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

Abstract

The application provides a bulk acoustic wave filter packaging structure and a preparation method thereof and a radio frequency device, and relates to the technical field of semiconductors. The packaging cover plate is provided with a groove area, and a normal projection of the groove area in a first direction covers at least a normal projection of a working area of the bulk acoustic wave filter, so as to form a cavity area required by the bulk acoustic wave filter packaging structure. An annular wall structure is arranged between the bulk acoustic wave filter and the packaging cover plate to achieve the purpose of isolating water vapor, so that the air tightness is better. Based on the characteristics of the packaging cover plate and the dry film, the strength of the packaging cover plate is stronger than that of the dry film. In the process of layout, the packaging cover plate only needs to be surrounded by a circle around the chip based on the cavity area, so that the area of the chip is smaller compared with the existing dry film packaging technology, and the support problem does not need to be considered. In general, the technical scheme of the application has great improvement in stability, support and air tightness compared with the prior art.

Description

TECHNICAL FIELD

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

[0002] The BAW (full name: Bulk Acoustic Wave) filter is the abbreviation of the bulk acoustic wave filter. When an alternating electric field is applied to both ends of the piezoelectric material, the piezoelectric material will produce mechanical vibration. This vibration propagates in the form of bulk acoustic wave inside the piezoelectric material. By skillfully designing the structure and size, the bulk acoustic wave of a specific frequency can be smoothly propagated in the filter, while the acoustic waves of other frequencies are suppressed, thereby realizing the filtering function. It is widely used in various fields, such as the radio frequency field.

[0003] At present, the bulk acoustic wave filter packaging structure is bonded with the bulk acoustic wave filter through the dry film on the packaging cover plate to form a cavity region above the working area of the bulk acoustic wave filter. At this time, the dry film also plays a supporting and sealing function.

[0004] However, since the material of the dry film is usually an organic material, it cannot completely isolate water vapor; and since the dry film is not rigid enough, in order to improve the strength of the dry film support, the width of the dry film is usually increased. Obviously, this operation is not conducive to the miniaturization design of the chip.

[0005] Therefore, how to optimize the bulk acoustic wave filter packaging structure is a technical problem to be solved by those skilled in the art. SUMMARY

[0006] In view of the above problems, the present application provides a bulk acoustic wave filter packaging structure, a preparation method thereof and a radio frequency device, which realizes the purposes of improving the stability of the bulk acoustic wave filter packaging structure and reducing the chip area. The specific scheme is as follows:

[0007] The first aspect of the present application provides a bulk acoustic wave filter packaging structure, which comprises:

[0008] The bulk acoustic wave filter and the packaging cover plate are oppositely arranged; the bulk acoustic wave filter has a working area, and the packaging cover plate comprises a groove region arranged on the side facing the bulk acoustic wave filter; in the first direction, the orthographic projection of the groove region covers at least the orthographic projection of the working area; the first direction is perpendicular to the plane where the bulk acoustic wave filter is located;

[0009] The annular wall structure is located between the bulk acoustic wave filter and the packaging cover plate and on the bulk acoustic wave filter;

[0010] The working area and the groove area are both located inside the ring wall structure.

[0011] Preferably, in the above-mentioned bulk acoustic wave filter packaging structure, the material of the ring wall structure is a metal material or an inorganic material.

[0012] Preferably, in the above-mentioned bulk acoustic wave filter packaging structure, the width of the ring wall structure ranges from 2 μm to 5 μm.

[0013] The thickness of the ring wall structure ranges from 1 μm to 2 μm.

[0014] Preferably, in the above-mentioned bulk acoustic wave filter packaging structure, the depth of the groove area ranges from 5 μm to 15 μm.

[0015] Preferably, in the above-mentioned bulk acoustic wave filter packaging structure, the packaging cover plate is a Si cover plate.

[0016] Preferably, in the above-mentioned bulk acoustic wave filter packaging structure, the bulk acoustic wave filter packaging structure further comprises:

[0017] a pad structure located between the bulk acoustic wave filter and the packaging cover plate and on the bulk acoustic wave filter.

