Advantages of a Tantalum Capacitor
Tantalum capacitors are known for their demanding applications in critical and implantable medical electronics, automotive, telecommunications and consumer devices. These capacitors are designed to withstand high pulse currents and can operate at elevated temperatures.
Unlike ceramic capacitors, tantalum capacitors can be used with a modest amount of reverse voltage for short periods. The polarity and markings on the capacitors help in easy identification of the lead/anode.
Low Leakage Current
The low leakage current of a tantalum capacitor makes it ideal for use in high-frequency circuits. This is due to their lower equivalent series resistance (ESR) than electrolytic capacitors, which can cause problems with filter circuits because of a mismatch between the ESR and the magnitude of AC ripple in the circuit.
The lower ESR of a tantalum capacitor also means that it can be used for DC or pulsing circuits that may need to be held at a constant voltage for an extended period of time. However, it is important to choose the correct size of tantalum chip capacitor to ensure that the circuit will not be overloaded and that the dielectric film will not be damaged.
Many of the common reasons for the failure of tantalum capacitors are caused by factors that tantalum capacitor are easily corrected during production, assembly and use. These include poor manufacturing techniques, such as direct soldering of the chip to the circuit board, or improper thermal handling of the products.
For example, if the capacitor is heated for too long or at too high a temperature, the conductivity of the oxide film can be reduced, which can result in a sudden breakdown under both thermal and electrical stress. This is why it is important to select a high-quality tantalum chip capacitor and ensure that it is properly handled during the manufacturing process.
High Capacity
Compared to other types of capacitors, the thin oxide layer in a tantalum capacitor allows for a high capacitance value per volume. This feature makes it a popular choice in electronic circuits that need to quickly pass surge currents at a high frequency.
This is why a tantalum capacitor is often utilized in power supplies and audio amplifiers. However, it’s important to choose a capacitor with the right specifications for these applications. For example, a capacitor with a large peak output current may burn out due to overheating. Another factor that affects the reliability of a tantalum capacitor is its ESR. ESR refers to the equivalent series resistance of a capacitor and it can vary widely between different products. A higher ESR means that more heat will be generated in the capacitor, which can lead to early failure.
Like other electrolytic capacitors, tantalum capacitors are polarized. This means that they can only be used with a DC supply that observes the correct terminal polarity. They are not designed to be exposed to reverse voltage for long periods of time, as doing so can cause them to explode. This is why they are often commutated or fused with current limiters to protect them from dangerous chemical reactions that produce smoke and flame.
High Temperature Capabilities
A tantalum capacitor is highly stable at high temperatures, making it a perfect choice for applications in which the Electronic component temperature will change frequently. It is also resistant to vibrations and shocks, ensuring that it will remain in good condition even under harsh environmental conditions.
The process of manufacturing a tantalum capacitor starts with powdering the material and compressing it around a metal wire, which will later become the negative lead. Then, the mixture is vacuum sintered at a high temperature, forming a pellet with a predictable mechanical strength and density. The vacuum also drives off impurities and produces a single, monolithic spatial lattice. This makes it possible to guarantee the quality of a tantalum capacitor, and allows for the creation of different models based on specific requirements.
During the sintering process, a dielectric layer is formed outside the tantalum particle surfaces by transforming some of the outside layer into Ta2O5. This thickness is directly proportional to the voltage proof of the capacitor. Therefore, it is important to maintain a safety margin in the oxide layer thickness to ensure reliable functionality.
Due to the crystalline structure of solid tantalum’s Ta2O5 dielectric oxide layer, it possesses unidirectional conductivity. When a reverse voltage is applied, it causes tiny hot-spots to appear in the dielectric surface. These microcracks or other defects produce a very high current density which can convert amorphous tantalum pentoxide to its more conductive crystalline form. This effect is referred to as heat failure.
Long Lifespan
Despite their relatively small size, tantalum capacitors have a long lifespan. They don’t dry out or change their capacitance over time, making them a popular replacement for aluminum electrolytic capacitors in military applications.
A tantalum capacitor’s lifespan is based on its ability to withstand its rated voltage, referred to as the rated operational voltage (UR). The UR is the maximum DC voltage that a tantalum capacitor can safely operate at.
When exposed to a high-frequency current, the amorphous tantalum pentoxide within the solid-state dielectric of a capacitor may convert some areas to a more crystalline state. These areas can then act as tiny hot-spots and cause a current to flow, creating a small thermal avalanche. This can cause the capacitor to fail by shorting its anode to its cathode, resulting in a very destructive failure mode known as “thermal runaway.”
Continuous improvements in powder and capacitor technologies have led to lower impurity levels in manufactured tantalum powder. This, in turn, leads to much lower avalanche resistance and the risk of field crystallization. As a result, commercially available tantalum capacitors have reached high reliability standards such as MIL-PRF-55365 at 85 degC and 0.5 UR, or equivalently in FIT at 0.01% per 1000 hours.
Tantalum capacitors are a key component in medical electronic devices, including implantable life-support equipment like pacemakers and defibrillators. AVX’s patented Q-Process and other advancements in manufacturing technology have led to a range of medical-grade tantalum capacitor products with lower DC leakage and higher volumetric efficiency, which help medical professionals optimize device performance and battery life.