A packaging structure of a cavity filter and a manufacturing method thereof

Abstract

The present invention discloses a packaging structure for a cavity filter and a method for manufacturing the same. The packaging structure includes a filter chip, a cap layer, and a sealing structure. The sealing structure forms a closed ring on the non-resonant region of the filter chip. A bump is provided above the chip pad of the filter chip. The chip pad is provided inside or outside the closed ring. The cap layer includes a reinforcement structure layer and an annular metal structure and a block metal structure respectively embedded in the reinforcement structure layer and spaced apart. The sealing structure and the bump are aligned and bonded to the annular metal structure and the block metal structure respectively between the cap layer and the filter chip through an alignment structure to form a cavity above the resonant region. A metal lead is provided on the surface of the cap layer away from the cavity. Alignment can be achieved through the alignment structure, which can effectively improve chip offset, wafer warping, and cavity limitations, thereby achieving ultra-thin packaging with better performance while saving costs.

Description

Technical Field

[0001] The present invention relates to the field of wafer-level packaging, and in particular to a packaging structure of a cavity filter and a manufacturing method thereof. Background Art

[0002] Filters offer advantages such as small size, light weight, low loss, and good frequency selectivity. The filter market is growing rapidly as wireless communication frequency bands increase. Filters are widely used in RF front-end chips, and surface acoustic wave (SAW) filters are also core components within duplexers and multiplexers. Currently, the primary packaging technology for SAW filters is still wire-bonded ceramic, metal, and plastic packaging, as well as surface mount and flip-chip packaging. Existing packaging and structures for these filters have the following disadvantages:

[0003] 1. Existing packaging has strict requirements on the flatness of the substrate and sealing cover, which can easily cause product reliability failure.

[0004] 2. A series of uncertainties such as device installation accuracy, the influence of signal wires, and welding angles will lead to inconsistency in device performance and even damage the filter.

[0005] 3. The size of the existing packaging substrate is large and does not meet the current requirements for miniaturization.

[0006] 4. Some existing packaging forms are too thick and do not meet the requirements of current RF modules.

[0007] 5. The following problems are prone to occur when the back of existing surface acoustic wave filters is plastic-sealed: excessive plastic encapsulation material enters the cavity formed by the package, resulting in performance degradation or failure; insufficient plastic encapsulation material filling leads to gaps, and water vapor or other materials may invade the finished product during use, affecting product reliability; the shape and size of the holes filled by the plastic encapsulation material are uncontrolled and may vary with differences in product type, material batch, and plastic encapsulation surface condition, resulting in poor process repeatability and stability. Summary of the Invention

[0008] The purpose of the present invention is to overcome the deficiencies in the prior art and to provide a packaging structure of a cavity filter and a manufacturing method thereof.

[0009] In order to achieve the above objectives, the technical solution of the present invention is:

[0010] A packaging structure of a cavity filter, comprising:

[0011] A filter chip, the filter chip comprising a resonant region and a non-resonant region outside the resonant region, a chip pad being provided on the non-resonant region, and a bump being provided on the chip pad;

[0012] A sealing structure, wherein the sealing structure forms a closed ring on the non-resonant region of the filter chip, and the chip pad is located inside or outside the closed ring;

[0013] a capping layer, the capping layer comprising a strengthening structure layer and an annular metal structure and a plurality of block metal structures embedded in the strengthening structure layer and spaced apart, the annular metal structure and the block metal structure being flush with a surface of the strengthening structure layer;

[0014] an alignment structure, disposed on a surface of the cap layer facing the filter chip, and aligning and bonding the sealing structure and the bumps on the filter chip to the annular metal structure and the block metal structure, respectively, to form a cavity above the resonance region;

[0015] The metal lead-out terminal is arranged on a surface of the cap layer away from the cavity.

[0016] Preferably, the alignment structure includes a barrier layer and a first through hole and a second through hole on the barrier layer, wherein the first through hole and the second through hole correspond to positions of the annular metal structure and the block metal structure, respectively.

[0017] Preferably, the material of the barrier layer is photoresist or dry film, and the thickness of the barrier layer is in the range of 10-40 um.

