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. The electromagnetic shielding film includes a shielding layer and an adhesive film layer; the adhesive film layer is disposed on one surface of the shielding layer; wherein, when the unit of the roughness Rz is micrometer and the unit of the adhesive weight parameter is grams per square decimeter, the ratio of the numerical value of the roughness Rz of the surface of the shielding layer close to the adhesive film layer to the adhesive weight parameter of the adhesive film layer is 2 - 300. The electromagnetic shielding film and the circuit board provided by the present invention can simultaneously have the following advantages: good shielding effectiveness, good adhesion strength with the circuit board, and good appearance of the circuit board after being laminated to the circuit board.

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 circuit boards, thus 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, 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, the commonly used electromagnetic shielding film for existing circuit boards includes a shielding layer and an adhesive film layer. One side of the shielding layer close to the adhesive film layer has roughness and can pierce the adhesive film layer to contact and connect with the ground layer of the circuit board, thereby introducing interference charges into the ground layer of the circuit board, thus achieving shielding.

[0005] In the process of implementing the present invention, the inventor found that the following technical problems exist in the prior art: in the process of laminating an existing electromagnetic shielding film onto a circuit board, in order to enable the roughness of the side of the shielding layer close to the adhesive film layer to effectively pierce the adhesive film layer and contact and connect with the ground layer of the circuit board, a relatively large pressing force often needs to be applied. In this process, the adhesive of the adhesive film layer easily overflows from the edge between the electromagnetic shielding film and the circuit board, which will cause problems with the appearance of the circuit board. In order to avoid the adhesive of the adhesive film layer from easily overflowing from the edge between the electromagnetic shielding film and the circuit board during the lamination of the electromagnetic shielding film, the amount of adhesive of the adhesive film layer can be reduced or a smaller pressing force can be applied. However, both of these methods will easily cause delamination and explosion of the circuit board between the electromagnetic shielding film and the circuit board. Especially when the thickness of the adhesive film layer is not reduced, applying a smaller pressing force to the electromagnetic shielding film may also cause the shielding layer to be unable to effectively pierce the adhesive film layer, resulting in the shielding layer being unable to contact and connect with the ground layer of the circuit board, thereby causing the shielding efficiency of the electromagnetic shielding film to be relatively low. It can be seen that the existing electromagnetic shielding film cannot simultaneously have the following advantages: good shielding efficiency, good adhesion strength to the circuit board, and good appearance of the circuit board after being laminated onto 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 that can simultaneously have the following advantages: good shielding efficiency, good adhesion strength to the circuit board, and good appearance of the circuit board after being laminated onto the circuit board.

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

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

[0009] Wherein, when the unit of the roughness Rz is micrometers and the unit of the adhesive weight parameter of the adhesive film layer is grams per square decimeter, the ratio of the roughness Rz of the side of the shielding layer close to the adhesive film layer to the adhesive weight parameter of the adhesive film layer is 2 - 300.

[0010] As an improvement of the above solution, the electromagnetic shielding film further includes an insulating layer; the shielding layer is formed on one side of the insulating layer; the ratio of the roughness Rz of the one side of the insulating layer to the thickness of the shielding layer is 1.25 - 65.

[0011] As an improvement of 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.

[0012] As an improvement of the above solution, the insulating layer is formed on one side of the carrier layer; the ratio of the roughness Rz of the said one side of the carrier layer to the thickness of the insulating layer is 0.3 - 3.

[0013] As an improvement of the above solution, the ratio of the roughness Rz of the side of the shielding layer close to the adhesive film layer to the thickness of the adhesive film layer is 0.1 - 9.

[0014] As an improvement of the above solution, the adhesive weight parameter of the adhesive film layer is 0.01 - 1 g / dm².

[0015] As an improvement of the above solution, the roughness Rz of the side of the shielding layer close to the adhesive film layer is 0.5 - 20 μm.

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

[0017] As an improvement of the above solution, the conductive protrusion includes a conductive base portion and at least one conductive spike portion integrally formed with the conductive base portion; the conductive base portion extends outward from the side of the shielding layer close to the adhesive film layer, and at least one of the conductive spike portions extends outward from the surface of the conductive base portion.

