Multi-layer chip shielding structure and preparation method thereof

Abstract

The invention discloses a multi-layer chip shielding structure and a preparation method thereof, and relates to the technical field of shielding covers, and the multi-layer chip shielding structure comprises a metal cover which is of a multi-layer structure and comprises an inhibition layer, an absorption layer and a reflection layer. Through the structural design, a shielding structure is still formed by adopting a metal cover form, but different from the prior art, the shielding structure is of a multi-layer structure, the inhibition layer made of a nano-silver coating or gradient pore metal foam is located on the innermost side, and the inhibition effect on a near-field electric field is achieved. And the absorption layer can realize high-frequency absorption, and the phenomenon of hot accumulation is avoided. The reflecting layer can reflect low-frequency electromagnetic waves, so that the low-frequency reflection effect is achieved. According to the invention, a multi-layer structure design is introduced while the metal cover is used as a shielding structure, so that the problems that the shielding efficiency of a single-layer shielding structure on a high-frequency signal is limited, hot accumulation is easily generated by plastic packaging shielding, and the shielding wave band range of a composite material is narrow are effectively solved.

Description

Technical Field

[0001] The present invention relates to the technical field of shielding covers, and more specifically, to a multi-layer chip shielding structure and a preparation method thereof. Background Art

[0002] With the popularization of 5G communication, Internet of Things, and high-frequency electronic devices, the problem of electromagnetic interference (EMI) has become increasingly prominent. In the prior art, the shielding structures of chips are mainly the following three types:

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

[0004] 2. Plastic-sealed shielding layer: For example, the chip packaging structure mentioned in the patent with the patent number 202323168414.9 by Vanchip Semiconductor Co., Ltd.

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

[0006] However, the above three shielding structures all have defects. For example, the single-layer shielding structure has limited shielding efficiency for high-frequency signals and cannot cope with multi-band electromagnetic interference; the multi-layer interconnection structure of the plastic-sealed shielding layer complicates the processing technology, has low heat dissipation efficiency, is prone to heat accumulation, and is difficult to cope with multi-band interference; the composite material has excellent shielding effect, but the shielding band range is relatively narrow. Therefore, how to combine the shielding advantages of the above three and overcome their respective defects is the technical problem to be solved by the present invention. Summary of the Invention

[0007] A series of simplified concepts are introduced in the Summary of the Invention section, which will be further elaborated in detail in the Detailed Description section. The Summary of the Invention section of the present invention does not mean to attempt to define the key features and essential technical features of the claimed technical solution, nor does it mean to attempt to determine the protection scope of the claimed technical solution.

[0008] To at least partially solve the above problems, the present invention provides a multi-layer chip shielding structure, including: a metal cover, the metal cover being a multi-layer structure, namely a suppression layer, an absorption layer, and a reflection layer;

[0009] The suppression layer is located inside the metal cover and is used to suppress the near-field electric field;

[0010] The absorption layer is located between the suppression layer and the reflection layer, or is embedded in the reflection layer, and is used to absorb electromagnetic waves;

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

[0012] Preferably, the metal cover is a double-layer structure, including 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 reflective layer.

[0013] Preferably, the metal cover is a three-layer structure, including an inner layer, a middle layer, and an outer layer. 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 grid.

[0015] Preferably, the grid voids are filled with an absorption layer.

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

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

[0018] Preferably, the reflective layer is a high-conductivity metal layer.

[0019] A preparation method of a multi-layer chip shielding structure for preparing the multi-layer chip shielding structure is as follows:

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

[0021] S2: Graphic 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 preparation method of a multi-layer chip shielding structure for preparing the multi-layer chip shielding structure is as follows:

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

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

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

[0029] S4: Performance testing.

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

[0031] Through the design of the above structure, the present invention still forms a shielding structure in the form of a metal cover. However, different from the prior art, the present invention is a multi-layer structure, and the innermost layer is an inhibition layer made of a nano-silver coating or gradient pore metal foam. When the inhibition layer is a nano-silver coating, the near-field coupling interference of the chip can be inhibited through the local electric field enhancement effect of the nano-structure; when the inhibition layer is gradient pore metal foam, the gradient pore structure can attenuate the residual electromagnetic waves through multiple reflections, thereby achieving the inhibition effect on the near-field electric field.

