Piezo-electric phenomenon

Safety Application Guide for Multilayer Ceramic Chip Capacitors

Design

Electrical factors

Some capacitors (Class 2) show piezo-electric phenomenon which transforms electric energy into machine energy, and vice versa.

(1) Effect of size of capacitor
When a signal of a certain specific frequency is applied to a capacitor, the capacitor resonates at the character frequency decided by the size of capacitor, and may generate a noise.
(2) Effect of mechanical shock
When a mechanical vibration or shock is applied to a capacitor, the mechanical energy is changed into an electrical signal and the capacitor may generate a noise. (Caution is particularly required for use near an amplifier part.)
As a practical measure, changing the dielectric material used in a capacitor to a low loss material not subject to the piezo-electric phenomenon is effective. Changing to the temperature compensating capacitor (Class 1) is also effective.
(3) Effect to the performance and reliability
Although the phenomenon may cause no problem on the component performance and reliability, the roar of the capacitor may worry some users。
Since this may result in generating of a noise, confirm generating of a noise in actual equipment operation.

　As a practical measure, it is effective to replace the capacitor with one whose structure,size and characteristics differ from those as shown above Climatic factors and Electrical factors. It is effective to change the dielectric material of the capacitor to a low loss material which is not affected by the piezo-electric phenomenon, or changing to a Class 1 capacitor.
As for other methods, in order to suppress resonance with the steel case of a printed circuit board, changing the mounting direction of the capacitor or affixing the capacitor to the steel case of the printed circuit board with adhesives may also be effective.

Safety Application Guide for Multilayer Ceramic Chip Capacitors All Lists