Electromagnetic shielding film and circuit board

Abstract

The present invention discloses an electromagnetic shielding film and a circuit board, wherein the electromagnetic shielding film includes a first insulating layer, a shielding layer, and a conductive adhesive film layer. The conductive adhesive film layer has a first side surface and a second side surface arranged opposite each other. The first side surface is used to adhere to the second insulating layer of the circuit board, and the second side surface is provided with the shielding layer. The first insulating layer includes an insulating base layer, which is arranged on the first side surface of the shielding layer. The edge of the insulating base layer extends toward the side surface where the conductive adhesive film layer is located to form a shielding wall. The inner side surface of the shielding wall adheres to and shields the side edges of the shielding layer and the conductive adhesive film layer. The electromagnetic shielding film of the present invention has a simple structure, does not overflow glue, effectively prevents the occurrence of short circuits, and has high bonding strength between the layers, making it difficult for separation to occur.

Description

Technical Field

[0001] The present invention relates to the technical field of circuit boards, and in particular to an electromagnetic shielding film and a circuit board comprising the electromagnetic shielding film. Background Art

[0002] A circuit board typically consists of a substrate and a circuit layer positioned on one side of the substrate. As the integration of electronic products increases, the circuit structures within the circuit board become increasingly complex, and the distances between circuit layers within the circuit layer are becoming increasingly close. Coupled with the increasing frequency of circuit board operation, this leads to electromagnetic interference between electronic components and circuit layers, impacting the performance of electronic products. Therefore, electromagnetic shielding films are currently being designed to be applied to the circuit layer of the circuit board to reduce electromagnetic interference.

[0003] Existing electromagnetic shielding films, such as those described in Chinese patent document CN107484324B, comprise an insulating resin layer, a metal film layer, and a conductive adhesive layer. The insulating resin layer is disposed on one side of the metal film layer, and the conductive adhesive layer is disposed on the other side of the metal film layer. This electromagnetic shielding film is bonded to a printed wiring board (PCB). The PCB includes a substrate having a printed circuit disposed on at least one side thereof. An insulating film is disposed on the surface of the PCB on which the printed circuit is disposed. The conductive adhesive is bonded to the insulating film, and the conductive adhesive is electrically connected to the printed circuit via through-holes formed in the insulating film. While existing technologies can address the electromagnetic wave shielding problem, because the electromagnetic wave shielding film is pressed onto the PCB, the conductive adhesive layer of the PCB is fluid and can overflow from the edges of the PCB and flow into the through-holes, causing the conductive adhesive to contact the sides of the PCB. This can potentially lead to electrical contact with locations on the PCB where the electromagnetic wave shielding film is not required to be electrically connected, thus causing a short circuit. Summary of the Invention

[0004] The purpose of the embodiments of the present invention is to provide an electromagnetic shielding film and a circuit board, which have good anti-glue overflow effect and high bonding strength between layers.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] In a first aspect, an electromagnetic shielding film is provided, comprising a first insulating layer, a shielding layer and a conductive adhesive film layer, wherein the conductive adhesive film layer has a first side surface and a second side surface arranged opposite to each other, wherein the first side surface is used to adhere to the second insulating layer of the circuit board, and the shielding layer is provided on the second side surface, and the first insulating layer comprises an insulating base layer, which is arranged on the first side surface of the shielding layer, and the edge of the insulating base layer extends toward the side surface where the conductive adhesive film layer is located to form a shielding wall, and the inner side surface of the shielding wall adheres to and shields the side edges of the shielding layer and the conductive adhesive film layer.

[0007] As a preferred solution for the electromagnetic shielding film, the shielding wall has a limiting layer extending from one end of the insulating base layer toward the center of the shielding wall, and the limiting layer is provided with an avoidance hole. The conductive adhesive film layer includes an adhesive film base layer, and the adhesive film base layer is sandwiched between the limiting layer and the shielding layer. The conductive adhesive film layer also includes a filling layer connected to the adhesive film base layer, and the filling layer fills the avoidance hole.

