Piezoelectric Buzzer Technology
Structure, Chemical Composition and Working Principle
Piezoelectric buzzer is a compact, energy efficient sound producing device, which is an assembly of a vibration mechanism attached to a piezoelectric ceramic plate with two electrodes on both sides. When AC electricity of a given frequency is applied to the electrodes, an audible vibrating sound with the same frequency is produced by the assembly. The materials used to manufacture the buzzer plates are derivatives of lead zirconium-titanate (PZT) with a general chemical formula: Pd x Sry (MZr. NTi)z0n + Nba0b.
a) Preparation of powder material
The proper starting ingredients are mixed thoroughly, ground and made into small cakes, which are then heated in a high temperature furnace. The following main reaction takes place:
PbTiOn + PbO + ZrOm- ------------------ > Pb(MZr, N Ti)Om The heated cakes are then further finely ground into a powder form.
The powder thus obtained is mixed with PEG binder and pressed into a thin film, from which the product blanks with desired shapes are prepared.
c) Binder removal and sintering
The product blanks are then heated to remove the binder and then sintered to give piezoelectric ceramic plates.
d) Polarization and testing
Both sides of the ceramic plate are then coated with silver electrodes, which are further strengthened through a polarization process. The resonance resistance of the piezoelectric ceramic plates thus obtained should be below 4.8 ohms.
e) Buzzer assembling and QC
The piezoelectric ceramic plates are then attached to the vibration mechanisms with epoxy resin to give the buzzers. The product QC of the buzzers obtained through the above sophisticated manufacturing process is carried out with special instruments. The major electroacoustic parameter, Kp, should be better than 60%