The article explains construction, manufacturing, application and features of ceramic capacitors.
Ceramic dielectric electrostatic capacitors are dominating capacitor market in number of fields:
- Largest volume capacitor technology (by far)
- Largest value capacitor technology
- Smallest dimension discrete components among all passives
- High flexibility of design to meet specific requirements such as low ESL / high frequency operation
- Strong presence in both low voltage, low power and high voltage, high power applications
despite all the above benefits there are some limitations of the technology that has to be understand for the correct use and design-in. In the following chapters we will also discuss two major groups of ceramic dielectric materials:
The basic construction types include simple – single layer SLCC ceramic capacitors and major types made by stacking technology – MLCC multilayer ceramic capacitors.
Single layer ceramic capacitor SLCC
- simple construction
- low cost technology
- lower CV
- higher ESR
- wide voltage range
- high voltage, high power applications
- RF/microwave applications
Multilayer MLCC ceramic capacitors
- mass volume
- miniaturization
- low ESR
- high CV
- flexible technology
MLCCs chips are by far the leading downsizing and miniaturization technology among passive components. Chart bellow is illustrating shift of the case size mix in MLCCs. While the most popular case size in 1995 was 0805, 0603 in 2000, 0402 in 2009, the most often used case size since 2018 is 0201 that is a capacitor in dimensions 0.6×0.3×0.3mm. The smallest so far MLCC in mass manufacturing is 008004 case introduced to volume production in 2019 with dimensions as small as 0.2×0.1×0.1 mm.
The enormous volumetric downsizing is illustrated in Figure 1. and 2. bellow – about the same volume taken by 10 pieces of 1210 case size is occupied by 100 000 pieces of 008004 capacitors !
Ceramic Dielectric Classifications
The different ceramic dielectric materials used for ceramic capacitors with linear (paraelectric), ferroelectric, relaxor-ferroelectic or anti-ferroelectric behaviour (Figure 3.), influences the electrical characteristics of the capacitors. Using mixtures of linear substances mostly based on titanium dioxide results in very stable and linear behavior of the capacitance value within a specified temperature range and low losses at high frequencies. But these mixtures have a relatively low permittivity so that the capacitance values of these capacitors are relatively small.
Specific group of materials are anti-ferroelectric dielectrics. In opposite to ferroelectrics, where permittivity decrease with applied voltage, permittivity of anti-ferroelectics is low at low voltage and increase with electric field / appled voltage. These materials can be used to achieve high CV, high capacitance at high voltage applications such as energy generation or EV/HEV vehicles in automotive industry. See Figure 3. bellow for comparison of polarisation curves between linear dielectrics (class 1), ferroelectrics (class 2) and anti-ferroelectric materials. We will discuss more in class 2. ceramic capacitors chapter.
Higher capacitance values for ceramic capacitors can be attained by using mixtures of ferroelectric materials like barium titanate together with specific oxides. These dielectric materials have much higher permittivities, but at the same time their capacitance value are more or less nonlinear over the temperature range, and losses at high frequencies are much higher. These different electrical characteristics of ceramic capacitors requires to group them into “application classes”.
The definitions of the application classes given in the two standards are different. The following table shows the different definitions of the application classes for ceramic capacitors:
| Definition regarding to IEC/EN 60384-1 and IEC/EN 60384-8/9/21/22 | Definition regarding to EIA RS-198 |
|---|---|
| Class 1 ceramic capacitors offer high stability and low losses for resonant circuit applications. | Class I (or written class 1) ceramic capacitors offer high stability and low losses for resonant circuit application |
| Class 2 ceramic capacitors offer high volumetric efficiency for smoothing, by-pass, coupling and decoupling applications | Class II (or written class 2) ceramic capacitors offer high volumetric efficiency with change of capacitance lower than −15% to +15% and a temperature range greater than −55 °C to +125 °C, for smoothing, by-pass, coupling and decoupling applications |
| Class 3 ceramic capacitors are barrier layer capacitors which are not standardized anymore | Class III (or written class 3) ceramic capacitors offer higher volumetric efficiency than EIA class II and typical change of capacitance by −22% to +56% over a lower temperature range of 10 °C to 55 °C. They can be substituted with EIA class 2- Y5U/Y5V or Z5U/Z5V capacitors |
| – | Class IV (or written class 4) ceramic capacitors are barrier layer capacitors which are not standardized anymore |
The most common Class I. (low loss, low capacitance density) and Class II. (high loss, high capacitance density) materials are discussed in next chapters.
