Electromagnetic shielding film, circuit board and preparation method of electromagnetic shielding film

Abstract

Embodiments of the present invention provide an electromagnetic shielding film, a circuit board, and a preparation method of the electromagnetic shielding film. The electromagnetic shielding film includes a resin film layer, a first shielding layer, and an adhesive film layer. A first through hole is provided in the resin film layer, and a resin protrusion is provided at the first through hole. The resin protrusion is formed by the resin flowing from one side of the first through hole to the other side and then solidifying. The first shielding layer is provided on the side of the resin film layer close to the resin protrusion and covers the resin protrusion, so that a protrusion portion is formed at a position corresponding to the resin protrusion on the outer surface of the first shielding layer. The adhesive film layer is provided on the side of the first shielding layer away from the resin film layer, and the protrusion portion extends into the adhesive film layer, so that the protrusion portion ensures that the first shielding layer can smoothly pierce the adhesive film layer during the pressing process and contact the ground layer of the circuit board, thereby ensuring the normal conduction of interfering charges and realizing the shielding function.

Description

Technical Field

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

[0002] With the rapid development of the electronics 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 index for evaluating the performance of functional flexible circuit boards is electromagnetic 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 of mobile phones, the camera function has become an essential function, 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, the attenuation of signals during transmission, and the problems of insertion loss and jitter caused by high frequency and high speed are gradually becoming serious.

[0004] Currently, the commonly used shielding films for existing circuit boards include a shielding layer and a conductive adhesive layer. The shielding layer is connected to the ground layer of the circuit board through the conductive adhesive layer, and then the interfering charges are introduced into the ground layer of the circuit board to achieve shielding. However, at high temperatures, due to the expansion of the conductive adhesive layer, the conductive particles that were originally in contact with each other inside the conductive adhesive layer are separated, or the conductive particles that were originally in contact with the ground layer of the circuit board are separated, resulting in grounding failure and the inability to quickly export the interfering charges, and the shielding function cannot be achieved. Summary of the Invention

[0005] The purpose of the embodiments of the present invention is to provide an electromagnetic shielding film, a circuit board, and a preparation method of the electromagnetic shielding film, which can realize a reliable connection between the shielding film and the ground layer of the circuit board, and further realize a high-reliability shielding function.

[0006] To achieve the above object, an embodiment of the present invention provides an electromagnetic shielding film, which includes a resin film layer, a first shielding layer, and an adhesive film layer. A first through hole penetrating the upper and lower surfaces is provided on the resin film layer. The first through hole is provided with a resin protrusion, and the resin protrusion is formed by resin flowing from one side of the first through hole to the other side and then solidifying; the first shielding layer is disposed on one side of the resin film layer close to the resin protrusion and covers the resin protrusion, so that a protrusion portion is formed at a position corresponding to the resin protrusion on the outer surface of the first shielding layer; the adhesive film layer is disposed on one side of the first shielding layer away from the resin film layer, and the protrusion portion extends into the adhesive film layer.

[0007] As an improvement of the above solution, the resin protrusion is formed by resin flowing from one side of the first through hole to the other side at room temperature and then solidifying at a curing temperature; or,

[0008] The resin protrusion is formed by resin flowing from one side of the first through hole to the other side at a melting temperature and then instantaneously cooled.

[0009] As an improvement of the above solution, the surface of the protrusion portion is provided with convex conductor particles; the height of the conductor particles is 0.1 μm - 30 μm.

[0010] As an improvement of the above solution, the adhesive film layer includes an adhesive layer containing conductive particles; or, the adhesive film layer includes an adhesive layer without conductive particles.

[0011] As an improvement of the above solution, the first shielding layer includes one or more of a metal shielding layer, a carbon nanotube shielding layer, a ferrite shielding layer, and a graphene shielding layer.

[0012] As an improvement of the above solution, the metal shielding layer includes a single-metal shielding layer and / or an alloy shielding layer; wherein, 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.

[0013] As an improvement of the above solution, the electromagnetic shielding film further includes a protective film layer, and the protective film layer is disposed on one side of the resin film layer away from the first shielding layer.

