JP2005012635A - Piezoelectric device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface-mounted piezoelectric device which is enabled in miniaturization and enhances the strength of bonding with a conductive adhesive used as a means for connecting a piezoelectric vibrating element into a package. <P>SOLUTION: The piezoelectric device is characterized by comprising a crystal oscillator element 1 equipped with a crystal oscillator element body (AT cut crystal substrate) 1a which has the same notched portion 1d in each of both corners in one terminal (on one short side) in the lengthwise direction and becomes shorter and smaller than the other short side, an exciting electrode 1b which is disposed approximately in the center of each of both principal surfaces of the crystal substrate 1a, and a lead electrode 1c extending from the exciting electrode 1b to the edge of the notched portion 1d, a ceramic package (printed wiring board) 2 equipped with a recessed portion 3 for housing the crystal oscillator element 1 on its upper surface, and a metal lid member 4 for sealing an opening of the recessed portion 3. The piezoelectric device is also characterized by having a structure for air-tightly sealing the recessed portion 3 with the lid member 4 after cantilever support and electrical connection using one terminal of the crystal oscillator element 1 in the lengthwise direction with the conductive adhesive 6 to a pad electrode 5 which is formed on an inner bottom face of the recessed portion 3. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a surface-mounted piezoelectric device used as a vibrator, a filter, or the like, and in particular, a surface that solves various problems that occur when a conductive adhesive is used as a means for connecting a piezoelectric vibration element in a package. The present invention relates to a mounting type piezoelectric device.
[0002]
[Prior art]
Due to the rapid progress in price reduction and miniaturization accompanying the popularization of mobile communication devices such as mobile phones, the cost of crystal resonators (vibrators, filters) used as frequency control devices in these communication devices is also low. There is a growing demand for downsizing and downsizing.
[0003]
Hereinafter, a conventional piezoelectric device will be described.
Conventional electronic component packages include
For example, there is something proposed in Japanese Patent Application Laid-Open No. 2001-77656,
This will be described using an oscillator.
FIG. 3A is a longitudinal sectional view showing a configuration of a crystal resonator which is a conventional piezoelectric device, and FIG. 3B is a perspective view showing a joint portion of the crystal resonator element.
This piezoelectric device is a crystal resonator packaged for surface mounting. The quartz crystal resonator 100 includes a substantially rectangular quartz crystal vibration including excitation electrodes disposed on both main surfaces and an extraction electrode 101a extending from one of the excitation electrodes to one end (one short side) in the longitudinal direction. It is composed of an element 101, a ceramic package 102 having a cavity 103 for accommodating the crystal resonator element 101 on the upper surface, and a lid 104 for sealing the opening of the cavity 103. . The crystal resonator element 101 is fixedly connected in a cantilever manner to the electrode pad 105 disposed on the inner bottom surface of the cavity portion 103 via a conductive adhesive 106, and the opening of the cavity portion 103 is opened to the lid 104. Airtightly sealed.
[0004]
The conductive adhesive 106 is generally a silicone-based conductive adhesive that is excellent in flexibility and can minimize distortion (curing strain) to the adherend (the quartz crystal vibration element 101). . However, when a silicone-based conductive adhesive is used, the adhesive strength is weak, so peeling easily occurs due to shock such as impact, and in a crystal resonator used in mobile communication equipment with strict specifications for impact, Soft adhesives with weak adhesive strength are not suitable. Therefore, conventionally, the conductive adhesive 106 is applied to the electrode pad 105 so as to be at the outer positions in the width direction of the one end portion (one short side) and the long side of the long side. The crystal resonator element 101 is placed so that the extraction electrode 101a comes into contact therewith. At that time, the quartz vibrating element 101 is placed so that the corners at both ends of one short side are located outward from both the short side and the long side with respect to the central part of the conductive adhesive 106 (the peak portion of the bulge). ing. As a result, the conductive adhesive member is applied to the end surfaces that are both corners of one short side of the piezoelectric vibrator, that is, the short side end surface and the long side end surface, respectively. As a result, the ceramic package 102 and the crystal resonator element 101 are bonded to each other at one short side end surface and two long side end surfaces of the crystal resonator element 101, and are bonded and fixed at a total of three end surfaces. Will be. Accordingly, the bonding strength is improved, and when an impact is applied from the outside due to dropping or the like, peeling does not easily occur at the bonded portion, and the oscillation frequency does not change greatly or an oscillation failure does not occur.