[0018] The pad structure is located inside the ring wall structure.

[0019] Preferably, in the above-mentioned bulk acoustic wave filter packaging structure, the thickness of the pad structure ranges from 1 μm to 2 μm.

[0020] Preferably, in the above-mentioned bulk acoustic wave filter packaging structure, the bulk acoustic wave filter packaging structure further comprises:

[0021] a first through hole penetrating through the bulk acoustic wave filter, the first through hole exposing part of the surface of the pad structure.

[0022] Preferably, in the above-mentioned bulk acoustic wave filter packaging structure, the bulk acoustic wave filter packaging structure further comprises:

[0023] an RDL lead structure, the RDL lead structure being electrically connected with the pad structure through the first through hole.

[0024] Preferably, in the above-mentioned bulk acoustic wave filter packaging structure, the bulk acoustic wave filter packaging structure further comprises:

[0025] a protective layer located on the side of the bulk acoustic wave filter away from the packaging cover plate; the protective layer has a second through hole, the second through hole exposing part of the surface of the RDL lead structure.

[0026] Preferably, in the above-mentioned bulk acoustic wave filter packaging structure, the bulk acoustic wave filter packaging structure further comprises:

[0027] Solder balls located on the side of the bulk acoustic wave filter away from the packaging cover plate; the solder balls are electrically connected with the RDL lead structure.

[0028] The second aspect of the present application provides a preparation method of a bulk acoustic wave filter packaging structure, the preparation method of the bulk acoustic wave filter packaging structure comprising:

[0029] Providing a bulk acoustic wave filter, the bulk acoustic wave filter having a working area and an annular wall structure located on the bulk acoustic wave filter;

[0030] Providing a packaging cover plate, and processing the packaging cover plate to form a recessed area;

[0031] Bonding the packaging cover plate and the bulk acoustic wave filter; after the bonding is completed, the recessed area is located on the side of the bulk acoustic wave filter, and the annular wall structure is located between the bulk acoustic wave filter and the packaging cover plate; in a first direction, the orthographic projection of the recessed area covers at least the orthographic projection of the working area; the first direction is perpendicular to the plane where the bulk acoustic wave filter is located; wherein the working area and the recessed area are both located inside the annular wall structure.

[0032] Preferably, in the above-mentioned preparation method of the bulk acoustic wave filter packaging structure, the bonding of the packaging cover plate and the bulk acoustic wave filter comprises:

[0033] Bonding the packaging cover plate and the bulk acoustic wave filter by means of coating glue.

[0034] Preferably, in the above-mentioned preparation method of the bulk acoustic wave filter packaging structure, the bonding of the packaging cover plate and the bulk acoustic wave filter by means of coating glue comprises:

[0035] Bonding the packaging cover plate and the bulk acoustic wave filter by means of coating glue under the condition that the temperature range is 130-170℃ and the pressure range is 4000-6000N.

[0036] Preferably, in the above-mentioned preparation method of the bulk acoustic wave filter packaging structure, the bulk acoustic wave filter packaging structure further comprises: a pad structure located between the bulk acoustic wave filter and the packaging cover plate and located on the bulk acoustic wave filter; the pad structure is located inside the annular wall structure.

[0037] The preparation method of the bulk acoustic wave filter packaging structure further comprises:

[0038] The bulk acoustic wave filter is processed to form a first through hole penetrating through the bulk acoustic wave filter, and the first through hole exposes part of the surface of the pad structure.

[0039] Preferably, in the preparation method of the bulk acoustic wave filter packaging structure, the preparation method of the bulk acoustic wave filter packaging structure further comprises:

[0040] An RDL lead structure is formed, which is electrically connected to the pad structure through the first through hole.

[0041] Preferably, in the preparation method of the bulk acoustic wave filter packaging structure, the preparation method of the bulk acoustic wave filter packaging structure further comprises:

[0042] A protective layer is formed on the side of the bulk acoustic wave filter away from the packaging cover plate; the protective layer has a second through hole, and the second through hole exposes part of the surface of the RDL lead structure.

