1. The importance of capacitors

Capacitor is a commonly used electronic component. It is used in basically every circuit and is used in filtering, delay, coupling, resonance and other circuits. So why do capacitors leak electrolyte or even explode?

2. Analysis of the causes of capacitor explosion

There are actually many reasons for capacitor explosion, such as the current is greater than the allowed steady wave current, the voltage used exceeds the working voltage, reverse voltage or frequent charging and discharging, etc.

High temperature is the most direct cause of capacitor explosion.

We know that an important parameter of a capacitor is the temperature resistance value, which refers to the boiling point of the electrolyte inside the capacitor. Therefore, general electrolytic capacitors will indicate the operating temperature range. For example, the operating temperature of electrolytic capacitors is between -40°C and 105°C, and you will find that most capacitors basically work within this temperature range.

Because as the temperature rises, when the internal temperature of the capacitor reaches the boiling point of the electrolyte, the electrolyte begins to boil, and the pressure inside the capacitor rises. When the pressure exceeds the endurance limit of the explosion-proof valve, explosion occurs. This is also the main reason for designing explosion-proof valves. The reason is so that when the electrolytic capacitor explodes, there will be a gap to vent the explosion in a direction.

3.Why does temperature have such a big impact?

In fact, for any component, temperature is basically an important factor in maintaining good performance. For electrolytic capacitors, temperature will accelerate chemical reactions and cause the medium to degrade and fail over time. The general design service life of a capacitor is approximately 20,000 hours, which is greatly affected by the ambient temperature. Especially for capacitors used for voltage reduction, full consideration must be given to their attenuation characteristics, otherwise the entire device will become unusable within a few years. The service life of the capacitor decreases as the temperature increases. Experiments have shown that for every 10°C increase in ambient temperature, the life of the capacitor will be halved.

4. Precautions for capacitance in circuit design

Knowing the reasons for capacitor explosion, you need to pay attention to the following points when designing the circuit:

A. In order to ensure the stability of the capacitor, the capacitor must undergo a long-term high-temperature environment test before production, so as to ensure the quality of the capacitor.

B.The operating temperature and applied ripple current must comply with the capacitor specifications.

C. The main chemical solvents of the electrolyte and electrolytic paper are flammable, and the electrolyte is conductive. When the electrolyte comes into contact with the PC board, it may corrode the circuits on the PC board or cause a short circuit, resulting in smoke or fire. Therefore there should not be any wiring under the capacitor seal.

D. For circuits that require fast and frequent charging and discharging, aluminum electrolytic capacitors should not be used, but specially designed capacitors with long life should be selected.

E. The peak voltage after the superposition of DC voltage and ripple voltage should not exceed the rated operating voltage.

F. If more than two capacitors are connected in series, ensure that the applied voltage is lower than the rated value, and a balancing resistor should be connected in parallel to make the voltage applied to each capacitor equal.

In any case, if you want the circuit to be more reliable, you must fully consider various parameters at the beginning of the design, select appropriate capacitors for different circuit design requirements, and choose electrolytic capacitors that meet specifications and are of high quality.

Hongda Capacitors is chip capacitors manufacturer since 1999. Now we own 5 advanced production lines, have complete quality control system, and advanced chip capacitors technology in China. We have two chip capacitors research centers and one reliability test lab in the factory.