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, a shielding layer, an adhesive film layer, and a protective film layer that are laminated in sequence; the surface roughness Sz of the side of the insulating layer away from the shielding layer is 0.5 - 20 micrometers. The present invention can effectively improve the bonding strength between the carrier layer and the insulating layer, thereby effectively reducing the phenomenon that the protective film layer is not completely torn off while the carrier layer detaches from the insulating layer first during the process of tearing off the protective film layer.

Description

Technical Field

[0001] The present invention relates to the field of electronic technology, and in particular 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 index 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, the camera function has become an essential function of mobile phones, 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, an electromagnetic shielding film generally includes a carrier layer, an insulating layer, a shielding layer, an adhesive film layer, and a protective film layer stacked in sequence. Among them, when the electromagnetic shielding film is not yet laminated onto the circuit board, the protective film layer is used to protect the adhesive film layer, and the carrier layer is used to protect the insulating layer. The process of laminating the electromagnetic shielding film onto the circuit board is as follows: Fix the outer surface of the carrier layer with a workpiece, and use the workpiece to first tear the protective film layer from the surface of the adhesive film layer, then laminate the electromagnetic shielding film onto the circuit board through the adhesive film layer, and finally tear the carrier layer from the electromagnetic shielding film.

[0005] The inventor of the present invention found the following technical problems in the process of implementing the present invention: During the process of tearing the protective film layer, it is easy to occur that the protective film layer is not completely torn off but the carrier layer detaches from the insulating layer first, resulting in the inability to normally laminate the electromagnetic shielding film onto the circuit board, which will affect the efficiency of laminating the electromagnetic shielding film onto the circuit board. Summary of the Invention

[0006] In view of the above problems, the object of the present invention is to provide an electromagnetic shielding film and a circuit board, which can effectively improve the bonding strength between the carrier layer and the insulating layer, thereby effectively reducing the phenomenon that the protective film layer is not completely torn off while the carrier layer is detached from the insulating layer first during the process of tearing off the protective film layer.

[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, a shielding layer, a film adhesive layer, and a protective film layer stacked in sequence;

[0008] The roughness Sz of the surface of the insulating layer away from the shielding layer is 0.5 - 20 microns.

[0009] As an improvement of the above solution, the roughness Sz of the surface of the insulating layer away from the shielding layer is 5.1 - 10.8 microns.

[0010] As an improvement of the above solution, the roughness Sz of the surface of the insulating layer away from the shielding layer is 2.5 - 18 microns.

[0011] As an improvement of the above solution, the dyne value of the surface of the insulating layer away from the shielding layer is greater than or equal to 28.

[0012] As an improvement of the above solution, the insulating layer is formed on one surface of the carrier layer, and the ratio of the roughness Sz of the one surface of the carrier layer to the thickness of the insulating layer is 0.375 - 3.6.

[0013] As an improvement of the above solution, conductive protrusions are provided on the surface of the shielding layer close to the film adhesive layer.

[0014] As an improvement of the above solution, through holes penetrating the upper and lower surfaces of the shielding layer are provided on the shielding layer.

[0015] As an improvement of the above solution, the number of through holes per square centimeter on the shielding layer is 1 - 1000.

[0016] As an improvement of the above solution, the ratio of the sum of the cross-sectional areas of all the through holes per square centimeter in the shielding layer to the cross-sectional area of the shielding layer where the cross-section is located is 1% - 70%.

[0017] 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 as described in any one of the above; the electromagnetic shielding film is press-fitted with the circuit board body through the film adhesive layer; the surface of the shielding layer away from the insulating layer is electrically connected to the ground layer of the circuit board body.

[0018] 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:

[0019] Since the sum of the maximum peak height and the maximum valley depth of the surface of the insulating layer away from the shielding layer is 0.5 - 20 microns, the surface of the insulating layer away from the shielding layer can have better bonding performance, so that the carrier layer can be firmly attached to the insulating layer and is not easily detached. In this way, it can effectively reduce the problem that when the protective film layer is torn off from the surface of the adhesive film layer, the protective film layer is not completely torn off while the carrier layer detaches from the insulating layer first, reducing the impact on the efficiency of laminating the electromagnetic shielding film to the circuit board. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions of the present invention, the drawings required for 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.

