A surface acoustic wave filter package structure and a method of packaging the same

Abstract

The application discloses a surface acoustic wave filter packaging structure and a packaging method thereof. The packaging structure comprises a substrate, solder resist layers arranged on the front surface of the substrate, filter chips and non-filter chips which are inverted on the front surface of the substrate and are arranged between the solder resist layers, and an injection molding layer covering the filter chips, the solder resist layers and the non-filter chips. The filter chips are uniformly provided with first protrusions on the side facing the substrate. The lower surface of the filter chip is overlapped with the upper surface of the adjacent solder resist layer, and a sealed cavity is formed between the filter chip, the solder resist layer and the substrate. The non-filter chips are uniformly provided with second protrusions on the side facing the substrate. A gap is left between the periphery of the non-filter chip and the adjacent solder resist layer, and the injection molding layer is filled below the non-filter chip. The application ensures the existence of the cavity at the bottom of the filter chip and protects the protrusions of the non-filter chip, thereby further improving the reliability of the product.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor processing, and in particular to a surface acoustic wave filter packaging structure and a packaging method thereof. BACKGROUND

[0002] The working principle of the surface acoustic wave filter is that the sound wave is transmitted on the surface of the chip, and a cavity needs to be ensured on the surface of the IDT, otherwise the signal transmission will be affected. There are various packaging schemes in the industry:

[0003] (1) WLP packaging scheme, that is, a WLP element that has been pre-packaged is directly flip-chip bonded to a carrier board for mold encapsulation of the module; the technical conditions of the WLP packaging scheme are high, the cost is very high, and it is not convenient to popularize.

[0004] (2) Overall film encapsulation, that is, epoxy resin film encapsulation, that is, the chip is first flip-chip bonded to the carrier board, and then a layer of epoxy resin film is attached to the carrier board containing the flip-chip to complete the encapsulation. This film can be controlled not to flow to the bottom of the chip to ensure that a cavity exists at the bottom of the chip, so that the surface acoustic wave filter can work normally. Therefore, the overall film encapsulation scheme has high cost, poor high-temperature resistance, and uneven appearance.

[0005] (3) Isolation film plus injection encapsulation, that is, the bare chip is first flip-chip bonded to the carrier board, then a thin isolation film is attached to the surface to prevent the material in the subsequent injection process from entering the bottom of the filter element and causing failure, and finally the injection process is performed to complete the plastic encapsulation; therefore, the filter tin ball of the isolation film plus injection encapsulation scheme is prone to crack failure under the direct pressure of injection, and the bottom filling effect of the non-filter element is poor.

[0006] Meanwhile, the prior art CN216120295U discloses a surface acoustic wave filter radio frequency module packaging structure and electronic equipment. The packaging structure includes a substrate, at least one filter chip, at least one non-filter chip, and an epoxy resin film; the front surface of the substrate is provided with a solder resist layer and an electrode area; the filter chip is flip-chip bonded to the front surface of the substrate, and the filter chip is provided with an interdigital transducer and a first bump; the non-filter chip is flip-chip bonded to the front surface of the substrate, and the non-filter chip is provided with a non-filter function part and a second bump; the epoxy resin film is integrally pressed onto the front surface of the substrate, the filter chip, and the non-filter chip, and a closed cavity is formed between the filter chip and the substrate and the epoxy resin film, and a closed cavity is also formed between the non-filter chip and the substrate and the epoxy resin film. The cavity below the filter chip and the cavity below the non-filter chip are both provided with a closed cavity, and if the cavity below the non-filter chip is not filled or is not filled sufficiently, a local cavity is easily generated near the bump, and when the product is subjected to high temperature reflow soldering, the cavity expands and a siphon effect occurs, causing tin flow short circuit and reducing the reliability of the product.

[0007] Therefore, the above problems need to be solved. SUMMARY

[0008] The first object of the present application is to provide a surface acoustic wave filter packaging structure with high reliability and low cost.

[0009] The second object of the present application is to provide a packaging method of the surface acoustic wave filter packaging structure.

