Electromagnetic shielding film and circuit board

Abstract

The invention discloses an electromagnetic shielding film and a circuit board, the electromagnetic shielding film comprises a shielding layer, the shielding layer is provided with a plurality of holes, and the residual rate Y of the shielding layer and the impedance change rate X of the circuit board applying the electromagnetic shielding film meet the following linear regression relation: Y = AX + B, wherein the residual rate Y is the weight ratio between the shielding layer after opening and the shielding layer before opening; a and B are constants, the value range of A is 1-10, and the value range of B is-2-1. The impedance change rate of the circuit board is utilized to restrain the residual rate of the shielding layer, and the impedance stability of the circuit board applying the electromagnetic shielding film is ensured while it is ensured that water vapor on the surface of the circuit board can be effectively discharged through holes in the shielding layer to reduce the short circuit probability of the circuit board.

Description

Technical Field

[0001] The present invention relates to the technical field of electronic materials, 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 has greatly promoted the development of flexible circuit boards, thereby realizing the integration of component devices and wire connections. Flexible circuit boards can be widely used in industries such as mobile phones, liquid crystal displays, communications, and aerospace. Driven by the international market, functional flexible circuit boards dominate the flexible circuit board market, and electromagnetic interference shielding (EMI shielding) is an important indicator for evaluating the performance of functional flexible circuit boards. The internal components of mobile phones and other communication devices are rapidly becoming high-frequency and high-speed with the integration of functions. 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 the high-frequency and high-speed trends, the electromagnetic interference problems inside and outside the components, the problem of signal attenuation during transmission, and the problems of insertion loss and jitter will gradually become more serious.

[0003] In the prior art, the electromagnetic shielding film laminated on the circuit board includes a shielding layer and an adhesive film layer, which connects the shielding layer to the ground layer of the circuit board through the adhesive film layer, thereby introducing the interference charge into the ground layer of the circuit board, thereby achieving shielding. However, after the existing electromagnetic shielding film is laminated on the circuit board substrate, the surface of the circuit board is prone to moisture accumulation, which greatly increases the probability of short circuit of the circuit board, thereby affecting the quality of the circuit board. Summary of the invention

[0004] The present invention provides an electromagnetic shielding film and a circuit board to solve the technical problem that a circuit board short circuit easily occurs after the existing electromagnetic shielding film is pressed onto a circuit board substrate, and can effectively improve the use quality of the circuit board.

[0005] In order to solve the above technical problems, the first aspect of the embodiment of the present invention provides an electromagnetic shielding film, including a shielding layer, wherein a plurality of holes are opened on the shielding layer, and the residual rate Y of the shielding layer and the impedance change rate X of the circuit board to which the electromagnetic shielding film is applied satisfy the following linear regression relationship: Y=AX+B;

[0006] Wherein, the residual rate Y is the weight ratio between the shielding layer after the opening and the shielding layer before the opening;

[0007] The impedance change rate X is calculated as follows: impedance change rate X=|impedance of the circuit board to which the electromagnetic shielding film is applied-initial impedance of the circuit board| / initial impedance of the circuit board;

[0008] A and B are both constants. The value range of A is 1 to 10, and the value range of B is -2 to 1.

[0009] As a preferred solution, the impedance change rate X and the thickness D of the shielding layer satisfy the following relationship: D=KX+Q; wherein K and Q are both constants, the value range of K is 20 to 150, and the value range of Q is -20 to -1, and the above relationship is dimensionless.

[0010] As a preferred solution, the impedance change rate X is less than 20%, and the thickness D of the shielding layer is 0.1 μm to 3.5 μm.

[0011] As a preferred solution, the shape of the hole includes a regular shape and / or an irregular shape.

[0012] As a preferred solution, the shape of the hole includes at least one of a circle, an ellipse, a rectangle, a rhombus, a triangle, and a regular polygon.

[0013] As a preferred solution, it also includes an adhesive film layer, and the adhesive film layer and the shielding layer are stacked.

[0014] As a preferred solution, a protruding structure is provided on one side of the shielding layer close to the adhesive film layer, and the adhesive film layer includes an adhesive layer that does not contain conductive particles.

