Surface acoustic wave filter packaging structure, preparation method thereof and radio frequency equipment

Abstract

The invention provides a surface acoustic wave filter packaging structure, a preparation method thereof and radio frequency equipment, and relates to the technical field of semiconductors. By arranging the annular enclosing wall structure, the interdigital electrode is located inside the annular enclosing wall structure, the solder ball is located outside the annular enclosing wall structure, after the plastic packaging layer is prepared, the plastic packaging layer at least wraps the solder ball, at the moment, the solder ball is not in an isolated state, and the risk that the solder ball cracks or even falls off is greatly reduced in the cold and hot impact process; and the stability of the packaging structure of the surface acoustic wave filter is improved. According to the surface acoustic wave filter, the interdigital electrode is located in the annular enclosing wall structure, and the annular enclosing wall structure is in contact with the substrate and the bearing substrate in the first direction, so that the interdigital electrode and the bearing substrate are separated from each other, and the separated area is a cavity area of the surface acoustic wave filter; therefore, in the preparation process of the plastic packaging layer, the arrangement of the annular enclosing wall structure can prevent the plastic packaging material from entering the cavity area, and the effective protection of the working area of the packaging structure of the surface acoustic wave filter is realized.

Description

Technical Field

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

[0002] SAW (Surface Acoustic Wave) filter is the abbreviation of surface acoustic wave filter. It is a special filtering device made by using its piezoelectric effect and the physical characteristics of surface acoustic wave propagation. It is widely used in various fields, such as radio frequency. Among them, surface acoustic wave is an elastic wave with energy concentrated near the surface.

[0003] At present, the SAW filter packaging structure forms a cavity by coating, in which the solder ball exists in isolation without protection around. Due to the large difference between the thermal expansion coefficient of the solder ball and the thermal expansion coefficient of the substrate and the carrier substrate, the solder ball is prone to cracking or even falling off during the thermal shock (also known as temperature cycling test, the full name in English is: Temperature Cycling Test, abbreviated in English: TCT) process.

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

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

[0006] In a first aspect, the present application provides a surface acoustic wave filter packaging structure, the surface acoustic wave filter packaging structure comprising: 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, interdigitated electrodes and an annular wall structure; the substrate and the carrier substrate are arranged opposite to each other in a first direction, and the first direction is perpendicular to the plane where the substrate is located;

[0008] The interdigitated electrodes and the annular wall structure are located on a 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; wherein the annular wall structure is in contact with 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;

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

[0010] Preferably, in the above-mentioned surface acoustic wave filter packaging structure, the surface acoustic wave filter further comprises: a pad structure;

[0011] The pad structures are electrically connected to the interdigitated electrodes and the solder balls respectively;

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

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

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

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

[0016] A protective layer, the protective layer covering the interdigitated electrodes and the pad structure;

[0017] The protection layer has a first through hole, and the first through hole exposes a portion of the surface of the pad structure.

[0018] Preferably, in the above-mentioned surface acoustic wave filter packaging structure, the surface acoustic wave filter packaging structure further includes:

[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 above-mentioned surface acoustic wave filter packaging structure, the interdigitated electrodes include a first bus bar and a second bus bar arranged opposite to each other in the second direction, and a first electrode finger located on the first bus bar and a second electrode finger located on the second bus bar;

[0022] The first bus bar and the second bus bar have the same length extension 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.

[0023] A second aspect of the present application provides a method for preparing a surface acoustic wave filter packaging structure, the method for preparing a surface acoustic wave filter packaging structure comprising:

[0024] A surface acoustic wave filter is provided, wherein the surface acoustic wave filter comprises a substrate and interdigital electrodes;

[0025] forming an annular wall structure on the surface acoustic wave filter, wherein the interdigitated electrodes are located inside the annular wall structure;

[0026] forming solder balls on the surface acoustic wave filter, wherein the solder balls are located outside the annular wall structure;

[0027] The structure provided with the solder balls is flipped on a carrier substrate, wherein the substrate and the carrier substrate are arranged relative to each other in a first direction, and the first direction is perpendicular to the plane where the substrate is located; wherein the annular wall structure is in contact with 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;

[0028] A plastic encapsulation layer is formed for encapsulating the surface acoustic wave filter, wherein the plastic encapsulation layer at least wraps the solder ball.

