Electromagnetic shielding film and circuit board

Abstract

The invention discloses an electromagnetic shielding film and a circuit board, the battery shielding film comprises a protective layer, the tensile strength of the protective layer is greater than or equal to 40MPa, and the elongation of the protective layer is greater than or equal to 50%. According to the electromagnetic shielding film, the tensile strength of the protective layer is controlled to be larger than or equal to 40 MPa, and the elongation is controlled to be larger than or equal to 50%, so that the protective layer can bear large tension and has good flexibility and ductility, the tear resistance of the electromagnetic shielding film can be effectively improved, and the service life of the electromagnetic shielding film is prolonged. Therefore, the electromagnetic shielding film can be prevented from being damaged when being pressed on an area with offset on the circuit board while ensuring the complex effect and the shielding effectiveness of pressing.

Description

Technical Field

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

[0002] In modern electronic manufacturing, the complexity of circuit boards is continuously increasing, and the functional requirements are also increasing, especially in the application scenarios of multi-layer boards and high-frequency signal transmission. In order to ensure signal integrity, reduce electromagnetic interference, and improve the reliability of electromagnetic shielding films, when it comes to the circuit board lamination process, it is a problem to be solved currently that the electromagnetic shielding film does not break when laminated on the area with height difference on the circuit board.

[0003] When the existing electromagnetic shielding film is laminated on the area with a conventional height difference (such as 20μm - 100μm) on the circuit board, it is prone to breakage, which seriously affects the signal transmission and the reliability of the electromagnetic shielding film. Summary of the Invention

[0004] Embodiments of the present invention provide an electromagnetic shielding film and a circuit board to solve the technical problem that the existing electromagnetic shielding film is prone to breakage when laminated on the area with height difference on the circuit board.

[0005] To solve the above technical problem, in the first aspect of the embodiments of the present invention, an electromagnetic shielding film is provided. The electromagnetic shielding film includes a protective layer, the tensile strength of the protective layer is greater than or equal to 40MPa, and the elongation rate of the protective layer is greater than or equal to 50%.

[0006] As a preferred solution, the protective layer includes a support layer and a filling layer, and the thickness of the support layer is less than the thickness of the filling layer.

[0007] As a preferred solution, filler particles are provided in the filling layer, and in the sliced state, within the observation range of every 400μm 2 the number of the filler particles is greater than or equal to 2.

[0008] As a preferred solution, the maximum diameter of the filler particles is 0.1μm - 4μm; wherein, the maximum diameter of the filler particles is the maximum distance between the outer contours of the filler particles.

[0009] As a preferred solution, the molecular weight of the protective layer is 700g / mol - 3000g / mol.

[0010] As a preferred solution, the electromagnetic shielding film further includes a metal layer, the metal layer is disposed on one side surface of the protective layer, and the ratio of the thickness of the metal layer to the thickness of the protective layer is 0.1 - 0.8.

[0011] As a preferred embodiment, in the sliced state, the metal layer is undulating.

[0012] As a preferred embodiment, the electromagnetic shielding film further includes an adhesive film layer, which is disposed on the surface of the metal layer facing away from the protective layer, and the ratio of the thickness of the adhesive film layer to the thickness of the metal layer is 1.2-20.

[0013] As a preferred embodiment, the tensile strength of the electromagnetic shielding film is greater than or equal to 15 MPa, and the elongation rate of the electromagnetic shielding film is greater than or equal to 10%.

[0014] As a preferred embodiment, the change rate of the tensile strength of the electromagnetic shielding film before and after curing is less than 20%; and / or,

[0015] The change rate of the elongation rate of the electromagnetic shielding film before and after curing is less than or equal to 60%.

[0016] As a preferred embodiment, conductive particles are provided in the adhesive film layer, and the metal layer is used to be electrically connected to the ground layer of the circuit board through the conductive particles.

[0017] As a preferred embodiment, the maximum diameter of the conductive particles is 0.5 μm-5 μm; wherein, the maximum diameter of the conductive particles is the maximum distance between the outer contours of the conductive particles.

[0018] As a preferred embodiment, the ratio of the maximum diameter of the conductive particles to the thickness of the metal layer is 0.1-1.5.

[0019] A second aspect of the embodiments of the present invention provides a circuit board, which includes the electromagnetic shielding film according to any one of the first aspect.

