Electromagnetic shielding film

Abstract

The invention discloses an electromagnetic shielding film. The electromagnetic shielding film comprises an insulating layer and a shielding layer, the insulating layer is provided with a first side surface, and the first side surface is provided with a plurality of first open holes; the shielding layer is arranged on the first side face, a plurality of second open holes are formed in the shielding layer, the number of the second open holes is smaller than that of the first open holes, and at least part of the second open holes are communicated with the first open holes. According to the electromagnetic shielding film, the insulating layer is provided with the plurality of first open holes, and the shielding layer is provided with the plurality of second open holes which are at least partially communicated with the first open holes, so that the heat dissipation performance of the electromagnetic shielding film can be remarkably improved without forming a large number of holes with large apertures in the shielding layer; meanwhile, the shielding effectiveness of the electromagnetic shielding film is guaranteed, in addition, the number of the second openings formed in the shielding layer can be reduced while the heat dissipation performance is guaranteed, and therefore the shielding effectiveness of the electromagnetic shielding film can be further guaranteed.

Description

Technical Field

[0001] The present invention relates to the technical field of electronic materials, and in particular to an electromagnetic shielding film. Background Art

[0002] As the performance requirements for data transmission of communication devices are getting higher and higher, the power consumption of communication devices is also increasing continuously, which also increases the heat dissipation requirements for electronic devices. In the field of the circuit board industry, high-temperature process flows such as reflow soldering and SMT (Surface Mount Technology) are often required. At the same time, the circuit board often undergoes multiple high-temperature process flows during assembly. Therefore, the electromagnetic shielding film laminated on the circuit board needs to have good heat dissipation performance.

[0003] In the prior art, in order to improve the heat dissipation performance of the electromagnetic shielding film, processes such as laser are usually used to form holes in the metal layer of the electromagnetic shielding film, so that the circuit board can achieve effective heat dissipation during the high-temperature process flow. However, this method requires the holes formed in the metal layer to have a larger aperture and a larger number, which will seriously affect the shielding effect of the electromagnetic shielding film. Summary of the Invention

[0004] The present invention provides an electromagnetic shielding film, which can improve the heat dissipation performance of the electromagnetic shielding film while ensuring the shielding effectiveness of the electromagnetic shielding film.

[0005] To solve the above technical problems, in the first aspect of the embodiments of the present invention, an electromagnetic shielding film is provided. The electromagnetic shielding film includes an insulating layer and a shielding layer;

[0006] The insulating layer has a first side surface, and a plurality of first openings are formed on the first side surface;

[0007] The shielding layer is disposed on the first side surface. The shielding layer is provided with a plurality of second openings. The number of the second openings is less than the number of the first openings, and at least some of the second openings are communicated with the first openings.

[0008] As a preferred solution, in a preset observation area, the difference between the number of the second openings and the number of the first openings is greater than or equal to 1.

[0009] As a preferred solution, in a preset observation area, the ratio between the number of the second openings with an aperture ratio less than 1 and the total number of the second openings is greater than 50%; wherein, the aperture ratio is the ratio between the maximum aperture of the second opening and the maximum aperture of the first opening.

[0010] As a preferred solution, within the preset observation area, the ratio between the number of second openings with an aperture ratio of 0.1 to 1 and the total number of the second openings is greater than 40%.

[0011] As a preferred solution, the minimum distance between two adjacent first openings is greater than 0.5 μm.

[0012] As a preferred solution, the maximum depth of the first opening is 0.1 μm to 5 μm; and / or,

[0013] The second opening is a blind hole or a perforation.

[0014] As a preferred solution, the thickness of the shielding layer is 1 μm to 10 μm.

[0015] As a preferred solution, there is at least one second opening whose maximum aperture is smaller than the maximum aperture of the first opening connected thereto.

[0016] As a preferred solution, the electromagnetic shielding film further includes a connection layer, and the connection layer is disposed on a side surface of the shielding layer facing away from the insulating layer.

[0017] As a preferred solution, a protruding portion is provided on a side surface of the shielding layer facing away from the first side surface, and the protruding portion is used for electrically connecting to the ground layer of the circuit board substrate after the electromagnetic shielding film is laminated with the circuit board substrate.

[0018] As a preferred solution, conductive particles are provided in the connection layer.

[0019] As a preferred solution, the insulating layer includes a base layer and a filling layer, and the first side surface is disposed on a side surface of the filling layer facing away from the base layer.

[0020] Compared with the prior art, the beneficial effects of the embodiments of the present invention are as follows:

[0021] (1) By providing a plurality of first openings in the insulating layer and a plurality of second openings in the shielding layer that are at least partially connected to the first openings, the heat dissipation performance of the electromagnetic shielding film can be significantly improved without forming holes with a large aperture and a large number in the shielding layer, while ensuring the shielding effectiveness of the electromagnetic shielding film.

