JP3843716B2 - AT cut piezoelectric vibrator package structure and frequency adjusting method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a surface-mount type AT-cut piezoelectric vibrator used in an electronic device, and more particularly to a package structure in which a piezoelectric vibrating piece is mounted and hermetically sealed, and a method for adjusting the frequency thereof.
[0002]
[Prior art]
Conventionally, piezoelectric vibrators have been widely used as clock sources for electronic circuits in various electronic devices including information communication devices such as mobile phones and PHS, OA devices such as computers, and consumer devices such as electronic watches. Particularly recently, with the improvement in performance of electronic devices, piezoelectric vibrators with higher frequency accuracy are required.
[0003]
Conventionally, a structure in which a piezoelectric vibrating piece such as a crystal is fixed in a package made of an insulating material such as ceramic and hermetically sealed is widely used for a surface-mount AT-cut piezoelectric vibrator. In general, a package includes a thin rectangular box-shaped base on which a piezoelectric vibrating piece is mounted in a cantilever manner, and a thin plate-like cap bonded on the base. The frequency adjustment of the piezoelectric vibrator is performed by using a dry method such as ion beam etching while measuring the frequency of the piezoelectric vibrator piece mounted on the base and before the cap is joined. Is partially removed, or metal is deposited on the metal electrode excitation portion to increase the mass. The cap is bonded by melting the low melting point glass by a high temperature treatment of about 300 to 400 ° C. The base has a small through-hole for degassing when the package is finally vacuum-sealed, and this is hermetically sealed by welding a metal ball such as Au-Sn in a vacuum atmosphere after joining the cap. Block.
[0004]
[Problems to be solved by the invention]
However, since such a conventional piezoelectric vibrator is exposed to a high temperature when the cap is joined, it is made of a conductive adhesive that holds the vibrating piece, a low melting point glass that joins the cap and the base, or the like. Gas is generated and may adhere to the resonator element and adversely affect its oscillation frequency. For this reason, there is a possibility that the frequency once adjusted is fluctuated after the sealing or the dispersion becomes large, and the frequency accuracy of the piezoelectric vibrator is lowered. In recent years, with the downsizing and thinning of electronic devices, further downsizing of piezoelectric vibrators has been required, and it has become more difficult to improve frequency accuracy.
[0005]
Therefore, the present invention has been made in view of the above-described conventional problems, and its purpose is to meet the recent demands for high performance and miniaturization in surface-mounted AT-cut piezoelectric vibrators. The object is to provide a package structure capable of realizing higher frequency accuracy.
[0006]
It is another object of the present invention to provide a method that can adjust the frequency of an AT-cut piezoelectric vibrator with higher accuracy.
[0007]
[Means for Solving the Problems]
According to the present invention, in order to achieve the above object, in a piezoelectric vibrator in which an AT-cut piezoelectric vibrating piece is mounted inside a package and hermetically sealed, the package mounts the piezoelectric vibrating piece on the mounting surface. A base made of an insulating material and a cap joined on the base, and either the base or the cap is formed with a through hole formed in alignment with the metal electrode excitation portion of the piezoelectric vibrating piece, A package structure of an AT-cut piezoelectric vibrator, comprising: a first metallized portion formed at a peripheral edge of an opening on the outer surface of the through-hole, and the first metallized portion connected to a terminal on the outer surface of the package Is provided.
[0008]
Thus, after the cap is joined to the base in the manufacturing process of the AT-cut piezoelectric vibrator, the metal electrode excitation portion of the piezoelectric vibrating piece is ion beam etched through the through hole in the reaction gas atmosphere. The frequency can be adjusted, and the positive ions reaching the piezoelectric vibrating reed inside the package through the through hole can be obtained by appropriately setting the potential of the first metallized portion via the terminal on the outer surface of the package. Since the etching rate can be adjusted by control, high-accuracy frequency adjustment is possible. Furthermore, after that, as in the conventional case, the inside of the package can be hermetically sealed by closing the through hole in a vacuum or an atmosphere of inert gas or dry air.
