Piezoelectric wafer cutting method of surface acoustic wave filter

Abstract

The invention discloses a piezoelectric wafer cutting method for a surface acoustic wave filter, which comprises the following steps of: S1, providing a piezoelectric wafer, and arranging a plurality of discrete metal interdigital circuits on the front surface of the piezoelectric wafer; s2, smearing protective glue on the front surface of the piezoelectric wafer, wherein the protective glue covers the corresponding metal interdigital circuit; s3, pasting a layer of back protection film on the back surface of the piezoelectric wafer; s4, the piezoelectric wafer is placed on a cutting table to be fixed, a cutting knife is used for conducting linear cutting on the front face of the piezoelectric wafer to form a #-shaped cutting groove, and the cutting face of the cutting groove is provided with a functional face which is connected with the front face of the piezoelectric wafer and reflects sound waves towards the back face; the cutting grooves divide the piezoelectric wafer and the metal interdigital circuit into a plurality of independent bare chips. And S5, removing the protective glue on the front surface of each bare chip and the protective film on the back surface of each bare chip. The surface acoustic wave filter obtained by the cutting method can reduce energy reflected back from the edge.

Description

Technical Field

[0001] The invention relates to the technical field of surface acoustic wave filters, and in particular to a piezoelectric wafer cutting method for surface acoustic wave filters. Background Art

[0002] In recent years, with the rapid development of mobile communication technology, the number of surface acoustic wave filters (SAW) required in electronic products such as mobile phones and base stations has also increased rapidly, which has put forward new requirements and challenges for the performance of SAW. At present, when the SAW filter is working, the resonator inside will leak some energy. The leaked energy will be reflected by the edge of the chip and flow back into the resonator, which will interfere with the normal operation of the SAW resonator, resulting in poor performance of the SAW resonator. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a piezoelectric wafer cutting method for a surface acoustic wave filter, wherein the surface acoustic wave filter obtained by the cutting method can reduce the energy reflected back from the edge.

[0004] In order to solve the above technical problems, the technical solution of the present invention is: a piezoelectric wafer cutting method for a surface acoustic wave filter, comprising the following steps:

[0005] S1. providing a piezoelectric wafer, wherein a plurality of discrete metal interdigital circuits are arranged on the front side of the piezoelectric wafer;

[0006] S2. Apply protective glue on the front side of the piezoelectric wafer, so that the protective glue covers the corresponding metal finger circuit;

[0007] S3, applying a back protective film on the back of the piezoelectric wafer;

[0008] S4, placing the piezoelectric wafer on a cutting table and fixing it, using a cutting knife to perform a straight-line cutting from the front side of the piezoelectric wafer to form a tic-tac-toe-shaped cutting groove, wherein the cutting surface of the cutting groove has a functional surface connected to the front side of the piezoelectric wafer for reflecting the sound wave toward the back side; the cutting groove divides the piezoelectric wafer and the metal interdigital circuit into a plurality of independent bare chips;

[0009] S5. Remove the protective glue on the front side and the protective film on the back side of each bare chip.

[0010] As a preferred solution, the cutting knife cuts the front side of the piezoelectric wafer once or twice, and the cutting speed of the cutting knife is 5 mm / s-50 mm / s.

[0011] As a preferred solution, the cutting edge of the cutting knife is V-shaped, and the corresponding functional surface is a plane, and the angle between the functional surface and the front surface of the piezoelectric wafer is an obtuse angle.

[0012] As a preferred solution, when the cutting knife cuts once, the cutting depth of the cutting knife is greater than the thickness of the piezoelectric wafer, and the cross-section of the cutting groove formed after cutting is V-shaped; when the cutting knife cuts twice, the first cutting uses a thick cutting knife with a V-shaped blade, and the cutting depth is less than the thickness of the piezoelectric wafer, and the functional surface is formed after the first cutting; the second cutting uses a thin cutting knife with a thickness less than that of the subsequent cutting knife for complete cutting.