[0020] Compared with the prior art, the beneficial effect of the embodiments of the present invention is that by controlling that in the electromagnetic shielding film, the tensile strength of the protective layer is greater than or equal to 40 MPa, and the elongation rate is greater than or equal to 50%, the protective layer can withstand a large tensile force, and has good flexibility and ductility, which can effectively improve the tear resistance of the electromagnetic shielding film, so that while ensuring the conformal effect and shielding efficiency of lamination, the electromagnetic shielding film can avoid the phenomenon of breakage when laminated on the area with a step difference on the circuit board. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is a schematic structural diagram of a preferred embodiment of the electromagnetic shielding film provided by the present invention;

[0022] Figure 2 is a schematic structural diagram of another preferred embodiment of the electromagnetic shielding film provided by the present invention;

[0023] Figure 3It is a schematic structural diagram of another preferred embodiment of the electromagnetic shielding film provided by the present invention;

[0024] Figure 4 It is a schematic structural diagram of another preferred embodiment of the electromagnetic shielding film provided by the present invention;

[0025] Figure 5 It is a schematic structural diagram of another preferred embodiment of the electromagnetic shielding film provided by the present invention;

[0026] Figure 6 It is a schematic structural diagram of another preferred embodiment of the electromagnetic shielding film provided by the present invention;

[0027] Figure 7 It is a schematic structural diagram of another preferred embodiment of the electromagnetic shielding film provided by the present invention;

[0028] Among them, 1 is the electromagnetic shielding film; 101 is the protective layer; 102 is the support layer; 103 is the filling layer; 104 is the filler particles; 105 is the metal layer; 106 is the adhesive film layer; 107 is the conductive particles. Specific Embodiments

[0029] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. 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 those of ordinary skill in the art without making creative efforts fall within the scope of protection of the present invention.

[0030] In the description of this application, the terms "first", "second", "third", etc. are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first", "second", "third", etc. may explicitly or implicitly include one or more of such features. In the description of this application, unless otherwise specified, the meaning of "a plurality" is two or more.

[0031] In the description of the present application, it should be noted that unless otherwise clearly defined and limited, the terms "installed", "connected", and "coupled" should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the communication inside two components. The terms "vertical", "horizontal", "left", "right", "upper", "lower" and similar expressions used herein are only for the purpose of illustration, rather than indicating or implying that the device or component referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus 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 of the related listed items. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific circumstances.

[0032] In the description of the present application, it should be noted that unless otherwise defined, all technical and scientific terms used in the present invention have the same meanings as those commonly understood by those skilled in the technical field to which the present invention belongs. 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 application can be understood according to specific circumstances.

[0033] Please refer to Figure 1 , the first aspect of the embodiment of the present invention provides an electromagnetic shielding film 1, and the electromagnetic shielding film 1 includes a protective layer 101. The tensile strength of the protective layer 101 is greater than or equal to 40 MPa, and the elongation of the protective layer 101 is greater than or equal to 50%.

[0034] Specifically, the electromagnetic shielding film 1 in this embodiment includes a protective layer 101. As a part of the electromagnetic shielding film 1, the protective layer 101 mainly provides insulation performance and protection performance. Therefore, its tensile strength, flexibility, and ductility can affect the tear resistance of the entire electromagnetic shielding film 1. It has been found through research that when the existing electromagnetic shielding film is laminated on the area with a step on the circuit board, it is prone to breakage, which is mainly related to the low tensile strength and elongation rate of the electromagnetic shielding film. For the electromagnetic shielding film with low tensile strength and elongation rate, during the lamination and filling process, the adhesive film layer starts to flow when heated. At the bonding position between the adhesive film layer and the position with a step on the circuit board, the adhesive film layer will drive the metal layer to slide downward together, and finally tear the upper metal layer and the insulating layer together, resulting in the breakage phenomenon after the electromagnetic shielding film is laminated. Therefore, in this embodiment, by controlling the tensile strength of the protective layer 101 to be greater than or equal to 40 MPa. For example, controlling the tensile strength of the protective layer 101 to be 40 MPa, 43 MPa, 47 MPa, 50 MPa, 52 MPa, 54 MPa, 57 MPa, 59 MPa, 60 MPa, 62 MPa, 65 MPa, 67 MPa, 69 MPa, 72 MPa, 75 MPa, etc. This embodiment does not make specific limitations here, so that the protective layer 101 can withstand a large tensile force and improve the overall tensile strength of the electromagnetic shielding film 1. It can be understood that the tensile strength, also known as the ultimate tensile strength, refers to the maximum tensile stress that a material can withstand before tensile fracture. A higher tensile strength indicates that the protective layer 101 can withstand a greater tensile force. When a tensile force is applied to it, as the tensile force gradually increases, the protective layer 101 will deform. In this process, due to the high tensile strength of the protective layer 101 in this embodiment, it can withstand a greater tensile force without breaking. In addition, the area with a step on the circuit board includes the cover film step area and the etched pad step area. The step is used to describe the height difference or step height between two adjacent surfaces or components. When the electromagnetic shielding film 1 is laminated on the area with a step on the circuit board, due to the height difference, the position with a step will generate a pulling force on the electromagnetic shielding film 1. And because the protective layer 101 in this embodiment has a high tensile strength, the overall tensile performance of the electromagnetic shielding film 1 is improved, which can effectively resist this pulling force and reduce the risk of being torn.

