Base film for electromagnetic shielding film, electromagnetic shielding film and circuit board

Abstract

The invention relates to the technical field of electromagnetic shielding, in particular to a base film for an electromagnetic shielding film, the electromagnetic shielding film and a circuit board. According to the base film for the electromagnetic shielding film, at least one face of the base film is an uneven surface, the uneven surface comprises concave parts and convex parts, the vertical height difference delta H between the adjacent concave parts and convex parts meets the relation that delta H is larger than or equal to 1 micrometer and smaller than or equal to 10 micrometers, and the thickness of the base film at the bottommost ends of the concave parts is larger than or equal to 1 / 5 of the average thickness of the base film. By limiting the height difference between the concave part and the convex part on the uneven surface of the base film and the thickness of the base film at the bottom end of the concave part, the bending resistance and the high section difference resistance of the base film are improved.

Description

Technical Field

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

[0002] With the development of miniaturization and thinness of electronic devices, the development of electromagnetic shielding films has also experienced a transformation from single function to multi-function, from low efficiency to high efficiency, and from heavy type to light type. Early electromagnetic shielding materials mainly relied on metal sheets or woven meshes, but because the materials were too thick and heavy, they could not meet the requirements of miniaturization and thinness. Therefore, metal plating, conductive polymers and multi-layer composite materials are currently used to replace early materials, which improves the shielding effect while reducing the weight of the electromagnetic shielding film.

[0003] Most multi-layer composite materials use a base film as the supporting structure of the electromagnetic shielding film. Therefore, the performance of the base film directly affects the electromagnetic shielding film and the application performance of the electromagnetic shielding film. The base film used in the electromagnetic shielding film provided by the prior art adopts materials with good flexibility, such as polymer materials such as polyimide or polyester. Through the interaction between molecules inside the polymer material, the material maintains good elastic recovery and avoids bending of the electromagnetic shielding film. However, when used in electronic devices that need to be bent frequently, such as folding screen mobile phones, the base film provided by the prior art cannot guarantee that the electromagnetic shielding film can maintain structural integrity and not break during frequent bending, and it cannot better improve the bending resistance of the circuit board or FPC. Summary of the invention

[0004] Therefore, the technical problem to be solved by the present invention is to overcome the poor bending resistance of the circuit board or FPC board containing the electromagnetic shielding film in the prior art, thereby providing a base film for an electromagnetic shielding film, an electromagnetic shielding film and a circuit board.

[0005] Another technical problem to be solved by the present invention is to overcome the defect of poor step resistance of the electromagnetic shielding film in the prior art, and to provide a base film for the electromagnetic shielding film, and an electromagnetic shielding film and a circuit board prepared with the base film.

[0006] See also Figure 1 The present invention provides a base film 1 for an electromagnetic shielding film, wherein at least one side of the base film is a non-flat surface, the non-flat surface contains concave portions and convex portions, the vertical height difference ΔH between adjacent concave portions and convex portions satisfies the relationship 1μm≤ΔH≤10μm, and the base film thickness at the thinnest part of the concave portion is greater than or equal to 1 / 5 of the average thickness of the base film, see Figure 2, the thinnest part of the concave portion is Δh, wherein the average thickness of the base film refers to the average value of the thickness of the entire base film (when calculating the average thickness of the base film, the thicknesses of all adjacent concave portions and convex portions or the adjacent concave portions and convex portions of the measured part can be measured and the average value can be calculated, wherein the more values ​​of adjacent concave portions and convex portions, the more accurate the result of the average thickness of the base film).

