Electromagnetic shielding film and circuit board

Abstract

The present invention relates to the field of electronic technology, and discloses an electromagnetic shielding film and a circuit board, wherein the electromagnetic shielding film comprises a shielding layer and an adhesive film layer; the adhesive film layer is arranged on one side of the shielding layer; the roughness Sdr of one side of the shielding layer close to the adhesive film layer is greater than 0.1%, and the adhesive weight of the adhesive film layer is 0.01-1 grams per square decimeter. The present invention can avoid the problem of adhesive overflow at the edge of the electromagnetic shielding film during the process of laminating the electromagnetic shielding film to the circuit board, and can effectively improve the shielding effectiveness of the electromagnetic shielding film.

Description

Technical Field

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

[0002] With the rapid development of the electronics industry, electronic products are further developing towards miniaturization, lightness, 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, LCD 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 interference shielding (EMI shielding). With the integration of functions of mobile phones and other communication devices, 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 a necessary 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 rapid high-frequency and high-speed components is even more inevitable. Driven by high frequency and high speed, the electromagnetic interference inside and outside the components, signal attenuation during transmission, insertion loss and jitter problems are becoming increasingly serious.

[0004] At present, the electromagnetic shielding film commonly used in existing circuit boards includes a shielding layer and an adhesive film layer. The side of the shielding layer close to the adhesive film layer is a rough surface, and the rough surface is used to pierce the adhesive film layer to contact and connect with the ground layer of the circuit board, so as to introduce the interference charge into the ground layer of the circuit board, thereby achieving shielding. However, the inventors found in the process of implementing the present invention that there are the following technical problems in the prior art: in the process of pressing the electromagnetic shielding film of the above structure onto the circuit board, there is a problem that the rough surface of the shielding layer cannot pierce the adhesive film layer well, resulting in poor effective connectivity between the shielding layer and the ground layer of the circuit board, resulting in poor electromagnetic shielding performance, and there is also a problem that the adhesive in the adhesive film layer easily overflows from the edge between the electromagnetic shielding film and the circuit board. Summary of the invention

[0005] 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 avoid the problem of glue overflow at the edge of the electromagnetic shielding film during pressing onto the circuit board, and can effectively improve the shielding effectiveness of the electromagnetic shielding film.

[0006] In order to achieve the above-mentioned object, an embodiment of the present invention provides an electromagnetic shielding film, which includes a shielding layer and an adhesive film layer;

[0007] The adhesive film layer is arranged on one side of the shielding layer;

[0008] The roughness Sdr of a side of the shielding layer close to the adhesive film layer is greater than 0.1%, and the adhesive gram weight of the adhesive film layer is 0.01-1 gram per square decimeter.

[0009] As an improvement of the above solution, the roughness Sdr of a side of the shielding layer close to the adhesive film layer is 0.1%-8000%.

[0010] As an improvement of the above solution, the roughness Sdr of a side of the shielding layer close to the adhesive film layer is 1%-2000%.

[0011] As an improvement of the above solution, the roughness Sdr of a side of the shielding layer close to the adhesive film layer is 20%-600%.

[0012] As an improvement of the above solution, the roughness Rz of a side of the shielding layer close to the adhesive film layer is 0.5-20 microns.

[0013] As an improvement of the above solution, the ratio of the arithmetic mean thickness of the adhesive film layer to the roughness Rz of a side of the shielding layer close to the adhesive film layer is greater than or equal to 1 / 4.

[0014] As an improvement of the above solution, the electromagnetic shielding film further comprises an insulating layer; the insulating layer is arranged on a side of the shielding layer away from the adhesive film layer, and a roughness Sdr of a side of the insulating layer close to the shielding layer is greater than 0.1%.

[0015] As an improvement of the above solution, the roughness Sdr of a side of the insulating layer close to the shielding layer is 0.1%-96%.

[0016] As an improvement of the above solution, the roughness Rz of a side of the insulating layer close to the shielding layer is 0.09-14.68 microns.

