Electromagnetic shielding film and circuit board

Abstract

The present invention relates to the field of electronic technology, and discloses an electromagnetic shielding film and a circuit board. Among them, the electromagnetic shielding film includes a carrier layer, an insulating layer and a shielding layer; the carrier layer is disposed on one surface of the insulating layer, and the shielding layer is disposed on the surface of the insulating layer away from the carrier layer; the surface roughness Sz of the surface of the carrier layer close to the insulating layer is 0.5 - 20 microns. The present invention can improve the adhesion strength between the carrier layer and the insulating layer of the electromagnetic shielding film, and avoid the phenomenon that the carrier layer and the insulating layer are easily delaminated when the electromagnetic shielding film is bent.

Description

Technical Field

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

[0002] With the rapid development of the electronic industry, electronic products are further developing towards miniaturization, light weight, and high-density assembly, which greatly promotes the development of flexible circuit boards, thereby realizing the integration of component devices and wire connections. Flexible circuit boards can be widely used in industries such as mobile phones, liquid crystal displays, communications, and aerospace.

[0003] Driven by the international market, functional flexible circuit boards dominate the flexible circuit board market, and an important indicator for evaluating the performance of functional flexible circuit boards is electromagnetic shielding (Electromagnetic Interference Shielding, abbreviated as EMI Shielding). With the integration of functions of communication devices such as mobile phones, the internal components thereof have become extremely high-frequency and high-speed. For example: In addition to the original audio transmission function, the camera function has become an essential 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 components becoming extremely high-frequency and high-speed is even more inevitable. The electromagnetic interference inside and outside the components, signal attenuation during transmission, insertion loss, and jitter problems caused by high-frequency and high-speed driving are gradually becoming serious.

[0004] Currently, the commonly used electromagnetic shielding film for existing circuit boards includes a carrier layer, an insulating layer, and a shielding layer. During use, the electromagnetic shielding film needs to be hot-pressed with the circuit board at a high temperature. After the hot pressing is completed, the carrier layer is peeled off, so that the shielding layer is electrically connected to the ground layer of the circuit board, and then the interfering charges are introduced into the ground layer of the circuit board, thereby achieving shielding.

[0005] The inventor of the present invention found the following technical problems in the process of implementing the present invention: The bonding strength between the carrier layer and the insulating layer of the existing electromagnetic shielding film is poor, and when the electromagnetic shielding film is bent, it is easy for the carrier layer and the insulating layer to be delaminated. Summary of the Invention

[0006] Aiming at the above problems, the purpose of the present invention is to provide an electromagnetic shielding film and a circuit board, which can improve the bonding strength between the carrier layer and the insulating layer of the electromagnetic shielding film, and avoid the phenomenon that the carrier layer and the insulating layer are easily delaminated when the electromagnetic shielding film is bent.

[0007] To achieve the above object, an embodiment of the present invention provides an electromagnetic shielding film, which includes a carrier layer, an insulating layer and a shielding layer;

[0008] The carrier layer is disposed on one surface of the insulating layer, and the shielding layer is disposed on the surface of the insulating layer away from the carrier layer;

[0009] The surface roughness Sz of the surface of the carrier layer close to the insulating layer is 0.5 - 20 microns.

[0010] As an improvement to the above solution, the surface roughness Sz of the surface of the carrier layer close to the insulating layer is 5.2 - 14.6 microns.

[0011] As an improvement to the above solution, the thickness of the carrier layer is 7 - 150 microns.

[0012] As an improvement to the above solution, the surface roughness Sz of the surface of the insulating layer close to the carrier layer is 1 - 16 microns.

[0013] As an improvement to the above solution, the surface roughness Rz of the surface of the insulating layer close to the carrier layer is 1 - 15 microns.

[0014] As an improvement to the above solution, the electromagnetic shielding film further includes an adhesive film layer; the adhesive film layer is disposed on the surface of the shielding layer away from the insulating layer.

[0015] As an improvement to the above solution, conductive protrusions are provided on the surface of the shielding layer close to the adhesive film layer.

[0016] As an improvement to the above solution, the ratio of the surface roughness Sz of the surface of the carrier layer close to the insulating layer to the thickness of the insulating layer is 0.375 - 3.6.