[0018] As an improvement of the above solution, the protrusion height of the conductive spike portion is 0.1 - 8 μm.

[0019] 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 of the above solutions; the electromagnetic shielding film is press - bonded to the circuit board body through the adhesive film layer; the rough surface of the shielding layer pierces through the adhesive film layer and is electrically connected to the ground layer of the circuit board body.

[0020] 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:

[0021] When laminating the electromagnetic shielding film onto the circuit board, since the surface of the shielding layer close to the adhesive film layer has roughness, and under the condition that the unit of roughness Rz is micrometer and the unit of the adhesive weight parameter of the adhesive film layer is grams per square decimeter, the ratio of the roughness Rz of the surface of the shielding layer close to the adhesive film layer to the adhesive weight parameter of the adhesive film layer is 2 - 300. Thus, under the application of a certain pressing force, the shielding layer can be effectively in contact and connected with the ground layer of the circuit board, so that the interfering charges of the shielding layer can be effectively introduced into the ground layer of the circuit board, thereby effectively improving the shielding effectiveness of the electromagnetic shielding film. And at the same time, since the ratio of the roughness Rz of the surface of the shielding layer close to the adhesive film layer to the adhesive weight parameter of the adhesive film layer is 2 - 300, the adhesive in the adhesive film layer can be effectively accommodated by the surface of the shielding layer close to the adhesive film layer, and it is not easy for a large amount of adhesive substances to move towards the edge of the circuit board, resulting in an obvious adhesive overflow problem at the edge between the electromagnetic shielding film and the circuit board. Therefore, the circuit board after laminating the shielding film can have a good appearance. In addition, at the same time, since the ratio of the roughness Rz of the surface of the shielding layer close to the adhesive film layer to the adhesive weight parameter of the adhesive film layer is 2 - 300, the amount of adhesive of the adhesive film layer and the roughness of the surface of the shielding layer can have a proper ratio. Thus, while enabling the shielding layer to be effectively in contact and connected with the ground layer of the circuit board and making the circuit board have a good appearance after being laminated onto the circuit board, it is not necessary to make the amount of adhesive of the adhesive film layer too small or deliberately reduce the pressing force on the shielding film, and the shielding film and the circuit board can still have a good bonding strength. In summary, the embodiments of the present invention can simultaneously have the following advantages: good shielding effectiveness, good bonding strength with the circuit board, and the circuit board has a good appearance after being laminated onto the circuit board. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] 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.

[0023] Figure 1 is a schematic structural diagram of the first electromagnetic shielding film provided by an embodiment of the present invention;

[0024] Figure 2 is a schematic structural diagram of the second electromagnetic shielding film provided by an embodiment of the present invention;

[0025] Figure 3 is a schematic structural diagram of the third electromagnetic shielding film provided by an embodiment of the present invention;

[0026] Figure 4 It is a schematic structural diagram of the fourth electromagnetic shielding film provided by an embodiment of the present invention;

[0027] Figure 5 It is a schematic structural diagram of a conductive protrusion provided by an embodiment of the present invention;

[0028] Figure 6 It is a schematic structural diagram of the fifth electromagnetic shielding film provided by an embodiment of the present invention;

[0029] Figure 7 It is a schematic structural diagram of a circuit board provided by an embodiment of the present invention.

[0030] Explanation of the reference numerals in the drawings: 1. Carrier layer; 2. Insulating layer; 3. Shielding layer; 4. Adhesive film layer; 5. Protective film layer; 6. Conductive protrusion; 60. Conductive matrix part; 61. Conductive spike part; 7. Circuit board body. Detailed implementation manners

[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 of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0032] In the description of the specification and the 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 accompanying 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 therefore 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 the 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 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 the features.

[0034] Refer to Figure 1 , an embodiment of the present invention provides an electromagnetic shielding film, which includes a shielding layer 3 and an adhesive film layer 4;

[0035] The adhesive film layer 4 is disposed on one surface of the shielding layer 3;

[0036] Wherein, when the unit of the roughness Rz is micrometers and the unit of the glue weight parameter is grams per square decimeter, the ratio of the value of the roughness Rz of the side of the shielding layer 3 close to the glue film layer 4 to the glue weight parameter of the glue film layer 4 is 2 - 300.

