SMD ceramic capacitors are very small or tiny size capacitors, perfect to be soldered directly to a surface mount PCB.
This type of capacitors are also called Multilayer Chip Capacitors which consist of a large number of individual capacitors stacked on top of each other, connected in parallel but these are smaller in size than the Multilayer ceramic capacitors used in through hole assemblies.
Regarding its classification according to the behavior of the capacity with the temperature, it obeys the same criteria as the capacitors for through-hole pcb. They would be the following:
- Class 1 ceramics: Capacitors offer high stability and low losses for resonant circuit applications. Ex: NP0, C0G, P100, N75, N100,… N1500. In NP0 (NPO sometimes so called in Europe) the temperature characteristic is approximately 0. But there are also those with negative temperature coefficients like all N100, N75, etc. For example, an N1500 will have a deviation of −1500 ppm / ºK. Often times these with negative temperature coefficients are used to compensate for the effects of temperature in a circuit, where there are other components with positive temperature coefficients. P100 would be a class 1 capacitor where the deviation is +100 ppm / ºK
- Class 2 ceramics - Offer high volume efficiency for damping, bypass and coupling applications. Ex: X5R, X7R. It used to be called a low-frequency ceramic capacitor (Low-frequency ceramic capacitor), which refers to the ferroelectric ceramic as the dielectric capacitor, so it is also called a ferroelectric ceramic capacitor. This type of capacitor has a large specific capacity, a non-linear change in capacity with temperature, and a large loss.
- Class 3 ceramics: These have a very high permittivity, up to 50,000, and therefore better volumetric efficiency than Class 2 capacitors. However, these capacitors have poorer electrical characteristics, including lower accuracy and stability. The dielectric is characterized by a very high non-linear capacitance change over the temperature range. The capacitance value also depends on the applied voltage. In addition, they have very high losses and age over time. Ex: Y5V, Z5U