[0032] The absorption layer is made of a ferrite-graphene composite material, and 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%. Also, because the plastic encapsulation shielding technology of the prior art is not adopted, the phenomenon of heat accumulation will not occur in the present invention.

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

[0034] By adopting the multi-layer structure design, the total shielding effectiveness (SE) is the sum of the reflection loss (R) (generated by the reflection 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 considers the additional attenuation caused by multiple reflections), that is, SE = R + A + B, and B is a negative value.

[0035] Thus, while using the metal cover as the shielding structure, the present invention introduces the multi-layer structure design, effectively overcoming the problems of limited shielding efficiency of the single-layer shielding structure for high-frequency signals, easy generation of heat accumulation in plastic encapsulation shielding, and relatively narrow shielding band range of the composite material shielding.

[0036] For the multi-layer chip shielding structure and its preparation method described in the present invention, other advantages, objectives, and features of the present invention will be partially reflected by the following description, and partially will also be understood by those skilled in the art through the research and practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The drawings are used to provide a further understanding of the present invention, and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention, and do not constitute a limitation to the present invention. In the drawings:

[0038] Figure 1 It is a schematic diagram of the first embodiment of the multi-layer chip shielding structure described in the present invention.

[0039] Figure 2Schematic diagram of the second embodiment of the multi-layer chip shielding structure described in the present invention.

[0040] In the figure: 1 suppression layer, 2 absorption layer, 3 reflection layer. Specific implementation mode

[0041] The following further elaborates on the present invention in conjunction with the accompanying drawings and embodiments, so that those skilled in the art can implement it with reference to the text of the specification.

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

[0043] As Figure 1 - Figure 2 shown, the present invention provides a multi-layer chip shielding structure, including: a metal cover, the metal cover is a multi-layer structure, namely a suppression layer 1, an absorption layer 2, and a reflection layer 3;

[0044] The suppression layer 1 is located inside the metal cover and is used to suppress the near-field electric field;

[0045] 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 to absorb electromagnetic waves;

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

[0047] The suppression layer 1 is a nano-silver coating or gradient pore metal foam. Among them, the nano-silver coating (usually 20 - 50 nm) forms an equivalent capacitance-inductance network in the near field of the chip (<1 mm) through the local 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 intensity is reduced by 60%.

[0048] The gradient pore metal foam (such as nickel foam) is divided into a surface dense area and a bottom loose area. Usually, the porosity of the surface dense area is 10%, and the porosity of the bottom loose area is 80%. The surface dense area can reflect the residual electromagnetic waves, and the bottom loose area can enhance heat dissipation through turbulence.

[0049] The absorption layer 2 is a composite material containing ferrite-graphene, usually a ferrite-graphene composite material. Among them, the hysteresis loss of the ferrite (such as NiZn ferrite) and the interfacial polarization loss of graphene can effectively form a complement. At the same time, graphene can also be used as a heat dissipation channel to avoid heat accumulation.

[0050] The reflection layer 3 is a highly conductive metal layer, usually copper or aluminum. As the first line of defense of the present invention, the reflection layer 3 mainly relies on the reflection characteristics of highly conductive metals (such as copper, aluminum, nickel alloys) to reflect the incident low-frequency electromagnetic waves back to the external environment. The free electrons of highly conductive metals can generate induced currents under the action of an external electromagnetic field, thereby forming a reverse electromagnetic field, which further cancels the incident energy.

[0051] In addition to the conductive properties, highly conductive metals also have the structural strength and corrosion resistance of metals. For example, an aluminum layer forms an Al2O3 protective film through anodic oxidation treatment, and the corrosion resistance time in a salt spray test can reach more than 500 hours, which is suitable for in-vehicle electronic devices. At the same time, highly conductive metals have strong ductility and can effectively adapt to thermal stress deformation during the encapsulation process.

