What Causes Capacitor Failure?

Why Do Capacitors Fail?#

Capacitors are generally reliable, but they don't last forever. Understanding why they fail helps in selecting better components for your designs or repairs.

1. Excessive Heat (The #1 Killer)#

For every 10°C rise in temperature, the life of an electrolytic capacitor is typically cut in half.

Cause: Poor ventilation, placing capacitors near heat sinks/processors, or high ripple current causing internal heating.
Result: Electrolyte evaporates ("dries out"), ESR increases, and capacitance drops.

2. Over-Voltage#

Applying a voltage higher than the rated maximum can cause dielectric breakdown.

Tantalum: Can ignite or fail short-circuit.
Electrolytic: Can vent or explode if significant over-voltage is applied.
Preventing it: If you are building a high-voltage string, use our Series Capacitor Calculator to ensure perfect voltage balancing.

3. Voltage Reversal#

Polarized capacitors (Aluminum Electrolytic, Tantalum) must be connected correctly.

Connecting positive to negative will cause rapid heating, gas generation, and likely explosion or venting.

4. Mechanical Stress#

Vibration: Can break leads or internal connections.
Flex Cracking: Ceramic capacitors (MLCCs) can crack if the PCB is bent during assembly, leading to shorts.

Summary#

To maximize life:

Keep them cool.
De-rate voltage (use a 25V cap on a 12V line).
Ensure correct polarity.

Why Do Capacitors Fail?#

Capacitors are generally reliable, but they don't last forever. Understanding why they fail helps in selecting better components for your designs or repairs.

1. Excessive Heat (The #1 Killer)#

For every 10°C rise in temperature, the life of an electrolytic capacitor is typically cut in half.

Cause: Poor ventilation, placing capacitors near heat sinks/processors, or high ripple current causing internal heating.
Result: Electrolyte evaporates ("dries out"), ESR increases, and capacitance drops.

2. Over-Voltage#

Applying a voltage higher than the rated maximum can cause dielectric breakdown.

Tantalum: Can ignite or fail short-circuit.
Electrolytic: Can vent or explode if significant over-voltage is applied.
Preventing it: If you are building a high-voltage string, use our Series Capacitor Calculator to ensure perfect voltage balancing.

3. Voltage Reversal#

Polarized capacitors (Aluminum Electrolytic, Tantalum) must be connected correctly.

Connecting positive to negative will cause rapid heating, gas generation, and likely explosion or venting.

4. Mechanical Stress#

Vibration: Can break leads or internal connections.
Flex Cracking: Ceramic capacitors (MLCCs) can crack if the PCB is bent during assembly, leading to shorts.

Summary#

To maximize life:

Keep them cool.
De-rate voltage (use a 25V cap on a 12V line).
Ensure correct polarity.

What Causes Capacitor Failure?

Why Do Capacitors Fail?#

1. Excessive Heat (The #1 Killer)#

2. Over-Voltage#

3. Voltage Reversal#

4. Mechanical Stress#

Summary#

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Why Do Capacitors Fail?#

1. Excessive Heat (The #1 Killer)#

2. Over-Voltage#

3. Voltage Reversal#

4. Mechanical Stress#

Summary#