[0014] Compared with the prior art, an embodiment of the present invention discloses an electromagnetic shielding film. By providing a first through hole in the resin film layer and providing a resin protrusion formed by resin solidifying after flowing from one side of the first through hole to the other side at the first through hole, and simultaneously disposing the first shielding layer on one side of the resin film layer close to the resin protrusion and covering the resin protrusion, a protrusion portion is formed at a position corresponding to the resin protrusion on the outer surface of the first shielding layer, and the adhesive film layer is disposed on one side of the first shielding layer away from the resin film layer, so that the protrusion portion ensures that the first shielding layer can smoothly pierce through the adhesive film layer during the pressing process to achieve reliable grounding, and further ensure the normal export of interference charges to realize the shielding function.

[0015] An embodiment of the present invention also correspondingly provides a circuit board, including a printed circuit board and the electromagnetic shielding film described in any one of the above. The electromagnetic shielding film is pressed with the printed circuit board through its adhesive film layer; the protrusion portion pierces through the adhesive film layer and extends to the ground layer of the printed circuit board.

[0016] Compared with the prior art, an embodiment of the present invention discloses a circuit board. The circuit board includes a printed circuit board and the electromagnetic shielding film described in any one of the above. The electromagnetic shielding film is pressed with the printed circuit board through its adhesive film layer. The protrusion portion pierces through the adhesive film layer and is connected to the ground layer of the printed circuit board to realize the smooth export of interference charges, and further realize the shielding function.

[0017] An embodiment of the present invention also correspondingly provides a preparation method of an electromagnetic shielding film, which is applicable to preparing the electromagnetic shielding film described in any one of the above, and includes the steps:

[0018] S1. Form a resin film layer; wherein, the resin film layer has a first through hole penetrating its upper and lower surfaces;

[0019] S2. Form a resin protrusion at the first through hole; wherein, the resin protrusion extends out of the first through hole;

[0020] S3. Form a first shielding layer on one side of the resin film layer where the resin protrusion is formed, and make the first shielding layer cover the resin protrusion, so as to form a protrusion portion at a position corresponding to the resin protrusion on the outer surface of the first shielding layer;

[0021] S4. Form an adhesive film layer on one side of the first shielding layer away from the resin film layer.

[0022] As an improvement of the above solution, in step S2, the forming of the resin protrusion at the first through hole is specifically:

[0023] Resin is provided at the first through-hole, and the resin flows from one side of the first through-hole to the other side and then solidifies, so as to form a resin protrusion at the first through-hole.

[0024] As an improvement of the above solution, before forming the adhesive film layer on the side of the first shielding layer away from the resin film layer, the following steps are further included:

[0025] Conductor particles are formed on the outer surface of the protrusion part by one or more processes among physical roughening, electroless plating, physical vapor deposition, chemical vapor deposition, evaporation plating, sputtering plating, electroplating, and mixed plating.

[0026] As an improvement of the above solution, in step S4, forming the adhesive film layer on the side of the first shielding layer away from the resin film layer specifically includes:

[0027] Coat the adhesive film layer on the release film, and then laminate and transfer the adhesive film layer to the side of the first shielding layer away from the resin film layer, so as to form an adhesive film layer on the side of the first shielding layer away from the resin film layer; or

[0028] Directly coat the adhesive film layer on the side of the first shielding layer where the protrusion part is formed, so as to form an adhesive film layer on the side of the first shielding layer away from the resin film layer.

[0029] Compared with the prior art, the preparation method of the electromagnetic shielding film provided by the embodiment of the present invention forms a first shielding layer on the side of the resin film layer where the resin protrusion is formed, and at the same time makes the first shielding layer cover the resin protrusion, so as to form a protrusion part at the position corresponding to the resin protrusion on the outer surface of the first shielding layer, and form the adhesive film layer on one side of the first shielding layer, so that the formed protrusion part can ensure that the first shielding layer smoothly pierces the adhesive film layer during the lamination process, realizing reliable grounding, and has strong practicability. Description of the Drawings

[0030] Figure 1 It is a schematic structural diagram of an electromagnetic shielding film at an angle in Embodiment 1 of the present invention;

[0031] Figure 2 It is a schematic structural diagram of the electromagnetic shielding film in Embodiment 1 of the present invention from another angle;

[0032] Figure 3 It is a schematic structural diagram of the electromagnetic shielding film in Embodiment 2 of the present invention;

[0033] Figure 4 It is a schematic structural diagram of a circuit board in Embodiment 3 of the present invention;

[0034] Figure 5It is a schematic flow chart of the preparation method of the electromagnetic shielding film in Embodiment 4 of the present invention.