[0015] As a preferred solution, a side of the shielding layer close to the adhesive film layer is a flat surface, and the adhesive film layer includes an adhesive layer containing conductive particles.

[0016] As a preferred solution, it also includes an insulating layer, which is arranged on a surface of the shielding layer on a side away from the adhesive film layer.

[0017] A second aspect of an embodiment of the present invention provides a circuit board, comprising a circuit board substrate and an electromagnetic shielding film as described in any one of the first aspects; the electromagnetic shielding film is pressed together with the circuit board substrate.

[0018] Compared with the prior art, the embodiments of the present invention have the following advantages:

[0019] (1) By opening a plurality of holes on the shielding layer, the air permeability of the circuit board can be increased after the electromagnetic shielding film is pressed onto the circuit board substrate, so that the water vapor on the surface of the circuit board can be discharged through the holes on the shielding layer, thereby reducing the moisture accumulated on the surface of the circuit board and significantly reducing the probability of short circuit on the circuit board.

[0020] (2) By limiting the residual rate of the shielding layer and the impedance change rate of the circuit board using the electromagnetic shielding film to satisfy a linear regression relationship, the impedance change rate of the circuit board can be used to constrain the residual rate of the shielding layer, thereby preventing the residual rate of the shielding layer from being too large or too small. This ensures that water vapor on the surface of the circuit board can be effectively discharged through the holes in the shielding layer to reduce the probability of a short circuit on the circuit board, while ensuring the impedance stability of the circuit board using the electromagnetic shielding film. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is a schematic structural diagram of a first electromagnetic shielding film provided by an embodiment of the present invention;

[0022] Figure 2 is an electron microscope image of an opening on the surface of the shielding layer in an embodiment of the present invention;

[0023] Figure 3 is a schematic diagram of a linear regression fitting curve of an impedance change rate of a circuit board and a residual rate of a shielding layer in one embodiment of the present invention;

[0024] Figure 4 is a schematic diagram of the opening structure on the surface of the shielding layer in an embodiment of the present invention;

[0025] Figure 5 is a schematic structural diagram of a second electromagnetic shielding film provided by an embodiment of the present invention;

[0026] Figure 6 is a schematic structural diagram of a third electromagnetic shielding film provided by an embodiment of the present invention;

[0027] Figure 7 is an electron microscope image of an electromagnetic shielding film with a protruding structure pressed onto a circuit board substrate in an embodiment of the present invention;

[0028] Figure 8 is a schematic structural diagram of a fourth electromagnetic shielding film provided by an embodiment of the present invention;

[0029] Fig. 9 is a schematic diagram of a linear regression fitting curve of the impedance change rate of the circuit board and the residual rate of the shielding layer in Examples 1-5 of the present invention;

[0030] Fig.10 is a schematic diagram of a linear relationship curve between the impedance change rate of the circuit board and the thickness of the shielding layer in Examples 1-5 of the present invention;

[0031] Among them, 100, electromagnetic shielding film; 101, shielding layer; 102, film layer; 103, insulating layer; 104, protruding structure; 105, hole. DETAILED DESCRIPTION

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] See also Figure 1According to a first aspect of an embodiment of the present invention, an electromagnetic shielding film 100 is provided, comprising a shielding layer 101, wherein a plurality of holes 105 are formed on the shielding layer 101, and a residual rate Y of the shielding layer 101 and an impedance change rate X of a circuit board to which the electromagnetic shielding film 100 is applied satisfy the following linear regression relationship: Y=AX+B;

[0037] The residual rate Y is the weight ratio of the shielding layer 101 after the opening to the shielding layer 101 before the opening;

[0038] The impedance change rate X is calculated as follows: impedance change rate X=|impedance of the circuit board to which the electromagnetic shielding film 100 is applied-initial impedance of the circuit board| / initial impedance of the circuit board;

[0039] A and B are both constants. The value range of A is 1 to 10, and the value range of B is -2 to 1.