[0043] Preferably, in the preparation method of the bulk acoustic wave filter packaging structure, the preparation method of the bulk acoustic wave filter packaging structure further comprises:

[0044] Solder balls are formed on the side of the bulk acoustic wave filter away from the packaging cover plate; the solder balls are electrically connected to the RDL lead structure.

[0045] The third aspect of the present application provides a radio frequency device, which comprises the bulk acoustic wave filter packaging structure of any one of the above.

[0046] Through the above technical solution, the present application provides a bulk acoustic wave filter packaging structure, a preparation method thereof, and a radio frequency device. The packaging cover plate is provided with a groove area, and in the first direction, the orthographic projection of the groove area covers at least the orthographic projection of the working area of the bulk acoustic wave filter, thereby forming the required cavity area of the bulk acoustic wave filter packaging structure.

[0047] The annular wall structure is arranged between the bulk acoustic wave filter and the packaging cover plate to achieve the purpose of isolating water vapor, so that the air tightness of the bulk acoustic wave filter packaging structure is better.

[0048] Based on the characteristics of the packaging cover plate and the dry film, the strength of the packaging cover plate is stronger than that of the dry film. During the layout process, the packaging cover plate only needs to be formed into a circle around the chip based on the cavity area. Compared with the existing dry film packaging technology, the area of the chip can be smaller, and the support problem does not need to be considered.

[0049] Overall, the technical solution of the present application has great improvement in stability, support, and air tightness compared with the prior art. BRIEF DESCRIPTION OF DRAWINGS

[0050] The above and other features, advantages, and aspects of the embodiments of this disclosure will become more apparent from the accompanying drawings and the following detailed description. Throughout the drawings, the same or similar reference numerals denote 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.

[0051] Figure 1 This is a schematic diagram of a bulk acoustic wave filter packaging structure provided in an embodiment of the present invention;

[0052] Figure 2 This is a schematic diagram of another bulk acoustic wave filter packaging structure provided in an embodiment of the present invention;

[0053] Figure 3 A schematic flowchart illustrating a method for fabricating a bulk acoustic wave filter packaging structure according to an embodiment of the present invention;

[0054] Figures 4-9 for Figure 3 A partial structural schematic diagram corresponding to the preparation method shown. Detailed Implementation

[0055] The embodiments of this application are described below with reference to the accompanying drawings. The terminology used in the implementation section of this application is only for explaining specific embodiments and is not intended to limit the application. Those skilled in the art will recognize that, with technological advancements and the emergence of new scenarios, the technical solutions provided in the embodiments of this application are also applicable to similar technical problems.

[0056] It should be noted that the directional terms appearing in this invention are based on the relative positional relationships shown in the accompanying drawings and should not be taken as absolute limitations on this application.

[0057] In the case of bulk acoustic wave filters, when an alternating electric field is applied to both ends of a piezoelectric material, the piezoelectric material will generate mechanical vibration. This vibration propagates inside the piezoelectric material in the form of bulk acoustic waves. By cleverly designing the structure and size, bulk acoustic waves of a specific frequency can be allowed to propagate smoothly in the filter, while other frequencies of sound waves are suppressed, thereby achieving the filtering function. It is widely used in a variety of fields, such as the radio frequency field.

[0058] BAW filter has an irreplaceable position in the field of high-frequency communication. In 5G, 5.5G, and even future 6G devices, it is the core component of the radio frequency front-end, responsible for precise filtering of high-frequency signals. In 5G devices, BAW filter acts as a "signal guard", effectively filtering out interference signals in the 5G frequency band, greatly improving signal transmission quality and speed. In base stations and routers, BAW filter also plays a key role. For example, in 5G base stations, it can help the base station accurately transmit and receive 5G signals, improving the signal processing capability and coverage of the base station. Moreover, in wireless connection terminals such as Internet of Things devices and smart wearable devices, BAW filter can also be seen. For example, in smart watches, it can filter out unwanted signals, improving the communication performance and battery life of the watch.

[0059] At present, the packaging structure of the bulk acoustic wave filter is bonded with the bulk acoustic wave filter through the dry film on the packaging cover plate to form a cavity area above the working area of the bulk acoustic wave filter, and the dry film also plays a supporting and sealing function at this time.