[0035] Among them, 1 is the resin film layer; 11 is the first through hole; 12 is the resin protrusion; 2 is the first shielding layer; 21 is the protruding part; 22 is the conductor particles; 3 is the adhesive film layer; 4 is the protective film layer; 5 is the printed circuit board. Detailed implementation manners

[0036] 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. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0037] Refer to Figure 1 , which is a schematic structural diagram of the electromagnetic shielding film provided by Embodiment 1 of the present invention from one angle;

[0038] Refer to Figure 2 , which is a schematic structural diagram of the electromagnetic shielding film provided by Embodiment 1 of the present invention from another angle;

[0039] Combined with Figure 1 and Figure 2 As shown, the electromagnetic shielding film includes a resin film layer 1, a first shielding layer 2, and an adhesive film layer 3. The resin film layer 1 is provided with a first through hole 11 penetrating through its upper and lower surfaces. A resin protrusion 12 is provided at the first through hole 11. The resin protrusion 12 is formed by resin flowing from one side of the first through hole 11 to the other side and then solidifying; the first shielding layer 2 is disposed on the side of the resin film layer close to the resin protrusion 12 and covers the resin protrusion 12, so as to form a protruding part 21 at a position corresponding to the resin protrusion 12 on the outer surface of the first shielding layer 2; the adhesive film layer is disposed on the side of the first shielding layer away from the resin film layer, and the protruding part 21 extends into the adhesive film layer 3.

[0040] In an embodiment of the present invention, by providing the first through hole 11 on the resin film layer 1 and providing the resin protrusion 12 formed by resin solidifying after flowing from one side of the first through hole 11 to the other side at the first through hole 11, and at the same time disposing the first shielding layer 2 on the side of the resin film layer 1 close to the resin protrusion 12 and covering the resin protrusion 12, a protrusion 21 is formed at a position corresponding to the resin protrusion 12 on the outer surface of the first shielding layer 2, and the adhesive film layer 3 is disposed on the side of the first shielding layer 2 away from the resin film layer 1, so that the protrusion 21 ensures that the first shielding layer 2 can smoothly pierce the adhesive film layer 3 during the pressing process to achieve reliable grounding, and further ensure the normal conduction of interference charges under the cooperation of the resin film layer 1 and the first shielding layer 2 to realize the shielding function. The electromagnetic shielding film of this embodiment does not need to be provided with a conductive adhesive layer, so effectively avoids the problem of grounding failure caused by the expansion of the conductive adhesive layer at high temperature.

[0041] In an embodiment of the present invention, the process of forming the resin protrusion 12 is specifically as follows: In one preferred embodiment, the resin protrusion 12 is formed by resin flowing from one side of the first through hole 11 to the other side at the melting temperature and then instantaneously cooled. In another preferred embodiment, the resin is a curable adhesive, and the process of forming the resin protrusion 12 is specifically as follows: At room temperature, the liquefied resin flows from one side of the first through hole 11 to the other side and solidifies at the curing temperature, thereby forming the resin protrusion 12.

[0042] In an embodiment of the present invention, it should be noted that the structure of the resin protrusion 12 shown in the drawings is only exemplary. Since the resin protrusion 12 is formed by resin flowing from one side of the first through hole 11 to the other side and then solidifying, in one case, the resin almost completely flows out of the first through hole 11 without residue in the first through hole 11, so the formed resin protrusion 12 can be as shown in the drawings, and the resin protrusion 12 is formed at the boundary between the first through hole 11 and the first shielding layer 2; in another case, there is resin residue in the first through hole 11, and the first through hole 11 is even filled with resin, so one end of the formed resin protrusion 12 is located in the first through hole 11, and the other end of the resin protrusion 12 extends out of the first through hole 11; in yet another case, there is resin remaining on the surface of the resin film layer 1 away from the first shielding layer 2, so the formed resin protrusion 12 can penetrate the first through hole 11. In addition, the resin protrusion 12 in the present invention is not limited by the illustrated and above shapes, as long as it is a resin protrusion with piercing ability, it is within the protection scope of the present invention.