[0029] Preferably, in the method for preparing 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 annular wall structure;

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

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

[0033] The solder balls are formed on the metal layer, and the pad structures are electrically connected to the interdigitated electrodes and the solder balls respectively.

[0034] Preferably, in the method for preparing the above-mentioned surface acoustic wave filter packaging structure, flipping the structure provided with the solder balls on a carrier substrate comprises:

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

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

[0037] The structure provided 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 holes.

[0038] Preferably, in the method for preparing the surface acoustic wave filter packaging structure, before flipping the structure provided with the solder balls on the carrier substrate, the method for preparing the surface acoustic wave filter packaging structure further comprises:

[0039] performing a grinding process on the substrate;

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

[0041] Preferably, in the method for preparing the surface acoustic wave filter packaging structure, after forming the plastic packaging layer, the method for preparing 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] A third aspect of the present application provides a radio frequency device, which includes the surface acoustic wave filter packaging structure described in any one of the above items.

[0044] By means of the above technical scheme, the present application provides a surface acoustic wave filter packaging structure and its preparation method, and a radio frequency device. By setting an annular wall structure, the interdigitated electrodes are located inside the annular wall structure, and the solder balls are located outside the annular wall structure. After the plastic encapsulation layer is prepared, the plastic encapsulation layer will at least wrap the solder balls. At this time, the solder balls are not in an isolated state, and the risk of the solder balls cracking or even falling off is greatly reduced during the hot and cold shock process, thereby improving the stability of the surface acoustic wave filter packaging structure. There is a gap between the interdigitated electrodes and the carrier substrate in the first direction, and this gap area is the cavity area of ​​the surface acoustic wave filter. Since the interdigitated electrodes are located inside the annular wall structure, and the annular wall structure is in contact with the substrate and the carrier substrate in the first direction, the setting of the annular wall structure during the preparation of the plastic encapsulation layer will prevent the plastic encapsulation material from entering the cavity area, thereby achieving effective protection of the working area of ​​the surface acoustic wave filter packaging structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] The above and other features, advantages and aspects of the embodiments of the present disclosure will become more apparent with reference to the following detailed description in conjunction with the accompanying drawings. Throughout the accompanying drawings, the same or similar reference numerals represent the same or similar elements. It should be understood that the drawings are schematic and the originals and elements are not necessarily drawn to scale.

[0046] Figure 1 A schematic structural diagram of a surface acoustic wave filter packaging structure provided by an embodiment of the present invention;

[0047] Figure 2 A schematic structural diagram of another surface acoustic wave filter packaging structure provided by an embodiment of the present invention;

[0048] Figure 3 A schematic diagram of the structure of an interdigital electrode provided by an embodiment of the present invention;

[0049] Figure 4A schematic flow chart of a method for preparing a surface acoustic wave filter packaging structure provided by an embodiment of the present invention;

[0050] Figure 5-Figure 12 for Figure 4 Schematic diagram of the partial structure corresponding to the preparation method shown. DETAILED DESCRIPTION

[0051] The embodiments of the present application are described below in conjunction with the drawings in the embodiments of the present application. The terms used in the implementation mode 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. It is known to those skilled in the art that with the development of technology and the emergence of new scenarios, the technical solutions provided in the embodiments of the present application are also applicable to similar technical problems.

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

[0053] Combined with the content recorded in the background technology, surface acoustic wave resonator and filter are a kind of acoustic device widely used in the radio frequency field. It combines low insertion loss and good suppression performance, and is relatively small in size. It is used to filter out the interference of heterofrequency signals, attenuate some frequency components, and only allow specified frequency components. It is the technical basis for the application of wireless spectrum as a non-renewable scarce resource.

[0054] Its specific principle can be simply understood as based on the piezoelectric properties of piezoelectric materials, using input and output transducer devices such as interdigital transducers to convert electrical signals into mechanical energy, which are then converted back into electrical signals after processing, in order to amplify the required signals, filter out noise signals and improve signal quality. It is widely used in various wireless communication equipment.

