JPH0983290A - Surface mount piezoelectric filter - Google Patents

Abstract

(57) Abstract: Even if the distance between two sets of electrode groups is reduced in order to reduce the mounting area, these electrode groups are caused by the lines of electric force generated between each other. Less affected,
(EN) Provided is a surface-mounted piezoelectric filter which is small in size and can exhibit excellent guaranteed attenuation characteristics. SOLUTION: Two pits 31 and 32 are formed in a cage 3, and the piezoelectric substrates 10 and 20 are formed so that the input / output vibrating electrode pairs 11 and 21 face the bottom side of these pits 31 and 32, respectively. Fixed to the peripheral area of 32, each pit 31,
The bottom surfaces 31a, 32a of 32 are filled with the conductive materials 41, 42, and the conductive material 5 is provided along the partition wall 33 between the pits 31, 32, and the conductive materials 41, 42, 5 are connected to the ground connection terminal 61. Connect to ~ 63.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-stage connection type surface mount type piezoelectric filter among multimode piezoelectric filters using a piezoelectric substrate.

[0002]

2. Description of the Related Art Generally, in a piezoelectric filter utilizing thickness-shear vibration of a piezoelectric substrate, a pair of input / output vibration electrodes (separation electrodes) are formed on one surface of the piezoelectric substrate and the opposite side is formed. A ground electrode is formed on the surface of the above so as to face them, and the entire structure is housed in a holder.

In this type of piezoelectric filter, normally,
In order to obtain high attenuation characteristics, it is necessary to connect a plurality of piezoelectric filters in cascade, so-called multi-stage connection.
In the case where one piezoelectric filter is housed in one cage, the mounting area becomes large when such multi-stage connection is performed, which becomes a cause of hindering the miniaturization of the device.

In order to solve such a problem, conventionally,
A multi-stage connection type element in which two sets of input / output electrode pairs and a ground electrode are formed on one piezoelectric substrate and housed in a holder has been proposed and put into practical use.

By the way, substantially two piezoelectric substrates are formed on one piezoelectric substrate.
When two piezoelectric filters are formed and housed in one cage, acoustic coupling between the filters occurs, and the distance between the piezoelectric filters is inevitably small, so electromagnetic coupling also occurs. It will be easier. In order to block such acoustic and electromagnetic coupling, conventionally, a groove is formed between two sets of electrode groups on a piezoelectric substrate, and strip-shaped metal layers are formed on both sides of the groove (Japanese Patent Publication No. 57-56819) or a structure in which a linear electrode connected to the ground electrode is formed at a position separating the two electrode groups on the piezoelectric substrate, and a damping material such as silver paste is further applied thereon. (Japanese Patent Laid-Open No. 61-
No. 17826) has been proposed.

[0006]

By the way, in recent years, when such a piezoelectric filter is incorporated into, for example, a communication device or the like, the cage is a surface mount type for the purpose of simplifying the mounting process and the like. In addition, it is required to make the mounting area smaller. In the structure in which two sets of electrode groups are housed in such a minute surface mount type retainer, the distance between the electrode groups is extremely short. It is difficult to avoid mutual interference due to lines of electric force based on the electric field created by each of the input and output vibrating electrode pairs.

The present invention has been made in view of such circumstances, and even if the mounting area is made extremely small and the distance between the two electrode groups is reduced, the influence of the lines of electric force between these electrode groups is influenced. It is an object of the present invention to provide a surface-mounted piezoelectric filter that is hard to receive and is small in size, and that can exhibit a good guaranteed attenuation amount characteristic.

