All types of capacitors for PCB: from basics to advanced

As an important member of electronic products, capacitors play a vital role in the design and manufacture of various equipment. On PCBs (printed circuit boards), capacitors are widely used in functions such as filtering, energy storage, decoupling and signal regulation. And this article will introduce all types of capacitors in PCB in detail to help you better understand and apply these powerful components.

Quick knowledge: what is a PCB and what is a capacitor?

PCB, printed circuit boards, are key components in electronic devices that connect, support and achieve electrical performance. They are mainly composed of thin sheets made of insulating materials such as glass fiber or epoxy resin, whose surfaces are etched or printed with conductive paths (also known as wires), which are usually made of copper. PCB provides a stable and organized platform for installing and interconnecting various electronic components (such as resistors, capacitors, and integrated circuits) so that they can work together to perform specific tasks within electronic devices.

While capacitors are important components for storing electricity, all types of capacitors play a variety of important roles in the circuit. A capacitor consists of two conductors close to each other, sandwiched by a layer of non-conductive insulating medium. When a voltage is applied between the two plates of a capacitor, the capacitor stores charge. The charging process of the capacitor is to store the electrical energy obtained from the power supply in the capacitor, so that the two plates respectively carry an equal amount of dissimilar charges. While the discharge process of the capacitor is to release the stored charge and electrical energy, so that the charges on the two plates neutralize each other.

Detailed information of all types of capacitors for PCB

After understanding the basics concerning what is a PCB and what is a capacitor, we come to the detailed classification of all types of capacitors for PCB.

Multilayer Ceramic Capacitors (MLCC)

MLCC consists of multiple ceramic layers with metal electrodes sandwiched between each layer, which are then stacked together and connected with conductor leads at both ends to form an overall structure. The exterior is usually covered with an insulating packaging material to protect the capacitor. The structure of MLCC consists of three components: ceramic medium (porcelain body), metal inner electrode and metal end electrode. According to the metal electrode materials used, it is divided into precious metal electrodes (such as silver, palladium silver, gold, etc.).

And this type of capacitor has a variety of characteristics which make it suitable for various applications.

Characteristics of MLCC
Large capacitance	MLCC greatly increases the capacity of the capacitor by means of multi-layer superposition.
Small size	MLCC has a compact structure and small space, which is very suitable for the miniaturization needs of modern electronic equipment.
Easy to chip	MLCC can be easily integrated into the chip circuit to improve the integration and reliability of the circuit.
High frequency characteristics	MLCC has a structure that can reduce resistance (ESR) and residual inductance (ESL), so it can ensure the operation of the capacitor at high frequency conditions.
Good temperature stability	The capacitance value of MLCC changes with the temperature, which is suitable for use under various temperature conditions.

Thanks to its unique characteristics, MLCC is widely used in various fields, such as in mobile phones and communication base stations, MLCC is popularly applied in power amplifiers, transceivers, filters and other components to improve the performance and stability of the communication system. Moreover, MLCC is an indispensable component on computer boards such as motherboards and graphics cards to provide stable power supply and signal quality. Besides, in household appliances such as televisions, stereos, and washing machines, MLCC is also frequently used for filtering, decoupling, and timing control to improve our living experience.

MLCC is one type of capacitor with excellent performance and wide application prospects. Its multi-layered structure and compact volume make it ideal for the miniaturization and high-performance requirements of modern electronic devices.

Electrolytic capacitor (2 types)

Electrolytic capacitors are mainly divided into aluminum electrolytic capacitors and tantalum electrolytic capacitors. And the comparison of these two electrolytic capacitors is making them perform differently in two divergent fields.

Comparison of two major types of electrolytic capacitors
aluminum electrolytic capacitors	Structure	Its capacitance can be made relatively large, usually having a positive and negative electrode.
	Features	It can store more charges and is suitable for circuits that require large capacity capacitors, such as power filter circuits.
		The capacitance value varies greatly with temperature and voltage, and the service life is relatively short.
tantalum electrolytic capacitors	Structure	The anode is made of tantalum particles, covered by an insulating oxide as a dielectric, and surrounded by a liquid or solid electrolyte as a cathode.
	Features	Smaller size, in the same capacitance, tantalum electrolytic capacitors than aluminum electrolytic capacitors occupy less PCB space.
		With higher capacitance stability and lower equivalent series resistance (ESR), it performs well in circuits that require high power supply stability, such as those in high-end audio devices.

