Filter and packaging method therefor

Abstract

Provided in the present invention is a filter packaging method. The filter packaging method comprises: providing a substrate, wherein a resonance structure is formed on the surface of the substrate, the resonance structure comprises a resonance body and electrodes located on two sides of the resonance body, and the surface of each electrode comprises a first area close to the resonance body and a second area away from the resonance body; forming walls in the first areas on the electrodes, the walls surrounding the resonance body; forming a second thin film layer on a carrier plate, and performing a patterning treatment on the second thin film layer to form a roof; aligning the surface of the carrier plate where the roof is formed with the surface of the substrate where the resonance structure is formed, and then bonding the roof to the walls so as to form a cavity required for the operation of the resonance body; and removing the carrier plate. In this way, the problems of an uneven covered film and a poor bonding strength of the covered film when the film covers the wall to manufacture a cavity can be prevented, thereby improving the reliability of a filter; moreover, the process cost is low, the control difficulty is small, and the yield of finished products is high. Further provided in the present invention is a filter manufactured by using the packaging method.

Description

Filter and packaging method thereof Technical Field

[0001] The present invention relates to the field of packaging technology, and in particular to a filter and a packaging method for the filter. Background Art

[0002] Surface acoustic wave (SAW) filters are important components in the RF front end. Their working principle is that sound waves are transmitted on the chip surface. The packaging of the SAW filter must prevent the surface of the IDT from contacting other substances to ensure the working space of the IDT.

[0003] Figure 1 is a cross-sectional schematic diagram of an existing filter. Referring to Figure 1, the packaging method of the filter includes: attaching a first PI film layer (Polyimide Film) to the surface of a wafer 101, and forming a support wall 102 (wall) by exposure, development, and photolithography; attaching a second PI film layer as a cover film 106 (Roof) to the surface of the wafer 101 again to form a cavity 104 required for the operation of the interdigital transducer 103; removing the first PI film layer and the second PI film layer above the signal port 107 by exposure, development, and photolithography again to expose the signal port 107; applying solder paste or solder balls to the exposed area of ​​the signal port 107, and then reflowing to form a pin 105 leading to the signal port 107. However, in the packaging method of the filter, when attaching the second PI film layer to the support wall 102, problems such as uneven coating and poor coating bonding strength are easily encountered, which can easily lead to reliability problems such as cavity collapse and peeling of the cover film.

[0004] Another existing filter packaging method includes: forming an amorphous layer in a first wafer through ion implantation, then etching the first wafer to form a cover plate on one side of the first wafer, which is located on the amorphous layer; bonding the cover plate of the first wafer to a second wafer with an IDT formed on its surface to form a cavity required for the IDT to operate; and then separating the cover plate from the non-cover plate side of the first wafer at the location of the amorphous layer. However, this process for making a bonded cover plate is complex and costly, and the thickness and flatness of the amorphous layer formed by ion implantation are difficult to control, resulting in high process control difficulties and low product yield. Summary of the Invention

[0005] One of the purposes of the present invention is to provide a filter and a packaging method thereof, which can avoid the problems of uneven coating and poor coating bonding when the cavity is made by coating on the support wall, improve the reliability of the filter, and have a simple process flow, low process cost, low process control difficulty, and high finished product yield.

[0006] To achieve the above-mentioned object, one aspect of the present invention provides a method for packaging a filter. The method comprises: providing a substrate, wherein a resonant structure is formed on a surface of the substrate, wherein the resonant structure includes a resonator and electrodes located on both sides of the resonator, wherein the surface of the electrode includes a first region close to the resonator and a second region away from the resonator; forming a support wall on the first region of the electrode, wherein the support wall surrounds the resonator; providing a carrier; forming a second thin film layer on the carrier, and patterning the second thin film layer to form a cover film; aligning the surface of the carrier with the cover film formed on the surface of the substrate with the resonant structure formed, bonding the cover film and the support wall to form a cavity required for the operation of the resonator; and removing the carrier.

[0007] Optionally, the method for forming the support wall on the first region of the electrode includes: forming a first thin film layer on the substrate; and patterning the first thin film layer to form the support wall.

