Electromagnetic shielding film and circuit board

Abstract

The invention relates to an electromagnetic shielding film and a circuit board, and the electromagnetic shielding film comprises a shielding layer, the thickness d of the shielding layer in a slicing state and in a preset observation range satisfies # imgabs0 #, the thickness uniformity of the shielding layer is less than or equal to 20% through the modes of adjusting a production technology and the like, the shielding layer with uniform thickness is formed, the consistency of impedance characteristics can be improved, and the electromagnetic shielding film has good electromagnetic shielding performance. And meanwhile, the skin effect of the shielding layer is reduced, the surface current is better borne, the influence of electromagnetic interference of a high-frequency and high-speed line on an internal circuit is reduced, the shielding effect of the electromagnetic shielding film on the high-frequency and high-speed line is improved, and the working reliability of the circuit board is further improved. Besides, the first protection layer forms an undulating surface through the particle member, and the shielding layer conformal to the undulating surface of the first protection layer can be grounded with the circuit board by using a downward projection, so that non-conductive particle grounding is realized, more use scenes are satisfied, and the material applicability is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of electromagnetic shielding materials, and in particular to an electromagnetic shielding film and a circuit board. Background Art

[0002] The rapid development of the electronics industry has driven the further miniaturization, lightweighting, and high-density assembly of electronic products, significantly driving the development of flexible printed circuits (FPCs), enabling the integration of components and wiring. Electromagnetic interference shielding (EMI shielding) is a key performance metric for FPCs. With the integration of audio and sensor components in mobile devices like smartphones, the signal transmission between these components is trending toward higher frequencies and higher speeds.

[0003] Existing circuit boards are often covered with shielding films to shield signals and reduce electromagnetic interference (EMI). Commonly used electromagnetic shielding films primarily consist of a shielding layer and an adhesive layer. The adhesive layer connects the shielding layer to the circuit board's ground plane, thereby directing interfering charges into the ground plane to achieve shielding. However, when pressed onto the circuit board, current electromagnetic shielding films are ineffective at shielding high-frequency, high-speed signals, thus hindering the high-frequency, high-speed transmission of signals on the circuit board. Summary of the Invention

[0004] Based on this, it is necessary to provide an electromagnetic shielding film and circuit board to address the above problems, meet the shielding requirements of high-frequency and high-speed line transmission, and improve the working reliability of the circuit board.

[0005] The technical solution is further described below:

[0006] An electromagnetic shielding film, comprising: a shielding layer; in a sliced ​​state, a thickness d of the shielding layer within a preset observation range satisfies:

[0007] In one embodiment, the electromagnetic shielding film further includes a first protective layer, wherein a side of the first protective layer close to the shielding layer is formed with an undulating surface, and the shielding layer is conformal to the undulating surface.

[0008] In one embodiment, the electromagnetic shielding film further includes particle members, and the particle members are arranged on one side and / or inside of the first protective layer to form an undulating surface of the first protective layer.

[0009] In one embodiment, the particles are non-conductive particles.

[0010] In one embodiment, the maximum length of the particle is 0.5-8 μm.

[0011] In one embodiment, the thermal conductivity of the particle member is greater than the thermal conductivity of the first protective layer.

[0012] In one embodiment, the shielding layer is formed with a protrusion facing away from the first protective layer, and within a preset observation range, the number of the protrusions is greater than 3.

[0013] In one embodiment, each of the protrusions is correspondingly provided with at least one particle member.

[0014] In one embodiment, the ratio of the height H to the width W of the protrusion satisfies: 0.2≤H / W≤1.

[0015] In one embodiment, the first protective layer includes an insulating layer and a buffer layer. The buffer layer is disposed on a side of the insulating layer away from the shielding layer, and the particle members are disposed in the insulating layer.

[0016] In one embodiment, the first protective layer further includes an aluminum oxide filler, and the aluminum oxide filler is disposed in the insulating layer.

[0017] In one embodiment, the elongation of the buffer layer is greater than that of the insulating layer.

[0018] In one embodiment, the electromagnetic shielding film further includes a connecting layer, which is disposed on a side of the shielding layer facing away from the first protective layer, and the connecting layer is used to connect to a substrate.

[0019] In one embodiment, conductive particles are provided in the connection layer, and the shielding layer is grounded to the circuit board through the conductive particles.