[0009]
In one embodiment, since the terminal on the outer surface of the package is a ground terminal, the ion beam etching can be performed while the first metallized portion is maintained at the ground potential.
[0010]
In one embodiment, the through hole and the first metallized portion are formed in a base, and the first metallized portion has a size corresponding to at least the metal electrode excitation portion of the piezoelectric vibrating piece, so that the piezoelectric When the frequency is roughly adjusted by ion beam etching with the resonator element mounted on the base, the etching rate can be controlled by adjusting the potential of the first metallized portion. In particular, if the potential of the first metallization part is set to be negative, the positive ions can be selectively focused with high density by the metal electrode excitation part, so that the etching rate is increased and the rough adjustment of the frequency is made shorter. Can be done efficiently in time.
[0011]
In another embodiment, the through-hole and the first metallized part are formed in the base, and the base has a second metallized part formed on the outer side separately from the first metallized part. When frequency adjustment is performed by beam etching, the first and second metallized portions can be adjusted to different potentials, and the etching rate can be controlled over a wider range and selectively. For example, when the frequency is roughly adjusted with the piezoelectric resonator element mounted on the base, the etching rate can be further increased by making the first metallized portion a negative potential lower than that of the second metallized portion. can do.
[0012]
Further, in one embodiment, the base has a laminated structure of an upper thin plate member having a mounting surface of a piezoelectric vibrating piece and a lower thin plate member having a bottom surface of the package, and the through hole is formed in the upper thin plate member. The metallized portion is formed on a joint surface with the lower thin plate member of the upper thin plate member. The metallized portion is formed of a small diameter portion formed on the lower thin plate member and a large diameter portion formed concentrically with the small diameter portion. As a result, the metallized portion does not interfere with external terminals provided on the bottom surface of the base for surface mounting of the package, so that these can be freely designed regardless of their position, shape and dimensions. Further, when the piezoelectric vibrator is mounted on a substrate or the like, there is no possibility of contact with terminals or solder on the surface, which is convenient.
[0013]
In addition, since the metal electrode excitation portion of the piezoelectric vibrating piece is located approximately in the center of the package, if the through hole is provided in the center of the package, the metal electrode excitation portion can be reliably etched and the base Conveniently, interference with the electrodes of the package provided on the bottom surface can be avoided.
[0014]
According to another aspect of the present invention, after mounting the AT-cut piezoelectric vibrating piece on the base of the package having the through hole and the first metallized portion of the present invention described above, measuring the frequency of the piezoelectric vibrating piece, A first frequency adjustment process for partially removing the metal electrode excitation part, and after joining a cap on the base, measuring the frequency of the piezoelectric vibrating piece through the through-hole in an inert gas atmosphere There is provided an AT-cut piezoelectric vibrator frequency adjustment method characterized by comprising a second frequency adjustment process in which the metal electrode excitation part is partially removed by performing ion beam etching.
[0015]
In this way, after the frequency of the piezoelectric vibrating piece was roughly adjusted to a predetermined range by the first frequency adjustment process, the frequency variation and variation were caused by joining the cap to the base using the low melting point glass. Even in this case, the frequency of the piezoelectric vibrating piece can be finely adjusted in the second frequency adjustment process, and finally, the package can be vacuum-sealed in the same manner as in the prior art.
[0016]
The ion beam etching is preferably performed in an atmosphere of Ar gas generally used as a reaction gas.
[0017]
In an embodiment, when ion beam etching is performed in the second frequency adjustment process, the first metallized portion is grounded, so that positive ions can be more easily focused on the through hole and the etching rate is increased. Can do.
[0018]
In another embodiment, when ion beam etching is performed in the second frequency adjustment process, the first metallized portion is set to a slightly positive potential, thereby controlling the focusing of positive ions to the through-hole and performing etching. By adjusting the rate, it is possible to achieve more accurate frequency adjustment.
[0019]
In one embodiment, in the first frequency adjustment process, the first metallized portion is set to a negative potential, and the metal electrode excitation portion is removed by ion beam etching, so that the etching rate is increased and the frequency is increased. Can be adjusted in a short time.
