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. A first protruding part is arranged on the side, close to the interlayer, of the first shielding layer, a second protruding part is arranged on the side, away from the interlayer, of the second shielding layer, the median line width of the first protruding part is 3-15 micrometers, and the median line width of the second protruding part is 5-26 micrometers. And the bending resistance of 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 soft board or circuit board of the foldable mobile phone. However, the shielding film in the prior art is attached to the 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. The existing shielding film is difficult to meet such high requirements, which leads to damage to the internal circuits of the circuit board or soft board, causing damage to the internal fine circuits of the circuit board or soft board.

[0003] It can be seen that in order to adapt to the application requirements of existing circuit boards or flexible boards, an electromagnetic shielding film that meets the performance requirements is urgently needed. 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, which can effectively improve the bending resistance of the electromagnetic shielding film itself and the circuit board or flexible board containing the electromagnetic shielding film.

[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, the surface of the first shielding layer close to the interlayer contains a first protrusion, the second shielding layer is provided with a second protrusion on the side away from the interlayer, the median width of the first protrusion is 3-15 microns, and the median width of the second protrusion is 5-26 microns.

[0006] As a preferred solution, the density of the first protrusions is 2-12 per 100 microns.

[0007] As a preferred solution, the sum of the median widths of the first protrusions is 1 / 5-1 / 2 of the total horizontal length of the first shielding layer.

[0008] As a preferred solution, the density of the second protrusions is 3-14 per 100 microns.

[0009] As a preferred solution, the sum of the median widths of the second protruding portions is 1 / 2-3 / 4 of the total horizontal length of the first shielding layer.

[0010] As a preferred solution, the difference between the sum of the median widths of the first protruding portion and the sum of the median widths of the second protruding portion is less than a preset difference threshold.

[0011] As a preferred solution, the horizontal distance between the median lines of adjacent first protrusions is 2-36 microns.

[0012] As a preferred solution, the horizontal distance between the median lines of adjacent second protrusions is 0.3-23 microns.

[0013] As a preferred embodiment, the horizontal distance between the midline of adjacent first protrusions is 2-30 times the average thickness of the first shielding layer between the corresponding adjacent first protrusions; and / or the horizontal distance between the midline of adjacent second protrusions is 0.1-14 times the average thickness of the second shielding layer between the corresponding adjacent second protrusions.

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

[0015] As a preferred solution, a substrate layer is provided on a surface of the first shielding layer away from the second shielding layer.

[0016] 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.

[0017] Compared with the prior art, the embodiments of the present invention provide 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, thereby improving the shielding effectiveness of the electromagnetic shielding film compared with an electromagnetic shielding film with a single shielding layer; an interlayer is arranged between the first shielding layer and the second shielding layer, thereby effectively increasing the bending resistance of the electromagnetic shielding film itself and the circuit board or flexible board containing the electromagnetic shielding film; further, 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 median width of the first protrusion is 3-15 microns, and the median width of the second protrusion is 5-26 microns, thereby improving the bending resistance of the electromagnetic shielding film while ensuring the shielding effectiveness of the electromagnetic shielding film. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is a schematic structural diagram of an electromagnetic shielding film in an embodiment of the present invention;

[0019] Figure 2 is a schematic structural diagram of another implementation manner of the electromagnetic shielding film in an embodiment of the present invention;

[0020] Figure 3is a schematic structural diagram of another implementation manner of the electromagnetic shielding film in an embodiment of the present invention;

[0021] Figure 4 is a schematic diagram of the structure of a circuit board in an embodiment of the present invention;

[0022] 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

[0023] 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.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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. The first shielding layer 1, the interlayer 2 and the second shielding layer 3 are stacked in sequence, and 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 side of the second shielding layer 3 away from the interlayer 2; the median width of the first protrusion 11 is 3-15 microns, and the median width of the second protrusion 31 is 5-26 microns.