[0021] Figure 1 is a schematic structural diagram of a first electromagnetic shielding film provided by an embodiment of the present invention;

[0022] Figure 2 is a schematic structural diagram of a second electromagnetic shielding film provided by an embodiment of the present invention;

[0023] Figure 3 is a schematic structural diagram of a third electromagnetic shielding film provided by an embodiment of the present invention;

[0024] Figure 4 is a schematic structural diagram of a conductive protrusion provided by an embodiment of the present invention;

[0025] Figure 5 is a schematic structural diagram of a circuit board provided by an embodiment of the present invention;

[0026] Wherein, 1, insulating layer; 2, shielding layer; 3, carrier layer; 4, adhesive film layer; 5, protective film layer; 6, circuit board body; 21, conductive protrusion; 211, conductive base part; 212, conductive spike part. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0027] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only some 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 shall fall within the protection scope of the present invention.

[0028] In the descriptions 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. It 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. Therefore, it should not be construed as a limitation to the embodiments of the present invention.

[0029] In addition, the terms first, second, etc. in the specification and claims are only used for the purpose of distinguishing the descriptions of the same technical features, and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features, nor necessarily describing the order or time sequence. The terms can be interchanged under appropriate circumstances. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one of such features.

[0030] See Figure 1 , an embodiment of the present invention provides an electromagnetic shielding film, which includes a carrier layer 3, an insulating layer 1, a shielding layer 2, an adhesive film layer 4, and a protective film layer 5 laminated in sequence; the surface roughness Sz of the insulating layer 1 away from the shielding layer 2 is 0.5 - 20 microns.

[0031] Among them, the insulating layer 1 can effectively electrically isolate the shielding layer 2 from the outside, so as to ensure the electromagnetic shielding effect of the shielding layer 2.

[0032] In the embodiment of the present invention, since the sum of the maximum peak height and the maximum valley depth of the surface roughness of the insulating layer 1 away from the shielding layer 2 is 0.5 - 20 microns, the surface of the insulating layer 1 away from the shielding layer 2 can have better bonding performance, so that the carrier layer 3 can be firmly attached to the insulating layer 1 and is not easily detached. In this way, it can effectively reduce the problem that when the protective film layer 5 is torn off from the surface of the adhesive film layer 4, the protective film layer 5 is not completely torn off while the carrier layer 3 is detached from the insulating layer 1 first, and reduce the impact on the efficiency of laminating the electromagnetic shielding film to the circuit board.

[0033] It should be noted that the roughness Sz represents the sum of the maximum peak height and the maximum valley depth in a certain area of a surface.

[0034] In this embodiment, in order to ensure that the shielding layer 2 has good electrical conductivity, the shielding layer 2 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.

[0035] Specifically, in this embodiment, the roughness Sz of the surface of the insulating layer away from the shielding layer is 2.5 - 18 micrometers.

[0036] Furthermore, the roughness Sz of the surface of the insulating layer 1 away from the shielding layer 2 is 5.1 - 10.8 micrometers.

[0037] In this embodiment, the roughness Sz of the surface of the insulating layer 1 away from the shielding layer 2 is 5.1 - 10.8 micrometers, which can further improve the bonding performance of the surface of the insulating layer 1 away from the shielding layer 2, thereby further reducing the problem that when the protective film layer 5 is torn off from the surface of the adhesive film layer 4, the protective film layer 5 is not completely torn off and the carrier layer 3 detaches from the insulating layer 1 first.

[0038] It should be noted that the roughness Sku represents a parameter for judging the sharpness of the roughness shape.

