Package structure and method of forming the same

Abstract

The application discloses a packaging structure and a forming method thereof. The forming method of the packaging structure comprises the following steps: providing a dielectric layer; forming a microsphere enrichment layer on the dielectric layer, wherein a plurality of hollow microspheres are distributed in the microsphere enrichment layer, and the hollow microspheres have microcavities inside; performing a perforation treatment on the hollow microspheres in a partial surface layer of the microsphere enrichment layer away from the dielectric layer, so as to expose the microcavities in the hollow microspheres in the partial surface layer; and forming a covering layer on the microsphere enrichment layer, wherein the covering layer is filled with the microcavities. The method can prevent the covering layer from being peeled off, falling off or delaminated from the dielectric layer, and can avoid causing a short circuit, corrosion or reliability risk.

Description

Technical Field

[0001] This application relates to the field of packaging, and more particularly to a packaging structure and a method for forming the same. Background Technology

[0002] In advanced packaging, the coefficients of thermal expansion (CTE) of different materials (such as the build-up dielectric layer / PP and solder mask, and the polyimide (PI) dielectric layer and epoxy molding compound EMC) are mismatched, which can easily lead to stress concentration at the interface during thermal cycling and moisture absorption reflow. In particular, some dielectric materials have low surface energy (such as polyimide (PI), making it difficult to form strong chemical bonds with other materials, resulting in insufficient interfacial adhesion.

[0003] For these reasons, the interface between heterogeneous materials in existing packaging structures is prone to peeling, detachment, or delamination, affecting the long-term reliability of the packaging structure and product yield. Summary of the Invention

[0004] The purpose of this application is to provide a packaging structure and a method for forming the same to prevent peeling, detachment or delamination between heterogeneous interfaces in the package, thereby avoiding short circuits, corrosion or reliability risks.

[0005] To achieve the above objectives, in a first aspect, embodiments of this application provide a method for forming an encapsulation structure, including:

[0006] Provide a dielectric layer; A microsphere enrichment layer is formed on the dielectric layer, and a plurality of hollow microspheres are distributed in the microsphere enrichment layer, the hollow microspheres having microcavities inside; Hollow microspheres in a portion of the surface layer of the microsphere enrichment layer away from the dielectric layer are perforated to expose the microcavities inside the hollow microspheres in that portion of the surface layer. A capping layer is formed on the microsphere enrichment layer, and the capping layer material fills the microcavity.

[0007] In some embodiments of this application, The material of the microsphere enrichment layer includes resin and hollow microspheres, wherein the hollow microspheres are distributed in the resin.

[0008] In some embodiments of this application, the resin includes one or a combination of epoxy resin, polyimide resin, benzocyclobutene resin or polybenzoxazole resin.

[0009] In some embodiments of this application, the hollow microspheres include a shell and a microcavity located inside the shell; The material of the housing includes silicate glass or polystyrene.

[0010] In some embodiments of this application, the volume percentage of hollow microspheres in the microsphere enrichment layer ranges from 20% to 60%.

[0011] In some embodiments of this application, the particle size range of the hollow microspheres or the outer diameter range of the shell is 0.5 micrometers to 10 micrometers; The diameter of the microcavity is smaller than the particle size of the hollow microspheres, and the diameter of the microcavity ranges from 0.3 micrometers to 9 micrometers.

[0012] In some embodiments of this application, the particle size of the capping material is smaller than the diameter of the microcavity; The thickness of the microsphere enrichment layer is greater than the particle size of the hollow microspheres.

[0013] In some embodiments of this application, the particle sizes of the hollow microspheres in the microsphere enrichment layer may be the same or different.

[0014] In some embodiments of this application, the microsphere enrichment layer includes a bottom layer and a surface layer located on the bottom layer, the bottom layer being close to the dielectric layer, the surface layer being far from the dielectric layer, and the distribution density of hollow microspheres in the surface layer being greater than or equal to the distribution density of hollow microspheres in the bottom layer.

[0015] In some embodiments of this application, the formation process of the microsphere enrichment layer includes a coating process and a curing process.

[0016] In some embodiments of this application, the coating process includes roller coating or blade coating.

[0017] In some embodiments of this application, during the coating process, additional hollow microspheres are sprinkled onto the surface of the microsphere enrichment layer, such that the distribution density of hollow microspheres in the surface layer is greater than that in the bottom layer.

[0018] In some embodiments of this application, the curing process includes a first curing process and a second curing process performed sequentially. The temperature range of the first curing process is 60℃-90℃, and the time is 30min-40min. During the first curing process, some hollow microspheres in the bottom layer float to the surface layer, making the distribution density of hollow microspheres in the surface layer greater than that in the bottom layer. The temperature range of the second curing process is 100℃-150℃, and the time is 30min-60min, so that the microsphere enrichment layer is cured and shaped.

[0019] In some embodiments of this application, Before performing the opening process, the method further includes: covering a portion of the surface of the microsphere enrichment layer away from the dielectric layer with a mask layer, the mask layer exposing the surface of the microsphere enrichment layer that needs to be opened; During the opening process, the mask layer is used as a mask to remove part of the shell, exposing the microcavity.

[0020] In some embodiments of this application, the aperture treatment includes plasma etching, wet etching, or laser etching.

[0021] In some embodiments of this application, the dielectric layer has metallic wiring; Prior to the opening process, pads are formed on the surface of the microsphere enrichment layer away from the dielectric layer, and the pads are electrically connected to the metal wiring. The process of opening holes in the hollow microspheres in the portion of the surface layer of the microsphere enrichment layer away from the dielectric layer includes: opening holes in the hollow microspheres in the portion of the surface layer of the microsphere enrichment layer on one or more sides of the pad.

[0022] In some embodiments of this application, the cover layer includes a solder resist layer; the encapsulation structure includes an encapsulation structure, and the cover layer is a solder resist layer; When the cover layer is a solder mask layer, after the cover layer is formed, the method further includes: patterning the cover layer so that the cover layer exposes the surface of the solder pad.

[0023] In some embodiments of this application, the cover layer includes a molding layer.

[0024] In some embodiments of this application, the method for forming the encapsulation structure further includes: A semiconductor chip is provided, on which an electrical connection structure is formed; The electrical connection structure of the semiconductor chip is soldered to the pads on the package structure.

[0025] Secondly, embodiments of this application also provide a packaging structure, including: Dielectric layer; A microsphere enrichment layer is located on the dielectric layer, wherein a plurality of hollow microspheres are distributed in the microsphere enrichment layer, wherein the hollow microspheres have microcavities inside, and the microcavities in the hollow microspheres in a portion of the surface layer of the microsphere enrichment layer away from the dielectric layer are exposed. A capping layer is located on the microsphere enrichment layer, and the capping layer material fills the microcavity.

