A surface acoustic wave device miniaturization packaging method and packaging structure

Abstract

The application belongs to the technical field of information electronic materials, and particularly relates to a surface acoustic wave device miniaturized packaging method and packaging structure; comprising: preparing a first filter on a first wafer, and preparing a second filter on a second wafer; constructing a support layer structure on the first filter and setting a plurality of ball mounting positions in the support layer structure; constructing a support layer structure corresponding to the support layer structure of the first filter on the second filter; embedding a plurality of balls in the support layer structure of the second filter, and the balls are in contact with electrodes, the balls on the second filter correspond to the ball mounting positions on the first filter one by one; flipping the second filter above the first filter, so that the second filter is electrically connected with the first filter by the balls, and the device packaging is completed; the application reduces the electrical loss of long-span electrodes and the filter loss, improves the DMS filter Q value, and realizes the miniaturization of the surface acoustic wave device packaging.

Description

Technical Field

[0001] The present invention belongs to the technical field of information electronic materials, and in particular relates to a miniaturized packaging method and packaging structure for a surface acoustic wave device. Background Art

[0002] With the rapid development of the field of wireless communications, the performance requirements for RF filters that process RF signals have been further improved. RF filters are the components with the highest proportion in the entire RF front-end, and are also one of the important components for national defense, military industry, mobile communications and automotive electronics. Their function is to filter out useless signals in the communication process and retain useful signals. Surface acoustic wave (SAW) filters are widely used in various fields due to their small size, low insertion loss, good selectivity, low cost and high reliability. Wireless communication equipment has a strong demand for miniaturization of SAW filters, and it is necessary to develop miniaturized and small-volume SAW filters to meet market development needs. The size of SAW filters is affected by the packaging process. As a design structure of SAW filters, longitudinally coupled dual-mode surface acoustic wave filters (DMS) need to construct a support layer structure around the DMS filter during wafer-level packaging (WLP), and then cover the support layer structure with a protective layer material to package and protect the DMS filter (such as Figure 1 For low-frequency DMS filters, the large electrode apertures and long electrode spans increase processing complexity and reduce filter performance. Furthermore, the large interdigitated electrode area results in a larger chip size after WLP packaging. Therefore, a filter packaging method and structure that can achieve both performance improvement and miniaturization is needed for DMS filters. Summary of the Invention

[0003] In view of the shortcomings of the prior art, the present invention proposes a miniaturized packaging method and packaging structure for a surface acoustic wave device. The packaging method includes:

[0004] S1: preparing a first wafer and a second wafer, fabricating a first filter on the first wafer, and fabricating a second filter on the second wafer;

[0005] S2: constructing a support layer structure on the first filter and setting a plurality of ball planting positions in the support layer structure;

[0006] S3: constructing a support layer structure corresponding to the support layer structure of the first filter on the second filter; embedding a plurality of planting balls in the support layer structure of the second filter, and the planting balls are in contact with the electrodes, and the planting balls on the second filter correspond to the planting balls on the first filter in a one-to-one manner;

[0007] S4: flip-mount the second filter on top of the first filter so that the second filter is electrically connected to the first filter by ball implantation. That is, the first filter and the second filter are electrically connected in parallel to form a complete DMS filter, thereby completing the device packaging.

[0008] Preferably, the electrode extension portion of the second filter is shorter than the electrode extension portion of the first filter.

[0009] Preferably, there is at least one implant ball above and in contact with each electrode.

[0010] Preferably, the ball diameter is 40-100 μm.

[0011] Preferably, the aperture ratio of the first filter and the second filter is 0.8-1.2.

[0012] Preferably, the ball implant material is gold, aluminum or an alloy.

[0013] Preferably, the material of the support layer structure is photosensitive polyimide, benzocyclobutene or polybenzoxazole.

[0014] A miniaturized packaging structure for a surface acoustic wave device comprises a first wafer, a second wafer, a first filter, a second filter, a ball implant, and a support layer structure; the electrode extension portion of the second filter is shorter than the electrode extension portion of the first filter, the first filter is located on the first wafer, and the second filter is located on the second wafer; the support layer structure is arranged at the same position as the first filter and the second filter; the ball implant is embedded in the support layer structure of the second filter, and a ball implant position corresponding to the ball implant of the second filter is provided in the support layer structure of the first filter; the second wafer is flip-chip mounted on the first wafer, so that the second filter is electrically connected to the first filter via the ball implant.

[0015] The beneficial effects of the present invention are:

[0016] (1) Improved filter performance. The present invention splits the DMS filter into two filters through a parallel electrical connection, shortening the length span of the filter's interdigital electrodes, reducing the electrical loss of the electrodes, and improving the Q value of the DMS filter.

[0017] (2) Reduced processing difficulty. The wide aperture of the DMS filter results in a large electrode length span, which can easily lead to problems such as low finger peeling yield, poor finger morphology, and low finger linearity during processing. The present invention shortens the length of the interdigitated electrode fingers by parallel splitting, which can improve the finger peeling yield and finger linearity during processing, optimize the finger morphology, reduce processing difficulty and the requirements for the processing equipment, and thus reduce processing costs.