[0039] In the above embodiment, the carrier layer 3 can be used to protect the insulating layer 1 so that the insulating layer 1 is not damaged by external contact, collision, etc. After the electromagnetic shielding film is hot-pressed with the circuit board, the carrier layer 3 needs to be torn off, and character printing is performed on the circuit board with the electromagnetic shielding film having the above structure. Therefore, since the roughness Sz of the surface of the insulating layer away from the shielding layer is 0.5 - 20 micrometers, this can also make the surface of the insulating layer 1 away from the shielding layer 2 have better surface tension, thereby improving the adhesion firmness of the ink on this surface of the insulating layer 1. When printing characters on this surface of the insulating layer 1, the printing ink can firmly adhere to it and is not prone to bleeding, so that the characters can be clearly displayed. Furthermore, the dyne value of the surface of the insulating layer 1 away from the shielding layer 2 is greater than or equal to 28, so that the printing ink has better adhesion on the surface of the insulating layer 1 away from the shielding layer 2, and can further reduce the bleeding phenomenon when printing ink on the surface of the insulating layer 1 of the electromagnetic shielding film, thereby achieving a better character printing effect.

[0040] Exemplarily, the material of the carrier layer 3 is PET, whose English name is Polyethylene terephthalate and is commonly known as polyester resin. The thickness of the carrier layer 3 is 50 microns.

[0041] In the above embodiment, exemplarily, the roughness Sz of the surface of the carrier layer 3 close to the insulating layer 1 is 3 - 18 microns, which can improve the bonding strength between the insulating layer 1 and the carrier layer 3 and avoid the phenomenon that the insulating layer 1 and the carrier layer 3 are prone to peeling off. Moreover, when the insulating layer 1 is formed on the surface of the carrier layer 3 with a roughness Sz of 3 - 18 microns, it is easy to make the roughness Sz of the surface of the insulating layer 1 far from the shielding layer 2 be 0.5 - 20 microns, so that the surface of the insulating layer 1 far from the shielding layer 2 has a good bonding strength with the carrier layer 3 and the printing ink.

[0042] In the above embodiment, exemplarily, the carrier layer 3 can be used as the base film for forming the insulating layer 1, and the insulating layer 1 is formed on one surface of the carrier layer 3.

[0043] Specifically, the ratio of the roughness Sz of the surface of the carrier layer 3 close to the insulating layer 1 to the thickness of the insulating layer 1 is 0.375 - 3.6. In this way, when the insulating layer 1 is formed on one surface of the carrier layer 3, it is easy to make the roughness Sz of the surface of the insulating layer 1 far from the shielding layer 2 be 0.5 - 20 microns. It should be noted that the roughness of the surface of the insulating layer 1 can be formed by the roughness of the carrier layer 3 or can also be further processed by other methods, which is not limited herein.

[0044] In the above embodiment, the adhesive film layer 4 is provided on the surface of the shielding layer 2 far from the insulating layer 1.

[0045] Among them, the materials used for the adhesive film layer 4 are selected from the following: modified epoxy resin type, acrylic type, modified rubber type, modified thermoplastic polyimide type.

[0046] In this embodiment, the side of the shielding layer 2 close to the adhesive film layer 4 is a rough surface. Therefore, after the electromagnetic shielding film is pressed onto the circuit board, the rough surface of the shielding layer 2 can effectively pierce the adhesive film layer 4 to achieve effective electrical connection with the ground layer of the circuit board, so that the interference circuit of the shielding layer 2 can be effectively introduced into the ground layer of the circuit board, thereby effectively improving the shielding effectiveness of the electromagnetic shielding layer 2. Moreover, the rough surface of the shielding layer 2 can enhance the bonding strength between the shielding layer 2 and the circuit board, making it difficult for the electromagnetic shielding film to be delaminated. In addition, the adhesive film layer 4 can effectively maintain the bonding strength between the electromagnetic shielding film and the circuit board, making it difficult for the electromagnetic shielding film and the circuit board to explode. Furthermore, when the electromagnetic shielding film is pressed onto the circuit board, since one side of the shielding layer 2 close to the adhesive film layer 4 is a rough surface, the adhesive substance constituting the adhesive film layer 4 is squeezed into the recessed position of the rough surface of the shielding layer 2, 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 pressing, thereby enabling the circuit board to have a good appearance after the shielding film is pressed.