[0060] However, since the material of the dry film is usually an organic material, it cannot completely isolate water vapor; and since the dry film is not rigid enough, in order to improve the strength of the dry film support, the width of the dry film is usually increased, which obviously is not conducive to the miniaturization design of the chip.

[0061] Therefore, the embodiment of the present application provides a bulk acoustic wave filter packaging structure and a preparation method thereof and a radio frequency device, which realizes the purposes of improving the stability of the bulk acoustic wave filter packaging structure and reducing the chip area. In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the present application will be further described in detail below with reference to the drawings and specific embodiments.

[0062] Reference Figure 1 , Figure 1 The structure diagram of the bulk acoustic wave filter packaging structure provided by the embodiment of the present application is shown in FIG. 1. Figure 2 , Figure 2 The structure diagram of another bulk acoustic wave filter packaging structure provided by the embodiment of the present application is shown in FIG. 2. The bulk acoustic wave filter packaging structure provided by the embodiment of the present application comprises:

[0063] The bulk acoustic wave filter 11 and the packaging cover plate 12 are oppositely arranged; the bulk acoustic wave filter 11 has a working area 13, and the packaging cover plate 12 comprises a groove area 14 arranged on the side facing the bulk acoustic wave filter 11; in a first direction X, the orthographic projection of the groove area 14 covers at least the orthographic projection of the working area 13; and the first direction X is perpendicular to the plane where the bulk acoustic wave filter 11 is located.

[0064] An annular wall structure 15 is arranged between the bulk acoustic wave filter 11 and the package cover plate 12 and on the bulk acoustic wave filter 11.

[0065] The working area 13 and the recessed area 14 are both arranged inside the annular wall structure 15.

[0066] Specifically, the bulk acoustic wave filter package structure in the embodiment of the application is mainly divided into two parts in terms of structure, namely, a Device Wafer and a Cap Wafer. The Device Wafer is the part where the bulk acoustic wave filter 11 is located, which is the main working area of the filter; and the Cap Wafer is the structural member used for wafer-level packaging and buckled on the Device Wafer, namely, the package cover plate 12 in the embodiment of the application. In other words, the bulk acoustic wave filter package structure provided by the technical solution of the application belongs to a wafer-level packaging structure.

[0067] The package cover plate 12 in the embodiment of the application includes but is not limited to a Si cover plate, that is, the package cover plate 12 can be obtained by processing a Si wafer.

[0068] The package cover plate 12 is provided with a recessed area 14, and in the first direction X, the orthographic projection of the recessed area 14 covers at least the orthographic projection of the working area 13 of the bulk acoustic wave filter 11, so as to form a cavity area required by the bulk acoustic wave filter package structure.

[0069] The annular wall structure 15 is arranged between the bulk acoustic wave filter 11 and the package cover plate 12 to achieve the purpose of isolating water vapor, so that the air tightness of the bulk acoustic wave filter package structure is better. In an optional embodiment of the application, the material of the annular wall structure 15 is a metal material or an inorganic material, which has a better water vapor isolation effect and a lower cost compared with a dry film of an organic material, and can meet the high reliability requirements of subsequent industrial and automotive electronic products.

[0070] Based on the characteristics of the package cover plate 12 and the dry film, the strength of the package cover plate 12 is stronger than that of the dry film. In the process of layout, based on the cavity area, the package cover plate 12 only needs to be arranged around the chip, which can make the area of the chip smaller compared with the existing dry film packaging technology, and there is no need to consider the support problem. In other words, based on the existing dry film packaging technology, in order to improve the strength of the dry film support, the width of the dry film is usually increased, which is obviously not conducive to the miniaturization design of the chip. However, in the embodiment of the application, there is no problem of support strength, which can also indirectly indicate that the technical solution of the application has great improvement in the aspect of chip miniaturization design compared with the existing dry film packaging technology.

[0071] In general, the technical scheme of the present application has great improvement in stability, support and air tightness compared with the prior art.

