JP4389948B2 - Piezoelectric device manufacturing method and base manufacturing method - Google Patents

Description

  The present invention relates to a piezoelectric device used in an electronic apparatus, and more particularly to a piezoelectric device having a hermetic sealing hole at the bottom of a package containing a piezoelectric vibrating piece and a method for manufacturing the piezoelectric device.

  Piezoelectric devices such as piezoelectric vibrators are required to be small and thin as electronic devices become smaller and thinner. For this reason, in recent years, surface-mount type piezoelectric devices have been developed. Some piezoelectric devices are sealed by evacuating the inside of a package containing the piezoelectric vibrating piece in order to avoid the influence of vibration of the piezoelectric vibrating piece due to air. Conventionally, when a package is vacuum-sealed, a sealing hole is provided at the center of the bottom of the package, and a metal ball disposed in the sealing hole is melted and sealed (for example, Patent Document 1). FIG. 5 shows a piezoelectric vibrator which is an example of a conventional piezoelectric device whose package is vacuum-sealed.

  As shown in FIG. 5A, the piezoelectric vibrator 10 includes a piezoelectric vibrating piece 12 and a package 14 that accommodates the piezoelectric vibrating piece 12. The piezoelectric vibrating piece 12 is formed in a flat plate shape by a piezoelectric material such as quartz. The piezoelectric vibrating reed 12 has excitation electrodes 12a and 12b made of a metal thin film of, for example, gold (Au) and chromium (Cr) at the center of the upper and lower surfaces. On the other hand, the package 14 has a base portion 16 and a lid 18. The base portion 16 is formed in a box shape by laminating a first base sheet 20, a second base sheet 22, and a frame material 24 made of a ceramic sheet as an insulating material in this order. The piezoelectric vibrating piece 12 is accommodated in a cavity (accommodating space) 26 formed by the base portion 16.

  That is, the mount electrode 28 is provided on the upper surface of the second base sheet 22, and the piezoelectric vibrating reed 12 is fixed to the mount electrode 28 in a cantilever shape by the conductive adhesive 30. A lid 18 is airtightly bonded to the upper end surface of the base portion 16 by a sealing material 32 such as low melting point glass. The lid 18 is made of glass, ceramic, metal plate, or the like.

  Sealing holes 34 and 36 are concentrically formed in the first base sheet 20 and the second base sheet 22. These sealing holes 34 and 36 are formed in the bottom part of the base part 16, ie, the center part of the 1st base sheet 20 and the 2nd base sheet 22, as shown in the figure (2). Further, the sealing hole 36 provided in the second base sheet 22 is formed to have a smaller diameter than the sealing hole 34 provided in the first base sheet 20. This is because the small-diameter sealing hole 36 serves as a receiving portion of a sealing metal ball (not shown) disposed inside the large-diameter sealing hole 34, and the metal ball falls into the package 14. This is to prevent this. Then, the metal balls arranged in the sealing hole 34 are melted by the laser, and as shown in FIG. 5A, the sealing material 38 is hermetically sealed for the sealing holes 34 and 36. The first base sheet 20 is provided with external electrodes 40 at the four corners of the lower surface, which is the outer surface. These external electrodes 40 are for mounting the piezoelectric vibrator 10 on a substrate (not shown).

  The piezoelectric vibrator 10 thus configured is vacuum-sealed inside the package 14 as follows. First, the piezoelectric vibrating reed 12 is fixed to the mount electrode 28 provided on the base portion 16 in a cantilever shape with the conductive adhesive 30. Thereafter, after fine adjustment of the frequency of the piezoelectric vibrating piece 12, the lid 18 is airtightly joined to the upper end of the base portion 16 by the sealing material 32. Next, the package 14 containing the piezoelectric vibrating reed 12 is placed in a vacuum chamber so that the first base sheet 20 is on top, and the metal ball (sealing material 38) placed in the sealing hole 34 is melted. Then, the sealing material 38 is welded to the wall surfaces of the sealing holes 34 and 36 to hermetically seal the sealing holes 34 and 36.

