CN112351665A - Electromagnetic shielding film, circuit board and preparation method of electromagnetic shielding film - Google Patents
Electromagnetic shielding film, circuit board and preparation method of electromagnetic shielding film Download PDFInfo
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- CN112351665A CN112351665A CN201911394605.2A CN201911394605A CN112351665A CN 112351665 A CN112351665 A CN 112351665A CN 201911394605 A CN201911394605 A CN 201911394605A CN 112351665 A CN112351665 A CN 112351665A
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K9/00—Screening of apparatus or components against electric or magnetic fields
- H05K9/0073—Shielding materials
- H05K9/0081—Electromagnetic shielding materials, e.g. EMI, RFI shielding
- H05K9/0088—Electromagnetic shielding materials, e.g. EMI, RFI shielding comprising a plurality of shielding layers; combining different shielding material structure
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K1/00—Printed circuits
- H05K1/02—Details
- H05K1/0213—Electrical arrangements not otherwise provided for
- H05K1/0216—Reduction of cross-talk, noise or electromagnetic interference
Abstract
The invention relates to the technical field of shielding films, and discloses an electromagnetic shielding film, a circuit board and a preparation method of the electromagnetic shielding film, wherein the electromagnetic shielding film comprises a shielding layer, a first absorption layer and an adhesive film layer, and the first absorption layer is arranged between the shielding layer and the adhesive film layer; the first absorption layer includes a plurality of first electromagnetic wave absorption sublayers stacked, and electromagnetic wave absorption rates of the plurality of first electromagnetic wave absorption sublayers increase in a vertical direction. Through setting up a plurality of first electromagnetic wave absorption sublayers of range upon range of to the electromagnetic wave absorption rate that makes a plurality of first electromagnetic wave absorption sublayers is in the vertical direction and increases progressively, has improved the electromagnetic loss efficiency of first absorption layer, thereby makes the electromagnetic wave of projecting on first absorption layer can be by furthest's absorption, and then has realized the effective shielding to electromagnetic interference.
Description
Technical Field
The invention relates to the technical field of shielding films, in particular to an electromagnetic shielding film, a circuit board and a preparation method of the electromagnetic shielding film.
Background
With the development of miniaturization, light weight, multiple functions and high assembly density of modern electronic equipment, the structure of the circuit board tends to be fine and highly integrated, and is required to bear high-speed signal transmission. Therefore, the circuit density on the circuit board is increased, the circuit spacing is closer, and the operating frequency is higher and wider, which leads to more and more serious electromagnetic interference between circuits.
At present, in order to realize electromagnetic shielding, an electromagnetic shielding film is generally provided on a circuit board. However, the existing electromagnetic shielding film has an unsatisfactory shielding effect, and cannot effectively shield electromagnetic interference in the circuit board, so that the circuit board still has a large electromagnetic interference problem in signal transmission.
In view of the above, it is desirable to develop a shielding film capable of effectively absorbing electromagnetic waves and solving the problem of electromagnetic interference.
Disclosure of Invention
The invention aims to provide an electromagnetic shielding film which can effectively absorb electromagnetic waves so as to solve the problem of electromagnetic interference.
In order to solve the technical problem, the invention provides an electromagnetic shielding film, which comprises a shielding layer, a first absorption layer and a film adhesive layer, wherein the first absorption layer is arranged between the shielding layer and the film adhesive layer;
the first absorption layer includes a plurality of stacked first electromagnetic wave absorption sublayers, and electromagnetic wave absorption rates of the plurality of first electromagnetic wave absorption sublayers increase in a vertical direction.
Preferably, the electromagnetic wave absorption rates of the plurality of first electromagnetic wave absorption sublayers increase sequentially along a first direction; wherein the first direction is a direction from the first absorption layer to the shielding layer perpendicularly.
Preferably, the electromagnetic shielding film further comprises a second absorption layer, and the second absorption layer is arranged on one surface of the shielding layer far away from the first absorption layer;
the second absorption layer includes a plurality of stacked second electromagnetic wave absorption sublayers, and electromagnetic wave absorption rates of the plurality of second electromagnetic wave absorption sublayers increase in a vertical direction.
Preferably, the electromagnetic wave absorption rates of the plurality of second electromagnetic wave absorption sublayers sequentially increase along the second direction; wherein the second direction is a direction from the second absorption layer to the shielding layer perpendicularly.
Preferably, one surface of the shielding layer close to the first absorption layer is provided with a conductive protrusion, and the conductive protrusion is embedded in the first absorption layer.
Preferably, a conductive bump is arranged on one surface of the shielding layer close to the first absorption layer, the conductive bump comprises a plurality of bumps, and the first absorption layer is arranged on the first region of the shielding layer and/or the second region of the conductive bump; the first region is a region where the conductive bumps are not arranged in one surface, close to the first absorption layer, of the shielding layer, and the second region is a region formed between any two adjacent bumps in the conductive bumps.
Preferably, the surface of the conductive bump is provided with conductive particles.
Preferably, the first electromagnetic wave absorption sublayer has conductivity, and the conductivity of the first electromagnetic wave absorption sublayer is smaller than that of the shielding layer; or the like, or, alternatively,
the first electromagnetic wave absorption sublayer has no conductivity.
Preferably, the second electromagnetic wave absorption sub-layer has conductivity, and the conductivity of the second electromagnetic wave absorption sub-layer is smaller than the conductivity of the shielding layer; or the like, or, alternatively,
the second electromagnetic wave absorption sublayer has no conductivity.
Preferably, at least one of the first electromagnetic wave absorption sublayer and the second electromagnetic wave absorption sublayer is composed of a binder and a wave-absorbing medium.
As a preferred scheme, the wave-absorbing medium is composed of any one of a carbon-series wave-absorbing material, an iron-series wave-absorbing material, a ceramic-series wave-absorbing material and a composite wave-absorbing material.
Preferably, the thickness of the first absorption layer is: 0.1-45 μm; the thickness of the second absorption layer is as follows: 0.1-45 μm.
Preferably, the adhesive layer comprises an adhesive layer containing conductive particles; or the like, or, alternatively,
the adhesive film layer comprises an adhesion layer without conductive particles.
Preferably, the electromagnetic shielding film further includes an insulating layer, and the insulating layer is disposed on a surface of the shielding layer away from the first absorption layer.
Preferably, the electromagnetic shielding film further includes an insulating layer, and the insulating layer is disposed on a surface of the second absorption layer away from the shielding layer.
