Flexible electromagnetic shielding cover

Abstract

This invention relates to a flexible electromagnetic shielding cover, comprising an insulating layer, an adhesive layer, a shielding layer, and a conductive adhesive layer stacked sequentially. Conductive particles are dispersed within the conductive adhesive layer. At least one micropore penetrating the shielding layer is formed on the shielding layer, creating a channel connecting the adhesive layer and the conductive adhesive layer. The pore size D of the micropore is smaller than the particle size d of the conductive particles. The side of the conductive adhesive layer closest to the shielding layer is the upper side, and the side furthest from the shielding layer is the lower side. The conductive particles in the conductive adhesive layer satisfy the following conditions: the average vertical distance H1 between the conductive particles and the upper side is greater than the average vertical distance H2 between the conductive particles and the lower side; and the particle size d of the conductive particles is less than half the thickness T of the conductive adhesive layer.

Description

Technical Field

[0001] This invention relates to the field of electromagnetic shielding materials, and in particular to a flexible electromagnetic shielding cover. Background Technology

[0002] In recent years, electronic products such as foldable phones and wearable devices have increasingly demanded greater flexibility in their internal components. Electromagnetic shielding covers, as key components for suppressing electromagnetic interference, are also gradually evolving from traditional rigid stamped parts to flexible composite membrane materials. Common flexible electromagnetic shielding covers employ multi-layer structures.

[0003] In practical applications, flexible electromagnetic shielding covers need to be installed in the bending areas of equipment and undergo repeated bending or large-angle folding along with the equipment. However, some existing flexible electromagnetic shielding cover products suffer from insufficient flexibility, making them prone to interlayer separation during bending, which compromises the integrity of the shielding structure. After separation, the electromagnetic shielding effect of the cover decreases, or even completely loses its grounding conductivity, affecting the normal operation of electronic equipment. Therefore, existing technologies use softer adhesive materials or reduce the thickness of copper foil. However, while these solutions improve flexibility, they often weaken the interlayer bonding force of the shielding cover, making it difficult to balance resistance to bending separation and structural stability.

[0004] In summary, how to improve the bending and separation resistance of flexible electromagnetic shielding without sacrificing interlayer bonding strength has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] Therefore, it is necessary to provide a flexible electromagnetic shield that can improve the bending and separation resistance of the flexible electromagnetic shield without sacrificing the interlayer bonding strength.

[0006] The technical solution is as follows:

[0007] A flexible electromagnetic shielding cover includes an insulating layer, an adhesive layer, a shielding layer, and a conductive adhesive layer stacked sequentially. Conductive particles are dispersed within the conductive adhesive layer. At least one micropore penetrating the shielding layer is formed on the shielding layer, creating a channel connecting the adhesive layer and the conductive adhesive layer. The pore size D of the micropore is smaller than the particle size d of the conductive particles. The side of the conductive adhesive layer closest to the shielding layer is the upper side, and the side furthest from the shielding layer is the lower side. The conductive particles in the conductive adhesive layer satisfy the following conditions: the average vertical distance H1 between the conductive particles and the upper side is greater than the average vertical distance H2 between the conductive particles and the lower side; and the particle size d of the conductive particles is less than half the thickness T of the conductive adhesive layer.

[0008] In one embodiment, the conductive particles include a first conductive particle and a second conductive particle, wherein the particle size d1 of the first conductive particle is larger than the particle size d2 of the second conductive particle; and the pore size D of the micropore is smaller than the particle size d2 of the second conductive particle.

[0009] In one embodiment, the particle size d1 of the first conductive particle satisfies: 0.3T ≤ d1 ≤ 0.5T; the particle size d2 of the second conductive particle satisfies: 0.1T ≤ d2 ≤ 0.25T; and the ratio of the number of the first conductive particle to the number of the second conductive particle is 1:5 to 1:20.

[0010] In one embodiment, the number of the first conductive particles accounts for 5% to 15% of the total number of conductive particles, and the number of the second conductive particles accounts for 85% to 95% of the total number of conductive particles.

[0011] In one embodiment, the average center distance P12 between the first conductive particle and the adjacent second conductive particle satisfies: 1.5d1 ≤ P12 ≤ 5d1; the average center distance P22 between any two second conductive particles satisfies: 2d2 ≤ P22 ≤ 6d2; and the average center distance P11 between any two first conductive particles satisfies: 5d1 ≤ P11 ≤ 15d1.

[0012] In one embodiment, the shape of the first conductive particle is selected from ellipsoidal, rod-shaped or dumbbell-shaped, and the length ratio of its major axis to minor axis is 1.5:1 to 3:1; the shape of the second conductive particle is spherical or near-spherical.