[0047] Exemplarily, the side of the insulating layer 1 close to the shielding layer 2 is a rough surface, which can improve the bending resistance of the insulating layer 1, thereby improving the bending resistance of the electromagnetic shielding film. In addition, when the shielding layer 2 is formed on one side of the insulating layer 1, since the thickness of the shielding layer 2 is constant, the shielding layer 2 will rise and fall along the rough surface of the insulating layer 1, and finally make the side of the shielding layer 2 close to the adhesive film layer 4 a rough surface.

[0048] In the above embodiment, further, see Figure 2 , the shielding layer 2 is provided with through holes penetrating the upper and lower surfaces thereof. By providing the through holes penetrating the shielding layer 2, when the electromagnetic shielding film is pressed onto the circuit board at high temperature, the volatile gas generated in the adhesive film layer 4 can be effectively exhausted through the through holes of the shielding layer 2, so as to avoid the difficulty of volatiles in the adhesive film layer 4 to be discharged at high temperature, thereby avoiding the electromagnetic shielding film from bubbling and delamination, causing the electromagnetic shielding film to peel off from the ground layer of the circuit board, thereby ensuring that the electromagnetic shielding film is grounded and the interference charge is discharged.

[0049] 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 gas of the adhesive film layer 4 during the high-temperature pressing process.

[0050] In this embodiment, the number of vias per square centimeter on the shielding layer 2 is 1 - 1000. By setting the number of vias to 1 - 1000, it is ensured that volatiles in the adhesive film layer 4 can exhaust through a sufficient number of the vias at high temperatures, thereby avoiding the difficulty of discharging volatile gases in the adhesive film layer 4 at high temperatures, and further avoiding the peeling between the electromagnetic shielding film and the ground layer of the circuit board due to the blistering and delamination of the electromagnetic shielding film, so as to ensure that the electromagnetic shielding film is grounded and effectively conducts interference charges.

[0051] In this embodiment, the ratio of the sum of the cross-sectional areas of all the vias per square centimeter in the shielding layer 2 to the cross-sectional area of the shielding layer where the cross-section is located is 1% - 70%. By setting the ratio of the sum of the cross-sectional areas of all the vias per square centimeter in the shielding layer 2 to the cross-sectional area of the shielding layer where the cross-section is located to 1% - 70%, the electromagnetic shielding effect of the shielding layer 2 will not be affected due to excessive number of vias.

[0052] As an example, see Figure 3 , on the side of the shielding layer 2 close to the adhesive film layer 4, there are conductive protrusions 21, so that the shielding layer 2 can more effectively pierce the adhesive film layer 4, thereby further ensuring the electrical connection between the electromagnetic shielding film and the ground layer of the circuit board.

[0053] Specifically, the number of conductive protrusions with a longitudinal height greater than 5 μm on the shielding film per square centimeter on the one side of the shielding layer 2 is 1 - 1000. This can more effectively pierce the adhesive film layer 4, thereby further ensuring the electrical connection between the electromagnetic shielding film and the ground layer of the circuit board.

[0054] See Figure 4 , in the above embodiment, further, the conductive protrusion 21 includes a conductive base portion 211 and at least one conductive spike portion 212; the conductive base portion 211 extends outward from the one side of the shielding layer 2, and at least one conductive spike portion 212 extends outward from the surface of the conductive base portion 211. Among them, the conductive spike portion 212 extending from the surface of the conductive base portion 211 can more effectively pierce the adhesive film layer 4, so that the shielding layer 2 can be better electrically connected to the ground layer of the circuit board.

[0055] Specifically, the protruding height of the conductive spike portion 212 is 1 - 10 microns. This can enable the conductive spike portion 212 to effectively pierce the adhesive film layer 4, thereby further ensuring the electrical connection between the electromagnetic shielding film and the ground layer of the circuit board.

[0056] In an embodiment of the present invention, the conductive spike portions 212 may be distributed on the surface of the conductive substrate portion 211 regularly or irregularly. In this embodiment, the shapes of the conductive spike portions 212 are the same, and / or the distances between the conductive spike portions 212 are the same. Preferably, the shapes of the plurality of conductive spike portions 212 are the same, and the plurality of conductive spike portions 212 are uniformly distributed on the surface of the conductive substrate portion 211. In addition, at least one surface of the shielding layer 2 is a undulating structure. For example, the surface of the shielding layer 2 close to the adhesive film layer 4 is a undulating structure, which can improve the bending performance of the shielding layer 2, enhance the piercing ability of the surface of the shielding layer 2 close to the adhesive film layer 4 on the adhesive film layer 4, and also improve the adhesive capacity of this surface of the shielding layer 2.