[0008] As a preferred solution for the electromagnetic shielding film, the distance between the side of the filling layer away from the film base layer and the shielding layer is H1, and the distance between the side of the limiting layer away from the film base layer and the shielding layer is H2, H1≤H2.

[0009] As a preferred solution for the electromagnetic shielding film, the filling layer is provided with a recessed receiving groove on a side away from the adhesive film base layer, the circuit board includes a carrier board, a circuit layer is provided on one side of the carrier board, the second insulating layer is provided on a side of the circuit layer away from the carrier board, a grounding portion is provided on the circuit layer at a position corresponding to the grounding circuit, the grounding portion is protruding, a through hole is provided on the second insulating layer, and the grounding portion is inserted into the receiving groove through the through hole.

[0010] As a preferred solution for the electromagnetic shielding film, a plurality of glue overflow grooves are concavely provided on the inner side of the shielding wall.

[0011] As a preferred solution of the electromagnetic shielding film, the side of the insulating base layer close to the shielding layer is roughened; and / or,

[0012] The inner side surface of the shielding wall is roughened.

[0013] As a preferred solution of the electromagnetic shielding film, the shielding layer is provided with a plurality of glue overflow holes; or the shielding layer is a foaming layer.

[0014] As a preferred solution of the electromagnetic shielding film, the glue overflow hole is a blind hole, and the glue overflow hole only passes through one side of the shielding layer close to the conductive adhesive film layer.

[0015] As a preferred solution of the electromagnetic shielding film, the first insulating layer is an insulating foam layer.

[0016] In the second aspect, a circuit board is also provided, comprising a carrier board, a circuit layer, a second insulating layer and the electromagnetic shielding film, wherein the circuit layer is arranged on one side of the carrier board, and the second insulating layer is arranged on a side of the circuit layer away from the carrier board, and a through hole is provided on the second insulating layer corresponding to the grounding circuit on the circuit layer, the electromagnetic shielding film is adhered to the side of the second insulating layer away from the circuit layer, and the conductive adhesive film layer is adhered to the second insulating layer, and a portion of the conductive adhesive film layer passes through the through hole to be connected to the grounding circuit and electrically conductive.

[0017] The beneficial effects of the present invention are: by extending the edge of the insulating base layer to form a shielding wall, the shielding wall can shield the side edges of the shielding layer and the conductive film layer. When the electromagnetic shielding film is attached to the second insulating layer of the circuit board, the electromagnetic shielding film is squeezed so that part of the conductive film layer passes through the through hole corresponding to the grounding circuit on the second insulating layer. The conductive film layer will be electrically connected to the grounding circuit, and due to the squeezing effect, the conductive film layer will extend laterally. At this time, the shielding wall can prevent the conductive film layer from overflowing from the side of the electromagnetic shielding film, completely eliminating the occurrence of short circuits. In addition, the setting of the shielding wall also increases the bonding strength between the first insulating layer, the shielding layer and the conductive film layer, effectively preventing separation between the layers. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The present invention will be described in further detail below with reference to the accompanying drawings and examples.

[0019] Figure 1 Schematic cross-sectional view of the electromagnetic shielding film according to the first embodiment of the present invention.

[0020] Figure 2 Schematic cross-sectional view of a circuit board according to embodiment 1 of the present invention.

[0021] Figure 3 It is a schematic cross-sectional view of the electromagnetic shielding film according to the second embodiment of the present invention.

[0022] Figure 4 Schematic cross-sectional view of a circuit board according to the second embodiment of the present invention.

[0023] Figure 5 Schematic cross-sectional view of the electromagnetic shielding film according to the third embodiment of the present invention.

[0024] Figure 6 Schematic cross-sectional view of the first insulating layer of the third embodiment of the present invention.

