Electromagnetic shielding film and circuit board

Abstract

The invention discloses an electromagnetic shielding film and a circuit board. The electromagnetic shielding film comprises an adhesive film layer, and after the electromagnetic shielding film is pressed on the circuit board, the gram weight W of the adhesive film layer and the impedance change rate delta Z meet the formula: delta Z = A / W + B, wherein A and B are constants, the value range of A is 1-10, the value range of B is 2-30, the unit of gram weight W is g / dm < 2 >, and calculation is dimensionless. The electromagnetic shielding film meeting the relation can be obtained by utilizing the relation between the gram weight of the adhesive film layer and the impedance change rate, so that a relatively small impedance change rate is achieved after lamination, impedance matching of the electromagnetic shielding film to a circuit board is realized, and the transmission efficiency of signals and the overall performance of equipment are ensured.

Description

Technical Field

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

[0002] With the rapid development of the electronics industry, electronic products are further developing towards miniaturization, light weight, and high-density assembly, which has greatly promoted the development of flexible circuit boards, thus realizing the integration of component devices and wire connections. Flexible circuit boards can be widely used in industries such as mobile phones, liquid crystal displays, communications, and aerospace. Driven by the international market, functional flexible circuit boards dominate the flexible circuit board market, and an important index for evaluating the performance of functional flexible circuit boards is electromagnetic shielding (abbreviated as EMI Shielding).

[0003] With the integration of functions of communication devices such as mobile phones, the internal components thereof have become extremely high-frequency and high-speed. For example, in addition to the original audio transmission function, the camera function has become an essential function of mobile phones, and WLAN (Wireless Local Area Networks), GPS (Global Positioning System), and Internet access functions have been popularized. Coupled with the integration of future sensing components, the trend of components becoming extremely high-frequency and high-speed is even more inevitable. Driven by the trend of high frequency and high speed, problems such as electromagnetic interference inside and outside components, signal attenuation during transmission, insertion loss, and jitter have gradually become serious.

[0004] Existing circuit boards often preset impedance values, which is crucial for the efficient transmission of high-speed signal lines and radio frequency lines. However, after the existing electromagnetic shielding film is laminated on the circuit board, the impedance of the circuit board changes greatly, resulting in non-matching, signal reflection, energy loss, and a decrease in signal integrity, affecting the overall performance of the device. Summary of the Invention

[0005] The present invention provides an electromagnetic shielding film and a circuit board, which achieve a smaller impedance change rate after lamination, realize the impedance matching of the electromagnetic shielding film to the circuit board, and ensure the signal transmission efficiency and the overall performance of the device.

[0006] In a first aspect, an embodiment of the present invention provides an electromagnetic shielding film, including: a glue film layer, and after the electromagnetic shielding film is laminated on a circuit board, the grammage W of the glue film layer and the impedance change rate ΔZ satisfy:

[0007] ΔZ = -A*W + B;

[0008] Among them, A and B are constants, and the value range of A is 0.0005 - 0.005, the value range of B is 0.1 - 1. The unit of grammage W is g / dm2, and the calculation is dimensionless.

[0009] Optionally, the value range of A is 0.001 - 0.004; and / or, the value range of B is 0.15 - 0.5.

[0010] Optionally, the electromagnetic shielding film further includes a shielding layer, the shielding layer is disposed on one side of the adhesive film layer, and the thickness d of the shielding layer and the impedance change rate ΔZ satisfy:

[0011] ΔZ = C * d + D;

[0012] Among them, C and D are constants, and the value range of C is -0.005 - 0.15, the value range of D is 0.01 - 0.5. The unit of thickness d is μm, and the calculation is dimensionless.

[0013] Optionally, the thickness range of the shielding layer is 0.5 - 8 μm.

[0014] Optionally, at least one side of the shielding layer is provided with conductive protrusions.

[0015] Optionally, the relative dielectric constant Δε of the adhesive film layer is 3 - 6.

[0016] Optionally, the relative dielectric constant Δε of the adhesive film layer and the impedance change rate ΔZ satisfy:

[0017]

[0018] Among them, E and F are constants, the value range of E is 0.02 - 0.5, the value range of F is -1 - -0.01, and the calculation is dimensionless.

[0019] Optionally, conductive particles are provided in the adhesive film layer, and in unit volume, the weight ratio of the conductive particles to the weight of the adhesive film layer is 0.01 - 0.6.

[0020] Optionally, the maximum width of the conductive particles is 0.5 - 5 μm.

[0021] Optionally, the electromagnetic shielding film further includes a protective layer, and the protective layer is disposed on the side of the shielding layer facing away from the adhesive film layer.

