JP2002118436A - Surface mount piezoelectric device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent pressed conductive adhesive, with which a piezoelectric transducer is mounted in a package, from protruding onto the side of the piezoelectric transducer on which excitation electrodes are formed, coming too close to the excitation electrodes, and giving harmful influence even if distances between the excitation electrodes and pad electrode coated with the conductive adhesive are very small. SOLUTION: One-to-one connections between two pad electrodes 6 on a piezoelectric transducer 2 and two conducting pads 12 and 13 on a bottom in a surface mount package are realized respectively with conductive adhesive. A recess 20 is formed along one edge of a lower main surface of a piezoelectric board, and at least the pad electrodes connected to lead terminals are placed in the recess to restrict the protruding range of the conductive adhesive within the recess.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface mount type piezoelectric device used as a vibrator, a filter, and the like, and more particularly to a case where a conductive adhesive is used as a means for connecting a piezoelectric vibrating element in a package. The present invention relates to a surface mount type piezoelectric device that has solved various problems.

[0002]

2. Description of the Related Art In recent years, as mobile communication devices such as mobile phones have become smaller and lighter, there has been a strong demand for higher functionality. In order to satisfy the two conflicting requirements at the same time,
It is becoming increasingly important to reduce the area of the printed circuit board that constitutes the electrical component and to effectively use the board area by increasing the density of mounted components and the like. Crystal resonators (vibrators and filters) used as frequency control devices in mobile communication equipment and transmission communication equipment are also strongly required to be miniaturized, and as a package structure of the device to support high-density mounting. Are mainly surface-mount type,
At the same time, demands for higher frequencies are increasing.

FIGS. 3A and 3B are a plan view of a crystal unit as an example of a conventional surface mount type piezoelectric device, and FIG.
It is a longitudinal cross-sectional view. This crystal resonator 1 includes a crystal resonator element 2
In the package 3 for surface mounting. The crystal vibrating element 1 is pulled out from the piezoelectric substrate 5, excitation electrodes 6 and 7 respectively formed on both upper and lower main surfaces of the piezoelectric substrate 5, and one end edge of the piezoelectric substrate from each of the excitation electrodes 6 and 7. Lead electrodes 6a, 7a and both lead electrodes 6a, 7a
And two pad electrodes 6b and 7b connected along one edge of the piezoelectric substrate 5 respectively. Pad electrodes 6b drawn from the upper and lower excitation electrodes 6 and 7, respectively.
7b may be arranged on the upper surface and the lower surface of the substrate as shown, respectively, or may be arranged on the lower surface of the substrate by extending the upper lead electrode 6a to the lower surface of the substrate via the side surface of the substrate. The package 3 has a package main body 10 made of, for example, ceramic, and a metal lid 11 for closing an upper opening of the package main body 10. The inner bottom surface of the package main body 10 has one-to-one correspondence with the pad electrodes 6b and 7b. And the corresponding conductive pads 12, 13. Each of the conductive pads 12 and 13 is conductively connected to an external electrode 14 provided on the outer bottom surface of the package body 10. When the quartz-crystal vibrating element 1 is supported on the inner bottom surface of the package body 10 in a cantilever state, the quartz-crystal vibrating element 1 is positioned such that the pad electrodes 6b and 7b correspond one-to-one with the conductive pads 12 and 13. In this state, it is fixed electrically and mechanically by the conductive adhesive 15. The metal lid 11 is fixed by welding or the like to a metal seam ring fixed to the upper surface of the outer frame of the package body. In the surface-mount type crystal resonator having the above-described configuration, the size of the piezoelectric substrate 5 is reduced in response to a demand for miniaturization, so that the excitation electrode 6 is relatively small.
7 becomes large. As a result, the excitation electrode occupies the main surface of the piezoelectric substrate over a wide range close to the entire surface electrode. When the area of the excitation electrode is enlarged as described above, since the pad electrodes 6b and 7b and the excitation electrodes 6 and 7 are close to each other, the conductive adhesive 15 applied to the pad electrodes 6b and 7b is applied to the excitation electrode 6b. , 7 in the vicinity. In particular, when the crystal resonator element is mounted, the conductive adhesive 15 is pressed between the lower surface of the substrate and the conductive pads 12 and 13, so that a part of the pressed conductive adhesive is formed on the lower side. It easily flows out and protrudes toward the excitation electrode 6b. As is well known, the vibration energy of the quartz vibrating element is concentrated on a large portion of the piezoelectric substrate, so that the vibration energy is applied to the excitation electrodes 6 and 7.
However, when the conductive adhesive 15 approaches the excitation electrode 6 as shown in the figure, it becomes difficult to confine the energy within the range of the excitation electrode.
This causes deterioration of the characteristics of the crystal resonator element.

