Surface Acoustic Wave Filter

Abstract

The present invention relates to the field of acoustic wave communication technology, and discloses a surface acoustic wave filter, including a piezoelectric substrate, a first metal connection layer, a first passivation layer, and a second metal connection layer. A plurality of resonators are arranged at the active end of the piezoelectric substrate, and the series resonators and the parallel resonators are sequentially connected through the first metal connection layer. The first passivation layer wraps the resonators and the first metal connection layer to isolate moisture and improve performance reliability. A connection window is etched in the first passivation layer, and a ball is arranged in the connection window to contact the first metal connection layer, and the other end of the ball is in contact with a peripheral circuit (such as a ceramic or resin carrier) to realize input and output signals; the second metal connection layer is connected to the first metal connection layer through an open window on the first passivation layer, which can improve the connection freedom of the resonator, reduce the size of the surface acoustic wave filter, increase the heat dissipation efficiency, and improve the input power that the surface acoustic wave filter can withstand.

Description

Technical Field

[0001] The present invention relates to the technical field of acoustic wave communication, and in particular to a surface acoustic wave filter. Background Art

[0002] Surface acoustic wave (SAW) is an elastic wave that is generated and propagated on the surface of a piezoelectric substrate material, and whose amplitude decreases rapidly as the depth of the substrate material increases. The basic structure of a surface acoustic wave filter is to make an acoustic-electric transducer on the polished surface of a substrate material with piezoelectric properties, using the planar process of semiconductor integrated circuits, and can be used as an input transducer and an output transducer. Its working principle is that the input transducer converts the electrical signal into an acoustic signal, which propagates along the surface of the crystal, and the output transducer converts the received acoustic signal into an electrical signal for output.

[0003] Surface acoustic wave filters play a good role in suppressing high-order harmonics, image information, transmission leakage signals and various parasitic interferences of electronic information equipment. They can achieve filtering of amplitude-frequency and phase-frequency characteristics with any required accuracy, which is difficult to accomplish with other filters. In recent years, related technologies have made surface acoustic wave filters chip-type, which have the advantages of low cost, small size, superior performance and reliable quality. They have been widely used in mobile communications, navigation, new energy vehicles and other fields. In addition, due to the use of new crystal materials and the latest fine processing technology, the upper limit frequency of use is increased, which has promoted the wider application of surface acoustic wave filters in the field of anti-EMI.

[0004] At present, the development direction of surface acoustic wave filters is miniaturization and multifunctionality. It is expected that the size of the filter will become smaller and smaller, for example, from the common specification of 1.8mm×1.4mm to 1.6mm×1.2mm, or even to a smaller size of 1.4mm×1.0mm; or more frequency bands can be included in the same size. While meeting the small size, the filter is also required to withstand higher and higher input power. Therefore, the design of small-size, high-power surface acoustic wave filters has become a difficult problem in the industry. Summary of the invention

[0005] The object of the present invention is to provide a surface acoustic wave filter with high freedom of structural design, good heat dissipation efficiency, stronger working performance and the ability to achieve the purpose of reducing size.

[0006] To achieve this object, the present invention adopts the following technical solutions:

[0007] Surface acoustic wave filters, including:

[0008] A piezoelectric substrate, wherein a plurality of resonators are arranged at the active end of the piezoelectric substrate, and the resonators are divided into series resonators and parallel resonators;

[0009] A first metal connection layer, wherein the first metal connection layer is stacked on the active end of the piezoelectric substrate, each of the series resonators is selectively connected to a corresponding parallel resonator through the first metal connection layer, and all the series resonators are sequentially connected through the first metal connection layer;

[0010] A first passivation layer, wherein the first passivation layer is stacked on the first metal connection layer, the first passivation layer is provided with a plurality of connection windows, a plurality of balls are arranged in the connection windows, the balls are connected to the first metal connection layer, and the balls are divided into signal input balls, signal output balls and ground balls; the output end of the parallel resonator is connected to any of the ground balls through the first metal connection layer; one of the series resonators at the two ends is connected to the signal input ball through the first metal connection layer, and the other is connected to the signal output ball through the first metal connection layer; the first passivation layer is also provided with an opening window;

[0011] A second metal connection layer is stacked on the first passivation layer, and the second metal connection layer is connected to the first metal connection layer through the window.