[0035] Furthermore, in this embodiment, the elongation rate of the protective layer 101 is also controlled to be greater than or equal to 50%. For example, the elongation rate of the protective layer 101 is controlled to be 50%, 53%, 55%, 57%, 59%, 60%, 62%, 64%, 66%, 68%, 70%, etc. This embodiment does not make specific limitations here, so that the protective layer 101 has good flexibility and ductility, and can improve the overall elongation rate of the electromagnetic shielding film 1. It can be understood that the elongation rate is an important index to measure the plastic deformation ability of a material when it is stretched under force. During the process of stretching the material until it breaks, the elongation rate is calculated by the ratio of the length of the material after breaking to the original length, and is expressed as a percentage. When the electromagnetic shielding film 1 is laminated on the area with a height difference on the circuit board, due to the height difference, the position with the height difference will generate a pulling force on the electromagnetic shielding film 1. When the protective layer 101 is subjected to this pulling force, its length will change. Controlling its elongation rate to be greater than or equal to 50% means that the length of the protective layer 101 at break is at least 50% of its original length, and it can well buffer the stress through its own stretching deformation, avoiding stress concentration at a certain point and resulting in being torn. Therefore, when the electromagnetic shielding film 1 is laminated on the area with a height difference on the circuit board, the protective layer 101 can undergo a large degree of deformation as the adhesive film layer 106 and the metal layer 105 move, thus avoiding being torn due to insufficient deformation ability, effectively improving the overall tear resistance of the electromagnetic shielding film 1, and ensuring the shielding effectiveness of the electromagnetic shielding film 1.

[0036] As a preferred solution, the protective layer 101 includes a support layer 102 and a filling layer 103, and the thickness of the support layer 102 is less than the thickness of the filling layer 103.

[0037] Specifically, as Figure 2 shown, the protective layer 101 in this embodiment further includes a support layer 102 and a filling layer 103. The support layer 102 serves as the base for manufacturing the protective layer 101, which can improve the tensile strength of the protective layer 101 and at the same time enhance the toughness of the protective layer 101. During the use of the electromagnetic shielding film 1, whether it is laminated on the circuit board or subjected to external forces in the subsequent use environment, the support layer 102 can maintain the shape and structural integrity of the protective layer 101, preventing the protective layer 101 from undergoing excessive deformation or damage due to external forces. Further, the filling layer 103 can provide insulation performance and protection performance, and the support layer 102 and the filling layer 103 jointly form the overall protective layer 101 after curing.

[0038] In addition, in this embodiment, the thickness of the support layer 102 is further limited to be less than that of the filling layer 103, so as to improve the insulation performance and protection ability of the protective layer 101 while ensuring the tensile strength of the protective layer 101. Considering that the cost of the support layer 102 is usually high, after the filling layer 103 is cured, it forms an integral protective layer 101 with the support layer 102, so that the thickness of the support layer 102 can be thinner, which is beneficial to reducing the production cost.

[0039] In an alternative embodiment, the support layer 102 can be film materials such as polyimide film, polyethylene terephthalate film, and polypropylene film, which are not specifically limited in this embodiment; the filling material of the filling layer 103 can be bisphenol A epoxy resin, acrylic resin, polyester resin, etc. In addition, the resin used can also be any one or a mixture of at least two selected from epoxy resin, cyanate resin, polyphenylene ether resin, polybutadiene resin, styrene-butadiene resin, bismaleimide-triazine resin (BT), bismaleimide resin, polytetrafluoroethylene resin, polyimide resin, phenolic resin, acrylic resin, liquid crystal resin, benzoxazine resin, phenoxy resin, nitrile rubber, carboxyl-terminated nitrile rubber, or hydroxyl-terminated nitrile rubber, but not limited thereto, and all resin materials disclosed in the prior art can be used. The mixture is, for example, a mixture of epoxy resin and cyanate resin, a mixture of polyphenylene ether resin and polybutadiene resin, a mixture of styrene-butadiene resin and BT resin, a mixture of polytetrafluoroethylene resin and polyimide resin, a mixture of phenolic resin and acrylic resin, a mixture of epoxy resin, cyanate resin, and polyphenylene ether resin, polybutadiene resin, styrene-butadiene resin, and BT resin, a mixture of polytetrafluoroethylene resin, polyimide resin, phenolic resin, and acrylic resin. That is, a mixture of two or more resins can be used, which is not specifically limited in this embodiment.

[0040] As a preferred solution, filler particles 104 are provided in the filling layer 103, and in the sliced state, within the observation range of every 400 μm 2 the number of the filler particles 104 is greater than or equal to 2.

[0041] Specifically, as Figure 3 shown, further filler particles 104 are provided in the filling layer 103 in this embodiment. These filler particles 104 can play a role in dispersing stress in the filling layer 103. By limiting that in the sliced state, within the observation range of every 400 μm 2 the number of the filler particles 104 is greater than or equal to 2, for example, within every 400 μm 2The number of filler particles 104 within the observation range is 2, 3, 4, 5, 6, etc. There is no specific limitation in this embodiment. It can ensure that the filler particles 104 are dispersed in the filling layer 103, enabling the protective layer 101 to better avoid stress concentration when subjected to a pulling force and improving the tensile strength of the protective layer 101. It can be understood that the uniform dispersion of the filler can hinder the propagation path of microcracks, that is, the crack needs to bypass the filler particles 104 or consume more energy to pass through the interface, thereby improving the fracture toughness of the protective layer 101.

