Difference Between Carbon Film and Metal Film Resistors

Carbon film resistors and metal film resistors are the most commonly used resistors. Although they look similar. But in fact they have many differences. In this article, we'll dive into the nuances of these two resistor types to help you make an informed decision for your electronic projects.

What is a Metal Film Resistor?

Metal film resistor metal film resistor symbol RJ as a symbol.

Metal film resistors are resistors that use special metals or alloys as resistance materials, and use vacuum evaporation or sputtering methods to form a resistance film layer on ceramic or glass. This type of resistor is generally made by a vacuum evaporation process, that is, the alloy is heated in a vacuum, the alloy evaporates, and a conductive metal film is formed on the surface of the porcelain rod. Grooving and varying the thickness of the metal film can control the resistance. Its electrical properties such as heat resistance, noise potential, temperature coefficient, and voltage coefficient are superior to those of carbon film resistors.

The manufacturing process of metal film resistors is relatively flexible. Not only can its material composition and film thickness be adjusted, but the resistance value can also be adjusted by notching grooves. Therefore, resistors with good performance and a wide resistance range can be made.

5 color code metal film resistors

What is Carbon Film Resistor?

Carbon film resistors are made by using an organic binder to prepare a suspension of carbon ink, graphite and fillers, coated on an insulating substrate, and polymerized by heating. Gaseous hydrocarbons decompose at high temperatures and vacuum, and the carbon is deposited on the porcelain rod or tube to form a crystallized carbon film. Different resistance values can be obtained by changing the thickness of the carbon film and changing the length of the carbon film by notching.

Carbon film resistors have low cost, poor electrical performance and stability, and are generally not suitable for use as general-purpose resistors. However, because it is easy to make a high-resistance film, it is mainly used as a high-resistance and high-voltage resistor. Its purpose is the same as that of high voltage resistor.

Three 10 ohm carbon film resistors

Compare metal film resistors and carbon film resistor

Aspect	Metal Film Resistors	Carbon Film Resistors
Construction	Thin metal layer on ceramic or glass	Carbon composition on ceramic
Tolerance	Typically 1% or better	Tolerance varies, often 5% or 10%
Temperature Coefficient	Lower temperature coefficient	Higher temperature coefficient
Stability	Highly stable over time	Less stable over time
Noise Level	Low noise	Moderate noise
Power Rating	Usually lower (e.g., 0.125W)	Higher (e.g., 0.25W or more)
Precision Applications	Common in precise circuits	Less common in precise applications
Cost	Typically more expensive	Generally more cost-effective
Applications	Audio equipment, instrumentation	General-purpose applications
Environmental Impact	Environmentally friendly	Potential environmental concerns
Resistance Range	Wide range available	Limited range

Metal film resistors are preferred in applications requiring high precision and stability, such as in audio equipment and precise instrumentation. Carbon film resistors, on the other hand, are more cost-effective and are used in general-purpose applications where tight tolerances and stability are not critical.

Final Evaluation and Conclusion

All in all, the debate between metal film resistors and carbon film resistors comes down to accuracy versus practicality. Both types have their own unique advantages and disadvantages, with carbon film resistors being cheaper but less accurate. Metal film resistors are relatively more expensive and have better accuracy, etc.

The decision of which type to use ultimately depends on the specific requirements of the electronic circuit and the balance between accuracy and practicality.