Why Tantalum Capacitors Fail Without Proper Derating?

Introduction

 

Tantalum capacitors are widely used in power supplies, smart meters, industrial control systems, and other high-reliability applications due to their stable electrical performance and high capacitance in compact size.

However, many engineers encounter a common issue:

Tantalum capacitors perform well during prototype testing but fail during mass production or field operation.

In reality: Improper derating is one of the main root causes of failure.

 

 

What Is Derating in Tantalum Capacitors?

 

Derating refers to operating a capacitor at a voltage significantly lower than its rated voltage to improve reliability and lifespan.

Industry practice: Operate at 50%–70% of rated voltage.

Example:

Circuit voltage: 10V → Recommended capacitor: ≥20V

 

Why Tantalum Capacitors Fail Without Proper Derating?

 

a. Sensitivity to Surge Voltage

Tantalum capacitors are sensitive to surge voltage and transient spikes.

Even if the nominal voltage is stable, real circuits may include:

·  Power-on surge

·  Switching noise

·  Transient spikes

 

Without sufficient derating, these can exceed safe limits and lead to instant failure.

 

b. Increased Leakage and Thermal Stress

Operating near rated voltage increases:

* Leakage current

* Internal temperature

 

This accelerates degradation and may lead to:

* Thermal runaway

* Short circuit or burning

 

c. Lack of Safety Margin

Real-world applications are not ideal and often include:

* Temperature variation

* Ripple current

* Aging effects

 

Without derating, there is no safety margin, especially in industrial environments.

 

d. Sample vs Real Conditions

Prototype testing is usually done under controlled conditions.

However, real applications involve:

* Long operating time

* Environmental stress

* Electrical fluctuations

 

Without proper derating, failures often appear only in mass production or field use.

 

Common Design Mistakes

 

Many failures are caused by incorrect design assumptions:

- Using a 16V capacitor in a 12V circuit

- Ignoring surge voltage during startup

- Focusing only on capacitance and ESR

- Selecting components based only on price

These mistakes create hidden risks that may not appear immediately.

 

Proper Derating Guidelines

 

Voltage Derating (Key Rule)

- MnO2 tantalum: ≤50% (general), ≤30% (power circuit)

- Polymer tantalum: ≤80% (general), ≤50% (pulse)

 

Temperature Consideration

When operating above 85°C, additional derating must be applied.

Higher temperature → higher failure risk

 

Application-Based Selection

Different applications require different capacitor types:

1. Low leakage requirement → standard MnO₂ tantalum
2. High current / pulse → polymer tantalum

Improper selection may lead to performance mismatch or failure

 

How to Avoid Failure in Real Projects

 

To ensure long-term reliability:

- Apply proper voltage derating

- Consider surge and real operating conditions

- Choose correct capacitor type (low leakage vs low ESR)

- Work with experienced suppliers who understand applications

 

UF Capacitors Solution

 

At UF Capacitors, we focus on application-based capacitor selection, not just supplying components.

 What We Offer:

CA42 Series – Radial Epoxy Dipped Tantalum Capacitors

CA45 Series – Chip Tantalum Capacitors(General Purpose)

CA45U Series – Low ESR Chip Tantalum Capacitors

CA55 Series – Polymer Tantalum Capacitors

Our Strength:

- Low leakage options

- Replace AVX / Kemet / Vishay

- Short lead time and competitive pricing

 

Tell us your application, voltage, and target — we will help you select the right tantalum capacitor solution and support your project with reliable quality and fast delivery.

Cross to:

Photo	Description	UF Capacitors Series Code	Kemet	AVX	Vishay
	Polymer Tantalum Capacitors	CA55 Series	T520 Series T521 Series	TCJ Series	T55 Series
	Tantalum Chip Capacitors, General Purpose, A,B,C,D,E Case	CA45 Series	T491 Series T490 Series T489 Series	TAJ Series F913 Series TLJ Series	293D Series
	Low ESR Chip Tantalum Capacitors, A,B,C,D,E Case	CA45U Series	T494 Series T495 Series	TPS Series F93 Series	593D Series 594D Series TR3 Series
	Radial Epoxy Dipped Tantalum Capacitor	CA42 Series	T350-T390 Series	TAP Series	199D Series 489D Series ETPW Series ETQW  Series