[0040] Specifically, after the electromagnetic shielding film 100 is pressed onto the circuit board substrate, the adhesive film layer 102 and the shielding layer 101 on the circuit board surface have a certain degree of sparseness, that is, there are small gaps on the adhesive film layer 102 and the shielding layer 101, so that the water vapor accumulated on the circuit board surface during use can be slowly discharged through the shielding layer 101, and in this embodiment, a plurality of holes 105 are opened on the shielding layer 101, such as Figure 2 As shown, after the electromagnetic shielding film 100 is pressed onto the circuit board, water vapor on the surface of the circuit board can be discharged through the holes 105 on the shielding layer 101, which better reduces the moisture accumulated on the surface of the circuit board, reduces the relative humidity on the surface of the circuit board, and effectively avoids short circuits between copper circuits.

[0041] Furthermore, since the shapes of the holes 105 opened on the shielding layer 101 include different regular shapes and / or irregular shapes, and their areas are difficult to measure accurately, the present embodiment adopts the ratio between the weight of the shielding layer 101 after the holes are opened and the weight of the shielding layer 101 before the holes are opened, i.e., the residual rate, to characterize the volume occupied by the opening of the holes 105. In addition, since the size of the volume of the holes opened on the shielding layer 101 will cause the residual rate of the shielding layer 101 to change, and when the electromagnetic shielding film 100 is pressed on the circuit board substrate, the impedance of the circuit board will change, thereby affecting the stability of subsequent applications of the circuit board. Therefore, this embodiment defines the relationship between the residual rate Y of the shielding layer 101 and the impedance change rate X of the circuit board using the electromagnetic shielding film 100, that is, the two satisfy the linear regression relationship: Y=AX+B, and the impedance change rate of the circuit board is used to constrain the residual rate of the shielding layer 101. On the basis of maintaining the impedance stability of the circuit board using the electromagnetic shielding film 100, it is possible to avoid the residual rate of the shielding layer 101 being too large or too small, thereby ensuring that the water vapor on the surface of the circuit board can be effectively discharged through the holes 105 on the shielding layer 101 to reduce the probability of short circuit on the circuit board, while ensuring the impedance stability of the circuit board using the electromagnetic shielding film 100.

[0042] Furthermore, this embodiment defines the determination coefficient r of the linear regression relationship between the residual rate of the shielding layer 101 and the impedance change rate of the circuit board to which the electromagnetic shielding film 100 is applied as follows: 2 The determination coefficient r 2 It is determined by the actual fitting curve and is not specifically limited in this embodiment. It can be understood that the determination coefficient r 2 The closer it is to 1, the closer the fitted curve is to the actual situation, and the fitting effect of the linear regression relationship in this embodiment is good.

[0043] Furthermore, the present embodiment also limits the parameters A and B in the above linear regression relationship. Specifically, the value range of A is 1 to 10, for example, A is 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, etc., which is not specifically limited in the present embodiment; the value range of B is -2 to 1, for example, B is -2, -1, -0.5, 0.5, 1, etc., which is not specifically limited in the present embodiment. Based on the value ranges of the above parameters, it can further ensure that the linear regression fitting effect is better.

[0044] As a preferred solution, the value of A is 6.548 and the value of B is -0.4165.

[0045] Generally speaking, after the electromagnetic shielding film 100 covers the circuit board substrate, the impedance change rate of the circuit board is preferably less than 20%. Figure 3As shown, this embodiment further limits A to 6.548 and B to -0.4165, so that the impedance change rate of the circuit board can be less than 20%, and at the same time ensure that the opening volume is sufficient to effectively discharge the water vapor on the surface of the circuit board to avoid short circuit, as shown in FIG. Figure 3 As shown in the fitting curve in , the horizontal axis is the impedance change rate of the circuit board after the shielding screen is applied, and the vertical axis is the residual rate of the shielding layer 101. The residual rate of the shielding layer 101 is preferably 40% to 80%. For example, the residual rate can be 40%, 41%, 46%, 49%, 51%, 53%, 55%, 57%, 60%, 63%, 65%, 69%, 70%, 73%, 76%, 80%, etc., which is not specifically limited in this embodiment. Within this residual rate range, it can be ensured that the volume occupied by the opening of the hole 105 will not be too small, that is, the residual rate is less than or equal to 80%, so as to ensure that the proportion of the hole 105 on the shielding layer 101 is relatively large, and the exhaust efficiency of the circuit board surface is ensured. At the same time, it can be ensured that the volume occupied by the opening of the hole 105 will not be too large, that is, the residual rate is greater than or equal to 40%, so as to ensure the shielding effectiveness of the shielding layer 101.