[0007] In the present invention, the surface state of the base film will seriously affect the overall performance of the circuit board or FPC board containing the electromagnetic shielding film, especially the bending resistance of the circuit board or FPC board containing the electromagnetic shielding film and the step resistance of the electromagnetic shielding film. The uneven surface of the base film has concave parts, convex parts and relatively flat areas, and the height difference between adjacent concave parts and convex parts will affect the bending resistance of the circuit board or FPC board containing the electromagnetic shielding film. When the vertical height difference between adjacent concave parts and convex parts exceeds 10μm, it will not only affect the bending resistance of the circuit board or FPC board containing the electromagnetic shielding film, but also cause the electromagnetic shielding film to have poor step resistance, which can easily cause the shielding layer to break and cause the electromagnetic shielding effectiveness to drop rapidly. The base film provided by the present invention satisfies that the vertical height difference between adjacent concave parts and convex parts is less than or equal to 10μm, which can ensure that the electromagnetic shielding film prepared using the base film can have a higher shielding effectiveness. Among them, the vertical height difference between adjacent concave and convex parts on the uneven surface of the base film can be 1μm, 3μm, 4μm, 5μm, 8μm, 10μm or an interval consisting of any two values. At the same time, the base film should also satisfy that the base film thickness at the thinnest part of the concave part is greater than or equal to 1 / 5 of the average thickness of the base film in order to meet the application requirements. If the base film thickness at the thinnest part of the concave part is less than 1 / 5 of the average thickness of the base film, the base film will be easy to break, and the overall structure of the circuit board or FPC board containing the electromagnetic shielding film will have poor bending resistance. Among them, the vertical height difference refers to the vertical height difference between the thinnest part of a concave part and the highest part of the adjacent convex part. Adjacent is not interval.

[0008] In the present invention, the average thickness of the base film is the average value of the vertical distance between the two surfaces of the base film. In some embodiments, the parameters of the above-mentioned base film, including the concave portion, the convex portion, and the thickness of the base film, can be measured by slices using a scanning electron microscope, an optical electron microscope, or a focused ion beam, or other measurement methods can be used. The present invention is not limited to this, as long as the various parameters of the base film can be accurately measured.

[0009] In order to make the application effect of the base film better, in some embodiments, the concave and convex parts of the uneven surface of the base film are spaced apart. The limitation of the spacing between the concave and convex parts of the uneven surface of the base film can avoid excessive concentration of convex parts in the base film, which in turn causes stress concentration or uneven stress transfer between the electromagnetic shielding film and the circuit board or FPC board, and causes the circuit board or FPC board containing the electromagnetic shielding film to break or delaminate when bent. Among them, the concave part of the uneven surface of the base film can be a single concave part, or a concave part composed of several tiny depressions. Similarly, the convex part of the uneven surface of the base film can be a single convex part, or a convex part composed of several tiny protrusions.

[0010] In order to make the step resistance performance of the electromagnetic shielding film containing the base film more stable, and the bending resistance performance of the circuit board or FPC board structure containing the electromagnetic shielding film more stable, in some embodiments, the distance between adjacent recesses is greater than or equal to 2μm. Exemplarily, the distance between adjacent recesses is 2μm, 3μm, 4μm, 5μm, 6μm, 8μm, 10μm, 15μm, 20μm, 30μm, 40μm, 50μm, 60μm, 70μm, 80μm, 90μm, 100μm or an interval consisting of any two values.

[0011] In order to optimize the above technical effects, avoid the problem of internal delamination of the electromagnetic shielding film containing the base film or the breakage of the internal circuit of the corresponding circuit board or FPC board, or to improve the step resistance performance of the electromagnetic shielding film containing the base film, in some embodiments, within the range of 260μm of the uneven surface of the base film, the number of recesses is less than or equal to 30. Exemplarily, within the range of 260μm, the number of recesses on the uneven surface of the base film is 30, 25, 15, 10, 5 or an interval consisting of any two values.

[0012] In some embodiments, the vertical distance between the bottom end of the concave portion and the center line is 0.5 μm-6 μm, and the center line is the center line between the lowest point of all concave portions and the highest point of all convex portions in the test view. If the vertical distance between the bottom end of the concave portion and the center line is less than 0.5 μm, it means that the concave portion and the convex portion are too flat, resulting in a decrease in the step resistance of the electromagnetic shielding film prepared with the base film. If the vertical distance between the bottom end of the concave portion and the center line is greater than 6 μm, it will instead cause the circuit board or FPC board containing the electromagnetic shielding film of the base film to have a decreased bending resistance. Therefore, the vertical distance between the bottom end of the concave portion and the center line is 0.5 μm, 1 μm, 2 μm, 4 μm, 5 μm, 6 μm, or an interval consisting of any two values.

