SAW filter

Abstract

The utility model provides an SAW filter. The SAW filter comprises a piezoelectric substrate, an interdigital transducer and two electrodes, the interdigital transducer and the two electrodes are located on the top face of the piezoelectric substrate, the two electrodes are located on the two sides of the interdigital transducer, and the piezoelectric substrate is provided with two end faces located on the two sides of the two electrodes. And the part, close to the top surface of the piezoelectric substrate, of at least each end surface is a rough surface and is inclined relative to the top surface of the piezoelectric substrate. In this way, diffuse reflection occurs when clutters generated when the SAW filter works are propagated to the end face of the piezoelectric substrate, so that the clutters can be reflected into the piezoelectric substrate, the problem that the clutters interfere devices when passing through the interdigital transducer again can be solved, the performance of the SAW filter can be improved, and the service life of the SAW filter can be prolonged. And meanwhile, the end face including the rough surface is formed when the piezoelectric substrate is cut, so that the design difficulty and the process surface difficulty are low.

Description

TECHNICAL FIELD

[0001] The utility model relates to filter technical field, especially a kind of SAW filter. BACKGROUND

[0002] Surface Acoustic Wave (SAW) filter is a kind of transducing passive band-pass filter made by using the piezoelectric effect of lithium tantalate, lithium niobate, quartz and other crystals and the physical characteristics of acoustic surface wave propagation.

[0003] Figure 1 It is the schematic diagram of traditional SAW filter. Figure 1 As shown, the traditional SAW filter includes piezoelectric substrate 10 and interdigital transducer (IDT) 20 on the top surface of piezoelectric substrate 10, and the end surface of piezoelectric substrate 10 is smooth and perpendicular to the top surface of piezoelectric substrate 10. When the traditional SAW filter works, it brings body wave, shallow body wave and other unnecessary spurious waves when exciting surface wave, and when these spurious waves are reflected to the end surface, they will be reflected back to the interdigital transducer, which will interfere with the main signal and affect the performance of SAW filter.

[0004] There are two common methods to reduce spurious wave interference at present: one is process, which uses silk screen printing method to coat sound-absorbing glue on the surface of the entire piezoelectric substrate to absorb false signals by using sound-absorbing glue, but this needs to increase the process of sound-absorbing glue coating, and the end surface produced after cutting the piezoelectric substrate cannot be covered by sound-absorbing glue, so the end surface sound-absorbing effect is not ideal; the second is design, which increases the reflection angle at both ends of the chip to make the reflection and incidence direction of acoustic surface wave form a certain angle, and SAW produces phase difference of mutual cancellation due to different propagation lengths, so as to make the false signal attenuate, but the design of increasing reflection angle needs to deduce and model the distribution of SAW, which has great design difficulty, and at the same time, it will also affect the main signal when suppressing false signal, which will increase the loss of SAW filter, and also will lead to the increase of chip area, and further lead to the increase of packaging volume. Therefore, the problem of how to simply and effectively reduce spurious wave interference still needs to be solved. UTILITY MODEL CONTENTS

[0005] One of the purposes of the utility model is to simply and effectively reduce spurious wave interference and improve the performance of SAW filter.

[0006] In order to achieve the above object, the utility model provides a SAW filter. The SAW filter includes piezoelectric substrate and interdigital transducer and two electrodes on the top surface of piezoelectric substrate, two electrodes are located on both sides of interdigital transducer, piezoelectric substrate has two end surfaces on both sides of two electrodes, at least the part of each end surface close to the top surface of piezoelectric substrate is rough surface and is inclined to the top surface of piezoelectric substrate.

[0007] Optionally, the rough surface is irregular rough surface.

[0008] Optionally, the included angle between each end surface and the top surface of piezoelectric substrate is obtuse angle.

[0009] Optionally, each end surface is rough surface.

[0010] Optionally, each end surface includes first section close to the top surface of piezoelectric substrate and second section away from the top surface of piezoelectric substrate, the first section is rough surface, and the second section is flat surface.

[0011] Optionally, the second section is perpendicular to the top surface of piezoelectric substrate.

