require resistors having the advantages of the non-metallic types and which at the same time are highly precise and stable. T h e problem, thus, is t h a t of imparting precision and stability to non-metallic resistive materials or of employing metallic ones in new ways. Oxides, sulfides, nitrides, carbides and non-metallic elements such as carbon, germanium, a n d silicon are among the m a n y materials which have been employed in making resistors.