[0013] Based on the same analysis as above, in some embodiments, the vertical distance between the top of the convex portion and the center line is 1μm-7μm. Exemplarily, the vertical distance between the top of the convex portion and the center line is 1μm, 2μm, 5μm, 6μm, 7μm or an interval consisting of any two values. The vertical distance between the top of the convex portion and the center line is specifically limited, thereby optimizing the bending resistance and step resistance performance of the circuit board or FPC board containing the corresponding electromagnetic shielding film.

[0014] In order to further optimize the bending resistance and step resistance of the circuit board or FPC board using the corresponding electromagnetic shielding film, in some embodiments, the ratio of the width D of the concave portion of the uneven surface of the base film to the depth of the concave portion is 0.03≤D / H≤1, wherein the width D refers to the maximum width of the concave portion at the uneven surface. Exemplarily, the ratio of the width of the concave portion of the uneven surface of the base film to the depth of the concave portion is 1, 0.9, 0.8, 0.7, 0.6, 0.5, 0.3, 0.2, 0.1, 0.08, 0.06, 0.04, 0.03 or an interval consisting of any two values. The ratio of the width and depth of the concave portion of the uneven surface of the base film is specifically limited, and then the morphological structure of the concave portion of the base film is limited. Within this limited range, the bending resistance of the circuit board or FPC board containing the corresponding electromagnetic shielding film and the high step resistance of the electromagnetic shielding film containing the base film are better.

[0015] In the present invention, the measurement of the concave width is generally carried out by making slices and then measuring the maximum width of the concave, or by using other available detection instruments to directly measure the maximum width of the concave.

[0016] The number of concave portions on the uneven surface of the base film has a great influence on the bending resistance of the circuit board or FPC board containing the corresponding electromagnetic shielding film and the step resistance of the corresponding electromagnetic shielding film. In some embodiments, the proportion of the concave portions whose bottom end is 1μm-5μm away from the center line is greater than or equal to 80%. The proportion of the number of concave portions whose bottom end is 1μm-5μm away from the center line to the total number of concave portions is specifically defined. The structure of the base film within this proportion range is relatively uniform. When the electromagnetic shielding film is prepared by using it, the electromagnetic shielding film has good step resistance and the circuit board or FPC board containing the electromagnetic shielding film has good bending resistance, and the electromagnetic shielding film has good shielding effectiveness. Exemplarily, the proportion of the concave portions whose bottom end is 1μm-5μm away from the center line is 80%, 85%, 90%, 95%, 100% or an interval consisting of any two values.

[0017] In order to make the electromagnetic shielding film using the base film more stable in terms of the step resistance, shielding effectiveness, and the bending resistance of the circuit board or FPC board containing the electromagnetic shielding film, in some embodiments, the number of recesses whose lowest end of the recess is 2μm-4μm from the center line accounts for greater than or equal to 50%. Exemplarily, the number of recesses whose lowest end of the recess is 2-4μm from the center line accounts for 50%, 55%, 60%, 70%, 80%, 90%, 95%, 100%, or an interval consisting of any two values.