[0017] As an improvement to the above solution, through holes penetrating the upper and lower surfaces are provided on the shielding layer.

[0018] To solve the same technical problem, another embodiment of the present invention further provides a circuit board, which includes a circuit board body and the electromagnetic shielding film according to any one of the above solutions; the electromagnetic shielding film is pressed together with the circuit board body; the surface of the shielding layer away from the insulating layer is electrically connected to the ground layer of the circuit board body.

[0019] Compared with the prior art, the electromagnetic shielding film and the circuit board provided by the embodiments of the present invention have at least one of the following beneficial effects:

[0020] The sum of the maximum peak height and the maximum valley depth of the roughness of the side of the carrier layer close to the insulating layer is 0.5 - 20 micrometers, which can improve the adhesion strength between the carrier layer and the insulating layer of the electromagnetic shielding film and avoid the phenomenon that the carrier layer and the insulating layer are easily delaminated when the electromagnetic shielding film is bent. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions of the present invention, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0022] Figure 1 is a schematic structural diagram of the first electromagnetic shielding film provided by an embodiment of the present invention;

[0023] Figure 2 is a schematic structural diagram of the second electromagnetic shielding film provided by an embodiment of the present invention;

[0024] Figure 3 is a schematic structural diagram of the third electromagnetic shielding film provided by an embodiment of the present invention;

[0025] Figure 4 is a schematic structural diagram of the fourth electromagnetic shielding film provided by an embodiment of the present invention;

[0026] Figure 5 is a schematic structural diagram of the fourth electromagnetic shielding film provided by an embodiment of the present invention;

[0027] Figure 6 is a schematic structural diagram of the electromagnetic shielding film and the circuit board body after lamination;

[0028] Wherein, 1, carrier layer; 2, insulating layer; 3, shielding layer; 4, adhesive film layer; 5, protective film layer; 6, circuit board body; 31, conductive protrusion. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0029] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0030] In the descriptions of the specification and claims, it should be understood that the orientation or positional relationships indicated by terms such as "upper", "lower", "left", "right", "front", "rear", "top", "bottom", "inner", "outer", etc. are based on the orientation or positional relationships shown in the drawings. This is only for the convenience of describing the embodiments of the present invention, rather than indicating or implying that the device or component referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation on the embodiments of the present invention.

[0031] In addition, terms such as first and second in the specification and claims are only used for the purpose of distinguishing the descriptions of the same technical features, and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features, nor necessarily describing the order or time sequence. The terms can be interchanged under appropriate circumstances. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one of such features.

[0032] See Figure 1 , an embodiment of the present invention provides an electromagnetic shielding film, which includes a carrier layer 1, an insulating layer 2 and a shielding layer 3; the carrier layer 1 is disposed on one surface of the insulating layer 2, and the shielding layer 3 is disposed on the surface of the insulating layer 2 away from the carrier layer 1; the surface roughness Sz of the side of the carrier layer 1 close to the insulating layer 2 is 0.5 - 20 microns.

[0033] In the embodiment of the present invention, by making the sum of the maximum peak height and the maximum valley depth of the surface of the carrier layer 1 close to the insulating layer 2 be 0.5 - 20 microns, the adhesion strength between the carrier layer and the insulating layer of the electromagnetic shielding film can be improved, and the phenomenon that the carrier layer and the insulating layer are prone to delamination when the electromagnetic shielding film is bent can be avoided. Preferably, the surface roughness Sz of the side of the carrier layer 1 close to the insulating layer 2 is 5.2 - 14.6 microns. Moreover, since the surface roughness Sz of the side of the carrier layer 1 close to the insulating layer 2 is 0.5 - 20 microns, compared with the carrier layer 1 having a flat surface structure, when the electromagnetic shielding film is laminated with the circuit board, the carrier layer 1 is not prone to large-scale horizontal movement during the lamination process. Therefore, it is not easy to have the problem that the overall electromagnetic shielding film moves horizontally due to the horizontal movement of the carrier layer 1 when the electromagnetic shielding film is laminated onto the circuit board, and the electromagnetic shielding film can be laminated at the corresponding position on the circuit board.

[0034] It can be understood that the roughness Sz represents the sum of the maximum peak height and the maximum valley depth in a certain area of a surface.

