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Non-Wirewound Resistors: Film, Foil & Metal Oxide

Author: Geym

Sep. 09, 2024

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Tags: Electronic Components & Supplies

Non-Wirewound Resistors: Film, Foil & Metal Oxide

Metal Film / Thin Film

Link to Xieyuan Electronic

Today the most dominant type of resistor is the metal film. Sometimes it is called thin film. From the beginning precious metals or resistive alloys were evaporated in a vacuum process and evaporated on ceramic rods. But the TCR specifications especially were hard to fulfil (TCR = temperature coefficient of resistance). Stability and TCR accuracy took a leap forward when one passed to metal ion bombardment of the rods (so called sputtering). Today all the techniques have been developed and refined.

The evaporation technique works both with a vacuum process and a chemical volatility process. Sput­tering and ion implanting have become synonymous concepts. The technical progress today motivates manufacturing of high precision resistors. We talk about the third generation of metal/thin film resistors.

Common film alloys are nichrome (CrNi) or tantalum nitride (Ta2N), often with additives of aluminum (Al), silicon (Si) or titanium (Ti). The tantalum nitride has very fine low noise characteristics and is superior in hi-fi applications. Generally, metal film resistors keep noise down by means of laser spiraling that properly utilized produces even tracks free from irregularities. Noise is discussed in section R1.9.

Occurrence of non-linearity &#; distortion &#; is mastered by measurement of the third harmonic distortion and automatic screening, where failing parts not meeting stated requirements are removed from the lot.

Distinctive of the metal films is their thin layers &#; 50&#; Å or,  0.005&#;0.5 μm (0.2 &#;20 microinches). The thinnest films correspond to the highest resistance values where the film starts approaching molecular thicknesses and to some extent deviates from the noise-free conduction capability of metals. Thus the noise is increasingly greater in the high resistance range. Films thinner than 350 Å should be avoided in noise sensitive designs. Another reason for avoiding them is their extreme sensitivity to moisture related electrolytic corrosion, especially if the film consists of a chromium-nickel alloys. Since the film thickness is not stated in the data sheets we may obtain a certain guidance of where the film is getting too thin for high-reliability applications by dividing the manufactured maximum value by 10. Then choose from several serious manufactures the highest manufactured value of the size in question. If the maximum value is, for example, 15 MΩ this rule of thumb gives an upper limit value of 1.5 MΩ. If the application is a dry room environment without large temperature variations (no risk of condensation) and low noise requirements we may use considerably higher resistive values. But still we should, both for reliability and above all availability reasons, take care not to use the highest manufactured maximum value.

Check with other serious manufacturers where their maximum values are and purchase a little bit below the lowest maximum value.

Also, the relatively thickest films are thin and corrosion disposed in moisture, especially if they are working with DC loads. A good encapsulation therefore is necessary. US MIL components exist with hermetic seals but they are relatively expensive. Epoxy/plast­ic molding does not always offer the same good protection as lacquered coverings, at least not if the lacquer is applied in several thin layers. Farthest in there are one or several &#; often transparent &#; coatings of lacquer followed by several layers of colored lacquer. Here the Europeans are far ahead. Duplicated production of cheap standard components with multilayer lacquered coverings probably will come rather close to optimum with regard to price and quality.

Another risk zone for metal film resistors is the ESD &#; electrostatic discharge. The closer the tolerances, the more important is part protection against ESD.

Finally, metal film resistors are sensitive to power pulses. The power will warm up the thin resistance track very rapidly. Consequently also short pulses may lead to a risk of burning-off or too high temperatures that may hazard the stability. Conservative recommendations talk of maximum 2 x PR where PR stands for rated power. At all events we should not exceed 4 x PR even if the mean power is within specified limits. Single pulses may be much higher but we have to inquire into every particular case: type, manufacturer, value, environment&#;

Low ohmic designs

Values below 10 ohms previously have been manufactured  so that the ceramic rods are plated with a resistive alloy, in a bath or a burning process, or by electroplating. The plated layer then will become proportionately thick &#; between 1 and 5 μm (0.04 and 0.2 mils) &#; and will have a very good pulse power capability. But tolerances and TC values will be poorer. In the lowest resistance values there is no spiraling which will improve the pulse capability further.

