Everything You Need To Know About Film Resistor

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Resistors are designed for one function: to resist the normal flow of current. There are different types of resistors and each has unique features and specifications. One type of resistor that you should know is the film resistor. What is it? How does it work? How different is it from other resistors and what are some of its application areas?

To answer such questions, we are going to get into the details of all you should know about film resistors.

What is a film resistor?

Film resistors are made of a thin layer of resistive material on a metal foil. The foil is coated with a thin layer of another material, like a polymer or a metal.

Resistors are made of different types of materials but film resistors are made of only one type of material. Even though there are different types of metals used in making film resistors, they all have the same resistance value.

The film resistor is designed to have a certain resistance value which depends on the type and thickness of the layer it is made from. The higher the voltage applied to the resistor, the more current it can withstand and this makes it suitable for use in high voltage circuits.

Construction of a film resistor

A film resistor comprises a metal film that is laid on an insulating substrate. Usually, the metal fil is laid on the substrate using the evaporation technique. The resistors are then formed by screen printing carbon paste on the substrate or by electroplating the resistive material on the substrate.

Current limiting resistors are made in two ways, either as a strip or as a chip. A strip is used in high voltage applications where the resistance value is fixed for a certain voltage. A chip resistor is used in low voltage applications where the resistance value can be varied depending on the voltage applied to it.

Resistors are manufactured by fabricating several layers of different materials on a substrate and then forming them into a single part. The first layer is usually an insulating film that protects the metal film from oxidation and is also used to give good adhesion between layers. The second layer is made of copper foil that acts as an electrical conductor and has high conductivity properties.

The third layer is called a dielectric which acts as an insulator that prevents current leakage between layers and also provides mechanical strength to the resistor. Finally, another thin layer of metal, such as silver or gold, is deposited onto it so that it can act as an electrical conductor thus making it conductive.

Structure of a film resistor

The film resistor has two terminals – one end which connects to the ground and another end which connects to the positive terminal of the power supply (usually 12 volts). It also has two leads – one lead connects to the positive terminal and the other lead connects to the negative terminal of the power supply (usually 12 volts).

It also has three wires – one wire connects from lead which connects to the negative terminal of the power supply (sometimes called ‘shield’) and the other two wires connect from other ends of the resistor.

How does a fil resistor work?

The film resistor actually consists of two different components: a metal foil and a resistive material (a thin layer). The metal foil acts as an electrode while the thin layer acts as an electrical conductor.

When an electric current passes through this layer, it creates heat and friction which increases its resistance value (the more current passes through, the higher temperature created). This is why you must keep your fingers away from such resistors to avoid burns or any other damage caused by heat generated from them. It also makes them unsuitable for use at high temperatures because heat generated by these resistors can affect their performance negatively.

These two components work together to create electrical resistance which depends on both temperature and voltage levels applied to them. The greater amount of current that passes through these layers means that they tend to get hot faster than normal resistors with less amount of current passing through them. This is why the heating effect of these resistors is more pronounced at high currents.

Types of Film Resistors

There are many types of film resistors, and each one has its specific purpose. Let’s take a look at some of the most popular types.

Carbon film resistor

As the name suggests, this is a carbon film resistor. It is made from carbon and has two different types of carbon in it. One is the standard type, while the other type has a higher resistance value. Carbon Film Resistors are often used in audio applications where low noise and high impedance are required.

Metal oxide film resistor

These resistors are made from metal oxides and have very high resistance. Metal Oxide Resistors are commonly used in power applications as they offer high power handling capability. They are also very reliable and do not suffer from the same problems that other types of film resistors do.

Metal film resistor

Metal film resistors are also known as metalized-film resistors. They are made of a thin layer of metal over a base material. Metal Film Resistors have a very high resistance value and have the same characteristics as carbon film resistors in most cases.

Planar film resistor

Planar film resistors are made of a laminate of different types of resistors. They have a higher resistance value than carbon or metal oxide film resistors. They are usually used in power applications where high power handling capability is required.

Thick film resistor

Thick Film Resistors (TFR) are made of a very thick film of metal oxide and are used in high power applications. These resistors have higher power handling capability than carbon film resistors and have some of the same properties as metal oxide film resistors.

Mixed type

A mixed type is usually formed from an alloy of two types of resistor, where one type has higher resistance than the other. Mixed types can be used for specific applications, for example if you need to match the value of two different types together for a specific application. Mixed types can be formed by combining two types together, or by adding one type to another type in an existing mixed type design.