[0022] In a second aspect, an embodiment of the present invention provides a circuit board, and the circuit board includes the electromagnetic shielding film according to any embodiment of the present invention.

[0023] In the embodiments of the present invention, by establishing a functional relationship between the grammage of the adhesive film layer and the impedance change rate of the electromagnetic shielding film, and using the relationship between the grammage of the adhesive film layer and the impedance change rate, the grammage of the adhesive film layer can be adjusted according to specific requirements during design, so as to obtain an electromagnetic shielding film with a smaller impedance change rate after lamination, realize the impedance matching of the electromagnetic shielding film to the circuit board, and ensure the signal transmission efficiency and the overall performance of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 FIG. is a schematic structural diagram of an electromagnetic shielding film provided by an embodiment of the present invention;

[0025] Figure 2 FIG. is a schematic structural diagram of another electromagnetic shielding film provided by an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0026] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Apparently, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0027] The designed impedance of the existing shielding film is matched with the designed impedance of the circuit board. The designed impedance of the circuit board is the comprehensive resistance of the circuit to alternating current, including the influence of resistance, inductance, and capacitance effects. Maintaining a constant characteristic impedance (such as 50Ω or 100Ω) is crucial for the efficient transmission of high-speed signal lines and radio frequency lines. However, after the existing electromagnetic shielding film is laminated on the circuit board, the impedance of the circuit board changes greatly, resulting in inability to match, thus exceeding the requirements of quality management and unable to be applied in the terminal.

[0028] In view of this, the embodiments of the present invention provide an electromagnetic shielding film, Figure 1 FIG. is a schematic structural diagram of an electromagnetic shielding film provided by an embodiment of the present invention. Refer to Figure 1 , including: an adhesive film layer 110. After the electromagnetic shielding film is laminated on the circuit board, the grammage W of the adhesive film layer 110 and the impedance change rate ΔZ satisfy:

[0029] ΔZ = -A * W + B;

[0030] wherein, A and B are constants, the value range of A is 0.0005 - 0.005, the value range of B is 0.1 - 1, the unit of the grammage W is g / dm 2 , and the calculation is dimensionless.

[0031] Specifically, the electromagnetic shielding film includes a laminated adhesive film layer 110, a shielding layer 120, and an insulating layer 140. Among them, the electromagnetic shielding film is connected to the circuit board by pressing the adhesive film layer 110. The adhesive film layer 110 can have an adhesive effect and can be a modified epoxy resin type, an acrylic acid type, a modified rubber type, or a modified thermoplastic polyimide type. The shielding layer 120 has a conductive material. For example, the shielding layer 120 can be a metal layer or a material layer with a conductive coating on the surface, and the shielding layer 120 can play an electromagnetic shielding role. The insulating layer 140 covers the surface of the shielding layer 120, and the insulating layer 140 can be a resin material, such as acrylic resin or polyester resin, etc. The impedance change rate can be understood as the relative change amount of the impedance of the electromagnetic shielding film before and after being pressed on the circuit board (PCB). The grammage of the adhesive film layer 110 refers to the mass of the adhesive film layer 110 material per unit volume. Through research, it is found that the grammage of the adhesive film layer 110 in the electromagnetic shielding film can affect the impedance change rate of the electromagnetic shielding film. When the grammage of the adhesive film layer 110 is relatively large, the change rate of the adhesive film layer 110 to the impedance is smaller. This is because the material of the adhesive film layer 110 with a high grammage will affect the thickness of the electromagnetic shielding film. When the grammage of the adhesive film layer 110 increases, the thickness of the adhesive film layer 110 increases, which can effectively reduce the penetration depth of electromagnetic waves, reduce impedance mutation, and thus achieve impedance reduction and reduce signal reflection and loss caused by impedance mismatch. When the grammage of the adhesive film layer 110 increases, it can also increase the overall thickness of the electromagnetic shielding film, which also helps to enhance the electromagnetic shielding effect of the electromagnetic shielding film. A thicker adhesive film layer 110 can provide better electromagnetic shielding and reduce the influence of external electromagnetic interference on the circuit board. Therefore, in the embodiment of the present invention, by establishing the relationship between the impedance change rate of the circuit board and the grammage of the adhesive film layer 110, the grammage of the adhesive film layer 110 can be adjusted according to specific requirements during design. Among them, in the embodiment of the present invention, A and B are constants, and the value range of A is 0.0005 - 0.005, and the value range of B is 0.1 - 1. According to the relationship between the impedance change rate and the grammage of the adhesive film layer 110, the plane region range of the impedance change rate and the grammage of the adhesive film layer 110 distributed in the numerical coordinate system can be obtained. Further, the value range of A is 0.001 - 0.004; and / or, the value range of B is 0.15 - 0.5. For example, A can be 0.001, 0.002, 0.003, or 0.004, and B can be 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, or 0.5, etc., but not limited to the above values. The unlisted values are also applicable. In this way, the fluctuation of the impedance change rate obtained will be smaller, so as to obtain an electromagnetic shielding film, achieving a smaller impedance change rate after pressing, realizing the impedance matching of the electromagnetic shielding film to the circuit board, and ensuring the signal transmission efficiency and the overall performance of the device.