Today some manufacturers have succeeded in producing low ohmic resistors down to 0.1 ohm with the sputtering technique. This eliminates the plating technique difficulties with TCR and tolerance but impairs the pulse capability.

 Power and precision types

If we load a conventionally power rated metal film resistor with a higher power the temperature will raise and this in turn will decrease stability. Thus power resistors in metal film often have the tolerance ±5% in the E24 series. Alloys and lacquers have been chosen in order to endure higher operation temperatures.

If we go in the other direction and reduce the power &#; derate &#; and, moreover, lower the maximum permissible ambient temperature, we get a very stable resistor. IEC 115-5 divides in that way the same sizes in different stability classes, from 0.5 to 0.05 %. It&#;s the same philosophy as behind Figure R2-9 for precision wirewound resistors. High stability resistors can be worth producing in fine tolerances and TC values. Thus precision resistors of the market are characterized by a low power rating, fine tolerances, low TCR values and a high stability. Note, however, that TC information sometimes is connected to restrictions in the temperature range. The finer the TC, the more narrow the temperature range.

In order to increase the stability further, high precision components are subjected to aging processes where one already under the manufacture releases prospective changes.

Linear PTC designs

If we choose metal film alloys that bring out the positive TC of the metals &#; positive temperature coefficient, PTC &#; we get relatively linear PTC resistors. Values between + and + ppm/°C are offered. Just as for the wirewound counterparts the resistance range is limited upwards.

Mounting

At least 0.5 mm air space or additional insulation  should separate the resistors from adjacent metal parts, for example conductive patterns on printed circuit boards.

Metal Foil

Carbon Film vs. Metal Film Resistor: What's the Difference?

Carbon Film vs. Metal Film Resistor: What&#;s the Difference?

If you are looking for a resistor, there are two main types to choose from: carbon film or metal film. Both have their own unique benefits and drawbacks, so it can be tough to decide which one is right for your needs.

In this article, we will compare and contrast these two resistor types so that you can make an informed decision about which one is best for you.

What are Metal Film Resistors?

Metal film resistors are made from thin metal films that are put on a ceramic core.

The resistor is then covered with an insulating material to protect it from electrical interference and corrosion.

 

These resistors have good temperature stability, low noise levels, and high accuracy ratings, which makes them perfect for many applications. They are also more durable than carbon film resistors and can handle higher voltages and currents. [1]

Brief Intro to the Resistors

A resistor is an electrical component that limits the flow of electricity. This is done by creating resistance to the current, which then reduces its intensity.

Resistors are essential in electronic circuits as they help protect against damage caused by overcurrent and short circuits.

They also help regulate voltage levels and reduce noise in audio circuits. [2]

What are Carbon Film Resistors?

Carbon film resistors are made from a thin carbon film that is applied to an insulating substrate. The resistor is then covered with a protective coating for protection against environmental factors such as moisture and dust.

These resistors have good temperature stability, low noise levels, and high accuracy ratings. They are also inexpensive and are often used in low-power applications. [1]

Overview and Key Difference

Both carbon film and metal film resistors have their own unique benefits and drawbacks. Metal film resistors are more durable, accurate, and have higher power ratings ideal for high-power circuits.

 

Carbon film resistors are less expensive and typically used in low-power applications where accuracy is not as important.

The key difference between the two is that metal film resistors are more durable and accurate, while carbon film resistors are cheaper and less durable.

Voltage and Temperature Coefficient

Both types of resistors have a voltage and temperature coefficient that affects how they behave in different conditions.

Metal film resistors are typically more stable when exposed to changes in voltage or temperature, while carbon film resistors can be more unpredictable. Thicker metal layers make metal film resistors more stable than carbon film resistors. [2]

Size and Form Factor

Metal film resistors are usually smaller than carbon film resistors because they have a thin metal layer. This makes them ideal for use in applications where size and heat dissipation are important factors.

 

Carbon film resistors, on the other hand, can be larger due to their thicker layers. However, they dissipate heat more effectively than metal film resistors.

Noise Design

Metal film resistors are typically quieter than carbon film resistors. This is because metal films can better dissipate heat and also reduce electrical noise.