[0025] Figure 7 Schematic cross-sectional view of a circuit board according to embodiment 3 of the present invention.

[0026] Figure 8 Schematic cross-sectional view of the electromagnetic shielding film according to the fourth embodiment of the present invention.

[0027] Figure 9 Schematic cross-sectional view of a circuit board according to a fourth embodiment of the present invention.

[0028] In the picture:

[0029] 1. First insulation layer; 11. Insulation base layer; 12. Blocking wall; 13. Limiting layer; 14. Avoidance hole; 15. Glue overflow groove; 2. Shielding layer; 21. Glue overflow hole; 3. Conductive adhesive film layer; 31. Adhesive film base layer; 32. Filling layer; 4. Second insulation layer; 5. Carrier board; 6. Circuit layer. DETAILED DESCRIPTION

[0030] To make the technical problems solved, the technical solutions adopted, and the technical effects achieved by the present invention more clearly understood, the technical solutions of the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings. It is apparent that the described embodiments are only some of the embodiments of the present invention, not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort shall fall within the scope of protection of the present invention.

[0031] In the description of the present invention, unless otherwise expressly specified or limited, the terms "connected," "connected," and "fixed" should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integration; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and internal communication between two components or interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention in specific circumstances.

[0032] Example 1:

[0033] like Figure 1 As shown (and refer to the attached Figure 2), the present invention provides an electromagnetic shielding film, comprising a first insulating layer 1, a shielding layer 2 and a conductive adhesive film layer 3, the conductive adhesive film layer 3 having a first side surface and a second side surface arranged opposite to each other, wherein the first side surface is used to adhere to the second insulating layer 4 of the circuit board, and the second side surface is provided with the shielding layer 2, the first insulating layer 1 comprises an insulating base layer 11, the insulating base layer 11 is arranged on the first side surface of the shielding layer 2, the edge of the insulating base layer 11 extends toward the side surface where the conductive adhesive film layer 3 is located to form a shielding wall 12, the inner side surface of the shielding wall 12 adheres to and shields the side edges of the shielding layer 2 and the conductive adhesive film layer 3. By extending the edge of the insulating base layer 11 to form a shielding wall 12, the shielding wall 12 can shield the side edges of the shielding layer 2 and the conductive film layer 3. When the electromagnetic shielding film is attached to the second insulating layer 4 of the circuit board, the electromagnetic shielding film is squeezed so that part of the conductive film layer 3 passes through the through hole corresponding to the grounding circuit on the second insulating layer 4. The conductive film layer 3 will be electrically connected to the grounding circuit, and due to the squeezing effect, the conductive film layer 3 will extend laterally. At this time, the shielding wall 12 can prevent the conductive film layer 3 from overflowing from the side of the electromagnetic shielding film, completely eliminating the occurrence of short circuits. In addition, the setting of the shielding wall 12 also increases the bonding strength between the first insulating layer 1, the shielding layer 2 and the conductive film layer 3, effectively preventing separation between the layers.

[0034] In an embodiment of the present invention, the first insulating layer 1 may be an adhesive, which may be composed of a thermoplastic resin such as polystyrene, vinyl acetate, polyester, polyethylene, polypropylene, polyamide, rubber, or acrylic, or a thermosetting resin such as phenol, epoxy, polyurethane, melamine, or alkyd. It should be noted that the adhesive may be a single resin or a mixture of the above resins. Furthermore, the adhesive may further contain a tackifier, such as a fatty acid hydrocarbon resin, a C5 / C9 mixed resin, rosin, a rosin derivative, a terpene resin, an aromatic hydrocarbon resin, or a thermoreactive resin.

