JP2006311110A - Piezoelectric vibrator and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a piezoelectric vibrator by which it is unnecessary to form extra electrodesto to attain a downsizing, the time needed for frequency adjustment can be shortened and also its frequency can accurately be adjusted. <P>SOLUTION: A frequency adjusting stage comprises: roughly adjusting the frequency by irradiating an excitation portion of an electrode with laser light until the difference between a measured frequency and a set frequency to be adjusted to becomes smaller than a designated value (steps ST4 to ST6); and finely adjusting the frequency after the rough adjustment by irradiating a lead-out wire portion of the electrode with laser light (steps ST7 to ST9). <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a piezoelectric vibrator manufacturing method and a piezoelectric vibrator, and more particularly to a piezoelectric vibrator whose frequency is adjusted by a laser trimming method and a manufacturing method thereof.

In recent years, with the development of small information devices such as mobile computers and IC cards, and mobile communication devices such as mobile phones, it has become a major goal to increase the accuracy and miniaturization of piezoelectric vibrators used as clock sources thereof. It is said that.
Conventionally, in order to make the frequency generated by the piezoelectric vibrator accurate, the frequency is adjusted by, for example, a laser trimming method or the like before the piezoelectric vibrator is hermetically sealed (packaged) (for example, Patent Document 1).
By the way, as disclosed in Patent Document 1, when one of the overlapping portions of the electrodes formed on both surfaces of the piezoelectric vibrator is trimmed by laser light irradiation, the electrodes on both surfaces are trimmed at the same time and excessive. Since the electrodes are removed, fine adjustment of the frequency is difficult. For this reason, Patent Document 1 discloses a technique in which an unnecessary dummy electrode that does not overlap is formed on one of the main surfaces of the piezoelectric substrate, and the frequency is accurately adjusted by irradiating the dummy electrode with laser light. Yes. The reason why the dummy electrode is formed is that, for example, if the lead line portion of the electrode is trimmed, disconnection may occur.
JP 2002-185286 A

  However, the technique disclosed in Patent Document 1 requires a space for forming an extra dummy electrode, and it is difficult to reduce the size of the piezoelectric vibrator. In addition, the amount of change in frequency when the dummy electrode is irradiated with laser is very small compared to the amount of change in frequency when the overlapped portion of the electrode is irradiated with laser light. It takes a long time to reduce productivity.

  The present invention has been made in view of the above circumstances, and the object of the present invention is to reduce the size without requiring the formation of an extra electrode, shorten the time required for frequency adjustment, and adjust accurately. Another object of the present invention is to provide a method for manufacturing a piezoelectric vibrator.

In the method for manufacturing a piezoelectric vibrator according to the present invention, electrodes are provided on both main surfaces of a piezoelectric substrate so as to have excitation portions for applying voltage that overlap each other and lead portions for electrical connection that do not overlap each other. An electrode forming step to be formed, and a frequency adjusting step for adjusting the frequency by irradiating the electrode with laser light, and the frequency adjusting step includes irradiating the excitation portion of the electrode with laser light and trimming the rough adjusting step and the electrode And a fine adjustment step of performing trimming by irradiating the lead line portion with laser light.
According to this configuration, in the frequency adjustment process, both the excitation part of the electrode whose frequency changes greatly with laser light irradiation and the leader part whose frequency changes small with laser light irradiation are irradiated with laser light. By adjusting the frequency, the time required for frequency adjustment can be shortened and the frequency can be adjusted accurately.

In the above-described configuration, the frequency adjustment step irradiates the excitation portion of the electrode with laser light until the difference between the measured frequency and the set frequency is equal to or less than a predetermined value, coarsely adjusts the frequency, and then performs electrode adjustment. A configuration in which the line portion is irradiated with laser light to finely adjust the frequency can be employed.
According to this configuration, after performing rough frequency adjustment by coarse adjustment, fine adjustment of the frequency is performed after reducing the difference between the measured frequency and the set frequency to some extent, so the time required for the frequency adjustment process is reduced. In addition to being significantly shortened, the amount of irradiation and the irradiation time of the laser beam to the leader line part can be shortened, so that the leader part can be prevented from being disconnected by the laser beam irradiation.

The said structure WHEREIN: The structure which forms an electrode so that it may consist of an excitation part and a leader part can be employ | adopted for an electrode formation process.
According to this configuration, in the electrode forming step, the electrode is constituted by the excitation portion for applying a voltage to the piezoelectric substrate and the lead wire portion for electrically connecting the excitation portion. As a result, the piezoelectric vibrator can be miniaturized.