[0008] Optionally, the first film layer and the second film layer are made of the same material.

[0009] Optionally, the second film layer includes a polyimide film, an epoxy resin film or a semiconductor material layer.

[0010] Optionally, in the step of providing a carrier board, an adhesive layer is formed on the surface of the carrier board; and the second film layer is formed on the adhesive layer.

[0011] Optionally, the packaging method of the filter also includes: after removing the carrier board, forming a redistribution layer on the substrate, a portion of the redistribution layer is located on the cover film, and another portion of the redistribution layer covers the second area of ​​the electrode to be electrically connected to the electrode; and forming a signal pin on the redistribution layer.

[0012] Optionally, the signal pin is located on a redistribution layer above the cover film.

[0013] Optionally, the signal pin corresponds to the position of the supporting wall.

[0014] Optionally, the support wall is annular, and the width of the cover film is greater than the inner ring width of the support wall and less than or equal to the outer ring width of the support wall.

[0015] Another aspect of the present invention provides a filter, which is manufactured using the above-mentioned filter packaging method.

[0016] In the filter and packaging method thereof provided by the present invention, a support wall is formed on the first area of ​​the electrode, a cover film is formed on the carrier, and then the cover film is bonded to the support wall to form a cavity required for the operation of the resonator. This avoids the cavity formation method of forming a cavity by covering the support wall with a film, avoids the problems of uneven covering and poor bonding force, and further improves the problems of easy deformation of the cavity and easy peeling of the cover film, thereby improving the reliability of the filter, and has a simple process flow, low process cost, low process control difficulty, and high finished product yield.

[0017] Furthermore, after removing the carrier board, a rewiring layer electrically connected to the electrode and covering part of the cover film is formed on the substrate, and then a signal pin is formed on the rewiring layer above the cover film. In this way, the signal pin is located at the top of the filter. When the filter is flipped on the substrate for secondary packaging, the air around the signal pin is easily discharged, so that the plastic encapsulation material can be fully filled around the signal pin, which can improve the problem of voids around the signal pin. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] FIG1 is a cross-sectional schematic diagram of an existing filter.

[0019] FIG2 is a flow chart of a filter packaging method provided by an embodiment of the present invention.

[0020] 3 to 10 are schematic structural diagrams of the steps of a filter packaging method according to an embodiment of the present invention.

[0021] FIG11 is a cross-sectional schematic diagram of a filter provided in accordance with an embodiment of the present invention.

[0022] Description of reference numerals:

[0023] (Figure 1) 101 - wafer; 102 - support wall; 103 - IDT; 104 - cavity; 105 - pin; 106 - cover film; 107 - signal port;

[0024] (Figures 3 to 11) 201-substrate; 202-electrode; 202a-second region of the electrode; 203-resonator; 204-support wall; 301-carrier; 302a-second thin film layer; 302-cover film; 401-cavity; 402-rewiring layer; 403-signal pin. DETAILED DESCRIPTION

[0025] The filter and packaging method proposed in the present invention are further described in detail below, with reference to the accompanying drawings and specific embodiments. The advantages and features of the present invention will become more apparent from the following description. It should be noted that the accompanying drawings are highly simplified and not to exact scale, and are intended solely to facilitate and clearly illustrate the embodiments of the present invention.

[0026] As used in the present invention, the singular forms "a", "an", and "the" include plural objects, and the term "or" is generally used in a sense including "and / or". Unless otherwise indicated, "upper / upper layer" and / or "lower / lower layer" and similar words are only for convenience of explanation and are not limited to one position or one spatial orientation. The terms "first", "second", and "third" are used for descriptive purposes only and are not to be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features specified as "first", "second", and "third" may explicitly or implicitly include one or at least two of the features.

[0027] The core idea of ​​the present invention is to pre-fabricate a cover film on a carrier board, bond the cover film to the supporting wall on the electrode to form a cavity required for the resonator to work, and then remove the carrier board. This avoids the cavity formation method of forming a cavity by covering the support wall with a film, avoids the problems of uneven covering and poor bonding force, and thus improves the problems of easy deformation of the cavity and easy peeling of the cover film, thereby improving the reliability of the filter. In addition, the process flow is simple, the process cost is low, the process control difficulty is small, and the finished product yield is high.