[0057] In specific implementation, the shielding layer 2 may be formed first, and then the conductive protrusions 21 may be formed on the shielding layer 2 through other processes. Of course, the shielding layer 2 and the conductive protrusions 21 may also be an integral structure formed by a one-step forming process. It should be noted that the material of the conductive protrusions 21 may be the same as or different from the material of the shielding layer 2, which is not limited herein.

[0058] It should be noted that the shielding layer 2 in this embodiment may be a single-layer structure or a multi-layer structure. When the shielding layer 2 is a single layer, the conductive protrusions 21 may be provided on the surface of the shielding layer 2 close to the adhesive film layer 4; when the shielding layer 2 is a multi-layer, the conductive protrusions 21 may also be provided on the surface of each layer of the shielding layer 2 close to the adhesive film layer 4. In addition, according to the actual production and application needs, the shielding layer 2 in this embodiment may be set in a mesh shape, a foamed shape, etc.

[0059] It should be noted that Figure 3 and Figure 4 the shape of the conductive protrusions 21 in

[0060] In an 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, thereby improving the anti-bending property of the circuit board while enhancing the shielding effectiveness.

[0061] It should be noted that the conductive particles can 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; while when the conductive particles are large particle conductive particles formed by aggregation, the piercing strength can be increased.

[0062] In this embodiment, the protective film layer 5 is disposed on the side of the adhesive film layer 4 away from the shielding layer 2. Since the protective film layer 5 has a protective effect to ensure that the adhesive film layer 4 is not scratched or damaged during use, when the electromagnetic shielding film is laminated onto the circuit board, the protective film layer 5 needs to be peeled off first. 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.

[0063] Specifically, when the electromagnetic shielding film includes a carrier layer 3, an insulating layer 1, a shielding layer 2, an adhesive film layer 4, and a protective film layer 5, the preparation method of the electromagnetic shielding film includes:

[0064] 1) Prepare the carrier layer 3;

[0065] 2) Form the insulating layer 1 on one side of the carrier layer 3;

[0066] 3) Form the shielding layer 2 on the side of the insulating layer 1 away from the carrier layer 3;

[0067] 4) Coat an adhesive on the side of the shielding layer 2 away from the insulating layer 1 to form the adhesive film layer 4;

[0068] 5) Bond the protective film layer 5 on the side of the adhesive film layer 4 away from the shielding layer 2.

[0069] For the convenience of understanding the above invention solutions, here, five specific embodiments are provided and these specific embodiments are tested: Specific Embodiment 1:

[0071] An electromagnetic shielding film, comprising a carrier layer 3, an insulating layer 1, a shielding layer 2, an adhesive film layer 4 and a protective film layer 5 which are laminated in sequence; the surface roughness Sz of the insulating layer 1 on the side away from the shielding layer 2 is 0.5 micrometers. Among them, the material of the insulating layer 1 is epoxy resin.

[0072] Test result: After testing, the peeling strength between the insulating layer 1 and the carrier layer 3 of the electromagnetic shielding film of this embodiment is 12.32 N / cm.

[0073] Thus, by applying the electromagnetic shielding film of this embodiment, the surface of the insulating layer 1 on the side away from the shielding layer 2 can have better bonding performance, so that the carrier layer 3 can be firmly attached to the insulating layer 1 and is not easily detached, which can effectively reduce the problem that when the protective film layer 5 is torn off from the surface of the adhesive film layer 4, the protective film layer 5 is not completely torn off and the carrier layer 3 detaches from the insulating layer 1 first. Specific Embodiment Two:

[0075] An electromagnetic shielding film, comprising a carrier layer 3, an insulating layer 1, a shielding layer 2, an adhesive film layer 4 and a protective film layer 5 which are laminated in sequence; the surface roughness Sz of the insulating layer 1 on the side away from the shielding layer 2 is 10.25 micrometers. Among them, the material of the insulating layer 1 is epoxy resin.

