JP2001217670

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DESCRIPTION JP2001217670
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
piezoelectric resonator component such as an oscillator, discriminator, or filter, and more
particularly to a structure for mounting a piezoelectric element utilizing longitudinal vibration on
a substrate.
[0002]
2. Description of the Related Art Conventionally, a conductive support is fixed to a central portion
(node portion) of a piezoelectric element utilizing a longitudinal vibration mode, and the support
is applied to a pattern electrode of a substrate by a conductive adhesive. There has been
proposed a piezoelectric resonance component in which a cap is fixed to the substrate for
connecting and fixing the substrate and covering the piezoelectric element. Among them, a
rubber-like elastic material such as silicone rubber or urethane rubber is injected from the
injection hole provided in the cap to cover the periphery of the piezoelectric element to give an
appropriate vibration load to the piezoelectric element, thereby mechanically applying the
piezoelectric element There is one which can adjust the quality factor Qm with high accuracy
(see Japanese Patent Application Laid-Open No. 11-112278).
[0003]
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1
In the case of using such a piezoelectric resonant component in a portable device such as a
portable telephone, it is necessary to provide a predetermined impact resistance against drop
impact. However, as described above, since the conductive support portion formed at the node
portion of the piezoelectric element is fixed to the pattern electrode of the substrate by the
conductive adhesive, the impact load is concentrated on this fixed portion, and the piezoelectric
element The following problems occur: the support portion of the substrate peels off the pattern
electrode of the substrate, or a crack occurs in the piezoelectric element. Since the drop impact is
an instantaneous load, covering the periphery of the piezoelectric element with a rubber-like
elastic body hardly contributes to the prevention of peeling.
[0004]
In order to solve such a problem, there is also a method of extending the conductive support in
the longitudinal direction of the piezoelectric element and bonding the support over a large area
of the pattern electrode of the substrate. In this case, although the impact resistance performance
is improved, the piezoelectric element adheres to the substrate up to the region beyond the node
portion, so the piezoelectric element and the substrate cause a resonance phenomenon and an
unnecessary response to the impedance characteristic of the piezoelectric element It has the
disadvantage that it occurs and the desired properties can not be obtained. Therefore, there are
limitations in increasing the length of the support.
[0005]
Therefore, an object of the present invention is to provide a piezoelectric resonance component
capable of reliably preventing a resonance phenomenon between a piezoelectric element and a
substrate while enhancing impact resistance performance.
[0006]
SUMMARY OF THE INVENTION In order to achieve the above object, the invention according to
claim 1 has a substrate having a pattern electrode formed on the upper surface and an electrode
on the lower surface, and a length disposed on the substrate A piezoelectric element utilizing
length vibration, and a cap attached to a substrate so as to cover the piezoelectric element, a
rubber-like elastic body is disposed on the inner surface of the cap, and the piezoelectric element
is A piezoelectric resonant component is provided, characterized in that the node portion of the
electrode is brought into conductive contact with the pattern electrode of the substrate by
pressing.
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[0007]
The node portions of the electrodes of the piezoelectric element are not bonded to the pattern
electrodes of the substrate, but are in contact conduction by the compressive stress of the
rubber-like elastic body.
Therefore, the piezoelectric element may momentarily separate from the pattern electrode of the
substrate when a drop impact is applied, but the compressive stress of the rubber-like elastic
body causes the piezoelectric element to contact the pattern electrode of the substrate again.
Stable electrical connection between the piezoelectric element and the substrate can be
maintained.
Further, since the impact load applied to the piezoelectric resonant component is widely
dispersed in the rubber-like elastic body without being concentrated on a part of the piezoelectric
element, generation of a crack in the piezoelectric element can be prevented. In addition, since
the electrical connection between the pattern electrode of the substrate and the piezoelectric
element is performed by the compressive stress of the rubber-like elastic body, the piezoelectric
element and the substrate are not mechanically restrained, and as a result, the piezoelectric
element and the substrate are Resonance can be prevented. Therefore, an unnecessary response
does not appear in the impedance characteristic of the piezoelectric element.