[0020]
Further, according to the present invention, after mounting the AT-cut piezoelectric vibrating piece on the base of the package having the second metallized portion in addition to the above-described through-hole and first metalized portion of the present invention, the frequency of the piezoelectric vibrating piece is In the inert gas atmosphere while measuring the frequency of the piezoelectric vibrating piece after measuring the frequency of the piezoelectric vibrating piece after first joining the cap on the base And performing a second frequency adjustment process of partially removing the metal electrode exciter by performing ion beam etching through the through hole. In the first or second frequency adjustment process, the first metallization unit The metal electrode excitation portion is partially removed by performing ion beam etching with the second metallization portion and the second metallization portion set at different potentials, respectively. Frequency adjustment method of the electrostatic vibrator is provided.
[0021]
As described above, when the first and second metallized portions are adjusted to different potentials, the etching rate can be controlled over a wider range and selectively. For example, in the first frequency adjustment, if the first metallized portion is set to a negative potential lower than that of the second metallized portion, the frequency can be roughly adjusted in a shorter time with a higher etching rate. it can. Further, in the second frequency adjustment, when the first metallized portion is grounded or slightly positive and the second metallized portion is a negative potential, positive ions are attracted to the periphery of the through hole. Therefore, the frequency can be adjusted with higher accuracy by controlling the etching rate. In addition to this, the metallized part at the periphery of the through-hole is damaged or peeled off by the collision of positive ions, and the weldability is lowered when the through-hole is sealed with a metal sphere such as Au-Sn in a later process. Can be suppressed.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 schematically shows a configuration of a first embodiment of a surface-mount type AT-cut crystal resonator to which the present invention is applied. In this crystal resonator, an AT-cut crystal resonator element 4 is mounted inside a package 3 including a base 1 made of a ceramic material and a cap 2. The base 1 is configured in a thin box shape in which a slightly smaller rectangular frame member 6 is integrally joined to an upper surface of a bottom plate portion 5 having a laminated structure in which two generally rectangular upper and lower thin plate members 5a and 5b are bonded together. ing. The cap 2 is formed of a thin plate of glass or ceramics and is airtightly joined to the upper end of the frame member 6 using low melting point glass.
[0023]
The quartz crystal vibrating piece 4 has excitation electrodes 7 and 7 formed on both sides of a rectangular quartz thin plate, and an extraction electrode from the excitation electrode formed on the base end thereof. As shown in FIG. 2A, on the mounting surface of the base 1, a pair of connection electrodes 8, 8 is formed near one end, and the lead electrode is adhered to the conductive electrode with a conductive adhesive. A crystal vibrating piece 4 is mounted on the base 1 in a cantilever manner. In addition, leads 9 and 9 made of a conductor are wired on the upper surface of the bottom plate portion 5, and the connection electrodes are electrically connected to the external terminals 10 and 10 formed at one diagonal corner of the back surface of the base. Connected. External terminals 11, 11 formed at the other diagonal corner of the back surface of the base are dummy ground terminals that are not connected to the crystal vibrating piece 4.
[0024]
A through hole 12 is formed at the center of the bottom plate portion 5 of the base 1. As shown in FIG. 2, the through-hole 12 includes a small-diameter portion 12a formed in the upper thin plate member 5a and a large-diameter portion 12b formed in the lower thin plate member 5b concentrically with the small-diameter portion 12a. A step 13 is provided in the through hole opening on the bottom side of the base 1. In this embodiment, the diameter of the small diameter portion is set to about 0.25 mm, and the diameter of the large diameter portion is set to about 0.55 mm. The step 13 is for placing a metal ball such as Au—Sn which is welded to close the through hole 12 when the inside of the package is vacuum-sealed in the final process.
