Filter

Abstract

The utility model provides a filter. According to the filter, a resonance structure, electrodes located on the two sides of the resonance structure and a retaining wall surrounding the resonance structure are formed on the front face of a wafer, first conductive columns are formed on the electrodes, a carrier plate is installed on the wafer, the front face of the carrier plate is opposite to the front face of the wafer, and bonding pads corresponding to the first conductive columns in position are arranged on the front face of the carrier plate. The bonding pad is in contact with and electrically connected with the first conductive column, a second conductive column is arranged in the carrier plate, penetrates through the carrier plate and is electrically connected with the bonding pad, and salient points are formed on the back surface of the carrier plate and cover the end surface of the second conductive column; wherein the retaining wall has elastic plasticity, the height of the retaining wall is larger than that of the first conductive column, the retaining wall is compressed between the wafer and the carrier plate and is tightly attached to the carrier plate, and the baffle surrounds a part of a gap between the wafer and the carrier plate to form a cavity. The air tightness of the cavity formed in this way is high, and the reliability of the filter is improved.

Description

Technical Field

[0001] The utility model relates to the technical field of filters, and particularly relates to a filter. Background Art

[0002] With the advent of 5G, the demand for filters in the radio frequency front-end module has increased exponentially. Since 5G requires more and more superimposed frequency bands, the requirements for the number, integration, and miniaturization of filters are getting higher and higher. At present, SAW (surface acoustic wave) filters, with their own advantages, are meeting the requirements of modern communication system devices and portable phones in terms of being thin, light, short, high-frequency, digital, high-performance, and high-reliability, and have occupied 70-80% of the market.

[0003] A SAW filter is a filter that propagates acoustic waves along the surface of a solid and is composed of a piezoelectric material and an interdigital transducer (IDT). To ensure the normal operation of the core functional area IDT, a sealed cavity structure needs to be formed on the surface of the IDT to prevent subsequent processes from contaminating the IDT functional area.

[0004] In an existing SAW filter, a metal retaining wall and conductive columns are formed on the front surface of the first wafer, and a plurality of pads are formed on the front surface of the second wafer. The bonding of the first wafer and the second wafer and the formation of the cavity required for the operation of the IDT are achieved by welding the metal retaining wall and metal columns of the first wafer to the corresponding pads on the front surface of the second wafer. However, in this SAW filter, it is difficult to make the welding heights of the metal retaining wall and the metal columns exactly the same, resulting in poor airtightness of the formed cavity. During the subsequent encapsulation process, it is very easy to cause contamination inside the cavity, leading to device failure. Summary of the Utility Model

[0005] One of the purposes of the utility model is to improve the airtightness of the cavity inside the filter and improve the reliability of the filter.

[0006] To achieve the above object, the present utility model provides a filter. The filter includes: a wafer, on the front surface of the wafer, a resonant structure, electrodes located on both sides of the resonant structure, and a retaining wall surrounding the resonant structure are formed, and first conductive posts are formed on the electrodes; a carrier plate, mounted on the wafer, and the front surface of the carrier plate faces the front surface of the wafer; the front surface of the carrier plate has bonding pads corresponding to the positions of the first conductive posts, the bonding pads are in contact with and electrically connected to the first conductive posts, and second conductive posts are provided in the carrier plate, the second conductive posts penetrate through the carrier plate and are electrically connected to the bonding pads; bumps are formed on the back surface of the carrier plate, and the bumps cover the end faces of the second conductive posts; wherein, the retaining wall has elastoplasticity, and the height of the retaining wall is greater than the height of the first conductive posts, the retaining wall is compressed between the wafer and the carrier plate and is in close fit with the carrier plate, and the baffle surrounds a part of the gap between the wafer and the carrier plate to form a cavity.

[0007] Optionally, the retaining wall is a polyimide material layer or a dry film layer.

[0008] Optionally, the retaining wall is located on the side of the electrode away from the resonant structure; or, the retaining wall surrounds and covers the edge region of the electrode, and the first conductive posts are formed in the retaining wall.

