Oct. 28, 2024
Electronic Components & Supplies
Carbon Film Resistor VS Metal Film: Definition
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A carbon film resistor is a type of resistor that slows the flow of electricity by using a thin layer of carbon. Unfortunately, carbon film resistors are more expensive to make than other types of thin film resistors. They also generate a lot of thermal noise and can portray low accuracy.
(carbon film resistor)
Despite its challenges, it can withstand high-energy pulses and thus are suitable for applications like surge protection electronic circuits, computers, test equipment, DC power supplies, and high-frequency applications.
A metal film resistor limits the flow of electricity by using a thin metal film. It is also the most popular type of thin film resistor. Moreover, metal resistors are cost-effective, compact, have low tolerance, generate less noise, and operate widely compared to carbon resistors.
(metal film resistors)
Therefore, you&#;ll find them in bridge circuits, active filters, and high-frequency applications.
Carbon Film Resistor vs Metal Film Resistor: Side-by-Side Comparison
Now that we&#;ve defined these resistor types individually, let&#;s look at a head-to-head comparison of them both. This will make it easier to know which use cases would suit each resistor type best. The properties this section will focus on are the voltage coefficient of resistance, stability, and temperature coefficient of resistance.
Temperature Coefficient of Resistance (TCR)
Similar to how the amount of voltage applied to a resistor can affect its resistance, changes in temperature have an effect, too.
Of course, this phenomenon isn&#;t exclusive to resistors. All conductors have resistance of some sort which increases in high temperatures and decreases in low temperatures.
We express this value as parts per million per degree Centigrade (ppm/°C) or Kelvin (ppm/K). As with the previous property the resistance value of metal film resistors is less susceptible to change in temperature than carbon film resistors.
Metal film resistors have a TCR between ± 20 and ± 200 ppm/k. On the other hand, carbon film resistors have a TCR between -200 to - ppm/k.
As such, the carbon film resistor TCR is substantially greater than the metal film resistors. This makes metal film resistors more reliable under extreme temperatures (both hot and cold).
Moreover, metal film resistors produce less thermal noise. This makes them ideal for devices such as radios, intercoms and radars.
Carbon Film Resistor Green Color
Voltage Coefficient of Resistance (VCR)
Applying voltage to a resistor may cause changes in its resistance value. Usually, applying voltage to a resistor causes the resistance to drop in near proportionality.
Regardless of decrease or increase, we represent the change in resistance against each applied volt (per volt).
This measurement is known as the Voltage Coefficient of Resistance (VCR) and is represented by the metric: parts per million per volt (ppm/V).
The VCR is important because it helps us predict and determine how well a resistor performs in high-voltage situations. While carbon film resistors perform well in high-voltage applications, their metal film counterparts perform even better. Metal film resistors have a VCR of just under 1 ppm/V, whereas carbon film resistors have a -10 ppm/V. This means metal film resistors are less susceptible to changes in resistance caused by applied voltage.
Stability
Since resistors are a part of machinery and electronics operating in various environments, we must know how they are fair against external stressors. These stressors can (potentially) affect the resistance value of the resistor. We refer to a resistor&#;s tolerance to environmental stressors over time as stability.
Some of the most common stressors are exposure to radiation, heat (high temperatures), and cold (low temperatures). Sudden or prolonged power spikes can also be categorized as stressors that can challenge the stability of the resistor.
Nevertheless, stability is another area in which metal-film resistors outperform carbon-film resistors. This is not to say that carbon-film resistors are unstable. They have moderate stability. On the other hand, metal film resistors exhibit good to exceptional stability.
Carbon Film Resistor VS Metal Film: Construction
The two resistor types have different processes.
Carbon film resistor construction
Manufacturers make carbon composition resistors from a solid, cylinder-shaped resistive element with wire leads and metal caps on the ends. Further on, the materials in the resistive element are a mixture of clay-based ceramic and graphite or carbon powder. Generally, the carbon powder lets electricity flow through it well.
