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The film of Metal film resistors are usually made of Nichrome, but also other materials such as tantalum nitride is used. The resistive film is sputtered or evaporated on a cylindrical or flat insulating substrate.
The resistive material is a combination of a Ceramic material and a Metal, and therefore these resistors are also referred to as Cermet.
The resistance value is adjusted by cutting a spiral pattern in the film. This can be done with an abrasive or a laser. The stability, temperature coefficient and tolerance could be very tight.
Typical tolerances of metal film resistors are 1% with a temperature coefficient between 50 and 100 ppm/K. Stability is lower than for wirewound, but the high frequency properties are better.
Thunder Precision Resistor Co., Ltd. manufactures high precision and ultra high precision metal film resistors of 0.50%, 0.25%, 0.10%, 0.05%, 0.025% and 0.01% guided with introduced production procedure and special imported materials.