A multilayer chip shielding structure and its fabrication method

Abstract

This invention discloses a multi-layer chip shielding structure and its fabrication method, relating to the field of shielding technology. The structure includes a metal shield, which is a multi-layered structure comprising a suppression layer, an absorption layer, and a reflection layer. While still using a metal shield to form the shielding structure, this invention differs from existing technologies in that it employs a multi-layered structure. The innermost layer is a suppression layer made of nano-silver coating or gradient porous metal foam, achieving suppression of near-field electric fields. The absorption layer enables high-frequency absorption without heat buildup. The reflection layer reflects low-frequency electromagnetic waves, achieving low-frequency reflection. This invention, while using a metal shield as the shielding structure, introduces a multi-layered design, effectively overcoming the limitations of single-layer shielding structures in high-frequency signal shielding, the tendency for heat buildup in plastic-encapsulated shielding, and the narrow bandgap of composite material shielding.

Description

Technical Field

[0001] This invention relates to the field of shielding technology, and more specifically, to a multilayer chip shielding structure and its preparation method. Background Technology

[0002] With the widespread adoption of 5G communication, the Internet of Things (IoT), and high-frequency electronic devices, electromagnetic interference (EMI) has become an increasingly prominent issue. Currently, chip shielding structures mainly fall into three categories:

[0003] 1. Single-layer metal shielding cover: For example, the electromagnetic shielding structure mentioned by Huawei in its patent with patent number 202210635054.X.

[0004] 2. Molded shielding layer: For example, the chip packaging structure mentioned in the patent of Vanchip Technology with patent number 202323168414.9.

[0005] 3. Composite shielding materials: For example, the composite material mentioned by the Graphene Polymer Composite Materials R&D Center of Shandong Lutai Holding Group Co., Ltd. in patent number 201810004138.7.

[0006] However, all three shielding structures mentioned above have drawbacks. For example, single-layer shielding structures have limited shielding efficiency for high-frequency signals and cannot cope with multi-band electromagnetic interference; the multi-layer interconnected structure of the plastic-encapsulated shielding layer complicates the manufacturing process, has low heat dissipation efficiency, easily leads to heat accumulation, and is difficult to cope with multi-band interference; composite materials offer excellent shielding performance, but have a narrow shielding band range. Therefore, how to combine the shielding advantages of the above three structures while overcoming their respective shortcomings is the technical problem that this invention aims to solve. Summary of the Invention

[0007] The summary section introduces a series of simplified concepts, which will be further explained in detail in the detailed description section. The summary section of this invention is not intended to limit the key features and essential technical features of the claimed technical solution, nor is it intended to determine the scope of protection of the claimed technical solution.

[0008] To at least partially solve the above problems, the present invention provides a multi-layer chip shielding structure, comprising: a metal shield, wherein the metal shield has a multi-layer structure, comprising an inhibition layer, an absorption layer and a reflection layer;

[0009] The suppression layer, located inside the metal shield, is used to suppress the near-field electric field.

[0010] An absorption layer, located between the suppression layer and the reflection layer, or embedded within the reflection layer, is used to absorb electromagnetic waves.

[0011] The reflective layer, located on the outside of the metal shield, is used to reflect incident low-frequency electromagnetic waves back to the external environment.

[0012] Preferably, the metal cover has a double-layer structure, consisting of an inner layer and an outer layer. The inner layer is an inhibition layer, and the outer layer is a composite layer composed of an absorption layer and a reflection layer.

[0013] Preferably, the metal cover has a three-layer structure, namely an inner layer, a middle layer, and an outer layer, wherein the inner layer is an inhibition layer, the middle layer is an absorption layer, and the outer layer is a reflective layer.

[0014] Preferably, the reflective layer is a Koch snowflake-shaped fractal mesh.

[0015] Preferably, the mesh gaps are filled with an absorption layer.

[0016] Preferably, the inhibition layer is a nano-silver coating or a gradient porous metal foam.