[0010] Technical scheme: To achieve the above object, the present application discloses a surface acoustic wave filter packaging structure, which comprises a substrate, solder resist layers arranged on the front side of the substrate, filter chips arranged on the front side of the substrate and between the solder resist layers, non-filter chips arranged on the front side of the substrate and between the solder resist layers, and an injection molding layer covering the filter chips, the solder resist layers and the non-filter chips, wherein the filter chips are uniformly distributed with first bumps for signal transmission on the side facing the substrate, the lower surface of the filter chips is overlapped with the upper surface of the adjacent solder resist layer, and a sealed cavity is formed between the filter chips, the solder resist layers and the substrate; the non-filter chips are uniformly distributed with second bumps for signal transmission on the side facing the substrate, and a gap is left between the periphery of the non-filter chips and the adjacent solder resist layer, and the injection molding layer is filled below the non-filter chips.

[0011] Among them, the solder resist layer above the filter chip has a second solder resist layer constituting a stepped structure, wherein a dam groove is formed between the filter chip, the solder resist layer and the second solder resist layer, and the dam groove is filled with glue.

[0012] Preferably, the solder resist layer and the second solder resist layer are integrally formed.

[0013] Furthermore, the solder resist layer above the filter chip has a sealing layer arranged along the periphery of the filter chip.

[0014] Further, the sealing layer is a soluble resin layer.

[0015] Preferably, the horizontal distance between the lower surface of the filter chip and the upper surface of the adjacent solder resist layer is >10um.

[0016] Furthermore, the first bumps and the second bumps are both tin balls.

[0017] The packaging method of the surface acoustic wave filter packaging structure of the present application comprises the following steps:

[0018] S1, lay the solder resist layer on the substrate, and the height of the solder resist layer is 5-30um; wherein a first solder resist layer opening is provided at the position corresponding to the filter chip, and the center of the first solder resist layer opening is inwardly recessed by a distance >10um relative to the size of the designed filter chip; a second solder resist layer opening is provided at the position corresponding to the non-filter chip, and the center of the second solder resist layer opening is outwardly expanded by a certain distance relative to the size of the designed non-filter chip;

[0019] S2, prepare a filter chip with first bumps and a non-filter chip with second bumps, the height of the first bumps is higher than the height of the solder resist layer;

[0020] S3, solder the filter chip with first bumps to the front surface of the substrate at the solder resist layer opening through reflow soldering, the first bumps melt under the action of high temperature, the height of the first bumps decreases to make the lower surface of the filter chip overlap with the upper surface of the adjacent solder resist layer, a sealed cavity is formed between the filter chip, the solder resist layer and the substrate, and the non-filter chip with second bumps is soldered to the front surface of the substrate at the solder resist layer opening through reflow soldering, a gap is left between the periphery of the non-filter chip and the adjacent solder resist layer;

[0021] S4, perform injection molding packaging to form an injection molding layer covering the filter chip, the solder resist layer and the non-filter chip, and the injection molding layer is filled to the lower side of the non-filter chip.

[0022] The packaging method of the surface acoustic wave filter packaging structure comprises the following steps:

[0023] S1, lay a solder resist layer and a second solder resist layer of an integrally formed structure on the substrate, the height of the solder resist layer is 5-30 um, and the height of the second solder resist layer is 5-50 um; wherein a stepped solder resist layer opening is arranged at the position corresponding to the filter chip, the lower opening of the stepped solder resist layer opening is inwardly recessed by a distance greater than 10 um from the center of the designed filter chip size, and the upper opening of the stepped solder resist layer opening is outwardly expanded by a distance of 10-100 um from the center of the designed filter chip size; a second solder resist layer opening is arranged at the position corresponding to the non-filter chip, the second solder resist layer opening is outwardly expanded by a certain distance from the center of the designed non-filter chip size; or a second stepped solder resist layer opening is arranged at the position corresponding to the non-filter chip, the lower opening and the upper opening of the second stepped solder resist layer opening are both outwardly expanded by a certain distance from the center of the designed filter chip size;

[0024] S2, prepare a filter chip with first bumps and a non-filter chip with second bumps, the height of the first bumps is higher than the height of the solder resist layer;

[0025] S3, solder the filter chip with first bumps to the front surface of the substrate at the solder resist layer opening through reflow soldering, the first bumps melt under the action of high temperature, the height of the first bumps decreases to make the lower surface of the filter chip overlap with the upper surface of the adjacent solder resist layer, a sealed cavity is formed between the filter chip, the solder resist layer and the substrate, and the non-filter chip with second bumps is soldered to the front surface of the substrate at the solder resist layer opening through reflow soldering, a gap is left between the periphery of the non-filter chip and the adjacent solder resist layer;

[0026] S4, glue, brush glue or spray glue in the retaining wall groove, glue seals the connection between the filter chip four sides and the solder resist layer;

[0027] S5, injection molding packaging, forming an injection molding layer covering the filter chip, the solder resist layer and the non-filter chip, and the injection molding layer fills to the bottom of the non-filter chip.

