A surface acoustic wave filter package structure and a preparation method thereof, and a radio frequency device

Abstract

The application provides a surface acoustic wave filter packaging structure and a preparation method thereof and a radio frequency device, and relates to the technical field of semiconductors. The interdigital electrode is arranged inside the ring-shaped fence structure, and the solder ball is arranged outside the ring-shaped fence structure. After the preparation of the plastic sealing layer, the plastic sealing layer at least wraps the solder ball. At this time, the solder ball is not in an isolated state, and the risk of cracking and even falling off of the solder ball is greatly reduced during cold and hot impact, and the stability of the surface acoustic wave filter packaging structure is improved. The interdigital electrode and the bearing substrate have a spacing, and the spacing region is a cavity region of the surface acoustic wave filter. Since the interdigital electrode is arranged inside the ring-shaped fence structure, and the ring-shaped fence structure is in contact with the substrate and the bearing substrate in the first direction, the arrangement of the ring-shaped fence structure blocks the plastic sealing material from entering the cavity region during the preparation of the plastic sealing layer, and the working region of the surface acoustic wave filter packaging structure is effectively protected.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor technology, in particular to a surface acoustic wave filter packaging structure, a preparation method thereof and a radio frequency device. BACKGROUND

[0002] The SAW (Surface Acoustic Wave) filter is a kind of filter device made by using the piezoelectric effect and the physical characteristics of the surface acoustic wave propagation, and is widely used in various fields, such as the radio frequency field. The surface acoustic wave is an elastic wave whose energy is concentrated near the surface.

[0003] At present, the surface acoustic wave filter packaging structure is formed by a film covering method to form a cavity, and the solder balls are isolated and not protected around. Due to the large difference between the thermal expansion coefficients of the solder balls, the substrate and the carrier substrate, the solder balls are prone to cracking or even falling off during the cold and hot impact (also known as temperature cycling test, English: Temperture Cycling Test, English abbreviation: TCT).

[0004] At present, how to improve the stability of the surface acoustic wave filter packaging structure is a technical problem to be solved by those skilled in the art. SUMMARY

[0005] In view of the above problems, the present application provides a surface acoustic wave filter packaging structure, a preparation method thereof and a radio frequency device, which realizes the purpose of improving the stability of the surface acoustic wave filter packaging structure. The specific scheme is as follows:

[0006] The first aspect of the present application provides a surface acoustic wave filter packaging structure, which comprises: a surface acoustic wave filter, a carrier substrate and a solder ball located between the surface acoustic wave filter and the carrier substrate.

[0007] The surface acoustic wave filter comprises a substrate, an interdigital electrode and a ring-shaped fence structure; the substrate and the carrier substrate are oppositely arranged in a first direction, and the first direction is perpendicular to the plane where the substrate is located.

[0008] The interdigital electrode and the ring-shaped fence structure are located on the side of the substrate facing the carrier substrate, the interdigital electrode is located inside the ring-shaped fence structure, and the solder ball is located outside the ring-shaped fence structure; wherein the ring-shaped fence structure is in contact with the substrate and the carrier substrate in the first direction, and there is a gap between the interdigital electrode and the carrier substrate in the first direction.

[0009] The surface acoustic wave filter packaging structure further comprises a plastic packaging layer for packaging the surface acoustic wave filter, and the plastic packaging layer at least wraps the solder balls.

[0010] Preferably, in the surface acoustic wave filter packaging structure, the surface acoustic wave filter further comprises a pad structure.

[0011] The pad structure is electrically connected to the interdigital electrode and the solder ball, respectively.

[0012] The pad structure is located outside the annular fence structure.

[0013] Preferably, in the surface acoustic wave filter packaging structure, the surface acoustic wave filter further comprises:

[0014] A metal layer located between the pad structure and the solder ball.

[0015] Preferably, in the surface acoustic wave filter packaging structure, the surface acoustic wave filter further comprises:

[0016] A protective layer covering the interdigital electrode and the pad structure.

[0017] The protective layer has a first through hole exposing part of the surface of the pad structure.

[0018] Preferably, in the surface acoustic wave filter packaging structure, the surface acoustic wave filter packaging structure further comprises:

[0019] A second through hole penetrating the carrier substrate, and an external lead structure.

[0020] The external lead structure is electrically connected to the solder ball through the second through hole.