[0005]
[Patent Literature]
JP 2001-77656 A.
[0006]
[Problems to be solved by the invention]
FIG. 4 is a schematic diagram showing the difference in the joint portion depending on the positional relationship between the crystal resonator element and the cavity portion.
However, in order to satisfy the demand for further miniaturization of the piezoelectric device in recent years, the ceramic package 102 is miniaturized, that is, the clearance between the inner wall surface of the cavity portion 103 and the end surface of the crystal resonator element 101 is narrowed. There must be. With this narrow clearance, the above-described positional relationship between the crystal resonator element 101 and the conductive adhesive 106 cannot be ensured, and the fillet 107 cannot be formed. When the fillet 107 is formed within this narrow clearance, the conductive adhesive 106 does not substantially adhere to the upper surface side of the crystal resonator element 101 as shown in FIG. However, as shown in FIG. 4B, the conductive adhesive 106 does not spread in the (planar) outward direction of the crystal resonator element 101 by the inner wall surface of the cavity portion 103 to which the conductive adhesive 106 is adjacent, and the upward direction. As a result, the conductive adhesive 106 may adhere to the upper surface of the crystal resonator element 101 (reference numeral 110) and the oscillation characteristics may vary.
[0007]
Therefore, as a means disclosed as a conventional example of the patent document, the conductive adhesive is applied on the electrode pad, the crystal resonator element is mounted, and then the upper surface side of the crystal resonator element Therefore, there is a means for applying the conductive adhesive again so as to be electrically connected to the previously applied conductive adhesive. With this means, the post-applied (second time) conductive adhesive can be applied to the intended position, so that the post-applied conductive adhesive does not affect the oscillation characteristics of the crystal resonator element. Since the above-described fillets 107 on the two long sides cannot be formed, it is not possible to improve the bonding strength.
[0008]
The present invention has been made in order to solve the above-described problems, and is capable of reducing the size and improving the bonding strength with a conductive adhesive used as a means for connecting a piezoelectric vibration element in a package. Another object is to provide a surface-mounted piezoelectric device.
[0009]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the invention according to claim 1 according to the present invention includes a piezoelectric vibration element including excitation electrodes disposed on both main surfaces and lead electrodes extending from the excitation electrodes, and an upper surface. A first printed wiring board having a recessed portion for accommodating the piezoelectric vibration element; and a metal lid member for closing the opening of the recessed portion, and formed on the inner bottom surface of the recessed portion. A piezoelectric vibration element in which the piezoelectric vibration element is mechanically and electrically connected to a pad electrode via a conductive adhesive, and the concave portion is hermetically sealed by the lid member, and the outer peripheral edge of the piezoelectric vibrator A notch is formed in the notch, and the end of the lead electrode is disposed on the periphery of the notch.
[0010]
According to a second aspect of the present invention, in the first aspect, the notch is formed at a corner of the piezoelectric vibration element.
[0011]
According to a third aspect of the present invention, in the first or second aspect, the notch portion is formed in a side portion of the piezoelectric vibration element.
[0012]
According to a fourth aspect of the present invention, in any one of the first to third aspects, a concave portion is formed on one main surface of the piezoelectric vibration element.
[0013]
A fifth aspect of the invention is characterized in that in any one of the first to fourth aspects, the conductive adhesive is applied twice.
[0014]
According to a sixth aspect of the present invention, in any one of the first to fifth aspects, a circuit element constituting an oscillation circuit and a temperature compensation circuit is accommodated in the recessed portion.
