JP2007208564A - Method of manufacturing piezoelectric vibrator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable a piezoelectric vibrator to be encapsulated in a state in which its CI value is kept low even when the piezoelectric vibrator is made to be a small piece. <P>SOLUTION: When a piezoelectric vibrator manufacturing method encapsulates a piezoelectric vibrator in a hermetically sealed case, the inner pressure of the case is raised up to the pressure higher than normal pressures by 0.3 MPa once using helium gas in a process of filling the case with a hermetically sealed atmosphere, and then the case is hermetically sealed up when its inner pressure is kept at a pressure slightly higher or 0.02 MPa or so higher than normal pressures in a process of returning the inner pressure of the case to normal pressures. Accordingly, the problem can be solved by the piezoelectric vibrator manufacturing method characterized by the fact that a CI value is set lower than the normal pressures. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to a method of manufacturing a piezoelectric vibrator that can keep the CI value of the piezoelectric vibrator low.

  Conventionally, a quartz plate is housed in an airtight container, and the lid is joined by melting a soldering material such as solder, or recently, the electron beam or laser beam is applied to the joint between the airtight container and the lid. The crystal unit is manufactured by sealing the container containing the crystal unit by fusing with heat.

  On the other hand, the outer dimensions of the container of the piezoelectric vibrator are currently extremely miniaturized and reduced in height due to the downsizing of the electronic equipment to be mounted. Here, examples of electronic devices include mobile phones and mobile terminals, and these electronic devices are becoming smaller and lighter every day.

Here, there exists a thing shown in patent document 1 about sealing by gas sealing with an airtight container. The manufacturing flow is shown in FIG. In addition, there is a manufacturing method of Patent Document 2 that the applicant presents, but in this case, there is an example in which sealing is performed with an extremely low internal pressure of the container.
JP 2002-16165 A JP 2004-153645 A

  As described in the prior art, in order to cope with the downsizing of electronic devices on which piezoelectric parts are mounted, especially for piezoelectric vibrators, the external dimensions and the mounting area occupied on the mounting board are extremely small (small). There is a strong demand and demand for this, and of course, to accept the request, the outer dimensions of the container that houses the piezoelectric plate, including reducing the outer dimensions of the piezoelectric plate itself that is housed inside the piezoelectric vibrator. The current situation is that the dimensions must be reduced.

  However, considering a crystal pendulum, for example, a piezoelectric plate with electrodes arranged on a strip-shaped crystal base plate, the area of the main surface of the crystal unit becomes small, and when the crystal unit becomes smaller, the vibration of the crystal unit Since the vibration energy to be increased increases the area of the main surface of the crystal unit and the electrode disposed on the crystal unit, the CI value of the crystal unit is required by requiring energy necessary for starting the crystal unit. (Crystal Impedance) tends to increase, and contrary to achieving the demand for miniaturization, the problem arises that the oscillation of the crystal resonator is hindered.

  On the other hand, for example, in Patent Document 2 in which the internal pressure of the container is extremely reduced, the external atmosphere gas is taken into the container because the gas from the external atmosphere of the container is reduced from the normal pressure. The problem that the case where the problem of being produced arises is considered.

  In order to solve the above-described problems, the present invention provides a piezoelectric vibrator manufacturing method in which a piezoelectric vibrator is accommodated in a sealed container, and in the process of making the container a sealed atmosphere, helium gas is once discharged from atmospheric pressure to a pressure of 0. In the process of pressurizing to a high internal pressure up to 3 MPa and then returning to the normal pressure, the CI value is reduced from the normal pressure by hermetically sealing to about 0.02 MPa in a state where a little pressure is applied than the normal pressure. This is a method for manufacturing a piezoelectric vibrator.

  Specifically, in the process of making the container of the method for manufacturing a piezoelectric vibrator into a sealed atmosphere, the CI value of the piezoelectric vibrator is measured in a normal pressure atmosphere, the piezoelectric vibrator is put in a chamber atmosphere, and helium A step of measuring the CI value in an atmosphere in which the gas is pressurized to about 0.3 MPa, a step of measuring the CI value by returning to the atmospheric pressure again, and an internal pressure of about 0.02 MPa higher than the normal pressure by helium gas. This is a method for manufacturing a piezoelectric vibrator characterized by sealing in an airtight container atmosphere, and is filled with helium gas in a pressurized atmosphere.