[0017] As an improvement of the above solution, the electromagnetic shielding film further comprises a carrier layer; the carrier layer is arranged on a side of the insulating layer away from the shielding layer.

[0018] 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 not containing conductive particles.

[0019] As an improvement of the above solution, a conductive protrusion is provided on a side of the shielding layer close to the adhesive film layer.

[0020] As an improvement of the above solution, the ratio of the arithmetic mean thickness of the adhesive film layer to the protrusion height of the conductive protrusion is greater than or equal to 2 / 7.

[0021] As an improvement of the above scheme, the conductive protrusion includes a conductive base portion and at least one conductive spike portion formed integrally with the conductive base portion; the conductive base portion extends outward from the one surface of the shielding layer, and at least one conductive spike portion extends outward from the surface of the conductive base portion.

[0022] In order to solve the same technical problem, another embodiment of the present invention also provides a circuit board, which includes a circuit board body and the electromagnetic shielding film described in any of the above schemes; the electromagnetic shielding film is pressed onto the circuit board body through the adhesive film layer; the side of the shielding layer close to the adhesive film layer pierces the adhesive film layer and is electrically connected to the ground layer of the circuit board body.

[0023] Compared with the prior art, the electromagnetic shielding film and circuit board provided in the embodiments of the present invention have at least one of the following beneficial effects:

[0024] By limiting the roughness Sdr of the side of the shielding layer close to the adhesive film layer to be greater than 0.1% and the adhesive weight of the adhesive film layer to be 0.01-1 g / m2, when the electromagnetic shielding film is pressed onto the circuit board, the side of the shielding layer close to the adhesive film layer can smoothly pierce the adhesive film layer, so that the shielding layer can be in contact with the ground layer of the circuit board, and then the interference charge of the shielding layer can be effectively introduced into the ground layer of the circuit board, effectively improving the shielding effectiveness of the electromagnetic shielding film. And when the electromagnetic shielding film is pressed onto the circuit board, the adhesive substance in the adhesive film layer with an adhesive weight of 0.01-1 g / m2 can be squeezed into the concave position of the side of the shielding layer close to the adhesive film layer, so that it is not easy for the adhesive substance to move to the edge of the circuit board in large quantities, resulting in obvious adhesive overflow at the edge between the electromagnetic shielding film and the circuit board, so that the circuit board after the shielding film is pressed has a good appearance. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solution of the present invention, the drawings required for use in the implementation mode will be briefly introduced below. Obviously, the drawings described below are only some implementation modes of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0026] Figure 1 is a schematic structural diagram of a first electromagnetic shielding film provided by an embodiment of the present invention;

[0027] Figure 2is a schematic structural diagram of a second electromagnetic shielding film provided by an embodiment of the present invention;

[0028] Figure 3 is a schematic structural diagram of a third electromagnetic shielding film provided by an embodiment of the present invention;

[0029] Figure 4 It is a schematic structural diagram of a third electromagnetic shielding film provided by an embodiment of the present invention.

[0030] Notes on the accompanying drawings: 1. Carrier layer; 2. Insulation layer; 3. Shielding layer; 4. Film layer; 6. Conductive protrusions. DETAILED DESCRIPTION

[0031] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] In the description of the specification and claims, it is necessary to understand that the terms "upper", "lower", "left", "right", "front", "back", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the drawings, and are 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 cannot be understood as a limitation on the embodiments of the present invention.

[0033] In addition, the terms first, second, etc. in the specification and claims are only used for the purpose of describing the same technical features, and are not to be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated, nor necessarily describing an order or time sequence. The terms are interchangeable where appropriate. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of the features.

[0034] See also Figure 1 An embodiment of the present invention provides an electromagnetic shielding film, which includes a shielding layer 3 and a film layer 4; the film layer 4 is arranged on one surface of the shielding layer 3; the roughness Sdr of the side of the shielding layer 3 close to the film layer 4 is greater than 0.1%, and the gram weight of the film layer 4 is 0.01-1 grams per square decimeter.