[0042] Optionally, the material of the filler particles 104 can be alumina, magnesia, zinc oxide or other metal oxide fillers, can also be aluminum hydroxide, magnesium hydroxide or other metal hydroxide fillers, can also be talc powder, mica powder, kaolin or other silicate fillers, can also be polystyrene microspheres, polytetrafluoroethylene, wood powder or other organic fillers, can also be core-shell structure fillers, inorganic-organic hybrid fillers or other composite fillers, or a mixture of two or more of the above fillers.

[0043] As a preferred solution, the maximum diameter of the filler particles 104 is 0.1 μm to 4 μm; wherein, the maximum diameter of the filler particles 104 is the maximum distance between the outer contours of the filler particles 104.

[0044] Specifically, this embodiment further limits the maximum diameter of the filler particles 104 to 0.1 μm to 4 μm. For example, the maximum diameter of the filler particles 104 is 0.1 μm, 0.3 μm, 0.5 μm, 0.7 μm, 0.9 μm, 1.2 μm, 1.5 μm, 1.7 μm, 2.0 μm, 2.2 μm, 2.5 μm, 2.8 μm, 3.0 μm, 3.3 μm, 3.5 μm, 3.8 μm, 4.0 μm, etc. There is no specific limitation in this embodiment. It can be understood that the filler particles 104 within this maximum diameter range can ensure the tensile strength of the protective layer 101, effectively disperse stress when subjected to a pulling force, and at the same time ensure that the maximum diameter of the filler particles 104 is not too large. If the maximum diameter of the filler particles 104 is too large, agglomeration is likely to occur, thereby destroying the uniformity of the film and resulting in the lack of film structure. Within this maximum diameter range, it can ensure that the filler particles 104 are evenly distributed within the filling layer 103, ensuring that the tear resistance performance of each part of the protective layer 101 is consistent.

[0045] It is worth noting that the maximum diameter of the filler particle 104 is the maximum distance between the outer contours of the filler particle 104. The present embodiment does not specifically limit the shape of the filler particle 104, and the filler particle 104 may be any of spherical, ellipsoidal, sheet-like, rod-like, geometrical, irregular, etc. For example, in a spherical filler particle 104, its diameter is equivalent to the maximum diameter, and in an ellipsoidal filler particle 104, its major axis is equivalent to the maximum diameter.

[0046] As a preferred solution, the molecular weight of the protective layer 101 is 700 g / mol to 3000 g / mol.

[0047] Specifically, the present embodiment further limits the molecular weight of the protective layer 101 to 700 g / mol to 3000 g / mol. For example, the molecular weight of the protective layer 101 can be 700 g / mol, 752 g / mol, 800 g / mol, 900 g / mol, 1100 g / mol, 1200 g / mol, 1500 g / mol, 1600 g / mol, 1800 g / mol, 2050 g / mol, 2420 g / mol, 2600 g / mol, 2800 g / mol, 2900 g / mol, 3000 g / mol, etc. The present embodiment does not make specific limitations here. It can be understood that within this molecular weight range, the molecular chain length in the protective layer 101 is moderate, and there is sufficient interaction force between the molecular chains. These forces can cooperate to resist deformation when the protective layer 101 is subjected to external force, so that the protective layer 101 has moderate mechanical strength. If the molecular weight is too low, the molecular chain is too short, the interaction force is weak, and the protective layer 101 is easily broken under the action of external force; if the molecular weight is too large, the molecular chain is too long, although the mechanical strength may increase, it is difficult to achieve a high elongation and the flexibility is poor.

[0048] Furthermore, within the above molecular weight range, the molecular structure in the protective layer 101 is relatively stable, and the interaction and arrangement between the molecular chains prevent the molecular movement from being too violent when heated, and can maintain a certain structural stability. When the temperature rises, the performance of the protective layer 101 will not be greatly reduced due to the rapid breakage of the molecular chains or the destruction of the interaction, so that the protective layer 101 has moderate heat resistance. Therefore, limiting the molecular weight of the protective layer 101 to 700g / mol to 3000g / mol can make the comprehensive performance of the protective layer 101 better, and the processing performance and curing performance are more balanced.

[0049] As a preferred solution, the electromagnetic shielding film 1 further comprises a metal layer 105 , which is disposed on one side surface of the protective layer 101 , and the ratio between the thickness of the metal layer 105 and the thickness of the protective layer 101 is 0.1 to 0.8.

[0050] Specifically,Figure 4 As shown in the figure, the electromagnetic shielding film 1 further includes a metal layer 105, and the metal layer 105 is disposed on one side surface of the protective layer 101. Since the protective layer 101 has an insulating effect, it is beneficial to ensure the shielding effectiveness of the metal layer 105. In addition, the protective layer 101 also has a protective effect to ensure that the metal layer 105 is not scratched or damaged during use, thereby being beneficial to maintaining the high shielding effectiveness of the metal layer 105. By defining the ratio between the thickness of the metal layer 105 and the thickness of the protective layer 101 to be 0.1 - 0.8, for example, the ratio between the thickness of the metal layer 105 and the thickness of the protective layer 101 is 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, etc., which is not specifically limited in this embodiment. It can be understood that since the thickness of the protective layer 101 is usually relatively thick, by defining the above thickness ratio range, the thickness of the metal layer 105 can be increased, which is beneficial to avoiding the fracture of the metal layer 105 when the electromagnetic shielding film 1 is pressed on the position with a step on the circuit board, and further improving the overall tear resistance of the electromagnetic shielding film 1. Preferably, the thickness of the metal layer 105 is 0.5 μm - 5 μm, and the thickness of the protective layer 101 is 5 μm - 80 μm.

