Electromagnetic shielding film and circuit board

Abstract

The invention discloses an electromagnetic shielding film and a circuit board, the electromagnetic shielding film comprises a substrate layer, a first shielding layer, an interlayer, a second shielding layer and a bonding layer, the substrate layer, the first shielding layer, the interlayer, the second shielding layer and the bonding layer are sequentially stacked, and the total elongation at break of the electromagnetic shielding film is 2%-15%. By adopting the electromagnetic shielding film, the phenomenon that the electromagnetic shielding film is broken after being bent for multiple times can be 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. The existing electromagnetic shielding film is difficult to meet such high requirements and is prone to internal circuit breakage in the FPC after multiple bends. Summary of the invention

[0004] The scheme of the present invention provides an electromagnetic shielding film and a circuit board, which have good bending resistance and shielding effectiveness, and can effectively prevent the electromagnetic shielding film from breaking after being bent multiple times.

[0005] The scheme of the present invention provides an electromagnetic shielding film, which includes a base layer, a first shielding layer, an interlayer, a second shielding layer and a bonding layer. The base layer, the first shielding layer, the interlayer, the second shielding layer and the bonding layer are stacked in sequence, and the total elongation at break of the electromagnetic shielding film is 2%-15%.

[0006] As an improvement of the above solution, the first breaking elongation between the base layer, the first shielding layer and the interlayer is 5%-10%.

[0007] As an improvement of the above solution, the second elongation at break between the interlayer, the second shielding layer and the bonding layer is 2%-10%.

[0008] As an improvement of the above solution, after the second shielding layer and the bonding layer are removed from the electromagnetic shielding film, a change rate of the first elongation at break relative to the total elongation at break is less than or equal to 40%.

[0009] As an improvement of the above solution, after the base layer and the first shielding layer are removed from the electromagnetic shielding film, a change rate of the second elongation at break relative to the total elongation at break is less than or equal to 30%.

[0010] As an improvement of the above solution, the third breaking elongation between the first shielding layer and the interlayer is 6%-18%.

[0011] As an improvement of the above solution, the fourth breaking elongation between the interlayer and the second shielding layer is 5%-15%.

[0012] As an improvement of the above-mentioned scheme, the first elongation at break between the base layer, the first shielding layer and the interlayer and the second elongation at break between the interlayer, the second shielding layer and the bonding layer satisfy the relationship |ε1-ε2| / ε1≤0.4, where ε1 is the first elongation at break and ε2 is the second elongation at break.

[0013] As an improvement of the above solution, the average thickness of the first shielding layer is 0.5-3 microns, and / or the average thickness of the second shielding layer is 1-5 microns.

[0014] As an improvement of the above solution, the average thickness of the electromagnetic shielding film is 6-20 microns.

[0015] As an improvement of the above solution, a protrusion is provided on a side of the second shielding layer away from the interlayer.

[0016] 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.

[0017] 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 the total elongation at break of the electromagnetic shielding film is set to 2%-15%, further improving the flexibility of the electromagnetic shielding film, so that the electromagnetic shielding film and the circuit board or soft board containing the electromagnetic shielding film have extremely strong bending resistance, which can effectively avoid the electromagnetic shielding film and the circuit board or soft board containing the electromagnetic shielding film from internal circuit breakage after bending multiple times. In addition, by setting the first shielding layer and the second shielding layer, compared with setting only one shielding layer, the electromagnetic shielding efficiency is greatly improved, and the electromagnetic shielding efficiency is still high after the high step difference, and the shielding efficiency reaches more than 62DB; by setting the bonding layer, the bonding force between the electromagnetic shielding film and the circuit board is improved, and the bonding force can reach more than 7N / cm, avoiding the delamination and explosion phenomenon between the electromagnetic shielding film and the circuit board or soft board; by setting the base layer, the scratch resistance of the electromagnetic shielding film is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is a schematic structural diagram of a first electromagnetic shielding film provided by an embodiment of the present invention;

[0019] Figure 2 is a schematic structural diagram of a second electromagnetic shielding film provided by an embodiment of the present invention;

[0020] Figure 3 It is a structural schematic diagram of a circuit board provided by one embodiment of the present invention.