[0013] In one embodiment, on a vertical cross-section perpendicular to the stacking direction, the number of conductive particles contained within every 10 μm distance along the thickness direction is 2 to 6; on a horizontal cross-section parallel to the stacking direction, the number of conductive particles contained within every 100 μm distance along any transverse direction is 15 to 40.

[0014] In one embodiment, the bulk density of the conductive particles in the conductive adhesive layer is 5,000 to 20,000 particles / mm³; and the bulk density of the conductive particles in the edge region of the micropores is 20% to 50% higher than that in the region away from the micropores.

[0015] In one embodiment, the conductive particles are composite particles with a polymer core surface coated with a metal layer, the metal layer material being gold, silver, nickel, or copper; the conductive adhesive layer is anisotropic conductive adhesive with a thickness T of 5 μm to 30 μm.

[0016] In one embodiment, the micropores are circular, elliptical, rhomboid, C-shaped, or cross-shaped; multiple micropores are distributed in a gradient within the bending area of ​​the shielding layer, wherein the micropore density in the bending center region is higher than the micropore density in the edge region.

[0017] In use, the aforementioned flexible electromagnetic shielding cover utilizes at least one micro-hole penetrating the shielding layer to allow the adhesive layer above the shielding layer and the conductive adhesive layer below the shielding layer to directly contact each other within the micro-hole. This anchors the adhesive layers on both sides of the shielding layer into a single unit. When the shielding cover is subjected to bending stress, it effectively resists shear slippage between the layers, suppressing the separation of the interfaces between the adhesive layer and the shielding layer, and between the shielding layer and the conductive adhesive layer during bending, thereby improving its bending resistance. Simultaneously, by making the pore size D of the micro-hole smaller than the particle size d of the conductive particles, it ensures that the conductive particles in the conductive adhesive layer cannot penetrate the micro-hole into the upper adhesive layer during pressing or bending. This avoids both the loss of conductive particles leading to conductivity failure and the risk of short circuits caused by conductive particles piercing the insulation layer, thus ensuring the integrity and stable adhesive strength of the conductive adhesive layer itself. Furthermore, this invention limits the conductive particles in the conductive adhesive layer to satisfy H1 > H2, meaning the conductive particles are closer to the lower side of the conductive adhesive layer (the side furthest from the shielding layer). During bending, the interface between the shielding layer and the conductive adhesive layer is typically a high-stress area. By placing the conductive particles relatively far from this interface, placing them in a low-stress zone during bending deformation, the debonding or puncturing of adjacent layers due to severe interfacial shear is effectively prevented. Furthermore, the particle size d of the conductive particles is less than half the thickness T of the conductive adhesive layer, allowing for sufficient embedding depth within the adhesive layer. This ensures the adhesive layer maintains good flexibility, resulting in a more uniform stress distribution during bending and preventing localized cracking caused by the "hard spot" effect of large particles. In summary, the aforementioned flexible electromagnetic shielding can improve its resistance to bending separation while maintaining interlayer bonding strength. Attached Figure Description

[0018] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of the structure of the flexible electromagnetic shielding cover described in one embodiment;

[0021] Figure 2 This is a schematic diagram of the cross-sectional structure of the shielding layer described in one embodiment.

[0022] Explanation of reference numerals in the attached figures:

[0023] 100. Insulating layer; 200. Adhesive layer; 300. Shielding layer; 310. Micropores; 320. Conductive particles; 400. Conductive adhesive layer; 500. Protective film layer. Detailed Implementation

[0024] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0025] 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 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. Therefore, they should not be construed as limitations on this invention.

[0026] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0027] 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 or an electrical connection; 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.

[0028] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0029] It should be noted that when an element is referred to as being "fixed to" or "set on" another element, it can be directly on the other element or there may be an intervening element. When an element is considered to be "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only possible implementation.

[0030] Combination Figure 1 and Figure 2 As shown, in one embodiment, a flexible electromagnetic shield includes an insulating layer 100, an adhesive layer 200, a shielding layer 300, and a conductive adhesive layer 400 stacked sequentially. Conductive particles 320 are dispersed within the conductive adhesive layer 400. At least one micropore 310 penetrating the shielding layer 300 forms a channel connecting the adhesive layer 200 and the conductive adhesive layer 400. The pore size D of the micropore 310 is smaller than the particle size d of the conductive particles 320. The side of the conductive adhesive layer 400 closest to the shielding layer 300 is the upper side, and the side of the conductive adhesive layer 400 furthest from the shielding layer 300 is the lower side. The conductive particles 320 in the conductive adhesive layer 400 satisfy the following conditions: the average vertical distance H1 between the conductive particles 320 and the upper side is greater than the average vertical distance H2 between the conductive particles 320 and the lower side; the particle size d of the conductive particles 320... It is less than 1 / 2 of the thickness T of the conductive adhesive layer 400.