[0018] Preferably, a third through hole exposing the cap layer is provided on the barrier layer, and the cavity is provided between the cap layer exposed through the third through hole and the filter chip.

[0019] Preferably, the projection area of the bulk metal structure on the filter chip is located in the non-resonant area.

[0020] Preferably, the reinforcement structure layer is made of insulating material, and the thickness of the cap layer is 20-50 μm.

[0021] Preferably, the sealing structure and the bumps are made of metal pillars or solder balls, and the thickness of the sealing structure and the bumps is 5-60 μm.

[0022] Preferably, the metal lead-out terminal is a solder pad or a solder ball, and a protective layer covering the solder ball is provided above the cap layer.

[0023] A method for manufacturing a packaging structure based on the above-mentioned cavity filter comprises the following steps:

[0024] 1) Providing a filter wafer, wherein a filter chip is provided on the filter wafer, wherein the filter chip includes a resonant region and a non-resonant region outside the resonant region, wherein a chip pad is provided on the non-resonant region, and a bump is formed on the chip pad. The sealing structure forms a closed loop on the non-resonant region on the filter chip, and the chip pad is located inside or outside the closed loop. The filter wafer is cut to obtain a single filter chip having the bump and the sealing structure;

[0025] 2) Providing a carrier wafer, wherein the carrier wafer surface is covered with an adhesive layer, and forming a cap layer above the adhesive layer, wherein the cap layer includes a strengthening structure layer and an annular metal structure and a plurality of block metal structures embedded in the strengthening structure layer and spaced apart, wherein the annular metal structure and the block metal structure are flush with the surface of the strengthening structure layer, and an alignment structure is formed on the surface of the cap layer;

[0026] 3) bonding the sealing structure and the bumps on the filter chip to the annular metal structure and the block metal structure respectively through the alignment structure to form a cavity above the resonance region;

[0027] 4) removing the adhesive layer and the carrier wafer, and fabricating metal leads above the cap layer.

[0028] Preferably, in step 2, a registration structure is produced on the surface of the cap layer, specifically comprising: producing a retaining layer on the surface of the cap layer, and patterning the retaining layer to form a first through hole and a second through hole that expose the annular metal structure and the block metal structure respectively.

[0029] Preferably, step 2 further includes: patterning the retaining layer at a position corresponding to the resonance region of the filter chip to form a third through hole, and forming the cavity between the cap layer exposed through the third through hole and the filter chip.

[0030] Preferably, in step 2, a capping layer is produced above the bonding layer, specifically comprising: producing the annular metal structure and several block metal structures above the bonding layer, coating a reinforcement structure layer covering the annular metal structure and the block metal structure above the bonding layer, and flattening the surface of the reinforcement structure layer until the annular metal structure and the block metal structure are exposed.

[0031] Preferably, the projection area of the bulk metal structure on the filter chip is located in the non-resonant area.

[0032] Preferably, reflow soldering is used for alignment bonding in step 3.

[0033] Preferably, the metal lead-out terminal is a pad, and the step 4 of manufacturing the metal lead-out terminal above the cap layer specifically includes: manufacturing the pad above the block metal structure.

[0034] Preferably, the metal lead-out terminal is a solder ball, and the step 4 of making the metal lead-out terminal above the cap layer specifically includes: making a solder ball above the bulk metal structure and a protective layer around the solder ball.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] (1) The present invention adopts wafer-level packaging to first form an annular metal structure and a block metal structure on a carrier wafer, then make a sealing structure on the filter chip and make bumps on the chip pad, and then flip-chip the cut filter chip onto the annular metal structure and the block metal structure for alignment bonding. The annular metal structure and the block metal structure are first formed and then aligned and bonded, and finally wafer-level packaging is performed. Compared with the existing technology, the substrate is omitted in the structure, and the wafer-level packaging can reduce the size and thickness of the package, and has better heat dissipation and electrical performance.

[0037] (2) The present invention adopts a sealing structure surrounding the outer periphery of the filter chip to play a protective role, eliminating the need for film and plastic packaging. It can not only reduce the process steps and save costs, but also improve the shortcomings of film and plastic packaging such as insufficient reliability, poor process repeatability and poor stability.