[0051] In an alternative embodiment, the metal layer 105 includes any one or more of aluminum, titanium, zinc, iron, nickel, chromium, cobalt, copper, silver, and gold.

[0052] In an alternative embodiment, the tensile strength of the metal layer 105 is greater than or equal to 20 MPa, and its elongation is greater than or equal to 5%.

[0053] As a preferred solution, in the sliced state, the metal layer 105 is undulating.

[0054] Specifically, as Figure 5 shown, this embodiment further defines that in the sliced state, the metal layer 105 is undulating. It can be understood that since there are many positions with steps on the circuit board, setting the metal layer 105 in the sliced state to be undulating enables the metal layer 105 to undergo elastic deformation like a spring when subjected to the pulling force generated by the step, absorbing and dispersing stress, and significantly improving the step resistance and tear resistance of the metal layer 105.

[0055] As a preferred solution, the electromagnetic shielding film 1 further includes an adhesive film layer 106, and the adhesive film layer 106 is disposed on the side surface of the metal layer 105 facing away from the protective layer 101. The ratio between the thickness of the adhesive film layer 106 and the thickness of the metal layer 105 is 1.2 - 20.

[0056] Specifically, as Figure 6As shown in the figure, the electromagnetic shielding film 1 in this embodiment further includes an adhesive film layer 106. The adhesive film layer 106 is disposed on the surface of the metal layer 105 facing away from the protective layer 101. After the electromagnetic shielding film 1 is laminated with the circuit board, the adhesive film layer 106 is disposed between the metal layer 105 and the circuit board, which can ensure that the electromagnetic shielding film 1 can be tightly adhered after being laminated with the circuit board. In an optional embodiment, the material of the adhesive film layer 106 includes resin materials such as epoxy resin, polyurethane, and polyolefin. These materials have good flexibility and processing performance.

[0057] Further, this embodiment also defines that the ratio of the thickness of the adhesive film layer 106 to the thickness of the metal layer 105 is 1.2 to 20. For example, the ratio of the thickness of the adhesive film layer 106 to the thickness of the metal layer 105 is 1.2, 1.5, 2.1, 2.6, 3.5, 4.0, 4.5, 5.0, 5.7, 6.5, 7.0, 7.5, 8.0, 8.5, 9.5, 10.0, 11.0, 12.0, 13.0, 14.0, 15.0, 16.0, 17.0, 18.0, 19.0, 20.0, etc. This embodiment does not make specific limitations here, so as to ensure that the thickness of the adhesive film layer 106 is not too thick, and to avoid the adhesive film layer 106 piercing through the metal layer 105 when the electromagnetic shielding film 1 is laminated on the circuit board, which may affect the reliability and performance of the electromagnetic shielding film 1.

[0058] As a preferred solution, the tensile strength of the electromagnetic shielding film 1 is greater than or equal to 15 MPa, and the elongation rate of the electromagnetic shielding film 1 is greater than or equal to 10%.

[0059] Specifically, in this embodiment, by controlling the overall tensile strength of the electromagnetic shielding film 1 to be greater than or equal to 15 MPa and the elongation rate to be greater than or equal to 10%. For example, the tensile strength of the electromagnetic shielding film 1 is controlled to be 15 MPa, 18 MPa, 20 MPa, 24 MPa, 26 MPa, 29 MPa, 32 MPa, 35 MPa, 37 MPa, 41 MPa, 43 MPa, 45 MPa, 47 MPa, 50 MPa, etc., and the elongation rate is controlled to be 10%, 12%, 15%, 17%, 19%, 22%, 25%, 27%, 30%, 35%, 40%, 45%, 52%, 57%, 60%, etc. This embodiment does not make specific limitations here, so that the electromagnetic shielding film 1 has sufficient tensile strength and elongation rate, and will not be torn by the pulling force caused by the step difference when laminated on the circuit board, enabling the electromagnetic shielding film 1 to deform with the undulation and step difference of the circuit board surface, closely fitting the circuit board, ensuring the lamination conforming effect, improving the stability of the combination between the electromagnetic shielding film 1 and the circuit board, and at the same time improving the tear resistance of the electromagnetic shielding film 1.

[0060] As a preferred solution, the change rate of the tensile strength of the electromagnetic shielding film 1 before and after curing is less than 20%.

[0061] Furthermore, the elongation rate change of the electromagnetic shielding film 1 before and after curing is less than or equal to 60%.

