The temperature characteristics of MLCC are determined by EIA standards and JIS standards. The classification table, as shown in the figure above, 5U/Y5V and Z5U/Z5V have also been changed to the second category. In fact, many scenes are no longer used. Therefore, general-purpose MLCCs can be roughly divided into two types: Type I (low permittivity series, paraelectric) and Type II (high permittivity series, ferroelectric).

One type is temperature-compensated NP0 dielectric. This capacitor has the most stable electrical performance and basically does not change with temperature, voltage, and time. It is an ultra-stable, low-loss capacitor material type and is suitable for high stability and reliability requirements. In high frequency, UHF, and VHF circuits.

 

 

The second category includes X5R, X8R, X6S, Y5V, etc. The main material is barium titanate, but the added precious metals are different. X7R dielectric Since X7R is a ferroelectric, capacitors with a larger capacity than NPO dielectrics can be manufactured. The performance of this kind of capacitor is relatively stable. With the change of temperature and voltage time, its unique performance changes are not significant. It is a type of stable capacitor material. It is used in direct isolation, coupling, bypass, filter circuit and high reliability requirements. Frequency circuit. Y5V dielectric capacitors have a high dielectric constant, and are often used to produce large-capacity capacitors with larger specific capacitance and higher nominal capacitance. However, its capacity stability is worse than that of X7R, and its capacity and loss are more sensitive to test conditions such as temperature and voltage. It is mainly used in the oscillation, coupling, filtering and bypass circuits of electronic complete machines.

 

Commonly used specifications of MLCC are C0G (NP0), X7R, Z5U, Y5V, etc. Different specifications have different characteristics and uses.

C0G capacitors have high temperature compensation characteristics, suitable for bypass capacitors and coupling capacitors

X7R capacitors are temperature-stable ceramic capacitors, suitable for low-demand industrial applications

Z5U capacitors are characterized by small size and low cost, especially suitable for decoupling circuits

Y5V capacitor has the worst temperature characteristics, but has a large capacity and can replace low-capacity aluminum electrolytic capacitors

The main difference between C0G, X7R, Z5U and Y5V is their different filling media. In the same volume, the capacity of the capacitor composed of different filling medium is different, and the dielectric loss and capacity stability of the capacitor are also different. Therefore, when using the capacitor, it should be based on the different function of the capacitor in the circuit. Choose different capacitors.

C0G (NP0) capacitor

C0G is one of the most commonly used MLCCs with temperature compensation characteristics. Its filling medium is composed of rubidium, samarium and some other rare oxides. C0G has the most stable capacitance and dielectric loss, and the widest operating temperature range. When the temperature is from -55°C to +125°C, the capacity change is 0±30ppm/°C, and the change in capacitance with frequency is less than ±0.3ΔC. The drift or hysteresis of the C0G capacitor is less than ±0.05%, which is negligible relative to film capacitors greater than ±2%. The variation of its typical capacity relative to the service life is less than ±0.1%.

C0G capacitors have different characteristics of capacitance and dielectric loss with frequency depending on the packaging form, and the frequency characteristics of the large package size are better than the frequency characteristics of the small package size. COG capacitors are suitable for bypass capacitors of oscillators and resonators, as well as coupling capacitors in high-frequency circuits.

It is a 1206 package, C0G temperature characteristic, 25V withstand voltage, 0.22μF capacitor capacitance value versus temperature curve. In the temperature range required by all specifications, the minimum value of the capacitor is 0.21996μF and the maximum value is 0.22016μF. The error is very small.

 

X7R capacitor

X7R capacitors are called temperature-stable ceramic capacitors. The temperature characteristic of X7R capacitor is inferior to C0G. When the temperature is between -55℃ and +125℃, its capacity change is 15%. It should be noted that the change of capacitor capacity is nonlinear at this time.

The capacity of X7R capacitors is also different under different voltage and frequency conditions. It changes with time, about 1% ΔC every 10 years, which represents a change of about 5% in 10 years.

