Electromagnetic shielding film and circuit board

Abstract

The invention discloses an electromagnetic shielding film and a circuit board, the electromagnetic shielding film comprises a first shielding layer, an interlayer and a second shielding layer, and the first shielding layer, the interlayer and the second shielding layer are stacked in sequence; the first stripping force between the first shielding layer and the interlayer is 5N / cm to 25N / cm; and the second stripping force between the interlayer and the second shielding layer is 5N / cm to 25N / cm. By adopting the electromagnetic shielding film, the bending resistance of the electromagnetic shielding film and the circuit board or the soft board containing the electromagnetic shielding film and the shielding effectiveness of the electromagnetic shielding film can be improved, and the phenomenon that the electromagnetic shielding film is delaminated or fractured after being bent for multiple times is effectively avoided.

Description

Technical Field

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

[0002] With the development of miniaturization of communication equipment, there are higher and higher requirements for the miniaturization of integrated circuit boards. However, the further miniaturization of integrated circuit boards has also reached a certain limit, so the miniaturization of communication equipment is also limited. In order to achieve further miniaturization of communication equipment, flexible printed circuits (FPC) came into being.

[0003] In order to allow the FPC to operate normally and avoid electromagnetic interference from the outside and itself, an electromagnetic shielding film needs to be applied to the surface of the FPC. However, the electromagnetic shielding film in the prior art is attached to a hard board and is not suitable for FPC. FPC requires high-frequency folding or opening and closing, and the existing electromagnetic shielding film is difficult to meet such high requirements. At the same time, high-frequency folding or opening and closing may also cause damage and breakage of the fine circuits inside the FPC board or circuit board. Summary of the invention

[0004] The scheme of the present invention provides an electromagnetic shielding film and a circuit board, which can improve the bending resistance of the circuit board or FPC board, thereby avoiding the damage and breakage of the fine circuits inside the circuit board or flexible board caused by high-frequency folding or opening and closing.

[0005] The solution of the present invention provides an electromagnetic shielding film, which includes a first shielding layer, an interlayer and a second shielding layer, wherein the first shielding layer, the interlayer and the second shielding layer are stacked in sequence; the first peeling force between the first shielding layer and the interlayer is 5N / cm-25N / cm; the second peeling force between the interlayer and the second shielding layer is 5N / cm-25N / cm.

[0006] As an improvement of the above solution, the first peeling force is greater than or equal to the second peeling force.

[0007] As an improvement of the above solution, after the electromagnetic shielding film is bent 2000 times, the change rate of the first peeling force is less than or equal to 50%, and / or the change rate of the second peeling force is less than or equal to 40%.

[0008] As an improvement of the above solution, the ratio of the second peeling force to the first peeling force is 0.8-1.

[0009] As an improvement of the above solution, the interlayer is provided with a through hole penetrating the upper and lower surfaces thereof; the area of ​​the through hole is 0.1 μm 2 -1mm2 , and / or, the number of the through holes is 10-1000 / cm 2 .

[0010] As an improvement of the above solution, the interlayer is non-metallic, and the non-metallic is made of at least one material selected from epoxy resin, polyester resin, polyurethane resin, acrylic resin, alkyd resin, polyamide resin, and polyimide resin.

[0011] As an improvement of the above solution, the first shielding layer and / or the second shielding layer is at least a two-layer structure.

[0012] As an improvement of the above solution, a protrusion is provided on a side of the second shielding layer away from the interlayer.

[0013] As an improvement of the above-mentioned scheme, the first shielding layer is made of at least one material selected from the group consisting of aluminum, titanium, zinc, iron, nickel, chromium, cobalt, copper, silver, and gold; and / or the second shielding layer is made of at least one material selected from the group consisting of aluminum, titanium, zinc, iron, nickel, chromium, cobalt, copper, silver, and gold.

[0014] Correspondingly, another embodiment of the present invention provides a circuit board, comprising a circuit board body and the electromagnetic shielding film as described in any one of the above items; the electromagnetic shielding film is pressed together with the circuit board body.