[0022] (2) By limiting the number of second openings to be less than the number of first openings, the heat dissipation performance of the electromagnetic shielding film can be ensured while reducing the number of second openings provided on the shielding layer, thereby further ensuring the shielding effectiveness of the electromagnetic shielding film. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is a schematic structural diagram of the first electromagnetic shielding film in the embodiments of the present invention;

[0024] Figure 2 It is a schematic structural diagram of the second electromagnetic shielding film in the embodiments of the present invention;

[0025] Figure 3 It is a schematic structural diagram of the third electromagnetic shielding film in the embodiments of the present invention;

[0026] Figure 4 It is a schematic structural diagram of the fourth electromagnetic shielding film in the embodiments of the present invention;

[0027] Figure 5 It is a schematic structural diagram of the fifth electromagnetic shielding film in the embodiments of the present invention;

[0028] Figure 6 It is a schematic flow diagram of the preparation method of the electromagnetic shielding film in the embodiments of the present invention;

[0029] Figure 7 It is a schematic flow diagram of the formation of the shielding layer in the embodiments of the present invention;

[0030] Wherein, 1. Insulating layer; 101. Base layer; 102. Filling layer; 2. Shielding layer; 3. First opening; 4. Second opening; 5. Connecting layer; 6. Protrusion; 7. Conductive particles. Detailed implementation manners

[0031] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. 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 those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.

[0032] In the description of the present application, the terms "first", "second", "third", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first", "second", "third", etc. may explicitly or implicitly include one or more of such features. In the description of the present application, unless otherwise specified, the meaning of "a plurality" is two or more.

[0033] In the description of the present application, it should be noted that unless otherwise clearly specified and defined, 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 directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two components. The terms "vertical", "horizontal", "left", "right", "upper", "lower" and similar expressions used herein are only for the purpose of illustration, rather than indicating or implying that the device or component referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation to the present invention. The term "and / or" used herein includes any and all combinations of one or more of the related listed items. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific circumstances.

[0034] In the description of the present application, it should be noted that unless otherwise defined, all technical and scientific terms used in the present invention have the same meanings as those commonly understood by those skilled in the technical field to which the present invention belongs. 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 the present application can be understood according to specific circumstances.

[0035] Please refer to Figure 1 , the first aspect of the embodiment of the present invention provides an electromagnetic shielding film, and the electromagnetic shielding film includes an insulating layer 1 and a shielding layer 2;

[0036] The insulating layer 1 has a first side surface, and a plurality of first openings 3 are formed on the first side surface;

[0037] The shielding layer 2 is disposed on the first side surface, and the shielding layer 2 is provided with a plurality of second openings 4. The number of the second openings 4 is less than the number of the first openings 3, and at least some of the second openings 4 communicate with the first openings 3.

[0038] Specifically, the electromagnetic shielding film in this embodiment includes an insulating layer 1 and a shielding layer 2. Since the insulating layer 1 has an insulating effect, it is beneficial to ensure the shielding efficiency of the shielding layer 2 by providing the insulating layer 1 on one side surface of the shielding layer 2; in addition, the insulating layer 1 also has a protective effect to ensure that the shielding layer 2 is not scratched or damaged during use, thereby being beneficial to maintaining the high shielding efficiency of the shielding layer 2.

[0039] In order to improve the heat dissipation performance of the electromagnetic shielding film while ensuring the shielding effectiveness of the shielding layer 2, in this embodiment, a plurality of first openings 3 are formed on the first side surface of the insulating layer 1, and the shielding layer 2 is also provided with at least partially second openings 4 communicating with the first openings 3. It can be understood that among all the second openings 4 formed in the shielding layer 2, 40% of the second openings 4 may communicate with the first openings 3, 75% of the second openings 4 may communicate with the first openings 3, or 100% of the second openings 4 may communicate with the first openings 3. As long as it is ensured that there are second openings 4 communicating with the first openings 3, this embodiment will not elaborate too much here. Thus, the effective heat dissipation area can be increased, enabling the electromagnetic shielding film to effectively discharge heat through the communicating first openings 3 and second openings 4 during the high-temperature process flow. In addition, since the communication between the first openings 3 on the insulating layer 1 and the second openings 4 on a part of the shielding layer 2 significantly improves the heat dissipation performance of the electromagnetic shielding film, there is no need to form holes with a large aperture and a large number on the shielding layer 2, thereby effectively ensuring the shielding effectiveness of the electromagnetic shielding film.

[0040] In addition, this embodiment also limits the number of the second openings 4 to be less than the number of the first openings 3. It is worth noting that if the number of the second openings 4 formed on the shielding layer 2 is too large, it will directly affect the shielding effectiveness of the shielding layer 2. Therefore, by limiting the number of the second openings 4 to be less than the number of the first openings 3 in this embodiment, it can be ensured that there are more first openings 3 formed in the insulating layer 1 and fewer second openings 4 formed in the shielding layer 2, thereby being able to avoid the influence on the shielding effectiveness caused by too many second openings 4 formed in the shielding layer 2 while ensuring the heat dissipation performance of the electromagnetic shielding film.

[0041] In a preferred embodiment, the maximum aperture of the first openings 3 on the insulating layer 1 is specifically limited to 1 μm to 10 μm. For example, the maximum aperture of the first openings 3 can be 1 μm, 1.5 μm, 2 μm, 2.3 μm, 2.7 μm, 3.1 μm, 3.4 μm, 3.9 μm, 4.2 μm, 4.6 μm, 5 μm, 5.5 μm, 6 μm, 6.3 μm, 6.7 μm, 7.3 μm, 7.5 μm, 8 μm, 8.2 μm, 8.7 μm, 9 μm, 9.5 μm, 10 μm, etc. This embodiment does not make specific limitations here. It can be understood that considering that the aperture of the opening is different at different depths, the maximum aperture of the first openings 3 is the maximum distance in any horizontal direction from the hole opening to the hole bottom under the sectional view or top view of the insulating layer 1, where the horizontal direction refers to the direction perpendicular to the thickness direction of the insulating layer 1. By limiting the maximum aperture of the first openings 3 within the above aperture range, it can be ensured that the first openings 3 will not affect the heat dissipation performance of the electromagnetic shielding film due to too small an aperture, ensuring sufficient heat dissipation area, and at the same time being able to avoid the influence on the electrical insulation performance of the insulating layer 1 caused by too large an aperture of the first openings 3.

