Electromagnetic shielding film and circuit board

Abstract

The present invention relates to the field of electronic technologies, and discloses an electromagnetic shielding film and a circuit board. Among them, the electromagnetic shielding film includes a carrier layer, an insulating layer, and a shielding layer; the carrier layer is disposed on one surface of the insulating layer, and the shielding layer is disposed on the surface of the insulating layer away from the carrier layer; the surface roughness Sku of the surface of the insulating layer close to the carrier layer is 0.5 - 50; the ratio of the surface roughness Sku of the surface of the carrier layer close to the insulating layer to the surface roughness Sku of the surface of the insulating layer close to the carrier layer is 0.01 - 100. The present invention can avoid easily tearing the insulating layer during the process of tearing the carrier layer from the insulating layer, enabling the insulating layer to have good airtightness and insulation performance, thereby avoiding problems such as oxidation of the shielding layer and poor shielding performance.

Description

Technical Field

[0001] The present invention relates to the field of electronic technology, and more particularly to an electromagnetic shielding film and a circuit board. Background Art

[0002] With the rapid development of the electronic industry, electronic products are further developing towards miniaturization, light weight, and high-density assembly, which greatly promotes the development of flexible circuit boards, thereby realizing the integration of component devices and wire connections. Flexible circuit boards can be widely used in industries such as mobile phones, liquid crystal displays, communications, and aerospace.

[0003] Driven by the international market, functional flexible circuit boards dominate the flexible circuit board market, and an important indicator for evaluating the performance of functional flexible circuit boards is electromagnetic shielding (Electromagnetic Interference Shielding, abbreviated as EMI Shielding). With the integration of functions of communication devices such as mobile phones, the internal components thereof have become extremely high-frequency and high-speed. For example: in addition to the original audio transmission function of mobile phones, the camera function has become an essential function, and WLAN (Wireless Local Area Networks), GPS (Global Positioning System), and Internet access functions have become popular. Coupled with the integration of future sensing components, the trend of components becoming extremely high-frequency and high-speed is even more inevitable. The electromagnetic interference inside and outside the components, signal attenuation during transmission, insertion loss, and jitter problems caused by high-frequency and high-speed driving are gradually becoming serious.

[0004] Currently, the commonly used electromagnetic shielding films for existing circuit boards include a carrier layer, an insulating layer, and a shielding layer. When in use, the electromagnetic shielding film needs to be hot-pressed with the circuit board at a high temperature. After the hot pressing is completed, the carrier layer is peeled off, so that the shielding layer is electrically connected to the ground layer of the circuit board, and then the interfering charges are introduced into the ground layer of the circuit board, thereby achieving shielding.

[0005] The inventor of the present invention found the following technical problems in the process of implementing the present invention: when the shape of the roughness of the carrier layer of the existing electromagnetic shielding film is too steep, during the process of peeling the carrier layer from the insulating layer, it is easy to tear the insulating layer, which will affect the airtightness and insulating performance of the insulating layer itself, and further cause problems such as oxidation of the shielding layer and poor shielding performance. Summary of the Invention

[0006] Aiming at the above problems, the purpose of the present invention is to provide an electromagnetic shielding film and a circuit board, which can avoid easily tearing the insulating layer during the process of peeling the carrier layer from the insulating layer, so that the insulating layer has good airtightness and insulating performance, thereby avoiding problems such as oxidation of the shielding layer and poor shielding performance.

[0007] To achieve the above object, an embodiment of the present invention provides an electromagnetic shielding film, which includes a carrier layer, an insulating layer, and a shielding layer;

[0008] The carrier layer is disposed on one surface of the insulating layer, and the shielding layer is disposed on the surface of the insulating layer away from the carrier layer;

[0009] The roughness Sku of the surface of the insulating layer close to the carrier layer is 0.5 - 50;

[0010] The ratio of the roughness Sku of the surface of the carrier layer close to the insulating layer to the roughness Sku of the surface of the insulating layer close to the carrier layer is 0.01 - 100.

[0011] As an improvement of the above solution, the roughness Sku of the surface of the insulating layer close to the carrier layer is 2 - 25.

[0012] As an improvement of the above solution, the roughness Sku of the surface of the insulating layer close to the carrier layer is 5 - 20.

[0013] As an improvement of the above solution, the roughness Sku of the surface of the carrier layer close to the insulating layer is 2 - 25.

[0014] As an improvement of the above solution, the roughness Sku of the surface of the carrier layer close to the insulating layer is 5 - 20.

[0015] As an improvement of the above solution, the electromagnetic shielding film further includes an adhesive film layer; the adhesive film layer is disposed on the surface of the shielding layer away from the insulating layer;

[0016] The adhesive film layer includes an adhesive layer containing conductive particles; or, the adhesive film layer includes an adhesive layer without conductive particles.

[0017] As an improvement of the above solution, conductive protrusions are provided on the surface of the shielding layer close to the adhesive film layer.

[0018] As an improvement of the above solution, the ratio of the arithmetic average thickness of the adhesive film layer to the protrusion height of the conductive protrusions is greater than or equal to 2 / 7.

[0019] As an improvement of the above solution, through holes penetrating the upper and lower surfaces are provided on the shielding layer.

[0020] To solve the same technical problem, another embodiment of the present invention further provides a circuit board, which includes a circuit board body and the electromagnetic shielding film according to any one of the above solutions; the electromagnetic shielding film is pressed together with the circuit board body; the surface of the shielding layer away from the insulating layer is electrically connected to the ground layer of the circuit board body.