[0046] As a preferred solution, the impedance change rate X and the thickness D of the shielding layer 101 satisfy the following relationship: D=KX+Q; wherein K and Q are both constants, the value range of K is 20 to 150, and the value range of Q is -20 to -1, and the above relationship is dimensionless.

[0047] Specifically, since the thickness of the shielding layer 101 affects the impedance change rate of the circuit board, the thickness of the shielding layer 101 is proportional to the impedance change rate of the circuit board. The greater the thickness of the shielding layer 101, the greater the impedance change rate of the circuit board, and the smaller the thickness of the shielding layer 101, the smaller the impedance change rate of the circuit board. Therefore, in this embodiment, the impedance change rate X and the thickness D of the shielding layer 101 are limited to satisfy the following relationship: D=KX+Q, wherein K and Q are both constants, the value range of K is 20 to 150, and the value range of Q is -20 to -1. For example, K can be 20, 40, 60, 80, 110, 130, 150, etc., and Q can be -20, -15, -10, -5, -3, -1, etc. This embodiment does not make specific limitations here. Within the above-mentioned value range of K and Q, it can be ensured that within a certain thickness of the shielding layer 101, the impedance change rate of the circuit board will not be too large. It is worth noting that the relationship: D=KX+Q is dimensionless.

[0048] As a preferred solution, the impedance change rate X is less than 20%, and the thickness D of the shielding layer 101 is 0.1 μm to 3.5 μm.

[0049] Specifically, the present embodiment further limits the impedance change rate of the circuit board applying the electromagnetic shielding film 100 to less than 20%. For example, the impedance change rate may be 2%, 4%, 6%, 8%, 10%, 11%, 13%, 15%, 17%, 19%, etc. The present embodiment does not make any specific limitation here, so as to avoid the impedance change rate of the circuit board being too large after applying the electromagnetic shielding film 100, thereby affecting the stability of subsequent applications.

[0050] Furthermore, the present embodiment further limits the thickness of the shielding layer 101 to 0.1μm to 3.5μm. For example, the thickness of the shielding layer 101 is 0.1μm, 0.2μm, 0.3μm, 0.5μm, 0.7μm, 0.9μm, 1.2μm, 1.4μm, 1.6μm, 1.9μm, 2.1μm, 2.3μm, 2.5μm, 2.7μm, 3μm, 3.1μm, 3.3μm, 3.5μm, etc. The present embodiment does not make any specific limitations here, so as to ensure that the thickness of the shielding layer 101 is moderate, and will not affect the overall thickness of the electromagnetic shielding film 100 and cause the impedance change rate of the circuit board to be too large due to being too thick, nor will it affect the shielding effectiveness of the electromagnetic shielding film 100 due to being too thin.

[0051] As a preferred solution, the shape of the hole 105 includes a regular shape and / or an irregular shape.

[0052] It is worth noting that the present embodiment does not specifically limit the shape of the hole 105 on the shielding layer 101, and the shape of the hole 105 may include different regular shapes, different irregular shapes, or different regular shapes and irregular shapes at the same time. Further, the shape of the hole 105 on the shielding layer 101 is preferably a regular shape, so as to facilitate the production of the electromagnetic shielding film 100, and the regular geometric shape facilitates the measurement of the maximum width of the hole 105 and the hole spacing.

[0053] In one of the optional embodiments, the holes 105 on the shielding layer 101 include blind holes and / or through holes, that is, the holes 105 on the shielding layer 101 may all be blind holes, may all be through holes, or may include both blind holes and through holes. Preferably, the holes 105 on the shielding layer 101 are all set as through holes. If the holes 105 on the shielding layer 101 include blind holes, the bottom surface of the blind holes is made of a material with low density, such as copper, which can be achieved by sputtering a thin layer of copper on the blind holes. Since the bottom surface of the blind holes has a certain degree of sparseness, the water vapor accumulated on the surface of the circuit board can be discharged through the bottom surface of the blind holes. Preferably, the sealing surface of the blind holes is arranged on the side away from the circuit board substrate, and the opening end thereof is arranged on the side close to the circuit board substrate, so as to effectively enhance the water vapor discharge effect.

