Electromagnetic shielding film

Abstract

The invention relates to the technical field of shielding films, in particular to an electromagnetic shielding film, in the mechanical direction, the expansion and shrinkage value delta L of the electromagnetic shielding film and the pressing pressure delta meet the formula that delta L = A * delta / E + B, the unit of delta L is # imgabs0 #, the unit of pressing pressure delta is MPa, E represents the overall elastic modulus of the electromagnetic shielding film, 0.5 < = E < = 2.5 GPa, A < 0, B > 0, and calculation is dimensionless. The electromagnetic shielding film meeting the relational expression has good expansion and shrinkage performance, the size stability of the electromagnetic shielding film in use can be guaranteed, and the processing performance is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of shielding films, and particularly to an electromagnetic shielding film. Background Art

[0002] With the popularization of electronic devices and the development of wireless communication technologies, the problem of electromagnetic interference (EMI) has become increasingly prominent. As an effective solution, electromagnetic shielding films are widely used in fields such as electronic devices, communication systems, and aerospace to reduce electromagnetic interference and improve device performance. From early simple metal shielding materials to modern high-performance composite materials, the electromagnetic shielding effect of electromagnetic shielding films has been continuously improved. The trend of miniaturization and lightweight of electronic devices has promoted the demand for flexible shielding materials. Developing shielding films with higher conductivity, higher shielding efficiency, and suitable for flexible electronics is an important requirement at present.

[0003] However, when the electromagnetic shielding film provided by the prior art is laminated under high temperature and high pressure conditions, due to excessive expansion and contraction, it cannot meet the hole position matching with the circuit board, resulting in a decrease in the yield rate of the circuit board. Summary of the Invention

[0004] Therefore, to solve the above technical problems, the present invention provides an electromagnetic shielding film. In the mechanical direction, the expansion and contraction value ΔL of the electromagnetic shielding film and the lamination pressure δ satisfy: ΔL = A×δ / E + B, where the unit of ΔL is The unit of the lamination pressure δ is MPa, E represents the overall elastic modulus of the electromagnetic shielding film, and 0.5 ≤ E ≤ 2.5 GPa, A < 0, B > 0, and the calculation is dimensionless. The electromagnetic shielding film satisfying the above relational expression has good expansion and contraction performance, and can ensure the dimensional stability of the electromagnetic shielding film during use and improve the processing performance.

[0005] During the research and development process, the inventor measured the expansion and contraction values of electromagnetic shielding films formed under different lamination pressures and found that the lamination pressure and the overall elastic modulus of the electromagnetic shielding film have a regular influence on the overall expansion and contraction value of the electromagnetic shielding film. When their change rules satisfy the above specific functional relationship, better hole position matching accuracy can be achieved. Therefore, by controlling the lamination pressure or adjusting the selection of interlayer materials to change the elastic modulus, the expansion and contraction value of the electromagnetic shielding film meeting the requirements can be obtained, thereby improving the manufacturing quality of the circuit board.

[0006] Among them, represents one ten-thousandth.

[0007] To further improve the dimensional stability of the electromagnetic shielding film, the value range of constant A is -0.8 to -0.05, and the value range of constant B is 20 to 80. In the embodiments of the present invention, by defining the correction factor, the upper and lower limits are set, and the expansion and contraction values of the electromagnetic shielding film whose test results fall within the range above and below the function curve show good performance and relatively good dimensional stability. Exemplarily, the constant A is -0.8, -0.75, -0.6, -0.45, -0.3, -0.15, -0.1, -0.07, -0.05 or an interval between any two values; the constant B is 20, 30, 35, 50, 60, 65, 70, 80 or an interval between any two values.

[0008] In some of the embodiments, the calculation method of the expansion and contraction value ΔE is as follows: ΔE = (expansion and contraction amount before and after lamination) / initial size × 100%; in this embodiment, the expansion and contraction value of the carrier layer is the expansion and contraction value data obtained after air lamination of the carrier layer, and the test method for the expansion and contraction value of the shielding film body is that before the carrier layer and the shielding film body are separated, they are laminated on the substrate surface of the flexible copper clad laminate (FCCL), and after curing, the carrier layer and the shielding film body are separated, and the expansion and contraction values of the two are calculated respectively.