[0035] Among them, the material of the carrier layer 1 can be PET (Polyethylene terephthalate, polyester resin). It can be understood that in order to ensure that the shielding layer 3 has good conductivity, the shielding layer 3 includes one or more of a metal shielding layer, a carbon nanotube shielding layer, a ferrite shielding layer, and a graphene shielding layer. Among them, the metal shielding layer includes a single-metal shielding layer and / or an alloy shielding layer; among them, the single-metal shielding layer is made of any one of aluminum, titanium, zinc, iron, nickel, chromium, cobalt, copper, silver, and gold, and the alloy shielding layer is made of any two or more of aluminum, titanium, zinc, iron, nickel, chromium, cobalt, copper, silver, and gold.

[0036] In this embodiment, the thickness of the carrier layer 1 is 7-150 microns. The carrier layer 1 can be used to protect the insulating layer 2 so that the insulating layer 2 is not damaged by external contact or collision, etc. Among them, when the thickness of the carrier layer 1 is 50 microns, it has better protection ability and can perfectly protect the insulating layer 2 from being damaged by external contact or collision, etc. In addition, the carrier layer 1 can be used as the base film for forming the insulating layer 2, that is, the insulating layer 2 can be formed on one side of the carrier layer 1.

[0037] In this embodiment, the roughness Rz of the surface of the carrier layer 1 close to the insulating layer 2 is 0.5-20 microns. When the roughness Rz of the surface of the carrier layer 1 close to the insulating layer 2 is 0.5-20 microns, it can ensure that the carrier layer 1 is not easily peeled off while being able to stably peel off the carrier layer 1 under the application of a certain force. Among them, the roughness Rz is the sum of the average value of the five largest profile peak heights and the average value of the five largest profile valley depths within the sampling length.

[0038] In this embodiment, the tensile force between the carrier layer 1 and the insulating layer 2 is 0.03-2.93 N / cm. By setting the tensile force between the carrier layer 1 and the insulating layer 2 to 0.03-2.93 N / cm, the problem of reverse release (that is, after lamination, there is a problem that part of the carrier layer remains on the surface of the insulating layer) can be solved, and the carrier layer 1 can be stably peeled off after laminating the electromagnetic shielding film, thereby avoiding the remaining carrier layer 1 on the insulating layer 2.

[0039] In this embodiment, before laminating the electromagnetic shielding film onto the circuit board, the tensile force between the carrier layer 1 and the insulating layer 2 is 0.1 - 2.93 N / cm. Setting the tensile force before lamination to 0.1 - 2.93 N / cm can prevent the detachment of the carrier layer 1 and play a role in protecting the insulating layer 2. After laminating the electromagnetic shielding film onto the circuit board, the tensile force between the carrier layer 1 and the insulating layer 2 is 0.03 - 2 N / cm. Setting the tensile force after lamination to 0.03 - 2 N / cm facilitates the stable peeling of the carrier layer 1.

[0040] In this embodiment, the thickness of the insulating layer 2 is 5 - 8 microns, and the ratio of the surface roughness Sz of the side of the carrier layer 1 close to the insulating layer 2 to the thickness of the insulating layer 2 is 0.375 - 3.6. During the process of forming the insulating layer 2 on the side of the carrier layer 1 close to the insulating layer 2, when the ratio of the surface roughness Sz of the side of the carrier layer 1 close to the insulating layer 2 to the thickness of the insulating layer 2 is 0.375 - 3.6, it is easy to make the surface roughness Sz of the side of the insulating layer 2 far from the carrier layer 1 be 0.5 - 20 microns. It should be noted that the surface roughness of the insulating layer 2 can be formed by the roughness of the carrier layer 1 or can also be further processed by other means, which is not limited herein.

[0041] Exemplarily, the surface roughness Sz of the side of the insulating layer 2 close to the carrier layer 1 is 1 - 16 microns, and the surface roughness Rz of the side of the insulating layer 2 close to the carrier layer 1 is 1 - 15 microns. This can improve the surface tension of the insulating layer. When printing ink on the insulating layer, the ink will not spread. For example, in an application, when printing characters on the surface of the insulating layer, the characters can be clearly displayed.