[0037] Wherein, the shielding layer 3 functions as electromagnetic shielding. In addition, the electromagnetic shielding film can be adhered to the circuit board through the glue film layer 4. Additionally, during use, an insulating substance can be provided on the side of the shielding layer 3 away from the glue film layer 4 to ensure effective electrical isolation between the shielding layer 3 and the outside.

[0038] In the embodiment of the present invention, when the electromagnetic shielding film is laminated onto the circuit board, since the side of the shielding layer 3 close to the glue film layer 4 has roughness, and when the unit of the roughness Rz is micrometers and the unit of the glue weight parameter is grams per square decimeter, the ratio of the value of the roughness Rz of the side of the shielding layer 3 close to the glue film layer 4 to the glue weight parameter of the glue film layer 4 is 2 - 300, it is possible to effectively contact and connect the shielding layer 3 with the ground layer of the circuit board under a certain pressing force, so that the interfering charges of the shielding layer 3 can be effectively introduced into the ground layer of the circuit board, thereby effectively improving the shielding efficiency of the electromagnetic shielding film; and at the same time, since the ratio of the value of the roughness Rz of the side of the shielding layer 3 close to the glue film layer 4 to the glue weight parameter of the glue film layer 4 is 2 - 300, it is also possible to effectively accommodate the glue in the glue film layer 4 by the side of the shielding layer 3 close to the glue film layer 4, and it is not easy for a large amount of glue substances to move towards the edge of the circuit board, resulting in an obvious glue overflow problem at the edge between the electromagnetic shielding film and the circuit board, so that the circuit board after laminating the shielding film has a good appearance; in addition, at the same time, since the ratio of the value of the roughness Rz of the side of the shielding layer 3 close to the glue film layer 4 to the glue weight parameter of the glue film layer 4 is 2 - 300, it is also possible to make the amount of glue in the glue film layer 4 and the roughness of the side of the shielding layer 3 have a suitable ratio, so that while the shielding layer 3 is effectively contact-connected with the ground layer of the circuit board and the circuit board has a good appearance after being laminated onto the circuit board, it is not necessary to make the amount of glue in the glue film layer 4 too small or deliberately reduce the pressing force on the shielding film, and it is also possible to make the shielding film and the circuit board have good adhesion strength. In summary, the embodiment of the present invention can simultaneously have the following advantages: good shielding efficiency, good adhesion strength with the circuit board, and the circuit board has a good appearance after being laminated onto the circuit board.

[0039] Exemplarily, the glue weight parameter of the glue film layer 4 is 0.01 - 1 gram per square decimeter.

[0040] In this embodiment, when laminating the electromagnetic shielding film onto the circuit board, the adhesive film layer 4 with an adhesive weight of 0.01 - 1 g per square decimeter is easily effectively pierced by the side of the shielding layer 3 close to the adhesive film layer 4, so that the shielding layer 3 is electrically connected to the ground layer of the circuit board. In this way, the interfering charges of the shielding layer 3 can be effectively introduced into the ground layer of the circuit board, thereby effectively improving the shielding effectiveness of the electromagnetic shielding layer 3. In addition, the adhesive film layer 4 with an adhesive weight of 0.01 - 1 g per square decimeter can effectively maintain the bonding strength between the electromagnetic shielding film and the circuit board, making it not easy for the electromagnetic shielding film and the circuit board to have a delamination phenomenon. As an example, the adhesive weight parameters of the adhesive film layer 4 are 0.01, 0.05, 0.1, 0.2, 0.505, 0.7, 1 g per square decimeter.

[0041] Exemplarily, the roughness Rz of the side of the shielding layer 3 close to the adhesive film layer 4 is 0.5 - 20 μm.

[0042] It can be understood 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.