[0043] In an embodiment of the present invention, it should be noted that the shape of the convex portion 21 may be the same as or different from the shape of the resin convex 12. The shape of the convex portion 21 shown in the attached drawings is only exemplary.

[0044] In an embodiment of the present invention, in order to further ensure that the resin convex 12 can be formed at the first through hole 11, preferably, the cross-sectional area of the first through hole 11 in this embodiment is 0.1 μm 2 -1 mm 2 。

[0045] In addition, in this embodiment, for every 1 cm 2 the number of the first through holes 11 in the resin film layer 1 is 10 - 1000. Correspondingly, for every 1 cm 2 the number of the resin convexes 12 in the resin film layer 1 is 10 - 1000; it should be noted that since the first shielding layer 2 covers the resin convexes 12, convex portions 21 are formed at positions corresponding to the resin convexes 12 on the outer surface of the first shielding layer 2. Therefore, the number of the convex portions 21 corresponds to the number of the resin convexes 12, thereby ensuring that the first shielding layer 2 can smoothly pierce through the adhesive film layer 3.

[0046] In an embodiment of the present invention, the first through holes 11 may be distributed regularly or irregularly on the resin film layer 1; among them, the first through holes 11 being regularly distributed on the resin film layer 1 means that the shapes of the first through holes 11 are the same and they are evenly distributed on the resin film layer 1; the first through holes 11 being irregularly distributed on the resin film layer 1 means that the shapes of the first through holes 11 are different from each other and they are disorderly distributed on the resin film layer 1. Preferably, the shapes of the first through holes 11 are the same and the first through holes 11 are evenly distributed on the resin film layer 1. In addition, the first through holes 11 may be circular through holes or through holes of any other shape. The attached drawings of the present invention only take the first through holes 11 being circular through holes as an example for illustration, but any other shaped first through holes 11 are within the protection scope of the present invention.

[0047] In an embodiment of the present invention, the resin film layer 1 includes a first surface and a second surface which are oppositely arranged. The first surface is in contact with the first shielding layer 2; the second surface is in contact with the protective film layer 4. It should be noted that the first surface and the second surface may be surfaces of any shape. For example, they may be Figure 1The flat surface shown can also be an undulating non-flat surface or other rough surfaces; in addition, the first surface and the second surface can be regular surfaces or irregular surfaces. In the accompanying drawings of the present invention, only the examples where both the first surface and the second surface are flat surfaces are given for illustration, and the first surfaces and second surfaces of any other shapes are within the protection scope of the present invention. In addition, it should be noted that the resin film layer 1 in the accompanying drawings of this embodiment can be a single-layer structure or a multi-layer structure.

[0048] In the embodiment of the present invention, the thickness of the first shielding layer 2 is 0.1 μm - 45 μm. To ensure that the first shielding layer 2 has good electrical conductivity, the first shielding layer 2 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 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.

[0049] In the embodiment of the present invention, it should be noted that the first shielding layer 2 in the accompanying drawings of this embodiment can be a single-layer structure or a multi-layer structure. In addition, according to the actual production and application needs, the first shielding layer 2 in the accompanying drawings of this embodiment can be set in a mesh shape, a foamed shape, etc.

[0050] In one structure of the adhesive film layer 3 in the embodiment of the present invention, specifically: the adhesive film layer 3 includes an adhesive layer containing conductive particles. By making the adhesive film layer 3 include an adhesive layer containing conductive particles, the adhesive film layer 3 not only has an adhesive effect to tightly adhere the wiring board and the electromagnetic shielding film, but also has a conductive function, which cooperates with the first shielding layer 2 to quickly conduct interfering electrons into the ground layer of the wiring board. Among them, the conductive particles can be separated conductive particles or large granular conductive particles formed by aggregation; when the conductive particles are separated conductive particles, the electrical contact area can be further increased and the uniformity of electrical contact can be improved; while when the conductive particles are large granular conductive particles formed by aggregation, the piercing strength can be increased.