[0018] In order to further optimize the above technical effects, the number of the concave portions whose bottom end is 0.5μm-2μm from the midline accounts for 15%-35%, the number of the concave portions whose vertical distance from the midline is 2μm-4μm accounts for 50%-75%, and the number of the concave portions whose vertical distance from the midline is 4μm-6μm accounts for 5%-25%. It should be noted that the sum of the number of the concave portions at different vertical distances from the bottom end of the above concave portions to the midline is less than or equal to 100%. Exemplarily, the number of recesses whose bottom end is 0.5μm-2μm (excluding 2μm) from the center line accounts for 15%, 18%, 20%, 25%, 30%, 35% or an interval consisting of any two values; the number of recesses whose bottom end is 2μm-4μm (excluding 4μm) from the center line accounts for 50%, 60%, 65%, 70%, 72%, 74%, 75% or an interval consisting of any two values; the number of recesses whose bottom end is 4-6μm from the center line accounts for 5%, 10%, 15%, 20%, 25% or an interval consisting of any two values. The number of recesses with different vertical distances from the bottom end of the recess to the center line is specifically limited, so that the step resistance performance of the electromagnetic shielding film using the base film, the bending resistance performance of the circuit board or FPC board containing the electromagnetic shielding film, and the shielding effectiveness of the electromagnetic shielding film are further optimized.

[0019] In the present invention, an electromagnetic shielding film is also provided. Figure 3 The electromagnetic shielding film includes a base film 1, a shielding layer 2 and an adhesive layer 3 which are stacked in sequence.

[0020] In some embodiments, the base film has a thickness of 2 μm-20 μm. Preferably, the base film has a thickness of 2 μm, 5 μm, 7 μm, 10 μm, 12 μm, 15 μm, 20 μm, or an interval consisting of any two values.

[0021] Preferably, the base film includes, but is not limited to, polystyrene resins, vinyl acetate resins, polyester resins, polyethylene resins, polyamide resins, rubber resins, acrylic resins, phenolic resins, epoxy resins, thermoplastic polyimide resins, carbamate resins, melamine resins, alkyd resins, and ABF resins. Any base film that can meet the carrier function is within the requirements of this solution and will not be listed in detail here. Exemplarily, the film layer is selected from modified epoxy resins, modified acrylic resins, polyethylene terephthalate, polybutylene terephthalate, polyethylene, polyethylene naphthalate, polystyrene, polyvinyl chloride, polysulfone, polyphenylene sulfide, polyetheretherketone, polyphenylene oxide, polytetrafluoroethylene, liquid crystal polymer, polyoxadiazole, epoxy glass cloth, and BT resin. Other base films that can meet the performance requirements are within the requirements of this solution and will not be listed in detail here.

[0022] In some embodiments, the shielding layer has an average thickness of 1 μm-9 μm.

[0023] Preferably, the thickness of the shielding layer can be 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm or an interval consisting of any two values. The average thickness of the shielding layer refers to the average value of the thickness of the shielding layer.

[0024] In some embodiments, 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. The metal shielding layer includes a single metal shielding layer and / or an alloy shielding layer; the single metal shielding layer is made of any one of aluminum, titanium, zinc, iron, nickel, chromium, cobalt, copper, silver, and gold, and the alloy shielding layer is made of any two or more of aluminum, titanium, zinc, iron, nickel, chromium, cobalt, copper, silver, and gold.

[0025] The thickness of the bonding layer is 2 μm-20 μm. The thickness of the bonding layer can be 2 μm, 5 μm, 7 μm, 10 μm, 12 μm, 15 μm, 20 μm, or an interval consisting of any two values.

[0026] Preferably, the adhesive layer includes at least one of resins selected from the group consisting of vinyl acetate, polyester, polyethylene, polyamide, rubber, acrylate, phenolic, epoxy, polyimide, urethane, melamine, alkyd, ABF and the like.

[0027] In some embodiments, the bonding layer contains conductive particles or does not contain conductive particles.

[0028] In some embodiments, a surface of the shielding layer away from the base film is provided with protrusions.

[0029] Preferably, when the adhesive layer does not contain conductive particles, grounding can be achieved by piercing the adhesive film layer through the protrusions provided in the shielding layer, and the insertion loss of the circuit board can be reduced. When the adhesive layer contains conductive particles, the conductive particles can enhance the grounding effect of the electromagnetic shielding film and improve the shielding effectiveness. The conductive particles can be conductive particles separated from each other, or they can be large-particle conductive particles agglomerated; when the conductive particles are conductive particles separated from each other, the grounding conductivity of the adhesive layer can be further improved; and when the conductive particles are large-particle conductive particles agglomerated, the piercing strength can be increased. The electromagnetic shielding film and the shielding film in the present invention refer to the same product.

