Electromagnetic shielding film and circuit board

Abstract

The invention discloses an electromagnetic shielding film and a circuit board, the electromagnetic shielding film comprises a first shielding layer, an interlayer and a second shielding layer which are stacked in sequence, the interlayer is arranged between the first shielding layer and the second shielding layer, the bending performance of the electromagnetic shielding film is effectively improved, and further, in the electromagnetic shielding film additionally provided with the interlayer, the electromagnetic shielding film is not prone to deformation. The side, close to the interlayer, of the first shielding layer is provided with first protruding parts, the side, away from the interlayer, of the second shielding layer is provided with second protruding parts, the density of the first protruding parts is 5-35 / 260 micrometers, and the density of the second protruding parts is 8-40 / 260 micrometers. And the bending resistance of the electromagnetic shielding film and the circuit board or the flexible board comprising the electromagnetic shielding film is improved.

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 development of miniaturization of communication equipment, there are higher and higher requirements for the miniaturization of integrated circuit boards. However, the further miniaturization of integrated circuit boards has also developed to a certain limit, so the miniaturization of communication equipment has also been restricted. In order to achieve further miniaturization of communication equipment, foldable mobile phones came into being. In order for foldable mobile phones to operate normally and avoid electromagnetic interference from the outside world and itself, it is necessary to apply a shielding film on the surface of the foldable mobile phone. However, the shielding film in the prior art is attached to a hard board and is not suitable for folding mobile phones or soft boards. Folding circuit boards or soft boards require long-term and high-frequency folding or opening and closing. Existing shielding films are difficult to meet such high requirements. After multiple bending, the circuits inside the circuit board or soft board will be broken or damaged.

[0003] It can be seen that in order to adapt to the application requirements of existing circuit boards or flexible boards, it is urgently necessary to develop a high-performance shielding film to improve the bending resistance of circuit boards or flexible boards. Summary of the invention

[0004] The purpose of the embodiments of the present invention is to provide an electromagnetic shielding film and a circuit board, so as to improve the bending resistance of the circuit board or flexible printed circuit (FPC), and the shielding film itself also has good bending resistance.

[0005] In order to solve the above technical problems, an embodiment of the present invention provides an electromagnetic shielding film, including a first shielding layer, an interlayer, and a second shielding layer. The first shielding layer, the interlayer and the second shielding layer are stacked in sequence, and a first protrusion is provided on the surface of the first shielding layer close to the interlayer, and a second protrusion is provided on the surface of the second shielding layer away from the interlayer. The density of the first protrusion is 5-35 / 260 microns, and the density of the second protrusion is 8-40 / 260 microns.

[0006] As a preferred solution, the density of the first protrusions is less than or equal to the density of the second protrusions.

[0007] As a preferred solution, the first protrusions are a base number, and at least 60% of the first protrusions overlap with the second protrusions.

[0008] As a preferred solution, a ratio A of the density of the first protrusions to the density of the second protrusions satisfies 0.8≤A≤1.

[0009] As a preferred solution, the interlayer is at least one of epoxy resin, polyester resin, polyurethane resin, acrylic resin, alkyd resin, polyamide resin and polyimide resin.

[0010] As a preferred solution, the ratio B of the average height of the first protrusion to the average thickness of the interlayer is 1.6≤A≤2.2.

[0011] As a preferred solution, the first shielding layer and / or the second shielding layer is at least a two-layer structure.

[0012] As a preferred solution, the first shielding layer and the second shielding layer are made of at least one of aluminum, titanium, zinc, iron, nickel, chromium, cobalt, copper, silver and gold.

[0013] As a preferred solution, an adhesive layer is provided on a surface of the second shielding layer away from the first shielding layer.

[0014] As a preferred solution, a base layer is provided on a surface of the first shielding layer away from the second shielding layer.

[0015] In order to solve the same technical problem, an embodiment of the present invention further provides a circuit board, which includes the electromagnetic shielding film as described in any of the above embodiments.