[0009] Optionally, the filter is a wafer-level packaging structure.

[0010] Optionally, a first welding auxiliary structure is formed on the front surface of the wafer, a second welding auxiliary structure corresponding to the position of the first welding auxiliary structure is formed on the front surface of the carrier plate, and the first welding auxiliary structure is welded to the corresponding second welding auxiliary structure.

[0011] Optionally, a part of the second welding auxiliary structure is located in the carrier plate, and the other part protrudes from the front surface of the carrier plate.

[0012] Optionally, the front surface of the carrier plate has a groove corresponding to the position of the retaining wall, and the retaining wall is partially embedded in the groove.

[0013] Optionally, the resonant structure is an interdigital transducer.

[0014] In the filter provided by the present utility model, a resonant structure, electrodes located on both sides of the resonant structure, and a retaining wall surrounding the resonant structure are formed on the front surface of the wafer. A first conductive post is formed on the electrode. The retaining wall has elastoplasticity, and the height of the retaining wall is greater than the height of the first conductive post. The carrier plate is mounted on the wafer. The carrier plate can squeeze the retaining wall. The retaining wall is tightly combined with the carrier plate and surrounds part of the gap between the wafer and the carrier plate to form a cavity. In this way, the airtightness problem of the cavity caused by the inconsistent welding heights of the retaining wall and the conductive post is solved. The formed cavity has good airtightness, which helps to ensure the normal operation of the resonant structure in the core functional area, prevent the resonant structure from being polluted in subsequent processes, and improve the reliability of the filter. In addition, in this application, the cavity is sealed by compressing the retaining wall between the wafer and the carrier plate. The retaining wall and the carrier plate are tightly fitted and do not require welding. In this way, it is beneficial to reduce the residue of welding residues in the cavity and avoid the risk of the resonant structure failing due to pollution. Description of the Drawings

[0015] Figure 1 It is a flowchart of the manufacturing method of the filter provided by an embodiment of the present utility model.

[0016] Figures 2 to 7 It is a schematic diagram of the manufacturing process of the filter provided by an embodiment of the present utility model.

[0017] Figure 8 It is a schematic structural diagram of the filter provided by an embodiment of the present utility model.

[0018] Figures 9 to 11 It is a schematic diagram of the manufacturing process of the filter provided by another embodiment of the present utility model.

[0019] Figure 12 It is a schematic structural diagram of the filter provided by another embodiment of the present utility model.

[0020] Figure 13 It is a top view of the wafer provided by an embodiment of the present utility model.

[0021] Figure 14 It is a schematic cross-sectional view of the carrier plate with a groove on the front surface provided by an embodiment of the present utility model.

[0022] Figure 15 It is a schematic cross-sectional view of the filter with a groove on the front surface of the carrier plate provided by an embodiment of the present utility model.

[0023] Description of the Reference Numerals: 100 - wafer; 101 - resonant structure; 102 - electrode; 103 - first conductive post; 104 - retaining wall; 105 - first welding auxiliary structure; 200 - carrier plate; 201 - second conductive post; 202 - bonding pad; 203 - bump; 204 - groove; 300 - cavity. Detailed Embodiments

[0024] In order to improve the airtightness of the inner cavity of the filter and enhance the reliability of the filter, the present application provides a filter and a manufacturing method thereof.

[0025] The following further elaborates on the filter and its manufacturing method proposed by the present utility model in conjunction with the accompanying drawings and specific embodiments. According to the following description, the advantages and features of the present utility model will be clearer. It should be noted that the accompanying drawings are all in a very simplified form and use non-precise scales, only for conveniently and clearly assisting in explaining the purpose of the embodiments of the present utility model.

[0026] Figure 1 It is a flowchart of the manufacturing method of the filter provided by an embodiment of the present utility model. As Figure 1 shown, the manufacturing method of the filter provided by the present utility model includes:

[0027] Step S1: Provide a wafer. A resonant structure, electrodes located on both sides of the resonant structure, and a retaining wall surrounding the resonant structure are formed on the front surface of the wafer. A first conductive pillar is formed on the electrode. The retaining wall has elastoplasticity, and the height of the retaining wall is greater than the height of the first conductive pillar.