[0021] Preferably, in the surface acoustic wave filter packaging structure, the interdigital electrode comprises a first bus bar and a second bus bar oppositely arranged in a second direction, and a first electrode finger strip on the first bus bar and a second electrode finger strip on the second bus bar.

[0022] The first bus bar and the second bus bar have the same length extension direction, and both extend along a third direction, the second direction and the third direction are parallel to the plane where the substrate is located, and the second direction and the third direction intersect.

[0023] The second aspect of the present application provides a preparation method of a surface acoustic wave filter packaging structure, the preparation method of the surface acoustic wave filter packaging structure comprises:

[0024] Providing a surface acoustic wave filter, the surface acoustic wave filter comprising a substrate and an interdigital electrode.

[0025] forming a ring wall structure on the surface acoustic wave filter, the interdigital electrode being located inside the ring wall structure;

[0026] forming a solder ball on the surface acoustic wave filter, the solder ball being located outside the ring wall structure;

[0027] flipping the structure provided with the solder ball on a carrier substrate, the substrate and the carrier substrate being oppositely arranged in a first direction, the first direction being perpendicular to a plane where the substrate is located; wherein the ring wall structure is in contact with the substrate and the carrier substrate respectively in the first direction, and there is a gap between the interdigital electrode and the carrier substrate in the first direction;

[0028] forming a plastic encapsulation layer for packaging the surface acoustic wave filter, the plastic encapsulation layer at least wrapping the solder ball.

[0029] Preferably, in the preparation method of the surface acoustic wave filter packaging structure, the surface acoustic wave filter further comprises a pad structure.

[0030] The pad structure is located outside the ring wall structure.

[0031] The forming of the solder ball on the surface acoustic wave filter comprises:

[0032] forming a metal layer on the pad structure;

[0033] forming the solder ball on the metal layer, the pad structure being electrically connected with the interdigital electrode and the solder ball respectively.

[0034] Preferably, in the preparation method of the surface acoustic wave filter packaging structure, the flipping of the structure provided with the solder ball on the carrier substrate comprises:

[0035] processing the carrier substrate to form a second through hole penetrating through the carrier substrate;

[0036] forming an external lead structure based on the second through hole;

[0037] flipping the structure provided with the solder ball on the carrier substrate, the external lead structure being electrically connected with the solder ball through the second through hole.

[0038] Preferably, in the preparation method of the surface acoustic wave filter packaging structure, before the structure provided with the solder ball is flipped on the carrier substrate, the preparation method of the surface acoustic wave filter packaging structure further comprises:

[0039] grinding the substrate;

[0040] A cutting process is performed to form a plurality of independent structures provided with the solder balls.

[0041] Preferably, in the preparation method of the surface acoustic wave filter packaging structure, after the plastic packaging layer is formed, the preparation method of the surface acoustic wave filter packaging structure further comprises:

[0042] A cutting process is performed along the cutting path to form a plurality of independent surface acoustic wave filter packaging structures.

[0043] The third aspect of the present application provides a radio frequency device, which comprises the surface acoustic wave filter packaging structure of any one of the above.

[0044] According to the technical solutions, the present application provides a surface acoustic wave filter packaging structure, a preparation method thereof, and a radio frequency device. By arranging the annular wall structure, the interdigital electrode is arranged inside the annular wall structure, and the solder ball is arranged outside the annular wall structure. After the plastic packaging layer is prepared, the plastic packaging layer at least wraps the solder ball. At this time, the solder ball is not in an isolated state, and the risk of cracking or even falling off of the solder ball during cold and hot impact is greatly reduced, so that the stability of the surface acoustic wave filter packaging structure is improved. In the first direction, the interdigital electrode and the bearing substrate are separated by a spacing, and the spacing region is a cavity region of the surface acoustic wave filter. Since the interdigital electrode is arranged inside the annular wall structure, and the annular wall structure is in contact with the substrate and the bearing substrate in the first direction, respectively, the arrangement of the annular wall structure can block the plastic packaging material from entering the cavity region during the preparation of the plastic packaging layer, so that the working region of the surface acoustic wave filter packaging structure is effectively protected. BRIEF DESCRIPTION OF DRAWINGS

[0045] The above and other features, advantages, and aspects of the present disclosure will become more apparent by describing in detail the embodiments thereof with reference to the attached drawings in which:

[0046] Figure 1 A structure diagram of a surface acoustic wave filter packaging structure provided by an embodiment of the present application is shown in the figure;

[0047] Figure 2 A structure diagram of another surface acoustic wave filter packaging structure provided by an embodiment of the present application is shown in the figure;

[0048] Figure 3 A structure diagram of an interdigital electrode provided by an embodiment of the present application is shown in the figure;

[0049] Figure 4A flowchart of a preparation method of a surface acoustic wave filter packaging structure provided by an embodiment of the present application is shown in the figure.