[0072] Optionally, the width of the annular wall structure 15 ranges from 2 μm to 5 μm; for example, the width of the annular wall structure 15 is 2 μm, 3.5 μm or 5 μm, etc. The specific parameters can be selected according to actual conditions, and are not limited in the embodiments of the present application.

[0073] Optionally, the thickness of the annular wall structure 15 ranges from 1 μm to 2 μm; for example, the thickness of the annular wall structure 15 is 1 μm, 1.5 μm or 2 μm, etc. The specific parameters can be selected according to actual conditions, and are not limited in the embodiments of the present application.

[0074] Optionally, the depth of the groove region 14 ranges from 5 μm to 15 μm; for example, the depth of the groove region 14 is 5 μm, 10 μm, 12.5 μm or 15 μm, etc. The specific parameters can be selected according to actual conditions, and are not limited in the embodiments of the present application.

[0075] In an optional embodiment of the present application, as shown in Figure 1 The body acoustic wave filter packaging structure provided by the embodiments of the present application further comprises a pad structure 16 located between the body acoustic wave filter 11 and the packaging cover plate 12 and on the body acoustic wave filter 11.

[0076] The pad structure 16 is located inside the annular wall structure 15.

[0077] The body acoustic wave filter packaging structure provided by the embodiments of the present application further comprises:

[0078] A first through hole 17 penetrating the body acoustic wave filter 11, and the first through hole 17 exposes part of the surface of the pad structure 16. It should be noted that the first through hole 17 is also called TSV (the full name in English: Through Silicon Via) hole in the field. Based on the body acoustic wave filter packaging structure provided by the embodiments of the present application, the first through hole 17 penetrates the body acoustic wave filter 11, but does not penetrate the packaging cover plate 12, that is, this opening mode is equivalent to the design of opening the TSV hole from the back.

[0079] The body acoustic wave filter packaging structure provided by the embodiments of the present application further comprises:

[0080] An RDL (the full name in English: ReDistribution Layer) lead structure 18, which is electrically connected with the pad structure 16 through the first through hole 17.

[0081] The body acoustic wave filter packaging structure provided by the embodiment of the present application further comprises:

[0082] A protective layer 19 is arranged on the side of the body acoustic wave filter 11 away from the packaging cover plate 12; the protective layer 19 has a second through hole, and the second through hole exposes part of the surface of the RDL lead structure 18. The protective layer 19 includes but is not limited to a polyimide layer, and the main function of the protective layer 19 is to protect the RDL lead structure 18, buffer the stress generated in the packaging process, prevent the overcurrent phenomenon from occurring, and the like, so as to improve the stability and reliability of the body acoustic wave filter packaging structure.

[0083] A solder ball 20 is arranged on the side of the body acoustic wave filter 11 away from the packaging cover plate 12; the solder ball 20 is electrically connected with the RDL lead structure 18.

[0084] Specifically, in the embodiment of the present application, the thickness of the pad structure 16 ranges from 1 μm to 2 μm, and for example, the thickness of the pad structure 16 is 1 μm, 1.5 μm or 2 μm, or the like. The material of the pad structure 16 includes but is not limited to a metal material, and for example, the material of the pad structure 16 is a copper material or an aluminum material, or the like. In the embodiment of the present application, the function of the pad structure 16 is to electrically interconnect the body acoustic wave filter 11 with other components in the external environment, and for example, the pad structure 16 is combined with the RDL lead structure 18 and the solder ball 20 to realize the electrical interconnection of the body acoustic wave filter 11 with other components in the external environment.

[0085] As shown in Figure 2 , four pad structures 16 are taken as an example for illustration. The TSV technology can greatly improve the integration of electronic components, reduce the geometric size and weight of the packaging, meet the requirements of multi-function and miniaturization of microelectronic products; the TSV technology can greatly shorten the length of electrical interconnection, thereby solving the problem of signal delay and improving the electrical performance of the device. The RDL technology is a technology for redistributing electrical connections in the process of chip packaging, and the input / output positions of the chip are redistributed by forming an additional wiring layer on the surface of the chip or other layers, so as to adapt to different packaging requirements and improve the flexibility of electrical connections.