[0035] By limiting the roughness Sdr of the side of the shielding layer close to the adhesive film layer to be greater than 0.1% and the adhesive weight of the adhesive film layer to be 0.01-1 g / m2, when the electromagnetic shielding film is pressed onto the circuit board, the side of the shielding layer close to the adhesive film layer can smoothly pierce the adhesive film layer, so that the shielding layer can be in contact with the ground layer of the circuit board, and then the interference charge of the shielding layer can be effectively introduced into the ground layer of the circuit board, effectively improving the shielding effectiveness of the electromagnetic shielding film. And when the electromagnetic shielding film is pressed onto the circuit board, the adhesive substance in the adhesive film layer with an adhesive weight of 0.01-1 g / m2 can be squeezed into the concave position of the side of the shielding layer close to the adhesive film layer, so that it is not easy for the adhesive substance to move to the edge of the circuit board in large quantities, resulting in obvious adhesive overflow at the edge between the electromagnetic shielding film and the circuit board, so that the circuit board after the shielding film is pressed has a good appearance.

[0036] Furthermore, in order to make the shielding layer 3 and the ground layer of the circuit board have a better effective electrical connection and the circuit board after the shielding film is pressed has a better appearance, the roughness Sdr of the side of the shielding layer 3 close to the adhesive film layer can be 0.1%-8000%. Preferably, the roughness Sdr of the side of the shielding layer 3 close to the adhesive film layer can be 1%-2000%. More preferably, the roughness Sdr of the side of the shielding layer 3 close to the adhesive film layer can be 20%-600%.

[0037] It can be understood that the roughness Sdr indicates how much the expanded area (surface area) of the region increases relative to the area of ​​the defined region. Among them, the Sdr of a completely flat surface is 0. For example, the roughness Sdr of one side of the shielding layer 3 is 20%, which means that the area of ​​the test area of ​​the shielding film increases by 20% after it is expanded to be flat compared to before expansion. The test standard for roughness Sdr is ISO25178.

[0038] 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.

[0039] Preferably, the outer surface of the adhesive film layer 4 may be a flat surface without undulations, or may be an uneven surface with gentle undulations.

[0040] In this embodiment, the roughness Rz of the side of the shielding layer 3 close to the adhesive film layer 4 is 0.5-20 microns. The rough surface of the shielding layer 3 with a roughness Rz of 0.5-20 microns can effectively pierce the adhesive film layer 4 with an adhesive weight of 0.01-1 grams per square decimeter, so that the shielding layer 3 is in contact with the ground layer of the circuit board.

[0041] Among them, Rz is 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.

[0042] Furthermore, the inventors have discovered through research that the ratio of the arithmetic mean thickness of the adhesive film layer 4 to the roughness Rz of the side of the shielding layer 3 close to the adhesive film layer 4 is greater than or equal to 1 / 4, so that the side of the shielding layer 3 can effectively pierce the adhesive film layer 4 and connect to the ground layer of the circuit board.

[0043] It is understandable that the arithmetic mean thickness of the adhesive film layer 4 can be measured by measuring the thickness of the adhesive film layer 4 at a certain number of different locations (e.g., 10 different test points) on the adhesive film layer 4, and then taking the average value to obtain the arithmetic mean thickness of the adhesive film layer 4. When taking the test points, they can be taken at equal intervals or at unequal intervals, which is not specifically limited here.

[0044] See also Figure 2 In the above embodiment, further, the electromagnetic shielding film further includes an insulating layer 2; the insulating layer 2 is arranged on the side of the shielding layer 3 away from the adhesive film layer 4. 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.

[0045] Exemplarily, the side of the insulating layer 2 close to the shielding layer 3 is a rough surface with a certain roughness, which can improve the bending resistance of the insulating layer 2, thereby improving the bending resistance of the electromagnetic shielding film. In addition, when the shielding layer 3 is formed on this side of the insulating layer 2, the shielding layer 3 will follow the roughness fluctuations of the surface of the insulating layer 2, so that the side of the shielding layer 3 away from the insulating layer can also be formed into a rough surface with a certain roughness.

