JP3781119B2 - Package for piezoelectric device and piezoelectric device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a piezoelectric device package and a piezoelectric device, and more particularly to a piezoelectric device package and a piezoelectric device which are thinned and mounted on a substrate.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, piezoelectric devices such as piezoelectric vibrators are widely used as clock sources for electronic circuits in information communication devices such as mobile phones and PHS, OA devices such as computers, and various electronic devices such as watches. In recent years, in particular, along with the downsizing and thinning of portable electronic devices such as mobile phones, the piezoelectric vibrator has been further reduced in size and thickness.
[0003]
In such a background, the piezoelectric device that is reduced in size and thickness is naturally reduced in the mounting area and the like in mounting, and there is a case where a sufficient bonding / bonding area cannot be secured in mounting. As a result, the bonding / bonding strength of the piezoelectric device to the substrate has been regarded as a problem as well as the package strength, such as peeling of the bonding surface due to warping or bending of the mounting substrate, external impact, or the like. As an example of solving such a problem, an invention described in Patent Document 1 can be cited.
[0004]
In the invention of Patent Document 1, a groove is provided on a package surface that faces the substrate mounting surface. When the piezoelectric device is mounted on the substrate, the groove is filled with an adhesive substance such as a conductive adhesive to ensure a bonding area, and to ensure a bonding strength at the time of mounting.
[0005]
[Patent Document 1]
Japanese Patent Laid-Open No. 2002-329806
[Problems to be solved by the invention]
However, in the invention of Patent Document 1, a certain mounting strength may be maintained, but it is contrary to the purpose of reducing the size and thickness of the piezoelectric device. First, the strength of the package itself is reduced by providing a groove on the package surface. Further, providing the groove makes it difficult to reduce the thickness in order to secure a necessary space inside the package.
[0007]
The present invention solves the above problems and provides a package for a piezoelectric device and a piezoelectric device that can maintain sufficient mounting strength while alleviating bending stress generated in the package when the size and thickness of the piezoelectric device are reduced. For the purpose.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, a piezoelectric device package according to the present invention is a piezoelectric device package in which a pair of external electrodes for mounting on a substrate is provided on the outer surface of the bottom of the package , and the length of the package in the longitudinal direction. When L is L, the distance between the pair of external electrodes is set to be less than 0.53L and 0.41L or more, and a notch is provided in the outer central portion of the external electrode.
[0009]
In the above configuration, if there is no separation between the substrate and the package, the bending stress applied to the substrate is transmitted to the package via the electrode. The bending action point is the center between the pair of electrodes. For this reason, the bending stress which arises in a package is reduced by shortening the distance to each electrode used as a power point from an action point to less than the conventional 0.53L. Further, when the substrate is bent, each electrode is positioned on a circular arc having a large curvature. Therefore, the bending rate applied to the package can be reduced by reducing the width between the electrodes. Furthermore, by setting the distance between the electrodes to 0.41 L or more, it is possible to avoid the electrode distance from becoming too narrow and short-circuiting. In addition, when the substrate is bent, stress is generated particularly in the central portion of the mounted package electrodes, which may cause electrode peeling or package damage. For this reason, by providing a notch outside the central part of each external electrode, the stress generated on the electrode mounting surface can be relieved, so that the stress on each part of the package can also be relieved.
[0011]
In the case where a cutout is provided in the external electrode, it is desirable that the cutout has an opening width w of 0.3a ≦ w ≦ 0.45a when the length of the external electrode is a.
As a result, the degree of relaxation of the stress generated in each part due to the notch is within a range of 5% or more, and a reliable adhesion surface to the mounting surface can be secured.
[0012]
Further, the notch is preferably formed in a U shape. By making the notch U-shaped, the concentrated stress generated in the corner can be dispersed.
Moreover, when producing a piezoelectric device, it is desirable to set it as the piezoelectric device which has a package of any one of Claims 1 thru | or 4.
[0013]
In the piezoelectric device as described above, the bending stress transmitted to the package is sufficiently relaxed even when bending is applied to the substrate which is the mounting surface, and the peeling of the electrode can be suppressed, so that the package is thinned. Even when the package strength is reduced, the package is less likely to be damaged.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a piezoelectric device package according to the present invention will be described in detail with reference to the drawings.
FIG. 1 is an embodiment showing a configuration of a piezoelectric device package and a piezoelectric device according to the present invention. A piezoelectric vibrator 10 which is a piezoelectric device has a structure in which a piezoelectric vibrating piece is housed in a package 12.
