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 an insulating layer and a shielding layer; the shielding layer is disposed on one surface of the insulating layer; the surface roughness Rz of the surface of the insulating layer away from the shielding layer is 0.5 - 20 microns. The present invention can effectively improve the adhesion firmness of the ink on the surface of the insulating layer, thereby effectively reducing the occurrence of ink bleeding when printing ink on the surface of the insulating layer of the electromagnetic shielding film.

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 electronics industry, electronic products are further moving towards miniaturization, lightweight, and high-density assembly, which greatly promotes the development of flexible printed circuits, thereby realizing the integration of component devices and wire connections. Flexible printed circuits can be widely used in industries such as mobile phones, liquid crystal displays, communications, and aerospace.

[0003] Driven by the international market, functional flexible printed circuits dominate the flexible printed circuit market, and an important indicator for evaluating the performance of functional flexible printed circuits is electromagnetic shielding (Electromagnetic Interference Shielding, abbreviated as EMI Shielding). With the integration of functions of communication devices such as mobile phones, their internal components 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. Under the drive of high frequency and high speed, problems such as electromagnetic interference inside and outside components, signal attenuation during transmission, insertion loss, and jitter are gradually becoming serious.

[0004] Currently, the commonly used electromagnetic shielding film for existing circuit boards includes an insulating layer and a shielding layer. The shielding layer is 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: Due to the poor roughness of the insulating layer of the electromagnetic shielding film, when printing characters on a circuit board with the above-mentioned structure of the electromagnetic shielding film, the printing ink cannot be firmly printed on the surface of the insulating layer, resulting in the problem of ink bleeding easily occurring, which affects the character printing effect of the circuit board. Summary of the Invention

[0006] In view of the above problems, an object of the present invention is to provide an electromagnetic shielding film and a circuit board, which can effectively improve the adhesion firmness of the ink on the surface of the insulating layer, thereby effectively reducing the occurrence of ink bleeding when printing ink on the surface of the insulating layer of the electromagnetic shielding film.

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

[0008] The shielding layer is disposed on one side of the insulating layer;

[0009] The roughness Rz of the side of the insulating layer away from the shielding layer is 0.5 - 20 microns.

[0010] As an improvement to the above solution, the roughness Rz of the side of the insulating layer away from the shielding layer is 1.5 - 6.3 microns.

[0011] As an improvement to the above solution, the roughness Rz of the side of the insulating layer away from the shielding layer is 1 - 10 microns.

[0012] As an improvement to the above solution, the dyne value of the side of the insulating layer away from the shielding layer is greater than or equal to 28.

[0013] As an improvement to the above solution, the electromagnetic shielding film further includes a carrier layer; the carrier layer is disposed on the side of the insulating layer away from the shielding layer.

[0014] As an improvement to the above solution, the insulating layer is formed on one side of the carrier layer, and the ratio of the roughness Rz of the one side of the carrier layer to the thickness of the insulating layer is 0.125 - 2.

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

[0016] As an improvement to the above solution, conductive protrusions are provided on the side of the shielding layer close to the adhesive film layer.

[0017] As an improvement to the above solution, the adhesive film layer includes an adhesive layer containing conductive particles; or, the adhesive film layer includes an adhesive layer without conductive particles.

[0018] To solve the same technical problem, another embodiment of the present invention further provides a circuit board, including a circuit board body and the electromagnetic shielding film as described in any one of the above; the electromagnetic shielding film is pressed together with the circuit board body; the side of the shielding layer away from the insulating layer is electrically connected to the ground layer of the circuit board body.

