PURPOSE: To erase the career due to heat at the post processes in advance, to reduce the frequency variation and the dispersion of resonant frequency, by heating the piezoelectric ceramic resonator at Curie point or less in advance.

CONSTITUTION: When the test piece after polarization and slice process is heated for 1hr at 150°C which is the highest temperature condition of the mold process in the post processes, the frequency variation due to the heat given in the processes is reduced to about 60%, and the dispersion due to distribution and calcined lot is reduced to about 40%. Further the yield rate of the resonant frequency is increased to 22∼61%.