The future development of monolithic ceramic capacitors
With the silence of electronic products, laptops, mobile phones, digital cameras, ultra-thin TV sets, etc., in a variety of application power circuits, the original "uncle" caused by capacitor vibration It has become one of the important design topics. In order to solve this whistling problem, Murata introduces small capacitors with metal terminals and commercialized mobile devices and audio-visual equipment.
Monolithic ceramic capacitors produce the principle of howling
Due to the electrostrictive effect of the ferroelectric ceramic (also known as the piezoelectric effect), the monolithic capacitor expands and contracts in the stacking direction when an alternating voltage is applied. This is based on the fact that the Poisson's ratio of the dielectric is generally 0.3, and the direction perpendicular to the stacking direction, that is, the direction parallel to the board, also causes expansion and contraction, and as a result, the surface of the equivalent board generates vibration and can hear sound. Because the acoustic impedance of a single capacitor and air is different, only sound is not heard at all, but if the capacitor is mounted on a circuit board, the circuit board vibrates as an impedance transformer, and the vibration frequency is in the human audible frequency range (20 Hz~ A sound of "吱" will occur within 20 kHz). Although the amplitude of the patch and the board is only about 1 pm to 1 nm, the vibration sound is large enough that the human ear can easily distinguish it.
As a measure against the howling of the capacitor caused by the vibration of the board, a material having a relatively low dielectric constant is used, and a product in which the amount of deformation of the capacitor is reduced and the howling is suppressed is commercialized. Another method of countermeasures for howling is to use a terminal plate or the like to mount a capacitor on a circuit board to suppress vibration from being transmitted to the circuit board. Murata's method of reducing howling is to install metal terminals on the external electrodes of the capacitors and develop capacitor products with metal terminals.
Future prospects
In addition to solving the howling problem, metal terminal ceramic capacitors may also solve the problem on the capacitor chip. For example, monolithic ceramic capacitors cause cracks in the ceramic due to the bending stress of the circuit board. As a result, a short-circuit fault may occur. Since the metal terminal can be used to allow the chip capacitor to be overhead on the circuit board, the bending resistance of the circuit board is greatly improved. Improvements to ensure high reliability. In the future, Murata will focus on smaller and larger-capacity products. While expanding its product lineup, it will also provide customers with more solutions such as advantageous metal terminal capacitors to assist customers in designing.