[0026] In some embodiments of this application, the material of the microsphere enrichment layer includes resin and hollow microspheres, wherein the hollow microspheres are distributed in the resin; The resin includes one or a combination of epoxy resin, polyimide resin, benzocyclobutene resin or polybenzoxazole resin.

[0027] In some embodiments of this application, the hollow microspheres include a shell and a microcavity located inside the shell; The material of the housing includes silicate glass or polystyrene.

[0028] In some embodiments of this application, the volume percentage of hollow microspheres in the microsphere enrichment layer ranges from 20% to 60%.

[0029] In some embodiments of this application, the particle size range of the hollow microspheres or the outer diameter range of the shell is 0.5 micrometers to 10 micrometers; The diameter of the microcavity is smaller than the particle size of the hollow microspheres, and the diameter of the microcavity ranges from 0.3 micrometers to 9 micrometers.

[0030] In some embodiments of this application, the particle size of the capping material is smaller than the diameter of the microcavity; The thickness of the microsphere enrichment layer is greater than the particle size of the hollow microspheres.

[0031] In some embodiments of this application, the particle sizes of the hollow microspheres in the microsphere enrichment layer may be the same or different.

[0032] In some embodiments of this application, the microsphere enrichment layer includes a bottom layer and a surface layer located on the bottom layer, the bottom layer being close to the dielectric layer, the surface layer being far from the dielectric layer, and the distribution density of hollow microspheres in the surface layer being greater than or equal to the distribution density of hollow microspheres in the bottom layer.

[0033] In some embodiments of this application, the dielectric layer has metallic wiring; The portion of the surface of the microsphere enrichment layer away from the dielectric layer has pads, which are electrically connected to the metal wiring. The microcavities of hollow microspheres in the surface layer of the microsphere enrichment layer on one or more sides of the pad are exposed. The overlay exposes the surface of the pad.

[0034] In some embodiments of this application, the cover layer includes a solder mask layer or a molding compound layer; When the cover layer is a solder mask layer, the cover layer is exposed on the surface of the solder pad.

[0035] In some embodiments of this application, the packaging structure further includes: A semiconductor chip having an electrical connection structure formed thereon; An electrical connection structure is formed on the semiconductor chip; the electrical connection structure on the semiconductor chip is electrically connected to the pad; the cover layer is a molding compound layer, and the molding compound layer covers at least a portion of the semiconductor chip.

[0036] The beneficial effects of this application are: The encapsulation structure and its forming method disclosed in this application include: providing a dielectric layer; forming a microsphere enrichment layer on the dielectric layer, wherein a plurality of hollow microspheres are distributed in the microsphere enrichment layer and each hollow microsphere has a microcavity inside; performing an opening process on a portion of the surface layer of the microsphere enrichment layer away from the dielectric layer to expose the microcavities inside the hollow microspheres in the portion of the surface layer; and forming a capping layer on the microsphere enrichment layer, wherein the capping layer material fills the microcavities. This application forms a microsphere enrichment layer on the dielectric layer, in which hollow microspheres are distributed. On the one hand, the microcavities of the hollow microspheres are filled with gas or vacuum (the dielectric constant of gas or vacuum is lower than that of the resin in the microsphere enrichment layer 102), which reduces the dielectric constant (Dk) and loss factor (Df) of the microsphere enrichment layer, as well as the coefficient of thermal expansion. On the other hand, this application selectively opens the hollow microspheres in the portion of the surface layer of the microsphere enrichment layer away from the dielectric layer, exposing the microcavities inside the hollow microspheres in the portion of the surface layer. When a capping layer is formed on the microsphere enrichment layer, the capping layer material fills the microcavities, thus achieving a mechanical interlock between the portion of the capping layer and the corresponding microcavities, increasing the bonding force between the capping layer and the microsphere enrichment layer. Therefore, it can effectively prevent the capping layer from peeling, falling off, or delamination defects, avoiding short circuits, corrosion, or reliability risks.

[0037] Furthermore, this application only performs pore-opening treatment on hollow microspheres in a portion of the surface layer of the microsphere-enriched layer (it does not perform pore-opening treatment on all hollow microspheres in the surface layer). That is, it can selectively perform pore-opening treatment on hollow microspheres in local areas of the microsphere-enriched layer (such as areas where the capping layer is prone to peeling off, areas where the capping layer is narrow, or edge areas), so that the formed capping layer and the exposed microcavities in the local area form a mechanical interlock, which increases the bonding force between the capping layer and the microsphere-enriched layer in that local area. Therefore, it can effectively prevent the capping layer from peeling off, falling off, or delaminating in the local area, avoiding short circuits, corrosion, or reliability risks. Since other areas of the microsphere-enriched layer are not pore-opened, the other areas of the microsphere-enriched layer can remain intact, so that the performance parameters (dielectric constant, loss factor, coefficient of thermal expansion, etc.) of the other areas of the microsphere-enriched layer remain stable, ensuring the electrical performance of the packaging structure. Attached Figure Description

[0038] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort. In addition, in the following drawings, the components are not necessarily drawn to scale, and components with similar related characteristics or features may have the same or similar reference numerals.

[0039] Figure 1 This is a schematic diagram of the process for forming the encapsulation structure provided in some embodiments of this application; Figure 2 This is a schematic diagram of the structure after a dielectric layer is provided in the method for forming the packaging structure provided in some embodiments of this application; Figure 3 This is a schematic diagram of the structure after forming a microsphere enrichment layer on the dielectric layer in the method of forming the encapsulation structure provided in some other embodiments of this application; Figure 4 This is a schematic diagram of the structure after the pads are formed in the method of forming the packaging structure provided in some embodiments of this application; Figure 5 This is a schematic diagram of the structure after opening holes in the hollow microspheres in the part of the surface layer of the microsphere enrichment layer away from the dielectric layer in the method of forming the encapsulation structure provided in some other embodiments of this application. Figure 6 This is a schematic diagram of the structure after the cover layer is formed in the method of forming the encapsulation structure provided in some other embodiments of this application; Figure 7 This is a schematic diagram of the structure of the cover layer after being graphically represented in the method of forming the encapsulation structure provided in some embodiments of this application; Figure 8 This is a schematic diagram of the structure after solder balls are formed in the method of forming the packaging structure provided in some other embodiments of this application; Figure 9 This is a schematic diagram of the structure in which the covering layer is a plastic encapsulation layer in the method of forming the encapsulation structure provided in some other embodiments of this application.