[0028] The packaging method of the surface acoustic wave filter packaging structure comprises the following steps:

[0029] S1, lay the solder resist layer on the substrate, the solder resist layer height is 5-30um; wherein the first solder resist layer opening is opened at the position corresponding to the filter chip, the first solder resist layer opening is 10-50um inwardly recessed from the center relative to the designed filter chip size; the second solder resist layer opening is opened at the position corresponding to the non-filter chip, the second solder resist layer opening is outwardly extended by a certain distance from the center relative to the designed non-filter chip size;

[0030] S2, set the ultrahigh temperature soluble resin layer above the solder resist layer corresponding to the filter chip, the edge of the soluble resin layer is outwardly extended by 30-100um from the edge of the designed filter chip, and the height of the soluble resin layer is 20-100um;

[0031] S3, prepare the filter chip with the first bump and the non-filter chip with the second bump, the height of the first bump is higher than the height of the solder resist layer;

[0032] S4, the filter chip with the first bump is welded to the front surface of the substrate at the solder resist layer opening through reflow soldering, the first bump melts under the action of high temperature, the height of the first bump decreases to make the lower surface of the filter chip lap the upper surface of the adjacent solder resist layer, and the sealed cavity is formed between the filter chip, the solder resist layer and the substrate; the non-filter chip with the second bump is welded to the front surface of the substrate at the solder resist layer opening through reflow soldering, and a gap is left between the four sides of the non-filter chip and the adjacent solder resist layer;

[0033] S5, the soluble resin layer melts and collapses to form a sealing ring around the filter chip through high temperature baking;

[0034] S6, injection molding packaging, forming an injection molding layer covering the filter chip, the solder resist layer and the non-filter chip, and the injection molding layer fills to the bottom of the non-filter chip.

[0035] Advantages: compared with the prior art, the present application has the following advantages:

[0036] (1) The present application utilizes the upper surface of the opening of the solder resist layer to overlap with the lower surface of the filter chip, so that a sealed cavity is formed among the filter chip, the solder resist layer and the substrate, which not only ensures the existence of the cavity at the bottom of the filter chip, but also has the advantages of low cost and high reliability; meanwhile, the injection molding material is filled below the non-filter chip to protect the bumps of the non-filter chip, avoiding the cracks of the bumps under the direct pressure of injection molding, thereby further improving the reliability of the product;

[0037] (2) The present application adopts the special stepped opening design of the substrate green oil layer, and cooperates with the process scheme of sealing the filter with special glue, which can effectively solve the problem of low yield caused by the invasion of glue from the bottom of the filter product due to general dispensing, and can also be applied to the product which needs to be welded. From the perspective of reliability, the bottom of the filter chip exists a cavity, and because the four wall glue can ensure the stability of the bumps under the high mold pressure of the subsequent injection molding process;

[0038] (3) The present application sets a layer of irreversible high-temperature soluble resin layer above the solder resist layer around the filter chip to form a sealing layer, which can effectively solve the problem of low yield caused by the invasion of glue from the bottom of the filter chip due to general dispensing, and can also be applied to the product which needs to be welded. In addition, from the perspective of product reliability, the bottom of the filter chip exists a closed cavity, and because the filter chip has a solidified soluble resin layer around it, the stability of the bumps can be ensured under the high mold pressure of the subsequent injection molding process;

[0039] (4) For the non-filter, the filling of the injection molding material at the bottom can well protect the bumps, thereby improving the reliability of the product; at the same time, the process is relatively simple, and the cost is lower than the current mainstream process. BRIEF DESCRIPTION OF DRAWINGS

[0040] Figures 1(a) to 1(c) It is a step schematic diagram of the packaging method in embodiment 1.

