JP2009071570A - Device and method for inspecting airtightness in piezoelectric vibrator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device and method for inspecting the airtightness of a package with the use of a highly accurate and simple means in spite of the miniaturization of a package size. <P>SOLUTION: The device includes: a pressurization chamber 3 for pressurizing the piezoelectric vibrator 2 to be inspected; an implement 10 arranged inside the pressurization chamber 3 and having an oscillation circuit; a temperature sensor 11 for detecting temperature in the pressurization chamber 3; and a measuring instrument 14 for measuring the frequency of an oscillation frequency signal to be output from the oscillation circuit when the piezoelectric vibrator 2 is set in the implement 10. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a hermetic inspection apparatus and a hermetic inspection method for a piezoelectric vibrator, and more particularly to a piezoelectric vibrator capable of accurately and easily determining fine leak and gross leak of a package even when the package size is extremely small. The present invention relates to an airtight inspection device and an airtight inspection method.

Conventionally, a piezoelectric vibrator using a piezoelectric material such as quartz has been widely used as a constituent element of a piezoelectric oscillator in electronic devices such as various information / communication devices and consumer devices. In recent years, especially in portable information communication devices, the size of the devices has been reduced, and further downsizing and high reliability have been demanded for the piezoelectric vibrators used therein.
In the case of a crystal resonator, a piezoelectric resonator is made of a ceramic resonator or the like, and a quartz resonator element having electrodes formed on a quartz substrate is bonded and fixed to the inner bottom surface of the package. The structure is hermetically sealed with a lid as an inert atmosphere.
In the lid sealing process, which is the manufacturing process of such a crystal unit, if the lid fixing position shifts, a hole opens and the inside of the package communicates with the outside air, and the vibration conditions of the crystal resonator element change. In addition, the corrosion of the electrode formed on the crystal resonator element may be advanced and damaged by the outside air. Therefore, in the manufacturing process of the crystal resonator, a package airtightness inspection process is required after the package is sealed with the lid. In the present invention, an airtightness inspection apparatus and method in the case where the piezoelectric vibrator is a quartz crystal vibrator will be described below.

The airtightness inspection method for inspecting the airtightness in the crystal unit package includes the gross leak determination corresponding to the airtight inspection of large holes generated in the lid sealing process and the like, and the fine leak determination corresponding to the airtight inspection of small holes. There is.
In general, the gloss leak determination method that has been conventionally used is a determination method using bubbles. When a quartz crystal unit that has been hermetically sealed for a package to be inspected is submerged in hot water and the inside is expanded, if the hermetic sealing is not sufficient and a large hole is formed, the expanded internal air is large. Since bubbles leak from the holes, the gross leak is determined by visually confirming this.

  As another conventional example of gloss leak determination, there is a method of performing gloss leak determination by measuring a differential pressure between two spaces in a pressure chamber. In this determination method, an airtight pressurized chamber is partitioned into a first space and a second space, and a diaphragm is disposed at the boundary between the first space and the second space. Then, a normal crystal unit having no leakage is accommodated in the first space, and a crystal unit in which the package to be inspected is hermetically sealed is accommodated in the second space. Then, an equal atmospheric pressure is applied to the first space and the second space. As a result, if there is a large hole in the crystal resonator to be inspected, the air in the second space enters the package, and the air pressure in the second space decreases accordingly. By detecting such a differential pressure between the first space and the second space, it is possible to detect a gross leak due to a large hole in the crystal resonator to be inspected.

  As another conventional gloss leak determination method, there is a specific example using fluorinate, which is a fluorinated inert liquid having a low viscosity and a low surface tension and is odorless and transparent. When a crystal resonator in which a package to be inspected is hermetically sealed is placed in a predetermined container and filled with florinart, the florinert enters the inside of the package when there is a large hole in the crystal resonator. Since the invaded florinate acts to stop the vibration of the crystal unit, it is possible to determine the gross leak of the crystal unit by checking the oscillation characteristics by connecting the crystal unit immersed in the florin to the oscillation circuit. Become.

