Aging phenomenon is explained by spontaneous polarization movement of Ferrodielectric. The direction of spontaneous polarization( Ps) arranged into same direction each boundary of domain that is composed with BaTiO3 Ceramic. Relative Permittivity (Relative dielectric constant) of total grain is average of random direction of crystal axis.
Different domain wall has the different direction of spontaneous polarization can be easily changed by AC voltage and it is reason to make high dielectric constant. As a result, capacitance become higher than it at stable stage. (b)
And the increasing of 90 degree domain as the decreasing of strain is the cause to decrease the dielectric constant according to time It is called as aging phenomenon. (c)
(b) This is domain stage after 1~2 minutes from soldering. In this stage, direction of spontaneous polarization can easily be changed as AC voltage. Therefore capacitance is higher than it at (c) stage.
(c) This is domain stage after aging forward stable stage. In this stage, direction of spontaneous polarization can’t easily be changed as AC voltage. Therefore capacitance is lower than it at (b) stage.
Ceramic capacitor is BaTiO3 powder product, which has piezoelectric characteristic. Piezoelectric material product, in general, has dipoles that make easy their arrangement with the change in temperature and time, resulting in inherent “aging” characteristic. This ‘aging’ characteristic makes critical influence on the capacitance value because capacitance value is determined by the arrangement status of dipoles in ceramic powder. BaTiO3 powder has curie point at a pproximately 125℃. The Curie Temperature of BaTiO3 is critical temperature that accompanies the change from a tetragonal to a cubic crystal habit, and spontaneous polarization no longer occurs. On cooling through and below the Curie point, the material again transforms from a cubic to a tetragonal crystal configuration, giving rise to a permanent electric dipole. This results in the change in the capacitance value
There is instable aging phase at initial stage after soldering but chip will be more stable according to time. Therefore, capacitance can not be exactly measured because of material Instability at initial stage after soldering.
– All MLCC of Samsung do according to EIA standard.
– Therefore, we sort all chips as standard of capacitance value at 1,000hours after heat treatment considering capacitance aging.