Wafer level surface acoustic wave filter and radio frequency module chip

Abstract

The application provides a wafer-level surface acoustic wave filter and a radio frequency module chip, and the wafer-level surface acoustic wave filter comprises a substrate, a finger assembly, a dam, a cover plate, a metal column, a metal common ground layer and a solder ball, wherein the finger assembly comprises fingers, bus bars and metal plates formed on the substrate by photoetching and silk printing; the dam is fixed to the substrate; the cover plate is arranged on the dam and is provided with a plurality of through holes; the metal column is fixed to the substrate and is inserted into a corresponding through hole; the metal common ground layer is arranged on the side of the cover plate away from the finger assembly, and part of the metal columns are electrically connected with the metal common ground layer to form a common ground signal end, and the other part of the metal columns are insulated from the metal common ground layer to form a signal input end and a signal output end; and the solder ball is arranged on the end of each metal column away from the substrate. The wafer-level surface acoustic wave filter has simple structure, good wear resistance and high WLP packaging reliability.

Description

Technical Field

[0001] This invention relates to the field of wireless communication technology, and in particular to a wafer-level surface acoustic wave filter and a radio frequency module chip. Background Technology

[0002] With the advent of the information age, wireless communication technology has developed rapidly, and radio frequency (RF) modules have become an indispensable part of social life and development. The advancement of wireless communication technology is inseparable from the development of RF circuits and microwave technology. Currently, in wireless transceiver systems, an RF module is a chip containing two or more components such as a low-noise amplifier (LNA), switch, filter, and power amplifier (PA). Due to their high integration and high performance, RF module chips are widely used in mobile terminals such as mobile phones and wearable devices. As space requirements in terminal devices become increasingly stringent, RF modules are becoming increasingly highly integrated. The increasing demand for miniaturization in RF modules also places stricter requirements on the dimensions of the various components within them.

[0003] Filters are one of the key components in radio frequency (RF) modules. To meet the size requirements of RF modules, wafer-level packaging (WLP) of filters has seen significant development. Typically, a dam is formed directly on the filter substrate using photolithography with organic materials, and then an organic cover plate is applied to complete the package. Because it does not require the substrate of traditional chip-scale packaging (CSP), the size of WLPs has been further reduced.

[0004] However, in traditional WLP packaging, the filter, unlike traditional CSP packaging, lacks its own substrate, making it difficult to guarantee both electrical and cavity performance. In traditional WLP packaging, the filter's surface is isolated from the outside world by only a low-dielectric-constant organic cover. Therefore, external interference and the quality of grounding can significantly impact filter performance. Grounding performance has always been a challenge in traditional WLP-packaged filters. Since WLP filters lack their own ground, grounding must be connected to the ground on the module substrate via solder balls. Due to the large size of the solder balls and the potential distance between the ground on the substrate and the surface, signals must pass through the solder balls and copper pillar vias in the module substrate before returning to ground, introducing a significant parasitic inductance effect. This parasitic inductance can degrade the out-of-band rejection performance of the WLP filter and risks altering its in-band performance, resulting in poor reliability. Summary of the Invention

[0005] To address the shortcomings of the existing technologies, this invention proposes a wafer-level surface acoustic wave filter and an RF module chip to solve the problems of inconvenient grounding, poor return current performance, and low reliability of traditional wafer-level surface acoustic wave filters in application.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0007] In a first aspect, embodiments of the present invention provide a wafer-level surface acoustic wave (SAW) filter, the wafer-level SAW filter comprising:

[0008] Substrate, wherein the substrate is made of a piezoelectric material;

[0009] An interpolation assembly includes interpolations, busbars, and a metal plate formed on the substrate by photolithography; the interpolations are connected to the busbars, and the busbars are connected to the metal plate;

[0010] A cofferdam, which has a ring structure, is fixed to the substrate, and is spaced around the insert finger and the bus bar. A metal plate passes through the cofferdam for electrical connection to the outside.

