Ceramic capacitor, also known as ceramic capacitor, is a non-polar capacitor with ceramic material as the dielectric and metal layer as the electrode. It is widely used in electronic circuits due to its excellent high-frequency performance, small size, and low cost. Here is a detailed analysis:
Basic Structure and Principle
Dielectric material: Using ceramics such as barium titanate (BaTiO) and strontium titanate (SrTiO) as the core, a dense structure is formed by high-temperature sintering.
Electrode: Coating metal layers such as silver, nickel, or copper on both sides of a ceramic medium to form an electrode.
Encapsulation:
Single layer ceramic capacitor: early form, with small capacity.
Multilayer Ceramic Chip Capacitor (MLCC): a mainstream type that significantly increases capacity by alternately stacking multiple layers of ceramics and electrodes (similar to a thousand layer cake).
Working principle:
Charge is stored through the polarization effect of ceramic media, and the metal electrode collects the charge to complete charging and discharging.
core features
(1) Advantages
Polarity free: No need to distinguish between positive and negative poles, suitable for AC circuits.
Excellent high-frequency performance: ESR (equivalent series resistance) and ESL (equivalent series inductance) are extremely low, suitable for high-frequency filtering (such as GHz level RF circuits).
Small size: Especially MLCC, it can achieve ultra small packaging (such as 0201 size: 0.6mm × 0.3mm).
Temperature stability: A type of ceramic (such as C0G) has an extremely small temperature coefficient (± 30ppm/℃) and is suitable for precision circuits.
Long lifespan: Without electrolyte aging issues, the theoretical lifespan is almost infinite.
Low cost: suitable for large-scale production.
(2) Disadvantage
Small capacity: usually ranging from pF to μ F (MLCC can reach up to 100 μ F, but the capacity drops sharply under high voltage).
Piezoelectric effect: Some ceramic materials (such as high dielectric constant type) may produce noise when subjected to mechanical stress or voltage changes.
DC bias characteristics: Capacity may significantly decrease with increasing applied voltage (especially for Class II ceramics).
Main classification
(1) Classified by ceramic materials
|Type | Dielectric Material | Temperature Characteristics | Capacity Range | Typical Applications|
|A type of ceramic | C0G (NP0) | Ultra stable (± 30ppm/℃) | 0.5pF~100nF | Oscillators, RF circuits, precision timing|
|Class II ceramics | X7R, X5R | Relatively stable (± 15%~± 15% tolerance) | 1nF~100 μ F | Power decoupling, low-frequency filtering|
|Three types of ceramics | Y5V, Z5U | Poor (+22%~82% tolerance) | 10nF~10 μ F | Low cost consumer electronics (with low precision requirements)|
(2) Classified by packaging form
Direct insertion: Early packaging, now gradually replaced by surface mount.
MLCC: mainstream types, such as 0402, 0603, 0805 and other sizes, suitable for SMT automation production.
Special packaging:
High voltage type: The withstand voltage can reach several thousand volts (such as surface mounted high-voltage MLCC).
Array capacitor: Multi capacitor integrated packaging, saving PCB space.
Typical application scenarios
High frequency filtering:
Eliminate high-frequency noise in RF circuits such as WiFi and Bluetooth modules.
Power decoupling:
Provide instantaneous current to the power pins of chips such as CPU and FPGA (such as the 0.1 μ F decoupling capacitor on the motherboard).
Resonance and Timing:
Forming an LC resonant circuit with an inductor (such as a crystal oscillator load capacitor).
Signal coupling:
Transmit AC signals in audio circuits and block DC components.
EMI suppression:
Suppress electromagnetic interference from switch mode power supplies (such as Y capacitor being connected across the primary ground).
Ceramic capacitor vs. other capacitors comparison
|Features | Ceramic Chip Capacitors (MLCC) | Aluminum Electrolytic Capacitors | Tantalum Capacitors|
|Polarity | Non polarity | Polarity | Polarity|
|Capacity range | 0.5pF~100 μ F | 1 μ F~1F | 0.1 μ F~1000 μ F|
|High frequency performance | Excellent (extremely low ESR) | Poor (high ESR) | Good (low ESR)|
|Volume | Extremely small (patch type) | Large | Small|
|Temperature stability | Excellent C0G type, Y5V difference | Poor (prone to failure at high temperatures) | Excellent (55 ℃~125 ℃)|
|Lifespan | Almost infinite | 2-5 years (electrolyte drying up) | 15 years+|
|Cost | Low (except for high-capacity high-voltage models) | Low | High|
Precautions for use
DC bias effect:
The actual capacity of Class II ceramics (such as X7R) may decrease by more than 50% with increasing voltage, and sufficient margin should be left for selection.
Mechanical stress:
PCB bending or impact may cause internal cracks in MLCC, leading to short circuits (flexible end models should be selected for automotive electronics).
Welding temperature:
Excessive reflow soldering temperature may damage the ceramic structure (following the manufacturer's temperature curve).
Piezoelectric noise:
High dielectric constant ceramics (such as Y5V) may produce audible noise under AC signals and are not suitable for audio sensitive circuits.
Common Problems and Solutions
Sudden drop in capacity:
Phenomenon: The capacity of MLCC decreases significantly under high voltage.
Solution: Choose a model with a rated voltage much higher than the operating voltage (such as a 50V capacitor for a 12V circuit).
Micro short circuit failure:
Phenomenon: Slight leakage of capacitors leads to circuit abnormalities.
Solution: Avoid using inferior capacitors and strengthen incoming material testing.
Ceramic capacitors, especially MLCCs, have become the "universal components" of modern electronic circuits due to their advantages such as polarity free, strong high-frequency performance, and small size. From mobile phones to satellites, they rely on their stable operation. However, its capacity limitations, DC bias characteristics, and mechanical brittleness need to be carefully considered in the design. Ceramic capacitors are irreplaceable core passive components in high-speed digital circuits, RF communications, and precision instruments.