[0031] When the aforementioned flexible electromagnetic shield is in use, by opening at least one microhole 310 penetrating the shielding layer 300, the adhesive layer 200 located above the shielding layer 300 and the conductive adhesive layer 400 located below the shielding layer 300 can directly contact each other within the microhole 310, anchoring the adhesive layers on both sides of the shielding layer 300 into a whole. When the shield is subjected to bending stress, it can effectively resist shear slippage between the layers and suppress the separation of the interface between the adhesive layer 200 and the shielding layer 300, and between the shielding layer 300 and the conductive adhesive layer 400 during bending, thereby improving the bending resistance performance. Meanwhile, by making the pore size D of the micropore 310 smaller than the particle size d of the conductive particles 320, it is ensured that the conductive particles 320 in the conductive adhesive layer 400 cannot pass through the micropore 310 and enter the upper adhesive layer 200 during pressing or bending. This avoids both the loss of conductive particles 320 leading to conductivity failure and the risk of conductive particles 320 piercing the insulating layer 100 and causing a short circuit, thereby ensuring the integrity and stable adhesive strength of the conductive adhesive layer 400 itself. Furthermore, this invention limits the conductive particles 320 in the conductive adhesive layer 400 to satisfy H1 > H2, that is, the conductive particles 320 are closer to the lower side of the conductive adhesive layer 400 (the side away from the shielding layer 300). During bending, the interface between the shielding layer 300 and the conductive adhesive layer 400 is usually a high-stress area. By arranging the conductive particles 320 relatively far away from this interface, placing them in a low-stress area during bending deformation, it is effectively prevented that the particles will detach or pierce adjacent film layers due to severe shearing at the interface. Furthermore, the particle size d of the conductive particles 320 is less than half the thickness T of the conductive adhesive layer 400, allowing the particles to have sufficient embedding depth within the adhesive layer. This enables the adhesive layer to maintain good flexibility, resulting in a more uniform stress distribution within the adhesive layer during bending and preventing localized cracking caused by the "hard spot" effect of large-sized particles. In summary, the aforementioned flexible electromagnetic shielding can improve the bending and separation resistance of the flexible electromagnetic shielding while ensuring interlayer bonding strength.

[0032] In one embodiment, the flexible electromagnetic shielding cover further includes a protective film layer 500, which is bonded to the shielding layer 300 via a conductive adhesive layer 400. The protective film layer 500 includes a release film.

[0033] In one embodiment, the average vertical distance H1 between the conductive particle 320 and the upper side of the conductive adhesive layer 400, and the average vertical distance H2 between the conductive particle 320 and the lower side of the conductive adhesive layer 400, are both measured with the geometric center of the conductive particle 320 as the measurement reference point. The specific measurement method is as follows: For any conductive particle 320, firstly, determine the geometric center of the particle on the thickness-direction section of the conductive adhesive layer 400, and then measure the vertical distance from the geometric center to the upper side and the vertical distance to the lower side, respectively. The "average vertical distance" refers to the result obtained by arithmetically averaging the above distance values ​​of all or a sufficient number of conductive particles 320 in the conductive adhesive layer 400.

[0034] Furthermore, the values ​​of H1 and H2 can be obtained as follows: Take a cross-sectional sample of the flexible electromagnetic shielding cover, and use a scanning electron microscope (SEM) to capture images in at least 20 different fields of view. Randomly select no fewer than 10 conductive particles 320 in each field of view, measure the vertical distance from the geometric center of each particle to the upper and lower sides, and then calculate the arithmetic mean of all measurements to obtain H1 and H2. It should be noted that for non-spherical conductive particles (e.g., ellipsoidal, rod-shaped, or dumbbell-shaped), the geometric center refers to the center point of the particle in the thickness direction, i.e., the midpoint of the line connecting the upper and lower ends of the particle; for spherical or near-spherical particles, the geometric center is the center of the sphere. Using the geometric center as a reference avoids measurement deviations caused by local protrusions on the particle surface or uneven coating thickness, and this reference basically coincides with the particle's center of gravity, accurately reflecting the spatial distribution characteristics of the particles in the thickness direction of the adhesive layer.

[0035] In one embodiment, the conductive particles 320 include a first conductive particle 320 and a second conductive particle 320, wherein the particle size d1 of the first conductive particle 320 is larger than the particle size d2 of the second conductive particle 320; and the pore size D of the micropore 310 is smaller than the particle size d2 of the second conductive particle 320. Specifically, using a mixture of conductive particles 320 of two different sizes can optimize the particle packing density and conduction path inside the conductive adhesive layer 400. The larger-sized first conductive particles 320 preferentially contact the shielding layer 300 during the hot pressing process, undergoing elastic or plastic deformation to form reliable conductive contacts and ensure low grounding resistance; the smaller-sized second conductive particles 320 fill the gaps between the larger particles, increasing the number of effective conductive paths per unit volume and improving conductivity redundancy and impact resistance.