X7R capacitors are mainly used in low-demand industrial applications, and their capacity changes within an acceptable range when the voltage changes. The main feature of X7R is that the capacitance can be made relatively large under the same volume.

X5R and X7R are mainly used because the upper limit temperature is not so high.

It is a 1206 package, X7R temperature characteristic, 25V withstand voltage, 0.22μF capacitor capacitance value versus temperature curve. In the temperature range required by all specifications, the minimum value of the capacitor is 0.204μF and the maximum value is 0.224μF. The error is an order of magnitude larger than C0G, but the temperature characteristics are still very good.

Z5U capacitor

Z5U capacitors are called "universal" ceramic monolithic capacitors. It should be noted here that the operating temperature range of Z5U is between +10°C and +85°C, the capacity change is +22% to -56%, and the maximum dielectric loss is 4%. The main feature of Z5U capacitor is its small size and low cost. For the above two MLCCs under the same volume, the Z5U capacitor has the largest capacitance, but its capacitance is greatly affected by the environment and working conditions, and its aging rate is also the largest, which can drop by 5% every 10 years .

Although its capacity is unstable, due to its small size, low equivalent series inductance (ESL) and equivalent series resistance (ESR), and good frequency response, it has a wide range of applications, especially in decoupling Application in the circuit.

The corresponding selection specifications can not be found on the official websites of some manufacturers. The figure below shows the comparison curves of temperature characteristics of NP0, X7R, Y5V, and Z5U.

 

Y5V capacitor

Y5V capacitor is a general-purpose capacitor with a certain temperature limit, and the maximum dielectric loss of Y5V is 5%. Y5V capacitors have poor temperature stability. Temperature changes will cause large changes in capacitance. It must be considered in the design. The capacitance changes from -30°C to 85°C can reach +22% to -82%, Y5V Will gradually be replaced by X7R and X5R with good temperature characteristics. The corresponding selection specifications can not be found on the official websites of some manufacturers. The figure below shows the measured data of netizens.

 

The temperature characteristics and reliability of C0G, X7R, Z5U, and Y5V decrease successively, and the cost is successively reduced. In the selection, if the requirements for working temperature and temperature coefficient are very low, you can consider using Y5V, but X7R is generally used, and C0G must be selected when the requirements are higher. In general, MLCCs are designed to maximize the capacitance of capacitors made of X7R and Y5V at room temperature. The change trajectory of the capacitance relative to the temperature is a parabola with an opening downward. As the temperature rises or falls, the capacitance decreases.

In addition, the dielectric constants of the C0G, X7R, Z5U, and Y5V media also decrease sequentially. Therefore, the maximum capacity that can be made under the same size and withstand voltage is also decreased sequentially. In practical applications, the development and design engineers of many companies use theoretical calculations and do not understand the actual production status of MLCC manufacturers. They often list some specifications that are rarely produced or even non-existent. This will not only increase the procurement cost but also affect the delivery time. For example, I want to use 0603/C0G/25V/3300pF capacitors, but 0603/C0G/25V MLCCs generally only achieve 1000pF.

What happens to the picture MLCC with temperature?

The temperature characteristics of C0G and NP0 Class 1 ceramic capacitors did not show significant changes in capacitance and temperature.

Generally, heat will reduce the capacitance value of Type 2 capacitors, but near the Curie point (BaTiO3 is about 120°C), the capacitance value will increase. This is because as the crystal structure of the ceramic changes from tetragonal to cubic, the dielectric constant increases accordingly.

EIA and JIS standards stipulate that in the operating temperature range, the change in capacitance will not exceed the specified tolerance. The chemical composition of ceramics is not included in the standard. Capacitor manufacturers will use different additives in the dielectric to change the performance of the capacitor. These additives can make the Curie point closer to room temperature (such as Z5U) or make the dielectric constant curve (such as X7R) smoother. The former has the highest unbiased dielectric constant, while the latter reduces the maximum dielectric constant to achieve higher temperature stability.