[0013] As a preferred solution, the cutting edge of the cutting knife is arc-shaped, and the corresponding functional surface is an arc surface, and the angle between the tangent line at any point of the arc surface and the front surface of the piezoelectric wafer is an obtuse angle.

[0014] As a preferred solution, the cutting knife cuts twice. The first cutting is performed using a cutting knife with an arc-shaped blade to form the functional surface, and the cutting depth is less than the thickness of the piezoelectric wafer; the second cutting is performed using a thin cutting knife with a V-shaped blade for complete cutting.

[0015] As a preferred solution, the protective glue in step S2 is photoresist, which is applied on the front side of the metal interdigital circuit of the piezoelectric wafer by a glue coating machine and then put into an oven for curing.

[0016] As a preferred solution, the method for removing the protective glue on the front side of each bare chip in step S5 is to use a degumming agent to clean the protective glue, and the back protective film is a UV protective film. The method for removing the back protective film is: placing the bare chip in a UV machine to irradiate UV to reduce the viscosity of the UV protective film, and then peeling the bare chip off the UV protective film.

[0017] After adopting the above technical scheme, the effect of the present invention is: the cutting method uses protective glue and back protective film to first protect the metal interdigital circuit and the back of the piezoelectric wafer, and then cuts the piezoelectric wafer so that the cutting surface of the cut groove has a functional surface connected to the front of the piezoelectric wafer to reflect the sound waves toward the back. In this way, when the subsequently manufactured SAW filter chip is in use, the resonator will leak part of the energy, and this energy will be reflected toward the back through the functional surface, so that the energy will not flow back into the resonator, thereby reducing the interference of the reflux energy and ensuring the stable performance of the SAW resonator.

[0018] Since the cutting blade is V-shaped, the corresponding functional surface is a plane, and the angle between the functional surface and the front surface of the piezoelectric wafer is an obtuse angle. The obtuse-angled functional surface can better reflect to the back of the piezoelectric wafer.

[0019] Furthermore, when the cutting knife cuts once, the cutting depth of the cutting knife is greater than the thickness of the piezoelectric wafer, and the cross-section of the cutting groove formed after cutting is V-shaped; when the cutting knife cuts twice, the first cutting uses a thick cutting knife with a V-shaped blade, and the cutting depth is less than the thickness of the piezoelectric wafer, and the functional surface is formed after the first cutting; during the second cutting, a thin cutting knife with a thickness less than that of the subsequent cutting knife is used for complete cutting. The above-mentioned cutting method can meet the cutting requirements of piezoelectric wafers of different thicknesses. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0021] Figure 1 is a cross-sectional view before cutting in Example 1 of the present invention;

[0022] Figure 2 is a cross-sectional view after the first cutting in Example 1 of the present invention;

[0023] Figure 3 is a cross-sectional view after the second cutting in Example 1 of the present invention;

[0024] Figure 4 is a cross-sectional view of a bare chip after cutting and debonding according to Embodiment 1 of the present invention;

[0025] Figure 5 is a cross-sectional view of Example 2 of the present invention after cutting;

[0026] Figure 6 is a cross-sectional view of a bare chip after cutting and debonding according to Embodiment 2 of the present invention;

[0027] Figure 7 is a cross-sectional view of embodiment 3 of the present invention after cutting;

[0028] Figure 8 is a cross-sectional view of a bare chip after cutting and debonding according to Embodiment 3 of the present invention;

[0029] In the attached figure: 1. piezoelectric wafer; 2. metal interdigital circuit; 3. protective glue; 4. back protective film; 5. functional surface; 6. cutting groove. DETAILED DESCRIPTION

[0030] The present invention is further described in detail below through specific examples.