Tolerance

The tolerance of a resistor is how much it can differ from its set value.

Metal film resistors typically have a higher tolerance than carbon film resistors because their layers are more consistent and uniform.

Similarities Between Metal Film and Carbon Film Resistors

There are two types of resistors &#; metal film and carbon film. They both control the flow of electricity in an electronic circuit. Metal film resistors have a voltage and temperature coefficient which affects how they work in different conditions.

Carbon film resistors come in many different sizes and shapes, making them good for a range of applications. Both metal film and carbon film resistors have a tolerance rating to indicate how close they come to their set value.

 

When choosing between metal film and carbon film resistors, it&#;s important to consider the application and its requirements. Metal film resistors are great for applications that require precision and accuracy, while carbon film resistors are more suited for general use.

You need to choose between metal film and carbon film resistors depending on your needs. Both types of resistors can help you have accurate results in electronic circuits, but there are differences between them in terms of durability and accuracy.

 

FAQ

Which is better: carbon film or metal film resistors?

It depends on what you need. Metal film resistors are more accurate and durable, but they can be more expensive and difficult to find.

Can I use a metal film resistor instead of carbon?

Yes, you can use a metal film resistor instead of carbon. However, it is important to consider the application and its requirements before making a decision.

Are metal film resistors more expensive than carbon?

Yes, metal film resistors are typically more expensive than carbon film resistors. This is due to their higher accuracy and durability compared to carbon film resistors.

Are metal film resistors better?

It depends on the application. Metal film resistors are more accurate and durable, but they can be more expensive and difficult to find. Carbon film resistors are cheaper, easier to find, and come in a variety of sizes, but they are not as accurate or durable as metal film resistors.

What are the advantages of using a metal film resistor versus a carbon composition resistor?

Metal film resistors are more accurate and durable than carbon composition resistors. They are also smaller in size and can handle more power.

Additionally, metal film resistors generate less electrical noise than carbon composition resistors. Carbon composition resistors are cheaper and come in a variety of sizes, but they are not as accurate or durable.

Are metal film resistors better?

It depends on the application. Metal film resistors are more accurate and durable, but they can be more expensive and difficult to find.

You need to choose between metal film and carbon film resistors depending on your needs. Both types of resistors can help you have accurate results in electronic circuits, but there are differences between them in terms of durability and accuracy.

Are metal film resistors better for high-frequency applications?

Yes, metal film resistors tend to be better for high-frequency applications due to their higher accuracy and durability compared to carbon film resistors.

Additionally, metal film resistors generate less electrical noise than carbon composition resistors.

However, it is important to consider the application and its requirements before making a decision.

Are metal film resistors better than carbon?

Carbon film resistors are cheaper, easier to find, and come in a variety of sizes. Metal film resistors are more accurate and durable, but they can be more expensive and difficult to find. You need to choose between metal film and carbon film resistors depending on your needs.

How do you know if a resistor is metal film?

Metal film resistors are typically labelled with a 4 or 5 digit code. This code consists of the first 2 or 3 digits which represent the resistance value, and the last 2 digits which indicate the resistor&#;s accuracy.

Do metal film resistors have polarity?

Metal film resistors have polarity. This means that there is a (+) or (-) sign near the terminals on the resistor. When connecting metal film resistors in an electronic circuit, it is important to make sure that the correct polarity is maintained.

Are metal film resistors inductive?

Metal film resistors are typically inductive. This means that they can store energy in the form of a magnetic field when an electric current passes through them.

It is important to consider the application and its requirements before making a decision about whether or not to use an inductive metal film resistor.

Are metal film resistors blue?

No, the colour of a resistor does not always indicate its type or accuracy. The best way to determine if a resistor is metal film is to look for the 4 or 5 digit code which indicates its resistance value and accuracy.

Additionally, metal film resistors are typically smaller and lighter than carbon composition resistors. They also generate less electrical noise and can handle more power.

What are the three types of film resistors?

There are three types of film resistors- metal film, carbon film, and wire wound. Metal film resistors are more accurate and durable than carbon composition resistors but they can be more expensive and difficult to find.

