Why Do MLCC Capacitors Fail? 7 Common Causes and How to Prevent Them

An MLCC capacitor is a small component, but a failure can cause a big problem.

A product may suddenly stop working. A PCB may fail a test. A power supply may become unstable. Sometimes, the problem only appears after the product has been operating for weeks or months.

When this happens, engineers often ask:

Why did the MLCC capacitor fail?

The answer is not always simple.

MLCC failure can be related to electrical stress, mechanical damage, temperature, soldering, PCB design, or even the way the component is handled during production.

In this article, we explain the 7 common causes of MLCC capacitor failure in simple terms and show what manufacturers can do to reduce the risk.

What Does MLCC Failure Mean?

Before looking at the causes, it is useful to understand what "failure" means.

An MLCC may fail in several different ways.

For example, it may develop:

• A short circuit
• High leakage current
• Low insulation resistance
• Loss of capacitance
• Capacitance outside the specified tolerance
• Cracks in the ceramic body
• Reduced reliability over time

Sometimes the capacitor stops working immediately.

In other cases, it continues to operate but becomes less reliable.

This makes MLCC failure particularly difficult to troubleshoot.

1. Excessive Voltage

One of the most straightforward causes of capacitor failure is excessive voltage.

Every MLCC has a rated voltage.

If the voltage applied to the capacitor is higher than the component is designed to handle, the ceramic dielectric can experience excessive electrical stress.

The problem is not limited to the normal operating voltage.

Engineers should also consider:

• Voltage spikes
• Switching transients
• Startup conditions
• Shutdown conditions
• Abnormal operating conditions

For example, a circuit may normally operate at a relatively stable voltage but experience a short voltage spike during switching.

If the capacitor cannot tolerate the electrical stress, its long‑term reliability may be affected.

How to reduce the risk

Check the maximum voltage that the capacitor can actually experience in the circuit, not just the average operating voltage.

Also review transient conditions during testing.

2. MLCC Cracking

Cracking is another important cause of MLCC failure.

As we discussed in our previous article, MLCCs are made from ceramic materials.

Ceramic is electrically useful but mechanically rigid.

If the PCB bends or excessive force is applied to the component, a crack can develop inside the ceramic body.

Possible causes include:

• PCB bending
• Depanelization
• Connector insertion
• Incorrect component handling
• Mechanical assembly stress
• Excessive vibration

The difficult part is that a small crack may not be visible during a normal visual inspection.

The component can look perfectly normal while already having internal damage.

How to reduce the risk

Pay attention to:

• PCB layout
• Component placement
• Depanelization methods
• Board handling
• Connector installation

For applications with higher mechanical requirements, engineers can also discuss flexible or soft‑termination MLCC options with their supplier.

3. Incorrect Soldering

The soldering process can have a major effect on MLCC reliability.

During reflow soldering, the component is exposed to high temperatures.

If the heating or cooling process is too aggressive, thermal stress can develop inside the MLCC.

Soldering problems can also occur when the solder joints are not balanced.

For example, if one side of an MLCC experiences significantly different conditions from the other side, mechanical stress can be transferred into the ceramic body.

How to reduce the risk

Follow the recommended soldering profile provided by the MLCC manufacturer.

Pay attention to:

• Heating rate
• Peak temperature
• Cooling rate
• Solder volume
• Pad design
• Component placement

Do not assume that every MLCC can be soldered using exactly the same process.

4. Temperature Stress

Temperature can affect MLCC reliability in several ways.

A capacitor operating continuously at high temperature may experience more electrical and material stress than one operating at room temperature.

Rapid temperature changes can also create mechanical stress because different materials expand and contract at different rates.

For example:

Heating → Expansion → Cooling → Contraction

If these changes happen repeatedly, the component and solder joints may experience additional stress.

This is particularly important in:

• Automotive electronics
• Industrial equipment
• Power supplies
• Battery systems
• Outdoor equipment

How to reduce the risk

Check the actual temperature range of the application.

Do not select an MLCC based only on room‑temperature specifications.

The component should be evaluated under the real operating conditions of the finished product.

5. DC Bias and Capacitance Loss

This type of problem is different from a physical crack.

Some ceramic dielectric types can experience capacitance reduction when DC voltage is applied.

This phenomenon is commonly called DC bias.

Imagine that an engineer needs a certain capacitance for a power circuit.

The nominal capacitance listed on the MLCC datasheet may look sufficient.

However, after the component is placed under its actual operating voltage, the effective capacitance may be lower.

The circuit may then perform differently from what was expected.

This does not necessarily mean that the MLCC is defective.

It may simply mean that the component was not evaluated under the correct operating conditions.

How to reduce the risk

Check the effective capacitance under:

• Actual operating voltage
• Actual temperature
• Required frequency

Do not look at nominal capacitance alone.

6. Aging and Long‑Term Capacitance Change

Some MLCC dielectric materials experience gradual capacitance changes over time.

This is known as aging.

The effect depends on the dielectric material and the operating conditions.

For many applications, the change is manageable.

However, for circuits that require stable capacitance over a long period, aging should be included in the design calculation.

This is especially important when the original capacitance tolerance is already very tight.

How to reduce the risk

Engineers should consider the expected capacitance change over the product's service life.

If long‑term stability is critical, select a dielectric and component specification appropriate for the application.

7. Poor PCB Layout

Sometimes the MLCC is not the real problem.