Here, a specific example of conventional fine leak determination will be described.
A commonly used fine leak determination method is a determination method using He (helium) gas. After placing the quartz resonator in which the hermetic sealing of the package to be inspected has been completed in the pressurizing chamber, when the He gas is sucked and pressurized for a predetermined time, the hermetic sealing is not sufficient and a small hole is generated. If so, He gas enters the interior of the package. Therefore, when this quartz crystal unit is accommodated in the chamber of the He gas detector and the inside of the chamber is evacuated, He gas is released from the quartz crystal unit, so that the fine leak can be detected by detecting the amount of released He gas. judge. He gas is the gas having the smallest molecular weight and is effective for fine leak determination corresponding to a small hole. In general, the fine leak determination is performed on a product that has been determined to be non-defective after the gloss leak determination.
An overview of the conventional gloss leak determination and fine leak determination methods described above is described in Patent Documents 1 to 3.
JP 2005-27089 A JP 2003-304134 A JP-A-8-237070 Japanese Patent Laid-Open No. 11-51802 Japanese Patent Laid-Open No. 11-108792

However, conventional airtightness inspection methods for quartz resonators have the following problems.
The gross leak judgment method using bubbles in which a crystal resonator element to be inspected is contained in a package and hermetically sealed is submerged in hot water is a judgment method for visually checking the bubbles. There was a problem of poor reliability. In addition, the method of performing gross leak determination by measuring the differential pressure between the two spaces in the chamber of the pressurizing chamber reduces the differential pressure generated in the two spaces as the size of the crystal resonator package decreases. However, it becomes difficult to detect this differential pressure, and there is a problem that it becomes impossible to cope with the further miniaturization of the crystal resonator that will be further advanced in the future.

In addition, the method for determining gross leak using florinate is a solution that has an adverse effect on the environment, and since it will be abolished in the future, the use of florinate for gross leak determination should be avoided to improve the environment. It is.
In addition, the fine leak determination method using He gas is a method in which a quartz resonator in which a package to be inspected has been hermetically sealed is placed in a pressurized chamber, and then He gas is sucked in for a predetermined time. It takes time to make a determination.
In addition, since the quartz resonator that has been pressurized with the He gas for a predetermined time is taken out of the pressurized chamber and accommodated in the chamber of the He gas detector, the amount of He gas that has entered the quartz resonator package is small. It is possible that it will be released, and an error may occur in the determination. When the size of the crystal resonator package is reduced, the amount of He gas that enters the crystal resonator package becomes minute, and thus this influence cannot be ignored. Therefore, it has been difficult to cope with the further miniaturization of crystal resonators that will progress further in the future.

Next, there is an airtight inspection method disclosed in Patent Document 4 and Patent Document 5 as a technique for solving the problems of the airtight inspection method of the conventional quartz resonator package as described above.
According to them, when a crystal resonator package to be inspected is pressurized, if a hole is formed in the package, pressure is applied to the crystal resonator element provided in the crystal resonator. Since the electrical characteristics of the crystal resonator element change when pressure is applied, the presence or absence of pressure change in the package is determined based on the crystal impedance value (hereinafter referred to as “CI value”) of the crystal resonator associated with the internal pressure change. By capturing it as a change, the package is airtightly inspected. Therefore, it is explained that a highly reliable inspection can be performed as compared with the conventional airtight inspection method by visual confirmation.
However, since the airtight inspection method disclosed in Patent Document 4 and Patent Document 5 determines whether the crystal resonator package is airtight by measuring a change in the CI value of the crystal resonator. For the measurement, a very expensive network analyzer is required, and the airtight inspection equipment becomes expensive, which is a problem.

Also, in these airtightness inspection methods, the CI value measurement of the crystal resonator is performed, but the amount of change in the CI value before and after the crystal resonator is pressed is small, and the measured value varies, so the fine leak determination with high accuracy. Is difficult.
In addition, when these airtightness inspection methods are performed by measuring the frequency of a crystal resonator, if the phase characteristics of the crystal resonator are measured in the vicinity of 0 deg, the amount of frequency change before and after the pressurization of the crystal resonator is small, and the measured value is also Because it varies, it is difficult to determine fine leak with high accuracy.
The present invention has been made to solve the above-described problems, and is highly accurate even when the package size of the crystal unit is further reduced. In addition, the airtightness of the crystal unit package can be improved by simple means. An object of the present invention is to provide an airtight inspection device and an airtight inspection method for a piezoelectric vibrator capable of performing inspection.