JP 2002-76815 A

  As described above, in the conventional piezoelectric vibrator 10 for vacuum sealing, the sealing hole 34 is provided in the center of the bottom of the package 14, and the metal ball (sealing material 38) disposed in the sealing hole 34 is melted. Thus, the package 14 is sealed. For this reason, it is necessary to prevent the metal ball for sealing disposed in the sealing hole 34 from falling into the cavity 26 of the package 14. The conventional package 14 has a bottom portion constituted by the first base sheet 20 and the second base sheet 22, and a sealing hole 36 having a smaller diameter than the sealing hole 34 of the first base sheet 20 in the second base sheet 22. The small-diameter sealing hole 36 is used as a metal ball receiving portion. Therefore, it is necessary for the conventional package 14 to be configured by the two base sheets 20 and 22 at the bottom, making it difficult to reduce the thickness of the package 14, that is, the piezoelectric vibrator 10.

  Further, in the conventional piezoelectric vibrator 10, sealing holes 34 and 36 are provided at the center of the bottom of the package 14. Therefore, the sealing hole 36 is formed facing the central portion of the excitation electrode 12 b of the piezoelectric vibrating piece 12. For this reason, when sealing the sealing holes 34 and 36, a splash of gas or the like generated when the sealing metal ball is melted enters the package 14 through the sealing hole 36, and the excitation electrode It adheres to 12b. As a result, the oscillation frequency of the piezoelectric vibrating piece 12 whose frequency is adjusted changes in the piezoelectric vibrator 10, causing variations in the oscillation frequency, making it difficult to make a high-performance piezoelectric vibrator.

The present invention has been made to solve the above-described drawbacks of the prior art, and aims to reduce the thickness of a piezoelectric device.
Another object of the present invention is to eliminate frequency fluctuations that occur during vacuum sealing.

  In order to achieve the above object, a piezoelectric device according to the present invention is a piezoelectric device in which a sealing hole provided at the bottom of a package containing a piezoelectric vibrating piece is sealed by melting a metal ball, The package includes a flat base sheet whose base portion forms the bottom, and a frame material that is stacked on the base sheet to form a housing space for the piezoelectric vibrating piece, and the sealing hole includes the frame material It is characterized by being formed through the base sheet at a position corresponding to the inner edge portion, and a part of the opening portion being blocked by the frame material.

  In the present invention thus configured, since the frame material blocks a part of the opening of the sealing hole formed through the base sheet, this part is used as a receiving part for the metal ball for sealing. be able to. Therefore, in the present invention, it is not necessary to form two sealing holes, that is, a large-diameter sealing hole and a small-diameter sealing hole for receiving the metal ball at the bottom of the package. For this reason, the bottom part of the package can be constituted by one base sheet, and the package can be thinned, that is, the piezoelectric device can be thinned. In the piezoelectric device of the present invention, the sealing hole is formed at a position corresponding to the inner edge portion of the frame portion. That is, since the sealing hole is formed at a position away from the excitation electrode of the piezoelectric vibrating piece, it is possible to greatly reduce the influence of splash that occurs when the metal ball is melted. Therefore, according to the present invention, it is possible to avoid affecting the vibration characteristics of the piezoelectric vibrating piece, to prevent a change in the oscillation frequency adjusted in frequency, and to obtain a high-performance piezoelectric device.

  In the base sheet, a mount portion for fixing the piezoelectric vibrating piece may be formed on one side, and a sealing hole may be formed on the other side. Thereby, there is no hindrance in formation of a mount part, and there is no possibility that the sealing material which sealed the sealing hole, and the mount part will short-circuit. The sealing hole can be formed at a position corresponding to the corner of the frame material. Thus, when the sealing hole is formed at the corner of the frame material, the distance between the excitation electrode and the sealing hole can be further increased, and the influence of splash can be further reduced. Further, the sealing hole can be formed at a position corresponding to the ground external electrode formed on the outer surface of the base sheet. Thereby, even when a positional deviation occurs when the piezoelectric device is mounted on the substrate, it is possible to avoid a short circuit between the circuit provided on the substrate and the metal sealing material present in the sealing hole.

  Further, the base sheet is provided with external electrodes for substrate mounting at each of the four corners of the outer surface, the piezoelectric vibrating piece is electrically connected to a pair of adjacent external electrodes, and the sealing hole is It can be provided on the other pair of external electrode sides. Thereby, since the sealing hole is formed on the side that becomes the ground external electrode or dummy electrode, it is possible to prevent a short circuit between the circuit provided on the substrate and the metal sealing material. In addition, since a pair of external electrodes electrically connected to the piezoelectric vibrating reed are adjacent to each other, these external electrodes can be disposed near the oscillation circuit IC provided on the substrate, and the wiring pattern formed on the substrate can be routed. This can be avoided and the substantial mounting area can be reduced.

