Metal Film vs Carbon Film vs Wirewound Resistors

Published on in Category Basics


Resistor, its a general term, but there are many types, not all are same and equal. In this article we try to explain you the difference between most used resistor type, and when and how to choose any one type.

You can be hobbyist or professional, but selecting the right type of resistor is very critical for stability and performance, lets explain the types, characteristics and differences between the resistor types in simple laymen terms. here are the types of resistor

  1. Carbon Composition
  2. Carbon Film
  3. Ceramic
  4. Metal Alloy
  5. Metal Film
  6. Metal Foil
  7. Metal Oxide
  8. Thick Film
  9. Thin Film
  10. Wirewound

Above are the general types, here were are not going to discuss all type, but the most commonly used type: Wirewound, Carbon Composition, Thick Film,

Wirewound Resistors

In the beginning of electronic and electrical circuits history, resistor means Wirewound resistors, there were no other alternative as today.

Wirewound resistors are one of the first practical resistors used since from the beginning. Wirewound resistors have longer life compared to other types.

  1. Precision: The important characteristics of Wirewound resistors is its precision. They can have very tight resistance tolerances say 0.005% is commonly achieved.
  2. Stability: Next is its stability, they are stable (15-50ppm/yr) maintaining their precision over time because they are made with stable materials
  3. TCR (Temperature Coefficient of Resistance) is low (<10ppm/°C) and can be controlled by selecting special wire alloys. (Usually, you need the lowest TCR, but a higher TCR has special interest in some applications.)

Carbon Composition Resistors

In the past, the bulk of the resistor market went to carbon composition products.

  1. Not accurate: Best tolerances of achivable is about 1%
  2. Unstable: have poor TCR (1000 ppm/C)
  3. Generate electrical noise
  4. Low cost is their advantage

Now, film technology products are replacing carbon resistors.

Film Resistors

There are two common film types

  1. Thick Film
  2. Metal Film
  3. Thin Film

Among them Metal film resistors are a better technology. They are made by an evaporation/deposition process where a base metal is vaporized in a vacuum and deposited on an insulating substrate. Compared to precision wirewounds, they are not as accurate (>0.01%), have higher TCR (20-200ppm/C), and are not as stable (200-600ppm/yr.) They can be small for “chip” applications, are low cost in high quantities, and are excellent in high frequency and fast rise time applications.

Which type of resistor to select

Here based on the properties and experience, we rule out the use of carbon resistors and carbon film resistor, at few extra faction of cost always go with Metal Film Resistors. Also failure rates are high with Carbon based resistors.

On a board with few precision resistors will have a small total cost impact.

So now we have narrowed down the comparison to Wirewound Resistor vs Metal Film resistor. The key deciding factor between wirewound or metal film precision resistor technology is depends on the application.

Use Metal Film Resistors

  1. Metal film resistors are best If the application involves fast rise times (microseconds) or high frequencies (in Mega Hertz).
  2. When cost is the only consideration, use metal films.
  3. If size is critical use metal films resistors.

Use Wirewound resistor

  1. When accuracy and stability are important
  2. Tolerances can be as tight as 0.005%, and long-term stability is factors better than for metal films
  3. TCR can be extremely low, or tailored for special circuit applications such as temperature compensation

Find more info from below resources: resistorguide.com, Wikipedia



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