[0028] Step S2: Provide a carrier plate. Bonding pads corresponding to the positions of the first conductive pillars are provided on the front surface of the carrier plate. A second conductive pillar is provided in the carrier plate, and the second conductive pillar penetrates the carrier plate and is electrically connected to the bonding pads.

[0029] Step S3: Mount the carrier plate on the wafer. The front surface of the wafer faces the front surface of the carrier plate. The bonding pads are in contact with and electrically connected to the first conductive pillars. Among them, in the step of mounting the carrier plate on the wafer, the carrier plate presses the retaining wall and the retaining wall is in close fit with the carrier plate. The retaining wall surrounds a part of the gap between the wafer and the carrier plate to form a cavity.

[0030] It should be understood that although Figure 1 the steps in the flowchart are sequentially shown according to the indication of the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless there is a clear description in this article, the execution of these steps has no strict order limit, and these steps can be executed in other orders. Moreover, Figure 1 at least a part of the steps in

[0031] Figures 2 to 7Schematic diagram of the manufacturing process of a filter provided by an embodiment of the present invention. Figure 8 Schematic diagram of the structure of a filter provided by an embodiment of the present invention, where Figure 5 is a top view schematic diagram after a retaining wall is formed on the front side of the wafer, and the rest are cross-sectional views of the wafer and / or the carrier plate. The manufacturing method of the filter in this embodiment will be described below in conjunction with Figures 1 to 8 this.

[0032] As Figure 4 shown, on the front side of the wafer provided in step S1, a resonant structure 101, electrodes 102 located on both sides of the resonant structure 101, and a retaining wall 104 surrounding the resonant structure 101 are formed. A first conductive pillar 103 is formed on the electrode 102. The retaining wall 104 has elastoplasticity, and the height of the retaining wall 104 is greater than the height of the first conductive pillar 103.

[0033] Specifically, as Figure 2 shown, a wafer 100 is provided. The wafer 100 can be a wafer that has completed surface treatment. The material of the wafer 100 includes a piezoelectric material, and the piezoelectric material includes but is not limited to LiTaO3 or LiNbO3.

[0034] As Figure 2 shown, a resonant structure 101 and electrodes 102 located on both sides of the resonant structure 101 are formed on the front side of the wafer 100. The resonant structure 101 includes but is not limited to an interdigital transducer (IDT). The electrode 102 is electrically connected to both ends of the resonant structure 101.

[0035] Exemplarily, the resonant structure 101 and the electrode 102 can be formed in the same process step. The materials of the resonant structure 101 and the electrode 102 can be the same. Exemplarily, the materials of the resonant structure 101 and the electrode 102 can include metal materials such as aluminum (Al), copper (Cu), gold (Au), silver (Ag), chromium (Cr), titanium (Ti), or tungsten (W), and can also include alloy materials of the above metal materials.

[0036] As Figure 3 shown, a first conductive pillar 103 is formed on the electrode 102. Specifically, first conductive pillars 103 are formed on the electrodes 102 on both sides of the resonant structure 101. The first conductive pillar 103 can be formed by an electroplating process. The material of the first conductive pillar 103 includes but is not limited to copper or tungsten.

[0037] As Figure 4 and Figure 5 shown, a retaining wall 104 is formed on the front side of the wafer 100. The retaining wall 104 is located on the side of the electrode 102 away from the resonant structure 101, and the retaining wall 104 surrounds the resonant structure 101.

[0038] It should be noted that in this embodiment, the retaining wall 104 is formed on the side of the electrode 102 away from the resonant structure 101, so that the retaining wall 104 does not occupy the effective area of the filter cavity, that is, the effective area of the cavity can be increased. Furthermore, a single filter chip can be made smaller, which is conducive to the miniaturization of the filter.