The invention aims to provide a circuit board, which is provided with the electromagnetic shielding film and can effectively absorb electromagnetic waves so as to solve the problem of electromagnetic interference.
In order to solve the above technical problem, an embodiment of the present invention provides a circuit board, including a circuit board body and the above electromagnetic shielding film, where the electromagnetic shielding film is disposed on the circuit board body.
The invention aims to provide a preparation method of an electromagnetic shielding film, and the prepared electromagnetic shielding film can effectively absorb electromagnetic waves so as to solve the problem of electromagnetic interference.
In order to solve the above technical problem, an embodiment of the present invention provides a method for preparing an electromagnetic shielding film, which is suitable for the electromagnetic shielding film, and the method for preparing the electromagnetic shielding film includes:
manufacturing and forming a shielding layer;
forming a plurality of first electromagnetic wave absorption sublayers stacked on one surface of the shielding layer; the plurality of first electromagnetic wave absorption sublayers form a first absorption layer, and the electromagnetic wave absorption rates of the plurality of first electromagnetic wave absorption sublayers are increased progressively in the vertical direction;
and forming a film adhesive layer on one surface of the first absorption layer far away from the shielding layer.
Compared with the prior art, the electromagnetic shielding film, the circuit board and the preparation method of the electromagnetic shielding film provided by the invention have the advantages that the first absorption layer is arranged between the shielding layer and the adhesive film layer, and the electromagnetic wave absorption rates of the first electromagnetic wave absorption sub-layers in the first absorption layer are increased progressively in the vertical direction, so that the electromagnetic loss efficiency of the first absorption layer is improved, the electromagnetic waves projected onto the first absorption layer can be absorbed to the maximum extent, and the effective shielding of electromagnetic interference is realized. Therefore, when the electromagnetic shielding film is applied to a circuit board, the first absorption layer can effectively absorb electromagnetic waves generated by the circuit board, so that the problem of large electromagnetic interference of the circuit board in signal transmission is avoided, and the normal work of the circuit board is ensured.
Drawings
Fig. 1 is a schematic structural diagram of an electromagnetic shielding film according to an embodiment of the present invention;
fig. 2 is a schematic structural view of another electromagnetic shielding film according to an embodiment of the present invention;
fig. 3 is a schematic structural view of an electromagnetic shielding film according to a second embodiment of the present invention;
fig. 4 is a schematic structural diagram of an electromagnetic shielding film according to a third embodiment of the present invention;
fig. 5 is a schematic structural view of another electromagnetic shielding film according to a third embodiment of the present invention;
fig. 6 is a schematic structural view of an electromagnetic shielding film according to a fourth embodiment of the present invention;
fig. 7 is a schematic structural diagram of an electromagnetic shielding film according to a fifth embodiment of the present invention;
fig. 8 is a schematic structural view of another electromagnetic shielding film according to a fifth embodiment of the present invention
Fig. 9 is a schematic structural diagram of a circuit board according to a sixth embodiment of the present invention;
fig. 10 is a schematic flowchart of a method for manufacturing an electromagnetic shielding film according to a seventh embodiment of the present invention.
Wherein, 1, a shielding layer; 11. a conductive bump; 111. a conductive particle; 12. a first region; 2. a first absorbent layer; 21. a first electromagnetic wave absorbing sublayer; 3. a glue film layer; 4. a second absorbent layer; 41. a second electromagnetic wave absorbing sublayer; 5. an insulating layer; 6. the circuit board body.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Example one
Referring to fig. 1 and fig. 2, an electromagnetic shielding film according to an embodiment of the present invention includes a shielding layer 1, a first absorption layer 2, and an adhesive film layer 3, where the first absorption layer 2 is disposed between the shielding layer 1 and the adhesive film layer 3;
the first absorption layer 2 includes a plurality of stacked first electromagnetic wave absorption sublayers 21, and electromagnetic wave absorption rates of the plurality of first electromagnetic wave absorption sublayers 21 increase in the vertical direction.
It should be noted that the first absorption layer 2 has a function of absorbing electromagnetic waves, that is, each of the first electromagnetic wave absorption sublayers 21 has a function of absorbing electromagnetic waves, and is capable of absorbing electromagnetic wave energy projected to its surface and converting the electromagnetic wave energy into heat energy or other forms of energy through dielectric loss. In addition, when the electromagnetic shielding film is applied to a circuit board, the electromagnetic shielding film is laminated with the circuit board.
In the embodiment of the present invention, the first absorption layer 2 is disposed between the shielding layer 1 and the adhesive film layer 3, and the electromagnetic wave absorption rates of the first electromagnetic wave absorption sub-layers 21 in the first absorption layer 2 are increased in the vertical direction, so that the electromagnetic loss efficiency of the first absorption layer 2 is improved, and thus the electromagnetic wave projected onto the first absorption layer 2 can be absorbed to the maximum extent, and effective shielding of electromagnetic interference is further achieved. Therefore, when the electromagnetic shielding film is applied to a circuit board, the first absorption layer 2 can effectively absorb electromagnetic waves generated by the circuit board, so that the problem of large electromagnetic interference of the circuit board in signal transmission is avoided, and the normal operation of the circuit board is ensured.
As can be understood, a plurality of signal lines are commonly disposed in the existing circuit board, and electromagnetic waves generated by the signal lines easily cause interference between the signal lines, thereby affecting signal transmission. In this embodiment, the shielding layer 1 and the first absorption layer 2 are disposed in the electromagnetic shielding film, so that when the electromagnetic shielding film is applied to the circuit board, the first absorption layer 2 can absorb the electromagnetic wave generated by the signal line in the circuit board projected on the first absorption layer 2, and the electromagnetic wave which is not completely absorbed is reflected when passing through the surface of the shielding layer 1 close to the first absorption layer 2, so as to be absorbed by the first absorption layer 2 for the second time, thereby greatly improving the electromagnetic wave absorption rate of the electromagnetic shielding film, and further achieving effective shielding of electromagnetic interference, thereby effectively avoiding the problem that signal transmission is affected due to interference generated between the signal lines in the circuit board, and ensuring normal operation of the circuit board.
In a preferred embodiment, the electromagnetic wave absorption rates of the plurality of first electromagnetic wave absorption sublayers 21 sequentially increase along a first direction; wherein the first direction is a direction from the first absorption layer 2 to the shielding layer 1.
