Surface Acoustic Wave Filter and Method for Manufacturing the Same

Abstract

The present invention relates to a surface acoustic wave filter and a manufacturing method thereof, which can improve the airtightness and product reliability of the CSP package of the surface acoustic wave filter and protect the chip from dissection. The surface acoustic wave filter includes: a substrate, on the upper surface of which steps are formed around the periphery; a chip, which is flip-chip welded on the substrate; and a packaging layer, which covers the upper part of the substrate and the chip, and forms a stepped coverage around the periphery of the upper surface of the substrate.

Description

Technical Field

[0001] The present invention relates to a surface acoustic wave filter and a manufacturing method thereof. Background Art

[0002] A surface acoustic wave filter (SAWF) is an electronic device that works based on the piezoelectric effect of a piezoelectric material and utilizes surface acoustic waves on the surface of the piezoelectric material. It uses interdigital transducers (IDTs) formed on the surface of the piezoelectric material to convert an electrical input signal into a surface acoustic wave, and is a key component of current communication devices.

[0003] Currently, the mainstream packaging process of surface acoustic wave filters in China is chip-scale packaging (CSP). The piezoelectric chip, substrate, metal balls, and resin packaging are subjected to CSP packaging through flip-chip and resin packaging processes to achieve the transmission of electrical signals and mechanical signals and the packaging protection of the device. CSP packaging has the advantages of small size, good performance, and light weight. Figure 1 The packaging structure of an existing surface acoustic wave filter is shown in. Figure 1 In, after ball planting and cutting of the metal balls 2C, the piezoelectric chip 2A with independent electrical performance is flip-chip welded to the substrate 2B through a thermocompression ultrasonic process. A resin 2D is covered above the substrate 2B and the piezoelectric chip 2A, and through processes such as lamination process and high-temperature baking process, a packaging structure of the surface acoustic wave filter is obtained. Summary of the Invention

[0004] Technical Problem to be Solved by the Invention

[0005] However, the CSP packaging of the existing surface acoustic wave filter has the following disadvantages: after the substrate 2B and the resin 2D are packaged, tiny gaps will be generated at the interface 2E, and water vapor enters the piezoelectric chip 2A from these tiny gaps, resulting in insufficient airtightness and a decrease in product reliability.

[0006] In addition, during the packaging process, multiple chips are usually packaged together to form a package body, and finally the package body is cut and separated to form a single surface acoustic wave filter. However, during the process of cutting and separating the package body, it is easy to dissect the chip, resulting in damage to the chip.

[0007] Therefore, how to solve the drawbacks of the CSP packaging process of surface acoustic wave filters in production and improve product reliability has become an urgent problem to be solved in the industry.

[0008] The object of the present invention is to provide a surface acoustic wave filter and a manufacturing method thereof, which can improve the airtightness and product reliability of the CSP package of the surface acoustic wave filter and protect the chip from dissection.

[0009] Technical solution for solving the technical problem

[0010] The present invention relates to a surface acoustic wave filter, which includes:

[0011] A substrate, on the upper surface of which steps are formed around the periphery;

[0012] A chip, which is flip-chip welded on the substrate; and

[0013] A packaging layer, which covers above the substrate and the chip, and forms a stepped coverage around the periphery of the upper surface of the substrate.

[0014] Preferably, in the above surface acoustic wave filter, the depth range of the steps is 10-100 μm, and the width range is 10-200 μm.

[0015] Preferably, in the above surface acoustic wave filter, the material of the packaging layer is resin.

[0016] Preferably, in the above surface acoustic wave filter, the chip is welded on the substrate via metal balls.

[0017] Preferably, in the above surface acoustic wave filter, the chip is a piezoelectric chip.

[0018] The present invention also relates to a manufacturing method of a surface acoustic wave filter, which includes the following steps:

[0019] Prepare a whole substrate;

[0020] Pretreat the upper surface of the whole substrate according to a preset cutting line to form a step channel along the cutting line;

[0021] Flip-chip weld a plurality of cut chips on the whole substrate;

[0022] Cover the packaging layer above the whole substrate and the plurality of chips to form a package; and

[0023] Cut and separate the package along the cutting line to form a single surface acoustic wave filter.

[0024] Preferably, in the above manufacturing method of the surface acoustic wave filter, the depth range of the step channel is 10-100 μm, and the width range is 10-200 μm.

[0025] Preferably, in the method for manufacturing the surface acoustic wave filter described above, the encapsulation layer is pressed onto the integral substrate by means of hot pressing.

[0026] Preferably, in the method for manufacturing the surface acoustic wave filter described above, the material of the encapsulation layer is resin.

[0027] Preferably, in the method for manufacturing the surface acoustic wave filter described above, the chip is soldered onto the integral substrate via metal balls by using a hot press ultrasonic soldering process.