[0016] Compared with the prior art, an embodiment of the present invention provides an electromagnetic shielding film and a circuit board, wherein the electromagnetic shielding film comprises a first shielding layer, an interlayer and a second shielding layer stacked in sequence, and the interlayer is arranged between the first shielding layer and the second shielding layer, which effectively increases the bending resistance of the electromagnetic shielding film and the circuit board or flexible board containing the electromagnetic shielding film. Furthermore, in the electromagnetic shielding film with the interlayer added, a first protrusion is arranged on a side of the first shielding layer close to the interlayer, and a second protrusion is arranged on a side of the second shielding layer away from the interlayer. The density of the first protrusion is 5-35 / 260 microns, and the density of the second protrusion is 8-40 / 260 microns. On the basis of ensuring the shielding effectiveness of the electromagnetic shielding film, the bending resistance of the electromagnetic shielding film itself and the circuit board or flexible board containing the electromagnetic shielding film is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a schematic structural diagram of an electromagnetic shielding film in an embodiment of the present invention;

[0018] Figure 2 is a schematic structural diagram of another implementation manner of the electromagnetic shielding film in an embodiment of the present invention;

[0019] Figure 3 is a schematic structural diagram of another implementation manner of the electromagnetic shielding film in an embodiment of the present invention;

[0020] Figure 4is a schematic diagram of the structure of a circuit board in an embodiment of the present invention;

[0021] Among them, 1. first shielding layer; 11. first protruding portion; 2. interlayer; 3. second shielding layer; 31. second protruding portion; 4. adhesive layer; 5. base layer; 6. circuit board body. DETAILED DESCRIPTION

[0022] 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. The purpose of providing these embodiments is to make the disclosure of the present invention more thorough and comprehensive. 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.

[0023] In the description of this application, the terms "first", "second", "third", etc. are used for descriptive purposes only and are not to be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first", "second", "third", etc. may explicitly or implicitly include one or more of the feature. In the description of this application, unless otherwise specified, "plurality" means two or more.

[0024] In the description of the present application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be a connection between the two elements. The terms "vertical", "horizontal", "left", "right", "upper", "lower" and similar expressions used herein are only for illustrative purposes, and do not indicate or imply that the device or element 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 present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0025] In the description of this application, it should be noted that, unless otherwise defined, all technical and scientific terms used in the present invention have the same meaning as those commonly understood by those skilled in the art. The terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood by specific circumstances.

[0026] See also Figure 1 A preferred embodiment of the present invention provides an electromagnetic shielding film, comprising a first shielding layer 1, an interlayer 2 and a second shielding layer 3, wherein the first shielding layer 1, the interlayer 2 and the second shielding layer 3 are stacked in sequence, a first protrusion 11 is provided on the surface of the first shielding layer 1 close to the interlayer 2, and a second protrusion 31 is provided on the surface of the second shielding layer 3 away from the interlayer 2; the density of the first protrusion 11 is 5-35 / 260 microns, and the density of the second protrusion 31 is 8-40 / 260 microns.

[0027] It should be noted that a first shielding layer 1 and a second shielding layer 3 are provided in the electromagnetic shielding film to improve the shielding performance of the electromagnetic shielding film, and an interlayer 2 is provided between the first shielding layer 1 and the second shielding layer 3 to improve the bending resistance of the electromagnetic shielding film itself or a circuit board or a flexible board containing the electromagnetic shielding film. Furthermore, the bending resistance of the electromagnetic shielding film itself or a circuit board or a flexible board containing the electromagnetic shielding film and the grounding performance of the electromagnetic shielding film are enhanced by providing a first protrusion 11 and a second protrusion 31. In the first shielding layer 1, only the protrusions whose vertical distance between the vertex of the protruding inner interlayer 2 and the center line is greater than 0.8 microns can be called the first protrusion 11, or the protrusions on the first shielding layer 1 whose maximum thickness is greater than or equal to the distance between the center line and the highest point of all protrusions can also be identified as the first protrusion 11; in the second shielding layer 3, only the protrusions whose vertical distance between the vertex of the protruding inner interlayer 2 and the center line is greater than 0.8 microns can be called the second protrusion 31 (similarly, the definition of the second protrusion 31 can also refer to the definition of the first protrusion 11); specifically, the method of determining the vertical distance of the protrusion can be obtained by obtaining a slice diagram of the electromagnetic shielding film or shielding layer, and using the slice diagram to measure the vertical distance between the first protrusion or the second protrusion and the center line. The center line is the center line between the lowest point in all the concave parts in the view to be tested and the highest point of all the protrusions. Among them, the direction toward the circuit board or the flexible board in the first shielding layer 1 and the second shielding layer 3 is defined as a protrusion.