[0025]
As shown in FIG. 2B, on the lower surface of the upper thin plate member 5a, that is, the joint surface with the lower thin plate member 5b, a circular metallized portion 14 larger than the large diameter portion 12b is formed on the peripheral edge of the through hole small diameter portion 12a. It is formed by screen-printing a conductive material such as. As shown in FIG. 1B, the metallized portion 14 is gold-plated at the portion exposed from the large diameter portion 12b, that is, the portion 14a corresponding to the bottom of the step 13, in order to obtain the above-described metal ball weldability. Further, the metallized portion 14 is electrically connected to a terminal 16 formed on the upper surface thereof through a metallized through hole 15 of the upper thin plate member 5a, and can be connected to the outside.
[0026]
The procedure for adjusting the frequency of the AT-cut quartz crystal resonator will be described using the package structure of the first embodiment. First, the base 1 on which the crystal vibrating piece 4 is mounted on the mounting surface (main surface) is disposed in, for example, an argon (Ar) atmosphere chamber. As shown in FIG. 3A, while measuring the oscillation frequency of the quartz crystal resonator element 4 as in the prior art, a mask 17 is placed between them, and ion beam etching is performed from above using an ion beam apparatus 18 such as an ion gun. Thereby, the metal material forming the excitation electrode on the upper surface of the crystal vibrating piece 4 is partially removed, and the frequency is roughly adjusted as a first step. In another embodiment, the frequency can be roughly adjusted by laser beam irradiation or the like.
[0027]
Here, if ion beam etching is performed in a state where the metallized portion 14 is set to a negative potential via the terminal 16, Ar ⁺ ions can be easily focused on the metalized portion 14. As described above, since the metallized portion 14 is provided at substantially the center position of the package 3, the Ar + ions are focused at a higher density near the center of the excitation electrode of the crystal vibrating piece 4 to increase the etching rate, and the frequency is roughened. Adjustment can be efficiently performed in a shorter time. Therefore, even an ion beam apparatus that does not have collimating means can be etched well, and the processing cost can be reduced.
[0028]
After the rough adjustment of the frequency, the base 1 is bonded to the cap 2 using a low-melting glass at the upper end after the cleaning process. Similarly, this package 3 is disposed in a chamber in an Ar atmosphere, and while measuring the oscillation frequency of the crystal vibrating piece 4, ion beam etching is performed from the bottom side using an ion beam device 18 as shown in FIG. 3B. The ion beam device 18 is disposed in front of the through hole 12 so that the ion beam is focused on the through hole 12. Thereby, the metal material that forms the excitation electrode on the upper surface of the crystal vibrating piece 4 is partially removed, and the frequency can be finely adjusted as the second stage. Therefore, even if the frequency slightly fluctuates or varies due to the high temperature at the time of joining the cap after rough frequency adjustment, it can be corrected here, so that higher frequency accuracy can be obtained. In addition, since the excitation electrodes on both sides of the quartz crystal resonator element are etched, the balance of the electrode film thickness on the front and back is good, and the vibration is more stable. Of course, if the diameter of the through-hole 12 is increased, the etching rate can be increased accordingly and the frequency adjustment range can be expanded.
[0029]
Here, by appropriately setting the potential of the metallized portion 14 through the terminal 16, the etching rate can be adjusted by controlling the Ar ⁺ ions passing through the through hole 12 and reaching the inside of the package. For example, when ion beam etching is performed with the metallized portion 14 at the ground potential (zero), Ar ⁺ ions can be relatively easily focused on the metalized portion 14. Further, if the metallized portion 14 is set to a slightly positive potential, Ar ⁺ ions passing through the through-hole 12 can be restricted, so that frequency adjustment is performed more gently and more accurately, and at the same time due to collision of Ar ⁺ ions. Damage to the gold plating portion 14a can be reduced, and the weldability of the Au—Sn metal ball can be maintained. Furthermore, by appropriately switching the potential of the metallized portion 14 between positive, ground, and negative, the entry of Ar ⁺ ions into the through hole 12 can be blocked, promoted, or restricted.
[0030]
The package that has finished fine adjustment of the frequency in this way is placed in, for example, a vacuum atmosphere in the final process, and an Au—Sn metal ball placed on the step 13 of the through hole 12 is welded with a laser beam, whereby a through hole is obtained. 12 is closed. Vacuum sealing is preferable because the resistance value of the crystal unit can be kept low. It can also be sealed in an atmosphere of inert gas or dry air.