[0008]

A structure for achieving the above-mentioned object will be described with reference to FIGS. 1 and 2 showing an embodiment of the present invention. An input / output vibrating electrode pair 11 (21) is formed on one surface of the substrate 10 (20) with a predetermined gap therebetween.
Two sets (1 and 2) of the multi-mode piezoelectric filter element, in which the ground electrode 12 (22) is formed so as to face them on the opposite surface, are one surface-mounted in a state in which they are cascade-connected to each other. A piezoelectric filter housed in a die-shaped holder 3, two pits 31 and 32 are formed adjacent to the holder 3, and the piezoelectric substrates 10 and 20 have respective input / output vibrating electrode pairs 11 and 21 respectively. Bottom 31 of pits 31, 32
Each of these pits 31 and 3 in the state of facing the a and 32a sides.
The pits 31 and 32 are fixed to the cage 3 at the peripheral portion of the pit 2, and the bottom surfaces 31a and 32a of the pits 31 and 32 are covered with the conductive materials 41 and 42.
The conductive material 5 is provided along the partition wall 33 between the first and the second 32, and each of the conductive materials 41, 42, and 5 is connected to the ground connection terminals 61 to 63 formed on the cage 3. Characterized.

As another configuration for achieving the same purpose, the present invention is a retainer 3'as illustrated in FIG.
Two pits 31 'and 32' are formed adjacent to each other, and the piezoelectric substrates 10 and 20 are oriented in the opposite direction, that is, each ground electrode 1
2 and 22 are fixed to the cage 3'at the peripheral portions of the pits 31 'and 32' with the bottoms of the pits 31 'and 32' facing each other, and the cage 3'is made of a conductive material. A lid 30 'is attached, and two pits 3
Along the partition 33 'between the 1'and 32', the upper side is the lid 30 '.
It is possible to adopt a configuration in which the conductive material 5 ′ reaching up to near the lower surface of the holder is provided, and the conductive material 5 ′ and the lid 30 ′ are connected to the ground terminals 64 and 65 formed on the cage 3. .

Here, two pits 31, 32 (3
1 ', 32') and the partition wall 33 (33 ') between the conductive material 5 (or 5'), as shown in FIG. 1 and FIG. 2 (or FIG. 8). 33 (33 ')
Insert a plate-shaped object inside along the
(Or FIG. 9), pits 31, 32 (31 ', 3)
2 ') inner surface 31b, 32b (31b', 32b ')
Is covered with the conductive material 5, or as shown in FIG. 7, a plurality of through holes 33a ... 33a are formed in the partition wall 33, and the conductive material 5 is embedded in each of the through holes 33a. be able to.

The two sets of piezoelectric filter elements 1 and 2 housed in the cage 3 (3 ') according to the present invention include:
2 separated from each other as shown in FIG. 1 and FIG. 2 (or FIG. 8)
In addition to the one in which one set of electrode groups is formed on each of the piezoelectric substrates 10 and 20, one in which two sets of electrode groups are formed on one common piezoelectric substrate 100 as illustrated in FIG. .

[0012]

According to the present invention, the two input / output vibrating electrode pairs for the piezoelectric filter elements housed in one surface mount type cage are electromagnetically shielded from each other by the structure of the cage itself. It is intended to prevent the interference of the lines of electric force between the pair of electrodes.

That is, the lines of electric force formed based on the electric field created by the two pairs of input / output vibrating electrode pairs 11 and 21 are shown in FIG.
As schematically shown in FIG. 1, the piezoelectric substrate 10 and the piezoelectric substrate 1 have an influence on each of the electrode pairs 11 and 21 via a space adjacent to the surface on which the input / output vibrating electrode pair 11 and 21 are formed.
0, 20, each of the input / output vibrating electrode pairs 11, 21 is a retainer 3
It is fixed to the cage 3 so as to face the pits 31 and 32 formed in the pits 31 and 32, and the bottom surfaces 31a and 32a of the pits 31 and 32 are formed.
By providing conductive materials 41, 42 and 5 along the partition wall 33 between the pits 31 and 32 and connecting them to the ground potential, the input / output vibration electrode pairs 11 and 21 are connected.
The influence of the lines of electric force between the two electrode groups can be suppressed, and the two electrode groups can be effectively electromagnetically shielded.

In the structure shown in FIG. 8 in which the piezoelectric substrates 10 and 20 are turned upside down, the lines of electric force are applied to the piezoelectric substrates 10 and 20.
20. The space that affects each other is on the upper surface side of each substrate 10, 20, but the lid 30 'is made of a conductive material and the upper side of the conductive material 5'along the partition walls 33' of the pits 31 ', 32'. To reach near the bottom surface of the lid 30 ',
Similar to the above configuration, it is possible to suppress the influence of the lines of electric force between the input / output vibrating electrode pairs 11 and 21.