[0018] (3) Reduce the chip size after packaging. The present invention stacks the first and second filters after parallel splitting into WLP packages by flip-chip implantation, which reduces the in-plane size of the DMS filter WLP package, reduces the chip size, realizes the miniaturization of the DMS filter packaging, and expands the application scenarios of the DMS filter. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a schematic diagram of the traditional WLP packaging process;

[0020] Figure 2 The structure and packaging diagram of a DMS filter in a preferred embodiment of the present invention;

[0021] Figure 3 A comparison diagram of a traditional WLP packaging structure and the WLP packaging structure of the present invention. DETAILED DESCRIPTION

[0022] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0023] The present invention proposes a surface acoustic wave device miniaturization packaging method and packaging structure, such as Figure 2 As shown, Figure 2 In the figure, (a) is a complete DMS filter; (b) is a first filter and a second filter electrically connected in parallel; (c) is the preparation of the first filter on the first wafer; (d) is the preparation of the second filter on the second wafer; (e) is the construction of a support layer structure on the first filter and the construction of a ball planting position; (f) is the construction of a support layer structure on the second filter and the ball planting; (g) is the flip-chip mounting of the second filter on top of the first filter; (h) is a side view of the DMS filter packaging structure after flip-chip mounting.

[0024] The packaging method comprises:

[0025] S1: Prepare the first wafer and the second wafer; Figure 2 c and Figure 2 As shown in FIG. 4 , a first filter is prepared on the first wafer, and a second filter is prepared on the second wafer.

[0026] like Figure 2 a and Figure 2As shown in FIG. 2 , the first filter and the second filter can be combined into a complete DMS filter by adopting a parallel electrical connection method; the impedance of the complete DMS filter is the same as the total impedance of the two filters electrically connected in parallel. The effect achieved by the present invention is equivalent to splitting the complete DMS filter that should be packaged into two filters by adopting a parallel electrical connection method and then packaging them.

[0027] In some embodiments, the aperture ratio of the first filter and the second filter electrically connected in parallel can be 0.2 to 3, preferably in the range of 0.8 to 1.2. Within this range, the aperture values ​​of the first and second filters are close. When aligning the bus bar electrodes for the subsequent ball planting operation, there is no need to extend the bus bar electrodes of one of the filters on a large scale, which saves chip area and is more conducive to the miniaturization of the filter package.

[0028] By splitting in parallel, the length of the electrode fingers of a single filter can be shortened, thereby reducing electrode loss, improving the filter Q value, and reducing the difficulty of process processing.

[0029] In some embodiments, the electrode extension of the second filter is shorter than the electrode extension of the first filter. This structure ensures that the second filter, located above, is shorter than the first filter. This in turn ensures that after the upper and lower filters are packaged, the electrodes of the first filter, located below, are partially exposed, facilitating subsequent wire bonding operations.

[0030] The present invention shortens the electrode extension portion of the second filter. Therefore, after the flip-chip operation, the second filter covers the first filter without affecting the subsequent wire bonding operation of the first filter.

[0031] S2: constructing a support layer structure on the first filter and setting a plurality of ball planting positions in the support layer structure.

[0032] S3: constructing a support layer structure corresponding to the support layer structure of the first filter on the second filter; embedding a plurality of planting balls in the support layer structure of the second filter, and the planting balls are in contact with the electrodes.

[0033] In some preferred embodiments, there is at least one ball above each electrode in contact with it; it should be noted that, in the present invention, the electrode refers to the bus bar portion; Figure 2 e and Figure 2 As shown in FIG. 5 , the balls are located above electrodes of different polarities and in contact with the electrodes, and the balls on the second filter correspond to the balls on the first filter in one-to-one position.

[0034] S4: flip-mounting the second filter on top of the first filter, so that the second filter is electrically connected to the first filter by using the implant ball, thereby completing the device packaging.

[0035] During packaging, the second filter is flipped and the ball of the second filter is aligned with the ball position of the first filter (such as Figure 2 g) under the back cover,

[0036] In this packaging structure, the second filter is electrically connected to the first filter by using a ball implant in a flip-chip form; at the same time, the first filter (or the second filter) serves as a protective layer structure for the second filter (or the first filter) (such as Figure 2 h).

[0037] In some embodiments, the material of the DMS filter support layer may be photosensitive polyimide (PI), benzocyclobutene (BCB), or polybenzoxazole (PBO).

[0038] In some embodiments, the ball implant material can be a metal or alloy such as gold or aluminum. The characteristic length of the ball implant position in the support layer can be 1 to 200 μm, preferably in the range of 40 to 100 μm. It should be noted that the ball implant position is not limited to a spherical shape, as long as the size can accommodate the implant. The ball implant diameter can be 1 to 200 μm, preferably in the range of 40 to 100 μm. Balls within this range are easy to process and are suitable for currently widely used implant technologies.