[0017] Preferably, the absorber layer is a composite material containing ferrite-graphene.

[0018] Preferably, the reflective layer is a highly conductive metal layer.

[0019] A method for fabricating a multilayer chip shielding structure, comprising the following steps:

[0020] S1: Fabricate a reflective layer on the substrate;

[0021] S2: Graphics processing;

[0022] S3: Fill the graphic grid with an absorption layer;

[0023] S4: Prepare an inhibition layer on the composite layer of the reflective layer and the absorption layer;

[0024] S5: Performance Testing.

[0025] A method for fabricating a multilayer chip shielding structure, comprising the following steps:

[0026] S1: Fabricate a reflective layer on the substrate;

[0027] S2: Fabricate an absorption layer on the reflective layer;

[0028] S3: Prepare an inhibition layer on the absorption layer;

[0029] S4: Performance test.

[0030] Compared with the prior art, the present invention has at least the following beneficial effects:

[0031] Through the above structural design, this invention still uses a metal shield to form a shielding structure. However, unlike existing technologies, this invention has a multi-layer structure, with the innermost layer being a suppression layer made of nano-silver coating or gradient porous metal foam. When the suppression layer is a nano-silver coating, the local electric field enhancement effect of the nanostructure can suppress near-field coupling interference of the chip; when the suppression layer is a gradient porous metal foam, the gradient porous structure can attenuate residual electromagnetic waves through multiple reflections, thereby achieving the suppression effect of the near-field electric field.

[0032] The absorption layer is made of ferrite-graphene composite material, which can convert high-frequency electromagnetic waves into heat energy through the magnetic loss of ferrite and the dielectric loss of graphene, thereby achieving high-frequency absorption. The absorption rate of the absorption layer is higher than 70%. Since the existing plastic encapsulation shielding technology is not used, the present invention will not have the phenomenon of heat accumulation.

[0033] The reflective layer is mainly made of highly conductive metals, such as copper or aluminum. Highly conductive metals can reflect low-frequency electromagnetic waves, thereby achieving the effect of low-frequency reflection. The reflectivity of the reflective layer is not less than 90%.

[0034] By adopting a multi-layer structure design, the total shielding effectiveness (SE) is the sum of the reflection loss (R) (generated by the reflective layer), the absorption loss (A) (generated by the absorption layer), and the multiple reflection correction term (B, representing the additional loss when the electromagnetic wave is reflected multiple times inside the shielding material, the correction term is usually a negative value because it takes into account the additional attenuation caused by multiple reflections) generated by the suppression layer, that is, SE = R + A + B, where B is a negative value.

[0035] Therefore, this invention introduces a multi-layer structure design while using a metal shield as the shielding structure, effectively overcoming the problems of limited shielding efficiency of single-layer shielding structures for high-frequency signals, easy heat accumulation in plastic-encapsulated shielding, and narrow shielding band range of composite materials.

[0036] The multilayer chip shielding structure and its preparation method described in this invention, as well as other advantages, objectives and features of this invention, will be partly apparent from the following description, and partly understood by those skilled in the art through study and practice of this invention. Attached Figure Description

[0037] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings:

[0038] Figure 1 This is a schematic diagram of the first embodiment of the multilayer chip shielding structure described in this invention.

[0039] Figure 2This is a schematic diagram of a second embodiment of the multilayer chip shielding structure described in this invention.

[0040] In the diagram: 1. Inhibition layer, 2. Absorption layer, 3. Reflection layer. Detailed Implementation

[0041] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments, so that those skilled in the art can implement it based on the description.

[0042] It should be understood that terms such as “having,” “comprising,” and “including” as used herein do not exclude the presence or addition of one or more other elements or combinations thereof.