[0031]
4 and 5 show a package according to a second embodiment of the present invention. The second embodiment differs from the first embodiment in that the metallized portion 14 on the lower surface of the upper thin plate member 5a is connected to one of the ground terminals 11 via diagonal leads 19. As a result, the potential of the metallized portion 14 can be adjusted by using the ground terminal 11 conventionally provided in this type of package, so it is necessary to provide the through hole 15 and the terminal 16 in the upper thin plate member 5a. This is preferable because it is easy to connect to the outside.
[0032]
6 and 7 show a package according to a modification of the second embodiment. In this modification, the metallized portion 14 on the lower surface of the upper thin plate member 5 a is connected to both ground terminals 11 in the diagonal direction via leads 19. This eliminates the need to define the front-rear direction of the package 3 when connecting the ground terminal 11 to the outside for frequency adjustment by ion beam etching, improving workability.
[0033]
8 and 9 show a package according to a third embodiment of the present invention. The third embodiment is different from the second embodiment in that the metallized portion 14 on the lower surface of the upper thin plate member 5a is formed in substantially the same size as that of the crystal vibrating piece 4 mounted on the upper surface thereof. . As a result, when the metallization portion 14 is set to a negative potential when performing rough adjustment of the frequency by ion beam etching before the cap 2 is bonded, Ar ⁺ ions are selectively selected over substantially the entire surface of the crystal vibrating piece 4. Can be focused. Therefore, the etching rate is increased, and the rough adjustment of the frequency can be efficiently performed in a shorter time.
[0034]
10 and 11 show a package according to a modification of the third embodiment. In this modification, as in the case of FIGS. 6 and 7, the metallized portion 14 on the lower surface of the upper thin plate member 5 a is connected to both ground terminals 11 in the diagonal direction via leads 19. Therefore, when connecting the ground terminal 11 to the outside for frequency adjustment by ion beam etching, there is no need to define the front-rear direction of the package 3, and workability is improved as well.
[0035]
12 and 13 show a package according to a fourth embodiment of the present invention. The fourth embodiment is different from the second embodiment in that the second metallized portion 20 is separated from the metallized portion 14 and is formed on the entire lower surface of the upper thin plate member 5a. The second metallization unit 20 is connected to the other ground terminal 11. Therefore, if ion beam etching is performed with both metallized portions 14 and 20 set to different potentials, the etching rate can be controlled over a wider range and selectively.
[0036]
For example, in the coarse adjustment of the frequency in the first stage, the central metallized portion 14 is set to a negative potential lower than that of the second metallized portion 20 outside thereof, so that Ar is placed near the center of the excitation electrode of the crystal vibrating piece 4. ⁺ Ions can be selectively focused more densely. Therefore, the rough adjustment of the frequency can be efficiently performed in a shorter time with a higher etching rate. In the second-stage frequency fine adjustment, the metallized portion 14 is grounded or slightly positive, and the second metalized portion 20 is negative. Thereby, since Ar ⁺ ions are attracted to the periphery of the through-hole 12, the etching rate can be controlled, and more accurate frequency adjustment and suppression of damage to the gold-plated portion 14a can be achieved.
[0037]
14 and 15 show a package according to a modification of the fourth embodiment. In this modified example, the metallized portion 14 is formed to have substantially the same dimensions as the quartz crystal vibrating piece 4 as in the third embodiment, and the second metallized portion 20 is formed separately from the outside thereof. Different from the fourth embodiment. Thereby, in combination with the features of the third embodiment and the fourth embodiment described above, it is possible to more effectively perform rough frequency adjustment by ion beam etching in a shorter time.