[0043] In this embodiment, since the roughness Rz of the side of the shielding layer 3 close to the adhesive film layer 4 is 0.5 - 20 μm, when laminating the electromagnetic shielding film onto the circuit board, the side of the shielding layer 3 close to the adhesive film layer 4 can effectively pierce the adhesive film layer 4, so that the shielding layer 3 is electrically connected to the ground layer of the circuit board. In this way, the interfering charges of the shielding layer 3 can be effectively introduced into the ground layer of the circuit board, thereby effectively improving the shielding effectiveness of the electromagnetic shielding layer 3. And when the roughness Rz of the side of the shielding layer 3 close to the adhesive film layer 4 is 0.5 - 20 μm, the glue holding effect is better, and it is not easy for a large amount of glue-like substances to move towards the edge of the circuit board, resulting in an obvious glue overflow problem at the edge of the circuit board. Thus, the circuit board after laminating the shielding film can have a good appearance. As an example, the roughness Rz of the side of the shielding layer 3 close to the adhesive film layer 4 is 0.5, 1.00, 5.00, 10.25, 15, 20.

[0044] In the above embodiment, the ratio of the roughness Rz of the side of the shielding layer 3 close to the adhesive film layer 4 to the thickness of the adhesive film layer 4 is 0.1 - 9.

[0045] In this embodiment, the ratio of the roughness Rz of the surface of the shielding layer 3 close to the adhesive film layer 4 to the thickness of the adhesive film layer 4 is 0.1 - 9. Therefore, when the electromagnetic shielding film is laminated onto the circuit board, the surface of the shielding layer 3 close to the adhesive film layer 4 can effectively pierce through the adhesive film layer 4 and be electrically connected to the ground layer of the circuit board. Furthermore, the interfering charges of the shielding layer 3 can be effectively introduced into the ground layer of the circuit board, thereby effectively improving the shielding effectiveness of the electromagnetic shielding layer 3.

[0046] Among them, the materials used for the adhesive film layer 4 are selected from the following: modified epoxy resin, acrylic, modified rubber, and modified thermoplastic polyimide. It can be understood that in order to ensure that the shielding layer has good 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.

[0047] In the above embodiment, further, referring to Figure 2 , the electromagnetic shielding film further includes an insulating layer 2; the insulating layer 2 is disposed on the surface of the shielding layer 3 away from the adhesive film layer 4. 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.

[0048] Specifically, the shielding layer 3 is formed on one surface of the insulating layer 2; the ratio of the roughness Rz of this surface of the insulating layer 2 to the thickness of the shielding layer 3 is 1.25 - 65. During the process of forming the shielding layer 3 on the rough surface of the insulating layer 2, the ratio of the roughness Rz of the rough surface of the insulating layer 2 to the thickness of the shielding layer 3 is 1.25 - 65, which can make the shielding layer 3 follow the undulations of the rough surface of the insulating layer 2, and it is easy for the surface of the shielding layer 3 away from the insulating layer 2 to have a roughness capable of piercing through the adhesive film layer 4, so that the shielding layer 3 can be effectively electrically connected to the ground layer of the circuit board.

[0049] In the above embodiment, further, referring to Figure 3, the electromagnetic shielding film further includes a carrier layer 1; the carrier layer 1 is disposed on a surface of the insulating layer 2 away from the shielding layer 3. 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, collision, etc. In addition, the carrier layer 1 can serve as a base film for forming the insulating layer 2, that is, the insulating layer 2 can be formed on one surface of the carrier layer 1.

[0050] Specifically, the insulating layer 2 is formed on one surface of the carrier layer 1; the ratio of the roughness Rz of the one surface of the carrier layer 1 to the thickness of the insulating layer 2 is 0.3 - 3. Wherein, during the process of forming the insulating layer 2 on the one surface of the carrier layer 1, the ratio of the roughness Rz of the one surface of the carrier layer 1 to the thickness of the insulating layer 2 is 0.3 - 3, so that the insulating layer 2 can follow the undulation of the one surface of the carrier layer 1, and it is easy to make the surface of the insulating layer 2 away from the carrier layer 1 have a certain roughness, so that finally the surface of the shielding layer 3 close to the adhesive film layer 4 has a roughness capable of piercing the adhesive film layer 4, enabling the shielding layer 3 to be effectively electrically connected to the ground layer of the circuit board.