[0012] As an optional technical solution for the surface acoustic wave filter, the window opening is located on the first metal connection layer connected to the output end of the parallel resonator, two window openings are arranged to correspond one to one with the first metal connection layer connected to any two output ends of the parallel resonators, and both ends of the second metal connection layer are respectively connected to the first metal connection layer through the two window openings.

[0013] As an optional technical solution of the surface acoustic wave filter, the two window openings and the second metal connection layer form a grounded inductance gain group, and the surface acoustic wave filter is provided with a plurality of the grounded inductance gain groups.

[0014] As an optional technical solution for the surface acoustic wave filter, the two window openings are respectively located on the first metal connection layer connected to the input end and the output end of any one of the series resonators; the second metal connection layer includes a first conductive member and a second conductive member, one end of the first conductive member is connected to the first metal connection layer through one of the window openings, and one end of the second conductive member is connected to the first metal connection layer through the other window opening.

[0015] As an optional technical solution of the surface acoustic wave filter, the two window openings and the second metal connection layer form a heat dissipation gain group, and the surface acoustic wave filter is provided with a plurality of the heat dissipation gain groups.

[0016] As an optional technical solution for the surface acoustic wave filter, the second metal connection layer also includes a finger capacitor, a first finger of the finger capacitor is connected to the other end of the first conductive member, a second finger of the finger capacitor is connected to the other end of the second conductive member, and a projection of the finger capacitor on the piezoelectric substrate does not overlap with the resonator.

[0017] As an optional technical solution of the surface acoustic wave filter, the two window openings and the second metal connection layer form a parallel capacitor gain group, and the surface acoustic wave filter is provided with a plurality of the parallel capacitor gain groups.

[0018] As an optional technical solution of the surface acoustic wave filter, the surface acoustic wave filter includes a second passivation layer, and the second passivation layer is stacked on the second metal connection layer.

[0019] As an optional technical solution of the surface acoustic wave filter, the surface acoustic wave filter includes a third metal connection layer, the third metal connection layer is stacked on the second passivation layer, and the third metal connection layer is connected to the second metal connection layer.

[0020] As an optional technical solution of the surface acoustic wave filter, the resonator includes an interdigitated finger region, and the projection of the second metal connection layer on the resonator does not overlap with the interdigitated finger region.

[0021] Beneficial effects of the present invention:

[0022] The surface acoustic wave filter provided by the present invention includes a piezoelectric substrate, a first metal connection layer, a first passivation layer and a second metal connection layer. A plurality of resonators are arranged at the active end of the piezoelectric substrate, and the resonators are divided into series resonators and parallel resonators. The first metal connection layer is stacked on the active end of the piezoelectric substrate, and each series resonator is selectively connected to a corresponding parallel resonator through the first metal connection layer, and all series resonators are sequentially connected through the first metal connection layer. A first passivation layer is stacked on the first metal connection layer, which can wrap the resonator and the first metal connection layer, isolate the intrusion of moisture in the air, and improve the performance reliability of the surface acoustic wave filter. Partial passivation is etched on the first passivation layer to open several connection windows at the ball planting position, exposing the first metal connection layer, and several balls are arranged in the connection windows to connect the balls to the first metal connection layer; the balls are divided into signal input balls, signal output balls and grounding balls, and the output end of the parallel resonator is connected to any grounding ball through the first metal connection layer to play the role of electrical signal grounding; one of the series resonators located at the two ends is connected to the signal input ball through the first metal connection layer, and the other is connected to the signal output ball through the first metal connection layer; the input, output and grounding signals of the surface acoustic wave filter can be connected to the external circuit. A window is opened in a specific area of ​​the first passivation layer, and the second metal connection layer stacked on the first passivation layer is connected to the first metal connection layer through the window, which can improve the freedom of resonator connection in the design of the surface acoustic wave filter; at the same time, the integrated structure saves the active end area of ​​the piezoelectric substrate, and achieves the purpose of reducing the size of the surface acoustic wave filter; and it can increase the heat dissipation efficiency and improve the input power that the surface acoustic wave filter can withstand. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 1 is a schematic structural diagram of a surface acoustic wave filter according to a comparative example 1 provided in a specific embodiment of the present invention;

