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. Wherein, the electromagnetic shielding film comprises an insulating layer, a shielding layer and an adhesive film layer; the shielding layer is formed on one surface of the insulating layer, and the adhesive film layer is disposed on the surface of the shielding layer away from the insulating layer; wherein, when 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 value of the roughness Rz of the surface of the insulating layer close to the shielding layer to the adhesive weight parameter of the adhesive film layer is 5 - 200. The electromagnetic shielding film and the circuit board provided by the present invention can simultaneously have the following advantages: the phenomenon of delamination is not likely to occur between the insulating layer and the shielding layer, and the circuit board has a good appearance after being laminated to the circuit board.

Description

Technical Field

[0001] The present invention relates to the field of electronic technologies, 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, their internal components are rapidly becoming high-frequency and high-speed. For example: in addition to the original audio transmission function, the camera function has become an essential function for mobile phones, and WLAN (Wireless Local Area Networks), GPS (Global Positioning System), and Internet access functions have been popularized. Coupled with the integration of future sensing components, the trend of components becoming high-frequency and high-speed is even more inevitable. The electromagnetic interference inside and outside 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 an insulating layer, a shielding layer, and an adhesive film layer. The shielding layer is formed on one side of the insulating layer, and the 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 interfering charges into the ground layer of the circuit board to achieve shielding.

[0005] The inventor of the present invention found the following technical problems in the process of implementing the present invention: during the process of laminating the existing electromagnetic shielding film onto the circuit board, 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. Moreover, the roughness of the side of the insulating layer close to the shielding layer is not ideal, resulting in poor bonding strength between the insulating layer and the shielding layer. When the electromagnetic shielding film is bent, delamination between the insulating layer and the shielding layer easily occurs. 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 simultaneously have the following advantages: it is not easy for delamination to occur between the insulating layer and the shielding layer, and the circuit board has a good appearance after being laminated onto the circuit board.

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

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

[0009] Wherein, when 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 surface of the insulating layer close to the shielding layer to the adhesive weight parameter of the adhesive film layer is 5 - 200.

[0010] As an improvement of the above solution, the roughness Rz of the surface of the insulating layer close to the shielding layer is 0.09 - 14.68 micrometers.

[0011] As an improvement of the above solution, the roughness Rz of the surface of the insulating layer close to the shielding layer is 2 - 10 micrometers.

[0012] As an improvement of the above solution, the adhesive weight parameter of the adhesive film layer is 0.01 - 1 gram per square decimeter.

[0013] As an improvement of the above solution, the ratio of the roughness Rz of the surface of the insulating layer close to the shielding layer to the thickness of the shielding layer is 1.25 - 65.

[0014] As an improvement of the above solution, the electromagnetic shielding film further includes a carrier layer; the carrier layer is disposed on the surface of the insulating layer away from the shielding layer.

[0015] As an improvement of the above solution, the insulating layer is formed on one surface of the carrier layer; the ratio of the roughness Rz of the surface of the carrier layer to the thickness of the insulating layer is 0.3 - 3.

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

[0017] As an improvement of 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, which includes a circuit board body and the electromagnetic shielding film described in any of the above solutions; the electromagnetic shielding film is laminated with the circuit board body through the adhesive film layer; one 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.

[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] When laminating the electromagnetic shielding film onto the circuit board, since the shielding layer is formed on one side of the insulating layer, and when the unit of the surface 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 surface roughness Rz of the side of the insulating layer close to the shielding layer to the adhesive weight parameter of the adhesive film layer is 5 - 200. This can improve the adhesion strength between the insulating layer and the shielding layer of the electromagnetic shielding film, avoid the phenomenon that the insulating layer and the shielding layer are prone to delamination when bending the electromagnetic shielding film. Moreover, this can also enable the adhesive in the adhesive film layer to be effectively accommodated by the side of the shielding layer far from the insulating 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. Thus, the circuit board after laminating the shielding film can have a good appearance. In summary, the embodiments of the present invention can simultaneously have the following advantages: the insulating layer and the shielding layer are not prone to delamination, and the circuit board has a good appearance after being laminated onto the circuit board. 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 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.

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

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

[0028] 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 base part; 61. Conductive spike part; 7. Circuit board body. Detailed implementation manners

[0029] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. 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.