[0040] Explanation of reference numerals in the attached figures: Dielectric layer 101; Microsphere enrichment layer 102; Hollow microsphere 103; Shell 103a; Microcavity 103b; Pad 104; Cover layer 105; Semiconductor chip 200; Electrical connection structure 201. Detailed Implementation

[0041] To facilitate understanding of this application, a more complete description will be provided below with reference to the accompanying drawings, which illustrate embodiments of the present application. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that the disclosure of this application will be thorough and complete.

[0042] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in this application's specification is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0043] In the description of this application, it should be noted that the use of terms such as "first" and "second" to define objects (such as elements, components, regions, layers, doping types and / or parts) is merely for the purpose of distinguishing different objects, and is not necessarily used to describe a specific order or sequence, unless the context clearly indicates otherwise.

[0044] In the description of this application, it should be understood that the singular forms “a,” “an,” and “the” may also include the plural forms unless the context clearly indicates otherwise. It should also be understood that when the terms “compose” and / or “comprise” are used in this specification, the presence of the stated feature, integer, step, operation, element, and / or part is established, but the presence or addition of one or more other features, integers, steps, operations, elements, parts, and / or groups is not excluded. Meanwhile, when used herein, the term “and / or” includes any and all combinations of the associated listed items.

[0045] In the description of this application, it should also be noted that when a component is referred to as "on another component," "connected to another component," or "in contact with another component," it can mean not only that a component is directly on, directly connected to, or directly in contact with the other component, but also that an intermediate component can be inserted between the two components. Furthermore, "connection" includes not only fixed connections but also detachable connections or integral connections. Similarly, when an element is referred to as "electrically connected," "electrically contacted," "electrically coupled," or "electrically coupled to" another element, the two elements can be in direct electrical contact or electrical coupling, or they can be in electrical contact or electrical coupling through an intermediate component.

[0046] In the description of this application, it should also be noted that the orientation or positional relationship indicated by directional terms such as "front, back, up, down, left, right", "horizontal, vertical, horizontal" and "top, bottom" is usually based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing this application and simplifying the description. Unless otherwise stated, these directional terms do not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the scope of protection of this application; the directional terms "inner" and "outer" refer to the inner and outer contours relative to the outline of each component itself.

[0047] Furthermore, in the description of this application, spatial relation terms such as "below," "under," "below," "below," "below," "above," "on the upper surface of," "above," etc., can be used to describe the spatial positional relationship between one element or feature shown in the figures and other elements or features. It should be understood that spatial relation terms, in addition to the orientation shown in the figures, also include different orientations of elements or features in use and operation. For example, if an element or feature in the figures is flipped or inverted, an element or feature described as "below" or "below" other elements or features will be oriented "above" other elements or features. Furthermore, elements may also include other orientations (e.g., rotated by an angle or other orientations).

[0048] The structure of the embodiments of this application should not be limited to the specific shape shown in the accompanying drawings, but includes shape deviations due to, for example, manufacturing techniques.

[0049] It is understood that in some of the accompanying drawings of this application, adjacent films with the same processing material are drawn as connected to make them resemble the actual structure.

[0050] The "packaging structure" claimed in this application is a general concept that encompasses various specific embodiments sharing a common inventive concept. For example, in one embodiment, the structure may be a package-package structure, wherein the dielectric layer is a specific dielectric layer on the surface of a substrate, and the cover layer is a solder resist layer. In another embodiment, the packaging structure may be a fan-out or 2.5D / 3D packaging structure including a redistribution layer and chip units, wherein the dielectric layer is an insulating dielectric or passivation layer on the surface of the RDL.

[0051] In this application, the term "dielectric layer" refers to an insulating layer formed on the surface of an electronic component (including but not limited to semiconductor chips, interposers, redistribution layer structures, or packaging substrates), and in the context of this application, it includes use as a passivation layer or other insulating dielectric layer. The dielectric layer serves for electrical insulation and surface protection, and in some embodiments, its material may be an organic polymer. The dielectric layer has openings that expose underlying conductive pads; in the packaging structure, the dielectric layer serves as a critical interface for bonding with other materials.

[0052] In this application, "semiconductor chip" is a broader concept. It generally refers to a functional unit with a specific function that is electrically connected through conductive connection structures (such as solder balls, bumps, copper pillars, etc.). This includes, but is not limited to: a single, unpackaged bare semiconductor chip; and multi-chip assemblies or chip packages (e.g., Chiplet, SiP, etc.) formed by stacking, side-by-side integration, or pre-packaging multiple semiconductor chips. Regardless of its internal structure, the "semiconductor chip" is electrically interconnected with pads through its exposed conductive connection structures.

[0053] This application first provides a method for forming an encapsulation structure. Figure 1 This is a flowchart illustrating the method for forming the encapsulation structure provided in some embodiments of this application. (Refer to...) Figure 1 The method for forming the encapsulation structure includes the following steps: Step S101: Provide a dielectric layer; Step S102: A microsphere enrichment layer is formed on the dielectric layer, wherein a plurality of hollow microspheres are distributed in the microsphere enrichment layer and the hollow microspheres have microcavities inside. Step S103: Open holes in the hollow microspheres in the part of the surface layer of the microsphere enrichment layer away from the dielectric layer to expose the microcavities inside the hollow microspheres in the part of the surface layer. Step S104: A capping layer is formed on the microsphere enrichment layer, and the capping layer material fills the microcavity.

[0054] The method for forming the aforementioned packaging structure will be described in detail below with reference to the accompanying drawings in some embodiments.

[0055] refer to Figure 1 In conjunction with references Figure 2 Step S101 is performed to provide dielectric layer 101.

[0056] The dielectric layer 101 serves as a support carrier and circuit carrier, providing electrical connection, protection, support, and heat dissipation. In some embodiments, the dielectric layer 101 is part of a packaging substrate or an interposer. In some embodiments, the dielectric layer 101 has metal wiring (not shown in the figure), which is used to electrically connect pads disposed on the upper and lower surfaces of the dielectric layer 101. The material of the metal wiring includes one or more of Al, Cu, W, Au, Ag, Pt, Ni, Ti, Ta, TiN, TaN, TaC, and WN.

[0057] In some embodiments, the dielectric layer 101 may be a prepreg or a laminated insulating film.

[0058] Prepreg, also known as PP sheet, is a key basic material in the manufacture of printed circuit boards (PCBs). The materials of prepreg include resin (primarily epoxy resin, but also bismaleimide triazine resin (BT), cyanate ester resin (CE), polyphenylene ether resin (PPE), polyimide resin (PI), etc.), filler (such as silica powder), and reinforcing material (mainly fiberglass cloth). In the manufacture of multilayer PCBs, prepreg acts as an adhesive and insulating layer, bonding the inner core board to the outer copper foil and providing electrical insulation.