  It is desirable to provide a metal film on the portion of the frame material where a part of the sealing hole is blocked and the wall surface of the sealing hole. As a result, when the metal ball for sealing (sealing material) arranged in the sealing hole is melted, the sealing material is welded well to the wall surface of the sealing hole or the portion closing the sealing hole of the frame material. It is also possible to prevent the molten sealing material from sagging in the package.

Preferred embodiments of a piezoelectric device according to the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is an explanatory view of a piezoelectric vibrator which is a piezoelectric device according to a first embodiment of the present invention, where (1) is a plan view excluding a lid, and (2) is an AA line of (1). (3) is a bottom view.

  As shown in FIG. 1B, the piezoelectric vibrator 50 according to the first embodiment includes a piezoelectric vibrating piece 52 and a package 60 that accommodates the piezoelectric vibrating piece 52. The piezoelectric vibrating piece 52 is made of a piezoelectric material such as quartz, and in the embodiment, is made of an AT cut quartz plate. In the piezoelectric vibrating piece 52, excitation electrodes 54 (54a, 54b) are formed at the center of the upper and lower surfaces. In addition, the piezoelectric vibrating piece 52 has connection electrodes 56 (56a, 56b) formed on one side in the longitudinal direction that is the X-axis direction of the crystal. The connection electrodes 56a and 56b are formed so as to be continuous with the upper and lower surfaces of the piezoelectric vibrating piece 52, respectively. Further, the connection electrode 56 is formed integrally with the corresponding excitation electrode 54. These electrodes are formed by a two-layer metal thin film of, for example, Au and Cr.

  The package 60 includes a base portion 62 and a lid 64 as main components. The base portion 62 includes a single flat base sheet 66 that forms the bottom of the package 60 and a frame material 68 that forms a cavity (accommodating space) 70 that accommodates the piezoelectric vibrating piece 52. The base portion 62 is formed in a box shape by laminating a base sheet 66 made of a ceramic sheet, which is an insulating material, and a frame material 68 and then sintering. The base sheet 66 is provided with a pair of mount electrodes 72 (72a, 72b) as a mounting portion for fixing the piezoelectric vibrating piece 52 on the upper surface on one side in the longitudinal direction, and the sealing hole 74 on the other side. Is formed. The piezoelectric vibrating piece 52 is fixed to the mount electrode 72 by a conductive adhesive 76, and the connection electrode 56 of the piezoelectric vibrating piece 52 is electrically connected.

  The sealing hole 74 is formed through the base sheet 66 at a position corresponding to the inner edge of the frame material 68, and a part of the opening is closed by the frame material 68 (FIG. 1 (2). )reference). Further, in the case of this embodiment, the sealing hole 74 is formed in the central portion of the short side of the package 60. For this reason, as shown in FIG. 1 (3), the sealing hole 74 includes a pair of external electrodes 80c of the external electrodes 80 (80a to 80d) provided at the four corners of the lower surface (outer surface) of the base sheet 66. It is located in the middle of 80d.

  A portion of the frame material 68 that covers the opening of the sealing hole 74 serves as a receiving portion for the sealing metal ball 82 disposed in the sealing hole 74, and the metal ball 82 falls into the cavity 70. To prevent. In the case of the embodiment, the sealing hole 74 is formed at a position where about half of the opening is blocked by the frame material 68, so that the metal ball 82 can be reliably stopped by the frame material 68. A metal ball 82 is welded to the wall surface of the sealing hole 74 and the portion exposed to the sealing hole 74 of the frame material 68 (the portion blocking the opening) so that the metal ball 82 can be easily and reliably welded. Films 84 (84a, 84b) are provided. In the embodiment, the metal film 84 is plated with nickel (Ni) and gold (Au) on tungsten (W). The metal ball 82 is made of an alloy such as Au—Sn or Au—Ge.

  The metal film 84a provided on the wall surface of the sealing hole 74 can be formed as shown in FIG. First, as shown in FIG. 2A, paste-like tungsten 86 is screen-printed on the base sheet 66 in which the sealing holes 74 are formed so as to cover the sealing holes 74. Next, as indicated by an arrow 87 in FIG. 2B, the sealing hole 74 is sucked from the side opposite to the side where the tungsten 86 is provided (the lower side in FIG. 2). As a result, the portion of the tungsten 86 film that has covered the sealing hole 74 is torn and adheres to the wall surface of the sealing hole 74. Thereafter, the tungsten 86 is baked, and Ni and Au are sequentially plated on the tungsten 86.