[0028] It should be noted that the first shielding layer 1 and the second shielding layer 3 are provided in the electromagnetic shielding film to improve the shielding performance of the electromagnetic shielding film, and the 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 and the circuit board or soft board containing the electromagnetic shielding film; further, the structural stability of the electromagnetic shielding film and the bending resistance of the electromagnetic shielding film itself and the circuit board or soft board containing the electromagnetic shielding film are enhanced by providing the first protrusion 11 and the second protrusion 31. In the first shielding layer 1, only the protrusion whose vertical distance from the protrusion vertex to the midline is greater than 3 microns can be called the first protrusion 11, and in the second shielding layer 3, only the protrusion whose vertical distance from the protrusion vertex to the midline is greater than 3 microns can be called the second protrusion 31. Specifically, the vertical distance of the protrusion can be determined by obtaining a slice diagram of the electromagnetic shielding film or the shielding layer, and using the slice diagram to measure the vertical distance of the protrusion. The midline is the midline between the lowest point in all the concave parts and the highest point of all the protrusions in the view to be measured. In the slice diagram, the length of the median line of each first protrusion 11 should be limited to a range of 3-15 microns, and the length of the median line of each second protrusion 31 should be limited to a range of 5-26 microns. The heights of each first protrusion 11 can be equal or unequal, and the heights of each second protrusion 31 can be equal or unequal. The widths of the median lines of each first protrusion 11 can be equal or unequal, and the widths of the median lines of each second protrusion 31 can be equal or unequal.

[0029] Preferably, the interlayer 2 is non-metallic, and the non-metallic may include but is not limited to at least one of polyurethane, polyester, alkyd resin, epoxy resin, acrylic resin, polyimide, polystyrene, polyvinyl acetate, polyethylene, polypropylene, polyamide, rubber, phenolic resin, urethane resin, alkyd resin, and ABF resin. In the technical means of the embodiment of the present invention, the interlayer 2 mainly serves to enhance the interaction force between the electromagnetic shielding films and improve the bending resistance of the electromagnetic shielding film itself and the circuit board or flexible board containing the electromagnetic shielding film.

[0030] Preferably, 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 are not specifically limited here.

[0031] In this embodiment, in order to avoid the electromagnetic shielding film having unstable structure between layers, which causes the electromagnetic shielding film itself and the circuit board or soft board containing the electromagnetic shielding film to fail to meet the requirements of long-term and high-frequency folding or opening and closing, it is easy to cause the internal circuit to break, affecting the product quality. In this 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, thereby finally improving the bending resistance of the electromagnetic shielding film itself and the circuit board or soft board containing the electromagnetic shielding film. Further, considering the width of the first raised portion 11 and the second raised portion 31, the median width of the first raised portion 11 is set to 3-15 microns, and the median width of the second raised portion 31 is set to 5-26 microns. Specifically, the median width of the first raised portion 11 is 3-15 microns, which is 3, 3.5, 3.9, 4.1, 4.8, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 or an interval consisting of any two values, and the unit is micron, and the median width of the second raised portion 31 is 5, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26 or an interval consisting of any two numbers. Of course, the median width of the first raised portion 11 can also be any other value between 3-15 microns, and the median width of the second raised portion 31 can also be any other value between 5-26 microns, which is not specifically limited here.

[0032] 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 and the circuit board or soft board containing the electromagnetic shielding film. Furthermore, the range of the median width of the first protrusion 11 and the second protrusion 31 is limited respectively, which can effectively control the size of the first protrusion 11 and the second protrusion 31, avoid stress concentration while ensuring the shielding performance of the electromagnetic shielding film, ensure the structural stability of the electromagnetic shielding film, improve the bending resistance of the electromagnetic shielding film itself and 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.

[0033] As a preferred embodiment, the density of the first protrusions 11 is 2-12 per 100 micrometers.

[0034] In the embodiment of the present invention, the density distribution of the first protrusions 11 is taken into consideration, and the density of the first protrusions 11 is set to 2-12 / 100 microns. The density value of the first protrusions 11 can specifically be an interval consisting of 2, 4, 6, 8, 10, 12 or any two values ​​within 100 microns. Of course, the density of the first protrusions 11 can also be any other value between 2-12 / 100 microns, which is not specifically limited here.

[0035] By adopting the technical means of the embodiment of the present invention, the density range of the first protrusion 11 is limited, and the first protrusion 11 can be effectively controlled to be within a reasonable range, so that the density of the first protrusion 11 will not be too small, thereby causing interlayer delamination of the electromagnetic shielding film, and the density of the first protrusion 11 will not be too high, causing stress concentration and reducing performance. The density range of the first protrusion 11 is limited, which ensures the bending resistance of the electromagnetic shielding film itself and the circuit board or soft board containing the electromagnetic shielding film, making the electromagnetic shielding film suitable for products that require long-term and high-frequency folding or opening and closing.