[0015] Compared with the prior art, the electromagnetic shielding film and circuit board provided by the scheme of the present invention ensure the flexibility of the electromagnetic shielding film by setting an interlayer between the first shielding layer and the second shielding layer, and setting the first peeling force between the first shielding layer and the interlayer to 5N / cm-25N / cm, and the second peeling force between the interlayer and the second shielding layer to 5N / cm-25N / cm, while ensuring that the electromagnetic shielding film has better flexibility, improves the bonding force between the layers of the electromagnetic shielding film, and can effectively avoid the phenomenon of delamination or breakage of the electromagnetic shielding film after bending many times, so that the circuit board or soft board containing the electromagnetic shielding film has extremely strong bending resistance, thereby avoiding the phenomenon of damage and breakage of the fine circuit inside the circuit board or soft board caused by high-frequency folding or opening and closing, and the electromagnetic shielding film itself also has good bending resistance. In addition, by setting the first shielding layer and the second shielding layer, compared with setting only one shielding layer, the shielding effectiveness is greatly improved, and the shielding effectiveness reaches more than 62DB. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a schematic structural diagram of a first electromagnetic shielding film provided by an embodiment of the present invention;

[0017] Figure 2 is a schematic structural diagram of a second electromagnetic shielding film provided by an embodiment of the present invention;

[0018] Figure 3 is a schematic structural diagram of a third electromagnetic shielding film provided by an embodiment of the present invention;

[0019] Figure 4 is a schematic structural diagram of a fourth electromagnetic shielding film provided by an embodiment of the present invention;

[0020] Figure 5 is a schematic diagram of the thickness of a first shielding layer provided by an embodiment of the present invention;

[0021] Figure 6 It is a structural schematic diagram of a circuit board provided by one embodiment of the present invention.

[0022] Notes on the accompanying drawings: 1. First shielding layer; 2. Interlayer; 3. Second shielding layer; 4. Adhesive layer; 5. Base layer; 6. Circuit board body. DETAILED DESCRIPTION

[0023] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. The purpose of providing these embodiments is to make the disclosure of the present invention more thorough and comprehensive. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] In the description of the present invention, the terms "first", "second", "third", etc. are used for descriptive purposes only and are not to be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first", "second", "third", etc. may explicitly or implicitly include one or more of the feature. In the description of the present invention, unless otherwise specified, "plurality" means two or more.

[0025] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected" and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be a connection between the two elements. The terms "vertical", "horizontal", "left", "right", "upper", "lower" and similar expressions used herein are only for illustrative purposes, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0026] In the description of the present invention, it should be noted that, unless otherwise defined, all technical and scientific terms used in the present invention have the same meaning as those commonly understood by those skilled in the art. The terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood by specific circumstances.

[0027] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0028] See also Figure 1 , is a schematic structural diagram of an electromagnetic shielding film provided by one embodiment of the present invention.

[0029] The present invention provides an electromagnetic shielding film, which includes a first shielding layer 1, an interlayer 2 and a second shielding layer 3. The first shielding layer 1, the interlayer 2 and the second shielding layer 3 are stacked in sequence; the first peeling force F1 between the first shielding layer 1 and the interlayer 2 is 5N / cm-25N / cm; the second peeling force F2 between the interlayer 2 and the second shielding layer 3 is 5N / cm-25N / cm.

[0030] It can be understood that the peel force refers to the peel force measured by performing a 90-degree peel test using a tensile testing machine; if the peel force between layers is too large, the structure formed between layers will not be easy to bend, and will have poor flexibility, and will be prone to breakage; if the peel force between layers is too small, the bonding force between layers will be poor, and interlayer peeling or falling off will be likely to occur; the embodiment of the present invention sets a moderate peel force to ensure that the electromagnetic shielding film has better flexibility while improving the bonding force between the layers of the electromagnetic shielding film, and at the same time can improve the circuit board or flexible board containing the electromagnetic shielding film to have higher bending resistance, and the electromagnetic shielding film itself also has good bending resistance.