[0051] In the above embodiment, further, referring to Figure 4 , a conductive protrusion 6 is provided on the surface of the shielding layer 3 close to the adhesive film layer 4, which 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.

[0052] Specifically, the number of conductive protrusions 6 with a longitudinal height greater than 5um on the shielding film per square centimeter on the one surface of the shielding layer 3 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.

[0053] In the embodiment of the present invention, the conductive protrusions 6 can be distributed regularly or irregularly on the surface of the shielding layer 3 close to the adhesive film layer 4. In this embodiment, the shapes of the plurality of conductive protrusions 6 can be the same or different, and the distances between the plurality of conductive protrusions 6 can be the same or different. Preferably, the shapes of the plurality of conductive protrusions 6 are the same, and the plurality of conductive protrusions 6 are evenly distributed on the surface of the shielding layer 3 close to the adhesive film layer 4 of the conductive matrix part. In specific implementation, the shielding layer 3 can be formed first, and then the conductive protrusions 6 can be formed on the shielding layer 3 through other processes. Of course, the shielding layer 3 and the conductive protrusions 6 can also be an integral structure formed by a one-step forming process.

[0054] Exemplarily, referring to Figure 5, the conductive protrusion 6 includes a conductive base portion 60 and at least one conductive spike portion 61; the conductive base portion 60 extends outward from one side of the shielding layer 3 close to the adhesive film layer 4, and at least one of the conductive spike portions 61 extends outward from the surface of the conductive base portion 60. Among them, the conductive spike portion 61 extending from the surface of the conductive base portion 60 can more effectively pierce the adhesive film layer 4, so that the shielding layer 3 can be better electrically connected to the ground layer of the circuit board.

[0055] Specifically, the protrusion height of the conductive spike portion 61 is 0.1-8 microns, so that the conductive spike portion 61 can 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] Preferably, the conductive protrusion 6 may have a certain distance from the outer surface of the adhesive film layer 4, may also be in contact with the outer surface of the adhesive film layer 4 or extend out of the outer surface of the adhesive film layer 4. In addition, the outer surface of the adhesive film layer 4 may be a flat surface without undulations or an uneven surface with gentle undulations.

[0057] It should be noted that Figure 4 and Figure 5 The shape of the conductive protrusion 6 in

[0058] is only exemplary. Due to differences in process means and parameters, the conductive protrusion 6 may also be in other shapes such as cluster shape, icicle shape, stalactite shape, dendritic shape, etc. In addition, the conductive protrusion 6 in the embodiments of the present invention is not limited by the illustrated and the above shapes. As long as the conductive protrusion 6 has the functions of piercing and conducting electricity, it is within the protection scope of the present invention.

[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, conductive protrusions may be provided on one side of each layer of the shielding layer 3 close to the adhesive film layer 4; when the shielding layer 3 is a multi-layer, conductive protrusions may also be provided on one side of each layer of the shielding layer 3 close to the adhesive film layer 4. In addition, according to the actual production and application needs, the shielding layer 3 in this embodiment may be set in a grid 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, in the embodiment of the present invention, 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] Please refer to Figure 6 As shown, the electromagnetic shielding film in this embodiment further includes a protective film layer 5, and the protective film layer 5 is disposed on the side of the adhesive film layer 4 away from the shielding layer 3. Since the protective film layer 5 has a protective effect, it can ensure that the insulating layer 2 is not scratched or damaged during use, thereby maintaining the high shielding effectiveness of the shielding layer 3. 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.

[0062] Specifically, when the electromagnetic shielding film includes a carrier layer 1, an insulating layer 2, a shielding layer 3, an adhesive film layer 4, and a protective film layer 5, the preparation method of the electromagnetic shielding film includes:

[0063] 1) Prepare the carrier layer 1;

[0064] 2) Form an insulating layer 2 on one side of the carrier layer 1;

[0065] 3) Form a shielding layer 3 on the side of the insulating layer 2 away from the carrier layer 1;

[0066] 4) Coat an adhesive on the side of the shielding layer 3 away from the insulating layer 2 to form an adhesive film layer 4;

[0067] 5) Bond the protective film layer 5 on the side of the adhesive film layer 4 away from the shielding layer 3.