[0042] It should be noted that the first opening 3 in this embodiment can be a blind hole or a through hole, that is, the first openings 3 on the insulating layer 1 can all be blind holes, all be through holes, or some be blind holes and some be through holes. Preferably, the first openings 3 are all blind holes.

[0043] In addition, the shape of the first opening 3 on the insulating layer 1 is not specifically limited in this embodiment. The shape of the first opening 3 can include different regular shapes, such as circular, elliptical, rectangular, rhombic, triangular, regular polygon, etc., can also include different irregular shapes, or can also include different regular shapes and irregular shapes at the same time.

[0044] In an alternative embodiment, the above shielding layer 2 includes any one or more than two materials among aluminum, titanium, zinc, iron, nickel, chromium, cobalt, copper, silver, and gold.

[0045] In an alternative embodiment, the above insulating layer 1 includes a PPS film layer, a PEN film layer, a polyester film layer, a polyimide film layer, a film layer formed after curing of epoxy resin ink, a film layer formed after curing of polyurethane ink, a film layer formed after curing of modified acrylic resin, or a film layer formed after curing of polyimide resin.

[0046] As a preferred solution, within a preset observation area, the difference between the number of the second openings 4 and the number of the first openings 3 is greater than or equal to 1. For example, the preset observation area is 5000 - 20000 μm 2 . In the sliced state, the preset observation area is a lateral observation distance of 30 - 200 μm.

[0047] Specifically, in this embodiment, by limiting that within a preset observation area, for example, in the sliced state, within every 100 - micron lateral observation area, the difference between the number of the second openings 4 and the number of the first openings 3 is greater than or equal to 1. For example, within this preset observation area, the difference between the number of the second openings 4 and the number of the first openings 3 is 1, 2, 3, 4, 5, etc., which is not specifically limited in this embodiment. Thus, overall, it can be ensured that the number of the first openings 3 is large while the number of the second openings 4 is small, so as to ensure the heat dissipation performance of the electromagnetic shielding film and better avoid that too many second openings 4 opened in the shielding layer 2 affect the shielding effectiveness.

[0048] In addition, by ensuring that the difference between the number of the second openings 4 and the number of the first openings 3 is greater than or equal to 1 in each preset observation area, the distribution uniformity of both the first openings 3 opened in the insulating layer 1 and the second openings 4 opened in the shielding layer 2 can be ensured simultaneously, guaranteeing the heat dissipation uniformity of the electromagnetic shielding film during the high - temperature process flow.

[0049] As a preferred solution, within a preset observation area, the ratio between the number of second openings 4 with an aperture ratio less than 1 and the total number of second openings is greater than 50%; wherein, the aperture ratio is the ratio between the maximum aperture of the second opening and the maximum aperture of the first opening.

[0050] Specifically, in this embodiment, by limiting that within the preset observation area, the ratio between the number of second openings 4 with an aperture ratio less than 1 and the total number of second openings is greater than 50%. For example, this ratio can be 51%, 53%, 55%, 57%, 60%, 63%, 67%, 69%, 71%, 73%, 75%, 78%, 80%, 81%, 83%, 85%, 87%, 89%, 91%, 93%, 95%, 97%, 99%, 100%, etc. This embodiment does not make specific limitations here, so as to ensure that there are enough second openings 4 with an aperture smaller than that of the first opening 3, ensuring that the apertures of the second openings 4 on the shielding layer 2 are small, and thus better ensuring the shielding effectiveness of the shielding layer 2 and further reducing the production cost.

[0051] Among them, the maximum aperture of the second opening 4 is the maximum distance in any horizontal direction from the orifice to the bottom of the hole under the sectional view or top view of the shielding layer 2, where this horizontal direction refers to the direction perpendicular to the thickness direction of the shielding layer 2.

[0052] As a preferred solution, within the preset observation area, the ratio between the number of second openings with an aperture ratio of 0.1 - 1 and the total number of second openings is greater than 40%.

[0053] Specifically, this embodiment further limits that within the preset observation area, the ratio between the number of second openings 4 with an aperture ratio of 0.1 - 1 and the total number of second openings is greater than 40%. For example, this ratio can be 41%, 43%, 45%, 47%, 50%, 51%, 53%, 55%, 57%, 60%, 63%, 67%, 69%, 71%, 73%, 75%, 78%, 80%, 81%, 83%, 85%, 87%, 89%, 91%, 93%, 95%, 97%, 99%, 100%, etc. This embodiment does not make specific limitations here, so as to ensure that the number of second openings 4 with an aperture less than or equal to that of the first opening 3 will not be too small to affect the shielding effectiveness of the electromagnetic shielding film, and at the same time ensure that the number of second openings 4 with an aperture less than or equal to that of the first opening 3 will not be too large, so as to ensure the heat dissipation effect of the electromagnetic shielding film.

[0054] As a preferred solution, the minimum distance between two adjacent first openings 3 is greater than 0.5 μm.

