Ceramic Multilayer Capacitors Overview

Ceramic Multilayer Capacitors Overview

At the fundamental level, a ceramic multilayer capacitor is the same as other types of capacitors. It is a passive electronic component. It consists of two leads and a dielectric. The materials of which ceramic multilayer capacitors and the way that they function, however, give them some advantageous properties, particularly when high capacitance values are called for in small components.

Ceramic multilayer capacitors are used extensively by cellular phone manufacturers and, in fact, their demand for efficient, cost-effective capacitors has done a great deal to promote the heavily usage of these components.

Ceramic multilayer capacitors are manufactured using a very complex process. The end result is a very efficient device that solves many of the issues—including ones as divergent as accuracy and overall cost—that technology manufacturers face.

 

Electrical Characteristics

The electrical characteristics of ceramic multilayer capacitors vary depending upon the materials used in their manufacture. Paraelectric substances are used in the manufacture of some of these devices. In cases where those substances are used, the resulting capacitor has excellent properties in terms of stability. The capacitance value within the specified temperature range of the device will behave in a linear fashion. The drawback with this material is that it is mostly restricted to capacitors with a low capacitance value.

Ferroelectric materials and oxides can be combined to create multilayer ceramic capacitors with higher capacitance values. The tradeoff is that the materials do not have the linear behavior that the paraelectric materials can offer over a specified temperature range.

There are different definitions applied to these capacitors that describe their application class. The International Electrotechnical Commission and the Electronic Industries Alliance have different definitions. Both are widely used, though the EIA is no longer operational, and the IEC definitions are given here.

Class 1 ceramic capacitors are used in resonant circuits. They have a high degree of stability and low loss.

Class 2 ceramic capacitors are used for coupling, decoupling, bypass and smoothing applications. They are notable for their high volumetric efficiency.

Class 3 ceramic capacitors are not a standardized class at this time, but the former class included barrier layer capacitors.

For stable voltages along with stable frequencies, Class 1 capacitors are excellent choices. They are known for their very low loss rates and are commonly used in resonant circuits, oscillators and high Q filters. The temperature characteristics of these capacitors are dictated by the materials used in their manufacture. Because the temperature coefficient is an important feature of these capacitors, a two-digit code is used to indicate it on the device. The ceramic name also provides a way to get this information at a glance.

While Class 2 capacitors aren’t as accurate or as stable as Class 1 capacitors, they do have excellent volumetric efficiency. This flows from the materials of which they are made, which have a high permittivity.

Class 2 capacitors have a nonlinear capacitance value, which can alter depending upon the temperature of the device and the amount of voltage applied to the device. The capacitors are labeled in a way that indicates how much their capacitance levels vary over their operating temperature range. The labels make use of a letter and number code, with letters indicating the low temperature and a number indicating the high temperature. The third character indicates how much the capacitance levels of the component will vary over the specified temperature range.

Ceramic multilayer capacitors are available in several different designs, which makes them suitable for being included in a variety of different applications.

 

Multilayer Ceramic Capacitor Designs

Multilayer ceramic capacitors come in different configurations. One of the most popular is the rectangular block design, which is ideally suited for compact applications. These are available from most major manufacturers, including names like Murata, RS and many others.

There are many other designs, however, including the familiar disc designs with two leads protruding from the body. Feed through capacitors have their leads protruding from either end of the component, offering a different configuration option.

 

How They’re Made

Manufacturing multilayer ceramic capacitors is a complex process involving precise engineering and quality control. The ferroelectric or paraelectric materials that make up the capacitor are mixed into a slurry and are modified with the addition of specific additives.

This material is made into a foil which is made into sheets and then into rolls, each of which is marked for quality control purposes. These rolls are then put through a printing process and made into sheets. Those sheets will become the electrodes for the capacitor.

The sheets are layered together to provide the desired capacitance. They are compacted down and, though a pressing process, made more solid. The electrodes are incorporated into the capacitors and then the entire sheet is cut into individual capacitors.

Being ceramic, the components have to be fired. There are different firing processed used, including ones that add terminals to the component.

After the capacitor is finished, it is put through rigorous testing to ensure that it has the desired capacitance value. Each batch of capacitors is labeled to ensure that, if there is a problem, it can be traced back to the original batch and manufacturing facility.

 

Applications for Multilayer Ceramic Capacitors

Multilayer ceramic capacitors are among the most common electrical components in the world and are indispensable for the manufacture of some devices. They are produced in quantities that amount to hundreds of billions of the devices every year.

The very small size of these capacitors make them ideal solutions for compact electronics applications. They also have advantages over other types of capacitors—see below—that make them more suitable for a multitude of different purposes. Their precision, however, is among the qualities that make them very useful for specific usages.

While their compact designs have made them popular, they do come in much larger designs. In those designs, they can handle a great deal of voltage, up to the 100kV range. They can also handle very high currents, which make them perfect for very demanding applications.