[0050] Figures 5-12 For Figure 4 A partial structure diagram corresponding to the preparation method is shown in the figure. DETAILED DESCRIPTION

[0051] The embodiments of the present application are described below with reference to the accompanying drawings. The terms used in the embodiment part of the present application are only used to explain the specific embodiments of the present application, and are not intended to limit the present application. As known by those skilled in the art, with the development of technology and the appearance of new scenarios, the technical solutions provided by the embodiments of the present application are also applicable to similar technical problems.

[0052] It should be noted that the orientation words appearing in the present application are based on the relative position relationship shown in the drawings, and cannot be used as an absolute limitation of the present application.

[0053] In terms of the content described in the background, the surface acoustic wave resonator and filter is an acoustic device widely used in the field of radio frequency, which integrates low insertion loss and good suppression performance, and has a relatively small size. It is used to filter out interference of foreign frequency signals, attenuate part of frequency components, and only allow specified frequency components. It is the technical basis for the application of wireless spectrum as a non-renewable and scarce resource.

[0054] The specific principle can be simply understood as follows: based on the piezoelectric property of piezoelectric material, an input and output transducer such as an interdigital transducer is used to convert an electrical signal into mechanical energy, which is processed and then converted into an electrical signal, so as to achieve the effect of amplifying the required signal, filtering out noise signals and improving signal quality. It is widely used in various wireless communication devices.

[0055] At present, filters are mainly divided into SAW filters and BAW (Bulk Acoustic Wave, bulk acoustic wave) filters. The surface acoustic wave is an elastic wave generated and propagated on the surface of a piezoelectric substrate with piezoelectric properties, and the amplitude decreases rapidly with the increase of the depth into the piezoelectric substrate. For SAW filters, the manufacturing cost is lower than that of BAW filters, and they are mainly used in low frequency bands, have low insertion loss and good suppression, and are highly temperature sensitive.

[0056] For SAW filters, the surface acoustic wave filter packaging structure is formed by a film coating method to form a cavity, and the solder balls exist in isolation without protection around them. Due to the large difference between the thermal expansion coefficients of the solder balls, the substrate and the carrier substrate, during cold and hot impact, the solder balls are prone to cracking and even falling off.

[0057] Based on this, the embodiment of the present application provides a surface acoustic wave filter packaging structure, a preparation method thereof and a radio frequency device, so as to realize the purpose of improving the stability of the surface acoustic wave filter packaging structure. In order to make the above-mentioned purpose, characteristics and advantages of the present application more obvious and easy to understand, the present application will be further described in detail below in combination with the drawings and specific embodiments.

[0058] Reference Figure 1 , Figure 1 The structure schematic diagram of the surface acoustic wave filter packaging structure provided by the embodiment of the present application is shown in FIG. 1. Figure 2 , Figure 2 The structure schematic diagram of another surface acoustic wave filter packaging structure provided by the embodiment of the present application is shown in FIG. 2. The surface acoustic wave filter packaging structure provided by the embodiment of the present application comprises a surface acoustic wave filter 11, a bearing substrate 12 and a solder ball 13 located between the surface acoustic wave filter 11 and the bearing substrate 12.

[0059] The surface acoustic wave filter 11 comprises a substrate 14, an interdigital electrode 15 and a ring-shaped wall structure 16; the substrate 14 and the bearing substrate 12 are oppositely arranged in a first direction X, and the first direction X is perpendicular to the plane where the substrate 14 is located.

[0060] The interdigital electrode 15 and the ring-shaped wall structure 16 are located on the side of the substrate 14 facing the bearing substrate 12, the interdigital electrode 15 is located inside the ring-shaped wall structure 16, and the solder ball 13 is located outside the ring-shaped wall structure 16; wherein the ring-shaped wall structure 16 is in contact with the substrate 14 and the bearing substrate 12 in the first direction X respectively, and there is a gap between the interdigital electrode 15 and the bearing substrate 12 in the first direction X.