[0028] FIG2 is a flow chart of a filter packaging method according to an embodiment of the present invention. As shown in FIG2 , the filter packaging method according to this embodiment includes:

[0029] Step S1, providing a substrate, wherein a resonant structure is formed on a surface of the substrate, wherein the resonant structure includes a resonator and electrodes located on both sides of the resonator, wherein a surface of the electrode includes a first region close to the resonator and a second region away from the resonator;

[0030] Step S2, forming a support wall on the first region of the electrode, wherein the support wall surrounds the resonator;

[0031] Step S3, providing a carrier board;

[0032] Step S4, forming a second thin film layer on the carrier, and performing patterning on the second thin film layer to form a cover film;

[0033] Step S5, aligning the surface of the carrier plate with the cover film formed thereon with the surface of the substrate with the resonant structure formed thereon, bonding the cover film and the support wall to form a cavity required for the resonator to work; and

[0034] Step S6: removing the carrier board.

[0035] It should be understood that, although the various steps in the flowchart of FIG2 are shown in sequence as indicated by the arrows, these steps are not necessarily performed in the order indicated by the arrows. Unless otherwise specified herein, there is no strict order restriction on the execution of these steps, and these steps can be performed in other orders. Moreover, at least a portion of the steps in FIG2 may include multiple steps or multiple stages, and these steps or stages are not necessarily performed at the same time, but can be performed at different times. The execution order of these steps or stages is not necessarily to be performed in sequence, but can be performed in turn or alternately with other steps or at least a portion of steps or stages in other steps.

[0036] Figures 3 to 10 are schematic diagrams illustrating the steps of a filter packaging method according to an embodiment of the present invention. Figure 11 is a schematic cross-sectional view of a filter according to an embodiment of the present invention. The filter packaging method according to this embodiment is described below in conjunction with Figures 2 and 3 to 11.

[0037] Perform step S1, as shown in Figure 3, to provide a substrate 201, wherein a resonant structure is formed on the surface of the substrate 201, and the resonant structure includes a resonator 203 and electrodes 202 located on both sides of the resonator 203, and the surface of the electrode 202 includes a first area close to the resonator 203 and a second area away from the resonator 203.

[0038] For example, the resonator 203 may be an interdigital transducer (IDT). Step S1 may include: forming a metal layer on the surface of the provided substrate 201; patterning the metal layer to form the resonator 203 and electrodes 202 on both sides of the resonator 203; and electroplating metal on the surface of the electrode 202 to increase the height of the electrode 202. Electroplating metal on the surface of the electrode 202 to increase the height of the electrode 202 can increase the height of the subsequently formed cavity, ensuring that a cavity that meets the normal operation requirements of the resonator 203 can be formed.

[0039] Exemplarily, the substrate 201 may be a piezoelectric substrate, and the material of the piezoelectric substrate may include piezoelectric materials such as aluminum nitride (AlN), quartz, lithium niobate or lithium tantalate. The material of the interdigital transducer, i.e., the material of the metal layer, may include metal materials such as aluminum (Al), copper (Cu), gold (Au), silver (Ag), chromium (Cr), titanium (Ti) or tungsten (W), and may also include alloy materials of the above metal materials. The metal electroplated on the electrode 202 may include nickel gold or nickel palladium gold. The thickness of the electrode 202 may be 1 μm to 5 μm, but is not limited thereto.

[0040] Step S2 is performed, as shown in FIG4 , to form a support wall 204 (wall) on the first region of the electrode 202 , wherein the support wall 204 surrounds the resonator 203 .

[0041] Specifically, step S2 may include: forming a first thin film layer on the substrate 201, the first thin film layer covering the electrode 202, the resonator 203 and the surface of the substrate 201; performing patterning on the first thin film layer, retaining the first thin film layer on the first area of ​​the electrode 202 to form a support wall 204, and removing the first thin film layer in other areas.