[0004]

The problem to be solved by the present invention is to solve the problem even when the excitation electrode on the piezoelectric vibrating element is close to the pad electrode to which the conductive adhesive is applied. In addition, when the piezoelectric vibration element is mounted in the package using the conductive adhesive, the conductive adhesive pressed can be effectively prevented from flowing out to the excitation electrode side and adversely affecting the excitation electrode. An object of the present invention is to provide a surface mount type piezoelectric device.

[0005]

In order to solve the above-mentioned problems, the invention according to claim 1 is directed to a piezoelectric substrate, excitation electrodes formed on both upper and lower main surfaces of the piezoelectric substrate, and the excitation electrodes drawn from the respective excitation electrodes. A piezoelectric vibrating element comprising: a lead electrode; and two pad electrodes respectively connected to the two lead electrodes and arranged along one edge of the piezoelectric substrate; and a conductive pad provided with the piezoelectric vibrating element on an inner bottom surface. A surface mounted package that electrically and mechanically connects and retains the piezoelectric device in a cantilevered state, wherein two pad electrodes on the piezoelectric vibrating element and two pad electrodes on the inner bottom surface of the surface mounted package are provided. In the one-to-one connection with the conductive pad, each using a conductive adhesive, a recess is formed along the one end edge of the lower main surface of the piezoelectric substrate, and at least the lower side is formed in the recess. Before forming on the main surface By disposing the pad electrode connected to the lead terminals, characterized in that the adhesion area of the conductive adhesive was extreme in the recess.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on an embodiment shown in the drawings. Fig. 1 (a) (b) and (c)
Is a plan view of a crystal resonator as an example of a surface-mount type piezoelectric device according to an embodiment of the present invention, its BB cross-sectional view,
FIG. 2 is a perspective view of an example of the crystal resonator element. This crystal resonator 1 has a configuration in which a crystal resonator element 2 is housed in a surface mounting package 3. The crystal vibrating element 2 includes a piezoelectric substrate 5, excitation electrodes 6 and 7 respectively formed on upper and lower main surfaces of the piezoelectric substrate 5, and excitation electrodes 6 and 7.
Lead electrodes 6a, 7a respectively drawn out toward the one edge of the piezoelectric substrate, and two pad electrodes 6b, 7b connected to the two lead electrodes 6a, 7a and arranged along one edge of the piezoelectric substrate 5, respectively. And. Upper and lower excitation electrodes 6,
The pad electrodes respectively drawn from the edge of the piezoelectric substrate to the edge of the piezoelectric substrate are arranged on the upper surface and the lower surface of the substrate, respectively. May be placed. This embodiment exemplifies the latter case, that is, a case where the pad electrode 6b is arranged on the lower surface of the substrate by extending the upper lead electrode 6a to the lower surface of the substrate via the side surface of the substrate. Piezoelectric substrate 5
Is a recess 2 having a constant width and a constant depth formed by half-etching along one edge on the side where the pad electrodes 6b and 7b are formed.
0 is formed to form the thin portion 21. Accordingly, the pad electrodes 6b, 7b located on the lower surface of the piezoelectric substrate are formed on the inner wall of the recess 20, and the lead electrodes 6a, 7a connecting the respective pad electrodes 6b, 7b and the excitation electrodes 6, 7 also extend along the inner wall of the recess 20. Wired. The package 3 has a package main body 10 made of, for example, ceramic, and a metal lid 11 for closing an upper opening of the package main body 10. The inner bottom surface of the package main body 10 has one-to-one correspondence with the pad electrodes 6b and 7b. And the corresponding conductive pads 12, 13. Each conductive pad 12, 13
It is electrically connected to an external electrode 14 provided on the outer bottom surface of the package body 10.

When the crystal vibrating element 1 is supported on the inner bottom surface of the package body 10 in a cantilever state, the crystal vibrating element 1 is arranged such that the pad electrodes 6b, 7b correspond to the conductive pads 12, 13 one-to-one. Is electrically and mechanically fixed by the conductive adhesive 15 in a state where is positioned. Each pad electrode 6
b and 7b are concave portions 20 formed along one edge of the lower surface of the substrate.
Are formed along the inner wall of the conductive pad 12, 1
As shown in FIGS. 1 (b) and 1 (c), the conductive adhesive 15 connecting between the first electrode 3 and the third electrode 3 cannot flow toward the excitation electrode 7 beyond the inner wall 20a of the concave portion 20. Even if the conductive adhesive is connected to the conductive pad while pressing the quartz-crystal vibrating element, the conductive adhesive is prevented from flowing out beyond the inner side wall 20a of the concave portion 20. , In a range that does not adversely affect the excitation electrode 7. The metal lid 11 is fixed by welding or the like to a metal seam ring fixed to the upper surface of the outer frame of the package body. In the surface mount type crystal resonator having the above-described configuration, the dimensions of the piezoelectric substrate 5 are reduced in response to a demand for miniaturization. The electrode occupies the main surface of the piezoelectric substrate over a wide range close to the entire surface electrode. When the area occupied by the excitation electrodes is increased, the pad electrodes 6b, 7
b and the excitation electrodes 6, 7 are close to each other, so that the pad electrodes 6b,
There is a possibility that the conductive adhesive 15 applied to 7b may have an adverse effect in the vicinity of the excitation electrodes 6 and 7. In particular, when mounting the crystal resonator element, the lower surface of the substrate and the conductive pads 12, 1
3, the conductive adhesive 15 is pressurized, so that a part of the pressurized conductive adhesive easily flows out and protrudes toward the lower excitation electrode 6b.