[0015]
The structure of the package 12 of this embodiment includes a base 14 on which a piezoelectric vibrating piece is mounted, and a lid 22 that serves as a lid for the base and seals the package. The base 14 includes a rectangular thin plate bottom 16 made of an insulating material such as ceramic, a rectangular thin plate intermediate portion 18 laminated on the top surface of the bottom portion 16, and a rectangular frame shape laminated on the upper edge of the intermediate portion 18. This is a three-layer structure composed of the side wall portion 20. Further, the bottom portion 16 and the intermediate portion 18 of the base 14 are provided with a sealing hole 28 and a sealing hole 29 in the center portion, respectively. The sealing hole 29 is desirably formed to have a slightly smaller diameter than the sealing hole 28, and the sealing hole 28 is sufficiently large so that it does not protrude when the alloy ball serving as the sealing material is melted. It is good to have a volume. The lid 22 is a transparent thin glass plate or ceramic thin plate, and is formed in a rectangular shape. After mounting the tuning fork type vibrating piece 26 which is a piezoelectric vibrating piece on the base 14 with a conductive adhesive 32 or the like, the lid is attached to the upper end surface of the base 14 (upper surface of the side wall portion 20) such as sealing glass or solder. Fix with a sealing material 24. Further, the package 12 having the above-described configuration includes a pair of external electrodes 30 on the lower surface of the bottom portion 16.
[0016]
The external electrodes 30 are arranged in parallel along the short side of the package 12. Further, in order to relieve stress generated in each part of the package when the package 12 is mounted on a substrate (not shown), it is preferable to arrange as shown in FIG. That is, when the long side of the bottom portion 16 is L, the distance d between the pair of external electrodes 30 is less than 0.53L.
[0017]
Similarly, when the package 12 is mounted on a substrate (not shown), the external electrodes 30 are notched at the outer central portions of the electrodes as shown in FIG. It is good to provide. In this case, if the length of the external electrode 30 is a, the width of the notch opening is preferably in the range of 0.3a ≦ w ≦ 0.45a. As shown in FIG. 4, a load stress 34 is generated on the external electrode 30 of the mounted package 12 as shown in FIG. Therefore, by providing the notch in the external electrode 30, it is possible to avoid the load stress 34 concentrated on the central portion, so that the stress generated in each portion of the package 12 can be reduced. Further, the shape of the external electrode 30 after the notch is preferably U-shaped in order to disperse the stress concentrated on the corners.
[0018]
In the package 12 including the external electrodes 30 for mounting on the board as described above, in order to demonstrate the relaxation degree of the bending stress, the electrode interval d is set to 0.53 L, the notch is not provided, and the package is mounted on the board (not shown). 12 is mounted, and the substrate (not shown) is bent. The bending stress generated in each part of the package at this time is defined as a reference stress.
[0019]
First, when the interval d between the external electrodes 30 is set to 0.41L ≦ d <0.53L, the bending stress generated in each part of the package is relieved as shown in FIGS. Can do. For example, the stress generated at the bottom 16 can be relaxed by up to about 25%. The stress generated in the sealing material 24 and the lid 22 can be relaxed by about 32% at the maximum.
[0020]
In the above-described relaxation action, when bending stress is applied to the substrate on which the package 12 is mounted, the bending stress is transmitted to the package 12 via the external electrode 30. The bending action point is the center of the distance d between the pair of external electrodes 30. For this reason, the force applied to the package is reduced by making the distance from the point of action to the position where each external electrode 30 serving as the power point is disposed shorter than the conventional 0.53L. Further, when the substrate is bent, each external electrode 30 is located on a circular arc having a large curvature. Therefore, by reducing the arrangement distance d of the external electrodes 30, although not shown, the amount of movement of the external electrodes 30 along the bending of the substrate is reduced, so that the bending rate applied to the package 12 can be reduced. The bending stress applied to each part of the package can be relaxed. As described above, the bending stress generated in each part of the package 12 is alleviated as the arrangement interval d of the external electrodes 30 is reduced. However, when d is smaller than 0.41 L, a short circuit occurs between the electrodes. There is a fear.
[0021]
Further, if a notch is provided in the outer central portion of each external electrode 30, bending stress generated in each portion of the package can be relaxed as shown in FIG. This is because the load stress 34 is generated in each external electrode 30 when mounted on the substrate when the substrate is bent, and the load stress 34 is particularly strongly generated in the central portion of the external electrode 30. By creating a state in which the electrodes are peeled in advance, the load stress 34 can be relieved, and the stress generated in each part of the package can be relieved. As a notch width that can exert a remarkable effect on stress relaxation, 0.3a ≦ w ≦ 0.45a can be satisfied. According to this, the bottom portion 16 can be relaxed by about 10 to 15%, the sealing material 24 can be 8 to 15%, and the lid 22 can be relaxed by about 5 to 14%.
