JP2011229167A - Surface-mount piezoelectric device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface-mount piezoelectric device (oscillator, filter) which solves the deterioration of various characteristics attributed to the occurence of thermal stress even when a piezoelectric vibration element is connected to an inner bottom surface of a ceramic package with a solid conductive adhesive.SOLUTION: In the piezoelectric device, a piezoelectric vibration element is electrically and mechanically connected to be open-sided and held in a surface-mounted package. Each of pad electrodes on one surface of the piezoelectric vibration element is connected to a corresponding conductive pad on an inner bottom surface of the surface-mount package with a solid conductive adhesive. The piezoelectric device is configured such that the main vibration part of the piezoelectric vibration element is positioned on an extended line connecting the spots of the conductive adhesive applied on the pad electrodes.

Description

  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.

In recent years, mobile communication devices such as mobile phones have been reduced in size and weight, and there has also been a strong demand for higher functionality, and there are two conflicts between the increase in the number of parts and the reduction in size associated with higher functionality. In order to satisfy the requirements at the same time, it is important to reduce the area of the printed circuit board constituting the electrical component and to effectively use the board area by increasing the density of mounted components.
Quartz resonators (vibrators, filters) used as frequency control devices in mobile communication devices and transmission communication devices are also strongly required to be miniaturized. As a device package structure to support high-density mounting, Surface mount type is the mainstream, and the demand for higher frequency is increasing.
FIG. 10 is a perspective view of an AT-cut quartz crystal resonator element having an ultra-thin portion for the purpose of increasing the frequency. This crystal resonator element 1 is a vibrator using the fundamental thickness shear vibration wave of an AT-cut crystal substrate. Since the resonance frequency is inversely proportional to the plate thickness, in order to increase the frequency while maintaining the mechanical strength, one main surface of the crystal substrate constituting the crystal resonator element 1 is recessed by etching, and the recess The bottom surface of 13 is an ultrathin vibrating portion 13a, and a thick annular surrounding portion 14 that supports the outer periphery of the vibrating portion 13a over the entire circumference is integrally formed. Furthermore, in addition to the main surface electrode 11 constituting the excitation electrode, the lead electrode 15 and the pad electrode 16 extending from the main surface electrode 11 on one main surface of the quartz substrate by gold mask vapor deposition or photolithography, a pad electrode 17 is formed. The pad electrode 17 is located at the end of the lead electrode 18 extending from the back electrode 12 constituting the excitation electrode similarly formed on the other main surface, and passes through the side surface of the quartz substrate. The lead electrode 18 is electrically connected.
In this type of crystal resonator element 1, the two pad electrodes 16 and 17 are arranged at a distance d along the width direction.

FIG. 11 is a longitudinal sectional view showing a package structure of a surface-mount type crystal resonator using the crystal resonator element 1. This crystal resonator has a structure in which the crystal resonator element 1 shown in FIG. 10 is housed in the ceramic package 2 and then the upper surface opening of the ceramic package 2 is hermetically sealed with a metal upper lid.
The ceramic package 2 includes a ceramic substrate 21 constituting the bottom, an annular frame 22 made of ceramic integrated on the outer periphery of the upper surface of the ceramic substrate 21, and an annular shape on the upper surface of the frame 22 for seam welding the upper lid 3. And has a box shape having a recess 24 for housing the crystal resonator element 1 at the center of the upper surface. Internal terminals (conductive pads) 25 and 26 formed by gold metallization are exposed on the upper surface of the ceramic substrate 21, that is, the inner bottom surface of the recess 24, and are connected to external terminals (not shown) provided on the lower surface of the package. ing.
The pad electrodes 16 and 17 of the crystal unit 1 are made to correspond to the internal terminals 25 and 26 on a one-to-one basis, and then both are connected and fixed using the conductive adhesive 4.
In the structure of such a type of crystal resonator, how to select the method for electrically and mechanically connecting the crystal resonator element 1 to the ceramic package 2 is to stabilize the frequency. It is important, and conventionally, using a soft silicone-based conductive adhesive 4, two internal terminals (conductive pads) 25 and 26 on the inner bottom surface of the ceramic package 2 and two pad electrodes 16 and 17 on the side of the crystal resonator element 1 are used. And one-to-one connection.
Since the silicone-based conductive adhesive is soft, it has an advantage of absorbing thermal strain. However, when a silicone-based conductive adhesive is used, the adhesive strength is weak, so that peeling is likely to occur due to shocks such as impact, and contamination of the vibration element surface due to outgas generated from the adhesive and conduction deterioration occur. And the like, resulting in significant deterioration of various characteristics of the crystal resonator element, such as frequency temperature characteristics and reliability, for example, aging characteristics. In particular, in the case of a crystal resonator used in a cellular phone, a soft adhesive having a low adhesive strength is unsuitable because specifications for impact are severe.
In particular, in the crystal resonator element 1 having the ultrathin vibrating portion of the type shown in FIG. 10, the adverse effect due to the above-mentioned problem caused by using a soft adhesive is serious, and the ultrathin film is used to increase the frequency. If the thickness of the meat vibration part is further reduced, the adverse effect becomes more serious.
On the other hand, compared with a silicone-based conductive adhesive, a hard epoxy-based or polyimide-based adhesive generates thermal stress in the crystal unit 1 or is cured by the heated conductive adhesive. Although there are problems in terms of absorbability against thermal distortion, such as the occurrence of internal stress in the quartz resonator element 1 sometimes, it is excellent in impact resistance, and in this respect, it is an adhesive suitable for mobile phones and the like.