[0021] Compared with the prior art, the electromagnetic shielding film and the circuit board provided by the embodiments of the present invention have at least one of the following beneficial effects:

[0022] When the sharpness of the roughness shape on the side of the insulating layer close to the carrier layer is 0.5 - 50, and the ratio of the Sku of the roughness on the side of the carrier layer close to the insulating layer to the Sku of the roughness on the side of the insulating layer close to the carrier layer is 0.01 - 100, it can be avoided that the insulating layer is easily torn during the process of tearing the carrier layer from the insulating layer, so that the insulating layer has good airtightness and insulation performance, thereby avoiding the problems of oxidation of the shielding layer and poor shielding performance. On the other hand, when the sharpness of the roughness shape on the side of the insulating layer close to the carrier layer is 0.5 - 50, and the ratio of the Sku of the roughness on the side of the carrier layer close to the insulating layer to the Sku of the roughness on the side of the insulating layer close to the carrier layer is 0.01 - 100, it is ensured that the carrier layer is not easily detached, so as to protect the insulating layer, and at the same time, it can be stably peeled off under a certain applied force, so as to facilitate use. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions of the present invention, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0024] Figure 1 is a schematic structural diagram of a first electromagnetic shielding film provided by an embodiment of the present invention;

[0025] Figure 2 is a schematic structural diagram of a second electromagnetic shielding film provided by an embodiment of the present invention;

[0026] Figure 3 is a schematic structural diagram of a third electromagnetic shielding film provided by an embodiment of the present invention;

[0027] Figure 4 is a schematic structural diagram of a fourth electromagnetic shielding film provided by an embodiment of the present invention;

[0028] Figure 5 is a schematic structural diagram of a fifth electromagnetic shielding film provided by an embodiment of the present invention;

[0029] Figure 6 is a schematic structural diagram of a circuit board laminated with an electromagnetic shielding film provided by an embodiment of the present invention.

[0030] Among them, 1. Carrier layer; 2. Insulating layer; 3. Shielding layer; 4. Adhesive film layer; 5. Protective film layer; 6. Circuit board body; 31. Conductive protrusion. Specific embodiments

[0031] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0032] In the description of the specification and claims, it should be understood that the orientation or positional relationship indicated by the terms "upper", "lower", "left", "right", "front", "rear", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the embodiments of the present invention, rather than indicating or implying that the device or component referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation to the embodiments of the present invention.

[0033] In addition, the terms first, second, etc. in the specification and claims are only used for the purpose of distinguishing the description of the same technical features, and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity of the technical features indicated, nor necessarily describing the order or time sequence. The terms can be interchanged under appropriate circumstances. Thus, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features.

[0034] See Figure 1 , an embodiment of the present invention provides an electromagnetic shielding film, which includes a carrier layer 1, an insulating layer 2 and a shielding layer 3; the carrier layer 1 is disposed on one surface of the insulating layer 2, and the shielding layer 3 is disposed on the surface of the insulating layer 2 away from the carrier layer 1; the surface roughness Sku of the surface of the insulating layer 2 close to the carrier layer 1 is 0.5 - 50; the ratio of the surface roughness Sku of the surface of the carrier layer 1 close to the insulating layer 2 to the surface roughness Sku of the surface of the insulating layer 2 close to the carrier layer 1 is 0.01 - 100.

[0035] In an embodiment of the present invention, when the shape sharpness of the roughness on the side of the insulating layer 2 close to the carrier layer 1 is 0.5 - 50, and the ratio of the roughness Sku of the side of the carrier layer 1 close to the insulating layer 2 to the roughness Sku of the side of the insulating layer 2 close to the carrier layer 1 is 0.01 - 100, it is possible to avoid easily tearing the insulating layer 2 during the process of peeling the carrier layer 1 from the insulating layer 2, so that the insulating layer 2 has good airtightness and insulation performance, thereby avoiding the problems of oxidation and poor shielding performance of the shielding layer 3. On the other hand, when the shape sharpness of the roughness on the side of the insulating layer 2 close to the carrier layer 1 is 0.5 - 50, and the ratio of the roughness Sku of the side of the carrier layer 1 close to the insulating layer 2 to the roughness Sku of the side of the insulating layer 2 close to the carrier layer 1 is 0.01 - 100, it is ensured that the carrier layer 1 is not easily detached, so as to protect the insulating layer 2, and at the same time, it can be stably peeled off under a certain applied force, thereby facilitating use. Moreover, since the ratio of the roughness Sku of the side of the carrier layer 1 close to the insulating layer 2 to the roughness Sku of the side of the insulating layer 2 close to the carrier layer 1 is 0.01 - 100, compared with the carrier layer and insulating layer with a flat surface structure, when the electromagnetic shielding film is laminated with the circuit board, the carrier layer 1 is not likely to undergo a large horizontal movement during the lamination process, thus not easily causing the problem that the overall electromagnetic shielding film moves horizontally due to the horizontal movement of the carrier layer 1 when the electromagnetic shielding film is laminated onto the circuit board, and the electromagnetic shielding film can be laminated at the corresponding position on the circuit board. Additionally, by making the roughness Sku of the side of the insulating layer 2 close to the carrier layer 1 be 0.5 - 50, the surface tension of the insulating layer 2 can be improved, and when printing ink on the insulating layer 2, the ink will not spread. For example, in an application, when printing characters on the surface of the insulating layer, the characters can be clearly displayed.

[0036] Preferably, the roughness Sku of the side of the insulating layer 2 close to the carrier layer 1 is 2 - 25. More preferably, the roughness Sku of the side of the insulating layer 2 close to the carrier layer 1 is 5 - 20.