[0020] In one embodiment, the electromagnetic shielding film further includes a second protective layer, which is disposed on a side of the connecting layer facing away from the shielding layer, and the second protective layer can be peeled off from the connecting layer.

[0021] A circuit board comprises a board body and the electromagnetic shielding film described in any one of the above items, wherein the board body is provided with a grounding layer, and the shielding layer of the electromagnetic shielding film is electrically connected to the grounding layer.

[0022] The electromagnetic shielding film and circuit board provided by the embodiment of the present invention, during the production process, by adjusting the production process and other methods, the thickness uniformity of the shielding layer is made less than or equal to 20%, forming a shielding layer with uniform thickness, which can improve the consistency of the impedance characteristics, avoid reflection and crosstalk problems, and at the same time reduce the skin effect of the shielding layer, better carry the surface current, reduce the impact of the electromagnetic interference of the high-frequency high-speed line on the internal circuit, and improve the shielding effect of the electromagnetic shielding film on the high-frequency high-speed line, thereby improving the working reliability of the circuit board. In addition, the first protective layer is formed into an undulating surface by the particle parts, and the shielding layer conforming to the undulating surface of the first protective layer can use the downward protrusions to form a ground with the circuit board to achieve non-conductive particle grounding, and the protrusions formed by the shielding layer can increase the contact area with the grounding layer during the pressing process, reduce the grounding resistance, and improve the grounding effect. In addition, it can also improve the overall mechanical properties of the electromagnetic shielding film, which is conducive to improving the elongation and bending resistance of the material, meeting more usage scenarios, and improving the applicability of the material. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The accompanying drawings, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0025] In addition, the drawings are not drawn to a 1:1 scale, and the relative sizes of the various elements are drawn only for illustrative purposes and are not necessarily drawn to true scale.

[0026] Figure 1 Schematic diagram of the structural decomposition of the electromagnetic shielding film described in one embodiment of the present invention.

[0027] Figure 2 Schematic diagram of the overall structure of the electromagnetic shielding film described in one embodiment of the present invention.

[0028] Figure 3 Schematic diagram of the internal structure of the electromagnetic shielding film described in one embodiment of the present invention.

[0029] Figure 4 Schematic diagram of the internal structure of the electromagnetic shielding film according to another embodiment of the present invention.

[0030] Figure 5 Schematic diagram of the overall structure of the electromagnetic shielding film described in another embodiment of the present invention.

[0031] Figure 6 Schematic diagram of the overall structure of the electromagnetic shielding film described in another embodiment of the present invention.

[0032] Description of reference numerals:

[0033] 100. Electromagnetic shielding film; 110. First protective layer; 111. Insulating layer; 112. Buffer layer; 113. Alumina filler; 114. Undulating surface; 120. Shielding layer; 121. Protrusion; 130. Granular member; 140. Connecting layer; 141. Conductive particles; 150. Second protective layer. DETAILED DESCRIPTION

[0034] To make the above-mentioned objects, features, and advantages of the present invention more readily apparent, specific embodiments of the present invention are described in detail below with reference to the accompanying drawings. The following description sets forth numerous specific details to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways than those described herein, and those skilled in the art may make similar modifications without departing from the scope of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0035] An embodiment of the present invention provides an electromagnetic shielding film 100 including a shielding layer 120. In a sliced ​​state, a thickness d of the shielding layer 120 within a preset observation range satisfies: Among them, d max is the maximum value of the shielding layer 120 within the preset observation range, d min is the minimum value of the shielding layer 120 within the preset observation range, is the average value of the shielding layer 120 within a preset observation range.

[0036] During the production process of the above-mentioned electromagnetic shielding film 100, by adjusting the production process, etc., the thickness uniformity of the shielding layer 120 is made less than or equal to 20%, thereby forming a shielding layer 120 with uniform thickness, which can improve the consistency of the impedance characteristics, avoid reflection and crosstalk problems, and at the same time reduce the skin effect of the shielding layer 120, better carry the surface current, reduce the impact of electromagnetic interference of high-frequency high-speed lines on internal circuits, and enhance the shielding effect of the electromagnetic shielding film 100 on high-frequency high-speed lines, thereby improving the working reliability of the circuit board.

[0037] It should be noted that the preset observation range can be of different shapes and different observation areas, for example, the observation range can be circular, rectangular, trapezoidal or other irregular shapes.