[0024] Figure 2 yes Figure 1 Sectional view at A-A';

[0025] Figure 3 1 is a schematic diagram of the structure of a surface acoustic wave filter according to a first embodiment of the present invention;

[0026] Figure 4 yes Figure 3 A partial cross-sectional view at B-B';

[0027] Figure 5 is a schematic structural diagram of a surface acoustic wave filter according to Example 2 provided in a specific implementation manner of the present invention;

[0028] Figure 6 1 is a schematic diagram of the structure of a surface acoustic wave filter according to a third embodiment of the present invention;

[0029] Figure 7 It is a partial cross-sectional view of the surface acoustic wave filter of Example 4 provided in the specific implementation manner of the present invention.

[0030] In the figure:

[0031] 100, piezoelectric substrate; 110, resonator; 1101, interdigitated finger region; 1102, reflective grating; 1110, series resonator; 1111, first series resonator; 1112, second series resonator; 1113, third series resonator; 1114, fourth series resonator; 1120, parallel resonator; 1121, first parallel resonator; 1122, second parallel resonator; 1123, third parallel resonator;

[0032] 200, first metal connection layer; 201, connection line;

[0033] 300, first passivation layer; 301, connection window; 302, window opening window; 311, signal input ball; 312, signal output ball; 313, ground ball;

[0034] 400, second metal connection layer; 410, first conductive element; 420, second conductive element; 430, interdigital capacitor; 431, first finger; 432, second finger;

[0035] 500. Second passivation layer. DETAILED DESCRIPTION

[0036] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention. It should also be noted that, for ease of description, only parts related to the present invention, rather than all structures, are shown in the accompanying drawings.

[0037] In the description of the present invention, unless otherwise clearly specified and limited, the terms "connected", "connected", and "fixed" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0038] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0039] In the description of this embodiment, the terms "upper", "lower", "right", "left" and other directions or positional relationships are based on the directions or positional relationships shown in the drawings, and are only for the convenience of description and simplification of operation, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operate in a specific direction, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are only used to distinguish in the description and have no special meaning.

[0040] like Figures 1 to 7 As shown, the present invention discloses a surface acoustic wave filter, comprising a piezoelectric substrate 100, a first metal connection layer 200, a first passivation layer 300 and a second metal connection layer 400. The general production process of the surface acoustic wave filter is to first make a resonator 110 on the piezoelectric substrate 100, set a plurality of resonators 110 on the active end of the piezoelectric substrate 100, and then make the first metal connection layer 200 at the input and output ends of the resonator 110. The resonator 110 is divided into a series resonator 1110 and a parallel resonator 1120; the first metal connection layer 200 is stacked on the active end of the piezoelectric substrate 100, each series resonator 1110 is selectively connected to a corresponding parallel resonator 1120 through the first metal connection layer 200, and all series resonators 1110 are sequentially connected through the first metal connection layer 200; the first passivation layer 300 is stacked on the first metal connection layer 200, which can wrap the resonator 110 and the first metal connection layer 200, isolate the moisture in the air from intrusion, and improve the performance reliability of the surface acoustic wave filter. Exemplarily, the first passivation layer 300 is generally a non-metallic compound such as silicon oxide or silicon nitride, and the piezoelectric substrate 100 is generally lithium tantalate, lithium niobate or other multilayer structure substrates. In actual production, the first passivation layer 300 will cover the entire area of ​​the piezoelectric substrate 100.