[0031] In the embodiment of the present invention, the interlayer 2 is provided between the first shielding layer 1 and the second shielding layer 3 to ensure the flexibility of the electromagnetic shielding film, and the first peeling force F1 between the first shielding layer 1 and the interlayer 2 is set to 5N / cm-25N / cm, and the second peeling force F2 between the interlayer 2 and the second shielding layer 3 is set to 5N / cm-25N / cm, so as to ensure that the electromagnetic shielding film has better flexibility and improve the bonding force between the layers of the electromagnetic shielding film, which can effectively avoid the phenomenon of delamination or breakage of the electromagnetic shielding film after bending multiple times, and at the same time make the circuit board or soft board containing the electromagnetic shielding film have higher bending resistance, thereby avoiding the phenomenon of damage and breakage of the fine circuit inside the circuit board or soft board caused by high-frequency folding or opening and closing, and the electromagnetic shielding film itself has strong bending resistance. In addition, by providing the first shielding layer 1 and the second shielding layer 3, compared with only providing one shielding layer, the shielding effectiveness is greatly improved, and the shielding effectiveness reaches more than 62DB.

[0032] Specifically, the first peeling force F1 can be 5N / cm, 8N / cm, 10N / cm, 12N / cm, 14N / cm, 16N / cm, 18N / cm, 20N / cm, 22N / cm, 24N / cm, or an interval consisting of any two values. Of course, the first peeling force F1 is not limited to the specific values ​​listed above, and can be set according to actual use requirements, which will not be further described here.

[0033] Specifically, the second peeling force F2 can be 5N / cm, 8N / cm, 10N / cm, 12N / cm, 14N / cm, 16N / cm, 18N / cm, 20N / cm, 22N / cm, 24N / cm, or an interval consisting of any two values. Of course, the second peeling force F2 is not limited to the specific values ​​listed above, and can be set according to actual use requirements, which will not be further described here.

[0034] In an embodiment of the present invention, in order to further improve the bending resistance of the electromagnetic shielding film itself and improve the bending resistance of the circuit board or flexible board containing the electromagnetic shielding film, the first peeling force F1 is greater than or equal to the second peeling force F2, which can well transfer stress between the first shielding layer 1 and the interlayer 2; when a base layer is present, it is also beneficial to transfer stress between the first shielding layer 1, the interlayer 2 and the base layer 5. Specifically, the first peeling force F1 and the second peeling force F2 can be any of the following combinations: the first peeling force F1 is 5N / cm, and the second peeling force F2 is 5N / cm; the first peeling force F1 is 8N / cm, and the second peeling force F2 is 6.5N / cm; the first peeling force F1 is 10N / cm, and the second peeling force F2 is 9N / cm; the first peeling force F1 is 11N / cm, and the second peeling force F2 is 9.5N / cm; the first peeling force F1 is 13N / cm, and the second peeling force F2 is 14N / cm. The second peeling force F2 is 11.9N / cm; the first peeling force F1 is 14N / cm, and the second peeling force F2 is 14N / cm; the first peeling force F1 is 15N / cm, and the second peeling force F2 is 13N / cm; the first peeling force F1 is 18N / cm, and the second peeling force F2 is 18N / cm; the first peeling force F1 is 20N / cm, and the second peeling force F2 is 19N / cm; the first peeling force F1 is 20N / cm, and the second peeling force F2 is 20N / cm. Of course, the combination of the first peeling force F1 and the second peeling force F2 is not limited to the specific values ​​listed above, and it can be set according to actual use requirements, and no further details are given here.

[0035] In an embodiment of the present invention, in order to stabilize the bending resistance of the circuit board or flexible board containing the electromagnetic shielding film and the electromagnetic shielding film itself, the change rate of the first peeling force F1 of the electromagnetic shielding film after being bent 2000 times is less than or equal to 50%; wherein, the change rate = (the first peeling force F1 before bending 2000 times - the first peeling force F1 after bending 2000 times) / the first peeling force F1 before bending 2000 times. Specifically, the change rate of the first peeling force F1 can be 5%, 10%, 20%, 30%, 40%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50% or an interval consisting of any two values. Of course, the change rate of the first peeling force F1 is not limited to the specific values ​​listed above, and it can be set according to actual use requirements, and no further elaboration is made here.