[0037] It can be understood that the roughness Sku is a parameter for judging the shape sharpness of the roughness. In addition, the test standard for the roughness Sku is ISO25178.

[0038] Among them, the material of the carrier layer 1 is PET (Polyethylene terephthalate, polyester resin). It can be understood that in order to ensure that the shielding layer 3 has good electrical conductivity, the shielding layer 3 includes one or more of a metal shielding layer, a carbon nanotube shielding layer, a ferrite shielding layer, and a graphene shielding layer. Among them, the metal shielding layer includes a single-metal shielding layer and / or an alloy shielding layer; among them, the single-metal shielding layer is made of any one of aluminum, titanium, zinc, iron, nickel, chromium, cobalt, copper, silver, and gold, and the alloy shielding layer is made of any two or more of aluminum, titanium, zinc, iron, nickel, chromium, cobalt, copper, silver, and gold.

[0039] In this embodiment, the tensile force between the carrier layer 1 and the insulating layer 2 is 0.01 - 3 N / cm. By setting the tensile force between the carrier layer 1 and the insulating layer 2 to 0.01 - 3 N / cm, the problem of reverse release (that is, after lamination, there is a problem that part of the carrier layer remains on the surface of the insulating layer) can be solved, and the carrier layer 1 can be stably peeled off after laminating the electromagnetic shielding film, thereby avoiding the residual carrier layer 1 on the insulating layer 2.

[0040] In this embodiment, the surface roughness Sku of the side of the carrier layer close to the insulating layer is 2 - 25, which can ensure that the carrier layer 1 is not easily detached before laminating the electromagnetic shielding film onto the circuit board, thereby playing a role in protecting the insulating layer 2, and at the same time, it can be stably peeled off under a certain force after laminating the electromagnetic shielding film onto the circuit board.

[0041] Preferably, the surface roughness Sku of the side of the carrier layer close to the insulating layer is 5 - 20.

[0042] In this embodiment, the thickness of the carrier layer 1 is 7 - 150 microns, and the thickness of the insulating layer is 3 - 25 microns. The carrier layer 1 can be used to protect the insulating layer 2 so that the insulating layer 2 is not damaged by external contact or collision, etc. Among them, when the thickness of the carrier layer 1 is 50 microns, it has better protection ability and can perfectly protect the insulating layer 2 from being damaged by external contact or collision, etc. In addition, the carrier layer 1 can be used as the base film for forming the insulating layer 2, that is: the insulating layer 2 can be formed on one side of the carrier layer 1.

[0043] In this embodiment, the ratio of the skewness Sku of the surface of the carrier layer 1 close to the insulating layer 2 to the thickness of the insulating layer 2 is 0.8 - 3, and the ratio of the skewness Sku of the surface of the insulating layer 2 close to the carrier layer 1 to the thickness of the carrier layer 1 is 0.8 - 3. During the process of forming the insulating layer 2 on one surface of the carrier layer 1, it is easy to make the skewness Sku of the surface of the insulating layer 2 far from the carrier layer 1 be 2 - 25.

[0044] In this embodiment, the skewness Sku of the surface of the insulating layer 2 close to the shielding layer 3 is 2 - 25, which can improve the bending resistance of the insulating layer 2, thereby improving the bending resistance of the electromagnetic shielding film. In addition, when forming the shielding layer 3 on one surface of the insulating layer 2, since the thickness of the shielding layer 3 is fixed, the skewness Sku of the surface of the shielding layer 3 close to the adhesive film layer can also be 2 - 25.

[0045] In this embodiment, the skewness Sku of the surface of the insulating layer 2 close to the shielding layer 3 is also 2 - 25. Among them, the insulating layer 2 can effectively electrically isolate the shielding layer 3 from the outside, thereby ensuring the electromagnetic shielding effect of the shielding layer 3. Moreover, the skewness Sku of the surface of the insulating layer 2 close to the shielding layer 3 is also 2 - 25, which can improve the bonding strength between the insulating layer 2 and the shielding layer 3, and avoid the phenomenon that the insulating layer 2 and the shielding layer 3 are prone to peeling off.

[0046] Further, referring to Figure 2 , the electromagnetic shielding film further includes an adhesive film layer 4; the adhesive film layer 4 is disposed on the surface of the shielding layer 3 far from the insulating layer 2. The electromagnetic shielding film is pressed against the circuit board body through the adhesive film layer 4; the surface of the shielding layer 3 close to the adhesive film layer 4 pierces through the adhesive film layer 4 and is electrically connected to the ground layer of the circuit board body.

[0047] Among them, the material used for the adhesive film layer 4 is selected from the following: modified epoxy resin type, acrylic type, modified rubber type, modified thermoplastic polyimide type.

[0048] In the embodiment of the present invention, the surface roughness Sku of the side of the shielding layer 3 close to the adhesive film layer 4 is 2 - 25. In this way, when the electromagnetic shielding film is laminated onto the circuit board, the side of the shielding layer 3 close to the adhesive film layer 4 can effectively pierce through the adhesive film layer 4. Moreover, with the surface roughness Sku of the shielding layer 3 being 2 - 25, the bonding force between the shielding layer 3 and the circuit board can be enhanced, making it difficult for the electromagnetic shielding film to delaminate. Also, when the electromagnetic shielding film is laminated with the circuit board, since the surface roughness Sku of the side of the shielding layer 3 close to the adhesive film layer 4 is 2 - 25, the adhesive of the adhesive film layer 4 is not prone to large - scale horizontal movement on the side of the shielding layer 3 during the lamination of the shielding film. Therefore, it is not easy to have the problem of obvious glue overflow at the edge of the circuit board due to glue displacement, so that the circuit board after laminating the shielding film has a good appearance. In addition, because the surface roughness Sku of the side of the shielding layer 3 close to the adhesive film layer 4 is 2 - 25, the glue - like substances constituting the adhesive film layer 4 are extruded into the concave positions on the side of the shielding layer 3, increasing the glue - containing capacity. On the one hand, it is not easy to have the phenomenon of board explosion, avoiding the problem of high - temperature board explosion caused by insufficient glue - containing capacity in the existing electromagnetic shielding film, and effectively ensuring the grounding of the electromagnetic shielding film, thereby conducting interference charges. On the other hand, it can prevent the glue from overflowing to the edge of the circuit board during lamination, so that the circuit board after laminating the shielding film has a good appearance.