[0042] Exemplary materials for the first thin film layer include, but are not limited to, polyimide film, epoxy resin film, or a semiconductor material layer. The semiconductor material layer is, for example, a silicon wafer. The first thin film layer can be a photosensitive resist material, allowing exposure and development of the first thin film layer to form the support walls 204. This simplifies the process and improves the precision of the support walls 204. The first thin film layer can also be a layer of other materials that lack photosensitive properties. When patterning the first thin film layer, a patterned mask layer can be first formed on the first thin film layer, and then, using the patterned mask layer as a mask, the first thin film layer can be etched to form the support walls 204.

[0043] As shown in FIG. 3 , a plurality of resonant structures may be formed on the substrate 201 , so that a plurality of filters may be packaged at the same time, thereby improving packaging efficiency.

[0044] Steps S3 and S4 are performed. Referring to Figures 5 and 6 , a carrier board 301 is provided. A second thin film layer 302a is formed on the carrier board 301. The second thin film layer 302a is patterned to form a cover film 302 (roof). As shown in Figure 6 , multiple cover films 302 can be formed simultaneously on the carrier board 301.

[0045] Exemplarily, the carrier 301 is a hard carrier, such as a wafer or a glass plate.

[0046] An adhesive layer (not shown) may be formed on the surface of the carrier 301 , and the second film layer 302 a may be attached to the adhesive layer, so as to facilitate subsequent separation of the carrier 301 and the cover film 302 .

[0047] Exemplarily, the material of the second thin film layer 302a may include, but is not limited to, a polyimide film, an epoxy resin film, or a semiconductor material layer. The semiconductor material layer may be, for example, a silicon wafer. The second thin film layer 302a may be a photosensitive resist material, so that the second thin film layer 302a can be exposed and developed to form the cap film 302. This simplifies the process and increases the precision of the cap film 302. The second thin film layer 302a may also be a layer of other material without photosensitive properties. When patterning the second thin film layer 302a, a patterned mask layer may be first formed on the second thin film layer 302a. The patterned mask layer is then used as a mask to etch the second thin film layer 302a to form the cap film 302.

[0048] Preferably, the material of the second film layer 302a is the same as that of the first film layer. This allows the bonded support walls 204 and cover film 302 to be made of the same material, eliminating the issue of a significant difference in coefficient of thermal expansion (CTE) between the two. This improves bonding reliability and the reliability of the filter. In other embodiments of the present application, the materials of the support walls 204 and cover film 302 may be different. For example, the materials of the support walls 204 and cover film 302 may be resin or PI-based materials, and the material of the cover film 302 may also be silicon or glass.

[0049] 7 , align the surface of the carrier 301 with the cover film 302 to the surface of the substrate 201 with the resonant structure, and bond the cover film 302 and the support wall 204 to form a cavity 401 required for the resonator 203 to work.

[0050] For example, the cover film 302 and the support wall 204 may be bonded by thermal compression bonding or the like.

[0051] As shown in Figure 7, the support wall 204 can be annular, and the width of the cover film 302 is greater than the inner ring width of the support wall 204 and less than or equal to the outer ring width of the support wall 204. In this way, after the cover film 302 is aligned and bonded to the support wall 204, the cover film 302 will not block the second area of ​​the electrode 202.

[0052] Step S6 is executed, as shown in FIG8 , in which the carrier 301 is removed to expose the second region 202 a of the electrode.

[0053] 9 , a redistribution layer 402 is formed on the substrate 201 . A portion of the redistribution layer 402 is located on the cap film 302 , and another portion of the redistribution layer 402 covers the second region of the electrode 202 to be electrically connected to the electrode 202 .

[0054] For example, the redistribution layer 402 may be formed by electroplating. The redistribution layer 402 may be made of metal such as copper.

[0055] It should be noted that, referring to Figures 8 and 9, the support wall 204 is bonded to the first area of ​​the electrode 202, and the second area 202a of the electrode is reserved, so that after removing the carrier 301, the second area 202a of the electrode can be exposed, and then the redistribution layer 402 can be directly formed on the second area of ​​the electrode 202, and the process flow is simple.