[0036] In an embodiment of the present invention, in order to stabilize the bending resistance of the circuit board or flexible board containing the electromagnetic shielding film and the electromagnetic shielding film itself, the change rate of the second peeling force F2 of the electromagnetic shielding film after being bent 2000 times is less than or equal to 40%; wherein, the change rate = (the second peeling force F2 before bending 2000 times - the second peeling force F2 after bending 2000 times) / the second peeling force F2 before bending 2000 times. Specifically, the change rate of the second peeling force F2 can be 5%, 10%, 15%, 20%, 21%, 23%, 24%, 27%, 29%, 31%, 35%, 38%, 40% or an interval consisting of any two values. Of course, the change rate of the second peeling force F2 is not limited to the specific values ​​listed above, and it can be set according to actual use requirements, and no further elaboration is made here.

[0037] In an embodiment of the present invention, in order to further improve the bending resistance of the electromagnetic shielding film itself and the circuit board or soft board containing the electromagnetic shielding film, the ratio between the second peeling force F2 and the first peeling force F1 is 0.8-1. Specifically, the value of F2 / F1 can be 0.800, 0.810, 0.820, 0.830, 0.840, 0.850, 0.851, 0.852, 0.860, 0.867, 0.870, 0.877, 0.881, 0.890, 0.900, 0.910, 0.930, 0.950, 0.980, 0.990 or an interval consisting of any two values. Of course, the value of F2 / F1 is not limited to the specific values ​​listed above, and it can be set according to actual use requirements, and no further details are given here.

[0038] like Figure 2 In an embodiment of the present invention, the interlayer 2 is provided with through holes penetrating the upper and lower surfaces thereof, so that during the pressing process, the gas generated due to thermal expansion and contraction can be discharged from the through holes, thereby avoiding debonding between the layers of the electromagnetic shielding film itself due to the difficulty in discharging the gas generated in the electromagnetic shielding film, thereby ensuring the stability of the overall structure of the electromagnetic shielding film.

[0039] In the embodiment of the present invention, the through holes can be regularly or irregularly distributed in the electromagnetic shielding film; wherein, the through holes are regularly distributed in the interlayer 2 means that the shapes of the through holes are the same and are evenly distributed on the interlayer 2; the through holes are irregularly distributed in the interlayer 2 means that the shapes of the through holes are different and are randomly distributed on the interlayer 2. Preferably, the shapes of the through holes are the same and are evenly distributed on the interlayer 2. In addition, the through holes can be circular through holes or through holes of any other shape. Figure 2The shape of the through hole shown is merely exemplary, and any shape of the through hole is within the protection scope of the present invention.

[0040] In the embodiment of the present invention, the area of ​​the through hole is preferably 0.1 μm 2- 0.1mm 2 , it is possible to ensure that the gas generated in the interlayer is discharged from the through hole, while ensuring the flexibility of the electromagnetic shielding film. Of course, the area of ​​the through hole is not limited to the above preferred range, and no specific limitation is made here. For example, the area of ​​the through hole can be 0.1 μm 2 , 1μm 2 , 5μm 2 , 10μm 2 , 20μm 2 、30μm 2 , 40μm 2 , 50μm 2 , 100μm 2 , 200μm 2 , 400μm 2 、600μm 2 , 1000μm 2 , 0.1mm 2 Or any interval between two values.

[0041] In the embodiment of the present invention, the number of the through holes is preferably 10-1000 / cm 2 That is, the number of through holes in the interlayer 2 per square centimeter is preferably 10-1000, which can ensure that the generated gas is discharged from the through holes while ensuring the flexibility of the electromagnetic shielding film. Exemplarily, the number of through holes can be 10, 15, 20, 50, 100, 500, 600, 800, 900 or an interval consisting of any two values. Of course, the number of through holes is not limited to the above preferred range, and no specific limitation is made here.

[0042] In the embodiment of the present invention, there is no special limitation on the material used for the interlayer 2. However, in order to further improve the bending resistance of the electromagnetic shielding film and the circuit board or flexible board containing the electromagnetic shielding film, the interlayer 2 is non-metallic, and the non-metallic is made of at least one material selected from epoxy resin, polyester resin, polyurethane resin, acrylic resin, alkyd resin, polyamide resin, and polyimide resin.