[0012] Optionally, the second section is inclined to the top surface of piezoelectric substrate.

[0013] Optionally, in the thickness direction of the SAW filter, the height of the first section is greater than or equal to 1 / 3 of the thickness of piezoelectric substrate.

[0014] Optionally, the heights of the first sections of two end surfaces in the thickness direction of the SAW filter are equal.

[0015] The SAW filter provided by the utility model includes piezoelectric substrate and interdigital transducer and two electrodes on the top surface of piezoelectric substrate, two electrodes are located on both sides of interdigital transducer, piezoelectric substrate has two end surfaces on both sides of two electrodes, at least the part of each end surface close to the top surface of piezoelectric substrate is rough surface and is inclined to the top surface of piezoelectric substrate, so that the spurious propagation to the end surface of piezoelectric substrate when the SAW filter works will occur diffuse reflection, thereby the spurious can be reflected to the inside of piezoelectric substrate, and then the problem that the spurious passes through interdigital transducer again and causes interference to the device can be improved, which helps to improve the performance of SAW filter, and the end surface including rough surface is formed when piezoelectric substrate is cut, without needing to increase sound absorption glue coating process and without needing to carry out complex derivation and modeling, and the design difficulty and process difficulty are small. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1This is a schematic diagram of a traditional SAW filter.

[0017] Figure 2 This is a three-dimensional structural diagram of a SAW filter provided in an embodiment of the present invention.

[0018] Figure 3 This is a cross-sectional structural diagram of a SAW filter provided in an embodiment of the present invention.

[0019] Figure 4 This is a cross-sectional structural diagram of a SAW filter provided in another embodiment of the present invention.

[0020] Figure 5 This is a cross-sectional structural diagram of a SAW filter with a rough surface on all end faces, provided in an embodiment of the present invention.

[0021] Figure 6 This is a three-dimensional structural diagram of an uncut piezoelectric substrate in one embodiment of the present invention.

[0022] Figure 7 This is a three-dimensional structural diagram of an embodiment of the present invention after an interdigital transducer and electrodes are formed on the top surface of a piezoelectric substrate.

[0023] Figure 8 This is a three-dimensional structural diagram of a piezoelectric substrate after a groove with a rough inner surface is formed on the dicing channel of the substrate.

[0024] Figure 9 This is a cross-sectional view of a piezoelectric substrate after a rough inner surface groove is formed on the dicing channel of the substrate in one embodiment of the present invention.

[0025] Explanation of reference numerals in the attached figures: 10-piezoelectric substrate; 11-end face; 11a-first segment; 11b-second segment; 20-interdigital transducer; 21-interdigital electrode; 22-busbar; 30-electrode; 40-groove. Detailed Implementation

[0026] To reduce clutter interference and improve the performance of SAW filters, this invention provides a SAW filter. The piezoelectric substrate of the SAW filter has two end faces located on either side of two electrodes. At least the portion of each end face near the top surface of the piezoelectric substrate is a rough surface and is inclined relative to the top surface of the piezoelectric substrate. Thus, when clutter generated by the SAW filter propagates to the end face of the piezoelectric substrate, diffuse reflection (i.e., irregular reflection) occurs, reflecting the clutter into the interior of the piezoelectric substrate. This improves the problem of clutter interfering with the device again through the interdigital transducer, contributing to improved SAW filter performance. Furthermore, the rough surface end face can be formed during the cutting of the piezoelectric substrate, eliminating the need for an additional sound-absorbing adhesive coating process and complex derivations and modeling, thus reducing design and manufacturing complexity.

[0027] The SAW filter proposed in this utility model will be further described in detail below with reference to the accompanying drawings and specific embodiments. The advantages and features of this utility model will become clearer from the following description. It should be noted that the drawings are all in a very simplified form and use non-precise proportions, and are only used to facilitate and clarify the illustration of the embodiments of this utility model.

[0028] In the description of this application, it should be understood that the terms "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "top," "bottom," "inner," and "outer," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the referred element must have a specific orientation or be constructed in a specific orientation, and therefore should not be construed as a limitation on this application. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined as "first" or "second" may explicitly or implicitly include one or more features. In the description of this application, "multiple" means two or more, and "at least one" can mean one, two, or more, unless otherwise explicitly specified.