The said structure WHEREIN: The structure formed so that the width | variety of the excitation part and leader line part of an electrode may become equal in an electrode formation process is employable.
According to this configuration, since the area of the leader line portion can be sufficiently secured, it is possible to prevent the leader line portion from being disconnected due to the irradiation of the laser beam to the leader line portion.

In the piezoelectric vibrator according to the present invention, electrodes are formed on both main surfaces of the piezoelectric substrate so as to have an excitation portion for applying voltage that overlaps with each other and a leader portion for electrical connection that does not overlap with each other. The piezoelectric vibrator is characterized in that a part of both the excitation part and the lead line part of the electrode are trimmed by laser light irradiation.
According to this configuration, since both the excitation part and the leader line part are trimmed by laser light irradiation, the frequency adjustment process is shortened, the manufacturing cost is reduced, and the piezoelectric vibration in which the frequency is accurately adjusted. A child is obtained.

In the above configuration, the electrodes are formed so that the widths of the excitation portion and the leader portion are equal, and are formed from both ends in the longitudinal direction of the piezoelectric substrate to midway. Can be adopted.
According to this configuration, since the area of the leader line portion can be sufficiently secured, it is possible to prevent the leader line portion from being disconnected due to the irradiation of the laser beam to the leader line portion.

According to the present invention, it is not necessary to form an extra electrode, and the piezoelectric vibrator can be miniaturized.
In addition, according to the present invention, the time required for frequency adjustment can be shortened and the frequency can be adjusted accurately.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, exemplary embodiments of the invention will be described with reference to the accompanying drawings.
1A and 1B are diagrams showing a piezoelectric vibrator according to an embodiment of the present invention, wherein FIG. 1A is a plan view of the piezoelectric vibrator viewed from above, and FIG. 1B is a cross-sectional view of the piezoelectric vibrator. .
As shown in FIG. 1, this piezoelectric vibrator is a so-called strip-type piezoelectric vibrator. The piezoelectric substrate 10 is formed in a rectangular shape, and the upper surface 10a and the lower surface 10b are both main surfaces of the piezoelectric substrate 10. The upper electrode 20 and the lower electrode 30 are formed respectively.

The piezoelectric substrate 10 is made of, for example, lithium tantalate (LiTaO3).
The upper surface electrode 20 and the lower surface electrode 30 are formed of a thin film in which a Ni—Cr film and an Au film are sequentially laminated on the surface of the piezoelectric substrate 10, and the film thickness thereof is, for example, about 50 nm for the Ni—Cr film and the Au film. It is about 200 nm. In this way, the upper electrode 20 and the lower electrode 30 are formed of Ni—Cr and Au thin films because the Au film alone has a weak adhesive strength with the piezoelectric substrate 2. A Ni—Cr film is interposed between the film and the piezoelectric substrate 10. In place of Ni—Cr, Cr or Au can be used instead of Cr or a mixture thereof.

The upper surface electrode 20 and the lower surface electrode 30 are formed all over the width direction of the piezoelectric substrate 10 and are formed from both ends in the longitudinal direction of the piezoelectric substrate 10 to the middle.
Moreover, the upper surface electrode 20 and the lower surface electrode 30 are comprised from excitation part 20A, 30A and leader part 20B, 30B, respectively. The excitation portions 20A and 30A and the leader portions 20B and 30B are formed so that the length (longitudinal direction) and the width (short direction) are equal.
The excitation portions 20A and 30A are portions that overlap each other with the piezoelectric substrate 10 interposed therebetween, and a voltage is applied to the piezoelectric substrate 10 by these. As will be described later, a part of the excitation portions 20A and 30A is trimmed by laser light irradiation in the piezoelectric vibrator manufacturing process.
The lead wire portions 20B and 30B are portions that do not overlap each other, and these are portions that electrically connect the excitation portions 20A and 30A to an external connection electrode described later. As will be described later, a part of the leader lines 20B and 30B is trimmed by laser light irradiation in the manufacturing process of the piezoelectric vibrator.

  As an example of the specification of the piezoelectric vibrator, the set frequency is 10 MHz, the dimensions of the piezoelectric substrate 10 are about 3.2 mm in length, about 0.4 mm in width, about 0.2 mm in thickness, the upper surface electrode 20 and the lower surface electrode. The length of 30 is about 2.0 mm, and the length of the excitation portions 20A and 30A is about 0.8 mm.