In the embodiment of the present invention, since the electromagnetic wave absorption rates of the plurality of first electromagnetic wave absorption sub-layers 21 are sequentially increased along the first direction, when the electromagnetic shielding film is applied to a circuit board, the electromagnetic wave generated by the circuit board is located at a side of the first electromagnetic wave absorption sub-layer 2 close to the adhesive film layer 3, that is, the electromagnetic wave generated by the circuit board is incident from a side of the first electromagnetic wave absorption sub-layer 21 with a lower electromagnetic wave absorption rate, so as to be absorbed by the first electromagnetic wave absorption layer 2 step by step; the electromagnetic wave which is not completely absorbed is reflected when passing through the first absorption layer 2 near one surface of the shielding layer 1, so that the electromagnetic wave is secondarily absorbed by the first absorption layer 2, and the electromagnetic wave absorption rate of the whole electromagnetic shielding film is greatly improved.
It should be noted that, in the first absorption layer 2, the electromagnetic wave absorption rate of each of the first electromagnetic wave absorption sublayers 21 may be set to be different from each other, so for two adjacent first electromagnetic wave absorption sublayers 21, the electromagnetic wave absorption rate of the first electromagnetic wave absorption sublayer 21 close to the shielding layer 1 is greater than that of the first electromagnetic wave absorption sublayer 21 far from the shielding layer 1. Of course, in the first absorption layer 2, the electromagnetic wave absorption rates of some of the first electromagnetic wave absorption sub-layers 21 may be set to be the same, and it is only necessary to ensure that the electromagnetic wave absorption rates of a plurality of the first electromagnetic wave absorption sub-layers 21 are increased in the vertical direction; for example, two first electromagnetic wave absorption sublayers 21 having the same electromagnetic wave absorption rate are stacked as a whole structure, the first absorption layer 2 is formed by stacking a plurality of the whole structures, and the electromagnetic wave absorption rates of the plurality of the whole structures increase in the vertical direction.
It should be understood that, here is only one specific implementation manner in which the electromagnetic wave absorption rates of the plurality of first electromagnetic wave absorption sublayers 21 increase in the vertical direction, the electromagnetic wave absorption rates of the plurality of first electromagnetic wave absorption sublayers 21 in this embodiment may also be set to have an increasing trend along the first direction, and the specific implementation manner in which the electromagnetic wave absorption rates of the plurality of first electromagnetic wave absorption sublayers 21 increase in the vertical direction is not limited in this embodiment of the present invention.
In a preferred embodiment, the first electromagnetic wave absorption sublayer 21 has conductivity, and the conductivity of the first electromagnetic wave absorption sublayer 21 is smaller than the conductivity of the shielding layer 1. By providing the first electromagnetic wave absorption sublayer 21 having conductivity in the electromagnetic shielding film, on the one hand, the first electromagnetic wave absorption sublayer 21 has a function of absorbing electromagnetic waves, which can absorb electromagnetic waves generated by the circuit board to ensure the normal operation of the circuit board; on the other hand, the first electromagnetic wave absorption sublayer 21 further has a conductive function, and can cooperate with the shielding layer 1 to achieve shielding effectiveness.
It should be noted that, in the present embodiment, the proportional relationship between the conductivity of the first electromagnetic wave absorption sublayer 21 and the conductivity of the shielding layer 1 can be set according to the actual use situation; preferably, in the present embodiment, the conductivity of the first electromagnetic wave absorption sublayer 21 is 10% to 50% of the conductivity of the shielding layer 1.
In another preferred embodiment, the first electromagnetic wave absorption sublayer 21 has no electrical conductivity. By providing the first electromagnetic wave absorption sublayer 21 having no conductivity in the electromagnetic shielding film, the insertion loss during use of the wiring board can be reduced.
In the embodiment of the present invention, the first electromagnetic wave absorption sublayer 21 may be configured according to actual use conditions, and only needs to ensure that it has a function of absorbing electromagnetic waves. Preferably, in this embodiment, the first electromagnetic wave absorption sublayer 21 is composed of a binder and a wave-absorbing medium. In specific implementation, the concentration of the wave-absorbing medium in the first electromagnetic wave-absorbing sublayers 21 is controlled to gradually increase the concentration of the wave-absorbing medium in the plurality of first electromagnetic wave-absorbing sublayers 21 along the first direction, so that the electromagnetic wave absorption rates of the plurality of first electromagnetic wave-absorbing sublayers 21 sequentially increase along the first direction. The wave-absorbing medium is composed of any one of a carbon-series wave-absorbing material, an iron-series wave-absorbing material, a ceramic-series wave-absorbing material and a composite wave-absorbing material. It should be noted that the carbon-based wave-absorbing material includes, but is not limited to, graphene, graphite, carbon black, carbon fiber, and carbon nanotube; the iron-based wave absorbing material comprises but is not limited to ferrite, a magnetic iron nano material, Fe-based alloy micro powder and an iron-based amorphous material; the ceramic-series wave-absorbing material comprises but is not limited to silicon carbide; the composite wave-absorbing material comprises but is not limited to a composite material formed by blending reduced graphene oxide/tin dioxide nano composite wave-absorbing material, manganese zinc ferrite/polypyrrole composite material, three-dimensional silver-graphene hybrid foam/epoxy resin composite material, rG0/Fe304@ Si02 composite material and soft magnetic powder and high molecular plastic. In addition, the wave absorbing medium can also be a conductive polymer, a chiral material, a plasma material, a porous hollow iron nanosphere, a self-skinning polyurethane lightweight material, a hollow sandwich microsphere metal sulfide and the like.
In the embodiment of the present invention, the thickness of the first absorption layer 2 can also be set according to the actual use situation. In order to ensure that the first absorption layer 2 can absorb the electromagnetic wave generated by the circuit board, the thickness of the first absorption layer 2 in this embodiment is preferably 0.1 μm to 45 μm. In addition, in this embodiment, the outer surface of the first absorption layer 2 may be a flat surface, or may be a non-flat surface, which is not limited in this embodiment.
In addition, it should be noted that the number of the first electromagnetic wave absorption layers 21 in the present embodiment may be set according to actual use cases; the drawings of the present invention only illustrate three first electromagnetic wave absorption layers 21, and other numbers are within the scope of the present invention.