[0046] Specifically, the roughness Sdr of the side of the insulating layer 2 close to the shielding layer 3 is greater than 0.1%, and preferably, the roughness Sdr of the side of the insulating layer 2 close to the shielding layer 3 is 0.1%-96%. Moreover, when the shielding layer 3 is formed on the rough surface of the insulating layer 2, it is easy for the shielding layer 3 to also have a rough surface with a certain roughness, so that the rough surface of the shielding layer 3 can better pierce the adhesive film layer 4.

[0047] Specifically, the roughness Rz of one side of the insulating layer 2 close to the shielding layer 3 is 0.09-14.68 microns. When the shielding layer 3 is formed on the rough surface of the insulating layer 2, it is easy for the shielding layer 3 to also have the above-mentioned rough surface, so that the rough surface of the shielding layer 3 can better pierce the adhesive film layer 4.

[0048] See also Figure 3 Furthermore, the electromagnetic shielding film further comprises 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 or collision. In addition, the carrier layer 1 can be used as a 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.

[0049] See also Figure 4 As an example, 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 that the electromagnetic shielding film is electrically connected to the ground layer of the circuit board.

[0050] Exemplarily, the material of the conductive protrusion 6 and the shielding layer 3 may be the same or different, which is not specifically limited here.

[0051] Specifically, the ratio of the arithmetic mean thickness of the adhesive film layer 4 to the protrusion height of the conductive protrusion 6 is greater than or equal to 2 / 7. This can more effectively pierce the adhesive film layer 4, thereby further ensuring that the electromagnetic shielding film is electrically connected to the ground layer of the circuit board.

[0052] Specifically, the number of conductive protrusions 6 with a protrusion height greater than 3 um per square centimeter on one side of the shielding layer 3 is 1-1000. This can more effectively pierce the adhesive film layer 4, thereby further ensuring that the electromagnetic shielding film is electrically connected to the ground layer of the circuit board.

[0053] The protrusion height of the conductive protrusion 6 is measured as follows: the vertical distance h between the root of the conductive protrusion 6 and the top of the conductive protrusion 6 is the protrusion height of the conductive protrusion 6 .

[0054] In the above embodiment, further, the conductive protrusion 6 includes a conductive base portion (not shown) and at least one conductive spike portion (not shown); the conductive base portion extends outward from the one surface of the shielding layer 3, and at least one conductive spike portion extends outward from the surface of the conductive base portion. The conductive spike portion extending from the surface of the conductive base portion 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 extension length of the conductive spike portion is 1-5 microns, so that the conductive spike portion can effectively pierce the adhesive film layer 4, thereby further ensuring that the electromagnetic shielding film is electrically connected to the ground layer of the circuit board. The extension length of the conductive spike portion can be measured as follows: the distance between one end of the conductive spike portion close to the conductive base portion and one end of the conductive spike portion away from the conductive base portion is the extension length of the conductive spike portion.

[0056] In the embodiment of the present invention, the plurality of conductive protrusions 6 may be regularly or irregularly distributed on the surface of the shielding layer 3 close to the adhesive film layer 4; wherein, the plurality of conductive protrusions 6 are regularly distributed on the surface of the shielding layer 3 close to the adhesive film layer 4, which means that the plurality of conductive protrusions 6 have the same shape and are evenly distributed on the surface of the shielding layer 3 close to the adhesive film layer 4; the plurality of conductive protrusions 6 are irregularly distributed on the surface of the shielding layer 3 close to the adhesive film layer 4, which means that the plurality of conductive protrusions 6 have different shapes and are randomly distributed on the surface of the shielding layer 3 close to the adhesive film layer 4. In this embodiment, the conductive protrusions 6 have the same shape, and / or the spacing between the conductive protrusions 6 is the same. Preferably, the plurality of conductive protrusions 6 have the same shape, 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. In addition, the surface of the shielding layer 3 away from the adhesive film layer 4 may be a surface of any shape, for example, a flat surface, an undulating non-flat surface, or other rough surfaces. The drawings of the present invention only illustrate that the side of the shielding layer 3 away from the adhesive film layer 4 is a flat surface, but any other shapes are within the protection scope of the present invention.