[0055] At present, filters are mainly divided into SAW filters and BAW (Bulk Acoustic Wave) filters. Surface acoustic waves are an elastic wave that is generated and propagated on the surface of a piezoelectric substrate with piezoelectric properties, and whose amplitude decreases rapidly as the depth of the piezoelectric substrate increases. For SAW filters, their manufacturing cost is lower than that of BAW filters. 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 current SAW filter packaging structure forms a cavity by coating, in which the solder balls are isolated and not protected on all sides. Since the thermal expansion coefficient of the solder balls is quite different from that of the substrate and the carrier substrate, the solder balls are prone to cracking or even falling off during the thermal shock process.

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

[0058] refer to Figure 1 , Figure 1 A schematic diagram of a surface acoustic wave filter packaging structure provided by an embodiment of the present invention, referring to Figure 2 , Figure 2 A schematic diagram of another surface acoustic wave filter packaging structure provided by an embodiment of the present invention. The surface acoustic wave filter packaging structure provided by an embodiment of the present invention comprises: a surface acoustic wave filter 11, a carrier substrate 12, and solder balls 13 located between the surface acoustic wave filter 11 and the carrier substrate 12.

[0059] The surface acoustic wave filter 11 includes a substrate 14 , interdigital electrodes 15 and an annular wall structure 16 ; the substrate 14 and the carrier substrate 12 are arranged opposite to each other in a first direction X, and the first direction X is perpendicular to the plane where the substrate 14 is located.

[0060] The interdigitated electrode 15 and the annular wall structure 16 are located on the side of the substrate 14 facing the carrier substrate 12, the interdigitated electrode 15 is located inside the annular wall structure 16, and the solder ball 13 is located outside the annular wall structure 16; wherein the annular wall structure 16 is in contact with the substrate 14 and the carrier substrate 12 respectively 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.

[0061] The surface acoustic wave filter packaging structure further includes 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 invention, the substrate 14 is a piezoelectric substrate, and the material of the substrate 14 includes but is not limited to lithium niobium oxide, niobium tantalate, etc. The material of the carrier substrate 12 includes but is not limited to organic materials. The material of the annular wall structure 16 includes but is not limited to polyimide materials; the setting of the annular wall structure 16 is mainly used to protect the interdigital electrodes 15 and the cavity area from being contaminated by the plastic packaging material during the subsequent plastic packaging, and can also play a supporting role to a certain extent. The thickness of the annular wall structure 16 in the first direction X ranges from 5μm to 10μm; for example, the thickness of the annular wall structure 16 in the first direction X is 5μm, 7.5μm or 10μm, etc. The width of the annular wall structure 16 ranges from 10μm to 15μm; for example, the width of the annular wall structure 16 is 10μm, 13.5μm or 15μm, etc.

[0063] The technical solution of the present application is to arrange a ring wall structure 16 on the surface acoustic wave filter 11 so that the interdigitated electrode 15 is located inside the ring wall structure 16 and the solder ball 13 is located outside the ring wall structure 16. After the plastic encapsulation layer 17 is prepared, the plastic encapsulation 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 the hot and cold shock process, thereby improving the stability of the surface acoustic wave filter packaging structure. There is a gap between the interdigitated 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 interdigitated electrode 15 is located inside the ring wall structure 16, and the ring wall structure 16 is in contact with the substrate 14 and the carrier substrate 12 in the first direction X, the setting of the ring wall structure 16 during the preparation of the plastic encapsulation layer 17 will prevent the plastic encapsulation material from entering the cavity area, thereby achieving effective protection of the working area of ​​the surface acoustic wave filter packaging structure.

[0064] In an optional embodiment of the present invention, Figure 1 and Figure 2 As shown, the surface acoustic wave filter provided by the embodiment of the present invention further includes: 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 to the interdigital electrodes 15 and the solder ball 13 respectively.