[0062] Specifically, during the use of the circuit board, a certain pulling force is always applied to the electromagnetic shielding film 1 in the area with height difference on the circuit board. Therefore, in order to ensure the tear resistance of the electromagnetic shielding film 1 during long-term use, in this embodiment, the tensile strength change rate of the electromagnetic shielding film 1 before and after curing is further limited to be less than 20%, and the elongation rate change rate is less than or equal to 60%. For example, the tensile strength change rates of the electromagnetic shielding film 1 before and after curing are 1%, 3%, 5%, 7%, 9%, 11%, 13%, 15%, 17%, 19%, etc., and the elongation rate change rates are 5%, 8%, 12%, 15%, 19%, 22%, 25%, 30%, 35%, 42%, 48%, 52%, 55%, 60%, etc., so that the strong tear resistance of the electromagnetic shielding film 1 before curing will not be weakened too much due to the curing process. Even when it is laminated on the circuit board and used for a long time, it can always maintain strong tear resistance, significantly improving the reliability of use of the electromagnetic shielding film 1.

[0063] As a preferred solution, conductive particles 107 are provided in the adhesive film layer 106, and the metal layer 105 is used to be electrically connected to the ground layer of the circuit board through the conductive particles 107.

[0064] Specifically, as Figure 7 shown, in order to further improve the effectiveness of electromagnetic shielding, in this embodiment, conductive particles 107 are further provided in the adhesive film layer 106. It can be understood that during the lamination process of the electromagnetic shielding film 1 and the circuit board, due to the interaction of forces, when the metal layer 105 approaches the adhesive film layer 106 under pressure, the circuit board also approaches the adhesive film layer 106 under pressure, causing the adhesive film layer 106 to be squeezed by two opposite forces. Furthermore, the metal layer 105 can be connected to the ground layer of the circuit board through the conductive particles 107 in the adhesive film layer 106, ensuring the normal conduction of interfering charges and realizing the electromagnetic shielding function.

[0065] As an alternative embodiment, the conductive particles 107 include graphene nanosheets, carbon nanotubes, magnetite, silver nanowires, pure silver, silver-plated copper, silver-plated aluminum, silver-plated nickel, etc. These conductive particles 107 can significantly improve the conductivity and electromagnetic shielding efficiency of the adhesive film layer 106. For example, silver nanowires are widely used in the preparation of the electromagnetic shielding film 1 due to their excellent conductivity and transparency.

[0066] As one of the optional embodiments, the conductive particles 107 in this embodiment can be separated conductive particles or agglomerated large particle conductive particles; when the conductive particles 107 are separated conductive particles, the electrical contact area can be further increased and the uniformity of the electrical contact can be improved; while when the conductive particles 107 are agglomerated large particle conductive particles, the piercing strength can be increased.

[0067] As a preferred solution, the maximum diameter of the conductive particles 107 is 0.5 μm to 5 μm; wherein, the maximum diameter of the conductive particles 107 is the maximum distance between the outer contours of the conductive particles 107.

[0068] Specifically, this embodiment further defines that the maximum diameter of the conductive particles 107 is 0.5 μm to 5 μm. For example, the maximum diameter of the conductive particles 107 is 0.5 μm, 0.8 μm, 1.2 μm, 1.5 μm, 1.8 μm, 2.0 μm, 2.4 μm, 2.8 μm, 3.1 μm, 3.5 μm, 3.8 μm, 4.5 μm, 5.0 μm, etc. This embodiment does not make specific limitations here, so as to ensure that the maximum diameter of the conductive particles 107 is sufficient to ensure effective electrical connection between the metal layer 105 and the ground layer of the circuit board, and at the same time avoid the size of the conductive particles 107 being too large to pierce through the metal layer 105 during the pressing and use of the electromagnetic shielding film 1.

[0069] It should be noted that the maximum diameter of the conductive particles 107 is the maximum distance between the outer contours of the conductive particles 107. This embodiment does not make specific limitations on the shape of the conductive particles 107. The shape of the conductive particles 107 can be granular, flaky, strip-shaped, filamentous, reticular, spherical, ellipsoidal or other shapes. Exemplarily, in the spherical conductive particles 107, its diameter is equivalent to the maximum diameter, and in the ellipsoidal conductive particles 107, its major axis is equivalent to the maximum diameter.

[0070] As a preferred solution, the ratio of the maximum diameter of the conductive particles 107 to the thickness of the metal layer 105 is 0.1 to 1.5.

[0071] Specifically, this embodiment further defines that the ratio of the maximum diameter of the conductive particles 107 to the thickness of the metal layer 105 is 0.1 to 1.5. For example, the ratio of the maximum diameter of the conductive particles 107 to the thickness of the metal layer 105 is 0.1, 0.3, 0.5, 0.7, 0.9, 1.1, 1.3, 1.5, etc. This embodiment does not make specific limitations here, so as to further avoid the size of the conductive particles 107 being too large to pierce through the metal layer 105 during the pressing and use of the electromagnetic shielding film 1.

[0072] In the second aspect of the embodiments of the present invention, a circuit board is provided. The circuit board includes the electromagnetic shielding film according to any one of the embodiments in the first aspect.