[0035] In addition, it should be noted that the first insulating layer 1 is not limited to adhesives, and the first insulating layer 1 can also be a "layer formed of other materials (a layer with other functions)". For example, it can be an insulating layer having an adhesive layer provided on at least one side of an engineering plastic. Among them, the material of the engineering plastic can be resins such as polyethylene terephthalate, polypropylene, cross-linked polyethylene, polyester, polybenzimidazole, polyimide, polyimide amide, polyetherimide, and polyphenylene sulfide (PPS). When the heat resistance requirement is low, it is preferred to use an inexpensive polyester film. When the flame retardancy requirement is high, it is preferred to use a polyphenylene sulfide (PPS) film. In addition, when heat resistance is required, it is preferred to use a polyimide film.

[0036] In the embodiment of the present invention, preferably, the thickness of the first insulating layer 1 is 1 μm-50 μm. Specifically, when the thickness of the first insulating layer 1 is required to be thinner, the thickness of the first insulating layer 1 is preferably 5 μm; when the thickness of the first insulating layer 1 is required to be thicker, the thickness of the first insulating layer 1 is preferably 30 μm.

[0037] In addition, the first insulating layer 1 can also be an insulating foam layer. The first insulating layer 1 of the insulating foam layer structure has many pore structures due to foaming. This pore structure can serve as a place for the conductive adhesive film layer 3 to store adhesive during extrusion, further preventing adhesive overflow.

[0038] In an embodiment of the present invention, the thickness of the shielding layer 2 is 0.1 μm-45 μm. It is understandable that in order to ensure that the shielding layer 2 has good conductivity, the 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. In addition, 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.

[0039] In the embodiment of the present invention, it should be noted that the shielding layer 2 shown in the drawings of this embodiment can be a single-layer structure or a multi-layer structure. In addition, according to the needs of actual production and application, the shielding layer 2 shown in the drawings of this embodiment can be configured in a grid shape, a foam shape, etc.

[0040] Refer to the attached Figure 2 An embodiment of the present invention further provides a circuit board, comprising a carrier board 5, a circuit layer 6 disposed on one side of the carrier board 5, a second insulating layer 4 disposed on a side of the circuit layer 6 facing away from the carrier board 5, and a through-hole formed in the second insulating layer 4 corresponding to the grounding circuit on the circuit layer 6. The circuit board also comprises an electromagnetic shielding film as described in the above embodiment, which is attached to the side of the second insulating layer 4 facing away from the circuit layer 6, and the conductive adhesive film layer 3 is attached to the second insulating layer 4, with a portion of the conductive adhesive film layer 3 passing through the through-hole to connect with the grounding circuit and provide electrical conduction. When assembling the circuit board, the electromagnetic shielding film is attached to the second insulating layer 4 and hot-pressed or cold-pressed to secure the electromagnetic shielding film, second insulating layer 4, circuit layer 6, and carrier board 5 together. At this time, due to the blocking effect of the shielding wall 12 of the first insulating layer 1 of the electromagnetic shielding film, the conductive adhesive film layer 3 does not overflow from the side of the electromagnetic shielding film, effectively preventing the occurrence of a short circuit.

[0041] Example 2:

[0042] like Figure 3 As shown (see attached Figure 4 ), the structure of the electromagnetic shielding film of this embodiment is similar to that of the embodiment 1, and the only difference is that the electromagnetic shielding film of this embodiment adds a limiting layer 13. Specifically, the blocking wall 12 has a limiting layer 13 extending from one end of the insulating base layer 11 toward the center of the blocking wall 12, and the limiting layer 13 is provided with an avoidance hole 14, and the conductive film layer 3 includes a film base layer 31, and the film base layer 31 is sandwiched between the limiting layer 13 and the shielding layer 2, and the conductive film layer 3 also includes a filling layer 32 connected to the film base layer 31, and the filling layer 32 fills the avoidance hole 14. By providing the limiting layer 13, the bonding strength between the first insulating layer 1 and the shielding layer 2 and the conductive film layer 3 can be increased, and the insulating base layer 11 can be effectively prevented from separating from the shielding layer 2, and the blocking wall 12 can be prevented from separating from the sides of the shielding layer 2 and the conductive film layer 3, so that the electromagnetic shielding film has good integrity.