[0055] Specifically, in this embodiment, the minimum distance between two adjacent first openings 3 is further limited to be greater than 0.5 μm. For example, the minimum distance between two adjacent first openings 3 can be 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1 μm, 1.2 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, 2 μm, etc. This embodiment will not elaborate further here. This can ensure that two adjacent first openings 3 are not too close to each other. If two adjacent first openings 3 are too close to each other, when manufacturing the shielding layer 2, the two first openings 3 that are too close to each other are likely to stick together, thus failing to play a heat dissipation role.

[0056] As a preferred solution, the maximum depth of the first opening 3 is 0.1 μm to 5 μm.

[0057] Specifically, in this embodiment, the maximum depth of the first opening 3 is further limited to 0.1 μm to 5 μm. For example, the maximum depth of the first opening 3 can be 0.1 μm, 0.3 μm, 0.5 μm, 0.7 μm, 0.9 μm, 1.2 μm, 1.5 μm, 1.7 μm, 1.9 μm, 2.1 μm, 2.3 μm, 2.6 μm, 2.8 μm, 3 μm, 3.2 μm, 3.5 μm, 3.8 μm, 4 μm, 4.2 μm, 4.3 μm, 4.5 μm, 4.7 μm, 4.9 μm, 5 μm, etc. This embodiment does not make specific limitations here. It can be understood that the first opening 3 in this embodiment is formed by coating a layer with metal particles on one side of the insulating layer 1, and when the coating is cured, the metal particles are etched. Therefore, the maximum depth of the first opening 3 is affected by the base layer 101 of the insulating layer 1 and the thickness and density of the layer with metal particles.

[0058] By limiting the maximum depth of the first opening 3 to the above depth range, it can ensure that the maximum depth of the first opening 3 is not too shallow, so as to ensure that there is sufficient heat dissipation area for heat dissipation during high-temperature process flows. In addition, since the maximum depth of the first opening 3 is related to the base layer 101 of the insulating layer 1 and the thickness and density of the layer with metal particles, the first opening 3 with an overly deep maximum depth cannot be obtained by etching. Therefore, this embodiment can ensure that the maximum depth of the first opening 3 is appropriate, neither too shallow nor too deep, which can not only improve the heat dissipation performance of the electromagnetic shielding layer 2 but also be successfully formed by etching.

[0059] As a preferred solution, the thickness of the shielding layer 2 is 1 μm to 10 μm.

[0060] Furthermore, the second opening 4 is a blind hole or a perforation.

[0061] Specifically, the thickness of the shielding layer 2 affects the shielding effectiveness of the electromagnetic shielding film. If the thickness of the shielding layer 2 is too thin, the shielding effectiveness of the electromagnetic shielding film will be low. However, if the thickness of the shielding layer 2 is too thick, the overall thickness of the electromagnetic shielding film will be too large. In this embodiment, the thickness of the shielding layer 2 is further limited to 1 μm to 10 μm. For example, the thickness of the shielding layer 2 can be 1 μm, 1.2 μm, 1.5 μm, 1.8 μm, 2 μm, 2.4 μm, 2.8 μm, 3.1 μm, 3.5 μm, 3.7 μm, 4 μm, 4.2 μm, 4.5 μm, 4.7 μm, 5 μm, 5.3 μm, 5.7 μm, 6 μm, 6.2 μm, 6.5 μm, 6.9 μm, 7.3 μm, 7.6 μm, 8 μm, 8.3 μm, 8.6 μm, 9.1 μm, 9.3 μm, 9.7 μm, 9.9 μm, 10 μm, etc. This embodiment does not make specific limitations here, so as to ensure that the thickness of the shielding layer 2 will not cause the shielding effectiveness of the electromagnetic shielding film to be low due to being too thin, nor will it make the overall thickness of the electromagnetic shielding film too large due to being too thick.

[0062] Furthermore, the second opening 4 in this embodiment can be a blind hole or a through hole. It can be understood that if the second opening 4 is a through hole, the air permeability of the shielding layer 2 is better, thereby improving the heat dissipation effect of the electromagnetic shielding film. If the second opening 4 is a blind hole, the overall thickness of the shielding layer 2 can be reduced, while ensuring the overall shielding effectiveness and improving the heat dissipation performance of the electromagnetic shielding film.

[0063] In addition, this embodiment does not make specific limitations on the shape of the second opening 4 on the insulating layer 1. The shape of the second opening 4 can include different regular shapes, such as circular, oval, rectangular, rhombic, triangular, regular polygon, etc., can also include different irregular shapes, or can also include different regular shapes and irregular shapes at the same time.

[0064] As a preferred solution, the maximum aperture of at least one second opening 4 is smaller than the maximum aperture of the first opening 3 connected thereto.