Carbon film resistors are cheaper, easier to find, and come in a variety of sizes. Wire wound resistors have the highest accuracy, but they can be very large and expensive. You need to choose between these types of resistors depending on your needs.

Are metals ESD safe?

Yes, metal film resistors are ESD safe. They are designed to protect against electrostatic discharge and usually have a high voltage rating. Additionally, metal film resistors generate less electrical noise than carbon composition resistors, so they are less likely to be affected by interference.

However, it is important to consider the application and its requirements before making a decision about which type of resistor to use.

Are metal film resistors available in standard power ratings?

Yes, metal film resistors are available in standard power ratings. These power ratings range from 0.25W to 5W and are generally indicated on the resistor&#;s packaging or specification sheet.

Are you interested in learning more about all industial resistor manufacturer? Contact us today to secure an expert consultation!

It is important to select a resistor with a higher wattage rating than the application requires so that it can handle any unexpected surges in current without being damaged. For example, if you need a 1W resistor, it is best to choose one with a rating of at least 2W.

What are the three types of film resistors?

There are three types of film resistors: metal, carbon, and wire wound. Metal film resistors are more accurate and durable than carbon composition resistors but they can be more expensive and difficult to find.

Carbon film resistors are cheaper, easier to find, come in a variety of sizes, and generate less electrical noise. Wire wound resistors have the highest accuracy but are very large and expensive. You need to choose between these types of resistors depending on your needs.

What are film resistors used for?

Film resistors are used in different devices, like power supplies, amplifiers, voltage dividers, and filters. They help make sure that the readings and measurements are accurate.

Film resistors also come in different sizes and wattage ratings so it&#;s important to pick the right resistor for the device you&#;re using it in.

What is a disadvantage of the circuit?

One disadvantage of using a circuit with film resistors is that they can generate electrical noise, which can interfere with other components in the circuit. Additionally, metal film resistors tend to be more expensive than carbon composition resistors.

Lastly, they don&#;t come in as many sizes and wattage ratings as some other types of resistors, so it can be difficult to find the exact size and rating you need.

What is the biggest disadvantage of direct current?

The biggest disadvantage of direct current (DC) is that it is not as flexible as alternating current (AC). This means that DC can only be transmitted in one direction and the voltage level has to remain constant.

Additionally, it takes more equipment to control DC than AC, which makes it more time-consuming and expensive to use. Lastly, the cost of batteries used for powering DC systems can be expensive.

There are many factors to consider when choosing between different types of resistors. Metal film resistors offer more accuracy and durability than carbon composition resistors, but they can be more expensive and difficult to find.

Carbon film resistors are cheaper, easier to find, come in a variety of sizes, and generate less electrical noise. Wire wound resistors have the highest accuracy but are very large and expensive. It is important to consider the application and its requirements before making a decision about which type of resistor to use.

Which is better: carbon film or metal film resistors?

The answer to this question depends on the application and its requirements. Metal film resistors are more accurate and durable than carbon composition resistors, but they can be more expensive and difficult to find. Carbon film resistors are cheaper, easier to find, come in a variety of sizes, and generate less electrical noise.

There are a few different types of resistors. Each one has different benefits and drawbacks. Wire wound resistors are the most accurate but they are also the largest and most expensive. You should consider the application and its requirements before making a decision about which type of resistor to use.

If accuracy is important, then metal film resistors would be a better choice. However, if cost or size is an issue, then carbon film resistors may be more appropriate. It all depends on what the application needs.

What should you consider when choosing a resistor?

When choosing a resistor, it is important to consider the size, wattage rating, accuracy, and cost. Resistors come in different sizes and wattage ratings, so make sure to choose one that fits your needs. It is also important to consider the accuracy of the resistor.

Metal film resistors are more accurate than carbon film resistors, but they can be more expensive and difficult to find. Lastly, consider cost when choosing a resistor as some types may be more expensive than others.

Ultimately, you need to choose between these different types of resistors depending on your needs.

Useful Video: Carbon Film Vs Metal Film Resistor: By ANEESH P THANKACHAN

 

Conclusion

So, what&#;s the difference between a carbon film resistor and metal film resistor? In short, carbon film resistors are less accurate and have a wider tolerance than metal film resistors.