[0009] In some of the embodiments, the method for measuring the expansion and contraction value of the shielding film is as follows: Cut an electromagnetic shielding film sample with a size of 250 × 300 mm, drill holes at the four corners of the test piece, and mark them as A, B, C, and D respectively. Use an image measuring instrument to measure the distances between the punched points A - B, C - D, A - C, and B - D of the test piece, and mark them as L A-B 、L C-D 、L A-C 、L B-D , stack them into a laminated structure of the electromagnetic shielding film and FCCL, make the connection layer side of the electromagnetic shielding film contact the substrate surface of the FCCL, preheat the fast press for 10 s, and the lamination conditions are: lamination temperature is 80 - 300 °C, lamination pressure is 60 - 180 kg / cm 2 , and the lamination time is 120 - 240 s. After laminating and curing under appropriate lamination conditions, use an image measuring instrument to measure the distances between the punched points A - B, C - D, A - C, and B - D of the test piece again, and mark them as F A-B 、F C-D 、F A-C 、F B-D , and the calculation formulas for the transverse expansion and contraction value and the longitudinal expansion and contraction value are as follows:

[0010] Transverse expansion and contraction value = [((F A-B - L A-B ) / (2 × L A-B ) + ((F C-D - L C-D ) / (2 × L C-D ))] × 100%;

[0011] Longitudinal expansion and contraction value = [(F A-C - L A-C ) / (2 × L A-C ) + (F B-D - L B-D ) / (2 × L B-D )] × 100%.

[0012] Furthermore, since the lateral expansion and contraction value is much smaller than the longitudinal expansion and contraction value, the longitudinal expansion and contraction value is used as the evaluation benchmark in the embodiments of the present invention.

[0013] The electromagnetic shielding film includes a protective layer. In the mechanical direction, the expansion and contraction value ΔL of the electromagnetic shielding film and the lamination temperature T satisfy: ΔL = C × α × ΔT + D, where α represents the thermal expansion coefficient of the protective layer, ranging from 100 to 280, with the unit of ppm / °C, and 0.0005 ≤ C ≤ 0.002. The value range of the constant D is from -10 to -2. ΔT is the difference between the lamination temperature T and the room temperature, with the unit of °C, and the calculation is dimensionless.

[0014] The expansion and contraction of the film generally refers to the dimensional change of the material when the environmental conditions (such as temperature and humidity) change. Among them, both the thermal expansion coefficient and the hygroscopic expansion coefficient of the material will affect the expansion and contraction change of the film material, which is specifically manifested as the expansion or contraction of the material in the length, width or thickness direction. Since there is no humidity influence during the lamination of the shielding film, the thermal expansion coefficient of the material has a greater influence on the expansion and contraction of the shielding film, and is respectively reflected in the length and width directions. In order to further control the expansion and contraction value of the electromagnetic shielding film within a certain range, the thermal expansion coefficient of the protective layer is controlled within 100 - 280 ppm / °C. At the same time, in order to further improve the dimensional stability of the electromagnetic shielding film, the value range of the constant C is 0.0005 - 0.002, and the value range of the constant D is -10 to -2. In the embodiments of the present invention, by limiting the correction factor, the upper and lower limits are set, and the expansion and contraction values of the electromagnetic shielding film whose test results fall within the range of the function curve show good performance and good dimensional stability. Exemplarily, the constant C is 0.0005, 0.0008, 0.001, 0.0012, 0.0015, 0.0018 / 0.002 or the interval of any two values; the constant B is -10, -8, -5, -4, -2 or the interval of any two values.

[0015] In order to further reduce the expansion and contraction amount of the electromagnetic shielding film and improve the quality of the circuit board, under the preset lamination conditions, in the mechanical direction, the expansion and contraction value ΔE1 of the protective layer is less than Exemplarily, the expansion and contraction value ΔE1 of the protective layer is or the interval of any two values.

[0016] The present invention provides a protective layer that insulates and protects the shielding layer, while also preventing wear of the shielding layer, thereby extending the lifespan of the electromagnetic shielding film. The material of the protective layer 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 is not limited thereto, and all resin materials disclosed in the prior art can be used. The mixture can be, 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. In some embodiments, the thickness of the protective layer is 2 - 80 μm. Preferably, the average thickness of the shielding layer can be 2 μm, 5 μm, 8 μm, 10 μm, 20 μm, 25 μm, 32 μm, 45 μm, 60 μm, 70 μm and 80 μm or an interval composed of any two values.