[0036] Preferably, the sum of the median widths of the first protrusions is 1 / 5-1 / 2 of the total horizontal length of the first shielding layer 1 .

[0037] It should be noted that the sum of the median widths of the first raised portions 11 can be determined in the following manner: obtain a slice diagram of the electromagnetic shielding film or the first shielding layer 1, measure and add the median lines of all the first raised portions 11 on the slice diagram, and obtain the sum of the median widths of the first raised portions 11 in the slice diagram. The total horizontal length of the first shielding layer 1 can be determined in the following manner: measure and calculate the total horizontal length of the first shielding layer 1 on the slice diagram. The method for determining the sum of the median widths of the first raised portions 11 and the total horizontal length of the first shielding layer 1 is not limited to the above-mentioned specific method and is not limited here.

[0038] In the embodiment of the present invention, in order to make the technical effect of the electromagnetic shielding film better, the embodiment of the present invention takes into account the distribution of the first protrusion 11 in the first shielding layer 1, and sets the sum of the median widths of the first protrusions 11 to be 1 / 5-1 / 2 of the total horizontal length of the first shielding layer 1. The ratio of the sum of the median widths of the first protrusions 11 to the total horizontal length of the first shielding layer 1 can be 1 / 5, 1 / 4, 1 / 3, 2 / 5, 1 / 2 or an interval consisting of any two values. Of course, it can also be any other value between 1 / 5 and 1 / 2, which is not specifically limited here.

[0039] By adopting the technical means of the embodiment of the present invention, on the basis of the median line width of the first protrusion 11 being 3-15 microns, the ratio of the sum of the median line widths of the first protrusion 11 to the total horizontal length of the first shielding layer is limited, so that the sum of the median line widths of the first protrusion 11 can be limited within a reasonable range, thereby ensuring the bending resistance of the electromagnetic shielding film itself and the circuit board or flexible board containing the electromagnetic shielding film, making the electromagnetic shielding film suitable for products that require long-term and high-frequency folding or opening and closing.

[0040] As a preferred embodiment, the density of the second protrusions 31 is 3-14 per 100 micrometers.

[0041] In the embodiment of the present invention, the density distribution of the second protrusions 31 is taken into consideration, and the density of the second protrusions 31 is set to 3-14 / 100 microns. The density of the second protrusions 31 can be specifically an interval of 3, 4, 5, 8, 10, 12, 14 or any two values ​​within 100 microns. Of course, the density of the second protrusions 31 can also be any other value between 3-14 / 100 microns, which is not specifically limited here.

[0042] By adopting the technical means of the embodiment of the present invention, the density range of the second protrusion 31 is limited, and the second protrusion 31 can be effectively controlled to be within a reasonable range, so that the density of the second protrusion 31 will not be too small, which will cause the electromagnetic shielding film to have a poor grounding effect, nor will the density of the second protrusion 31 be too large, resulting in poor sol volume and reducing the overall performance of the electromagnetic shielding film. The density range of the second protrusion 31 is limited, which ensures the bending resistance of the electromagnetic shielding film itself and 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.

[0043] Preferably, the density of the first protrusion 11 is less than the density of the second protrusion 31. For example, the density of the first protrusion 11 is 2 / 100 microns, and the density of the second protrusion 31 is 5 / 100 microns, or the density of the first protrusion 11 is 10 / 100 microns, and the density of the second protrusion 31 is 14 / mm, etc. Of course, the density of the first protrusion 11 can also be any other value between 2-12 / 100 microns, and the density of the second protrusion 31 can also be any other value between 3-14 / 100 microns. No specific limitation is made here, and it is only necessary to ensure that the density of the first protrusion 11 is less than the density of the second protrusion 31. In this embodiment, the structural stability and bending resistance of the electromagnetic shielding film are comprehensively considered, and the density of the first protrusion 11 is set to be less than the density of the second protrusion 31.

[0044] As a preferred embodiment, the sum of the median widths of the second protrusions is 1 / 2-3 / 4 of the total horizontal length of the first shielding layer.

[0045] It should be noted that the sum of the median widths of the second protrusions 31 can be determined by the following method: obtaining a slice diagram of the electromagnetic shielding film or the second shielding layer 3, measuring and adding the median widths of all the second protrusions 31 on the slice diagram, and obtaining the sum of the median widths of the second protrusions 31 in the slice diagram. The method for determining the sum of the median widths of the second protrusions 31 is not limited to the above specific method and is not limited here.