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

[0067] Specifically, in the embodiment of the present invention, the electrical connection between the surface acoustic wave filter 11 and other components is realized by providing the pad structure 18 in combination with the solder ball 13. Figure 2As shown, four pad structures 18 are used as an example for explanation. The material of the metal layer 19 includes but is not limited to nickel-gold material. The material of the solder ball 13 includes but is not limited to tin material, and the solder ball 13 is also called a tin ball in the field. The electrical connection stability between the solder ball 13 and the pad structure 18 can be improved by providing the metal layer 19.

[0068] In an optional embodiment of the present invention, Figure 1 As shown, the surface acoustic wave filter provided by the embodiment of the present invention also includes:

[0069] A protection layer 20 , wherein the protection layer 20 covers the interdigital electrodes 15 and the pad structure 18 .

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

[0071] Optionally, a dielectric layer 21 is also provided on the surface of the carrier substrate 12 facing the surface acoustic wave filter 11 to protect the surface of 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 by the embodiment of the present invention also includes:

[0073] A second through hole passes through 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 the embodiment of the present invention, a protective layer 20 is provided to protect the pad structure 18 and components such as the interdigital electrodes 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 Figure 3 , Figure 3 A schematic diagram of the structure of an interdigitated electrode provided in an embodiment of the present invention. The interdigitated electrode 15 comprises a first bus bar 151 and a second bus bar 152 arranged opposite to each other in a second direction Y, and a first electrode finger 153 located on the first bus bar 151 and a second electrode finger 154 located on the second bus bar 152.

[0077] The first bus bar 151 and the second bus bar 152 have the same length extension 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 invention, the second direction Y is perpendicular to the third direction Z. The first electrode fingers 153 and the second electrode fingers 154 have the same length extension direction, which are parallel to the second direction Y respectively. The multiple first electrode fingers 153 on the first bus bar 151 are arranged at intervals in the third direction Z, and the multiple second electrode fingers 154 on the second bus bar 152 are arranged at intervals in the third direction Z. The multiple first electrode fingers 153 on the first bus bar 151 and the multiple second electrode fingers 154 on the second bus bar 152 are arranged in sequence in the third direction Z in a cross-arranged manner, and there is a gap between the multiple first electrode fingers 153 on the first bus bar 151 and the second bus bar 152, and there is a gap between the multiple second electrode fingers 154 on the second bus bar 152 and the first bus bar 151. At this time, the bus bars and the electrode fingers are distributed in a manner similar to crossing fingers, forming a so-called interdigitated electrode 15. When the first bus bar 151 and the first electrode fingers 153 thereon are used as the transmitting end, the second bus bar 152 and the second electrode fingers 154 thereon are used as the receiving end. Conversely, when the first bus bar 151 and the first electrode fingers 153 thereon are used as the receiving end, the second bus bar 152 and the second electrode fingers 154 thereon are used as the transmitting end. The transmitting end part is used to convert the electrical signal into an acoustic wave, and the acoustic wave mainly propagates on the surface of the substrate, and the receiving end part is used to convert the received acoustic wave into an electrical signal output, thereby realizing filtering.

[0079] Based on the above embodiment of the present invention, another embodiment of the present invention further provides a method for preparing a surface acoustic wave filter packaging structure, referring to Figure 4 , Figure 4 A schematic flow chart of a method for preparing a surface acoustic wave filter packaging structure provided by an embodiment of the present invention. The method for preparing a surface acoustic wave filter packaging structure provided by an embodiment of the present invention comprises:

[0080] S101: Figure 5 As shown, a surface acoustic wave filter 11 is provided. The surface acoustic wave filter 11 includes a substrate 14 and interdigital electrodes 15 .

[0081] Specifically, in the embodiments of the present invention, Figure 5 As shown, the surface acoustic wave filter 11 further includes a pad structure 18; the pad structure 18 is located outside the annular wall structure 16. The surface acoustic wave filter 11 further includes: a protective layer 20, the protective layer 20 covers the interdigitated electrodes 15 and the pad structure 18. The protective layer 20 has a first through hole 23, and the first through hole 23 exposes a portion of the surface of the pad structure 18.