[0028] Preferably, in the method for manufacturing the surface acoustic wave filter described above, the chip is a piezoelectric chip.

[0029] Advantages of the Invention

[0030] According to the surface acoustic wave filter and the method for manufacturing the same of the present invention, by forming steps around the perimeter of the upper surface of the substrate and using the encapsulation layer to fill the steps to form a stepped coverage, moisture can be prevented from entering the chip through the planar gap formed between the encapsulation layer and the substrate, thereby improving the hermeticity and product reliability of the CSP packaging of the surface acoustic wave filter.

[0031] In addition, by using the stepped structure around the perimeter of the upper surface of the substrate, the chip can be protected from dissection during the process of cutting and separating the package, achieving the purpose of protecting the chip. Description of the Drawings

[0032] Figure 1 is a schematic diagram showing the packaging structure of a conventional surface acoustic wave filter.

[0033] Figure 2 is a schematic diagram showing the packaging structure of the surface acoustic wave filter according to an embodiment of the present invention.

[0034] Figure 3 is Figure 2 a top view of the substrate structure in the surface acoustic wave filter shown.

[0035] Figure 4 (A) is a top view showing the integral substrate before treatment, Figure 4 (B) is a side view showing the integral substrate before treatment.

[0036] Figure 5 (A) is a top view showing the integral substrate after treatment, Figure 5 (B) is a side view showing the integral substrate after treatment. Detailed Embodiments

[0037] Next, in order to more specifically illustrate the present invention, the embodiments for implementing the present invention will be described with reference to the drawings.

[0038] It should be noted that many specific details are set forth in the following description to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein, and those skilled in the art can make various extensions without departing from the gist of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed below.

[0039] Unless the context clearly requires otherwise, the words "including", "comprising", and the like in the entire specification and claims should be construed in an inclusive sense rather than an exclusive or exhaustive sense. That is, it is the meaning of "including but not limited to".

[0040] <Package Structure of Surface Acoustic Wave Filter>

[0041] Hereinafter, in conjunction with Figure 2 , the package structure of the surface acoustic wave filter 100 according to the embodiments of the present invention will be described.

[0042] Figure 2 It is a schematic diagram showing the package structure of the surface acoustic wave filter 100 according to the embodiments of the present invention.

[0043] As Figure 2 shown, the surface acoustic wave filter 100 is configured to include a chip 1A, a substrate 1B, and a package layer 1D.

[0044] The chip 1A is flip-chip bonded to the substrate 1B. The chip 1A is, for example, a piezoelectric chip having independent electrical properties. In the present embodiment, the chip 1A is a surface acoustic wave filter chip.

[0045] The chip 1A can be welded to the substrate 1B via metal balls 1C. The metal balls 1C can be tin balls or gold balls. In the present embodiment, the metal balls are set as gold balls, and the ball mounting is performed on the surface of the chip 1A by using a thermocompression ultrasonic method.

[0046] The substrate 1B plays a role of physical support and circuit connection in the entire structure. The top view shape of the substrate 1B is rectangular, but it is not limited to a rectangle. For example, it can also be a square. In addition, the substrate 1B is, for example, a ceramic substrate. The substrate 1B is not limited to a ceramic substrate. For example, it can also be a PCB substrate, a silicon substrate, a germanium substrate, a diamond substrate, a diamond-like carbon substrate, a lithium tantalate substrate, a lithium niobate substrate, etc.

[0047] In the present embodiment, as Figure 3 shown in the top view of the substrate structure, steps 1E are formed around the upper surface of the substrate 1B. The depth range of the steps 1E is preferably 10 - 100 μm, and the width range of the steps 1E is preferably 10 - 200 μm.

[0048] The encapsulation layer 1D covers the substrate 1B and the chip 1A, forming a stepped coverage around the perimeter of the upper surface of the substrate 1B. Among them, the material of the encapsulation layer 1D can be, for example, resin, and more preferably, it can be epoxy resin.

[0049] After the chip 1A completes the ball mounting of the metal balls 1C, it is subjected to flip-chip soldering treatment with the substrate 1B. Then, a film covering treatment is performed using the encapsulation layer 1D which is, for example, resin. At this time, using the fluidity of the encapsulation layer 1D, the step 1E is filled to form a stepped coverage.

[0050] For the surface acoustic wave filter according to this embodiment, by forming steps around the perimeter of the upper surface of the substrate and using the encapsulation layer to fill these steps to form a stepped coverage, it is possible to prevent water vapor from entering the chip through the planar gap formed between the encapsulation layer and the substrate, and improve the airtightness and product reliability of the CSP packaging of the surface acoustic wave filter.