[0032] In the embodiment of the present invention, by establishing a functional relationship between the gram weight of the adhesive film layer 110 and the impedance change rate of the electromagnetic shielding film, and using the relationship between the gram weight of the adhesive film layer 110 and the impedance change rate, the gram weight of the adhesive film layer 110 can be adjusted according to specific requirements during design, so as to obtain an electromagnetic shielding film with a smaller impedance change rate after lamination, realizing the impedance matching of the electromagnetic shielding film to the circuit board and ensuring the signal transmission efficiency and the overall performance of the device.

[0033] Furthermore, increasing the gram weight of the adhesive film layer 110 will also affect the relative permittivity Δε of the adhesive film layer 110. In the embodiment of the present invention, the relative permittivity Δε of the adhesive film layer 110 and the impedance change rate ΔZ satisfy:

[0034]

[0035] wherein, E and F are constants, the value range of E is 0.02 to 0.5, the value range of F is -1 to -0.01, and the calculation is dimensionless.

[0036] Specifically, the permittivity of the electromagnetic shielding film will significantly affect the impedance of the printed circuit board (PCB). The impedance mainly depends on the electric field distribution between the conductors and the surrounding medium in the PCB, and the permittivity determines the propagation speed and coupling strength of the electric field. When the permittivity increases, the impedance can be reduced. When the permittivity of the electromagnetic shielding film is relatively high, the propagation speed of the electric field in the medium decreases, resulting in an enhanced capacitance effect, thereby reducing the impedance and increasing the impedance change rate. An electromagnetic shielding film with a lower permittivity will reduce the coupling strength of the electric field, decrease the capacitance of the signal line, thereby increasing the impedance and reducing the impedance change rate. By adjusting the relative permittivity Δε of the adhesive film layer 110, the impedance matching with the circuit board can be optimized. Therefore, in the embodiment of the present invention, by establishing the relationship between the impedance change rate and the relative permittivity Δε of the adhesive film layer 110, the relative permittivity Δε of the adhesive film layer 110 can be adjusted according to specific requirements during design, so that the electromagnetic shielding film is within a suitable permittivity range and the impedance change rate is stabilized within a reasonable range. Among them, in the embodiment of the present invention, E and F are constants, the value range of E is 0.02 to 0.5, the value range of F is -1 to -0.01. According to the relationship between the impedance change rate and the relative permittivity Δε of the adhesive film layer 110, the plane region range of the distribution of the impedance change rate and the relative permittivity Δε of the adhesive film layer 110 in the numerical coordinate system can be obtained. Furthermore, the relative permittivity Δε of the adhesive film layer 110 can be 3 - 6. For example, it can be 3, 4, 5 or 6, etc., but not limited to the above values, and the unlisted values are also applicable. The impedance change rate obtained in this way will be smaller, so as to obtain an electromagnetic shielding film, realizing a smaller impedance change rate after lamination, realizing the impedance matching of the electromagnetic shielding film to the circuit board, and ensuring the signal transmission efficiency and the overall performance of the device.

[0037] Continue to refer to Figure 1 The electromagnetic shielding film further includes a shielding layer 120. The shielding layer 120 is disposed on one side of the adhesive film layer 110, and the thickness d of the shielding layer 120 and the impedance change rate ΔZ satisfy:

[0038] ΔZ = C*d + D;

[0039] wherein, C and D are constants, the value range of C is -0.005 to 0.15, the value range of D is 0.01 to 0.5, the unit of the thickness d is μm, and the calculation is dimensionless.