[0043] In an embodiment of the present invention, in order to better improve the shielding effectiveness of the electromagnetic shielding film, the first shielding layer 1 and the second shielding layer 3 can be a one-layer structure or at least a two-layer structure respectively; wherein, in order to ensure that the first shielding layer 1 has good conductivity, the first shielding layer 1 is made of at least one material selected from aluminum, titanium, zinc, iron, nickel, chromium, cobalt, copper, silver, and gold; in order to ensure that the second shielding layer 3 has good conductivity, the second shielding layer 3 is made of at least one material selected from aluminum, titanium, zinc, iron, nickel, chromium, cobalt, copper, silver, and gold. In addition, according to the needs of actual production and application, the first shielding layer 1 and the second shielding layer 3 of the embodiment of the present invention can be respectively set to a grid shape, a foam shape, etc., or can be solid. wherein, the average thickness of the first shielding layer 1 and the second shielding layer 3 are respectively 0.4 microns to 6 microns. The average thickness of the interlayer is 0.2 microns to 8 microns. The overall average thickness of the electromagnetic shielding film is 3 microns to 25 microns.

[0044] like Figure 3 In order to better improve the shielding effectiveness of the electromagnetic shielding film, a protrusion is provided on the side of the second shielding layer 3 away from the interlayer 2, so that the protrusion pierces during the pressing process to achieve reliable grounding of the second shielding layer 3, thereby effectively conducting away the interference charges accumulated in the electromagnetic shielding film and achieving the shielding function. It should be noted that Figure 3 The shape of the protrusion shown is merely exemplary, and the protrusion in the present invention is not limited to the shape shown in the figure. As long as the protrusion has piercing ability, it is within the protection scope of the present invention.

[0045] In the embodiments of the present invention, see Figure 4 , the electromagnetic shielding film also includes an adhesive layer 4; the adhesive layer 4 is arranged on the side of the second shielding layer 3 away from the interlayer 2. The adhesive layer 4 has an adhesive effect, which can improve the adhesion between the electromagnetic shielding film and the circuit board or the soft board. The adhesive force can reach 7N / cm, so that the electromagnetic shielding film is close to the surface of the circuit board or the soft board to avoid the phenomenon of delamination and explosion. Among them, the embodiment of the present invention does not specifically limit the material used for the adhesive layer 4, but from the perspective of further improving the bending resistance, the adhesive layer 4 is made of at least one material selected from polystyrene, vinyl acetate, polyester, polyethylene, polyamide, rubber, acrylic, phenolic, epoxy, polyimide, urethane, melamine, alkyd, and ABF resin. Exemplarily, the adhesive layer 4 is made of epoxy E44, polyimide, polyurethane, and acrylic.

[0046] In the embodiments of the present invention, see Figure 5, the electromagnetic shielding film also includes a base layer 5; the base layer 5 is arranged on the side of the first shielding layer 1 away from the interlayer 2. The base layer 5 has the function of protection and support, which can prevent the first shielding layer 1 from being damaged and thus reduce the shielding effectiveness; at the same time, the base layer 5 can play a good supporting role for the first shielding layer 1, which is convenient for the preparation of the first shielding layer 1 and subsequent structures. Among them, the embodiment of the present invention does not specifically limit the material used for the base layer 5, but from the perspective of further improving the bending resistance, the base layer 5 is made of at least one material selected from polystyrene, vinyl acetate, polyester, polyethylene, polyamide, rubber, acrylic, phenolic, epoxy, polyimide, urethane, melamine, alkyd, and ABF resin.

[0047] Specifically, when the electromagnetic shielding film includes a base layer 5, a first shielding layer 1, an interlayer 2, a second shielding layer 3 and a bonding layer 4, the method for preparing the electromagnetic shielding film includes:

[0048] 1) preparing a base layer 5;

[0049] 2) forming a first shielding layer 1 on one surface of the base layer 5;

[0050] 3) forming an interlayer 2 on a surface of the first shielding layer 1 away from the base layer 5;

[0051] 4) forming a second shielding layer 3 on a surface of the interlayer 2 away from the first shielding layer 1;

[0052] 5) An adhesive layer 4 is formed on the surface of the second shielding layer 3 away from the interlayer 2 .

[0053] Test examples are given below, but these examples are provided only for a better understanding of the present invention and its advantages, and are not intended to limit the present invention.