[0054] As a preferred solution, the shape of the hole 105 includes at least one of a circle, an ellipse, a rectangle, a rhombus, a triangle, and a regular polygon.

[0055] Specifically, the present embodiment limits the shape of the hole 105 to a regular geometric figure, thereby facilitating the production of the electromagnetic shielding film 100, and the regular geometric figure facilitates the measurement of the maximum width and the hole spacing of the hole 105. It is worth noting that the shape of the hole 105 in the present embodiment can be one of a circle, an ellipse, a rectangle, a rhombus, a triangle, and a regular polygon, such as Figure 4 As shown, the shapes of the holes 105 on the shielding layer 101 are all triangles, and may also include two or more of these geometric shapes. For example, the shapes of the holes 105 on the shielding layer 101 may all be circles, ellipses, rectangles, rhombuses, triangles or regular polygons, and may also include circles and ellipses, or rectangles, rhombuses and circles, or circles, triangles and regular polygons, or circles, ellipses, rectangles, rhombuses, triangles and regular polygons at the same time. This embodiment will not be repeated here.

[0056] See also Figure 5 As a preferred solution, it further includes a film layer 102 , and the film layer 102 and the shielding layer 101 are stacked.

[0057] Specifically, the adhesive film layer 102 in this embodiment is arranged between the shielding layer 101 and the circuit board substrate. The material of the adhesive film layer 102 is generally a polymer matrix, including polyethylene terephthalate, polyethylene, polyvinyl alcohol, cycloolefin copolymer, etc. These materials have good flexibility, transparency and processing performance, and are ideal substrates for preparing flexible transparent electromagnetic shielding film 100.

[0058] As a preferred solution, a protruding structure 104 is provided on one side of the shielding layer 101 close to the adhesive film layer 102 , and the adhesive film layer 102 includes an adhesive layer that does not contain conductive particles.

[0059] Specifically, Figure 6 As shown, in this embodiment, a protruding structure 104 is provided on one side of the shielding layer 101 close to the adhesive film layer 102. In order to ensure that the electromagnetic shielding film 100 can be tightly bonded to the circuit board substrate after being pressed together, the adhesive film layer 102 further includes an adhesive layer that does not contain conductive particles. When the electromagnetic shielding film 100 is pressed together with the circuit board substrate, the protruding structure 104 on the shielding layer 101 can pierce the adhesive film layer 102 so that the shielding layer 101 can be connected to the ground layer of the circuit board substrate, thereby ensuring that the interference charge is normally discharged and realizing the electromagnetic shielding function.

[0060] As one of the optional embodiments, the protruding structure 104 can extend into the adhesive film layer 102, so that the protruding structure 104 can more easily pierce the adhesive film layer 102 during the process of laminating the electromagnetic shielding film 100 with the circuit board substrate. Alternatively, the protruding structure 104 can also pierce the adhesive film layer 102, so that during the process of laminating the electromagnetic shielding film 100 with the circuit board substrate, the protruding structure 104 can be directly inserted into the ground layer of the circuit board substrate. Of course, the protruding structure 104 can also not extend into the adhesive film layer 102 but be covered by the adhesive film layer 102.

[0061] It is worth noting that the adhesive layer included in the film layer 102 in this embodiment is achieved by adding an adhesive to the film layer 102. Commonly used adhesives include silicone, silicone fluoride, EPDM (Ethylene Propylene Diene Monomer), fluorocarbon-silicon fluoride, etc. These adhesives have good adhesion and stability.

[0062] It is worth noting that the protruding structure 104 in this embodiment is formed by sputtering or electroplating when the shielding layer 101 is not perforated. After the protruding structure 104 is formed, a hole is opened on the shielding layer 101. The location of the opening is preferably at a location where there are fewer protruding structures 104, such as Figure 7 As shown, it is ensured as much as possible that after the hole is opened, the puncture grounding performance of the metal shielding film and the circuit board substrate is not affected when pressed together, thereby avoiding affecting the shielding effectiveness.