In those smaller sizes, however, the voltage and amperage handling might not be as large, but the devices can be fit onto printed circuit boards in great numbers. The layering process allows these devices to be created in enormously compact designs. These capacitors come in dimensions as small 0.6 x 0.3 x 0.33mm and smaller, which is excellent in terms of being able to fit a number of devices into a very small area. Some of these devices are literally not much larger than a grain of sand.

These devices continue to be miniaturized, as well. To miniaturize these components, manufacturers increase the number of layers in the components which, of course, requires that each of those layers is made thinner.

Capacitance values can be increased by using a thinner dielectric material, as was stated, or by increasing the size of the electrodes.

The classes of capacitors, described above, largely dictate what they’re used for. The Class 2 capacitors, for instance, are used in applications where high voltages are present. They’re used in applications as simple as circuit breakers and as complex as power supplies for very precise scientific equipment.

Class 2 capacitors have a tendency to exhibit what is called microphone. This is a phenomenon where the ceramics in the device start causing squealing in audio applications. Class 1 multilayer ceramic capacitors do not have this effect and are frequently employed in more sensitive audio applications because of this.

Capacitors are such basic electronic components that they are used in to many different applications to list, but they are found in just about every electronic device fulfilling various roles. Multilayer ceramic capacitors have some advantages that make them much safer and more reliable than other designs.

 

Advantages of Multilayer Ceramic Capacitors

Taking a look at other types of capacitors on the market, it’s easy enough to see why multilayer ceramic capacitors are so ideal for specific applications.

Polycarbonate capacitors have many of the same properties as multilayer ceramic capacitors and are used in very precise applications. They are, however, also very expensive, which makes them less desirable in that regard.

Mylar capacitors are very commonly used in audio applications, but they have voltage limitations that aren’t issues with multilayer ceramic capacitors.

Ceramic capacitors are not among the varieties that are polarized. This is an important feature, as it means that there is no risk in installing them related to doing so with the opposite polarity.

This is no small thing. Multilayer ceramic capacitors have largely replaced vastly more expensive tantalum capacitors in many applications. Those tantalum capacitors can actually explode if they are installed with the wrong polarity, which can cause injuries, in some unlikely circumstances, but which is almost certain to damage other components under any circumstances.

Multilayer ceramic capacitors also have no electrolyte liquid in them, which means that there are no leakage problems with the devices.

The consistent performance at varied temperatures also makes these capacitors very valuable for some applications. They are also more resistant to shock and vibration than electrolytic capacitors and do not need to be clamped to prevent damage from either as electrolytic typically are. However, they can be damaged by mechanical stresses if they are placed on a PCB where there is a great deal of vibration or shock and this has to be taken into account. The PCB transmits this force directly to the components affixed to it and, thus, a multilayer ceramic capacitor can be cracked or otherwise damaged if it is insufficient protected against stress.

Manufacturers have come up with designs that are intended to reduce the risk of a capacitor becoming damaged due to mechanical stresses. These designs reduce the risk of a short circuit or other issues should the component be subjected to stresses that it cannot handle and, thus, be damaged.

 

Safety Advantages

Ceramic multilayer capacitors aren’t flammable and that makes them idea for some uses. These are used as devices that provide radio frequency interference suppression and electromagnetic interference filters on AC lines because of this.

The resistance of these devices increases with the frequency applied to them, which gives them the properties required to provide noise suppression.

 

Variations

Ceramic capacitors used for high voltage applications are manufactured in a very similar process to their smaller cousins, but are usually regarded as belonging to a different class of capacitors. Their usages have more to do with preventing equipment from being damaged and with preventing people working on that equipment from being harmed, as well. These capacitors can be manufactured in many different designs, owing to the fact that the ceramic itself is very flexible in how it can be molded.

The highest power ceramic capacitors are very large compared to the ones that are found on circuit boards. They do not, however, have some of the disadvantages of other large types of capacitors, such as electrolytic, as detailed above.

Multilayer ceramic capacitors come in standardized sizes that make them easy to integrate into products. Many of the devices do not have their height listed. The height of the component is dependent upon how many layers it has in it and, thus, its capacitance value.

 

Getting Capacitors for Industrial Usage

Multilayer ceramic capacitors are among the most affordable of electronic components and among the most widely used. They’re available from large suppliers who stock them in many different variations. The standardization makes it easy to figure out which capacitor is suited for a given job.

Possibly the most impressive property of multilayer ceramic capacitors is their very low cost, particular given how reliable they are. Tantalum capacitors are used less and less because of this. Tantalum is a difficult-to-obtain material and that drives up the cost considerably. Conversely, ceramic is a very inexpensive material and, with the right treatments and manufacturing processes, it can be used for very demanding applications and provide excellent performance.

These capacitors are so inexpensive that they are generally sold in large quantities and it’s easily affordable to have many of them available for electronics work.

 

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