[0038] See also Figure 1 , Figure 1A schematic diagram of the structure of an electromagnetic shielding film 100 according to one embodiment of the present invention is shown. In one embodiment, the electromagnetic shielding film 100 further includes a first protective layer 110. A rippled surface 114 is formed on a side of the first protective layer 110 proximate to the shielding layer 120. The shielding layer 120 conforms to the rippled surface 114. The rippled surface 114 of the first protective layer 110 allows the shielding layer 120 to be undulated. The shielding layer 120, conforming to the rippled surface 114 of the first protective layer 110, can be electrically connected to the ground layer of the circuit board using downwardly directed protrusions, achieving grounding of non-conductive particles. Furthermore, the protrusions formed on the shielding layer 120 increase the contact area with the circuit board ground layer during the lamination process, reducing grounding resistance and improving grounding effectiveness. Furthermore, the overall mechanical properties of the electromagnetic shielding film 100 are enhanced, which helps improve the overall elongation and bending resistance of the material, meeting a wider range of application scenarios and improving the material's applicability.

[0039] Optionally, the first protective layer 110 may be formed into the undulating surface 114 by adjusting the roughness of the first protective layer 110 by pressing, etching, adding particles, etc. to form the undulating surface 114 .

[0040] Specifically, see Figure 2 , Figure 2 Figure 1 shows the overall structure of an electromagnetic shielding film 100 according to one embodiment of the present invention. Electromagnetic shielding film 100 also includes particulate members 130, which are disposed on one side and / or within a first protective layer 110 to form an undulating surface 114 on the first protective layer 110. Adding particulate members 130 utilizes their raised shape to create undulations on one side of the flat first protective layer 110, thereby reducing costs and facilitating adjustment of the height and amplitude of the undulations.

[0041] It should be noted that the particle members 130 are arranged on one side and / or inside the first protective layer 110 to form the undulating surface 114. It should be understood that there are three ways to arrange the particle members 130: the first is that a plurality of particle members 130 are arranged at intervals on one side of the first protective layer 110, and the particle members 130 form undulations on the surface; the second is to refer to Figure 5 , Figure 5 The overall structure of the electromagnetic shielding film 100 according to one embodiment of the present invention is shown in FIG. Figure 2 The plurality of particles 130 are disposed inside the first protective layer 110 , so that the surface of the first protective layer 110 is raised to form an undulating surface 114 ; the third type is a combination of the plurality of particles 130 disposed on one side of the first protective layer 110 and disposed inside the first protective layer 110 .

[0042] It should also be noted that the shielding layer 120 is disposed on the undulating surface 114 and conforms to the undulating surface 114 , which should be understood as the shielding layer 120 conforming to the contour of the undulating surface 114 , with the thickness at the protrusions and depressions being consistent.

[0043] Optionally, the shielding layer 120 has the function of conducting free electrons, and the materials used therefor may be the same or different, and specifically include one or more of a metal shielding layer 120, a carbon nanotube shielding layer 120, a ferrite shielding layer 120, and a graphene shielding layer 120. The metal shielding layer 120 includes a single metal shielding layer 120 and / or an alloy shielding layer 120; the single metal shielding layer 120 is made of any one of aluminum, titanium, zinc, iron, nickel, chromium, cobalt, copper, silver, and gold, and the alloy shielding layer 120 is made of any two or more of aluminum, titanium, zinc, iron, nickel, chromium, cobalt, copper, silver, and gold.

[0044] Furthermore, the shielding layer 120 may be a single layer or may be two or more layers. When the shielding layer 120 is two or more layers, different layers of the shielding layers 120 may be stacked with the same or different materials.

[0045] Furthermore, the thickness of the shielding layer 120 is 500 nm to 5 μm.

[0046] Optionally, the particle pieces 130 may be in the shape of blocks, columns, sheets, particles, strips or other irregular shapes.

[0047] In this example, see Figure 2 and Figure 5 The particles 130 are granular. When sliced, they appear blocky. This uniform shape and the uniform height of the undulating portions help ensure the grounding effect of the electromagnetic shielding film 100. It also ensures the amount of sol, preventing cracking during lamination and improving the performance of the electromagnetic shielding film 100.

[0048] Optionally, the material of the particle piece may be a metal material, a non-metal material, or a conductive or non-conductive material.