[0054] Test Example 1: An electromagnetic shielding film, comprising a base layer, a first shielding layer, an interlayer, a second shielding layer and an adhesive layer stacked in sequence, wherein the first peeling force F1 between the first shielding layer and the interlayer is 1 N / cm; the second peeling force F2 between the interlayer and the second shielding layer is 1 N / cm.

[0055] Test Example 2: An electromagnetic shielding film, comprising a base layer, a first shielding layer, an interlayer, a second shielding layer and an adhesive layer stacked in sequence, wherein the first peeling force F1 between the first shielding layer and the interlayer is 5 N / cm; the second peeling force F2 between the interlayer and the second shielding layer is 1 N / cm.

[0056] Test Example 3: An electromagnetic shielding film, comprising a base layer, a first shielding layer, an interlayer, a second shielding layer and an adhesive layer stacked in sequence, wherein a first peeling force F1 between the first shielding layer and the interlayer is 1 N / cm; a second peeling force F2 between the interlayer and the second shielding layer is 5 N / cm.

[0057] Test Example 4: An electromagnetic shielding film, comprising a base layer, a first shielding layer, an interlayer, a second shielding layer and an adhesive layer stacked in sequence, wherein the first peeling force F1 between the first shielding layer and the interlayer is 5N / cm; the second peeling force F2 between the interlayer and the second shielding layer is 5N / cm.

[0058] Test Example 5: An electromagnetic shielding film, comprising a base layer, a first shielding layer, an interlayer, a second shielding layer and an adhesive layer stacked in sequence, wherein the first peeling force F1 between the first shielding layer and the interlayer is 25 N / cm; the second peeling force F2 between the interlayer and the second shielding layer is 25 N / cm.

[0059] Test Example 6: An electromagnetic shielding film, comprising a base layer, a first shielding layer, an interlayer, a second shielding layer and an adhesive layer stacked in sequence, wherein a first peeling force F1 between the first shielding layer and the interlayer is 10 N / cm; a second peeling force F2 between the interlayer and the second shielding layer is 8 N / cm.

[0060] Test Example 7: An electromagnetic shielding film, comprising a base layer, a first shielding layer, an interlayer, a second shielding layer and an adhesive layer stacked in sequence, wherein the first peeling force F1 between the first shielding layer and the interlayer is 30 N / cm; the second peeling force F2 between the interlayer and the second shielding layer is 7 N / cm.

[0061] Test Example 8: An electromagnetic shielding film, comprising a base layer, a first shielding layer, an interlayer, a second shielding layer and an adhesive layer stacked in sequence, wherein the first peeling force F1 between the first shielding layer and the interlayer is 5 N / cm; the second peeling force F2 between the interlayer and the second shielding layer is 32 N / cm.

[0062] The average thickness of the base layer, the first shielding layer, the interlayer, the second shielding layer and the bonding layer in the electromagnetic shielding film of the above test examples 1-8 are basically consistent with other conditions. The overall average thickness of the electromagnetic shielding film is 11.5 microns, the average thickness of the first shielding layer is 0.9 microns, the average thickness of the second shielding layer is 1.7 microns, and the average thickness of the interlayer is 2.5 microns. MIT folding endurance test and shielding effectiveness test were performed on them respectively, and the test results are shown in Table 1.

[0063] The steps of the MIT folding endurance test include: pressing two electromagnetic shielding films on a folding plate in a counter-pressing manner, the pressing conditions are 185°C, pre-pressing for 10s, molding time for 180s, and molding pressure of 120kg / cm 2 , the pressing temperature is 185℃, and the baking and curing are carried out after pressing. The baking temperature is 160℃, the baking time is 90min, the strip width is 1.5cm, the R angle is 0.8, the speed is 60 rpm, the angle is ±135°, and the load is 500g; when the bending starts, when the line resistance changes by more than 10%, the machine automatically stops the test and records the number of bending times and the failure resistance value; the shielding effectiveness is tested in accordance with GB / T30142-2013.

[0064] Table 1

[0065]

[0066]

[0067] It can be seen from Table 1 that when the first peeling force between the first shielding layer 1 and the interlayer 2 is 5N / cm-25N / cm; the second peeling force between the interlayer 2 and the second shielding layer 3 is 5N / cm-25N / cm, the electromagnetic shielding film and the circuit board or flexible board containing the electromagnetic shielding film can have good bending resistance, and the shielding effectiveness reaches above 62DB.