[0061] The surface acoustic wave filter packaging structure further comprises a plastic packaging layer 17 for packaging the surface acoustic wave filter 11, and the plastic packaging layer 17 at least wraps the solder ball 13.

[0062] Specifically, in the embodiment of the present application, the substrate 14 is a piezoelectric substrate, and the material of the substrate 14 includes but is not limited to niobium lithium acid, niobium tantalum acid, etc. The material of the carrier substrate 12 includes but is not limited to an organic material. The material of the annular fence structure 16 includes but is not limited to a polyimide material; the annular fence structure 16 is mainly arranged for protecting the interdigital electrode 15 and the cavity area from being contaminated by the plastic sealing material during subsequent plastic sealing, and can also support to a certain extent. The thickness of the annular fence structure 16 in the first direction X ranges from 5 μm to 10 μm; for example, the thickness of the annular fence structure 16 in the first direction X is 5 μm, 7.5 μm or 10 μm, etc. The width of the annular fence structure 16 ranges from 10 μm to 15 μm; for example, the width of the annular fence structure 16 is 10 μm, 13.5 μm or 15 μm, etc.

[0063] The technical scheme of the present application adds the annular fence structure 16 on the surface acoustic wave filter 11, so that the interdigital electrode 15 is located inside the annular fence structure 16, and the solder ball 13 is located outside the annular fence structure 16. After the preparation of the plastic sealing layer 17, the plastic sealing layer 17 will at least wrap the solder ball 13, at this time the solder ball 13 is not in an isolated state, thereby greatly reducing the risk of cracking or even falling off of the solder ball 13 during cold and hot impact, so as to improve the stability of the surface acoustic wave filter packaging structure. There is a gap between the interdigital electrode 15 and the carrier substrate 12 in the first direction X, and this gap area is the cavity area of the surface acoustic wave filter. Since the interdigital electrode 15 is located inside the annular fence structure 16, and the annular fence structure 16 contacts the substrate 14 and the carrier substrate 12 in the first direction X respectively, therefore the arrangement of the annular fence structure 16 will block the plastic sealing material from entering the cavity area during the preparation of the plastic sealing layer 17, thereby effectively protecting the working area of the surface acoustic wave filter packaging structure.

[0064] In an optional embodiment of the present application, as shown in Figure 1 and Figure 2 The surface acoustic wave filter provided by the embodiment of the present application further comprises a pad structure 18 and a metal layer 19 located between the pad structure 18 and the solder ball 13.

[0065] The pad structure 18 is electrically connected with the interdigital electrode 15 and the solder ball 13 respectively.

[0066] The pad structure 18 is located outside the annular fence structure 16.

[0067] Specifically, in the embodiment of the present application, the pad structure 18 is arranged to realize the electrical connection between the surface acoustic wave filter 11 and other components in combination with the solder ball 13. As shown in Figure 2As shown, an example comprising a four-pad structure 18 will be described. The material of the metal layer 19 includes, but is not limited to, nickel-gold. The material of the solder balls 13 includes, but is not limited to, tin; in the art, solder balls 13 are also referred to as solder balls. By providing the metal layer 19, the electrical connection stability between the solder balls 13 and the pad structure 18 can be improved.

[0068] In an optional embodiment of the present invention, such as Figure 1 As shown, the surface acoustic wave filter provided in this embodiment of the invention further includes:

[0069] A protective layer 20 covers the interdigitated electrode 15 and the pad structure 18.

[0070] The protective layer 20 has a first through hole that exposes a portion of the surface of the pad structure 18.

[0071] Optionally, a dielectric layer 21 is also provided on the side of the carrier substrate 12 facing the surface acoustic wave filter 11 to protect one side of the carrier substrate 12 or to achieve other functions.

[0072] like Figure 1 As shown, the surface acoustic wave filter packaging structure provided in this embodiment of the invention further includes:

[0073] A second through hole penetrating the carrier substrate 12, and an external lead structure 22.

[0074] The external lead structure 22 is electrically connected to the solder ball 13 through the second through hole.

[0075] Specifically, in this embodiment of the invention, a protective layer 20 is provided to protect components such as the pad structure 18 and the interdigitated electrode 15, and a portion of the surface of the pad structure 18 is exposed through the first through hole to achieve electrical connection between the pad structure 18 and the solder ball 13.