[0021] 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

[0022] 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.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] See also Figure 1 , is a schematic structural diagram of an electromagnetic shielding film provided by one embodiment of the present invention.

[0028] The present invention provides an electromagnetic shielding film, which includes a base layer 5, a first shielding layer 1, an interlayer 2, a second shielding layer 3 and a bonding layer 4. The base layer 5, the first shielding layer 1, the interlayer 2, the second shielding layer 3 and the bonding layer 4 are stacked in sequence, and the total elongation at break ε of the electromagnetic shielding film is 2%-15%.

[0029] It can be understood that the total elongation at break ε indicates the flexibility of the entire electromagnetic shielding film. The better the total elongation at break, the better the bending resistance of the electromagnetic shielding film itself and the circuit board or soft board containing the electromagnetic shielding film. It should be noted that the total elongation at break of the electromagnetic shielding film cannot be too high, otherwise it will lead to a decrease in the electromagnetic shielding effectiveness of the entire electromagnetic shielding film, which is not conducive to resisting electromagnetic interference from the inside or outside; similarly, the elongation of the electromagnetic shielding film cannot be too low, otherwise it will lead to a decrease in the bending resistance of the electromagnetic shielding film itself and the circuit board or soft board containing the electromagnetic shielding film.

[0030] 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 total elongation at break ε of the electromagnetic shielding film is set to 2%-15%, so that the electromagnetic shielding film itself and the circuit board or soft board containing the electromagnetic shielding film have extremely strong bending resistance, while the electromagnetic shielding film also maintains a high electromagnetic shielding efficiency, which can effectively avoid the electromagnetic shielding film itself and the circuit board or soft board containing the electromagnetic shielding film from internal circuit breakage after bending multiple times. In addition, by providing the first shielding layer 1 and the second shielding layer 3, compared with only providing one shielding layer, the shielding efficiency is greatly improved, and the electromagnetic shielding efficiency is still high after a high step difference, and the shielding efficiency reaches more than 62DB; by providing the adhesive layer 4, the bonding force between the electromagnetic shielding film and the circuit board is improved, and the bonding force can reach more than 7N / cm, avoiding the delamination and explosion phenomenon between the electromagnetic shielding film and the circuit board or soft board; by providing the base layer, the scratch resistance of the electromagnetic shielding film is improved.

[0031] Specifically, the total elongation at break ε can be 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14% or an interval consisting of any two of the above values. Of course, the total elongation at break ε 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.

[0032] In an embodiment of the present invention, the first elongation at break ε1 between the base layer 5, the first shielding layer 1 and the interlayer 2 is preferably 5%-10%, which is beneficial to the stress transfer between the base layer 5, the first shielding layer 1 and the interlayer 2, and can improve the flexibility of the structure composed of the base layer 5, the first shielding layer 1 and the interlayer 2, and is beneficial to improving the bending resistance of the electromagnetic shielding film itself and the circuit board or soft board containing the electromagnetic shielding film. Specifically, the first elongation at break ε1 can be 5%, 6%, 7%, 8%, 9%, 10% or an interval consisting of any two values. Of course, the first elongation at break ε1 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.

[0033] In an embodiment of the present invention, the second elongation at break ε2 between the interlayer 2, the second shielding layer 3 and the bonding layer 4 is preferably 2%-10%, which is beneficial to the stress transfer between the interlayer 2, the second shielding layer 3 and the bonding layer 4, improves the flexibility of the structure composed of the interlayer 2, the second shielding layer 3 and the bonding layer 4, and helps to improve the bending resistance of the electromagnetic shielding film itself and the circuit board or soft board containing the electromagnetic shielding film. Specifically, the second elongation at break ε2 can be 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10% or an interval consisting of any two values. Of course, the second elongation at break ε2 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.