[0049] In one embodiment, see Figure 2 and Figure 4 The particles 130 are non-conductive particles. The provision of non-conductive particles enables the first protective layer 110 to ensure insulation and protection effects while not affecting the thickness uniformity of the shielding layer 120, thereby improving the shielding effect of high-frequency and high-speed lines.

[0050] The particle pieces 130 include solid particles and / or hollow particles.

[0051] Optionally, in the sliced ​​state, the maximum length of the particle members 130 is 0.5 to 8 μm. Within this size range, the particle members 130 can ensure that the height of the undulating surface 114 meets the grounding requirements, thereby enabling the conformal shielding layer 120 to have excellent mechanical properties and improving the overall bending and flexing resistance of the electromagnetic shielding film 100.

[0052] It should be noted that the maximum length of the particle member 130 is the maximum length within the particle member 130 when the electromagnetic shielding film 100 is sliced ​​in any direction.

[0053] Further, see Figure 2 and Figure 4 In the slicing state, the shortest straight-line distance between two adjacent particles 130 is greater than 0.5 μm. This ensures the undulating state and continuity of the shielding layer 120, avoids the accumulation of the shielding layer 120 during processing due to too small a gap, and prevents large thickness variations. This ensures the electromagnetic shielding effect of the electromagnetic shielding film 100 when applied to high-frequency and high-speed lines.

[0054] Optionally, the material of the particle members 130 may be diamond powder, matte powder, ceramic powder, quartz powder, mica powder, graphite or other non-conductive and thermally conductive materials.

[0055] In one embodiment, the thermal conductivity of the particle members 130 is greater than that of the first protective layer 110. Furthermore, the thermal conductivity of the particle members 130 is greater than that of the shielding layer 120. In this way, the thermal conductivity of the first protective layer 110 can be enhanced by the particle members 130, thereby improving the overall heat dissipation effect of the electromagnetic shielding film 100.

[0056] Furthermore, in the sliced ​​state, the thickness uniformity of the shielding layer 120 is less than 5%. This more uniform shielding layer 120 can further reduce the skin effect of the induced current, better carry the surface current, and effectively block or guide its flow, thereby reducing the impact of electromagnetic interference (EMI) on the internal circuit.

[0057] It should be noted that the slicing state refers to making a cross section of the electromagnetic shielding film 100 in any direction. Figure 5 As shown, Figure 5 The internal structure of the electromagnetic shielding film 100 according to one embodiment of the present invention is shown in FIG. Figure 2 , which includes two slicing directions: X direction and Y direction.

[0058] In one embodiment, see Figure 2The shielding layer 120 has a raised portion 121 formed on the back of the first protective layer 110. Within a predetermined observation range, the number of raised portions 121 is greater than three. This number of raised portions 121 can further ensure the grounding effect of the shielding layer 120, reduce grounding resistance and insertion loss, and improve electromagnetic shielding effect.

[0059] The preset observation range is the same as the above range.

[0060] In one embodiment, see Figure 5 Each raised portion 121 is provided with at least one particle member 130. Optionally, the number of particle members 130 provided for each raised portion 121 can be one, two, three, or another number. This reduces production costs and facilitates adjustment of the raised portion 121's height and width by varying the number and size of particle members 130, thereby adjusting the amount of sol and grounding effect, improving overall quality.

[0061] Furthermore, the ratio of the height H to the width W of the raised portion 121 satisfies the following condition: 0.2 ≤ H / W ≤ 1. The raised portion 121 meeting this ratio can provide a wider grounding area, which helps ensure thickness uniformity while further improving the grounding effect between the shielding layer 120 and the circuit board, reducing insertion loss and grounding resistance, thereby improving electromagnetic shielding effectiveness.

[0062] It should be noted that the height H of the raised portion 121 is the vertical distance between the horizontal line and the lowest point between two adjacent points of the shielding layer 120 closest to the first protective layer 110 along the thickness direction; the width of the raised portion 121 is the straight-line distance between two adjacent points of the shielding layer 120 closest to the first protective layer 110 along the thickness direction.