[0073] The electromagnetic shielding film and circuit board provided by the embodiments of the present invention have the following beneficial effects, at least one of which is as follows:

[0074] (1) By controlling the tensile strength of the protective layer in the electromagnetic shielding film to be greater than or equal to 40 MPa and the elongation rate to be greater than or equal to 50%, the protective layer can withstand a large tensile force, and has good flexibility and ductility, which can effectively improve the tear resistance of the electromagnetic shielding film. Therefore, while ensuring the conformal effect and shielding efficiency of lamination, the electromagnetic shielding film can avoid damage when laminated on the area with height difference on the circuit board.

[0075] (2) Since the protective layer includes a support layer and a filling layer, filler particles are provided in the filling layer, and in the sliced state, the number of filler particles is greater than or equal to 2 within the observation range of every 400 μm, it can ensure that the filler particles are dispersedly arranged in the filling layer, so that the protective layer can better avoid stress concentration when subjected to a pulling force, and improve the tensile strength of the protective layer. 2

[0076] (3) By controlling the molecular weight of the protective layer to be 700 g / mol to 3000 g / mol, the comprehensive performance of the protective layer can be better, with moderate mechanical strength, and the processing performance and curing performance are relatively balanced.

[0077] (4) By limiting the ratio of the thickness of the metal layer to the thickness of the protective layer to be 0.1 to 0.8, the thickness of the metal layer can be increased, which is beneficial to avoiding the fracture of the metal layer when the electromagnetic shielding film is laminated on the position with height difference on the circuit board, and further improving the overall tear resistance of the electromagnetic shielding film.

[0078] (5) By limiting that in the sliced state, the metal layer is undulating, the height difference resistance performance and tear resistance ability of the metal layer can be improved.

[0079] (6) By limiting that the change rate of the tensile strength of the electromagnetic shielding film before and after curing is less than 20%, and the change rate of the elongation rate is less than or equal to 60%, the strong tear resistance of the electromagnetic shielding film before curing will not be weakened too much due to the curing process. Even when laminated on the circuit board and used for a long time, it can always maintain strong tear resistance, significantly improving the use reliability of the electromagnetic shielding film.

[0080] In order to fully reflect the tear resistance of the electromagnetic shielding film in the embodiments of the present invention, several embodiments and comparative examples are described below.

[0081] Example 1

[0082] An electromagnetic shielding film, the electromagnetic shielding film includes a protective layer, the tensile strength of the protective layer is 56 MPa, and the elongation is 55%.

[0083] Example 2

[0084] An electromagnetic shielding film, the electromagnetic shielding film includes a protective layer, the tensile strength of the protective layer is 61 MPa, and the elongation is 63%. Among them, the protective layer includes a support layer and a filling layer, filler particles are provided in the filling layer, and in the sliced state, within the observation range of every 400 μm 2 the number of filler particles is 2, and the maximum diameter of the filler particles is 0.5 μm.

[0085] Example 3

[0086] An electromagnetic shielding film, the electromagnetic shielding film includes a protective layer, the tensile strength of the protective layer is 45 MPa, and the elongation is 68%. Among them, the protective layer includes a support layer and a filling layer, filler particles are provided in the filling layer, and in the sliced state, within the observation range of every 400 μm 2 the number of filler particles is 4, and the maximum diameter of the filler particles is 1.5 μm. The molecular weight of the protective layer is 1050 g / mol.

[0087] Example 4

[0088] An electromagnetic shielding film, the electromagnetic shielding film includes a protective layer, a metal layer and an adhesive film layer, the tensile strength of the protective layer is 70 MPa, and the elongation is 75%. Among them, the protective layer includes a support layer and a filling layer, filler particles are provided in the filling layer, and in the sliced state, within the observation range of every 400 μm 2 the number of filler particles is 5, and the maximum diameter of the filler particles is 2.0 μm. The molecular weight of the protective layer is 1500 g / mol. The metal layer is disposed on one side surface of the protective layer, the adhesive film layer is disposed on the side surface of the metal layer facing away from the protective layer, the thickness of the protective layer is 45 μm, the thickness of the metal layer is 4.5 μm, and the thickness of the adhesive film layer is 36 μm. In the sliced state, the metal layer is undulating.

[0089] Example 5

[0090] An electromagnetic shielding film, the electromagnetic shielding film includes a protective layer, a metal layer and an adhesive film layer, the tensile strength of the protective layer is 72 MPa, and the elongation is 64%. Among them, the protective layer includes a support layer and a filling layer, filler particles are provided in the filling layer, and in the sliced state, within the observation range of every 400 μm 2Within the observation range, the number of filler particles is 6, and the maximum diameter of the filler particles is 2.5 μm. The molecular weight of the protective layer is 2000 g / mol. The metal layer is disposed on one surface of the protective layer, and the adhesive film layer is disposed on the surface of the metal layer facing away from the protective layer. The thickness of the protective layer is 25 μm, the thickness of the metal layer is 5 μm, and the thickness of the adhesive film layer is 60 μm. In the sliced state, the metal layer is undulating. In addition, conductive particles are provided in the adhesive film layer, and the maximum diameter of the conductive particles is 2.5 μm.