[0028] In this embodiment, in order to avoid the problem that the electromagnetic shielding film itself or the circuit board or soft board containing the electromagnetic shielding film has insufficient bending resistance, resulting in the electromagnetic shielding film and the circuit board or soft board being unable to meet the requirements of long-term and high-frequency folding or opening and closing, and being prone to wrinkles, curling or breakage, thereby affecting product quality, the embodiment of the present invention provides a first protrusion 11 on the side of the first shielding layer 1 close to the interlayer 2, and provides a second protrusion 31 on the side of the second shielding layer 3 away from the interlayer 2, so as to improve the bending resistance of the electromagnetic shielding film and the circuit board or soft board containing the electromagnetic shielding film. Furthermore, the density distribution of the first protrusion 11 and the second protrusion 31 is taken into consideration. The density of the first protrusions 11 is set to 5-35 / 260 microns, and the density of the second protrusions 31 is set to 8-40 / 260 microns. Specifically, the density of the first protrusions 11 is 5, 7, 9, 10, 12, 14, 15, 16, 18, 20, 25, 30 or 35, and the density of the second protrusions 31 is 8, 10, 15, 20, 24, 28, 30, 34, 38 or 40. Of course, the density of the first protrusions 11 may also be any other value between 5-35 / 260 microns, and the density of the second protrusions 31 may also be any other value between 8-40 / 260 microns, which are not specifically limited here.

[0029] By adopting the technical means of the embodiment of the present invention, a first protrusion 11 is arranged on the side of the first shielding layer 1 close to the interlayer 2, and a second protrusion 31 is arranged on the side of the second shielding layer 3 away from the interlayer 2, which together with the interlayer 2 play a role in improving the bending resistance of the electromagnetic shielding film itself or the circuit board or soft board containing the electromagnetic shielding film, and the density range of the first protrusion 11 and the second protrusion 31 is limited respectively, which can effectively control the first protrusion 11 and the second protrusion 31 to be within a reasonable range. While ensuring the shielding performance of the electromagnetic shielding film, the grounding of the electromagnetic shielding film and the interlayer structure stability of the electromagnetic shielding film itself are also improved, thereby ensuring the bending resistance of the electromagnetic shielding film itself or the circuit board or soft board containing the electromagnetic shielding film, so that the electromagnetic shielding film is suitable for products that require long-term and high-frequency folding or opening and closing. In the present invention, the density of the first protrusion 11 needs to be moderate. If the density of the first protrusion 11 is too small, the interlayer structure of the electromagnetic shielding film itself will be unstable and delamination will occur. In addition, stress concentration will occur between the first shielding layer 1 and the interlayer 2, which is not conducive to stress transfer; if the density of the first protrusion 11 is too large, the overall structure of the electromagnetic shielding film will become brittle, which is not conducive to improving the bending resistance of the electromagnetic shielding film itself or the circuit board or soft board containing the electromagnetic shielding film; the density of the second protrusion 31 also needs to be moderate. If the density of the second protrusion 31 is too small, the grounding effect of the electromagnetic shielding film itself will be poor, which will easily lead to a decrease in shielding effectiveness; if the density of the second protrusion 31 is too large, it will also lead to a decrease in the bending resistance of the electromagnetic shielding film itself or the circuit board or soft board containing the electromagnetic shielding film, and may also damage the internal circuits of the circuit board or soft board.