[0038]
Although the preferred embodiments of the present invention have been described in detail with reference to the accompanying drawings, the present invention can be implemented with various modifications and changes within the technical scope thereof. For example, the through hole for performing ion beam etching can be formed in the cap instead of the base so as to be aligned with the position of the excitation electrode of the crystal vibrating piece. In this case, the through hole can be provided separately from the sealing through hole of the base, or can be sealed using the through hole of the cap. Further, the present invention can be similarly applied to a package having a structure in which a box-shaped cap is joined to a flat base, or a case where the cap is joined by another method such as seam welding instead of low-melting glass. Further, the through hole is not necessarily provided at the center position of the package, and can be appropriately selected as long as it is within the range of the excitation electrode of the crystal vibrating piece.
[0039]
【The invention's effect】
By configuring as described above, the present invention has special effects as described below.
[0040]
According to the package structure of the AT-cut piezoelectric vibrator of the present invention, after the cap is joined to the base in the manufacturing process, ion beam etching is performed through the through hole, and the potential of the first metallized portion is appropriately set. Since the etching rate can be adjusted and thereby the frequency can be adjusted with high accuracy, an AT-cut piezoelectric vibrator with higher frequency accuracy corresponding to the demand for high performance and miniaturization is realized. be able to. Furthermore, since the package can be finally sealed in a vacuum as in the conventional case, a high-performance AT-cut piezoelectric vibrator having a smaller resistance value can be obtained.
[0041]
Further, according to the frequency adjustment method for an AT-cut piezoelectric vibrator of the present invention, the second frequency after the frequency of the piezoelectric vibrating piece is roughly adjusted to a predetermined range and the cap is joined to the base by the first frequency adjustment process. The frequency of the piezoelectric resonator element can be finely adjusted in the frequency adjustment process, and the package can be vacuum-sealed to produce a high-performance AT-cut piezoelectric vibrator with high frequency accuracy and low resistance value relatively easily. can do.
[Brief description of the drawings]
FIG. 1A is a longitudinal sectional view of an AT-cut quartz crystal resonator according to a first embodiment of the present invention, and FIG. 1B is a bottom view thereof.
2A is a top view of the upper thin plate member of the first embodiment, FIG. 2B is a bottom view thereof, and FIG. 2C is a bottom view of the lower thin plate member.
FIG. 3A is a diagram showing ion beam etching for coarse frequency adjustment, and FIG. 3B is a diagram showing ion beam etching for fine frequency adjustment of the crystal resonator of the first embodiment.
FIG. 4 is a bottom view of a package according to a second embodiment of the present invention.
5A is a top view of the upper thin plate member of the second embodiment, FIG. 5B is a bottom view thereof, and FIG. C is a bottom view of the lower thin plate member.
FIG. 6 is a bottom view of a package according to a modification of the second embodiment.
7A is a top view of the upper thin plate member of the modification of FIG. 6, FIG. B is a bottom view thereof, and FIG. C is a bottom view of the lower thin plate member.
FIG. 8 is a bottom view of a package according to a third embodiment of the present invention.
9A is a top view of the upper thin plate member of the third embodiment, FIG. B is a bottom view thereof, and FIG. C is a bottom view of the lower thin plate member.
FIG. 10 is a bottom view of a package according to a modification of the third embodiment.
11A is a top view of the upper thin plate member of the modification of FIG. 10, FIG. B is a bottom view thereof, and FIG. C is a bottom view of the lower thin plate member.
FIG. 12 is a bottom view of a package according to a fourth embodiment of the present invention.
13A is a top view of the upper thin plate member of the fourth embodiment, FIG. B is a bottom view thereof, and FIG. C is a bottom view of the lower thin plate member.
FIG. 14 is a bottom view of a package according to a modification of the fourth embodiment.
15A is a top view of an upper thin plate member according to a modification of FIG. 14, FIG. B is a bottom view thereof, and FIG. C is a bottom view of the lower thin plate member.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Base 2 Cap 3 Package 4 AT cut crystal vibrating piece 5 Bottom plate part 5a Upper thin plate member 5b Lower thin plate member 6 Frame member 7 Excitation electrode 8 Connection electrode 9 Lead 10, 11 External terminal 12 Through hole 12a Small diameter part 12b Large diameter part 13 Step 14 Metallized part 14a Gold-plated part 15 Through hole 16 Terminal 17 Mask 18 Ion beam device 19 Lead 20 Metallized part

Claims (12)

In a piezoelectric vibrator in which an AT-cut piezoelectric vibrating piece is mounted inside a package and hermetically sealed,
The package includes a base made of an insulating material for mounting the piezoelectric vibrating piece on a mounting surface thereof, and a cap bonded to the base.