[0043] like Figures 1-2 As shown, the present invention provides a multi-layer chip shielding structure, including: a metal cover, wherein the metal cover has a multi-layer structure, namely an inhibition layer 1, an absorption layer 2 and a reflection layer 3;

[0044] Suppression layer 1, located inside the metal shield, is used to suppress the near-field electric field;

[0045] Absorption layer 2, located between suppression layer 1 and reflection layer 3, or embedded in reflection layer 3, is used to absorb electromagnetic waves;

[0046] The reflective layer 3, located on the outside of the metal cover, is used to reflect incident low-frequency electromagnetic waves back to the external environment.

[0047] The suppression layer 1 is a nano-silver coating or a gradient porous metal foam. The nano-silver coating (typically 20-50 nm) forms an equivalent capacitance-inductance network in the near field (<1 mm) of the chip through the localized surface plasmon resonance (LSPR) effect, thereby suppressing high-frequency coupling noise. For example, when the thickness of the nano-silver coating reaches 100 nm, the near-field electric field strength is reduced by 60%.

[0048] Gradient porosity metal foams (such as nickel foams) are divided into a dense surface region and a loose bottom region. Typically, the porosity of the dense surface region is 10%, while the porosity of the loose bottom region is 80%. The dense surface region can reflect residual electromagnetic waves, while the loose bottom region can enhance heat dissipation through turbulence.

[0049] The absorber layer 2 is a composite material containing ferrite and graphene, typically a ferrite-graphene composite material. The hysteresis loss of the ferrite (such as NiZn ferrite) and the interfacial polarization loss of the graphene can effectively complement each other. Simultaneously, the graphene can also be used as a heat dissipation channel to prevent heat buildup.

[0050] The reflective layer 3 is a highly conductive metal layer, typically copper or aluminum. As the first line of defense in this invention, the reflective layer 3 primarily relies on the reflective properties of highly conductive metals (such as copper, aluminum, and nickel alloys) to reflect incident low-frequency electromagnetic waves back to the external environment. Free electrons in the highly conductive metal can generate induced currents under the influence of an external electromagnetic field, thereby forming a reverse electromagnetic field that cancels out the incident energy.

[0051] In addition to their electrical conductivity, highly conductive metals also possess the structural strength and corrosion resistance of metals. For example, aluminum layers, through anodizing to form an Al2O3 protective film, can withstand corrosion for over 500 hours in salt spray tests, making them suitable for automotive electronic devices. Furthermore, highly conductive metals have high ductility, effectively accommodating thermal stress deformation during the packaging process.

[0052] The working principle and beneficial effects of the above technical solution are as follows: Through the design of the above structure, the present invention still uses a metal cover to form a shielding structure. However, unlike the prior art, the present invention has a multi-layer structure. The innermost layer is a suppression layer 1 made of nano-silver coating or gradient porous metal foam. When the suppression layer 1 is a nano-silver coating, the near-field coupling interference of the chip can be suppressed through the local electric field enhancement effect of the nanostructure. When the suppression layer 1 is a gradient porous metal foam, the gradient porous structure can attenuate residual electromagnetic waves through multiple reflections, thereby achieving the suppression effect of the near-field electric field.

[0053] The absorption layer 2 is made of ferrite-graphene composite material. It can convert high-frequency electromagnetic waves into heat energy through the magnetic loss of ferrite and the dielectric loss of graphene, thereby achieving high-frequency absorption. The absorption rate of the absorption layer 2 is higher than 70%. Since the existing plastic encapsulation shielding technology is not used, the present invention will not have the phenomenon of heat accumulation.

[0054] The reflective layer 3 is mainly made of highly conductive metal, such as copper or aluminum. Highly conductive metal can reflect low-frequency electromagnetic waves, thereby achieving the effect of low-frequency reflection. The reflectivity of the reflective layer 3 is not less than 90%.