[0029] Figure 2 This is a three-dimensional structural diagram of a SAW filter provided in an embodiment of the present invention. Figure 3 This is a schematic cross-sectional view of a SAW filter provided in one embodiment of the present invention. (Reference) Figure 2 and Figure 3As shown, the SAW filter provided in this embodiment includes a piezoelectric substrate 10, an interdigital transducer 20 and two electrodes 30 located on the top surface of the piezoelectric substrate 10. The two electrodes 30 are located on both sides of the interdigital transducer 20. The piezoelectric substrate 10 has two end faces 11 located on both sides of the two electrodes 30. At least the portion of each end face 11 near the top surface of the piezoelectric substrate 10 is a rough surface and is inclined relative to the top surface of the piezoelectric substrate 10.

[0030] The interdigital transducer 20 excites and detects surface acoustic waves on the top surface of the piezoelectric substrate 10, thereby realizing the mutual conversion between electrical and acoustic signals. (Reference) Figure 2 As shown, the interdigital transducer 20 includes two sets of interdigital electrodes 21 that are interlaced and periodically distributed, and each set of interdigital electrodes 21 is connected to a bus bar 22.

[0031] refer to Figure 2 As shown, the interdigital electrodes 21 of the interdigital transducer 20 are periodically arranged in the X direction and extend in the Y direction. The two electrodes 30 of the SAW filter are located on both sides of the interdigital transducer 20 in the X direction, and the two end faces 11 of the piezoelectric substrate 10 are located on both sides of the two electrodes in the X direction. The two end faces 11 of the piezoelectric substrate 10 are two end faces arranged in the direction of surface acoustic wave propagation.

[0032] For example, the interdigital transducer 20 and the electrode 30 can be made of the same material. For example, the materials of the interdigital transducer 20 and the electrode 30 can be any one of Al, Cu, Au, Cr, Ru, Ni, Mg, Ti, W, V, Ta, Mo, Ag, In and Sn, or a compound of any one of Al, Cu, Au, Cr, Ru, Ni, Mg, Ti, W, V, Ta, Mo, Ag, In and Sn with oxygen, nitrogen and silicon, or an alloy or intermetallic compound formed from at least two of Al, Cu, Au, Cr, Ru, Ni, Mg, Ti, W, V, Ta, Mo, Ag, In and Sn.

[0033] The piezoelectric substrate 10 is made of piezoelectric materials such as lithium niobate (LiNiO3 / LN), lithium tantalate (LiTaO3 / LT), or quartz. To reduce clutter interference, in this application, such as... Figure 3 As shown, at least the portions of the two end faces 11 of the piezoelectric substrate 10 near the top surface of the piezoelectric substrate 10 are rough surfaces and are inclined relative to the top surface of the piezoelectric substrate 10.

[0034] In some embodiments of this application, such as Figure 3 and Figure 4As shown, each end face 11 includes a first segment 11a near the top surface of the piezoelectric substrate 10 and a second segment 11b away from the top surface of the piezoelectric substrate 10. The first segment 11a is a rough surface, and the second segment 11b is a flat surface. For example, the rough surface of the first segment 11a can be formed by laser grooving, the rough surface of the end face 11 is an irregular rough surface, and the flat surface of the second segment 11b can be formed by cutting the piezoelectric substrate 10 with a blade.

[0035] In some embodiments of this application, in the thickness direction of the SAW filter (i.e. Figure 3 In the Z-direction, the height (Z-direction dimension) of the first segment 11a is greater than or equal to 1 / 3 of the thickness of the piezoelectric substrate 10. This ensures that clutter on the surface of the piezoelectric substrate is diffusely reflected (i.e., irregularly reflected) on the end face 11, reducing clutter passing through the interdigital transducer 20. In other embodiments, the height of the first segment 11a can be selected according to the performance of the SAW filter. The heights of the first segments 11a of the two end faces 11 in the thickness direction of the SAW filter can be equal, allowing the two end faces 11 to be formed in the same process, simplifying the process.