[0031] Example 1

[0032] like Figure 1 As shown, a method for cutting a piezoelectric wafer 1 of a surface acoustic wave filter comprises the following steps:

[0033] S1. Provide a piezoelectric wafer 1, on the front of which a plurality of discrete metal interdigital circuits 2 are arranged; wherein the thickness of the piezoelectric wafer 1 is usually 0.25 mm;

[0034] S2. Apply protective glue 3 on the front side of the piezoelectric wafer 1, and the protective glue 3 covers the corresponding metal interdigital circuit 2; wherein the protective glue 3 is photoresist, which is applied on the front side of the metal interdigital circuit 2 of the piezoelectric wafer 1 by a glue coating machine, and then put into an oven for curing, and the speed of the glue coating machine is set at 2000rpm-5000rpm.

[0035] S3, a back side protective film 4 is pasted on the back side of the piezoelectric wafer 1; the back side protective film 4 is a UV film, and the pasting process is completed on a film pasting machine.

[0036] S4. Place the piezoelectric wafer 1 on a cutting table and fix it thereon. Use a cutting knife to make a straight cut from the front side of the piezoelectric wafer 1 to form a tic-tac-toe cutting groove 6. The cutting surface of the cutting groove 6 has a functional surface 5 connected to the front side of the piezoelectric wafer 1 for reflecting the sound waves toward the back side. The cutting groove 6 divides the piezoelectric wafer 1 and the metal interdigital circuit 2 into a number of independent bare chips. The area between the metal interdigital circuits 2 on the piezoelectric wafer 1 is defined as a cutting path area, and the cutting groove 6 is located in the cutting path area.

[0037] S5, removing the protective glue 3 on the front side and the protective film 4 on the back side of each bare chip.

[0038] Among them, the method for removing the protective glue 3 on the front side of each bare chip in step S5 is to use a degumming agent to clean the protective glue 3, and the back protective film 4 is a UV protective film. The method for removing the back protective film 4 is: putting the bare chip into a UV machine to irradiate UV to reduce the viscosity of the UV protective film, and then peeling the bare chip off the UV protective film.

[0039] The cutting knife cuts the front side of the piezoelectric wafer 1 once or twice, and the cutting speed of the cutting knife is 5mm / s-50mm / s. Spraying is performed during cutting. The spraying liquid can not only cool down, but also wash the cut particles during cutting to ensure the quality of cutting.

[0040] In this embodiment, Figures 2 to 4 As shown, the cutting knife of this embodiment cuts twice. The first cutting uses a thick cutting knife with a V-shaped blade. The cutting depth is less than the thickness of the piezoelectric wafer 1. After the first cutting, the functional surface 5 is formed. Figure 2The structure in the second cutting is that a thin cutting knife with a thickness less than that of the last cutting knife is used for complete cutting. At this time, the cutting surface is perpendicular to the surface of the piezoelectric wafer 1. Since the thin cutting knife used for the second cutting is thinner than the thick cutting knife used for the first time, the functional surface 5 of the first cutting will be retained during cutting. The final bare chip is used for the thick process of the surface acoustic wave filter. As long as the functional surface 5 connected to the surface of the piezoelectric wafer 1 is ensured, the leaked energy can be reflected to the back.

[0041] Example 2

[0042] like Figure 5 and Figure 6 As shown, the cutting method of this embodiment is basically the same as the method of embodiment 1, except that the number of cuts in this embodiment is one, the cutting edge of the cutting knife is V-shaped, the corresponding functional surface 5 is a plane, and the angle between the functional surface 5 and the front surface of the piezoelectric wafer 1 is an obtuse angle. The cutting depth of the cutting knife is greater than the thickness of the piezoelectric wafer 1, and the cross-section of the cutting groove 6 formed after cutting is V-shaped. A V-shaped cutting groove 6 is formed on the piezoelectric wafer 1 through one cutting, and of course, the functional surface 5 is correspondingly formed.

[0043] Example 3

[0044] like Figure 7 and Figure 8 As shown, the cutting edge of the cutting knife in this embodiment is arc-shaped, and the corresponding functional surface 5 is an arc surface. The angle between the tangent line at any point of the arc surface and the front surface of the piezoelectric wafer 1 is an obtuse angle. The number of cutting times in this embodiment is preferably two. The first cutting uses an arc-shaped cutting knife, and the functional surface 5 is formed during cutting. The cutting depth is less than the thickness of the piezoelectric wafer 1. The second cutting uses a thin cutting knife with a V-shaped cutting edge for complete cutting.