[0042] In this embodiment, the side of the insulating layer 2 close to the shielding layer 3 is a rough surface, which can improve the anti-bending property of the insulating layer 2, thereby improving the anti-bending performance of the electromagnetic shielding film. In addition, when forming the shielding layer 3 on one side of the insulating layer 2, since the thickness of the shielding layer 3 is constant, the shielding layer 3 will undulate following the rough surface of the insulating layer 2, so that the side of the shielding layer 3 close to the adhesive film layer is also a rough surface.

[0043] In this embodiment, the side of the insulating layer 2 close to the shielding layer 3 is a rough surface. Among them, the insulating layer 2 can effectively electrically isolate the shielding layer 3 from the outside, thereby ensuring the electromagnetic shielding effect of the shielding layer 3. Moreover, the side of the insulating layer 2 close to the shielding layer 3 is a rough surface, which can improve the bonding strength between the insulating layer 2 and the shielding layer 3 and avoid the phenomenon that the insulating layer 2 and the shielding layer 3 are prone to detachment.

[0044] Further, referring to Figure 2 , the electromagnetic shielding film further includes an adhesive film layer 4; the adhesive film layer 4 is disposed on a surface of the shielding layer 3 away from the insulating layer 2; a surface of the shielding layer 3 close to the adhesive film layer 4 is a rough surface. The electromagnetic shielding film is press-fitted with the circuit board body through the adhesive film layer 4; the rough surface of the shielding layer 3 pierces through the adhesive film layer 4 and is electrically connected to the ground layer of the circuit board body.

[0045] Among them, the material used for the adhesive film layer 4 is selected from the following: modified epoxy resin type, acrylic type, modified rubber type, modified thermoplastic polyimide type.

[0046] In the embodiment of the present invention, a surface of the shielding layer 3 close to the adhesive film layer 4 is a rough surface. By making a surface of the shielding layer 3 close to the adhesive film layer 4 a rough surface, the rough surface of the shielding layer 3 can have piercing ability. Moreover, the rough surface of the shielding layer 3 can enhance the bonding force between the shielding layer 3 and the circuit board, so that the electromagnetic shielding film is not easily delaminated. And when the electromagnetic shielding film is press-fitted with the circuit board, since a surface of the shielding layer 3 close to the adhesive film layer 4 is a rough surface, the adhesive substances constituting the adhesive film layer 4 are squeezed into the concave positions of the rough surface of the shielding layer 3, increasing the glue capacity, and it is not easy to have the problem of board explosion, avoiding the problem of high-temperature board explosion of the existing electromagnetic shielding film due to insufficient glue capacity, and effectively ensuring the grounding of the electromagnetic shielding film, thereby leading out interference charges; on the other hand, it can prevent the glue from overflowing to the edge of the circuit board during press-fitting, so that the circuit board after press-fitting the shielding film has a good appearance.

[0047] In the embodiment of the present invention, referring to Figure 3 , through holes penetrating the upper and lower surfaces of the shielding layer 3 are provided on the shielding layer 3. By providing through holes penetrating the upper and lower surfaces of the shielding layer 3, when the electromagnetic shielding film is press-fitted to the circuit board at high temperature, the volatile gases generated in the adhesive film layer 4 can be effectively emitted through the through holes of the shielding layer 3, so that the electromagnetic shielding film will not have the problem of blistering and delamination.

[0048] As an example, referring to Figure 4 , conductive protrusions 31 are provided on a surface of the shielding layer 3 close to the adhesive film layer 4, so as to more effectively pierce through the adhesive film layer 4, thereby further ensuring the electrical connection between the electromagnetic shielding film and the ground layer of the circuit board. It should be noted that the materials of the conductive protrusions 31 and the shielding layer 3 may be the same or different, and the present invention does not make specific limitations here.

[0049] In the above embodiments, the conductive protrusion 31 includes a conductive base portion and at least one conductive spike portion; the conductive base portion extends outward from the side of the shielding layer close to the adhesive film layer 4, and at least one of the conductive spike portions extends outward from the surface of the conductive base portion. Among them, the conductive spike portion extending from the surface of the conductive base portion can more effectively pierce the adhesive film layer 4, so that the shielding layer 3 can be better electrically connected to the ground layer of the circuit board.

[0050] Specifically, the protrusion height of the conductive spike portion is 1-5 micrometers. This can more effectively pierce the adhesive film layer 4, thereby further ensuring the electrical connection between the electromagnetic shielding film and the ground layer of the circuit board.