In the embodiment of the present invention, the shielding layer 1 includes a first surface in contact with the first absorbing layer 2, and the first surface of the shielding layer 1 may be a surface of any shape, for example, a flat surface as shown in fig. 1, or a non-flat surface as shown in fig. 2; in addition, the first surface of the shielding layer 1 may be a regular surface or an irregular surface.
In the embodiment of the present invention, the shielding layer 1 further includes a second surface disposed opposite to the first surface. It should be noted that the second surface of the shielding layer 1 may be a surface of any shape, for example, a flat surface as shown in fig. 1, or a non-flat surface; in addition, the second surface of the shielding layer 1 may be a regular surface or an irregular surface. The second surface of the shielding layer 1 is merely illustrated as a flat surface in the drawings of the present invention, and any other shape of the second surface of the shielding layer 1 is within the scope of the present invention.
In the embodiment of the present invention, the thickness of the shielding layer 1 may be set according to actual use conditions; preferably, the thickness of the shielding layer 1 is 0.1 μm to 45 μm. In addition, in order to ensure that the shielding layer 1 has good conductivity, the shielding layer 1 includes one or more of a metal shielding layer, a carbon nanotube shielding layer, a ferrite shielding layer, and a graphene shielding layer. Wherein the metal shielding layer comprises a single metal shielding layer and/or an alloy shielding layer; 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.
In addition, the shielding layer 1 in the drawings of the present embodiment may have a single-layer structure or a multi-layer structure. In addition, the shielding layer 1 of the present embodiment can be arranged in a grid shape, a foaming shape, etc. according to the requirements of actual production and application.
In the embodiment of the present invention, one of the structures of the adhesive film layer 3 is specifically represented as follows: the adhesive layer 3 includes an adhesive layer containing conductive particles. The adhesive film layer 3 has an adhesive effect by including an adhesive layer containing conductive particles, so that the circuit board and the electromagnetic shielding film are tightly adhered, and the adhesive film layer 3 also has a conductive function and can be matched with the shielding layer 1 to realize shielding efficiency. The conductive particles can be mutually separated conductive particles or aggregated large-particle conductive particles; when the conductive particles are mutually separated, the area of electrical contact can be further increased, and the uniformity of the electrical contact is improved; and when the conductive particles are large agglomerated conductive particles, the piercing strength can be increased.
In the embodiment of the present invention, another structure of the adhesive film layer 3 is specifically represented as follows: the adhesive layer 3 includes an adhesive layer containing no conductive particles. The adhesive film layer 3 has an adhesive effect by enabling the adhesive film layer 3 to include an adhesive layer without containing conductive particles, so that the circuit board and the electromagnetic shielding film are tightly adhered, and meanwhile, because the adhesive film layer 3 includes an adhesive layer without containing conductive particles, the insertion loss of the circuit board in the using process is reduced, the shielding efficiency is improved, and meanwhile, the bending property of the circuit board is improved.
In addition, the thickness of the adhesive film layer 3 in this embodiment is 1 μm to 80 μm. The glue film layer 3 is made of the following materials: modified epoxy resins, acrylic resins, modified rubbers, and modified thermoplastic polyimides. In addition, it should be noted that the outer surface of the adhesive film layer 3 may be a flat surface or a non-flat surface, which is not limited in this embodiment.
Example two
As shown in fig. 3, the electromagnetic shielding film in this embodiment is different from the first embodiment in that the electromagnetic shielding film further includes a second absorption layer 4, and the second absorption layer 4 is disposed on a side of the shielding layer 1 away from the first absorption layer 2;
the second absorption layer 4 includes a plurality of stacked second electromagnetic wave absorption sublayers 41, and electromagnetic wave absorption rates of the plurality of second electromagnetic wave absorption sublayers 41 increase in a vertical direction.
It should be noted that the second absorption layer 4 has a function of absorbing electromagnetic waves, and can absorb electromagnetic wave energy projected to its surface and convert the electromagnetic wave energy into heat energy or other forms of energy through dielectric loss.
In the embodiment of the present invention, the second absorption layer 4 is disposed on a surface of the shielding layer 1 away from the first absorption layer 2, and the electromagnetic wave absorption rates of the plurality of second electromagnetic wave absorption sublayers 41 in the second absorption layer 4 are increased in a vertical direction, so that the electromagnetic loss efficiency of the second absorption layer 4 is improved, and thus the electromagnetic waves incident on the second absorption layer 4 can be absorbed to the maximum extent, thereby further ensuring effective shielding of electromagnetic interference. Therefore, when the electromagnetic shielding film is applied to a circuit board, the second absorption layer 4 can effectively absorb electromagnetic waves from the outside of the circuit board, thereby reducing electromagnetic interference in the circuit board, and further ensuring the normal operation of the circuit board.
It can be understood that, the circuit board is applied to electronic devices such as smart phones and tablet computers, and these electronic devices are usually provided with an antenna, and electromagnetic waves generated by the antenna also affect signal transmission in the circuit board. Therefore, by arranging the second absorption layer 4 on the surface of the shielding layer 1 far away from the first absorption layer 2, when the electromagnetic shielding film is applied to the circuit board, the second absorption layer 4 can absorb electromagnetic waves generated by devices such as antennas positioned outside the circuit board, and the electromagnetic waves which are not completely absorbed are reflected when passing through the surface of the shielding layer 1 near the second absorption layer 4, so that the electromagnetic waves are secondarily absorbed by the second absorption layer 4, the electromagnetic wave absorption rate of the electromagnetic shielding film is greatly improved, the interference of the electromagnetic waves generated by external devices on the circuit board is effectively avoided, and the normal signal transmission of the circuit board is further ensured.
In a preferred embodiment, the electromagnetic wave absorption rates of the plurality of second electromagnetic wave absorption sublayers 41 sequentially increase along the second direction; wherein the second direction is a direction from the second absorption layer 4 to the shielding layer 1 perpendicularly.
In the embodiment of the present invention, since the electromagnetic wave absorption rates of the plurality of second electromagnetic wave absorption sublayers 41 sequentially increase along the second direction, when the electromagnetic shielding film is applied to a circuit board, electromagnetic waves from outside the circuit board are located on the side of the second absorption layer 4 away from the shielding layer 1, that is, electromagnetic waves from outside the circuit board enter from the side of the second electromagnetic wave absorption sublayer 41 with a lower electromagnetic wave absorption rate, and are absorbed by the second absorption layer 4 step by step; and the electromagnetic wave which is not completely absorbed is reflected when passing through the side of the second absorption layer 4 close to the shielding layer 1, so that the electromagnetic wave is secondarily absorbed by the second absorption layer 4, and the electromagnetic wave absorption rate of the electromagnetic shielding film is greatly improved.