[0057] Exemplarily, at least one side of the shielding layer 3 has an undulating structure, for example, the side of the shielding layer 3 close to the adhesive film layer 4 has an undulating structure. This can improve the bending performance of the shielding layer 3, enhance the ability of the side of the shielding layer 3 close to the adhesive film layer 4 to pierce the adhesive film layer 4, and also improve the adhesive capacity of this side of the shielding layer 3.

[0058] Preferably, the conductive protrusion 6 may be composed of one or more clusters of conductive particles (not shown). Due to differences in process means and parameters, the conductive particles may be in other shapes such as clusters, hanging ice, stalactites, and dendrites. In addition, the conductive particles in the embodiments of the present invention are not limited to the shapes shown in the figure and described above. As long as the conductive particles have piercing and conductive functions, they are within the protection scope of the present invention.

[0059] In an embodiment of the present invention, the conductor 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 aluminum, titanium, zinc, iron, nickel, chromium, cobalt, copper, silver and gold, and the alloy particles are made of any two or more of aluminum, titanium, zinc, iron, nickel, chromium, cobalt, copper, silver and gold. It should be noted that the conductor particles may be the same as the material of the shielding layer 3, or may be different.

[0060] It should be noted that the shielding layer 3 of this embodiment can be a single-layer structure or a multi-layer structure. When the shielding layer 3 is a single-layer, the surface of the shielding layer close to the adhesive film layer 4 can be provided with conductor particles; when the shielding layer 3 is a multi-layer, each shielding layer can also be provided with conductor particles on its surface 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 can be set to a grid shape, a foam shape, etc.

[0061] 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. The adhesive film layer 4 includes an adhesive layer containing conductive particles to improve the conductivity of the adhesive film layer 4, thereby further ensuring the connection between the electromagnetic shielding film and the ground layer of the circuit board. Of course, the adhesive film layer 4 may include an adhesive layer without conductive particles to reduce the insertion loss of the circuit board with the electromagnetic shielding film, thereby improving the anti-bending property of the circuit board while improving the shielding effectiveness.

[0062] It should be noted that the conductive particles can be conductive particles separated from each other or large-particle conductive particles aggregated together; when the conductive particles are conductive particles separated from each other, the grounding conductivity of the adhesive film layer 4 can be further improved; and when the conductive particles are large-particle conductive particles aggregated together, the piercing strength can be increased.

[0063] The electromagnetic shielding film in this embodiment also includes a protective film layer (not shown), which is arranged on the side of the adhesive film layer 4 away from the shielding layer 3. Since the protective film layer has a protective effect, it ensures that the insulating layer 2 is not scratched or damaged during use, thereby maintaining the high shielding efficiency of the shielding layer 3. Among them, the protective film layer includes a PPS film layer, a PEN film layer, a polyester film layer, a polyimide film layer, a film layer formed after epoxy resin ink is cured, a film layer formed after polyurethane ink is cured, a film layer formed after modified acrylic resin is cured, or a film layer formed after polyimide resin is cured.

[0064] 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, the method for preparing the electromagnetic shielding film includes:

[0065] 1) preparing a carrier layer 1;

[0066] 2) forming an insulating layer 2 on one surface of the carrier layer 1;

[0067] 3) forming a shielding layer 3 on a surface of the insulating layer 2 away from the carrier layer 1;

[0068] 4) applying glue on the side of the shielding layer 3 away from the insulating layer 2 to form a glue film layer 4;

[0069] 5) A protective film layer is attached to the side of the adhesive film layer 4 away from the shielding layer 3 .