[0043] In this embodiment, the distance between the side of the filling layer 32 away from the adhesive film base 31 and the shielding layer 2 is H1, and the distance between the side of the limiting layer 13 away from the adhesive film base 31 and the shielding layer 2 is H2, and H1 is slightly smaller than H2. That is, the filling layer 32 does not fill the avoidance hole 14, refer to Figure 3 The lower surface of the filling layer 32 is slightly higher than the lower surface of the limiting layer 13, and the lower surface of the filling layer 32 is not flush with the lower surface of the limiting layer 13. This design can use the unfilled avoidance holes 14 to store glue after extrusion.

[0044] In other embodiments, the distance H1 between the side of the filling layer 32 away from the adhesive film base layer 31 and the shielding layer 2 can also be set to be equal to the distance H2 between the side of the limiting layer 13 away from the adhesive film base layer 31 and the shielding layer 2. The above setting allows the filling layer 32 to fill the entire avoidance hole 14, that is, the lower surface of the filling layer 32 shown in the figure is arranged flush with the lower surface of the limiting layer 13, ensuring that the conductive adhesive film layer 3 can better adhere to the second insulating layer 4 and can minimize the glue overflow of the conductive adhesive film layer 3. In addition, the limiting layer 13 surrounds the edge of the adhesive film base layer 31 of the conductive adhesive film layer 3, that is, the width of the limiting layer 13 is relatively narrow, so that the conductive adhesive film layer 3 has as much contact surface with the second insulating layer 4 as possible. In order to ensure that the limiting layer 13 and the second insulating layer 4 are not separated, the limiting layer 13 can also be set as a self-adhesive structure, that is, at least the side of the limiting layer 13 close to the second insulating layer 4 is provided with a structure that can be glued, or both opposite sides of the limiting layer 13 are provided with structures that can be glued.

[0045] like Figure 4As shown, an embodiment of the present invention further provides a circuit board, which includes a carrier board 5, a circuit layer 6 is provided on one side of the carrier board 5, and a second insulating layer 4 is provided on a side of the circuit layer 6 away from the carrier board 5. A through hole is provided on the second insulating layer 4 corresponding to the grounding circuit on the circuit layer 6. The circuit board also includes an electromagnetic shielding film as described in the above embodiment, which is attached to the side of the second insulating layer 4 away from the circuit layer 6, and the filling layer 32 and the limiting layer 13 of the conductive adhesive film layer 3 are attached to the second insulating layer 4. The filling layer 32 of the conductive adhesive film layer 3 partially passes through the through hole and is connected to the grounding circuit and is electrically conductive. When assembling the circuit board, the electromagnetic shielding film is attached to the second insulating layer 4 and hot-pressed or cold-pressed to fix the electromagnetic shielding film, the second insulating layer 4, the circuit layer 6, and the carrier board 5 together. At this time, due to the blocking effect of the shielding wall 12 of the first insulating layer 1 of the electromagnetic shielding film, the conductive adhesive film layer 3 will not overflow from the side of the electromagnetic shielding film, effectively avoiding the occurrence of short circuits. In addition, due to the setting of the limiting layer 13, the electromagnetic shielding film composed of the first insulating layer 1, the shielding layer 2 and the conductive film layer 3 has a high bonding strength and is not easy to separate. The conductive film layer 3 will not overflow at all because the first insulating layer 1 realizes a full-dimensional wrapping form.