It should be noted that, in the second absorption layer 4, the electromagnetic wave absorption rate of each of the second electromagnetic wave absorption sublayers 41 can be set to be different, so for two adjacent second electromagnetic wave absorption sublayers 41, the electromagnetic wave absorption rate of the second electromagnetic wave absorption sublayer 41 close to the shielding layer 1 is greater than that of the second electromagnetic wave absorption sublayer 41 far from the shielding layer 1. Of course, in the second absorption layer 4, the electromagnetic wave absorption rates of some of the second electromagnetic wave absorption sub-layers 41 may also be set to be the same, and it is only necessary to ensure that the electromagnetic wave absorption rates of a plurality of the second electromagnetic wave absorption sub-layers 41 are in an increasing trend in the vertical direction; for example, two stacked second electromagnetic wave absorption sublayers 41 having the same electromagnetic wave absorption rate are used as a whole structure, and the second absorption layer 4 is formed by stacking a plurality of the whole structures, and the electromagnetic wave absorption rates of the plurality of the whole structures increase in the vertical direction.
It should be understood that, here is only one specific implementation manner in which the electromagnetic wave absorption rates of the plurality of second electromagnetic wave absorption sublayers 41 increase in the vertical direction, the electromagnetic wave absorption rates of the plurality of second electromagnetic wave absorption sublayers 41 in this embodiment may also be set to have an increasing trend along the second direction, and the specific implementation manner in which the electromagnetic wave absorption rates of the plurality of second electromagnetic wave absorption sublayers 41 increase in the vertical direction is not limited in this embodiment of the present invention.
In a preferred embodiment, the second electromagnetic wave absorption sublayer 41 has conductivity, and the conductivity of the second electromagnetic wave absorption sublayer 41 is smaller than the conductivity of the shielding layer 1. By providing the second electromagnetic wave absorption sublayer 41 having conductivity in the electromagnetic shielding film, on the one hand, the second electromagnetic wave absorption sublayer 41 has a function of absorbing electromagnetic waves, which can absorb electromagnetic waves from the outside of the circuit board, to further ensure the normal operation of the circuit board; on the other hand, the second electromagnetic wave absorption sublayer 41 further has a conductive function, and can cooperate with the shielding layer 1 to achieve shielding effectiveness.
It should be noted that, in this embodiment, the proportional relationship between the conductivity of the second electromagnetic wave absorption sublayer 41 and the conductivity of the shielding layer 1 can be set according to the actual use situation; preferably, in this embodiment, the conductivity of the second electromagnetic wave absorption sublayer 41 is 10% to 50% of the conductivity of the shielding layer 1.
In another preferred embodiment, the second electromagnetic wave absorption sublayer 41 has no electrical conductivity. By providing the second electromagnetic wave absorption sublayer 41 having no conductivity in the electromagnetic shielding film, the insertion loss during use of the wiring board can be reduced.
In the embodiment of the present invention, the second electromagnetic wave absorption sublayer 41 may be configured according to actual use conditions, and only needs to ensure that it has a function of absorbing electromagnetic waves. Preferably, in this embodiment, the second electromagnetic wave absorption sublayer 41 is composed of a bonding agent and a wave-absorbing medium. In specific implementation, the concentration of the wave-absorbing medium in the second electromagnetic wave-absorbing sublayers 41 is controlled to gradually increase the concentration of the wave-absorbing medium in the plurality of second electromagnetic wave-absorbing sublayers 41 along the first direction, so that the electromagnetic wave absorption rates of the plurality of second electromagnetic wave-absorbing sublayers 41 sequentially increase along the first direction. The wave-absorbing medium is composed of any one of a carbon-series wave-absorbing material, an iron-series wave-absorbing material, a ceramic-series wave-absorbing material and a composite wave-absorbing material. It should be noted that the carbon-based wave-absorbing material includes, but is not limited to, graphene, graphite, carbon black, carbon fiber, and carbon nanotube; the iron-based wave absorbing material comprises but is not limited to ferrite, a magnetic iron nano material, Fe-based alloy micro powder and an iron-based amorphous material; the ceramic-series wave-absorbing material comprises but is not limited to silicon carbide; the composite wave-absorbing material comprises but is not limited to a composite material formed by blending reduced graphene oxide/tin dioxide nano composite wave-absorbing material, manganese zinc ferrite/polypyrrole composite material, three-dimensional silver-graphene hybrid foam/epoxy resin composite material, rG0/Fe304@ Si02 composite material and soft magnetic powder and high molecular plastic. In addition, the wave absorbing medium can also be a conductive polymer, a chiral material, a plasma material, a porous hollow iron nanosphere, a self-skinning polyurethane lightweight material, a hollow sandwich microsphere metal sulfide and the like.
In addition, the thickness of the second absorption layer 4 can be set according to actual use conditions. In order to ensure that the second absorption layer 4 can absorb electromagnetic waves from the outside of the circuit board, the thickness of the second absorption layer 4 in this embodiment is preferably 0.1 μm to 45 μm. In addition, in this embodiment, the outer surface of the second absorption layer 4 may be a flat surface, or may be a non-flat surface, which is not limited in this embodiment.
In the embodiment of the present invention, other structures and working principles of the electromagnetic shielding film of the present embodiment are the same as those of the first embodiment, and further details are not described herein.
EXAMPLE III
Referring to fig. 4 and 5, the electromagnetic shielding film in this embodiment is different from the first and second embodiments in that a surface of the shielding layer 1 adjacent to the first absorbing layer 2 is provided with a conductive protrusion 11, and the conductive protrusion 11 is embedded in the first absorbing layer 2.
It will be understood that the embedding of the conductive bumps 11 in the first absorbing layer 2 includes in particular two cases: (1) a certain distance exists between the conductive bump 11 and one surface of the first absorption layer 2 close to the adhesive film layer 3, that is, the conductive bump 11 is completely positioned inside the first absorption layer 2; (2) the conductive bumps 11 pass through the first absorbing layer 2. Under the condition that the conductive bump 11 is completely positioned in the first absorption layer 2, the first absorption layer 2 has fluidity at a certain pressing temperature, so that when the electromagnetic shielding film is pressed with the circuit board, the conductive bump 11 can sequentially pierce through the first absorption layer 2 and the adhesive film layer 3 so as to be connected with the ground layer of the circuit board, and then the interference charges accumulated in the electromagnetic shielding film are led out, thereby further improving the shielding effectiveness of the electromagnetic shielding film; in the case that the conductive bump 11 penetrates through the first absorption layer 2, the first absorption layer 2 may have no fluidity or fluidity at a certain pressing temperature, so that when the electromagnetic shielding film is pressed against the circuit board, the conductive bump 11 penetrates through the adhesive film layer 3 to connect with the ground layer of the circuit board.