[0040] Specifically, the shielding layer 120 has a conductive material. For example, the shielding layer 120 can be a metal layer or a material layer with a conductive coating on the surface. The shielding layer 120 can play an electromagnetic shielding role. In the embodiment of the present invention, exemplarily, one shielding layer 120 is provided. In other embodiments, the total number of shielding layers 120 can also be 3 layers, 4 layers or other numbers of layers. When the thickness of the shielding layer 120 is relatively thin, electromagnetic waves are easily transmitted through the shielding layer 120. At this time, the shielding effectiveness of the electromagnetic shielding film is relatively low, and the impedance change of the circuit board is relatively large. When the thickness of the shielding layer 120 is relatively thick, the shielding layer 120 can provide more absorption and reflection surfaces. The impedance of the shielding layer 120 tends to be stable, and the impedance change of the circuit board will also be relatively small. By adjusting the thickness d of the shielding layer 120, the impedance matching between the electromagnetic shielding film and the circuit board can be optimized. Therefore, in the embodiment of the present invention, by establishing the relationship between the impedance change rate and the thickness d of the shielding layer 120, the thickness d of the shielding layer 120 can be adjusted according to specific requirements during design, so that the impedance change rate of the electromagnetic shielding film is stable within a reasonable range within the appropriate thickness d range of the shielding layer 120. Among them, in the embodiment of the present invention, C and D are constants, the value range of C is -0.005 to 0.15, the value range of D is 0.01 to 0.5. According to the relationship between the impedance change rate and the thickness d of the shielding layer 120, the plane region range of the impedance change rate and the thickness d of the shielding layer 120 distributed in the numerical coordinate system can be obtained. Further, the thickness d of the shielding layer 120 can be 0.1 - 8 μm. For example, it can be 0.1 μm, 0.2 μm, 0.4 μm, 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm or 8 μm, etc., but not limited to the above values. The values not listed are also applicable, and the resulting impedance change rate will have less volatility, thereby obtaining an electromagnetic shielding film, achieving a smaller impedance change rate after lamination, realizing the impedance matching of the electromagnetic shielding film to the circuit board, and ensuring the signal transmission efficiency and the overall performance of the device.

[0041] Refer to Figure 1, at least one side of the shielding layer 120 is provided with a conductive protrusion. Specifically, at least one side of the shielding layer 120 is provided with a conductive protrusion. In the embodiment of the present invention, the conductive protrusion is arranged on the side of the shielding layer 120 close to the adhesive film layer 110. The conductive protrusion can generate needle-like protrusions through a magnetron sputtering process. When the electromagnetic shielding film is pressed, the conductive protrusion will squeeze and pierce the adhesive film layer 110, thereby achieving the effect of grounding connection with the circuit board, with lower production cost, higher shielding efficiency, and at the same time, significantly reducing the attenuation of high-frequency signals.

[0042] Combined with the above embodiments, Figure 2 FIG. is a schematic structural diagram of another electromagnetic shielding film provided by the embodiment of the present invention. Refer to Figure 2 , conductive particles 111 are provided in the adhesive film layer 110, and in a unit volume, the weight ratio of the conductive particles 111 to the weight of the adhesive film layer 110 is 0.01 - 0.6.

[0043] Specifically, a certain proportion of conductive particles 111 are filled in the adhesive film layer 110. The conductive particles 111 can be metal flakes, metal powders, metal fibers, etc. The shielding layer 120 can be grounded to the circuit board through the conductive particles 111, and the conductive particles 111 are used to optimize the current transmission path to conduct the electromagnetic interference signal on the shielding layer 120.

[0044] Furthermore, in a unit volume, the unit volume can be a preset specified volume, such as 1μm 3 , 4μm 3 , 10μm 3 , 15μm 3 , 50μm 3 , 65μm 3 , 90μm 3 , 105μm 3etc., but not limited to the above values, and the unlisted values are also applicable. The weight ratio of the conductive particles 111 to the adhesive film layer 110 needs to be within a preset range. If the weight ratio of the conductive particles 111 to the adhesive film layer 110 is small, the conductive effect of the conductive particles 111 in the adhesive film layer 110 is poor, the grounding resistance is too large, and the design requirements of the electromagnetic shielding film are not met. If the weight ratio of the conductive particles 111 to the adhesive film layer 110 is large, it means that the number of conductive particles 111 distributed in the adhesive film layer 110 is large, while the material of the adhesive film layer 110 is small. When coating the adhesive film layer 110, under the action of gravity, the conductive particles 111 are likely to settle in the substrate, resulting in stacking in a certain area, leading to uneven distribution of the conductive particles 111 in the adhesive film layer 110, and when the electromagnetic shielding film is bent, a large bending stress is easily formed here, resulting in bending damage. In the embodiment of the present invention, the weight ratio of the conductive particles 111 to the adhesive film layer 110 is distributed at any value between 0.01 and 0.6. For example, the weight ratio of the two can be 0.01, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55 or 0.6, etc., but not limited to the above values, and the unlisted values are also applicable. By filling the conductive particles 111 within the weight ratio range in the adhesive film layer 110, a uniform continuous conductive network can be formed in the adhesive film layer 110, thereby significantly reducing the resistivity, and it is beneficial to the uniform distribution of the conductive particles 111 in the adhesive film layer 110, reducing the grounding resistance. The conductive particles 111 can also support the adhesive film layer 110, avoid stress concentration after the adhesive film layer 110 is cured, and improve the bending performance of the electromagnetic shielding film.