[0045] The above-described embodiments are merely descriptions of preferred implementations of the present invention and are not intended to limit the scope of the present invention. Various modifications and alterations to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the scope of protection defined by the claims of the present invention.

Claims

1. A piezoelectric wafer cutting method for a surface acoustic wave filter, characterized in that: The following steps are involved: S1. providing a piezoelectric wafer, wherein a plurality of discrete metal interdigital circuits are arranged on the front side of the piezoelectric wafer; S2. Apply protective glue on the front side of the piezoelectric wafer, so that the protective glue covers the corresponding metal finger circuit; S3, applying a back protective film on the back of the piezoelectric wafer; S4, placing the piezoelectric wafer on a cutting table and fixing it, using a cutting knife to perform a straight-line cutting from the front side of the piezoelectric wafer to form a tic-tac-toe-shaped cutting groove, wherein the cutting surface of the cutting groove has a functional surface connected to the front side of the piezoelectric wafer for reflecting the sound wave toward the back side; the cutting groove divides the piezoelectric wafer and the metal interdigital circuit into a plurality of independent bare chips; S5. Remove the protective glue on the front side and the protective film on the back side of each bare chip.

2. The piezoelectric wafer cutting method of a surface acoustic wave filter according to claim 1, characterized in that: The cutting knife cuts the front side of the piezoelectric wafer once or twice, and the cutting speed of the cutting knife is 5mm / s-50mm / s.

3. The piezoelectric wafer cutting method of a surface acoustic wave filter according to claim 2, characterized in that: The cutting edge of the cutting knife is V-shaped, and the corresponding functional surface is a plane, and the angle between the functional surface and the front surface of the piezoelectric wafer is an obtuse angle.

4. The piezoelectric wafer cutting method of a surface acoustic wave filter according to claim 3, characterized in that: When the cutting knife cuts once, the cutting depth of the cutting knife is greater than the thickness of the piezoelectric wafer, and the cross-section of the cutting groove formed after cutting is V-shaped; when the cutting knife cuts twice, the first cutting uses a thick cutting knife with a V-shaped blade, and the cutting depth is less than the thickness of the piezoelectric wafer. After the first cutting, the functional surface is formed; during the second cutting, a thin cutting knife with a thickness less than that of the subsequent cutting knife is used for complete cutting.

5. The piezoelectric wafer cutting method of a surface acoustic wave filter according to claim 2, characterized in that: The cutting edge of the cutting knife is arc-shaped, and the corresponding functional surface is an arc surface. The angle between the tangent line at any point of the arc surface and the front surface of the piezoelectric wafer is an obtuse angle.

6. The piezoelectric wafer cutting method of a surface acoustic wave filter according to claim 5, characterized in that: The cutting knife cuts twice. The first cutting is performed using a cutting knife with an arc-shaped blade to form the functional surface, and the cutting depth is less than the thickness of the piezoelectric wafer. The second cutting is performed using a thin cutting knife with a V-shaped blade to perform complete cutting.

7. The piezoelectric wafer cutting method of a surface acoustic wave filter according to claim 1, characterized in that: The protective glue in step S2 is photoresist, which is applied on the front side of the metal interdigital circuit of the piezoelectric wafer by a glue coating machine and then put into an oven for curing.

8. The piezoelectric wafer cutting method of a surface acoustic wave filter according to claim 7, characterized in that: In step S5, the protective glue on the front of each bare chip is removed by using a degumming agent to clean the protective glue. The back protective film is a UV protective film. The method for removing the back protective film is: placing the bare chip in a UV machine to irradiate UV to reduce the viscosity of the UV protective film, and then peeling the bare chip off the UV protective film.

Images