[0030] The technical solution of the present invention has the following advantages:

[0031] 1. The base film for electromagnetic shielding film provided by the present invention has at least one side of a non-flat surface, the non-flat surface contains concave and convex parts, the vertical height difference ΔH between adjacent concave parts and convex parts satisfies the relationship 1μm≤ΔH≤10μm, and the base film thickness at the bottom of the concave part is greater than or equal to 1 / 5 of the average thickness of the base film. The present invention improves the bending resistance and high step resistance of the base film by limiting the height difference between the concave and convex parts of the non-flat surface of the base film and the base film thickness at the bottom of the concave part.

[0032] 2. The electromagnetic shielding film provided by the present invention comprises a base film, a shielding layer and an adhesive layer stacked in sequence, wherein the base film is the above-mentioned base film for electromagnetic shielding film. The present invention not only improves the step resistance performance of the electromagnetic shielding film and the bending resistance performance of the circuit board or FPC board containing the electromagnetic shielding film, but also effectively improves the electromagnetic shielding effectiveness of the electromagnetic shielding film by applying the above-mentioned base film for electromagnetic shielding film to the electromagnetic shielding film. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0034] Figure 1 Schematic diagram of the structure of a base film for an electromagnetic shielding film in an embodiment of the present invention;

[0035] Figure 2 yes Figure 1 Enlarged view of part A in the middle;

[0036] Figure 3 is a schematic diagram of the structure of an electromagnetic shielding film in an embodiment of the present invention;

[0037] Reference numerals:

[0038] 1-base film; 2-shielding layer; 3-adhesive layer. DETAILED DESCRIPTION

[0039] The following examples are provided for a better understanding of the present invention, but are not intended to limit the best mode of implementation, nor to limit the content and protection scope of the present invention. Any product identical 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 other prior arts shall fall within the protection scope of the present invention.

[0040] If no specific experimental steps or conditions are specified in the examples, the conventional experimental steps or conditions described in the literature in the field can be used. If no manufacturer is specified for the reagents or instruments used, they are all conventional reagent products that can be obtained commercially.

[0041] Example 1

[0042] This embodiment provides an electromagnetic shielding film, and its structural schematic diagram is shown in FIG. Figure 3 As shown, it includes a base film 1, a shielding layer 2 and an adhesive layer 3 which are stacked in sequence.

[0043] The shielding layer is made of copper with a thickness of 1.5μm.

[0044] The adhesive layer is made of acrylic resin and polyester resin with a thickness of 5μm.

[0045] The base film is made of polyimide and epoxy resin, with a thickness of 5μm.

[0046] The vertical height difference between the concave portion and the convex portion of the base film is 1 μm≤ΔH≤3 μm, and the thickness of the base film at the bottom of the concave portion is greater than or equal to 1 / 5 of the average thickness of the base film.

[0047] Example 2

[0048] This embodiment provides an electromagnetic shielding film, whose structure, structural materials and thickness are the same as those of Embodiment 1, except that the vertical height difference between the concave portion and the convex portion of the base film is 3 μm≤ΔH≤7 μm.

[0049] Example 3

[0050] This embodiment provides an electromagnetic shielding film, whose structure, structural materials and thickness are the same as those of Embodiment 1, except that the vertical height difference between the concave portion and the convex portion of the base film is 7 μm≤ΔH≤10 μm.

[0051] Example 4

[0052] This embodiment provides an electromagnetic shielding film, whose structure, structural materials and thickness are the same as those of Embodiment 2, except that the distance between adjacent recesses is greater than or equal to 2 μm.

[0053] Example 5

[0054] This embodiment provides an electromagnetic shielding film, whose structure, structural materials and thickness are the same as those of Embodiment 2, except that the number of recesses within a range of 260 μm on the uneven surface of the base film is 30.