[0022]
As described above, the notch is provided in each of the external electrodes 30, and the stress transmitted to each part of the package can be reduced as the width of the notch is increased. However, the notch width is wider than 0.45a. In this case, the mounting strength on the substrate may not be sufficient, so the above range is preferable.
[0023]
In the package 12 of the piezoelectric device as described above, when the arrangement direction length of the external electrode 30 on the outer surface of the bottom portion 16 of the package 12 is L, the arrangement interval of the pair of external electrodes 30 is less than 0.53L. Thus, when there is no separation between the substrate and the package 12, the bending stress applied to the substrate is transmitted to the package 12 through the electrodes. The bending action point is the center of the distance d between the pair of external electrodes 30. For this reason, the bending stress which arises in the package 12 can be reduced by making distance from the action point to each external electrode 30 used as a power point shorter than the conventional 0.53L. When the substrate is bent, each external electrode 30 is positioned on a circular arc having a large curvature. Therefore, the bending transmitted to the package 12 is reduced by reducing the interval between the external electrodes 30. The rate can be relaxed.
[0024]
Further, in order to relieve the bending stress generated in the package 12, the outer center portion of each external electrode 30 has a notch, which is generated on the electrode mounting surface that causes peeling of the electrode or breakage of the package 12. The stress generated can be relieved, and the stress generated in each part of the package can also be relieved.
[0025]
In addition, when the external electrode 30 is provided with a notch, the opening width w of the notch is 0.3a ≦ w ≦ 0.45a, where the length of the external electrode 30 is a. As a result, the degree of relaxation of stress generated in each part of the package is in the range of 5% or more compared to the case where there is no notch, and a reliable adhesion surface to the mounting surface can be secured.
Furthermore, by forming the notch in a U shape, the concentrated stress generated at the corner of the notch can be dispersed.
[0026]
In the above embodiment, the structure of the package 12 is a three-layer structure, but the present invention is not limited to this, and can be applied to a two-layer structure or the like. Moreover, although the piezoelectric vibrating piece mounted inside the package 12 is the tuning fork type vibrating piece 26, it may be an AT cut vibrating piece or the like.
[0027]
Moreover, although the numerical range is shown about the arrangement | positioning space | interval of the external electrode 30 and the width | variety of a notch in embodiment, a package is not only by narrowing the arrangement | positioning space | interval of the external electrode 30, but providing a notch in an electrode. The effect of relieving the stress generated in each part can be achieved, and the designated range is for ensuring a remarkable effect and safety.
[0028]
Further, in the embodiment, the adjustment of the arrangement interval of the external electrode 30 and the provision of the notch have been separately demonstrated, but the effect of alleviating the stress generated in each part of the package is equal or even more even by combining them. I can give you.
[0029]
In addition, when producing a piezoelectric device, it is desirable to set it as the piezoelectric device which has the package 12 demonstrated above.
In the piezoelectric device as described above, even when bending is applied to the substrate which is the mounting surface, the bending stress transmitted to the package is sufficiently relieved and electrode peeling can be suppressed. Therefore, even when the package is thinned and the package strength is reduced, the package is not easily damaged.
[Brief description of the drawings]
FIG. 1 is a side sectional view showing a structure of a piezoelectric vibrator according to the present invention.
FIG. 2 is a diagram showing an arrangement interval of external electrodes at the bottom of a package related to the present invention .
FIG. 3 is a view showing a cutout of an external electrode at the bottom of a package according to the present invention .
FIG. 4 is a diagram showing a state of a load stress generated in an external electrode when mounted on a substrate.
FIG. 5 is a diagram showing the degree of relaxation of stress generated in each part of the package when the interval between the external electrodes is narrowed.
FIG. 6 is a diagram showing the degree of relaxation of stress generated in each part of the package when notches are provided in the external electrode.
[Explanation of symbols]
10 ......... Piezoelectric vibrator, 12 ......... Package, 14 ......... Base, 16 ......... Bottom, 18 ......... Intermediate, 20 ......... Side, 22 ......... Lid, 24 ......... Sealing material 26... Tuning fork type vibrating piece 28... Sealing hole 29... Sealing hole 30... External electrode 32 32 Conductive adhesive 34. stress.

Claims (4)

A package for a piezoelectric device in which a pair of external electrodes for mounting on a substrate is provided on the outer surface of the bottom of the package, and when the longitudinal length of the package is L, the distance between the pair of external electrodes is 0. A package for a piezoelectric device, wherein the package is less than .53L and 0.41L or more, and a notch is provided in the outer central portion of the external electrode . 2. The package for a piezoelectric device according to claim 1 , wherein the notch has an opening width w of 0.3a ≦ w ≦ 0.45a when the length of the external electrode is a. The piezoelectric device package according to claim 1, wherein the notch is formed in a U shape. A piezoelectric device comprising the package according to claim 1 .

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