The wide usage of conventional ceramic capacitors brings acoustic noise issues to power system designs. However, there are solutions that approach the problem from different angles: changing the electronic.
Why do multilayer ceramic capacitors have acoustic noise?
The ferroelectrics used in multilayer ceramic capacitors always have piezoelectric properties. When an electric field is applied, deflection occurs and the chip expands and contracts, so acoustic noise is produced. As "sound" is the problem, the "sound pressure level" becomes the primary measurement.
Abstract: Multilayer ceramic capacitors (MLCC) are present in every electronic device. Unfortunately, due to the dielectric material they are made of, they vibrate in the presence of an electric field. This vibration is transferred to the PCB via the solder joint creating the acoustic noise known as “singing” capacitor phenomenon.
The wide usage of conventional ceramic capacitors brings acoustic noise issues to power system designs. However, there are solutions that approach the problem from different angles: changing the electronic characteristics of the MLCC itself, or minimizing its interaction with the PCB.
What type of capacitor should I use for acoustic noise?
Some applications can use electrolyte or tantalum-type capacitors, preferably thru-hole types when acoustic noise is problematic. But for applications that are more cost-sensitive or size-constrained (such as personal electronic devices), you cannot avoid thin, small ceramic capacitors, and the need to reduce noise immediately becomes critical.
How can MLCC capacitors reduce noise?
Fewer capacitors can then be used to get the same capacitance as several MLCCs placed in parallel for example. There are various ways to reduce the audible noise generated by MLCC capacitors. Working on the PCB layout, the PCB board specification or the capacitor selection will help reducing the SPL level, without eliminating it.
Why do capacitors make noise?
This is because a capacitor functions as the simplest noise filter by blocking DC current while allowing noise to pass. However, since there are many types of capacitors with different properties (frequency-impedance characteristics, etc.), if they are used in the wrong way, they can actually end up increasing noise.