[0059] Laminated insulating film, also known as ABF (Ajinomoto Build-up Film), is a crucial insulating material in encapsulation. It is a thin, sheet-like (film-like) photosensitive or thermosetting insulating medium with an epoxy resin core as its organic polymer backbone, giving it excellent mechanical properties, adhesion, heat resistance, and chemical stability. Besides resins (such as epoxy resin), laminated insulating film materials can also include fillers (such as silica powder), toughening agents, flame retardants, photosensitizers, solvents, and other additives to adjust properties.

[0060] In other embodiments, the dielectric layer 101 may also be other organic resin material layers.

[0061] In some embodiments, the dielectric layer 101 may or may not have hollow microspheres. When the dielectric layer 101 has hollow microspheres, the distribution density of the hollow microspheres in the dielectric layer 101 is lower than or much lower than that of the subsequent microsphere enrichment layer 102 (see reference). Figure 3 Distribution density of hollow microspheres 103 in ).

[0062] Next, refer to Figure 1 In conjunction with references Figure 3In step S102, a microsphere enrichment layer 102 is formed on the dielectric layer 101. A plurality of hollow microspheres 103 are distributed in the microsphere enrichment layer 102, and the hollow microspheres 103 have microcavities 103b inside.

[0063] As an electrically insulating dielectric material, the microsphere enrichment layer 102 contains hollow microspheres 103. On one hand, the microcavities 103b of the hollow microspheres 103 contain a low-dielectric-constant gas or vacuum (the dielectric constant of the gas or vacuum is lower than that of the resin in the microsphere enrichment layer 102), resulting in a decrease in the dielectric constant (Dk) and loss factor (Df) of the microsphere enrichment layer 102, as well as a decrease in the coefficient of thermal expansion. On the other hand, this application subsequently performs an opening process on the portion of the surface layer of the microsphere enrichment layer 102 away from the dielectric layer 101, exposing the microcavities 103b within the hollow microspheres 103 in that portion of the surface layer (see reference). Figure 5 When a capping layer 105 is formed on the microsphere enrichment layer 102, the material of the capping layer 105 fills the microcavity 103b (see reference). Figure 6 This ensures that a portion of the cover layer 105 is mechanically interlocked with the corresponding microcavity 103b, increasing the bonding force between the cover layer 105 and the microsphere enrichment layer 102. As a result, it can effectively prevent the cover layer 105 from peeling, falling off, or delamination defects, thus avoiding short circuits, corrosion, or reliability risks.

[0064] The thickness of the microsphere enrichment layer 102 is greater than the particle size of the hollow microspheres 103. In some embodiments, the thickness of the microsphere enrichment layer 102 ranges from 2 micrometers to 18 micrometers.

[0065] In some embodiments, the material of the microsphere enrichment layer 102 includes a resin and hollow microspheres 103, wherein the hollow microspheres 103 are distributed in the resin. The resin includes one or a combination of epoxy resin, polyimide resin, benzocyclobutene resin, or polybenzoxazole resin.

[0066] The hollow microsphere 103 includes a shell 103a and a microcavity 103b located inside the shell 103a. The shell 103a is made of silicate glass or polystyrene. The microcavity 103b contains air, an inert gas, a low-pressure gas, or a near-vacuum.

[0067] In some embodiments, the volume percentage of hollow microspheres 103 in the microsphere enrichment layer 102 ranges from 20% to 60%. This results in lower dielectric constant (Dk) and loss factor (Df) for the microsphere enrichment layer 102, and also ensures a sufficient number of hollow microspheres 103 on the surface of the microsphere enrichment layer 102. Subsequent pore-opening treatment of the hollow microspheres 103 on the surface allows for the formation of a sufficient number of microcavities 103b (see reference). Figure 5 When a capping layer 105 is formed on the microsphere enrichment layer 102, the material of the capping layer 105 fills the microcavity 103b (see reference). Figure 6 This ensures that a strong mechanical interlock is formed between the partial capping layer 105 and the corresponding microcavity 103b, further increasing the bonding force between the capping layer 105 and the microsphere enrichment layer 102.

[0068] In some embodiments, the particle size range of the hollow microspheres 103 or the outer diameter range of the shell 103a is 0.5 micrometers to 10 micrometers; The diameter of the microcavity 103b is smaller than the particle size of the hollow microspheres 103, and the diameter of the microcavity 103b ranges from 0.3 micrometers to 9 micrometers. The particle size of the subsequently formed capping layer 105 material is smaller than the diameter of the microcavity 103b, so that the capping layer 105 can completely fill the microcavity 103b.

[0069] In some embodiments, the particle sizes of the hollow microspheres 103 in the microsphere enrichment layer 102 may be the same or different. In one example, the particle sizes of the hollow microspheres 103 in the microsphere enrichment layer 102 are the same. In another example, some of the hollow microspheres 103 in the microsphere enrichment layer 102 have a first particle size, and some have a second particle size, where the first particle size is smaller than the second particle size. When the hollow microspheres 103 have different particle sizes, the packing voids can be reduced, that is, the smaller-sized hollow microspheres 103 can fill the spaces between the larger-sized hollow microspheres 103, increasing the volume ratio of the hollow microspheres 103, and improving the mechanical and thermal properties of the microsphere enrichment layer 102.

