What is a Ceramic Capacitor? Guide to MLCCs, Codes, and Stability for PCB Engineers

Table of Contents

1. 1. What is a Ceramic Capacitor?
2. 2. Major Classifications: From Disks to MLCCs
3. 3. Key Engineering Parameters and Temperature Coefficient
4. 4. Decoding Ceramic Cap Codes
5. 5. PCB Design and Manufacturing Considerations (DFM)
6. 6. Supply Chain Focus: From BOM to PCBA Realization
7. 7. Conclusion

1. What is a Ceramic Capacitor?

A ceramic capacitor uses ceramic material as its dielectric. It typically consists of two or more alternating layers of ceramic and metal, with the metal layers acting as electrodes. While they are often defined as having a “fixed value,” from an engineering perspective, it is crucial to understand that their effective capacitance is not absolutely constant; it is significantly influenced by external factors such as temperature, DC bias voltage, and operating frequency.

Thanks to ceramic materials' excellent insulating properties and adjustable dielectric constant, these capacitors excel in bypass, decoupling, filtering, and high-frequency applications. Their low Equivalent Series Inductance (ESL) and low Equivalent Series Resistance (ESR) make them indispensable in high-current and high-speed digital circuits.

2. Major Classifications: From Disks to MLCCs

Physically, ceramic capacitors primarily come in two forms, each dominating different application areas:

• Multi-Layer Ceramic Capacitor (MLCC): This is the most common form in Surface Mount Technology (SMT) today. They are constructed by stacking alternating layers of ceramic dielectric and conductive electrodes. MLCCs are dominant in high-frequency filtering and low-voltage IC power decoupling, offering relatively high capacitance values in extremely small packages (such as 0402 or even 01005).
• Ceramic Disk Capacitor: This is a Through-Hole Technology (THT) component, typically flat and circular. Although MLCCs dominate high-density PCBs, the ceramic disk capacitor is still widely used in high-voltage applications and EMI suppression (Safety Capacitors), and in certain low-frequency, high-power circuits, as its structure offers greater resistance to physical impact compared to MLCCs.

3. Key Engineering Parameters and Temperature Coefficient

Selecting a capacitor is about more than just its capacitance value. For engineers, understanding the capacitor temperature coefficient is crucial. This coefficient defines how stable the capacitance value is as the ambient temperature changes.

Ceramic capacitors are categorized into different classes based on the ceramic dielectric material used, which determines their stability and volumetric efficiency:

• C0G/NP0: This is the only choice when high-precision signal processing or timing is required.
• X7R: The workhorse of decoupling, offering excellent value. It maintains a stable capacitance within ±15% across a wide temperature range (-55°C to +125°C).
• Y5V: While providing extremely high capacitance density, its value can drop dramatically at high or low temperatures (potentially down to less than 20% of its nominal value). It should never be used in high-precision applications.

4. Decoding Ceramic Cap Codes

For through-hole or larger MLCCs, the component surface usually features printed codes. These ceramic cap codes often confuse beginners, but they adhere to strict industrial standards (EIA).

1. The Fundamental Three-Digit Rule

The most common encoding consists of three digits:

• First Two Digits: The significant figures (nominal value).
• Third Digit: The multiplier (the power of 10, or simply the number of zeros to add after the first two digits).
• Default Unit: Picofarads (pF).

2. Engineering Example: Identifying "104"

Suppose your BOM calls for a 100nf ceramic capacitor, and the component you are examining is marked "104."

• 10: The significant value.
• 4: The multiplier, meaning add 4 zeros after the 10.
• Calculation: 100,000 pF.
• Conversion: Since 1,000 pF = 1 nF, 100,000 pF precisely equals 100 nF (or 0.1 µF).

3. Quick Reference Table for Common Codes

Suffix Letters: Tolerance Rating

• A letter often follows the numeric code, which denotes the capacitor's Tolerance (accuracy).

