SLC vs. MLCC, Which Capacitor Is Better for Your Application?

Capacitors are essential passive components in circuit design. Today, there are so many capacitor sizes available on the market that it is not easy to determine which capacitor is best for your application. Early in the circuit design process, engineers need to decide whether to choose a single layer capacitor (SLC) or a multilayer ceramic capacitor (MLCC) to meet the application requirements.

In general, both seem to serve similar purposes, as either SLCs or MLCCs can be used for charging, filtering or bypassing in a circuit. SLC is the most basic type of capacitor, with only one layer of dielectric material or insulation between the positive and negative electrodes.

MLCCs are based on the basic principle of SLC design, where multiple layers of electrodes are embedded in a single capacitor's dielectric in layers, resulting in an MLCC with a capacitance equivalent to the capacity of multiple SLCs used in parallel. Although MLCCs are slightly thicker than SLCs in terms of thickness, they can achieve greater capacitance in a smaller footprint - a key consideration for RF and microwave applications where size, weight and power (SWaP) of capacitors are currently important. Figure 1 illustrates the basic structure of SLCs and MLCCs.

Figure 1. shows the structure of SLC on the left and the layers of MLCC stack on the right.

1. SLC is more suitable for the application scenario

SLC is specifically designed for microwave and RF applications. This is because the inherent self-resonant frequency (SRF, the point at which the capacitor will exhibit minimum impedance) of SLCs is the highest of discrete block fixed-value capacitors.

It is important to note that in general ESR (i.e., the internal resistance in series with the capacitor) varies with frequency, so it is essential to use capacitors with low ESR. In addition, because SLCs are monolithically integrated forms, they contain a limited number of mechanical components, which also contributes to lower ESR values.

However, SLC has a potential drawback - since it is only a single-layer structure, the capacitance value depends heavily on the dielectric constant of the used dielectric, which limits the maximum capacitance value that can be obtained to some extent. Therefore, SLC is mainly suitable for high frequency, low capacitance applications. Lou's Capacitors (KPD) is a leader in providing custom high value parallel plate capacitors for the LC filter market.

2. Application scenarios for which MLCCs are more suitable

In general, MLCCs have a much higher capacitance range than SLCs and can therefore be used in a variety of applications. MLCCs are composed of multilayer dielectrics and electrodes and can withstand higher operating voltages in addition to higher capacitance - MLCCs manufactured by Lou's Capacitors (KPD) can currently withstand voltages up to 12kV. however, due to the the use of multilayer electrodes and dielectrics, the ESR value of MLCCs is typically much higher than that of SLCs. As a result, MLCCs (containing high-Q, ultra-low-loss primary dielectric MLCCs), can only handle frequencies below 30 GHz, while SLCs can handle frequencies up to 100 GHz.

In RF and microwave applications, MLCC is a more suitable choice if there are high requirements for both capacitance and voltage; in applications other than RF microwave applications, MLCC, especially MLCC with innovative design made by Lou's capacitors (KPD), is ideal for demanding applications such as medical implantation, automotive electronics and high reliability blasting.

In summary, SLC and MLCC are not interchangeable in their applications because of their distinctive parameters in terms of voltage withstand, frequency, and capacitance. In short, SLC is very suitable for high frequency, low voltage RF microwave applications, while MLCC can be used in a more limited frequency range for various types of high voltage and high capacity applications.

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