Electrical Causes

Overvoltage (exceeding rated voltage)

The dielectric oxide layer breaks down, causing a short circuit. A large current instantly vaporizes the electrolyte, leading to a rapid pressure increase.

Power supply voltage spikes, lightning strikes, disconnection of inductive loads.

Reverse Polarity (for polarized capacitors)

Causes abnormal chemical reactions, rapidly increasing leakage current and generating excessive heat, boiling the electrolyte and producing gas.

Incorrect installation or reverse connection during circuit repair.

Excessive Ripple Current

Current flowing through the Equivalent Series Resistance (ESR) generates excess heat, continuously heating the electrolyte. This is common in high-frequency, high-current circuits like switch-mode power supplies.

Switch-mode power supplies, inverters.

Thermal Causes

Excessive Ambient Temperature

Lowers the boiling point of the electrolyte, making it easier to vaporize. Also accelerates the aging of sealing materials.

Poor device ventilation, proximity to heat sources.

Product Defects & Aging

Poor Electrolyte Formula / Drying Out

Impurities or lack of anti-corrosion components can lead to hydrogen gas generation during normal operation. Long-term use can cause the electrolyte to dry up, increasing ESR and leading to overheating.

The well-known "capacitor plague" event (1999-2007); aged equipment.

Pressure Relief Vent Design/Manufacturing Defects

When internal pressure reaches a critical point, a poorly designed or manufactured vent fails to open and release pressure, causing the casing to rupture explosively.

Use of low-quality or poorly manufactured capacitors.