[0063] As a preferred solution, the side of the shielding layer 101 close to the adhesive film layer 102 is a flat surface, and the adhesive film layer 102 includes an adhesive layer containing conductive particles.

[0064] Specifically, in this embodiment, the side of the shielding layer 101 close to the film layer 102 is a flat surface, so that in this embodiment, the film layer 102 includes an adhesive layer containing conductive particles. Therefore, in the process of pressing the electromagnetic shielding film 100 and the circuit board substrate, because the force is mutual, when the shielding layer 101 continues to approach the film layer 102 under the action of pressure, the circuit board substrate also approaches the film layer 102 under the action of pressure, so that the film layer 102 is squeezed by two forces in opposite directions, and then the shielding layer 101 can be connected to the ground layer of the circuit board substrate through the conductive particles in the film layer 102, thereby ensuring that the interference charge is normally discharged and realizing the electromagnetic shielding function.

[0065] As one optional embodiment, the conductive particles include graphene nanosheets, carbon nanotubes, ferroferric oxide, silver nanowires, pure silver, silver-plated copper, silver-plated aluminum, silver-plated nickel, etc. These conductive particles can significantly improve the conductivity and electromagnetic shielding effectiveness of the adhesive film layer 102. For example, silver nanowires are widely used in the preparation of the electromagnetic shielding film 100 due to their excellent conductivity and transparency.

[0066] As one of the optional embodiments, the conductive particles in this embodiment can be conductive particles separated from each other, or can be large-particle conductive particles formed by agglomeration; when the conductive particles are conductive particles separated from each other, the area of ​​electrical contact can be further increased, and the uniformity of electrical contact can be improved; and when the conductive particles are large-particle conductive particles formed by agglomeration, the piercing strength can be increased.

[0067] It is worth noting that, in order to firmly combine the conductive particles in the film layer 102, the adhesive layer included in the film layer 102 in this embodiment is achieved by adding an adhesive to the film layer 102. Commonly used adhesives include silicone, silicone fluoride, EPDM (Ethylene Propylene Diene Monomer), fluorocarbon-silicon fluoride, etc. These adhesives have good adhesion and stability, and can ensure the uniform distribution and long-term stability of the conductive particles in the film layer 102.

[0068] See also Figure 8 As a preferred solution, it further includes an insulating layer 103 , and the insulating layer 103 is disposed on a surface of the shielding layer 101 away from the adhesive film layer 102 .

[0069] It is worth mentioning that, since the insulating layer 103 has an isolation effect, arranging the insulating layer 103 on one side surface of the shielding layer 101 is helpful to ensure the shielding effectiveness of the shielding layer 101; in addition, the insulating layer 103 also has a protective effect to ensure that the shielding layer 101 is not scratched or damaged during use, thereby helping to maintain the high shielding effectiveness of the shielding layer 101.

[0070] The insulating layer 103 in this embodiment 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, etc. This embodiment is not specifically limited here.

[0071] A second aspect of the embodiments of the present invention provides a circuit board, comprising a circuit board substrate and the electromagnetic shielding film 100 as described in any embodiment of the first aspect; the electromagnetic shielding film 100 is pressed together with the circuit board substrate.

[0072] It is worth noting that the electromagnetic shielding film 100 in this embodiment is pressed against the circuit board substrate, and the ground layer of the circuit board substrate is connected to the shielding layer 101 in the electromagnetic shielding film 100, thereby ensuring that the interference charges are normally extracted.

[0073] The electromagnetic shielding film 100 and the circuit board provided by the embodiment of the present invention have the beneficial effects of at least one of the following:

[0074] (1) By opening a plurality of holes 105 on the shielding layer 101, the air permeability of the circuit board can be increased after the electromagnetic shielding film 100 is pressed onto the circuit board substrate, so that water vapor on the surface of the circuit board can be discharged through the holes 105 on the shielding layer 101, thereby reducing the moisture accumulated on the surface of the circuit board and significantly reducing the probability of a short circuit on the circuit board.