[0045] Optionally, in the cross-sectional state of any slice, the maximum width of the conductive particles 111 is 0.5 - 5 μm. That is to say, reference points are taken on the boundary of the conductive particles 111 in the cross-sectional state, and the range of the maximum width between the two reference points is 0.5 - 5 μm, where the cross-sectional state is any slice direction along the thickness direction of the electromagnetic shielding film. Within this width range, the conductive particles 111 can maintain good conductive performance. Wider particles can provide more conductive channels, which is beneficial to the transmission of current, thereby improving the overall conductivity of the material. The width range of 0.5 - 5 μm makes the filling rate of the conductive particles 111 in the adhesive film layer 110 moderate. Within this width range, the agglomeration phenomenon between particles can be reduced, the dispersion uniformity of the conductive particles 111 in the adhesive film layer 110 can be improved, thereby optimizing the current transmission path, enabling the current to flow in a specific direction, and thus producing a film with more uniform electromagnetic shielding performance, and this uniformity is particularly important for high-performance electronic devices.

[0046] Continue to refer to Figure 1, the electromagnetic shielding film further includes a protective layer 130 disposed on a side of the shielding layer 120 facing away from the adhesive film layer 110. Specifically, the protective layer 130 can play an insulating and protective role, preventing the shielding layer 120 from being damaged when the electromagnetic shielding film is collided or scratched, and reducing the shielding efficiency.

[0047] Optionally, the material of the protective layer 130 can be bisphenol A epoxy resin, acrylic resin, polyester resin, etc. In addition, the resin used can also be any one or at least two mixtures 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 mixtures include, 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, mixtures of two or more resins can be used.

[0048] The electromagnetic shielding film further includes a release layer 150 disposed on a side of the adhesive film layer 110 facing away from the shielding layer 120. Specifically, the release layer 150 can prevent the adhesive film layer 110 from being damaged when collided or scratched. Before lamination, the release layer 150 is removed and the electromagnetic shielding film is laminated onto the circuit board.

[0049] An embodiment of the present invention also provides a circuit board, which includes a printed circuit board, a PCB, etc., and has electronic components on the circuit board. The electromagnetic shielding film of any embodiment of the present invention is attached to the surface of the electronic components. Because it includes the electromagnetic shielding film of any embodiment of the present invention, it has the same beneficial effects and will not be elaborated here.

[0050] The present invention also provides a comparative verification of the relationship between the gram weight of the adhesive film layer of the electromagnetic shielding film and the impedance change rate.

[0051] Example 1

[0052] This embodiment provides an electromagnetic shielding film, including: an adhesive film layer 110, a shielding layer 120 and an insulating layer 140 stacked. The shielding layer 120 is a non-woven fabric of sputtered metal material, and the gram weight W of the adhesive film layer 110 is selected as 6.2 g / dm 2, the impedance change rate ΔZ can be calculated to be 0.3705988 based on the impedance before and after lamination. Among them, the gram weight W of the adhesive film layer 110 of the electromagnetic shielding film and the impedance change rate ΔZ satisfy: ΔZ = -0.0015W + 0.3826;

[0053] Example 2

[0054] This example provides an electromagnetic shielding film, including: an adhesive film layer 110, a shielding layer 120, and an insulating layer 140 which are stacked. The shielding layer 120 is a non-woven fabric of sputtered metal material, and the gram weight W of the adhesive film layer 110 is selected to be 12.5 g / dm 2 , the impedance change rate ΔZ can be calculated to be 0.3656225 based on the impedance before and after lamination. Among them, the gram weight W of the adhesive film layer 110 of the electromagnetic shielding film and the impedance change rate ΔZ satisfy ΔZ = -0.0015W + 0.3826;

[0055] Example 3

[0056] This example provides an electromagnetic shielding film, including: an adhesive film layer 110, a shielding layer 120, and an insulating layer 140 which are stacked. The shielding layer 120 is a non-woven fabric of sputtered metal material, and the gram weight W of the adhesive film layer 110 is selected to be 18.4 g / dm 2 , the impedance change rate ΔZ can be calculated to be 0.3519952 based on the impedance before and after lamination. Among them, the gram weight W of the adhesive film layer 110 of the electromagnetic shielding film and the impedance change rate ΔZ satisfy ΔZ = -0.0015W + 0.3826;