[0041] Figures 2(a) to 2(d) It is a step schematic diagram of the packaging method in embodiment 2.

[0042] Figures 3(a) to 3(e) It is a step schematic diagram of the packaging method in embodiment 3. DETAILED DESCRIPTION

[0043] The technical solutions of the present application will be further described below in combination with the drawings.

[0044] In order to make the purpose, technical solutions and advantages of the present application more clear and explicit, the present application will be further described in detail below in combination with the drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application, and are not used to limit the present application.

[0045] It is to be understood that the application can assume various alternative forms of embodiment, and it is not to be limited to the specific examples described and shown. Rather, the specific examples are provided for disclosing the general principles of the application and its practical application, to enable others skilled in the art to best utilize the application. In the drawings, the size and relative sizes of layers and regions can be exaggerated for clarity. Identical reference numerals have been used, where applicable, to designate corresponding elements throughout the figures.

[0046] It will be understood that when an element or layer is referred to as being "on" or "connected to" another element or layer, it can be directly on or connected to the other element or layer or intervening elements or layers can be present.

[0047] It will be understood that, although the terms first, second, third, etc. can be used herein to describe various elements, components, regions, layers and / or sections, these elements, components, regions, layers and / or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or section from another element, component, region, layer or section. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the present application.

[0048] Spatially relative terms, such as "beneath", "below", "lower", "under", "above", "upper" and the like, can be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use and / or operation in addition to the orientations depicted in the figures.

[0049] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and / or "comprising", when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. As used herein the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0050] Example 1

[0051] As shown in Fig. 1(c), the surface acoustic wave filter packaging structure of the application comprises a substrate 1, a solder resist layer 2, a filter chip 3, a non-filter chip 4, an injection molding layer 5, first bumps 6 and second bumps 7. The solder resist layer is located on the front surface of the substrate 1, and the solder resist layer can be made of different materials as required. An opening is formed in the solder resist layer to expose the substrate, so that the filter chip 3 and the non-filter chip 4 can be flip-chip mounted on the front surface of the substrate. The outer periphery of the filter chip 3 and the non-filter chip 4 is surrounded by the solder resist layer 2. The filter chip 3 is uniformly provided with first bumps 6 on the side facing the substrate, and the first bumps 6 are connected to the substrate for signal transmission of the filter chip. The non-filter chip 4 is uniformly provided with second bumps 7 on the side facing the substrate, and the second bumps 7 are connected to the substrate 1 for signal transmission of the non-filter chip. The first bumps 6 and the second bumps 7 are tin balls. The lower surface of the filter chip 3 is overlapped with the upper surface of the adjacent solder resist layer 2, and the horizontal overlapping distance is >10um. A sealed cavity is formed between the filter chip 3, the solder resist layer 2 and the substrate 1. A gap is left between the periphery of the non-filter chip 4 and the adjacent solder resist layer 2. The injection molding layer 5 covers the filter chip, the solder resist layer and the non-filter chip, and the injection molding layer 5 is filled below the non-filter chip 4.

[0052] The upper surface of the opening of the solder resist layer is overlapped with the lower surface of the filter chip, so that a sealed cavity is formed between the filter chip, the solder resist layer and the substrate. This not only ensures that there is a cavity at the bottom of the filter chip, but also has the advantages of low cost and high reliability. At the same time, the injection molding material is filled below the non-filter chip to protect the bumps of the non-filter chip, avoiding cracks in the bumps under the direct pressure of injection molding, thereby further improving the reliability of the product.

[0053] The packaging method of the surface acoustic wave filter packaging structure of the application comprises the following steps:

[0054] S1, a solder resist layer is laid on the substrate, and the height of the solder resist layer is 5-30um. A first solder resist layer opening is formed at the position corresponding to the filter chip, and the center of the first solder resist layer opening is inwardly recessed by a distance >10um relative to the designed size of the filter chip. A second solder resist layer opening is formed at the position corresponding to the non-filter chip, and the center of the second solder resist layer opening is outwardly expanded by a certain distance relative to the designed size of the non-filter chip.