[0017] In some embodiments, the electromagnetic shielding film further includes a shielding layer disposed on one side of the protective layer. The shielding layer includes one or more of a metal shielding layer, a carbon nanotube shielding layer, a ferrite shielding layer, and a graphene shielding layer. Among them, the metal shielding layer includes a single-metal shielding layer and / or an alloy shielding layer; wherein, the single-metal shielding layer is made of any one material selected from aluminum, titanium, zinc, iron, nickel, chromium, cobalt, copper, silver, and gold, and the alloy shielding layer is made of any two or more materials selected from aluminum, titanium, zinc, iron, nickel, chromium, cobalt, copper, silver, and gold.

[0018] In some embodiments, the thickness of the shielding layer is 0.5 - 15 μm. Preferably, the thickness of the shielding layer can be 0.5 μm, 1 μm, 2 μm, 5 μm, 10 μm, 15 μm or an interval composed of any two values.

[0019] The electromagnetic shielding film further includes a carrier layer, and the carrier layer is disposed on a side of the protective layer facing away from the shielding layer. Optionally, in order to further improve the expansion and contraction value of the carrier layer, a material with a suitable coefficient of thermal expansion is selected for the carrier film, which can specifically be at least one of polytetrafluoroethylene, cellulose, polyether ether ketone, or liquid crystal polymer, or can also be polyolefins, polysulfones, polyamides, polyesters, polycarbonates, polyvinyl alcohol, silicone rubber, etc. For example, high coefficient of thermal expansion materials can be obtained by modifying polyimide (PI), polyethylene terephthalate (PET), polypropylene (PP), polyvinyl chloride (PVC), polyester, or other polymer materials. Also, when applying an insulating layer on the carrier layer, the carrier layer can be pre-expanded and contracted, such as in a high-temperature or stretched state, and an insulating layer or subsequent layer is coated on the carrier film, so that the shielding film body and the carrier layer have pre-expansion and contraction, which is beneficial for subsequently laminating the electromagnetic shielding film onto the circuit board. The pre-expansion and contraction offsets the expansion and contraction amount generated during lamination, thereby stabilizing the size of the shielding film.

[0020] In some embodiments, the thickness of the carrier layer is 2 - 20 μm. Preferably, the thickness of the carrier layer can be 2 μm, 5 μm, 7 μm, 10 μm, 12 μm, 15 μm, 20 μm, or an interval composed of any two values.

[0021] In order to avoid delamination of the electromagnetic shielding film due to excessive stress, the coefficient of thermal expansion α1 of the carrier layer and the coefficient of thermal expansion α2 of the protective layer satisfy: 1 ≤ α1 / α2 ≤ 1.7; the coefficient of thermal expansion α1 of the carrier layer and the coefficient of thermal expansion α2 of the protective layer satisfy: |α1 - α2| ≤ 20 ppm / °C. By defining the relationship between the coefficients of thermal expansion of the carrier layer and the protective layer, the present invention reduces the stress change between the carrier layer and the protective layer, avoids delamination of the electromagnetic shielding film, and improves the quality of the circuit board.

[0022] Preferably, the ratio of the coefficient of thermal expansion α1 of the carrier layer to the coefficient of thermal expansion α2 of the protective layer is 1, 1.2, 1.4, 1.5, 1.6, 1.7, or an interval of any two values; the difference between the coefficient of thermal expansion α1 of the carrier layer and the coefficient of thermal expansion α2 of the protective layer is 0 ppm / °C, 1 ppm / °C, 2.5 ppm / °C, 4 ppm / °C, 5.5 ppm / °C, 8 ppm / °C, 10 ppm / °C, 15 ppm / °C, 20 ppm / °C, or an interval of any two values.

[0023] In order to reduce the ground resistance, improve the grounding effect and shielding efficiency, and reduce the production cost, a raised portion is provided on a side of the shielding layer facing away from the protective layer, and the raised portion is used for grounding with the circuit board.

[0024] In order to improve the dimensional stability and quality of the electromagnetic shielding film, the shielding film body further includes a connection layer, and the connection layer is disposed on a side of the shielding layer facing away from the protective layer. The material of the connection layer includes at least one of resins such as vinyl acetate, polyester, polyethylene, polyamide, rubber, acrylate, phenolic, epoxy, polyimide, urethane, melamine, alkyd, ABF, etc.

