MLCC (multilayer ceramic capacitor) is the most important and most used passive chip (chip) component in electronic machines. So what is MLCC and what characteristics does it have?
1. What is Multilayer Ceramic Capacitor
Multilayer ceramic capacitors are the most widely used type of chip components. They are also called chip monolithic capacitors. Their basic structure consists of stacking multiple layers of ceramic sheets and metal electrodes. The ceramic layer serves as a dielectric to store energy, and the metal electrodes are to connect the circuit.
MLCC has the characteristics of small size, high capacity density, low resistance, excellent high-frequency performance and stability. It can be mounted on printed circuit boards (PCB) and hybrid integrated circuit (HIC) substrates, effectively shrinking electronic information terminal products. (especially portable products), improve product reliability
MLCC can store charges, block DC, filter, combine, distinguish different frequencies, and tune circuits in electronic circuits.
It can partially replace organic film capacitors and electrolytic capacitors in high-frequency switching power supplies, computer network power supplies and mobile communication equipment, and greatly improve the filtering performance and anti-interference performance of high-frequency switching power supplies.
In order to comply with the development direction of miniaturization, lightweight, high performance and multi-function in the IT industry, new components such as surface mount components are the focus of the development of the electronics industry. It not only has simple packaging and good sealing performance, but also can effectively isolate opposite electrodes.
1) Miniaturization
For electronic products such as camcorders and mobile phones, more compact MLCC products are needed. On the other hand, due to advances in precision printed electrodes and lamination processes, ultra-small MLCC products have gradually become available and applied.
2) Low cost - base metal internal electrode MLCC
Traditional MLCCs use expensive palladium electrodes or palladium-silver alloy electrodes, and 70% of their manufacturing costs are accounted for by electrode materials. The new generation of MLCCs, including high-voltage MLCCs, use cheap base metal materials nickel and copper as electrodes, which greatly reduces the cost of MLCCs.
However, the base metal internal electrode MLCC needs to be sintered under a low oxygen partial pressure to ensure the conductivity of the electrode material. Too low an oxygen partial pressure will bring about the semiconducting tendency of the dielectric ceramic material, which is not conducive to the insulation and insulation of the component. reliability
Murata has developed several anti-reduction porcelain materials, which are sintered in a reducing atmosphere. The reliability of the capacitors made is comparable to the original capacitors using precious metal electrodes. Such capacitors quickly entered the market as soon as they were released. At present, the sales volume of base metal Y5V group capacitors has accounted for about half of the MLCCs in this group. In addition, we are seeking to expand the application of base metal electrodes in other groups of capacitors.
3) Large capacity and high frequency
On the one hand, with the low-voltage drive and low power consumption of semiconductor devices, the operating voltage of integrated circuits has been reduced from 5V to 3V and 1.5V; on the other hand, the miniaturization of power supplies requires small, large-capacity products to replace large aluminum electrolytic capacitors. . In order to meet the development and application of this type of low-voltage and large-capacity MLCC, in terms of materials, relaxation-type high-dielectric materials with a relative dielectric constant 1 to 2 times higher than BaTiO3 have been developed.
In the process of developing new products, three key technologies have been developed at the same time, namely, the technology for producing ultra-thin green sheet powder and dispersion, the technology for improving the film formation of green sheets, and the technology for matching the shrinkage rates of internal electrodes and ceramic green sheets.
Japan's Panasonic Electronic Components Company has successfully developed a large-capacity MLCC with a maximum capacitance of 100μF and a maximum withstand voltage of 25V. This product can be used in the power supply line of liquid crystal displays (LCDs).
The rapid development of communication products places higher and higher frequency requirements on components. The high-frequency characteristics of the Cer-F series launched by Vishay are comparable to those of film capacitors, and can replace film capacitors in some high-frequency applications.
2. Classification of multilayer ceramic capacitors
1) According to their material classification, multilayer ceramic capacitors include:
Standard ceramic capacitors:
Based on barium magnesium titanate (BaTi03), it has a high dielectric constant and good temperature stability. Standard ceramic capacitors are widely used in consumer electronics and industrial equipment
Ultra-low temperature ceramic capacitor:
Adding rare earth elements or other additives can significantly reduce the dielectric constant and temperature coefficient, improve the stability of capacitors in low-temperature environments, and is suitable for applications in high-end environments such as aerospace and aviation.
Ultra-high temperature ceramic capacitors:
Made of high-melting point materials, it can maintain stability in high-temperature environments and is suitable for electronic equipment in high-temperature environments such as automobile engines and power modules.
2) According to their structural classification, multilayer ceramic capacitors include:
X7R structure:
It has a certain dielectric constant, temperature coefficient and voltage stability and is the most commonly used structure. Suitable for most general application scenarios
X7R indicates that it works at -55~+125 degrees, with a deviation of plus or minus 15% within the entire temperature range.
X5R structure:
Compared with X7R, it has higher dielectric constant and larger temperature coefficient. Suitable for applications with large capacitance and high temperature environment stability requirements
X5R indicates that it works at -55~+85 degrees, with a deviation of plus or minus 15% within the entire temperature range.
X8R structure:
It has a low temperature coefficient and good high-temperature stability, and is suitable for circuit design in high-temperature environments.
3) Capacity classification
Multilayer ceramic capacitors have a wide range of capacitances. Selecting the appropriate capacitance according to specific application requirements is an important factor in ensuring stable circuit performance.
3. Characteristics of multilayer ceramic capacitors
MLCC has the following important characteristics:
1) High capacity density
The high capacity density of MLCC allows more energy to be stored in a limited space to meet the needs of the circuit, which is very important for applications with sensitive volume requirements.
3) Low resistance
Multilayer ceramic capacitors have low ESR (Equivalent Series Resistance), giving them good current response capabilities under high-frequency conditions. This makes it suitable for circuit designs requiring high frequency stability and low noise
4) High frequency performance
Multilayer ceramic capacitors have excellent high-frequency performance and can maintain stable capacitance values and low losses under high-frequency conditions. This makes it widely used in high-frequency applications such as wireless communications and video circuits.
4) Temperature stability
The temperature coefficient of multilayer ceramic capacitors can be adjusted according to specific structures and materials to adapt to different environments and application requirements. This temperature stability ensures that the capacitor remains stable across temperatures, resulting in more reliable performance
2. Application fields of multilayer ceramic capacitors
Multilayer ceramic capacitors are widely used in various electronic equipment and circuits. Some common application fields are as follows:
1) Communication field
Multilayer ceramic capacitors are used in circuits such as radio frequency receivers and power amplifiers in consumer electronics such as mobile phones and tablet computers to provide stable high-frequency performance
The development of 5G communication technology has put forward higher requirements for multilayer ceramic capacitors, requiring larger capacity and lower loss capacitors to support high-frequency transmission and low-noise signal processing.
2) Automotive electronics
Automotive electronic systems involve a large temperature range and vibration environment. The high temperature stability and reliability of multilayer ceramic capacitors make them important components in automotive electronics and are used in engine control, car audio, navigation systems, etc.
The popularity of new energy vehicles has also put forward higher requirements for multilayer ceramic capacitors, which require higher capacitance, lower ESR and better temperature stability to meet the high power needs of electric vehicles.
3) Industrial control and instrumentation
In industrial control systems and instrumentation, multilayer ceramic capacitors are used in filtering, noise reduction, rectification, terminal impedance matching and other applications. Stability and reliability are important factors to be considered in the design process.
The small size and high density of multilayer ceramic capacitors also make them suitable for space-constrained applications such as instrumentation
