MLCC (Multi-Layer Ceramic Chip) capacitors are the most widely used passive component in modern electronics. A typical smartphone contains over 1,000 MLCCs, while an automotive ECU may use 3,000+. Understanding their characteristics is essential for reliable circuit design.
What is an MLCC?
An MLCC consists of alternating layers of ceramic dielectric and metal electrodes, stacked and sintered into a monolithic block. The multilayer structure provides high capacitance in a small package.
Key advantages over other capacitor types:
- Very small size (down to 0201 / 01005)
- Low ESR (Equivalent Series Resistance)
- High frequency performance
- No polarity — can be used with AC signals
- Long lifetime (no electrolyte to dry out)
Dielectric Classes
Class 1: C0G / NP0
Temperature coefficient: ±30 ppm/°C
Capacitance range: 0.5 pF – 100 nF
C0G (also called NP0) capacitors have:
- Zero DC bias effect — capacitance doesn't change with applied voltage
- Negligible aging — capacitance stable over decades
- Excellent Q factor — very low losses at RF frequencies
- No piezoelectric effect — no audible noise
Limitation: Available only in smaller capacitance values and larger package sizes.
Class 2: X7R, X5R
Temperature coefficient: ±15% (X7R: -55°C to +125°C), ±15% (X5R: -55°C to +85°C)
X7R and X5R offer much higher volumetric capacitance:
- Significant DC bias effect — a 10µF X7R cap at rated voltage may only provide 4-5µF
- Aging: ~2.5% per decade (logarithmic scale)
- Piezoelectric effect — can produce audible noise ("singing capacitors")
- Available in high values: up to 100µF in small packages
Class 3: Y5V, Z5U
Temperature coefficient: +22% / -82% (Y5V)
Highest capacitance density but worst stability. Avoid for precision applications.
Critical MLCC Behaviors
DC Bias Effect
This is the most important — and most overlooked — MLCC characteristic. As DC voltage increases, capacitance decreases dramatically for Class 2 dielectrics.
| Capacitor | Rated at 0V | At 50% rated voltage | At rated voltage |
|---|---|---|---|
| 10µF 25V X5R | 10 µF | 6.5 µF | 3.5 µF |
| 10µF 10V X5R | 10 µF | 5.0 µF | 2.0 µF |
| 100nF 16V C0G | 100 nF | 100 nF | 100 nF |
Voltage Derating
Industry best practice for reliability:
- Consumer: Derate to 80% of rated voltage
- Industrial: Derate to 70%
- Automotive/Aerospace: Derate to 50%
Aging
Class 2 MLCCs lose capacitance logarithmically over time:
- ~2.5% per time decade (1 hr → 10 hr → 100 hr → 1000 hr)
- Aging resets when heated above Curie temperature (~125°C)
- After 10 years: approximately 10-12% loss
Flex Cracking
MLCCs are ceramic — they crack if the PCB flexes too much. For large packages (0805+):
- Use flex-rated terminations (soft termination)
- Add solder fillet reinforcement
- Avoid placing near board edges or mounting holes
Package Size Guide
| Size Code | Dimensions (mm) | Typical Use |
|---|---|---|
| 0201 | 0.6 × 0.3 | Mobile, wearable |
| 0402 | 1.0 × 0.5 | General purpose |
| 0603 | 1.6 × 0.8 | Most common |
| 0805 | 2.0 × 1.25 | Power, high voltage |
| 1206 | 3.2 × 1.6 | High capacitance, automotive |
| 1210 | 3.2 × 2.5 | Bulk bypass |
Application-Specific Selection
Power Supply Decoupling
- Use X7R or X5R, closest to the IC power pins
- Typical: 100nF (high frequency) + 10µF (bulk)
- Consider DC bias — a 4.7µF at operating voltage may suffice over a 10µF that derates heavily
High-Frequency / RF
- Use C0G/NP0 exclusively
- Consider parasitic inductance — smaller packages have lower ESL
- 0402 C0G for GHz applications
DC-DC Converter I/O
- Input: X7R, rated for input voltage ripple + DC bias
- Output: Low-ESR X5R/X7R, check transient response requirements
- Always consult the converter datasheet for recommended capacitor values
Conclusion
MLCCs are deceptively complex. The stated capacitance on the label is rarely what you get in your actual circuit. For reliable designs:
FPGACenter stocks a comprehensive range of MLCCs from Murata, Samsung, TDK, and Yageo. Contact us for volume pricing on any capacitor specification.