5 Things You Need to Know about MLCC: Size, Dielectric, Tolerance,Capacitance and Voltage

2025-01-25

MLCCs are indeed composed of numerous layers of dielectric ceramic material, interleaved with conductive plates. By stacking 500 layers or more (like the impressive 600 layers from Hongda), the effective capacitance increases significantly while maintaining a compact form factor.  This design allows for not only higher capacitance in a smaller footprint but also offers benefits like low ESR and ESL, making them excellent for high-frequency applications! They are commonly used in a wide range of electronics, including smartphones, computers, and power supply circuits, due to their efficiency and reliability.

1) MLCC Size

The size of a multilayer ceramic capacitor (MLCC) is denoted by a 4-digit code, such as 0201, 0402, or 0603. In this code, the first two digits specify the length, while the last two digits indicate the width. For example, a code of 0201 signifies an MLCC that measures 0.02 inches in length and 0.01 inches in width. Among various sizes, the 0402, 0603, and 0805 codes are the most frequently used, balancing compactness with performance in a wide range of electronic applications. 

2) MLCC Dielectric

Dielectric directly determines the performance of MLCC. The multi-layer ceramic capacitor dielectric can be categorized into 2 classes regarding the definition of IEC/EN 60384-1 and 60384-8/9/21/22. Class 1 of MLCC has higher stability and accuracy; while Class 2 of MLCC has higher permittivity (which means a higher capacitance over a fixed volume), but with lower stability and accuracy.

There are still other non-standardized classes for ceramic capacitors, but they cannot be manufactured with multi-layers, and there are more detailed explanations from Electronics Notes. 

Table 1. Class 1 and 2 of multi-layer ceramic capacitor dielectric (Source: Electronics Notes)

For Class 1 MLCC (like C0G, etc.), the first character refers to the temperature coefficient α, the second character refers to the multiplier, and the third character refers to the tolerance of the temperature coefficient. For example, C0G indicates an error of 0±30 ppm/°C, and U2J indicates an error of -750±120 ppm/°C.

Table 2. Code system for Class 1 regarding EIA-RS-198 (Source: Electronics Notes, Wikipedia)

For Class 2 MLCC (like X7R, X5R, Y5V, etc.), the first character refers to the lowest operating temperature, the second character refers to the highest operating temperature, and the third character refers to the capacitance change in the operating temperature range. For example, X7R indicates ±15% of capacitance change between -55°C and +125°C.

Table 3. Code system for Class 2 regarding EIA-RS-198 (Source: Electronics Notes, Wikipedia)

3) MLCC tolerance

As addressed above, the ceramic capacitor dielectric has already shown the tolerance of MLCC as well. In the range of -55 to +125°C., MLCCs of Class 1 have lower tolerances that are usually below 1%, while MLCCs of Class 2 have higher tolerances that are around 20%.

Fig. 1 Permittivity changes over temperature;
“K” refers to the relative permittivity of the dielectric material (Source: Kemet)

4) MLCC Capacitance

The capacitance of MLCCs can vary widely to suit different application requirements. Here's a quick overview of what each range is typically used for:

10pF to 1nF: These low capacitance values are often used in high-frequency applications, such as RF circuits and timing applications.

1nF to 1μF: This is the most common range for decoupling and filtering applications in digital circuits, providing stable performance with lower ESR.

1μF to hundreds of μF: Higher capacitance values are primarily used for power supply smoothing, bulk decoupling, and energy storage in various power applications. 

5) Rated Voltage

MLCCs can have rated voltages from just a few volts to several kilovolts, suitable for various applications from low-power devices to high-voltage systems. Capacitance Change, the capacitance of MLCCs, especially with dielectrics like X5R and X7R, can decrease when the rated voltage is applied. This behavior is known as "DC bias effect." X5R and X7R are types of ceramic dielectrics that exhibit non-linear capacitance properties under voltage stress, which makes it crucial to consider the effective capacitance in real-world applications.

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