(Internal part of a carbon film resistor)
So, during the deposition process, manufacturers start by heating the ceramic substrate in a hydrocarbon like methane. Next, at high temperatures of approximately °C, cracking reactions will occur in the gas. The pure graphite&#;s crystalline carbon then sticks to the ceramic.
Afterward, the resistive material gets a plastic covering to keep it safe from the heat generated from outside. Manufacturers finally apply copper to make the wire leads at both ends of the resistive element.
Metal film resistor construction
Contrarily, manufacturers use a special method for metal film resistors, where they artificially age the deposited metal in low temperatures for an extended time.
Here, the material employed as the resistance material is Nickel chromium (NiCr). However, in other applications, you&#;ll find other materials like tantalum nitride, gold with platinum, and tin plus antimony.
Then, the resistor&#;s stability and resistance often depend on the metal film thickness. Thus, a larger thickness will mean a lower resistance value and greater stability on both films ends.
Manufacturers use connection leads to press a metal cover for the final touches. They can now achieve the desired resistance via a spiral-shaped slot cut in the thin metal thickness.
Carbon Film Resistor VS Metal Film: Availability
Carbon Film Resistor
You&#;ll find carbon resistors in 1 ohm to 25megaohms with a power rating ranging between one-quarter watt and five watts.
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The three factors affecting the resistance of carbon film resistors are;
Metal Film
Usually, the available metal film resistors in the market have tolerances of 2%, 1%, 0.5%, 0.25%, and 0.1%. Additionally, the resistors are likely to have temperature coefficients ranging from 10 to 100 ppm/K and some resistance.
The two main factors affecting the resistance of metal film resistors include:
Carbon Film Resistor VS Metal Film: Similarities and Differences
The film resistors are similar in the following ways;
(Film resistors in a circuit board)
We have summarized the differences between the metal film and carbon film resistors in the table below.
Carbon Film Resistor VS Metal Film: Drawbacks
Both these resistor types have advantages. While metal film resistors have the best frequency response of all resistors, carbon film resistors are more affordable and have high resistance. However, both these resistor types have drawbacks and limitations.
For instance, as we previously discussed, one of the biggest disadvantages of using carbon film resistors is their high-temperature coefficient of resistance. In addition to this drawback, they also have comparatively subpar stability, especially when compared against wire-wound and metal-film resistors.
Another somewhat cumbersome feature of carbon-film resistors is their bulkiness.
As a consequence of their larger size, they can be a little difficult to maneuver and place, especially by hand. Contrastingly, metal-film resistors are compact, which makes them ideal for smaller electronics.
While, in many ways, metal-film resistors may be superior to carbon-film and carbon-composite resistors, they aren&#;t without their own drawbacks.
For one, they&#;re generally more pricier than carbon film resistors. Moreover, they have higher power dissipation.
Some may see this as an advantage, but it&#;s an attribute that makes them unsuitable for use cases that require low-power dissipation resistors.
Metal Film Resistor On Green Blur
Conclusion
Both carbon film and metal film resistors limit current flow through circuits. However, carbon film resistors use carbon, while metal film resistors use metal to reduce current flow.
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Your electronics can literally undergo full failure if their resistors are not performing well. What are resistors? These are a device&#;s special parts that resist the current flow.
Thus named resistors. Well, it&#;s pretty simple to understand them since their name fits fine with their purpose. When a resistor opposes the current, it means it is regulating it at the same time. You will find different types of resistors in the industry. Different producers are relying on these types as per the nature of their projects.
It is obvious that you need to determine the type of resistor as per your requirements, or else these can ruin your projects straight up! So what are the types of resistors that we are going to review in this post?
Hang on a second; there is no hurry! Sit back and relax since we are going to discuss all the important aspects of metal and carbon film resistors with you today! Let&#;s get going!