[0057] Example 4

[0058] This example provides an electromagnetic shielding film, including: an adhesive film layer 110, a shielding layer 120, and an insulating layer 140 which are stacked. The shielding layer 120 is a non-woven fabric of sputtered metal material, and the gram weight W of the adhesive film layer 110 is selected to be 24.7 g / dm 2 , the impedance change rate ΔZ can be calculated to be 0.3491121 based on the impedance before and after lamination. Among them, the gram weight W of the adhesive film layer 110 of the electromagnetic shielding film and the impedance change rate ΔZ satisfy ΔZ = -0.0015W + 0.3826;

[0059] Example 5

[0060] This example provides an electromagnetic shielding film, including: an adhesive film layer 110, a shielding layer 120, and an insulating layer 140 which are stacked. The shielding layer 120 is a non-woven fabric of sputtered metal material, and the gram weight W of the adhesive film layer 110 is selected to be 31 g / dm 2, the impedance change rate ΔZ can be calculated to be 0.3342646 based on the impedance before and after lamination. Among them, the grammage W of the adhesive film layer 110 of the electromagnetic shielding film and the impedance change rate ΔZ satisfy ΔZ = -0.0015W + 0.3826;

[0061] Example 6

[0062] This example provides an electromagnetic shielding film, including: an adhesive film layer 110, a shielding layer 120, and an insulating layer 140 that are stacked. The shielding layer 120 is a non-woven fabric of sputtered metal material, and the grammage W of the adhesive film layer 110 is selected as 36.8 g / dm 2 , the impedance change rate ΔZ can be calculated to be 0.3491121 based on the impedance before and after lamination. Among them, the grammage W of the adhesive film layer 110 of the electromagnetic shielding film and the impedance change rate ΔZ satisfy ΔZ = -0.0015W + 0.3826;

[0063] Example 7

[0064] This example provides an electromagnetic shielding film, including: an adhesive film layer 110, a shielding layer 120, and an insulating layer 140 that are stacked. The shielding layer 120 is a non-woven fabric of sputtered metal material, and the grammage W of the adhesive film layer 110 is selected as 42.9 g / dm 2 , the impedance change rate ΔZ can be calculated to be 0.3137744 based on the impedance before and after lamination. Among them, the grammage W of the adhesive film layer 110 of the electromagnetic shielding film and the impedance change rate ΔZ satisfy ΔZ = -0.0015W + 0.3826;

[0065] Comparative Example 1

[0066] This example provides an electromagnetic shielding film, including: an adhesive film layer 110, a shielding layer 120, and an insulating layer 140 that are stacked. The shielding layer 120 is a non-woven fabric of sputtered metal material, and the grammage W of the adhesive film layer 110 is selected as 6.2 g / dm 2 , the impedance change rate ΔZ can be calculated to be 1.45213 based on the impedance before and after lamination. Among them, the grammage W of the adhesive film layer 110 of the electromagnetic shielding film and the impedance change rate ΔZ satisfy ΔZ = -0.0065W + 1.5121;

[0067] Comparative Example 2

[0068] This example provides an electromagnetic shielding film, including: an adhesive film layer 110, a shielding layer 120, and an insulating layer 140 that are stacked. The shielding layer 120 is a non-woven fabric of sputtered metal material, and the grammage W of the adhesive film layer 110 is selected as 18.4 g / dm 2, the impedance change rate ΔZ can be calculated to be 1.40295 based on the impedance before and after lamination. Among them, the gram weight W of the adhesive film layer 110 of the electromagnetic shielding film and the impedance change rate ΔZ satisfy ΔZ = -0.0065W + 1.5121;

[0069] Table 1 Test parameters of each example and comparative example

[0070]

[0071] According to the comparison data, the impedance change rate ΔZ in Examples 1-7 of the present invention is between 0.3 and 0.38. An electromagnetic shielding film with a smaller impedance change rate after lamination can be obtained, which can meet the impedance matching of the circuit board.

[0072] The present invention also provides a comparative verification of the relationship between the relative dielectric constant and the impedance change rate of the adhesive film layer 110 of the electromagnetic shielding film.