[0075] (2) By limiting the residual rate of the shielding layer 101 and the impedance change rate of the circuit board using the electromagnetic shielding film 100 to satisfy a linear regression relationship, the impedance change rate of the circuit board can be used to constrain the residual rate of the shielding layer 101, thereby preventing the residual rate of the shielding layer 101 from being too large or too small. This ensures that water vapor on the surface of the circuit board can be effectively discharged through the holes 105 on the shielding layer 101 to reduce the probability of short circuit on the circuit board, while ensuring the impedance stability of the circuit board using the electromagnetic shielding film 100.

[0076] In order to demonstrate the beneficial effects of the electromagnetic shielding film and circuit board provided by the embodiments of the present invention, several embodiments and comparative examples are described below.

[0077] Example 1

[0078] An electromagnetic shielding film comprises a shielding layer, wherein the shielding layer is provided with a plurality of holes, the residual rate Y of the shielding layer is 70%, the impedance change rate X of a circuit board using the electromagnetic shielding film is 19%, and the thickness D of the shielding layer is 3.5 μm.

[0079] Example 2

[0080] An electromagnetic shielding film comprises a shielding layer, wherein the shielding layer is provided with a plurality of holes, the residual rate Y of the shielding layer is 66%, the impedance change rate X of a circuit board using the electromagnetic shielding film is 18%, and the thickness D of the shielding layer is 3 μm.

[0081] Example 3

[0082] An electromagnetic shielding film comprises a shielding layer, wherein the shielding layer is provided with a plurality of holes, the residual rate Y of the shielding layer is 60%, the impedance change rate X of a circuit board using the electromagnetic shielding film is 15%, and the thickness D of the shielding layer is 1.5 μm.

[0083] Example 4

[0084] An electromagnetic shielding film comprises a shielding layer, a film layer and an insulating layer, wherein the film layer and the shielding layer are stacked, and the insulating layer is arranged on a side of the shielding layer away from the film layer. The side of the shielding layer close to the film layer is a flat surface, and the film layer comprises an adhesive layer containing conductive particles. The shielding layer is provided with a plurality of holes, the residual rate Y of the shielding layer is 58%, the impedance change rate X of the circuit board using the electromagnetic shielding film is 14%, and the thickness D of the shielding layer is 1 μm.

[0085] Example 5

[0086] An electromagnetic shielding film comprises a shielding layer, a film layer and an insulating layer, wherein the film layer and the shielding layer are stacked, and the insulating layer is arranged on a surface of the shielding layer away from the film layer. The side of the shielding layer close to the film layer is a flat surface, and the film layer comprises an adhesive layer containing conductive particles. The shielding layer is provided with a plurality of holes, the residual rate Y of the shielding layer is 48%, the impedance change rate X of the circuit board using the electromagnetic shielding film is 12%, and the thickness D of the shielding layer is 0.3 μm.

[0087] Comparative Example 1

[0088] An electromagnetic shielding film comprises a shielding layer, a film layer and an insulating layer, wherein the film layer and the shielding layer are stacked, the insulating layer is arranged on a side of the shielding layer away from the film layer, and no hole is opened on the shielding layer. The impedance change rate X of the circuit board using the electromagnetic shielding film is 35%, and the thickness of the shielding layer is 2μm.

[0089] To detect whether a short circuit occurs during the use of the circuit board, the method for pressing the electromagnetic shielding film on the circuit board substrate is: at 185°C, use 120kg / cm 2 The electromagnetic shielding film was pressed onto the circuit board substrate with a pressure of 3 minutes. The test environment of the circuit board after pressing was as follows: the test temperature was 75°C, the humidity was 90% RH, the SIR test voltage was 50V, the test time was 24 hours, and the judgment standard for circuit board short circuit was: insulation resistance <100MΩ was considered to be a short circuit. The test results are shown in Table 1 below.