[0015]
According to a seventh aspect of the present invention, in any one of the first to fifth aspects, a second recessed portion is formed on a lower surface of the first printed wiring board, and the circuit element is mounted on the second recessed portion. It is characterized by that.
[0016]
According to an eighth aspect of the present invention, the piezoelectric device according to any one of the first to fifth aspects, the circuit element, and a second printed wiring board for mounting the circuit element are provided, and the piezoelectric element is provided. The second printed wiring board on which the circuit element is mounted is mechanically and electrically connected below the device.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail based on illustrated embodiments of the present invention.
[0018]
FIG. 1A is a top view of the piezoelectric device according to the first embodiment of the present invention in a state where the lid member of the crystal resonator is omitted, FIG. 1B is a longitudinal sectional view thereof, and FIG. It is a perspective view of the junction part of the crystal oscillation element concerning invention embodiment.
The crystal resonator according to the first embodiment includes a plate-shaped crystal resonator element 1 and a ceramic package (first printed wiring board) 2 including a concave portion 3 for accommodating the crystal resonator element 1 on the upper surface, And a metal lid member 4 that closes the opening of the recessed portion 3. The pad electrode 5 formed on the inner bottom surface of the recessed portion 3 is cantilevered at one end in the longitudinal direction of the quartz crystal vibration element 1 via the conductive adhesive 6 and electrically connected to the lid member. 4 has a structure in which the recess 3 is hermetically sealed.
[0019]
The crystal resonator element 1 has notches 1d having the same (position, shape, size, etc.) at both corners of one end (one short side) in the longitudinal direction, and is shorter than the other short side. In other words, the crystal resonator element main body (AT-cut crystal substrate) 1a having a substantially convex planar outer shape, the excitation electrode 1b disposed substantially at the center of both main surfaces of the crystal substrate 1a, and the excitation electrode 1b And a lead electrode 1c extending to the periphery of the notch 1d.
[0020]
The conductive adhesive 6 is a silicone-based conductive adhesive, and the central portion of the conductive adhesive 6 (the peak portion of the bulge) is inside the notch 1d, for example, the central portion of the conductive adhesive 6 Is applied to a position on the pad electrode 5 where the (planar) center of the notch 1d substantially coincides, and the crystal resonator element 1 is placed so that the lead electrode 1c contacts. Thereby, the conductive adhesive 6 is disposed on the gap between the lower surface periphery of the notch 1d and the pad electrode 5 and the inner end face of the notch 1d (fillet 7 is formed on the inner end face). become. As a result, the bonding strength is improved, and when an impact is applied from the outside due to dropping or the like, peeling is unlikely to occur at the bonded portion.
[0021]
In order to further improve the bonding strength, the conductive adhesive previously applied from the upper surface side of the quartz crystal vibration element (the lead electrode) placed on the pad electrode via the conductive adhesive. It is desirable to apply the conductive adhesive again (apply twice) so as to be conductive.
[0022]
Although the present invention has been described using the first embodiment, that is, the crystal resonator element 1 provided with the notches 1d (and the lead electrode 1c) at both corners of one short side, the other crystal vibrations have been described. A method of supporting the element, for example, four-point support (showing a method of mechanically and electrically joining at both corners of one short side of the crystal vibrating element and mechanically joining at both corners of the other short side). In this case, notches (and lead electrodes) are formed at the four corners of the crystal resonator element (the planar shape of the crystal resonator element is substantially cross-shaped), and the conductive adhesive and the crystal resonator element described above are used. By maintaining the positional relationship, the crystal resonator as the piezoelectric device of the second embodiment of the present invention is obtained.
[0023]
Although the present invention has been described using the first and second embodiments, that is, the crystal resonator element provided with the notches (and lead electrodes) at both corners of one short side and at the four corners, In the case of a support method, for example, both-end support (showing a method of mechanically and electrically joining at approximately the center of each of the opposing short sides of the crystal resonator element), the notch (and the lead electrode) is connected to the crystal resonator element. By forming at the approximate center of each of the opposing short sides (the planar shape of the crystal resonator element is substantially H-shaped), and maintaining the positional relationship between the conductive adhesive and the crystal resonator element described above, A crystal resonator is provided as the piezoelectric device according to the third embodiment of the present invention.