[0039] Figures 9 to 11 FIG. is a schematic diagram of the manufacturing process of a filter provided in another embodiment of the present invention, where Figure 9 and Figure 10 are cross-sectional schematic diagrams, Figure 11 is a top view of the wafer after the retaining wall is formed. In another embodiment of the present application, the method for providing a wafer may include: as shown in Figure 9 , a resonant structure 101 and electrodes 102 located on both sides of the resonant structure 101 are formed on the front surface of the wafer 100; as shown in Figure 10 and Figure 11 , a retaining wall 104 is formed on the front surface of the wafer 100, and the retaining wall 104 surrounds and covers the edge region of the electrode 102 and at least exposes a part of the surface of the electrode 102; a first conductive pillar 103 is formed on the electrode 102 and in the retaining wall 104.

[0040] Referring to Figure 4 and Figure 10 , in the direction perpendicular to the front surface of the wafer, that is, in the Figure 4 and Figure 10 vertically upward direction, the height of the retaining wall 104 is greater than the height of the first conductive pillar 103, and the end surface of the first conductive pillar 103 away from the wafer 100 is lower than the surface of the retaining wall 104 away from the wafer 100.

[0041] In the present application, the retaining wall 104 has a certain elastoplasticity. The material of the retaining wall 104 may include resin materials such as polyimide or dry film. It should be noted that the height difference between the retaining wall 104 and the first conductive pillar 103 needs to consider the elastic coefficient and yield strength of the material of the retaining wall 104, etc., to ensure that the welding force is greater than the reaction force of the retaining wall 104 after being squeezed after the subsequent welding of the wafer and the carrier plate, so as to ensure the bonding reliability of the wafer and the carrier plate.

[0042] In the present application, the retaining wall 104 can be formed by a lithography process. Exemplarily, the method for forming the retaining wall 104 may include: forming a retaining wall material layer on the wafer 100, and the retaining wall material layer covers the resonant structure 101 and the electrode 102; performing patterning on the retaining wall material layer by exposure and development to form the retaining wall 104.

[0043] Referring to Figure 6 , the material of the carrier plate 200 provided in step S2 includes but is not limited to silicon-based, composite materials, fiberglass materials, or ceramic materials, etc.

[0044] The front surface of the carrier board 200 has bonding pads 202 corresponding to the positions of the first conductive posts 103. The carrier board 200 has second conductive posts 201, and the second conductive posts 201 penetrate through the carrier board 200 and are electrically connected to the bonding pads 202.

[0045] Exemplarily, the method of forming the bonding pads 202 and the second conductive posts 201 on the carrier board 200 may include: forming the bonding pads 202 on the front surface of the carrier board 200; forming a through hole in the carrier board 200 by using processes such as laser drilling. The through hole penetrates through the carrier board 200, and the position of the through hole corresponds to that of the bonding pads 202; forming a metal seed layer on the back surface of the carrier board 200, and the metal seed layer covers the back surface of the carrier board 200 and the inner surface of the through hole; forming the second conductive posts 201 in the through hole by electroplating; and removing the excess metal seed layer on the back surface of the carrier board 200.

[0046] As Figure 7 shown, the carrier board 200 is mounted on the wafer 100, the front surface of the wafer 100 faces the front surface of the carrier board 200, and the bonding pads 202 are in contact with and electrically connected to the first conductive posts 103; in the step of mounting the carrier board 200 on the wafer 100, the carrier board 200 presses against the retaining wall 104, and the retaining wall 104 surrounds a part of the gap between the wafer 100 and the carrier board 200 to form a cavity 300.

[0047] In this embodiment, the bonding pads 202 and the first conductive posts 103 can be welded. The bonding pads 202 and the first conductive posts 103 can be welded by using bonding or flip-chip processes.

[0048] Since the retaining wall 104 has elastoplasticity and a height higher than that of the first conductive posts 103, in the step of mounting the carrier board 200 on the wafer 100, the carrier board 200 presses against the retaining wall 104, and the retaining wall 104 can undergo appropriate deformation and fit tightly with the carrier board 200, so that the formed cavity has high airtightness. On the other hand, the height of the retaining wall 104 does not limit the contact between the first conductive posts 103 and the bonding pads 202, and can ensure effective welding between the first conductive posts 103 and the bonding pads 202.