[0051] In the above embodiments, the conductive spike portions can be distributed regularly or irregularly on the surface of the conductive base portion. In this embodiment, the shapes of the conductive spike portions are the same, and / or the distances between the conductive spike portions are the same. Preferably, the shapes of the plurality of conductive spike portions are the same, and the plurality of conductive spike portions are evenly distributed on the surface of the conductive base portion. In addition, at least one surface of the shielding layer 3 is a undulating structure. For example, the surface of the shielding layer 3 close to the adhesive film layer is a undulating structure. This can improve the bending performance of the shielding layer 3, enhance the piercing ability of the surface of the shielding layer close to the adhesive film layer 4 to the adhesive film layer 4, and also improve the adhesive capacity of this surface of the shielding layer 3.

[0052] It should be noted that Figure 4 the shape of the conductive protrusion 31 in is only exemplary. Due to differences in process means and parameters, the conductive protrusion 31 can also be in other shapes such as cluster shape, icicle shape, stalactite shape, dendritic shape, etc. In addition, the conductive protrusion 31 in the embodiments of the present invention is not limited by the illustration and the above shapes. As long as the conductive protrusion 31 has the functions of piercing and conducting electricity, it is within the protection scope of the present invention.

[0053] It should be noted that the shielding layer 3 in this embodiment can be a single-layer structure or a multi-layer structure. When the shielding layer 3 is a single layer, the conductive protrusion 31 is provided on the surface of the shielding layer 3 close to the adhesive film layer 4; when the shielding layer 3 is a multi-layer, the conductive protrusion 31 can also be provided on the surface of each layer of the shielding layer 3 close to the adhesive film layer 4. In addition, according to the actual production and application needs, the shielding layer 3 in this embodiment can be set as a grid shape, a foam shape, etc.

[0054] In an embodiment of the present invention, in order to further ensure the connection between the electromagnetic shielding film and the ground layer of the circuit board, the adhesive film layer 4 in this embodiment includes an adhesive layer containing conductive particles. By including an adhesive layer containing conductive particles in the adhesive film layer 4, the conductivity of the adhesive film layer 4 is improved, thereby further ensuring the connection between the electromagnetic shielding film and the ground layer of the circuit board. Of course, the adhesive film layer 4 may include an adhesive layer without conductive particles to reduce the insertion loss of the circuit board with the electromagnetic shielding film.

[0055] It should be noted that the conductive particles can be separated conductive particles or large particle conductive particles formed by aggregation; when the conductive particles are separated conductive particles, the ground conductivity of the adhesive film layer 4 can be further improved; while when the conductive particles are large particle conductive particles formed by aggregation, the piercing strength can be increased.

[0056] Please refer to Figure 5 , the electromagnetic shielding film in this embodiment further includes a protective film layer 5, and the protective film layer 5 is disposed on a surface of the adhesive film layer 4 away from the shielding layer 3. Since the protective film layer 5 has a protective effect, it can ensure that the adhesive film layer 4 is not scratched or damaged during use. Among them, the protective film layer 5 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. Among them, when the electromagnetic shielding film is laminated onto the circuit board, the protective film layer 5 needs to be peeled off first.

[0057] Specifically, when the electromagnetic shielding film includes a carrier layer 1, an insulating layer 2, a shielding layer 3, an adhesive film layer 4, and a protective film layer 5, the preparation method of the electromagnetic shielding film includes:

[0058] 1) Prepare the carrier layer 1;

[0059] 2) Form an insulating layer 2 on one surface of the carrier layer 1;

[0060] 3) Form a shielding layer 3 on a surface of the insulating layer 2 away from the carrier layer 1;

[0061] 4) Coat an adhesive on a surface of the shielding layer 3 away from the insulating layer 2 to form the adhesive film layer 4;

[0062] 5) Bond the protective film layer 5 on a surface of the adhesive film layer 4 away from the shielding layer 3.