[0030] In the description of the specification and claims, it should be understood that the orientation or positional relationship indicated by the terms "upper", "lower", "left", "right", "front", "rear", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the embodiments of the present invention, rather than indicating or implying that the device or component referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the embodiments of the present invention.

[0031] In addition, the terms first, second, etc. in the specification and claims are only used for the purpose of distinguishing the description of the same technical features, and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity of the 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.

[0032] See Figure 1 , an embodiment of the present invention provides an electromagnetic shielding film, which includes an insulating layer 2, a shielding layer 3 and an adhesive film layer 4;

[0033] The shielding layer 3 is formed on one surface of the insulating layer 2, and the adhesive film layer 4 is disposed on the surface of the shielding layer 3 away from the insulating layer 2;

[0034] 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 value of the roughness Rz of the surface of the insulating layer 2 close to the shielding layer 3 to the adhesive weight parameter of the adhesive film layer 4 is 5-200.

[0035] Among them, the insulating layer 2 can effectively electrically isolate the shielding layer 3 from the outside world, thereby ensuring the electromagnetic shielding effect of the shielding layer 3. The shielding layer 3 plays the role of electromagnetic shielding. In addition, the electromagnetic shielding film can be adhered to the circuit board through the adhesive film layer 4.

[0036] It can be understood that one side of the insulating layer 2 where the shielding layer 3 is formed has a certain roughness. When the shielding layer 3 is formed on one side of the insulating layer 2, since the thickness of the shielding layer 3 is constant, the shielding layer 3 will follow the uneven surface of the insulating layer 2, so that one side of the shielding layer 3 close to the adhesive film layer 4 has a certain roughness.

[0037] In the embodiment of the present invention, when the electromagnetic shielding film is pressed onto the circuit board, since the shielding layer 3 is formed on one side of the insulating layer 2, and under the condition that the unit of the roughness Rz is micrometer and the unit of the adhesive weight parameter of the adhesive film layer 4 is g / dm², the ratio of the roughness Rz of the side of the insulating layer 2 close to the shielding layer 3 to the adhesive weight parameter of the adhesive film layer 4 is 5 - 200. This can improve the bonding strength between the insulating layer 2 and the shielding layer 3 of the electromagnetic shielding film, avoid the phenomenon that the insulating layer 2 and the shielding layer 3 are easily delaminated when the electromagnetic shielding film is bent, and moreover, this can also enable the adhesive in the adhesive film layer 4 to be effectively accommodated by the side of the shielding layer 3 away from the insulating layer 2, 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. Thus, the circuit board after pressing the shielding film can have a good appearance. In summary, the embodiment of the present invention can simultaneously have the following advantages: the insulating layer 2 and the shielding layer 3 are not easily delaminated, and the circuit board has a good appearance after being pressed onto the circuit board.

[0038] Exemplarily, the adhesive weight parameter of the adhesive film layer 4 is 0.01 - 1 g / dm².

[0039] In this embodiment, when the electromagnetic shielding film is laminated onto the circuit board, the adhesive film layer 4 with an adhesive weight of 0.01 - 1 gram per square decimeter can be effectively pierced by the side of the shielding layer 3 away from the insulating layer 2, enabling the shielding layer 3 to be electrically connected to the ground layer of the circuit board. This can effectively conduct the interfering charges of the shielding layer 3 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 gram per square decimeter can effectively maintain the bonding strength between the electromagnetic shielding film and the circuit board, making it less likely for the electromagnetic shielding film and the circuit board to experience delamination. 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 gram per square decimeter.

[0040] Exemplarily, the roughness Rz of the side of the insulating layer 2 close to the shielding layer 3 is 0.09 - 14.68 micrometers.

[0041] 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. Additionally, the test standard for the roughness Rz is ISO25178.

[0042] In this embodiment, the shielding layer 3 is formed on one side of the insulating layer 2, and the roughness Rz of the side of the insulating layer 2 close to the shielding layer 3 is 0.09 - 14.68 micrometers. During the process of forming the shielding layer 3 on this side of the insulating layer 2, the shielding layer 3 can follow the undulations of this side of the insulating layer 2, making it easy for the side of the shielding layer 3 away from the insulating layer 2 to have a roughness capable of piercing the adhesive film layer 4, thereby enabling the shielding layer 3 to be effectively electrically connected to the ground layer of the circuit board. As an example, the roughness Rz of the side of the insulating layer 2 close to the shielding layer 3 is 0.09, 0.50, 1.00, 5.00, 7.385, 10.00, 14.68.

