What is a tantalum electrolytic capacitor and what is its function

Solid tantalum capacitors were first successfully developed by Belle Laboratory in the United States in 1956. They have excellent performance and are the smallest of all capacitors with the largest capacitance. Tantalum capacitors have a variety of shapes and are easy to make into small and chip components suitable for surface mounting. They meet the needs of the current automation and miniaturization of electronic technology. Although tantalum raw materials are scarce and tantalum capacitors are expensive, tantalum electrolytic capacitors have developed rapidly and are increasingly widely used due to the large-scale use of high-specific capacitance tantalum powder (30KuF.g-100KuF.V/g) and the improvement and perfection of capacitor manufacturing technology. Tantalum capacitors are not only widely used in military communications, aerospace and other fields, but also in industrial control, film and television equipment, communication instruments and other products. The tantalum
electrolytic capacitors currently produced mainly include sintered solid, foil-shaped winding solid, and sintered liquid. Among them, sintered solid accounts for more than 95% of the current total production, and non-metallic sealed resin encapsulation is the main type. With the miniaturization and chip-type technology in the ascendant, chip-type sintered tantalum capacitors have gradually become the mainstream.
Solid tantalum capacitors have excellent electrical properties, a wide operating temperature range, and a variety of forms. They have excellent volume efficiency and unique characteristics:
the working medium of tantalum electrolytic capacitors is a very thin tantalum pentoxide film generated on the surface of tantalum metal.
This oxide film medium is completely combined with one end of the capacitor to form a whole and cannot exist alone. Therefore, the capacitance per unit volume is particularly large. That is, the specific capacitance is very high, so it is particularly suitable for miniaturization.
During the working process of tantalum electrolytic capacitors, it has the performance of automatically repairing or isolating the defects in the oxide film, so that the oxide film medium can be reinforced and restored to its proper insulation capacity at any time without suffering continuous cumulative damage. This unique self-healing performance ensures its advantages of long life and reliability.
Tantalum electrolytic capacitors have very high working electric field strength, which is larger than any other type of capacitor, thereby ensuring its miniaturization.
Tantalum electrolytic capacitors can easily obtain large capacitance, and there are few competitors in power supply filtering, AC bypass and other uses.
It has unidirectional conductivity, that is, it has "polarity". When used, the current should be connected in the positive and negative directions of the power supply. The anode (positive pole) of the capacitor is connected to the "+" pole of the power supply, and the cathode (negative pole) is connected to the "-" pole of the power supply. If it is connected incorrectly, not only will the capacitor not work, but the leakage current will be very large, and the core will heat up in a short time, destroying the oxide film and then failing.
The working voltage has a certain upper limit, but this disadvantage is not important for matching transistors or integrated circuit power supplies.
Electrolytic capacitors are generally considered to be an electronic component with excellent performance and long service life. Its failure rate can reach level seven under normal circumstances. But it always conforms to the general law of failure of electronic components, that is, the bathtub-shaped failure curve, and the early failure can be eliminated during the aging process. Therefore, there is only the possibility of random failure. This kind of ineffectiveness is caused by manufacturing process control problems, and is often accompanied by improper or overloaded products during use. Generally speaking, there are about three modes, namely current type, voltage type and heating type.
Tantalum electrolytic capacitors have the properties of storing electricity, charging and discharging, etc. They are mainly used in filtering, energy storage and conversion, sign bypass, coupling and decoupling, and as time constant elements. In the application, attention should be paid to its performance characteristics. Correct use will help to give full play to its functions, such as considering the working environment and heating temperature of the product, and taking measures such as derating. Improper use will affect the working life of the product.
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Tantalum electrolytic capacitors are a type of electrolytic capacitors. They are widely used in communications, aerospace and military industries, submarine cables and advanced electronic devices, civil appliances, televisions and other aspects. Tantalum electrolytic
capacitors are made of metal tantalum (Ta) as anode material. According to the different anode structures, they can be divided into foil type and tantalum sintered powder type. In tantalum powder sintered tantalum capacitors, they are divided into solid electrolyte tantalum capacitors and non-solid electrolyte tantalum capacitors due to different working electrolytes. Among them, solid tantalum electrolytic capacitors are used in large quantities, such as CA type, CA42 type, etc.
There is a CA mark on the shell of tantalum electrolytic capacitors, but the symbol in the circuit is the same as that of other electrolytic capacitors. The most common tantalum capacitor structure is shown in the figure above.

Compared with aluminum electrolytic capacitors, tantalum electrolytic capacitors have the following advantages:
1. Small volume. Since tantalum capacitors use very fine tantalum powder, and the dielectric constant ε of tantalum oxide film is 17 higher than that of aluminum oxide film, the capacitance per unit volume of tantalum capacitors is large.
2. Wide range of humidity. Generally, tantalum electrolytic capacitors can work normally at temperatures of -50℃~100℃. Although aluminum electrolytic capacitors can also work in this range, their electrical performance is far inferior to tantalum electrolytic capacitors.
3. Long life, high insulation resistance, and small leakage current. The tantalum oxide film medium in tantalum electrolytic capacitors is not only corrosion-resistant, but also can maintain good performance for a long time.
4. Good impedance frequency characteristics. For capacitors with poor frequency characteristics, when the operating frequency is high, the capacitance will drop significantly, and the loss (tgδ) will also rise sharply. However, solid electrolytic capacitors can work above 50kHz. As the frequency increases, the capacitance of tantalum capacitors will also decrease, but the decrease is small. Some data show that when working at 10kHz, the capacitance of tantalum capacitors decreases by less than 20%, while the capacitance of aluminum electrolytic capacitors decreases by 40%.
5. High reliability The chemical properties of tantalum oxide film are stable. Because the tantalum anode substrate Ta2O5 is resistant to strong acids and alkalis, it can use solid or acid-containing liquid electrolytes with very low resistivity. This makes the loss of tantalum electrolytic capacitors smaller than that of aluminum electrolytic capacitors, and has good temperature stability.