Filters, communication equipment, and multilayer boards

Abstract

The present invention improves a filter characteristic. In a planar view of a first surface, a first metal foil substantially does not overlap with a signal line, and overlaps with a ground wiring that is ground-connected with a parallel resonator.

Description

[Technical Field]

[0001] The present disclosure relates to a filter, a communication device, and a multilayer substrate. [Background technology]

[0002] Patent Document 1 discloses a surface acoustic wave device that includes a plurality of ground conductor films. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2002-111441 Summary of the Invention

[0004] A filter according to one embodiment of the present disclosure includes a multilayer substrate having a first surface and a second surface located opposite the first surface, and a piezoelectric substrate mounted on the first surface side of the multilayer substrate and having a parallel resonator, the multilayer substrate having a first metal foil located closer to the first surface than the second surface, and a signal line electrically connected to the parallel resonator, and in a planar view of the first surface, the first metal foil overlaps with a ground wiring connected to the parallel resonator by ground, and does not overlap with the signal line. [Brief explanation of the drawings]

[0005] [Figure 1] FIG. 1 is an equivalent circuit diagram of a filter according to the present disclosure. [Figure 2] 1A to 1C are six plan views showing a schematic configuration of a filter according to a comparative example. [Figure 3] 1A to 1C are six plan views showing a schematic configuration of a filter according to a first embodiment of the present disclosure. [Figure 4] 1A to 1C are six plan views showing a schematic configuration of a filter according to a modification of the first embodiment of the present disclosure. [Figure 5]10A to 10C are six plan views showing a schematic configuration of a filter according to a second embodiment of the present disclosure. [Figure 6] 10A to 10C are six plan views showing a schematic configuration of a filter according to a first modified example of the second embodiment of the present disclosure. [Figure 7] 10A to 10C are six plan views showing a schematic configuration of a filter according to a second modified example of the second embodiment of the present disclosure. [Figure 8] 10A to 10C are six plan views showing a schematic configuration of a filter according to a third modified example of the second embodiment of the present disclosure. [Figure 9] 6 is a graph comparing the characteristics of the filter shown in FIG. 2 with the characteristics of the filter shown in FIG. 5; [Figure 10] FIG. 10 is a plan view showing a schematic configuration of another filter according to the second embodiment of the present disclosure. [Figure 11] 11A to 11C are graphs comparing the characteristics of the filter shown in FIG. 5 with the characteristics of the filter shown in FIG. 10; [Figure 12] FIG. 10 is a block diagram showing a schematic configuration of a communication device according to a third embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0006] In the surface acoustic wave device disclosed in Patent Document 1, signal loss within the passband is large and signal attenuation outside the passband is small, so the filter characteristics of the surface acoustic wave device disclosed in Patent Document 1 are not good.

[0007] According to one aspect of the present disclosure, the filter characteristics can be improved.

[0008] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The following describes an embodiment of the present disclosure. For convenience of explanation, the same reference numerals are used to designate components having the same functions as those previously described, and the description thereof may not be repeated.

[0009] 1 is an equivalent circuit diagram of a filter 100 according to the present disclosure. The filter 100 includes series resonators 1 to 4, parallel resonators 5 to 7, and wiring 8 and 9. The filter 100 has a configuration in which the series resonators 1 to 4 and the parallel resonators 5 to 7 are connected in a ladder configuration. The wiring 8 is electrically connected to the series resonators 1 to 4 and the parallel resonators 5 to 7. The wiring 8 is a general term for wiring that constitutes a signal path from the input terminal IN of the filter 100 to the output terminal OUT of the filter 100. The wiring 9 is a general term for wiring that is connected to the corresponding one of the parallel resonators 5 to 7 and to ground.