[0082] S102: Figure 6As shown, a ring-shaped wall structure 16 is formed on the surface acoustic wave filter 11 , and the interdigital electrodes 15 are located inside the ring-shaped wall structure 16 .

[0083] Specifically, in the embodiment of the present invention, including but not limited to, a method of attaching a dry film on the surface, combined with exposure, development and baking, to form a dry film annular wall structure 16 around the interdigital electrode 15 .

[0084] S103: 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 wall structure 16 .

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

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

[0087] like Figure 8 As shown, the solder ball 13 is formed on the metal layer 19, and the pad structure 18 is electrically connected to the interdigital electrode 15 and the solder ball 13. For example, the solder ball 13 is formed by printing solder paste on the surface of the metal layer 19 in combination with a reflow process.

[0088] Before flipping the structure provided with the solder balls 13 onto the carrier substrate 12, the method for preparing the surface acoustic wave filter packaging structure further includes:

[0089] like Fig. 9 As shown, the substrate 14 is ground. For example, the substrate 14 with a thickness of about 350 μm is ground to a thickness in the range of 190 μm-210 μm. Then, a cutting process is performed to form a plurality of independent structures provided with the solder balls 13 .

[0090] S104: Fig.10 , Fig.11 as well as Fig.12 As shown, the structure provided with the solder ball 13 is flipped on the carrier substrate 12, and the substrate 14 and the carrier substrate 12 are arranged relative to each other in a first direction X, and the first direction X is perpendicular to the plane where the substrate 14 is located; wherein the annular wall structure 16 is in contact with the substrate 14 and the carrier substrate 12 respectively 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 the embodiment of the present invention, one possible implementation method of flip-chip mounting the structure provided with the solder balls 13 on the carrier substrate 12 is:

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

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

[0094] like Fig.12 As shown, the structure provided 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 surface of the carrier substrate 12 facing the surface acoustic wave filter 11 to protect the surface of one side of the carrier substrate 12 or to achieve other functions.

[0096] It should be noted that after the structure provided with the solder balls 13 is flipped onto the carrier substrate 12 , a reflow process may be performed, and finally the solder resist and other materials applied before the flipping may be cleaned.

[0097] S105: Figure 1 As shown, a plastic encapsulation layer 17 is formed to encapsulate the surface acoustic wave filter 11 , and the plastic encapsulation layer 17 at least wraps the solder ball 13 .

[0098] The technical solution of the present application is to arrange an annular wall structure 16 on the surface acoustic wave filter 11 so that the interdigitated electrode 15 is located inside the annular wall structure 16 and the solder ball 13 is located outside the annular wall structure 16. After the plastic encapsulation layer 17 is prepared, the plastic encapsulation 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 the hot and cold shock process, thereby improving the stability of the surface acoustic wave filter packaging structure. There is a gap between the interdigitated 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 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 plastic encapsulation layer 17 will prevent the plastic encapsulation material from entering the cavity area, thereby achieving effective protection of the working area of ​​the surface acoustic wave filter packaging structure.

[0099] After forming the plastic packaging layer 17 , the method for preparing the surface acoustic wave filter packaging structure further includes: performing a cutting process along the cutting path to form a plurality of independent surface acoustic wave filter packaging structures to complete the preparation of the surface acoustic wave filter packaging structure.

[0100] Based on the above embodiment of the present invention, a radio frequency device is provided in another embodiment of the present invention. The radio frequency device includes the surface acoustic wave filter packaging structure described in the above embodiment.

[0101] The above is a detailed introduction to a surface acoustic wave filter packaging structure and a preparation method and a radio frequency device provided by the present invention. Specific examples are used in this article to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea. At the same time, for general technicians in this field, according to the idea of ​​the present invention, there will be changes in the specific implementation method and application scope. In summary, the content of this specification should not be understood as a limitation on the present invention.

[0102] It should be noted that each embodiment in this specification is described in a progressive manner, and each embodiment focuses on the differences from other embodiments, and the same or similar parts between the embodiments can be referred to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part description.

[0103] It should also be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that the process, method, article or device that includes a series of elements is inherent to the elements, or also includes elements inherent to these processes, methods, articles or devices. In the absence of further restrictions, the elements defined by the sentence "including a..." do not exclude the presence of other identical elements in the process, method, article or device that includes the elements.

