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Do You Need A Tantalum Capacitor?

Capacitors are among the most common parts on a circuit board; you can find them in just about every power circuit and every microchip. In systems, they’re commonly used for filtering out unwanted frequencies, bypassing to lower the impact of the inductance of conductors, cleaning up DC power into a chip, and decoupling AC signals.

Since systems have become smaller, capacitors have been quite limiting since a specific size was required to get the capacitance needed. However, that changed with the introduction and application of tantalum capacitors.

Tantalum Capacitors Explained

Tantalum capacitors are generally a subtype of electrolytic capacitors. The anode is the tantalum metal used to make them, surrounded by a layer of oxide that acts as the dielectric, covered by a conductive cathode. Due to the application of tantalum, it allows a thin dielectric layer.

As a result, they have superior frequency characteristics, a greater capacitance value per volume, and outstanding stability over time compared to many other types of capacitors. In general, tantalum capacitors are polarized. That means that they might only be connected to a DC supply by ensuring the correct terminal polarity.

The con to using tantalum capacitors is their undesirable failure mode. Although this might result in small explosions, fires, and thermal runaway, this can be avoided by applying external failsafe devices such as thermal fuses and current limiters.

Due to the advancement in technology, tantalum capacitors can now be used in a wide range of circuits, mostly found in cell phones, automotive industry, laptops, and others, usually in the form of SMD (surface mounted devices). With these surface mount tantalum capacitors, they allow for higher packing densities and take significantly less space on a printed circuit board.

What Are the Features of Tantalum Capacitors?

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General Features

Typically, tantalum capacitors are designed with capacitance values varying from 1nF all through to 72mF. What’s more, they are significantly smaller in size compared to aluminum electrolytic capacitors with similar capacitance. With these tantalum capacitors, the voltage ranges from 2V to above 500V.

They consist of equivalent series resistance (ESR) about ten times smaller than the aluminum electrolytic capacitors’ ESR. As a result, it allows for significantly larger currents to pass via the capacitor with less heat produced. Tantalum capacitors are much stable over time, and they don’t have a drastic change in their capacitance with age, especially compared to aluminum electrolytic capacitors. Furthermore, they are much reliable when handled appropriately, and their shelf life is virtually limitless.

Polarity

As aforementioned, tantalum capacitors are basically polarized devices. Even though aluminum electrolytic capacitors, which are also polarized, may survive a shortly applied reverse voltage, these tantalum capacitors are much sensitive to reverse polarization. In case you apply a reverse polarity voltage, the dielectric oxide will break down, sometimes creating a short circuit. In the long run, this short circuit might lead to thermal runaway and damage to the capacitor.

You should know that tantalum capacitors often have their positive terminal marked, as opposed to aluminum electrolytic capacitors. The latter often have their negative terminal labeled on the casing.

Direct Components Inc has helped people out of pinches before, they might be able to help you!
Direct Components Inc has helped people out of pinches before, they might be able to help you!

Polarity

As aforementioned, tantalum capacitors are basically polarized devices. Even though aluminum electrolytic capacitors, which are also polarized, may survive a shortly applied reverse voltage, these tantalum capacitors are much sensitive to reverse polarization. In case you apply a reverse polarity voltage, the dielectric oxide will break down, sometimes creating a short circuit. In the long run, this short circuit might lead to thermal runaway and damage to the capacitor.

You should know that tantalum capacitors often have their positive terminal marked, as opposed to aluminum electrolytic capacitors. The latter often have their negative terminal labeled on the casing.

Direct Components uses only High Quality parts and products so you won't have to question whether it will work or not

Failure Mode

As mentioned earlier, tantalum capacitors have a possibly risky failure mode. If there are some voltage increases, the tantalum anode might come in touch with the manganese dioxide cathode, and in case the spike energy is sufficient, it might start a chemical reaction. Since this chemical reaction generates heat and is self-sustaining, it might also produce smoke and flame. When it comes to preventing this thermal runaway from occurring, external failsafe circuitry such as thermal fuses and current limiters should be used with tantalum capacitors. For voltages, the general rule is to derate a tantalum capacitor with a manganese oxide electrolyte by 50% and a polymer electrolyte by around 20%.

More About the Design and Properties of Tantalum Capacitors

Like other electrolytic capacitors, tantalum electrolytic capacitors are made up of an anode, a cathode, and some electrolyte. The anode if often isolated from the cathode so that only a minimal leakage DC current might flow via the capacitor. Furthermore, the anode consists of pure tantalum metal. At extremely high temperatures, the metal is ground into a very fine powder, and then sintered into a pellet. This creates a very porous anode that has a high surface area. The high surface area directly leads to an increased capacitance value.

For the anode, it is surrounded by a layer of insulating oxide that often acts as a dielectric. The entire process is known as anodization. The step should be properly controlled to minimize tolerances and ensure precise capacitance values since the extent of oxide growth plays a vital role in the dielectric thickness.

In the case of solid tantalum capacitors, the pyrolysis process is used to add electrolyte to the anode. Solid tantalum capacitors are later dipped into a specific solution and baked in an oven to create a manganese dioxide coat. Typically, to make sure that a thick coating is present on every internal and external surface of the pellet, the process is repeated.

Lastly, the pellet applied in solid tantalum capacitors is dipped into silver and graphite to ensure a good cathode connection. Wet tantalum capacitors utilize a liquid electrolyte, as opposed to solid tantalum capacitors. After the sintering of anode and dielectric is grown, it’s dipped into a liquid electrolyte in an enclosure. Both the electrolyte and the enclosure serve as the cathode when it comes to wet tantalum capacitors.

What Are the Applications of Tantalum Capacitors?

Most applications utilizing tantalum capacitors see the advantage of their reliability, long term stability, high capacity, and low leakage current. For instance, they are applied in the sample and hold circuits that depend on relatively low leakage current to obtain long hold duration. They are popularly used for power supply filtering on cell phones and computer motherboards because of their long term stability and small size, usually in the surface-mount form.

What’s more, you can find tantalum capacitors in military specifications versions, which provide a wider operating temperature range and tighter tolerances. Since they do not seem to change capacitance and dry out over time, they are a common replacement for aluminum electrolytes when it comes to military applications. What’s more, medical electronics also depend on tantalum due to their high stability. At times, audio amplifiers apply tantalum capacitors because stability is an essential factor.

When Can You Use a Tantalum Capacitor?

You might be wondering, “when should you consider using a tantalum capacitor?” In case you require maximum capacitance in a relatively small space such as decoupling next to a microchip. Perhaps when you need exceptional stability over a range of voltages or temperatures. As of now, you are aware of their excellent properties; they can be designed correctly and not risk your particular system with a fiery failure.

Why Should You Get a Quote from Direct Components?

At Direct Components, Inc., we have an extensive range of obsolete, allocated, challenging to find electronic parts. In case we do not have the parts you want in stock, our skilled purchasing agents will take advantage of our global worldwide network of trusted sources and get the parts you want at the best possible price.

In general, we can get all sorts of Active and Passive board level components. However, we specialize in Integrated Circuits, Capacitors (including tantalum capacitors), Semiconductors, Transistors, Memory Microprocessors, Connectors, Diodes, Relays, Resistors, and LEDs. What’s more, we work with all the leading manufacturers such as Altera, Analog Device, Linear Tech, Dallas/ MAXIM, Samsung, Intel, Fairchild, Cypress, Infineon, Hitachi, Motorola/On Semi/Freescale, Vishay, TI, National, and Xilinx.

You can check out our full list at https://www.directics.com/products/. Request for your quote today!

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