[0065] Specifically, since in this embodiment, the heat dissipation area of the electromagnetic shielding film is increased by opening the first opening 3 in the insulating layer 1, thereby significantly improving the heat dissipation performance of the electromagnetic shielding film. Further, by defining that the maximum aperture of at least a part of the second openings 4 on the shielding layer 2 is smaller than the maximum aperture of the first opening 3 communicating therewith, first, it is possible to ensure that the aperture of the second opening 4 is small while ensuring the heat dissipation performance, thereby ensuring the continuity and thickness uniformity of the shielding layer 2, and being able to better ensure the shielding effectiveness of the shielding layer 2. In addition, it is also possible to reduce the production cost. For example, after setting a metal seed layer on the insulating layer 1 by magnetron sputtering, electroplating can be carried out to form the shielding layer 2, without laser drilling, which is beneficial to improving the production efficiency and the yield rate, and the cost is low. It is worth noting that the reason why the method of forming the opening in this embodiment is superior to the laser method is as follows: Taking copper as an example, copper has a high absorption rate for laser. If the laser drilling method is used, the laser energy is mainly absorbed by the surface copper layer, resulting in possible carbonized residues on the hole wall. For the lower insulating layer, the laser energy is mainly absorbed by the insulating layer, resulting in possible side etching on the hole wall and forming a drum-shaped hole, that is, the hole mouth size is small and the hole waist size is large. Therefore, at the same laser power, the aperture of the insulating layer may be relatively large, resulting in an impact on the insulation effect. The embodiment of the present invention does not use external drilling, so that there are no holes in some positions of the shielding layer 2, which can ensure the shielding effect while improving the heat dissipation effect, and the processing cost is low.

[0066] As Figure 2 shown, as a preferred solution, the electromagnetic shielding film further includes a connection layer 5, and the connection layer 5 is disposed on a side surface of the shielding layer 2 facing away from the insulating layer 1.

[0067] Specifically, in this embodiment, the connection layer 5 is disposed on a side surface of the shielding layer 2 facing away from the insulating layer 1. After the electromagnetic shielding film is laminated with the circuit board substrate, the connection layer 5 is disposed between the shielding layer 2 and the circuit board substrate, which can ensure that the electromagnetic shielding film can be tightly adhered after being laminated with the circuit board substrate. In an alternative embodiment, the material of the connection layer 5 includes resin materials such as epoxy resin, polyurethane, and polyolefin, and these materials have good flexibility and processing performance.

[0068] As Figure 3 shown, as a preferred solution, a protrusion 6 is provided on a side surface of the shielding layer 2 facing away from the first side surface, and the protrusion 6 is used for electrically connecting with the ground layer of the circuit board substrate after the electromagnetic shielding film is laminated with the circuit board substrate.

[0069] Specifically, on the side of the shielding layer 2 facing away from the first side, that is, the side close to the connection layer 5, a convex portion 6 is provided. When the electromagnetic shielding film is pressed against the circuit board substrate, the convex portion 6 on the shielding layer 2 can pierce through the connection layer 5 so that the shielding layer 2 can be connected to the grounding layer of the circuit board substrate, ensuring the normal export of interference charges and realizing the electromagnetic shielding function.

[0070] As an alternative embodiment, the convex portion 6 can extend into the connection layer 5, which can make it easier for the convex portion 6 to pierce through the connection layer 5 during the pressing of the electromagnetic shielding film against the circuit board substrate. Or, the convex portion 6 can also pierce through the connection layer 5, so that during the pressing of the electromagnetic shielding film against the circuit board substrate, the convex portion 6 can directly insert into the grounding layer of the circuit board substrate. Of course, the convex portion 6 can also not extend into the connection layer 5 but be covered by the connection layer 5.

[0071] It should be noted that the convex portion 6 in this embodiment can be formed by sputtering or electroplating. After the formation of the convex portion 6, the formation position of the convex portion 6 is preferably set at a position with fewer first openings 3, so as to ensure as much as possible that after the opening, the puncture grounding performance during the pressing of the metal shielding film against the circuit board substrate is not affected, and the shielding effectiveness is not affected.

[0072] As Figure 4 shown, as a preferred solution, conductive particles 7 are provided in the connection layer 5.

[0073] Specifically, in order to further improve the effectiveness of electromagnetic shielding, conductive particles 7 are further provided in the connection layer 5 in this embodiment. It can be understood that during the pressing of the electromagnetic shielding film against the circuit board substrate, due to the interaction of forces, when the shielding layer 2 approaches the connection layer 5 under the action of pressure, the circuit board substrate also approaches the connection layer 5 under the action of pressure, causing the connection layer 5 to be squeezed by two opposite forces. Furthermore, the shielding layer 2 can be connected to the ground layer of the circuit board substrate through the conductive particles 7 in the connection layer 5, ensuring the normal export of interference charges and realizing the electromagnetic shielding function.

[0074] As an alternative embodiment, the conductive particles 7 include graphene nanosheets, carbon nanotubes, iron oxide, silver nanowires, pure silver, silver-plated copper, silver-plated aluminum, silver-plated nickel, etc. These conductive particles 7 can significantly improve the conductivity and electromagnetic shielding effectiveness of the connection layer 5. For example, silver nanowires are widely used in the preparation of electromagnetic shielding films due to their excellent conductivity and transparency.

[0075] Optionally, the shape of the conductive particles 7 can be granular, flaky, strip-shaped, filamentous, reticular or other shapes.

[0076] As one of the optional embodiments, the conductive particles 7 in this embodiment can be separated conductive particles 7 or agglomerated large-particle conductive particles 7. When the conductive particles 7 are separated conductive particles 7, the electrical contact area can be further increased and the uniformity of electrical contact can be improved. When the conductive particles 7 are agglomerated large-particle conductive particles 7, the piercing strength can be increased.

[0077] As Figure 5 shown, as a preferred solution, the insulating layer 1 includes a base layer 101 and a filling layer 102, and the first side surface is disposed on the side surface of the filling layer 102 facing away from the base layer 101.