  On the other hand, the lid 64 is made of flat glass, ceramic, metal, or the like. The lid 64 is airtightly joined to the upper end surface of the base portion 62 by a sealing material 89 such as low melting glass after the piezoelectric vibrating piece 52 is fixed to the mount electrode 72 in the cavity 70 of the package 60.

  In addition, as shown in FIG. 1C, the piezoelectric vibrating piece 52 includes external electrodes 80a and 80c in which a pair of excitation electrodes 54 are at diagonal positions of the base sheet 66 via connection electrodes 56 and mount electrodes 72. Is electrically connected. When the lid 64 is made of metal, one or both of the external electrodes 80b and 80d are connected to the ground potential of the substrate, and the lid 64 is electrically connected to the external electrode connected to the ground potential. Connected. As a result, the lid 64 serves as an electromagnetic shield, and frequency fluctuation due to external noise can be avoided. In FIG. 1B, the external electrode 80 is omitted.

  In the piezoelectric vibrator 50 configured as described above, since the frame material 68 that closes a part of the opening of the sealing hole 74 serves as a receiving portion of the metal ball 82, the two bases as in the prior art are used. It is not necessary to form the bottom of the package 60 by the sheet. That is, the piezoelectric vibrator 50 can be thinned because the bottom of the package 60 is formed by the single base sheet 66. Further, since the sealing hole 74 is provided at a position far from the excitation electrode 54b, the piezoelectric vibrator 50 has a splash such as a gas generated when the metal ball 82 is melted in order to vacuum seal the package 60. The influence of can be reduced. For this reason, in the piezoelectric vibrator 50, the oscillation frequency of the frequency-adjusted piezoelectric vibrating piece 52 is hardly changed by vacuum sealing. Therefore, variation in oscillation frequency can be reduced, and a high-performance piezoelectric vibrator can be obtained. Further, since the piezoelectric vibrator 50 has the sealing hole 74 formed on the side opposite to the side where the mount electrode 72 is provided, the piezoelectric vibrator 50 does not affect the formation of the mount electrode 72 and is sealed with the mount electrode 72. There is no possibility that the metal sealing material present in the hole 74 is short-circuited.

  FIG. 3 is an explanatory diagram of the second embodiment, wherein (1) is a plan view of the base portion, and (2) is a bottom view of the base portion. The base portion 62a according to this embodiment is formed by laminating a base sheet 66 and a frame material 68. The base sheet 66 is provided with a sealing hole 90. As shown in FIG. 3A, the sealing hole 90 is formed at a position corresponding to the corner of the frame material 68, and a part of the opening is blocked by the frame material 68. . Further, the sealing hole 90 is formed on the side opposite to the side where the mount electrode 72 is provided in the longitudinal direction of the base sheet 66. As shown in FIG. It is formed in the corresponding position. A metal film (not shown in the figure) is provided on the wall surface of the sealing hole 90 and the portion of the frame material 68 that covers the opening of the sealing hole 90.

  In the base portion 62a thus configured, as in the first embodiment, the portion blocking the opening of the sealing hole 90 of the frame material 68 serves as a receiving portion for the metal ball for sealing. . For this reason, the bottom portion can be constituted by one base sheet 66, the package can be thinned, and the piezoelectric vibrator can be thinned. Further, by providing the sealing hole 90 at a position corresponding to the ground external electrode 80 d, the metal film provided on the wall surface of the sealing hole 90 can be formed simultaneously with the external electrode 80. Further, by providing the sealing hole 90 at a position corresponding to the ground external electrode 80d, the power supply circuit of the substrate for driving the piezoelectric vibrator and the sealing in the sealing hole 90 when mounted on the substrate. There is no risk of shorting with the material.

