What are Solid Tantalum Capacitors?

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Editorial Team - everything PE

Sep 7, 2022

Solid tantalum capacitors are a subclass of electrolytic capacitors that uses a tantalum anode, tantalum oxide dielectric, and a conductive cathode as the fundamental three-layer capacitor structure (conductor-dielectric-conductor).

Solid tantalum capacitors are more stable than aluminum capacitors, which means that they can retain their characteristics under various operating conditions, including thermal stress. They are ideal for heavy industrial, medical, military, and aerospace applications.

Construction of Solid Tantalum Capacitors

The anode of a conventional solid tantalum capacitor is made of tantalum powder that has been compressed and sintered into a pellet. The dielectric is tantalum pentoxide oxide, and the cathode is a solid manganese dioxide electrolyte.

Tantalum capacitors are constructed from a powder extracted from elemental tantalum metal. To create a "pellet," the powder is squeezed around a tantalum wire known as the riser wire. In the end, the riser wire is the capacitor's anode connection.

After that, the pellet/wire combination is vacuum sintered at a high temperature (usually 1200–1800 °C), creating a mechanically robust pellet and expelling any impurities from the powder. The powder develops a sponge-like structure during sintering, with every particle joined together into a single, monolithic spatial lattice. Although this structure is very porous and has predictable mechanical strength and density, it also has a substantial internal surface area.

The electrochemical process of anodization is then used to create the dielectric on all tantalum particle surfaces.

Applications of Solid Tantalum Capacitors

Solid tantalum devices are frequently used to support voltage rails during peak current demand and are well-suited for bulk energy storage due to their high and stable capacitance values. Here, two elements must be taken into account. The first is the overall capacitance needed to provide the needed energy for the required amount of time. A single tantalum capacitor may be sufficient in some circumstances. Still, in more demanding applications, several capacitors may be set up in parallel so that their capacitance values add up and the array's total resistance is decreased. The ESR of the capacitors is the second factor. Higher deliverable current levels and less voltage drop during discharge are produced by lower ESR, which enhances circuit performance. Reduced heat generation during charge/discharge cycles is another benefit of using low-ESR tantalum components as bulk energy capacitors. This lowers the operating temperature of the circuit and increases circuit power efficiency. To further reduce costs, it might also make it possible to use smaller power supplies.

When smoothing a signal with low-ESR solid tantalum capacitors, such as output filter capacitors in switch-mode power supplies, the ripple current that appears on the DC bus is reduced. To achieve this, higher charge/discharge currents are permitted, allowing them to more closely follow the voltage cycles and provide energy during any peaks and valleys in the waveform. On each charge/discharge cycle, less heat is dissipated as the ripple current (peak to peak) is decreased. Additionally, ripple filter capacitors can be used successfully in circuits with higher-frequency AC noise components thanks to capacitors with lower ESR (and inductance).