[0076] In an optional embodiment of the present invention, reference is made to... Figure 3 , Figure 3 This is a schematic diagram of an interdigitated electrode provided in an embodiment of the present invention. The interdigitated electrode 15 includes a first busbar 151 and a second busbar 152 disposed opposite to each other in a second direction Y, and a first electrode finger 153 located on the first busbar 151 and a second electrode finger 154 located on the second busbar 152.

[0077] The first busbar 151 and the second busbar 152 extend in the same direction, both extending along the third direction Z. The second direction Y and the third direction Z are parallel to the plane where the substrate 14 is located, and the second direction Y and the third direction Z intersect.

[0078] Specifically, in the embodiment of the present application, the second direction Y and the third direction Z are perpendicular. The length extension directions of the first electrode fingers 153 and the second electrode fingers 154 are the same, and are parallel to the second direction Y. The plurality of first electrode fingers 153 on the first bus bar 151 are arranged in the third direction Z with intervals, the plurality of second electrode fingers 154 on the second bus bar 152 are arranged in the third direction Z with intervals, and the plurality of first electrode fingers 153 on the first bus bar 151 and the plurality of second electrode fingers 154 on the second bus bar 152 are arranged in the third direction Z with intervals in turn. The plurality of first electrode fingers 153 on the first bus bar 151 and the plurality of second electrode fingers 154 on the second bus bar 152 have intervals. At this time, the bus bars and the electrode fingers are distributed in a cross-finger manner, forming a so-called interdigital electrode 15. When the first bus bar 151 and the first electrode fingers 153 thereon serve as a transmitting end, the second bus bar 152 and the second electrode fingers 154 thereon serve as a receiving end, and vice versa. The transmitting end part is used to convert an electrical signal into a sound wave, and the sound wave mainly propagates on the surface of the substrate. The receiving end part is used to convert the received sound wave into an electrical signal output, thereby realizing filtering.

[0079] Based on the above-mentioned embodiment of the present application, in another embodiment of the present application, a preparation method of a surface acoustic wave filter packaging structure is also provided. Referring to Figure 4 , Figure 4 A flowchart of a preparation method of a surface acoustic wave filter packaging structure provided by an embodiment of the present application is shown. The preparation method of the surface acoustic wave filter packaging structure provided by the embodiment of the present application comprises the following steps.

[0080] S101: as shown in Figure 5 , a surface acoustic wave filter 11 is provided. The surface acoustic wave filter 11 comprises a substrate 14 and an interdigital electrode 15.

[0081] Specifically, in the embodiment of the present application, as shown in Figure 5 , the surface acoustic wave filter 11 further comprises a pad structure 18. The pad structure 18 is located outside the ring-shaped fence structure 16. The surface acoustic wave filter 11 further comprises a protective layer 20. The protective layer 20 covers the interdigital electrode 15 and the pad structure 18. The protective layer 20 has a first through hole 23. The first through hole 23 exposes part of the surface of the pad structure 18.

[0082] S102: as shown in Figure 6As shown, an annular wall structure 16 is formed on the surface acoustic wave filter 11, and the interdigitated electrode 15 is located inside the annular wall structure 16.

[0083] Specifically, in embodiments of the present invention, an annular wall structure 16 is formed around the interdigitated electrode 15 by means of applying a dry film to the surface, combined with exposure, development and baking.

[0084] S103: As Figure 7 and Figure 8 As shown, solder balls 13 are formed on the surface acoustic wave filter 11, and the solder balls 13 are located outside the annular enclosure structure 16.

[0085] Specifically, in one embodiment of the present invention, one possible way to form solder balls 13 on the surface acoustic wave filter 11 is as follows:

[0086] like Figure 7 As shown, a metal layer 19 is formed on the pad structure 18. Exemplary methods include, but are not limited to, forming the metal layer 19 by nickel-gold plating on the surface of the pad structure 18.

[0087] like Figure 8 As shown, the solder balls 13 are formed on the metal layer 19, and the pad structure 18 is electrically connected to the interdigitated electrodes 15 and the solder balls 13. Exemplary methods include, but are not limited to, forming the solder balls 13 by printing solder paste onto the surface of the metal layer 19, combined with processes such as reflow.