[0041] In comparative example 1, Figure 1 and Figure 2As shown in the figure, the passivation of some areas is removed by etching on the first passivation layer 300, and a plurality of connection windows 301 are opened at the ball implantation position to expose the first metal connection layer 200. A plurality of implant balls are arranged in the connection windows 301 to connect the implant balls to the first metal connection layer 200. It is worth noting that the opening area of ​​the connection window 301 is generally larger than the area required for the implant balls to be embedded. The implant balls are divided into signal input implant balls 311, signal output implant balls 312 and ground implant balls 313; the series resonator 1110 and the parallel resonator 1120 are connected to the signal input implant balls 311, signal output implant balls 312 and ground implant balls 313 through the first metal connection layer 200 to realize the signal input and output of the filter.

[0042] Exemplarily, four connection windows 301 and four implant balls are opened on the first passivation layer 300, including a signal input implant ball 311 and a signal output implant ball 312 arranged diagonally, and two ground implant balls 313 arranged diagonally; the resonator 110 includes a first series resonator 1111, a first parallel resonator 1121, a second series resonator 1112, a second parallel resonator 1122, a third series resonator 1113, a third parallel resonator 1123 and a fourth series resonator 1114, wherein each resonator 110 has a reflection grating 1102 at both ends.

[0043] Due to the requirement of small size of the surface acoustic wave filter, the resonator 110 occupies most of the area of ​​the piezoelectric substrate 100, resulting in a single connection method between the resonator 110 and the implant ball, and the grounding inductance of the parallel resonator 1120 is very small. The first parallel resonator 1121 can only be grounded to one of the ground implant balls 313, and the second parallel resonator 1122 and the third parallel resonator 1123 can only be grounded to the other ground implant ball 313. The connection freedom between the resonator 110 and the implant ball is too small, which increases the restriction of the design of the surface acoustic wave filter.

[0044] like Figure 3 and Figure 4 As shown, the surface acoustic wave filter provided in this embodiment is further provided with a window 302 in a specific area of ​​the first passivation layer 300, and the silicon oxide or silicon nitride of the first passivation layer 300 is removed in the area of ​​the window 302 to expose the first metal connection layer 200, and the second metal connection layer 400 stacked on the first passivation layer 300 is connected to the first metal connection layer 200 through the window 302. This method can improve the degree of freedom of connection of the resonator 110 in the design of the surface acoustic wave filter, and freely change the topological structure of the surface acoustic wave filter layout; at the same time, the integrated structure saves the active end area of ​​the piezoelectric substrate 100, and achieves the purpose of reducing the size of the surface acoustic wave filter; and can increase the heat dissipation efficiency and improve the input power that the surface acoustic wave filter can withstand.

[0045] Specifically, the resonator 110 includes an interdigitated finger area 1101, and the projection of the second metal connection layer 400 on the resonator 110 does not overlap with the interdigitated finger area 1101, and only needs to avoid the interdigitated finger area 1101 of the resonator 110 below the first passivation layer 300, otherwise it will affect the acoustic performance of the resonator 110, and the second metal connection layer 400 only overlaps with the connection line 201 of the first metal connection layer 200, and the window 302 is also only opened on the connection line 201 of the first metal connection layer 200. Exemplarily, the second metal connection layer 400 and the first metal connection layer 200 are both made of conductive metal.

[0046] Embodiment 1

[0047] Specific as Figure 3 and Figure 4 As shown in FIG. 1 , a first passivation layer 300 is provided above the first metal connection layer 200 connected to the output end of the parallel resonator 1120, and two window openings 302 are provided, and two ends of the second metal connection layer 400 are respectively connected to the first metal connection layer 200 through the two window openings 302. With this design, the second parallel resonator 1122 can be connected to the grounding ball 313 through the second metal connection layer 400, and can be grounded together with the first parallel resonator 1121, and the second parallel resonator 1122 can additionally obtain a smaller grounding inductance.

[0048] It can be understood that when the active end area of ​​the piezoelectric substrate 100 is small, the arrangement of the connecting wires 201 can be appropriately reduced, and instead a second metal connecting layer 400 can be superimposed on the first passivation layer 300 to save the size of the surface acoustic wave filter and improve the structural freedom. The grounding wiring of any parallel resonator 1120 in the surface acoustic wave filter can be connected to any grounding ball 313 through the second metal connecting layer 400.