[0070] In some embodiments, the microsphere enrichment layer 102 includes a bottom layer and a surface layer located on the bottom layer. The bottom layer is close to the dielectric layer 101, and the surface layer is far from the dielectric layer 101. The distribution density of hollow microspheres 103 in the surface layer is greater than or equal to the distribution density of hollow microspheres 103 in the bottom layer (distribution density is the number of hollow microspheres per unit volume). In one example, when the distribution density of hollow microspheres 103 in the surface layer of the microsphere enrichment layer 102 is greater than the distribution density of hollow microspheres 103 in the bottom layer, that is, when there are more hollow microspheres 103 per unit area of ​​the surface layer, on the one hand, since there are more microcavities 103b formed per unit area of ​​the surface layer, subsequent perforation treatment of the hollow microspheres 103 in the surface layer (refer to...) Figure 5 When a capping layer 105 is formed on the microsphere enrichment layer 102, the material of the capping layer 105 fills the microcavity 103b (see reference). Figure 6This ensures that the capping layer 105 and the corresponding microcavities 103b form a stronger mechanical interlock, further increasing the bonding force between the capping layer 105 and the microsphere enrichment layer 102, and better preventing the capping layer 105 from peeling, falling off, or delaminating. On the other hand, since the distribution density of the hollow microspheres 103 in the bottom layer of the microsphere enrichment layer 102 is lower than that in the surface layer, the continuity of the resin in the bottom layer is higher, which can cut off the path of continuous diffusion of water vapor along the gaps between the microspheres. This can form an interlocking structure on the surface and prevent the channels from penetrating the entire interfacial functional membrane. As a result, the continuous resin phase in the base film layer of the interfacial functional membrane in this application and the bottom layer of the microsphere enrichment layer can block the continuous pore network extending from the surface open microcavities to the film thickness direction, thereby effectively suppressing the formation of through channels and moisture absorption paths. On the other hand, because the distribution density of hollow microspheres 103 in the bottom layer of the microsphere enrichment layer 102 is low (or the number is small), the resin continuity in the bottom layer of the microsphere enrichment layer 102 is high, and the adhesion and bonding strength with the dielectric layer 101 are stronger, making it less prone to interface delamination and peeling; and the bottom layer of the microsphere enrichment layer 102 has higher modulus and hardness, and excellent compressive and shear resistance, making it less prone to cracking when subjected to mechanical loads, assembly stress, and thermal stress. On the other hand, since the thermal expansion coefficient of hollow microspheres 103 is much lower than that of resin, when hollow microspheres 103 are distributed in a gradient density or quantity in the microsphere enrichment layer 102, a gradual thermal expansion system is formed. That is, the thermal expansion coefficient of the bottom layer of the microsphere enrichment layer 102 is relatively high, the thermal expansion coefficient of the bottom layer of the microsphere enrichment layer 102 is close to the thermal expansion coefficient of the dielectric layer 101, and the thermal expansion coefficient of the surface layer of the microsphere enrichment layer 102 is relatively low. This achieves a smooth transition of the thermal expansion coefficient of the microsphere enrichment layer 102, eliminates abrupt stress at the interface, and under thermal cycling, reflow soldering, and high and low temperature environments, the internal stress in the microsphere enrichment layer 102 can be decomposed layer by layer, which greatly reduces the risk of overall warping, microcracks, and delamination, and significantly improves long-term reliability.

[0071] In some embodiments, the distribution density of hollow microspheres 103 in the surface layer of the microsphere enrichment layer 102 being greater than the distribution density of hollow microspheres 103 in the bottom layer includes: the distribution density of hollow microspheres 103 in the microsphere enrichment layer 102 decreasing in a stepwise manner from the surface layer to the bottom layer.

[0072] In some embodiments, the formation process of the microsphere enrichment layer 102 includes a coating process and a curing process performed sequentially, wherein the coating process includes roller coating or blade coating. In existing materials used to form the microsphere enrichment layer 102, the hollow microspheres 103 are uniformly distributed. Therefore, after forming the microsphere enrichment layer 102 using conventional coating and curing processes, the distribution density of hollow microspheres 103 in the surface layer of the formed microsphere enrichment layer 102 is equal to the distribution density of hollow microspheres 103 in the bottom layer.

[0073] To ensure that the distribution density of hollow microspheres 103 in the surface layer of the microsphere enrichment layer 102 is greater than that in the bottom layer, the formation process of the microsphere enrichment layer 102 needs to be improved. Specifically, improved process 1: During the coating process, additional hollow microspheres 103 are sprinkled onto the surface of the microsphere enrichment layer 102, so that the distribution density of hollow microspheres 103 in the surface layer is greater than that in the bottom layer. Improved Process 2: The curing process includes a first curing process and a second curing process performed sequentially. The first curing process has a temperature range of 60℃-90℃ and a time of 30 min-40 min. During the first curing process, the microsphere enrichment layer 102 is fluid (uncured and unformed), and some hollow microspheres 103 in the bottom layer float to the surface layer, resulting in a higher distribution density of hollow microspheres 103 in the surface layer than in the bottom layer. The second curing process has a temperature range of 100℃-150℃ and a time of 30 min-60 min, allowing the microsphere enrichment layer 102 to solidify and form. It should be noted that, to ensure a higher distribution density of hollow microspheres 103 in the surface layer of the microsphere enrichment layer 102 than in the bottom layer, only Improved Process 1 or Improved Process 2 can be performed, or both Improved Process 1 and Improved Process 2 can be performed.

[0074] In some embodiments, reference Figure 4 After forming the microsphere enrichment layer 102 and before performing subsequent aperture opening processing, the method further includes: forming a pad 104 on the surface of the microsphere enrichment layer 102 away from the dielectric layer 101, wherein the pad 104 is electrically connected to the metal wiring (not shown in the figure) in the dielectric layer 101. The material of the pad 104 includes one or more of Al, Cu, W, Au, Ag, Pt, Ni, Ti, Ta, TiN, TaN, TaC, and WN. In a specific example, the pad 104 may be located on the surface of the microsphere enrichment layer 102 (e.g., ...). Figure 4 (As shown), it can also be located on the surface of the microsphere enrichment layer 102 (e.g. Figure 9 (As shown).

[0075] Next, refer to Figure 1 In conjunction with references Figure 5 In step S103, the hollow microspheres 103 in the part of the surface layer of the microsphere enrichment layer 102 away from the dielectric layer 101 are opened to expose the microcavities 103b inside the hollow microspheres 103 in the part of the surface layer.

[0076] This application only performs pore-opening treatment on hollow microspheres 103 in a portion of the surface layer of the microsphere enrichment layer 102 (it does not perform pore-opening treatment on all hollow microspheres 103 in the surface layer). That is, it can selectively perform pore-opening treatment on hollow microspheres 103 in local areas of the microsphere enrichment layer 102 (such as the edge or corner areas of the microsphere enrichment layer 102, areas where the capping layer is prone to peeling off, areas with a small capping layer width, and the surrounding area of ​​the pad 104), so that the subsequently formed capping layer 105 (refer to...) can be opened. Figure 6 The exposed microcavities 103b in this localized area form a mechanical interlock, increasing the bonding force between the capping layer 105 and the microsphere enrichment layer 102 in this localized area. This effectively prevents peeling, detachment, or delamination defects of the capping layer 105 in this localized area, avoiding short circuits, corrosion, or reliability risks. Since other areas of the microsphere enrichment layer 102 do not undergo opening treatment, localized reinforcement can be achieved, particularly for the edge or corner areas of the microsphere enrichment layer 102, areas where the capping layer is prone to detachment, areas with small capping layer widths, and pads 104. The process involves treating high-risk areas such as the surrounding areas, allowing the cover layer 105 material to enter the microcavity 103b after the opening to form a mechanical interlock, while other non-risk areas maintain their original structure and stable performance. On the other hand, it can avoid the degradation of dielectric properties caused by full board roughening or full surface opening treatment, keeping the hollow microspheres in untreated areas intact, thereby maintaining the advantages of low dielectric constant and low loss factor. Furthermore, it can reduce the side effects on fine lines, pad appearance, impedance window and process cleanliness, and avoid over-treatment leading to contamination residue, moisture absorption, surface defects or reliability risks.

