JP5648745B2 - Elastic wave filter device - Google Patents

Description

  The present invention relates to an elastic wave filter device, and more particularly to a multiband elastic wave filter device in which a plurality of filter units are configured using a single piezoelectric substrate.

  In recent years, with the progress of downsizing and multibanding of mobile phones, there is a demand for downsizing and multibanding of acoustic wave filter devices used in RF circuits of mobile phones. As a measure for downsizing and multibanding the elastic wave filter device, it is conceivable to form a plurality of elastic wave filter units using a single piezoelectric substrate. However, in this case, the routing of the wiring becomes complicated, and a part of the wiring is close to generate parasitic capacitance. For example, when the input signal wiring through which the input signal flows and the output signal wiring through which the output signal flows are close to each other, there is no need from the input side to the output side via the parasitic capacitance formed between the input signal wiring and the output signal wiring. Signal leaks. As a result, the attenuation characteristic outside the passband of the acoustic wave filter device may be deteriorated by the leaked signal.

  As a method of reducing the parasitic capacitance formed between the wirings, for example, as described in Patent Document 1, a method of forming an insulating layer having a dielectric constant lower than that of the piezoelectric substrate under the wiring is conceivable. In Patent Document 1, specifically, an insulating layer is interposed between the ground wiring and the output-side signal wiring. Thereby, the parasitic capacitance generated between the ground wiring and the output side signal wiring is reduced, and the attenuation characteristic outside the passband is improved.

JP 2004-282707 A

  However, when the two wirings are close to each other over a long distance, the attenuation characteristics outside the passband may not be sufficiently improved only by interposing an insulating layer between the wirings. This problem is common to elastic wave filter devices other than the multiband elastic wave filter device.

  The main object of the present invention is to provide an elastic wave filter device having excellent attenuation characteristics outside the passband.

  An elastic wave filter device according to the present invention is an elastic wave filter device including an input terminal, an output terminal, and an elastic wave filter unit. The elastic wave filter unit is connected between the input terminal and the output terminal. The acoustic wave filter device according to the present invention includes a piezoelectric substrate, an input pad electrode, an output pad electrode, a filter electrode unit, an input signal wiring, an output signal wiring, and a ground wiring. The input pad electrode is disposed on the piezoelectric substrate. The input pad electrode constitutes an input terminal. The output pad electrode is disposed on the piezoelectric substrate. The output pad electrode constitutes an output terminal. The filter electrode portion is disposed on the piezoelectric substrate. The filter electrode part constitutes an elastic wave filter part. The input signal wiring is arranged on the piezoelectric substrate. The input signal wiring connects the filter electrode portion and the input pad electrode. The output signal wiring is arranged on the piezoelectric substrate. The output signal wiring connects the filter electrode portion and the output pad electrode. The ground wiring is arranged on the piezoelectric substrate. The ground wiring is connected to the ground potential. The input signal wiring has an adjacent portion adjacent to the output signal wiring. The distance between the adjacent portion and the ground wiring is shorter than the distance between the adjacent portion and the output signal wiring.

  In a specific aspect of the elastic wave filter device according to the present invention, the ground wiring is arranged so as to overlap the adjacent portion, and the elastic wave filter device according to the present invention insulates the ground wiring from the adjacent portion. An insulating layer.

  In another specific aspect of the elastic wave filter device according to the present invention, the filter electrode unit includes a plurality of IDT electrodes arranged along the elastic wave propagation direction. The elastic wave filter unit is a filter unit having a balanced-unbalanced conversion function. The output pad electrode includes two parallel output pad electrodes.

  In another specific aspect of the acoustic wave filter device according to the present invention, the input pad electrode includes first and second input pad electrodes. The output pad electrode includes first and second output pad electrodes. The filter electrode portion includes a first filter electrode portion connected between the first input pad electrode and the first output pad electrode, and a gap between the second input pad electrode and the second output pad electrode. And a connected second filter electrode part. The piezoelectric substrate has a rectangular shape. The first and second input pad electrodes are arranged along one side of the two opposite sides of the piezoelectric substrate, while the first and second output pad electrodes are on the other side. It is arranged along the side.

  ADVANTAGE OF THE INVENTION According to this invention, the elastic wave filter apparatus excellent in the attenuation | damping characteristic outside a pass band can be provided.