[0025] The thickness of the connection layer is 2 - 20 μm. Exemplarily, the thickness of the connection layer can be 2 μm, 3 μm, 4 μm, 5 μm, 8 μm, 12 μm, 20 μm, or an interval composed of any two values.

[0026] In some embodiments, conductive particles are provided in the connection layer, and the shielding layer can be grounded to a circuit board through the conductive particles. Preferably, the conductive particles and the protrusions can be used in combination or separately. When the connection layer does not contain conductive particles, grounding is achieved through the protrusions, which can not only reduce the grounding resistance but also reduce the cost. When the connection layer contains conductive particles, the conductive particles can enhance the grounding effect of the electromagnetic shielding film and improve the shielding efficiency. The conductive particles can be separated conductive particles or agglomerated large - particle conductive particles; when the conductive particles are separated conductive particles, the grounding conductivity of the bonding layer can be further improved; while when the conductive particles are agglomerated large - particle conductive particles, the piercing strength can be increased.

[0027] In order to further reduce the expansion and contraction of the electromagnetic shielding film, the thickness d1 of the carrier layer and the thickness value d2 of the shielding film body satisfy: 0.5 ≤ d1 / d2 ≤ 10. The present invention limits the degree of expansion and contraction of the electromagnetic shielding film by reducing the thickness of the carrier layer, thereby improving the dimensional stability of the electromagnetic shielding film. Exemplarily, the ratio of the thickness d1 of the carrier layer to the thickness value d2 of the shielding film body is 0.5, 1, 2, 2.5, 5, 7, 8, 8.5, 9, 10, or an interval composed of any two values.

[0028] To further reduce the expansion and contraction of the electromagnetic shielding film, the electromagnetic shielding film also includes a buffer layer, which is disposed between the carrier layer and the shielding film body. By disposing the buffer layer between the carrier layer and the shielding film body, it acts as a buffer during the lamination process, thereby reducing the expansion and contraction of the electromagnetic shielding film. The material of the buffer layer can be inorganic or organic. Exemplarily, the buffer layer is at least one of polyurethane, silica gel, polyimide, carbon nanotube aerogel, graphene aerogel, polyurethane foam, polyethylene foam, natural rubber, styrene-butadiene rubber, or polyurethane rubber. The thickness of the buffer layer is 2-20 μm. Exemplarily, the thickness of the buffer layer can be 2 μm, 3 μm, 4 μm, 5 μm, 8 μm, 12 μm, 20 μm, or an interval consisting of any two values.

[0029] More specifically, in the embodiment of the present invention, the shielding film body is the structure of the shielding film excluding the carrier layer, and may include a shielding layer, a protective layer, a connecting layer or a buffer layer.

[0030] In some embodiments, the electromagnetic shielding film includes a carrier layer, a protective layer, a shielding layer, and a connecting layer stacked in sequence. The shielding layer is formed on the protective layer by lamination, bonding, vacuum sputtering, electroplating, or the like. The side of the shielding layer facing away from the protective layer is uneven to form a protrusion for grounding to the circuit board. The connecting layer is applied to the side of the shielding layer facing away from the protective layer by bonding, coating, or the like. After the electromagnetic shielding film is pressed onto the circuit board, the connecting layer is cured and tightly connected to the circuit board. The shielding layer is electrically connected to the grounding layer of the circuit board through a grounding window on the circuit board to form a ground, thereby conducting electromagnetic interference and achieving electromagnetic shielding. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0032] Figure 1 is a schematic structural diagram of the electromagnetic shielding film of Example 1 of the present invention;

[0033] Figure 2 is a schematic structural diagram of an electromagnetic shielding film according to an eighth embodiment of the present invention;

[0034] Reference numerals:

[0035] 11-shielding layer; 12-protective layer; 13-connecting layer; 14-protrusion;

[0036] 15-conductive particles; 2-carrier layer; 3-buffer layer. Detailed implementation mode

[0037] The following embodiments are provided to better understand the present invention further, and are not limited to the described best implementation mode. They do not limit the content and protection scope of the present invention. Any product that is the same as or similar to the present invention obtained by anyone under the inspiration of the present invention or by combining the features of the present invention with those of other existing technologies falls within the protection scope of the present invention.