[0091] Comparative example

[0092] An electromagnetic shielding film, which includes a protective layer, a metal layer, and an adhesive film layer. The tensile strength of the protective layer is 28 MPa, and the elongation rate is 38%.

[0093] The electromagnetic shielding effectiveness and the resistance to step difference performance of the electromagnetic shielding films in Examples 1 to 5 and the comparative example were detected, and the detection results are shown in Table 1 below.

[0094] Among them, the shielding effectiveness of the electromagnetic shielding film was detected in accordance with GB / T30142-2013; for the resistance to step difference performance test, a step test board with different thickness covering films and a grounding window with the same aperture were used to measure the grounding resistance value of the electromagnetic shielding film, and the thickness of the covering film with a grounding resistance greater than 1 Ω was taken as the maximum step difference height.

[0095] Table 1 Detection results of the performance of the electromagnetic shielding film

[0096] Object to be detected Electromagnetic shielding effectiveness / dB Height tolerance of breakage / μm Example 1 68 dB 25 Example 2 71 dB 25 Example 3 73 dB 25 Example 4 69 dB 28 Example 5 78 dB 28 Comparative example < 60 dB 20

[0097] As can be seen from Table 1 above, for the electromagnetic shielding films in Examples 1 to 5, since the tensile strength of their protective layers meets the requirement of being greater than or equal to 40 MPa and the elongation rate meets the requirement of being greater than or equal to 50%, the protective layer can withstand a large tensile force, and has good flexibility and ductility, which can effectively improve the resistance to step difference performance of the electromagnetic shielding film, and at the same time can ensure the shielding effectiveness of the electromagnetic shielding film.

[0098] For the electromagnetic shielding film in the comparative example, the tensile strength of its protective layer is less than 40 MPa and the elongation rate is less than 50%, so it is prone to breakage when pressed at the position with a step difference, that is, the resistance to step difference performance is poor.

[0099] The above is the preferred embodiment of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and retouches can still be made, and these improvements and retouches are also regarded as the protection scope of the present invention.

Claims

1. An electromagnetic shielding film, characterized in that, The electromagnetic shielding film includes a protective layer, the tensile strength of the protective layer is greater than or equal to 40 MPa, and the elongation of the protective layer is greater than or equal to 50%.

2. The electromagnetic shielding film according to claim 1, wherein The protective layer includes a support layer and a filling layer, and the thickness of the support layer is less than the thickness of the filling layer.

3. The electromagnetic shielding film according to claim 2, wherein The filling layer is provided with filler particles, and in the sliced state, within the observation range of every 400 μm 2 , the number of the filler particles is greater than or equal to 2.

4. The electromagnetic shielding film according to claim 3, wherein The maximum diameter of the filler particles is 0.1 μm to 4 μm; wherein, the maximum diameter of the filler particles is the maximum distance between the outer contours of the filler particles.

5. The electromagnetic shielding film according to claim 1, wherein The molecular weight of the protective layer is 700 g / mol to 3000 g / mol.

6. The electromagnetic shielding film according to claim 1, wherein The electromagnetic shielding film further includes a metal layer, the metal layer is disposed on one surface of the protective layer, and the ratio of the thickness of the metal layer to the thickness of the protective layer is 0.1 to 0.

8.

7. The electromagnetic shielding film according to claim 6, characterized in that, In the sliced state, the metal layer is undulating.

8. The electromagnetic shielding film according to claim 6, wherein, The electromagnetic shielding film further includes an adhesive film layer, the adhesive film layer is disposed on the surface of the metal layer facing away from the protective layer, and the ratio of the thickness of the adhesive film layer to the thickness of the metal layer is 1.2 to 20.

9. The electromagnetic shielding film according to any one of claims 1 to 8, characterized in that, The tensile strength of the electromagnetic shielding film is greater than or equal to 15 MPa, and the elongation of the electromagnetic shielding film is greater than or equal to 10%.

10. The electromagnetic shielding film according to claim 9, characterized in that, The change rate of the tensile strength of the electromagnetic shielding film before and after curing is less than 20%; and / or, The change rate of the elongation of the electromagnetic shielding film before and after curing is less than or equal to 60%.

11. The electromagnetic shielding film according to claim 8, wherein, Conductive particles are provided in the adhesive film layer, and the metal layer is used to be electrically connected to the ground layer of the circuit board through the conductive particles.

12. The electromagnetic shielding film according to claim 11, wherein The maximum diameter of the conductive particles is 0.5 μm to 5 μm; wherein, the maximum diameter of the conductive particles is the maximum distance between the outer contours of the conductive particles.

13. The electromagnetic shielding film according to claim 12, wherein The ratio of the maximum diameter of the conductive particles to the thickness of the metal layer is 0.1 to 1.

5.

14. A circuit board, characterized in that, The circuit board includes the electromagnetic shielding film according to any one of claims 1 to 13.

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