By the way, when a hard epoxy adhesive or a polyimide adhesive is used as the conductive adhesive 4 shown in FIGS. 10 and 11, a straight line connecting two fixed portions by the hard conductive adhesive 4 is used. Thus, the main vibration portion 13a of the crystal resonator element 1 is positioned in a direction (side) orthogonal to the other. At first glance, this structure seems to be ideal because the main vibration part is separated from the fixing part, but in actuality, the inner bottom surface of the package and the crystal vibration element 1 are fixed by the hard conductive adhesive 4. Therefore, stress distortion due to the difference in thermal expansion coefficient is applied between the conductive adhesives 4, which also affects the main vibration portion 13 a and impairs the stability of the crystal resonator element.
More specifically, since the support restraining force of the quartz vibrating element by the hard conductive adhesive 4 is large, the hard conductive adhesive hinders the expansion and contraction of the quartz vibrating element 1 due to the temperature change, The thermal stress generated due to the temperature change has reached a level that cannot be ignored, and there has been a problem that the various characteristics of the crystal resonator element are adversely affected.
Incidentally, since the stress generated in the constrained portion by the hard conductive adhesive 4 is directed in the direction indicated by the arrow A, distortion occurs between the pad electrodes 16 and 17, and the main surface electrode 11 is deformed. As a result, stress such as crotch tears or wrinkles is applied in the direction of arrow C with the dotted line B as the action axis, and the frequency characteristics such as aging characteristics and frequency temperature characteristics of the crystal resonator element 1 may be degraded.
This is a problem not only for crystal resonators such as crystal resonators and filters, but also for piezoelectric resonators in general.

  The problem to be solved by the present invention is that even if the piezoelectric vibration element is connected to the inner bottom surface of the ceramic package by a rigid support portion using a hard conductive adhesive, various problems caused by thermal stress caused by a temperature change. An object of the present invention is to provide a surface-mount type piezoelectric device (vibrator, filter) capable of solving the deterioration of characteristics.