[0055] Example 6

[0056] This embodiment provides an electromagnetic shielding film, whose structure, structural materials and thickness are the same as those of Embodiment 2, except that the number of recesses within a range of 260 μm on the uneven surface of the base film is 20.

[0057] Example 7

[0058] This embodiment provides an electromagnetic shielding film, whose structure, structural materials and thickness are the same as those of Embodiment 2, except that the vertical distance between the bottom of the concave portion and the center line is 4 μm, and the vertical distance between the top of the convex portion and the center line is 5 μm.

[0059] Example 8

[0060] This embodiment provides an electromagnetic shielding film, whose structure, structural materials and thickness are the same as those of Embodiment 2, except that the vertical distance between the bottom of the concave portion and the center line is 2 μm.

[0061] The vertical distance between the top of the protrusion and the center line is 5 μm.

[0062] Example 9

[0063] This embodiment provides an electromagnetic shielding film, whose structure, structural materials and thickness are the same as those of Example 2, except that the ratio of the width D of the concave portion on the uneven surface of the base film to the depth of the concave portion satisfies D / H 0.1≤D / H≤0.5.

[0064] Example 10

[0065] This embodiment provides an electromagnetic shielding film, whose structure, structural materials and thickness are the same as those of Embodiment 9, except that the number of recesses whose bottom ends are at a vertical distance of 1-5 μm from the center line accounts for 92%.

[0066] Embodiment 11

[0067] This embodiment provides an electromagnetic shielding film, whose structure, structural materials and thickness are the same as those of Embodiment 9, except that the number of recesses whose lowest end is 2-4 μm away from the center line accounts for 83%.

[0068] Example 12

[0069] This embodiment provides an electromagnetic shielding film, whose structure, structural materials and thickness are the same as those of Embodiment 2, except that the number of recesses whose bottom ends are 0.5-2 μm away from the center line accounts for 21%,

[0070] The number of the concave portions whose bottom end is 2-4 μm away from the center line accounts for 64%.

[0071] The number of the concave portions whose bottom ends are at a vertical distance of 4-6 μm from the center line accounts for 15%.

[0072] Comparative Example

[0073] This comparative example provides an electromagnetic shielding film, whose structure, structural materials and thickness are the same as those of Example 2, except that the vertical height difference between the concave and convex parts of the base film is 16μm, and the thickness of the base film at the bottom of the concave part is 1 / 10 of the average thickness of the base film.

[0074] Experimental example

[0075] The electromagnetic shielding performance, bending resistance, and high step resistance of the electromagnetic shielding films of Examples 1-12 and the comparative example were tested, and the results are as follows:

[0076] The shielding effectiveness of the electromagnetic shielding film is tested in accordance with GB / T30142-2013; the step resistance performance test is to press the electromagnetic shielding film on the surface of the component with the corresponding step height, and test the grounding resistance of the electromagnetic shielding film. The grounding resistance shall not exceed 1 ohm, and it shall be deemed to be failed if it exceeds 1 ohm; the bending resistance is to stick two electromagnetic shielding films of the same model to be tested on the two surfaces of the bending plate (the bending plate contains the circuit) and press them (pre-pressing time 10 seconds, molding time 180 seconds, molding pressure 120kg, pressing temperature 185℃); after pressing, bake and cure (baking temperature 160℃, baking time 90min); the strip width is 1.5cm, and the bending conditions are: R angle 0.8mm, speed 60 rpm, angle ±135 degrees, load 500g, and when the resistance change of the bending line exceeds 10%, the test is stopped. The results are shown in Table 1.