[0024]
Although the present invention has been described using the first to third embodiments, that is, the crystal resonator element including the notch portion (and the lead electrode) only at the corner portion or the side portion, for example, It is mechanically and electrically joined at both corners of one short side and mechanically joined at the approximate center of the other short side (three-point support), and the conductive adhesive and the crystal resonator element described above By maintaining the positional relationship, the crystal resonator as the piezoelectric device of the fourth embodiment of the present invention is obtained.
[0025]
FIG. 2A is a top view of the piezoelectric device according to the fifth embodiment of the present invention with the lid member of the crystal resonator omitted, and FIG. 2B is a longitudinal sectional view thereof.
The crystal resonator of the fifth embodiment is different from the first to fourth embodiments in that a concave portion is formed on a part of one main surface of the crystal base plate 1a. As shown in FIG. 2, the quartz resonator element 21 (quartz substrate 21a) according to the fourth embodiment has a concave portion 21b formed in an arbitrary shape by using a technique such as chemical etching or ion etching at the center of one main surface. The thin plate region (vibrating portion) 21c is formed on the inner bottom surface of the recess 21b, and the outer peripheral portion surrounding the thin plate region 21c is a thick reinforcing portion 21d. Simultaneously with the formation of the recess 21b, notches 21e are formed at desired positions of the quartz base plate 21a, for example, at both corners at one end in the longitudinal direction. Excitation electrodes 22 are formed in arbitrary shapes on both main surfaces of the thin plate region 21c, and lead electrodes 23 are formed from the excitation electrodes 22 to the periphery of the cutout portion 21e. By maintaining the positional relationship between the adhesive and the crystal resonator element, a crystal resonator as a piezoelectric device according to the fourth embodiment of the present invention is obtained.
The present invention can also be applied to a multimode crystal filter in which a partial electrode is disposed in the thin plate region (vibrating portion) 21c.
[0026]
Although the present invention has been described using the first to fifth embodiments, that is, the crystal resonator, the second concave portion is formed on the inner bottom surface of the concave portion 3, and the oscillation circuit is formed on the inner bottom surface of the second concave portion. In addition, a so-called single-seal crystal oscillator (sixth embodiment of the present invention) in which a circuit element, such as an IC chip, constituting a temperature compensation circuit is mounted and the crystal resonator element is accommodated in the recess 3 may be used.
[0027]
Although the present invention has been described using the sixth embodiment, that is, a single seal type crystal oscillator, the crystal oscillator according to the seventh embodiment uses a ceramic container (second printed wiring board) mounted with the IC chip as a first. It is characterized by being mounted on the lower surface of the crystal unit according to any of the fourth to fourth embodiments. The ceramic container is provided with a recess for accommodating the IC chip on the upper surface thereof, the IC chip is flip-chip mounted on the inner bottom surface of the recess, the opening of the recess is closed by the crystal resonator, and electrical Also, a so-called double seal crystal oscillator that is mechanically connected may be used.
[0028]
In the crystal oscillator according to the eighth embodiment, a second recessed portion is integrally formed on the lower surface of the ceramic package, the IC chip is mounted on the inner bottom surface of the second recessed portion, and the crystal vibration is mounted on the recessed portion. A so-called H-type crystal oscillator that accommodates the element may be used.
[0029]
The circuit element may be not only the IC chip but also a discrete part constituting an oscillation circuit and a temperature compensation circuit. Further, an electronic component such as a capacitor for removing high frequency noise superimposed on the power supply voltage supplied to the IC chip may be accommodated in the recessed portion or the second recessed portion.
[0030]
Although the present invention has been described using TCXO, it goes without saying that it can be applied to devices such as fundamental or overtone crystal oscillators, VC-TCXO, VCXO, OCXO, and SAW oscillators.