[0036] Secondly, it is specified that the pore diameter D of the micro-pores 310 is smaller than the particle size d2 of the second conductive particles 320, which means that even the smallest conductive particles 320 cannot pass through the micro-pores 310 and enter the upper bonding layer 200. Three potential risks are avoided: ① The loss of the conductive particles 320 leads to a decrease in the local particle concentration in the conductive adhesive layer 400 and poor conduction; ② After the particles enter the bonding layer 200, they may pierce the insulating protective film, causing a short circuit; ③ The accumulation of particles in the micro-pores 310 hinders the formation of the adhesive nails and weakens the anchoring effect.

[0037] The following is a comparative analysis in combination with the examples and comparative examples:

[0038]

[0039] In summary, Example 1 (mixing large and small particles and D < d2) is superior to any single-particle solution in terms of bending life and resistance stability, and avoids particle leakage. In Comparative Example 3, the particles pass through the micro-pores 310 due to the too large pore diameter, seriously damaging the structural integrity.

[0040] In one embodiment, the particle size d1 of the first conductive particle 320 satisfies: 0.3T ≤ d1 ≤ 0.5T; the particle size d2 of the second conductive particle 320 satisfies: 0.1T ≤ d2 ≤ 0.25T; and the ratio of the number of the first conductive particle 320 to the number of the second conductive particle 320 is 1:5 to 1:20. Specifically, the particle size of the first conductive particle 320 is controlled between 0.3 and 0.5 times the thickness T of the conductive adhesive layer 400. This ensures that the particles are fully compressed during hot pressing and form reliable contact with the shielding layer 300 and the base layer, while also preventing the particles from being too large, which could cause the adhesive layer to be partially torn or protrude from both sides of the adhesive layer after pressing. If d1 < 0.3T, the particles are too small and cannot penetrate the thin resin film on the surface of the adhesive layer after pressing, resulting in a high grounding resistance; if d1 > 0.5T, the particles are too large and are prone to becoming stress concentration points during bending, accelerating the cracking of the adhesive layer. Secondly, the particle size d2 of the second conductive particle 320 is 0.1T to 0.25T, enabling it to effectively fill the gaps between the first conductive particles 320, increasing the number of conductive paths per unit volume and improving conductivity redundancy. Simultaneously, the smaller particle size of the second conductive particle 320 results in less deformation during bending, making it less prone to detachment due to interfacial shear. Thirdly, the ratio of the first conductive particle 320 to the second conductive particle 320 is limited to 1:5 to 1:20, meaning that the proportion of large particles is approximately 5% to 17%. This ratio ensures that large particles provide the main conductive contacts, while small particles fully fill and form auxiliary paths. If the proportion of large particles is too high (e.g., exceeding 1:5), the distance between particles will be too small, easily leading to particle aggregation during pressing, resulting in uneven local pressure and adhesive extrusion; if the proportion of large particles is too low (e.g., below 1:20), the number of large particles will be insufficient, making it difficult to form a continuous and reliable conductive path, increasing the grounding resistance. In summary, the above embodiments optimize the particle distribution inside the conductive adhesive layer 400 by limiting the ratio of particle size to adhesive thickness and the ratio of large to small particles, thereby improving the conductivity stability under bending conditions while ensuring low grounding resistance.

[0041] The following comparative analysis is conducted with reference to the embodiments and comparative examples:

[0042]

[0043] In summary, Example 1, with both particle size and quantity ratios falling within the range of this example, achieved the lowest stable grounding resistance and the longest bending life. Comparative Example 1 suffered from insufficient compaction due to excessively small large particles; Comparative Example 2 experienced accelerated fatigue failure due to excessively large large particles. Comparative Example 3 caused aggregation and debonding due to an excessive number of large particles.

