Selection and application of tantalum capacitor and aluminum electrolytic capacitor

Electrolytic capacitor is a short plate of the life of many electronic equipment. Power circuit cannot be separated from the use of a variety of capacitors for filtering, energy storage, bypass, etc., understand the failure mode of electrolytic capacitor, according to the application of appropriate parameters of electrolytic capacitor, is one of the essential skills to ensure the stability and reliability of power supply.

1. Application selection of tantalum capacitor

1. The excellent characteristics of tantalum capacitors may be irresistible to you

Tantalum capacitors have wide operating temperature range, stable temperature characteristics, large specific capacity and unique self-healing property, which can meet the long-term working stability.

2, tantalum capacitors inherent fatal weakness, so that you hate iron into steel

The key component of common tantalum capacitors is TA205. The stress of this medium will be unstable when heated, the voltage is kept down reliably, the ability to withstand surge voltage and surge current is poor, and the failure mode is short circuit, which is easy to cause high temperature, fire and other damages.

3. Key to reliable application of tantalum capacitors

For mno_tantalum capacitor, voltage reduction is carried out. The working voltage of mno_tantalum capacitor decreases with the increase of temperature. When the temperature is higher than 85 degrees, the recommended operating voltage is 33% of the rated voltage, and the failure risk can be greatly reduced.

Ii. Application selection of conventional aluminum electrolytic capacitors

1. Advantages and disadvantages of aluminum electrolytic capacitor:

Advantages: easy to obtain large capacity, high voltage resistance, low price and other significant advantages, commonly used in the power supply of the input and output filter circuit.

Disadvantages: afraid of high temperature, because the electrolyte of aluminum electrolytic capacitor is liquid, the core heat or high ambient temperature will lead to the evaporation of electrolyte, long-term high temperature will lead to the drying of electrolyte failure.

2. Matters needing attention in the application of aluminum electrolysis in power circuit

(1) prevent halogen corrosion

Aluminum electrolytic capacitors are very sensitive to chlorine elements, bromine elements, etc. If halogen containing flux, cleaning agent, fixator, fumigant is used, the halide may penetrate the inside of the capacitor through the sealant plug, easily cause corrosion of the capacitor anode, and accelerate the failure of the capacitor after power on. Therefore, it is necessary to strictly control the halogen components used in the production process.

(2) control and regular activation of the storage environment

It is necessary to control the storage environment and time of electrolytic capacitor, and power on it regularly.

After aluminum electrolysis is stored in a high temperature environment for a long time, chemical reactions will occur between the capacitor anodic oxidation film and electrolyte, resulting in a drop in pressure resistance and an increase in leakage current. When suddenly energized, the capacitor voltage is close to the rated voltage, which may cause voltage failure or leakage through the large lead to overheating failure.

Especially high voltage class capacitance of the corresponding monomers, activation treatment after long-term storage, suggest enated 1 k Ω protection resistance, pressure gradually to the rated voltage, lasts 1 hour or so, the capacitor anodic oxidation film was rebuilt, leakage current to return to normal levels.

(3) properly arrange devices on PCB to keep aluminum electrolytic capacitor away from heat source

(4) select solid capacitance according to product characteristics

For example, in the application of low voltage and high current output, solid capacitance of aluminum is used. Aluminum solid-state capacitors have very low ESR and high ripple current carrying capacity, which is very suitable for rectifying filter with low voltage and large current.