[0055] By adopting a multi-layer structure design, the total shielding effectiveness (SE) is the sum of the reflection loss (R) (generated by the reflection layer 3), the absorption loss (A) (generated by the absorption layer 2), and the multiple reflection correction term (B, representing the additional loss when the electromagnetic wave is reflected multiple times inside the shielding material, the correction term is usually a negative value because it takes into account the additional attenuation caused by multiple reflections) generated by the suppression layer 1, that is, SE = R + A + B, where B is a negative value.

[0056] Therefore, this invention introduces a multi-layer structure design while using a metal shield as the shielding structure, effectively overcoming the problems of limited shielding efficiency of single-layer shielding structures for high-frequency signals, easy heat accumulation in plastic-encapsulated shielding, and narrow shielding band range of composite materials.

[0057] In one embodiment, the metal cover has a double-layer structure, consisting of an inner layer and an outer layer. The inner layer is a suppression layer 1, and the outer layer is a composite layer composed of an absorption layer 2 and a reflective layer 3. To fabricate the composite layer, the reflective layer 3 is typically used as the main mesh to cover the suppression layer 1, and then the absorption layer 2 is embedded within the mesh of the reflective layer 3.

[0058] In this embodiment, the reflective layer 3 adopts a hollow structure design. The hollow size is usually no greater than λ / 10, where λ is the wavelength corresponding to the highest shielding frequency. For example, 40GHz corresponds to a wavelength of 7.5mm, and the hollow aperture must be <0.75mm.

[0059] Furthermore, the reflective layer 3 is a Koch snowflake-shaped fractal mesh. The mesh gaps are filled with an absorption layer 2. By setting the reflective layer 3 as a hollow structure, the overall weight of the invention can be reduced by 30%-50%. The specific weight reduction percentage depends on the shape of the fractal mesh; for example, using a Koch snowflake-shaped fractal mesh can reduce weight by 30%, while using a Menger sponge-like fractal mesh can reduce weight by up to 50%. Simultaneously, the heat dissipation area of ​​the reflective layer 3 is increased by at least 40%, increasing heat diffusion efficiency. The hollow structure design also allows the reflective layer 3 to be folded. Although the hollow structure design sacrifices reflection loss for weight reduction compared to a solid structure, and its shielding effect is weaker, it is more suitable for devices requiring weight reduction, such as drone communication modules and wearable devices.

[0060] A method for fabricating a multilayer chip shielding structure, used to prepare the multilayer chip shielding structure described in the first embodiment, includes the following steps:

[0061] S1: Surface treatment is performed on the substrate (such as a ceramic substrate or flexible polyimide film) to remove organic matter and oxide layer, improve adhesion, and then a highly conductive metal is deposited using magnetron sputtering process to create reflective layer 3;

[0062] S2: Perform fractal mesh processing on the reflective layer 3, and fabricate the fractal mesh through photolithography or oxidation processes;

[0063] S3: Prepare the composite material slurry of the absorption layer 2, apply the slurry to the grid of the reflective layer 3, and perform curing treatment. After the treatment is completed, apply an insulating layer to improve the pressure resistance.

[0064] S4: An inhibition layer 1 is prepared on the composite layer of reflective layer 3 and absorber layer 2. A nano-silver coating is prepared by chemical silver plating, or a gradient porous metal foam is prepared by powder metallurgy forming process.

[0065] S5: Conduct electromagnetic shielding effectiveness testing, thermal resistance testing, and reliability verification.

[0066] In the second embodiment, the metal shield has a three-layer structure: an inner layer, a middle layer, and an outer layer. The inner layer is the suppression layer 1, the middle layer is the absorption layer 2, and the outer layer is the reflective layer 3. In this embodiment, the reflective layer 3 eliminates the perforated structure design and adopts a solid structure design, thereby ensuring that the shielding effect is not affected. Because of the three-layer stacked structure design, the choice of absorption layer 2 is more diversified. In addition to ferrite-graphene composite materials, magnetic fluid can also be used as absorption layer 2. For example, a copper-polyimide folded film can be used as the outer layer, a magnetic fluid as the middle layer, and a nano-silver coating as the inner layer. It is only necessary to ensure the seal after injecting the magnetic fluid.