[0076] Test result: After testing, the peeling strength between the insulating layer 1 and the carrier layer 3 of the electromagnetic shielding film of this embodiment is 15.52 N / cm.

[0077] Thus, by applying the electromagnetic shielding film of this embodiment, the surface of the insulating layer 1 on the side away from the shielding layer 2 can have better bonding performance, so that the carrier layer 3 can be firmly attached to the insulating layer 1 and is not easily detached, which can effectively reduce the problem that when the protective film layer 5 is torn off from the surface of the adhesive film layer 4, the protective film layer 5 is not completely torn off and the carrier layer 3 detaches from the insulating layer 1 first. Specific Embodiment Three:

[0079] An electromagnetic shielding film, comprising a carrier layer 3, an insulating layer 1, a shielding layer 2, an adhesive film layer 4 and a protective film layer 5 which are laminated in sequence; the surface roughness Sz of the insulating layer 1 on the side away from the shielding layer 2 is 20 micrometers. Among them, the material of the insulating layer 1 is epoxy resin.

[0080] Test result: After testing, the peeling strength between the insulating layer 1 and the carrier layer 3 of the electromagnetic shielding film of this embodiment is 19.3 N / cm.

[0081] It can be seen that by applying the electromagnetic shielding film of this embodiment, the side of the insulating layer 1 away from the shielding layer 2 can have better bonding performance, so that the carrier layer 3 can be firmly attached to the insulating layer 1 and is not easily detached. In this way, it can effectively reduce the problem that when the protective film layer 5 is torn off from the surface of the adhesive film layer 4, the protective film layer 5 is not completely torn off and the carrier layer 3 detaches from the insulating layer 1 first. Specific Embodiment Four:

[0083] An electromagnetic shielding film includes a carrier layer 3, an insulating layer 1, a shielding layer 2, an adhesive film layer 4, and a protective film layer 5 stacked in sequence; the surface roughness Sz of the side of the insulating layer 1 away from the shielding layer 2 is 5.1 micrometers. Among them, the material of the insulating layer 1 is epoxy resin.

[0084] Test result: After testing, the peel strength between the insulating layer 1 and the carrier layer 3 of the electromagnetic shielding film of this embodiment is 15.03 N / cm.

[0085] It can be seen that by applying the electromagnetic shielding film of this embodiment, the side of the insulating layer 1 away from the shielding layer 2 can have better bonding performance, so that the carrier layer 3 can be firmly attached to the insulating layer 1 and is not easily detached. In this way, it can effectively reduce the problem that when the protective film layer 5 is torn off from the surface of the adhesive film layer 4, the protective film layer 5 is not completely torn off and the carrier layer 3 detaches from the insulating layer 1 first. Specific Embodiment Five:

[0087] An electromagnetic shielding film includes a carrier layer 3, an insulating layer 1, a shielding layer 2, an adhesive film layer 4, and a protective film layer 5 stacked in sequence; the surface roughness Sz of the side of the insulating layer 1 away from the shielding layer 2 is 10.8 micrometers. Among them, the material of the insulating layer 1 is epoxy resin.

[0088] Test result: After testing, the peel strength between the insulating layer 1 and the carrier layer 3 of the electromagnetic shielding film of this embodiment is 17.69 N / cm.

[0089] It can be seen that by applying the electromagnetic shielding film of this embodiment, the side of the insulating layer 1 away from the shielding layer 2 can have better bonding performance, so that the carrier layer 3 can be firmly attached to the insulating layer 1 and is not easily detached. In this way, it can effectively reduce the problem that when the protective film layer 5 is torn off from the surface of the adhesive film layer 4, the protective film layer 5 is not completely torn off and the carrier layer 3 detaches from the insulating layer 1 first.