[0068] For the convenience of understanding the above invention scheme, here, five specific embodiments are provided and these specific embodiments are tested:

[0069] Embodiment 1:

[0070] An electromagnetic shielding film, comprising a shielding layer and an adhesive film layer; the adhesive film layer is disposed on one side of the shielding layer; wherein, the roughness Rz of the side of the shielding layer close to the adhesive film layer is 1 micron, the adhesive weight parameter of the adhesive film layer is 0.5 grams per square decimeter, and the ratio of the value of the roughness Rz of the side of the shielding layer close to the adhesive film layer to the adhesive weight parameter of the adhesive film layer is 2.

[0071] Test results: After the electromagnetic shielding film of this embodiment is laminated to a circuit board and tested, the grounding resistance between the shielding layer of the electromagnetic shielding film of this embodiment and the ground layer of the circuit board is less than 213 mΩ. Moreover, the good peel strength of the electromagnetic shielding film of this embodiment and the circuit board is greater than 12.23 N / cm, and the length of the adhesive overflow of the adhesive film layer after the electromagnetic shielding film of this embodiment is laminated to the circuit board is less than 70 μm.

[0072] Thus, by applying the electromagnetic shielding film of this embodiment, the interfering charges of the shielding layer can be effectively introduced into the ground layer of the circuit board, thereby having good shielding performance. And after being laminated to the circuit board, while having good adhesion strength between the electromagnetic shielding film and the circuit board, it can also make the circuit board have a good appearance.

[0073] Embodiment Two:

[0074] An electromagnetic shielding film, comprising a shielding layer and an adhesive film layer; the adhesive film layer is disposed on one side of the shielding layer; wherein, the roughness Rz of the side of the shielding layer close to the adhesive film layer is 15.1 microns, the adhesive weight parameter of the adhesive film layer is 0.1 grams per square decimeter, and the ratio of the value of the roughness Rz of the side of the shielding layer close to the adhesive film layer to the adhesive weight parameter of the adhesive film layer is 151.

[0075] Test results: After the electromagnetic shielding film of this embodiment is laminated to a circuit board and tested, the grounding resistance between the shielding layer of the electromagnetic shielding film of this embodiment and the ground layer of the circuit board is less than 78 mΩ. Moreover, the good peel strength of the electromagnetic shielding film of this embodiment and the circuit board is greater than 10.18 N / cm, and the length of the adhesive overflow of the adhesive film layer after the electromagnetic shielding film of this embodiment is laminated to the circuit board is less than 56 μm.

[0076] Thus, by applying the electromagnetic shielding film of this embodiment, the interfering charges of the shielding layer can be effectively introduced into the ground layer of the circuit board, thereby having good shielding performance. And after being laminated to the circuit board, while having good adhesion strength between the electromagnetic shielding film and the circuit board, it can also make the circuit board have a good appearance.

[0077] Embodiment Three:

[0078] An electromagnetic shielding film, comprising a shielding layer and an adhesive film layer; the adhesive film layer is disposed on one side of the shielding layer; wherein, the roughness Rz of the side of the shielding layer close to the adhesive film layer is 0.5 micrometers, the adhesive weight parameter of the adhesive film layer is 0.01 grams per square decimeter, and the ratio of the value of the roughness Rz of the side of the shielding layer close to the adhesive film layer to the adhesive weight parameter of the adhesive film layer is 50.

[0079] Test results: After pressing the electromagnetic shielding film of this embodiment onto the circuit board and testing, the grounding resistance between the shielding layer of the electromagnetic shielding film of this embodiment and the ground layer of the circuit board is less than 345 mΩ. Moreover, the good peeling strength of the electromagnetic shielding film of this embodiment from the circuit board is greater than 10.21 N / cm, and the length of the adhesive overflow of the adhesive film layer after pressing the electromagnetic shielding film of this embodiment onto the circuit board is less than 90 μm.

[0080] Thus, by applying the electromagnetic shielding film of this embodiment, the interfering charges of the shielding layer can be effectively introduced into the ground layer of the circuit board, thereby having good shielding performance. And after being pressed onto the circuit board, while having good adhesion strength between the electromagnetic shielding film and the circuit board, it can also make the circuit board have a good appearance.