In order to solve the above-mentioned problem, a first embodiment of the present invention is an electromechanical device in a cantilever state on a conductive pad provided on the inner bottom surface of a surface mount package with a piezoelectric vibration element having an excitation electrode. A piezoelectric device held in contact with each other, wherein a one-to-one connection between two pad electrodes on one side of the piezoelectric vibration element and two conductive pads on the bottom surface of the surface mount type package is made using a conductive adhesive, respectively. What was used was that the excitation electrode was arranged on an extension of a line segment connecting the conductive adhesives on the two pad electrodes.
The second embodiment of the present invention is a piezoelectric device in which a piezoelectric vibration element having an excitation electrode is electrically and mechanically connected and held in a cantilever manner on a conduction pad provided on the inner bottom surface of a surface mount package. When the three pad electrodes provided on the piezoelectric vibration element and the three conductive pads in the surface mount package are connected in a one-to-one relationship, at least two sets of pad electrodes and the conductive pads are electrically connected. What was performed using the adhesive agent WHEREIN: The said excitation electrode was arrange | positioned on the extension of the line segment which connected each said conductive adhesive agent on the said two pad electrodes, It was characterized by the above-mentioned.
A third embodiment of the present invention is characterized in that the piezoelectric vibration element has a groove extending in a direction intersecting with an extension line connecting the two pad electrodes in the middle of the two pad electrodes. To do.
According to a fourth embodiment of the present invention, the piezoelectric vibration element connects the pad electrode and the excitation electrode between the excitation electrode and the pad electrode closer to the excitation electrode of the two pad electrodes. It has the groove | channel extended in the direction which cross | intersects an extension line, It is characterized by the above-mentioned.
The fifth embodiment of the present invention is characterized in that the distance between the two pad electrodes is 500 μm or less.
In a sixth embodiment of the present invention, an AT-cut quartz crystal substrate is used as the piezoelectric substrate constituting the piezoelectric vibration element, and the two pad electrodes are set at 60 degrees with respect to the crystal axis X-axis of the AT-cut quartz crystal substrate. It is characterized by being adjacently disposed along the line segment having an angle of 120 degrees.
The seventh embodiment of the present invention is characterized in that the conductive adhesives fixed on the two pad electrodes are arranged in a straight line along the line segment.
In an eighth embodiment of the present invention, as a piezoelectric substrate constituting the piezoelectric vibration element, an ultrathin vibrating portion and a thick annular surrounding portion that supports the outer periphery of the vibrating portion are integrally configured. It is characterized by using a piezoelectric substrate.

As described above, according to the present invention, the two pad electrodes provided on the piezoelectric vibration element are arranged adjacent to each other with a slight gap, and the conductive adhesives fixed on the pad electrodes are arranged in a straight line. Since the piezoelectric vibration element is connected to the inner bottom surface of the ceramic package via the conductive adhesive, the support restraining force of the conductive adhesive fixing portion is prevented from preventing the expansion and contraction accompanying the temperature change of the piezoelectric vibration element. In addition, the generation of thermal stress can be suppressed, and deterioration of various characteristics can be prevented.
As described above, in the present invention, the bottom surface of the package fixedly supports the one end of the piezoelectric vibration element via the linearly arranged conductive adhesives, which accompanies the temperature change of the piezoelectric vibration element. Generation of thermal stress can be suppressed without hindering expansion and contraction. In particular, it is apparent that extremely stable characteristics with small thermal hysteresis can be obtained, and further, thermal stress can be suppressed and characteristic deterioration can be avoided in other reliability such as aging property and reflow characteristics.
Furthermore, according to the present invention, since the piezoelectric vibration element has a structure extending in the direction intersecting with the extension line connecting the two pad electrodes in the middle of the two pad electrodes, the stress generated between the pad electrodes is transferred to the groove. Therefore, the absolute value of the stress transmitted to the vibrating part can be further reduced.
Further, according to the present invention, the piezoelectric vibration element extends in a direction intersecting with an extension line connecting the pad electrode and the excitation electrode between the pad electrode closer to the excitation electrode of the two pad electrodes and the excitation electrode. Since the groove is provided, the stress generated between the pad electrodes is relaxed and absorbed by the groove, so that the absolute value of the stress transmitted to the vibrating portion can be further reduced.

The perspective view of the AT cut quartz crystal resonator as one example of embodiment of this study. Sectional drawing which shows the package structure of the piezoelectric device as one embodiment of this invention. The figure which shows the improvement effect at the time of using the embodiment of this invention. The figure explaining the principle of this invention. (A) And (b) is a structure explanatory drawing of the crystal oscillation element of other embodiment of this invention. (A) And (b) is a structure explanatory drawing of the crystal oscillation element of other embodiment of this invention. The structure explanatory view of the crystal oscillation element of other embodiments of the present invention. The structure explanatory view of the crystal oscillation element of other embodiments of the present invention. (A) is explanatory drawing of other embodiment of this invention, (b) is explanatory drawing of a prior art example. The perspective view of the conventional AT cut crystal oscillator. Sectional drawing which shows the package structure of the conventional piezoelectric device.

Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.
FIG. 1 is a perspective view of an AT-cut quartz crystal resonator element having an ultra-thin portion for the purpose of increasing the frequency. Since the resonance frequency is inversely proportional to the plate thickness, in order to increase the frequency while maintaining the mechanical strength, one main surface of the crystal substrate constituting the crystal resonator element 1 is recessed by etching to form the recessed portion 13. The configuration is as follows. Therefore, in this quartz crystal substrate, the bottom surface of the recess 13 is an ultrathin vibrating portion 13a, and the outer periphery of the vibrating portion 13a is integrally supported by the thick annular surrounding portion 14 over the entire circumference. It has a configuration. Further, gold is deposited using a mask, or a main surface electrode 11 constituting an excitation electrode is formed on one main surface (vibrating portion 13a) of the quartz substrate by photolithography, and a lead electrode 15 extending therefrom. In addition to the pad electrode 16, the pad electrode 17 is formed. Note that the pad electrode 17 is formed by drawing a lead electrode 18 extending from the back electrode 12 constituting the excitation electrode similarly formed on the other main surface to the surface side through the side end surface of the quartz substrate. And continuity.
In the following description, it is assumed that the quartz substrate has dimensions of 3 mm in length and width, a thickness of 80 μm, and a thickness of the vibrating portion 13 a of about 10 μm. According to the vibrating portion 13a, a resonance frequency exceeding 100 MHz can be obtained.

FIG. 2 is a cross-sectional view showing the structure of a surface-mounted crystal resonator as an example of a piezoelectric device using the crystal resonator element 1. The structure of the ceramic package itself is the same as that shown in FIG. 11, and the same portions will be described with the same reference numerals.
The quartz resonator element 1 shown in FIG. 1 is housed in the ceramic package 2, and the upper surface opening of the recess 24 of the ceramic package 2 is hermetically sealed by the metal upper lid 3.
The ceramic package 2 includes a ceramic substrate 21 constituting a bottom portion, a ceramic annular frame 22 standing and integrated on the outer periphery of the upper surface of the ceramic substrate 21, and a top of the frame 22 for seam welding the upper lid 3. It has a seam ring 23 that is annularly fixed to the end face, and has a recess 24 for accommodating the crystal resonator element 1 at the center as a whole, and has a box shape with an annular portion on the outer periphery. Internal terminals (conductive pads) 25 and 26 formed by gold metallization are exposed on the upper surface of the ceramic substrate 21, and are connected to external terminals (not shown) provided on the bottom surface of the package. The internal terminals 25 and 26 are arranged at a positional relationship and an interval corresponding to the pad electrodes 16 and 17 on the crystal resonator side.
When the crystal resonator element 1 is cantilevered in the ceramic package 2, the pad electrodes 16 and 17 of the crystal resonator element 1 and the input / output internal terminals 25 and 26 of the ceramic package are opposed to each other in a one-to-one correspondence. After that, fixing is performed through a required amount of hard conductive adhesive (epoxy-based or polyimide-based adhesive) 4.

In the crystal oscillating device shown in FIG. 10, the two pad electrodes 16 and 17 are disposed at both ends in the width direction of the crystal oscillating device (in the Z-axis direction in the case of AT-cut crystal) by a distance d. In the crystal resonator element of this embodiment, the two pad electrodes 16 and 17 are not separated in the width direction, but rather the width direction inner ends 16a and 17a of the pad electrodes partially overlap in the width direction. It is close. The inner end portions 16a and 17a of the overlapped pad electrodes are spaced apart from each other with a predetermined gap d1 in a direction orthogonal to the width direction (X-axis direction in the case of AT cut quartz). Here, the gap d1 between the pad electrodes 16 and 17 of the crystal resonator element 1 is set to a close value of 500 μm or less, and the conductive adhesive 4 is disposed on the overlap portion of the pad electrodes 16 and 17. In this embodiment, the positions in the width direction of the conductive adhesives 4 on the pad electrodes 16 and 17 are the same, and there is no deviation along the X-axis extending from the center of the main surface electrode 11 as the excitation electrode. It is arranged in a straight line.
In addition, the internal terminals 25 and 26 in the ceramic package 2 that are connected to the pad electrodes 16 and 17 on a one-to-one basis through the hard conductive adhesive 4 also face the pad electrodes 16 and 17. consider. That is, the internal terminals 25 and 26 are arranged to face each other with a gap of 500 μm or less in a direction orthogonal to the width direction.
As described above, the force with which the hard conductive adhesive 4 supports and restrains the crystal resonator element is considerably larger than that of the soft silicone-based conductive adhesive. Since the hard conductive adhesives 4 are arranged in a row (in a straight line) on the overlap portions of the pad electrodes, the conductive adhesives are arranged at the center of one end edge of the crystal resonator element 1. Will be supported rigidly. Since each conductive adhesive 4 is arranged in a row at the center of one end edge of the crystal resonator, expansion and contraction of the crystal resonator element 1 due to a temperature change in the direction orthogonal to the arrangement of the conductive adhesive 4. Is not hindered by the conductive adhesive, and the stress generated in the crystal unit 1 due to the fixing with the conductive adhesive remains between the pad electrodes 16 and 17. Due to the thermal stress generated, the vibration part 13a is not distorted, and the problem of adversely affecting various characteristics of the crystal resonator element is eliminated. For example, FIG. 3 is a table showing an example of the hysteresis characteristic with respect to the frequency-temperature characteristic. As is clear from this table, an extremely stable characteristic with a small thermal hysteresis could be obtained. Further, it is clear that thermal stress can be suppressed and characteristic deterioration can be avoided also in other reliability such as aging property and reflow characteristic.
Further, the pad electrode and the conductive adhesive 4 do not necessarily have to be arranged along the X axis, and may be arranged along one straight line extending radially from the excitation electrode.

