JPH04342308A - Piezoelectric resonator - Google Patents

Abstract

PURPOSE:To obtain the piezoelectric resonator improving the damping amount out of a passed band without enlarging the size. CONSTITUTION:Piezoelectric substrates 1 and 10 and a low-dielectric constant material 20 are adhered by the adhesive agent of epoxy resin, etc., and formed into one plate. For example, the ceramics substrate of PZT having about 800-1600 dielectric constant is used for the piezoelectric substrates 1 and 10, and a porcelain plate having about 30 dielectric constant is used for the low- dielectric constant material 20. On the front and rear faces of the substrates 1 and 10, a relay conductor 8 respectively connecting vibrating electrodes 3, 4, 5, 12, 13 with 14 and electrodes 4 with 12, a relay conductor 9 is connecting the electrodes 5 with 14, and input and output electrodes 6 and 7 connected to the respective electrodes 3 and 13 are provided. An input terminal 21, output terminal 22 and ground terminal 23 are soldered and connected to the electrodes 6 and 7 and the conductor 9 respectively. The respective vibrations generated at the substrates 1 and 10 by the electrodes 3-5 and the electrodes 13-14 are not propagated to the other substrates 10 and 1 by the low-dielectric constant material 20.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric resonator used in filter circuits and the like.

0002

2. Description of the Related Art A piezoelectric resonator using thickness shear vibration, as shown in FIG. 4, has been known as a piezoelectric resonator used in a dual mode filter. This piezoelectric resonator includes two filter sections 52 and 53 electrically connected in series to one piezoelectric substrate 51. By the way, in order to improve the amount of attenuation outside the passband of this piezoelectric resonator, the length L of the substrate 51 is increased to increase the dimension between the filter sections 52 and 53, so that the vibration generated in one filter section is reduced. It is known that the electromagnetic coupling between the filter sections 52 and 53 can be made weaker by making it difficult for the signal to be transmitted to the other filter section. However, if the length L of the substrate 51 is increased, (1) the size of the filter increases;

(2) Since the size of the substrate 51 increases, there is a risk that the material properties within the same substrate will vary greatly. (3) Since a large tightening stress is applied to the board 51 by the exterior resin, environmental reliability such as temperature characteristics is deteriorated. There were other problems.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a piezoelectric resonator with improved attenuation outside the passband without increasing the size.

[0005]

[Means for Solving the Problems] In order to solve the above problems, a first piezoelectric resonator according to the present invention includes a plurality of piezoelectric substrates and a gap between the plurality of piezoelectric substrates. The piezoelectric substrate is characterized in that it includes a ground terminal that is held in a fixed state, and an input terminal and an output terminal that are electrically connected to the vibrating electrodes provided on each of the piezoelectric substrates.

[0006] Furthermore, the second piezoelectric resonator according to the present invention includes:
A low dielectric constant material, a plurality of piezoelectric substrates integrally formed through the low dielectric constant material, and an input terminal and an output terminal electrically connected to a vibrating electrode provided on each of the piezoelectric substrates. It is characterized by having a ground terminal.

[0007]

[Operation] With the above structure, vibrations generated in each piezoelectric substrate are not transmitted to other piezoelectric substrates due to the gaps provided between the piezoelectric substrates and the low dielectric constant material. Therefore, the vibrating electrodes provided on each piezoelectric substrate do not have to be affected by vibrations generated on other piezoelectric substrates.

[0008]

Embodiments Hereinafter, embodiments of a piezoelectric resonator according to the present invention will be described with reference to the accompanying drawings. [First Embodiment, FIGS. 1 and 2] FIG. 1 is a perspective view of a piezoelectric resonator used in a dual mode filter using thickness shear vibration. The piezoelectric resonator includes a low dielectric constant material 20, two piezoelectric substrates 1 and 10 that are integrally formed via the low dielectric constant material 20, an input terminal 21, an output terminal 22,
A ground terminal 23 is provided. Piezoelectric substrate 1, 10
A filter section 2, 11 is provided in each of the filter sections 2 and 11.

The piezoelectric substrates 1 and 10 are made of rectangular PZT ceramic substrates or the like. One end of each of the substrates 1 and 10 is joined via a low dielectric constant material 20, and the substrates 1 and 10 and the low dielectric constant material 20 are in the shape of a single plate. The material for the low dielectric constant material 20 includes a material that prevents vibrations generated in the filter portions 2 and 11 provided on each piezoelectric substrate 1 and 10 from being transmitted to the other piezoelectric substrate;
That is, it is made of a material that has physical properties that make the electromagnetic coupling between the filter parts 2 and 11 loose. For example, for the PZT piezoelectric substrates 1 and 10 (with a dielectric constant of about 800 to 1600), the low dielectric constant material 20 is a porcelain plate with a dielectric constant of about 20 to 30, an epoxy resin material for adhesive, etc. be done. When a porcelain plate is used, the piezoelectric substrates 1 and 10 and the porcelain plate are fixed and integrated with an adhesive such as epoxy resin.