[0068] See also Figure 6 Another embodiment of the present invention further provides a circuit board, which includes a circuit board body 6 and an electromagnetic shielding film as described in any of the above embodiments; the electromagnetic shielding film is pressed against the circuit board body 6. The side of the second shielding layer 3 away from the interlayer 2 is electrically connected to the ground layer of the circuit board body 6.

[0069] Preferably, the circuit board body 6 is one of a flexible single-sided board, a flexible double-sided board, a flexible multi-layer board, and a rigid-flexible board.

[0070] In an embodiment of the present invention, a side of the second shielding layer 3 away from the interlayer 2 is electrically connected to the ground layer of the circuit board body 6, thereby introducing the interference charges in the electromagnetic shielding film into the ground, avoiding the accumulation of interference charges to form an interference source that affects the normal operation of the circuit board.

[0071] Compared with the prior art, the circuit board provided in the embodiment of the present invention ensures the flexibility of the electromagnetic shielding film by setting the interlayer 2 between the first shielding layer 1 and the second shielding layer 3, and sets the first peeling force F1 between the first shielding layer 1 and the interlayer 2 to 5N / cm-25N / cm, and the second peeling force F2 between the interlayer 2 and the second shielding layer 3 to 5N / cm-25N / cm, so as to ensure that the electromagnetic shielding film has better flexibility and improve the bonding force between the layers of the electromagnetic shielding film, which can effectively avoid the phenomenon of delamination or breakage of the electromagnetic shielding film after bending many times, so that the circuit board or soft board containing the electromagnetic shielding film has extremely strong bending resistance, thereby avoiding the phenomenon of damage and breakage of the fine circuit inside the circuit board or soft board caused by high-frequency folding or opening and closing, and the electromagnetic shielding film itself also has good bending resistance. In addition, by setting the first shielding layer 1 and the second shielding layer 3, compared with setting only one shielding layer, the shielding effectiveness is greatly improved, and the shielding effectiveness reaches more than 62DB.

[0072] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the patent of the present invention. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. An electromagnetic shielding film, characterized in that: The electromagnetic shielding film includes a first shielding layer, an interlayer and a second shielding layer, and the first shielding layer, the interlayer and the second shielding layer are stacked in sequence; the first peeling force between the first shielding layer and the interlayer is 5N / cm-25N / cm; the second peeling force between the interlayer and the second shielding layer is 5N / cm-25N / cm.

2. The electromagnetic shielding film according to claim 1, wherein The first peeling force is greater than or equal to the second peeling force.

3. The electromagnetic shielding film according to claim 1, wherein After the electromagnetic shielding film is bent 2000 times, the change rate of the first peeling force is less than or equal to 50%, and / or the change rate of the second peeling force is less than or equal to 40%.

4. The electromagnetic shielding film according to claim 1, wherein The ratio of the second peeling force to the first peeling force is 0.8-1.

5. The electromagnetic shielding film according to claim 1, wherein The interlayer is provided with through holes penetrating the upper and lower surfaces thereof; the area of ​​the through holes is 0.1 μm 2 -0.1mm 2 , and / or, the number of the through holes is 10-1000 / cm 2 .

6. The electromagnetic shielding film according to claim 1, wherein The interlayer is non-metallic, and the non-metallic is made of at least one material selected from epoxy resin, polyester resin, polyurethane resin, acrylic resin, alkyd resin, polyamide resin, and polyimide resin.

7. The electromagnetic shielding film according to claim 1, wherein The first shielding layer and / or the second shielding layer are at least two-layer structures.

8. The electromagnetic shielding film according to claim 1, wherein A protrusion is provided on a side of the second shielding layer away from the interlayer.

9. The electromagnetic shielding film according to claim 1, wherein The first shielding layer is made of at least one material selected from the group consisting of aluminum, titanium, zinc, iron, nickel, chromium, cobalt, copper, silver, and gold; and / or the second shielding layer is made of at least one material selected from the group consisting of aluminum, titanium, zinc, iron, nickel, chromium, cobalt, copper, silver, and gold.

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

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