Specifications for the film resistors

Before you buy a film resistor, you should check out its technical specifications which include:

Resistance value

The resistance value of a film resistor is measured in ohms. The lower the resistance value, the higher the power handling capability.

Temperature Coefficient or Power Factor

This specification measures how much a film resistor changes in resistance value when it is subjected to a change in temperature. Film resistors are usually rated on the basis of their temperature coefficient or power factor. A low-temperature coefficient or power factor means that your power supply will not need to be as powerful as it would otherwise need to be, so you can save money by having a smaller power supply.

Power Dissipation (power rating)

This specification measures how much heat that is generated by an electrical component can be dissipated by air and other components within a circuit when the component is operating at its maximum rated current for its specified voltage and frequency. This specification allows you to calculate how much heat is generated by your circuit and how much heat must be dissipated from the components within your circuit in order for them to operate at their maximum ratings.

Load life

The load life of a film resistor is the amount of time that it can be safely used before it will cause damage to a circuit due to excessive current, temperature or voltage. Some film resistors are rated for 1000 hour, while others can withstand 5000 hours or longer.

Maximum noise

Noise is a measure of the random electromagnetic interference that can be introduced into a circuit. The noise generated by a resistor is different than that generated by other components. It is important to know the maximum noise level of your resistors so that they will not affect the performance of your circuit.

Dielectric strength

A dielectric strength rating is an indication of the internal electrical resistance of a film resistor and how much electrical noise it can tolerate before its internal resistance exceeds its ability to dissipate heat, which is what we are looking for in this specification. The higher the dielectric strength rating, the better.

Power rating

Metal film resistor power rating defines the maximum amount of power that a resistor can safely handle at any given time before it gets damaged. A resistor with a higher power rating can tolerate more heat before it fails.

How do I calculate the size of a film resistor?

The formula requires the value of the resistor, the power rating, and the voltage. Using these data and a calculator, you will be able to calculate the size of your resistor.

A good rule of thumb is to use a 1% tolerance for all resistors with a power rating higher than 30W.

Film resistor color code

Film resistors are marked with a color code to help engineers quickly identify the type of resistor. The color code is typically written on a tag or sticker and is an important part of troubleshooting. Most film resistors have three color bands. The first band indicates the resistance value. The second band indicates the power rating (in watts, for example). The third band indicates the voltage rating (in volts, for example).

Advantages of Film Resistor

If we talk about the advantages of film resistors, then here are some of the most important ones.

– Stability: The stability of film resistors is very high, and they are very accurate. Generally, the tolerance of a film resistor is less than 1%, but this may vary from one manufacturer to another.

– Cost: The cost of film resistors is lower than the cost of wirewound resistors. They are cheaper because they do not need to be woven with a metal.

– Size: In terms of size, they are smaller than wirewound resistors. – Power Rating: They have a very high power rating and can handle very high voltages.

– Operating Temp: They have a high operating temperature, and you can use them in extreme conditions.

– Noise: They are very low in noise, and you can use them in sensitive electronics. – Resistance Tolerance: The resistance tolerance of a film resistor is higher than the tolerance of a wirewound resistor.

How to choose a film resistor?

Choosing the right film resistor can be tricky. You have to consider many factors such as size, power rating, temperature rating, and tolerance. Generally, when choosing film resistors, you have to choose between carbon film and metal oxide film resistors.

Carbon film resistors are lower cost, but they don’t have as high a voltage rating. Metal oxide resistors are more expensive, but they have a higher voltage rating. It is important to remember that the tolerance of a carbon film resistor is usually better than a metal oxide resistor.

If you are choosing a film resistor to be used in a circuit where the current flow is different in different sections, then a carbon film resistor is the best option.

If you are choosing a film resistor to be used in a circuit where there is uniform current flow in all directions, then a metal oxide resistor is the best option.

Applications Of Film Resistors

It is used to reduce the voltage in a circuit. Also, it is used to control the flow of electric current in a circuit by reducing the voltage in a circuit.

– Home Appliances: In appliances such as refrigerators, washing machines, and microwave ovens, film resistors are used in circuit boards as power resistors to provide heat and control the current flow.

– Automobiles: In automobiles, they are used as high-voltage resistors and voltage-sensitive resistors.

– Industrial Circuits: They are used in control circuits and are mostly controlled by temperature.

– Medical Equipment: In medical equipment such as electrocardiograms, electromyograms, and electroencephalograms, are used as voltage dividers.

Buy film resistors in China

I hope that with this guide, you are now able to choose the right type of film resistor for your circuit. If you have any questions, please feel free to ask us. ICRFQ is a reliable sourcing agent for electronic components in China.