[0088] Before flip-chipping the structure with the solder balls 13 onto the carrier substrate 12, the method for fabricating the surface acoustic wave filter packaging structure further includes:

[0089] like Figure 9 As shown, the substrate 14 is polished. For example, a substrate 14 with a thickness of approximately 350 μm is polished to a thickness range of 190 μm-210 μm. Afterwards, a cutting process is performed to form multiple independent structures each containing the solder balls 13.

[0090] S104: As Figure 10 , Figure 11 as well as Figure 12 As shown, the structure with solder balls 13 is flip-chip mounted on the carrier substrate 12. The substrate 14 and the carrier substrate 12 are disposed opposite each other in a first direction X, which is perpendicular to the plane of the substrate 14. The annular wall structure 16 contacts the substrate 14 and the carrier substrate 12 in the first direction X, and there is a gap between the interdigitated electrode 15 and the carrier substrate 12 in the first direction X.

[0091] Specifically, in one embodiment of the present invention, the structure having the solder balls 13 is flip-chip mounted on the carrier substrate 12 as follows:

[0092] like Figure 10 As shown, the carrier substrate 12 is processed to form a second through hole 24 penetrating the carrier substrate 12.

[0093] like Figure 11 As shown, an external lead structure 22 is formed based on the second through hole 24.

[0094] like Figure 12 As shown, the structure with the solder ball 13 is flipped onto the carrier substrate 12, and the external lead structure 22 is electrically connected to the solder ball 13 through the second through hole 24.

[0095] Optionally, a dielectric layer 21 is also provided on the side of the carrier substrate 12 facing the surface acoustic wave filter 11 to protect one side of the carrier substrate 12 or to achieve other functions.

[0096] It should be noted that after the structure with the solder balls 13 is flip-mounted onto the carrier substrate 12, a reflow process can be performed, and finally the solder resist and other substances applied before flip-mounting can be cleaned.

[0097] S105: As Figure 1 As shown, a molding compound 17 is formed for encapsulating the surface acoustic wave filter 11, and the molding compound 17 at least covers the solder balls 13.

[0098] This application's technical solution adds an annular wall structure 16 to the surface acoustic wave (SAW) filter 11, placing the interdigitated electrode 15 inside the annular wall structure 16 and the solder ball 13 outside the annular wall structure 16. After the molding compound 17 is prepared, the molding compound 17 will at least encapsulate the solder ball 13. At this time, the solder ball 13 is not in an isolated state, thus greatly reducing the risk of the solder ball 13 cracking or even falling off during thermal shock, thereby improving the stability of the SAW filter packaging structure. There is a gap between the interdigitated electrode 15 and the carrier substrate 12 in the first direction X. This gap area is the cavity area of ​​the SAW filter 11. Since the interdigitated electrode 15 is located inside the annular wall structure 16, and the annular wall structure 16 is in contact with the substrate 14 and the carrier substrate 12 in the first direction X, the setting of the annular wall structure 16 during the preparation of the molding compound 17 will prevent the molding compound material from entering the cavity area, thus effectively protecting the working area of ​​the SAW filter packaging structure.

[0099] After forming the molding layer 17, the method for preparing the surface acoustic wave filter packaging structure further includes: cutting along the cutting path to form multiple independent surface acoustic wave filter packaging structures, so as to complete the preparation of the surface acoustic wave filter packaging structure.

[0100] Based on the above embodiments of the present invention, another embodiment of the present invention also provides a radio frequency device, which includes the surface acoustic wave filter packaging structure described in the above embodiments.

[0101] The foregoing has provided a detailed description of the surface acoustic wave filter packaging structure, its fabrication method, and radio frequency equipment provided by the present invention. Specific examples have been used to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

[0102] It should be noted that the various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since it corresponds to the method disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0103] It should also be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that elements inherent to a process, method, article, or apparatus that comprises a list of elements, or elements inherent to such processes, methods, articles, or apparatus, are also included. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0104] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A surface acoustic wave filter packaging structure, characterized in that, The surface acoustic wave filter packaging structure includes: a surface acoustic wave filter, a carrier substrate, and solder balls located between the surface acoustic wave filter and the carrier substrate; The surface acoustic wave filter includes a substrate, interdigitated electrodes, and an annular wall structure; the substrate and the supporting substrate are disposed opposite to each other in a first direction, the first direction being perpendicular to the plane in which the substrate is located; The interdigitated electrodes and the annular wall structure are located on the side of the substrate facing the carrier substrate. The interdigitated electrodes are located inside the annular wall structure, and the solder balls are located outside the annular wall structure. The annular wall structure contacts the substrate and the carrier substrate respectively in the first direction, and there is a gap between the interdigitated electrodes and the carrier substrate in the first direction. The surface acoustic wave filter packaging structure further includes a molding layer for encapsulating the surface acoustic wave filter, the molding layer at least covering the solder balls; The surface acoustic wave filter further includes: a pad structure; The pad structure is electrically connected to the interdigitated electrode and the solder ball, respectively. The pad structure is located outside the annular wall structure; The surface acoustic wave filter further includes: A protective layer covering the interdigitated electrodes and the pad structure; The protective layer has a first through-hole that exposes a portion of the surface of the pad structure.