[0015]

1 is an exploded perspective view showing an embodiment of the present invention, and FIG. 2 shows a lid 30 in its assembled state.
It is an AA sectional view shown excepting.

The two piezoelectric filter elements 1 and 2 are housed in a single surface mount type holder 3, and a lid 30 is placed on the upper edge of the holder 3 to seal these elements. It In this example, each piezoelectric filter element 1,
2 is formed by forming input / output electrode pairs 11 and 21 on one surface of the piezoelectric substrates 10 and 20, and forming ground electrodes 12 and 22 on the opposite surfaces thereof so as to face them. .

The cage 3 is made of, for example, ceramics,
Two pits 31 and 32 are formed adjacent to each other on the bottom surface. The piezoelectric substrates 10 and 20 of the piezoelectric filter elements 1 and 2 have the input / output vibrating electrode pair 1 respectively.
1, 21 with the bottoms 31a and 32a of the pits 31 and 32 facing the pits 31 and 32, respectively.
It is fixed to the peripheral part of 1,32.

That is, the input / output vibrating electrode pairs 11 and 21 and the ground electrodes 12 and 22 of the respective piezoelectric substrates 10 and 20 are
Piezoelectric substrate 1 with lead electrodes corresponding to each
The retainer 3 has six connection pads P formed on the peripheral portions of the pits 31 and 32 at positions corresponding to the respective corner portions of the pits 31 and 32. ing. And each piezoelectric substrate 1
0 and 20 are mechanically fixed on each connection pad P in a state where vibration is not hindered by the conductive adhesive B at each of the three corners thereof, and at the same time, the respective input / output electrode pairs 11 and 21. And the ground electrodes 12, 22 are
It is electrically connected to each connection pad P. In addition,
Each connection pad P penetrates the cage 3 and is connected to an external connection pad (not shown) for surface mounting formed on the back surface thereof. The two piezoelectric filter elements 1 and 2 are
It may be cascaded via this external connection pad,
The holders 3 may be connected in cascade.

Now, the bottom surface 31a of each pit 31, 32,
Each of the pits 32a is covered with a conductive material 41, 42 made of, for example, an alloy of W and Au by metallization, and is formed in the center of a partition 33 interposed between the two pits 31 and 32. A plate-shaped conductive material 5 is inserted so as to partition the space. Each of the conductive materials 41, 42 and 5 is connected to the dedicated ground connection pads 61 to 63 formed on the back surface side of the cage 3 so as to penetrate therethrough.

According to the above-described embodiment of the present invention, the lines of electric force between the input / output vibrating electrode pairs 11 and 12 do not affect the other. That is, as schematically shown in FIG. 3, in the state where the conductive materials 41, 42 and 5 do not exist, the two input / output vibrating electrode pairs 11 and 21 are
Based on the electric field created by each of the electrode pairs 11 and 21, the lines of electric force interfere with each other due to the influence of the lines of electric force formed in the space adjacent to the formation surface of these electrode pairs 11 and 21. Conductive material 41, 4 with earth potential in space
By interposing 2 and 5, each electrode pair 11,
It is possible to prevent 21 from being affected by the lines of electric force from the other.

As a result, when the conductive materials 41, 42 and 5 are not provided, the characteristics shown in FIG. 4 (A) are exhibited, but the conductive materials 41, 42 and 5 are provided. As a result, as shown in FIG. 7B, a very good guaranteed attenuation amount characteristic is exhibited.

In the above example, each conductive material 41,
42 and 5 each with a dedicated ground connection pad 6
1 to 63, each of these conductive materials 41, 4
2 and 5 are connected to each other at appropriate points in the cage 3,
It may be connected to a common ground connection pad.