[0043] Specifically, the roughness Rz of the side of the insulating layer 2 close to the shielding layer 3 is 2 - 10 micrometers.

[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 side of the shielding layer 3 close to the film layer 4 to the thickness of the film layer 4 is 0.1-9. Therefore, when the electromagnetic shielding film is pressed onto the circuit board, the side of the shielding layer 3 close to the film layer 4 can effectively pierce the film layer 4 and be electrically connected to the ground layer of the circuit board, thereby effectively introducing the interference charge of the shielding layer 3 into the ground layer of the circuit board, thereby effectively improving the shielding effectiveness of the electromagnetic shielding layer 3.

[0046] The material used for the adhesive film layer 4 is selected from the following: modified epoxy resin, acrylic, modified rubber, modified thermoplastic polyimide. It can be understood that in order to ensure that the shielding layer 3 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. The metal shielding layer includes a single metal shielding layer and / or an alloy shielding layer; 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, the ratio of the roughness Rz of the side of the insulating layer 2 close to the shielding layer 3 to the thickness of the shielding layer 3 is 1.25-65. In 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, so that the shielding layer 3 can rise and fall with the rough surface of the insulating layer 2, and it can be easy to make the side of the shielding layer 3 away from the insulating layer 2 have a roughness that can pierce the adhesive film layer 4, so that the shielding layer 3 can be effectively electrically connected to the ground layer of the circuit board.

[0048] In the above embodiment, further, the shielding layer 3 is provided with through holes penetrating the upper and lower surfaces thereof. By providing the through holes penetrating the shielding layer 3, 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 3, 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 through-holes per square centimeter on the shielding layer 3 is 1 - 1000. By setting the number of through-holes to 1 - 1000, it is ensured that the volatiles in the adhesive film layer 4 can exhaust through a sufficient number of the through-holes at high temperatures, thereby avoiding the difficulty of discharging the 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 caused by the foaming and delamination of the electromagnetic shielding film, so as to ensure that the electromagnetic shielding film is grounded and effectively conducts the interfering charges.

[0051] In this embodiment, the ratio of the sum of the cross-sectional areas of all the through-holes in the shielding layer 3 per square centimeter to the cross-sectional area of the shielding layer where the cross-section is located is 1% - 70%. By making the ratio of the sum of the cross-sectional areas of all the through-holes in the shielding layer 3 per square centimeter to the cross-sectional area of the shielding layer where the cross-section is located 1% - 70%, while ensuring that the volatile gases generated in the adhesive film layer 4 can effectively exhaust through the through-holes of the shielding layer 3, the electromagnetic shielding effect of the shielding layer 3 will not be affected due to excessive through-hole quantity.

[0052] In the above embodiment, further, referring to Figure 2 , the electromagnetic shielding film further includes a carrier layer 1; the carrier layer 1 is disposed on the side 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 the base film for forming the insulating layer 2, that is: the insulating layer 2 can be formed on one side of the carrier layer 1.

[0053] Specifically, the insulating layer 2 is formed on one side of the carrier layer 1; the ratio of the roughness Rz of the one side of the carrier layer 1 to the thickness of the insulating layer 2 is 0.3 - 3. Among them, during the process of forming the insulating layer 2 on one side of the carrier layer 1, the ratio of the roughness Rz of the one side 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 one side of the carrier layer 1, and it is easy to make the side of the insulating layer 2 away from the carrier layer 1 have a certain roughness, so that finally the side of the shielding layer 3 away from the insulating layer 2 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.

[0054] In the above embodiment, further, referring to Figure 3 , a conductive protrusion 6 is provided on the side 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.

[0055] Specifically, the number of conductive protrusions 6 with a longitudinal height greater than 5 μm on the shielding layer 3 per square centimeter on one side thereof 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.

[0056] In the embodiment of the present invention, the conductive protrusions 6 can be distributed regularly or irregularly on the side 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 side of the shielding layer 3 of the conductive matrix portion close to the adhesive film layer 4. 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.

[0057] Exemplarily, referring to Figure 4 , the conductive protrusion 6 includes a conductive matrix portion 60 and at least one conductive spike portion 61; the conductive matrix portion 60 extends outward from the one side of the shielding layer 3, and at least one conductive spike portion 61 extends outward from the surface of the conductive matrix portion 60. Among them, the conductive spike portion 61 extending from the surface of the conductive matrix 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.