[0008]
As the rubber-like elastic body in the present invention, any rubber-like elastic body such as
silicone rubber or urethane rubber may be used as long as it has flexible rubber elasticity and
insulation properties. The rubber-like elastic body may be applied to the inner surface of the cap
in an uncured state as in claim 2, and the rubber-like elastic body may be cured while holding the
upper surface portion of the piezoelectric element. . That is, since the rubber-like elastic body has
a function of connecting the cap and the piezoelectric element, the positional relationship
between the cap, the piezoelectric element, and the substrate is always stable, and the rubber-like
elastic body provides appropriate vibration load to the piezoelectric element. To adjust the
mechanical quality factor Qm of the piezoelectric element. The piezoelectric element may be
disposed after applying and curing the rubber-like elastic body on the inner surface of the cap, or
the rubber-like elastic body is formed in advance into a predetermined shape, and this rubberlike elastic body is used. It may be disposed inside the cap.
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[0009]
As a piezoelectric element used for the present piezoelectric resonant component, as in claim 3, a
columnar base in which a piezoelectric layer and an internal electrode are stacked in the length
direction, and the internal electrode alternately on one side surface of the base It is possible to
use one in which the piezoelectric layer is polarized in the longitudinal direction of the substrate,
including two external electrodes formed to be connected. In the case of this piezoelectric
element, since the piezoelectric longitudinal effect in which the polarization direction, the electric
field direction, and the vibration direction coincide is used, compared to the piezoelectric element
utilizing the piezoelectric transverse effect in which the polarization direction, the electric field
direction and the vibration direction are different, The electromechanical coupling factor can be
increased.
[0010]
1 to 3 show an example of a piezoelectric resonant component A according to the present
invention. The piezoelectric resonant component A of this embodiment is a surface mount
oscillator, 1 is a piezoelectric element, 20 is a substrate, and 30 is a cap.
[0011]
The piezoelectric element 1 utilizes a length vibration mode, and includes a rectangular
parallelepiped base 2 as shown in FIG. The base 2 has a structure in which a plurality of
piezoelectric layers 3 made of a piezoelectric ceramic material and a plurality of internal
electrodes 4 are alternately stacked, and piezoelectrics on both sides of one internal electrode 4
are shown in FIG. It is polarized in the longitudinal direction of the base 2 so that the polarization
axes of the body layer 3 are opposite to each other. However, both ends of the substrate 2 are
not polarized.
[0012]
A groove 5 extending in the longitudinal direction of the base 2 is formed on one side of the base
2, and the groove 5 divides one side of the base 2 into two. Furthermore, the first insulating film
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6 and the second insulating film 7 are formed on the side surfaces divided by the groove 5. Every
other exposed portion of the internal electrode 4 is covered with the first insulating film 6 on one
side divided by the groove 5 of the base 2, and the other side divided by the groove 5 on the base
2 is insulated Every other exposed portion of the internal electrode 4 not covered with the film 6
is covered with the second insulating film 7.
[0013]
External electrodes 8 and 9 are formed on portions of the base 2 where the insulating films 6
and 7 are formed, that is, on both sides of the groove 5. Therefore, the internal electrode 4 not
covered with the first insulating film 6 is connected to the external electrode 8, and the internal
electrode 4 not covered with the second insulating film 7 is connected to the external electrode
9. That is, the internal electrodes 4 are alternately connected to the external electrodes 8 and 9.
[0014]
In the piezoelectric element 1, the external electrodes 8 and 9 are used as input and output
electrodes. At this time, an electric field is applied between the adjacent internal electrodes 4 in
portions other than the both ends of the substrate 2 and thus becomes piezoelectrically active,
but the substrate 2 is not polarized at both ends of the substrate 2 Since the electrodes are not
formed on the two end faces, no electric field is applied, and the electrode is piezoelectrically
inactive. Therefore, by applying a signal between the external electrodes 8 and 9, an alternating
electric field in the longitudinal direction of the base 2 is applied to each piezoelectric layer 3 in
the active portion, and an expansion and contraction driving force is generated in each
piezoelectric layer 3 The basic vibration of the length vibration mode is excited in the base 2 as
In addition, although the inactive part was provided in the both ends of the base ¦ substrate 2,
this inactive part is not essential and it is good also considering the base ¦ substrate 2 whole as
an active part.