[0049] Further, referring to Figure 3 , through - holes penetrating the upper and lower surfaces of the shielding layer 3 are provided on the shielding layer 3. By providing through - holes penetrating the upper and lower surfaces of the shielding layer 3, when the electromagnetic shielding film is laminated onto the circuit board at high temperature, the volatile gases generated in the adhesive film layer 4 can effectively escape through the through - holes of the shielding layer 3, so that the electromagnetic shielding film will not have the problem of blistering and delamination.

[0050] In this embodiment, the aperture of the through - hole is 0.1 - 10 microns. By setting the aperture of the through - hole to 0.1 - 10 microns, it can be ensured that the through - hole can smoothly discharge the volatile gases in the adhesive film layer 4 during the high - temperature lamination process.

[0051] In this embodiment, the number of through - holes per square centimeter of the shielding layer is 1 - 1000. By setting the number of through - holes to 1 - 1000, it is ensured that the volatiles in the adhesive film layer 4 can exhaust through a sufficient number of the through - holes at high temperature, thus avoiding the difficulty of discharging the volatile gases in the adhesive film layer at high temperature, and further avoiding the peeling between the electromagnetic shielding film and the ground layer of the circuit board caused by blistering and delamination of the electromagnetic shielding film, so as to ensure the grounding of the electromagnetic shielding film and effectively conduct interference charges.

[0052] In this embodiment, the ratio of the sum of the cross-sectional areas of all the through holes in the shielding layer 2 per square centimeter on average to the cross-sectional area of the shielding layer where the cross-section is located is 1% to 70%. By making the ratio of the sum of the cross-sectional areas of all the through holes in the shielding layer per square centimeter on average to the cross-sectional area of the shielding layer where the cross-section is located be 1% to 70%, it can not only ensure the effective discharge of the volatile gases in the adhesive film layer at high temperatures, but also ensure the electromagnetic shielding effect of the shielding layer.

[0053] See Figure 4 , in the embodiment of the present invention, a conductive protrusion 31 is provided on the surface of the shielding layer 3 close to the adhesive film layer 4, so that the adhesive film layer 4 can be more effectively pierced, thereby further ensuring the electrical connection between the electromagnetic shielding film and the ground layer of the circuit board. It should be noted that the materials of the conductive protrusion 31 and the shielding layer 3 may be the same or different, and the present invention does not make specific limitations here.

[0054] Specifically, the ratio of the arithmetic mean thickness of the adhesive film layer 4 to the protrusion height of the conductive protrusion 6 is greater than or equal to 2 / 7. In this way, the adhesive film layer 4 can be more effectively pierced, thereby further ensuring the electrical connection between the electromagnetic shielding film and the ground layer of the circuit board.

[0055] In the above embodiment, further, the conductive protrusion 31 includes a conductive base portion and at least one conductive spike portion; the conductive base portion extends outward from the surface of the shielding layer, and at least one of the conductive spike portions extends outward from the surface of the conductive base portion. Among them, the conductive spike portion extending from the surface of the conductive base portion can more effectively pierce the adhesive film layer, so that the shielding layer can be better electrically connected to the ground layer of the circuit board.

[0056] Specifically, the protrusion height of the conductive spike portion is 0.1 - 8 micrometers. In this way, the adhesive film layer 4 can be more effectively pierced, thereby further ensuring the electrical connection between the electromagnetic shielding film and the ground layer of the circuit board.

[0057] In the above embodiment, the conductive spike portions can be distributed regularly or irregularly on the surface of the conductive base portion. In this embodiment, the shapes of the conductive spike portions are the same, and / or the distances between the conductive spike portions are the same. Preferably, the shapes of the plurality of conductive spike portions are the same, and the plurality of conductive spike portions are evenly distributed on the surface of the conductive base portion. In addition, at least one surface of the shielding layer 3 is a undulating structure. For example, the surface of the shielding layer close to the adhesive film layer is a undulating structure, which can improve the bending performance of the shielding layer, enhance the piercing ability of the surface of the shielding layer close to the adhesive film layer on the adhesive film layer, and also improve the adhesive capacity of the surface of the shielding layer.

[0058] As another example, the conductive protrusions 31 may be composed of one or more conductive particles. The conductive particles include one or more of metal particles, carbon nanotube particles, and ferrite particles. In addition, the metal particles include single-metal particles and / or alloy particles; wherein, the single-metal particles are made of any one of the materials of aluminum, titanium, zinc, iron, nickel, chromium, cobalt, copper, silver, and gold, and the alloy particles are made of any two or more of the materials of aluminum, titanium, zinc, iron, nickel, chromium, cobalt, copper, silver, and gold.