[0039] The present invention also provides a surface acoustic wave device miniaturization packaging structure packaged using the surface acoustic wave device miniaturization packaging method designed by the present invention, comprising: a first wafer, a second wafer, a first filter, a second filter, a planting ball and a support layer structure; the electrode extension portion of the second filter is shorter than the electrode extension portion of the first filter, the first filter is located on the first wafer, and the second filter is located on the second wafer; the support layer structure is arranged at the same position of the first filter and the second filter; the planting ball is embedded in the support layer structure of the second filter, and a planting ball position corresponding to the planting ball of the second filter is arranged in the support layer structure of the first filter; the second wafer is flip-chip mounted on the first wafer, so that the second filter is electrically connected to the first filter using the planting ball.

[0040] In some preferred embodiments, the structural parameters of the first filter and the second filter in the DMS filter are a half-period of 4.5 μm, a duty cycle of 0.36, and a duty cycle of 350 μm. The first and second filters respectively include three resonators, and the number of fingers of the three resonators are 17, 25, and 17, respectively, with reflection gratings on both sides. The apertures of the first and second filters are both 350 μm. A support layer structure is constructed around the first filter, and the support layer material is PI. Six ball planting positions are prepared in the support layer, and the ball planting position diameter is 80 μm. A support layer structure is constructed around the second filter, and the support layer material is PI. Six ball planting positions are prepared in the support layer, and the ball planting operation is performed. The ball planting material is gold, and the ball planting diameter is 60 μm. The second filter is flip-chip assembled on top of the first filter, and the ball planting of the second filter is aligned with the ball planting position of the first filter.

[0041] Evaluation of the present invention:

[0042] like Figure 3 As shown in a, when the traditional DMS filter is WLP packaged, it is necessary to construct a support layer and a protective layer around the interdigital electrode area, resulting in a larger size of the DMS filter after WLP packaging.

[0043] like Figure 3 As shown in b, in order to improve the performance of the DMS filter and achieve miniaturized packaging, the present invention first conceptually splits the DMS filter in parallel from the perspective of electrical connection to reduce the span of the electrode aperture size; then the split first filter and the second filter are prepared separately. During WLP packaging, the second filter is placed on the left and right of the protective layer of the first filter, and the two filters are electrically connected by flip-chip ball implantation. Through the design optimization of the DMS filter of the present invention, the processing difficulty of long-span electrodes is reduced, the electrical loss and filter loss of long-span electrodes are reduced, and the Q value of the DMS filter is improved; on the other hand, the first filter and the second filter are stacked at the wafer level using the WLP packaging method of flip-chip ball implantation, so that the chip size of the DMS filter is reduced after packaging, which is conducive to the miniaturized application of the DMS filter.

[0044] The above embodiments further illustrate the purpose, technical solutions and advantages of the present invention in detail. It should be understood that the above embodiments are only preferred implementation plans 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 in the scope of protection of the present invention.

Claims

1. A method for miniaturizing a surface acoustic wave device packaging, characterized in that: include: S1: preparing a first wafer and a second wafer, fabricating a first filter on the first wafer, and fabricating a second filter on the second wafer; S2: constructing a support layer structure on the first filter and setting a plurality of ball planting positions in the support layer structure; S3: constructing a support layer structure corresponding to the support layer structure of the first filter on the second filter; embedding a plurality of planting balls in the support layer structure of the second filter, and the planting balls are in contact with the electrodes, and the planting balls on the second filter correspond to the planting balls on the first filter in a one-to-one manner; S4: flip-mount the second filter on top of the first filter so that the second filter is electrically connected to the first filter by ball implantation. That is, the first filter and the second filter are electrically connected in parallel to form a complete DMS filter, thereby completing the device packaging.

2. The method for miniaturizing the surface acoustic wave device packaging according to claim 1, wherein: The electrode extension portion of the second filter is shorter than the electrode extension portion of the first filter.

3. The method for miniaturizing the surface acoustic wave device packaging according to claim 1, wherein: There is at least one planting ball on top of each electrode in contact with the electrode.

4. The method for miniaturizing the surface acoustic wave device packaging according to claim 1, wherein: The ball diameter is 40~100μm.

5. The method for miniaturizing the surface acoustic wave device packaging according to claim 1, wherein: The aperture ratio of the first filter and the second filter is 0.8-1.

2.

6. The method for miniaturizing and packaging a surface acoustic wave device according to claim 1, wherein: The ball planting material is gold, aluminum or alloy.

7. The method for miniaturizing and packaging a surface acoustic wave device according to claim 1, wherein: The material of the supporting layer structure is photosensitive polyimide, benzocyclobutene or polybenzoxazole.

8. A miniaturized packaging structure for a surface acoustic wave device, wherein the packaging structure is obtained by packaging a surface acoustic wave device using the packaging method according to any one of claims 1 to 7, wherein: include: A first wafer, a second wafer, a first filter, a second filter, a ball implant and a support layer structure; the electrode extension portion of the second filter is shorter than the electrode extension portion of the first filter, the first filter is located on the first wafer, and the second filter is located on the second wafer; the support layer structure is arranged at the same position of the first filter and the second filter; the ball implant is embedded in the support layer structure of the second filter, and a ball implant position corresponding to the ball implant of the second filter is arranged in the support layer structure of the first filter; the second wafer is flip-chip mounted on the first wafer, so that the second filter is electrically connected to the first filter by means of the ball implant.

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