[0052] The working principle and beneficial effects of the above technical solution: Through the design of the above structure, the present invention still forms a shielding structure in the form of a metal cover. However, different from the prior art, the present invention is a multi-layer structure, and the innermost layer is the suppression layer 1 made of a nano-silver coating or gradient pore 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 nano-structure; when the suppression layer 1 is gradient pore metal foam, the gradient pore structure can attenuate the residual electromagnetic waves through multiple reflections, thereby achieving the suppression effect on the near-field electric field.

[0053] The absorption layer 2 is made of a ferrite-graphene composite material, and 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%. Also, because the plastic encapsulation shielding technology of the prior art is not used, the present invention will not have the phenomenon of heat accumulation.

[0054] The reflection layer 3 is mainly made of a highly conductive metal, such as copper or aluminum. The highly conductive metal can reflect low-frequency electromagnetic waves, thereby achieving the effect of low-frequency reflection. The reflectivity of the reflection 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, which represents 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 considers the additional attenuation caused by multiple reflections), that is, SE = R + A + B, and B is a negative value.

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

[0057] As a first embodiment, the metal cover is a double-layer structure, including 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 an absorption layer 2 and a reflection layer 3. To fabricate the composite layer, typically, the reflection layer 3 is used as the main grid to cover the suppression layer 1, and then the absorption layer 2 is embedded in the grid of the reflection layer 3.

[0058] In this embodiment, the reflection layer 3 adopts a hollow structure design. The hollow size is generally no larger than λ / 10, where λ is the wavelength corresponding to the highest shielding frequency. For example, for 40 GHz, the corresponding wavelength is 7.5 mm, and the hollow aperture needs to be <0.75 mm.

[0059] Furthermore, the reflection layer 3 is a Koch snowflake-shaped fractal grid. The grid voids are filled with the absorption layer 2. By setting the reflection layer 3 as a hollow structure, the overall weight of the present invention can be reduced by 30% - 50%. The specific weight reduction ratio depends on the shape of the fractal grid. For example, using a Koch snowflake-shaped fractal grid can achieve a 30% weight reduction, and using a Menger sponge-shaped fractal grid can reduce the weight to 50%. While reducing the weight, the heat dissipation area of the reflection layer 3 is increased by at least 40%, improving the efficiency of heat diffusion. At the same time, the hollow structure design enables the reflection layer 3 to be folded and other operations. Although the hollow structure design sacrifices reflection loss for weight reduction compared to the solid structure, and the shielding effect is weaker than that of the solid structure, it is more suitable for devices that need weight reduction such as unmanned aerial vehicle communication modules and wearable devices.

[0060] A preparation method for a multi-layer chip shielding structure, used to prepare the multi-layer chip shielding structure described in the first embodiment, the steps are as follows:

[0061] S1: Perform surface treatment on the substrate (such as a ceramic substrate or a flexible polyimide film), remove organic substances and oxide layers, improve adhesion, and then deposit a highly conductive metal using a magnetron sputtering process to fabricate the reflection layer 3;

[0062] S2: Perform fractal grid treatment on the reflection layer 3, and fabricate the fractal grid through a photolithography process or an oxidation process;

[0063] S3: Prepare the composite material slurry of the absorption layer 2, coat the slurry in the grid of the reflection layer 3, and perform a curing treatment. After the treatment is completed, coat an insulating layer to improve the voltage resistance performance;

[0064] S4: Prepare the suppression layer 1 on the composite layer of the reflection layer 3 and the absorption layer 2, prepare a nano-silver coating through electroless silver plating, or prepare a gradient pore metal foam through a powder metallurgy forming process;

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

[0066] As a second embodiment, the metal cover has a three-layer structure, namely 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. In this embodiment, the reflection layer 3 cancels the hollow structure design and adopts a solid structure design, so as to ensure that the shielding effect will not be affected. Because of the three-layer stacked structure design, the choice of the absorption layer 2 is more diversified. In addition to the ferrite-graphene composite material, magnetic fluid can also be selected as the absorption layer 2. For example, a copper-polyimide folded film can be used as the outer layer, magnetic fluid as the middle layer, and a nano-silver coating as the inner layer. It only needs to ensure the sealing after injecting the magnetic fluid.