[0010] Comparative Example FIG. 2 shows six plan views of a schematic configuration of a filter 101 according to a comparative example. The filter 101 is one of the specific configurations of the filter 100. The filter 101 includes a multilayer substrate 10 and a piezoelectric substrate 11. The six plan views respectively show the following (1) to (6). In the six plan views, views other than the top surface are shown as see-through as necessary.

[0011] (1) The top surface of the entire filter (2) Upper surface of the piezoelectric substrate 11 (3) Top surface of the fourth layer 10d (4) Top surface of the third layer 10c (5) Upper surface of the second layer 10b (6) Top surface of the first layer 10a Wiring 8 and wiring 9 are provided across multilayer substrate 10 and piezoelectric substrate 11, respectively. In FIG. 2, wiring 8 is hatched with solid lines and wiring 9 is shaded, thereby distinguishing between wiring 8 and wiring 9. Of wiring 8, the portion provided on multilayer substrate 10 is referred to as signal line 12, and the portion provided on piezoelectric substrate 11 is referred to as wiring 13. Of wiring 9, the portion provided on multilayer substrate 10 is referred to as ground wiring 14, and the portion provided on piezoelectric substrate 11 is referred to as wiring 15.

[0012] The multilayer substrate 10 has a first layer 10a, a second layer 10b, a third layer 10c, and a fourth layer 10d. The first layer 10a, the second layer 10b, the third layer 10c, and the fourth layer 10d are stacked in this order. The surface of the fourth layer 10d opposite the third layer 10c is the first surface 10e, and the surface of the first layer 10a opposite the second layer 10b is the second surface 10f. The second surface 10f is the surface on the reverse side of the surface shown on the top surface of the first layer 10a (6). The second surface 10f is located opposite the first surface 10e.

[0013] The first layer 10a, the second layer 10b, the third layer 10c, and the fourth layer 10d may be made of, for example, electrically insulating ceramics or resin. The multilayer substrate 10 has signal lines 12 and ground lines 14.

[0014] The piezoelectric substrate 11 is provided on the multilayer substrate 10, and its bottom surface is mounted on the first surface 10e of the fourth layer 10d. The piezoelectric substrate 11 is mounted on the first surface 10e side of the multilayer substrate 10. The piezoelectric substrate 11 has series resonators 1 to 4, parallel resonators 5 to 7, and wirings 13 and 15.

[0015] In the filter 101, the signal line 12 and the line 13 are electrically connected to form the line 8. In the filter 101, the ground line 14 and the line 15 are electrically connected to form the line 9. The signal line 12 is electrically connected to the parallel resonators 5 to 7. The ground line 14 is ground-connected to the parallel resonators 5 to 7.

[0016] The multilayer substrate 10 has a metal foil 16 on the first surface 10e. In a plan view of the first surface 10e, the metal foil 16 fully overlaps both the signal lines 12 and the ground wiring 14. The plan view of the first surface 10e is from the same perspective as the top surface of the (3) fourth layer 10d.

[0017] The multilayer substrate 10 has electrodes 17-19 on the second surface 10f. Because the electrodes 17-19 are provided on the second surface 10f, they are provided on the surface behind the surface shown on the top surface of the (6) first layer 10a. For convenience of illustration, however, the electrodes 17-19 are shown in perspective in FIG. 2. An example of the material for each of the electrodes 17-19 is copper. The number of electrodes is not limited to three, and may be one, two, or four or more.

[0018] [Embodiment 1] FIG. 3 shows six plan views illustrating a schematic configuration of a filter 102 according to the first embodiment of the present disclosure. FIG. 4 shows six plan views illustrating a schematic configuration of a filter 103 according to a modification of the first embodiment of the present disclosure. Each of the filters 102 and 103 is a specific configuration of the filter 100. Each of these two sets of six plan views illustrates the above-mentioned (1) to (6). In each of these two sets of six plan views, parts other than the top surface are shown as see-through as necessary.

[0019] The configuration of filter 102 differs from the configuration of filter 101 in the following respects, but is otherwise the same.