[0019] 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:

[0020] Since the roughness Rz of the side of the insulating layer away from the shielding layer is 0.5 - 20 micrometers, the side of the insulating layer away from the shielding layer can have better surface tension, thereby improving the adhesion firmness of the ink on this side of the insulating layer. In this way, when printing characters on this side of the insulating layer, the printing ink can firmly adhere to it and is not prone to bleeding, so that the characters can be clearly displayed. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] 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 described below are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0022] Figure 1 is a schematic structural diagram of the first electromagnetic shielding film provided by an embodiment of the present invention;

[0023] Figure 2 is a schematic structural diagram of the second electromagnetic shielding film provided by an embodiment of the present invention;

[0024] Figure 3 is a schematic structural diagram of the third electromagnetic shielding film provided by an embodiment of the present invention;

[0025] Figure 4 is a schematic structural diagram of a conductive protrusion provided by an embodiment of the present invention;

[0026] Figure 5 is a schematic structural diagram of the fourth electromagnetic shielding film provided by an embodiment of the present invention;

[0027] Figure 6 is a schematic structural diagram of a circuit board provided by an embodiment of the present invention;

[0028] Among them, 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 matrix part; 212, conductive spike part. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0029] 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, rather than all, of the embodiments of the present invention. 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.

[0030] In the description of the specification and claims, it should be understood that the orientation or positional relationship indicated by terms such as "upper", "lower", "left", "right", "front", "rear", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. This 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 on the embodiments of the present invention.

[0031] In addition, terms such as first and second in the specification and claims are only used for the purpose of distinguishing the description of the same technical features, and should not be construed as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features, nor necessarily describing the order or time sequence. Under appropriate circumstances, the terms are interchangeable. Thus, features defined with "first" and "second" may explicitly or implicitly include at least one of such features.

[0032] See Figure 1 , an embodiment of the present invention provides an electromagnetic shielding film, which includes an insulating layer 1 and a shielding layer 2; the shielding layer 2 is disposed on one surface of the insulating layer 1; the roughness Rz of the surface of the insulating layer 1 away from the shielding layer 2 is 0.5 - 20 microns.

[0033] Among them, the insulating layer 1 can effectively electrically isolate the shielding layer 2 from the outside, thereby ensuring the electromagnetic shielding effect of the shielding layer 2.

[0034] In the embodiment of the present invention, since the roughness Rz of the surface 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 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.

[0035] It should be noted that the roughness Rz represents the sum of the average value of the five largest profile peak heights and the average value of the five largest profile valley depths within the sampling length.

[0036] In this embodiment, in order to ensure that the shielding layer 2 has good 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.

[0037] Specifically, the roughness Rz of the surface of the insulating layer 1 away from the shielding layer 2 is 1.5 - 6.3 microns.

[0038] In this embodiment, the roughness Rz of the surface of the insulating layer 1 away from the shielding layer 2 is 1 - 10 microns. This can further improve the surface tension of the surface of the insulating layer 1 away from the shielding layer 2, thereby further reducing the phenomenon of ink bleeding when printing ink on the surface of the insulating layer 1 of the electromagnetic shielding film. Moreover, this can also further improve the bonding performance of the surface of the insulating layer 1 away from the shielding layer 2, thereby further reducing the phenomenon of delamination between the reinforcing plate and the insulating layer 1 when the reinforcing plate is bonded to the electromagnetic shielding film.

[0039] 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. In this way, the printed ink has better adhesion on the surface of the insulating layer 1 away from the shielding layer 2, which can further reduce the phenomenon of ink bleeding when printing ink on the surface of the insulating layer 1 of the electromagnetic shielding film, thereby achieving a better character printing effect.

[0040] In the above embodiment, further, referring to Figure 2 , the electromagnetic shielding film further includes a carrier layer 3; the carrier layer 3 is disposed on the surface of the insulating layer 1 away from the shielding layer 2. 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 or collision, etc. After the electromagnetic shielding film is hot-pressed with the circuit board, the carrier layer 3 needs to be peeled off.

[0041] Exemplarily, the material of the carrier layer 3 is PET, whose English name is Polyethylene terephthalate, commonly known as polyester resin. The thickness of the carrier layer 3 is 50 microns.

[0042] In the above embodiment, exemplarily, the roughness Rz of the surface of the carrier layer 3 close to the insulating layer 1 is 0.5 - 20 microns. This 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 likely to fall off. Moreover, when the insulating layer 1 is formed on the surface of the carrier layer 3 with a roughness Rz of 0.5 - 20 microns, it is easy to make the roughness Rz of the surface of the insulating layer 1 away from the shielding layer 2 be 0.5 - 20 microns, so that the surface of the insulating layer 1 away from the shielding layer 2 has good bonding strength with the printed ink and the reinforcing plate.

