JP2002171150A - Package structure of piezoelectric device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectric device having a package in which a lid made of a glass material is bonded with a low melting point glass on the upper surface of a base on which a piezoelectric vibrating reed is mounted, especially between the base and the lid against external force from the side. Reduce the size and thickness while ensuring sufficient bonding strength. SOLUTION: A thin plate-shaped lid 12 made of a glass material is
A thin rectangular box-shaped base 1 made of a ceramic material and having a step 20 formed all around the lower surface peripheral portion.
On top of the side wall 1, the side wall 16 is arranged so that the step is aligned with the inner peripheral corner of the upper end surface. The base and the lid use the low melting point glass 19 between the vertical side surface 20a and the horizontal downward surface 20b of the step, and the inner side surface 16a and the upper end surface 16b of the side wall portion adjacent to and facing each other. And a hermetic joint, and seals the tuning-fork type quartz vibrating piece 14 inside the package 13.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric device such as a crystal unit, a crystal oscillator, and a SAW device used in electronic equipment. The present invention relates to a structure of a package of a piezoelectric device hermetically sealed with glass.

[0002]

2. Description of the Related Art Conventionally, in electronic devices such as various information / communication devices, OA devices, and consumer devices, a piezoelectric vibrator, a piezoelectric vibrating piece and an IC chip are sealed in the same package as a clock source of an electronic circuit. Piezoelectric devices such as oscillators and real-time clock modules are widely used. In particular, recently, in the field of small information devices such as mobile computers and IC cards, and communication devices such as mobile phones, further miniaturization and thinning of piezoelectric devices have been demanded as devices become smaller and thinner. I have.

In general, a surface mount type piezoelectric device has a package structure in which a lid is bonded to a base on which a piezoelectric vibrating reed and, if necessary, an IC element is mounted and sealed, and a lid made of a glass material is particularly used. It is known that the frequency can be adjusted by irradiating a laser beam to the piezoelectric vibrating reed from outside after sealing. FIG. 8 shows an example of a conventional tuning-fork type piezoelectric vibrator having such a package structure. This piezoelectric vibrator has a package 3 consisting of a rectangular box-shaped base 1 made of an insulating material and a thin plate-shaped lid 2 made of a glass material, in which a tuning-fork type quartz vibrating piece 4 has a base end 4a. And is supported on the bottom surface of the base 1 in a cantilever manner. The lower edge of the lid 2 is joined to the upper end face of the base 1 using low-melting glass 5 to hermetically seal the inside of the package.

[0004]

An external force acts on the package of the piezoelectric device by, for example, an impact such as a drop or the like, or being gripped during mounting. However, the above-described conventional piezoelectric device having a package structure in which the lid is simply placed on the upper end surface of the base and joined, in particular, receives all the forces acting from the sides of the package on the joining surface in the horizontal direction. There is a property that the joint strength against external force from the side is weak. For this reason, conventionally, the bonding area is widened, that is, the sealing width (w in FIG. 8) is increased to increase the bonding strength so that the airtightness of the package is not lost due to breakage of the low-melting glass. However, it is necessary to set the vertical and horizontal dimensions of the package accordingly,
There is a problem that the size of the piezoelectric device cannot be reduced.

Further, in the conventional package structure, the height dimension is determined by the individual heights of the base and the lid only by adding the height of the base and the lid. Therefore, there is a problem that the thickness of the piezoelectric device cannot be sufficiently reduced.

On the other hand, if the outer dimensions of the base are reduced while a sufficient sealing width is secured, there is a possibility that the low-melting-point glass 5 protrudes and causes a sag 5 a on the outer wall of the base 1 as shown in FIG. When an external force acts on such a package from the side, a crack 6 is generated between the sealing portion of the low-melting glass 5 and the sag 5a, and the airtightness of the package is lost. May be caused. In order to prevent such sagging, it is necessary to secure a sufficient margin on the upper surface of the base outside the sealing width, and it is difficult to reduce the size of the piezoelectric device.

Accordingly, the present invention has been made in view of the above-mentioned conventional problems, and an object of the present invention is to provide a piezoelectric device having a package in which a lid made of a glass material is joined to an upper surface of a base on which a piezoelectric vibrating reed is mounted. It is another object of the present invention to provide a package structure capable of ensuring a sufficient bonding strength between a base and a lid against external force acting from all directions, and achieving a reduction in size and thickness.