They also tend to be more susceptible to noise interference. However, they are cheaper and easier to produce than metal film resistors. Metal film resistors offer greater accuracy and stability, but come at a higher price tag.

If you need a resistor for a low-precision or general purpose application, a carbon film resistor is likely your best bet. If you need something more precise, go with a metal film resistor.

Have you ever used either of these types of resistors in one of your projects? Let us know in the comments!

Metal-oxide film resistors and power applications

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Those articles you are seeing are speaking from an implicit contexts, and everything is relative. There are many degrees of freedom.

For example:

thin film resistors are not suitable for pulse power

thick film resistors are more suitable for pulse power than thin film

but thick film is still pretty crummy so you could go even farther say film resistors (both thin and thick film) in general are not suitable for pulse power compared to other bulk element resistors

SMD components are not suitable for pulse power ("SMD" here might refer to chip components but there are components that are surface mount that are not chip and can handle pulse power just fine, like MELF)

but there are double-sided SMD components with a film on both sides for increased surface area which are more suitable for pulse power than single-sided SMD components, but still not as suitable as MELF (or axial) where the trace can be printed around the entire surface area of the component

axial and MELF (which are also an surface mount component, by the way) components are suitable for pulse power

metal oxide film is not suitable for pulse power

carbon is suitable for pulse power and could be carbon composition or carbon film (NOTE: I fairly certain this is not carbon thin film and that there is no such thing as carbon thin film).

carbon film is less suitable for pulse power than carbon composition, because it is pure carbon and must be printed and therefore cannot be a bulk material like carbon composition. But the fact it is pure carbon means it is much more controllable and stable than carbon (mixed) composition

So what does that mean? It means the following for pulse powering capability (is not quite the same as high temperature cycling stability, and nothing to do with other performance metrics such as tolerance or noise):

Carbon composition > carbon film > metal oxide thick film > metal oxide thin film

axial/MELF > double-sided SMD > single-sided SMD

But you can mix and match material with construction. So you can end up with a metal-oxide film on an axial/MELF body that might be more suitable for pulse power than carbon film on a single-sided SMD component.

Usually these articles are speaking only in a limited scope or context so will shorten their wording.

It can be difficult to tell when an article is actually referring exclusively to thin film SMD of if they actually mean all thin film when they say "thin film".

It can be difficult to tell whether an article is referring exclusively to chip components or to all surface-mounted components (such as MELF) when it says "SMD component".

The article could also be speaking from the point of view of a component manufacturer. For example, if you were making resistors it might be optimal in terms of pulse power to use carbon composition, which would be fine if that was all you cared about, but you sacrifice accuracy, noise, and cost. So you might instead choose to go with carbon film for more stability and lower tolerances and design your way around the deficiencies compared to carbon composition. Or you might decide to cut costs even more and go with metal oxide film and design your way around it the deficiencies in the material.

Or it might just be impossible to make a wirewound resistor with sufficiently high resistance so you need to go with metal oxide film, as is the case in your quote. You could go with carbon, but you might not need to and it probably costs more in terms of tooling, etc.

The Difference between Carbon Film and Metal Film Resistors

 

1. Introduction

Invented by Boykin in , resistors are today commonly used in almost all electronic circuits. Resistors can be described as a device that resists the flow of current flowing through itself, back when the resistor size was very huge and the tolerance value reached as high as 10 percent when it was implemented. Besides, they are usually made of compressed carbon. Resistors are mostly made from metal films and are available in small SMD packets with a tolerance value of as little as 2%, or even less, in the case of precision resistors. Carmet, KWK, Epcos India Pvt Ltd. and more are some of the leading manufacturers of resistors in India. If you didn't know, India accounts for some 34% of the market for passive components such as resistors by importing them, the remainder being imported.

If you are interested in learning more about the work and characteristics of resistors, then you can try reading this article. We will address the difference between carbon film resistors and metal film resistors in this article.

 

 

 

2. Brief Intro to the Resistors

The word "resistor" is born from the word "resist," meaning to withstand the impact. A resistor resists the movement of electrons that move through it, guides it, or controls it. With the support of the conductive material that it is made of, this is achieved. Now, the name makes sense, does it not? In parallel and series, resistors are connected according to the specifications for current and voltage.