[0077] In some embodiments, during the opening process, a portion of the shell 103a of the hollow microspheres 103 is removed, exposing the microcavities 103b. It should be noted that during the opening process, a portion of the resin in the microsphere enrichment layer 102 is also removed.

[0078] In some embodiments, before the aperture opening process, the areas of the microsphere enrichment layer 102 that do not require aperture opening are covered by a mask layer (not shown in the figure). The mask layer exposes the areas of the microsphere enrichment layer 102 that require aperture opening. Using the mask layer as a mask, aperture opening is performed on the hollow microspheres 103 in the surface layer of the microsphere enrichment layer 102 exposed by the mask layer to expose the microcavities 103b within the hollow microspheres 103 in that portion of the surface layer. In one example, the mask layer may also cover the pads 104.

[0079] In some embodiments, the aperture treatment includes plasma etching, wet etching, or laser etching. In a specific example, the plasma etching may employ argon plasma. Wet etching may employ an acidic or alkaline etching solution capable of dissolving the shell 103a of the hollow microspheres 103. Laser etching directly employs laser melting and vaporization of the shell 103a of the hollow microspheres 103.

[0080] In some embodiments, opening holes in the hollow microspheres 103 in a portion of the surface layer of the microsphere enrichment layer 102 away from the dielectric layer 101 includes: opening holes in the hollow microspheres 103 in a portion of the surface layer of the microsphere enrichment layer 102 on one or more sides of the pads 104. Specifically, in one example, opening holes is performed on the hollow microspheres 103 in a portion of the surface layer of the microsphere enrichment layer 102 between two pads 104 with small spacing. In another example, opening holes is performed on the hollow microspheres 103 in a portion of the surface layer of the microsphere enrichment layer 102 on one or more sides of the pads 104 located in the edge region of the microsphere enrichment layer 102.

[0081] Next, refer to Figure 1 In conjunction with references Figure 6 In step S104, a capping layer 105 is formed on the microsphere enrichment layer 102, and the material of the capping layer 105 fills the microcavity 103b.

[0082] In some embodiments, the cover layer 105 may be a solder resist layer, also known as a solder resist film, green oil layer, solder mask, or welding mask. It is a heat-resistant polymer protective coating applied to the surface of the microsphere enrichment layer 102. Its core function is to selectively cover non-welding areas to prevent solder bridging and short circuits during subsequent welding processes, while protecting the metal circuit (copper circuit) from oxidation, corrosion, and mechanical damage, and providing electrical insulation.

[0083] The solder resist layer is a liquid photosensitive solder resist ink, formed by spin coating, and patterned by exposure, development, and baking processes. In some embodiments, the solder resist layer comprises resin base, solvent, filler, and pigment, etc. The resin, as the main component, is often epoxy resin, polyimide resin, or acrylic resin, etc., to provide excellent heat resistance and electrical insulation properties; fillers such as silica and alumina are used to adjust viscosity and increase impact and abrasion resistance; pigments are used to adjust the color.

[0084] In other embodiments, reference is made to Figure 9The cover layer 105 can be a molding compound, which protects and secures the flip-chip semiconductor chip 200 and provides insulation, moisture protection, dust protection, corrosion protection, and antistatic properties. In some embodiments, the material of the molding compound can be epoxy resin, polyimide resin, benzocyclobutene resin, or polybenzoxazole resin with or without fillers; or it can be polybutylene terephthalate, polycarbonate, polyethylene terephthalate, polyethylene, polypropylene, polyolefin, polyurethane, polyolefin, polyethersulfone, polyamide, polyimide, ethylene-vinyl acetate copolymer, or polyvinyl alcohol with fillers. The filler can be inorganic or organic. The process for forming the molding compound includes compression molding or transfer molding.

[0085] It should be noted that when the cover layer 105 is a molding compound, before forming the cover layer 105, the semiconductor chip 200 is flip-chip mounted on the microsphere enrichment layer 102, and the semiconductor chip 200 is soldered to the pad 104 and electrically connected through solder balls; after the semiconductor chip 200 is flip-chip mounted on the microsphere enrichment layer 102, a cover layer 105 covering the semiconductor chip 200 is formed on the microsphere enrichment layer 102, the material of the cover layer 105 fills the microcavity 103b, and the cover layer 105 may or may not expose the surface of the semiconductor chip 200 away from the microsphere enrichment layer 102.

[0086] In some embodiments, reference Figure 7 When the cover layer 105 is a solder resist layer, the method further includes: patterning the cover layer 105 so that the cover layer 105 exposes the surface of the solder pad 104.

[0087] In some embodiments, reference Figure 8 The forming method further includes: A semiconductor chip 200 is provided, on which an electrical connection structure 201 is formed, the electrical connection structure 201 including solder balls; The semiconductor chip is mounted on the microsphere enrichment layer 102, and the electrical connection structure 201 on the semiconductor chip 200 is soldered to the pad 104.

[0088] In some embodiments, the solder ball material includes one or more of the following: tin, tin silver, tin indium, tin gold, tin copper, tin lead, tin silver copper, tin silver zinc, tin zinc, tin bismuth indium, tin zinc indium, or tin silver antimony.

[0089] This application also provides a packaging structure, see reference. Figure 7 or Figure 9 ,include: Dielectric layer 101; A microsphere enrichment layer 102 is located on the dielectric layer 101. A plurality of hollow microspheres 103 are distributed in the microsphere enrichment layer 102. The hollow microspheres 103 have microcavities 103b inside, and the microcavities 103b in the hollow microspheres 103 in a part of the surface layer of the microsphere enrichment layer 102 away from the dielectric layer 101 are exposed. A capping layer 105 is located on the microsphere enrichment layer 102, and the material of the capping layer 105 fills the microcavity 103b.

[0090] In some embodiments, the material of the microsphere enrichment layer 102 includes resin and hollow microspheres 103, wherein the hollow microspheres 103 are distributed in the resin; The resin includes one or a combination of epoxy resin, polyimide resin, benzocyclobutene resin or polybenzoxazole resin.