[0049] In this application, a rigid carrier board 200 is used to cover above the retaining wall 104 to seal out the cavity 300. Compared with the process of using a thin film to cover the retaining wall to form a cavity, the cavity 300 formed in this application has greater strength, which is beneficial for welding and pressing to achieve airtightness.

[0050] Figure 13 This is a top view of a wafer provided by an embodiment of the present utility model. In an embodiment of the present application, as Figure 13As shown, a first welding auxiliary structure 105 is formed on the front side of the wafer 100. Correspondingly, a second welding auxiliary structure corresponding to the position of the first welding auxiliary structure 105 is formed on the front side of the carrier plate 200. In the step of mounting the carrier plate 200 on the wafer 100, the first welding auxiliary structure 105 and the second welding auxiliary structure are butt-welded, so that the welding force between the wafer 100 and the carrier plate 200 can be increased.

[0051] Figure 14 It is a schematic cross-sectional view of a carrier plate with a groove on the front side provided by an embodiment of the present invention. Figure 15 It is a schematic cross-sectional view of a filter with a groove on the front side of the carrier plate provided by an embodiment of the present invention.

[0052] In an embodiment of the present application, as Figure 14 and Figure 15 shown, the front side of the carrier plate 200 may have a groove 204, and the groove 204 corresponds to the position of the retaining wall 104; after the carrier plate 200 is mounted on the wafer 100, a part of the retaining wall 104 can be embedded in the groove 204, and the surface of the retaining wall 104 is closely combined with the bottom surface of the groove 204, so that it is convenient to align and mount the carrier plate 200 on the wafer 100 and facilitate the formation of a sealed cavity 300.

[0053] Refer to Figure 8 、 Figure 12 and Figure 15 shown, after the carrier plate 200 is mounted on the wafer 100, bumps 203 are formed on the back side of the carrier plate 200, and the bumps 203 cover the end faces of the second conductive posts 201. Exemplarily, the bumps 203 include but are not limited to solder balls. The material of the solder balls includes tin or tin alloy. The bumps 203 can be formed on the back side of the carrier plate 200 by a ball mounting and solder printing process.

[0054] The present application also provides a filter, and the filter can be manufactured by using the manufacturing method of the above filter.

[0055] Refer to Figure 8 shown, the filter includes a wafer 100 and a carrier plate 200.

[0056] On the front side of the wafer 100, a resonant structure 101, electrodes 102 located on both sides of the resonant structure 101, and a retaining wall 104 surrounding the resonant structure 101 are formed, and first conductive posts 103 are formed on the electrodes 102.

[0057] The carrier board 200 is mounted on the wafer 100, and the front sides of the carrier board 200 and the wafer 100 face each other; the front side of the carrier board 200 has bonding pads 202 corresponding to the positions of the first conductive posts 103. The bonding pads 202 are in contact with and electrically connected to the first conductive posts 103. The carrier board 200 has second conductive posts 201, and the second conductive posts 201 penetrate through the carrier board 200 and are electrically connected to the bonding pads 202. Exemplarily, the bonding pads 202 are welded to the first conductive posts 103.

[0058] Among them, the retaining wall 104 has elastoplasticity, and the height of the retaining wall 104 is greater than the height of the first conductive posts 103. The retaining wall 104 is compressed between the wafer 100 and the carrier board 200 and is in close contact with the carrier board 200. The baffle 104 surrounds a part of the gap between the wafer 100 and the carrier board 200 to form a cavity 300.

[0059] In this embodiment, the resonant structure 101 may be an interdigital transducer, and the filter may be a SAW filter, but is not limited thereto.

[0060] The material of the retaining wall 104 may include resin. Exemplarily, the retaining wall 104 is a polyimide material layer or a dry film layer.