[0063] For the convenience of understanding the above invention solutions, here, three specific embodiments are provided and these specific embodiments are tested: Specific Embodiment 1:

[0065] An electromagnetic shielding film, comprising a carrier layer 1, an insulating layer 2 and a shielding layer 3; the carrier layer 1 is disposed on one side of the insulating layer 2, and the shielding layer 3 is disposed on the side of the insulating layer 2 away from the carrier layer 1; the surface roughness Sz of the side of the carrier layer 1 close to the insulating layer 2 is 0.5 micrometers. Among them, the material of the carrier layer 1 is PET, the material of the insulating layer 2 is epoxy resin, and the insulating layer 2 may be formed on one side of the carrier layer 1.

[0066] Test results: After testing, before the electromagnetic shielding film of this embodiment is laminated to the circuit board, when the carrier layer 1 is peeled off, the tensile force between the carrier layer 1 and the insulating layer 2 is 0.24 N / cm; after the electromagnetic shielding film of this embodiment is laminated to the circuit board, when the carrier layer 1 is peeled off, the tensile force between the carrier layer 1 and the insulating layer 2 is 0.06 N / cm.

[0067] It can be seen that by applying the electromagnetic shielding film of this embodiment, the bonding strength between the carrier layer 1 and the insulating layer 2 of the electromagnetic shielding film can be improved, and the phenomenon that the carrier layer 1 and the insulating layer 2 are easily delaminated when the electromagnetic shielding film is bent can be avoided. Specific Embodiment Two:

[0069] An electromagnetic shielding film, comprising a carrier layer 1, an insulating layer 2 and a shielding layer 3; the carrier layer 1 is disposed on one side of the insulating layer 2, and the shielding layer 3 is disposed on the side of the insulating layer 2 away from the carrier layer 1; the surface roughness Sz of the side of the carrier layer 1 close to the insulating layer 2 is 5.2 micrometers. Among them, the material of the carrier layer 1 is PET, the material of the insulating layer 2 is epoxy resin, and the insulating layer 2 may be formed on one side of the carrier layer 1.

[0070] Test results: After testing, before the electromagnetic shielding film of this embodiment is laminated to the circuit board, when the carrier layer 1 is peeled off, the tensile force between the carrier layer 1 and the insulating layer 2 is 0.34 N / cm; after the electromagnetic shielding film of this embodiment is laminated to the circuit board, when the carrier layer 1 is peeled off, the tensile force between the carrier layer 1 and the insulating layer 2 is 0.09 N / cm.

[0071] It can be seen that by applying the electromagnetic shielding film of this embodiment, the bonding strength between the carrier layer 1 and the insulating layer 2 of the electromagnetic shielding film can be improved, and the phenomenon that the carrier layer 1 and the insulating layer 2 are easily delaminated when the electromagnetic shielding film is bent can be avoided. Specific Embodiment Three:

[0073] An electromagnetic shielding film, comprising a carrier layer 1, an insulating layer 2 and a shielding layer 3; the carrier layer 1 is disposed on one side of the insulating layer 2, and the shielding layer 3 is disposed on the side of the insulating layer 2 away from the carrier layer 1; the roughness Sz of the surface of the carrier layer 1 close to the insulating layer 2 is 10.25 microns. Wherein, the material of the carrier layer 1 is PET, the material of the insulating layer 2 is epoxy resin, and the insulating layer 2 may be formed on one side of the carrier layer 1.

[0074] Test results: After testing, before the electromagnetic shielding film of this embodiment is laminated to the circuit board, when peeling the carrier layer 1, the tensile force between the carrier layer 1 and the insulating layer 2 is 1.13 N / cm; after the electromagnetic shielding film of this embodiment is laminated to the circuit board, when peeling the carrier layer 1, the tensile force between the carrier layer 1 and the insulating layer 2 is 0.1 N / cm.

[0075] Thus, by applying the electromagnetic shielding film of this embodiment, the adhesion strength between the carrier layer 1 and the insulating layer 2 of the electromagnetic shielding film can be improved, and the phenomenon that the carrier layer 1 and the insulating layer 2 are easily delaminated when the electromagnetic shielding film is bent can be avoided. Specific Embodiment Four:

[0077] An electromagnetic shielding film, comprising a carrier layer 1, an insulating layer 2 and a shielding layer 3; the carrier layer 1 is disposed on one side of the insulating layer 2, and the shielding layer 3 is disposed on the side of the insulating layer 2 away from the carrier layer 1; the roughness Sz of the surface of the carrier layer 1 close to the insulating layer 2 is 14.6 microns. Wherein, the material of the carrier layer 1 is PET, the material of the insulating layer 2 is epoxy resin, and the insulating layer 2 may be formed on one side of the carrier layer 1.