[0090] In summary, when the surface roughness Sz of the side of the insulating layer 1 away from the shielding layer 2 is 0.5 - 20 micrometers (for example, 0.5, 1, 1.5, 5.1, 10.8, 15, 20 micrometers), by applying the electromagnetic shielding film of this embodiment, the side of the insulating layer 1 away from the shielding layer 2 can have better bonding performance, so that the carrier layer 3 can be firmly attached to the insulating layer 1 and is not easily detached. This can effectively reduce the problem that when the protective film layer 5 is torn off from the surface of the adhesive film layer 4, the protective film layer 5 is not completely torn off while the carrier layer 3 detaches from the insulating layer 1 first.

[0091] See Figure 5 , another embodiment of the present invention further provides a circuit board, which includes a circuit board body 6 and the electromagnetic shielding film as described in any of the above embodiments; the electromagnetic shielding film is pressed and bonded to the circuit board body 6 through the adhesive film layer 4; the side of the shielding layer 2 away from the insulating layer 1 is electrically connected to the ground layer of the circuit board body 6.

[0092] Preferably, the circuit board body 6 is one of a flexible single-sided, flexible double-sided, flexible multi-layer board, and a rigid-flexible board.

[0093] In the embodiment of the present invention, the side of the shielding layer 2 away from the insulating layer 1 is electrically connected to the ground layer of the circuit board body 6, so as to realize guiding the interfering charges in the shielding layer 2 into the ground, avoiding the accumulation of interfering charges to form an interference source and affecting the normal operation of the circuit board.

[0094] Specifically, due to the application of the electromagnetic shielding film in the circuit board of the embodiment of the present invention, since the sum of the maximum peak height and the maximum valley depth of the surface roughness of the side of the insulating layer away from the shielding layer is 0.5 - 20 micrometers, the side of the insulating layer 1 away from the shielding layer 2 can have better bonding performance, so that the carrier layer 3 can be firmly attached to the insulating layer 1 and is not easily detached. Thus, when the electromagnetic shielding film is pressed and bonded to the circuit board body 6, it can effectively reduce the problem that when the protective film layer 5 is torn off from the surface of the adhesive film layer 4, the protective film layer 5 is not completely torn off while the carrier layer 3 detaches from the insulating layer 1 first, reducing the impact on the efficiency of pressing the electromagnetic shielding film onto the circuit board body 6.

[0095] The above is only the specific implementation manner 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 those skilled in the art within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims

1. An electromagnetic shielding film, characterized in that, It includes a carrier layer, an insulating layer, a shielding layer, a film layer, and a protective film layer stacked in sequence; The roughness Sz of the surface of the insulating layer away from the shielding layer is 0.5 - 20 microns; The insulating layer is formed on one surface of the carrier layer, and the ratio of the roughness Sz of the said surface of the carrier layer to the thickness of the insulating layer is 0.375 - 3.6; There are conductive protrusions on the surface of the shielding layer close to the film layer.

2. The electromagnetic shielding film according to claim 1, characterized in that, The roughness Sz of the surface of the insulating layer away from the shielding layer is 2.5 - 18 microns.

3. The electromagnetic shielding film according to claim 1, characterized in that, The roughness Sz of the surface of the insulating layer away from the shielding layer is 5.1 - 10.8 microns.

4. The electromagnetic shielding film according to claim 1, wherein The dyne value of the surface of the insulating layer away from the shielding layer is greater than or equal to 28.

5. The electromagnetic shielding film according to claim 1, characterized in that, There are through holes penetrating the upper and lower surfaces of the shielding layer.

6. The electromagnetic shielding film according to claim 5, characterized in that, The number of through holes per square centimeter on the shielding layer is 1 - 1000.

7. The electromagnetic shielding film according to claim 5, characterized in that The ratio of the sum of the cross-sectional areas of all the through holes in the shielding layer per square centimeter to the cross-sectional area of the shielding layer where the cross-section is located is 1% - 70%.

8. A circuit board, characterized in that, It includes a circuit board body and the electromagnetic shielding film according to any one of claims 1 - 7; the electromagnetic shielding film is pressed and bonded to the circuit board body through the film layer; the surface of the shielding layer away from the insulating layer is electrically connected to the ground layer of the circuit board body.

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