[0049] Embodiment 2

[0050] Specific as Figure 5As shown in , there is a first passivation layer 300 above the first metal connection layer 200 connected to the input end and the output end of any series resonator 1110, and two window windows 302 are respectively provided; the second metal connection layer 400 includes a first conductive member 410 and a second conductive member 420, one end of the first conductive member 410 is connected to the first metal connection layer 200 through one of the window windows 302, and one end of the second conductive member 420 is connected to the first metal connection layer 200 through the other window window 302. With this design, the two window windows 302 are respectively located on the connection line 201 connected to the input end and the output end of the second series resonator 1112, and the first conductive member 410 and the second conductive member 420 are respectively connected to the input end and the output end of the second series resonator 1112, so as to increase the metal conduction area at both ends of the second series resonator 1112, and enhance the heat dissipation capacity of the second series resonator 1112.

[0051] At the same time, since the first passivation layer 300 has a heat insulation effect, the connection line 201 under the first passivation layer 300 can be extended and connected to the first passivation layer 300, further increasing the heat dissipation capability. The two window openings 302 and the second metal connection layer 400 form a heat dissipation gain group, and the surface acoustic wave filter is provided with multiple heat dissipation gain groups.

[0052] Embodiment 3

[0053] like Figure 6 As shown in , if a capacitor structure is connected in parallel to the series resonator 1110, the anti-resonance point frequency of the surface acoustic wave resonator 110 can be moved to a low frequency, while the resonance point frequency does not change, which can reduce the coupling coefficient of the resonator 110, and is beneficial to improve the roll-off coefficient of the passband edge of the filter. Specifically, there is no extra space near the second series resonator 1112 to place the capacitor structure, but there is extra space near the implanted ball on the other side that is not used. The arrangement of the two window windows 302 is the same as that of the second embodiment. The second metal connection layer 400 also includes a finger capacitor 430. The projection of the finger capacitor 430 on the piezoelectric substrate 100 does not overlap with the resonator 110. The finger capacitor 430 is arranged in the non-resonator 110 area. The finger capacitor 430 is composed of a first finger 431 and a second finger 432. The first conductor One end of the conductive element 410 is connected to the connecting line 201 through one of the window openings 302, the first finger 431 is connected to the other end of the first conductive element 410, one end of the second conductive element 420 is connected to the connecting line 201 through another window opening 302, the second finger 432 is connected to the other end of the second conductive element 420, the first conductive element 410 and the second conductive element 420 are respectively connected to the input end and the output end of the second series resonator 1112, so as to complete a reasonable parallel capacitor structure on the resonator 110.

[0054] Similarly, the two window openings 302 and the second metal connection layer 400 form a parallel capacitor gain group, and the surface acoustic wave filter is provided with a plurality of parallel capacitor gain groups.

[0055] Embodiment 4

[0056] like Figure 7 As shown in , the surface acoustic wave filter includes a second passivation layer 500, which can be further stacked on the second metal connection layer 400. The first passivation layer 300 and the second passivation layer 500 can wrap the second metal connection layer 400 to protect the second metal connection layer 400 from the intrusion of moisture in the air.

[0057] Optionally, in order to integrate more functions, improve various high-demand surface acoustic wave filters, and expand the scope of application of the surface acoustic wave filter, the surface acoustic wave filter can also include a third metal connection layer, and the third metal connection layer is stacked on the second passivation layer 500. The third metal connection layer is connected to the second metal connection layer 400. The third metal connection layer can be set to a metal conduction structure with the same function as the second metal connection layer 400 in Example 1, Example 2 or Example 3, and can be accumulated as needed.

