A high-reliability packaging structure of a surface acoustic wave filter

Abstract

The application belongs to the technical field of information electronic materials, and particularly relates to a high-reliability packaging structure of a surface acoustic wave filter; the packaging structure comprises a surface acoustic wave filter, a supporting layer and a protective layer; a transition area is arranged in the middle part of an interdigital electrode area of the surface acoustic wave filter, electrode fingers of the transition area are arranged in a bent state, and the electrode fingers of the transition area only keep electrical connection, wherein the bent shape of the electrode fingers is composed of a plurality of continuous bending units; the supporting layer is arranged around the transition area and the periphery of the interdigital electrode area of the surface acoustic wave filter; the protective layer is arranged on the supporting layer, and the supporting layer and the protective layer form a closed cavity; the application provides support for the upper protective layer packaging material without expanding the size area of the filter, avoids the collapse and deformation of the protective layer material, and improves the reliability and pressure resistance of the WLP packaging of the DMS filter.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of information electronic materials, and particularly relates to a high-reliability packaging structure of a surface acoustic wave filter. BACKGROUND

[0002] With the rapid development of the wireless communication field, the performance requirements of the radio frequency filter for processing radio frequency signals are further improved. The radio frequency filter is one of the most important components in the entire radio frequency front end, and is also one of the important components in the national defense, mobile communication and automobile electronics. The radio frequency filter filters out the useless signals in the communication process and retains the useful signals. The surface acoustic wave (SAW) filter is widely used in various fields due to its small size, low insertion loss, good selectivity, low cost and high reliability. Wireless communication equipment has a strong demand for miniaturization of the SAW filter, and it is necessary to develop a small-sized SAW filter to meet the market development demand. The size of the SAW filter is affected by the packaging process. As a design structure of the SAW filter, the longitudinal coupling dual-mode surface acoustic wave filter (DMS) needs to build a support layer structure around the DMS filter when wafer-level packaging (WLP) is performed, and then a protective layer material is covered on the support layer structure to package and protect the DMS filter. For a low-frequency DMS filter, the area of the interdigital electrode region is large, and the support layer material is only established around the interdigital electrode to cover the protective layer. At this time, the protective layer material is prone to collapse, thereby affecting the performance of the DMS filter. If the support layer is established inside the interdigital electrode to support the protective layer material, the support layer material above the electrode will have an adverse effect on the performance of the DMS filter. Therefore, it is urgent to develop a high-reliability packaging design structure of the SAW filter. SUMMARY

[0003] In view of the deficiencies in the prior art, the application provides a high-reliability packaging structure of a surface acoustic wave filter, which comprises a surface acoustic wave filter, a support layer and a protective layer. The middle part of the interdigital electrode region of the surface acoustic wave filter is set as a transition zone, the electrode fingers of the transition zone are set in a bent state, and the electrode fingers of the transition zone only retain electrical connection, wherein the bent shape of the electrode fingers is composed of a plurality of continuous bending units.

[0004] Preferably, the bent shape of the electrode fingers is a fold line shape, a symmetrical fold line shape, an arc line shape or a symmetrical arc line shape.

[0005] Preferably, the bending angle of each bending unit of the electrode fingers of the transition zone is 30°-120°.

[0006] Preferably, the number of bending units of the electrode fingers of the transition zone is 1-100.

[0007] Preferably, the length of the bending unit of the electrode finger strip in the transition zone along the electrode direction is 1~50 μm.

[0008] Preferably, the bending angles of the bending units of the two adjacent electrode fingers in the transition zone are different.

[0009] Preferably, the overall length of the transition region along the electrode direction is 10~200 μm.

[0010] Preferably, the structure of the support layer is a single line, multiple lines, segmented lines, a single row of cylinders, multiple rows of cylinders, or a polygon.

[0011] Preferably, the material of the support layer is photosensitive polyimide, benzocyclobutene, or polybenzoxazole, and the material of the protective layer is photosensitive polyimide, benzocyclobutene, polybenzoxazole, silicon, or polycrystalline silicon.

[0012] The beneficial effects of this invention are as follows:

[0013] This invention adds a WLP package support layer structure to the DMS filter, which avoids the collapse and deformation of the upper protective layer material and improves the reliability of the WLP package. At the same time, the geometric design of the transition region of the DMS filter ensures that it avoids the introduction of additional clutter interference into the DMS filter while maintaining electrical connection.