Aluminum electrolytic capacitors and tantalum electrolytic capacitors are different in structure and characteristics, and each is suitable for different application fields. Aluminum electrolytic capacitors are suitable for applications requiring large capacity and high cost performance, for instance, energy-efficient lighting, televisions, monitors, vehicles. While tantalum electrolytic capacitors are suitable for applications requiring high volume, temperature range and stability. For example, tantalum electrolytic capacitors are widely applied in military communications, aerospace and other relevant fields.

Film capacitor

The structure of the film capacitor mainly includes two parts: electrode and dielectric layer. The electrode is usually made of metal foil or metal film, and the dielectric layer is made of insulating materials such as polyester film and polypropylene film.

Compared to other types of capacitors for PCB, film capacitor owns its unique features and advantages.

Features and advantages of film capacitor
Self-healing	When a fault inside the capacitor causes a leakage current, the electrode material near the local fault in the capacitor dielectric is thin enough to vaporize, thus eliminating the fault at the cost of losing some capacity.
Temperature stability	The stability of the film capacitor is good, and the temperature generally has little effect on the capacity of the capacitor.
High insulation resistance	Compared with other capacitors, the insulation resistance of film capacitors is not easy to decrease even if the temperature increases, thus maintaining the performance.
Non-polarity	Film capacitors are non-polar, which means that you do not need to distinguish between positive and negative terminals when using them. Film capacitors can be used not only in direct current circuits, but also in AC circuits.

Film capacitors are widely used in computer, digital camera, audio and other electronic products, and can be used as filters, oscillators, and couplers. Meanwhile, this type of capacitor is also applied in solar panels, lithium batteries and other fields to assist in circuit stability and energy storage.

Mica capacitor

The structure of a mica capacitor usually includes a mica sheet as a dielectric, and a metal foil or metal film as an electrode. The electrode can be a metal foil directly attached to the mica sheet, or a metal film electrode formed by spraying a metal layer on the mica sheet. The manufacturing process of mica capacitors usually involves layering mica sheets and electrodes, and then fixing the structure by die casting or sealing in epoxy resin.

Mica has a low dielectric loss, which means that in high-frequency applications, mica capacitors are able to efficiently store and release electrical energy, reducing energy loss.

Furthermore, the excellent insulation properties of mica make it possible for mica capacitors to withstand higher voltages without breakdown. And the thermal stability of mica is also good, so the capacitance value of mica capacitors changes little at different temperatures, and it is suitable for use in environments with large temperature changes.

Due to the high dielectric constant of mica, mica capacitors show good performance in high frequency circuits and can effectively filter out high frequency noise.

Mica capacitors are often used in electronic instruments that require high capacitance stability and reliability, such as oscilloscopes and signal generators.

Safety capacitance

Safety capacitor is a specially designed capacitor that is mainly used to limit current and protect circuits. When the voltage in the circuit exceeds a certain value, the safety capacitor will quickly release the charge, thereby preventing the current in the circuit from being too large, protecting the circuit and equipment from damage.

The safety capacitor can filter the high frequency noise on the power line and improve the stability and reliability of the circuit. However, in order to improve the insulation and voltage resistance of the safety capacitor, its size is relatively large compared with some ordinary capacitors. And due to the need to meet strict standards in design and manufacture, they are more expensive than ordinary capacitors.

Safety capacitors are also widely used in various electronic devices, such as power adapters, power input terminals of electronic devices, home appliances, office equipment and so on, to ensure the safety and reliability of daily-used equipment.

How to choose the best among all types of capacitors for PCB

Choosing the best capacitor type on a PCB requires a combination of factors such as capacitor type, operating voltage and current, frequency response, temperature endurance, size, stability, cost, etc.

Firstly, if you are finding a capacitor for general electronic equipment, then

electrolytic capacitors may be the best choice, for it has higher capacitance and lower cost, suitable for normal electronic devices.

Secondly, if you want to choose a capacitor used for circuits that require high frequency response and stability, such as audio amplifiers, RF circuits, tantalum capacitor and MLCC can be your first choice. And MLCC with smaller size and higher capacitance are suitable for high-density circuit boards.

Thirdly, for low frequency circuits, electrolytic or film capacitors can be selected. Under the premise of meeting the circuit requirements, consider the cost of capacitors. Choose cost-effective capacitors to reduce the overall cost of the product.

The End

All types of capacitors for PCB have their own advantages and disadvantages. The selection of suitable capacitors requires comprehensive consideration of factors like capacitance, characteristics, cost, etc.