[0043] 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.

[0044] Specifically, the ratio of the roughness Rz of the side of the carrier layer 3 close to the insulating layer 1 to the thickness of the insulating layer 1 is 0.125 - 2. In this way, when forming the insulating layer 1 on one side of the carrier layer 3, it is easy to make the roughness Rz of the side of the insulating layer 1 far from the shielding layer 2 be 0.5 - 20 microns.

[0045] In the above embodiment, 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 side of the shielding layer 2 far from the insulating layer 1.

[0046] 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.

[0047] 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. In this way, 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 efficiency 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 the electromagnetic shielding film not easily delaminate. In addition, the adhesive film layer 4 can effectively maintain the bonding strength between the electromagnetic shielding film and the circuit board, making it not easy to have the phenomenon of board explosion between the electromagnetic shielding film and the circuit board. And when pressing the electromagnetic shielding film onto the circuit board, since the side of the shielding layer 2 close to the adhesive film layer 4 is a rough surface, the adhesive substances in the adhesive film layer 4 are squeezed into the concave positions of the rough surface of the shielding layer 2, increasing the glue capacity. On the one hand, it is not easy to have the phenomenon of board explosion, avoiding the problem of high-temperature board explosion of the existing electromagnetic shielding film due to insufficient glue capacity, and thus effectively ensuring the grounding of the electromagnetic shielding film and leading out the interfering charges; on the other hand, it can prevent the glue from overflowing to the edge of the circuit board during pressing, so that the circuit board after pressing the shielding film has a good appearance.

[0048] Exemplarily, the side of the insulating layer 1 close to the shielding layer 2 is a rough surface, which can improve the anti-bending performance of the insulating layer 1, thereby improving the anti-bending performance of the electromagnetic shielding film. In addition, when forming the shielding layer 2 on one side of the insulating layer 1, due to the fixed thickness of the shielding layer 2, the shielding layer 2 will fluctuate along with the rough surface of the insulating layer 1, and finally the side of the shielding layer 2 close to the adhesive film layer 4 becomes a rough surface.

[0049] As an example, referring toFigure 3 On one 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 through the adhesive film layer 4, thereby further ensuring the electrical connection between the electromagnetic shielding film and the ground layer of the circuit board.

[0050] Specifically, the number of conductive protrusions with a longitudinal height greater than 5 μm on the shielding film per square centimeter on this side of the shielding layer 2 is 1 - 1000. This can more effectively pierce through the adhesive film layer 4, thereby further ensuring the electrical connection between the electromagnetic shielding film and the ground layer of the circuit board.

[0051] 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 this 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 through the adhesive film layer 4, so that the shielding layer 2 can be better electrically connected to the ground layer of the circuit board.

[0052] Specifically, the protrusion height of the conductive spike portion 212 is 1 - 10 microns. This can enable the conductive spike portion 212 to effectively pierce through 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] In the embodiment of the present invention, the conductive spike portions 212 can be distributed regularly or irregularly on the surface of the conductive base portion 211. 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 multiple conductive spike portions 212 are the same, and multiple conductive spike portions 212 are evenly distributed on the surface of the conductive base portion 211. In addition, at least one side of the shielding layer 2 is a undulating structure. For example, the side 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 side of the shielding layer 2 close to the adhesive film layer 4 on the adhesive film layer 4, and also improve the glue holding ability of this side of the shielding layer 2.

[0054] In specific implementation, the shielding layer 2 can be formed first, and then the conductive protrusions 21 can be formed on the shielding layer 2 through other processes. Of course, the shielding layer 2 and the conductive protrusions 21 can also be an integral structure formed by a one - step forming process. It should be noted that the material of the conductive protrusions 21 can be the same as that of the shielding layer 2 or different from that of the shielding layer 2, which is not limited here.