[0008]

According to the present invention, in order to achieve the above object, there is provided a base for mounting a piezoelectric vibrating reed, and a lid made of a glass material and joined to an upper surface of the base. In a piezoelectric device that includes a package and hermetically seals a piezoelectric vibrating reed inside the package, the base and the lid each have a horizontal bonding surface and a vertical bonding surface, and the base and the lid face each other. The present invention provides a piezoelectric device package structure in which low-melting-point glass is used for bonding between horizontal bonding surfaces and vertical bonding surfaces facing each other.

[0009] By joining the base and the lid in this manner, a considerable portion of the external force acting on the package can be received by the joining surface in the vertical direction, in particular, from the side. Moreover, since the low-melting glass exerts a relatively large strength against compressive stress, the area of the joining surface in the horizontal direction can be reduced, that is, the sealing width can be made smaller than before, and the plane size can be made smaller. A package structure exhibiting sufficient strength against an external force acting from any direction can be obtained.

In one embodiment, it is preferable to roughen at least one of the joining surfaces opposing each other, since the adhesion to the low-melting glass is strengthened by the anchor effect, and a larger adhesive strength is obtained.

In one embodiment, the horizontal and vertical joint surfaces of the lid are formed by steps provided on the lower surface of the lid over the entire circumference. By joining the upper end of the base to the step and joining the two, the height of the package can be reduced by the vertical dimension of the step, and the piezoelectric device can be made thinner.

This step can be formed by chemical processing such as mechanical processing or etching, or by integral molding such as press molding. In particular, when this step is formed by attaching low-melting glass to the lower surface of the lid, the step and the lower surface of the lid can be easily formed into a desired shape.
In this case, the softening point of the low-melting glass adhered to the lower surface of the lid may be higher than the softening point of the low-melting glass for joining the base and the lid. It is preferable not to let them.

In another embodiment, when the lid is joined to the base when the lid is joined to the base, the horizontal and vertical joining surfaces of the base are formed by steps provided over the entire periphery of the base. Its alignment is easier. Further, the step serves as a partition wall, which effectively prevents excess low-melting glass from protruding from the joint between the base and the lid and causing sagging on the outer surface of the base. This step can be formed by a metallized portion attached to the upper surface of the base. Further, this step can be integrally formed by further laminating one thin plate member on the upper surface of a base having a multilayer structure in which a plurality of thin plate members made of an insulating material such as ceramics are laminated.

According to another aspect of the present invention, there is provided a package structure of a piezoelectric device further including an IC element mounted on a base.

[0015]

Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In each of the drawings, similar components are denoted by the same reference numerals.

FIG. 1 schematically shows the structure of a first embodiment of a piezoelectric vibrator to which the present invention is applied. This piezoelectric vibrator has a package 13 comprising a thin rectangular box-shaped base 11 and a lid 12, and a tuning fork type quartz vibrating piece 14 is hermetically sealed therein. The base 11 is a bottom plate 1 in which two thin plate members made of an insulating material such as ceramics are laminated.
5 and a rectangular frame-like side wall portion 16 integrally joined to the upper surface thereof
It is composed of A tuning-fork type quartz vibrating piece 14 is fixed to the bottom plate 15 at a base end 14a of the tuning fork-type quartz vibrating piece 14 in a cantilever manner and substantially horizontally by a conductive adhesive 17 and is attached to a free end 14b at the tip of the tuning fork-type quartz vibrating piece 14. A concave portion 18 is provided in an adjacent region so that the free end portion 14b does not collide with the surface of the bottom plate portion 15 even when the free end portion 14b swings downward due to an external impact or the like. The lid 12 is formed of a rectangular thin plate made of a transparent glass material, and is hermetically bonded to the upper end surface of the side wall 16 with a low-melting glass 19.

As shown in FIG. 1B, a step 20 is formed all around the lower edge of the lid 12.
The lid 12 is arranged on the base 11 such that the step is aligned with the inner peripheral corner of the upper end face of the side wall 16. The step 20 has a vertical side surface 20a and a horizontal downward surface 20b, and the inner side surface 16 of the side wall portion 16 adjacent to and opposed to the side surface 20a.
low melting glass 1 filled between a and the upper end face 16b
9, the base 11 and the lid 12 are joined.

The base 11 and the lid 1 are formed by using such a step.
2 and, in particular, a considerable part of the external force acting from the side of the package 13 is
a, and between 16a and between the low melting point glass. Low-melting glass exhibits relatively high strength with respect to compressive stress, and is therefore less likely to crack. Therefore, the area of the bonding surface in the horizontal direction can be reduced, that is, the sealing width w can be made smaller than before, so that the planar size of the package 13 is reduced while ensuring sufficient bonding strength against external forces acting from all directions. be able to.