A through hole formed so that either the base or the cap can perform ion beam etching of the metal electrode excitation portion from the outside of the package at a position corresponding to the metal electrode excitation portion of the piezoelectric vibrating piece, and its outer surface A first metallized portion formed at the periphery of the through-hole opening of
A package structure of an AT cut piezoelectric vibrator, wherein the first metallized portion is connected to a terminal on the outer surface of the package.     2. The package structure of an AT cut piezoelectric vibrator according to claim 1, wherein the terminal is a ground terminal. 2. The AT-cut piezoelectric device according to claim 1, wherein the through hole and the first metallized part are formed in the base, and the first metallized part has the same dimensions as the piezoelectric vibrating piece. The package structure of the vibrator.     The through hole and the first metallized part are formed in the base, and the base has a second metallized part that is separated from the first metallized part and formed outside thereof. Item 3. The package structure of the AT-cut piezoelectric vibrator according to Item 1 or 2.     The base has a laminated structure of an upper thin plate member having the mounting surface and a lower thin plate member having a bottom surface of the package, and the through hole has a small diameter portion formed in the upper thin plate member, and the lower side 2. A thin plate member comprising a large diameter portion concentrically formed with the small diameter portion, and the metallized portion is formed on a joint surface of the upper thin plate member with the lower thin plate member. The package structure of the AT cut piezoelectric vibrator according to any one of claims 1 to 4.     6. The package structure of an AT-cut piezoelectric vibrator according to claim 1, wherein the through hole is provided at a substantially central position of the package. After mounting the AT-cut piezoelectric vibrating piece on the base of the package according to any one of claims 1 to 3, 5, or 6, the metal electrode excitation portion is partially arranged while measuring the frequency of the piezoelectric vibrating piece. A first frequency adjustment process to be removed;
After the cap is bonded on the base, the metal electrode excitation portion is partially removed by performing ion beam etching through the through hole while measuring the frequency of the piezoelectric vibrating piece. A method for adjusting the frequency of an AT-cut piezoelectric vibrator, comprising the step of: 5. A first frequency adjustment process in which an AT-cut piezoelectric vibrating piece is mounted on the base of the package according to claim 4, and then the metal electrode excitation portion is partially removed while measuring the frequency of the piezoelectric vibrating piece. When,
After joining the cap on the base, the metal electrode excitation unit is formed by performing ion beam etching through the through hole in an inert gas atmosphere while measuring the frequency of the piezoelectric vibrating piece. A second frequency adjustment process that partially removes,
In the first or second frequency adjustment process, by performing ion beam etching with the first metallization unit and the second metallization unit set to different potentials, the metal electrode excitation unit is partially A method of adjusting the frequency of an AT-cut piezoelectric vibrator, characterized in that     9. The frequency adjusting method for an AT-cut piezoelectric vibrator according to claim 7, wherein the ion beam etching is performed in an Ar gas atmosphere.   10. The frequency adjustment method for an AT-cut piezoelectric vibrator according to claim 7, wherein the first metallized portion is grounded when performing ion beam etching in the second frequency adjustment process. .   10. The AT-cut piezoelectric vibration according to claim 7, wherein the first metallized portion is set to a slightly positive potential when performing ion beam etching in the second frequency adjustment process. Child frequency adjustment method.   The said metal electrode part is made into a negative electric potential in the said 1st frequency adjustment process, The said metal electrode excitation part is removed by ion beam etching, The one of Claim 7 thru | or 11 characterized by the above-mentioned. A method for adjusting the frequency of an AT-cut piezoelectric vibrator.

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