Murata Manufacturing Co., Ltd.

Mikio Nakajima

Akio Ikeda

Yukio Yoshino

Kenichi Kotani

Keiichi Kami

Hiroshi Tomohiro

Naoki Fujii

Toru Kasanami

A manufacturing method for a ceramic oscillator capable of controlling the oscillation frequency with a high accuracy is disclosed. In this method, a mother substrate is polarized, electrodes in discrete ceramic oscillator units are formed, the mother substrate is cut into discrete ceramic oscillator units, an outer package is applied to each of the ceramic oscillators, and thus a ceramic oscillator as a finished product is achieved. Herein, the polarization processing for the mother substrate is executed by finishing the application of a high DC voltage, when the antiresonant frequency f of the mother substrate in a thickness vibration mode is measured while the voltage is applied to the mother substrate, and the antiresonant frequency f which is being measured has reached a target value of the antiresonant frequency of the mother substrate during polarization corresponding to a target oscillation frequency of the ceramic oscillator as a finished product.

Manufacturing method for ceramic oscillator

In a polarization method of the multi-layered piezoelectric body in which a plurality of piezoelectric layers and a plurality of internal electrodes are alternately laminated and adjacent piezoelectric layers are polarized in the thickness direction such that the polarized directions thereof are in opposite directions, a first polarization process in which an electric field in one direction is applied in the thickness direction to the multi-layered piezoelectric body and a polarization is uniformly performed in the thickness direction, and a secondary polarization process in which an electric field in the opposite direction is applied to the piezoelectric layers on both sides of one of the internal electrodes and the direction of polarization of only one of the piezoelectric layers on one side of the internal electrode is reversed are provided. The secondary polarization is performed in the range such that the remaining polarization degree Pr that exists after the secondary polarization in the piezoelectric layer in which the direction of polarization is reversed does not exceed the remaining polarization degree of Pr that exists after the first polarization.

Polarization method of a multi-layered piezoelectric body

A method of polarizing a piezoelectric body having a plurality of piezoelectric layers and internal electrodes which are alternately laminated, includes the steps of applying an electric field to the piezoelectric body to polarize the body uniformly in the thickness direction, applying electric field in the opposite directions to the piezoelectric layers on both sides of each internal electrode whereby the piezoelectric layer only on one side of the internal electrode is polarization-inverted. The polarization degree polarization is made uniform by the polarization-inversion.

Method of polarizing piezoelectric body

A piezoelectric device is essentially composed of a piezoelectric transducer and a light transmitting protector. The protector is made of heat resisting glass, heat resisting acrylic, transparent ceramics or the like. By exposing the piezoelectric device to a laser beam and thereby causing it to penetrate through the protector to the piezoelectric transducer and to partly cut the surface of the piezoelectric transducer, or to change the intensity of polarization, mechanical coupling coefficient or dielectric constant of the piezoelectric transducer, its vibration frequency and resonance characteristic can be adjusted. If an ultraviolet-ray setting agent is used as adhesive, it can be hardened by exposing the piezoelectric device to ultraviolet rays to thereby cause it penetrate through the protector.

Growing community of inventors

Toyama-ken, Japan

Mikio Nakajima