Further, since the lower surface of the lid 12 protrudes into the base 11 due to the step 20, the height of the package 13 can be made smaller by the vertical sealing width h than before, and the thickness of the piezoelectric vibrator can be reduced. Can be achieved.

In this embodiment, the step 20 of the lid is formed by etching a lower peripheral portion of a glass thin plate having a predetermined size. The step due to the etching does not cause microcracks as in the case of machining, and there is no risk of lowering the strength of the lid itself. In addition, since the surfaces of the steps 20a and 20b of the step formed by the etching are rough, the adhesion to the low melting point glass 19 is enhanced by the anchor effect, and a larger adhesive strength is obtained.

In another embodiment, the step can be formed by known mechanical processing or other physical / chemical processing. Furthermore, by an integral molding method such as stamping molding,
The lid having the step can be easily formed.

Actually, with respect to the quartz resonator having the structure shown in FIG. 1, a drop impact test was performed on a large number of samples while the sealing width w of the upper end surface of the base 11 was gradually changed. In the drop impact test, three crystal oscillators of three samples were changed on the upper surface and one side surface of a rectangular parallelepiped stainless steel jig having a predetermined weight so that the impact force was applied in three directions orthogonal to each other. After dropping it on the floor from a certain height, for example, about 150 cm, and repeating this several times, remove each crystal oscillator and measure its frequency. To calculate the non-defective rate. As a result, the sealing width w is reduced to about 60
%, The non-defective rate did not decrease.

FIG. 2 shows a modification of the first embodiment shown in FIG. This piezoelectric vibrator is provided with a concave portion
1 is different from the embodiment of FIG. Thereby, even if the free end portion 14b of the quartz vibrating piece swings upward due to an impact or the like, the free end portion 14b does not collide with the lower surface of the lid 12, thereby improving the impact resistance.

The step 20 and the concave portion 21 in this embodiment can be formed by etching the lower surface of a thin glass plate, as in the first embodiment. In another embodiment, the lid 12 can be relatively easily formed into a desired shape by attaching low-melting glass to the lower surface of the thin glass plate, and the thickness of the lid at the step 20 can be always kept constant. it can. In this case, the low-melting glass for forming the step 20 and the concave portion 21 on the lower surface of the thin glass plate is the low-melting glass 1.
When the package is sealed at 9, the softening point, that is, the temperature at which softening / deformation starts, is preferably higher than that of the low-melting glass 19 so as not to deform or eliminate the steps and recesses. For example, when the low melting point glass 19 has a melting point of 320 ° C., the steps 20 and the concave portions 21 may be formed using low melting point glass having a melting point of about 400 ° C.

FIG. 3 shows another modification of the first embodiment. This piezoelectric vibrator differs from the embodiment of FIG. 1 in that a step 20 is formed by a ridge 22 provided on the lower surface of the lid 12. The ridges 22 can be formed relatively easily by attaching low-melting glass to the lower surface of the thin glass plate, whereby the thickness of the lid can always be kept constant. The base 11 and the lid 12 are arranged between the vertical outer peripheral surface 22a of the ridge 22 and the lower peripheral edge 12b of the lid 12, and the inner side surface 16a and the upper end surface 16b of the side wall 16 adjacent to and opposed to the outer peripheral surface 22a. And low melting point glass 19. The softening point of the low melting point glass forming the ridges 22 is set higher than that of the low melting point glass 19 so as not to be deformed or disappear when the package is sealed with the low melting point glass 19. For example, when the melting point of the low melting point glass 19 is 320 ° C., a low melting point glass having a melting point of about 400 ° C. is used for the ridge 22.

FIG. 4 schematically shows the configuration of a second embodiment of the piezoelectric vibrator according to the present invention. This piezoelectric vibrator
The lid 12 is made of a thin plate of a uniform glass material having no steps as in the related art, whereas the base 11 is provided with a step 23 all around its upper end surface. As shown in FIG. 4B, the step 23 is formed by sintering a metallized portion formed by, for example, screen printing tungsten on the upper end surface of the side wall portion 16 along the outer peripheral edge thereof, and then forming a metal material (Ni, Au or the like is deposited by vapor deposition, plating, or the like, and is formed by laminating to a desired height.

The lid 12 is arranged on the base 11 so as to be positioned inside the step 23 as a marker with the step 23 as a marker, so that the position can be adjusted more easily. The base 11 and the lid 12 are composed of a vertical inner peripheral surface 23 a of the step 23, a side wall upper end surface 16 b inside the step 23, a vertical end surface 12 a adjacent to the opposing surface and a lower peripheral edge of the lid 12. 12
b is joined by a low melting point glass 19. By joining the base 11 and the lid 12 using such a step, similar to the case of the first embodiment, a considerable part of the external force acting from the side of the package 13 is reduced to the vertical joining surfaces 23a, 12b. It can be received by the low-melting glass between and in between, and the bonding strength is improved against external forces acting from all directions.