[0046] Example 3:

[0047] like Figure 5 and Figure 6 As shown (see attached Figure 7 ), the structure of this embodiment is similar to that of the first embodiment, and the only difference is that: this embodiment is provided with a glue overflow groove 15, specifically, a plurality of glue overflow grooves 15 are recessed on the inner side of the shielding wall 12. By providing the glue overflow groove 15, the glue overflow groove 15 can be hollow when the electromagnetic shielding film is not adhered and pressed against the second insulating layer 4. When the electromagnetic shielding film is adhered and pressed against the second insulating layer 4, due to the presence of the glue overflow groove 15, the glue overflowing from the side of the conductive adhesive film layer 3 is stored in the glue overflow groove 15, ensuring that the glue will not be exposed to the first insulating layer 1, and the conductive adhesive film layer 3 in the glue overflow groove 15 can also increase the bonding strength between the shielding wall 12, the conductive adhesive film layer 3 and the shielding layer 2.

[0048] In this embodiment, the glue overflow groove 15 provided on the inner sidewall of the shielding wall 12 surrounds the outer periphery of the conductive adhesive film layer 3, and two annular glue overflow grooves 15 are provided along the thickness direction of the entire electromagnetic shielding film. In other embodiments, non-annular glue overflow grooves 15 can also be provided, and multiple glue overflow grooves 15 can be provided at intervals on the shielding wall 12.

[0049] In addition to setting the glue overflow groove 15, other structures that increase the bonding strength can also be set. For example, a roughened structure is set on the inner wall of the shielding wall 12 to increase the bonding tightness between the inner wall of the shielding wall 12 and the shielding layer 2 and the conductive adhesive film layer 3.

[0050] In addition, a roughened structure may be provided on a side of the insulating base layer 11 close to the shielding layer 2 , so as to increase the bonding strength between the insulating base layer 11 and the shielding layer 2 .

[0051] Of course, the addition of the overflow glue groove 15 is not limited to the first embodiment, and the overflow glue groove 15 can also be added on the basis of the second embodiment. The structure and setting position of the overflow glue groove 15 are similar, so the specific embodiment will not be used for further details here.

[0052] Example 4:

[0053] like Figure 8 As shown (see attached Figure 9 ), this embodiment is similar in structure to the first embodiment, with the only difference being that: a glue overflow hole 21 is provided on the shielding layer 2 of this embodiment. Specifically, a plurality of glue overflow holes 21 are provided on one side of the shielding layer 2 close to the conductive adhesive film layer 3. The glue overflow holes 21 are in an unfilled state before the insulating shielding film and the second insulating layer 4 are attached and pressed together, that is, the glue overflow holes 21 are hollow. When the electromagnetic shielding film and the second insulating layer 4 are attached and pressed together (as shown in FIG. 2 ), the glue overflow holes 21 are in an unfilled state before the insulating shielding film and the second insulating layer 4 are attached and pressed together (as shown in FIG. 2 ). Figure 9 As shown), due to the existence of the glue overflow hole 21, the conductive adhesive film layer 3 partially enters the glue overflow hole 21 in the thickness direction, ensuring that the glue will not overflow from the side of the electromagnetic shielding film.

[0054] The overflow hole 21 is a blind hole that penetrates the side of the shielding layer 2 near the conductive adhesive film layer 3. The overflow hole 21 provided as a blind hole not only ensures that the glue overflowing from the conductive adhesive film layer 3 can be properly received, but also prevents the shielding layer 2 from being penetrated, effectively preventing the shielding effect of the shielding layer 2 from being lost.

[0055] In this embodiment, a plurality of glue overflow holes 21 are arranged at intervals on the shielding layer 2 .

[0056] In addition to adding the glue overflow hole 21 of this embodiment on the basis of the structure of the first embodiment, the glue overflow hole 21 can also be added on the basis of the second and third embodiments. The structure and setting position of the glue overflow hole 21 are similar, so the specific embodiments will not be used here for further details.