In order to achieve the above object, the present invention provides a hermetic inspection device for a piezoelectric vibrator that inspects the air tightness of a piezoelectric vibrator that houses a piezoelectric vibration element in a package, and pressurizes the piezoelectric vibrator to be inspected. A pressurization chamber, a jig provided in the pressurization chamber and having an oscillation circuit, and a measuring instrument for measuring the frequency of an oscillation frequency signal output from the oscillation circuit when the piezoelectric vibrator is set in the jig And so on.
According to the present invention as described above, the hermetic inspection of the piezoelectric vibrator of the ultra-small package can be performed, and the determination from the gross leak to the fine leak can be performed by a single hermetic inspection, thereby shortening the hermetic inspection time. Great effect on the top. Further, even in a normal size package, an airtight inspection without an undetectable region can be performed by using it together with a conventional He gas leak inspection method.
Further, according to the present invention, since the gross leak determination using florinate that adversely affects the environment is not required, it is possible to eliminate the florinate and improve the environmental problem. Further, the hermeticity inspection apparatus for a crystal resonator package according to the present invention can be configured to be overwhelmingly less expensive than the conventional airtightness inspection apparatus.

According to the present invention, the oscillation circuit constitutes a Colpitts type oscillation circuit.
According to the present invention, since the crystal resonator is oscillated by the Colpitts type oscillation circuit, if the crystal resonator package has a hole, the frequency fluctuation before and after the pressurization of the oscillation frequency of the crystal resonator is reduced. Large numerical values can be obtained, and a highly reliable airtight inspection can be performed.
The present invention further includes a constant current control circuit that controls the piezoelectric current flowing through the piezoelectric vibration element of the piezoelectric vibrator to be constant.
According to the present invention as described above, by controlling the piezoelectric current flowing through the piezoelectric vibration element of the piezoelectric vibrator to be inspected to be constant, the piezoelectric current fluctuates when pressurized and the oscillation frequency changes. This can be prevented and the measurement accuracy of the airtightness inspection can be improved.

Further, the present invention includes a temperature sensor that measures the temperature in the pressurizing chamber, and a circuit that performs temperature compensation of the piezoelectric vibration element based on the temperature detection result of the temperature sensor.
According to the present invention, the temperature in the pressurization chamber is detected by the temperature sensor, and the frequency temperature characteristic of the piezoelectric vibrator is compensated by the temperature compensation circuit based on the temperature detection result. Even if the temperature changes, the frequency of the oscillation frequency signal output from the oscillation circuit is kept at a constant value, so that the measurement accuracy of the hermetic inspection can be improved.
There is also a method of correcting the frequency measured on the software without using the temperature compensation circuit. When this method is used, switching of the temperature compensation system is facilitated when inspecting various types of crystal resonators having various frequencies and temperature characteristics.
In the present invention, the pressurized gas for pressurizing the inside of the pressurized chamber is helium gas.
According to the present invention as described above, helium (He) gas has the smallest molecular weight compared to other air gases, for example, 1/7 of the molecular weight of N2 (nitrogen) gas. In addition, the determination speed can be shortened and the determination accuracy can be improved.

The present invention also relates to an intake opening / closing valve provided in the intake passage of the pressurization chamber, an exhaust opening / closing valve provided in the exhaust passage of the pressurization chamber, and a valve control circuit for controlling the opening / closing operation of the intake opening / closing valve and the exhaust opening / closing valve. , Was prepared.
According to the present invention as described above, for example, after the pressurized gas is sucked into the pressurized chamber by the valve control circuit, the pressure is reduced due to the pressurized gas in the pressurized chamber leaking in the operation of the intake opening / closing valve. By performing intermittent control so that the valve is sometimes opened, the temperature increase of the intake valve is suppressed and the temperature change in the pressurizing chamber is suppressed, so that the measurement accuracy of the airtight inspection can be improved.
In the present invention, a sub-chamber for storing a predetermined amount of pressurized gas is provided in the intake passage of the pressurized chamber.
According to the present invention as described above, the amount of pressurized gas used can be saved by using the sub-chamber and setting the amount of pressurized gas sucked into the pressurized chamber to be a constant amount. In addition, when the pressurized gas is inhaled, the temperature in the pressurized chamber is lowered by the pressurized gas, but the temperature change in the pressurized chamber can be reduced by using the sub-chamber, and the measurement of the air tightness test is performed. The accuracy is improved.

The present invention also relates to an airtightness inspection method for a piezoelectric vibrator that inspects the airtightness of a piezoelectric vibrator in which a piezoelectric vibration element is housed in a package, wherein the piezoelectric vibrator to be inspected is oscillated by an oscillation method to cause piezoelectric vibration. A step of measuring the oscillation frequency of the child, a step of measuring the oscillation frequency of the piezoelectric vibrator by oscillating by an oscillation method in a state where the piezoelectric vibrator is pressurized, and an oscillation frequency and pressurization before the piezoelectric vibrator is pressurized Determining whether or not the hermeticity of the package of the piezoelectric vibration element is maintained based on a frequency difference from the later oscillation frequency.
According to the present invention, an airtight inspection can be performed even for a piezoelectric vibrator of a micro package, and a determination from a gross leak to a fine leak can be performed by a single airtight inspection. Great effect in shortening. Further, even in a normal size package, an airtight inspection without an undetectable region can be performed by using it together with a conventional He gas leak inspection method.