[0063] In one embodiment, see Figure 5 The first protective layer 110 includes an insulating layer 111 and a buffer layer 112. The buffer layer 112 is disposed on the side of the insulating layer 111 facing away from the shielding layer 120. The particles 130 are disposed within the insulating layer 111 and form a contoured surface 114 on the side of the insulating layer 111 facing away from the buffer layer 112. The insulating layer 111 ensures the overall electrical insulation performance of the electromagnetic shielding film 100, preventing the shielding layer 120 from contacting other components and causing electrical conduction, thereby ensuring the shielding effect. The provision of the buffer layer 112 helps improve the overall mechanical properties of the first protective layer 110, enhancing its bending resistance.

[0064] Optionally, the thickness of the insulating layer 111 is 1-10 μm. The thickness of the buffer layer 112 is 1-10 μm.

[0065] It should be noted that the material of the insulating layer 111 can be bisphenol A epoxy resin, acrylic resin, polyester resin, etc. In addition, the resin used can also be selected from any one of epoxy resin, cyanate resin, polyphenylene ether resin, polybutadiene resin, styrene-butadiene resin, bismaleimide-triazine resin (BT), bismaleimide resin, polytetrafluoroethylene resin, polyimide resin, phenolic resin, acrylic resin, liquid crystal resin, benzoxazine resin, phenoxy resin, nitrile rubber, carboxyl-terminated nitrile rubber or hydroxyl-terminated nitrile rubber, or a mixture of at least two thereof, but is not limited thereto, and all resin materials disclosed in the prior art can be used. The mixture may be a mixture of epoxy resin and cyanate resin, a mixture of polyphenylene oxide resin and polybutadiene resin, a mixture of styrene butadiene resin and BT resin, a mixture of polytetrafluoroethylene resin and polyimide resin, a mixture of phenolic resin and acrylic resin, a mixture of epoxy resin, cyanate resin and polyphenylene oxide resin, a mixture of polybutadiene resin, styrene butadiene resin and BT resin, a mixture of polytetrafluoroethylene resin, polyimide resin, phenolic resin and acrylic resin. That is, a mixture of two or more resins may be used.

[0066] It should also be noted that the material of the buffer layer 112 can be a PPS film layer, a PEN film layer, a polyester film layer, a polyimide film layer, a film layer formed after epoxy resin ink is cured, a film layer formed after polyurethane ink is cured, a film layer formed after modified acrylic resin is cured, or a film layer formed after polyimide resin is cured, etc.

[0067] See also Figure 6 , Figure 6 The structure of the electromagnetic shielding film 100 in one embodiment of the present invention is shown in FIG. Figure 3 . In one embodiment, the first protective layer 110 also includes an alumina filler 113, and the alumina filler 113 is disposed in the insulating layer 111. Alumina has good thermal conductivity. When it is added to the insulating layer 111, first, it can significantly improve the heat dissipation performance of the material, contribute to the rapid conduction of heat in electronic equipment, and prevent overheating. Secondly, the alumina particles can act as a reinforcing agent to improve the strength, hardness and wear resistance of the polymer material. In addition, adding alumina to the insulating layer 111 can improve the thermal stability and heat resistance of the material, and improve the overall heat resistance of the electromagnetic shielding film 100. The addition of alumina can also effectively reduce the thermal expansion coefficient of the material and improve the dimensional stability of the first protective layer 110.

[0068] In one embodiment, see Figure 1 and Figure 2 The elongation of the buffer layer 112 is greater than that of the insulating layer 111. The buffer layer 112 can provide a base for the insulating layer 111 and improve the overall elongation of the first protective layer 110 through a larger elongation, thereby improving the bending performance and tensile strength.

[0069] In one embodiment, Figure 3 As shown, the electromagnetic shielding film 100 further includes a connecting layer 140 . The connecting layer 140 is disposed on a side of the shielding layer 120 facing away from the first protective layer 110 . The connecting layer 140 is used to connect to the substrate.

[0070] Optionally, the thickness of the connecting layer 140 is 1 μm to 20 μm. Specifically, the thickness of the connecting layer 140 affects the propagation and attenuation of electromagnetic waves therein. A suitable thickness of the connecting layer 140 can reduce insertion loss to a certain extent. Within a certain range, the thicker the connecting layer 140, the lower the insertion loss of the circuit board. However, the thickness should not be too thick. An excessively thick connecting layer 140 may cause other problems, such as increased weight, reduced flexibility, and poor bonding to the circuit board. Therefore, in this embodiment of the present invention, the thickness of the connecting layer 140 is set at 1 μm to 20 μm, which can optimize the insertion loss of the circuit board while not significantly affecting other properties of the electromagnetic shielding film 100. Exemplarily, the thickness of the connecting layer 140 is 1 μm, 1.5 μm, 3 μm, 4.5 μm, 5 μm, 6.5 μm, 7 μm, 8.5 μm, 9 μm, 10.5 μm, 11 μm, 12.5 μm, 13 μm, 14.5 μm, 17 μm, 18.5 μm, 19 μm, 19.5 μm, 20 μm and / or an interval consisting of any two values.