[0078] Test results: After testing, before the electromagnetic shielding film of this embodiment is laminated to the circuit board, when peeling the carrier layer 1, the tensile force between the carrier layer 1 and the insulating layer 2 is 1.56 N / cm; after the electromagnetic shielding film of this embodiment is laminated to the circuit board, when peeling the carrier layer 1, the tensile force between the carrier layer 1 and the insulating layer 2 is 0.3 N / cm.

[0079] Thus, by applying the electromagnetic shielding film of this embodiment, the adhesion strength between the carrier layer 1 and the insulating layer 2 of the electromagnetic shielding film can be improved, and the phenomenon that the carrier layer 1 and the insulating layer 2 are easily delaminated when the electromagnetic shielding film is bent can be avoided. Specific Embodiment Five:

[0081] An electromagnetic shielding film, comprising a carrier layer 1, an insulating layer 2 and a shielding layer 3; the carrier layer 1 is disposed on one side of the insulating layer 2, and the shielding layer 3 is disposed on the side of the insulating layer 2 away from the carrier layer 1; the roughness Sz of the surface of the carrier layer 1 close to the insulating layer 2 is 20 microns. Wherein, the material of the carrier layer 1 is PET, the material of the insulating layer 2 is epoxy resin, and the insulating layer 2 can be formed on one side of the carrier layer 1.

[0082] Test results: After testing, before the electromagnetic shielding film of this embodiment is laminated to the circuit board, when peeling the carrier layer 1, the tensile force between the carrier layer 1 and the insulating layer 2 is 2.93 N / cm; after the electromagnetic shielding film of this embodiment is laminated to the circuit board, when peeling the carrier layer 1, the tensile force between the carrier layer 1 and the insulating layer 2 is 1.57 N / cm.

[0083] Thus, by applying the electromagnetic shielding film of this embodiment, the adhesion strength between the carrier layer 1 and the insulating layer 2 of the electromagnetic shielding film can be improved, and the phenomenon that the carrier layer 1 and the insulating layer 2 are easily delaminated when the electromagnetic shielding film is bent can be avoided.

[0084] In summary, the roughness Sz of the surface of the carrier layer close to the insulating layer is 0.5 - 20 microns (such as 0.5, 5.2, 10.25, 14.6, 20 microns). By applying the electromagnetic shielding film of this embodiment, the adhesion strength between the carrier layer 1 and the insulating layer 2 of the electromagnetic shielding film can be improved, and the phenomenon that the carrier layer 1 and the insulating layer 2 are easily delaminated when the electromagnetic shielding film is bent can be avoided.

[0085] See Figure 6 , another embodiment of the present invention further provides a circuit board, which comprises a circuit board body 6 and the electromagnetic shielding film described in any one of the above embodiments; the electromagnetic shielding film is laminated with the circuit board body 6; the side of the shielding layer 3 away from the insulating layer 2 is electrically connected to the ground layer of the circuit board body 6.

[0086] Preferably, the circuit board body 6 is one of a flexible single-sided, flexible double-sided, flexible multi-layer board, and a rigid-flexible combination board.

[0087] In the embodiment of the present invention, when the electromagnetic shielding film and the circuit board body 6 are laminated, the rough surface of the shielding layer 3 can pierce through the adhesive film layer 4 and be connected to the ground layer of the circuit board body 6, thereby ensuring the connection between the shielding layer 3 and the ground layer of the circuit board body 6, and realizing the introduction of the interfering charges in the shielding layer 3 into the ground, avoiding the accumulation of interfering charges to form an interference source and affecting the normal operation of the circuit board.