[0058] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, various obvious changes, readjustments and substitutions can be made without departing from the protection scope of the present invention. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A surface acoustic wave filter, characterized in that: include: A piezoelectric substrate (100), wherein a plurality of resonators (110) are arranged at an active end of the piezoelectric substrate (100), and the resonators (110) are divided into series resonators (1110) and parallel resonators (1120); A first metal connection layer (200), the first metal connection layer (200) being stacked on the active end of the piezoelectric substrate (100), each of the series resonators (1110) being selectively connected to a corresponding parallel resonator (1120) through the first metal connection layer (200), and all of the series resonators (1110) being connected in sequence through the first metal connection layer (200); A first passivation layer (300), the first passivation layer (300) is stacked on the first metal connection layer (200), the first passivation layer (300) is provided with a plurality of connection windows (301), a plurality of planting balls are arranged in the connection windows (301), the planting balls are connected to the first metal connection layer (200), and the planting balls are divided into signal input planting balls (311), signal output planting balls (312) and grounding planting balls (313); the output end of the parallel resonator (1120) is connected to any of the grounding planting balls (313) through the first metal connection layer (200); one of the series resonators (1110) located at the two ends is connected to the signal input planting ball (311) through the first metal connection layer (200), and the other is connected to the signal output planting ball (312) through the first metal connection layer (200); the first passivation layer (300) is also provided with an opening window (302); A second metal connection layer (400), the second metal connection layer (400) is stacked on the first passivation layer (300), and the second metal connection layer (400) is connected to the first metal connection layer (200) through the window opening (302).

2. The surface acoustic wave filter according to claim 1, characterized in that The window opening (302) is located on the first metal connection layer (200) connected to the output end of the parallel resonator (1120), and two window opening windows (302) are arranged to correspond one to one with the first metal connection layer (200) connected to the output ends of any two parallel resonators (1120), and two ends of the second metal connection layer (400) are respectively connected to the first metal connection layer (200) through the two window opening windows (302).

3. The surface acoustic wave filter according to claim 2, characterized in that The two window openings (302) and the second metal connection layer (400) form a grounded inductance gain group, and the surface acoustic wave filter is provided with a plurality of the grounded inductance gain groups.

4. The surface acoustic wave filter according to claim 1, wherein: The two window openings (302) are respectively located on the first metal connection layer (200) connected to the input end and the output end of any one of the series resonators (1110); the second metal connection layer (400) includes a first conductive element (410) and a second conductive element (420), one end of the first conductive element (410) is connected to the first metal connection layer (200) through one of the window openings (302), and one end of the second conductive element (420) is connected to the first metal connection layer (200) through the other window opening (302).

5. The surface acoustic wave filter according to claim 4, characterized in that The two window openings (302) and the second metal connection layer (400) form a heat dissipation gain group, and the surface acoustic wave filter is provided with a plurality of the heat dissipation gain groups.

6. The surface acoustic wave filter according to claim 4, characterized in that The second metal connection layer (400) further comprises an interdigital capacitor (430), wherein a first finger (431) of the interdigital capacitor (430) is connected to the other end of the first conductive member (410), and a second finger (432) of the interdigital capacitor (430) is connected to the other end of the second conductive member (420), and a projection of the interdigital capacitor (430) on the piezoelectric substrate (100) does not overlap with the resonator (110).

7. The surface acoustic wave filter according to claim 6, characterized in that The two window openings (302) and the second metal connection layer (400) form a parallel capacitance gain group, and the surface acoustic wave filter is provided with a plurality of the parallel capacitance gain groups.

8. The surface acoustic wave filter according to any one of claims 1 to 7, characterized in that: The surface acoustic wave filter comprises a second passivation layer (500), wherein the second passivation layer (500) is stacked on the second metal connection layer (400).

9. The surface acoustic wave filter according to claim 8, characterized in that The surface acoustic wave filter comprises a third metal connection layer, wherein the third metal connection layer is stacked on the second passivation layer (500), and the third metal connection layer is connected to the second metal connection layer (400).

10. The surface acoustic wave filter according to any one of claims 1 to 7, characterized in that: The resonator (110) comprises an interdigitated finger region (1101), and a projection of the second metal connection layer (400) on the resonator (110) does not overlap with the interdigitated finger region (1101).

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