Here, FIG. 2 is a cross-sectional view for explaining an example of a method of using the piezoelectric vibrator.
As shown in FIG. 2, the piezoelectric vibrator is mounted in a package 50 including, for example, a ceramic package body 50A and a lid 50B.
The piezoelectric vibrator is fixed to the bottom surface of the package body 50 </ b> A by the conductive resins 60 and 61, and the top electrode 20 has a lead wire portion 20 </ b> B protruding outside from the bottom surface of the package body 50 </ b> A through the conductive resin 60. The lower surface electrode 30 is provided such that the lead wire portion 30B protrudes from the bottom surface of the package body 50A to the outside through the conductive resin 61. The external connection electrode 71 is electrically connected.
The lid 50B is fixed to the package body 50A so as to hermetically seal the inside of the package 50. Thus, by using the piezoelectric vibrator mounted on the package 50, the reliability of the piezoelectric vibrator can be improved.

FIG. 3 is a diagram for explaining another example of how to use the piezoelectric vibrator.
As shown in FIG. 3, the piezoelectric vibrator is mounted in a ceramic package 150 as shown in FIG. 2. However, the difference from the configuration shown in FIG. Internal capacitors 100A and 100B connected in series are incorporated.

One end of the internal capacitor 100A is electrically connected to an external connection electrode 80 provided so as to protrude outside from the bottom surface of the package body 150A, and the other end is provided so as to protrude outside from the bottom surface of the package body 150A. The ground terminal 82 is electrically connected.
One end of the internal capacitor 100B is electrically connected to an external connection electrode 81 provided so as to protrude from the bottom surface of the package body 150A, and the other end is electrically connected to a ground terminal 82.

In this example, the piezoelectric vibrator has three terminals, and the external connection electrodes 80 and 81 are used as input and output.
By using such a package 150, it is not necessary to mount a capacitor when mounting a piezoelectric vibrator on a substrate of a mobile communication device such as a mobile phone, so the number of components can be reduced.

Next, a method for manufacturing the piezoelectric vibrator will be described with reference to FIGS.
Here, FIG. 4 is a process diagram showing the manufacturing procedure of the piezoelectric vibrator, FIG. 5 is a diagram for explaining the relationship between the irradiation position of the laser beam and the amount of change in frequency, and FIG. 6 is the frequency adjustment process. It is a flowchart which shows an example of the process sequence in.
As shown in FIG. 4, the piezoelectric vibrator manufacturing process includes an electrode forming process PR10 for forming an electrode, a process PR20 for mounting the piezoelectric vibrator on a package, a frequency adjusting process PR30 for adjusting the frequency of the piezoelectric vibrator, and a piezoelectric vibration. The process PR40 etc. which airtightly seal the package carrying the child.
First, in the electrode formation process PR10, the upper surface electrode 20 and the lower surface electrode 30 are formed on the piezoelectric substrate 10 formed in a rectangular shape using a known film formation technique.
In step PR20, the piezoelectric vibrator obtained by forming the upper surface electrode 20 and the lower surface electrode 30 on the piezoelectric substrate 10 is mounted on the package described with reference to FIGS.

In the frequency adjustment step PR30, the frequency adjustment is performed by irradiating the upper surface electrode 20 of the piezoelectric vibrator mounted on the package (before being hermetically sealed) with laser light.
In the frequency adjustment step PR30, for example, a step of irradiating the excitation portion 20A of the upper surface electrode 20 with laser light to coarsely adjust the frequency, and a step of irradiating the lead wire portion 20B of the upper surface electrode 20 with laser light to finely adjust the frequency. Process.

  Here, it is known that even if the piezoelectric vibrator irradiates laser light with the same irradiation amount, the amount of change in frequency differs depending on the irradiation position. Specifically, as shown in FIG. 5, in the longitudinal direction of the piezoelectric vibrator, the amount of frequency change is greatest when the central position of the excitation portion 20A is irradiated with laser light, and the frequency changes toward the leader line portion 20B. The amount of change becomes smaller. In the present embodiment, utilizing this, the excitation portion 20A is irradiated with laser light to roughly adjust the frequency, and the leader portion 20B is irradiated with laser light to finely adjust the frequency.