[0030] As a preferred embodiment, the density of the first protrusions 11 is less than or equal to the density of the second protrusions 31 .

[0031] In the embodiment of the present invention, the density of the first protrusion 11 is in the range of 10-20 pieces / mm, and the density of the second protrusion 31 is in the range of 20-40 pieces / mm. For example, the density of the first protrusion 11 is 15 pieces / mm, and the density of the second protrusion 31 is 20 pieces / mm, or the density of the first protrusion 11 is 18 pieces / mm, and the density of the second protrusion 31 is 25 pieces / mm, etc. Of course, the density of the first protrusion 11 can also be any other value between 10-20 pieces / mm, and the density of the second protrusion 31 can also be any other value between 20-40 pieces / mm. No specific limitation is made here, and it is only necessary to ensure that the density of the first protrusion 11 is less than or equal to the density of the second protrusion 31. In this embodiment, the density of the first protrusion 11 of the electromagnetic shielding film is less than or equal to the density of the second protrusion 31, which can make the performance stability of the electromagnetic shielding film better and have more excellent electromagnetic shielding effectiveness and grounding performance. At the same time, the electromagnetic shielding film itself or the circuit board or flexible board containing the electromagnetic shielding film has better bending resistance, and the electromagnetic shielding film has better structural stability and bending resistance.

[0032] As a preferred embodiment, based on the first protrusions 11 , at least 60% of the first protrusions 11 overlap with the second protrusions 31 .

[0033] It should be noted that when the horizontal distance between the vertical line at the top of the first protrusion 11 and the vertical line at the top of the second protrusion 31 is less than 1 / 2 of the width of the first protrusion 11, the first protrusion 11 and the second protrusion 31 are considered to overlap. The highest point of the first protrusion 11 pointing to the second shielding layer 3 is the top of the first protrusion 11; the top of the second protrusion 31 is the highest point corresponding to the point away from the first shielding layer 1. The width of the protrusion refers to the horizontal width of the lowest point adjacent to both sides of the top of the protrusion.

[0034] In an embodiment of the present invention, in order to make the electromagnetic shielding film itself or the circuit board or flexible board containing the shielding film more resistant to bending, the embodiment of the present invention takes into account the degree of overlap between the first protrusion 11 and the second protrusion 31, and sets at least 60% of the first protrusion 11 to overlap with the second protrusion 31. The proportion of the first protrusion 11 overlapping with the second protrusion 31 can be 60%, 74%, 87%, 93%, 100% or an interval consisting of any two values. Of course, it can also be any other value between 60% and 100%, which is not specifically limited here.

[0035] By adopting the technical means of the embodiment of the present invention, on the basis of the density of the first protrusion 11 being 5-35 / 260 microns and the density of the second protrusion 31 being 8-40 / 260 microns, for better technical effects, the overlap degree between the first protrusion 11 and the second protrusion 31 is limited, so that the overlap degree between the first protrusion 11 and the second protrusion 31 can be limited within a reasonable range, thereby achieving better stress transfer between the first shielding layer 1, the interlayer 2 and the second shielding layer 3, thereby ensuring the bending resistance of the electromagnetic shielding film itself or the circuit board or flexible board containing the electromagnetic shielding film.

[0036] As a preferred embodiment, a ratio A between the density of the first protrusion 11 and the density of the second protrusion 31 satisfies 0.8≤A≤1.