[0014] Since the added WLP package support layer structure is located inside the interdigitated electrodes (transition region) of the DMS filter, the present invention improves the reliability of the WLP package without increasing the size of the DMS filter chip, which is beneficial to the miniaturization development and application of the DMS filter.

[0015] The packaging structure designed in this invention not only increases the reliability of the WLP package itself, but also increases the withstand voltage of the packaged DMS filter, expanding the application scenarios and scope of the DMS filter. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the support layer and protective layer on a single filter during packaging, according to a preferred embodiment of the present invention;

[0017] Figure 2 This is a schematic diagram of the electrode structure of a preferred embodiment of the present invention;

[0018] Figure 3 This is a schematic diagram of the polygonal transition region structure in some preferred embodiments of the present invention;

[0019] Figure 4 This is a schematic diagram of the arc-shaped transition region structure in some preferred embodiments of the present invention;

[0020] Figure 5 This is a partial schematic diagram of the transition region between two adjacent electrodes in the interdigitated electrode region of some preferred embodiments of the present invention;

[0021] Figure 6 This is a schematic diagram of the material structure of the transition zone support layer in some preferred embodiments of the present invention. Detailed Implementation

[0022] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] This invention proposes a high-reliability packaging structure for surface acoustic wave filters, such as... Figure 1 As shown, the reliable packaging structure includes: a surface acoustic wave filter, a support layer, and a protective layer; as... Figure 2 As shown, the middle part of the interdigitated electrode region of the surface acoustic wave filter is set as a transition region. The electrode strips in the transition region are set to a bent state and only electrical connections are retained in the strips in the transition region. The bent shape of the electrode strips is composed of multiple consecutive bent units. The support layer is set around the transition region and the interdigitated electrode region of the surface acoustic wave filter. The protective layer covers the support layer, and the support layer and the protective layer form a closed cavity.

[0024] like Figure 3 , Figure 4 As shown, in some preferred embodiments, the bending shape of the electrode fingers is a broken line, a symmetrical broken line, an arc, or a symmetrical arc. Figure 3 (a) is a broken-line transition zone. Figure 3 (b) is a symmetrical polygonal transition zone. Figure 4 (a) An arc-shaped transition zone, Figure 4 (b) is a symmetrical arc-shaped transition zone.

[0025] The bending angle of each bending unit of the electrode finger strip in the transition zone can be 1° to 175°. In some preferred embodiments, the bending angle of each bending unit of the electrode finger strip in the transition zone is 30° to 120°. It should be noted that when the bending shape is an arc or a symmetrical arc, the bending shape is obtained by chamfering the corner of the broken line or symmetrical broken line into an arc. In this case, the bending angle refers to the angle when the arc is turned back into a corner.

[0026] In this invention, such as Figure 5As shown, in order to achieve electrical connection only without generating sound waves, the bending angles of the bending units of the two adjacent electrode strips in the transition zone are different.

[0027] The number of bending units of the electrode fingers in the transition region can be 1 to 200. In some preferred embodiments, the number of bending units of the electrode fingers in the transition region is 1 to 100. Too many bending units will lead to a larger size of the transition region. On the one hand, long electrodes will increase the electrical loss of the electrodes and have a negative impact on the performance of the filter. On the other hand, it will lead to an increase in chip size, which is not conducive to miniaturized packaging. Therefore, it is preferred to select a bending unit number of 1 to 100.

[0028] The length of the bending unit of the electrode finger strip in the transition zone along the electrode direction can be 1~200 μm. In some preferred embodiments, the length of the bending unit of the electrode finger strip in the transition zone along the electrode direction is 1~50 μm. If the length of the bending unit along the electrode direction is too long, it will increase the tendency and degree of the two adjacent fingers to be parallel to each other. When the two adjacent fingers tend to be parallel, additional acoustic excitation will be generated, forming additional clutter interference, thereby affecting the performance of the filter and making it difficult to achieve the purpose of retaining only electrical connection without acoustic excitation. Therefore, it is preferred to select a bending unit length of 1~50 μm along the electrode direction.