However, according to the present invention, the pad electrodes 6b and 7b located on the lower surface of the substrate are not arranged on a flat surface which is the same surface as the excitation electrode 7, but the concave portions 20 formed by half etching on the edge of the lower surface of the substrate. Because of this step, the conductive adhesive 15 is accommodated in the recess 20 and is prevented from flowing out to the lower surface of the substrate on which the excitation electrodes 7 are formed. The position of the inner side wall 20a of the concave portion 20 is set to a position where the conductive adhesive is not blocked on the inner side wall so as not to adversely affect the excitation electrode 7. As a result, even if the bonding is performed while pressing the conductive adhesive between the quartz vibrating element and the conductive pad, the conductive adhesive 1
5 does not approach the excitation electrode 7 and causes interference, thereby preventing the vibration energy from being concentrated on the excitation electrodes 6 and 7. When the pad electrode 6b connected to the upper excitation electrode 6 is arranged on the upper surface of the piezoelectric substrate 5, the conductive adhesive 15 is of course placed in the recess 20 as shown by a dashed line in FIG. The coating is applied to the upper surface of the substrate, but also in this case, the inner wall 20a of the concave portion 20 limits the range in which the conductive adhesive spreads, so that the conductive adhesive 15 is prevented from approaching and interfering with the excitation electrode 7. Is done. In the above embodiment, the crystal resonator is described as an example. However, the present invention can be applied to a piezoelectric resonator and a piezoelectric device using a piezoelectric material other than crystal. In the above embodiment, the case where the piezoelectric vibrating element is supported in a cantilever manner in the package has been described. However, in the present invention, the pad electrodes provided on the opposite end edges of the piezoelectric vibrating element are respectively bonded to the conductive pads in the package. It is also possible to apply to cases. In this case, a recess is formed on the lower surface of each of the opposing edges of the piezoelectric vibration substrate,
A pad electrode will be formed in the recess.

[0009]

As described above, according to the present invention, when the piezoelectric vibrating element is supported in the package by the conductive adhesive, the pad electrode formed on the piezoelectric vibrator side is provided on the lower surface of the edge of the substrate. The conductive adhesive does not approach the excitation electrode more than necessary. Because of this,
Even when the excitation electrode on the piezoelectric vibration element is close to the pad electrode to which the conductive adhesive is applied, when the piezoelectric vibration element is mounted in the package using the conductive adhesive, It is possible to effectively prevent the pressurized conductive adhesive from flowing out to the excitation electrode side and being too close to the excitation electrode to have an adverse effect.

[Brief description of the drawings]

FIGS. 1A, 1B and 1C are plan views of a quartz oscillator as an example of a piezoelectric device according to an embodiment of the present invention, and FIGS.
Sectional drawing and CC sectional drawing.

FIG. 2 is a perspective view of a crystal resonator element according to an example of the present invention.

FIGS. 3A and 3B are a plan view and a cross-sectional view taken along line AA of a piezoelectric device according to a conventional example.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 crystal resonator, 2 crystal resonator, 3 surface mounting package, 5 piezoelectric substrate, 6, 7 excitation electrode, 6 a, 7
a Lead electrode, 6b, 7b Pad electrode, 20 recess, 21 thin part.

Claims (1)

[Claims] 1. A piezoelectric substrate, excitation electrodes formed on both upper and lower main surfaces of the piezoelectric substrate, lead electrodes drawn from the respective excitation electrodes, and one end of the piezoelectric substrate connected to both the lead electrodes. A piezoelectric vibrating element comprising: two pad electrodes disposed along the surface; and a surface-mount package for electrically and mechanically connecting and holding the piezoelectric vibrating element in a cantilever state on a conductive pad provided on an inner bottom surface. And a one-to-one connection between two pad electrodes on the piezoelectric vibrating element and two conductive pads on the inner bottom surface of the surface mount type package using a conductive adhesive. In the performed, a concave portion is formed along the one end edge of the lower main surface of the piezoelectric substrate, and the pad electrode connected to the lead terminal formed on at least the lower main surface is arranged in the concave portion. By The surface mount type piezoelectric device which is characterized in that the adhesion area of the conductive adhesive was extreme in the recess.