[0038] (3) The packaging structure of the cavity filter of the present invention utilizes a convex point and a sealing structure to form a cavity, which not only has excellent anti-molding performance and can be applied to the field of products requiring large cavities, but also has cost advantages. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 This is a schematic structural diagram of the packaging structure of the cavity filter according to the first embodiment of the present application;

[0040] Figures 2a-2f This is a flow chart of a method for manufacturing a packaging structure of a cavity filter according to the first embodiment of the present application;

[0041] Figure 3 This is a schematic structural diagram of the packaging structure of the cavity filter of the second embodiment of the present application. DETAILED DESCRIPTION

[0042] The present invention is further explained below with reference to the accompanying drawings and specific embodiments. The drawings are provided for illustrative purposes only to facilitate understanding of the present invention, and their specific proportions may be adjusted according to design requirements. Those skilled in the art will understand that the vertical relationships between components and the definitions of front and back in the figures described herein refer to the relative positions of components. Therefore, they can be flipped to present the same components, and all such representations are within the scope of this specification.

[0043] Example 1

[0044] refer to Figure 1 The embodiment of the present application proposes a packaging structure for a cavity filter, comprising a filter chip 401, a cap layer 301, a sealing structure 407, and an alignment structure. The filter chip 401 comprises a resonant region 402 and a non-resonant region outside the resonant region 402, wherein a chip pad 403 is provided on the non-resonant region, and a bump 405 is provided on the chip pad 403. The cap layer 301 comprises a reinforcement structure layer 304, and an annular metal structure 306 and a block metal structure 302 embedded in the reinforcement structure layer 304. The annular metal structure 306 and the block metal structure 302 are spaced apart in the reinforcement structure layer 304, and the annular metal structure 306 and the block metal structure 302 are flush with the surface of the reinforcement structure layer 304. The sealing structure 407 forms a closed ring on the non-resonant region of the filter chip 401, and the chip pad 403 and the bump 405 are located inside or outside the closed ring. That is, the sealing structure 407 surrounds the periphery of the chip pad 403 to form a closed structure, preventing water vapor erosion or dirt from entering the interior of the filter chip 401, which would affect the performance of the filter chip 401. The sealing structure 407 and the bump 405 are made of metal pillars or solder balls, and the thickness of the sealing structure 407 and the bump 405 is 5-60um. The alignment structure is arranged on the surface of the cap layer 301 facing the filter chip 401, and the sealing structure 407 and the bump 405 on the filter chip 401 are aligned and bonded to the annular metal structure 306 and the block metal structure 302 respectively through the alignment structure to form a cavity 303 above the resonance region 402, and a metal lead-out terminal is provided on the surface of the block metal structure 302 away from the cavity 303. The filter chip 401 can be a surface acoustic wave (SAW) filter chip, but is not limited thereto. The resonance region 402 on the first surface of the filter chip 401 can only function properly when not in contact with or covered by any foreign objects. In other words, a cavity 303 must be formed above the filter chip 401 to protect the resonance region 402. The reinforcement layer 304 is an insulating material, which can be an organic material such as polyimide, a molding compound, or a mixture of an organic material and an inorganic filler.

[0045] In a specific embodiment, the alignment structure includes a barrier layer 404 and a first through hole 408 and a second through hole 406 on the barrier layer 404, wherein the first through hole 408 and the second through hole 406 correspond to the positions of the annular metal structure 306 and the block metal structure 302, respectively. The first through hole 408 and the second through hole 406 also correspond to the positions of the sealing structure 407 and the bump 405 on the filter chip 401, respectively, to facilitate alignment bonding. Due to the height difference between the cap layer 301 and the barrier layer 404, a very accurate alignment area can be obtained during the manufacturing process to avoid misalignment and movement of the filter chip 401. In other optional embodiments, the alignment structure may adopt other structures with grooves, etc.