FIG. 1 is a schematic cross-sectional view of an acoustic wave filter device according to an embodiment of the present invention. FIG. 2 is a schematic plan view of an acoustic wave filter chip according to an embodiment of the present invention. FIG. 3 is a schematic plan view of an acoustic wave filter chip in a comparative example. FIG. 4 is a graph showing insertion loss when a signal is applied from the first input pad electrode 31a to the balanced output pad electrode 32a1. FIG. 5 is a graph showing insertion loss when a signal is applied from the first input pad electrode 31a to the balanced output pad electrode 32a2. FIG. 6 is a graph showing insertion loss when balanced output pad electrodes 32a1 and 32a2 are balancedly connected.

  Hereinafter, an example of the preferable form which implemented this invention is demonstrated. However, the following embodiment is merely an example. The present invention is not limited to the following embodiments.

  Moreover, in each drawing referred in embodiment etc., the member which has a substantially the same function shall be referred with the same code | symbol. The drawings referred to in the embodiments and the like are schematically described, and the ratio of the dimensions of the objects drawn in the drawings may be different from the ratio of the dimensions of the actual objects. The dimensional ratio of the object may be different between the drawings. The specific dimensional ratio of the object should be determined in consideration of the following description.

(First embodiment)
FIG. 1 is a schematic cross-sectional view of an acoustic wave filter device according to this embodiment. The elastic wave filter device 1 shown in FIG. 1 includes a reception filter unit corresponding to a communication system of GSM (registered trademark) 850 (used band: 869 to 894 MHz), GSM (registered trademark) 900 (used band: 925 to 960 MHz). A reception filter unit corresponding to a communication system, a reception filter unit corresponding to a communication system of GSM (registered trademark) 1800 (used band: 1805 to 1880 MHz), and a communication system of GSM (registered trademark) 1900 (used band 1930 to 1990 MHz). A total of four reception filter units 21 to 24 corresponding reception filter units are provided. The acoustic wave filter device 1 may be a surface acoustic wave filter device using a surface acoustic wave or a boundary acoustic wave filter device using a boundary acoustic wave.

  As shown in FIG. 1, the elastic wave filter device 1 includes a wiring board 10 and an elastic wave filter chip 11. The acoustic wave filter chip 11 is flip-chip mounted on the mounting surface 10 a of the wiring substrate 10. The elastic wave filter chip 11 is connected to an electrode 13 disposed on the back surface 10 b of the wiring substrate 10. The acoustic wave filter chip 11 is sealed with a resin sealing material 12 provided on the wiring substrate 10. Thus, the elastic wave filter device 1 has a CSP (chip size package) structure. In the present embodiment, an example in which the wiring board 10 is made of alumina will be described. However, the constituent material of the wiring board is not particularly limited in the present invention. The wiring board 10 can be made of, for example, an appropriate ceramic material or resin material.

As shown in FIG. 2, the acoustic wave filter chip 11 includes a piezoelectric substrate 20. The piezoelectric substrate 20 has a rectangular shape. The piezoelectric substrate 20 can be composed of, for example, a LiTaO ₃ substrate, a LiNbO ₃ substrate, a quartz substrate, or the like. In the present embodiment, a case where the piezoelectric substrate 20 is composed of a LiTaO ₃ substrate will be described.

  On the surface 20a of the piezoelectric substrate 20 on the wiring substrate 10 side, a first filter electrode portion 21a, a second filter electrode portion 22a, a third filter electrode portion 23a, and a fourth filter electrode portion 24a. And are arranged. The first filter electrode portion 21 a constitutes the first elastic wave filter portion 21. The second filter electrode part 22 a constitutes a second elastic wave filter part 22. The third filter electrode part 23 a constitutes a third elastic wave filter part 23. The fourth filter electrode part 24 a constitutes a fourth elastic wave filter part 24.

  The first filter electrode portion 21 a is disposed on the surface 20 a of the piezoelectric substrate 20, and the first input pad electrode 31 a constituting the first input terminal 31 and the surface 20 a of the piezoelectric substrate 20. The first output pad electrode 32 a constituting the first output terminal 32 is connected to the first output pad electrode 32 a. The first output pad electrode 32 a includes two balanced output pad electrodes 32 a 1 and 32 a 2 disposed on the surface 20 a of the piezoelectric substrate 20.

  The first input pad electrode 31 a and the first filter electrode portion 21 a are connected by an input signal wiring 41 disposed on the surface 20 a of the piezoelectric substrate 20. The balanced output pad electrode 32a1 and the first filter electrode portion 21a are connected by an output signal wiring 51a disposed on the surface 20a of the piezoelectric substrate 20. The balanced output pad electrode 32a2 and the first filter electrode portion 21a are connected by an output signal wiring 51b disposed on the surface 20a of the piezoelectric substrate 20.

  The second filter electrode portion 22a is disposed on the surface 20a of the piezoelectric substrate 20, and includes a second input pad electrode 33a constituting the second input terminal 33, and balanced output pad electrodes 32a1 and 32a2. Connected between.