[0059] It should be noted that the shielding layer 3 in this embodiment may be a single-layer structure or a multi-layer structure. When the shielding layer 3 is a single layer, the conductive protrusions 31 are provided on the surface of the shielding layer 3 close to the adhesive film layer 4; when the shielding layer 3 is a multi-layer, the conductive protrusions 31 may also be provided on the surface of each layer of the shielding layer 3 close to the adhesive film layer 4. In addition, according to the needs of actual production and application, the shielding layer 3 in this embodiment may be set in a mesh shape, a foamed shape, etc.

[0060] In the embodiment of the present invention, in order to further ensure the connection between the electromagnetic shielding film and the ground layer of the circuit board, the adhesive film layer 4 in this embodiment includes an adhesive layer containing conductive particles. By including an adhesive layer containing conductive particles in the adhesive film layer 4, the conductivity of the adhesive film layer 4 is improved, thereby further ensuring the connection between the electromagnetic shielding film and the ground layer of the circuit board. Of course, the adhesive film layer 4 may include an adhesive layer without conductive particles to reduce the insertion loss of the circuit board with the electromagnetic shielding film.

[0061] It should be noted that the conductive particles may be separated conductive particles or large particle conductive particles formed by aggregation; when the conductive particles are separated conductive particles, the ground conductivity of the adhesive film layer 4 can be further improved; and when the conductive particles are large particle conductive particles formed by aggregation, the piercing strength can be increased.

[0062] Please refer to Figure 5 , the electromagnetic shielding film in this embodiment further includes a protective film layer 5, and the protective film layer 5 is provided on the surface of the adhesive film layer 4 away from the shielding layer 3. The protective film layer 5 has a protective effect to ensure that the adhesive film layer 4 is not scratched or damaged during use. Among them, the protective film layer 5 includes a PPS film layer, a PEN film layer, a polyester film layer, a polyimide film layer, a film layer formed after curing of epoxy resin ink, a film layer formed after curing of polyurethane ink, a film layer formed after curing of modified acrylic resin, or a film layer formed after curing of polyimide resin. Among them, when the electromagnetic shielding film is laminated onto the circuit board, the protective film layer 5 needs to be peeled off first.

[0063] For the convenience of understanding the above invention solution, three specific embodiments are provided here and these specific embodiments are tested: Specific Embodiment 1:

[0065] An electromagnetic shielding film, comprising a carrier layer 1, an insulating layer 2 and a shielding layer 3; the carrier layer 1 is disposed on one surface of the insulating layer 2, and the shielding layer 3 is disposed on the surface of the insulating layer 2 away from the carrier layer 1; the roughness Sku of the surface of the insulating layer close to the carrier layer is 0.5, and the ratio of the roughness Sku of the surface of the carrier layer close to the insulating layer to the roughness Sku of the surface of the insulating layer close to the carrier layer is 1:100. Wherein, the material of the carrier layer 1 is PET, the material of the insulating layer 2 is epoxy resin, and the insulating layer 2 may be formed on one surface of the carrier layer 1.

[0066] Test result: After testing, the insulation resistance of the insulating layer of the electromagnetic shielding film of this embodiment is greater than 10 5 ohms. Among them, the test method for the insulation resistance of the insulating layer is: after tearing off the carrier layer, use a surface resistance tester (it can be an SL-030B surface resistance tester) to measure the insulation resistance of the outer surface of the insulating layer; wherein, place two heavy hammers (each heavy hammer weighs about 2.5 kg) of the surface resistance tester at different places on the outer surface of the insulating layer, and then measure the insulation resistance of the insulating layer. And the insulation resistance of the electromagnetic shielding film of this embodiment is greater than 10 5 ohms, and the insulation resistance is still very large, which indicates that the insulating layer is not torn during the process of tearing off the carrier layer from the insulating layer.

[0067] Thus, by applying the electromagnetic shielding film of this embodiment, it is possible to avoid easily tearing the insulating layer 2 during the process of tearing off the carrier layer 1 from the insulating layer 2, so that the insulating layer 2 has good airtightness and insulation performance, thereby avoiding the problems of oxidation of the shielding layer 3 and poor shielding performance.

[0068] It can be understood that the thickness of the insulating layer in this specific embodiment and the following specific embodiments can correspond to the thickness of the insulating layer of the existing electromagnetic shielding film. Specific Embodiment 2:

[0070] An electromagnetic shielding film, comprising a carrier layer 1, an insulating layer 2 and a shielding layer 3; the carrier layer 1 is disposed on one side of the insulating layer 2, and the shielding layer 3 is disposed on the side of the insulating layer 2 away from the carrier layer 1; the roughness Sku of the side of the insulating layer close to the carrier layer is 0.5, and the ratio of the roughness Sku of the side of the carrier layer close to the insulating layer to the roughness Sku of the side of the insulating layer close to the carrier layer is 50:1. Wherein, the material of the carrier layer 1 is PET, the material of the insulating layer 2 is epoxy resin, and the insulating layer 2 can be formed on one side of the carrier layer 1.

[0071] Test results: After testing, the insulation resistance of the insulating layer of the electromagnetic shielding film of this embodiment is greater than 10 6 ohms, and the insulation resistance is still very large, indicating that the insulating layer is not torn during the process of tearing the carrier layer from the insulating layer.

[0072] Thus, by applying the electromagnetic shielding film of this embodiment, it is possible to avoid easily tearing the insulating layer 2 during the process of tearing the carrier layer 1 from the insulating layer 2, so that the insulating layer 2 has good airtightness and insulation performance, thereby avoiding problems such as oxidation of the shielding layer 3 and poor shielding performance. Specific Embodiment Three:

[0074] An electromagnetic shielding film, comprising a carrier layer 1, an insulating layer 2 and a shielding layer 3; the carrier layer 1 is disposed on one side of the insulating layer 2, and the shielding layer 3 is disposed on the side of the insulating layer 2 away from the carrier layer 1; the roughness Sku of the side of the insulating layer close to the carrier layer is 0.5, and the ratio of the roughness Sku of the side of the carrier layer close to the insulating layer to the roughness Sku of the side of the insulating layer close to the carrier layer is 100:1. Wherein, the material of the carrier layer 1 is PET, the material of the insulating layer 2 is epoxy resin, and the insulating layer 2 can be formed on one side of the carrier layer 1.