[0067] A preparation method of a multi-layer chip shielding structure is used to prepare the multi-layer chip shielding structure described in the second embodiment. The steps are as follows:

[0068] S1: Perform surface treatment on the substrate (such as a ceramic substrate or a flexible polyimide film) to remove organic substances and oxide layers and improve adhesion, and then deposit a highly conductive metal by magnetron sputtering to fabricate the reflection layer 3;

[0069] S2: Prepare the composite material slurry of the absorption layer 2 and coat the slurry on the reflection layer 3;

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

[0071] S4: Perform electromagnetic shielding effectiveness test, thermal resistance test and reliability verification.

[0072] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention.

[0073] In the present invention, unless otherwise clearly specified or limited, terms such as "installed", "connected", "coupled", "fixed", etc. shall be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or integrated; it may be a mechanical connection, an electrical connection, or capable of communicating with each other; it may be directly connected, or indirectly connected through an intermediate medium, and it may be the internal communication of two components or the interaction relationship between two components, unless otherwise clearly limited. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0074] Although the embodiments of the present invention have been disclosed as above, it is not limited to only the applications listed in the specification and embodiments. It can be fully applied to various fields suitable for the present invention. For those familiar with the field, additional modifications can be easily achieved. Therefore, without departing from the general concept defined by the claims and the equivalent scope, the present invention is not limited to the specific details and the illustrated and described examples here.

Claims

1. A multi-layer chip shielding structure, comprising: The metal cover is characterized in that the metal cover is a multi-layer structure, which comprises a suppression layer (1), an absorption layer (2) and a reflection layer (3); A suppression layer (1), located on the inner side of the metal cover, is used to suppress the near-field electric field; An absorption layer (2), located between the suppression layer (1) and the reflection layer (3), or embedded in the reflection layer (3), for absorbing electromagnetic waves; The reflection layer (3) is located outside the metal cover and is used to reflect the incident low-frequency electromagnetic waves back to the external environment.

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

3. The multi-layer chip shielding structure according to claim 1, characterized in that: The metal cover has a three-layer structure, which includes an inner layer, a middle layer and an outer layer. The inner layer is a suppression layer (1), the middle layer is an absorption layer (2), and the outer layer is a 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 fractal grid in the shape of a Koch snowflake.

5. The multi-layer chip shielding structure according to claim 4, characterized in that: The grid gaps are filled with an absorption layer (2).

6. The multi-layer chip shielding structure according to claim 1, characterized in that: The inhibition layer (1) is a nano silver coating or a gradient pore metal foam.

7. The multi-layer chip shielding structure according to claim 1, characterized in that: The absorption layer (2) is a composite material containing ferrite-graphene.

8. The multi-layer chip shielding structure according to claim 1, characterized in that: The reflective layer (3) is a highly conductive metal layer.

9. A method for preparing a multi-layer chip shielding structure, used for preparing the multi-layer chip shielding structure as claimed in any one of claims 1-2 and 4-8, characterized in that: Here are the steps: S1: forming a reflective layer (3) on a substrate; S2: Graphics processing; S3: Fill the graphics grid with an absorption layer (2); S4: preparing an inhibition layer (1) on the composite layer of the reflection layer (3) and the absorption layer (2); S5: Performance test.

10. A method for preparing a multi-layer chip shielding structure, used for preparing the multi-layer chip shielding structure as claimed in any one of claims 1, 3-4, 6-8, characterized in that: Here are the steps: S1: forming a reflective layer (3) on a substrate; S2: forming an absorption layer (2) on the reflection layer (3); S3: preparing an inhibition layer (1) on the absorption layer (2); S4: Performance test.

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