Electrolytic capacitors are everywhere. Power supplies, motor drives, industrial controls, medical devices, EV systems, consumer electronics. If a product converts, stores, filters, or smooths power, there is a strong chance an electrolytic capacitor is involved.
They are also one of the most common points of failure in electronic assemblies.
For new manufacturing and design engineers, understanding why electrolytic capacitors fail and how to prevent them is essential for improving reliability, reducing RMAs, and avoiding costly field failures.
Electrolytic capacitors achieve high capacitance values in a small footprint by using a liquid or gel electrolyte and a very thin oxide dielectric layer.
That construction gives them advantages:
It also gives them inherent weaknesses:
In short, electrolytics are not “install and forget” components. They age.
2.1 Electrolyte Dry-Out (The #1 Failure Mode)
Over time, the electrolyte slowly evaporates or chemically degrades.
This causes:
High temperature accelerates this dramatically.
A common rule of thumb: every 10°C increase cuts capacitor life roughly in half.
2.2 Excessive Ripple Current
Ripple current flows through the capacitor during normal operation, especially in:
If ripple current exceeds the capacitor’s rating:
This is one of the most frequent design-stage mistakes.
2.3 Overvoltage Stress
Applying voltage too close to or beyond the rated value damages the oxide dielectric.
Consequences include:
Transient spikes and poor derating practices are common culprits.
2.4 Temperature Exposure (Ambient and Self-Heating)
Electrolytic capacitors suffer from both:
Mounting a capacitor near:
…can significantly reduce its lifespan, even if the datasheet ratings appear acceptable.
2.5 Reverse Polarity or Incorrect Installation
Most electrolytic capacitors are polarized.
Reverse installation can cause:
This failure often appears during:
2.6 Mechanical and Manufacturing Stress
Manufacturing-related issues are often overlooked:
These stresses can crack internal connections or compromise seals, accelerating electrolyte loss.
Manufacturing and quality teams often encounter:
In many cases, the capacitor still “measures okay” at room temperature, masking the root cause.
4.1 Apply Proper Voltage Derating
A common best practice:
Example:
Use a 50V capacitor on a 24V rail, not a 25V part.
This reduces dielectric stress and leakage current.
4.2 Design for Ripple Current Margin
Never design to the limit.
Recommendations:
When in doubt, use multiple capacitors in parallel to share ripple current.
4.3 Control Temperature Aggressively
Thermal layout decisions matter just as much as electrical ones.
4.4 Choose the Right Capacitor Type
Not all electrolytics are the same:
In some designs, replacing electrolytics with:
…can eliminate failure mechanisms entirely.
4.5 Respect Manufacturing Best Practices
For manufacturing engineers:
Small process changes can prevent large reliability problems.
Datasheets are written under controlled conditions.
Real products live in:
Electrolytic capacitors are often the clock that determines system life.
Design engineers who treat them as consumable components and plan accordingly produce more reliable products.
Final Thought
If a system fails in the field after three to five years, the electrolytic capacitor is often the first suspect.
Understanding why they fail and how to prevent it turns a common weakness into a controlled design variable.