[0058] Specifically, the protruding 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.

[0059] Preferably, the conductive protrusion 6 can have a certain distance from the outer surface of the adhesive film layer 4, can 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 can be a flat surface without undulations, or can also be an uneven surface with gentle undulations.

[0060] It should be noted that Figure 3 and Figure 4 the shapes of the conductive protrusions 6 in are only exemplary. Due to differences in process means and parameters, the conductive protrusions 6 can also be in other shapes such as cluster shape, icicle shape, stalactite shape, dendritic shape, etc. In addition, the conductive protrusions 6 in the embodiment of the present invention are not limited by the drawings and the above shapes. As long as the conductive protrusions 6 have the functions of piercing and conducting electricity, they are all within the protection scope of the present invention.

[0061] As another example, the conductive protrusion 6 may be composed of one or more conductive particles. The conductive particles include one or more of metal particles, carbon nanotube particles, and ferrite particles. In addition, the metal particles include single-metal particles and / or alloy particles; wherein, the single-metal particles are made of any one of materials such as aluminum, titanium, zinc, iron, nickel, chromium, cobalt, copper, silver, and gold, and the alloy particles are made of any two or more of materials such as aluminum, titanium, zinc, iron, nickel, chromium, cobalt, copper, silver, and gold. It should be noted that the conductive protrusion 6 may be the same as or different from the material of the shielding layer 3.

[0062] It should be noted that the shielding layer 3 of 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 the surface 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 the surface of each layer of the shielding layer 3 close to the adhesive film layer 4. In addition, according to the needs of actual production and application, the shielding layer 3 of this embodiment may be set in a mesh shape, a foamed shape, etc.

[0063] 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 improving the shielding effectiveness.

[0064] Please refer to Figure 5 As shown, the electromagnetic shielding film in this embodiment further includes a protective film layer 5, and the protective film layer 5 is provided on the surface of the adhesive film layer 4 away from the shielding layer 3. Since the protective film layer 5 has a protective effect, it ensures 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.

[0065] 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:

[0066] 1) Prepare the carrier layer 1;

[0067] 2) Form an insulating layer 2 on one side of the carrier layer 1;

[0068] 3) Form a shielding layer 3 on the side of the insulating layer 2 away from the carrier layer 1;

[0069] 4) Coat glue on the side of the shielding layer 3 away from the insulating layer 2 to form an adhesive film layer 4;

[0070] 5) Bond a protective film layer 5 on the side of the adhesive film layer 4 away from the shielding layer 3.

[0071] For the convenience of understanding the above invention solution, here, five specific embodiments are provided and these specific embodiments are tested:

[0072] Embodiment 1:

[0073] An electromagnetic shielding film, comprising an insulating layer, a shielding layer and an adhesive film layer; the shielding layer is formed on one side of the insulating layer, and the adhesive film layer is provided on the side of the shielding layer away from the insulating layer; wherein, the roughness Rz of the side of the insulating layer close to the shielding layer is 0.09 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 insulating layer close to the shielding layer to the adhesive weight parameter of the adhesive film layer is 9.

[0074] Test result: After testing, the separation tensile force between the insulating layer and the shielding layer of the electromagnetic shielding film in this embodiment is greater than 12.23 N / cm, and the length of the glue overflow of the adhesive film layer after the electromagnetic shielding film in this embodiment is pressed onto the circuit board is less than 78 μm.

[0075] It can be seen that by applying the electromagnetic shielding film of this embodiment, the bonding strength between the insulating layer and the shielding layer of the electromagnetic shielding film can be improved, the phenomenon that the insulating layer and the shielding layer are prone to delamination when the electromagnetic shielding film is bent can be avoided, and after the electromagnetic shielding film is pressed onto 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.

[0076] Embodiment 2:

[0077] An electromagnetic shielding film, comprising an insulating layer, a shielding layer and an adhesive film layer; the shielding layer is formed on one side of the insulating layer, and the adhesive film layer is provided on the side of the shielding layer away from the insulating layer; wherein, the roughness Rz of the side of the insulating layer close to the shielding layer is 14.68 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 insulating layer close to the shielding layer to the adhesive weight parameter of the adhesive film layer is 14.68.