[0036] In one embodiment of this application, as Figure 3 As shown, the second segment 11b of the end face can be perpendicular to the top surface of the piezoelectric substrate 10. In another embodiment of this application, as... Figure 4 As shown, the second segment 11b of the end face can be tilted relative to the top surface of the piezoelectric substrate 10.

[0037] In another embodiment of this application, such as Figure 5 As shown, each end face 11 can be a rough surface, and each end face 11 is tilted relative to the top surface of the piezoelectric substrate 10, so that clutter in the piezoelectric substrate 10 can be diffusely reflected at any position on the end face 11. In this case, the end face 11 can be formed entirely by laser processing, and the entire end face 11 is an irregular rough surface.

[0038] In this application, such as Figures 3 to 5 As shown, the angle between each end face 11 and the top surface of the piezoelectric substrate 10 is an obtuse angle, as indicated by the reference. Figure 3 As shown, this allows more clutter to enter the piezoelectric substrate 10 after being reflected by the end face 11, reducing clutter interference to the interdigital transducer 20. Specifically, when the end face 11 includes a first segment 11a and a second segment 11b, at least the angle between the first segment 11a and the top surface of the piezoelectric substrate 11 is an obtuse angle.

[0039] This application also provides a method for manufacturing a SAW filter, which can be used to manufacture the aforementioned SAW filter.

[0040] In one embodiment of this application, the method for fabricating a SAW filter may include: providing a piezoelectric substrate; forming a plurality of interdigital transducers on the top surface of the piezoelectric substrate, and forming two electrodes on both sides of each interdigital transducer; forming a groove on a cutting path of the piezoelectric substrate by laser processing, wherein the sidewall of the groove is inclined relative to the top surface of the piezoelectric substrate and the inner surface of the groove is a rough surface; and then cutting the piezoelectric substrate from the bottom of the groove to form a single SAW filter.

[0041] Figures 6 to 9 This is a step-by-step schematic diagram of a method for fabricating a SAW filter according to an embodiment of the present invention. The following is in conjunction with... Figures 6 to 9 The method for manufacturing the SAW filter is described.

[0042] like Figure 6 As shown, a piezoelectric substrate 10 is provided, which is an uncut piezoelectric substrate. Exemplarily, the piezoelectric substrate 10 may be a rectangular substrate, but is not limited thereto.

[0043] like Figure 7 As shown, a plurality of interdigital transducers 20 are formed on the top surface of the piezoelectric substrate 10, and two electrodes 30 are formed on both sides of each interdigital transducer 20.

[0044] An exemplary method for forming an interdigital transducer 20 and an electrode 30 on the top surface of a piezoelectric substrate 10 may include: forming a metal material layer on the top surface of the piezoelectric substrate 10; and patterning the metal material layer using a lift-off or dry-etch process to form the interdigital transducer 20 and the electrode 30. The material of the interdigital transducer 20 may be Al, TiAl, or AlCu, etc.

[0045] After forming the interdigital transducer 20 and the electrode 30 on the top surface of the piezoelectric substrate 10, a protective layer can also be formed on the surface of the interdigital transducer 20 to protect the interdigital transducer 20.

[0046] like Figure 8 and Figure 9 As shown, a groove 40 is formed on the cut path of the piezoelectric substrate 10 by laser process. The sidewall of the groove 40 is inclined relative to the top surface of the piezoelectric substrate 10 and the inner surface of the groove 40 is a rough surface.

[0047] The rough surface formed by laser processing is an irregular rough surface. The groove 40 can be a V-shaped groove.

[0048] refer to Figure 9 , Figure 2 and Figure 3As shown, the piezoelectric substrate 10 is cut off from the bottom of the groove 40 to form a single SAW filter. The two end faces 11 of the piezoelectric substrate 10 of the single SAW filter include a sidewall of the groove 40 and a surface formed by cutting the piezoelectric substrate at the bottom of the groove 40. The sidewall of the groove 40 serves as the first segment 11a of the end face 11, and the surface formed by cutting the piezoelectric substrate at the bottom of the groove 40 serves as the second segment 11b of the end face 11.