[0055] It should be noted that the shielding layer 2 in this embodiment can be a single-layer structure or a multi-layer structure. When the shielding layer 2 is a single layer, conductive protrusions 21 can be provided on the surface of the shielding layer 2 close to the adhesive film layer 4; when the shielding layer 2 is multi-layer, conductive protrusions 21 can 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 needs of actual production and application, the shielding layer 2 in this embodiment can be arranged in a mesh shape, a foamed shape, etc.

[0056] It should be noted that Figure 4 and Figure 5 the shapes of the conductive protrusions 21 in are merely exemplary. Due to differences in process means and parameters, the conductive protrusions 21 can also be in other shapes such as cluster shape, icicle shape, stalactite shape, dendritic shape, etc. In addition, the conductive protrusions 21 in the embodiments of the present invention are not limited by the illustrations and the above shapes. As long as the conductive protrusions 21 have the functions of piercing and conducting electricity, they are all within the protection scope of the present invention.

[0057] In the embodiments 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 can 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 improving the shielding efficiency.

[0058] 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 grounding 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.

[0059] 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 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 pressed 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.

[0060] 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 method for preparing the electromagnetic shielding film includes:

[0061] 1) Prepare the carrier layer 3;

[0062] 2) Form the insulating layer 1 on one side of the carrier layer 3;

[0063] 3) Form the shielding layer 2 on the side of the insulating layer 1 away from the carrier layer 3;

[0064] 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;

[0065] 5) Bond the protective film layer 5 on the side of the adhesive film layer 4 away from the shielding layer 2.

[0066] For the convenience of understanding the above invention solution, here, five specific embodiments are provided and these specific embodiments are tested: Specific Embodiment 1:

[0068] An electromagnetic shielding film includes an insulating layer 1 and a shielding layer 2; the shielding layer 2 is disposed on one side of the insulating layer 1; the roughness Rz of the side of the insulating layer 1 away from the shielding layer 2 is 0.5 micrometers. Among them, the material of the insulating layer 1 is epoxy resin.

[0069] Test result: After testing, the dyne value of the side of the insulating layer 1 of the electromagnetic shielding film in this embodiment away from the shielding layer 2 is 30.

[0070] It can be seen that by applying the electromagnetic shielding film of this embodiment, the side of the insulating layer away from the shielding layer can have better surface tension, so that when printing characters on this side of the insulating layer, the printing ink can firmly adhere to it and is not easy to bleed. Specific Embodiment 2:

[0072] An electromagnetic shielding film includes an insulating layer 1 and a shielding layer 2; the shielding layer 2 is disposed on one side of the insulating layer 1; the roughness Rz of the side of the insulating layer 1 away from the shielding layer 2 is 10.25 micrometers. Among them, the material of the insulating layer 1 is epoxy resin.

[0073] Test result: After testing, the dyne value of the side of the insulating layer 1 of the electromagnetic shielding film in this embodiment away from the shielding layer 2 is 32.

[0074] It can be seen that by applying the electromagnetic shielding film of this embodiment, the surface away from the shielding layer of the insulating layer can have better surface tension. In this way, when printing characters on this surface of the insulating layer, the printing ink can firmly adhere to it and is not prone to ink bleeding. Specific Embodiment Three:

[0076] An electromagnetic shielding film includes an insulating layer 1 and a shielding layer 2; the shielding layer 2 is disposed on one surface of the insulating layer 1; the roughness Rz of the surface of the insulating layer 1 away from the shielding layer 2 is 20 micrometers. Among them, the material of the insulating layer 1 is epoxy resin.

[0077] Test Result: After testing, the dyne value of the surface of the insulating layer 1 of the electromagnetic shielding film of this embodiment away from the shielding layer 2 is 38.

[0078] It can be seen that by applying the electromagnetic shielding film of this embodiment, the surface away from the shielding layer of the insulating layer can have better surface tension. In this way, when printing characters on this surface of the insulating layer, the printing ink can firmly adhere to it and is not prone to ink bleeding. Specific Embodiment Four:

[0080] An electromagnetic shielding film includes an insulating layer 1 and a shielding layer 2; the shielding layer 2 is disposed on one surface of the insulating layer 1; the roughness Rz of the surface of the insulating layer 1 away from the shielding layer 2 is 1.5 micrometers. Among them, the material of the insulating layer 1 is epoxy resin.