[0020] In the filter 102, the multilayer substrate 10 does not have a metal foil 16. In the filter 102, the multilayer substrate 10 has a first metal foil 20. The first metal foil 20 is located on the first surface 10e. The location of the first metal foil 20 is not limited to the first surface 10e, and may be on a surface of the multilayer substrate 10 other than the first surface 10e, as long as it is located closer to the first surface 10e than the second surface 10f. An example of a material for the first metal foil 20 is tungsten. Instead of tungsten, various metals such as copper or silver may be used as the material for the first metal foil 20.

[0021] In a plan view of the first surface 10e, the first metal foil 20 overlaps the wiring 9 that is connected to the parallel resonators 5 to 7 and the ground, and particularly overlaps the ground wiring 14.

[0022] In a plan view of the first surface 10e, the first metal foil 20 does not overlap substantially with the signal wire 12. A part of the first metal foil 20 may protrude toward the signal wire 12 and slightly overlap with the signal wire 12. The configuration in which the first metal foil 20 does not overlap substantially with the signal wire 12 may be a configuration that satisfies at least one of the following (A) to (C).

[0023] (A) There is no overlap with signal line 12 (B) There is a slight overlap with the signal line 12, but the effect this has on the change in filter characteristics is negligible. (C) It does not overlap with 90% or more of the area of ​​one line belonging to the signal line 12. As a specific example, it does not overlap with 99% or more of the area of ​​the one line.

[0024] As in the filter 102 and as in (A) above, the first metal foil 20 may not overlap the signal line 12 at all in a plan view of the first surface 10e. In the filter 102, the signal line 12 is provided on the second layer 10b and the third layer 10c. In this way, the signal line 12 may be provided on an inner layer of the multilayer substrate 10. The first metal foil 20 may be connected to ground.

[0025] In a plan view of the first surface 10e, the shape of the first metal foil 20 is not limited to the rectangle shown in FIG. 2, and various shapes such as various polygons other than rectangles and circles can be used.

[0026] In the filter 103, in a plan view of the first surface 10e, the area of ​​the first metal foil 20 is larger than that of the filter 102, and the shape of the first metal foil 20 is shaped to avoid a position where the first metal foil 20 and the signal line 12 overlap. The configuration of the filter 103 is otherwise identical to the configuration of the filter 102.

[0027] Each of the filters 102 and 103 has a small signal loss within the passband and a large amount of signal attenuation outside the passband, that is, it is possible to improve the filter characteristics.

[0028] [Embodiment 2] FIG. 5 shows six plan views of a schematic configuration of filter 104 according to the second embodiment of the present disclosure. FIG. 6 shows six plan views of a schematic configuration of filter 105 according to a first modified example of the second embodiment of the present disclosure. FIG. 7 shows six plan views of a schematic configuration of filter 106 according to a second modified example of the second embodiment of the present disclosure. FIG. 8 shows six plan views of a schematic configuration of filter 107 according to a third modified example of the second embodiment of the present disclosure. Each of filters 104 to 107 is one of the specific configurations of filter 100. Each of these four sets of six plan views respectively shows (1) to (6) described above. In each of these four sets of six plan views, parts other than the top surface are shown in perspective as necessary.

[0029] The configuration of filter 104 is the same as that of filter 102 except for the following points.

[0030] In the filter 104, the multilayer substrate 10 has a second metal foil 21 in addition to the first metal foil 20. The second metal foil 21 is located on the first surface 10e. The location of the second metal foil 21 is not limited to the first surface 10e, and may be on a surface of the multilayer substrate 10 other than the first surface 10e, as long as it is located closer to the first surface 10e than the second surface 10f. An example of a material for the second metal foil 21 is tungsten. Instead of tungsten, various metals such as copper or silver may be used as the material for the second metal foil 21. The first metal foil 20 and the second metal foil 21 are not electrically connected to each other.