  The second input pad electrode 33 a and the second filter electrode portion 22 a are connected by an input signal wiring 42 disposed on the surface 20 a of the piezoelectric substrate 20. The balanced output pad electrode 32a1 and the second filter electrode portion 22a are connected by an output signal wiring 51a. The balanced output pad electrode 32a2 and the second filter electrode portion 22a are connected by an output signal wiring 51b.

  The third filter electrode portion 23 a is arranged on the second input pad electrode 33 a and the second output pad electrode 34 a that is arranged on the surface 20 a of the piezoelectric substrate 20 and constitutes the second output terminal 34. Connected between. The second output pad electrode 34 a includes two balanced output pad electrodes 34 a 1 and 34 a 2 disposed on the surface 20 a of the piezoelectric substrate 20.

  The second input pad electrode 33 a and the third filter electrode portion 23 a are connected by an input signal wiring 43 disposed on the surface 20 a of the piezoelectric substrate 20. The balanced output pad electrode 34a1 and the third filter electrode portion 23a are connected by an output signal wiring 52a disposed on the surface 20a of the piezoelectric substrate 20. The balanced output pad electrode 34a2 and the third filter electrode portion 23a are connected by an output signal wiring 52b disposed on the surface 20a of the piezoelectric substrate 20.

  The fourth filter electrode portion 24a is connected between the first input pad electrode 31a and the balanced output pad electrodes 34a1 and 34a2.

  The first input pad electrode 31 a and the fourth filter electrode portion 24 a are connected by an input signal wiring 44 disposed on the surface 20 a of the piezoelectric substrate 20. The balanced output pad electrode 34a1 and the fourth filter electrode portion 24a are connected by an output signal wiring 52a. The balanced output pad electrode 34a2 and the fourth filter electrode portion 24a are connected by an output signal wiring 52b.

  Thus, the 1st filter electrode part 21a and the 4th filter electrode part 24a are connected to the 1st input pad electrode 31a in common. A second filter electrode portion 22a and a third filter electrode portion 23a are commonly connected to the second input pad electrode 33a. A first filter electrode part 21a and a second filter electrode part 22a are commonly connected to the balanced output pad electrodes 32a1 and 32a2. A third filter electrode portion 23a and a fourth filter electrode portion 24a are commonly connected to the balanced output pad electrodes 34a1 and 34a2.

  The first and second input pad electrodes 31 a and 33 a are arranged along one end side 20 </ b> A of two opposing side edges 20 </ b> A and 20 </ b> B of the piezoelectric substrate 20. The balanced output pad electrodes 32a1 and 32a2 constituting the first output pad electrode 32a and the balanced output pad electrodes 34a1 and 34a2 constituting the second output pad electrode 34a are the end 20B of the piezoelectric substrate 20. Are arranged along.

  Each of the first to fourth filter electrode portions 21a to 24a is a longitudinally coupled resonator type acoustic wave filter portion including a plurality of IDT electrodes 25 arranged along the acoustic wave propagation direction. Each of the first to fourth elastic wave filter units 21 to 24 is a balance type filter unit having a balance-unbalance conversion function. An unbalanced signal is input from the input terminals 31 and 33, and a balanced signal is output from the balanced output pad electrodes 32a1, 32a2, 34a1, and 34a2.

  Each of the plurality of IDT electrodes 25 constituting the first to fourth filter electrode portions 21a to 24a is composed of a pair of comb-like electrodes that are interleaved with each other. One of the pair of comb electrodes is connected to the ground potential. Specifically, one comb-like electrode of the IDT electrode included in the first and second filter electrode portions 21a and 22a is connected to the ground electrode 51 connected to the ground potential. On the other hand, one comb-like electrode of the IDT electrode included in the third and fourth filter electrode portions 23a and 24a is connected to the ground electrode 52 connected to the ground potential.

  Further, a ground wiring 61 connected to the ground electrode 51 and a ground wiring 62 connected to the ground electrode 52 are disposed on the surface 20 a of the piezoelectric substrate 20.

  The electrodes included in the acoustic wave filter chip 11, such as wiring, pad electrodes, and IDT electrodes, are, for example, metals selected from the group consisting of Al, Pt, Au, Ag, Cu, Ni, Ti, Cr, and Pd, Or it can also form with the alloy containing 1 or more types of metals chosen from the group which consists of Al, Pt, Au, Ag, Cu, Ni, Ti, Cr, and Pd. Moreover, the electrode may be comprised by the laminated body of the some conductive layer which consists of said metal and an alloy. In the present embodiment, an example in which the electrode is made of an Al—Cu alloy will be described.