Hereinafter, the present invention will be described in detail based on the illustrated embodiments.
FIG. 1 is a diagram showing a configuration of a hermetic inspection apparatus for a crystal resonator package according to the present invention.
The airtight inspection apparatus 1 includes a pressurizing chamber 3 that accommodates and pressurizes a quartz crystal resonator 2 to be inspected, a gas cylinder 4 filled with He gas, and a flow restrictor that adjusts the flow rate of He gas discharged from the gas cylinder 4. The valve 5, the sub-chamber 6 that temporarily stores a certain amount of He gas released from the gas cylinder 4, the intake opening / closing valve 7 that opens and closes when the He gas is sucked into the pressurization chamber 3, and the pressurization chamber 3 is exhausted. An exhaust on-off valve 8 that opens and closes at the time, an intake on-off valve 7 and an on-off valve control circuit 9 that controls the opening and closing operation of the exhaust on-off valve 8 are provided. Further, a jig 10 provided in the pressurizing chamber 3 and having a Colpitts type oscillation circuit, a temperature sensor 11 for detecting the temperature in the pressurization chamber 3, and a Colpitts type oscillation circuit or crystal vibration via the jig 10. When the piezoelectric vibrator 2 is set to the constant current control circuit 13 and the jig 10 for supplying power to the child 2 and controlling the piezoelectric current flowing through the piezoelectric vibration element of the crystal vibrator 2 to be constant, the Colpitts type And a measuring instrument 14 for measuring the frequency of the oscillation frequency signal output from the oscillation circuit.

In the case of performing an inspection using the airtight inspection apparatus 1 of the present embodiment configured as described above, a crystal resonator 2 to be inspected is a jig provided with an oscillation circuit such as a Colpitts type in a pressurized chamber 3. Set to 10 and measure the oscillation frequency. Next, He gas is sucked into the pressurizing chamber 3 and pressurized, and the oscillation frequency immediately after pressurizing the crystal unit 2 and the oscillation frequency after pressurizing for a certain time are measured. Then, it is determined whether or not the oscillation frequency of the crystal unit 2 changes before and after the pressurization and the leak determination is performed. For example, if the frequency fluctuation is larger than a predetermined value immediately after the crystal unit 2 is pressurized, it is determined that the gross leak has a large amount of leak, and the frequency fluctuation more than the predetermined value occurs after pressing for a certain time. In this case, it is determined that the fine leak has a small leak amount.
Although not shown, the crystal resonator 2 includes a crystal resonator element in which an electrode is formed on a crystal substrate. When the crystal resonator is pressurized, a hole is opened in the package so that the internal crystal resonator element is added. When pressed, it has the property of changing its electrical characteristics, and this property is used to perform an airtight inspection. In other words, the present invention utilizes the change in the oscillation frequency of the crystal unit 2 and causes the crystal unit 2 to oscillate with an oscillation circuit such as a Colpitts type to change the oscillation frequency before and after pressurization of the crystal unit. The airtight inspection is performed by discriminating the above.

FIG. 2 is a diagram showing the phase characteristics of the crystal resonator.
FIG. 2 shows the phase characteristics before and after pressurizing the crystal unit 2 when a hole is formed in the package of the crystal unit 2.
As shown in FIG. 2, the phase characteristics greatly change in the vicinity of 60 deg to 80 deg when the quartz resonator 2 is pressurized when a hole is formed in the quartz resonator package.
Therefore, in this embodiment, a Colpitts type oscillation circuit in which the phase of the crystal unit 2 is 60 deg to 80 deg is provided in the jig 10 in which the crystal unit 2 is set.