[0075] Test results: After testing, the insulation resistance of the insulating layer of the electromagnetic shielding film of this embodiment is greater than 10 6 ohms, and the insulation resistance is still very large, indicating that the insulating layer is not torn during the process of tearing the carrier layer from the insulating layer.

[0076] Thus, by applying the electromagnetic shielding film of this embodiment, it is possible to avoid easily tearing the insulating layer 2 during the process of tearing the carrier layer 1 from the insulating layer 2, so that the insulating layer 2 has good airtightness and insulation performance, thereby avoiding problems such as oxidation of the shielding layer 3 and poor shielding performance. Specific Embodiment Four:

[0078] An electromagnetic shielding film, comprising a carrier layer 1, an insulating layer 2 and a shielding layer 3; the carrier layer 1 is disposed on one side of the insulating layer 2, and the shielding layer 3 is disposed on the side of the insulating layer 2 away from the carrier layer 1; the roughness Sku of the side of the insulating layer close to the carrier layer is 25.25, and the ratio of the roughness Sku of the side of the carrier layer close to the insulating layer to the roughness Sku of the side of the insulating layer close to the carrier layer is 1:100. Wherein, the material of the carrier layer 1 is PET, the material of the insulating layer 2 is epoxy resin, and the insulating layer 2 may be formed on one side of the carrier layer 1.

[0079] Test result: After testing, the insulation resistance of the insulating layer of the electromagnetic shielding film of this embodiment is greater than 10 5 Ohms, and the insulation resistance is still very large, indicating that the insulating layer is not torn during the process of tearing the carrier layer from the insulating layer.

[0080] Thus, by applying the electromagnetic shielding film of this embodiment, it is possible to avoid easily tearing the insulating layer 2 during the process of tearing the carrier layer 1 from the insulating layer 2, so that the insulating layer 2 has good airtightness and insulation performance, thereby avoiding problems such as oxidation of the shielding layer 3 and poor shielding performance. Specific Embodiment Five:

[0082] An electromagnetic shielding film, comprising a carrier layer 1, an insulating layer 2 and a shielding layer 3; the carrier layer 1 is disposed on one side of the insulating layer 2, and the shielding layer 3 is disposed on the side of the insulating layer 2 away from the carrier layer 1; the roughness Sku of the side of the insulating layer close to the carrier layer is 25.25, and the ratio of the roughness Sku of the side of the carrier layer close to the insulating layer to the roughness Sku of the side of the insulating layer close to the carrier layer is 50:1. Wherein, the material of the carrier layer 1 is PET, the material of the insulating layer 2 is epoxy resin, and the insulating layer 2 may be formed on one side of the carrier layer 1.

[0083] Test result: After testing, the insulation resistance of the insulating layer of the electromagnetic shielding film of this embodiment is greater than 10 5 Ohms, and the insulation resistance is still very large, indicating that the insulating layer is not torn during the process of tearing the carrier layer from the insulating layer.

[0084] Thus, by applying the electromagnetic shielding film of this embodiment, it is possible to avoid easily tearing the insulating layer 2 during the process of tearing the carrier layer 1 from the insulating layer 2, so that the insulating layer 2 has good airtightness and insulation performance, thereby avoiding problems such as oxidation of the shielding layer 3 and poor shielding performance. Specific Embodiment Six:

[0086] An electromagnetic shielding film, comprising a carrier layer 1, an insulating layer 2 and a shielding layer 3; the carrier layer 1 is disposed on one side of the insulating layer 2, and the shielding layer 3 is disposed on the side of the insulating layer 2 away from the carrier layer 1; the roughness Sku of the side of the insulating layer close to the carrier layer is 25.25, and the ratio of the roughness Sku of the side of the carrier layer close to the insulating layer to the roughness Sku of the side of the insulating layer close to the carrier layer is 100:1. Wherein, the material of the carrier layer 1 is PET, the material of the insulating layer 2 is epoxy resin, and the insulating layer 2 can be formed on one side of the carrier layer 1.

[0087] Test results: After testing, the insulation resistance of the insulating layer of the electromagnetic shielding film in this embodiment is greater than 10 5 ohms, and the insulation resistance is still very large, indicating that the insulating layer is not torn during the process of tearing the carrier layer from the insulating layer.

[0088] Thus, by applying the electromagnetic shielding film of this embodiment, it is possible to avoid easily tearing the insulating layer 2 during the process of tearing the carrier layer 1 from the insulating layer 2, so that the insulating layer 2 has good airtightness and insulation performance, thereby avoiding problems such as oxidation of the shielding layer 3 and poor shielding performance. Specific Embodiment Seven:

[0090] An electromagnetic shielding film, comprising a carrier layer 1, an insulating layer 2 and a shielding layer 3; the carrier layer 1 is disposed on one side of the insulating layer 2, and the shielding layer 3 is disposed on the side of the insulating layer 2 away from the carrier layer 1; the roughness Sku of the side of the insulating layer close to the carrier layer is 50, and the ratio of the roughness Sku of the side of the carrier layer close to the insulating layer to the roughness Sku of the side of the insulating layer close to the carrier layer is 1:100. Wherein, the material of the carrier layer 1 is PET, the material of the insulating layer 2 is epoxy resin, and the insulating layer 2 can be formed on one side of the carrier layer 1.