[0046] In a specific embodiment, the material of the enclosure layer 404 is photoresist or dry film, and the thickness of the enclosure layer 404 is in the range of 10-40um. The enclosure layer 404 is provided with a third through hole exposing the cap layer 301, and the cavity 303 is arranged between the cap layer 301 exposed through the third through hole and the filter chip 401. The third through hole becomes a part of the cavity 303. The bump 405 is embedded in the second through hole 406, one end of the bump 405 is connected to the chip pad 403, and the other end of the bump 405 is connected to the bulk metal structure 302, so that electrical connection can be achieved between the chip pad 403, the bump 405 and the bulk metal structure 302. The sealing structure 407 is embedded in the first through-hole 408 and connected to the annular metal structure 306. The annular metal structure 306 and the bulk metal structure 302 are made of metal or other conductive compounds, which facilitates the bonding of the sealing structure 407 to the annular metal structure 306 and the bonding of the bump 405 to the bulk metal structure 302. The thickness of the sealing structure 407 and the bump 405 is equal to the thickness of the cavity 303. Together, they can adjust the height of the cavity 303, making it suitable for applications requiring large cavities.

[0047] In a specific embodiment, the reinforcement layer 304 has the same thickness as the annular metal structure 306 and the bulk metal structure 302, and their upper and lower surfaces are flush, with a thickness of 20-50 μm. Solder pads 601 are provided on the surface of the bulk metal structure 302, facing away from the cavity 303, as metal lead terminals. The position and distribution of the bulk metal structure 302 enable wafer-level packaging. Because the cavity 303 is achieved solely by the cap layer 301 and the filter chip 401, an ultra-thin package can be achieved.

[0048] Corresponding to the packaging structure of the cavity filter described above, an embodiment of the present application further proposes a method for manufacturing the packaging structure based on the cavity filter described above, comprising the following steps:

[0049] (1)Reference Figure 2a , providing a filter wafer, on which a filter chip 401 is provided, the filter chip 401 including a resonance area 402 and a non-resonance area outside the resonance area 402, a chip pad 403 is provided on the non-resonance area, a bump 405 is made on the chip pad 403, the sealing structure 407 forms a closed ring on the non-resonance area of the filter chip 401, the chip pad 403 is located inside or outside the closed ring, and then the filter wafer is cut into filter chips 401 with bumps 405 and sealing structures 407.

[0050] (2)Reference Figure 2b 、 2c2d, providing a carrier wafer 101, wherein the surface of the carrier wafer 101 is covered with an adhesive layer 201 having a thickness of approximately 100 μm, wherein the adhesive layer 201 is made of a thermal foam film. An annular metal structure 306 and a block metal structure 302 having a thickness of 20-50 μm are first fabricated on top of the adhesive layer 201. The annular metal structure 306 and the block metal structure 302 are fabricated simultaneously on top of the adhesive layer 201. A strengthening structure layer 304 is then fabricated on the adhesive layer 201. The strengthening structure layer 304 covers the annular metal structure 306 and the block metal structure 302. The surface of the strengthening structure layer 304 is planarized to expose the annular metal structure 306 and the block metal structure 302 and to make the surface of the strengthening structure layer 304 flush with the surfaces of the annular metal structure 306 and the block metal structure 302. The strengthening structure layer 304 and the annular metal structure 306 and the block metal structure 302 embedded in the strengthening structure layer 304 constitute a capping layer 301. Specifically, the reinforcement structure layer 304 is an insulating material, which can be an organic material such as polyimide, or a molding compound, or a mixture of an organic material and an inorganic filler. The annular metal structure 306 and the bulk metal structure 302 can be metals or other conductive compounds. A positioning structure is made on the surface of the cap layer 301. Specifically, the positioning structure includes a barrier layer 404 and a first through hole 408 and a second through hole 406 on the barrier layer 404. The material of the barrier layer 404 is photoresist or dry film, and the thickness of the barrier layer 404 ranges from 10 to 40 μm. Patterning is performed on the barrier layer 404 at positions corresponding to the annular metal structure 306 and the bulk metal structure 302 to form a first through hole 408 and a second through hole 406. The positions of the annular metal structure 306 and the first through hole 408 correspond to the sealing structure 407, and the positions of the block metal structure 302 and the second through hole 406 correspond to the chip pad 403 of the filter chip 401. The second through hole 406 formed on the enclosure layer 404 can realize the alignment function to prevent the filter chip 401 from shifting when the filter chip 401 is bonded to the carrier wafer 101. A third through hole is patterned on the enclosure layer 404 at a position corresponding to the resonance region 402 of the filter chip 401, and the cavity 303 is formed between the cap layer 301 exposed through the third through hole and the filter chip 401. In other optional embodiments, the alignment structure can adopt other structures with grooves, etc.