In a preferred embodiment, as shown in fig. 5, in order to improve the piercing strength of the conductive bump 11, the surface of the conductive bump 11 is provided with conductive particles 111. Through set up on the surface of electrically conductive protruding 11 conductor granule 111 has increased electrically conductive protruding 11 impales the dynamics to further guaranteed when the electromagnetic shield membrane with circuit board pressfitting, electrically conductive protruding 11 can pierce smoothly first absorption layer 2 with the glued membrane layer 3 and with the stratum of circuit is connected, and then guarantees the normal derivation of interference electric charge.
In the embodiment of the present invention, the height of the conductive particles 111 may be set according to actual use conditions; in order to ensure that the piercing strength of the conductive bump 11 can be increased, the height of the conductive particles in this embodiment is preferably 0.1 μm to 30 μm.
In an embodiment of the present invention, the conductive particles 111 include one or more of metal particles, carbon nanotube particles, and ferrite particles. Wherein the metal particles comprise single metal particles and/or alloy particles; the single metal particles are made of any one of aluminum, titanium, zinc, iron, nickel, chromium, cobalt, copper, silver and gold, and the alloy particles are made of any two or more of aluminum, titanium, zinc, iron, nickel, chromium, cobalt, copper, silver and gold.
In the embodiment of the present invention, the shape of the conductive particles 111 is illustrated only for an example, and due to differences in process means and parameters, the conductive particles 111 may have other shapes such as cluster, ice, stalactite, and dendritic shapes. The conductive particles 111 in the present invention are not limited to the shapes shown in the drawings and described above, and any conductive particles having piercing and conductive functions are within the scope of the present invention.
In the embodiment of the present invention, it should be noted that the conductive particles 111 may be the same as or different from the material of the conductive bumps 11. Therefore, in a specific implementation, the conductive bump 11 may be formed first, and then the conductive particles 111 may be formed on the outer surface of the conductive bump 11 through another process. Of course, the conductive bumps 11 and the conductive particles 111 may be formed as a single structure by a single molding process.
Further, it should be noted that the structure of the conductive bump 11 shown in the drawings is merely exemplary. The present invention provides a conductive protrusion 11 is not limited by the shape of the figure and the above shape, and is provided with a conductive protrusion that pierces through and has a conductive function, which is within the protection scope of the present invention.
In the embodiment of the present invention, the shielding layer 1 may be formed first, and then the conductive protrusion 11 is formed on the first surface of the shielding layer 1 by other processes, as shown in fig. 4. Of course, the shielding layer 1 and the conductive bump 11 may be an integral structure formed by a one-step molding process.
In the embodiment of the present invention, other structures and working principles of the electromagnetic shielding film of the present embodiment are the same as those of the first and second embodiments, and further details are not described herein.
Example four
As shown in fig. 6, the electromagnetic shielding film in this embodiment is different from the third embodiment in that a conductive protrusion 11 is disposed on a surface of the shielding layer close to the first absorption layer 2, the conductive protrusion 11 includes a plurality of protrusions, and the first absorption layer 2 is disposed on a first region 12 of the shielding layer 1 and/or a second region of the conductive protrusion 11; the first region 12 is a region where the conductive bump 11 is not disposed in one surface of the shielding layer 1 close to the first absorption layer 2, and the second region is a region formed between any two adjacent bumps in the conductive bump 11.
It can be understood that the first absorption layer 2 is disposed on the first region 12 of the shielding layer 1 and/or the second region of the conductive bump 11, and at this time, the first absorption layer 2 does not cover the conductive bump 11, so that when the electromagnetic shielding film is laminated with the circuit board, the conductive bump 11 can be connected with the ground layer of the circuit board only by piercing the adhesive film layer 3. Specifically, the arrangement of the conductive bump 11 specifically includes two cases: (1) the height of the conductive bump 11 is less than or equal to the thickness of the first absorption layer 2; (2) the height of the conductive bump 11 is greater than the thickness of the first absorption layer 2. Under the condition that the height of the conductive bump 11 is less than or equal to the thickness of the first absorption layer 2, the first absorption layer 2 has fluidity at a certain pressing temperature, so that when the electromagnetic shielding film is pressed with the circuit board, the conductive bump 11 can pierce the adhesive film layer 3 and be connected with the ground layer of the circuit board; and under the condition that the height of the conductive protrusion 11 is greater than the thickness of the first absorption layer 2, the first absorption layer 2 may have no fluidity or fluidity at a certain pressing temperature, so that when the electromagnetic shielding film is pressed against the circuit board, the conductive protrusion 11 can directly pierce the adhesive film layer 3 to connect with the ground layer of the circuit board.
It should be noted that the first absorption layer 2 is disposed in the first region of the shielding layer 1 and/or the second region of the conductive bump 11 specifically includes three conditions: (1) the first absorption layer 2 is only arranged in the first region 12; (2) the first absorption layer 2 is only arranged in the second area; (3) the first absorbent layer 2 is provided in the first region 12 and the second region. One specific implementation manner of the first absorption layer 2 disposed on the first region 12 of the shielding layer 1 is as follows: through holes penetrating through the upper and lower surfaces of the first absorption layer 2 are formed in the first absorption layer 2, and the conductive protrusions 11 penetrate through the through holes, so that the first absorption layer 2 is only arranged in a region where the conductive protrusions 11 are not formed in one surface of the shielding layer 1 close to the first absorption layer 2. In addition, another specific implementation manner of disposing the first absorption layer 2 on the first region 12 of the shielding layer 1 is as follows: the first absorption layer 2 is composed of a plurality of absorption sublayers, each of the absorption sublayers includes a plurality of stacked first electromagnetic wave absorption sublayers, and each of the absorption sublayers is respectively disposed on the first region 12 of the shielding layer 1.