[0029] The overall length of the transition region along the electrode direction can be 1~800 μm. In some preferred embodiments, the overall length of the transition region along the electrode direction is 10~200 μm. If the overall length of the transition region along the electrode direction is too short, it is insufficient to construct a stable support layer structure, and the reliability of the support layer and the package cannot be improved. If the overall length of the transition region along the electrode direction is too long, it will increase the electrical loss of the electrode and lead to an increase in chip size, thus failing to achieve the goal of miniaturized and highly reliable packaging. Therefore, the overall length of the transition region along the electrode direction is preferably selected to be 10~200 μm.

[0030] In some preferred embodiments, such as Figure 6 As shown, the structure of the support layer can be a single line, multiple lines, segmented lines, a single row of cylinders, multiple rows of cylinders, or a polygon. Figure 6 (a) consists of multiple linear support layers; Figure 6 (b) is a segmented linear support layer; Figure 6 (c) is a single-row cylindrical support layer; Figure 6 (d) is a multi-row cylindrical support layer.

[0031] In some preferred embodiments, the material of the DMS filter support layer can be photosensitive polyimide (PI), benzocyclobutene (BCB), polybenzoxazole (PBO), and the material of the protective layer can be photosensitive polyimide (PI), benzocyclobutene (BCB), polybenzoxazole (PBO), silicon, polycrystalline silicon, etc.

[0032] In summary, when packaging a DMS filter using WLP (Wafer Level Package), a support layer is first constructed around the perimeter of the filter. To prevent the subsequent protective layer material from collapsing due to suspension, additional support structures are needed for the protective layer. Adding support structures around the filter would increase the filter chip area, resulting in a larger packaged filter volume. To achieve miniaturized and highly reliable packaging, the DMS filter packaging structure designed in this invention can incorporate a support layer structure in the transition region, followed by the construction of the protective layer material on top of the support layer. Here, due to sufficient support beneath the protective layer material, deformation and collapse of the protective layer material caused by large-area suspension can be avoided. This invention provides support for the upper protective layer packaging material without increasing the filter's size, preventing collapse and deformation of the protective layer material, and improving the reliability and withstand voltage of the DMS filter WLP packaging.

[0033] The above-described embodiments further illustrate the purpose, technical solution, and advantages of the present invention. It should be understood that the above-described embodiments are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made to the present invention within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A high-reliability packaging structure for a surface acoustic wave filter, characterized in that, The application relates to a surface acoustic wave filter, a support layer and a protective layer. The middle part of an interdigital electrode area of the surface acoustic wave filter is a transition area, electrode fingers of the transition area are arranged in a bent state, and the electrode fingers of the transition area only remain electrical connection, the bent shape of the electrode fingers is composed of continuous multiple bending units, the support layer is arranged around the periphery of the transition area and the interdigital electrode area of the surface acoustic wave filter, the protective layer is arranged on the support layer, the support layer and the protective layer form a closed cavity, and the bending angles of the bending units of two adjacent electrode fingers of the transition area are different. The bent shape of the electrode fingers is a fold line shape, a symmetrical fold line shape, an arc line shape or a symmetrical arc line shape.

2. The high-reliability packaging structure of a surface acoustic wave filter according to claim 1, wherein The bending angle of each bending unit of the electrode fingers of the transition area is 30-120 degrees.

3. The high-reliability package structure of a surface acoustic wave filter according to claim 1, wherein The number of the bending units of the electrode fingers of the transition area is 1-100.

4. The high-reliability package structure of a surface acoustic wave filter according to claim 1, wherein The length of the bending units of the electrode fingers of the transition area along the electrode direction is 1-50 microns.

5. The high-reliability package structure of a surface acoustic wave filter according to claim 1, wherein The length of the transition area along the electrode direction is 10-200 microns.

6. The high-reliability package structure of a surface acoustic wave filter according to claim 1, wherein The structure of the support layer is single-line, multi-line, segmented line, single-row cylinder, multi-row cylinder or polygon.

7. The high-reliability package structure of a surface acoustic wave filter according to claim 1, wherein The material of the support layer is photosensitive polyimide, benzocyclobutene or polybenzoxazole, and the material of the protective layer is photosensitive polyimide, benzocyclobutene, polybenzoxazole, silicon or polycrystalline silicon.

8. The high-reliability package structure of a surface acoustic wave filter according to claim 1, wherein ​

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