[0015]
The structure of the piezoelectric element is not limited to that shown in FIG. 4, but may be a
structure as shown in FIG. In the case of this piezoelectric element 1 ′, two types of
piezoelectric layers 3 a and 3 b as shown in FIG. 6 are alternately stacked to expose the internal
electrodes 4 in two rows on one side surface of the base 2. Then, the external electrodes 8 and 9
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are formed in portions where the internal electrodes 4 are exposed in two rows, whereby the
internal electrodes 4 are connected to the external electrodes 8 and 9 every other one. In this
case, it is not necessary to form the groove 5.
[0016]
The substrate 20 is a rectangular insulating thin plate made of alumina ceramic, glass ceramic,
glass epoxy resin, heat resistant resin, etc. The pattern electrodes 21 and 22 on the input side
and the output side are sputtered, deposited, printed on the upper surface of the substrate 20
And so on. The external connection portion of each of the pattern electrodes 21 and 22 is
extended to the back side through the side edge of the substrate 20. Conductive lands 23 and 24
are convexly formed on the inner end portions of the pattern electrodes 21 and 22, respectively.
The lands 23 and 24 may be formed by applying a conductive paste on the pattern electrodes 21
and 22 with a predetermined thickness and then curing the conductive paste, or may use a
solder bump, a gold bump, or the like. The input and output external electrodes 8 and 9 of the
piezoelectric element 1 are electrically connected to the pattern electrodes 21 and 22 of the
substrate 20. That is, the external electrode 8 is in contact with the land 23 of the input-side
pattern electrode 21, and the external electrode 9 is in contact with the land 24 of the outputside pattern electrode 22.
[0017]
A cap 30 covering the piezoelectric element 1 is bonded onto the substrate 20 by an insulating
adhesive 31 so that the periphery of the piezoelectric element 1 is sealed. The cap 30 in this
embodiment is formed by pressing a metal plate, but may be a resin cap or a ceramic cap. A
rubber-like elastic body 32 such as silicone rubber or urethane rubber is disposed inside the cap
30, and the compression stress of the elastic body 32 causes the central portions (node portions)
of the external electrodes 8 and 9 of the piezoelectric element 1 to The lands 23 and 24 of the
pattern electrodes 21 and 22 of the substrate 20 are respectively in pressure contact and
electrically conducted. The compressive stress of the rubber-like elastic body 32 is configured to
act uniformly on the piezoelectric element 1 in the length direction. Therefore, the piezoelectric
element 1 is attached horizontally to the substrate 20, and the end of the piezoelectric element 1
is prevented from contacting the upper surface of the substrate 20.
[0018]
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Here, a method of assembling the piezoelectric resonant component A having the above
configuration will be described according to FIG. First, as shown in (a), a predetermined amount
of the uncured rubber-like elastic body 32 is applied to the inside of the cap 30. Next, the surface
on the opposite side to the surface on which the external electrodes 8 and 9 of the piezoelectric
element 1 are formed is attached to the uncured elastic body 32 as in (b), and the elastic body 32
is cured. At this time, the external electrodes 8 and 9 of the piezoelectric element 1 are set to
protrude from the opening of the cap 30 by a predetermined amount D, and the piezoelectric
element 1 is attached parallel to the cap 30. Next, as shown in (c), an adhesive 31 for adhering
the cap 30 is applied to a predetermined position of the substrate 20. The adhesive 31 may be
applied to the opening of the cap 30. Next, the opening of the cap 30 is adhered to the substrate
20 as shown in (d). At this time, the rubber-like elastic body 32 is compressed, and the central
portions (node portions) of the external electrodes 8 and 9 of the piezoelectric element 1
attached to the cap 30 are respectively in pressure contact with the lands 23 and 24 of the
substrate 20 by the compression stress. Electrically connected. Finally, when the adhesive 31 is
cured in a state where the cap 30 is pressed against the substrate 20 as shown in (e), the inside
of the cap 30 is sealed, and the surface mount type piezoelectric resonant component A is
obtained. You can get it.