[0086] It should be noted that, Figure 1 Reference numeral 21 represents glue, and it can be explained that in an optional embodiment of the present application, the packaging cover plate 12 is bonded with the body acoustic wave filter 11 by means of coating glue 21.

[0087] Based on the above-mentioned embodiment of the present application, in another embodiment of the present application, a preparation method of a body acoustic wave filter packaging structure is further provided, and reference is made to Figure 3 , Figure 3This is a schematic flowchart illustrating a method for fabricating a bulk acoustic wave filter packaging structure according to an embodiment of the present invention. The method for fabricating the bulk acoustic wave filter packaging structure according to an embodiment of the present invention includes:

[0088] S101: As Figure 4 As shown, an integrated acoustic filter 11 is provided, the bulk acoustic filter 11 having a working area 13 and an annular wall structure 15 located on the bulk acoustic filter 11.

[0089] Specifically, in this embodiment of the invention, the bulk acoustic wave filter 11 may further include a pad structure 16, which is located inside the annular wall structure 15.

[0090] S102: As Figure 5 As shown, a packaging cover plate 12 is provided, and the packaging cover plate 12 is processed to form a groove region 14.

[0091] Specifically, in the embodiments of the present invention, the area to be formed in the groove region 14 is exposed by means of coating photoresist, exposure, development and other methods, and then the groove region 14 is formed by means of dry etching, and finally the photoresist is removed.

[0092] S103: As Figure 6 As shown, the encapsulation cover plate 12 is bonded to the bulk acoustic wave filter 11; after bonding, the groove region 14 faces the side of the bulk acoustic wave filter 11, and the annular wall structure 15 is located between the bulk acoustic wave filter 11 and the encapsulation cover plate 12; in the first direction X, the orthographic projection of the groove region 14 at least covers the orthographic projection of the working region 13; the first direction X is perpendicular to the plane where the bulk acoustic wave filter 11 is located; wherein, both the working region 13 and the groove region 14 are located inside the annular wall structure 15.

[0093] Specifically, in this embodiment of the invention, one possible way to bond the encapsulation cover plate 12 to the bulk acoustic wave filter 11 is as follows:

[0094] The encapsulation cover plate 12 is bonded to the bulk acoustic wave filter 11 by applying adhesive 21.

[0095] For example, under conditions of a temperature range of 130℃-170℃ and a pressure range of 4000N-6000N, the encapsulation cover plate 12 and the bulk acoustic wave filter 11 are bonded by applying adhesive 21. Specifically, adhesive 21 is applied to the surface of the encapsulation cover plate 12, and the bonding process is performed using wafer-level bonding equipment.

[0096] like Figure 7As shown in the figure, the preparation method of the bulk acoustic wave filter packaging structure further includes:

[0097] The bulk acoustic wave filter 11 is processed to form a first through hole 17 penetrating through the bulk acoustic wave filter 11, and the first through hole 17 exposes part of the surface of the pad structure 16.

[0098] For example, first, the bulk acoustic wave filter 11 is thinned to a target thickness, for example, to a thickness range of 90 μm-110 μm; then, for example, but not limited to, by coating photoresist, the area where the first through hole 17 needs to be formed is exposed through exposure, development and the like; then, for example, but not limited to, by dry etching, the first through hole 17 is formed, and finally the photoresist is removed.

[0099] As shown in the figure, the preparation method of the bulk acoustic wave filter packaging structure further includes: Figure 8 The RDL lead structure 18 is formed, and the RDL lead structure 18 is electrically connected with the pad structure 16 through the first through hole 17.

[0100] For example, first, titanium and copper metal are deposited on the side surface of the bulk acoustic wave filter 11 away from the packaging cover plate 12, then copper is plated on the surface of the bulk acoustic wave filter 11 by using a plating device, then, for example, but not limited to, by coating photoresist, the position where the RDL lead structure 18 needs to be formed is protected through exposure, development and the like, and finally the excess metal is etched away, and the photoresist is removed to form the RDL lead structure 18.