[0011] A cover plate, which is placed on the cofferdam, and has multiple through holes therethrough;

[0012] Metal pillars, including multiple metal pillars located inside the cofferdam, are respectively fixed to the substrate and inserted into a corresponding through hole, and exposed outside the cover plate;

[0013] A common ground layer is provided on the side of the cover plate away from the interposer assembly, wherein a portion of the metal pillars are electrically connected to the common ground layer to form a common ground signal terminal, and another portion of the metal pillars are insulated from the common ground layer to form a signal input terminal and a signal output terminal; and,

[0014] Solder balls, comprising a plurality of solder balls, with one solder ball fixedly disposed at one end of each metal pillar away from the substrate.

[0015] Preferably, the metal co-layer is formed on the cover plate by wire mesh printing.

[0016] Preferably, the substrate is made of any one of lithium niobate, lithium tantalate, piezoelectric ceramics, and piezoelectric quartz.

[0017] Preferably, the interdigitated fingers include a plurality of interdigitated fingers and are spaced apart on the substrate.

[0018] Preferably, the cofferdam is formed on the substrate using an organic material and a photolithography screen printing process.

[0019] Preferably, the cover plate is formed on the top surface of the cofferdam using organic materials and a corresponding film application method.

[0020] Preferably, the orthographic projection of the plurality of through holes relative to the substrate is located inside the dike.

[0021] Preferably, the metal pillar is formed on the substrate by electroplating.

[0022] Secondly, embodiments of the present invention provide an RF module chip, including the aforementioned wafer-level surface acoustic wave filter.

[0023] Compared with related technologies, in the embodiments of the present invention, interpolation fingers and dams are photolithographically formed on a substrate. The dams are spaced around the interpolation fingers and the busbars, and a metal plate passes through the dams for external electrical connection. A cover plate is placed on the dams, and multiple through holes are provided on the cover plate. Multiple metal pillars are fixed to the substrate and inserted into a corresponding through hole, exposed outside the cover plate. A common ground layer is attached to the side of the cover plate away from the interpolation finger assembly. Some of the metal pillars are electrically connected to the common ground layer to form a common ground signal terminal, while other metal pillars are insulated from the common ground layer to form a signal input terminal and a signal output terminal. A solder ball is fixed at the end of each metal pillar away from the substrate. This common ground layer, formed by the metal pillars, enhances the ground return current, thereby improving the out-of-band performance of the WLP filter. Shortening the distance between the common ground layer on the filter chip and the external ground layer enhances the ground return current performance of the WLP filter, thus improving its out-of-band performance. Meanwhile, the ground plane connects all the solder balls, and the parasitic inductance brought by the solder balls is paralleled, reducing the parasitic inductance value and further mitigating the adverse effects of parasitic inductance. In addition, it also provides some electromagnetic interference shielding, further improving the grounding performance of the WLP filter; the metal common ground layer also has a higher Young's modulus, improving the WLP filter's resistance to molding and enhancing the reliability of the WLP filter package. Attached Figure Description

[0024] The present invention will now be described in detail with reference to the accompanying drawings. The above and other aspects of the present invention will become clearer and more readily understood through the detailed description following the accompanying drawings. In the drawings:

[0025] Figure 1 This is a schematic diagram of the structure of the wafer-level surface acoustic wave filter in an embodiment of the present invention;

[0026] Figure 2 for Figure 1 A sectional view along line AA.

[0027] Among them, 100 is a wafer-level surface acoustic wave filter, 1 is a substrate, 2 is an interpolation assembly, 21 is an interpolation, 3 is a dike, 4 is a metal pillar, 5 is a cover plate, 6 is a metal common ground layer, 7 is a solder ball, 8 is a cavity, and 9 is a through hole. Detailed Implementation

[0028] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein in the specification of the application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application; the terms "comprising" and "having," and any variations thereof, in the specification, claims, and foregoing drawings of this application, are intended to cover non-exclusive inclusion. The terms "first," "second," etc., in the specification, claims, or foregoing drawings of this application are used to distinguish different objects, not to describe a particular order.

[0029] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0030] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] Example 1

[0032] Please see Figure 1-2 As shown, this embodiment of the invention provides a wafer-level surface acoustic wave filter 100, which includes: a substrate 1, an interdigitated assembly 2, a dike 3, a cover plate 5, a metal pillar 4, a metal ground layer 6, and a solder ball 7.