The filter parts 2 and 11 each have a vibrating electrode 3
, 4, 5, 12, 13, and 14. A part of the vibrating electrode 3 is pulled out to the left end of the substrate 1 and is connected to the input electrode 6.
A part of the vibrating electrode 13 is drawn out to the right end of the substrate 10 and electrically connected to the output electrode 7 . The vibrating electrodes 4 and 12 are electrically connected by a relay conductor 8. Furthermore, between the vibrating electrodes 5 and 14 is a relay conductor 9.
The relay conductor 9 also functions as a ground electrode. Note that these vibrating electrodes 3, 4, 5, 12, 13, 14, relay conductors 8, 9, input electrode 6, and output electrode 7 are made by integrally fixing a low dielectric constant material 20 and piezoelectric substrates 1, 10. It may be provided later. Alternatively, piezoelectric substrates 1 and 10 on which vibrating electrodes 3, 4, 5, 12, 13, 14, input electrodes 6, and output electrodes 7 are provided in advance are fixed together via a low dielectric constant material 20, and then a relay conductor is formed. 8,
9 may be provided.

[0011] The input terminal 21 has a connection part 21a and a terminal part 21.
b, the output terminal 22 is composed of a connecting part 22a and a terminal part 22b, and the ground terminal 23 is composed of a connecting part 23a and a terminal part 22b.
and a terminal portion 23b. These terminals 21
, 22, 23 are fixed to the input electrode 6, output electrode 7, and relay conductor 9, respectively, by means of soldering or the like. Thereafter, a damping material such as silicone rubber is coated on the surfaces of the piezoelectric substrates 1 and 10 and the low dielectric constant material. Furthermore, the dual mode filter is completed by coating with epoxy resin or the like. FIG. 2 is a graph showing the results of measuring the relationship between frequency and attenuation of the dual mode filter thus obtained. A solid line 25 shows the measurement results of the filter obtained in this example. For comparison, the measurement results of a conventional filter are indicated by a dotted line 26. FIG. 2 shows that the low dielectric constant material 20 sandwiched between the piezoelectric substrates 1 and 10 loosens the electromagnetic coupling between the filter parts 2 and 11, improving the attenuation outside the passband of the filter. It is shown.

[Second Embodiment, FIG. 3] FIG. 3 is a perspective view of another piezoelectric resonator used in a dual mode filter utilizing thickness shear vibration. In FIG. 3, the same parts and portions as in the first embodiment are given the same reference numerals. The piezoelectric resonator is composed of two piezoelectric substrates 1 and 10, an input terminal 21, an output terminal 22, and a ground terminal 23.

A portion of the vibrating electrode 4 is drawn out to the left end of the substrate 1, and a portion of the vibrating electrode 12 is drawn out to the right end of the substrate 10. The vibrating electrodes 4 and 12 are connected to the relay conductor 3.
They are electrically connected via 0. For the relay conductor 30, a lead wire or the like connected by means such as wire bonding is used, for example. Further, a part of the vibrating electrode 5 is connected to the substrate 1
A part of the vibrating electrode 14 is drawn out to the right end of the substrate 10 and electrically connected to the ground electrode 34 , and a part of the vibrating electrode 14 is drawn out to the left end of the substrate 10 and electrically connected to the ground electrode 35 .

The connecting portion 23a of the ground terminal 23 is fixed to the ground electrodes 34, 35 of the piezoelectric substrates 1, 10 by means such as soldering, and is electrically connected. At this time, the substrates 1 and 10 are arranged so that a gap G is maintained between the substrates 1 and 10. Vibrations generated in the filter sections 2 and 11 provided on each piezoelectric substrate 1 and 10 are not transmitted to the other piezoelectric substrate due to this gap (in this embodiment, the size of the gap is about 4 mm). Furthermore, the connection part 21a of the input terminal 21
is fixed to the input electrode 6 of the substrate 1 by means such as soldering,
electrically connected. Similarly, the connecting portion 22a of the output terminal 22 is fixed to the output electrode 7 of the substrate 10 by means such as soldering, and is electrically connected. Thereafter, the surfaces of the piezoelectric substrates 1 and 10 are coated with a damping material such as silicone rubber, and covered with an epoxy resin or the like to form a dual mode filter.

[Other Embodiments] The piezoelectric resonator according to the present invention is not limited to the embodiments described above, and can be modified in various ways within the scope of the gist. In particular, the piezoelectric resonator may be composed of three or more piezoelectric substrates.

[0016]

[Effects of the Invention] As is clear from the above explanation, according to the present invention, since a gap and a low dielectric constant material are provided between each piezoelectric substrate, vibrations generated in each piezoelectric substrate are transmitted to other piezoelectric substrates. It is not transmitted to the board. Therefore, a piezoelectric resonator with improved out-of-passband attenuation can be obtained without increasing the size.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing a first embodiment of a piezoelectric resonator according to the present invention.

FIG. 2 is a graph showing the results of measuring the relationship between frequency and attenuation of a dual mode filter using the piezoelectric resonator shown in FIG. 1;

FIG. 3 is a perspective view showing a second embodiment of a piezoelectric resonator according to the present invention.

FIG. 4 is a perspective view showing a conventional example.

[Explanation of symbols]

1...Piezoelectric substrate 3, 4, 5... vibrating electrode 10...Piezoelectric substrate 12, 13, 14... Vibrating electrode 20...Low dielectric constant material 21...Input terminal 22...Output terminal 23...Ground terminal G...Gap

Claims (2)

[Claims] 1. A plurality of piezoelectric substrates, a ground terminal that holds the plurality of piezoelectric substrates with a gap therebetween, and electrically connected to a vibrating electrode provided on each of the piezoelectric substrates. A piezoelectric resonator comprising an input terminal and an output terminal. 2. A low dielectric constant material, a plurality of piezoelectric substrates integrally formed through the low dielectric constant material, and an input electrically connected to a vibrating electrode provided on each of the piezoelectric substrates. A piezoelectric resonator characterized by comprising a terminal, an output terminal, and a ground terminal.