[0101] As shown in the figure, the preparation method of the bulk acoustic wave filter packaging structure further includes:

[0102] Figure 9 The protective layer 19 is formed on the side of the bulk acoustic wave filter 11 away from the packaging cover plate 12; the protective layer 19 has a second through hole 22, and the second through hole 22 exposes part of the surface of the RDL lead structure 18. The protective layer 19 includes, but is not limited to, a polyimide layer, which mainly functions to protect the RDL lead structure 18, buffer the stress generated during packaging, prevent overcurrent phenomenon, and the like, so as to improve the stability and reliability of the bulk acoustic wave filter packaging structure.

[0103] As shown in the figure, the preparation method of the bulk acoustic wave filter packaging structure further includes:

[0104] The solder ball 20 is formed on the side of the bulk acoustic wave filter 11 away from the packaging cover plate 12; and the solder ball 20 is electrically connected with the RDL lead structure 18. Figure 1

[0105]

[0106] ​​​For example, first, on the side of the bulk acoustic wave filter 11 away from the package cover plate 12, the area where the solder ball 20 is to be formed is exposed by coating photoresist and exposing, developing, etc., and then the solder ball 20 is placed in the corresponding area by a ball placement machine, and reflow and cleaning are performed to form the solder ball 20.

[0107] Based on the above embodiments of the present application, in another embodiment of the present application, a radio frequency device is provided, which includes the bulk acoustic wave filter package structure of the above embodiments.

[0108] The bulk acoustic wave filter package structure, the preparation method thereof, and the radio frequency device provided by the present application are described in detail above, and the principles and implementation manners of the present application are described by using specific examples in this paper. The above embodiment descriptions are only used to help understand the method of the present application and its core idea. Meanwhile, for those skilled in the art, according to the idea of the present application, the specific implementation manners and application ranges will be changed, and the above description should not be understood as a limitation of the present application.

[0109] It should be noted that each of the embodiments in the present specification is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same and similar parts between the embodiments can be referred to each other. For the device disclosed in the embodiments, since it corresponds to the method disclosed in the embodiments, the description is relatively simple, and the related parts can be referred to the method part.

[0110] It should also be noted that in this paper, the relationship terms such as first and second 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 the entities or operations. Moreover, the terms "include", "contain" or any other variants thereof are intended to cover non-exclusive inclusion, so that the process, method, article or device including a series of elements, or including the elements inherent in the process, method, article or device. Without more limitations, the element defined by the statement "including a" does not exclude the presence of other identical elements in the process, method, article or device including the element.

[0111] The foregoing description of the disclosed embodiments enables a person skilled in the art to make or use the application. Modifications of these embodiments will occur to persons of skill in the art, and that the appended claims are intended to cover all such modifications that do not depart from the true spirit and scope of the application. Therefore, the application is not limited to the embodiments shown but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A bulk acoustic wave filter, characterized in that, The packaging structure of the bulk acoustic wave filter includes: A bulk acoustic wave filter and an encapsulation cover are disposed opposite to each other; the bulk acoustic wave filter has a working area, and the encapsulation cover includes a groove area disposed facing one side of the bulk acoustic wave filter; in a first direction, the orthogonal projection of the groove area at least covers the orthogonal projection of the working area; the first direction is perpendicular to the plane in which the bulk acoustic wave filter is located. An annular wall structure located between the bulk acoustic wave filter and the encapsulation cover, and located on the bulk acoustic wave filter; The working area and the groove area are both located inside the annular wall structure; The packaging structure of the bulk acoustic wave filter also includes: A pad structure located between the bulk acoustic wave filter and the package cover, and located on the bulk acoustic wave filter; The pad structure is located inside the annular enclosure structure.

2. The bulk acoustic wave filter according to claim 1, characterized in that, The material of the ring wall structure is either metallic or inorganic.

3. The bulk acoustic wave filter according to claim 1, characterized in that, The width of the ring-shaped wall structure ranges from 2μm to 5μm; The thickness of the ring-shaped wall structure ranges from 1μm to 2μm.

4. The bulk acoustic wave filter according to claim 1, characterized in that, The depth of the groove region ranges from 5μm to 15μm.