[0056] Referring to FIG. 10 , signal pins 403 are formed on the redistribution layer 402 .

[0057] In this embodiment, the signal pins 403 may be solder balls. A method for forming the signal pins 403 on the redistribution layer 402 may include: planting solder balls on the redistribution layer 402, and then performing a reflow process to solder the solder balls to the redistribution layer 402 to form the signal pins 403. In other embodiments, the signal pins 403 may also be formed on the redistribution layer 402 through an electroplating process.

[0058] As shown in reference figure 10, the signal pin 403 can be located on the redistribution layer 402 above the cover film 302. In this way, the signal pin is located on the top of the filter. When the filter is subsequently flipped on the substrate for secondary packaging, the air around the signal pin is easily discharged, so that the plastic encapsulation material can be fully filled around the signal pin, which can improve the problem of voids around the signal pin.

[0059] In this embodiment, the signal pin 403 corresponds to the position of the support wall 204, that is, the signal pin 403 is located directly above the support wall 204, thereby avoiding the formation of the signal pin 403 directly above the cavity 401, which is beneficial to avoiding the influence of the signal pin 403 on the reliability of the cavity.

[0060] 10 and 11 , the substrate 201 is cut to obtain a plurality of individual filters.

[0061] This embodiment further provides a filter, which can be manufactured using the above-mentioned filter packaging method.

[0062] As shown in Figure 11, the filter includes a substrate 201, a resonant structure, support walls 204, and a cover film 302. The resonant structure is formed on the surface of the substrate 201 and includes a resonator 203 and electrodes 202 located on either side of the resonator 203. The electrodes 202 include a first region proximal to the resonator 203 and a second region distal to the resonator 203. The support walls 204 are formed on the first region of the electrodes 202 and surround the resonator 203. The cover film 302 is pre-formed on a carrier board and bonded to the support walls 204 to form a cavity 401 necessary for the operation of the resonator 203.

[0063] The filter further includes a redistribution layer 402 and a signal pin 403. A portion of the redistribution layer 402 is located on the cover film 302, while another portion of the redistribution layer 402 covers the second region of the electrode 202 to provide electrical connection thereto. The signal pin 403 is formed on the redistribution layer 402 above the cover film 302. Preferably, the signal pin 403 corresponds to the position of the support wall 204.

[0064] In the filter and packaging method thereof provided in this embodiment, a support wall 204 is formed on the first area of ​​the electrode 202, a cover film 302 is formed on the carrier 301, and then the cover film 302 is bonded to the support wall 204 to form a cavity 401 required for the operation of the resonator 203. This avoids the cavity formation method of forming a cavity by coating the support wall, avoids the problems of uneven coating and poor bonding force, and further improves the problems of easy deformation of the cavity and easy peeling of the cover film, thereby improving the reliability of the filter. In addition, the process flow is simple, the process cost is low, the process control difficulty is small, and the finished product yield is high.

[0065] Furthermore, after removing the carrier 301, a redistribution layer 402 is formed on the substrate 201, which is electrically connected to the electrode 202 and covers a portion of the cover film 302, and then a signal pin 403 is formed on the redistribution layer 402 above the cover film 302. In this way, the signal pin is located at the top of the filter. When the filter is flipped on the substrate for secondary packaging, the air around the signal pin is easily discharged, so that the plastic encapsulation material can be fully filled around the signal pin, which can improve the problem of voids around the signal pin.

[0066] It should be noted that this specification adopts a progressive description method, and the later description parts focus on the differences from the previous description parts. The same and similar parts between the various parts can be referred to each other.

[0067] The above description is only a description of the preferred embodiment of the present invention, and does not limit the scope of the rights of the present invention. Any person skilled in the art can make possible changes and modifications to the technical solution of the present invention by using the methods and technical contents disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall fall within the scope of protection of the technical solution of the present invention.