[0078] It should be noted that the insulating layer 1 in this embodiment specifically includes a base layer 101 and a filling layer 102, and the base layer 101 is disposed on one side surface of the filling layer 102, and a shielding layer 2 is disposed on the other side surface of the filling layer 102. Thus, a plurality of first openings 3 are formed in the filling layer 102 and cooperate with a plurality of second openings 4 on the shielding layer 2 to achieve the heat dissipation effect in the high-temperature process flow.

[0079] Please refer to Figure 6 , the second aspect of the embodiment of the present invention provides a method for preparing an electromagnetic shielding film, including the following steps S1 to S4:

[0080] Step S1, coating a layer with metal particles on one side surface of the insulating layer;

[0081] Step S2, when the coating is cured, etching the metal particles to form a first side surface having a plurality of first openings;

[0082] Step S3, forming a shielding layer on the first side surface;

[0083] Step S4, coating a connection layer on the side surface of the shielding layer facing away from the insulating layer to obtain the electromagnetic shielding film according to any one of the first aspect.

[0084] In step S1, the method of coating a layer with metal particles on one side surface of the insulating layer includes die coating, rod coating, roll coating, and gravure coating. Further, in step S2, in order to make the structure of the finally formed insulating layer stable, the metal particles carried by the coating are etched off after the coating is cured, so that an insulating layer having a plurality of first openings formed on one side surface can be formed, and this side surface is the first side surface. Among them, the aperture of the first openings formed on the first side surface is 1 μm to 10 μm.

[0085] In an optional embodiment, the minimum distance between two adjacent first openings is greater than 0.5 μm; and / or, the maximum depth of the first openings is 0.1 μm to 5 μm.

[0086] Further, in step S3, a shielding layer is formed on the first side surface having a plurality of first openings. It should be noted that a plurality of second openings that are at least partially communicated with the first openings are provided on one side surface of the shielding layer provided on the first side surface.

[0087] In an alternative embodiment, in order to ensure the electromagnetic shielding function of the electromagnetic shielding film, after the shielding layer is formed, a raised portion is formed on the shielding layer by one or more processes of physical roughening, electroless plating, physical vapor deposition, chemical vapor deposition, evaporation plating, sputtering plating, electroplating, and mixed plating.

[0088] Further, in step S4, a connection layer is coated on the side surface of the shielding layer facing away from the insulating layer. The coating methods include die coating, rod coating, roll coating, and gravure coating. The specific details are not limited in this embodiment.

[0089] As Figure 7 shown, as a preferred solution, forming a shielding layer on the first side surface specifically includes the following steps S31 and S32:

[0090] Step S31, a metal seed layer is provided on the first side surface by magnetron sputtering;

[0091] Step S32, electroplating the metal seed layer to form a shielding layer.

[0092] The electromagnetic shielding film and its preparation method provided by the embodiments of the present invention have at least one of the following beneficial effects:

[0093] (1) By providing a plurality of first openings in the insulating layer and a plurality of second openings that are at least partially communicated with the first openings on the shielding layer, the heat dissipation performance of the electromagnetic shielding film can be significantly improved without forming holes with larger diameters and more quantities in the shielding layer, while ensuring the shielding effectiveness of the electromagnetic shielding film.

[0094] (2) By limiting the number of second openings to be less than the number of first openings, the number of second openings formed on the shielding layer can be reduced while ensuring the heat dissipation performance of the electromagnetic shielding film, thereby further ensuring the shielding effectiveness of the electromagnetic shielding film.

[0095] (3) By limiting that in a preset observation area, the difference between the number of second openings and the number of first openings is greater than or equal to 1, it can be ensured as a whole that the number of first openings is large and the number of second openings is small, so as to ensure the heat dissipation performance of the electromagnetic shielding film and better avoid the excessive number of second openings formed on the shielding layer from affecting the shielding effectiveness. In addition, the heat dissipation uniformity of the electromagnetic shielding film during high-temperature process flows can also be ensured.

[0096] (4) By limiting the ratio between the number of second openings with an aperture ratio less than 1 and the total number of second openings to be greater than 50% within a preset observation area, it can be ensured that there are enough second openings with an aperture smaller than that of the first opening, guaranteeing that the apertures of the second openings on the shielding layer are small, thus better ensuring the shielding effectiveness of the shielding layer and further reducing the production cost.

[0097] (5) By limiting the minimum distance between two adjacent first openings to be greater than 0.5 μm, it can be ensured that two adjacent first openings will not stick together easily during the production of the shielding layer due to being too close, guaranteeing the heat dissipation effect of the electromagnetic shielding film.

[0098] (6) By limiting the maximum depth of the first opening to be 0.1 μm - 5 μm, it can be ensured that the maximum depth of the first opening is appropriate, neither too shallow nor too deep, which can not only improve the heat dissipation performance of the electromagnetic shielding layer but also be formed smoothly through etching.

[0099] To illustrate the beneficial effects of the electromagnetic shielding film and its preparation method provided by the embodiments of the present invention, several embodiments and comparative examples are described below.