[0038] For those embodiments where specific experimental steps or conditions are not indicated, the operations or conditions of the conventional experimental steps described in the literature in this field can be followed. For reagents or instruments whose manufacturers are not indicated, they are all conventional reagent products that can be obtained through commercial purchase.

[0039] Embodiment 1

[0040] This embodiment provides an electromagnetic shielding film, and its structural schematic diagram is as Figure 1 shown. The electromagnetic shielding film includes a protective layer 12 and a shielding layer 11 that are stacked in sequence. The protective layer is based on a modified polyimide glue and filled with a mixture of epoxy resin, cyanate resin, rubber, and modified polyester. The thickness of the protective layer is 8 μm, and the shielding layer is copper with a thickness of 1.5 μm;

[0041] At a lamination temperature of 185 °C, the electromagnetic shielding film with a carrier layer 2 is laminated onto a test board at 12 MPa for 180 s (a Shenzhen Bion fast press is used for the press).

[0042] Through measurement, the expansion and contraction value ΔL and the lamination pressure δ of the electromagnetic shielding film satisfy ΔL = A × δ / E + B, where, δ = 12 MPa, E = 1.2 GPa, A = -0.5, B = 20.

[0043] Embodiment 2

[0044] Other technical features of this embodiment are the same as those of Embodiment 1. The difference is that the protective layer is based on modified polytetrafluoroethylene and filled with a mixture of epoxy resin and nitrile rubber, and the thickness of the protective layer is 8 μm;

[0045] Through measurement, the expansion and contraction value ΔL and the lamination pressure δ of the electromagnetic shielding film satisfy ΔL = A × δ / E + B, where, δ = 10 MPa, E = 1 GPa, A = -0.8, B = 33.

[0046] Embodiment 3

[0047] Other technical features of this embodiment are the same as those of Embodiment 1. The difference lies in that through measurement, the expansion and contraction value ΔL of the electromagnetic shielding film and the lamination pressure satisfy ΔL = A×δ / E + B. At the same time, the expansion and contraction value ΔL of the electromagnetic shielding film and the lamination temperature satisfy ΔL = C×α×ΔT + D, where, α = 200 ppm / ℃, C = 0.0015, ΔT = 130℃ - 25℃ = 115, D = -5.

[0048] Embodiment 4

[0049] Other technical features of this embodiment are the same as those of Embodiment 2. The difference lies in that through measurement, the expansion and contraction value ΔL of the electromagnetic shielding film and the lamination pressure satisfy ΔL = A×δ / E + B. Through measurement, the expansion and contraction value ΔL of the electromagnetic shielding film satisfies ΔL = C×α×ΔT + D, where, α = 250 ppm / ℃, C = 0.002, ΔT = 175℃ - 25℃ = 155, D = -10.

[0050] Embodiment 5

[0051] Other technical features of this embodiment are the same as those of Embodiment 1. The difference lies in that through measurement, in the longitudinal direction, the expansion and contraction value ΔE1 of the protective layer is

[0052] Embodiment 6

[0053] Other technical features of this embodiment are the same as those of Embodiment 2. The difference lies in that through measurement, in the longitudinal direction, the expansion and contraction value ΔE1 of the protective layer is

[0054] Embodiment 7

[0055] This embodiment provides an electromagnetic shielding film. The shielding film body includes a protective layer 12 and a shielding layer 11 which are sequentially stacked. The protective layer uses a polyimide substrate and is filled with a mixture of epoxy resin and cyanate resin, with a thickness of 12 μm. The shielding layer is copper with a thickness of 1.5 μm, and the carrier layer is polyether ether ketone with a thickness of 8 μm;

[0056] At the same time, the ratio α1 / α2 of the thermal expansion coefficient α1 of the carrier layer to the thermal expansion coefficient α2 of the protective layer is 1.2.

[0057] At a lamination temperature of 300℃, the electromagnetic shielding film with a carrier layer 2 is laminated on the circuit board at a pressure of 16 MPa. Specifically, the protective layer is connected to the carrier layer and laminated for 180 s (the press uses a Shenzhen Bion fast press);

[0058] Through measurement, the expansion and contraction value ΔL of the electromagnetic shielding film and the lamination pressure δ satisfy ΔL = A×δ / E + B, where, δ = 16 MPa, E = 2 GPa, A = -0.05, B = 35.