[0046] In the embodiment of the present invention, in order to make the technical effect of the electromagnetic shielding film better, the embodiment of the present invention takes into account the length relationship between the second protrusion 31 and the first shielding layer 1, and sets the sum of the median widths of the second protrusion 31 to be 1 / 2-3 / 4 of the total horizontal length of the first shielding layer 1. The ratio of the sum of the median widths of the second protrusion 31 to the total horizontal length of the first shielding layer 1 can be 1 / 2, 1 / 16, 1 / 8, 11 / 16, 3 / 4 or an interval consisting of any two values. Of course, it can also be any other value between 1 / 2 and 3 / 4, which is not specifically limited here.

[0047] By adopting the technical means of the embodiment of the present invention, on the basis of the median line width of the second protrusion 31 being 5-26 microns, the difficulty of the manufacturing process, the shielding performance and the bending resistance of the electromagnetic shielding layer are comprehensively considered, and the ratio of the sum of the median line widths of the second protrusion 31 to the horizontal total length 1 of the first shielding layer is limited. The sum of the median line widths of the second protrusion 31 can be limited within a reasonable range, thereby ensuring the bending resistance of the electromagnetic shielding film itself and the circuit board or flexible 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.

[0048] Preferably, the absolute value of the difference between the sum of the median widths of the first protrusion 11 and the sum of the median widths of the second protrusion 31 is less than a preset difference threshold. The preset difference threshold is 40, which can be any two of 0, 5, 10, 15, 18, 23, 26, 30, 35, and 38.

[0049] It should be understood that in order to make the technical effect of the electromagnetic shielding film more stable, a preset difference threshold is set, and the difference between the sum of the median widths of the first protrusion 11 and the sum of the median widths of the second protrusion 31 is limited within the preset difference threshold. In this way, the first shielding layer 1, the second shielding layer 3 and the interlayer 2 have good structural stability, and the electromagnetic shielding film has a good grounding effect. The electromagnetic shielding film itself and the circuit board or soft board containing the electromagnetic shielding film have good bending resistance, so that the electromagnetic shielding film is suitable for products that require long-term and high-frequency folding or opening and closing.

[0050] As a preferred embodiment, the horizontal distance between the median lines of adjacent first protrusions 11 is 2-36 micrometers.

[0051] In the embodiment of the present invention, the distance between adjacent first protrusions 11 is taken into consideration, and the horizontal distance between the median lines of adjacent first protrusions 11 is set to 2-36 microns. The horizontal distance can be 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 25, 28, 30, 32, 34, 36 microns or an interval consisting of any two values. Of course, it can also be any other value between 2 microns and 5 microns, which is not specifically limited here.

[0052] By adopting the technical means of the embodiment of the present invention, the distance between adjacent first protrusions 11 is limited, and the horizontal distance between the midline of adjacent first protrusions 11 can be effectively controlled to be within a reasonable range, so that there is a better bonding force between the first shielding layer 1 and the interlayer 2 in the electromagnetic shielding film, which is beneficial to the transfer of stress between the first shielding layer 1 and the interlayer 2, thereby improving the bending resistance of the electromagnetic shielding film itself and the circuit board or flexible board containing the electromagnetic shielding film, making the electromagnetic shielding film suitable for products that require long-term and high-frequency folding or opening and closing.

[0053] As a preferred embodiment, the horizontal distance between the median lines of adjacent second protrusions 31 is 0.3-23 microns.

[0054] In the embodiment of the present invention, the distance between adjacent second protrusions 31 is taken into consideration, and the horizontal distance between the median lines of adjacent second protrusions 31 is set to 0.3-23 microns. The horizontal distance can specifically be 0.4, 1, 3, 5, 8, 12, 15, 18, 20, 21, 22 microns or an interval consisting of any two values. Of course, it can also be any other value between 0.3 microns and 23 microns, which is not specifically limited here.

[0055] By adopting the technical means of the embodiment of the present invention, the distance between adjacent second protrusions 31 is limited, and the horizontal distance between the midlines of adjacent second protrusions 31 can be effectively controlled to be within a reasonable range, so that the second shielding layer 3 and the interlayer 2 in the electromagnetic shielding film have better bonding force, which is beneficial to the transfer of stress between the second shielding layer 3 and the interlayer 2. The electromagnetic shielding film itself and the circuit board or flexible board containing the electromagnetic shielding film have good bending resistance, so that the electromagnetic shielding film is suitable for products that require long-term and high-frequency folding or opening and closing.