  The input signal wiring 41 has an adjacent portion 41a adjacent to the output signal wiring 51a. The input signal wiring 41 is provided such that the distance between the adjacent portion 41a and the ground wiring 61 is shorter than the distance between the adjacent portion 41a and the output signal wiring 51a. Specifically, the ground wiring 61 is arranged so that at least a part thereof overlaps the adjacent portion 41 a and the thickness direction of the wiring board 10. An insulating layer 71 is disposed between the portion overlapping the adjacent portion 41a of the ground wiring 61 and the adjacent portion 41a. The insulating layer 71 insulates the portion overlapping the adjacent portion 41a of the ground wiring 61 from the adjacent portion 41a.

  The input signal wiring 43 has an adjacent portion 43a adjacent to the output signal wiring 52b. The input signal wiring 43 is provided such that the distance between the adjacent portion 43a and the ground wiring 62 is shorter than the distance between the adjacent portion 43a and the output signal wiring 52b. Specifically, the ground wiring 62 is arranged so that at least a part thereof overlaps the adjacent portion 43 a and the thickness direction of the wiring board 10. An insulating layer 72 is disposed between the portion overlapping the adjacent portion 43a of the ground wiring 62 and the adjacent portion 43a. The insulating layer 72 insulates the adjacent portion 43 a from the portion overlapping the adjacent portion 43 a of the ground wiring 62.

  The insulating layers 71 and 72 can be made of a material having a high relative dielectric constant such as polyimide, epoxy resin, acrylic resin, or ceramic material. The insulating layers 71 and 72 are preferably made of a material having a relative dielectric constant of 2 to 6. Here, a case where the insulating layers 71 and 72 are made of polyimide having a relative dielectric constant of about 3.5 and a relative dielectric constant smaller than that of the piezoelectric substrate 20 having a relative dielectric constant of 20 or more will be described.

  As described above, in the present embodiment, the distance between the adjacent portions 41a and 43a and the ground wirings 61 and 62 is shorter than the distance between the adjacent portions 41a and 43a and the output signal wirings 51a and 52b. For this reason, an excellent attenuation characteristic outside the passband can be realized. This is thought to be due to the following reasons. That is, since the distance between the adjacent portions 41a and 43a and the ground wirings 61 and 62 is shorter than the distance between the adjacent portions 41a and 43a and the output signal wires 51a and 52b, the adjacent portions 41a and 43a and the output signal are output. The parasitic capacitance formed between the adjacent portions 41a and 43a and the ground wirings 61 and 62 is larger than the parasitic capacitance formed between the wirings 51a and 52b. For this reason, the output signal wiring without passing through the acoustic wave filter units 21 to 24 from the input signal wiring 41 and 43 through the parasitic capacitance formed between the adjacent portions 41a and 43a and the output signal wirings 51a and 52b. Signals are suppressed from flowing through 51a and 52b, and flow to the ground potential via the ground lines 61 and 62. As a result, it is considered that excellent attenuation characteristics outside the passband can be realized.

  This effect will be described in more detail based on specific examples and comparative examples.

  As an example, a surface acoustic wave filter device having a configuration substantially similar to that of the surface acoustic wave filter device 1 according to the above embodiment was manufactured. As a comparative example, a surface acoustic wave filter device having substantially the same configuration as the surface acoustic wave filter device according to the example except that the ground wirings 61 and 62 are not provided as shown in FIG. In addition, among the structural requirements included in the surface acoustic wave filter device according to the comparative example that shows the configuration of the surface acoustic wave chip in FIG. The members having the structure are referred to by the same reference numerals.

  FIG. 4 shows insertion loss when a signal is applied from the first input pad electrode 31a to the balanced output pad electrode 32a1. FIG. 5 shows insertion loss when a signal is applied from the first input pad electrode 31a to the balanced output pad electrode 32a2. FIG. 6 shows insertion loss when balanced connection is made between the balanced output pad electrodes 32a1 and 32a2. In FIG. 4 to FIG. 6, graphs indicated by dotted lines represent examples, and graphs indicated by solid lines represent comparative examples.

  As shown in FIG. 4, it can be seen that the embodiment having the ground wiring 61 has greatly improved attenuation characteristics outside the passband on the balanced output pad electrode 32a1 side as compared with the comparative example. On the other hand, as shown in FIG. 5, since the balanced output pad electrode 32a2 side has the same structure in the example and the comparative example, the attenuation characteristics outside the passband are the same in the example and the comparative example. However, since the balance is improved between the balanced output pad electrode 32a1 side and the balanced output pad electrode 32a2 side, as shown in FIG. 6, in the differential output, the embodiment is larger than the comparative example and out of the passband. The damping characteristics have been improved.