[0051] In another structure of the adhesive film layer 3 in the embodiment of the present invention, specifically: the adhesive film layer 3 includes an adhesive layer without conductive particles. By making the adhesive film layer 3 include an adhesive layer without conductive particles, the adhesive film layer 3 has an adhesive effect to tightly adhere the wiring board and the electromagnetic shielding film, and at the same time, since the adhesive film layer 3 does not contain conductive particles, the insertion loss of the circuit board during use is reduced, the shielding effectiveness is improved, and the bending property of the circuit board is improved.

[0052] In an embodiment of the present invention, the thickness of the adhesive film layer 3 is 1 μm - 80 μm. The material used for the adhesive film layer 3 is selected from the following types: modified epoxy resin, acrylic acid, modified rubber, and modified thermoplastic polyimide. In addition, the outer surface of the adhesive film layer 3 can be a flat surface without undulations or a non-flat surface with gentle undulations.

[0053] As Figure 1 shown, in order to protect the resin film layer 1, the electromagnetic shielding film in this embodiment further includes a protective film layer 4, and the protective film layer 4 is disposed on the side of the resin film layer 1 away from the first shielding layer 2. The protective film layer 4 plays a protective role, thereby ensuring that the resin film layer 1 is not scratched or damaged during use and maintaining the high shielding efficiency of the resin film layer 1. The protective film layer 4 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.

[0054] In an embodiment of the present invention, it should be noted that the electromagnetic shielding film can be a repeated multi-layer structure. Specifically, the electromagnetic shielding film can include a plurality of the resin film layers 1 stacked in sequence, and the first shielding layer 2 and the adhesive film layer 3 are sequentially provided on one side of the whole formed by the plurality of resin film layers 1, and the protective film layer 4 is provided on the other side; a resin protrusion 12 is provided at a first through hole 11 on the resin film layer 1 in contact with the first shielding layer 2, and the first shielding layer 2 covers the resin protrusion 12, so that a protrusion 21 is formed at a position corresponding to the resin protrusion 12 on the outer surface of the first shielding layer 2, and the protrusion 21 extends into the adhesive film layer 2.

[0055] See Figure 3 , which is a schematic structural diagram of the electromagnetic shielding film provided in Embodiment 2 of the present invention;

[0056] As Figure 3 shown, the difference between the electromagnetic shielding film in this embodiment and that in Embodiment 1 is that a convex conductor particle 22 is provided on the surface of the protrusion 21. By providing the conductor particle 22 on the surface of the protrusion 21, it is further ensured that the protrusion 21 can ensure that the first shielding layer 2 smoothly pierces the adhesive film layer 3 during the pressing process, thereby ensuring the normal export of interfering charges.

[0057] Preferably, the conductor particles 22 are concentratedly distributed at the outwardly protruding positions on the surface of the convex portion 21, making it easier to pierce the adhesive film layer 3. Of course, the conductor particles 22 may also be distributed on the non-convex portions of the surface of the convex portion 21. In addition, the conductor particles 22 may also be distributed at other positions on the side of the first shielding layer 2 close to the adhesive film layer 3, not only distributed on the surface of the convex portion 21, such as Figure 3 as shown. Of course, the conductor particles 22 may also be distributed only on the convex portion 21.

[0058] In specific implementation, as Figure 3 shown, the first shielding layer 2 may be formed first, and then the conductor particles 22 may be formed on the side of the first shielding layer 2 away from the resin film layer 1 through other processes. Of course, the first shielding layer 2 and the conductor particles 22 may also be an integral structure formed by a one-step forming process. It should be noted that the conductor particles 22 are concentratedly distributed on the convex portion 21.

[0059] In the embodiments of the present invention, the conductor particles 22 may have a certain distance from the outer surface of the adhesive film layer 3, or may be in contact with the outer surface of the adhesive film layer 3 or extend out of the outer surface of the adhesive film layer 3.

[0060] In the embodiments of the present invention, in order to ensure that the convex portion 21 can smoothly pierce the adhesive film layer 3, preferably, the height of the conductor particles 22 is 0.1 μm - 30 μm.