In the embodiment of the present invention, by disposing the first absorption layer 2 on the first region 12 of the shielding layer 1 and/or the second region of the conductive bump 11, on one hand, it is ensured that the electromagnetic shielding film can absorb the electromagnetic wave generated by the circuit board through the first absorption layer 2, so as to achieve effective shielding of electromagnetic interference; on the other hand, when the electromagnetic screen film is laminated with the circuit board, the conductive bump 11 can be connected with the ground layer of the circuit board only by piercing the glue film layer 3 without piercing the first absorption layer 2, so that the requirement on the piercing strength of the conductive bump 11 is reduced, and the structure of the conductive bump 11 is simplified.
In a preferred embodiment, in order to improve the piercing strength of the conductive bump 11, the surface of the conductive bump 11 is provided with conductive particles 111. Through the surface of electrically conductive protruding 11 sets up conductor granule 111 has increased electrically conductive protruding 11 impales the dynamics to further guaranteed electromagnetic shielding membrane with during the circuit board pressfitting, electrically conductive protruding 11 can pierce smoothly glue film layer 3 and with the stratum of circuit is connected, and then guarantees the normal derivation of disturbing charge. Specifically, the shape and the structure of the conductive particles 111 can be described with reference to the third embodiment, and the description of this embodiment is not repeated herein.
In the embodiment of the present invention, other structures and working principles of the electromagnetic shielding film of the embodiment are the same as those of the embodiment, and further details are not described herein.
EXAMPLE five
As shown in fig. 7, the present embodiment provides an electromagnetic shielding film, which is different from the first embodiment in that the electromagnetic shielding film further includes an insulating layer 5, and the insulating layer 5 is disposed on a side of the shielding layer 1 away from the first absorption layer 2.
As shown in fig. 8, this embodiment further provides another electromagnetic shielding film, which is different from the second embodiment in that the electromagnetic shielding film further includes an insulating layer 5, and the insulating layer 5 is disposed on a side of the second absorption layer 4 away from the shielding layer 1.
In the embodiment of the present invention, the insulating layer 5 is disposed in the electromagnetic shielding film to insulate the electromagnetic shielding film from the surrounding environment or the adjacent conductors, so as to ensure the shielding effectiveness of the electromagnetic shielding film.
In the embodiment of the present invention, other structures and working principles of the electromagnetic shielding film of the present embodiment are the same as those of the first and second embodiments, and further details are not described herein.
EXAMPLE six
As shown in fig. 9, an embodiment of the present invention further provides a circuit board, which includes a circuit board body 6 and the electromagnetic shielding film according to any one of the first to fifth embodiments, where the electromagnetic shielding film is disposed on the circuit board body 6.
It should be noted that, when the conductive bumps 11 are disposed in the electromagnetic shielding film, the conductive bumps 11 of the electromagnetic shielding film pierce the adhesive film layer 3 and are connected to the ground layer in the circuit board body 6.
In this embodiment of the present invention, the conductive bumps 11 in the electromagnetic shielding film may all be in contact with the ground layer of the circuit board body 6, or may be partially in contact with the ground layer of the circuit board body 6, which is not limited in this embodiment.
In addition, for the implementation of the electromagnetic shielding film, reference may be made to the descriptions of the first to fifth embodiments, which are not repeated herein.
In the embodiment of the invention, the type of the circuit board body 6 can be set according to the actual use condition; preferably, the circuit board body 6 in this embodiment is one of a flexible single-sided circuit board, a flexible double-sided circuit board, a flexible multilayer board, and a rigid-flex printed circuit board.
In addition, in the specific implementation, when the circuit board is applied to an electronic device, a free grounding film may be further disposed, so that one surface of the free grounding film is electrically connected to a housing of the electronic device, and the other surface of the free grounding film is electrically connected to the electromagnetic shielding film, thereby conducting out interference charges accumulated in the electromagnetic shielding film.
In the embodiment of the present invention, the circuit board is composed of the circuit board body 6 and the electromagnetic shielding film, and the electromagnetic wave absorption rates of the first electromagnetic wave absorption sublayers in the electromagnetic shielding film are increased in the vertical direction, so that the electromagnetic loss efficiency of the first absorption layer 2 is improved, and thus the electromagnetic waves projected onto the first absorption layer 2 can be absorbed to the maximum extent, thereby achieving effective shielding of electromagnetic interference, and effectively avoiding the problem of large electromagnetic interference in signal transmission of the circuit board, thereby ensuring the normal operation of the circuit board.
EXAMPLE seven
As shown in fig. 10, an embodiment of the present invention provides a method for preparing an electro-magnetic shielding film, which is suitable for preparing the electro-magnetic shielding film according to the first embodiment, the method including the following steps S11-S13:
and S11, manufacturing and forming a shielding layer.
Wherein the shielding layer is formed in step S11 by:
forming a protective film layer on a carrier film, the shielding layer being formed on the protective film layer; or
The method comprises the steps of forming a peelable layer on a carrier film, forming the shielding layer on a surface of the peelable layer, and peeling the carrier film after forming a protective film layer on a side of the shielding layer remote from the peelable layer.
The shielding layer can be formed by adopting an electroless plating mode, PVD, CVD, evaporation plating, sputtering plating, electroplating or a composite process thereof.
S12, forming a plurality of stacked first electromagnetic wave absorption sublayers on one surface of the shielding layer; the plurality of first electromagnetic wave absorption sublayers constitute a first absorption layer, and the electromagnetic wave absorption rates of the plurality of first electromagnetic wave absorption sublayers increase progressively in the vertical direction.
And S13, forming an adhesive film layer on one surface of the first absorption layer far away from the shielding layer.
In step S13, forming an adhesive film layer on a surface of the first absorption layer away from the shielding layer, specifically:
coating an adhesive film layer on a release film, and then transferring the adhesive film layer to one surface of the first absorption layer far away from the shielding layer in a pressing mode, so that the adhesive film layer is formed on one surface of the first absorption layer far away from the shielding layer; or
And directly coating an adhesive film layer on one side of the first absorption layer far away from the shielding layer, so that the adhesive film layer is formed on one side of the first absorption layer far away from the shielding layer.
In addition, it should be noted that the method for manufacturing the electromagnetic shielding film provided in this embodiment is only one example for manufacturing the electromagnetic shielding film described in the first embodiment, and the electromagnetic shielding film described in the first embodiment may also be manufactured by other manufacturing methods. In addition, the preparation method of the electromagnetic shielding film according to the second to fifth embodiments may specifically refer to the preparation method of the electromagnetic shielding film provided in this embodiment, and will not be further described herein.