[0071] It should be noted that the thickness of the connection layer 140 is the minimum distance between one side of the shielding layer 120 close to the connection layer 140 and the other side of the connection layer 140 .

[0072] Among them, the grounding method of the shielding layer 120 can be that the shielding layer 120 relies on the protrusions formed by the conformal undulating surface 114 to be grounded through the connecting layer 140 after pressing, or the shielding layer 120 can be grounded indirectly to the grounding layer of the circuit board through the conductive particles 141 by adding conductive particles 141 to the connecting layer 140.

[0073] Further, see Figure 6 Conductive particles 141 are provided within the connecting layer 140, and the shielding layer 120 is grounded to the circuit board via the conductive particles 141. Grounding via the conductive particles 141 further enhances the grounding effect, reduces insertion loss and grounding resistance of the electromagnetic shielding film 100, and simplifies the grounding process during circuit board production, improving assembly efficiency and reducing overall production costs.

[0074] It should be noted that the conductive particles 141 include graphene nanosheets, carbon nanotubes (CNTs), ferroferric oxide (Fe3O4), silver nanowires (AgNWs), pure silver, silver-plated copper, silver-plated aluminum, silver-plated nickel, and the like. These conductive particles 141 can significantly improve the conductivity and electromagnetic shielding effectiveness of the connecting layer 140. For example, silver nanowires are widely used in the preparation of the electromagnetic shielding film 100 due to their excellent conductivity and transparency.

[0075] In one embodiment, see Figure 6 The electromagnetic shielding film 100 also includes a second protective layer 150, which is disposed on the side of the connecting layer 140 facing away from the shielding layer 120. The second protective layer 150 can be peeled off from the connecting layer 140. The second protective layer 150 protects the connecting layer 140 from scratches and damage during use. Before laminating the electromagnetic shielding film 100 to the circuit board, the second protective layer 150 must be peeled off first.

[0076] Optionally, the second protective layer 150 includes a PPS film, a PEN film, a polyester film, a polyimide film, or other film materials that meet the release function.

[0077] In one embodiment, a circuit board (not shown) is further included. The circuit board includes a board body and any one of the electromagnetic shielding films 100 described above. The board body is provided with a ground layer, and the shielding layer 120 is electrically connected to the ground layer.

[0078] During the production process of the above-mentioned electromagnetic shielding film 100, by setting particulate members 130 in the protective layer, an undulating surface 114 is formed on one side of the protective layer, and then the shielding layer 120 is processed on the undulating surface 114, the shielding layer 120 can be conformal to the undulating surface 114 to form a uniformly curved shielding layer 120. On the one hand, the downwardly protruding positions in the undulating surface 114 allow the shielding layer 120 to be grounded with the grounding layer of the circuit board after being pressed with the circuit board, thereby ensuring the shielding effect. On the other hand, the uniformly curved shielding layer 120 can improve the consistency of the impedance characteristics, avoid reflection and crosstalk problems, and at the same time reduce the skin effect of the shielding layer 120, better carry the surface current, reduce the influence of electromagnetic interference of high-frequency high-speed lines on the internal circuit, and improve the shielding effect of the electromagnetic shielding film 100 on high-frequency high-speed lines, thereby improving the working reliability of the circuit board.

[0079] In the description of the present invention, it should be understood that if the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. appear, the orientation or position relationship indicated by these terms is based on the orientation or position relationship shown in the accompanying drawings, which is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore cannot be understood as limiting the present invention.

[0080] Furthermore, if the terms "first" or "second" appear, these terms are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of the technical features indicated. Thus, a feature specified as "first" or "second" may explicitly or implicitly include at least one of such features. In the description of the present invention, if the term "plurality" appears, "plurality" means at least two, for example, two, three, etc., unless otherwise specifically defined.