[0070] To facilitate the understanding of the above invention scheme, the following five specific implementation modes are provided and tested:

[0071] Embodiment 1:

[0072] An electromagnetic shielding film comprises a shielding layer 3 and an adhesive film layer 4; the adhesive film layer 4 is arranged on one surface of the shielding layer 3; the roughness Sdr of one surface of the shielding layer 3 close to the adhesive film layer 4 is 0.1%, and the adhesive gram weight parameter of the adhesive film layer 4 is 0.01 grams per square decimeter.

[0073] Test results: After testing, the length of the glue overflow from the edge of the electromagnetic shielding film of this embodiment during the process of pressing it onto the circuit board is less than 67 microns, and the grounding resistance between the shielding layer 3 and the ground layer of the circuit board is less than 75mΩ. Resistance test description: Select a test board (a circuit board designed for simulation test), where the window (the window is circular) on the test board is 1mm in size, and the distance between the two windows is 1.5mm. Attach the shielding film to the test board, and then use the TH2512 intelligent DC low resistance tester for testing. It can be understood that when the grounding resistance between the shielding layer 3 and the ground layer of the circuit board is less than 1Ω, it can be said that the shielding layer 3 and the ground layer of the circuit board can be effectively electrically connected.

[0074] It can be seen that by applying the electromagnetic shielding film of this embodiment, the problem of glue overflow at the edge of the electromagnetic shielding film during pressing onto the circuit board can be effectively avoided, the shielding layer and the ground layer of the circuit board can be effectively electrically connected, and the shielding effectiveness of the electromagnetic shielding film can be effectively improved.

[0075] Embodiment 2:

[0076] An electromagnetic shielding film comprises a shielding layer 3 and an adhesive film layer 4; the adhesive film layer 4 is arranged on one surface of the shielding layer 3; the roughness Sdr of one surface of the shielding layer 3 close to the adhesive film layer 4 is 0.1%, and the adhesive gram weight parameter of the adhesive film layer 4 is 1 gram per square decimeter.

[0077] Test results: After testing, the length of the glue overflow from the edge of the electromagnetic shielding film of this embodiment during the pressing process to the circuit board is less than 430 microns, and the grounding resistance between the shielding layer 3 and the ground layer of the circuit board is less than 390mΩ. The resistance testing method is the same as that of Example 1.

[0078] It can be seen that by applying the electromagnetic shielding film of this embodiment, the problem of glue overflow at the edge of the electromagnetic shielding film during pressing onto the circuit board can be effectively avoided, the shielding layer and the ground layer of the circuit board can be effectively electrically connected, and the shielding effectiveness of the electromagnetic shielding film can be effectively improved.

[0079] Embodiment three:

[0080] An electromagnetic shielding film comprises a shielding layer 3 and an adhesive film layer 4; the adhesive film layer 4 is arranged on one surface of the shielding layer 3; the roughness Sdr of one surface of the shielding layer 3 close to the adhesive film layer 4 is 560%, and the adhesive gram weight parameter of the adhesive film layer 4 is 0.01 grams per square decimeter.

[0081] Test results: After testing, the length of the glue overflow from the edge of the electromagnetic shielding film of this embodiment during the pressing process to the circuit board is less than 26 microns, and the grounding resistance between the shielding layer 3 and the ground layer of the circuit board is less than 43mΩ. The resistance testing method is the same as that of Example 1.

[0082] It can be seen that by applying the electromagnetic shielding film of this embodiment, the problem of glue overflow at the edge of the electromagnetic shielding film during pressing onto the circuit board can be effectively avoided, the shielding layer and the ground layer of the circuit board can be effectively electrically connected, and the shielding effectiveness of the electromagnetic shielding film can be effectively improved.

[0083] Embodiment 4:

[0084] An electromagnetic shielding film comprises a shielding layer 3 and an adhesive film layer 4; the adhesive film layer 4 is arranged on one surface of the shielding layer 3; the roughness Sdr of one surface of the shielding layer 3 close to the adhesive film layer 4 is 560%, and the adhesive gram weight parameter of the adhesive film layer 4 is 1 gram per square decimeter.

