JP2004214808A - Elastic surface wave filter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a compact, low-cost and highly reliable elastic surface wave filter by omitting the wire bonding process and eliminating the need of a space for laying a wiring pattern. <P>SOLUTION: The elastic surface wave filter comprises an IDT for connecting a first stage elastic surface wave resonator, an IDT for connecting a second stage elastic surface wave resonator a first wiring pattern for electrically connecting these IDTs, a bridging capacitance connected between an input terminal and the first wiring pattern, and inter-stage capacitance connected between the first wiring pattern and ground. The input terminal and one bus bar of the reflector of the first stage elastic surface wave resonator are electrically connected with a second wiring pattern, and the other bus bar of the reflector and the bridging capacitance are electrically connected with a third wiring pattern. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface acoustic wave filter, and more particularly to a highly reliable surface acoustic wave filter suitable for miniaturization.
[0002]
2. Description of the Related Art At present, there is a demand for downsizing of electronic components incorporated in electric equipment, and downsizing in units of 0.1 mm is progressing now.
[0003]
A surface acoustic wave filter, which is one of the electronic components, will be described using a longitudinally coupled dual mode surface acoustic wave filter as an example. 3 and 4 show a conventional longitudinally coupled dual mode surface acoustic wave filter. Note that the same numbers in both figures indicate the same components.
[0004]
An input interdigital transducer (hereinafter referred to as IDT) 302 connected to an input terminal 301 and a first connection IDT 303 are arranged close to each other in the traveling direction of the surface acoustic wave, and reflectors 304 and 305 are arranged on both sides thereof. The first-stage surface acoustic wave resonator 300, the output IDT 312 connected to the output terminal 311 and the second connection IDT 313 are arranged close to each other along the traveling direction of the surface acoustic wave. A second surface acoustic wave resonator 310 in which 314 and 315 are arranged, and the first connection IDT 303 and the second connection IDT 313 are electrically connected by a first wiring pattern 321. A configuration in which a bridging capacitance 331 is connected between the input terminal 301 and the first wiring pattern 321 and an interstage capacitance 332 is connected between the first wiring pattern 321 and the ground. A.
[0005]
The bridging capacitance 331 is connected to improve the attenuation near the pass band, and the inter-stage capacitance 332 is connected to adjust the pass bandwidth.
[0006]
Conventionally, the electrical connection between the input terminal 301 and the bridging capacitor 331 is performed by connecting a wire made of metal such as gold between the electrode pad forming the input terminal 301 and the electrode pad connecting to the bridging capacitor as shown in FIG. The reflector 305 is short-circuited and connected by bonding, or as shown in FIG. 4, the wiring pattern is routed so as to bypass the outside of the reflector 305 to electrically connect the input terminal 301 and the bridge capacitor 331. A surface acoustic wave filter having a structure connected to the filter has been used.
[0007]
The following documents are disclosed for the surface acoustic wave filter.
[0008]
[Patent Document 1]
Japanese Patent Application Laid-Open No. Hei 9-116381 [Patent Document 2]
JP-A-9-172342
The applicant has not found any prior art documents related to the present invention other than the prior art documents specified in the above-mentioned prior art document information by the time of filing the present application.
[0010]
Among the conventional surface acoustic wave filters, when wire bonding is used to connect the input terminal and the bridging capacitance as shown in FIG. 3, additional man-hours for wire bonding are required. The occurrence of wire breakage or wire breakage cannot be reduced to 0, and there is a possibility that the wire breakage or wire breakage may cause a short circuit with the electrode constituting the resonator, which is considered to be one of the causes of defective products.
[0011]
In the structure in which the wiring pattern is routed so as to bypass the outside of the reflector as shown in FIG. 4 and the input terminal and the bridging capacitor are electrically connected, a space for the routing is required, and miniaturization is achieved. This is a major problem.
[0012]
SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems. An input IDT connected to an input terminal and a first connection IDT are arranged close to each other along a traveling direction of a surface acoustic wave. A first-stage surface acoustic wave resonator having reflectors disposed on both sides thereof, and an output IDT and a second connection IDT connected to an output terminal are arranged close to each other along the traveling direction of the surface acoustic wave. A second-stage surface acoustic wave resonator having reflectors disposed on both sides thereof, and electrically connecting the first connection IDT and the second connection IDT with a first wiring pattern. A surface acoustic wave filter in which a bridging capacitance is connected between the input terminal and the first wiring pattern and an interstage capacitance is connected between the first wiring pattern and the ground; A second wiring pattern electrically connects one of the bus bars of the reflector of the surface acoustic wave resonator. Connected to a and a surface acoustic wave filter, characterized in that the other bus bar and bridging capacitance of the reflector is electrically connected by the third wiring pattern.