[0044] In one embodiment, the first conductive particles 320 account for 5% to 15% of the total number of conductive particles 320, and the second conductive particles 320 account for 85% to 95% of the total number of conductive particles 320. Specifically, the first conductive particles 320, accounting for 5% to 15%, are conductive particles with a relatively large particle size and a moderate number. These large particles are compressed between the shielding layer 300 and the base layer during the hot-pressing process, undergoing elastic or plastic deformation to form stable low-resistance conductive contacts. Because the number of large particles is sufficient but not too dense, there is enough space around each large particle for its compression deformation, preventing interference from adjacent particles, and allowing it to be fully flattened and pierced through the thin resin film on the surface of the adhesive layer, achieving reliable metal contact. Secondly, the second conductive particles 320, accounting for 85% to 95%, are conductive particles with a smaller particle size, filling the gaps between the first conductive particles 320 in large quantities. Although the individual grounding resistance of these small particles may be slightly higher than that of the large particles, due to their large number, they form a large number of parallel conductive paths. When the shielding cover is bent, even if individual large particles experience slight displacement or poor contact due to stress, the densely distributed small particles around them can still maintain conductivity, ensuring the stability of the overall grounding resistance. In summary, the above embodiment enables large particles to provide a low-resistance main path and small particles to provide a flexible redundant path, improving conductivity stability under bending conditions while ensuring low grounding resistance.

[0045] The following comparative analysis is conducted with reference to the embodiments and comparative examples:

[0046]

[0047] In one embodiment, the average center-to-center distance P12 between the first conductive particle 320 and the adjacent second conductive particle 320 satisfies: 1.5d1 ≤ P12 ≤ 5d1; the average center-to-center distance P22 between any two second conductive particles 320 satisfies: 2d2 ≤ P22 ≤ 6d2; and the average center-to-center distance P11 between any two first conductive particles 320 satisfies: 5d1 ≤ P11 ≤ 15d1. Specifically, the lower limit of P12 is set to 1.5d1 to ensure sufficient gap between the first conductive particle 320 and the surrounding second conductive particles 320, preventing particles of different sizes from crowding together. If a large particle and its adjacent small particle are too close, the small particle may be deformed by the large particle during compression, which would affect the normal compression of the large particle. At the same time, the upper limit of P12 is 5d1 to ensure that each large particle is surrounded by a sufficient number of small particles, forming a locally dense conductive network. When the shielding layer bends, the smaller particles surrounding the larger particles act as buffers and assist in conduction, sharing the stress borne by the larger particles. The spacing P22 between the second conductive particles 320 is limited to between 2d2 and 6d2. This range ensures that the smaller particles are neither too close together to clump together, nor too far apart to leave large gaps in the adhesive layer without conductive particles 320. The spacing P11 between the first conductive particles 320 is limited to between 5d1 and 15d1. The larger particles are relatively sparsely distributed in the adhesive layer. Each large particle has sufficient space around it to fully expand and deform during compression without interfering with each other. The sparse distribution of large particles combined with the dense distribution of small particles ensures both a low-resistance backbone pathway and maintains the overall flexibility of the adhesive layer.

[0048] The following comparative analysis is conducted with reference to the embodiments and comparative examples:

[0049]

[0050] In summary, Example 1 exhibits the best resistance and bending life within the spacing range defined in this example. Comparative Examples 1 to 3 all showed varying degrees of performance degradation due to unreasonable particle distribution caused by deviations from a certain spacing range.

[0051] In one embodiment, the shape of the first conductive particle 320 is selected from ellipsoidal, rod-shaped, or dumbbell-shaped, with a length ratio of its major axis to minor axis of 1.5:1 to 3:1; the shape of the second conductive particle 320 is spherical or near-spherical. Specifically, the first conductive particle 320 adopts a non-spherical shape (ellipsoidal, rod-shaped, or dumbbell-shaped) and has a certain aspect ratio. During the hot pressing process, these particles will be oriented along the pressure direction. Because the particles have a relatively long major axis, the contact area between the particles and the shielding layer 300 after pressing is larger than that of spherical particles of the same volume, thereby obtaining a lower grounding resistance. In the conductive adhesive layer 400, the long axis direction of the non-spherical particles forms a certain angle or embedding depth with the plane of the adhesive layer. When the shield is subjected to bending stress, the particles are not easily pulled out of the adhesive layer or rolled away, enhancing the fatigue resistance of the conductive contacts. The aspect ratio is controlled between 1.5:1 and 3:1, ensuring the advantages of significant shape anisotropy without causing breakage or orientation difficulties during lamination due to excessively elongated particles. The second conductive particle 320 is spherical or near-spherical, offering advantages in flowability and filling properties. Spherical particles can roll freely during adhesive layer preparation and lamination, easily and evenly dispersing in the gaps between larger particles, unlike non-spherical particles which tend to agglomerate or have inconsistent orientation. The spherical symmetry structure ensures uniform stress distribution in all directions, reducing stress concentration during bending and maintaining the overall flexibility of the adhesive layer. The combination of large and small particle shapes achieves functional complementarity: non-spherical large particles provide low resistance and pull-out resistance, while spherical small particles provide uniform filling and flexible cushioning.