[0085] Test results: After testing, the length of the glue overflow from the edge of the electromagnetic shielding film of this embodiment during the pressing process to the circuit board is less than 280 microns, and the grounding resistance between the shielding layer 3 and the ground layer of the circuit board is less than 187mΩ. The resistance testing method is the same as that of Example 1.

[0086] It can be seen that by applying the electromagnetic shielding film of this embodiment, the problem of glue overflow at the edge of the electromagnetic shielding film during pressing onto the circuit board can be effectively avoided, the shielding layer and the ground layer of the circuit board can be effectively electrically connected, and the shielding effectiveness of the electromagnetic shielding film can be effectively improved.

[0087] Embodiment five:

[0088] An electromagnetic shielding film comprises a shielding layer 3 and a film layer 4; the film layer 4 is arranged on one surface of the shielding layer 3; the roughness Sdr of one surface of the shielding layer 3 close to the film layer 4 is 230%, and the adhesive gram weight parameter of the film layer 4 is 0.5 grams per square decimeter.

[0089] Test results: After testing, the length of the glue overflow from the edge of the electromagnetic shielding film of this embodiment during the pressing process to the circuit board is less than 86 microns, and the grounding resistance between the shielding layer 3 and the ground layer of the circuit board is less than 97mΩ. The resistance testing method is the same as that of Example 1.

[0090] It can be seen that by applying the electromagnetic shielding film of this embodiment, the problem of glue overflow at the edge of the electromagnetic shielding film during pressing onto the circuit board can be effectively avoided, the shielding layer and the ground layer of the circuit board can be effectively electrically connected, and the shielding effectiveness of the electromagnetic shielding film can be effectively improved.

[0091] Embodiment six:

[0092] An electromagnetic shielding film comprises a shielding layer 3 and a film layer 4; the film layer 4 is arranged on one surface of the shielding layer 3; the roughness Sdr of one surface of the shielding layer 3 close to the film layer 4 is 2100%, and the adhesive gram weight parameter of the film layer 4 is 0.5 grams per square decimeter.

[0093] Test results: After testing, the length of the glue overflow from the edge of the electromagnetic shielding film of this embodiment during the pressing process to the circuit board is less than 56 microns, and the grounding resistance between the shielding layer 3 and the ground layer of the circuit board is less than 72mΩ. The resistance testing method is the same as that of Example 1.

[0094] It can be seen that by applying the electromagnetic shielding film of this embodiment, the problem of glue overflow at the edge of the electromagnetic shielding film during lamination to the circuit board can be effectively avoided, the shielding layer and the ground layer of the circuit board can be effectively electrically connected, and the shielding effectiveness of the electromagnetic shielding film can be effectively improved. It should be noted that the roughness Sdr of the side of the shielding layer 3 close to the glue film layer 4 in this solution is only an example, and the actual value can be even larger, which will not be illustrated one by one here.

[0095] In general, the above effects can be achieved when the roughness Sdr of the side of the shielding layer close to the film layer and the gram weight of the film layer is 0.01-1 gram per square decimeter. For example, the gram weight of the film layer is 0.01, 0.02, 0.05, 0.07, 0.1, 0.2, 0.5, 0.7, or 1 gram per square decimeter.

[0096] Another embodiment of the present invention also provides a circuit board, which includes a circuit board body (not shown) and the electromagnetic shielding film described in any of the above embodiments; the electromagnetic shielding film is pressed against the circuit board body through the adhesive film layer 4; the side of the shielding layer 3 close to the adhesive film layer 4 pierces the adhesive film layer 4 and is electrically connected to the ground layer of the circuit board body.

[0097] Preferably, the circuit board body is one of a flexible single-sided board, a flexible double-sided board, a flexible multi-layer board, and a rigid-flexible board.