[0037] In the embodiment of the present invention, in order to improve the bending resistance of the electromagnetic shielding film itself or the circuit board or flexible board containing the electromagnetic shielding film and the grounding performance and shielding effectiveness of the electromagnetic shielding film, the embodiment of the present invention takes into account the density relationship between the first protrusion 11 and the second protrusion 31, and sets the ratio of the density of the first protrusion 11 to the density of the second protrusion 31 to be at least 0.8 and at most 1. The density ratio of the first protrusion 11 to the second protrusion 31 can specifically be 0.8, 0.83, 0.9, 0.95 or 1. Of course, it can also be any other value between 0.8 and 0.9, which is not specifically limited here.

[0038] By adopting the technical means of the embodiment of the present invention, on the basis of the density of the first protrusion 11 being 5-35 / 260 microns and the density of the second protrusion 31 being 8-40 / 260 microns, for better technical effects, the density relationship between the first protrusion 11 and the second protrusion 31 is limited, so that the density ratio of the first protrusion 11 and the second protrusion 31 can be limited within a reasonable range, thereby effectively transmitting stress and avoiding stress concentration. At the same time, it is also beneficial to the adhesion between layers and avoids delamination, thereby ensuring the grounding performance of the electromagnetic shielding film, improving the shielding performance, and improving the bending resistance of the electromagnetic shielding film or the circuit board or flexible board containing the shielding film.

[0039] As a preferred embodiment, the interlayer 2 is at least one of epoxy resin, polyester resin, polyurethane resin, acrylic resin, alkyd resin, polyamide resin and polyimide resin.

[0040] It should be noted that the interlayer 2 is non-metallic, and the non-metallic may include but is not limited to at least one of epoxy resin, polyester resin, polyurethane resin, acrylic resin, alkyd resin, polyamide resin, and polyimide resin, that is, the material of the interlayer 2 may be selected from at least one of epoxy resin, polyester resin, polyurethane resin, acrylic resin, alkyd resin, polyamide resin, and polyimide resin. In the technical means of the embodiment of the present invention, the interlayer 2 mainly serves to improve the bending resistance and the bonding between layers.

[0041] As a preferred embodiment, a ratio B of an average height of the first protrusion to an average thickness of the interlayer is 1.6≤B≤2.2.

[0042] In an embodiment of the present invention, in order to make the electromagnetic shielding film or the circuit board or soft board containing the electromagnetic shielding film more resistant to bending, the embodiment of the present invention takes into account the height relationship between the first protrusion 11 and the interlayer 2, and sets the ratio B between the average height of the first protrusion 11 and the average thickness of the interlayer 2 to satisfy a certain relationship, and sets the ratio B to 1.6≤B≤2.2. The set ratio can be 1.7, 1.8, 1.9, 2.0, 2.1, 2.2 or an interval consisting of any two values, which is not specifically limited here. In this embodiment, such a setting can ensure better stress transfer between the first protrusion 11 and the interlayer 2. The average height is the average value of the heights of multiple first protrusions 11. The more values ​​the first protrusion 11 takes, the more accurate it is. The average thickness of the interlayer 2 refers to the average value between the maximum and minimum values ​​of the thickness of the interlayer 2. The maximum and minimum values ​​in the above range are the maximum and minimum values ​​in the detection data, preferably detected by a 2000x scanning electron microscope. The average thickness of the interlayer is 0.1 micron to 8 microns, and specifically, the average thickness of the interlayer can be an interval consisting of any two values ​​of 0.5 micron, 0.8 micron, 1.0 micron, 2.0 micron, 3.0 micron, 4.0 micron, 5.0 micron, 6.0 micron, 7.0 micron or 8 micron. The overall thickness of the electromagnetic shielding film is 5-25 microns, and can be an interval consisting of any two values ​​of 5 microns, 10 microns, 15 microns, and 20 microns.

[0043] By adopting the technical means of the embodiment of the present invention, on the basis that the density of the first protrusion 11 is 5-35 / 260 microns, the density of the second protrusion 31 is 8-40 / 260 microns, and the interlayer 2 is at least one of epoxy resin, polyester resin, polyurethane resin, acrylic resin, alkyd resin, polyamide resin, and polyimide resin, for better technical effects, the height relationship between the first protrusion 11 and the interlayer 2 is limited, thereby ensuring the bending resistance of the electromagnetic shielding film itself or the circuit board or flexible board containing the electromagnetic shielding film.