[0077] Table 1 Performance measurement results of electromagnetic shielding film

[0078] Electromagnetic shielding effectiveness / DB Bending resistance / times Step resistance performance / μm Example 1 More than 60 More than 12000 Greater than 75 Example 2 More than 60 More than 12000 Greater than 75 Example 3 More than 60 More than 12000 Greater than 75 Example 4 More than 60 More than 12000 Greater than 75 Example 5 More than 60 More than 12000 Greater than 75 Example 6 More than 60 More than 12000 Greater than 75 Example 7 More than 60 More than 12000 Greater than 75 Example 8 More than 60 More than 12000 Greater than 75 Example 9 More than 60 Greater than 12500 Greater than 75 Example 10 More than 60 Greater than 12500 Greater than 75 Embodiment 11 More than 60 Greater than 12500 Greater than 75 Example 12 More than 60 Greater than 12500 Greater than 75 Comparative Example 58 8461 38

[0079] According to the data in Table 1, the electromagnetic shielding film formed by the base film provided by the present invention has good performance in resistance to step difference and improves the electromagnetic shielding efficiency. In addition, the circuit board or FPC board containing the electromagnetic shielding film has good bending resistance.

[0080] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled 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 list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the invention.

Claims

1. A base film for an electromagnetic shielding film, characterized in that: At least one side of the base film is a non-flat surface, and the non-flat surface contains concave parts and convex parts. The vertical height difference ΔH between the adjacent concave portions and the adjacent convex portions satisfies the relationship 1 μm≤ΔH≤10 μm, The thickness of the base film at the bottom of the recess is greater than or equal to 1 / 5 of the average thickness of the base film.

2. The base film for electromagnetic shielding film according to claim 1, characterized in that The concave and convex portions of the uneven surface of the base film are arranged at intervals; and / or, The distance between adjacent recesses is greater than or equal to 2 μm.

3. The base film for electromagnetic shielding film according to claim 2, characterized in that: Within a range of 260 μm on the uneven surface of the base film, the number of recesses is less than or equal to 30; and / or, The vertical distance between the bottom end of the concave portion and the center line is 0.5 μm-6 μm, and the center line is the center line between the highest point of the convex portion and the lowest point of the concave portion.

4. The base film for electromagnetic shielding film according to claim 3, characterized in that The vertical distance between the top of the protrusion and the midline is 1 μm-7 μm; and / or, The ratio of the width D of the concave portion on the uneven surface of the base film to the depth of the concave portion is 0.03≤D / H≤1, and the width D refers to the maximum width of the concave portion on the uneven surface.

5. The base film for electromagnetic shielding film according to any one of claims 1 to 4, characterized in that: The number of the concave portions whose bottom ends are vertically spaced from the center line by 1 μm to 5 μm accounts for greater than or equal to 80%.

6. The base film for electromagnetic shielding film according to claim 5, characterized in that The number of the concave portions whose lowest ends are vertically spaced from the center line by 2 μm to 4 μm accounts for greater than or equal to 50%.

7. The base film for electromagnetic shielding film according to claim 3, characterized in that: The number of the concave portions whose bottom ends are vertically spaced from the center line by 0.5 μm to 2 μm accounts for 15% to 35%. The number of the concave portions whose bottom ends are vertically spaced 2 μm to 4 μm from the center line accounts for 50% to 75%. The number of the concave portions whose bottom ends are vertically spaced 4 μm to 6 μm from the center line accounts for 5% to 25%.

8. An electromagnetic shielding film, characterized in that: The invention comprises a base film, a shielding layer and an adhesive layer which are stacked in sequence, and the base film is the base film for electromagnetic shielding film according to any one of claims 1 to 7.

9. The electromagnetic shielding film according to claim 8, characterized in that The thickness of the base film is 2 μm-20 μm, The thickness of the shielding layer is 1 μm-9 μm, The thickness of the bonding layer is 2 μm-20 μm; and / or, The bonding layer contains conductive particles or does not contain conductive particles; and / or, The surface of the shielding layer away from the base film is provided with protrusions.

10. A circuit board, characterized in that: The circuit board comprises the base film for the electromagnetic shielding film according to any one of claims 1 to 7 or the electromagnetic shielding film according to any one of claims 8 to 9.

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