[0091] In some embodiments, the hollow microsphere 103 includes a shell 103a and a microcavity 103b located inside the shell 103a; The material of the housing 103a includes silicate glass or polystyrene.

[0092] In some embodiments, the volume percentage of hollow microspheres 103 in the microsphere enrichment layer 102 ranges from 20% to 60%.

[0093] In some embodiments, the particle size range of the hollow microspheres 103 or the outer diameter range of the shell 103a is 0.5 micrometers to 10 micrometers; The diameter of the microcavity 103b is smaller than the particle size of the hollow microsphere 103, and the diameter of the microcavity 103b ranges from 0.3 micrometers to 9 micrometers.

[0094] In some embodiments, the particle size of the capping layer 105 material is smaller than the diameter of the microcavity 103b; the thickness of the microsphere enrichment layer 102 is greater than the particle size of the hollow microspheres 103.

[0095] In some embodiments, the particle sizes of the hollow microspheres 103 in the microsphere enrichment layer 102 may be the same or different.

[0096] In some embodiments, the microsphere enrichment layer 102 includes a bottom layer and a surface layer located on the bottom layer, the bottom layer being close to the dielectric layer 101, the surface layer being far from the dielectric layer 101, and the distribution density of hollow microspheres 103 in the surface layer being greater than or equal to the distribution density of hollow microspheres 103 in the bottom layer.

[0097] In some embodiments, the dielectric layer 101 has metal wiring; The portion of the surface of the microsphere enrichment layer 102 away from the dielectric layer 101 has pads 104, which are electrically connected to the metal wiring. The microcavities 103b of hollow microspheres 103 in the surface layer of the microsphere enrichment layer 102 on one or more sides of the pad 104 are exposed.

[0098] In some embodiments, the cover layer 105 includes a solder mask layer (reference 2). Figure 7 ) or encapsulation layer (see reference) Figure 9 ); When the cover layer 105 is a solder resist layer, the cover layer 105 exposes the surface of the solder pad 104.

[0099] In some embodiments, reference Figure 8 Or refer to Figure 9 It also includes: Semiconductor chip 200, on which solder balls are formed; The solder balls on the semiconductor chip 200 are soldered to the pads 104 on the package structure.

[0100] In some embodiments, reference Figure 8 When the cover layer 105 is a solder resist layer, the cover layer 105 is located on the microsphere enrichment layer 102, exposing the surface of the solder pad 104, and the material of the cover layer 105 fills the microcavity 103b.

[0101] In other embodiments, reference is made to Figure 8 When the cover layer 105 is a molding layer, the cover layer 105 is located on the microsphere enrichment layer 102, the material of the cover layer 105 fills the microcavity 103b, and the cover layer covers the semiconductor chip 200.

[0102] In summary, the encapsulation structure and its formation method of this application, due to the formation of a microsphere enrichment layer on the dielectric layer, in which hollow microspheres are distributed, on the one hand, the microcavities of the hollow microspheres are filled with air (with a dielectric constant of 1, lower than the dielectric constant of the resin in the microsphere enrichment layer), which reduces the dielectric constant (Dk) and loss factor (Df) of the microsphere enrichment layer, and also reduces the coefficient of thermal expansion; on the other hand, this application performs an opening treatment on the hollow microspheres in a portion of the surface layer of the microsphere enrichment layer away from the dielectric layer, exposing the microcavities inside the hollow microspheres in the portion of the surface layer. When a capping layer is formed on the microsphere enrichment layer, the capping layer material fills the microcavities, thus achieving a mechanical interlock between the portion of the capping layer and the corresponding microcavities, increasing the bonding force between the capping layer and the microsphere enrichment layer, thereby effectively preventing capping layer peeling, detachment, or delamination defects, and avoiding short circuits, corrosion, or reliability risks.

[0103] Furthermore, this application only performs pore-opening treatment on hollow microspheres in a portion of the surface layer of the microsphere-enriched layer (it does not perform pore-opening treatment on all hollow microspheres in the surface layer). That is, it can selectively perform pore-opening treatment on hollow microspheres in local areas of the microsphere-enriched layer (such as areas where the capping layer is prone to peeling off, areas where the capping layer is narrow, or edge areas), so that the formed capping layer and the exposed microcavities in the local area form a mechanical interlock, which increases the bonding force between the capping layer and the microsphere-enriched layer in that local area. Therefore, it can effectively prevent the capping layer from peeling off, falling off, or delaminating in the local area, avoiding short circuits, corrosion, or reliability risks. Since other areas of the microsphere-enriched layer are not pore-opened, the other areas of the microsphere-enriched layer can remain intact, so that the performance parameters (dielectric constant, loss factor, coefficient of thermal expansion, etc.) of the other areas of the microsphere-enriched layer remain stable, ensuring the electrical performance of the packaging structure.

[0104] In the description of this specification, the references to terms such as "some embodiments," "other embodiments," "ideal embodiments," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example that are included in at least one embodiment or example of this application. In this specification, the illustrative descriptions of the above terms do not necessarily refer to the same embodiments or examples.

[0105] It should be noted that, where there is no conflict, the features in the different embodiments of this application described above can be combined with each other. Furthermore, in each of the above embodiments, the focus is on describing the differences from other embodiments; other specific descriptions of the same / similar parts between the embodiments can be referred to (or referenced) interchangeably. In addition, descriptions of well-known components and technologies have been omitted in the above description to avoid unnecessarily obscuring the concepts of this application.

[0106] Although this application has been disclosed above with reference to preferred embodiments, it is not intended to limit this application. Any person skilled in the art can make possible changes and modifications to the technical solutions of this application by utilizing the methods and techniques disclosed above without departing from the spirit and scope of this application. Therefore, any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of this application without departing from the content of the technical solutions of this application shall fall within the protection scope of the technical solutions of this application.

Claims

1. A method for forming an encapsulation structure, characterized in that, include: Provide a dielectric layer; A microsphere enrichment layer is formed on the dielectric layer. A plurality of hollow microspheres are distributed in the microsphere enrichment layer. The hollow microspheres have microcavities inside. The microsphere enrichment layer includes a bottom layer and a surface layer located on the bottom layer. The bottom layer is close to the dielectric layer, and the surface layer is far away from the dielectric layer. The distribution density of hollow microspheres in the surface layer is greater than the distribution density of hollow microspheres in the bottom layer. Hollow microspheres in a portion of the surface layer of the microsphere enrichment layer away from the dielectric layer are perforated to expose the microcavities inside the hollow microspheres in that portion of the surface layer. A capping layer is formed on the microsphere enrichment layer, and the capping layer material fills the microcavity.