[0100] Example 1

[0101] An electromagnetic shielding film includes an insulating layer and a shielding layer. The insulating layer has a first side surface, and a plurality of first openings are formed on the first side surface. The maximum aperture of the first openings is 2.3 μm - 4.6 μm, that is, among all the first openings, there are some first openings with a maximum aperture of 2.3 μm, some first openings with a maximum aperture of 4.6 μm, and some first openings with a maximum aperture between 2.3 μm and 4.6 μm; the minimum distance between two adjacent first openings is 0.8 μm; the maximum depth of the first openings is 1.2 μm. The shielding layer is disposed on the first side surface, and a plurality of second openings are formed in the shielding layer. Among all the second openings, 45% of the second openings are connected to the first openings; the thickness of the shielding layer is 1.5 μm.

[0102] Example 2

[0103] An electromagnetic shielding film includes an insulating layer and a shielding layer. The insulating layer has a first side surface, and a plurality of first openings are formed in the first side surface. The maximum aperture of the first openings is 1.3 μm to 3.7 μm, that is, among all the first openings, there are some first openings with a maximum aperture of 1.3 μm, some first openings with a maximum aperture of 3.7 μm, and some first openings with a maximum aperture between 1.3 μm and 3.7 μm. The minimum distance between two adjacent first openings is 1.9 μm. The maximum depth of the first openings is 1.9 μm. The shielding layer is disposed on the first side surface, and a plurality of second openings are formed in the shielding layer. Among all the second openings, 65% of the second openings are communicated with the first openings. The thickness of the shielding layer is 2.5 μm.

[0104] In the sliced state, in each 100-μm transverse observation area, the difference between the number of the second openings and the number of the first openings is 1 to 2.

[0105] Example 3

[0106] An electromagnetic shielding film includes an insulating layer and a shielding layer. The insulating layer has a first side surface, and a plurality of first openings are formed in the first side surface. The maximum aperture of the first openings is 3.6 μm to 5.7 μm, that is, among all the first openings, there are some first openings with a maximum aperture of 3.6 μm, some first openings with a maximum aperture of 5.7 μm, and some first openings with a maximum aperture between 3.6 μm and 5.7 μm. The minimum distance between two adjacent first openings is 3.2 μm. The maximum depth of the first openings is 2.4 μm. The shielding layer is disposed on the first side surface, and a plurality of second openings are formed in the shielding layer. Among all the second openings, 85% of the second openings are communicated with the first openings. The thickness of the shielding layer is 3 μm.

[0107] In the sliced state, in each 100-μm transverse observation area, the difference between the number of the second openings and the number of the first openings is 1 to 3, and the ratio between the number of the second openings with an aperture ratio less than 1 and the total number of the second openings is 82%.

[0108] Example 4

[0109] An electromagnetic shielding film, comprising an insulating layer, a shielding layer and a connecting layer. The insulating layer has a first side surface, and a plurality of first openings are formed in the first side surface. The maximum aperture of the first openings is 2.7 μm to 7.5 μm, that is, among all the first openings, there are some first openings with a maximum aperture of 2.7 μm, there are some first openings with a maximum aperture of 7.5 μm, and there are also some first openings with a maximum aperture between 2.7 μm and 7.5 μm; the minimum distance between two adjacent first openings is 3.6 μm; the maximum depth of the first openings is 3.5 μm. The shielding layer is disposed on the first side surface, and a plurality of second openings are formed in the shielding layer. Among all the second openings, 51% of the second openings are communicated with the first openings; the thickness of the shielding layer is 3.5 μm. The connecting layer is disposed on the side surface of the shielding layer facing away from the insulating layer, and a convex portion is provided on the side surface of the shielding layer facing away from the first side surface.

[0110] In the sliced state, in each 100-μm transverse observation region, the difference between the number of the second openings and the number of the first openings is 2 to 3, and the ratio between the number of the second openings with an aperture ratio less than 1 and the total number of the second openings is 58%.

[0111] Example 5

[0112] An electromagnetic shielding film, comprising an insulating layer, a shielding layer and a connecting layer. The insulating layer has a first side surface, and a plurality of first openings are formed in the first side surface. The maximum aperture of the first openings is 4.2 μm to 8.6 μm, that is, among all the first openings, there are some first openings with a maximum aperture of 4.2 μm, there are some first openings with a maximum aperture of 8.6 μm, and there are also some first openings with a maximum aperture between 4.2 μm and 8.6 μm; the minimum distance between two adjacent first openings is 5.5 μm; the maximum depth of the first openings is 4.2 μm. The shielding layer is disposed on the first side surface, and a plurality of second openings are formed in the shielding layer. Among all the second openings, 90% of the second openings are communicated with the first openings; the thickness of the shielding layer is 4 μm. The connecting layer is disposed on the side surface of the shielding layer facing away from the insulating layer, and conductive particles are provided in the connecting layer.

[0113] In the sliced state, in each 100-μm transverse observation region, the difference between the number of the second openings and the number of the first openings is 2 to 3, and the ratio between the number of the second openings with an aperture ratio of 0.1 to 1 and the total number of the second openings is 68%.

[0114] Comparative Example 1

[0115] An electromagnetic shielding film, comprising an insulating layer, a shielding layer and a connecting layer which are sequentially stacked. No openings are formed in the insulating layer and the shielding layer.

[0116] Comparative Example 2

[0117] An electromagnetic shielding film, comprising an insulating layer, a shielding layer and a connecting layer which are sequentially stacked. There are no openings on the insulating layer, and a plurality of openings with a pore diameter of 20 μm to 100 μm are formed in the shielding layer by using a laser process.