In the above example, the two piezoelectric filter elements 1 and 2 are obtained by forming the required electrode groups on the individual piezoelectric substrates 10 and 20, respectively. As illustrated in FIG.
The input / output electrode pairs 11 and 21 may be formed on one surface of the upper surface, and the ground electrodes 12 and 22 may be formed on the opposite surface thereof so as to face the respective pairs. In this case, the piezoelectric substrate 10
0 is exactly the same as in the previous example, with respect to the total of 6 connection huds P of the cage 3, the pits 31 and 3 at 6 positions in total.
It is fixed at the peripheral part of 2.

The partition wall 3 between the two pits 31 and 32
As for the conductive material 5 provided along with 3, a plate-like material is inserted into the partition wall 33 as in the above example, and as shown in FIG.
7 and FIG. 7 may each take the form of a partially cutaway perspective view of only the retainer 3.

In the example shown in FIG. 6, the inner side surfaces 31b and 32b of the two pits 31 and 32 of the cage 3 are covered with the conductive material 5. In this case, the pits 31 and 32 have bottom surfaces 31a and 32a. Conductive material 41, 4 for coating
In addition to 2, the entire inner surface is covered with the conductive material. In addition, the conductive material 5 has pits 31 and 3
Of the two inner side surfaces 31b and 32b, at least the partition wall 33
It is sufficient to cover the surfaces on both sides of the input / output vibrating electrode pairs 11 and 21 by simultaneously covering the surfaces orthogonal to it.
It is possible to eliminate the influence of the lines of electric force generated by the electric field on the external circuit, which is preferable. Also, as shown in the drawing, the partition wall 3
If a similar conductive material is formed on the upper surface of 3 and the conductive materials 41, 42 and 5 in both pits 31 and 32 are connected to each other by this, all the conductive materials can be formed by one earth connection pad. The materials 41, 42 and 5 can be grounded.

In the example shown in FIG. 7, a plurality of through holes 33a ... 33a are formed in the partition wall 33 between the two pits 31 and 32 of the cage 3 along the surface separating the pits 31 and 32. Conductive materials 5, 5 are embedded in the through holes 33a, 33a, respectively, and these are connected to a common ground connection pad 6 formed on the back surface of the cage 3.

In the configurations shown in FIGS. 6 and 7, the method of fixing the piezoelectric substrate and the like are exactly the same as in the previous example, and the configurations shown in FIGS. 6 and 7 also show the configurations shown in FIGS. It has been confirmed that the same effect as the above example is obtained.

Next, an embodiment will be described in which the direction of fixing the piezoelectric substrate in the holder is reversed. FIG. 8 shows a vertical sectional view of the embodiment. In this example, 2
The two piezoelectric filter elements 1 and 2 are exactly the same as those shown in FIGS. 1 and 2, and the two pits 31 'and 32' are formed adjacently on the retainer 3 '. Similar to the example, flat pits 31c 'and 32c' are formed in the pits 31 'and 32' so as to make a turn along the inner side surface at a position of a depth of about 1/2, respectively.
Piezoelectric substrate 10, 2 constituting the piezoelectric filter element 1, 2
0 is in the opposite direction to the example of FIGS. 1 and 2, that is, the ground electrode 1
2 and 22 are bottom surfaces 31a 'and 32 of pits 31' and 32 '.
Each pit 31 ', 3 facing the a'side
It is fixed to the 2'steps 31c 'and 32c'.

That is, the connection pads P shown in the examples of FIGS. 1 and 2 are the step portions 31c ', 32 of the pits 31', 32 '.
The piezoelectric substrates 10 and 20 are mechanically fixed on the respective connection pads P by the conductive adhesive B as in the previous example, and at the same time, are formed on the respective input / output electrodes. The pairs 11 and 21 and the ground electrodes 12 and 22 are electrically connected to the corresponding connection pads P.

A metal cover ring 34 is fixed to the retainer 3'along the upper surface of the retainer 3 ', and a metal cover 30' is fixed on the cover ring 34 by seam welding.