[0081] Test Result: After testing, the dyne value of the surface of the insulating layer 1 of the electromagnetic shielding film of this embodiment away from the shielding layer 2 is 30.

[0082] It can be seen that by applying the electromagnetic shielding film of this embodiment, the surface away from the shielding layer of the insulating layer can have better surface tension. In this way, when printing characters on this surface of the insulating layer, the printing ink can firmly adhere to it and is not prone to ink bleeding. Specific Embodiment Five:

[0084] An electromagnetic shielding film includes an insulating layer 1 and a shielding layer 2; the shielding layer 2 is disposed on one surface of the insulating layer 1; the roughness Rz of the surface of the insulating layer 1 away from the shielding layer 2 is 6.3 micrometers. Among them, the material of the insulating layer 1 is epoxy resin.

[0085] Test Result: After testing, the dyne value of the surface of the insulating layer 1 of the electromagnetic shielding film of this embodiment away from the shielding layer 2 is 32.

[0086] It can be seen that by applying the electromagnetic shielding film of this embodiment, the surface away from the shielding layer of the insulating layer can have better surface tension. In this way, when printing characters on this surface of the insulating layer, the printing ink can firmly adhere to it and is not prone to bleeding.

[0087] In summary, when the roughness Rz of the surface of the insulating layer 1 away from the shielding layer 2 is 0.5 - 20 microns (such as 0.5, 1, 1.5, 5, 6.3, 10, 15, 20 microns), by applying the electromagnetic shielding film of this embodiment, the surface of the insulating layer 1 away from the shielding layer 2 can have better surface tension. In this way, 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.

[0088] 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 as described in any of the above embodiments; the electromagnetic shielding film is laminated with the circuit board body 6; the surface of the shielding layer 2 away from the insulating layer 1 is electrically connected to the ground layer of the circuit board body 6.

[0089] 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.

[0090] In the embodiment of the present invention, the surface of the shielding layer 2 away from the insulating layer 1 is electrically connected to the ground layer of the circuit board body 6, thereby realizing the introduction of interference charges in the shielding layer 2 into the ground, avoiding the accumulation of interference charges to form an interference source and affecting the normal operation of the circuit board.

[0091] Specifically, due to the application of the electromagnetic shielding film in the circuit board of the embodiment of the present invention, since the roughness Rz of the surface 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 surface tension, thereby improving the adhesion firmness of the ink on this surface of the insulating layer 1. In this way, 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.

[0092] 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 an insulating layer and a shielding layer; The shielding layer is provided on one side of the insulating layer; The roughness Rz of the side of the insulating layer away from the shielding layer is 0.5 - 20 microns; The electromagnetic shielding film further includes a carrier layer; the carrier layer is provided on the side of the insulating layer away from the shielding layer; the insulating layer is formed on one side of the carrier layer, and the ratio of the roughness Rz of the said one side of the carrier layer to the thickness of the insulating layer is 0.125 - 2; The electromagnetic shielding film further includes an adhesive film layer; the adhesive film layer is provided on the side of the shielding layer away from the insulating layer.

2. The electromagnetic shielding film according to claim 1, wherein The roughness Rz of the side of the insulating layer away from the shielding layer is 1.5 - 6.3 microns.

3. The electromagnetic shielding film according to claim 1, wherein The roughness Rz of the side of the insulating layer away from the shielding layer is 1 - 10 microns.

4. The electromagnetic shielding film according to claim 1, wherein The dyne value of the side 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, wherein Conductive protrusions are provided on the side of the shielding layer close to the adhesive film layer.

6. The electromagnetic shielding film according to claim 1, wherein The adhesive film layer includes an adhesive layer containing conductive particles; or, the adhesive film layer includes an adhesive layer without conductive particles.

7. A circuit board, characterized in that, It includes a circuit board body and the electromagnetic shielding film according to any one of claims 1 - 6; the electromagnetic shielding film is press - bonded with the circuit board body; the side 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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