[0055] S2, a filter chip with first bumps and a non-filter chip with second bumps are prepared, and the height of the first bumps is higher than the height of the solder resist layer, as shown in Fig. 1(a),

[0056] S3, soldering the filter chip with the first bump to the front surface of the substrate at the opening of the solder resist layer by reflow soldering, the first bump melts under the action of high temperature, the height of the first bump decreases to make the lower surface of the filter chip overlap with the upper surface of the adjacent solder resist layer, and a sealed cavity is formed among the filter chip, the solder resist layer and the substrate; soldering the non-filter chip with the second bump to the front surface of the substrate at the opening of the solder resist layer by reflow soldering, leaving a gap between the periphery of the non-filter chip and the adjacent solder resist layer, as shown in Fig. 1(b);

[0057] S4, performing injection molding packaging to form an injection molding layer covering the filter chip, the solder resist layer and the non-filter chip, and the injection molding layer fills to the lower surface of the non-filter chip, as shown in Fig. 1(c).

[0058] Embodiment 2

[0059] As shown in Fig. 2(d), the surface acoustic wave filter packaging structure of the application includes a substrate 1, a solder resist layer 2, a filter chip 3, a non-filter chip 4, an injection molding layer 5, a first bump 6, a second bump 7, a second solder resist layer 8, a barrier groove 9 and glue 10. The solder resist layer is located on the front surface of the substrate 1, and the second solder resist layer 8 is located above the solder resist layer 2 to form a stepped structure with the solder resist layer 2, and the solder resist layer 2 and the second solder resist layer 8 are integrally formed. The solder resist layer and the second solder resist layer can be made of different materials as needed, and the solder resist layer and the second solder resist layer are formed by opening the stepped layer of the solder resist material to expose the substrate for flip-chip mounting of the filter chip 3 and the non-filter chip 4 on the front surface of the substrate, and the outer circle of the filter chip 3 and the non-filter chip 4 is surrounded by the solder resist layer 2 and the second solder resist layer 8.

[0060] The filter chip 3 is uniformly distributed with the first bump 6 on the side facing the substrate, and the first bump 6 is connected to the substrate for signal transmission of the filter chip. The non-filter chip 4 is uniformly distributed with the second bump 7 on the side facing the substrate, and the second bump 7 is connected to the substrate 1 for signal transmission of the non-filter chip. The first bump 6 and the second bump 7 are both tin balls. The lower surface of the filter chip 3 overlaps with the upper surface of the adjacent solder resist layer 2, and the horizontal distance of the overlap is >10um; the filter chip 3, the solder resist layer 2 and the second solder resist layer 8 form a barrier groove 9, and the barrier groove 9 is filled with glue 10; so that a sealed cavity is formed among the filter chip 3, the solder resist layer 2 and the substrate 1. There is a gap between the periphery of the non-filter chip 4 and the adjacent solder resist layer 2, and the injection molding layer 5 covers the filter chip, the solder resist layer and the non-filter chip, and the injection molding layer 5 fills to the lower surface of the non-filter chip 4.

[0061] The present application utilizes the stepped structure formed by the solder resist layer and the second solder resist layer, and the glue located in the dam groove around the filter chip to guarantee the sealing of the sealed cavity between the filter chip 3, the solder resist layer 2 and the substrate 1, which ensures the existence of the cavity at the bottom of the filter chip and has the advantages of low cost and high reliability; meanwhile, the injection molding material is filled below the non-filter chip to protect the bump of the non-filter chip, so that the crack failure of the bump under the direct pressure of injection molding is avoided, thereby further improving the reliability of the product.

[0062] The present application is the first time to adopt the special stepped opening design of the substrate green oil layer, and simultaneously adopt the special glue sealing process around the filter, which can effectively solve the problem of low yield caused by the glue invasion from the bottom of the filter product due to the ordinary dispensing, and can be used on the product which needs to be welded, and from the reliability point of view, for the filter, there is a cavity at the bottom, and because of the solidified glue around, the stability of the bump can be maintained under the high mold pressure of the subsequent injection molding process, for the non-filter, the filling of the injection molding material at the bottom can well protect the bump, thereby improving the reliability of the product. The process is relatively simple, and the cost is lower than the current mainstream process.