5. The bulk acoustic wave filter according to claim 1, characterized in that, The encapsulation cover is a Si cover.

6. The bulk acoustic wave filter according to claim 1, characterized in that, The thickness of the pad structure ranges from 1μm to 2μm.

7. The bulk acoustic wave filter according to claim 1, characterized in that, The packaging structure of the bulk acoustic wave filter also includes: A first via extends through the bulk acoustic wave filter, exposing a portion of the surface of the pad structure.

8. The bulk acoustic wave filter according to claim 7, characterized in that, The packaging structure of the bulk acoustic wave filter also includes: The RDL lead structure is electrically connected to the pad structure through the first through-hole.

9. The bulk acoustic wave filter according to claim 8, characterized in that, The packaging structure of the bulk acoustic wave filter also includes: A protective layer is located on the side of the bulk acoustic wave filter opposite to the package cover; the protective layer has a second through hole that exposes a portion of the surface of the RDL lead structure.

10. The bulk acoustic wave filter according to claim 9, characterized in that, The packaging structure of the bulk acoustic wave filter also includes: Solder balls located on the side of the bulk acoustic wave filter facing away from the package cover; the solder balls are electrically connected to the RDL lead structure.

11. A method for fabricating a bulk acoustic wave filter, characterized in that, The method for fabricating the packaging structure of the bulk acoustic wave filter includes: An integrated acoustic filter is provided, the bulk acoustic filter having a working area and an annular wall structure located on the bulk acoustic filter; A packaging cover is provided, and the packaging cover is processed to form a groove area; The encapsulation cover is bonded to the bulk acoustic wave filter; after bonding, the groove region faces the side of the bulk acoustic wave filter, and the annular wall structure is located between the bulk acoustic wave filter and the encapsulation cover; in a first direction, the orthogonal projection of the groove region at least covers the orthogonal projection of the working area; the first direction is perpendicular to the plane where the bulk acoustic wave filter is located; wherein, both the working area and the groove region are located inside the annular wall structure; the encapsulation structure of the bulk acoustic wave filter further includes: a pad structure located between the bulk acoustic wave filter and the encapsulation cover, and located on the bulk acoustic wave filter; the pad structure is located inside the annular wall structure.

12. The method for fabricating a bulk acoustic wave filter according to claim 11, characterized in that, The bonding of the encapsulation cover to the bulk acoustic wave filter includes: The encapsulation cover plate is bonded to the bulk acoustic wave filter by applying adhesive.

13. The method for fabricating a bulk acoustic wave filter according to claim 12, characterized in that, The bonding of the encapsulation cover to the bulk acoustic wave filter using adhesive coating includes: Under conditions of temperature range of 130℃-170℃ and pressure range of 4000N-6000N, the encapsulation cover plate is bonded to the bulk acoustic wave filter by applying adhesive.

14. The method for fabricating a bulk acoustic wave filter according to any one of claims 11-13, characterized in that, The method for fabricating the packaging structure of the bulk acoustic wave filter further includes: The bulk acoustic wave filter is processed to form a first through-hole that penetrates the bulk acoustic wave filter, and the first through-hole exposes a portion of the surface of the pad structure.

15. The method for fabricating a bulk acoustic wave filter according to claim 14, characterized in that, The method for fabricating the packaging structure of the bulk acoustic wave filter further includes: An RDL lead structure is formed, which is electrically connected to the pad structure through the first through hole.

16. The method for fabricating a bulk acoustic wave filter according to claim 15, characterized in that, The method for fabricating the packaging structure of the bulk acoustic wave filter further includes: A protective layer is formed on the side of the bulk acoustic wave filter away from the package cover; the protective layer has a second through hole that exposes a portion of the surface of the RDL lead structure.

17. The method for fabricating a bulk acoustic wave filter according to claim 16, characterized in that, The method for fabricating the packaging structure of the bulk acoustic wave filter further includes: Solder balls are formed on the side of the bulk acoustic wave filter away from the package cover; the solder balls are electrically connected to the RDL lead structure.

18. A radio frequency device, characterized in that, The radio frequency device includes the bulk acoustic wave filter according to any one of claims 1-10.

Images