The basic function of this resistor is the same. It is responsible for resisting the current. However, a carbon resistor does this job by using a carbon film. These resistors are incredible when it comes to enduring intense pulses and frequent transmissions. Therefore, due to these features, these are useful to be a part of electronics like PCs, testing tools, and more.
There is no carbon film in these resistors. Instead, the function of these resistors directly depends on metal films. There are different features of metal film resistors that make them a crucial component of several electronics used in daily life. These are more reliable than the carbon film resistors, and the possible reasons are:
Simply put, resistors are for resisting the current in a system. It can also re-route the current path, making it change its original one. Also, resistors are beneficial for the regulation of the current so that you can give sufficient current to your system.
In the case of higher and lower currents, the system can collapse and fail to function properly. You can take advantage of resistors by aligning them in parallel and series circuits. However, this depends on your project as well. You can even use a resistor for monitoring and stopping voltage. These are completely sourceless, which makes handling them much easier. When the current goes through a resistor, it will dissipate heat. It means there will be a definite loss of power.
Resistors work on the ohm&#;s low, and due to this reason, these are behind the efficient performance of devices that you use almost every day in your life. There is a wide range of varieties that you will find in resistors. You can divide them into different factors like their composition, films, and wiring. Now its time to check the factors that greatly influence the working of resistors:
In the further sections, we are going to take an extensive look at the carbon film resistors. So that you can understand their function completely through our discussion, you will also get to compare them with metal oxide film resistors. We are affirmative that there will be no confusion left for you regarding carbon film resistors. So let&#;s crush it!
The design of these resistors mainly depends on a carbon film. This special covering is present on an insulative substrate or a ceramic substance. It is a thin layer, and you might even have to use a microscope to see this layer precisely. Now you can compile this entire process under a single word called sputtering to save you time. When the film fully takes over the substrate, it will resist the current. Pretty obvious since this is what a resistor is supposed to do!
Why are we using an insulative ceramic material in this setup? Well, it is because of the heat. The ceramic substance will trap the heat from going out and enables the resistor to endure extremely high temperatures. These temperatures never ruin the resistor because of this little component &#; a ceramic substance. When you need to observe and work with the tolerance, you can fully rely on carbon film resistors. These have a negative resistance which will reduce as you will enhance the temperature.
Some resistors come with a metal oxide film which imparts different properties in them as compared to the carbon film resistors. Similar to carbon resistors, the metal oxide layer will cover the ceramic substance instead of the carbon film. The oxide layer fully adheres to the ceramic substance.
Now if you use antimony oxide for this purpose, it will be just icing on the cake. It has remarkable properties that will enhance the quality of your projects on the whole. Just like carbon film resistors, these offer impressive endurance for high temperatures. It is because we are using a ceramic substance that traps heat, just like carbon film resistors. The trick to using metal oxide for this purpose is that it will stop the current to a large extent. It means the metal layer you are using for this resistor can greatly influence the resistance as well.
Also, you need to determine the width of the metal oxide layer. Insufficient thickness can lead to complications in the devices. A thin layer will allow more heat to pass through, causing the system to overheat and undergo major damage.
It&#;s time to compare carbon film resistors and metal oxide film resistors. It will allow you to understand the strong and weak points of both these types. Also, it will help you to choose the most appropriate resistor for private projects and assignments at the same time. Experts believe that metal oxide resistors are always reliable as compared to carbon film resistors. Let&#;s see why:
The carbon film resistor has more power rating than metal oxide film resistors. It can go up to 5 watts. At the same time, metal oxide resistors have a power rating of just 3 watts.
The appropriate metal films for a metal oxide resistor are available in the following:
The design and construction of both resistors are different due to the assembly of different components in them. This construction sets them apart from each other, making them application-specific. So carefully read out the constructions of both resistors and choose the best fit for yourself later.
It is hard to choose between carbon film resistors and metal oxide film resistors. We totally understand this. Therefore, we hope this guide was of some use to you to evaluate the features and drawbacks of these resistors to make your future projects shine! Till then, we will catch you in the next post with something amazing from the world of physics!
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