That is, as shown in FIG. 4, the excitation electrode and the conductive adhesive along any one of the straight lines L extending radially through the center point of the main surface electrode 11 (or the back electrode 12) as the excitation electrode. 4 is arranged, the stress is generated only in the arrow direction perpendicular to the straight line between the pad electrodes 16 and 17 along the straight line. Further, the stress that is slightly propagated to the vibrating portion 13a may be avoided by avoiding the excitation electrodes 11 and 12 away from the position of the pad electrode 16, for example.
However, when it is required to avoid such a situation that affects the frequency even slightly, the excitation electrode and the conductive adhesive 4 are linearly arranged almost along the radiation having a specific angle as follows. It is effective to arrange in
That is, for example, when an AT-cut quartz substrate is used, the pad electrodes 16 and 17 and the conductive adhesive 4 are arranged close to each other along a straight line having an angle of 60 degrees or 120 degrees with respect to the quartz crystal axis X axis. In this case, since the compressive (tensile) stress sensitivity becomes zero, the generation of thermal stress can be further suppressed. In other words, if the pad electrode and the conductive adhesive are arranged along any one of the straight lines, even if a stress due to the binding force of the conductive adhesive is generated, the portion along the straight line is originally caused by the stress. Since this is a unique angular region in which no frequency fluctuation occurs, there is almost no change in frequency.

That is, FIG. 5 (a) shows that each pad electrode is closely arranged along a straight line having an angle of 60 degrees or 120 degrees with respect to the X-axis of the crystal crystal axis, and conductive bonding is linearly formed on each pad electrode. It is a figure which shows the example of arrangement | positioning of each pad electrode in the case of arrange | positioning an agent, (b) has shown the top view of the crystal oscillation element which has arrange | positioned each pad electrode along the position of 60 degree | times with respect to the X-axis. .
As shown in FIG. 5A, the pad electrodes 16 and 17 are arranged close to each other (d2 ≦ 500 μm) along a straight line having an angle of 60 degrees or 120 degrees with respect to the X-axis of the crystal crystal axis. Even if the stress caused by the supporting restraint force at the fixing portion is generated by fixing the internal terminals 25 and 26 facing the pins 16 and 17 to the rigid through the hard conductive adhesive 4, There is no adverse effect on the frequency characteristics of the crystal resonator element. In addition, in this embodiment, since the hard conductive adhesives 4 on the two pad electrodes 16 and 17 arranged along each line are arranged linearly, a stress in a direction perpendicular to the arrangement direction is generated. It is difficult to do. That is, the hard conductive adhesive does not hinder the expansion and contraction of the crystal resonator element 1 due to the temperature change, and the thermal stress generated due to the temperature change adversely affects various characteristics of the crystal resonator element. Since there is no problem, the characteristics of the crystal resonator element can be stabilized.
FIG. 5B shows a specific configuration example of the crystal resonator element when two pad electrodes are arranged close to each other along a straight line having an angle of 60 degrees with respect to the X axis. For example, 18 is wired by a route as shown. A cantilever support structure can be realized by connecting and fixing the pad electrodes 16 and 17 to the internal terminals 25 and 26 provided on the inner bottom surface of the package (not shown) via the conductive adhesive 4. .