[0078] Test results: After testing, the separation tensile force between the insulating layer and the shielding layer of the electromagnetic shielding film in this embodiment is greater than 16.78 N / cm, and the length of the glue overflow of the glue film layer after the electromagnetic shielding film in this embodiment is pressed onto the circuit board is less than 90 μm.

[0079] Thus, by applying the electromagnetic shielding film of this embodiment, the bonding strength between the insulating layer and the shielding layer of the electromagnetic shielding film can be improved, the phenomenon that the insulating layer and the shielding layer are prone to delamination when the electromagnetic shielding film is bent can be avoided, and after the electromagnetic shielding film is pressed onto the circuit board, the circuit board can also have a good appearance.

[0080] Embodiment 3:

[0081] An electromagnetic shielding film, comprising an insulating layer, a shielding layer and a glue film layer; the shielding layer is formed on one surface of the insulating layer, and the glue film layer is disposed on the surface of the shielding layer away from the insulating layer; wherein, the roughness Rz of the surface of the insulating layer close to the shielding layer is 2.5 microns, the glue weight parameter of the glue film layer is 0.5 g per square decimeter, and the ratio of the numerical values of the roughness Rz of the surface of the insulating layer close to the shielding layer and the glue weight parameter of the glue film layer is 5.

[0082] Test results: After testing, the separation tensile force between the insulating layer and the shielding layer of the electromagnetic shielding film in this embodiment is greater than 13.79 N / cm, and the length of the glue overflow of the glue film layer after the electromagnetic shielding film in this embodiment is pressed onto the circuit board is less than 73 μm.

[0083] Thus, by applying the electromagnetic shielding film of this embodiment, the bonding strength between the insulating layer and the shielding layer of the electromagnetic shielding film can be improved, the phenomenon that the insulating layer and the shielding layer are prone to delamination when the electromagnetic shielding film is bent can be avoided, and after the electromagnetic shielding film is pressed onto the circuit board, the circuit board can also have a good appearance.

[0084] Embodiment 4:

[0085] An electromagnetic shielding film, comprising an insulating layer, a shielding layer and a glue film layer; the shielding layer is formed on one surface of the insulating layer, and the glue film layer is disposed on the surface of the shielding layer away from the insulating layer; wherein, the roughness Rz of the surface of the insulating layer close to the shielding layer is 8.2 microns, the glue weight parameter of the glue film layer is 0.08 g per square decimeter, and the ratio of the numerical values of the roughness Rz of the surface of the insulating layer close to the shielding layer and the glue weight parameter of the glue film layer is 102.5.

[0086] Test results: After testing, the separation tensile force between the insulating layer and the shielding layer of the electromagnetic shielding film of this embodiment is greater than 9.8 N / cm, and the length of the glue overflow of the glue film layer after the electromagnetic shielding film of this embodiment is laminated to the circuit board is less than 62 μm.

[0087] It can be seen that by applying the electromagnetic shielding film of this embodiment, the bonding strength between the insulating layer and the shielding layer of the electromagnetic shielding film can be improved, the phenomenon that the insulating layer and the shielding layer are prone to delamination when the electromagnetic shielding film is bent can be avoided, and after the electromagnetic shielding film is laminated to the circuit board, the circuit board can also have a good appearance.

[0088] Embodiment Five:

[0089] An electromagnetic shielding film includes an insulating layer, a shielding layer and a glue film layer; the shielding layer is formed on one side of the insulating layer, and the glue film layer is arranged on the side of the shielding layer away from the insulating layer; wherein, the roughness Rz of the side of the insulating layer close to the shielding layer is 6 microns, the glue weight parameter of the glue film layer is 0.03 grams per square decimeter, and the ratio of the value of the roughness Rz of the side of the insulating layer close to the shielding layer to the glue weight parameter of the glue film layer is 200.

[0090] Test results: After testing, the separation tensile force between the insulating layer and the shielding layer of the electromagnetic shielding film of this embodiment is greater than 11.23 N / cm, and the length of the glue overflow of the glue film layer after the electromagnetic shielding film of this embodiment is laminated to the circuit board is less than 83 μm.

[0091] It can be seen that by applying the electromagnetic shielding film of this embodiment, the bonding strength between the insulating layer and the shielding layer of the electromagnetic shielding film can be improved, the phenomenon that the insulating layer and the shielding layer are prone to delamination when the electromagnetic shielding film is bent can be avoided, and after the electromagnetic shielding film is laminated to the circuit board, the circuit board can also have a good appearance.