[0034] In an embodiment of the present invention, in order to stabilize the performance of the electromagnetic shielding film, after removing the second shielding layer 3 and the bonding layer 4, the change rate of the first elongation at break ε1 relative to the total elongation at break ε is less than or equal to 40%; specifically, the change rate can be 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40% or an interval consisting of any two values. Wherein, the change rate = (the first elongation at break ε1 after removing the second shielding layer 3 and the bonding layer 4-the total elongation at break ε of the complete electromagnetic shielding film) / the total elongation at break ε of the complete electromagnetic shielding film. The complete electromagnetic shielding film refers to an electromagnetic shielding film including a base layer 5, a first shielding layer 1, an interlayer 2, a second shielding layer 3 and a bonding layer 4.

[0035] In an embodiment of the present invention, in order to further improve the bending resistance of the electromagnetic shielding film, after the base layer 5 and the first shielding layer 1 are removed from the electromagnetic shielding film, the change rate of the second elongation at break relative to the total elongation at break is less than or equal to 30%; the change rate can be 5%, 10%, 15%, 20%, 25%, 30% or an interval consisting of any two values. Wherein, the change rate = (the second elongation at break ε2 after removing the base layer 5 and the first shielding layer 1-the total elongation at break ε of the complete electromagnetic shielding film) / the total elongation at break ε of the complete electromagnetic shielding film. The complete electromagnetic shielding film refers to an electromagnetic shielding film including a base layer 5, a first shielding layer 1, an interlayer 2, a second shielding layer 3 and an adhesive layer 4.

[0036] In an embodiment of the present invention, in order to further optimize the technical effect, the third elongation at break ε3 between the first shielding layer 1 and the interlayer 2 is preferably 6%-18%. The stress transfer between the first shielding layer 1 and the interlayer 2 can avoid stress concentration, and can improve the flexibility of the structure composed of the first shielding layer 1 and the interlayer 2, which is beneficial to improve the bending resistance of the electromagnetic shielding film itself and the circuit board or soft board containing the electromagnetic shielding film. Specifically, the third elongation at break ε3 can be 6%, 8%, 10%, 11%, 12%, 15%, 18% or an interval consisting of any two values. Of course, the third elongation at break ε3 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, for better technical effects, the fourth elongation at break ε4 between the interlayer 2 and the second shielding layer 3 is preferably 5%-15%. The stress transfer between the second shielding layer 3 and the interlayer 2 can avoid stress concentration, and can improve the flexibility of the structure composed of the second shielding layer 3 and the interlayer 2, which is beneficial to improving the bending resistance of the electromagnetic shielding film itself and the circuit board or soft board containing the electromagnetic shielding film. Specifically, the fourth elongation at break ε4 can be 5%, 9%, 11%, 12%, 13%, 14%, 15% or an interval consisting of any two values. Of course, the fourth elongation at break ε4 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.

[0038] In the 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 first elongation at break ε1 between the base layer 5, the first shielding layer 1 and the interlayer 2 and the second elongation at break between the interlayer 2, the second shielding layer 3 and the bonding layer 4 satisfy the relationship |ε1-ε2| / ε1≤0.4. The relationship can also be less than or equal to any one of 0.1, 0.2, and 0.3.

[0039] In an 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, 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, and polyamide resin.

[0040] In the embodiment of the present invention, there is no particular limitation on the average thickness of the first shielding layer, but considering the effect of improving the anti-bending performance, the average thickness of the first shielding layer is preferably 0.5-3 microns. Specifically, the average thickness of the first shielding layer can be 0.5 microns, 1.2 microns, 1.55 microns, 2 microns, 2.3 microns, 3 microns, or an interval consisting of any two values. Of course, the average thickness of the first shielding layer 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.

[0041] In the embodiment of the present invention, there is no special limitation on the average thickness of the second shielding layer, but considering the effect of improving the anti-bending performance, the average thickness of the second shielding layer is preferably 1-5 microns. Specifically, the average thickness of the first shielding layer can be 1 micron, 2 microns, 2.3 microns, 3.2 microns, 3.6 microns, 3.7 microns, 4.1 microns, 4.5 microns, 4.8 microns or an interval consisting of any two values. Of course, the average thickness of the second shielding layer 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. In addition, the double-layer shielding layer has better shielding effectiveness than the single-layer shielding layer.