  From the above results, the ground lines 61, 43a and the ground wirings 61, 62 are made shorter than the distances between the adjacent parts 41a, 43a and the output signal lines 51a, 52b. It can be seen that by providing 62, an excellent attenuation characteristic outside the passband can be realized. In particular, as in the present embodiment, a plurality of filter electrode portions are formed on one piezoelectric substrate 20, and input pad electrodes 31a and 33a and output pad electrodes 32a and 33a are formed on two opposite sides 20A and 20B of the piezoelectric substrate 20. Are arranged in such a manner that signal wirings having different potentials are close to each other. For this reason, the effect of improving the attenuation characteristics outside the pass band becomes more remarkable. The ground wirings 61 and 62 can be formed in the same formation process as other wirings, and the insulating layers 71 and 72 can also be formed in the same formation process as other three-dimensional wiring insulating layers. Therefore, since it is not necessary to add a new process, an increase in manufacturing cost of the acoustic wave filter device can be suppressed.

  Note that the size of the parasitic capacitance generated between the adjacent portions 41a and 43a and the ground wirings 61 and 62 depends on the opposing area between the adjacent portions 41a and 43a and the ground wirings 61 and 62 and the thickness of the insulating layers 71 and 72. It can be adjusted by changing.

DESCRIPTION OF SYMBOLS 1 ... Elastic wave filter apparatus 10 ... Wiring board | substrate 10a ... Mounting surface 10b ... Back surface 11 ... Elastic wave filter chip 12 ... Sealing material 13 ... Electrode 20 ... Piezoelectric substrate 20A, 20B ... End side 20a ... Surface 21 ... First elasticity Wave filter unit 21a ... First filter electrode unit 22 ... Second elastic wave filter unit 22a ... Second filter electrode unit 23 ... Third elastic wave filter unit 23a ... Third filter electrode unit 24 ... Fourth Elastic wave filter unit 24a ... fourth filter electrode unit 25 ... IDT electrode 31 ... first input terminal 31a ... first input pad electrode 32 ... first output terminal 32a ... first output pad electrode 32a1, 32a2 ... Balanced output pad electrode 33 ... second input terminal 33a ... second input pad electrode 34 ... second output terminal 34a ... second output pad electrode 34a1, 43a2 ... balanced output pad electrode 4 To 44 ... input signal lines 41a, 43a ... adjacent portions 51, 52 ... ground electrode 51a, 51b, 52a, 52b ... Output signal lines 61, 62 ... ground wire 71, 72 ... insulating layer

Claims (4)

An input terminal and an output terminal;
An elastic wave filter unit connected between the input terminal and the output terminal;
An elastic wave filter device comprising:
A piezoelectric substrate;
An input pad electrode disposed on the piezoelectric substrate and constituting the input terminal;
An output pad electrode disposed on the piezoelectric substrate and constituting the output terminal;
A filter electrode portion disposed on the piezoelectric substrate and constituting the acoustic wave filter portion;
An input signal wiring disposed on the piezoelectric substrate and connecting the filter electrode portion and the input pad electrode;
An output signal wiring arranged on the piezoelectric substrate and connecting the filter electrode portion and the output pad electrode;
A ground wiring disposed on the piezoelectric substrate and connected to a ground potential;
With
The input signal wiring has an adjacent portion adjacent to the output signal wiring;
An elastic wave filter device in which a distance between the adjacent portion and the ground wiring is shorter than a distance between the adjacent portion and the output signal wiring. The ground wiring is arranged so as to overlap with the adjacent portion,
The acoustic wave filter device according to claim 1, further comprising an insulating layer that insulates the ground wiring from the adjacent portion. The filter electrode unit includes a plurality of IDT electrodes arranged along an elastic wave propagation direction, and the elastic wave filter unit is a filter unit having a balance-unbalance conversion function,
The acoustic wave filter device according to claim 1, wherein the output pad electrode includes two parallel output pad electrodes. The input pad electrode includes first and second input pad electrodes,
The output pad electrode includes first and second output pad electrodes,
The filter electrode unit includes a first filter electrode unit connected between the first input pad electrode and the first output pad electrode, the second input pad electrode, and the second output pad. A second filter electrode part connected between the electrodes,
The piezoelectric substrate has a rectangular shape,
The first and second input pad electrodes are arranged along one end of two opposing sides of the piezoelectric substrate, while the first and second output pad electrodes are the other The elastic wave filter apparatus as described in any one of Claims 1-3 currently arranged along the edge of a side.

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