[0088] Specifically, the circuit board of the embodiment of the present invention uses the electromagnetic shielding film, and by making the sum of the maximum peak height and the maximum valley depth of the roughness of the side of the carrier layer 1 close to the insulating layer 2 0.5-20 microns, the bonding strength between the carrier layer and the insulating layer of the electromagnetic shielding film can be improved, and the phenomenon of stratification between the carrier layer and the insulating layer when the electromagnetic shielding film is bent can be avoided. In addition, since the roughness Sz of the side of the carrier layer 1 close to the insulating layer 2 is 0.5-20 microns, compared with the carrier layer 1 with a flat surface structure, when the electromagnetic shielding film and the circuit board are pressed together, the carrier layer 1 is not easy to move horizontally to a large extent during the pressing process, so it is not easy to cause the electromagnetic shielding film to move horizontally as a whole due to the horizontal movement of the carrier layer 1 when the electromagnetic shielding film is pressed onto the circuit board, and the electromagnetic shielding film can be pressed onto the corresponding position of the circuit board. By making the side of the shielding layer 3 close to the adhesive film layer 4 a rough surface, the rough surface of the shielding layer 3 can be made to have piercing ability. Moreover, the rough surface of the shielding layer 3 can enhance the bonding force between the shielding layer 3 and the circuit board, so that the electromagnetic shielding film is not easy to delaminate. In addition, when the electromagnetic shielding film is pressed together with the circuit board, since the side of the shielding layer 3 close to the adhesive film layer 4 is a rough surface, and since the amount of adhesive per unit area on the rough surface of the shielding layer 3 is not too much, the adhesive of the adhesive film layer 4 is not easy to move horizontally on the rough surface of the shielding layer 3 when the shielding film is pressed together, so it is not easy to cause adhesive displacement and cause obvious adhesive overflow at the edge of the circuit board, so the circuit board after the shielding film is pressed together can have a good appearance. In addition, since the side of the shielding layer 3 close to the adhesive film layer 4 is a rough surface, the adhesive substance constituting the adhesive film layer 4 is squeezed into the recessed position of the rough surface of the shielding layer 3, thereby increasing the adhesive capacity. On the one hand, it is less likely to cause board bursting, thereby avoiding the problem of high-temperature board bursting due to insufficient adhesive capacity of the existing electromagnetic shielding film, thereby effectively ensuring the grounding of the electromagnetic shielding film, thereby conducting away the interference charge; on the other hand, it can prevent the adhesive from overflowing to the edge of the circuit board during lamination, thereby enabling the circuit board after laminating the shielding film to have a good appearance.

[0089] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by any technician familiar with the art within the technical scope disclosed in the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be based on the protection scope of the claims.

Claims

1. An electromagnetic shielding film, characterized in that, It includes a carrier layer, an insulating layer and a shielding layer; The carrier layer is disposed on one side of the insulating layer, and the shielding layer is disposed on the side of the insulating layer away from the carrier layer; The surface roughness Sz of the side of the carrier layer close to the insulating layer is 0.5 - 20 microns; the ratio of the surface roughness Sz of the side of the carrier layer close to the insulating layer to the thickness of the insulating layer is 0.375 - 3.6; the tensile force between the carrier layer and the insulating layer is 0.03 - 2.93 N / cm.

2. The electromagnetic shielding film according to claim 1, wherein, The surface roughness Sz of the side of the carrier layer close to the insulating layer is 5.2 - 14.6 microns.

3. The electromagnetic shielding film according to claim 1, wherein The thickness of the carrier layer is 7 - 150 microns.

4. The electromagnetic shielding film according to claim 1, wherein, The insulating layer is formed on one side of the carrier layer, and the surface roughness Sz of the side of the insulating layer close to the carrier layer is 1 - 16 microns.

5. The electromagnetic shielding film according to claim 1, characterized in that, The surface roughness Rz of the side of the insulating layer close to the carrier layer is 1 - 15 microns.

6. The electromagnetic shielding film according to claim 1, characterized in that, The electromagnetic shielding film further includes an adhesive film layer; the adhesive film layer is disposed on the side of the shielding layer away from the insulating layer.

7. The electromagnetic shielding film according to claim 6, wherein Conductive protrusions are provided on the side of the shielding layer close to the adhesive film layer.

8. The electromagnetic shielding film according to claim 1, characterized in that, Through holes penetrating the upper and lower surfaces are provided on the shielding layer.

9. A circuit board, characterized in that, It includes a circuit board body and the electromagnetic shielding film according to any one of claims 1 - 8; the electromagnetic shielding film is press-fitted with the circuit board body; the side of the shielding layer away from the insulating layer is electrically connected to the ground layer of the circuit board body.

Images