[0061] In an embodiment of the present application, as Figure 8 shown, the retaining wall 104 is located on the side of the electrode 102 away from the resonant structure 101. In this way, the retaining wall 104 will not occupy the effective area of the filter cavity, that is, the effective area of the cavity 300 can be increased. Furthermore, a single filter chip can be made smaller, which is beneficial to the miniaturization of the filter.

[0062] In another embodiment of the present application, as Figure 12 shown, the retaining wall 104 surrounds and covers the edge region of the electrode 102, and through holes corresponding to the surface positions of the electrodes are formed in the retaining wall 104. The first conductive posts 103 are filled in the through holes formed in the retaining wall 104.

[0063] Referring to Figure 8 and Figure 12 shown, in the direction perpendicular to the front side of the wafer, that is, Figure 8 and Figure 12 in the vertically upward direction, the height of the retaining wall 104 is greater than the height of the first conductive posts 103, and the end surface of the first conductive posts 103 away from the wafer 100 is lower than the surface of the retaining wall 104 away from the wafer.

[0064] In the present application, the filter is a wafer-level packaging (WLP) structure.

[0065] In an embodiment of the present application, as Figure 13As shown, a first welding auxiliary structure 105 is formed on the front side of the wafer 100. Correspondingly, a second welding auxiliary structure corresponding to the position of the first welding auxiliary structure 105 is formed on the front side of the carrier plate 200. The first welding auxiliary structure 105 and the second welding auxiliary structure are welded in alignment, so that the welding force between the wafer 100 and the carrier plate 200 can be increased, and the bonding reliability of the wafer-level packaging structure can be enhanced.

[0066] Among them, the first welding auxiliary structure 105 may include a first pad located on the wafer 100 and a welding post located on the first pad. The thickness of the first pad may be the same as the thickness of the electrode 102, and the height of the welding post may be the same as the height of the first conductive post 103.

[0067] A part of the second welding auxiliary structure may be located in the carrier plate 200, and the other part protrudes from the front side of the carrier plate 200. In this way, the second welding auxiliary structure is embedded in the carrier plate 200, which is beneficial to enhancing the bonding reliability between the wafer and the carrier plate. Exemplarily, the second welding auxiliary structure may include a second pad located on the front side of the carrier plate 200 and a connecting post located in the carrier plate 200. The thickness of the second pad may be the same as the thickness of the bonding pad 202 on the front side of the carrier plate 200. The connecting post may penetrate the carrier plate 200 and be connected to the second pad. The height of the connecting post may be equal to the height of the second conductive post 201. The cross-sectional shape of the connecting post may be the same as or different from the cross-sectional shape of the second conductive post 201.

[0068] In this application, the first pad and the electrode 102 may be formed in the same process, the welding post and the first conductive post 103 may be formed in the same process, the second pad and the bonding pad 202 may be formed in the same process, and the connecting post and the second conductive post 201 may be formed in the same process.

[0069] Reference Figure 13 As shown, a plurality of first conductive posts 103 are formed on the wafer 100, and a plurality of first welding auxiliary structures 105 may be distributed between the plurality of first conductive posts 103. A plurality of second conductive posts 201 may be formed in the carrier plate 200, and a plurality of second welding auxiliary structures may be distributed between the plurality of second conductive posts 201.

[0070] In an embodiment of this application, as Figure 15 shown, the front side of the carrier plate 200 may have a groove 204, which corresponds to the position of the retaining wall 104. A part of the retaining wall 104 may be embedded in the groove 204, and the surface of the retaining wall 104 is closely combined with the bottom surface of the groove 204. In this way, it is convenient for the carrier plate 200 to be aligned and installed on the wafer 100, that is, it is convenient for alignment and installation during wafer-level packaging, and it is convenient to form a sealed cavity 300.

[0071] As Figure 8 、Figure 12 and Figure 15 As shown in Figure 15 , bumps 203 are formed on the back surface of the carrier plate 200, and the bumps 203 cover the end faces of the second conductive posts 201.