In summary, the present invention provides an electromagnetic shielding film and a circuit board, wherein the electromagnetic shielding film includes a shielding layer 1, a first absorption layer 2 and a glue film layer 3, and the first absorption layer 2 is disposed between the shielding layer 1 and the glue film layer 3; the first absorption layer 2 includes a plurality of stacked first electromagnetic wave absorption sublayers 21, and electromagnetic wave absorption rates of the plurality of first electromagnetic wave absorption sublayers 21 increase in the vertical direction. The first absorption layer 2 is arranged between the shielding layer 1 and the adhesive film layer 3, and the electromagnetic wave absorption rate of the first electromagnetic wave absorption sub-layers in the first absorption layer 2 is increased in the vertical direction, so that the electromagnetic loss efficiency of the first absorption layer 2 is improved, the electromagnetic waves projected onto the first absorption layer 2 can be absorbed to the maximum extent, and the effective shielding of electromagnetic interference is realized. Therefore, when the electromagnetic shielding film is applied to a circuit board, the first absorption layer 2 can effectively absorb electromagnetic waves generated by the circuit board, so that the problem of large electromagnetic interference of the circuit board in signal transmission is avoided, and the normal operation of the circuit board is ensured.
The above description is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and substitutions can be made without departing from the technical principle of the present invention, and these modifications and substitutions should also be regarded as the protection scope of the present invention.
Claims (17)
1. The electromagnetic shielding film is characterized by comprising a shielding layer, a first absorption layer and an adhesive film layer, wherein the first absorption layer is arranged between the shielding layer and the adhesive film layer;
the first absorption layer includes a plurality of stacked first electromagnetic wave absorption sublayers, and electromagnetic wave absorption rates of the plurality of first electromagnetic wave absorption sublayers increase in a vertical direction.
2. The electro-magnetic shielding film according to claim 1, wherein the electro-magnetic wave absorption rates of the plurality of first electro-magnetic wave absorption sublayers sequentially increase along a first direction; wherein the first direction is a direction from the first absorption layer to the shielding layer perpendicularly.
3. The electromagnetic shielding film of claim 1, further comprising a second absorbing layer disposed on a side of the shielding layer away from the first absorbing layer;
the second absorption layer includes a plurality of stacked second electromagnetic wave absorption sublayers, and electromagnetic wave absorption rates of the plurality of second electromagnetic wave absorption sublayers increase in a vertical direction.
4. The electro-magnetic shielding film according to claim 3, wherein the electro-magnetic wave absorption rates of the plurality of second electro-magnetic wave absorption sublayers increase sequentially along the second direction; wherein the second direction is a direction from the second absorption layer to the shielding layer perpendicularly.
5. The electromagnetic shielding film according to any one of claims 1 to 4, wherein the shielding layer has a conductive protrusion on a surface thereof adjacent to the first absorbing layer, and the conductive protrusion is embedded in the first absorbing layer.
6. The electromagnetic shielding film according to any one of claims 1 to 4, wherein a conductive bump is disposed on a surface of the shielding layer adjacent to the first absorption layer, the conductive bump includes a plurality of protrusions, and the first absorption layer is disposed on the first region of the shielding layer and/or the second region of the conductive bump; the first region is a region where the conductive bumps are not arranged in one surface, close to the first absorption layer, of the shielding layer, and the second region is a region formed between any two adjacent bumps in the conductive bumps.
7. The electro-magnetic shielding film of claim 5 or 6, wherein the conductive protrusions are provided at their surfaces with conductive particles.
8. The electromagnetic shielding film according to any one of claims 1 to 4, wherein the first electromagnetic wave absorption sublayer has electrical conductivity, and the electrical conductivity of the first electromagnetic wave absorption sublayer is smaller than the electrical conductivity of the shielding layer; or the like, or, alternatively,
the first electromagnetic wave absorption sublayer has no conductivity.
9. The electro-magnetic shielding film of claim 3, wherein the second electro-magnetic wave absorption sub-layer has electrical conductivity, and the electrical conductivity of the second electro-magnetic wave absorption sub-layer is less than the electrical conductivity of the shielding layer; or the like, or, alternatively,
the second electromagnetic wave absorption sublayer has no conductivity.
10. The electro-magnetic shielding film of claim 3 wherein at least one of the first electro-magnetic wave absorbing sub-layer and the second electro-magnetic wave absorbing sub-layer is comprised of a binder and a wave absorbing medium.
11. The electromagnetic shielding film according to claim 10, wherein the wave-absorbing medium is made of any one of a carbon-based wave-absorbing material, an iron-based wave-absorbing material, a ceramic-based wave-absorbing material, and a composite wave-absorbing material.
12. The electromagnetic shielding film according to claim 3, wherein the first absorption layer has a thickness of: 0.1-45 μm; the thickness of the second absorption layer is as follows: 0.1-45 μm.
13. The electromagnetic shielding film according to any one of claims 1 to 4, wherein the adhesive layer comprises an adhesive layer containing conductive particles; or the like, or, alternatively,
the adhesive film layer comprises an adhesion layer without conductive particles.
14. The electromagnetic shielding film according to claim 1 or 2, further comprising an insulating layer disposed on a side of the shielding layer away from the first absorbing layer.
15. The EMI shielding film of claim 3 or 4, further comprising an insulating layer disposed on a side of said second absorbing layer remote from said shielding layer.
16. A wiring board comprising a wiring board body and the electromagnetic shielding film according to any one of claims 1 to 15, provided on the wiring board body.
17. A method for manufacturing an electro-magnetic shielding film, which is suitable for manufacturing the electro-magnetic shielding film according to any one of claims 1 to 15, the method comprising:
manufacturing and forming a shielding layer;
forming a plurality of first electromagnetic wave absorption sublayers stacked on one surface of the shielding layer; the plurality of first electromagnetic wave absorption sublayers form a first absorption layer, and the electromagnetic wave absorption rates of the plurality of first electromagnetic wave absorption sublayers are increased progressively in the vertical direction;
and forming a film adhesive layer on one surface of the first absorption layer far away from the shielding layer.
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| CN201911394605.2A CN112351665A (en) | 2019-12-30 | 2019-12-30 | Electromagnetic shielding film, circuit board and preparation method of electromagnetic shielding film |
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