[0049] In some embodiments of this application, a blade can be used to cut the piezoelectric substrate 10 below the groove 40 to sever the piezoelectric substrate 10. In this case, the second segment 11b of the end face 11 is a flat surface. When it is necessary for the second segment 11b to be inclined relative to the top surface of the piezoelectric substrate 10, a blade with a large cutting angle can be used to cut the piezoelectric substrate 10 below the groove 40.

[0050] In another embodiment of this application, reference is made to... Figure 7 and Figure 5 Multiple interdigital transducers 20 are formed on the top surface of the piezoelectric substrate 10, and two electrodes 30 are formed on both sides of each interdigital transducer 20. Then, the piezoelectric substrate 10 can be cut from the dicing channel of the piezoelectric substrate 10 by laser process to form an end face 11. At this time, the entire end face 11 is a rough surface and the entire surface is inclined relative to the top surface of the piezoelectric substrate 10.

[0051] The SAW filter provided by this utility model includes a piezoelectric substrate 10, an interdigital transducer 20 located on the top surface of the piezoelectric substrate 10, and two electrodes 30. The two electrodes 30 are located on both sides of the interdigital transducer 20. The piezoelectric substrate 10 has two end faces 11 located on both sides of the two electrodes 30. At least the portion of each end face 11 near the top surface of the piezoelectric substrate 10 is a rough surface and is inclined relative to the top surface of the piezoelectric substrate 10. In this way, when the clutter generated by the operation of the SAW filter propagates to the end face 11 of the piezoelectric substrate, diffuse reflection will occur, thereby reflecting the clutter into the interior of the piezoelectric substrate 10. This can improve the problem of clutter interfering with the device again through the interdigital transducer 20, which helps to improve the performance of the SAW filter. At the same time, the end face 11 with the rough surface is formed when cutting the piezoelectric substrate 10, which does not require an additional sound-absorbing adhesive coating process and does not require complex derivation and modeling, thus reducing the design and process difficulty.

[0052] The above description is only a description of the preferred embodiment of the present utility model and is not intended to limit the scope of the present utility model. Any person skilled in the art can make possible changes and modifications to the technical solution of the present utility model by using the methods and techniques disclosed above without departing from the spirit and scope of the present utility model. Therefore, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present utility model without departing from the content of the technical solution of the present utility model shall fall within the protection scope of the technical solution of the present utility model.

Claims

1. A SAW filter, characterized in that, The device includes a piezoelectric substrate, an interdigital transducer located on the top surface of the piezoelectric substrate, and two electrodes located on both sides of the interdigital transducer. The piezoelectric substrate has two end faces located on both sides of the two electrodes, and at least the portion of each end face near the top surface of the piezoelectric substrate is a rough surface and is inclined relative to the top surface of the piezoelectric substrate.

2. The SAW filter as described in claim 1, characterized in that, The rough surface is an irregular rough surface.

3. The SAW filter as described in claim 1, characterized in that, The angle between each end face and the top surface of the piezoelectric substrate is an obtuse angle.

4. The SAW filter as described in claim 1, characterized in that, Each of the aforementioned end faces has a rough surface.

5. The SAW filter as described in claim 1, characterized in that, Each of the end faces includes a first segment near the top surface of the piezoelectric substrate and a second segment away from the top surface of the piezoelectric substrate, wherein the first segment is a rough surface and the second segment is a flat surface.

6. The SAW filter as described in claim 5, characterized in that, The second segment is perpendicular to the top surface of the piezoelectric substrate.

7. The SAW filter as described in claim 5, characterized in that, The second segment is inclined relative to the top surface of the piezoelectric substrate.

8. The SAW filter as described in claim 5, characterized in that, In the thickness direction of the SAW filter, the height of the first segment is greater than or equal to 1 / 3 of the thickness of the piezoelectric substrate.

9. The SAW filter as described in claim 5, characterized in that, The first segments of the two end faces have the same height in the thickness direction of the SAW filter.

10. The SAW filter as described in claim 1, characterized in that, The piezoelectric substrate is made of lithium niobate, lithium tantalate, or quartz.

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