[0052] The following comparative analysis is conducted with reference to the embodiments and comparative examples:

[0053]

[0054] In summary, within the aspect ratio range of 1.5:1 to 3:1, the non-spherical shape of the first conductive particle 320 can effectively reduce grounding resistance and improve bending life. Among them, the aspect ratio of 2:1 in Example 1 is the best, and although Comparative Examples 1 to 3 are near the boundary, their performance is still better than the traditional spherical large particle scheme.

[0055] In one embodiment, on a vertical cross-section perpendicular to the stacking direction, the number of conductive particles 320 contained within every 10 μm distance along the thickness direction is 2 to 6; on a horizontal cross-section parallel to the stacking direction, the number of conductive particles 320 contained within every 100 μm distance along any transverse direction is 15 to 40. Specifically, the number of particles in the thickness direction on the vertical cross-section reflects the longitudinal distribution of conductive particles 320 in the adhesive layer thickness. 2 to 6 particles per 10 μm thickness means that the particles are relatively densely distributed in the thickness direction, while leaving sufficient space in the adhesive layer. If there are fewer than 2 particles, the particles are too sparse, making it difficult to form sufficient conductive paths after compression, resulting in a high grounding resistance; if there are more than 6 particles, the particles are too tightly packed, interfering with each other during compression, affecting not only the normal compression deformation of the particles but also occupying too much adhesive layer resin, leading to a decrease in the cohesive force of the adhesive layer. This range of 2 to 6 particles allows for multi-layer stacking of particles in the thickness direction without excessive crowding, ensuring that each layer has particles participating in conduction while maintaining the integrity of the adhesive layer. The number of transverse particles on the horizontal cross-section reflects the distribution density of conductive particles 320 within the adhesive layer plane. There are 15–40 particles per 100 μm distance, corresponding to an average distance of approximately 2.5–6.7 μm between particles. This density ensures the continuity and redundancy of the conductive path in the horizontal direction. If there are fewer than 15 particles, the particle spacing is too large, and if local particles detach during bending, open circuits can easily occur. If there are more than 40 particles, the particles are too dense, the adhesive layer becomes "hard," and bending stress tends to concentrate in the particle aggregation area, accelerating fatigue cracking of the adhesive layer. The range of 15–40 particles ensures that the particle distribution is sufficient without being too dense, and the shielding cover has enough parallel paths in the horizontal direction to maintain conductivity during bending.

[0056] The following comparative analysis is conducted with reference to the embodiments and comparative examples:

[0057]

[0058] In summary, Example 1 exhibited the best resistance and bending life within the defined density range. Comparative Examples 1 and 2 showed higher resistance or were prone to open circuits after bending due to insufficient density; Comparative Example 3 showed embrittlement of the adhesive layer and reduced lifespan due to excessive density.

[0059] In one embodiment, the bulk density of the conductive particles 320 in the conductive adhesive layer 400 is 5,000 to 20,000 particles / mm³; and in the edge region of the micropores 310, the bulk density of the conductive particles 320 is 20% to 50% higher than that in the region farther from the micropores 310. Specifically, firstly, the overall bulk density of the conductive particles 320 is controlled within the range of 5,000 to 20,000 particles / mm³, resulting in a moderate number of conductive particles 320 per unit volume. If the bulk density is lower than 5,000 particles / mm³, the particles are too sparse, resulting in insufficient conductive paths after compression, high grounding resistance, and a lack of replacement pathways after local particles detach during bending, which can easily lead to conduction interruption. If the bulk density is higher than 20,000 particles / mm³, the particles are too dense, causing mutual crowding between particles and excessive internal stress in the adhesive layer during compression; on the other hand, the relative reduction in resin in the adhesive layer leads to brittleness of the adhesive layer itself, making it prone to cracking during bending. The range of 5000–20000 particles / mm³ ensures sufficient conductive path density while maintaining good flexibility and cohesion of the adhesive layer. Secondly, the density of conductive particles 320 at the edge of the micropores 310 is 20%–50% higher than in areas farther from the micropores 310. The micropores 310 are key areas where the shielding layer 300 forms the "adhesive nails" after opening, and are also areas where stress is concentrated during bending. Increasing the density of conductive particles 320 in this area creates a particle-rich region around the adhesive nails. When the shielding is subjected to bending stress, the particle-rich region at the edge of the micropores 310 provides local reinforcement: on the one hand, the dense particles can buffer and disperse the stress concentration at the root of the adhesive nails; on the other hand, these particles form a composite reinforcement structure with the adhesive nails, improving the tear resistance of the adhesive layer around the micropores 310. Simultaneously, the 20%–50% increase provides a significant reinforcement effect without causing abrupt changes in the adhesive layer's performance due to excessive density differences.