[0063] The present application is a packaging method of a surface acoustic wave filter packaging structure, comprising the following steps:

[0064] S1, as shown in Fig. 2(a), a solder resist layer and a second solder resist layer of an integral molding structure are laid on the substrate, the solder resist layer has a height of 5-30 um, and the second solder resist layer has a height of 5-50 um; wherein a stepped solder resist layer opening is opened at the position corresponding to the filter chip, the lower opening of the stepped solder resist layer opening is inwardly recessed by a distance >10 um from the center of the designed filter chip size, and the upper opening of the stepped solder resist layer opening is outwardly expanded by a distance of 10-100 um from the center of the designed filter chip size; a second solder resist layer opening is opened at the position corresponding to the non-filter chip, the second solder resist layer opening is outwardly expanded by a certain distance from the center of the designed non-filter chip size; or a second stepped solder resist layer opening is opened at the position corresponding to the non-filter chip, the lower opening and the upper opening of the second stepped solder resist layer opening are both outwardly expanded by a certain distance from the center of the designed filter chip size;

[0065] S2, a filter chip with a first bump and a non-filter chip with a second bump are prepared, and the height of the first bump is higher than the height of the solder resist layer;

[0066] S3, as shown in Fig. 2(b), the filter chip with the first bump is welded to the front surface of the substrate at the opening of the resist layer by reflow soldering, the first bump melts under the action of high temperature, the height of the first bump decreases to make the lower surface of the filter chip overlap with the upper surface of the adjacent resist layer, the filter chip, the resist layer and the second resist layer form a dam groove, and the filter chip, the resist layer and the substrate form a sealed cavity; the non-filter chip with the second bump is welded to the front surface of the substrate at the opening of the resist layer by reflow soldering, and a gap is left between the periphery of the non-filter chip and the adjacent resist layer;

[0067] S4, as shown in Fig. 2(c), the dam groove is glued, brushed or sprayed with glue, and the glue seals the connection between the periphery of the filter chip and the resist layer.

[0068] S5, as shown in Fig. 2(d), injection molding is performed to form an injection molding layer covering the filter chip, the resist layer and the non-filter chip, and the injection molding layer fills the lower part of the non-filter chip.

[0069] Embodiment 3

[0070] As shown in Fig. 3(e), the surface acoustic wave filter packaging structure of the application includes a substrate 1, a resist layer 2, a filter chip 3, a non-filter chip 4, an injection molding layer 5, a first bump 6, a second bump 7 and a sealing layer 11. The resist layer 2 is located on the front surface of the substrate 1, and the resist layer 2 can be made of different materials as needed. An opening is formed in the resist layer to expose the substrate to facilitate the flip-chip mounting of the filter chip 3 and the non-filter chip 4 on the front surface of the substrate, and the outer circle of the filter chip 3 and the non-filter chip 4 is surrounded by the resist layer 2. The filter chip 3 is uniformly distributed with the first bump 6 on the side facing the substrate, and the first bump 6 is connected to the substrate for signal transmission of the filter chip. The non-filter chip 4 is uniformly distributed with the second bump 7 on the side facing the substrate, and the second bump 7 is connected to the substrate 1 for signal transmission of the non-filter chip. The first bump 6 and the second bump 7 are both tin balls. The lower surface of the filter chip 3 overlaps with the upper surface of the adjacent resist layer 2, and the horizontal distance of the overlap is >10um; the sealing layer 11 is arranged along the periphery of the filter chip above the resist layer, and the sealing layer 11 is a soluble resin layer; a sealed cavity is formed between the filter chip 3, the resist layer 2 and the substrate 1, and the soluble resin layer further ensures the airtightness of the sealed cavity. A gap is left between the periphery of the non-filter chip 4 and the adjacent resist layer 2, the injection molding layer 5 covers the filter chip, the resist layer and the non-filter chip, and the injection molding layer 5 fills the lower part of the non-filter chip 4.

[0071] The present application sets a layer of irreversible high-temperature soluble resin layer on the solder resist layer around the filter chip to form a sealing layer, which can effectively solve the problem of low yield caused by the glue from the bottom of the filter chip, and can also be applied to the product which needs to be welded. In addition, from the perspective of product reliability, the present application can ensure the stability of the bump under the subsequent high mold pressure, and the filling of the injection molding material at the bottom of the non-filter chip can well protect the bump, thereby improving the reliability of the product.