[0067] A method for preparing a multilayer chip shielding structure, used to prepare the multilayer chip shielding structure described in the second embodiment, includes the following steps:

[0068] S1: Surface treatment is performed on the substrate (such as a ceramic substrate or flexible polyimide film) to remove organic matter and oxide layer, improve adhesion, and then a highly conductive metal is deposited using magnetron sputtering process to create reflective layer 3;

[0069] S2: Prepare the composite material slurry for the absorption layer 2, and coat the slurry onto the reflective layer 3;

[0070] S3: Prepare inhibition layer 1 on the composite layer of absorption layer 2, prepare nano-silver coating by chemical silver plating, or prepare gradient porous metal foam by powder metallurgy forming process;

[0071] S4: Conduct electromagnetic shielding effectiveness testing, thermal resistance testing, and reliability verification.

[0072] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0073] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between them; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0074] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. Other modifications can be easily made by those skilled in the art. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and illustrations shown and described herein.

Claims

1. A multilayer chip shield structure, comprising: The metal cover is characterized in that the metal cover is a multilayer structure, and the multilayer structure comprises a suppression layer (1), an absorption layer (2) and a reflection layer (3) respectively. The suppression layer (1) is a nano-silver coating or a gradient-pore metal foam; the suppression layer (1) is located at the inner side of the metal cover and is used for suppressing a near-field electric field. The nano-silver coating forms an equivalent capacitance inductance network in the near field of the chip through a localized surface plasmon resonance effect, so as to suppress high-frequency coupling noise. The gradient-pore metal foam is divided into a surface dense layer and a bottom loose layer; the surface dense layer is used for reflecting residual electromagnetic waves, and the bottom loose layer is used for enhancing heat dissipation. The absorption layer (2) comprises a ferrite-graphene composite material; the absorption layer (2) is located between the suppression layer (1) and the reflection layer (3), or is embedded in the reflection layer (3), and is used for absorbing electromagnetic waves. The reflection layer (3) is a high-conductivity metal layer; the reflection layer (3) is located at the outer side of the metal cover and is used for reflecting incident low-frequency electromagnetic waves back to the external environment.

2. The multi-layer chip shielding structure of claim 1, wherein, The metal cover is a double-layer structure, and the double-layer structure comprises an inner layer and an outer layer; the inner layer is the suppression layer (1), and the outer layer is a composite layer composed of the absorption layer (2) and the reflection layer (3).

3. The multi-layer chip shielding structure of claim 1, wherein, The metal cover is a three-layer structure, and the three-layer structure comprises an inner layer, a middle layer and an outer layer; the inner layer is the suppression layer (1), the middle layer is the absorption layer (2), and the outer layer is the reflection layer (3).

4. The multi-layer chip shielding structure according to claim 2 or 3, characterized in that, The reflection layer (3) is a Koch snowflake-shaped fractal grid.

5. The multi-layer chip shielding structure of claim 4, wherein, The grid gap is filled with the absorption layer (2).

6. A method for producing a multilayer chip shielding structure, for producing the multilayer chip shielding structure according to any one of claims 1 to 2, 4 to 5, characterized by, The steps are as follows: S1: manufacturing the reflection layer (3) on a substrate; S2: performing pattern processing; S3: filling the absorption layer (2) in the pattern grid; S4: manufacturing the suppression layer (1) on the composite layer of the reflection layer (3) and the absorption layer (2); S5: performance testing.

7. A method for producing a multilayer chip shielding structure, for producing the multilayer chip shielding structure according to any one of claims 1, 3 to 4, characterized by, The steps are as follows: S1: manufacturing the reflection layer (3) on a substrate; S2: manufacturing the absorption layer (2) on the reflection layer (3); S3: manufacturing the suppression layer (1) on the absorption layer (2); S4: performance testing.

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