[0073] Example 8

[0074] This example provides an electromagnetic shielding film, including: an adhesive film layer 110, a shielding layer 120, and an insulating layer 140 that are stacked. The shielding layer 120 is a non-woven fabric of a sputtered metal material. The relative dielectric constant Δε of the adhesive film layer 110 is selected to be 3.03. The impedance change rate ΔZ can be calculated to be 0.177521 based on the impedance before and after lamination. Among them, the relative dielectric constant Δε of the adhesive film layer 110 of the electromagnetic shielding film and the impedance change rate ΔZ satisfy:

[0075] Example 9

[0076] This example provides an electromagnetic shielding film, including: an adhesive film layer 110, a shielding layer 120, and an insulating layer 140 that are stacked. The shielding layer 120 is a non-woven fabric of a sputtered metal material. The relative dielectric constant Δε of the adhesive film layer 110 is selected to be 4.88. The impedance change rate ΔZ can be calculated to be 0.235632 based on the impedance before and after lamination. Among them, the relative dielectric constant Δε of the adhesive film layer 110 of the electromagnetic shielding film and the impedance change rate ΔZ satisfy:

[0077] Comparative Example 3

[0078] This example provides an electromagnetic shielding film, including: an adhesive film layer 110, a shielding layer 120, and an insulating layer 140 that are stacked. The shielding layer 120 is a non-woven fabric of a sputtered metal material. The relative dielectric constant Δε of the adhesive film layer 110 is selected to be 2.1. The impedance change rate ΔZ can be calculated to be 0.758572 based on the impedance before and after lamination. Among them, the relative dielectric constant Δε of the adhesive film layer 110 of the electromagnetic shielding film and the impedance change rate ΔZ satisfy:

[0079] Comparative Example 4

[0080] This embodiment provides an electromagnetic shielding film, which includes: a film adhesive layer 110, a shielding layer 120, and an insulating layer 140 that are stacked. The shielding layer 120 is a non-woven fabric of sputtered metal material. The relative dielectric constant Δε of the film adhesive layer 110 is selected to be 7.3. According to the impedance before and after lamination, the impedance change rate ΔZ can be calculated to be 1.873488. Among them, the relative dielectric constant Δε and the impedance change rate ΔZ of the film adhesive layer 110 of the electromagnetic shielding film satisfy:

[0081] Table 1 Test parameters of each embodiment and comparative example

[0082]

[0083]

[0084] According to the comparison data, it can be known that in Embodiments 8-9 of the present invention, the impedance change rate ΔZ can be controlled within 0.1-0.3, and an electromagnetic shielding film with a relatively small impedance change rate after lamination can be obtained, which can meet the impedance matching of the circuit board. Among them, the relative dielectric constant Δε of the film adhesive layer 110 is 3-6. Within this range, the stability of the impedance change rate can be improved, and the grounding effect can be ensured.

[0085] The present invention also provides a comparative verification of the relationship between the thickness of the shielding layer 120 of the electromagnetic shielding film and the impedance change rate.

[0086] Embodiment 10

[0087] This embodiment provides an electromagnetic shielding film, which includes: a film adhesive layer 110, a shielding layer 120, and an insulating layer 140 that are stacked. The shielding layer 120 is a non-woven fabric of sputtered metal material. The thickness d of the shielding layer 120 is selected to be 0.3 μm. According to the impedance before and after lamination, the impedance change rate ΔZ can be calculated to be 0.1333. Among them, the thickness d of the shielding layer 120 of the electromagnetic shielding film and the impedance change rate ΔZ satisfy: ΔZ = 0.0156 * d + 0.1424;

[0088] Embodiment 11

[0089] This embodiment provides an electromagnetic shielding film, which includes: a film adhesive layer 110, a shielding layer 120, and an insulating layer 140 that are stacked. The shielding layer 120 is a non-woven fabric of sputtered metal material. The thickness d of the shielding layer 120 is selected to be 1.5 μm. According to the impedance before and after lamination, the impedance change rate ΔZ can be calculated to be 0.1816. Among them, the thickness d of the shielding layer 120 of the electromagnetic shielding film and the impedance change rate ΔZ satisfy: ΔZ = 0.0156 * d + 0.1424;

[0090] Example 12

[0091] This example provides an electromagnetic shielding film, including: a laminated adhesive film layer 110, a shielding layer 120, and an insulating layer 140. The shielding layer 120 is a non-woven fabric of sputtered metal material. The thickness d of the shielding layer 120 is selected as 2 μm. According to the impedance before and after lamination, the impedance change rate ΔZ can be calculated to be 0.1812. Among them, the thickness d of the shielding layer 120 of the electromagnetic shielding film and the impedance change rate ΔZ satisfy: ΔZ = 0.0156 * d + 0.1424

[0092] Example 13

[0093] This example provides an electromagnetic shielding film, including: a laminated adhesive film layer 110, a shielding layer 120, and an insulating layer 140. The shielding layer 120 is a non-woven fabric of sputtered metal material. The thickness d of the shielding layer 120 is selected as 3 μm. According to the impedance before and after lamination, the impedance change rate ΔZ can be calculated to be 0.1873. Among them, the thickness d of the shielding layer 120 of the electromagnetic shielding film and the impedance change rate ΔZ satisfy: ΔZ = 0.0156 * d + 0.1421;