As shown in FIG. 2, when the crystal resonator 2 has a phase characteristic in the vicinity of 70 deg, it is a region where the phase characteristic before and after pressing is large when the crystal resonator 2 is pressed. Therefore, if the crystal resonator 2 package has a hole, when the crystal resonator 2 is pressurized, the frequency fluctuation before and after the pressurization of the oscillation frequency of the oscillation circuit becomes a large value. In the conventional airtightness inspection methods shown in Patent Document 4 and Patent Document 5, the CI value of the crystal resonator is measured, but when the crystal resonator is pressurized, a hole is opened in the crystal resonator package. However, there was little change in the CI value before and after pressurization, and the measured values varied, so the reliability of the airtight inspection was a problem. In addition, when these airtightness inspection methods are performed by measuring the frequency of a crystal resonator, if the phase characteristics of the crystal resonator are measured in the vicinity of 0 deg, the amount of frequency change before and after the pressurization of the crystal resonator is small, and the measured value is also Because it varies, it is difficult to determine fine leak with high accuracy. On the other hand, in this embodiment, since the crystal unit 2 is oscillated by an oscillation circuit such as a Colpitts type, if a hole is opened in the package of the crystal unit 2, the oscillation frequency of the crystal unit 2 is increased. A large numerical value is obtained for frequency fluctuations before and after pressure, and a highly reliable airtight inspection can be performed.
Therefore, according to the airtightness inspection apparatus 1 of the present embodiment, the airtightness inspection of the piezoelectric vibrator of the ultra-small package can be performed, and the determination from the gross leak to the fine leak can be performed by one airtightness inspection. Inspection time can be shortened.

Further, even in a normal size package, an airtight inspection without an undetectable region can be performed by using it together with a conventional He gas leak inspection method.
Furthermore, since the airtightness inspection apparatus 1 according to this embodiment eliminates the need for gross leak determination using florinate that adversely affects the environment, it is possible to eliminate the florinate and improve environmental problems.
In this embodiment, He gas is used as a gas for pressurizing the crystal unit 2 set in the pressurizing chamber 3. Since the pressurized gas has high humidity when the atmosphere is used, it is desirable to use dry air such as He gas. He gas has the smallest molecular weight compared to other air gases, for example, the molecular weight of 1/7 of the molecular weight of N2 (nitrogen) gas, shortening the judgment speed and improving the judgment accuracy when judging fine leak Can be made.

Next, the function of each component which comprises the airtight inspection apparatus 1 of this embodiment is demonstrated.
From the gas cylinder 4 filled with He gas, He gas is discharged into the sub-chamber 6 via the flow restrictor 5, and a certain amount of He gas is stored in the sub-chamber 6. The flow restrictor 5 is for adjusting the flow rate to an appropriate level when the sub-chamber 6 is filled with He gas, and is fixed after the initial setting.
The sub-chamber 6 stores a minimum amount of He gas necessary for filling the pressurizing chamber 3 with a certain amount of He gas by opening and closing the intake on-off valve 7. When the pressurization chamber 3 is filled with He gas and pressurized, the atmosphere remaining in the pressurization chamber 3 needs to be exhausted. The He gas stored in the sub-chamber 6 and sucked in the pressurizing chamber 3 is sucked. Thus, in this embodiment, the amount of He gas used can be saved by making the amount of He gas sucked into the pressurizing chamber 3 constant using the sub-chamber 6. Further, when the He gas is inhaled, the temperature in the pressurization chamber 3 is lowered by the He gas. However, the temperature change in the pressurization chamber 3 can be reduced by using the sub-chamber 6, and the airtight inspection can be performed. Measurement accuracy can be improved.
The sub-chamber 6 is preferably provided in the airtightness inspection apparatus 1, but the sub-chamber 6 may not be provided, and air may be directly taken into the pressurizing chamber 3 from the gas cylinder 4 via the intake opening / closing valve 7.

The intake opening / closing valve 7 is an opening / closing valve that opens and closes when He gas stored in the sub-chamber 6 is sucked into the pressurizing chamber 3, and the opening / closing valve is generally constituted by an electromagnetic valve. Since the electromagnetic valve is likely to generate heat if it is left open to pressurize the pressurizing chamber 3, in this embodiment, after the He gas stored in the subchamber 6 is sucked into the pressurizing chamber 3, The intake on / off valve 7 was closed, and intermittent control was performed so that it was reopened only when the pressure decreased due to He gas leakage in the pressurizing chamber 3. Therefore, since the temperature rise of the intake valve 7 is suppressed and the temperature change in the pressurizing chamber 3 is suppressed, the measurement accuracy of the airtight inspection can be improved.
The pressurizing chamber 3 incorporates an oscillation circuit such as a Colpitts type as an oscillation circuit for oscillating the crystal resonator to be inspected, and accommodates the crystal resonator to be inspected and pressurizes it with He gas. The container. Then, by controlling the opening / closing operation of the intake opening / closing valve 7 and the exhaust opening / closing valve 8, the inside of the pressurizing chamber 3 is sucked or exhausted. The pressurization chamber 3 is desirably made as small as possible in order to minimize the internal temperature change during pressure increase / decrease, and the pressurization chamber 3 is made of a material having high thermal conductivity such as aluminum. To do. Thereby, the temperature change of the crystal resonator to be inspected is minimized, and the fluctuation of the oscillation frequency due to the temperature characteristics of the crystal resonator is suppressed.
The exhaust open / close valve 8 is an open / close valve that opens and closes when the atmosphere remaining in the pressurization chamber 3 is exhausted before pressurizing the pressurization chamber 3 with He gas, and is opened during exhaust. , Otherwise closed.
The on-off valve control circuit 9 is a circuit for controlling the opening / closing operation of the intake on-off valve 7 and the exhaust on-off valve 8, and controls the opening / closing of the electromagnetic valve at a predetermined timing.