Further, FIG. 6 shows a configuration diagram of another embodiment of the crystal resonator element according to the present invention.
The configuration of the crystal resonator element 1 shown in FIG. 1A is different from the configuration of the crystal resonator element 1 of FIG. 1 in that it extends in the width direction in the middle of the gap d1 of the overlap portion between the pad electrode 16 and the pad electrode 17. For example, such a groove can be formed in the same etching process when the recess 13 is formed.
Then, when the crystal resonator element 1 having such a configuration is housed in the ceramic package 2 as shown in FIG. 5B, the crystal resonator element 1 is arranged such that the recessed portion 13 faces the ceramic substrate 21 side. The pad terminals 16 and 17 and the internal terminals 25 and 26 are bonded with the conductive adhesive 4 so as to be in the arrangement state.
In addition, although it demonstrated using the crystal vibrating element 1 which formed the groove | channel 19 and the recessed part 13 in the same main surface side, what formed the groove | channel 19 in one main surface different from the recessed part 13 may be sufficient. The mounting state of the crystal resonator element 1 in the ceramic package 2 is desirably mounted so that the recessed portion 13 faces the upper lid 3 side, as in the state shown in FIG.
In the crystal resonator element 1 having such a configuration, since the stress generated between the pad electrodes 16 and 17 is relaxed (absorbed) by the groove 19, the absolute value of the stress transmitted to the vibrating portion 13a is further increased. Can be small.

Further, FIG. 7 shows a configuration diagram of another embodiment of the crystal resonator element according to the present invention.
A feature of the configuration of the crystal resonator element 1 shown in the figure is that a groove 20 is formed in the middle of the pad electrode 16 and the recessed portion 13 so as to extend in the width direction.
In the crystal resonator element 1 having such a configuration, the pad electrodes 16 and 17 are bonded to the internal terminals 25 and 26 of the ceramic package 2 by using the conductive adhesive 4. Even if a part of the stress generated in the step is transmitted to the vibration part 13a, the groove 20 functions to block the stress transmission path and relieve the transmitted stress, so that the stress is transmitted to the vibration part 13a. Can be suppressed.

Further, the crystal resonator element shown in FIG. 8 may be obtained by adding the features of the crystal resonator element shown in FIG. 6 and the features of the crystal resonator element shown in FIG.
That is, FIG. 8 shows a configuration diagram of another embodiment of the crystal resonator element according to the present invention.
The feature of the crystal resonator element 1 shown in the figure is that a groove 19 extending in the width direction is formed in the middle of the gap d1, and a groove 20 extending in the width direction in the middle of the pad electrode 16 and the vibrating portion 13a. Is where it was formed.
The crystal resonator element 1 having such a configuration can obtain a function having both the function of the crystal resonator element shown in FIG. 6 and the function of the crystal resonator shown in FIG. It is possible to block the transmission of stress.
In the above-described embodiment, an example in which the piezoelectric vibration element having a configuration in which the outer periphery of the ultrathin vibrating portion 13a is integrally surrounded by the thick annular surrounding portion 14 is cantilevered in the package is shown. The present invention is merely an example, and the present invention can also be applied to piezoelectric vibration elements and filters using piezoelectric substrates of all types and shapes such as flat plates, convexes, beveled plates, etc., and obtain the same effects as the above embodiment. Can do.