[0061] In the embodiments of the present invention, the conductor particles 22 include one or more of metal particles, carbon nanotube particles, and ferrite particles. In addition, the metal particles include single metal particles and / or alloy particles; among them, the single metal particles are made of any one of aluminum, titanium, zinc, iron, nickel, chromium, cobalt, copper, silver, and gold, and the alloy particles are made of any two or more of aluminum, titanium, zinc, iron, nickel, chromium, cobalt, copper, silver, and gold. It should be noted that the conductor particles 22 may be the same as or different from the material of the first shielding layer 2.

[0062] In the embodiments of the present invention, it should be noted that as Figure 3 shown, the shape of the conductor particles 22 is only exemplary. Due to differences in process means and parameters, the conductor particles 22 may also be in other shapes such as cluster shape, icicle shape, stalactite shape, dendritic shape, etc. In addition, the conductor particles 22 in the present invention are not limited by the illustrated and above-mentioned shapes. As long as they are conductor particles with piercing and conductive functions, they are within the protection scope of the present invention.

[0063] In the embodiments of the present invention, it should be noted that the electromagnetic shielding film may be a repeated multi-layer structure; specifically, the electromagnetic shielding film may include a plurality of resin film layers 1 arranged in a stacked manner in sequence, and the first shielding layer 2 and the adhesive film layer 3 are sequentially provided on one side of the whole formed by the plurality of resin film layers 1, and the protective film layer 4 is provided on the other side; a resin protrusion 12 is provided at the first through hole 11 on the resin film layer 1 in contact with the first shielding layer 2, and the first shielding layer 2 covers the resin protrusion 12, so as to form a protrusion 21 at a position corresponding to the resin protrusion 12 on the outer surface of the first shielding layer 2, the protrusion 21 extends into the adhesive film layer 3, and the surface of the protrusion 21 is provided with the conductor particles 22. In addition, the other structures and working principles of the electromagnetic shielding film in this embodiment are the same as those in Embodiment 1, and will not be elaborated here.

[0064] See Figure 4 , which is a schematic structural diagram of the circuit board provided in Embodiment 3 of the present invention;

[0065] As Figure 4 shown, the embodiments of the present invention also provide a circuit board including a printed circuit board 5 and the electromagnetic shielding film described in Embodiment 1, and the electromagnetic shielding film is press-fitted with the printed circuit board 5 through its adhesive film layer 3; the protrusion 21 pierces through the adhesive film layer 3 and extends to the ground layer of the printed circuit board 5.

[0066] In this embodiment, for the implementation manner of the electromagnetic shielding film, reference may be made to the description of Embodiment 1 above, and details will not be repeated here.

[0067] Preferably, the printed circuit board 5 is one of a flexible single-sided board, a flexible double-sided board, a flexible multi-layer board, and a rigid-flex board.

[0068] In the embodiments of the present invention, through the above structure, during the press-fitting process, the protrusion 21 on the first shielding layer 2 is used to pierce through the adhesive film layer 3, so that at least a part of the outer surface of the first shielding layer 2 is connected to the ground layer of the printed circuit board 5, thereby realizing the smooth export of interference charges. In addition, it should be noted that the electromagnetic shielding film described in Embodiment 1 adopted in the structure of the circuit board in this embodiment can be replaced with the electromagnetic shielding film described in Embodiment 2, and details will not be repeated here.

[0069] See Figure 5 , which is a schematic flow chart of the method for preparing the electromagnetic shielding film provided in Embodiment 4 of the present invention;

[0070] As Figure 5 shown, this method is applicable to the preparation of the electromagnetic shielding film described in Embodiment 1, and includes the steps:

[0071] S1. Form a resin film layer; wherein, the resin film layer has a first through hole penetrating its upper and lower surfaces;

[0072] Specifically, the resin film layer is formed in the following manner: form a protective film layer on a carrier film, and form a resin film layer on the protective film layer; or

[0073] Form a resin film layer on the surface of a peelable layer with a carrier, form a protective film layer on the resin film layer, and peel off the peelable layer with the carrier;

[0074] Wherein, the resin film layer has a first through hole penetrating its upper and lower surfaces. The cross-sectional area of the first through hole is 0.1 μm 2 -1 mm 2 ; per 1 cm 2 The number of the first through holes in the resin film layer is 10 - 1000.