[0059] Example 8

[0060] This example provides an electromagnetic shielding film, the structural schematic diagram of which is as Figure 2 shown. The shielding film body includes a buffer layer 3, a protective layer 12, a shielding layer 11, and a connection layer 13 that are stacked in sequence. A convex portion 14 is provided on the side of the shielding layer facing away from the protective layer, and conductive particles 15 are provided in the connection layer;

[0061] The material of the shielding layer in the shielding film body is copper, with a thickness of 1.5 μm. The material of the carrier layer is modified PET glue, with a thickness of 5 μm. The protective layer is a mixture of polymethyl methacrylate and rubber, with a thickness of 3 μm. The connection layer is an acrylate adhesive, with a thickness of 4 μm. The buffer layer is polyurethane, with a thickness of 7 μm. The thickness d1 of the carrier layer and the thickness value d2 of the shielding film body satisfy that d1 / d2 is 2.5, which meets 0.5 ≤ d1 / d2 ≤ 10;

[0062] The thermal expansion coefficient α1 of the carrier layer and the thermal expansion coefficient α2 of the protective layer satisfy |α1 - α2| to be 15 ppm / °C;

[0063] At a lamination temperature of 300 °C, the electromagnetic shielding film is laminated to the carrier layer 2 with a pressure of 16 MPa. Specifically, the buffer layer is connected to the carrier layer, and the lamination is carried out for 180 s (a Shenzhen Bion fast press is used for the press);

[0064] Through measurement, the expansion and contraction value ΔL of the electromagnetic shielding film satisfies ΔL = A×δ / E + B, where δ = 16 MPa, E = 2.5 GPa, A = -0.8, B = 40.12.

[0065] Example 9

[0066] Other technical features of this example are the same as those of Example 1. The difference is that the lamination pressures are 61 kg / cm 2 , 73 kg / cm 2 , 91 kg / cm 2 , 110 kg / cm 2 , 120 kg / cm 2 respectively, and the measured expansion and contraction values of the electromagnetic shielding film are successively

[0067] The R2 of the fitting curve of the lamination pressure and the measured expansion and contraction value of the electromagnetic shielding film is 0.9018. It can be seen that the lamination pressure and the expansion and contraction value of the electromagnetic shielding film are negatively correlated, and the fitting degree is good.

[0068] Example 10

[0069] The other technical features of this embodiment are the same as those of embodiment 1, except that the pressing temperatures are 80°C, 100°C, 120°C, 140°C, and 180°C, respectively, and the expansion and contraction values of the electromagnetic shielding film are measured as follows:

[0070] It can be seen that the pressing temperature is positively correlated with the expansion and contraction value of the electromagnetic shielding film.

[0071] Comparative Example 1

[0072] The other technical features of this comparative example are the same as those of Example 1, except that the thickness of the shielding layer is 15 μm. Through measurement, the expansion and contraction value ΔL and the pressing pressure δ of the electromagnetic shielding film do not satisfy ΔL=A×δ / E+B, where, δ=12MPa,E=2GPa.

[0073] Comparative Example 2

[0074] The other technical features of this comparative example are the same as those of Example 1, except that the thickness of the protective layer is 1 μm. Through measurement, the expansion and contraction value ΔL and the pressing pressure δ of the electromagnetic shielding film do not satisfy ΔL=A×δ / E+B, where, δ=12MPa,E=1GPa.

[0075] Experimental example

[0076] The electromagnetic shielding films formed in Examples 1-8 and Comparative Examples 1-2 were pressed onto the FPC test board using a fast press. The pressing conditions were: temperature 185°C, pressing time 180s, pressing pressure 120kg / cm 2 The hole position offset of the shielding films of the embodiment and the comparative example on the FPC circuit board was measured and calculated, and the results are shown in Table 1.

[0077] Hole offset measurement: Using an optical measurement method, using a high-resolution electron microscope, accurately measure and mark the holes on the circuit board before lamination of the shielding film. Record the center coordinates of each hole. Use the microscope's built-in measurement software or image analysis software to determine the center position of the hole. After lamination of the shielding film, observe and measure the center coordinates of the same hole again using the microscope. By comparing the coordinate changes before and after lamination, calculate the hole offset in the X and Y axes, and take the average value to obtain the total hole offset.