[0092] The above numerical ratio of the roughness Rz to the glue weight parameter is only an example, and the numerical ratio can also be other numerical situations, such as 25, 75, 100, 125, 175, etc.

[0093] See Figure 6 , another embodiment of the present invention also provides a circuit board, which includes a circuit board body 7 and the electromagnetic shielding film described in any one of the above embodiments; the electromagnetic shielding film is laminated to the circuit board body 7 through the glue film layer 4; the side of the shielding layer 3 close to the glue film layer 4 pierces through the glue film layer 4 and is electrically connected to the ground layer of the circuit board body 7.

[0094] Preferably, the circuit board body 7 is one of a flexible single-sided board, a flexible double-sided board, a flexible multi-layer board, and a rigid-flex board.

[0095] In the embodiment of the present invention, when the electromagnetic shielding film is laminated with the circuit board body 7, the side of the shielding layer 3 close to the adhesive film layer 4 can pierce the adhesive film layer 4 and be connected to the ground layer of 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 thus realizing the introduction of the interference charges in the shielding layer 3 and the shielding layer 3 into the ground, avoiding the accumulation of interference charges to form an interference source and affecting the normal operation of the circuit board.

[0096] In the embodiment of the present invention, since the shielding layer 3 is formed on one side of the insulating layer 2, and when the unit of the roughness Rz is micrometers and the unit of the adhesive weight parameter is grams per square decimeter, the ratio of the roughness Rz of the side of the insulating layer 2 close to the shielding layer 3 to the adhesive weight parameter of the adhesive film layer 4 is 5 - 200. This can improve the bonding strength between the insulating layer 2 and the shielding layer 3 of the electromagnetic shielding film, avoid the delamination phenomenon between the insulating layer 2 and the shielding layer 3 easily occurring when the electromagnetic shielding film is bent. Moreover, this can also enable the adhesive in the adhesive film layer 4 to be effectively accommodated by the side of the shielding layer 3 away from the insulating layer 2, 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. Thus, the circuit board after laminating the shielding film can have a good appearance. In summary, the embodiment of the present invention can simultaneously have the following advantages: the delamination phenomenon between the insulating layer 2 and the shielding layer 3 is not easy to occur and it has a good appearance.

[0097] As described above, only the specific embodiments of the present invention are provided, 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, a shielding layer and an adhesive film layer; the shielding layer is formed on one surface of the insulating layer, and the adhesive film layer is disposed on the surface of the shielding layer away from the insulating layer; wherein, when the unit of roughness Rz is micron and the unit of adhesive weight parameter is g / dm², the ratio of the value of the roughness Rz of the surface of the insulating layer close to the shielding layer to the adhesive weight parameter of the adhesive film layer is 5 - 200, and the adhesive weight parameter of the adhesive film layer is 0.01 - 1 g / dm².

2. The electromagnetic shielding film according to claim 1, characterized in that, the roughness Rz of the surface of the insulating layer close to the shielding layer is 0.09 - 14.68 microns.

3. The electromagnetic shielding film according to claim 1, characterized in that, the roughness Rz of the surface of the insulating layer close to the shielding layer is 2 - 10 microns.

4. The electromagnetic shielding film according to claim 1, characterized in that, the ratio of the roughness Rz of the surface of the insulating layer close to the shielding layer to the thickness of the shielding layer is 1.25 - 65.

5. The electromagnetic shielding film according to claim 1, characterized in that, the electromagnetic shielding film further includes a carrier layer; the carrier layer is disposed on the surface of the insulating layer away from the shielding layer.

6. The electromagnetic shielding film according to claim 5, characterized in that, the insulating layer is formed on one surface of the carrier layer; the ratio of the roughness Rz of the one surface of the carrier layer to the thickness of the insulating layer is 0.3 - 3.

7. The electromagnetic shielding film according to claim 1, characterized in that, conductive protrusions are provided on the surface of the shielding layer close to the adhesive film layer.

8. The electromagnetic shielding film according to claim 1, characterized in that, the adhesive film layer includes an adhesive layer containing conductive particles; or, the adhesive film layer includes an adhesive layer without conductive particles.

9. A circuit board, characterized in that, it includes a circuit board body and the electromagnetic shielding film according to any one of claims 1 - 8; the electromagnetic shielding film is press - bonded to the circuit board body through the adhesive film layer; the surface 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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