Further, as shown in FIG. 5, when the irradiation position of the laser beam is changed in the longitudinal direction of the piezoelectric vibrator, a different amount of frequency change can be obtained, but the irradiation position is changed in the width direction (short direction) of the piezoelectric vibrator. However, it is known that the obtained frequency change amounts are substantially the same.
For this reason, in this embodiment, as shown in FIG. 5, when irradiating the excitation part 20A and the leader line part 20B with the dot-shaped laser beam and changing the irradiation position, the irradiation position in the excitation part 20A Are sequentially moved in the width direction of the piezoelectric vibrator, such as DB1, DB2, and DB3, in the lead line portion 20B. Thereby, the frequency change amount for each irradiation of the laser beam can be made substantially constant in each of the excitation portion 20A and the leader portion 20B.

Next, a specific procedure for frequency adjustment will be described with reference to FIG.
First, the frequency generated by the piezoelectric vibrator obtained through the electrode formation process PR10 is measured (step ST1). In the frequency adjustment, the frequency is increased by trimming the electrode. Therefore, in the electrode formation process PR10, the frequency adjustment is scheduled so that the frequency when the electrodes 20 and 30 are formed is lower than the set frequency. I have to.

Next, the measured frequency is compared with a set frequency (for example, 10 MHz) (step ST2), and it is selected whether the frequency is coarsely adjusted or finely adjusted (step ST3).
Specifically, for example, when the measurement frequency is 50 ppm or more lower than the set frequency, coarse adjustment is selected, and when the measurement frequency is less than 50 ppm, fine adjustment of the frequency is performed.

  When coarse adjustment of the frequency is selected, as described above, the irradiation position DA1 of the excitation portion 20A is irradiated with dot-shaped laser light (step ST4), and the frequency is measured again (step ST5). Is compared with the set frequency to determine whether or not the rough adjustment is to be finished (step ST6). For example, similarly to the above, when the measurement frequency is 50 ppm or more lower than the set frequency, the coarse adjustment is continued, and when it is less than 50 ppm, the coarse adjustment is terminated. When the rough adjustment is continued, the laser light irradiation position is changed in the width direction of the piezoelectric vibrator.

  When the rough adjustment is finished, the leader line portion 20B is irradiated with laser light to finely adjust the frequency (step ST7). Then, the frequency is measured (step ST8), and the measured frequency is compared with the set frequency to determine whether the fine adjustment of the frequency is finished (step ST9). For example, when it is determined that the measurement frequency matches the set frequency or the difference is very small, fine adjustment of the frequency is terminated. When the difference between the measurement frequency and the set frequency is large, fine adjustment is continued while changing the irradiation position of the laser light in the width direction of the piezoelectric vibrator as described above.

In the electrode 20 of the piezoelectric vibrator that has been subjected to the coarse adjustment and fine adjustment of the frequency in the above procedure, trimming portions are generated by laser light irradiation in both the excitation portion 20A and the leader portion 20B.
Then, the package after the frequency adjustment is hermetically sealed to complete the manufacture of the piezoelectric vibrator.

Here, FIG. 7 is a graph showing the frequency measurement results of a plurality of piezoelectric vibrators manufactured (frequency adjusted) by the manufacturing method of the present embodiment. For comparison, FIG. 7 also shows the frequency measurement results of a plurality of piezoelectric vibrators whose frequencies are adjusted by irradiating only the excitation portion 20A with laser light.
As can be seen from FIG. 7, according to the present embodiment, it can be seen that the variation from the set frequency is greatly improved as compared with the frequency adjusted by irradiating only the excitation portion 20 </ b> A with laser light.

As described above, according to the present embodiment, the electrodes 20 and 30 are configured by the excitation portions 20A and 30A and the lead wire portions 20B and 30B, and no extra electrode is formed. As a result, the piezoelectric vibrator is reduced in size. it can.
Further, according to the present embodiment, at the time of frequency adjustment, as described in steps ST4 to ST6 above, the difference from the set frequency is reduced to a certain value by rough adjustment, and then the frequency is finely adjusted. Therefore, the time required for the adjustment can be greatly shortened as compared with the case where the frequency adjustment is performed by irradiating only the leader line portion 20B with the laser beam, and the frequency can be accurately adjusted by fine adjustment.
Furthermore, according to the present embodiment, the amount of laser light applied to the leader line portion 20B can be suppressed to the minimum necessary by performing rough adjustment of the frequency, due to excessive trimming of the leader line portion 20B. It can prevent disconnection.