[0033] The substrate 1 is used to support the mounting interdigitated finger assembly 2 and the dike 3.

[0034] The intercalation component 2 includes intercalation fingers 21, a busbar, and a metal plate formed on the substrate by photolithography; the intercalation fingers 21 are connected to the busbar, and the busbar is connected to the metal plate. The cover plate 5, the dam 3, and the substrate 1 together form a cavity 8.

[0035] The cofferdam 3 has a ring structure and is fixed to the substrate 1. The cofferdam 3 is arranged around the interposer 21 and the busbar at intervals. The metal plate passes through the cofferdam 3 for external electrical connection.

[0036] The cover plate 5 is placed on the cofferdam 3, and the cover plate 5 has multiple through holes 9.

[0037] The metal pillars 4 include multiple ones and are located inside the cofferdam 3. The multiple metal pillars 4 are respectively fixed to the substrate 1 and respectively inserted into a corresponding through hole 9, and exposed outside the cover plate 5.

[0038] The metal ground layer 6 is attached to the side of the cover plate 5 away from the interposer assembly 2. Some of the metal pillars 4 are electrically connected to the metal ground layer 6 to form a ground signal terminal, while other parts of the metal pillars 4 are insulated from the metal ground layer 6 to form a signal input terminal and a signal output terminal.

[0039] The solder balls 7 comprise multiple units, with one solder ball 7 fixed at the end of each metal pillar 4 furthest from the substrate 1. This shortens the distance between the metal common ground layer 6 on the filter chip and the external ground layer, enhancing the ground return current performance of the WLP filter and improving its out-of-band performance. Simultaneously, the ground plane connects all the solder balls 7, paralleling the parasitic inductance introduced by the solder balls 7, reducing their value and further mitigating the adverse effects of parasitic inductance. Additionally, it provides some electromagnetic interference shielding, further improving the grounding performance of the WLP filter; the metal common ground layer 6 also has a higher Young's modulus, enhancing the WLP filter's resistance to molding and improving the reliability of the WLP filter package.

[0040] In particular, by creating a complete ground structure on the metal common ground layer 6 of WLP, the metal pillars 4 in the package that need to be grounded are connected together, so that the grounding signal is connected through its own metal common ground layer 6, which greatly improves the ground plane and improves the return current performance of the filter.

[0041] In this embodiment, the metal ground layer 6 is formed on the cover plate 5 by screen printing. The screen printing refers to a screen printing plate with images and text, made using a photosensitive plate-making method, with a screen as the substrate. This results in a metal ground layer 6 with good conductivity and a higher Young's modulus, improving the molding resistance of the WLP filter and enhancing the reliability of the WLP filter packaging.

[0042] In this embodiment, the substrate 1 is made of any one of lithium niobate, lithium tantalate, piezoelectric ceramic, and piezoelectric quartz. It is a crystalline material that causes a voltage to appear between its two end faces when pressure is applied.

[0043] In this embodiment, the interdigitated fingers 21 include a plurality of fingers, which are spaced apart on the substrate 1.

[0044] In this embodiment, the dike 3 is formed on the substrate 1 using organic material and photolithography. This method is easy to manufacture and results in good filter performance.

[0045] In this embodiment, after the cofferdam 3 has solidified, the cover plate 5 is formed on the top surface of the cofferdam 3 using organic materials and a corresponding film application method. The cover plate 5 is easy to manufacture and has a good adhesion effect to the cofferdam 3.

[0046] In this embodiment, the orthographic projection of the plurality of through holes 9 relative to the substrate 1 is located inside the dike 3. This facilitates the installation and fixation of the metal pillars 4 and improves the packaging efficiency of the WLP filter.

[0047] In this embodiment, the metal pillar 4 is formed on the substrate 1 by electroplating. The metal pillar 4 has good conductivity, which facilitates its connection with the metal ground layer 6 to form a common ground connection and improves reflow performance.