[0098] In an embodiment of the present invention, one side of the shielding layer 3 is able to pierce the adhesive film layer 4 and connect to the ground layer of the circuit board body when the electromagnetic shielding film is pressed onto the circuit board body, thereby ensuring that the shielding layer 3 is connected to the ground layer of the circuit board body, thereby achieving the shielding layer 3 and the interference charges in the shielding layer 3 being introduced into the ground, avoiding the accumulation of interference charges to form an interference source that affects the normal operation of the circuit board.

[0099] Specifically, the electromagnetic shielding film applied to the circuit board of the embodiment of the present invention has the following beneficial effects: by limiting the roughness Sdr of the side of the shielding layer close to the adhesive film layer to be greater than 0.1% and the adhesive weight of the adhesive film layer to be 0.01-1 g / m2, when the electromagnetic shielding film is pressed onto the circuit board, the side of the shielding layer close to the adhesive film layer can smoothly pierce the adhesive film layer, so that the shielding layer can be in contact with the ground layer of the circuit board, and then the interference charge of the shielding layer can be effectively introduced into the ground layer of the circuit board, effectively improving the shielding effectiveness of the electromagnetic shielding film. And when the electromagnetic shielding film is pressed onto the circuit board, the adhesive substance in the adhesive film layer with an adhesive weight of 0.01-1 g / m2 can be squeezed into the concave position of the side of the shielding layer close to the adhesive film layer, so that it is not easy for the adhesive substance to move to the edge of the circuit board in large quantities, resulting in obvious adhesive overflow at the edge between the electromagnetic shielding film and the circuit board, so that the circuit board after the shielding film is pressed has a good appearance.

[0100] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by any technician familiar with the art within the technical scope disclosed in the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be based on the protection scope of the claims.

Claims

1. An electromagnetic shielding film, characterized in that: Including a shielding layer and a film layer; The adhesive film layer is arranged on one side of the shielding layer; The roughness Sdr of one side of the shielding layer close to the adhesive film layer is greater than 0.1%, and the adhesive weight of the adhesive film layer is 0.01-1 g / sq.dm; the outer surface of the adhesive film layer is a flat surface without undulations, or the outer surface of the adhesive film layer is an uneven surface with gentle undulations.

2. The electromagnetic shielding film according to claim 1, characterized in that The roughness Sdr of a side of the shielding layer close to the adhesive film layer is 0.1%-8000%.

3. The electromagnetic shielding film according to claim 2, characterized in that The roughness Sdr of a side of the shielding layer close to the adhesive film layer is 1%-2000%.

4. The electromagnetic shielding film according to claim 3, characterized in that The roughness Sdr of a side of the shielding layer close to the adhesive film layer is 20%-600%.

5. The electromagnetic shielding film according to claim 1, characterized in that The roughness Rz of one side of the shielding layer close to the adhesive film layer is 0.5-20 microns, and the ratio of the arithmetic mean thickness of the adhesive film layer to the roughness Rz of one side of the shielding layer close to the adhesive film layer is greater than or equal to 1 / 4.

6. The electromagnetic shielding film according to claim 1, characterized in that The electromagnetic shielding film further comprises an insulating layer; the insulating layer is arranged on a side of the shielding layer away from the adhesive film layer, and a roughness Sdr of a side of the insulating layer close to the shielding layer is greater than 0.1%.

7. The electromagnetic shielding film according to claim 6, characterized in that The roughness Rz of a side of the insulating layer close to the shielding layer is 0.09-14.68 microns.

8. The electromagnetic shielding film according to claim 1, characterized in that A conductive protrusion is arranged on one side of the shielding layer close to the adhesive film layer.

9. The electromagnetic shielding film according to claim 8, characterized in that The ratio of the arithmetic mean thickness of the adhesive film layer to the protrusion height of the conductive protrusion is greater than or equal to 2 / 7.

10. A circuit board, characterized in that: It comprises a circuit board body and the electromagnetic shielding film as described in any one of claims 1-9; the electromagnetic shielding film is pressed onto the circuit board body through the adhesive film layer; a side of the shielding layer close to the adhesive film layer pierces the adhesive film layer and is electrically connected to the ground layer of the circuit board body.

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