[0057] Embodiment 5:

[0058] Refer to the attached Figure 3 and attached Figure 4This embodiment has a similar structure to the second embodiment, differing only in that a recessed receiving groove is provided on the side of the filling layer 32 facing away from the adhesive film base layer 31. A grounding portion is provided on the circuit layer of the circuit board at a location corresponding to the grounding circuit. The grounding portion protrudes from the second insulating layer 4 and is inserted into the receiving groove through a through-hole. The grounding portion protrudes outward and embeds within the receiving groove of the filling layer 32, fully enveloping the grounding portion within the conductive adhesive film layer 3. This significantly increases the contact area and, in turn, enhances the grounding effect.

[0059] Example 6:

[0060] Refer to the attached Figure 1 and attached Figure 2 The structure of this embodiment is similar to that of embodiments one to four, with the only difference being that the shielding layer 2 in this embodiment is a foam layer, and the shielding layer 2 of the foam structure has foam pores. These foam pores can accommodate the conductive film layer 3 that overflows when the electromagnetic shielding film is pressed against the second insulating layer 4 on the carrier board 5, thereby reducing the amount of the conductive film layer 3 that overflows from the edge of the electromagnetic shielding film. After pressing, the pore structure absorbs the conductive film layer 3, making the conductive film layer 3 and the shielding layer 2 more tightly bonded.

[0061] In this embodiment, the shielding layer 2 is a metal foam layer, which is obtained by foaming a metal layer. Specifically, the metal layer is placed in an acidic electrolyte, and the surface of the metal layer is treated by an acid sedimentation method to obtain a foamed metal layer.

[0062] In addition, in this embodiment, the shielding layer 2 can be set as a foaming layer, and the shielding layer 2 has a blind hole structure with an overflow hole 21, that is, the shielding layer 2 is combined with the foaming structure and the overflow hole 21, as shown in FIG. Figure 8 and attached Figure 9 Specifically, a plurality of overflow holes 21 are provided on one side of the shielding layer 2 close to the conductive adhesive film layer 3. The overflow holes 21 are in an unfilled state before the insulating shielding film and the second insulating layer 4 are attached and pressed together. That is, the overflow holes 21 are hollow. When the electromagnetic shielding film and the second insulating layer 4 are attached and pressed together (e.g. Figure 9 As shown), the overflow hole 21 cooperates with the foaming structure of the shielding layer 2 itself to accommodate more conductive film layers 3, thereby further reducing the amount of conductive film layers 3 overflowing from the edge of the electromagnetic shielding film.

[0063] Embodiment seven:

[0064] The main structure of this embodiment is consistent with that of the first and second embodiments, except that some specific anti-overflow glue structures are added to the first and second embodiments. Figure 1, taking the case where the main structure is consistent with that of the first embodiment as an example, in this embodiment, the first insulating layer 1 and the shielding layer 2 are both foam layers, the first insulating layer 1 is a non-metallic foam layer, and the shielding layer 2 is a metal foam layer, and an overflowing glue groove 15 is provided on the inner side wall of the shielding wall 12 (refer to the attached Figure 5 To the attached Figure 7 ), a glue overflow hole 21 is also provided on the shielding layer 2 (refer to the attached Figure 8 and attached Figure 9 ).

[0065] By setting both the first insulating layer 1 and the shielding layer 2 as foam layers, the foam pores of the first insulating layer 1 and the shielding layer 2 of the foam structure themselves can absorb a portion of the glue overflowing when the conductive adhesive film layer 3 is pressed, and the glue overflow groove 15 on the inner side of the shielding wall 12 and the glue overflow hole 21 on the shielding layer 2 can also respectively absorb a portion of the glue overflowing when the conductive adhesive film layer 3 is pressed. Combined with the shielding effect of the shielding wall 12, the conductive adhesive film layer 3 will not overflow with glue at all when pressed. Moreover, the combined use of the foam pores, the glue overflow groove 15 and the glue overflow hole 21 can also greatly increase the connection tightness of the three components of the first insulating layer 1, the shielding layer 2 and the conductive adhesive film layer 3, and enhance the peel strength.