[0118] Using the above embodiments and comparative examples, measure the shielding effectiveness according to the GB / T - 30142 - 2013 test standard and detect whether the electromagnetic shielding film shows delamination due to poor heat dissipation performance during the high - temperature process flow of the circuit board.

[0119] Table 1 Shielding effectiveness of the electromagnetic shielding film and delamination situation of the electromagnetic shielding film

[0120] Object to be detected Electromagnetic shielding effectiveness of electromagnetic shielding film Lamination condition Example 1 ≥70dB No lamination phenomenon occurred due to high temperature Example 2 ≥70dB No lamination phenomenon occurred due to high temperature Example 3 ≥70dB No lamination phenomenon occurred due to high temperature Example 4 ≥70dB No lamination phenomenon occurred due to high temperature Example 5 ≥70dB No lamination phenomenon occurred due to high temperature Comparative example 1 ≥70dB Lamination phenomenon occurred Comparative example 2 Less than 70dB No lamination phenomenon occurred

[0121] As can be seen from Table 1 above, in Embodiments 1 - 5, since both the insulating layer and the shielding layer are provided with openings, and at least part of the second openings on the shielding layer communicate with the first openings on the insulating layer, the heat dissipation performance of the electromagnetic shielding film can be significantly improved, so that the electromagnetic shielding film does not show delamination during the high - temperature process flow. In addition, since a plurality of first openings are provided on the insulating layer, and each first opening satisfies: the pore diameter of the first opening is 1 μm to 10 μm, it is possible to significantly improve the heat dissipation performance of the electromagnetic shielding film without forming holes with a large pore diameter and a large number in the shielding layer, while ensuring the shielding effectiveness of the electromagnetic shielding film. At the same time, in the sliced state, within every 100 - micron transverse observation area, the difference between the number of second openings and the number of first openings is greater than or equal to 1, the ratio of the number of second openings with a pore diameter ratio less than 1 to the total number of second openings is greater than 50%, or the ratio of the number of second openings with a pore diameter ratio of 0.1 - 1 to the total number of second openings is greater than 40%. Therefore, while ensuring the shielding effectiveness of the electromagnetic shielding film, the heat dissipation performance of the electromagnetic shielding film can be significantly improved.

[0122] In Comparative Example 1, there are no openings on both the insulating layer and the shielding layer. Although it can ensure good shielding effectiveness of the electromagnetic shielding film, during the high - temperature process flow, delamination occurs between its shielding layer and the connecting layer due to poor heat dissipation performance, which greatly affects the quality of the electromagnetic shielding film.

[0123] In Comparative Example 2, there are no openings on the insulating layer, and a plurality of openings with a pore diameter of 20 μm to 100 μm are formed in the shielding layer by using a laser process. Although Comparative Example 2 can ensure the heat dissipation performance of the electromagnetic shielding film and no delamination occurs during the high - temperature process flow, since the pore diameter of the openings formed in the shielding layer is too large and the number is extremely large, the shielding effectiveness of the shielding layer is seriously affected.

[0124] The above are the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements are also regarded as the protection scope of the present invention.

Claims

1. An electromagnetic shielding film, characterized in that: The electromagnetic shielding film comprises an insulating layer and a shielding layer; The insulating layer has a first side surface, and the first side surface is provided with a plurality of first openings; The shielding layer is disposed on the first side surface, and a plurality of second openings are formed on the shielding layer. The number of the second openings is less than the number of the first openings, and at least some of the second openings are connected to the first openings.

2. The electromagnetic shielding film according to claim 1, wherein In a preset observation area, a difference between the number of the second openings and the number of the first openings is greater than or equal to one.

3. The electromagnetic shielding film according to claim 1, wherein In a preset observation area, the ratio between the number of second openings satisfying an aperture ratio less than 1 and the total number of the second openings is greater than 50%; wherein the aperture ratio is the ratio between the maximum aperture of the second opening and the maximum aperture of the first opening.

4. The electromagnetic shielding film according to claim 3, characterized in that In the preset observation area, the ratio of the number of second openings satisfying an aperture ratio of 0.1 to 1 to the total number of the second openings is greater than 40%.

5. The electromagnetic shielding film according to claim 1, wherein The minimum distance between two adjacent first openings is greater than 0.5 μm.

6. The electromagnetic shielding film according to claim 1, wherein The maximum depth of the first opening is 0.1 μm to 5 μm; and / or, The second opening is a blind hole or a through hole.

7. The electromagnetic shielding film according to claim 1, wherein The thickness of the shielding layer is 1 μm to 10 μm.

8. The electromagnetic shielding film according to claim 1, wherein There is at least one second opening whose maximum pore size is smaller than the maximum pore size of the first opening connected thereto.

9. The electromagnetic shielding film according to claim 1, wherein The electromagnetic shielding film further comprises a connecting layer, and the connecting layer is arranged on a side of the shielding layer facing away from the insulating layer.

10. The electromagnetic shielding film according to claim 9, wherein A protrusion is provided on a side surface of the shielding layer that is away from the first side surface. The protrusion is used to be electrically connected to the ground layer of the circuit board substrate after the electromagnetic shielding film is pressed together with the circuit board substrate.

11. The electromagnetic shielding film according to claim 9, wherein Conductive particles are arranged in the connection layer.

12. The electromagnetic shielding film according to any one of claims 1 to 11, characterized in that: The insulating layer includes a base layer and a filling layer, and the first side surface is arranged on a side surface of the filling layer facing away from the base layer.

Images