[0104] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one 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 present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to 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 comprises: a surface acoustic wave filter, a carrier substrate, and a solder ball located between the surface acoustic wave filter and the carrier substrate; The surface acoustic wave filter comprises a substrate, interdigitated electrodes and an annular wall structure; the substrate and the carrier substrate are arranged opposite to each other in a first direction, and the first direction is perpendicular to the plane where the substrate is located; The interdigitated electrodes and the annular wall structure are located on a 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; wherein the annular wall structure is in contact with 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 plastic packaging layer for packaging the surface acoustic wave filter, and the plastic packaging layer at least wraps the solder ball.

2. The surface acoustic wave filter packaging structure according to claim 1, characterized in that: The surface acoustic wave filter further comprises: a pad structure; The pad structures are electrically connected to the interdigitated electrodes and the solder balls respectively; The pad structure is located outside the annular wall structure.

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

4. The surface acoustic wave filter packaging structure according to claim 2, characterized in that: The surface acoustic wave filter further comprises: A protective layer, the protective layer covering the interdigitated electrodes and the pad structure; The protection layer has a first through hole, and the first through hole exposes a portion of the surface of the pad structure.

5. 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 carrier substrate, and an external lead structure; The external lead structure is electrically connected to the solder ball through the second through hole.

6. The surface acoustic wave filter packaging structure according to any one of claims 1 to 5, characterized in that: The interdigitated electrodes include a first bus bar and a second bus bar disposed opposite to each other in a second direction, and a first electrode finger located on the first bus bar and a second electrode finger located on the second bus bar; The first bus bar and the second bus bar have the same length extension 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.

7. A method for preparing a surface acoustic wave filter packaging structure, characterized in that: The preparation method of the surface acoustic wave filter packaging structure comprises: A surface acoustic wave filter is provided, wherein the surface acoustic wave filter comprises a substrate and interdigital electrodes; forming an annular wall structure on the surface acoustic wave filter, wherein the interdigitated electrodes are located inside the annular wall structure; forming solder balls on the surface acoustic wave filter, wherein the solder balls are located outside the annular wall structure; The structure provided with the solder balls is flipped on a carrier substrate, wherein the substrate and the carrier substrate are arranged relative to each other in a first direction, and the first direction is perpendicular to the plane where the substrate is located; wherein the annular wall structure is in contact with 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; A plastic encapsulation layer is formed for encapsulating the surface acoustic wave filter, wherein the plastic encapsulation layer at least wraps the solder ball.

8. The method for preparing a surface acoustic wave filter packaging structure according to claim 7, characterized in that: The surface acoustic wave filter further comprises: a pad structure; The pad structure is located outside the annular wall structure; The step of forming solder balls on the surface acoustic wave filter comprises: forming a metal layer on the pad structure; The solder balls are formed on the metal layer, and the pad structures are electrically connected to the interdigitated electrodes and the solder balls respectively.

9. The method for preparing a surface acoustic wave filter packaging structure according to claim 7 or 8, characterized in that: The method of flipping the structure provided with the solder balls on a carrier substrate comprises: Processing the carrier substrate to form a second through hole penetrating the carrier substrate; forming an external lead structure based on the second through hole; The structure provided 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 holes.

10. The method for preparing a surface acoustic wave filter packaging structure according to claim 9, characterized in that: Before flipping the structure provided with the solder balls onto the carrier substrate, the method for preparing the surface acoustic wave filter packaging structure further includes: performing a grinding process on the substrate; A cutting process is performed to form a plurality of independent structures provided with the solder balls.

11. The method for preparing a surface acoustic wave filter packaging structure according to claim 10, characterized in that: After forming the plastic packaging layer, the method for preparing the surface acoustic wave filter packaging structure further includes: A cutting process is performed along the cutting path to form a plurality of independent surface acoustic wave filter packaging structures.

12. A radio frequency device, characterized in that: The radio frequency device comprises the surface acoustic wave filter packaging structure according to any one of claims 1 to 6.

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