These small devices monitor, attenuate or decrease voltage and current, but do not have a power source of their own. The current flows through them in a controlled manner, resulting in a heat-like loss of energy. Only when there is a potential difference do two resistors bind and carry on a current between them. Yeah, they obey the Rule of Ohm. You must have heard, we're sure, of this statute. Oh, in the field of electronics and electrics, it is something to swear by.

Moving on, depending on their characteristics, there is an infinite list of various types of resistors including composition form, film type, and wire-wound type of resistors. Physical size, durability, temperature rating, noise, temperature coefficient, and voltage coefficient, to name a few of these features.

Well, the drill is known to you. We are here, however, to address two very significant types of resistors that are capable of transforming your electronic circuits.

 

3. Carbon Film Resistors

Let us first contemplate what film resistors are before we begin talking about this. Well, after depositing oxide film or pure metals on a substrate or some insulating ceramic, these are simply those resistors that are formed. The layer is extremely thin and sputtering is known as the entire process.

By depositing carbon film on the ceramic substrate that is an insulator, the carbon film resistor is prepared. The electric current is blocked by the carbon film to a certain degree. The insulating ceramic, on the other hand, does not allow heat to move through it, which in turn allows the carbon film resistor to withstand massive temperatures without being harmed. Carbon film resistors have a good tolerance rating, available from 1 ohm to 1 megaohm.

Speaking of the resistance coefficient of negative temperature - the property of observing a decrease in resistance in response to a rise in temperature, these have a high coefficient of negative temperature that makes them susceptible to decreasing resistance as the temperature increases.

 

These resistors are also available and have a very low tolerance at a low cost. They have a large variety of activities. Carbon film resistor applications are commonly used in X-Rays, power supplies and RADAR.

 

4. Metal Oxide Film Resistors

Metal oxide film resistors use thin metal oxide films to coat an insulating ceramic rod, in contrast to carbon film resistors. Informing a coating film, the compound made from oxygen atoms and other atoms performs wonders. Using tin oxide, however, metal oxide film resistors are made. To produce better resistance, antimony oxide is also added.

Because of the existence of an insulating ceramic rod that does not let heat pass through itself, these resistors are capable of withstanding high temperatures. Metal oxide resists the current at the same time. The greater the sum of antimony, the greater the resistance. But that doesn't even stop here, for good resistance metal oxide film resistors rely heavily on the thickness of the metal oxide and the width of the helical metal oxide film cut. The helical metal oxide film cut width and metal oxide thickness are inversely proportional to the resistance.

 

Wondering what makes them special? Resistors come at a very low cost and withstand high temperatures while making much less sound. Also, along with high reliability and stability, they are small in scale.

 

5. Carbon Film Resistor VS Metal Oxide Film Resistor

Well, engineers are still in a dilemma about which to use one. Whether to use the resistor for the carbon film or the resistor for the metal oxide film. All right, let us break it down, bit by bit, for you. You want your experiments, after all, to go spot on.

According to our contrast between Metal Film and Carbon Film Resistors, due to certain properties they possess that are listed below, we feel that metal-oxide film resistors prevail over carbon film resistors.

 

6. Voltage and Temperature Coefficient

There are a stronger voltage coefficient and temperature coefficient for Metal Oxide film resistors than for carbon film resistors. The coefficient of voltage is the change in resistance concerning the change in voltage. In short, it is the ratio of the resistance change to the voltage change. Metal oxide film resistors operate in a wide range of resistors and can withstand a higher temperature than the resistors of the carbon film.

Noise Design In contrast to carbon film resistors, metal oxide film resistors has a low noise design. They keep the minimum current. Therefore, it ensures less noise.

If you didn't know, metal oxide film resistors, relative to carbon film resistors, make up for stronger resistors for radio frequency or high-frequency applications. Tolerance The 2 percent minimum carbon film resistor tolerance level does not stand a chance against metal oxide film resistors that can go as low as 0.1 percent.

 

7. Size

Finally, compared to the carbon film resistors, the size of the metal oxide film resistors is smaller, making them a safer choice to go for. Now that we've done our bit to make you see the complexities of the resistors of both kinds, you can take your pick.

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