Further, the upper surface of the partition wall 33 'between the two pits 31', 32 'reaches the vicinity of the lower surface of the lid 30', and the plate-shaped conductive material 5'is placed in the partition wall 33 '. Is inserted, and the upper surface of the conductive material 5 ′ reaches the upper surface of the partition wall 33 ′, so that the upper surface of the conductive material 5 ′ reaches the vicinity of the lower surface of the lid 30 ′.

The lid 30 'is formed on the ground connection pad 64 formed on the lower surface of the holder 3'through the cover ring 34, and the conductive material 5'is formed on the lower surface of the holder 3'. It is connected to the ground connection pad 65.

In the above structure, the lines of electric force formed in the space adjacent to the formation surface of the electrode pairs 11 and 12 are based on the electric field created by the input / output vibrating electrode pairs 11 and 12. It is shielded by the metal lid 30 'of earth potential and the conductive material 5'arranged in the space so that the piezoelectric filter elements 1 and 2 do not affect each other.

As described above, even when the piezoelectric filter elements 1 and 2 are housed in the holder 3'so that the input / output vibrating electrode pairs 11 and 21 face upward, two pits are formed. The form of the conductive material 5'disposed along the partition wall 33 'between the 31' and 32 'is not limited to the plate-like form, and the same modifications as those shown in FIGS. 6 and 7 are possible. is there.

That is, instead of the plate-shaped conductive material 5 ', as shown in the partial cutaway sectional view in FIG. 9, the two pits 31', 32 'above the stepped portions 31c', 32c '. Even if the inner side surfaces 31b 'and 32b' are covered with the conductive material 5 ', the same effect as the above can be obtained.
In this case, the grounding of the conductive material 5'covering the inner side surfaces of the pits 31 ', 32' may be done, for example, as shown in FIG.
If a part of the conductive material 5'on the inner surface of 1 ', 32' is extended to the step portions 31c ', 32c', and the portions are connected to the ground connection pad on the bottom surface of the cage 3'by through holes. Good.

Although not shown, the partition wall 33 'is replaced by the plate-shaped conductive material 5'in the same manner as in the example shown in FIG.
A plurality of through holes may be provided in a row so as to partition the two pits 31 'and 32' therein, and the conductive material 5'may be embedded in each of the through holes.

Here, in the example shown in FIGS. 8 and 9, the bottom surfaces 31a 'and 32a' of the pits 31 'and 32' are formed.
It is more preferable to cover the inner side surface below the step portions 31c 'and 32c' with a conductive material as well, because electromagnetic shielding to the outside of the cage 3'is possible.

Further, in order to fill the gap between the conductive material 5'arranged along the partition wall 33 'and the metallic lid 30' with the conductive material, the partition wall 33 'and the lid 30' are joined together. A conductive adhesive may be interposed therebetween, and instead of such a conductive adhesive, the cover ring 34 is arranged not only on the peripheral portion of the upper surface of the retainer 3 ′ but also on the partition wall 34. You may make it a letter shape. Then, when electrically connecting the conductive material 5'along the partition wall 33 'and the metallic lid 30' in this way, the ground connection pad for setting them to the ground potential is shown in FIG. It goes without saying that any one of 64 and 65 is sufficient.

[0039]

According to the present invention, a piezoelectric substrate in which two piezoelectric filter elements each consisting of two sets of electrode groups are housed in one surface mount type holder, and each electrode group is formed, Each input / output vibrating electrode pair is fixed to the retainer in the peripheral portion of each pit so that the pair of input / output vibrating electrodes face the bottom side of the two pits formed in the retainer, and along the bottom face of each pit and the partition wall between each pit Since the conductive materials are arranged at the respective positions, it is possible to suppress mutual interference between the electrode groups due to electric lines of force based on the electric field created by the two input / output vibrating electrode pairs, and thus to reduce the mounting area. Even if the distance between the two electrode groups is reduced to reduce the size, it is possible to obtain a highly accurate multi-stage connection type piezoelectric filter having a good guaranteed attenuation amount characteristic.

Further, as another structure of the present invention, two piezoelectric filter elements are provided, each of which is opposite to the above, and each ground electrode pair has two electrodes.
The pits should be fixed to the cage at the periphery of each pit so that they face the bottom side, and a lid made of a conductive material should be attached to the cage. Even if a conductive material reaching the lower surface of the above is arranged, the same effect as the above can be obtained.