[0042] In the embodiment of the present invention, there is no particular limitation on the thickness of the electromagnetic shielding film, but considering the effect of improving the anti-bending performance, the overall average thickness of the electromagnetic shielding film is preferably 6-20 microns. Specifically, the thickness of the electromagnetic shielding film can be 6 microns, 6.3 microns, 7 microns, 7.1 microns, 8 microns, 12 microns, 15 microns, 16 microns, 17 microns, 20 microns or an interval consisting of any two values. Of course, the thickness of the electromagnetic shielding film is not limited to the specific values ​​listed above, and it can be set according to the actual use requirements, and no further details are given here. Among them, the average thickness of the interlayer is 0.2 microns-8 microns.

[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 at least two-layer structures respectively; wherein, in order to ensure that the first shielding layer 1 has good electrical 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 electrical 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.

[0044] like Figure 2In order to further 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 only exemplary, and the protrusion in the present invention is not limited by the shape shown in the figure, as long as it is a protrusion with piercing ability, it is within the protection scope of the present invention. Among them, the side of the first shielding layer 1 close to the interlayer 2 can also be provided with a protrusion as needed.

[0045] In the embodiment of the present invention, there is no particular limitation on the material used for the bonding layer 4. However, from the perspective of further improving the bending resistance, the bonding layer 4 is made of at least one material selected from the group consisting of polystyrene, vinyl acetate resin, polyester, polyethylene, polyamide, rubber, acrylic resin, phenolic resin, epoxy resin, polyimide, urethane resin, melamine resin, alkyd resin, and ABF resin.

[0046] In the embodiment of the present invention, the material used for the base layer 5 is not particularly limited, 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 resin, polyester, polyethylene, polyamide, rubber, acrylic resin, phenolic resin, epoxy resin, polyimide, urethane resin, melamine resin, alkyd resin, and ABF resin. In the present invention, the method of removing the first shielding layer, the second shielding layer, the bonding layer, or the base layer includes but is not limited to grinding, soaking, etching, etc.

[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 a bonding layer stacked in sequence, the total elongation at break of the electromagnetic shielding film is 2%, the first shielding layer and the second shielding layer are made of copper, the overall average thickness of the electromagnetic shielding film is 12 microns, the average thickness of the first shielding layer is 1 micron, the average thickness of the second shielding layer is 1.9 microns, a protrusion is provided on one side of the first shielding layer close to the interlayer, and a protrusion is provided on the side of the second shielding layer away from the interlayer.

[0055] Test Example 2: This test example is the same as Test Example 1 in other conditions, except that the total elongation at break of the electromagnetic shielding film is 15%.

[0056] Test Example 3: This test example is the same as Test Example 1 in other conditions, except that the total elongation at break of the electromagnetic shielding film is 9%.

[0057] Test Example 4: This test example is the same as Test Example 3 in other conditions, except that the first elongation at break between the base layer, the first shielding layer and the interlayer is 8%.

[0058] Test Example 5: This test example is the same as Test Example 4 in other conditions, except that the second elongation at break between the interlayer, the second shielding layer and the bonding layer is 6%.

[0059] Test Example 6: An electromagnetic shielding film, comprising a base layer, a first shielding layer, and an adhesive layer stacked in sequence, wherein the thickness of the first shielding layer is the same as that of Test Example 1.

[0060] Test Example 7: The other conditions of this test example are the same as those of Test Example 1, and the total elongation at break of the electromagnetic shielding film is 25%.

[0061] The electromagnetic shielding films of the above test examples 1-7 were subjected to MIT folding endurance test and shielding effectiveness test respectively. The test results are shown in Table 1.

[0062] 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.