  In the above embodiment, the case of adjusting the frequency by irradiating the upper surface electrode 20 with laser light has been described. However, the present invention is not limited to this, and the frequency can be adjusted by irradiating the lower surface electrode 30 with laser light. The frequency can be adjusted by irradiating both the upper surface electrode 20 and the lower surface electrode 30 with laser light.

  In the above embodiment, the case where the fine adjustment is performed after the coarse adjustment of the frequency has been described. However, the present invention is not limited to this, and the frequency is measured first, and the coarse adjustment is performed based on the difference between the measurement frequency and the set frequency. It is also possible to adopt a configuration in which coarse adjustment and fine adjustment are performed simultaneously by determining the irradiation amount of laser light necessary for adjustment and the irradiation amount of laser light necessary for fine adjustment.

  In the above embodiment, the case of irradiating the dot-shaped laser light while moving in the width direction of the piezoelectric vibrator has been described. However, the present invention is not limited to this, and the irradiation method and irradiation position can be changed as appropriate. It is.

  In the above embodiment, the case where the piezoelectric substrate 10 is formed of lithium tantalate has been described. However, for example, a quartz substrate can be used as the piezoelectric substrate.

  In the above embodiment, the case where the electrode has a configuration including the excitation portion and the leader portion has been described. However, the present invention is not limited to this, and the present invention can also be applied to an electrode having other portions. .

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows the piezoelectric vibrator which concerns on one Embodiment of this invention, Comprising: (a) is the top view which looked at the piezoelectric vibrator from upper direction, (b) is the cross section of the AA line direction in (a). FIG. It is sectional drawing which shows an example which mounted the piezoelectric vibrator in the package. It is sectional drawing which shows the other example which mounted the piezoelectric vibrator in the package. It is process drawing which shows the manufacture procedure of the piezoelectric vibrator which concerns on one Embodiment of this invention. It is a figure for demonstrating the relationship between the irradiation position of a laser beam, and the variation | change_quantity of a frequency. It is a flowchart which shows an example of the process sequence in a frequency adjustment process. It is a graph which shows the variation from the setting frequency of the frequency measured after frequency adjustment.

Explanation of symbols

10 ... piezoelectric substrate 20 ... upper surface electrode (electrode)
20A ... excitation portion 20B ... leader portion 30 ... lower electrode (electrode)
50, 150 ... packages 50A, 150A ... package main bodies 50B, 150B ... lids 60, 61 ... conductive resins 70, 71, 80, 81 ... external connection electrodes 82 ... ground terminals 100A, 100B ... built-in capacitors

Claims (8)

An electrode forming step of forming electrodes on both principal surfaces of the piezoelectric substrate so as to have an excitation portion for applying a voltage overlapping each other and a leader portion for electrical connection not overlapping each other; and a laser beam on the electrode A frequency adjustment step of adjusting the frequency by irradiating
The frequency adjusting step includes both a step of irradiating a laser beam to the excitation portion of the electrode to roughly adjust the frequency and a step of irradiating a laser beam to the lead portion of the electrode to finely adjust the frequency. A method for manufacturing a piezoelectric vibrator. The frequency adjustment step irradiates the excitation portion of the electrode with a laser beam until the difference between the measured frequency and the set frequency is equal to or less than a predetermined value, and then roughly adjusts the frequency, and after performing the rough adjustment, the electrode is extracted. 2. The method of manufacturing a piezoelectric vibrator according to claim 1, wherein the line portion is irradiated with laser light to finely adjust the frequency. 3. The method of manufacturing a piezoelectric vibrator according to claim 1, wherein in the electrode forming step, the electrode is formed to include the excitation portion and the lead wire portion. 4. The method for manufacturing a piezoelectric vibrator according to claim 1, wherein in the electrode forming step, the excitation portion and the leader portion of the electrode are formed to have the same width. A piezoelectric vibrator in which electrodes are formed on both main surfaces of a piezoelectric substrate so as to have an excitation part for voltage application overlapping each other and a lead part for electrical connection not overlapping each other,
A part of both an excitation part and a leader line part of the electrode is trimmed by laser light irradiation. The piezoelectric substrate is formed in a rectangular shape,
The electrode is formed so that the widths of the excitation part and the leader line part are equal, and each electrode is formed from both longitudinal ends of the piezoelectric substrate to midway. Item 6. The piezoelectric vibrator according to Item 5. The piezoelectric vibrator according to claim 5 or 6, wherein the piezoelectric vibrator is mounted in a package. The piezoelectric vibrator according to claim 5, wherein the piezoelectric substrate is made of lithium tantalate.

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