[0048] In this embodiment, the substrate 1 facilitates the formation of interdigitated components 2 through multiple photolithography processes. An organic material dam 3 is then fabricated using photolithography. The dam 3 must avoid the interdigitated component 2 structure and the metal ground layer 6 to be connected to the outside world, allowing for subsequent processes and the formation of the cavity 8. After the dam 3 solidifies, an organic material and a corresponding lamination process are used to form a cover plate 5 on top of the dam 3, exposing the positions of the subsequent metal pillars 4. Then, the metal pillars 4 are grown and connected to the outside of the package through processes such as electroplating. Finally, solder balls 7 are grown on the metal pillars 4 using a solder ball brushing process, completing the entire package and proceeding to subsequent dicing and packaging processes. A metal ground layer 6 connecting different grounded solder balls 7 is coated onto the WLP dry film to create a WLP package with a ground layer. The ground signal metal pillars 4 are connected to the metal ground layer 6, while the signal metal pillars 4 for the signal input and signal output terminals are not connected to the metal ground layer 6. This shortens the distance between the metal ground layer 6 on the filter chip and the external ground layer, enhancing the ground return performance of the WLP filter and thus improving the out-of-band performance of the WLP filter.

[0049] Example 2

[0050] This invention provides an RF module chip, including the wafer-level surface acoustic wave filter 100 of Embodiment 1 above. This facilitates enhancement of the RF module chip's reflow performance and out-of-band performance.

[0051] It should be noted that the various embodiments described above with reference to the accompanying drawings are merely illustrative of the present invention and not intended to limit its scope. Those skilled in the art should understand that any modifications or equivalent substitutions made to the present invention without departing from its spirit and scope should be included within the scope of the present invention. Furthermore, unless the context otherwise requires, words appearing in the singular include those in the plural, and vice versa. Additionally, unless specifically stated otherwise, all or part of any embodiment may be used in conjunction with all or part of any other embodiment.

Claims

1. A wafer level surface acoustic wave filter, characterized by, The wafer-level surface acoustic wave filter includes: Substrate, wherein the substrate is made of a piezoelectric material; An interpolation assembly includes interpolations, busbars, and a metal plate formed on the substrate by photolithography; the interpolations are connected to the busbars, and the busbars are connected to the metal plate; A cofferdam, which has a ring structure, is fixed to the substrate, and is spaced around the insert finger and the bus bar. A metal plate passes through the cofferdam for electrical connection to the outside. A cover plate, which is placed on the cofferdam, and has multiple through holes therethrough; Metal pillars, including multiple metal pillars located inside the cofferdam, are respectively fixed to the substrate and inserted into a corresponding through hole, and exposed outside the cover plate; A common ground layer is provided on the side of the cover plate away from the interposer assembly, wherein a portion of the metal pillars are electrically connected to the common ground layer to form a common ground signal terminal, and another portion of the metal pillars are insulated from the common ground layer to form a signal input terminal and a signal output terminal; and, Solder balls, comprising a plurality of solder balls, with one solder ball fixedly disposed at one end of each metal pillar away from the substrate.

2. The wafer level surface acoustic wave filter according to claim 1, wherein, The metal co-layer is formed on the cover plate by wire mesh printing.

3. The wafer level surface acoustic wave filter according to claim 1, wherein, The substrate is made of any one of the following materials: lithium niobate, lithium tantalate, piezoelectric ceramics, and piezoelectric quartz.

4. The wafer level surface acoustic wave filter of claim 1, wherein, The interdigitated fingers include a plurality of interdigitated fingers, which are spaced apart on the substrate.

5. The wafer level surface acoustic wave filter of claim 1, wherein, The cofferdam is formed on the substrate using organic materials and a photolithography screen printing process.

6. The wafer level surface acoustic wave filter according to claim 5, wherein, The cover plate is formed on the top surface of the cofferdam using organic materials and a corresponding film application method.

7. The wafer level surface acoustic wave filter of claim 1, wherein, The orthographic projection of the plurality of through holes relative to the substrate is located inside the dike.

8. The wafer level surface acoustic wave filter of claim 1, wherein, The metal pillars are formed on the substrate by electroplating.

9. A radio module chip, characterized in that Includes the wafer-level surface acoustic wave filter as described in any one of claims 1-8.

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