[0060] The following comparative analysis is conducted with reference to the embodiments and comparative examples:

[0061]

[0062] In summary, Example 1 achieved optimal resistance and bending life under the dual constraints of bulk density and edge enrichment. Comparative Example 1 had high resistance due to insufficient density; Comparative Example 2 had brittle adhesive layer due to excessive density; Comparative Example 3 had no edge enrichment, and the area around the micropores 310 became a weak zone, causing cracking around the adhesive pins first during bending.

[0063] In one embodiment, the conductive particles 320 are composite particles with a polymer core and a metal layer plated on the surface, and the metal layer material is gold, silver, nickel, or copper; the conductive adhesive layer 400 is anisotropic conductive adhesive with a thickness T of 5μm to 30μm. Specifically, firstly, composite particles with a polymer core and a metal layer plated on the surface are used. This structure of conductive particles 320 combines conductivity and elasticity. During the hot-pressing process, the composite particles undergo recoverable elastic deformation under pressure, increasing the contact area between the particles and the shielding layer 300 and the base layer, and reducing the grounding resistance. At the same time, the elastic deformation can compensate for minor unevenness or thickness fluctuations between layers, ensuring that each particle can effectively participate in conduction. In addition, the elasticity of the polymer core can also buffer the mechanical stress generated during bending, reducing the risk of particles detaching from the adhesive layer. The metal layer material is selected from gold, silver, nickel, or copper. All four materials have excellent conductivity. Gold and silver have strong oxidation resistance, while nickel and copper are lower in cost and have good compatibility with solder, allowing for flexible selection according to different application scenarios. Secondly, the conductive adhesive layer 400 uses anisotropic conductive adhesive (ACF). The anisotropic conductive adhesive is characterized by its conductivity in the direction perpendicular to the adhesive layer plane (i.e., the lamination direction) and its insulation in the direction parallel to the adhesive layer plane. This characteristic allows the conductive particles 320 to conduct through the shielding layer 300 and other layers only in the thickness direction, without causing short circuits in the horizontal direction. When there are multiple adjacent grounding lines inside the shield, the anisotropic conductive adhesive can effectively prevent lateral leakage and ensure the electrical safety of the shield. Finally, the thickness T of the conductive adhesive layer 400 is limited to 5μm to 30μm. The lower limit of 5μm ensures that the adhesive layer can accommodate a sufficient number of conductive particles 320 to form a continuous and reliable conductive path; the upper limit of 30μm ensures that the adhesive layer is not too thick and affects the overall flexibility, while also preventing excessive extrusion of the adhesive layer during lamination. This thickness range matches the aforementioned particle size range (d1 is 0.3T to 0.5T, d2 is 0.1T to 0.25T), ensuring a reasonable distribution of particles in the thickness direction and meeting the requirements for contact between particles and the upper and lower interfaces after lamination.

[0064] The following comparative analysis is conducted with reference to the embodiments and comparative examples:

[0065]

[0066] In summary, Example 1 exhibits the best overall performance due to its composite particles, anisotropic conductive adhesive, and suitable thickness. Comparative Example 1 suffers from high grounding resistance and easy detachment after bending due to the lack of elasticity of solid particles; Comparative Example 2 suffers from insufficient lateral insulation due to the anisotropic nature of the conductive adhesive; and Comparative Example 3 suffers from insufficient bonding and reduced bending life due to excessive thickness.

[0067] In one embodiment, the micropores 310 are circular, elliptical, rhomboid, C-shaped, or cross-shaped. Multiple micropores 310 are distributed in a gradient within the bending region of the shielding layer 300, with a higher density of micropores 310 in the central bending region than in the edge region. Specifically, the diverse shapes of the micropores 310 result in different mechanical response characteristics in the adhesive nail structure. Circular holes experience uniform stress in all directions; elliptical and rhomboid holes have longer hole walls in specific directions. When the shielding cover bends along a main direction, the direction of the longer holes, perpendicular to the bending axis, better resists interfacial shear. C-shaped and cross-shaped holes have concave angles or branch structures, forming anchor points with undercuts after the adhesive layer is filled, greatly enhancing the pull-out resistance of the adhesive nail. Different shapes of micropores 310 can be selected and combined according to the stress distribution characteristics of the bending region, matching the anchoring effect with the bending deformation mode. Secondly, the density of the micropores 310 exhibits a gradient distribution within the bending region—high density in the central bending area and low density in the edge area. This design fully considers the stress distribution during bending. The central bending area is typically where the curvature is greatest and the interlayer shear stress is most concentrated. A higher micropore density in this area means more adhesive anchors are densely anchored at the point of maximum stress, effectively suppressing the initiation and propagation of interfacial delamination. Conversely, the stress in the edge area is relatively lower, and a lower micropore density satisfies the anchoring requirements while avoiding excessive perforation that could weaken the strength of the shielding layer 300. This gradient distribution creates a gradual structure of "strong anchoring at the center and weak anchoring at the edges" within the bending region. During bending, stress is smoothly transferred from the center to the edges, preventing new stress concentration points from abruptly changing in density.