[0056] As a preferred embodiment, the horizontal distance between the midlines of adjacent first protrusions 11 is 2-30 times the average thickness of the first shielding layer 1 between the corresponding adjacent first protrusions 11; and / or, the horizontal distance between the midlines of adjacent second protrusions 31 is 0.1-14 times the average thickness of the second shielding layer 3 between the corresponding adjacent second protrusions 31.

[0057] In the embodiment of the present invention, after research, it is found that the ratio of the horizontal distance between adjacent first protrusions 11 to the thickness of the first shielding layer 1 between adjacent first protrusions 11 has a great influence on the performance of the electromagnetic shielding film, especially on the bending resistance, and the ratio of the horizontal distance between adjacent second protrusions 31 to the thickness of the second shielding layer 3 between adjacent second protrusions 31 has a great influence on the performance of the electromagnetic shielding film. The ratio of the horizontal distance between the midlines of adjacent first protrusions 11 to the average thickness of the first shielding layer 1 between the corresponding adjacent first protrusions 11 is set to 2-30, and the specific ratio can be 3, 5, 8, 12, 17, 20, 22, 24, 25, 28, 30 or an interval consisting of any two values. Of course, it can also be any other value between 3 and 5, which is not specifically limited here. The ratio of the horizontal distance between the median lines of adjacent second protrusions 31 to the average thickness of the second shielding layer 3 between the corresponding adjacent second protrusions 31 is set to be 0.1-14, and the specific ratio can be an interval consisting of any two values ​​of 0.2, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, of course, it can also be any other arbitrary value between 0.1 and 14, and no specific limitation is made here. Among them, the average thickness of the electromagnetic shielding film is 5-20 microns, and can be 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 or an interval consisting of any two values, in microns. The average thickness of the interlayer is 0.1-6 microns, and can be 0.5, 1, 2, 3, 4, 5 or an interval consisting of any two numbers, in microns.

[0058] By adopting the technical means of the embodiment of the present invention, the horizontal distance between the center lines of the corresponding adjacent first protrusions 11 is limited according to the average thickness of the first shielding layer 1 between the adjacent first protrusions 11, and the horizontal distance between the center lines of the corresponding adjacent second protrusions 31 is limited according to the average thickness of the second shielding layer 3 between the adjacent second protrusions 31, thereby facilitating the first shielding layer 1 and the second shielding layer 3 to absorb energy well and transfer it between the interlayer 2 when bending, thereby ensuring the bending resistance of the electromagnetic shielding film itself and the circuit board or flexible 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. It should be noted that the horizontal distance between adjacent center lines refers to the horizontal distance between adjacent endpoints between two adjacent center lines.

[0059] 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 .

[0060] See also Figure 2In 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 is not easy to bubble and delaminate, avoid separation, wrinkles and other problems, and ensure the peel strength between the second shielding layer 3 and the circuit board body 6. Preferably, the adhesive layer includes at least one of polyvinyl acetate, polyester, polyethylene, polypropylene, polyamide, rubber, acrylic, phenolic resin, epoxy resin, polyimide, urethane resin, melamine resin, alkyd resin, ABF and other resins. The adhesive layer may contain or not contain conductive particles.

[0061] 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 can play a good supporting and protective role. The base layer includes but is not limited to at least one of polystyrene, vinyl acetate resin, polyester, polyethylene, polyamide, rubber, acrylic resin, phenolic resin, epoxy resin, polyimide, urethane resin, melamine resin, alkyd resin, and ABF resin.

[0062] The various properties of the electromagnetic shielding film were tested respectively using specific examples. The structural parameters and test results of the electromagnetic shielding film are specifically shown in Table 1.

[0063] Test Example 1

[0064] 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, the surface of the first shielding layer close to the interlayer comprises a first protrusion, the second shielding layer is provided with a second protrusion on the side away from the interlayer, the median width of the first protrusion is 3 microns, the median width of the second protrusion is 5 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 microns, the average thickness of the first shielding layer is 0.9 microns, and the average thickness of the second shielding layer is 2.0 microns.