  FIG. 3 is a diagram showing the control operation of the intake on / off valve and the exhaust on / off valve. As shown in FIG. 3, when He gas is sucked into the pressurizing chamber 3, both the intake on / off valve 7 and the exhaust on / off valve 8 are opened, and the time required for this is approximately 0.2 seconds. . Next, when pressurizing the pressurizing chamber 3 for a certain time, the intake opening / closing valve 7 is opened, and the exhaust opening / closing valve 8 is closed. Usually, in order to perform an airtight inspection with high accuracy, a pressurization time of about 1 to 5 minutes is required. Note that, as described above, the intake air on-off valve 7 during pressurization is intermittently controlled so as to be opened only when the pressure is reduced due to leakage of He gas in the pressurization chamber 3 or the like. Next, when the air in the pressurizing chamber 3 is exhausted, the intake on / off valve 7 is closed and the exhaust on / off valve 8 is opened. The time required for exhausting the atmosphere is approximately 0.2 seconds.

Next, an oscillation circuit that is built in the jig 10 in the pressurizing chamber 3 and measures the oscillation frequency before and after the pressurization of the crystal resonator to be inspected will be described.
4A and 4B are diagrams showing a configuration example of the oscillation circuit. FIG. 4A is an overall configuration diagram of the oscillation circuit, and FIG. 4B is a detailed diagram of the temperature compensation circuit. The oscillation circuit 20 shown in FIG. 4 includes a temperature compensation circuit 16 provided with a temperature compensation circuit 16 so that the oscillation frequency does not change due to the temperature characteristics of the crystal resonator 2 to be inspected when the temperature in the pressurizing chamber 3 changes. A crystal oscillation circuit is configured. The temperature sensor 5 of the airtightness inspection apparatus 1 shown in FIG. 1 is provided in the temperature compensation circuit 16 shown in FIG.
The oscillation circuit 20 is an indirect temperature compensation crystal oscillation circuit, and includes a voltage control crystal oscillation circuit (hereinafter referred to as a Colpitts type VCXO) 15 having a Colpitts oscillation circuit, a temperature compensation circuit 16, and a reference voltage source. 17. The Colpitts type VCXO 15 is an oscillation circuit whose oscillation frequency is changed by a control voltage inputted from the outside, and forms a Colpitts type oscillation circuit composed of a feedback amplifier circuit. As described above, the Colpitts type oscillation circuit oscillates in the range where the phase characteristic of the crystal unit is around 70 deg. When the crystal unit package has a hole, before and after the press of the crystal unit, The oscillation frequency varies greatly.

The Colpitts-type VCXO 15 is controlled by the voltage output from the temperature compensation circuit 16 connected to the reference voltage source 17 and outputs a predetermined oscillation frequency signal.
As shown in FIG. 4B, the temperature compensation circuit 16 includes a circuit network including a plurality of resistors R and a plurality of thermistors TH whose electric resistance values change depending on the temperature. Then, the voltage output from the reference voltage source 17 is changed in response to the change in the ambient temperature, and the oscillation temperature signal output from the Colpitts-type VCXO 15 even if the ambient temperature changes by compensating the frequency temperature characteristics of the crystal resonator. Is set to a constant value.
Since the crystal current of the crystal unit 2 to be inspected varies when the pressure is applied and the oscillation frequency changes, the constant frequency control circuit 13 drives the crystal unit 2 at a constant current to prevent unnecessary frequency changes. To do.
The measuring instrument 14 measures the frequency of the oscillation frequency signal output from the oscillation circuit 10 before and after the crystal resonator 2 is pressed. The measuring instrument 14 is a counter used for general purposes.