[0091] Test results: After testing, the insulation resistance of the insulating layer of the electromagnetic shielding film in this embodiment is greater than 10 5 ohms, and the insulation resistance is still very large, indicating that the insulating layer is not torn during the process of tearing the carrier layer from the insulating layer.

[0092] Thus, by applying the electromagnetic shielding film of this embodiment, it is possible to avoid easily tearing the insulating layer 2 during the process of tearing the carrier layer 1 from the insulating layer 2, so that the insulating layer 2 has good airtightness and insulation performance, thereby avoiding problems such as oxidation of the shielding layer 3 and poor shielding performance. Specific Embodiment Eight:

[0094] An electromagnetic shielding film, comprising a carrier layer 1, an insulating layer 2 and a shielding layer 3; the carrier layer 1 is disposed on one side of the insulating layer 2, and the shielding layer 3 is disposed on the side of the insulating layer 2 away from the carrier layer 1; the roughness Sku of the side of the insulating layer close to the carrier layer is 50, and the ratio of the roughness Sku of the side of the carrier layer close to the insulating layer to the roughness Sku of the side of the insulating layer close to the carrier layer is 50:1. Wherein, the material of the carrier layer 1 is PET, the material of the insulating layer 2 is epoxy resin, and the insulating layer 2 may be formed on one side of the carrier layer 1.

[0095] Test result: The insulation resistance of the insulating layer of the electromagnetic shielding film in this embodiment is greater than 10 5 ohms, and the insulation resistance is still very large, indicating that the insulating layer is not torn during the process of tearing the carrier layer from the insulating layer.

[0096] Thus, by applying the electromagnetic shielding film of this embodiment, it is possible to avoid easily tearing the insulating layer 2 during the process of tearing the carrier layer 1 from the insulating layer 2, so that the insulating layer 2 has good airtightness and insulation performance, thereby avoiding problems such as oxidation of the shielding layer 3 and poor shielding performance. Specific Embodiment Nine:

[0098] An electromagnetic shielding film, comprising a carrier layer 1, an insulating layer 2 and a shielding layer 3; the carrier layer 1 is disposed on one side of the insulating layer 2, and the shielding layer 3 is disposed on the side of the insulating layer 2 away from the carrier layer 1; the roughness Sku of the side of the insulating layer close to the carrier layer is 50, and the ratio of the roughness Sku of the side of the carrier layer close to the insulating layer to the roughness Sku of the side of the insulating layer close to the carrier layer is 100:1. Wherein, the material of the carrier layer 1 is PET, the material of the insulating layer 2 is epoxy resin, and the insulating layer 2 may be formed on one side of the carrier layer 1.

[0099] Test result: After testing, the insulation resistance of the insulating layer of the electromagnetic shielding film in this embodiment is greater than 10 5 ohms, and the insulation resistance is still very large, indicating that the insulating layer is not torn during the process of tearing the carrier layer from the insulating layer.

[0100] Thus, by applying the electromagnetic shielding film of this embodiment, it is possible to avoid easily tearing the insulating layer 2 during the process of tearing the carrier layer 1 from the insulating layer 2, so that the insulating layer 2 has good airtightness and insulation performance, thereby avoiding problems such as oxidation of the shielding layer 3 and poor shielding performance.

[0101] In summary, the roughness Sku of the side of the insulating layer close to the carrier layer is 0.5 - 50 (for example, 0.5, 20.25, 50), and the ratio of the roughness Sku of the side of the carrier layer close to the insulating layer to the roughness Sku of the side of the insulating layer close to the carrier layer is 0.01 - 100 (for example, 0.01, 50, 100). By applying the electromagnetic shielding film of this embodiment, it is possible to avoid easily tearing the insulating layer 2 during the process of peeling the carrier layer 1 from the insulating layer 2, so that the insulating layer 2 has good airtightness and insulation performance, thereby avoiding the problems of oxidation of the shielding layer 3 and poor shielding performance.

[0102] See Figure 6 , another embodiment of the present invention further provides a circuit board, which includes a circuit board body 6 and the electromagnetic shielding film described in any of the above embodiments; the electromagnetic shielding film is pressed and bonded with the circuit board body 6; the side of the shielding layer 3 away from the insulating layer 2 is electrically connected to the ground layer of the circuit board body 6.

[0103] Preferably, the circuit board body 6 is one of a flexible single-sided, flexible double-sided, flexible multi-layer board, and a rigid-flex board.

[0104] In the embodiment of the present invention, the roughness Sku of the side of the shielding layer 3 close to the adhesive film layer 4 is 0.5 - 15. When the electromagnetic shielding film is pressed and bonded with the circuit board body 6, it can pierce the adhesive film layer 4 and be connected to the ground layer of the circuit board body 6, thereby ensuring the connection between the shielding layer 3 and the ground layer of the circuit board body 6, and thus realizing the introduction of the interfering charges in the shielding layer 3 into the ground, avoiding the accumulation of interfering charges to form an interference source and affecting the normal operation of the circuit board.