[Brief description of drawings]

FIG. 1 is an exploded perspective view of an embodiment of the present invention.

FIG. 2 A- in an assembled state excluding its lid 30
Section A

FIG. 3 is an operation explanatory view of the embodiment of the present invention.

FIG. 4 is an explanatory diagram of the effect of the embodiment of the present invention;
Is a graph showing the filter characteristics with the conductive materials 41, 42, 5 removed, and (B) is the conductive material 4
Graph showing filter characteristics with 1, 42 and 5 provided

FIG. 5: Piezoelectric filters 1 and 2 according to another embodiment of the present invention.
Front view showing the configuration of

FIG. 6 is a conductive material 5 in the embodiment of FIGS. 1 and 2.
Partial cutaway perspective view showing another arrangement method of

FIG. 7 is a conductive material 5 according to the embodiment shown in FIGS.
FIG. 3 is a partially cutaway perspective view showing still another arrangement method of FIG.

FIG. 8 is a longitudinal sectional view showing still another embodiment of the present invention.

9 is a partial cutaway perspective view showing another method of disposing the conductive material 5'in the embodiment of FIG.

[Explanation of symbols]

 1, 2 Piezoelectric filter element 10, 20, 100 Piezoelectric substrate 11, 21 Input / output vibrating electrode pair 12, 22 Earth electrode 3, 3'Holder 30, 30 'Lid 31, 32, 31', 32 'Pit 31a, 32a , 31a ', 32a' Bottom surface 31b, 32b, 31b ', 32b' Inner side surface 31c ', 32c' Stepped portion 33, 33 'Partition wall 33a Through hole 41, 42, 5, 5' Conductive material 61, 62, 63, 64,65 Ground connection pad B Conductive adhesive P Connection pad

Claims (5)

[Claims] 1. A multi-mode piezoelectric filter in which a pair of input / output vibrating electrodes are formed on a surface of a piezoelectric substrate with a predetermined gap therebetween, and a ground electrode is formed on a surface on the opposite side of the pair of input / output vibrating electrodes so as to face them. A piezoelectric filter in which two sets of elements are housed in one surface mount type holder in a state where they are connected in cascade, and two pits are formed adjacent to the holder, and the piezoelectric substrate is The output vibrating electrode pairs are fixed to a retainer in the peripheral portion of each pit in a state of facing the bottom side of each pit, and the bottom of each pit is covered with a conductive material, and
A conductive material is provided along the partition between the two pits,
A surface-mounted piezoelectric filter, wherein each of these conductive materials is connected to a ground connection terminal formed on the cage. 2. A multi-mode piezoelectric filter in which a pair of input / output vibrating electrodes are formed on one surface of a piezoelectric substrate with a predetermined gap therebetween, and a ground electrode is formed on the opposite surface of the pair of input / output vibrating electrodes so as to face the electrodes. A piezoelectric filter in which two sets of elements are housed in one surface mount type holder in a cascade connection with each other, and two pits are formed adjacent to each other in the holder, and the piezoelectric substrate has each ground. The electrodes are fixed to the holders at the peripheral portions of the pits with the electrodes facing the bottom side of the pits, and the holders are fitted with a lid made of a conductive material.
A conductive material whose upper end reaches at least the vicinity of the lower surface of the lid is provided along the partition wall between the two pits, and the conductive material and the lid are connected to a ground terminal formed on the cage. A surface mount piezoelectric filter characterized by: 3. The surface mount type piezoelectric filter according to claim 1, wherein the conductive material along the partition wall between the two pits is a conductive material which covers the inner surface of each pit. . 4. The conductive material along the partition wall between the two pits is a plate-shaped conductive material inserted in the partition wall between the pits. Surface mount piezoelectric filter. 5. The conductive material along the partition wall between the two pits is a plurality of conductive materials embedded in a plurality of through holes formed in the partition wall between the pits, respectively. The surface mount piezoelectric filter according to claim 1 or 2.