1. J: ±5% (Common for high-precision C0G/NP0)
2. K: ±10% (Common for X7R)
3. M: ±20%
4. Z: +80% / -20% (Common for Y5V)

Special Case: Values Less Than 10pF

• For very small capacitance values (typically <10pF), the letter 'R' is used in industrial standards to replace the decimal point, preventing reading confusion during printing.

1. 2R2: Represents 2.2 pF.
2. 4R7: Represents 4.7 pF.

5. PCB Design and Manufacturing Considerations (DFM)

When designing a PCB, engineers must not only calculate parameters but also consider Design for Manufacturability (DFM). Ceramic capacitors, especially MLCCs, have a brittle ceramic body, making them highly susceptible to mechanical stress.

Failure Risk: When a PCB is subjected to bending, vibration, or excessive stress, the MLCC body can crack. This internal crack is a critical failure mode: it can cause electrode misalignment, leading to a short circuit (the most dangerous and common failure), increased leakage current, or in severe cases, an open circuit.

Layout Advice: Avoid placing large MLCCs near connectors, screw holes, or V-cut separation lines. These areas bear the maximum mechanical stress (bending moment) during assembly or separation, significantly increasing the risk of capacitor damage. If placement is unavoidable, adjust the capacitor's orientation so its long axis runs parallel to the direction of the expected mechanical stress.

6. Supply Chain Focus: From BOM to PCBA Realization

After the design is finalized, the real challenge is transforming the design files into reliable physical hardware. For engineers, solving component "availability" is just as critical as solving circuit problems.

> Recommend reading: What Is Component Sourcing? A Complete Guide for PCB Designers & Manufacturers

In this phase, NextPCB collaborates closely with HQ Online (a prominent electronic component distributor based in Shenzhen, the Silicon Valley of Hardware), both operating under the HQ Electronics umbrella. This deep resource integration model is specifically designed to solve manufacturing pain points:

• Smart BOM Matching and Obsolescence Solutions: Leveraging HQ Online's extensive database (covering 3,000+ brands and 600,000+ stock components), NextPCB's BOM services not only quickly identify the ceramic capacitor specifications you need but, more importantly, the system can recommend suitable alternatives based on parameters (voltage, tolerance, temperature coefficient) when a specific part is out of stock, preventing project delays.
• Authenticity and Quality Control: Counterfeit components are a silent killer in hardware development. Through unified supply chain management, we ensure that every 100nf ceramic capacitor or critical chip is sourced directly from the original manufacturer or authorized channels, guaranteeing the electrical performance of the finished PCBA meets design expectations.
• Efficiency Boost: Integrating PCB manufacturing and component procurement within the same ecosystem significantly shortens the lead time from files to final products.

Keep Reading:

> PCB Capacitors: Why Is It Important and How to Choose?

> Capacitor Symbols: A Guide to Understanding the Different Types

7. Conclusion

Whether it's a ceramic disk capacitor used for suppressing power noise or a precision MLCC for high-frequency signal paths, the ceramic capacitor is a cornerstone of the electronic world. Mastering the reading of ceramic cap codes and the rules for selecting the correct capacitor temperature coefficient will make your circuit designs more robust.

On the path of hardware development, solid foundational knowledge combined with reliable manufacturing and supply chain support (such as the one-stop PCB and BOM service provided by NextPCB) is the key to successful project execution.

Note: This article aims to disseminate fundamental electronic component knowledge. For separate component search or purchase, please refer to professional distribution platforms like HQ Online; for comprehensive PCBA services including PCB manufacturing and BOM matching, NextPCB provides the necessary engineering support.

About the Author

Lolly Zheng- Sales Account Manager at NextPCB.com

Four years of proven sales experience across electronic components and PCBA industries, with strong expertise in key account acquisition, customer relationship management, and contract negotiations. Focused on driving revenue growth through strategic client development and solution-based selling. Experienced in expanding high-value accounts, securing long-term partnerships, and consistently exceeding sales targets in competitive markets.

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