[0105] Specifically, when the sharpness of the roughness shape on the side of the insulating layer close to the carrier layer is 0.5 - 50, and the ratio of the roughness Sku of the side of the carrier layer close to the insulating layer to the roughness Sku of the side of the insulating layer close to the carrier layer is 0.01 - 100, it is possible to avoid easily tearing the insulating layer during the process of peeling the carrier layer from the insulating layer, so that the insulating layer has good airtightness and insulation performance, thereby avoiding problems such as oxidation of the shielding layer and poor shielding performance. On the other hand, when the sharpness of the roughness shape on the side of the insulating layer close to the carrier layer is 0.5 - 50, and the ratio of the roughness Sku of the side of the carrier layer close to the insulating layer to the roughness Sku of the side of the insulating layer close to the carrier layer is 0.01 - 100, it can be ensured that the carrier layer 1 is not easily detached before the electromagnetic shielding film is laminated onto the circuit board, thus playing a role in protecting the insulating layer. At the same time, after the electromagnetic shielding film is laminated onto the circuit board, the carrier layer 1 and the insulating layer 2 will not be too tightly adhered, and the carrier layer 1 can be stably peeled off under a certain force, which is convenient for use. Moreover, since the ratio of the roughness Sku of the side of the carrier layer close to the insulating layer to the roughness Sku of the side of the insulating layer close to the carrier layer is 0.01 - 100, compared with the carrier layer and insulating layer with a flat surface structure, during the lamination of the electromagnetic shielding film and the circuit board, the carrier layer is not likely to undergo a large horizontal movement during the lamination process, so it is not easy to have the problem that the overall electromagnetic shielding film moves horizontally due to the horizontal movement of the carrier layer when the electromagnetic shielding film is laminated onto the circuit board, and the electromagnetic shielding film can be laminated at the corresponding position on the circuit board. And by making the roughness Sku of the side of the insulating layer close to the carrier layer be 0.5 - 50, the surface tension of the insulating layer can be improved, and when printing ink on the insulating layer, the ink will not spread. By making the roughness Sku of the side of the shielding layer 3 close to the adhesive film layer 4 be 2 - 25, the shielding layer 3 can have piercing ability on one side. Moreover, when the roughness Sku of the shielding layer 3 is 2 - 25, the bonding force between the shielding layer 3 and the circuit board can be enhanced, making the electromagnetic shielding film not easily delaminate. And during the lamination of the electromagnetic shielding film and the circuit board, since the roughness Sku of the side of the shielding layer 3 close to the adhesive film layer 4 is 2 - 25, the adhesive of the adhesive film layer 4 is not likely to undergo a large horizontal movement on the side of the shielding layer 3 during the lamination of the shielding film, so it is not easy to have the problem of obvious adhesive overflow at the edge of the circuit board due to adhesive displacement, so that the circuit board after laminating the shielding film has a good appearance.In addition, since the roughness Sku of one side of the shielding layer 3 close to the adhesive film layer 4 is 2-25, the adhesive substance constituting the adhesive film layer 4 is squeezed into the recessed position on one side of the shielding layer 3, thereby increasing the adhesive capacity. On the one hand, it is less likely to cause board bursting, thereby avoiding the problem of high-temperature board bursting due to insufficient adhesive capacity of the existing electromagnetic shielding film, thereby effectively ensuring the grounding of the electromagnetic shielding film, thereby conducting away the interference charge; on the other hand, it can prevent the adhesive from overflowing to the edge of the circuit board during lamination, thereby enabling the circuit board after laminating the shielding film to have a good appearance.

[0106] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by any technician familiar with the art within the technical scope disclosed in the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be based on the protection scope of the claims.

Claims

1. An electromagnetic shielding film, characterized in that, It includes a carrier layer, an insulating layer and a shielding layer; The carrier layer is disposed on one surface of the insulating layer, and the shielding layer is disposed on the surface of the insulating layer away from the carrier layer; The skewness Sku of the surface of the insulating layer close to the carrier layer is 0.5 - 50, and the skewness Sku is a parameter for judging the sharpness of the roughness shape; The ratio of the skewness Sku of the surface of the carrier layer close to the insulating layer to the skewness Sku of the surface of the insulating layer close to the carrier layer is 0.01 - 100; The shielding layer includes one or more of a metal shielding layer, a carbon nanotube shielding layer, a ferrite shielding layer and a graphene shielding layer.

2. The electromagnetic shielding film according to claim 1, characterized in that, The skewness Sku of the surface of the insulating layer close to the carrier layer is 2 - 25.

3. The electromagnetic shielding film according to claim 1, wherein The skewness Sku of the surface of the insulating layer close to the carrier layer is 5 - 20.

4. The electromagnetic shielding film according to claim 1, characterized in that, The skewness Sku of the surface of the carrier layer close to the insulating layer is 2 - 25.

5. The electromagnetic shielding film according to claim 1, characterized in that, The skewness Sku of the surface of the carrier layer close to the insulating layer is 5 - 20.

6. The electromagnetic shielding film according to claim 1, wherein The electromagnetic shielding film further includes an adhesive film layer; the adhesive film layer is disposed on the surface of the shielding layer away from the insulating layer; The adhesive film layer includes an adhesive layer containing conductive particles; or the adhesive film layer includes an adhesive layer without conductive particles.

7. The electromagnetic shielding film according to claim 6, wherein, Conductive protrusions are provided on the surface of the shielding layer close to the adhesive film layer.

8. The electromagnetic shielding film according to claim 7, wherein The ratio of the arithmetic average thickness of the adhesive film layer to the protrusion height of the conductive protrusions is greater than or equal to 2 / 7.

9. The electromagnetic shielding film according to claim 1, characterized in that, Through holes penetrating the upper and lower surfaces are provided on the shielding layer.

10. A circuit board, characterized in that, It includes a circuit board body and the electromagnetic shielding film according to any one of claims 1 - 9; the electromagnetic shielding film is press-fitted with the circuit board body; the surface of the shielding layer away from the insulating layer is electrically connected to the ground layer of the circuit board body.

Images