[0078] Table 1 Test results of electromagnetic shielding film

[0079]

[0080] According to the data in Table 1, compared with the expansion and contraction values ΔL and lamination pressures δ measured for the electromagnetic shielding films provided in Comparative Examples 1-2, which do not satisfy the formula ΔL = A×δ / E + B, with hole position offsets of 98.4 mm and 122.4 mm respectively, while the expansion and contraction values ΔL and lamination pressures δ measured for the electromagnetic shielding films provided in Embodiments 1-8 of the present invention satisfy the formula ΔL = A×δ / E + B, and the hole position offsets are between 2.1 - 12.7 mm, which proves that the electromagnetic shielding film with expansion and contraction values ΔL and lamination pressures δ satisfying the formula ΔL = A×δ / E + B has strong stability and good processing performance.

[0081] Obviously, the above embodiments are merely examples given for clear illustration and not limitations on the implementation manners. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to enumerate all the implementation manners here. And the obvious changes or modifications derived therefrom still fall within the protection scope of the present invention.

Claims

1. An electromagnetic shielding film, characterized in that, In the mechanical direction, the expansion and contraction value ΔL of the electromagnetic shielding film and the pressing pressure δ satisfy: ΔL = A×δ / E + B, wherein, the unit of ΔL is The unit of the lamination pressure δ is MPa, E represents the overall elastic modulus of the electromagnetic shielding film, and 0.5 ≤ E ≤ 2.5 GPa, A < 0, B > 0, and the calculation is dimensionless.

2. The electromagnetic shielding film according to claim 1, wherein The value range of the constant A is -0.8 to -0.05, and the value range of the constant B is 20 to 80.

3. The electromagnetic shielding film according to claim 1, characterized in that, The electromagnetic shielding film includes a protective layer. In the mechanical direction, the expansion and contraction value ΔL of the electromagnetic shielding film and the pressing temperature T satisfy: ΔL = C×α×ΔT + D, where α represents the thermal expansion coefficient of the protective layer, with a range of 100 to 280, in units of ppm / °C, and 0.0005 ≤ C ≤ 0.

002. The value range of the constant D is -10 to -2, and ΔT is the difference between the pressing temperature T and the room temperature, in units of °C, dimensionless for calculation.

4. The electromagnetic shielding film according to claim 3, wherein Under the preset lamination conditions, in the machine direction, the expansion and contraction value ΔE1 of the protective layer is less than 40 5. The electromagnetic shielding film according to claim 3, wherein, The electromagnetic shielding film further includes a shielding layer, and the shielding layer is disposed on one side of the protective layer.

6. The electromagnetic shielding film according to claim 5, wherein The electromagnetic shielding film further includes a carrier layer, and the carrier layer is disposed on the side of the protective layer opposite to the shielding layer.

7. The electromagnetic shielding film according to claim 6, wherein The thermal expansion coefficient α1 of the carrier layer and the thermal expansion coefficient α2 of the protective layer satisfy: 1 ≤ α1 / α2 ≤ 1.7; and / or, The thermal expansion coefficient α1 of the carrier layer and the thermal expansion coefficient α2 of the protective layer satisfy: |α1 - α2| ≤ 50 ppm / °C.

8. The electromagnetic shielding film according to claim 5, wherein A convex portion is provided on the side of the shielding layer opposite to the protective layer, and the convex portion is used for grounding with the circuit board.

9. The electromagnetic shielding film according to claim 5, characterized in that, The electromagnetic shielding film further includes a connection layer, and the connection layer is disposed on the side of the shielding layer opposite to the protective layer.

10. The electromagnetic shielding film according to claim 9, characterized in that, Conductive particles are provided in the connection layer.

11. The electromagnetic shielding film according to claim 6, wherein The thickness d1 of the carrier layer and the thickness value d2 of the shielding film body satisfy: 0.5 ≤ d1 / d2 ≤ 10.

12. The electromagnetic shielding film according to any one of claims 6-11, characterized in that, The electromagnetic shielding film further includes a buffer layer, and the buffer layer is disposed between the carrier layer and the protective layer, and / or, the buffer layer is disposed between the protective layer and the shielding layer.

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