[0031] In a plan view of the first surface 10e, the second metal foil 21 overlaps with the signal line 12. In a plan view of the first surface 10e, the area where the second metal foil 21 and the signal line 12 overlap is larger than the area where the first metal foil 20 and the signal line 12 overlap.

[0032] In a plan view of the first surface 10e, the second metal foil 21 does not overlap with the ground wiring 14. The configuration in which the second metal foil 21 does not overlap with the ground wiring 14 may be a configuration that satisfies the following (D) or (E).

[0033] (D) There is no overlap with the ground wiring 14. (E) Although there is a slight overlap with the ground wiring 14, the effect this has on changes in the filter characteristics is negligible.

[0034] 9A and 9B are graphs comparing the characteristics of filter 101 and filter 104. In Fig. 9, the horizontal axis represents frequency in MHz. In Fig. 9, the vertical axis represents passband characteristics or voltage standing wave ratio in dB. The passbands of filter 101 and filter 104 are each, for example, in the range of 4800 MHz or higher and 4900 MHz or lower.

[0035] 9, it can be seen that filter 104 has a smaller signal loss within the pass band than filter 101. It can also be seen from Fig. 9 that filter 104 has a larger amount of attenuation of signals outside the pass band, such as signals at frequencies higher than the pass band, than filter 101.

[0036] In the filter 105, in a plan view of the first surface 10e, a portion 22 of the first metal foil 20 facing the second metal foil 21 and a portion 23 of the second metal foil 21 facing the first metal foil 20 are curved. The configuration of the filter 105 is otherwise the same as the configuration of the filter 104.

[0037] In the filter 106, in a plan view of the first surface 10e, the second metal foil 21 does not overlap the signal line 12. The configuration of the filter 106 is the same as the configuration of the filter 104 in other respects.

[0038] The configuration of filter 107 differs from the configuration of filter 104 in the points described below, but is otherwise the same.

[0039] In the filter 107, the multilayer substrate 10 includes a first metal foil 20 and a second metal foil 21. The second metal foil 21 may be divided. For example, the second metal foil 21 includes a third metal foil 24. The third metal foil 24 is located on the first surface 10e. The location of the third metal foil 24 is not limited to the first surface 10e, and may be on a surface of the multilayer substrate 10 other than the first surface 10e, as long as it is located closer to the first surface 10e than the second surface 10f. An example of a material for the third metal foil 24 is tungsten. Instead of tungsten, various metals such as copper or silver may be used as appropriate for the material of the third metal foil 24. The third metal foil 24 may have the same function as the second metal foil 21. A signal line 12 may be provided between the second metal foil 21 and the third metal foil 24 at a position where they overlap in a plan view.

[0040] The effect of each of the filters 105 to 107 is the same as that of the filter 104 .

[0041] The electric field tends to be stronger at sharply curved portions of the signal line 12. In view of this tendency, the second metal foil 21 may be located at sharply curved portions of the signal line 12 in a plan view of the first surface 10e.

[0042] Fig. 10 is a plan view showing a schematic configuration of a filter 108 according to a second embodiment of the present disclosure. Fig. 10 shows the top surface of the entire filter 108 in a manner similar to the top surface of the entire filter (1) above. The filter 108 is a modification of the filter 104 such that the second metal foil 21 is located at the sharply curved portion 25 of the signal line 12.

[0043] FIG. 11 shows various graphs comparing the characteristics of filter 104 and filter 108. In FIG. 11, the horizontal axis represents frequency in MHz. In FIG. 11, the vertical axis represents passband characteristics or voltage standing wave ratio in dB. FIG. 11 shows that filter 108 has improved local signal level drops within the passband compared to filter 104. In other words, FIG. 11 shows that filter 108 has improved band depressions compared to filter 104.

[0044] [Other notes regarding filters] Each of the filters 102 to 108 may have the following configuration.