2. The surface acoustic wave filter packaging structure according to claim 1, characterized in that, The surface acoustic wave filter further includes: The metal layer located between the pad structure and the solder ball.

3. The surface acoustic wave filter packaging structure according to claim 1, characterized in that, The surface acoustic wave filter packaging structure also includes: A second through hole penetrating the substrate, and an external lead structure; The external lead structure is electrically connected to the solder ball through the second through hole.

4. The surface acoustic wave filter packaging structure according to any one of claims 1-3, characterized in that, The interdigitated electrode includes a first busbar and a second busbar disposed opposite each other in a second direction, as well as a first electrode finger located on the first busbar and a second electrode finger located on the second busbar; The first busbar and the second busbar extend in the same direction, both extending along a third direction. The second direction and the third direction are parallel to the plane where the substrate is located, and the second direction and the third direction intersect.

5. A method for fabricating a surface acoustic wave filter packaging structure, characterized in that, The fabrication method of the surface acoustic wave filter packaging structure includes: A surface acoustic wave (SAW) filter is provided, the SAW filter comprising a substrate and interdigitated electrodes; An annular wall structure is formed on the surface acoustic wave filter, and the interdigitated electrodes are located inside the annular wall structure. Solder balls are formed on the surface acoustic wave filter, and the solder balls are located outside the annular enclosure structure; The structure with the solder balls is flip-chip mounted on a carrier substrate. The substrate and the carrier substrate are disposed opposite each other in a first direction, which is perpendicular to the plane of the substrate. The annular wall structure contacts the substrate and the carrier substrate in the first direction, and there is a gap between the interdigitated electrodes and the carrier substrate in the first direction. A molding compound is formed for encapsulating the surface acoustic wave filter, the molding compound at least covering the solder balls; The surface acoustic wave filter further includes: a pad structure; the pad structure is electrically connected to the interdigitated electrodes and the solder balls respectively; the pad structure is located outside the annular wall structure; the surface acoustic wave filter further includes: a protective layer, the protective layer covering the interdigitated electrodes and the pad structure; the protective layer has a first through hole, the first through hole exposing a portion of the surface of the pad structure.

6. The method for fabricating the surface acoustic wave filter packaging structure according to claim 5, characterized in that, The process of forming solder balls on the surface acoustic wave filter includes: A metal layer is formed on the pad structure; The solder balls are formed on the metal layer, and the solder pad structure is electrically connected to the interdigitated electrodes and the solder balls, respectively.

7. The method for fabricating the surface acoustic wave filter packaging structure according to claim 5 or 6, characterized in that, The step of flipping the structure with the solder balls onto the carrier substrate includes: The carrier substrate is processed to form a second through hole penetrating the carrier substrate; An external lead structure is formed based on the second through hole; The structure with the solder balls is flipped onto the carrier substrate, and the external lead structure is electrically connected to the solder balls through the second through hole.

8. The method for fabricating the surface acoustic wave filter packaging structure according to claim 7, characterized in that, Before flip-mounting the structure with the solder balls onto the carrier substrate, the method for fabricating the surface acoustic wave filter packaging structure further includes: The substrate is polished. The material is cut to form multiple independent structures, each containing the aforementioned solder balls.

9. The method for fabricating the surface acoustic wave filter packaging structure according to claim 8, characterized in that, After forming the molding layer, the method for fabricating the surface acoustic wave filter packaging structure further includes: The material is cut along the cutting path to form multiple independent surface acoustic wave filter packaging structures.

10. A radio frequency device, characterized in that, The radio frequency device includes the surface acoustic wave filter packaging structure as described in any one of claims 1-4.

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