[0072] The present application is a packaging method of a surface acoustic wave filter packaging structure, comprising the following steps:

[0073] S1, a solder resist layer is laid on the substrate, and the height of the solder resist layer is 5-30 um; wherein a first solder resist layer opening is opened at the position corresponding to the filter chip, and the first solder resist layer opening is inwardly recessed by 10-50 um from the center of the designed filter chip size; a second solder resist layer opening is opened at the position corresponding to the non-filter chip, and the second solder resist layer opening is outwardly extended by a certain distance from the center of the designed non-filter chip size;

[0074] S2, as shown in Fig. 3(a), an ultrahigh-temperature soluble resin layer is set on the solder resist layer corresponding to the filter chip, and the edge of the soluble resin layer is outwardly extended by 30-100 um from the edge of the designed filter chip, and the height of the soluble resin layer is 20-100 um;

[0075] S3, as shown in Fig. 3(b), a filter chip with a first bump and a non-filter chip with a second bump are prepared, and the height of the first bump is higher than the height of the solder resist layer;

[0076] S4, as shown in Fig. 3(c), the filter chip with the first bump is welded to the front surface of the substrate at the position of the solder resist layer opening through reflow soldering, the first bump melts under the action of high temperature, the height of the first bump decreases to make the lower surface of the filter chip lap the upper surface of the adjacent solder resist layer, and a sealed cavity is formed between the filter chip, the solder resist layer and the substrate; the non-filter chip with the second bump is welded to the front surface of the substrate at the position of the solder resist layer opening through reflow soldering, and a gap is left between the periphery of the non-filter chip and the adjacent solder resist layer;

[0077] S5, as shown in Fig. 3(d), the soluble resin layer is melted and collapsed to form a sealing ring around the filter chip through high-temperature baking;

[0078] S6, as shown in Fig. 3(e), injection molding is performed to form an injection molding layer covering the filter chip, the solder resist layer and the non-filter chip, and the injection molding layer is filled to the lower side of the non-filter chip.

[0079] The process of the present application is relatively simple, and the cost is relatively lower than current mainstream processes.

Claims

1. A surface acoustic wave (SAW) filter packaging structure, characterized in that: The system includes a substrate (1), solder resist layers (2) spaced apart on the front side of the substrate, a filter chip (3) flip-chip mounted on the front side of the substrate and located between the solder resist layers, and a non-filter chip (4) flip-chip mounted on the front side of the substrate and located between the solder resist layers, and an injection molding layer (5) covering the filter chip, the solder resist layers, and the non-filter chip. The filter chip has first bumps (6) evenly distributed on the side facing the substrate for transmitting signals. The lower surface of the filter chip (3) overlaps with the upper surface of the adjacent solder resist layer (2), and a sealed cavity is formed between the filter chip (3), the solder resist layer (2), and the substrate (1). The non-filter chip (4) has second bumps (7) evenly distributed on the side facing the substrate for transmitting signals. There is a gap between the filter chip (3) and the adjacent solder resist layer (2), and the injection molding layer (5) fills the area below the non-filter chip (4); above the solder resist layer adjacent to the filter chip (3), there is a second solder resist layer (8) forming a stepped structure, wherein the filter chip (3), the solder resist layer (2) and the second solder resist layer (8) form a retaining wall groove (9), and the retaining wall groove (9) is filled with glue (10), which seals the connection between the filter chip and the solder resist layer around the filter chip; the solder resist layer (2) and the second solder resist layer (8) are integrally formed structures; the horizontal distance between the lower surface of the filter chip (3) and the upper surface of the adjacent solder resist layer (2) is >10um; the first bump (6) and the second bump (7) are both solder balls.