[0051] (3)Reference Figure 2eThe sealing structure 407 and bumps 405 on the filter chip 401 are aligned and bonded to the annular metal structure 306 and the bulk metal structure 302 exposed by the first through-hole 408 and the second through-hole 406 of the carrier wafer 101, respectively, to form a cavity 303 above the resonant region 402. The filter chip 401 and the bulk metal structure 302 are electrically interconnected via the bumps 405 on the surface of the chip pad 403. The sealing structure 407 and the annular metal structure 306 are bonded together. The sealing structure 407 and the bumps 405 can be made of metal pillars or solder balls. The annular metal structure 306 and the bulk metal structure 302 are made of metal or other conductive compounds. Therefore, reflow soldering or other metal bonding techniques are used for alignment bonding. After bonding, the height of the bumps 405 and sealing structure 407 is 5-60 μm. Of course, other bonding materials can also be used for the bumps 405 and sealing structure 407, and the bonding method can also be selected according to needs. After bonding, the distance between the surface of the filter chip 401 and the surface of the barrier layer 404 is 10-20 μm. Due to the presence of the sealing structure 407 , water vapor cannot flow into the chip functional area, thereby improving the reliability of the device.

[0052] (4)Reference Figure 2f and Figure 1 The adhesive layer 201 and the carrier wafer 101 are removed. Since the adhesive layer 201 is made of a thermal foam film, heating is used to cause the adhesive layer 201 to foam and thereby remove the carrier wafer 101. After removing the adhesive layer 201 and the carrier wafer 101, the bulk metal structure 302 is exposed. Metal leads are formed above the exposed bulk metal structure 302. The metal leads are solder pads 601. Specifically, solder pads 601 are formed above the bulk metal structure 302.

[0053] The wafer-level filter packaging structure of the present invention has the advantages of small size, good radio frequency filtering performance and high reliability, and can also significantly optimize the production process and reduce product costs.

[0054] Example 2

[0055] The difference between the second embodiment of the present application and the first embodiment is that: Figure 3 In the second embodiment, the metal lead-out terminals are solder balls 611, rather than pads, and a protective layer 711 is formed around the solder balls 611. Solder balls 611 can also be formed at any location on the bulk metal structure 302 to achieve wafer-level packaging. The protective layer 711 is made of a dry film or photoresist. Protective layer 711 covers the solder balls 611 to resist mold compression and increase the compressive strength of the device. The remaining configuration is the same as in the first embodiment.

[0056] The above embodiments are only used to further illustrate a packaging structure of a cavity filter and a manufacturing method thereof of the present invention, but the present invention is not limited to the embodiments. Any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention fall within the protection scope of the technical solution of the present invention.

Claims

1. A cavity filter packaging structure, characterized in that: include: A filter chip, the filter chip comprising a resonant region and a non-resonant region outside the resonant region, a chip pad being provided on the non-resonant region, and a bump being provided on the chip pad; A sealing structure, wherein the sealing structure forms a closed ring on the non-resonant region of the filter chip, the chip pad is located inside or outside the closed ring, and the material of the sealing structure is a metal column or a solder ball; a capping layer, the capping layer comprising a strengthening structure layer and an annular metal structure and a plurality of block metal structures embedded in the strengthening structure layer and spaced apart, the annular metal structure and the block metal structure being flush with a surface of the strengthening structure layer; an alignment structure, disposed on a surface of the cap layer facing the filter chip, the alignment structure comprising a barrier layer and a first through hole and a second through hole in the barrier layer, the first through hole and the second through hole corresponding to positions of the annular metal structure and the block metal structure, respectively, and the sealing structure and the bump on the filter chip are aligned and bonded to the annular metal structure and the block metal structure, respectively, through the alignment structure to form a cavity above the resonance region; The metal lead-out terminal is arranged on a surface of the cap layer away from the cavity.

2. The packaging structure of the cavity filter according to claim 1, wherein: The material of the barrier layer is photoresist or dry film, and the thickness of the barrier layer is in the range of 10-40 μm.