[0044] As a preferred embodiment, the first shielding layer 1 and / or the second shielding layer 3 is at least a two-layer structure.

[0045] In this embodiment, the structure of the shielding layer is analyzed, and the number of structural layers of the first shielding layer 1 and / or the second shielding layer 3 is set to at least two layers, thereby improving the shielding performance of the electromagnetic shielding film.

[0046] As a preferred embodiment, the material of the first shielding layer 1 and the second shielding layer 3 is at least one of aluminum, titanium, zinc, iron, nickel, chromium, cobalt, copper, silver, and gold. It is understandable that the material of the first shielding layer 1 and the second shielding layer 3 can be metal or alloy. In order to ensure that the first shielding layer 1 and the second shielding layer 3 have good electrical conductivity, the first shielding layer 1 and the second shielding layer 3 are made of at least one material of aluminum, titanium, zinc, iron, nickel, chromium, cobalt, copper, silver, and gold. The materials of the first shielding layer 1 and the second shielding layer 3 can be the same or different, and no specific limitation is made here. In addition, when the first shielding layer 1 is a structure of at least two layers or the second shielding layer 3 is a structure of at least two layers, the materials between the layers can be the same or different.

[0047] As a preferred embodiment, an adhesive layer 4 is provided on a surface of the second shielding layer 3 away from the first shielding layer 1 .

[0048] See also Figure 2 In the embodiment of the present invention, the adhesive layer 4 mainly plays a bonding role, thereby improving the adhesion between two adjacent material layers. In order to improve the adhesion between the second shielding layer 3 and the circuit board body 6, the adhesive layer 4 is arranged on the surface of the second shielding layer 3 away from the first shielding layer 1, which enhances the bonding force between the electromagnetic shielding film and the circuit board body 6, so that the electromagnetic shielding film and the circuit board are not prone to blistering and delamination, avoiding separation, wrinkles and other problems, and ensuring the peeling strength between the second shielding layer 3 and the circuit board body 6. Among them, the adhesive layer is selected from at least one material selected from polystyrene, vinyl acetate, polyester, polyethylene, polyamide, rubber, acrylate, phenolic, epoxy, polyimide, carbamate, melamine, alkyd, and ABF resin. The adhesive layer mainly improves the bonding performance between the electromagnetic shielding film and the circuit board or soft board. Among them, conductive particles may or may not be arranged in the adhesive layer, and the arrangement of conductive particles is arranged according to actual needs.

[0049] As a preferred embodiment, the second shielding layer 3 has a protrusion on a side away from the first shielding layer 1 .

[0050] In an embodiment of the present invention, a protrusion is provided on the side of the second shielding layer 3 away from the first shielding layer 1, which can increase the contact area between the second shielding layer 3 and the adhesive layer 4, thereby making the bonding force between the second shielding layer 3 and the circuit board body 6 stronger, thereby making it less likely for the electromagnetic shielding film to bubble and delaminate, thereby effectively ensuring that the electromagnetic shielding film is grounded, thereby conducting out interference charges.

[0051] As a preferred embodiment, please refer to Figure 3 , a base layer 5 is provided on the surface of the first shielding layer 1 away from the second shielding layer 3. The base layer has the function of protection and support, which can prevent the first shielding layer 1 from being damaged and thus reduce the shielding effectiveness; at the same time, the base layer can play a good supporting role for the first shielding layer 1, which is convenient for the preparation of the first shielding layer 1 and subsequent structures. Among them, the embodiment of the present invention does not specifically limit the material used for the base layer, but from the perspective of further improving the bending resistance, the base layer is made of at least one material selected from polystyrene, vinyl acetate, polyester, polyethylene, polyamide, rubber, acrylic, phenolic, epoxy, polyimide, urethane, melamine, alkyd, and ABF resin.