[0045] At least one of the first metal foil 20 and the second metal foil 21 may not be used to connect the multilayer substrate 10 and the piezoelectric substrate 11.

[0046] In a plan view of the first surface 10e, the sum of the area of ​​the first metal foil 20 and the area of ​​the second metal foil 21 may be 30% or more, or may be 44% or more, of the total area of ​​the electrodes 17 to 19. The greater the ratio of the sum of the area of ​​the first metal foil 20 and the area of ​​the second metal foil 21 to the total area of ​​the electrodes 17 to 19, the less likely the multilayer substrate 10 will warp when formed by firing. If this ratio is 44% or more, the multilayer substrate 10 will be sufficiently less likely to warp.

[0047] [Embodiment 3] 12 is a block diagram showing a schematic configuration of a communication device 200 according to a third embodiment of the present disclosure. The communication device 200 includes a filter 109. The filter 109 is any one of the filters 102 to 108. The communication device 200 including the filter 109 is also included in the scope of the present disclosure. The communication device 200 may perform wireless communication using radio waves. In the communication device 200, the filter 109 may be used, for example, as a filter for a duplexer.

[0048] [Embodiment 4] The multilayer substrate 10 itself is also included in the scope of the present disclosure. The multilayer substrate 10 includes a first surface 10e, a second surface 10f located on the opposite side of the first surface 10e, a first metal foil 20 located closer to the first surface 10e than the second surface 10f, and a signal line 12 electrically connectable to the parallel resonators 5 to 7. In a plan view of the first surface 10e, the first metal foil 20 overlaps with a ground wiring 14 connectable to the parallel resonators 5 to 7, but does not overlap with the signal line 12.

[0049] The present disclosure is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present disclosure. [Explanation of symbols]

[0050] 1~4 Series resonators 5~7 parallel resonators 8, 9, 13, 15 Wiring 12 Signal line 14 Ground wiring 10 Multilayer board 10a 1st layer 10b 2nd layer 10c 3rd layer 10d 4th layer 10e 1st page 10f 2nd side 11 Piezoelectric substrate 16 Metal foil 17~19 electrode 20 First metal foil 21 Second metal foil 22 Portion of the first metal foil facing the second metal foil 23 Portion of second metal foil facing first metal foil 24 Third metal foil 25 Sharp curves in signal lines 100~109 filter 200 Communication Equipment

Claims

1. a first surface and a second surface opposite the first surface; a first layer having a first metal foil located closer to the first surface than the second surface, and a second metal foil located closer to the first surface than the second surface; a second layer having a ground wiring that can be connected to the parallel resonator and a signal line that can be electrically connected to the parallel resonator; and the first metal foil and the second metal foil are not electrically connected to each other, In a plan view of the first surface, The first metal foil overlaps the ground wiring and does not overlap the signal line. The second metal foil does not overlap the ground wiring but overlaps the signal line. Multilayer board.

2. The multilayer substrate according to claim 1 , wherein the first metal foil does not overlap the signal line at all in a plan view of the first surface.

3. 3. The multilayer board according to claim 1, wherein the signal line is provided on an inner layer of the multilayer board.

4. The multilayer substrate according to claim 1 , wherein, in a plan view of the first surface, an area where the second metal foil and the signal line overlap is larger than an area where the first metal foil and the signal line overlap.

5. the multilayer substrate has at least one electrode provided on the second surface; 3. The multilayer substrate according to claim 1, wherein, in a plan view of the first surface, the sum of the area of ​​the first metal foil and the area of ​​the second metal foil is 30% or more of the total area of ​​the at least one electrode.

6. The multilayer substrate according to claim 1 , wherein the first metal foil is connected to ground.

7. A multilayer substrate as described in claim 1 or 2, wherein the second layer is located closer to the second surface than the first layer in the stacking direction of the multilayer substrate.

8. A filter comprising a multilayer substrate as described in claim 1 or 2.

9. A communication device comprising the filter according to claim 8.

Images