Next, the support structure of the piezoelectric vibration element of the present invention can also be applied to a monolithic multimode filter. That is, FIG. 9B is a plan view of a filter element 30 used in a conventional monolithic multimode filter. Electrodes 33 and 34 are provided on one side of the main vibration portion 32 of the plate-like piezoelectric substrate 31 and on the other side. Electrodes 35 are respectively formed, and pad electrodes 33b, 34b, and 35b are disposed at end portions of the lead electrodes 33a, 34a, and 35a extending from the electrodes 33, 34, and 35 toward one end edge of the substrate. The filter element 30 is sealed in a ceramic package for surface mounting (not shown). At this time, at least two pad electrodes, in this example, pad electrodes 33b and 34b, are provided with respect to the internal terminals provided on the bottom surface of the package. Is fixed by a conductive adhesive.
When a hard conductive adhesive is used as this conductive adhesive, as in the case of the quartz crystal resonator described in the above-mentioned conventional example, various characteristics are deteriorated due to the thermal stress generated due to the temperature change. Cannot be avoided.
Therefore, in the present embodiment, as shown in FIG. 9A, at least two pad electrodes 33b and 34b are arranged in a straight line, and the main vibration part 32 is positioned on the extension of the straight line. .
As described above, in the present embodiment, since the hard conductive adhesives 4 on the two pad electrodes 33b and 34b are linearly arranged, it is difficult to generate stress in a direction orthogonal to the arrangement direction. ing. That is, the hard conductive adhesive 4 does not hinder the expansion and contraction of the filter element 30 due to the temperature change, and the thermal stress generated due to the temperature change adversely affects various characteristics of the filter element. Therefore, the characteristics of the filter element can be stabilized.
In the above embodiment, an example in which a flat piezoelectric substrate is used as the filter element is shown. However, this is an example, and the outer periphery of the ultrathin vibrating portion is surrounded and integrated by a thick annular surrounding portion. A piezoelectric substrate having a configuration may be used.

DESCRIPTION OF SYMBOLS 1 Quartz vibration element, 2 Ceramic package, 3 Top cover, 4 Hard conductive adhesive, 11 Main surface electrode, 12 Back surface electrode, 13 Recessed part, 13a Vibration part, 14 Annular surrounding part, 15 Lead electrode, 16, 17 Pad Electrode, 18 lead electrode, 19, 20 groove, 21 ceramic substrate, 22 annular frame, 23 seam ring, 24 recess, 25, 26 internal terminal, 30 filter element, 31 piezoelectric substrate, 32 main vibration part, 33, 34 Electrode, 35 electrode, 33a, 34a, 35a Lead electrode, 33b, 34b, 35b Pad electrode.

Claims (8)

A piezoelectric device in which a piezoelectric vibration element including an excitation electrode is electrically and mechanically connected and held in a cantilever manner on a conduction pad provided on an inner bottom surface of a surface mount package, the piezoelectric vibration element on one side of the piezoelectric vibration element In one-to-one connection between two pad electrodes and two conductive pads on the inner bottom surface of the surface mount package, each using a conductive adhesive,
A surface-mount type piezoelectric device, wherein the excitation electrode is disposed on an extension of a line connecting the conductive adhesives on the two pad electrodes. A piezoelectric device in which a piezoelectric vibration element including an excitation electrode is electrically and mechanically connected and held in a cantilever manner on a conduction pad provided on an inner bottom surface of a surface-mount package, and is provided on the piezoelectric vibration element. In one-to-one connection between one pad electrode and three conductive pads in the surface-mount package, at least two sets of pad electrodes and conductive pads were each formed using a conductive adhesive,
A surface-mount type piezoelectric device, wherein the excitation electrode is disposed on an extension of a line connecting the conductive adhesives on the two pad electrodes.   3. The surface mounting type according to claim 1, wherein the piezoelectric vibration element has a groove extending in a direction intersecting with an extension line connecting the two pad electrodes in the middle of the two pad electrodes. Piezoelectric device.   The piezoelectric vibration element has a groove extending in a direction intersecting with an extension line connecting the pad electrode and the excitation electrode between the excitation electrode and the pad electrode closer to the excitation electrode of the two pad electrodes. 4. The surface-mount type piezoelectric device according to claim 1, wherein the surface-mount type piezoelectric device is formed.   5. The surface-mount type piezoelectric device according to claim 1, wherein a distance between the two pad electrodes is 500 μm or less.   An AT-cut quartz crystal substrate is used as the piezoelectric substrate constituting the piezoelectric vibration element, and the two pad electrodes are arranged on the line segment having an angle of 60 degrees or 120 degrees with respect to the crystal axis X axis of the AT-cut quartz crystal substrate. 6. The surface-mount type piezoelectric device according to claim 1, wherein the surface-mount type piezoelectric device is disposed adjacently along the surface.   7. The surface mount type piezoelectric device according to claim 1, wherein the conductive adhesives fixed on the two pad electrodes are arranged in a straight line along the line segment.   As the piezoelectric substrate constituting the piezoelectric vibration element, a piezoelectric substrate in which an ultra-thin vibrating portion and a thick annular surrounding portion supporting the outer periphery of the vibrating portion are integrally formed is used. The surface-mount type piezoelectric device according to claim 1.

Images