[0031]
Although the present invention has been described using an AT-cut quartz substrate, the present invention is not limited to an AT-cut, but can be applied to a quartz substrate having a cut angle such as a BT cut, CT cut, DT cut, SC cut, or GT cut. Needless to say.
[0032]
Needless to say, the present invention is not limited to a quartz substrate, but can be applied to piezoelectric vibration elements such as langasite, lithium tetragonate, lithium tantalate, lithium niobate, and the like.
[0033]
【The invention's effect】
According to the present invention, it is possible to obtain a surface-mount type piezoelectric device that can be miniaturized and that has improved bonding strength with a conductive adhesive used as a means for connecting a piezoelectric vibration element in a package. Have.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a crystal resonator according to a first embodiment of the invention.
(A) The top view of the state which omitted the cover member.
(B) AA longitudinal cross-sectional view.
(C) The perspective view of the junction part of the crystal oscillation element concerning embodiment of this invention.
FIG. 2 is a configuration diagram of a crystal resonator as a fifth embodiment of the invention.
(A) The top view of the state which omitted the cover member.
(B) AA longitudinal cross-sectional view.
FIG. 3 is a configuration diagram of a conventional crystal unit.
(A) Longitudinal sectional view.
(B) The perspective view which shows the junction part of a crystal oscillation element.
FIG. 4 is a schematic diagram showing a difference in a joint portion of a conventional crystal resonator element.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Crystal oscillation element 1a ... Crystal oscillation element main body (AT cut crystal substrate)
DESCRIPTION OF SYMBOLS 1b ... Excitation electrode 1c ... Lead electrode 1d ... Notch part 2 ... Ceramic package (printed wiring board) 3 ... Recessed part 4 ... Lid member 5 ... Pad electrode 6 ... Conductive adhesive 7 ... Fillet 21 ... Quartz vibration element 21a ... Quartz substrate 21b ... Recess 21c ... Thin plate region (vibration part) 21d ... Reinforcement part 21e ... Notch part 22 ... Excitation electrode 23 ... Lead electrode 100 ... Crystal oscillator 101 ... Crystal oscillation element 101a ... Lead electrode 102 ... Ceramic package 103 ... Cavity part 104 ... Lid 105 ... Electrode pad 106 ... Conductive adhesive 107 ... Fillet

Claims (8)

A piezoelectric vibration element comprising an excitation electrode disposed on both main surfaces and a lead electrode extending from each of the excitation electrodes;
A first printed wiring board having a recessed portion for accommodating the piezoelectric vibration element on the upper surface;
A metal lid member for closing the opening of the recess,
With
The piezoelectric vibration element is formed by mechanically and electrically connecting the piezoelectric vibration element to a pad electrode formed on the inner bottom surface of the depression through a conductive adhesive and hermetically sealing the depression by the lid member. And
A piezoelectric device comprising a cutout portion formed on an outer peripheral edge of the piezoelectric vibrator, and a terminal end of the lead electrode disposed on the peripheral edge of the cutout portion. The piezoelectric device according to claim 1, wherein the notch is formed at a corner of the piezoelectric vibration element. The piezoelectric device according to claim 1, wherein the notch is formed in a side portion of the piezoelectric vibration element. The piezoelectric device according to claim 1, wherein a concave portion is formed on one main surface of the piezoelectric vibration element. The piezoelectric device according to claim 1, wherein the conductive adhesive is applied twice. 6. The piezoelectric device according to claim 1, wherein circuit elements constituting an oscillation circuit and a temperature compensation circuit are accommodated in the recess. 6. The piezoelectric device according to claim 1, wherein a second recessed portion is formed on a lower surface of the first printed wiring board, and the circuit element is mounted on the second recessed portion. . A piezoelectric device according to any one of claims 1 to 5, the circuit element, and a second printed wiring board for mounting the circuit element,
A piezoelectric device in which the second printed wiring board on which the circuit element is mounted is mechanically and electrically connected below the piezoelectric device.

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