2. A surface acoustic wave (SAW) filter packaging structure, characterized in that: The system includes a substrate (1), solder resist layers (2) spaced apart on the front side of the substrate, a filter chip (3) flip-chip mounted on the front side of the substrate and located between the solder resist layers, and a non-filter chip (4) flip-chip mounted on the front side of the substrate and located between the solder resist layers, and an injection molding layer (5) covering the filter chip, the solder resist layers, and the non-filter chip. The filter chip has first bumps (6) evenly distributed on the side facing the substrate for transmitting signals. The lower surface of the filter chip (3) overlaps with the upper surface of the adjacent solder resist layer (2), and a sealed cavity is formed between the filter chip (3), the solder resist layer (2), and the substrate (1). The non-filter chip (4) has first bumps (6) evenly distributed on the side facing the substrate. The filter chip (4) is provided with a second bump (7) for transmitting signals. There is a gap between the non-filter chip (4) and the adjacent solder mask layer (2), and the injection molding layer (5) fills the non-filter chip (4) below. The solder mask layer adjacent to the filter chip (3) has a sealing layer (11) arranged around the filter chip. The sealing layer (11) is an irreversible high-temperature soluble resin layer. Heating causes the soluble resin layer to melt and collapse around the filter chip to form a sealing ring. The horizontal distance between the lower surface of the filter chip (3) and the upper surface of the adjacent solder mask layer (2) is >10um. The first bump (6) and the second bump (7) are both solder balls.

3. A packaging method for the surface acoustic wave filter packaging structure according to claim 1, characterized in that, Includes the following steps: S1. An integrally formed solder resist layer and a second solder resist layer are deposited on the substrate. The height of the solder resist layer is 5~30um and the height of the second solder resist layer is 5~50um. A stepped solder resist layer opening is made at the location where the filter chip is set. The lower opening of the stepped solder resist layer opening is recessed by a distance >10um from the center relative to the designed filter chip size, and the upper opening of the stepped solder resist layer opening is expanded by a distance 10~100um from the center relative to the designed filter chip size. A second-step solder mask opening is provided at the non-filter chip location. The lower and upper openings of the second-step solder mask opening are both extended outwards from the center by a certain distance relative to the designed non-filter chip size. S2. Fabricate a filter chip with a first bump and a non-filter chip with a second bump, wherein the height of the first bump is higher than the height of the solder resist layer; S3. The filter chip with the first bump is soldered to the front side of the substrate at the opening of the stepped solder mask by reflow soldering. The first bump melts under high temperature, and the height of the first bump decreases so that the lower surface of the filter chip overlaps with the upper surface of the adjacent solder mask. A retaining wall groove is formed between the filter chip, the solder mask, and the second solder mask. A sealed cavity is formed between the filter chip, the solder mask, and the substrate. The non-filter chip with the second bump is soldered to the front side of the substrate at the opening of the second stepped solder mask by reflow soldering. A gap is left between the non-filter chip and the adjacent solder mask around its perimeter. S4. Apply glue, brush glue, or spray glue into the groove of the retaining wall to seal the connection between the filter chip and the solder mask layer. S5. Perform injection molding to form an injection molding layer covering the filter chip, solder mask layer and non-filter chip, and the injection molding layer fills under the non-filter chip.

4. A packaging method for the surface acoustic wave filter packaging structure according to claim 2, characterized in that, Includes the following steps: S1. A solder resist layer is laid on the substrate, and the height of the solder resist layer is 5~30um; a first solder resist layer opening is opened at the location where the filter chip is set, and the first solder resist layer opening is 10~50um inward relative to the designed filter chip size; a second solder resist layer opening is opened at the location where the non-filter chip is set, and the second solder resist layer opening is a certain distance outward relative to the designed non-filter chip size. S2. An ultra-high temperature soluble resin layer is set above the solder resist layer of the corresponding filter chip. The edge of the soluble resin layer extends 30~100um outward relative to the edge of the designed filter chip, and the height of the soluble resin layer is 20~100um. S3. Fabricate a filter chip with a first bump and a non-filter chip with a second bump, wherein the height of the first bump is higher than the height of the solder resist layer; S4. The filter chip with the first bump is soldered to the front side of the substrate at the opening of the solder mask layer by reflow soldering. The first bump melts under high temperature and the height of the first bump decreases so that the lower surface of the filter chip overlaps with the upper surface of the adjacent solder mask layer, forming a sealed cavity between the filter chip, the solder mask layer and the substrate. The non-filter chip with the second bump is soldered to the front side of the substrate at the opening of the solder mask layer by reflow soldering. A gap is left between the non-filter chip and the adjacent solder mask layer around its perimeter. S5. By baking at high temperature, the soluble resin layer melts and collapses to form a sealing ring around the filter chip; S6. Perform injection molding to form an injection molding layer covering the filter chip, solder mask layer and non-filter chip, and the injection molding layer fills under the non-filter chip.

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