[0072] In the filter and its manufacturing method provided by the present utility model, a resonant structure 101, electrodes 102 located on both sides of the resonant structure 101, and a retaining wall 104 surrounding the resonant structure 101 are formed on the front surface of the wafer 100. First conductive posts 103 are formed on the electrodes 102. The retaining wall 104 has elastoplasticity, and the height of the retaining wall 104 is greater than the height of the first conductive posts 103. The carrier plate 200 is mounted on the wafer 100. The carrier plate 200 can squeeze the retaining wall 104. The retaining wall 104 is tightly combined with the carrier plate 200 and surrounds a part of the gap between the wafer 100 and the carrier plate 200 to form a cavity 300. In this way, the problem of airtightness of the cavity caused by inconsistent welding heights of the retaining wall and the conductive posts is solved. The formed cavity 300 has good airtightness, which helps to ensure the normal operation of the resonant structure 101 in the core functional area, prevent the resonant structure 101 from being polluted in subsequent processes, and improve the reliability of the filter. In addition, in this application, the cavity 300 is sealed by compressing the retaining wall 104 between the wafer 100 and the carrier plate 200. The retaining wall 104 and the carrier plate 200 are tightly fitted and do not require welding. This is beneficial to reducing the residue of welding residues in the cavity 300 and avoiding the risk of the resonant structure failing due to pollution.

[0073] It should be noted that this specification is described in a progressive manner. The parts described later mainly focus on the differences from the parts described earlier. For the same and similar parts between each part, reference can be made to each other.

[0074] The above description is only a description of the preferred embodiments of the present utility model, and does not limit the scope of the rights of the present utility model in any way. Any person skilled in the art can make possible changes and modifications to the technical solutions of the present utility model by using the methods and technical contents disclosed above without departing from the spirit and scope of the present utility model. Therefore, any simple modifications, equivalent changes, and decorations made to the above embodiments according to the technical essence of the present utility model without departing from the content of the technical solution of the present utility model all belong to the protection scope of the technical solution of the present utility model.

Claims

1. A filter, characterized in that: include: A wafer, wherein a resonant structure, electrodes located on both sides of the resonant structure and a retaining wall surrounding the resonant structure are formed on the front side of the wafer, and a first conductive column is formed on the electrode; A carrier plate, mounted on the wafer, with a front side of the carrier plate facing the front side of the wafer; The front side of the carrier has a bonding pad corresponding to the position of the first conductive column, the bonding pad is in contact with and electrically connected to the first conductive column, the carrier has a second conductive column, the second conductive column passes through the carrier and is electrically connected to the bonding pad; the back side of the carrier has a bump formed, the bump covers the end face of the second conductive column; The retaining wall is elastic-plastic, and its height is greater than that of the first conductive column. The retaining wall is compressed between the wafer and the carrier and fits tightly with the carrier. The retaining plate surrounds part of the gap between the wafer and the carrier to form a cavity.

2. The filter according to claim 1, characterized in that The retaining wall is a polyimide material layer or a dry film layer.

3. The filter according to claim 1, characterized in that The retaining wall is located at a side of the electrode away from the resonant structure; or, the retaining wall surrounds and covers an edge area of ​​the electrode, and the first conductive column is formed in the retaining wall.

4. The filter according to claim 1, characterized in that The filter is a wafer-level packaging structure.

5. The filter according to claim 4, characterized in that A first welding auxiliary structure is formed on the front side of the wafer, a second welding auxiliary structure corresponding to the position of the first welding auxiliary structure is formed on the front side of the carrier, and the first welding auxiliary structure is welded to the corresponding second welding auxiliary structure.

6. The filter according to claim 5, characterized in that A portion of the second welding auxiliary structure is located in the carrier plate, and another portion protrudes from the front side of the carrier plate.

7. The filter according to claim 4, characterized in that The front side of the carrier plate is provided with a groove, the groove corresponds to the position of the retaining wall, and the retaining wall is partially embedded in the groove.

8. The filter according to any one of claims 1 to 7, characterized in that: The resonant structure is an interdigital transducer.

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