[0052] The various properties of the electromagnetic shielding film were tested respectively with specific examples. The structural parameters and test results of the electromagnetic shielding film are shown in Table 1. The specific test examples are as follows:

[0053] Test Example 1

[0054] An electromagnetic shielding film comprises a base layer, a first shielding layer, an interlayer, a second shielding layer and an adhesive layer which are stacked in sequence, a first protrusion is provided on the surface of the first shielding layer close to the interlayer, and a second protrusion is provided on the surface of the second shielding layer away from the interlayer, the density of the first protrusions is 11 / 260 microns, the density of the second protrusions is 13 / 260 microns, the first shielding layer and the second shielding layer are made of copper, the overall average thickness of the electromagnetic shielding film is 11.8 microns, the average thickness of the first shielding layer is 1.0 microns, the average thickness of the second shielding layer is 1.9 microns, and the average thickness of the interlayer is 2.8 microns.

[0055] Test Example 2

[0056] The other conditions of this test example are the same as those of test example 1, except that the density of the first protrusions is 5 / 260 microns, and the density of the second protrusions is 8 / 260 microns.

[0057] Test Example 3

[0058] The other conditions of this test example are the same as those of test example 1, except that the density of the first protrusions is 35 / 260 microns, and the density of the second protrusions is 40 / 260 microns.

[0059] Test Example 4

[0060] This test example is the same as test example 1 in other conditions, except that at least 60% of the first protrusions overlap with the second protrusions.

[0061] Test Example 5

[0062] This test example is the same as test example 4 in other conditions, except that the ratio B of the average height of the first protrusion to the average thickness of the interlayer is 1.8.

[0063] Test Example 6

[0064] The other conditions of this test example are the same as those of test example 1, except that the density of the first protrusions is 40 / 260 microns, and the density of the second protrusions is 7 / 260 microns.

[0065] Test Example 7

[0066] An electromagnetic shielding film comprises a base layer, a first shielding layer and an adhesive layer which are stacked in sequence, wherein the thickness of the first shielding layer is the same as that of test example 1.

[0067] Table 1

[0068]

[0069]

[0070] It should be noted that in order to improve the accuracy of the test results, each set of data was tested repeatedly for multiple times, and the multiple test results were combined to obtain the final test results. In the multiple repeated tests of test examples 1 to 5, the material of the interlayer was non-metal, and the tests were performed when the interlayer material was epoxy resin, polyester resin, polyurethane resin, acrylic resin, alkyd resin, polyamide resin, polyimide resin, and a mixture of epoxy resin and polyester resin. The material of the interlayer in test example 6 was a mixture of epoxy resin and polyester resin.

[0071] The testing method for the bending resistance of the electromagnetic shielding film is as follows: the steps of the MIT folding resistance test include: pressing two shielding films against each other on a bending plate, the pressing conditions are 185°C, pre-pressing 10s, molding time 180s, molding pressure 120kg / cm2, pressing temperature at 185°C, baking and curing after pressing, baking temperature 160°C, baking time 90min, strip width: 1.5cm, R angle 0.8, speed 60 rpm, angle ±135°, load 500g; when bending starts, when the line resistance changes by more than 10%, the machine automatically stops the test and records the number of bends and failure resistance; the shielding effectiveness is tested in accordance with GB / T30142-2013.

[0072] It can be seen from the above table that the electromagnetic shielding film provided by the embodiment of the present invention has better electromagnetic shielding performance, and the electromagnetic shielding film itself and the circuit board or flexible board containing the electromagnetic shielding film have better bending resistance.

[0073] In order to solve the same technical problem, an embodiment of the present invention further provides a circuit board, which includes the electromagnetic shielding film as described in any of the above embodiments.