Claims

1. A packaging method for a filter, characterized in that, Comprising: Providing a substrate, on the surface of which a resonant structure is formed, the resonant structure including a resonator and electrodes located on both sides of the resonator, and the surface of the electrodes including a first region close to the resonator and a second region far from the resonator; Forming a support wall on the first region of the electrodes, the support wall surrounding the resonator; Providing a carrier plate; Forming a second thin film layer on the carrier plate and patterning the second thin film layer to form a cover film; Aligning the surface of the carrier plate with the cover film formed thereon with the surface of the substrate with the resonant structure formed thereon, and bonding the cover film and the support wall to form a cavity required for the resonator to operate; And Removing the carrier plate.

2. The encapsulation method of the filter according to claim 1, characterized in that The method of forming a support wall on the first region of the electrodes includes: Forming a first thin film layer on the substrate; and Patterning the first thin film layer to form the support wall.

3. The encapsulation method of the filter according to claim 2, wherein, The first thin film layer and the second thin film layer are made of the same material.

4. The encapsulation method of the filter according to claim 1, characterized in that The second thin film layer includes a polyimide film, an epoxy resin film or a semiconductor material layer.

5. The encapsulation method of the filter according to claim 1, wherein, In the step of providing a carrier plate, an adhesive layer is formed on the surface of the carrier plate; the second thin film layer is formed on the adhesive layer.

6. The encapsulation method of the filter according to claim 1, characterized in that, Further comprising: After removing the carrier plate, forming a redistribution layer on the substrate, a part of the redistribution layer being located on the cover film, and another part of the redistribution layer covering the second region of the electrodes to be electrically connected to the electrodes; And Forming signal pins on the redistribution layer.

7. The encapsulation method of the filter according to claim 6, characterized in that, The signal pins are located on the redistribution layer above the cover film.

8. The encapsulation method of the filter according to claim 7, characterized in that, The signal pins correspond to the positions of the support walls.

9. The encapsulation method of the filter according to any one of claims 1 to 8, characterized in that, The support wall is annular, and the width of the cover film is greater than the inner ring width of the support wall and less than or equal to the outer ring width of the support wall.

10. The encapsulation method of the filter according to claim 1, characterized in that, The method of forming a resonant structure on the surface of the substrate includes: forming a metal layer on the surface of the substrate; patterning the metal layer to form the resonator and the electrodes on both sides of the resonator; electroplating metal on the surface of the electrodes to increase the thickness of the electrodes.

11. The encapsulation method of the filter according to claim 10, characterized in that, The metal electroplated on the electrodes includes nickel-gold or nickel-palladium-gold.

12. The encapsulation method of the filter according to claim 1, characterized in that, The second thin film layer is a photosensitive resist material.

13. The packaging method of the filter according to claim 6, characterized in that, The method of forming signal pins on the redistribution layer includes: implanting solder balls on the redistribution layer and then performing a reflow soldering process to solder the solder balls on the redistribution layer to form the signal pins.

14. The encapsulation method of the filter according to claim 1, characterized in that The thickness of the electrodes is 1μm - 5μm.

15. A filter, characterized in that, The filter is manufactured by using the packaging method of the filter according to any one of claims 1 to 14, and the filter includes: A substrate, on the surface of which a resonant structure is formed, the resonant structure including a resonator and electrodes located on both sides of the resonator, and the surface of the electrodes including a first region close to the resonator and a second region far from the resonator; A support wall, formed on the first region of the electrodes and surrounding the resonator; and A cover film, bonded to the support wall to form a cavity required for the resonator to operate.

16. The filter according to claim 15, wherein, Further comprising a redistribution layer, a part of the redistribution layer being located on the cover film, and another part of the redistribution layer covering the second region of the electrodes to be electrically connected to the electrodes.

17. The filter according to claim 16, wherein It further includes signal pins, which are formed on a redistribution layer above the cover film.

18. The filter according to claim 17, wherein The signal pins correspond to the positions of the support walls.

19. The filter according to claim 15, characterized in that, The support walls are annular, and the width of the cover film is greater than the inner ring width of the support walls and less than or equal to the outer ring width of the support walls.

20. The filter according to claim 15, characterized in that, The thickness of the electrode is 1 μm to 5 μm.

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