When it comes to the factors causing the failure of surface mount aluminum electrolytic capacitors, the first thing that people understand is that the failure factor of surface mount aluminum electrolytic capacitors is that the temperature rises during operation, and the electrolyte inside turns into steam and evaporates. Where there is loss, there will be depletion. Surface mount aluminum electrolytic capacitors will also have this outcome. Is the only factor causing the failure of surface mount aluminum electrolytic capacitors a problem with the electrolyte? No, the author has summarized the factors that cause the failure rate of surface mount aluminum electrolytic capacitors through multiple experiments and tests.

1. Open the riot control valve:

The reasons for the general valve opening: during use, excessive voltage is applied, ripple current is too large, reverse voltage is applied, frequent charging and discharging occur, AC power is applied, and the operating temperature is too high. How do we know if the riot control valve is open?

We can see from its phenomenon that when an explosion-proof valve is opened, it usually shows an increase in internal pressure and temperature. Then we can use a multimeter to test whether the voltage of the surface mounted aluminum electrolytic capacitor is higher than the original standard, to know if the explosion-proof valve is open.

2. Capacity reduction:

There are two reasons for the decrease in capacity of surface mount aluminum electrolytic capacitors. Firstly, the manufacturer may have cut corners, insufficient electrolyte, or defects in the quality of the electrolyte. Secondly, applying overvoltage, excessive ripple current, applying reverse voltage, frequent charging and discharging, applying alternating current, and using at high temperatures. How do we know that the capacity of surface mount aluminum electrolytic capacitors is decreasing? We can determine whether the anode foil capacity of the surface mounted aluminum electrolytic capacitor has decreased, whether the cathode foil capacity has decreased, and whether the electrolyte has dried up (the main reason).

3. Increased losses:

The increase in losses and the decrease in capacity are closely related, and their causes are similar

There are two reasons for this: firstly, the manufacturer is cutting corners, the electrolyte is insufficient, or there are quality defects in the electrolyte. Secondly, applying overvoltage, excessive ripple current, applying reverse voltage, frequent charging and discharging, applying alternating current, and using at high temperatures. Long usage time. We can determine whether the anode foil capacity of the surface mounted aluminum electrolytic capacitor has decreased, whether the cathode foil capacity has decreased, and whether the electrolyte has dried up (the main reason).

4. Leakage current phenomenon:

Deterioration of oxide film, invasion of chloride ions, reasons: manufacturing defects in oxide film, usage issues, application of overvoltage, excessive ripple current, application of reverse voltage, frequent charging and discharging, application of alternating current, high usage temperature, long-term use, use of halogen containing cleaning agents, use of adhesives, use of coating agents. These all have a certain impact on the failure rate of surface mount aluminum electrolytic capacitors during operation.

5. Short circuit:

Phenomenon: Deterioration of oxide film, damage to the insulation function of oxide film and electrolytic paper.

Reason: Manufacturing reasons, defects in oxide film, adhesion of metal particles, aluminum foil, lead burrs, usage reasons, lead subjected to abnormal external stress

6. Open circuit:

Phenomenon: Poor contact between the lead wire and aluminum foil, corrosion, and invasion of chloride ions.

Reason: Due to manufacturing reasons, the lead wire is not firmly riveted to the aluminum foil, and mechanical stress is applied. Reason for use, lead wire

Under abnormal external stress, the use of chloride ion cleaning agents, adhesives, and coating agents.

Technical Support

Surface mount aluminum electrolytic capacitors are most commonly used in power filter circuits. When the input voltage changes or the load suddenly opens, the voltage at both ends of the filter capacitor will change accordingly. If the derating design is not carried out, it is likely to cause the capacitor to break down. In addition, the AC voltage coming in from the input terminal is not a sine wave voltage. Generally, the peak voltage of non sine waves is higher than that of sine waves, which can have a significant impact on the lifespan and reliability of capacitors. Therefore, during design and use, the operating voltage of electrolytic capacitors should be significantly reduced.

The magnitude of voltage reduction for electrolytic capacitors should be determined based on the reliability requirements of the entire machine and the specific circuit used for the capacitor. Generally, it can be divided into three levels, with the first level being 50% of the rated voltage; The second level is 60%; The third level is 70%. High voltage and large capacity capacitors should be selected with a larger derating amplitude. The larger the capacity of a capacitor, the larger the area of the oxide film, and the higher the probability of dielectric defects, resulting in lower reliability.