Next, the airtight inspection method by the airtight inspection apparatus of this embodiment will be described.
FIG. 5 is a flowchart of the airtightness inspection method for the crystal resonator according to the present embodiment.
First, the crystal resonator 2 to be inspected after the hermetic sealing of the package is completed is placed in the pressurization chamber 3 and connected to a Colpitts type oscillation circuit provided in the pressurization chamber 3 to measure the oscillation frequency. The initial value is set (ST1). Next, immediately after the pressurization chamber 3 is filled with He gas and pressurized, the oscillation frequency of the crystal resonator 2 is measured and set as an initial variation value (ST2).
Here, it is determined whether or not the measured initial fluctuation value has changed by a predetermined value or more with respect to the initial value (ST3). If there has been a change by a predetermined value or more, the crystal resonator is grossly leaked. (ST4). And the pressurization of a pressurization chamber is cancelled | released (ST5), and an airtight test is complete | finished. In step ST3, if the measured initial fluctuation value does not change more than a predetermined value with respect to the initial value, the pressurizing chamber is pressurized with He gas for a certain period of time. Then, after pressurizing for a certain time, the oscillation frequency of the crystal resonator is measured (ST6).

Next, it is determined whether or not a value obtained by subtracting the initial value and the initial variation value from the oscillation frequency value after pressurizing for a certain period of time is a predetermined value or more (ST7). It is determined that the crystal resonator has a fine leak (ST8). And the pressurization of a pressurization chamber is cancelled | released (ST5), and an airtight test is complete | finished. On the other hand, if the value obtained by subtracting the initial value and the initial variation value from the measured oscillation frequency value after pressurizing for a predetermined time in step ST7 is equal to or smaller than a predetermined value, the crystal resonator is determined to be non-defective (ST9). . Then, the pressurization of the chamber is released (ST5), and the airtight inspection ends.
In step ST7, the initial fluctuation value is subtracted from the measured oscillation frequency value after pressurizing for a certain time. This treatment is performed even if the crystal resonator to be inspected is a non-defective product. When the pressure is applied, the oscillation frequency may slightly change due to a factor due to stress, and this change in the oscillation frequency is necessary to exclude from the fine leak determination.

Next, an example of measurement data when an airtight inspection is performed using the airtightness inspection apparatus for a crystal resonator package according to the present embodiment will be described.
FIG. 6 is a graph showing an example of measurement data of the hermetic inspection apparatus for a crystal resonator package according to the present invention. In FIG. 6, the vertical axis represents the frequency fluctuation value (ppm) indicating the fluctuation range of the oscillation frequency before and after the pressurization of the crystal resonator to be inspected, and the horizontal axis represents the leak rate indicating the airtight amount of the crystal resonator package. Value (Pa · m ³ / sec) is shown. As the pressurized gas, an example using He gas and an example using N2 gas are described for reference. A description will be given of an example of measurement data using He gas. Usually, a leak rate as a good product required for a crystal resonator package is as follows. E-09 (Pa · m ³ / sec) or less, and indicated by a dotted line in the graph. Further, this required leak rate is 0.2 ppm in terms of the oscillation frequency fluctuation value before and after pressurization of the crystal resonator, and is indicated by a dotted line in the graph. Therefore, in the airtight inspection of the crystal unit package, if the oscillation frequency fluctuation value before and after pressurization is within 0.2 ppm after pressurizing the target crystal unit for a certain time, the leak rate is 1. E−09 (Pa · m ³ / sec) or less is satisfied, and the crystal resonator to be inspected is determined as a non-defective product. Next, after pressurizing the crystal resonator to be inspected for a certain period of time, if the oscillation frequency fluctuation value before and after pressurization exceeds 0.2 ppm and is within 5 ppm, the leak rate is 1. From E-09 (Pa · m ³ / sec) to 6. E−07 (Pa · m ³ / sec) or less. In this case, the crystal resonator to be inspected is determined to be fine leak. Further, if the oscillation frequency fluctuation value before and after pressurization is 6 ppm or more immediately after pressurizing the crystal resonator to be inspected, the leak rate is 1. E-05 (Pa · m ³ / sec) or more, and the crystal resonator to be inspected is determined to be gross leak.
As shown in FIG. 6, when N2 gas is used as the pressurized gas, the determination of gross leak corresponding to a large hole is not much different from the determination when using He gas, Compared to the case of using He gas, when the fine leak corresponding to the determination of a small hole is used, the fluctuation range of oscillation frequency becomes smaller and the numerical value varies, and the measurement accuracy is better when using He gas. I understand.