3. The packaging structure of the cavity filter according to claim 1, wherein: The barrier layer is provided with a third through hole exposing the cap layer, and the cavity is provided between the cap layer exposed through the third through hole and the filter chip.

4. The packaging structure of the cavity filter according to claim 1, wherein: The projection area of the bulk metal structure on the filter chip is located in the non-resonance area.

5. The packaging structure of the cavity filter according to claim 1, wherein: The reinforcing structure layer is made of insulating material, and the thickness of the cap layer is 20-50 μm.

6. The packaging structure of the cavity filter according to claim 1, wherein: The material of the bumps is a metal column or a solder ball, and the thickness of the sealing structure and the bumps is 5-60 μm.

7. The packaging structure of the cavity filter according to claim 1, wherein: The metal lead-out end is a solder pad or a solder ball, and a protective layer covering the solder ball is provided above the cap layer.

8. A method for manufacturing a packaging structure of a cavity filter according to any one of claims 1 to 7, characterized in that: The following steps are involved: 1) Providing a filter wafer, wherein a filter chip is provided on the filter wafer, wherein the filter chip includes a resonant region and a non-resonant region outside the resonant region, wherein a chip pad is provided on the non-resonant region, and a bump is formed on the chip pad. The sealing structure forms a closed loop on the non-resonant region on the filter chip, and the chip pad is located inside or outside the closed loop. The filter wafer is cut to obtain a single filter chip having the bump and the sealing structure; 2) Providing a carrier wafer, wherein the surface of the carrier wafer is covered with an adhesive layer, and forming a cap layer above the adhesive layer, wherein the cap layer includes a strengthening structure layer and an annular metal structure and a plurality of block metal structures embedded in the strengthening structure layer and spaced apart, wherein the annular metal structure and the block metal structure are flush with the surface of the strengthening structure layer, and forming an alignment structure on the surface of the cap layer, wherein the alignment structure includes an enclosure layer and a first through hole and a second through hole in the enclosure layer, wherein the first through hole and the second through hole correspond to the positions of the annular metal structure and the block metal structure, respectively; 3) bonding the sealing structure and the bumps on the filter chip to the annular metal structure and the block metal structure respectively through the alignment structure to form a cavity above the resonance region; 4) removing the adhesive layer and the carrier wafer, and fabricating metal leads above the cap layer.

9. The method for manufacturing a cavity filter packaging structure according to claim 8, wherein: In step 2, an alignment structure is produced on the surface of the cap layer, specifically comprising: producing a barrier layer on the surface of the cap layer, and patterning the barrier layer to form a first through hole and a second through hole that expose the annular metal structure and the block metal structure respectively.

10. The method for manufacturing a cavity filter packaging structure according to claim 9, wherein: The step 2 further includes: performing patterning on the barrier layer at a position corresponding to the resonance region of the filter chip to form a third through hole, and forming the cavity between the cap layer exposed through the third through hole and the filter chip.

11. The method for manufacturing a cavity filter packaging structure according to claim 8, wherein: In step 2, a capping layer is produced above the bonding layer, specifically comprising: producing the annular metal structure and several block metal structures above the bonding layer, coating a reinforcement structure layer covering the annular metal structure and the block metal structure above the bonding layer, and flattening the surface of the reinforcement structure layer until the annular metal structure and the block metal structure are exposed.

12. The method for manufacturing a cavity filter packaging structure according to claim 8, wherein: The projection area of the bulk metal structure on the filter chip is located in the non-resonance area.

13. The method for manufacturing a cavity filter packaging structure according to claim 8, wherein: In step 3, reflow soldering is used for alignment bonding.

14. The method for manufacturing a cavity filter packaging structure according to claim 8, wherein: The metal lead-out terminal is a pad. The step 4 of manufacturing the metal lead-out terminal above the cap layer specifically includes: manufacturing the pad above the block metal structure.

15. The method for manufacturing a cavity filter packaging structure according to claim 8, wherein: The metal lead-out terminal is a solder ball. The metal lead-out terminal is made above the cap layer in step 4, specifically comprising: making a solder ball above the bulk metal structure and a protective layer around the solder ball.

Images