[0013]
Also, the first interdigital transducer connected to the input terminal and the first interdigital transducer for connection are arranged close to each other along the traveling direction of the surface acoustic wave, and reflectors are arranged on both sides of the first interdigital transducer. A second arrangement in which a surface acoustic wave resonator, an output interdigital transducer connected to an output terminal, and a second connection interdigital transducer are arranged close to each other along the traveling direction of a surface acoustic wave, and reflectors are arranged on both sides thereof. A first surface acoustic wave resonator, electrically connecting the first connection interdigital transducer and the second connection interdigital transducer with a first wiring pattern, and further comprising an input terminal A surface acoustic wave filter having a configuration in which a bridging capacitance is connected between the first wiring pattern and an interstage capacitance between the first wiring pattern and ground. A fourth wiring pattern for electrically connecting the input terminal to the bridging capacitance is formed outside the traveling direction of the surface acoustic wave of the reflector of the first surface acoustic wave resonator; In addition, the surface acoustic wave filter is characterized in that a part of the fourth wiring pattern is shaped to reflect the surface acoustic wave from the reflector.
[0014]
The surface acoustic wave filter having the above-mentioned shape can electrically connect an input terminal to a bridging capacitor without using wire bonding and without providing a space for routing wiring, and further has various characteristics as a surface acoustic wave filter. Has the effect of causing no change.
[0015]
Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a configuration diagram of a longitudinally coupled dual mode surface acoustic wave filter according to one embodiment of the present invention. FIG. 2 is a configuration diagram of a longitudinally coupled dual mode surface acoustic wave filter according to another embodiment of the present invention. In the drawings, the same numbers indicate the same components, and some of the components are not shown for clarity of the drawings and the description. Also, some dimensions are exaggerated in the drawings.
[0016]
In this embodiment, the electrodes constituting the longitudinally coupled dual mode surface acoustic wave filter are formed on the surface of the piezoelectric element 150. That is, the first IDT 103 connected to the input terminal 102 and the first IDT 104 for connection are arranged close to each other along the traveling direction of the surface acoustic wave, and the reflectors 105 and 106 are arranged on both sides of the first IDT 103. A surface acoustic wave resonator 101 is formed.
[0017]
The output IDT 113 connected to the output terminal 112 and the second connection IDT 114 are arranged close to each other in the longitudinal direction of the surface acoustic wave so as to be juxtaposed in the longitudinal direction of the first surface acoustic wave resonator 101. A second surface acoustic wave resonator 111 having reflectors 115 and 116 disposed on both sides thereof is formed.
[0018]
The first connection IDT 104 and the second connection IDT 114 are electrically connected by a first wiring pattern 121, and the first-stage surface acoustic wave resonator 101 and the second-stage surface acoustic wave resonance The child is cascaded. Further, between the first wiring pattern 121 and the ground, an inter-stage capacitor 126 is formed by a comb electrode in order to adjust a pass bandwidth.
[0019]
The input terminal 102 and one bus bar 107 of the reflector 106 constituting the first-stage surface acoustic wave resonator are electrically connected by a second wiring pattern 122. Also, the other bus bar 108 of the reflector 106 and one of the pair of comb-teeth electrodes in which the respective electrode fingers constituting the bridging capacitor 124 provided for improving the attenuation in the vicinity of the pass band are interposed. Are electrically connected by a third wiring pattern 125. The other comb-shaped electrode of the bridging capacitor 124 is connected to the first wiring pattern 121. That is, the input terminal 102 is electrically connected to the first wiring pattern 121 via the reflector 106 and the bridging capacitor 124.
[0020]
With the longitudinally coupled dual mode surface acoustic wave filter having such a configuration, a wiring pattern between the input terminal 102 and the bridging capacitance can be formed simultaneously with the step of forming other electrodes and the like. Can be omitted. Further, since wire bonding is not used for some of the wiring, the probability of occurrence of defective products due to wire disconnection or wire breakage can be reduced. Further, by using the reflector as a part of the wiring, the wiring is not routed, and the space for forming the wiring can be further reduced. It has been confirmed by various measurements in the present embodiment that no problem occurs in the characteristics of the surface acoustic wave filter even when the reflector is used as a part of the wiring.