[0090] Table 1 Circuit board short circuit situation

[0091] Impedance change rate Residual rate Circuit board short circuit Example 1 19％ 70％ No short circuit Example 2 18％ 66％ No short circuit Example 3 15％ 60％ No short circuit Example 4 14％ 58％ No short circuit Example 5 12％ 48％ No short circuit Comparative Example 1 35％ 100％ Short circuit occurs

[0092] As can be seen from Table 1 above, the shielding layers in Examples 1 to 5 are all provided with a plurality of holes, and the residual rate of the shielding layer and the impedance change of the circuit board using the electromagnetic shielding film satisfy the following relationship: Fig. 9 The linear regression relationship shown is: Y = 2.8554X + 0.1586, R 2=0.9558, where the values ​​of A and B are within the ranges described in the embodiments of the present invention. At the same time, the impedance change rate and the thickness of the shielding layer also satisfy the following conditions: Fig.10 The linear relationship shown is: D = 46.747X-5.4325, R 2 =0.9949, where the values ​​of K and Q are within the ranges described in the embodiments of the present invention. In addition, no short circuit occurs in the above embodiments 1 to 5. In comparative example 1, since no holes are provided on the shielding layer, water vapor gradually accumulates on the surface of the circuit board during use, resulting in a short circuit in the etched copper circuit on the circuit board.

[0093] Therefore, through the verification of the above-mentioned embodiments, it can be known that the present invention can effectively utilize the impedance change rate of the circuit board to constrain the residual rate of the shielding layer, thereby avoiding the residual rate of the shielding layer being too large or too small, thereby ensuring that the water vapor on the surface of the circuit board can be effectively discharged through the holes in the shielding layer to reduce the probability of short circuit in the circuit board, while ensuring the impedance stability of the circuit board using the electromagnetic shielding film.

[0094] The above is a preferred embodiment of the present invention. It should be pointed out that a person skilled in the art can make several improvements and modifications without departing from the principle of the present invention. These improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. An electromagnetic shielding film, characterized in that: The invention comprises a shielding layer, wherein a plurality of holes are formed on the shielding layer, and a residual rate Y of the shielding layer and an impedance change rate X of a circuit board to which the electromagnetic shielding film is applied satisfy the following linear regression relationship: Y=AX+B; Wherein, the residual rate Y is the weight ratio between the shielding layer after the opening and the shielding layer before the opening; The impedance change rate X is calculated as follows: impedance change rate X=|impedance of the circuit board to which the electromagnetic shielding film is applied-initial impedance of the circuit board| / initial impedance of the circuit board; A and B are both constants. The value range of A is 1 to 10, and the value range of B is -2 to 1.

2. The electromagnetic shielding film according to claim 1, wherein The impedance change rate X and the thickness D of the shielding layer satisfy the following relationship: D=KX+Q; wherein K and Q are both constants, the value range of K is 20 to 150, and the value range of Q is -20 to -1, and the above relationship is dimensionless.

3. The electromagnetic shielding film according to claim 2, wherein: The impedance change rate X is less than 20%, and the thickness D of the shielding layer is 0.1 μm to 3.5 μm.

4. The electromagnetic shielding film according to any one of claims 1 to 3, characterized in that: The shape of the holes includes regular shape and / or irregular shape.

5. The electromagnetic shielding film according to claim 4, characterized in that The shape of the hole includes at least one of a circle, an ellipse, a rectangle, a rhombus, a triangle, and a regular polygon.

6. The electromagnetic shielding film according to any one of claims 1 to 3, characterized in that: It also includes a glue film layer, and the glue film layer and the shielding layer are stacked.

7. The electromagnetic shielding film according to claim 6, wherein A protruding structure is arranged on one side of the shielding layer close to the adhesive film layer, and the adhesive film layer includes an adhesive layer without conductive particles.

8. The electromagnetic shielding film according to claim 6, wherein The side of the shielding layer close to the adhesive film layer is a flat surface, and the adhesive film layer includes an adhesive layer containing conductive particles.

9. The electromagnetic shielding film according to claim 6, wherein: It also includes an insulating layer, which is arranged on a surface of the shielding layer on one side away from the adhesive film layer.

10. A circuit board, characterized in that: It comprises a circuit board substrate and the electromagnetic shielding film as claimed in any one of claims 1 to 9; the electromagnetic shielding film is pressed together with the circuit board substrate.

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