The PCB design may be contributing to the failure.

For example, placing an MLCC too close to:

• A PCB edge
• A screw hole
• A connector
• A depanelization line
• A high‑stress area

can increase mechanical stress.

The component may work perfectly in a laboratory test but fail during actual assembly.

This is why MLCC reliability should be considered together with PCB design.

How to reduce the risk

Before mass production, review:

• Component placement
• PCB thickness
• Board bending
• Mounting points
• Depanelization
• Connector insertion forces

A small layout change can sometimes reduce a significant reliability problem.

How Can You Tell Why an MLCC Failed?

Finding the cause is often more difficult than finding the failed capacitor.

Replacing the component immediately may make the product work again, but it does not necessarily solve the real problem.

A better troubleshooting process is to ask:

When did the failure happen?

Was it:

• During soldering?
• During PCB testing?
• During final assembly?
• During transportation?
• After several hours of operation?
• After several months of use?

The timing can provide an important clue.

Where is the failed MLCC located?

If several failed capacitors are located in the same area of the PCB, check whether that area experiences unusual mechanical or thermal stress.

What type of electrical failure occurred?

Check whether the problem is:

• Short circuit
• Leakage
• Low capacitance
• Open circuit
• Insulation failure

Different failure modes can point toward different causes.

A Simple MLCC Failure Troubleshooting Process

When an MLCC fails, you can use the following process.

Step 1: Record the Failure

Write down the failed component's:

• Part number
• Capacitance
• Voltage
• Package
• Dielectric
• PCB location

Step 2: Check the Electrical Conditions

Measure:

• Working voltage
• Voltage spikes
• Current
• Temperature
• Frequency

Step 3: Check the PCB

Look for:

• Bending
• Cracks
• Poor solder joints
• Incorrect pad design
• High‑stress locations

Step 4: Review the Assembly Process

Check whether the failure started after:

• Reflow
• Wave soldering
• Depanelization
• Connector installation
• Mechanical assembly

Step 5: Compare Failed and Normal Components

Testing a failed MLCC alongside a normal sample can help identify the difference.

Step 6: Work With the Supplier

If the failure cannot be explained by the application or assembly process, provide the supplier with the relevant test information.

A supplier with technical support capabilities can help investigate the failure instead of simply replacing the parts.

How Can You Prevent MLCC Failure?

The best time to solve an MLCC reliability problem is before mass production.

A few simple practices can help.

Choose the Component Based on the Real Application

Do not select an MLCC using only capacitance and voltage.

Consider:

• Temperature
• Frequency
• DC bias
• Mechanical stress
• PCB conditions
• Reliability requirements

Follow the Manufacturer's Soldering Recommendations

A correct component can still be damaged by an unsuitable assembly process.

Always review the recommended soldering conditions.

Avoid Unnecessary PCB Stress

Be careful when:

• Cutting PCBs
• Installing connectors
• Tightening screws
• Handling boards
• Packaging finished products

Test Before Mass Production

Prototype testing can identify problems before they become expensive production failures.

If the application is demanding, test the MLCC under conditions close to the final product.

What Should You Ask an MLCC Supplier?

If you are buying MLCCs for a new project, a few questions can help you evaluate the supplier.

Ask about:

Product specifications

• Capacitance
• Voltage
• Tolerance
• Dielectric
• Package size
• Temperature range

Reliability

• Reliability testing
• Quality control
• Inspection methods
• Failure analysis support

Production

• Monthly production capacity
• Lead time
• Sample availability
• Packaging
• Traceability

Technical support

• Application recommendations
• Soldering guidance
• Failure analysis
• Replacement recommendations

A supplier that can answer these questions clearly can make the development and purchasing process much easier.

FAQ

What is the most common cause of MLCC failure?

There is no single cause for every application. Mechanical cracking, excessive electrical stress, soldering problems, temperature stress, and unsuitable operating conditions are among the important causes to investigate.

Can an MLCC fail even if the voltage is within the rated value?

Yes. MLCC reliability depends on more than voltage. Mechanical stress, temperature, soldering, PCB design, and other operating conditions can also affect the component.

Can a cracked MLCC still work?

Yes. A cracked MLCC may continue to operate temporarily. However, internal damage can increase leakage or create a future short‑circuit risk.

How can I prevent MLCC failure during PCB assembly?

Control the reflow process, reduce PCB bending, use appropriate depanelization methods, and avoid placing MLCCs in areas exposed to high mechanical stress.

Should I replace the MLCC when a PCB fails?

Replacing the capacitor may restore operation, but it is better to identify why the original component failed first. Otherwise, the replacement may fail for the same reason.

Can an MLCC supplier help investigate failures?

Yes. Depending on the supplier's technical capabilities, they may be able to provide failure analysis, application advice, test information, or alternative component recommendations.

Conclusion

An MLCC capacitor can fail for many different reasons.

Sometimes the problem is electrical. Sometimes it is mechanical. Sometimes it comes from soldering or PCB design.

The most important point is that an MLCC failure should not automatically be blamed on the capacitor itself.

Look at the complete system:

MLCC + PCB + Assembly Process + Electrical Conditions + Temperature + Mechanical Stress

When these factors are considered together, it becomes much easier to find the real cause and prevent the same problem from happening again.

For engineers and purchasing teams, working with an MLCC supplier that can provide both stable products and technical support can also make a significant difference during product development and mass production.