Next, a modified example of the present invention will be described.
The airtightness inspection apparatus for a quartz crystal resonator according to the present embodiment has a timing to leave it pressurized for a predetermined time, for example, about 4 minutes after being pressurized as described above. Therefore, a step of performing an inspection of other electrical characteristics (for example, excitation level dependency (DLD characteristics), crystal impedance characteristics (CI characteristics), etc.) of the crystal resonator is added within this standing time, and the crystal oscillation is performed. The hermetic inspection apparatus may be configured to shorten the entire inspection process time of the child.
As described above, in the description of the present invention, a crystal resonator is used as an example of a piezoelectric resonator. However, the present invention can be applied to other piezoelectric resonators that can oscillate in an oscillation circuit such as a Colpitts type. Even if the vibrator package is extremely small, high-precision gross leak determination and fine leak determination can be performed by a single airtight inspection.

It is a figure which shows the structure of the airtight test | inspection apparatus of the crystal oscillator which concerns on embodiment of this invention. It is the figure which showed the phase characteristic of the crystal oscillator. It is a figure which shows the control action table | surface of an intake on-off valve and an exhaust on-off valve. It is a figure which shows the structural example of the oscillation circuit of this embodiment. It is a flowchart of the airtight test | inspection method of the crystal oscillator of this embodiment. It is the figure which showed an example of the measurement data by the airtight inspection apparatus of this embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Airtight inspection apparatus, 2 ... Crystal oscillator to be examined, 3 ... Pressurization chamber, 4 ... Gas cylinder, 5 ... Flow throttle valve, 6 ... Subchamber, 7 ... Intake on / off valve, 8 ... Exhaust on / off valve, 9 ... Open / close valve control circuit, 10 ... jig, 11 ... temperature sensor, 13 ... constant current control circuit, 14 ... measuring instrument, 15 ... Colpitts type VCXO, 16 ... temperature compensation circuit, 17 ... reference voltage source, 20 ... oscillation circuit, R ... resistance, TH ... thermistor

Claims (8)

A piezoelectric vibrator air-tightness inspection device for inspecting the airtightness of a piezoelectric vibrator containing a piezoelectric vibration element in a package,
A pressurizing chamber for pressurizing the piezoelectric vibrator to be inspected;
A jig provided in the pressure chamber and having an oscillation circuit;
A measuring instrument for measuring the frequency of an oscillation frequency signal output from an oscillation circuit when the piezoelectric vibrator is set in the jig;
An airtight inspection device for a piezoelectric vibrator, comprising:   2. The piezoelectric vibrator hermeticity inspection apparatus according to claim 1, wherein the oscillation circuit is a Colpitts type.   3. The air tightness inspection apparatus for a piezoelectric vibrator according to claim 1, further comprising a constant current control circuit that controls the piezoelectric current flowing through the piezoelectric vibration element of the piezoelectric vibrator to be constant.   The temperature sensor which measures the temperature in the said pressurization chamber, and the means to perform temperature compensation of the said piezoelectric vibration element based on the temperature detection result of the said temperature sensor, The 1st thru | or 3 characterized by the above-mentioned. The airtight inspection device for a piezoelectric vibrator according to any one of the above.   5. The airtight inspection apparatus for a piezoelectric vibrator according to claim 1, wherein the pressurized gas for pressurizing the inside of the pressurized chamber is helium gas. 6.   An intake on-off valve provided in the intake path of the pressurization chamber; an exhaust on-off valve provided in the exhaust path of the pressurization chamber; a valve control circuit for controlling the opening / closing operation of the intake on-off valve and the exhaust on-off valve; The airtightness inspection apparatus for a piezoelectric vibrator according to any one of claims 1 to 5, further comprising:   The airtight inspection device for a piezoelectric vibrator according to any one of claims 1 to 6, wherein a sub-chamber for storing a predetermined amount of the pressurized gas is provided in an intake path of the pressurized chamber. A piezoelectric vibrator air-tightness inspection method for inspecting the airtightness of a piezoelectric vibrator containing a piezoelectric vibration element in a package,
Oscillating a piezoelectric vibrator to be inspected by an oscillation method and measuring an oscillation frequency of the piezoelectric vibrator;
Oscillating by an oscillation method in a state where the piezoelectric vibrator is pressurized and measuring an oscillation frequency of the piezoelectric vibrator;
Determining whether the hermeticity of the package of the piezoelectric vibration element is maintained based on the frequency difference between the oscillation frequency before pressurization of the piezoelectric vibrator and the oscillation frequency after pressurization;
An airtight inspection method for a piezoelectric vibrator, comprising:

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