[0021]
As another embodiment, as shown in FIG. 2, the reflector 106 is formed by reducing the number of electrodes, and the input terminal 102 and the bridging capacitor 124 are electrically connected to the open space by reducing the number of electrodes. A fourth wiring pattern 127 to be formed is formed. The shape of the portion of the fourth wiring pattern 127 facing the outermost electrode of the reflector 106 is made to reflect the surface acoustic wave transmitted from the reflector 106. With such a shape, the decrease in the reflection ability of the reflector 106 due to the reduction in the number of electrodes is reflected by the reflection of the surface acoustic wave by the shape portion having the reflection function formed on the fourth wiring pattern. I can make up for it.
[0022]
In this embodiment, the surface acoustic wave filter using the surface acoustic wave resonator in two stages is disclosed. Of course, in a multi-stage surface acoustic wave filter having three or more stages, a reflector is used as a part of the wiring. It is also possible to electrically connect the input terminal to the bridging capacitance provided in the second and subsequent stages.
[0023]
Further, in this embodiment, the case where the configuration of the present invention is used only for the connection between the input terminal and the bridging capacitance is disclosed in order to exemplify the case of the two-stage vertical junction. In the surface acoustic wave filter, a configuration in which the reflector according to the present invention is used as a part of a connection wiring pattern is also used to electrically connect a plurality of interstage capacitances formed between the resonators to be formed. be able to. By using the present invention, in a surface acoustic wave filter in which surface acoustic wave resonators are connected in multiple stages, in addition to the bridging capacitance, the number of wires and the number of steps of wire bonding for connecting the interstage capacitance can be further reduced. In addition, it is possible to form a multi-stage surface acoustic wave filter that is more compact, less expensive, and more reliable.
[0024]
According to the present invention, it is possible to omit the wire bonding step, and it is not necessary to provide a space for routing the wiring pattern. Therefore, the surface acoustic wave has high reliability, and is excellent in miniaturization and cost reduction. An effect is obtained that a filter can be obtained.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a surface acoustic wave filter according to an embodiment of the present invention.
FIG. 2 is a configuration diagram of a surface acoustic wave filter according to another embodiment of the present invention.
FIG. 3 is a configuration diagram of a conventional surface acoustic wave filter.
FIG. 4 is a configuration diagram of a conventional surface acoustic wave filter.
[Explanation of symbols]
101, first-stage surface acoustic wave resonator 102, input terminal 103, input IDT
104, first connection IDT
105, reflector 106, reflector 107, bus bar 108, bus bar 111, surface acoustic wave resonator 112 of second stage, output terminal 113, IDT for output
114, second connection IDT
115, reflector 116, reflector 121, first wiring pattern 122, second wiring pattern 124, bridging capacitance 125, third wiring pattern 126, inter-stage capacitance 127, fourth wiring pattern

Claims (2)

A first-stage surface acoustic wave in which an input interdigital transducer connected to an input terminal and a first connection interdigital transducer are arranged close to each other along the traveling direction of a surface acoustic wave, and reflectors are arranged on both sides of the interdigital transducer. A second stage in which the resonator, the output interdigital transducer connected to the output terminal, and the second connection interdigital transducer are arranged close to each other along the traveling direction of the surface acoustic wave, and reflectors are arranged on both sides thereof Having a surface acoustic wave resonator,
The first connection interdigital transducer and the second connection interdigital transducer are electrically connected with a first wiring pattern, and a bridge is formed between the input terminal and the first wiring pattern. A capacitance, and a surface acoustic wave filter having a configuration in which an interstage capacitance is connected between the first wiring pattern and ground.
The input terminal and one bus bar of the reflector of the first surface acoustic wave resonator are electrically connected by a second wiring pattern, and the other bus bar of the reflector is connected to the bridging capacitance. Are electrically connected to each other by a third wiring pattern. A first-stage surface acoustic wave in which an input interdigital transducer connected to an input terminal and a first connection interdigital transducer are arranged close to each other along the traveling direction of a surface acoustic wave, and reflectors are arranged on both sides of the interdigital transducer. A second stage in which the resonator, the output interdigital transducer connected to the output terminal, and the second connection interdigital transducer are arranged close to each other along the traveling direction of the surface acoustic wave, and reflectors are arranged on both sides thereof Having a surface acoustic wave resonator,
The first connection interdigital transducer and the second connection interdigital transducer are electrically connected with a first wiring pattern, and a bridge is formed between the input terminal and the first wiring pattern. A capacitance, and a surface acoustic wave filter having a configuration in which an interstage capacitance is connected between the first wiring pattern and ground.
Forming a fourth wiring pattern for electrically connecting the input terminal and the bridging capacitance to the outside of the first surface acoustic wave resonator in the traveling direction of the surface acoustic wave of the reflector; A surface acoustic wave filter characterized in that a part of the fourth wiring pattern is shaped to reflect a surface acoustic wave from the reflector.

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