[0068] The following comparative analysis is conducted with reference to the embodiments and comparative examples:

[0069]

[0070] In summary, Example 1 exhibits the longest bending life under the constraints of diverse shapes and gradient density. Comparative Examples 1 and 2, due to unreasonable hole patterns or density distributions, have weak points in their central areas; Comparative Example 3, although retaining gradient density, cannot provide directional anchorage due to its single hole pattern, resulting in stress concentration in the transition zone.

[0071] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0072] The above embodiments merely illustrate several implementation methods of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A flexible electromagnetic shielding cover, comprising an insulating layer, an adhesive layer, a shielding layer, and a conductive adhesive layer stacked sequentially, wherein conductive particles are dispersed within the conductive adhesive layer, characterized in that: At least one micropore penetrating the shielding layer is formed on the shielding layer, and the micropore forms a channel connecting the adhesive layer and the conductive adhesive layer; The pore size D of the micropore is smaller than the particle size d of the conductive particles; The side of the conductive adhesive layer closest to the shielding layer is the upper side, and the side of the conductive adhesive layer furthest from the shielding layer is the lower side. The conductive particles in the conductive adhesive layer satisfy the following condition: the average vertical distance H1 between the conductive particles and the upper side is greater than the average vertical distance H2 between the conductive particles and the lower side. The particle size d of the conductive particles is less than 1 / 2 of the thickness T of the conductive adhesive layer.

2. The flexible electromagnetic shielding cover according to claim 1, characterized in that: The conductive particles include a first conductive particle and a second conductive particle, wherein the particle size d1 of the first conductive particle is larger than the particle size d2 of the second conductive particle; and the pore size D of the micropore is smaller than the particle size d2 of the second conductive particle.

3. The flexible electromagnetic shielding cover according to claim 2, characterized in that: The particle size d1 of the first conductive particle satisfies: 0.3T ≤ d1 ≤ 0.5T; the particle size d2 of the second conductive particle satisfies: 0.1T ≤ d2 ≤ 0.25T; and the ratio of the number of the first conductive particle to the number of the second conductive particle is 1:5 to 1:

20.

4. The flexible electromagnetic shielding cover according to claim 2, characterized in that: The first conductive particle accounts for 5% to 15% of the total number of conductive particles, and the second conductive particle accounts for 85% to 95% of the total number of conductive particles.

5. The flexible electromagnetic shielding cover according to claim 2, characterized in that: The average center distance P12 between the first conductive particle and the adjacent second conductive particle satisfies: 1.5d1 ≤ P12 ≤ 5d1; the average center distance P22 between any two second conductive particles satisfies: 2d2 ≤ P22 ≤ 6d2; the average center distance P11 between any two first conductive particles satisfies: 5d1 ≤ P11 ≤ 15d1.

6. The flexible electromagnetic shielding cover according to claim 2, characterized in that: The first conductive particle is selected from ellipsoidal, rod-shaped or dumbbell-shaped, and the ratio of its major axis to minor axis is 1.5:1 to 3:1; the second conductive particle is spherical or near-spherical.

7. The flexible electromagnetic shielding cover according to claim 1 or 2, characterized in that: In a vertical section perpendicular to the stacking direction, the number of conductive particles contained within every 10 μm distance along the thickness direction is 2 to 6; in a horizontal section parallel to the stacking direction, the number of conductive particles contained within every 100 μm distance along any transverse direction is 15 to 40.

8. The flexible electromagnetic shielding cover according to claim 7, characterized in that: The volume density of the conductive particles in the conductive adhesive layer is 5,000 to 20,000 particles / mm³; and the volume density of the conductive particles in the edge region of the micropores is 20% to 50% higher than that in the region away from the micropores.

9. The flexible electromagnetic shielding cover according to claim 1, characterized in that: The conductive particles are composite particles with a polymer core and a metal layer plated on the surface, and the metal layer material is gold, silver, nickel or copper; the conductive adhesive layer is anisotropic conductive adhesive with a thickness T of 5μm to 30μm.

10. The flexible electromagnetic shielding cover according to claim 1, characterized in that: The micropores are circular, elliptical, rhomboid, C-shaped, or cross-shaped; multiple micropores are distributed in a gradient within the bending area of ​​the shielding layer, wherein the micropore density in the bending center region is higher than that in the edge region.

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