[0065] Test Example 2

[0066] The other conditions of this test example are the same as those of the test example 1, except that the median width of the first protrusion is 15 micrometers, and the median width of the second protrusion is 26 micrometers.

[0067] Test Example 3

[0068] The other conditions of this test example are the same as those of the test example 1, except that the median width of the first protrusion is 8 micrometers, and the median width of the second protrusion is 10 micrometers.

[0069] Test Example 4

[0070] The other conditions of this test example are the same as those of test example 3, except that the density of the first protrusions is 10 / 100 microns.

[0071] Test Example 5

[0072] The other conditions of this test example are the same as those of test example 4, except that the density of the second protrusions is 10 / 100 microns.

[0073] Test Example 6

[0074] The other conditions of this test example are the same as those of test example 5, except that the horizontal distance between the median lines of adjacent first protrusions is 15 micrometers.

[0075] Test Example 7

[0076] The other conditions of this test example are the same as those of test example 6, except that the horizontal distance between the median lines of adjacent second protrusions is 8 micrometers.

[0077] Test Case 8

[0078] This test example is the same as test example 7 in other conditions, except that the horizontal distance between the midline of adjacent first protrusions is 10 times the average thickness of the first shielding layer between the corresponding adjacent first protrusions; the horizontal distance between the midline of adjacent second protrusions is 3 times the average thickness of the second shielding layer between the corresponding adjacent second protrusions.

[0079] Test Example 9

[0080] 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.

[0081] Test Example 10

[0082] The other conditions of this test example are the same as those of test example 1, except that the median width of the first protrusion is 1 micron, and the median width of the second protrusion is 30 microns.

[0083] Table 1

[0084]

[0085]

[0086] 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 8, the material of the interlayer was non-metallic, and the tests were conducted 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. In test example 10, the material of the interlayer was a mixture of epoxy resin and polyester resin.

[0087] It can be seen from Table 1 that when the median line width of the first raised portion of the electromagnetic shielding film is 3-15 microns and the median line width of the second raised portion is 5-26 microns, the electromagnetic shielding film itself and the circuit board or flexible board containing the electromagnetic shielding film have good bending resistance and still have high shielding effectiveness after a high step difference, and the shielding effectiveness reaches above 62DB.

[0088] 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.

[0089] 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.

[0090] 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.

[0091] 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.

[0092] 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 median width of the first protrusion 11 is 2-5 microns, and the median width of the second protrusion 31 is 2-6 microns. 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.

[0093] 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. The first shielding layer, the interlayer and the second shielding layer are stacked in sequence. The first shielding layer contains a first protrusion on the surface close to the interlayer, and the second shielding layer is provided with a second protrusion on the side away from the interlayer. The median width of the first protrusion is 3-15 microns, and the median width of the second protrusion is 5-26 microns.

2. The electromagnetic shielding film according to claim 1, wherein The density of the first protrusions is 2-12 per 100 micrometers.

3. The electromagnetic shielding film according to claim 2, wherein: The sum of the median widths of the first protrusions is 1 / 5-1 / 2 of the total horizontal length of the first shielding layer.

4. The electromagnetic shielding film according to claim 1, wherein The density of the second protrusions is 3-14 per 100 micrometers.

5. The electromagnetic shielding film according to claim 1, wherein The sum of the median widths of the second protrusions is 1 / 2-3 / 4 of the total horizontal length of the first shielding layer.

6. The electromagnetic shielding film according to claim 5, characterized in that A difference between a sum of median widths of the first protruding portion and a sum of median widths of the second protruding portion is less than a preset difference threshold.

7. The electromagnetic shielding film according to claim 1, wherein The horizontal distance between the median lines of adjacent first protrusions is 2-36 micrometers.

8. The electromagnetic shielding film according to claim 1, wherein The horizontal distance between the median lines of adjacent second protrusions is 0.3-23 microns.

9. The electromagnetic shielding film according to claim 7 or 8, characterized in that The horizontal distance between the midlines of adjacent first protrusions is 2-30 times the average thickness of the first shielding layer between the corresponding adjacent first protrusions; and / or, the horizontal distance between the midlines of adjacent second protrusions is 0.1-14 times the average thickness of the second shielding layer between the corresponding adjacent second protrusions.

10. 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.

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

12. A circuit board, characterized in that: The circuit board comprises the electromagnetic shielding film according to any one of claims 1-11.

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