  That is, an electrode pattern 92 (92a to 92d) corresponding to the external electrode 80 is formed on a substrate (not shown) on which the piezoelectric vibrator is mounted, as indicated by a two-dot chain line in FIG. . These electrode patterns 92 are formed larger than the external electrodes 80 so as to cope with the positional deviation of the piezoelectric vibrator during mounting. For this reason, in the piezoelectric vibrator 50 of the first embodiment, since the sealing hole 74 is formed in the middle of the external electrodes 80c and 80d, if the positional deviation occurs during mounting, the sealing hole 74 becomes a piezoelectric vibrating piece. There is a possibility that the electrode 52 comes in contact with the electrode pattern 92c that electrically connects the electrodes 52 and short-circuits. Therefore, the piezoelectric vibrator 50 according to the first embodiment is required to be positioned with high accuracy when mounted on the substrate, and is subject to mounting restrictions. In contrast, in the piezoelectric vibrator using the base portion 62a according to the second embodiment, there is no possibility that the sealing material is short-circuited with the electrode pattern 92c.

  FIG. 4 is an explanatory diagram of the third embodiment and is a bottom view of the piezoelectric vibrator. In the piezoelectric vibrator 100 of this embodiment, the base portion 62 of the package is formed as a laminated body of the base sheet 66 and the frame material 68 as described above. Further, the base sheet 66 is provided with external electrodes 80 at the four corners of the lower surface. The piezoelectric vibrating piece 52 accommodated in the package is electrically connected to a pair of external electrodes 80 a and 80 b provided on one side in the longitudinal direction of the base sheet 66. On the other hand, the sealing hole 74 is formed between the pair of external electrodes 80c and 80d on the other side. In the piezoelectric vibrator 100 according to the third embodiment configured as described above, since the external terminals 80c and 80d on the side where the sealing hole 74 is formed serve as a ground or dummy electrode, the sealing in the sealing hole 74 is performed. There is no risk of material shorting with the power circuit.

  The sealing hole 74 may be formed at a position corresponding to the external terminal 80c or the external terminal 80d. Further, the sealing hole 74 may be formed at a position corresponding to the inner edge of the long side of the frame material 68 as shown by a two-dot chain line in FIG. In the above embodiment, the piezoelectric vibrating piece 52 is an AT-cut piezoelectric vibrating piece. However, the piezoelectric vibrating piece may be a tuning fork type piezoelectric vibrating piece or the like.

It is explanatory drawing of the piezoelectric device which concerns on 1st Embodiment. It is explanatory drawing of the method of forming a metal film in the wall surface of a sealing hole. It is explanatory drawing of the base part which concerns on 2nd Embodiment. It is a bottom view of the piezoelectric device which concerns on 3rd Embodiment. It is explanatory drawing of the conventional piezoelectric device.

Explanation of symbols

50, 100 ......... Piezoelectric device (piezoelectric vibrator), 52 ......... Piezoelectric vibrating piece, 54a, 54b ......... Excitation electrode, 56a, 56b ......... Connection electrode, 60 ......... Package, 62 ......... Base part, 64 ......... Lid, 66 ......... Base sheet, 68 ......... Frame material, 70 ......... Accommodating space (cavity), 72a, 72b ......... Mount part (mount electrode), 74, 90 ... ... Sealing holes, 80a to 80d ... External electrodes, 84a, 84b ... Metal films.

Claims (2)

A frame-like second ceramic sheet forming a cavity for accommodating the piezoelectric vibrating piece is placed on a flat plate-like first ceramic sheet having a through-hole, and a part of the inner edge thereof overlaps with the opening of the through-hole in a plan view. And a method of manufacturing a piezoelectric device including a step of forming a sealing hole in which a part of the opening is closed by the second ceramic sheet.
The sealing hole is a hole to be sealed by melting a sealing material,
The method for manufacturing the piezoelectric device includes:
Covering the sealing hole is screen-printed with paste-like tungsten, sucking the sealing hole from the side opposite to the side where the tungsten is provided, firing the tungsten, and nickel and gold on the tungsten. A method of manufacturing a piezoelectric device comprising the step of forming a metal film on the wall surface of the sealing hole by sequentially plating the layers .   A plate-like first ceramic sheet having a through hole is laminated with a frame-like second ceramic sheet forming a cavity so that a part of its inner edge overlaps the opening of the through hole in plan view, A method of manufacturing a base including a step of forming a sealing hole in which a part of the opening is closed by the second ceramic sheet,
  The sealing hole is a hole that is sealed by melting a sealing material,
  The manufacturing method of the base is:
  Covering the sealing hole is screen-printed with paste-like tungsten, sucking the sealing hole from the side opposite to the side where the tungsten is provided, firing the tungsten, and nickel and gold on the tungsten. A method of manufacturing a base, comprising the step of forming a metal film on the wall surface of the sealing hole by sequentially plating.

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