[0063] Table 1

[0064] MIT folding test / times Shielding effectiveness test / DB Test Example 1 More than 9000 Greater than 62 Test Example 2 More than 9000 Greater than 62 Test Example 3 More than 9000 Greater than 62 Test Example 4 Greater than 9100 Greater than 62 Test Example 5 Greater than 9100 Greater than 62 Test Example 6 About 8000 45 Test Example 7 Approx. 8,200 Greater than 62

[0065] It can be seen from Table 1 that when the total elongation at break of the electromagnetic shielding film is 2%-15%, the electromagnetic shielding film itself and the circuit board or flexible board containing the electromagnetic shielding film have good bending resistance and still have high shielding effectiveness after a high step difference, with the shielding effectiveness reaching above 62DB.

[0066] See also Figure 3 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 adhesive layer 4 away from the second shielding layer 3 is electrically connected to the ground layer of the circuit board body 6.

[0067] 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.

[0068] In an embodiment of the present invention, the side of the adhesive layer 4 away from the second shielding layer 3 is electrically connected to the ground layer of the circuit board body 6, thereby realizing the introduction of interference charges in the electromagnetic shielding film into the ground, avoiding the accumulation of interference charges to form an interference source affecting the normal operation of the circuit board.

[0069] 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 total elongation at break ε of the electromagnetic shielding film to 2%-15%, further improving the flexibility of the electromagnetic shielding film, so that the electromagnetic shielding film and the circuit board or soft board containing the electromagnetic shielding film have extremely strong bending resistance, which can effectively avoid the electromagnetic shielding film and the circuit board or soft board containing the electromagnetic shielding film from internal circuit breakage after bending multiple times. 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 is still high after the high step difference, and the shielding effectiveness reaches more than 62DB; by setting the adhesive layer 4, the bonding force between the electromagnetic shielding film and the circuit board is improved, and the bonding force can reach more than 7N / cm, avoiding the delamination and explosion between the electromagnetic shielding film and the circuit board or soft board; by setting the base layer, the scratch resistance of the electromagnetic shielding film is improved.

[0070] The above is a preferred embodiment of the present invention. It should be pointed out that a person skilled in the art can make several improvements and modifications without departing from the principle of the present invention. These improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. An electromagnetic shielding film, characterized in that: The electromagnetic shielding film comprises a base layer, a first shielding layer, an interlayer, a second shielding layer and a bonding layer. The base layer, the first shielding layer, the interlayer, the second shielding layer and the bonding layer are stacked in sequence. The total elongation at break of the electromagnetic shielding film is 2%-15%.

2. The electromagnetic shielding film according to claim 1, wherein The first breaking elongation between the base layer, the first shielding layer and the interlayer is 5%-10%.

3. The electromagnetic shielding film according to claim 1, wherein The second breaking elongation between the interlayer, the second shielding layer and the bonding layer is 2%-10%.

4. The electromagnetic shielding film according to claim 2, wherein: After the second shielding layer and the adhesive layer are removed from the electromagnetic shielding film, a change rate of the first elongation at break relative to the total elongation at break is less than or equal to 40%.

5. The electromagnetic shielding film according to claim 3, characterized in that After the base layer and the first shielding layer are removed from the electromagnetic shielding film, a change rate of the second elongation at break relative to the total elongation at break is less than or equal to 30%.

6. The electromagnetic shielding film according to claim 1, wherein The third breaking elongation between the first shielding layer and the interlayer is 6%-18%.

7. The electromagnetic shielding film according to claim 1, wherein The fourth breaking elongation between the interlayer and the second shielding layer is 5%-15%.

8. The electromagnetic shielding film according to claim 6 or 7, characterized in that The first elongation at break between the base layer, the first shielding layer and the interlayer and the second elongation at break between the interlayer, the second shielding layer and the bonding layer satisfy the relationship |ε1-ε2| / ε1≤0.4, where ε1 is the first elongation at break and ε2 is the second elongation at break.

9. The electromagnetic shielding film according to claim 1, wherein The average thickness of the first shielding layer is 0.5-3 micrometers, and / or the average thickness of the second shielding layer is 1-5 micrometers.

10. The electromagnetic shielding film according to claim 1, wherein The average thickness of the electromagnetic shielding film is 6-20 microns.

11. 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.

12. 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 11; the electromagnetic shielding film is pressed together with the circuit board body.

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