[0081] Example Four:

[0082] An electromagnetic shielding film, comprising a shielding layer and an adhesive film layer; the adhesive film layer is disposed on one side of the shielding layer; wherein, the roughness Rz of the side of the shielding layer close to the adhesive film layer is 20 micrometers, the adhesive weight parameter of the adhesive film layer is 1 gram per square decimeter, and the ratio of the value of the roughness Rz of the side of the shielding layer close to the adhesive film layer to the adhesive weight parameter of the adhesive film layer is 20.

[0083] Test results: After pressing the electromagnetic shielding film of this embodiment onto the circuit board and testing, the grounding resistance between the shielding layer of the electromagnetic shielding film of this embodiment and the ground layer of the circuit board is less than 118 mΩ. Moreover, the good peeling strength of the electromagnetic shielding film of this embodiment from the circuit board is greater than 16.79 N / cm, and the length of the adhesive overflow of the adhesive film layer after pressing the electromagnetic shielding film of this embodiment onto the circuit board is less than 106 μm.

[0084] Thus, by applying the electromagnetic shielding film of this embodiment, the interfering charges of the shielding layer can be effectively introduced into the ground layer of the circuit board, thereby having good shielding performance. And after being pressed onto the circuit board, while having good adhesion strength between the electromagnetic shielding film and the circuit board, it can also make the circuit board have a good appearance.

[0085] Example Five:

[0086] An electromagnetic shielding film, comprising a shielding layer and an adhesive film layer; the adhesive film layer is disposed on one side of the shielding layer; wherein, the roughness Rz of the side of the shielding layer close to the adhesive film layer is 3 microns, the adhesive weight parameter of the adhesive film layer is 0.01 grams per square decimeter, and the ratio of the value of the roughness Rz of the side of the shielding layer close to the adhesive film layer to the adhesive weight parameter of the adhesive film layer is 300.

[0087] Test results: After the electromagnetic shielding film of this embodiment is laminated to the circuit board and tested, the grounding resistance between the shielding layer of the electromagnetic shielding film of this embodiment and the ground layer of the circuit board is less than 107 mΩ. Moreover, the good peeling strength of the electromagnetic shielding film of this embodiment and the circuit board is greater than 10.37 N / cm, and the length of the adhesive overflow of the adhesive film layer after the electromagnetic shielding film of this embodiment is laminated to the circuit board is less than 85 μm.

[0088] Thus, by applying the electromagnetic shielding film of this embodiment, the interfering charges of the shielding layer can be effectively introduced into the ground layer of the circuit board, thereby having good shielding effectiveness. And after being laminated to the circuit board, while having good adhesion strength between the electromagnetic shielding film and the circuit board, the circuit board can also have a good appearance.

[0089] The above numerical ratio of the roughness Rz to the adhesive weight parameter is only an example, and the numerical ratio can also be other numerical situations, such as 10, 25, 75, 100, 125, 175, 225, 275, etc.

[0090] See Figure 7 , another embodiment of the present invention further provides a circuit board, which includes a circuit board body 7 and the electromagnetic shielding film described in any of the above embodiments; the electromagnetic shielding film is laminated to the circuit board body 7 through the adhesive film layer 4; the side 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 7.

[0091] Preferably, the circuit board body 7 is one of a flexible single-sided, flexible double-sided, flexible multi-layer, or rigid-flex printed circuit board.

[0092] In the embodiment of the present invention, the side of the shielding layer 3 close to the adhesive film layer 4 can pierce through the adhesive film layer 4 and be connected to the ground layer of the circuit board body 7 when the electromagnetic shielding film is laminated to the circuit board body 7, thereby ensuring the connection between the shielding layer 3 and the ground layer of the circuit board body 7, and realizing the introduction of the interfering charges in the shielding layer 3 and 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.