[0074] In the embodiment of the present invention, please refer to Figure 4 The circuit board includes a circuit board body 6 and an electromagnetic shielding film as described in any of the above embodiments, wherein the electromagnetic shielding film is pressed together with the circuit board body 6 through an adhesive layer 4; the second shielding layer 3 pierces the adhesive layer 4 and is electrically connected to the ground layer of the circuit board body 6, thereby ensuring that the first shielding layer 1 and the second shielding layer 3 are connected to the ground layer of the circuit board body 6, thereby achieving the goal of introducing interference charges in the first shielding layer 1 and the second shielding layer 3 into the ground, avoiding the accumulation of interference charges to form an interference source that affects the normal operation of the circuit board.

[0075] Preferably, the circuit board body 6 is one of a flexible single-sided board, a flexible double-sided board, a flexible multilayer board, and a rigid-flexible board. It is worth noting that the circuit board body 6 is not limited to the above specific types and can be set according to actual conditions.

[0076] Compared with the prior art, the circuit board provided in the embodiment of the present invention includes an electromagnetic shielding film, which includes a first shielding layer 1, an interlayer 2 and a second shielding layer 3 stacked in sequence. The interlayer 2 is arranged between the first shielding layer 1 and the second shielding layer 3, which effectively increases the bendability of the electromagnetic shielding film. Furthermore, in the electromagnetic shielding film with the interlayer 2 added, a first protrusion 11 is arranged on the side of the first shielding layer 1 close to the interlayer 2, and a second protrusion 31 is arranged on the side of the second shielding layer 3 away from the interlayer 2. The density of the first protrusion 11 is 10-20 pieces / mm, and the density of the second protrusion 31 is 20-40 pieces / mm. The electromagnetic shielding film in the present invention still has a high shielding effectiveness after a high step difference, and the shielding effectiveness can reach more than 60DB. On the basis of ensuring the shielding effectiveness of the electromagnetic shielding film, the bending resistance of the electromagnetic shielding film is improved.

[0077] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the patent of the present invention. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. An electromagnetic shielding film, characterized in that: The electromagnetic shielding film includes a first shielding layer, an interlayer and a second shielding layer, which are stacked in sequence. The first shielding layer is provided with a first protrusion on the surface close to the interlayer, and the second shielding layer is provided with a second protrusion on the surface away from the interlayer. The density of the first protrusion is 5-35 / 260 microns, and the density of the second protrusion is 8-40 / 260 microns.

2. The electromagnetic shielding film according to claim 1, wherein The density of the first protrusions is less than or equal to the density of the second protrusions.

3. The electromagnetic shielding film according to claim 2, wherein: Taking the first protrusions as a base, at least 60% of the first protrusions overlap with the second protrusions.

4. The electromagnetic shielding film according to claim 1, wherein A ratio A of the density of the first protrusions to the density of the second protrusions satisfies 0.8≤A≤1.

5. The electromagnetic shielding film according to claim 1, wherein The interlayer is at least one of epoxy resin, polyester resin, polyurethane resin, acrylic resin, alkyd resin, polyamide resin and polyimide resin.

6. The electromagnetic shielding film according to claim 5, characterized in that A ratio B of an average height of the first protrusions to an average thickness of the interlayer is 1.6≤B≤2.

2.

7. The electromagnetic shielding film according to claim 1, wherein The first shielding layer and / or the second shielding layer are at least two-layer structures.

8. The electromagnetic shielding film according to claim 1, wherein The material of the first shielding layer and the second shielding layer is at least one of aluminum, titanium, zinc, iron, nickel, chromium, cobalt, copper, silver, and gold.

9. The electromagnetic shielding film according to claim 1, wherein An adhesive layer is disposed on a surface of the second shielding layer away from the first shielding layer.

10. The electromagnetic shielding film according to claim 8 or 9, characterized in that A base layer is disposed on a surface of the first shielding layer away from the second shielding layer.

11. A circuit board, characterized in that: The circuit board includes the electromagnetic shielding film as described in any one of claims 1-10.

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