Capacitors made of tantalum are metals that are subtypes of electrolytic capacitors. It is surrounded by a conductive cathode, covered with oxide layers acting as dielectric, and the metal itself works as an anode. The thin dielectric layer consists of tantalum metal. Read more about the capacitors when you click this link.
The results are superior frequency, higher capacity of value per volume, and more. They have excellent stability when you compare them to other types, and they are polarized. This means that they can only connect to a direct current supply that observes the correct terminal polarities during the connection.
However, there is a downside to using these capacitors. There may be very little chance of failure, resulting in small explosions, fire, and thermal runaway. Fortunately, these instances can be prevented by using failsafe devices like thermal fuses or current limiters.
Today’s technology allows the capacitors to use various circuits often found in the automotive, laptop, and cell phone industries. Most of them are in the form of surface-mounted devices. These surface mount capacitors can claim less space in a circuit board, and the density of the entire device is more.
General Characteristics to Know About
These are the ones made with capacitance values that range from 1nF to 72mF. They come in smaller sizes compared to the aluminum variety with the same capacity. Voltages may range from 2V to over 500V.
The equivalent series resistance is much smaller than its aluminum counterpart. As a result, they can allow larger currents to pass through them without generating too much heat.
Tantalum metals are very stable, and their capacity usually does not change while they age, which is better, especially when you compare them with aluminum. Learn more about this metal at this link: https://www.britannica.com/science/tantalum. This makes them more reliable electrolytic capacitors, and the shelf life is unlimited when there’s proper maintenance.
Information with Polarity
These electrolytic capacitors are very polarized devices. While aluminum is considered polarized, it cannot usually survive, especially when there’s a brief application from a reverse voltage. They can be sensitive when it comes to processes like reverse polarization.
When applying a reverse voltage, there is a high chance that the dielectric will break. This will form short circuits, and they can result in thermal runaway. The tantalum varieties usually used the marked positive terminals in the system, while the aluminum ones had negative marks on their casings.
About the Failure Mode
Tantalum metals can potentially become dangerous when they are in failure modes. There are cases where the voltage spikes and the anode will come in contact with the cathode of manganese dioxide. This is when the energy spike is sufficient to result in a chemical reaction.
The chemical reactions produce high heat and are self-sufficient for more extended periods to cause a fire. They may produce flame and smoke when left alone. You may want to prevent this from happening by installing external failsafe circuitries like thermal fuses and current limiters.
Properties and Construction of the Capacitor
The tantalum electrolytic capacitor, similar to others, consists of anodes that have cathodes and electrolytes. Anodes are often isolated from their cathode with minimal leakage and DC that may be flowing through the capacitors. Anodes are made with pure metals.
The ground metal is made into fine powders, and they are forged into small pellets at very high temperatures. This will result in a more porous anode with a high surface area that translates directly into increased capacitance value.
Anodes are then covered with layers of insulating oxide, which will act as the dielectric. The process is also known as anodization, and this is where most manufacturers carefully control the steps so that the resulting capacitance will be just right and reduce tolerances.
Electrolytes are added to the anodes with a method called pyrolysis when it comes to the solid varieties of tantalum. The capacitors are dipped in a chemical solution and baked into the oven to produce manganese oxide.
This process is repeated until the pellet develops a thick coating on its external and internal sides. The pellets that are part of the tantalum capacitors are then dipped into silver and graphite, providing an excellent cathode connection. This is in contrast with the wet varieties that use liquid electrolytes. After the anode is forged and the dielectric layer is thick enough, the entire pellet is dipped into electrolytes contained in an enclosure. The electrolytes are going to act as cathodes into the wet tantalum capacitor.
Applications
Applications usually take advantage of the low leakage of current, reliability, long-term stability, and high capacity. For example, these things are often used to hold circuits and samples that rely on the low leakage of current. This will achieve an overall long-term duration, and these are usually used for power supply filtering on cell phones and computer motherboards.
It can have military value in some cases because it can often have tighter tolerance within a higher operating temperature range. These are better alternatives to aluminum electrolytes in the military because they do not change capacitance and rarely dry out for extended periods. Many medical electronics companies may also rely on tantalum because of its relatively high stability. Sometimes, they are used in audio amplifiers because stability is one of its most essential features.
There are tantalum chip capacitors that will provide an SMD style that is very ideal for surface mounts. Other options with styles include the pears that have single-ended and resin-dipped PCB mounting, and the axial lead with their non-solid electrolytes.