Further, since the step 23 serves as a partition,
Extra low melting glass 19 between base 11 and lid 12
It is possible to effectively prevent the protrusion from protruding and causing the sagging on the outer surface of the base 11 as described above with reference to FIG. 9.

FIG. 5 shows a modification of the second embodiment shown in FIG. This piezoelectric vibrator differs from the embodiment of FIG. 4 in that a step 24 is provided directly on the upper end surface of the side wall portion 16. Such a step 24 can be obtained by partially removing the upper end face of the side wall portion 16 by, for example, mechanical processing, or as shown in FIG.
As shown in FIG. 2B, it can be formed by further laminating separate rectangular frame-shaped thin plate members 16 ′ made of an insulating material such as ceramics on the side wall portion 16 and joining them together.

Also in this embodiment, the base 11 and the lid 12
Similarly, the low melting point glass is formed between the vertical side surface 24a and the horizontal upward surface 24b of the step 24 and the vertical end surface 12a and the lower surface peripheral portion 12b of the lid 12 which is adjacent to and opposed to the vertical side surface 24a. 19.
Thereby, a considerable part of the external force acting from the side of the package 13 can be received by the low melting point glass between the joining surfaces 24a and 12a in the vertical direction and the joining strength is improved with respect to the external force acting from all directions. I do.

FIG. 6 schematically shows the structure of a third embodiment of the piezoelectric vibrator according to the present invention. This piezoelectric vibrator
As in the first embodiment, the lid 12 has a step 20 formed on the entire periphery of the lower surface thereof, while the base 11 has the upper end surface as in the second embodiment. Is provided with a step 23 over the entire circumference. As in the embodiment of FIG. 4, the step 23 is formed by sintering a metallized portion formed by, for example, screen printing of tungsten on the upper end surface of the side wall portion 16 along the outer peripheral edge thereof, and then forming a metal material (Ni,
Au or the like is deposited by vapor deposition, plating, or the like, and is formed by laminating to a desired height.

In this embodiment, as shown in FIG. 6B,
The lid 12 has its end surface 12a as a vertical joining surface and the side surface 20a of the step 20, and has a downward surface 20b of the step 20 as a horizontal joining surface. Base 11
Has a vertical inner peripheral surface 23a of the step 23 and an inner surface 16a of the side wall 16 as a vertical bonding surface, and has a side wall upper end surface 16b inside the step 23 as a horizontal bonding surface. .

The lid 12 is arranged on the base 11 so that the step 23 of the base 11 is positioned inside the step 11 as a marker, and the step 20 of the lid protrudes inside the side wall portion 16. Then, the end surface 12a of the lid 12 and the step side surface 20
a between the inner peripheral surface 23a of the step 11 and the inner side surface 16a of the side wall of the base 11 which are adjacent to and opposed to each other;
The base 11 and the lid 12 are joined by the low-melting glass 19 between the step-downward surface 20b of the above and the upper end surface 16b of the side wall portion of the base 11 which is adjacent to and opposes the lower surface.

By joining using the steps provided on both the base 11 and the lid 12, the lid can be easily and properly positioned at a predetermined position on the base, and can be joined in the vertical direction. Since the area of the surface is increased, the joining strength against external force acting particularly from the side of the package 13 is further improved. Further, since the lower surface of the lid 12 protrudes into the base 11 due to the step 20, the height of the package 13 can be reduced by the height of the step 20 as compared with the conventional case, and the thickness of the piezoelectric vibrator can be reduced. .
Further, since the step 23 of the base 11 can be reduced accordingly, it is easy to form it.
(1) Leaning on the outer surface can be effectively prevented.

FIG. 7 schematically shows the configuration of an embodiment of the piezoelectric oscillator according to the present invention. This piezoelectric oscillator is shown in FIG.
This embodiment has a similar configuration to that of the first embodiment, but is basically different in that an IC chip 26 for driving the crystal vibrating reed 14 is mounted in a recess 25 provided in the bottom portion 13 of the base 11. A wiring pattern (not shown) for connecting to the outside and the crystal vibrating piece 14 is formed on the upper surface of the bottom portion 13 of the base 11, and is connected to the electrode terminals on the upper surface of the IC chip 26 by bonding wires 27.