[0051] In addition, by using the stepped structure around the perimeter of the upper surface of the substrate, the chip can be protected from dissection during the process of cutting and separating the package body, achieving the purpose of protecting the chip.

[0052] <Manufacturing method of surface acoustic wave filter>

[0053] Next, in combination with Figure 4 and Figure 5 the manufacturing method of the surface acoustic wave filter according to the embodiment of the present invention will be described.

[0054] Figure 4 (A) is a top view showing the overall substrate before processing, Figure 4 (B) is a side view showing the overall substrate before processing. Figure 5 (A) is a top view showing the overall substrate after processing, Figure 5 (B) is a side view showing the overall substrate after processing.

[0055] The manufacturing method of the surface acoustic wave filter according to the embodiment of the present invention includes the following steps.

[0056] Step S1, prepare an overall substrate 3B. As shown in Figure 4 (A), a preset cutting line 3F is formed on the upper surface of the overall substrate 3B.

[0057] Step S2, perform pretreatment on the upper surface of the overall substrate 3B according to the preset cutting line 3F above to form Figure 5 (A) the step channel 3E along the cutting line 3F. In Figure 5 (B), the position of the step channel 3E is shown from the side. Specifically, the depth range of the step channel 3E is preferably 10 - 100 μm, and the width range of the step channel is preferably 10 - 200 μm.

[0058] Step S3: Flip-chip solder the multiple cut chips onto the overall substrate 3B. Specifically, for example, the chips can be soldered onto the overall substrate 3B via metal balls using a thermocompression ultrasonic soldering process.

[0059] Step S4: Cover the overall substrate 3B and the multiple chips with a packaging layer to form a package. For example, the packaging layer can be pressed onto the overall substrate 3B by thermocompression. In addition, the material of the packaging layer can be, for example, resin, and more preferably, epoxy resin.

[0060] Step S5: Cut and separate the package along the cutting line to form a single-chip surface acoustic wave filter as shown in Figure 2 Specifically, for example, a grinding wheel dicing machine is used for cutting and separation to form the final product.

[0061] According to the manufacturing method of the surface acoustic wave filter of the present embodiment, by forming steps around the upper surface of the substrate and filling the steps with a packaging layer to form a stepped coverage, moisture can be prevented from entering the chips through the planar gap formed between the packaging layer and the substrate, thereby improving the airtightness and product reliability of the CSP packaging of the surface acoustic wave filter.

[0062] In addition, by using the stepped structure around the upper surface of the substrate, the chips can be protected from dissection during the process of cutting and separating the package, achieving the purpose of protecting the chips.

[0063] The present invention has been described in detail, but the above embodiments are only examples among all embodiments, and the present invention is not limited thereto. The present invention can freely combine the various embodiments within the scope of the invention, or deform any constituent elements of the various embodiments, or omit any constituent elements of the various embodiments.

[0064] Industrial Applicability

[0065] The surface acoustic wave filter involved in the present invention can be used as a filter in the mobile phone radio frequency front end, etc.

[0066] Reference Numeral Explanation

[0067] 1A, 2A Chips

[0068] 1B, 2B Substrates

[0069] 1C, 2C Metal Balls

[0070] 1D, 2D Packaging Layers

[0071] 1E Steps

[0072] 2E Interface

[0073] 3B Overall Substrate

[0074] 3E Step Channel

[0075] 3F Dividing Line.

Claims

1. A manufacturing method of a surface acoustic wave filter, characterized in that, It includes the following steps: Prepare a whole substrate; Pre-treat the upper surface of the whole substrate according to a preset cutting line to form a stepped channel along the cutting line; Flip-chip solder multiple cut chips onto the whole substrate; Cover the whole substrate and the multiple chips with a packaging layer, and utilize the fluidity of the packaging layer to fill the stepped channel to form a package; and Cut and separate the package along the cutting line to form a single surface acoustic wave filter, The material of the packaging layer is resin.

2. The manufacturing method of the surface acoustic wave filter according to claim 1, wherein The depth range of the stepped channel is 10 - 100 μm, and the width range is 10 - 200 μm.

3. The manufacturing method of the surface acoustic wave filter according to claim 1 or 2, wherein Press the packaging layer onto the whole substrate by hot pressing.

4. The manufacturing method of the surface acoustic wave filter according to claim 1 or 2, wherein Utilize the thermocompression ultrasonic soldering process to solder the chip to the whole substrate via a metal ball.

5. The manufacturing method of the surface acoustic wave filter according to claim 1 or 2, wherein The chip is a piezoelectric chip.

6. A surface acoustic wave filter, characterized in that, The surface acoustic wave filter is obtained by using the manufacturing method of the surface acoustic wave filter according to any one of claims 1 to 5.

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