[0019]
FIG. 8 is a graph comparing impedance characteristics of the piezoelectric resonant component A
according to the present invention and the piezoelectric resonant component B in which the
piezoelectric element is bonded to the substrate over a wide area. As apparent from FIG. 8, in the
case of the piezoelectric resonance component B in which the piezoelectric element is bonded to
the substrate in a wide area, unnecessary resonance occurs between the piezoelectric element
and the substrate on the low frequency side from the resonance point and the high frequency
side from the antiresonance point. While the response appears, in the piezoelectric resonant
component A according to the present invention, the unnecessary response due to the resonance
between the piezoelectric element and the substrate is eliminated. Therefore, good impedance
characteristics can be obtained.
[0020]
FIGS. 9 to 11 show other examples of the piezoelectric resonant component according to the
present invention, and show an example applied to a ladder filter as shown in FIG. In this ladder
filter C, four pattern electrodes 41 to 44 are formed on a substrate 40, and five land portions 41a
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to 44a, 42b are arranged in a row at intervals in these pattern electrodes 41 to 44. Is formed.
The land portion 41a is formed on the pattern electrode 41 on the input side, the land portions
42a and 42b are formed on the intermediate pattern electrode 42, the land portion 43a is
formed on the pattern electrode 43 on the ground side, and the land 44a is a pattern on the
output side The electrode 44 is formed. The pattern electrode 43a on the ground side passes
through the back surface of the substrate 40 and wraps around to the other end.
[0021]
Four piezoelectric elements 50 to 53 are disposed on the substrate 40. These piezoelectric
elements 50 to 53 have the same structure as that of the piezoelectric element 1 shown in FIG. 4
or 5 and are brought into contact with the lands 41 a to 44 a of the pattern electrodes 41 to 44
by contacting the external electrodes 8 and 9. Electrically connected. Specifically, the external
electrodes 8 of the piezoelectric element 50 are land portions 41a, the external electrodes 9 of
the piezoelectric element 50 and the external electrodes 8 of the piezoelectric element 51 are
lands 42a, and the external electrodes 9 of the piezoelectric elements 51 and piezoelectric
element 52. The external electrode 8 is in contact with the land portion 43a, the external
electrode 9 of the piezoelectric element 52 and the external electrode 8 of the piezoelectric
element 53 are in contact with the land portion 44a, and the external electrode 9 of the
piezoelectric element 53 is in contact with the land portion 42b.
[0022]
The cap 60 is integrally formed of a metal material, and on the inner surface thereof, a rubberlike elastic body 61 is disposed which presses the upper surfaces of the piezoelectric elements
50 to 53 to press the external electrodes 8 and 9 against the lands 41a to 44a. . Also in this
embodiment, the rubbery elastic body 61 is applied to the inner surface of the cap 60, the
piezoelectric elements 50 to 53 are attached to the uncured elastic body 61, and the elastic body
61 is cured. In the cap 60. Then, by pressure-adhering the cap 60 to the substrate 40, the
external electrodes 8 and 9 of the piezoelectric elements 50 to 53 can be in pressure contact
with the land portions 41a to 44a and 42b.
[0023]
FIG. 13 shows a ladder filter C having the above configuration, a ladder filter D in which a
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piezoelectric element is adhered to a substrate in a large area, and a ladder in which the
periphery of the piezoelectric element is covered with a rubber-like elastic body as disclosed in It
is a characteristic comparison figure of filter E. As apparent from FIG. 13, when the piezoelectric
element is bonded to the substrate in a large area (see D), an unnecessary response appears due
to the resonance between the piezoelectric element and the substrate, and rubber around the
piezoelectric element appears In the case of covering with an elastic body (see E), although the
unnecessary response is eliminated, there is a disadvantage that the insertion loss becomes large.
On the other hand, in the ladder filter A according to the present invention, the insertion loss is
small, and the unnecessary response due to the resonance between the piezoelectric element and
the substrate can be eliminated. Therefore, good filter characteristics can be obtained.