[0093] In an embodiment of the present invention, since the surface of the shielding layer 3 close to the adhesive film layer 4 has roughness, and under the condition that the unit of the roughness Rz is micron and the unit of the adhesive weight parameter is grams per square decimeter, the ratio of the roughness Rz of the surface of the shielding layer 3 close to the adhesive film layer 4 to the adhesive weight parameter of the adhesive film layer 4 is 2 - 300. Thus, under the application of a certain pressing force, the shielding layer 3 can be effectively contacted and connected with the ground layer of the circuit board, so that the interfering charges of the shielding layer 3 can be effectively introduced into the ground layer of the circuit board, thereby effectively improving the shielding effectiveness of the electromagnetic shielding film. And at the same time, since the ratio of the roughness Rz of the surface of the shielding layer 3 close to the adhesive film layer 4 to the adhesive weight parameter of the adhesive film layer 4 is 2 - 300, the adhesive in the adhesive film layer 4 can be effectively accommodated by the surface of the shielding layer 3 close to the adhesive film layer 4, and it is not easy for a large amount of adhesive substances to move to the edge of the circuit board, resulting in an obvious adhesive overflow problem at the edge between the electromagnetic shielding film and the circuit board. Thus, the circuit board after pressing the shielding film can have a good appearance. In addition, at the same time, since the ratio of the roughness Rz of the surface of the shielding layer 3 close to the adhesive film layer 4 to the adhesive weight parameter of the adhesive film layer 4 is 2 - 300, the amount of the adhesive of the adhesive film layer 4 and the roughness of the surface of the shielding layer 3 can have a suitable ratio. Thus, while the shielding layer 3 is effectively contacted and connected with the ground layer of the circuit board and the circuit board has a good appearance after being pressed onto the circuit board, it is not necessary to make the amount of the adhesive of the adhesive film layer 4 too small or deliberately reduce the pressing force on the shielding film. Therefore, a good bonding strength can also be achieved between the shielding film and the circuit board. In summary, the embodiment of the present invention can simultaneously have the following advantages: good shielding effectiveness, good bonding strength with the circuit board, and a good appearance of the circuit board after being pressed onto the circuit board.

[0094] As described above, the above is only the specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any change or replacement that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be covered by 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 shielding layer and an adhesive film layer; The adhesive film layer is disposed on one side of the shielding layer; Wherein, under the condition that the unit of the roughness Rz is micrometer and the unit of the adhesive weight parameter is gram per square decimeter, the ratio of the value of the roughness Rz of the side of the shielding layer close to the adhesive film layer to the adhesive weight parameter of the adhesive film layer is 2 - 300; The electromagnetic shielding film further includes a carrier layer and an insulating layer; the shielding layer is formed on one side of the insulating layer, and the carrier layer is disposed on the side of the insulating layer away from the shielding layer; the ratio of the roughness Rz of the one side of the insulating layer to the thickness of the shielding layer is 1.25 - 65; the insulating layer is formed on one side of the carrier layer; the ratio of the roughness Rz of the one side of the carrier layer to the thickness of the insulating layer is 0.3 - 3; Conductive protrusions are provided on the side of the shielding layer close to the adhesive film layer.

2. The electromagnetic shielding film according to claim 1, characterized in that, The ratio of the roughness Rz of the side of the shielding layer close to the adhesive film layer to the thickness of the adhesive film layer is 0.1 - 9.

3. The electromagnetic shielding film according to claim 1, wherein The adhesive weight parameter of the adhesive film layer is 0.01 - 1 gram per square decimeter.

4. The electromagnetic shielding film according to claim 1, characterized in that, The roughness Rz of the side of the shielding layer close to the adhesive film layer is 0.5 - 20 micrometers.

5. The electromagnetic shielding film according to claim 1, characterized in that, The conductive protrusion includes a conductive base part and at least one conductive spike part integrally formed with the conductive base part; the conductive base part extends outward from the side of the shielding layer close to the adhesive film layer, and at least one conductive spike part extends outward from the surface of the conductive base part.

6. The electromagnetic shielding film according to claim 5, wherein The protrusion height of the conductive spike part is 0.1 - 8 micrometers.

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 to the circuit board body through the adhesive film layer; the side of the shielding layer close to the adhesive film layer pierces through the adhesive film layer and is electrically connected to the ground layer of the circuit board body.

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