[0081] In this disclosure, unless otherwise specified or limited, the terms "mounted," "connected," "connected," "fixed," etc., should be interpreted broadly. For example, these terms may refer to fixed connections, removable connections, or integration; mechanical connections or electrical connections; direct connections or indirect connections through an intermediary; and internal communication between two components or interaction between two components, unless otherwise specified. Those skilled in the art will understand the specific meanings of these terms in this disclosure based on the specific circumstances.

[0082] In the present invention, unless otherwise expressly specified or limited, if a first feature is described as being "above" or "below" a second feature, or similar descriptions, this may mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediary. Furthermore, the phrase "above," "above," or "above" a first feature may mean that the first feature is directly above or diagonally above the second feature, or simply means that the first feature is at a higher level than the second feature. The phrase "below," "below," or "below" a first feature may mean that the first feature is directly below or diagonally below the second feature, or simply means that the first feature is at a lower level than the second feature.

[0083] It should be noted that if an element is referred to as being "fixed to" or "disposed on" another element, it may be directly on the other element or there may be an intermediate element. If an element is referred to as being "connected to" another element, it may be directly connected to the other element or there may be an intermediate element. If any, the terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used in this invention are for illustrative purposes only and do not represent the only implementation method.

[0084] The technical features of the above embodiments can be combined arbitrarily. To make the description concise, 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.

[0085] The above embodiments merely illustrate several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art would be able to make various modifications and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be determined by the appended claims.

Claims

1. An electromagnetic shielding film, characterized in that: The electromagnetic shielding film comprises: a shielding layer, in a sliced ​​state, a thickness d of the shielding layer within a preset observation range satisfies:

2. The electromagnetic shielding film according to claim 1, characterized in that The electromagnetic shielding film further includes a first protective layer, a side of the first protective layer close to the shielding layer is formed with an undulating surface, and the shielding layer is conformal to the undulating surface.

3. The electromagnetic shielding film according to claim 2, characterized in that The electromagnetic shielding film further includes particle members, and the particle members are arranged on one side and / or inside of the first protective layer so that the first protective layer forms an undulating surface.

4. The electromagnetic shielding film according to claim 3, characterized in that The particle pieces are non-conductive particles; and / or, The thermal conductivity of the particle member is greater than the thermal conductivity of the first protective layer.

5. The electromagnetic shielding film according to claim 3, characterized in that The maximum length of the particle is 0.5 to 8 μm.

6. The electromagnetic shielding film according to claim 3, characterized in that The shielding layer is formed with a protrusion facing away from the first protective layer, and within a preset observation range, the number of the protrusions is greater than 3.

7. The electromagnetic shielding film according to claim 6, characterized in that Each of the protrusions is correspondingly provided with at least one particle member.

8. The electromagnetic shielding film according to claim 6, characterized in that The ratio of the height H to the width W of the protrusion satisfies: 0.2≤H / W≤1.

9. The electromagnetic shielding film according to claim 3, characterized in that The first protection layer includes an insulating layer and a buffer layer. The buffer layer is arranged on a side of the insulating layer away from the shielding layer, and the particle members are arranged in the insulating layer.

10. The electromagnetic shielding film according to claim 9, characterized in that The first protective layer further comprises an aluminum oxide filler, and the aluminum oxide filler is arranged in the insulating layer; and / or, The buffer layer has a greater elongation than the insulating layer.

11. The electromagnetic shielding film according to any one of claims 1 to 10, characterized in that: The electromagnetic shielding film further includes a connecting layer, which is disposed on a side of the shielding layer facing away from the first protective layer, and is used to be connected to a substrate.

12. The electromagnetic shielding film according to claim 11, characterized in that Conductive particles are arranged in the connection layer, and the shielding layer is grounded to the circuit board through the conductive particles.

13. The electromagnetic shielding film according to claim 11, characterized in that The electromagnetic shielding film further includes a second protective layer, which is arranged on a side of the connecting layer facing away from the shielding layer, and the second protective layer can be peeled off from the connecting layer.

14. A circuit board, characterized in that: The circuit board comprises a board body and the electromagnetic shielding film described in any one of claims 1 to 13, wherein the board body is provided with a grounding layer, and the shielding layer of the electromagnetic shielding film is electrically connected to the grounding layer.

Images