[0066] In the description herein, it should be understood that the terms "upper," "lower," "left," "right," and other orientations or positional relationships are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely for ease of description and simplified operation. They do not indicate or imply that the devices or components referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on the present invention. Furthermore, the terms "first" and "second" are used solely for descriptive purposes and have no special meaning.

[0067] In this specification, reference to terms such as "one embodiment" or "example" means that a specific feature, structure, material, or characteristic described in conjunction with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example.

[0068] In addition, it should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

[0069] The technical principles of the present invention have been described above with reference to specific embodiments. These descriptions are intended solely to illustrate the principles of the present invention and are not to be construed in any way as limiting the scope of protection of the present invention. Based on the explanations herein, those skilled in the art will readily conceive of other specific embodiments of the present invention without inventive effort, and such embodiments will fall within the scope of protection of the present invention.

Claims

1. An electromagnetic shielding film, characterized in that The present invention comprises a first insulating layer, a shielding layer and a conductive film layer, wherein the conductive film layer has a first side surface and a second side surface arranged opposite to each other, wherein the first side surface is used to be bonded to the second insulating layer of the circuit board, and the shielding layer is provided on the second side surface. The first insulating layer comprises an insulating base layer, which is provided on the first side surface of the shielding layer. The edge of the insulating base layer extends toward the side surface where the conductive film layer is located to form a shielding wall, and the inner side surface of the shielding wall is bonded to and shields the side edges of the shielding layer and the conductive film layer. A limiting layer is extended from one end of the shielding wall away from the insulating base layer toward the center of the shielding wall, and an avoidance hole is provided on the limiting layer. The conductive film layer includes a film base layer, and the film base layer is sandwiched between the limiting layer and the shielding layer. The conductive film layer also includes a filling layer connected to the film base layer, and the filling layer fills the avoidance hole. The distance between the shielding layer and one side of the filling layer away from the adhesive film base layer is H1, and the distance between the shielding layer and one side of the limiting layer away from the adhesive film base layer is H2, where H1≤H2.

2. The electromagnetic shielding film according to claim 1, wherein A receiving groove is recessed on a side of the filling layer away from the adhesive film base layer. The circuit board includes a carrier board. A circuit layer is provided on one side of the carrier board. The second insulating layer is provided on a side of the circuit layer away from the carrier board. A grounding portion is provided on the circuit layer at a position corresponding to the grounding circuit. The grounding portion is protruding. A through hole is provided on the second insulating layer. The grounding portion passes through the through hole and is inserted into the receiving groove.

3. The electromagnetic shielding film according to claim 1, wherein A plurality of glue overflow grooves are concavely provided on the inner side of the shielding wall.

4. The electromagnetic shielding film according to claim 1, wherein The side of the insulating base layer close to the shielding layer is roughened; and / or, The inner side surface of the shielding wall is roughened.

5. The electromagnetic shielding film according to any one of claims 1 to 4, characterized in that The shielding layer is provided with a plurality of glue overflow holes; or, The shielding layer is a foaming layer.

6. The electromagnetic shielding film according to claim 5, characterized in that The glue overflow hole is a blind hole, and the glue overflow hole only passes through one side of the shielding layer close to the conductive adhesive film layer.

7. The electromagnetic shielding film according to any one of claims 1 to 4, characterized in that The first insulating layer is an insulating foam layer.

8. A circuit board comprising a carrier board, a circuit layer disposed on one side of the carrier board, a second insulating layer disposed on a side of the circuit layer away from the carrier board, a through hole formed on the second insulating layer corresponding to a grounding circuit on the circuit layer, wherein: It also includes the electromagnetic shielding film as described in any one of claims 1-7, wherein the electromagnetic shielding film is adhered to a side of the second insulating layer away from the circuit layer, and the conductive adhesive film layer is adhered to the second insulating layer, and the conductive adhesive film layer partially passes through the through hole and is connected to the ground circuit and electrically conductive.

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