[0075] S2. Form a resin protrusion at the first through hole; wherein, the resin protrusion extends out of the first through hole;

[0076] Wherein, forming the resin protrusion at the first through hole is specifically: set resin at the first through hole, and make the resin flow from one side of the first through hole to the other side and then solidify, so as to form a resin protrusion at the first through hole. Specifically, in one preferred method, set resin at the first through hole, and make the resin flow from one side of the first through hole to the other side at normal temperature and then solidify at the curing temperature, so as to form a resin protrusion at the first through hole. In another preferred embodiment, set resin at the first through hole, and make the resin flow from one side of the first through hole to the other side at the melting temperature and then undergo instant cooling, so as to form a resin protrusion at the first through hole.

[0077] S3. Form a first shielding layer on the side of the resin film layer where the resin protrusion is formed, and make the first shielding layer cover the resin protrusion, so as to form a protrusion part at the position corresponding to the resin protrusion on the outer surface of the first shielding layer;

[0078] S4. Form a glue film layer on the side of the first shielding layer away from the resin film layer.

[0079] Specifically, coat a glue film layer on a release film, and then laminate and transfer the glue film layer to the side of the first shielding layer away from the resin film layer, so as to form a glue film layer on the side of the first shielding layer away from the resin film layer; or

[0080] Directly coat a glue film layer on the side of the first shielding layer where the protrusion part is formed, so as to form a glue film layer on the side of the first shielding layer away from the resin film layer.

[0081] In another preferred embodiment applicable to the preparation of the electromagnetic shielding film described in Example 2, before step S4, the following step is further included:

[0082] Conductor particles are formed on the outer surface of the raised portion by one or more processes of physical roughening, electroless plating, physical vapor deposition, chemical vapor deposition, evaporation plating, sputtering plating, electroplating, and mixed plating.

[0083] In the embodiment of the present invention, in the method for preparing the electromagnetic shielding film, a first shielding layer is formed on the side of the resin film layer where the resin protrusion is formed, and at the same time, the first shielding layer covers the resin protrusion, so as to form a raised portion at the position corresponding to the resin protrusion on the outer surface of the first shielding layer, and a glue film layer is formed on the side of the first shielding layer away from the resin film layer, so that the formed raised portion can ensure that the first shielding layer smoothly pierces the glue film layer during the lamination process, realizing reliable grounding and strong practicability.

[0084] In summary, the embodiment of the present invention provides an electromagnetic shielding film, a circuit board, and a method for preparing the electromagnetic shielding film. The electromagnetic shielding film includes a resin film layer 1, a first shielding layer 2, and a glue film layer 3. A first through hole 11 penetrating the upper and lower surfaces is provided on the resin film layer 1. A resin protrusion 12 is provided at the first through hole 11. The resin protrusion 12 is formed by resin flowing from one side of the first through hole 11 to the other side and then solidifying; the first shielding layer 2 is provided on the side of the first shielding film 1 close to the resin protrusion 12 and covers the resin protrusion 12, so as to form a raised portion 21 at the position corresponding to the resin protrusion 12 on the outer surface of the first shielding layer 2; the glue film layer is provided on the side of the first shielding layer away from the resin film layer, and the raised portion 21 extends into the glue film layer 3. By providing the first through hole 11 on the resin film layer 1 and providing the resin protrusion 12 formed by resin flowing from one side of the first through hole 11 to the other side and then solidifying at the first through hole 11, and at the same time, arranging the first shielding layer 2 on the side of the first shielding film 1 close to the resin protrusion 12 and covering the resin protrusion 12, so as to form a raised portion 21 at the position corresponding to the resin protrusion 12 on the outer surface of the first shielding layer 2, and arranging the glue film layer 3 on the side of the first shielding layer 2 away from the resin film layer 1, the raised portion 21 ensures that the first shielding layer 2 can smoothly pierce the glue film layer 3 during the lamination process, so as to realize reliable grounding, and further ensure the normal export of interference charges and realize the shielding function.

[0085] 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 modifications can be made, and these improvements and modifications are also regarded as the protection scope of the present invention.