2. The method for forming the packaging structure according to claim 1, characterized in that, The material of the microsphere enrichment layer includes resin and hollow microspheres, wherein the hollow microspheres are distributed in the resin.

3. The method for forming the packaging structure according to claim 2, characterized in that, The resin includes one or a combination of epoxy resin, polyimide resin, benzocyclobutene resin or polybenzoxazole resin.

4. The method for forming the packaging structure according to claim 2, characterized in that, The hollow microspheres include a shell and a microcavity located inside the shell; The material of the housing includes silicate glass or polystyrene.

5. The method for forming the packaging structure according to claim 4, characterized in that, The volume percentage of hollow microspheres in the microsphere enrichment layer ranges from 20% to 60%.

6. The method for forming the packaging structure according to claim 4 or 5, characterized in that, The particle size range of the hollow microspheres or the outer diameter range of the shell is 0.5 micrometers to 10 micrometers; The diameter of the microcavity is smaller than the particle size of the hollow microspheres, and the diameter of the microcavity ranges from 0.3 micrometers to 9 micrometers.

7. The method for forming the packaging structure according to claim 6, characterized in that, The particle size of the capping material is smaller than the diameter of the microcavity; The thickness of the microsphere enrichment layer is greater than the particle size of the hollow microspheres.

8. The method for forming the packaging structure according to claim 2, characterized in that, The hollow microspheres in the microsphere enrichment layer may have the same or different particle sizes.

9. The method for forming the packaging structure according to claim 1, characterized in that, The formation process of the microsphere enrichment layer includes a coating process and a curing process.

10. The method for forming the packaging structure according to claim 9, characterized in that, The coating process includes roller coating or blade coating.

11. The method for forming the packaging structure according to claim 9, characterized in that, During the coating process, additional hollow microspheres are sprinkled onto the surface of the microsphere enrichment layer, so that the distribution density of hollow microspheres in the surface layer is greater than that in the bottom layer.

12. The method for forming the packaging structure according to claim 9 or 11, characterized in that, The curing process includes a first curing process and a second curing process performed sequentially. The temperature range of the first curing process is 60℃-90℃, and the time is 30 min-40 min. During the first curing process, some hollow microspheres in the bottom layer float to the surface layer, making the distribution density of hollow microspheres in the surface layer greater than that in the bottom layer. The temperature range of the second curing process is 100℃-150℃, and the time is 30 min-60 min, which allows the microsphere enrichment layer to solidify and take shape.

13. The method for forming the packaging structure according to claim 4, characterized in that, Before performing the opening process, the method further includes: covering a portion of the surface of the microsphere enrichment layer away from the dielectric layer with a mask layer, the mask layer exposing the surface of the microsphere enrichment layer that needs to be opened; During the opening process, the mask layer is used as a mask to remove part of the shell, exposing the microcavity.

14. The method for forming the packaging structure according to claim 13, characterized in that, The hole-opening process includes plasma etching, wet etching, or laser etching.

15. The method for forming the packaging structure according to claim 1, characterized in that, The dielectric layer contains metallic wiring; Prior to the opening process, pads are formed on the surface of the microsphere enrichment layer away from the dielectric layer, and the pads are electrically connected to the metal wiring. The process of opening holes in the hollow microspheres in the portion of the surface layer of the microsphere enrichment layer away from the dielectric layer includes: opening holes in the hollow microspheres in the portion of the surface layer of the microsphere enrichment layer on one or more sides of the pad.

16. The method for forming the packaging structure according to claim 15, characterized in that, The cover layer includes a solder mask layer; after forming the solder mask layer, the method further includes: patterning the solder mask layer so that the solder mask layer is exposed on the surface of the pad.

17. The method for forming the packaging structure according to claim 15, characterized in that, The cover layer includes a molding layer.

18. A packaging structure, characterized in that, include: Dielectric layer; A microsphere enrichment layer is located on the dielectric layer, wherein a plurality of hollow microspheres are distributed in the microsphere enrichment layer, and each hollow microsphere has a microcavity inside. The microsphere enrichment layer includes a bottom layer and a surface layer located on the bottom layer. The bottom layer is close to the dielectric layer, and the surface layer is far away from the dielectric layer. The distribution density of hollow microspheres in the surface layer is greater than that in the bottom layer, and the microcavities in the hollow microspheres in a portion of the surface layer on the side of the microsphere enrichment layer away from the dielectric layer are exposed. A capping layer is located on the microsphere enrichment layer, and the capping layer material fills the microcavity.

19. The packaging structure according to claim 18, characterized in that, The material of the microsphere enrichment layer includes resin and hollow microspheres, wherein the hollow microspheres are distributed in the resin; The resin includes one or a combination of epoxy resin, polyimide resin, benzocyclobutene resin or polybenzoxazole resin.

20. The packaging structure according to claim 19, characterized in that, The hollow microspheres include a shell and a microcavity located inside the shell; The material of the housing includes silicate glass or polystyrene.

21. The packaging structure according to claim 20, characterized in that, The volume percentage of hollow microspheres in the microsphere enrichment layer ranges from 20% to 60%.

22. The packaging structure according to claim 20 or 21, characterized in that, The particle size range of the hollow microspheres or the outer diameter range of the shell is 0.5 micrometers to 10 micrometers; The diameter of the microcavity is smaller than the particle size of the hollow microspheres, and the diameter of the microcavity ranges from 0.3 micrometers to 9 micrometers.

23. The packaging structure according to claim 20, characterized in that, The particle size of the capping material is smaller than the diameter of the microcavity; The thickness of the microsphere enrichment layer is greater than the particle size of the hollow microspheres.

24. The packaging structure according to claim 20, characterized in that, The hollow microspheres in the microsphere enrichment layer may have the same or different particle sizes.

25. The packaging structure according to claim 18, characterized in that, The dielectric layer contains metallic wiring; The portion of the surface of the microsphere enrichment layer away from the dielectric layer has pads, which are electrically connected to the metal wiring. The microcavities of hollow microspheres are exposed in the surface layer of the microsphere enrichment layer on one or more sides of the pad.

26. The packaging structure according to claim 25, characterized in that, The cover layer includes a solder mask layer or a plastic sealant layer; When the cover layer is a solder mask layer, the cover layer is exposed on the surface of the solder pad.

27. The packaging structure according to claim 25, characterized in that, Also includes: A semiconductor chip having an electrical connection structure formed thereon; the electrical connection structure on the semiconductor chip being soldered to a pad; the cover layer being a molding compound that covers at least a portion of the semiconductor chip.

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