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Metal Film Resistors Features

Writer:万利隆电子 Page View:Date:2019-08-14
Metal film resistors have a thin metal layer as resistive element on a non-conducting body. They are amongst the most common types of axial resistors. Microhm's metal film resistors consist of PMRY series, MCC series and more. Other film type resistors are carbon film and thick and thin film resistors. In most literature referrals to metal film, usually it is a cylindrical axial resistor. However, thin film chip resistors use the same manufacturing principle for the metal layer. The appearance of metal film resistors is similar to carbon film resistors, but their properties for stability, accuracy and reliability are considerably better.
Metal film resistors are axial resistors with a thin metal film as resistive element. The thin film is deposited on usually a ceramic body. The resistive element is a thin metal layer that is usually sputtered (vacuum deposition) on a cylindrical high purity ceramic core. Sometimes other techniques than sputtering are used. The deposited metal is artificially aged by keeping it for a long period at a low temperature. This is usually done by lasers, while in the past sandblasting and grinding techniques were used.
Metal film resistors have good characteristics for tolerance, stability and TCR. Furthermore, the resistors feature low noise properties and a high linearity because of a low voltage coefficient. Therefore, in circuits where tight tolerance, low temperature coefficient and low noise properties are important, often metal film resistors are used. Examples of applications are active filters or bridge circuits.

For a good reliability, metal film resistors are normally operated between 20 and 80 percent of their specified power rating.  Reliability is generally increased by derating 50%. However, in very specific situations, at lower than 20% of the power rating in a humid environment the reliability decreases. Compared to wirewound or carbon composition resistors, these resistors are easier damaged by voltage surges and power overloads. Customer can find various metal film resistor from Microhm Electronics.


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