Conventionally, after performing baking (thermal) treatment, sealing was performed in a nitrogen gas atmosphere. After performing baking treatment, the process of the present invention was performed, and helium gas was filled to perform sealing. Is what you do.
In the present invention, the CI value of the piezoelectric vibrator has been improved by experiment. With the above-described manufacturing method, the helium gas atmosphere is more effective in the sealed gas atmosphere than the conventional sealed container atmosphere in which nitrogen gas is sealed. This is considered to be easy to vibrate in the initial oscillation operation in which the crystal resonator vibrates.

  As described above, by improving the CI value of the piezoelectric vibrator according to the present invention, the product yield can be greatly improved. In particular, compared with the conventionally used vacuum atmosphere or nitrogen gas atmosphere sealing atmosphere. The CI value of the piezoelectric vibrator can be improved by 20 to 25% of the conventional value by the helium gas filling atmosphere which is the manufacturing method of the present invention.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. In each figure, the same numerals indicate the same objects. FIG. 1 is a diagram showing a part of the method for manufacturing a piezoelectric vibrator according to the present invention and a manufacturing flow after baking that is a feature of the present invention. A chamber or the like is used to create a sealed atmosphere (vacuum environment), and the piezoelectric vibrator is housed therein and baked. The baked (thermal) treated piezoelectric vibrator is filled with helium (He) gas from a vacuum atmosphere. Press. At this time, the atmospheric pressure is about 0.3 MPa (megapascal).

  Thereafter, the helium gas in the chamber is gradually reduced to an atmospheric pressure of about 0.02 MPa, and the piezoelectric vibrator is sealed in an atmosphere of helium gas (0.02 MPa pressure).

  FIG. 2 is a flowchart showing the CI value measurement in the method for manufacturing a piezoelectric vibrator of the present invention. The procedure of FIG. 2 will be explained. In order to measure the CI value of the piezoelectric vibrator, for example, in a measurement system configured by π circuit calibration, the piezoelectric vibrator is set in a measurement jig, and the CI value is measured in an atmospheric pressure atmosphere. Measure. Thereafter, the atmosphere of the piezoelectric vibrator is changed to helium gas, pressurized to about 0.3 MPa, and the CI value is measured again in this state. Again, the ambient pressure of the piezoelectric vibrator is returned to normal pressure, and the CI value is measured.

  In the measurement flow of FIG. 2, the inventor has verified the change in the CI value by measuring the CI value by 0.1 MPa in the course of gradually increasing the pressure from about 0.3 MPa. Finally, the sealed container that houses the piezoelectric vibrator is sealed in a state where the pressure is slightly reduced (about 0.02 MPa). The change of the CI value at this time is shown in FIG.

  FIG. 3 is a graph of the pressure value and the CI value that the inventor experimented to verify the present invention. FIG. 3A shows a change in the CI value when the container of the piezoelectric vibrator is filled with helium gas, and FIG. 3B shows a change in the CI value when the gas is filled with nitrogen gas. In addition, the vertical axis of the graph shows the CI value, and the horizontal axis shows the environmental atmospheric pressure of the piezoelectric vibrator, and the transition of the CI value due to the pressure is measured. As can be seen from the graph, the CI value changes when the ambient pressure around the piezoelectric vibrator is once lowered and increased. The goodness of the CI value difference between the nitrogen gas atmosphere and the helium gas atmosphere can also be seen from the graph.

It is a flowchart of this invention. It is a flowchart which shows one Example which measures CI value. It is a graph which shows the change of CI value which it experimented and verified by this invention. It is a conventional flowchart.

Claims (3)

In a method for manufacturing a piezoelectric vibrator that houses a piezoelectric vibrator in a sealed container,
In the process of making the container hermetically sealed, the CI value of the piezoelectric vibrator is measured at least in a reduced-pressure atmosphere lower than normal pressure, and the container is sealed with the air-tight container atmosphere having a container internal pressure about 0.02 MPa higher than the normal pressure. A method of manufacturing a piezoelectric vibrator. In a method for manufacturing a piezoelectric vibrator that houses a piezoelectric vibrator in a sealed container,
Measuring the CI value of the piezoelectric vibrator in a normal pressure atmosphere in the process of putting the container in a sealed atmosphere; placing the piezoelectric vibrator in a chamber atmosphere; and increasing the helium gas to about 0.3 MPa with respect to the normal pressure A step of measuring the CI value in a pressurized atmosphere, a step of measuring the CI value by returning to the atmospheric pressure again, and an airtight container atmosphere in which the helium gas is about 0.02 MPa higher than the normal pressure in the airtight container atmosphere. A method of manufacturing a piezoelectric vibrator characterized by a sealing step. 3. The method of manufacturing a piezoelectric vibrator according to claim 1, wherein the helium gas injection according to claim 1 is filled at the time of pressurization.

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