[0094] Example 14

[0095] This example provides an electromagnetic shielding film, including: a laminated adhesive film layer 110, a shielding layer 120, and an insulating layer 140. The shielding layer 120 is a non-woven fabric of sputtered metal material. The thickness d of the shielding layer 120 is selected as 3.5 μm. According to the impedance before and after lamination, the impedance change rate ΔZ can be calculated to be 0.1879. Among them, the thickness d of the shielding layer 120 of the electromagnetic shielding film and the impedance change rate ΔZ satisfy: ΔZ = 0.0156 * d + 0.1424;

[0096] Comparative Example 5

[0097] This example provides an electromagnetic shielding film, including: a laminated adhesive film layer 110, a shielding layer 120, and an insulating layer 140. The shielding layer 120 is a non-woven fabric of sputtered metal material. The thickness d of the shielding layer 120 is selected as 9 μm. According to the impedance before and after lamination, the impedance change rate ΔZ can be calculated to be 2.4142. Among them, the thickness d of the shielding layer 120 of the electromagnetic shielding film and the impedance change rate ΔZ satisfy: ΔZ = 0.21 * d + 0.524

[0098] Comparative Example 6

[0099] This embodiment provides an electromagnetic shielding film, comprising: a film layer 110, a shielding layer 120, and an insulating layer 140 which are stacked. The shielding layer 120 is a non-woven fabric of sputtered metal material. The thickness d of the shielding layer 120 is selected to be 10 μm, and the impedance change rate ΔZ can be calculated to be 2.624 according to the impedance before and after lamination. Among them, the thickness d of the shielding layer 120 and the impedance change rate ΔZ of the electromagnetic shielding film satisfy: ΔZ = 0.21 * d + 0.524

[0100] Table 1 Test parameters of each embodiment and comparative example

[0101]

[0102]

[0103] It can be seen that in Embodiments 10-14 of the present invention, the impedance change rate ΔZ is 0.1-0.2, and an electromagnetic shielding film with a relatively small impedance change rate after lamination can be obtained, which can meet the impedance matching of the circuit board. Among them, the thickness of the shielding layer 120 is 0.1-8 μm, within this range, it can not only meet the shielding effect but also ensure a relatively low impedance change rate.

[0104] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features. These modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An electromagnetic shielding film, characterized in that, Comprising: A film layer, and after the electromagnetic shielding film is laminated on the circuit board, the grammage W of the film layer and the impedance change rate ΔZ satisfy: ΔZ = -A*W + B; where A and B are constants, the value range of A is 0.0005 - 0.005, the value range of B is 0.1 - 1, and the unit of grammage W is g / dm 2 , and the calculation is dimensionless.

2. The electromagnetic shielding film according to claim 1, wherein The value range of A is 0.001 to 0.004; and / or, the value range of B is 0.15 - 0.

5.

3. The electromagnetic shielding film according to claim 1, wherein The electromagnetic shielding film further includes a shielding layer, the shielding layer is disposed on one side of the film layer, and the thickness d of the shielding layer and the impedance change rate ΔZ satisfy: ΔZ = C*d + D; Wherein, C and D are constants, and the value range of C is -0.005 to 0.15, the value range of D is 0.01 to 0.5, the unit of the thickness d is μm, and the calculation is dimensionless.

4. The electromagnetic shielding film according to claim 3, wherein The thickness range of the shielding layer is 0.1 - 8 μm.

5. The electromagnetic shielding film according to claim 3, characterized in that, At least one side of the shielding layer is provided with conductive protrusions.

6. The electromagnetic shielding film according to claim 1, characterized in that, The relative dielectric constant Δε of the film layer is 3 - 6.

7. The electromagnetic shielding film according to claim 1, wherein, The relative dielectric constant Δε of the film layer and the impedance change rate ΔZ satisfy: Wherein, E and F are constants, the value range of E is 0.02 to 0.5, the value range of F is -1 to -0.01, and the calculation is dimensionless.

8. The electromagnetic shielding film according to claim 1, characterized in that, Conductive particles are provided in the film layer, and in unit volume, the weight ratio of the conductive particles to the weight of the film layer is 0.01 - 0.

6.

9. The electromagnetic shielding film according to claim 8, wherein The maximum width of the conductive particles is 0.5 - 5 μm.

10. The electromagnetic shielding film according to claim 3, wherein The electromagnetic shielding film further includes a protective layer, and the protective layer is disposed on the side of the shielding layer facing away from the film layer.

11. A circuit board, characterized in that, The circuit board includes a circuit board body and the electromagnetic shielding film according to any one of claims 1 - 10.

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