[0024]
In the above embodiment, the lands of the substrate are convex, and the external electrodes of
the piezoelectric element are brought into pressure contact with the lands. Conversely, as shown
in FIG. The conductive and convex supports 10 and 11 may be fixed to the node portions of the
external electrodes 8 and 9 ', and these supports 10 and 11 may be pressed against the lands of
the substrate. The supports 10 and 11 may be formed by applying a conductive paste on the
external electrodes 8 and 9 to a predetermined thickness and then curing the conductive paste, a
solder bump, a gold bump, or the like. Since the structure is the same as that of the piezoelectric
element 1 shown in FIG. 4 except for the supports 10 and 11, the same parts as those of the
piezoelectric element 1 in FIG. In this embodiment, since the convex supports 10 and 11 are
provided at the node portions of the external electrodes 8 and 9, it is not necessary to form the
land portions of the pattern electrodes of the substrate in a convex shape.
[0025]
The rubber-like elastic body of the above embodiment is applied to the inside of the cap in an
uncured state, and after the piezoelectric element is attached to the rubber-like elastic body, the
rubber-like elastic body is cured. The piezoelectric element may be pressed against the substrate
by a cured rubber-like elastic body after curing. Alternatively, the rubber-like elastic body may be
formed into a predetermined shape in advance, and the rubber-like elastic body may be fitted
inside the cap, and the piezoelectric element may be pressed against the substrate by the rubberlike elastic body. In any case, it is preferable to form a recess in which the piezoelectric element
is fitted in the rubber-like elastic body so that the rubber-like elastic body and the piezoelectric
element do not shift.
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[0026]
Although the piezoelectric element of the said Example demonstrated the example which
comprised the length vibration mode element as a whole by laminating ¦ stacking several
piezoelectric material layers, as shown to FIG. 4, FIG. 5, It restricts to this Instead, it may be a
length vibration mode element in which electrodes are formed on both main surfaces of one
piezoelectric substrate as in the prior art.
[0027]
As apparent from the above description, according to the present invention, the node portion of
the electrode of the piezoelectric element is brought into contact with the pattern electrode of
the substrate by the compressive stress of the rubber-like elastic body, Even when an impact or
the like is applied, stable electrical connection between the piezoelectric element and the
substrate can be maintained, and impact resistance performance can be improved.
Further, since the impact load applied to the piezoelectric resonant component is widely
dispersed in the rubber-like elastic body without being concentrated on a part of the piezoelectric
element, generation of a crack in the piezoelectric element can be prevented. In addition, since
the electrical connection between the pattern electrode of the substrate and the piezoelectric
element is performed by the compressive stress of the rubber-like elastic body, the piezoelectric
element and the substrate are not mechanically restrained, and as a result, the piezoelectric
element and the substrate are Resonance can be prevented. Therefore, an unnecessary response
does not appear in the impedance characteristic of the piezoelectric element.
[0028]
Brief description of the drawings
[0029]
1 is a cross-sectional view of an example of a piezoelectric resonant component according to the
present invention.
[0030]
2 is a cross-sectional view of FIG. 1 XX line.
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[0031]
3 is an exploded perspective view of the piezoelectric resonance component shown in FIG.
[0032]
4 is a perspective view of an example of a piezoelectric element used in the piezoelectric
resonance component of FIG.
[0033]
5 is a perspective view of another example of a piezoelectric element used for the piezoelectric
resonance component of FIG.
[0034]
6 is a front view of a piezoelectric layer constituting the piezoelectric element of FIG.
[0035]
7 is a manufacturing process diagram of the piezoelectric resonance component shown in FIG.
[0036]
8 is a diagram comparing impedance characteristics of the piezoelectric resonance component
shown in FIG. 1 and a comparative example.
[0037]
9 is a cross-sectional view of another example of the piezoelectric resonant component according
to the present invention.
[0038]
10 is a cross-sectional view taken along the line Y-Y of FIG.
[0039]
11 is an exploded perspective view of the piezoelectric element and the substrate of the
piezoelectric resonance component shown in FIG.
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[0040]
12 is a circuit diagram of the piezoelectric resonance component shown in FIG.
[0041]
13 is a filter characteristic comparison diagram of the piezoelectric resonance component shown
in FIG. 9 and a comparative example.
[0042]
14 is a perspective view of still another example of the piezoelectric element.
[0043]
Explanation of sign
[0044]
1, 50-53 Piezoelectric element 20, 40 Substrates 21, 22 Pattern electrodes 23, 24 Land 30, 60
Cap 32, 61 Rubber-like elastic body
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