Claims

1. An electromagnetic shielding film, characterized in that, It includes a resin film layer, a first shielding layer, and an adhesive film layer. A first through hole penetrating the upper and lower surfaces is provided on the resin film layer. A resin protrusion is provided at the first through hole, and the resin protrusion is formed by resin flowing from one side of the first through hole to the other side and then solidifying; the first shielding layer is provided on one side of the resin film layer close to the resin protrusion and covers the resin protrusion, so as to form a protrusion portion at a position corresponding to the resin protrusion on the outer surface of the first shielding layer; the adhesive film layer is provided on one side of the first shielding layer away from the resin film layer, and the protrusion portion extends into the adhesive film layer; the protrusion portion pierces the adhesive film layer during the lamination process.

2. The electromagnetic shielding film according to claim 1, wherein, The resin protrusion is formed by resin flowing from one side of the first through hole to the other side at normal temperature and then solidifying at the curing temperature; or, The resin protrusion is formed by resin flowing from one side of the first through hole to the other side at the melting temperature and then instantaneously cooled.

3. The electromagnetic shielding film according to claim 1, wherein, The surface of the protrusion portion is provided with convex conductor particles; the height of the conductor particles is 0.1 μm - 30 μm.

4. The electromagnetic shielding film according to claim 1, wherein The adhesive film layer includes an adhesive layer containing conductive particles; or, The adhesive film layer includes an adhesive layer without conductive particles.

5. The electromagnetic shielding film according to any one of claims 1-4, characterized in that, The first shielding layer includes one or more of a metal shielding layer, a carbon nanotube shielding layer, a ferrite shielding layer, and a graphene shielding layer.

6. The electromagnetic shielding film according to claim 5, wherein The metal shielding layer includes a single-metal shielding layer and / or an alloy shielding layer; wherein, 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.

7. The electromagnetic shielding film according to any one of claims 1 to 4, characterized in that, The electromagnetic shielding film further includes a protective film layer, and the protective film layer is provided on one side of the resin film layer away from the first shielding layer.

8. A circuit board, characterized in that, It includes a printed circuit board and the electromagnetic shielding film according to any one of claims 1 to 7. The electromagnetic shielding film is laminated with the printed circuit board through its adhesive film layer; the protrusion portion pierces the adhesive film layer and extends to the ground layer of the printed circuit board.

9. A method for preparing an electromagnetic shielding film, characterized in that, Suitable for preparing the electromagnetic shielding film according to any one of claims 1 to 7, including the steps: S1. Form a resin film layer; wherein, the resin film layer has a first through hole penetrating its upper and lower surfaces; S2. Form a resin protrusion at the first through hole; wherein, the resin protrusion extends out of the first through hole; S3. Form a first shielding layer on one side of the resin film layer where the resin protrusion is formed, and make the first shielding layer cover the resin protrusion, so as to form a protrusion portion at a position corresponding to the resin protrusion on the outer surface of the first shielding layer; S4. Form an adhesive film layer on one side of the first shielding layer away from the resin film layer.

10. The method for preparing an electromagnetic shielding film according to claim 9, wherein, In step S2, the forming of the resin protrusion at the first through hole specifically is: Set resin at the first through hole, and make the resin flow from one side of the first through hole to the other side and then solidify, so as to form a resin protrusion at the first through hole.

11. The method for preparing an electromagnetic shielding film according to claim 9, wherein Before forming the adhesive film layer on one side of the first shielding layer away from the resin film layer, the following steps are further included: Conductor particles are formed on the outer surface of the raised portion by one or more processes among physical roughening, electroless plating, physical vapor deposition, chemical vapor deposition, evaporation plating, sputtering plating, electroplating, and hybrid plating.

12. The method for preparing an electromagnetic shielding film according to claim 9, wherein In step S4, forming the adhesive film layer on the side of the first shielding layer away from the resin film layer specifically includes: Coating the adhesive film layer on the release film, and then laminating and transferring the adhesive film layer to the side of the first shielding layer away from the resin film layer, thereby forming the adhesive film layer on the side of the first shielding layer away from the resin film layer; Or Directly coating the adhesive film layer on the side of the first shielding layer away from the resin film layer, thereby forming the adhesive film layer on the side of the first shielding layer away from the resin film layer.

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