The base 11 and the lid 12 are connected to a vertical outer peripheral surface 22a of the ridge 22 and a lower peripheral edge 12b of the lid 12,
A low-melting glass 19 is used to bond between the inner surface 16a and the upper end surface 16b of the side wall 16 which is adjacent to and opposes them. Accordingly, the bonding strength against an external force acting particularly from the side of the package 13 is improved, and the sealing width in the horizontal direction can be reduced, so that the size of the piezoelectric oscillator can be reduced.

Although the preferred embodiments of the present invention have been described in detail above, as will be apparent to those skilled in the art, the present invention can be implemented by adding various changes and modifications to the above embodiments within the technical scope thereof. be able to.

[0038]

According to the piezoelectric device of the present invention, since the package structure in which the base and the lid are joined as described above, an external force acting particularly from the side of the package can be received on the joining surface in the vertical direction. In order to ensure the package's airtightness by improving the joint strength between the base and the lid against external forces acting from all directions, the sealing width in the horizontal direction can be made smaller than before, The size can be reduced and the size can be reduced.

[Brief description of the drawings]

1A is a longitudinal sectional view showing a first embodiment of a piezoelectric vibrator according to the present invention, and FIG. 1B is an enlarged partial sectional view showing a joint between a base and a lid thereof.

FIG. 2 is a longitudinal sectional view showing a modification of the first embodiment.

FIG. 3A is a longitudinal sectional view showing another modified example of the first embodiment, and FIG. 3B is an enlarged partial sectional view showing a joint between a base and a lid.

FIG. 4A is a longitudinal sectional view showing a second embodiment of the piezoelectric vibrator according to the present invention, and FIG. 4B is an enlarged partial sectional view showing a joint between a base and a lid thereof.

FIG. 5A is a longitudinal sectional view showing a modification of the second embodiment, and FIG.
The figure is an enlarged partial sectional view showing the joint between the base and the lid.

FIG. 6A is a longitudinal sectional view showing a third embodiment of the piezoelectric vibrator according to the present invention, and FIG. 6B is an enlarged partial sectional view showing a joint between a base and a lid thereof.

FIG. 7 is a longitudinal sectional view showing an embodiment of a piezoelectric oscillator according to the present invention.

8A is a longitudinal sectional view showing a conventional piezoelectric vibrator, and FIG. 8B is an enlarged partial sectional view showing a joint between a base and a lid thereof.

FIG. 9 is an enlarged partial cross-sectional view showing a joint between a base and a lid of a conventional piezoelectric vibrator.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1, 11 Base 2, 12 Lid 3, 13 Package 4, 14 Tuning fork type crystal vibrating piece 4a Base end 5, 19 Low melting point glass 5a Sagging 6 Crack 12a End face 12b Lower peripheral edge 14b Free end 15 Bottom plate 16 Side wall 16 'Thin plate member 16a Inner side surface 16b Upper end surface 17 Conductive adhesive 18 Depression 19 Low melting point glass 20 Step 20a Side surface 20b Downward surface 21 Depression 22 Protrusion 22a Outer peripheral surface 23 Step 23a Inner peripheral surface 24 Step 24a Side surface 24b Upward surface 25 Recess 26 IC chip 27 Bonding wire

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) H03B 5/32 H01L 41/08 C

Claims (8)

[Claims] 1. A package having a base for mounting a piezoelectric vibrating reed and a lid made of a glass material bonded to an upper surface of the base, wherein the piezoelectric vibrating reed is hermetically sealed inside the package. In the piezoelectric device, the base and the lid each have a horizontal bonding surface and a vertical bonding surface, and the base and the lid are between the horizontal bonding surfaces facing each other, and A package structure for a piezoelectric device, wherein the vertical bonding surfaces facing each other are bonded using low-melting glass. 2. The package structure for a piezoelectric device according to claim 1, wherein at least one of the joining surfaces facing each other is roughened. 3. The piezoelectric device according to claim 1, wherein the horizontal and vertical joint surfaces of the lid are formed by steps provided over the entire lower surface of the lid. Device package structure. 4. The package structure for a piezoelectric device according to claim 3, wherein the step is formed by attaching a low-melting glass to a lower surface of the lid. 5. The piezoelectric material according to claim 4, wherein the softening point of the low-melting glass adhered to the lower surface of the lid is higher than the softening point of the low-melting glass joining the base and the lid. Device package structure. 6. The base according to claim 1, wherein the horizontal and vertical joining surfaces of the base are formed by steps provided over the entire periphery of the upper surface of the base.
The package structure of the piezoelectric device according to 1. 7. The package structure for a piezoelectric device according to claim 6, wherein the step is formed by a metallized portion attached to an upper surface of the base. 8. The package structure of a piezoelectric device according to claim 1, further comprising an IC element mounted on said base.