Electromagnetic shielding film with segment difference resistance and circuit board

Abstract

The invention relates to the technical field of electromagnetic shielding films, in particular to a segment-difference-resistant electromagnetic shielding film and a circuit board. According to the electromagnetic shielding film provided by the invention, the electromagnetic shielding film comprises a substrate layer and a shielding layer which are stacked, the elongation percentage delta of the substrate layer is 60%-140%, and the elastic modulus E1 of the substrate layer is 80-130 MPa. According to the electromagnetic shielding film, by limiting the range of the elongation rate and the elastic modulus of the substrate layer, the shielding performance of the electromagnetic shielding film can be improved, and the segment difference resistance of the electromagnetic shielding film can also be improved.

Description

Technical Field

[0001] The invention relates to the technical field of electromagnetic shielding films, and in particular to an electromagnetic shielding film and a circuit board that are resistant to step differences. Background Art

[0002] With the development of miniaturization of communication equipment, the requirements for the miniaturization of integrated circuit boards are getting higher and higher, especially in terms of electromagnetic shielding effectiveness and physical properties of miniaturized communication equipment. The electromagnetic shielding film can be used on the surface of high-step circuit boards or FPC boards, and at the same time, it can have good shielding effectiveness. In addition, the bending resistance of circuit boards or FPC boards can be improved to a certain extent during application.

[0003] The prior art discloses an electromagnetic shielding film containing a substrate layer, which can improve the electromagnetic shielding effectiveness of the electromagnetic shielding film. However, the electromagnetic shielding film has a narrow application range, and especially when used in folding mobile phones, its bending resistance and step resistance are poor. Summary of the invention

[0004] Therefore, the 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. The circuit board or FPC board containing the electromagnetic shielding film has poor bending resistance, thereby providing an electromagnetic shielding film and circuit board that are resistant to step differences.

[0005] The present invention provides an electromagnetic shielding film, see Figure 1 As shown, the electromagnetic shielding film comprises a laminated base layer 2 and a shielding layer 1, the elongation δ of the base layer is between 60% and 140%, and the elastic modulus E1 of the base layer is between 80 and 130 MPa.

[0006] In the present invention, the elongation is the percentage of the increase in the length of the base layer when the base layer is stretched to break, and the bending resistance and step resistance of the electromagnetic shielding film are improved by limiting the elongation of the base layer. The elongation of the base layer is limited to 60%-140%. When the elongation of the base layer is lower than 60%, the electromagnetic shielding film will have poor ductility, and further lead to poor step resistance. The circuit board or FPC board containing the electromagnetic shielding film is prone to stress concentration, which leads to poor bending resistance. When the elongation of the base layer is higher than 140%, the strength of the electromagnetic shielding film will be reduced, which is not conducive to the formation of a shielding layer on the surface of the base layer in the later process. When the elongation of the base layer is between 60% and 140%, the various performances of the electromagnetic shielding film are moderate, and the prepared electromagnetic shielding film fits tightly to the circuit board, meeting the application requirements of bending resistance and step resistance. At the same time, it was found during the experiment that the elastic modulus of the base layer affects the overall performance of the electromagnetic shielding film. The present invention limits the elastic modulus of the base layer to 80-130 MPa. On the one hand, the rigidity of the base layer is moderate, so that the circuit board or flexible circuit board (FPC board) containing the electromagnetic shielding film can show a certain resistance when bending, and the overall structure has good bending resistance, and the electromagnetic shielding film has good step resistance, so that the electromagnetic shielding film can meet the application requirements. On the other hand, the base layer has a certain bearing capacity, which is convenient for the subsequent process to prepare the shielding layer on the surface of the base layer. In the present invention, by controlling the elongation δ of the base layer to 60%-140%, the elastic modulus E of the base layer 1 Controlled at 80~130MPa, elongation δ and elastic modulus E 1 The synergistic effect of these two control factors can greatly improve the step resistance performance of the electromagnetic shielding film and facilitate subsequent processing, while also making the circuit board or FPC board containing the electromagnetic shielding film have excellent bending resistance.

[0007] It can improve the bending resistance and step resistance, and at the same time improve the shielding effectiveness. For example, the elongation of the base layer is 60%, 70%, 85%, 100%, 120% and 140% or an interval consisting of any two values; the elastic modulus of the base layer is 80MPa, 90MPa, 100MPa, 120MPa, 130MPa or an interval consisting of any two values.

[0008] In some of the embodiments, the elongation is a percentage of the ratio of the total deformation ΔL of the gauge length after the specimen is tensile fractured to the original gauge length L: δ = ΔL / L×100%.

[0009] In some of the embodiments, the elastic modulus is an indicator to measure the ease of elastic deformation of a material, and refers to the stress required for a material to produce unit elastic deformation under the action of an external force. Preferably, the elastic modulus is tested by measuring the strain in the range of 0%-1%.

[0010] In order to achieve better technical effects and make the electromagnetic shielding film more superior in terms of its step resistance and shielding effectiveness, the electromagnetic shielding film, in some embodiments, has an elastic modulus E of the base layer. 1 and the elastic modulus E of the electromagnetic shielding film 2 The relationship between them is 0.06≤E 1 / E 2 ≤0.16. Exemplarily, the elastic modulus E of the base layer 1 and the elastic modulus E of the electromagnetic shielding film 2 The relationship E is satisfied 1 / E 2 It can be 0.06, 0.08, 0.09, 0.12, 0.15, 0.16 or a range consisting of any two values. The proportional relationship between the elastic modulus of the substrate layer and the electromagnetic shielding film is specifically limited, so that the elastic modulus of the substrate layer and the elastic modulus of the entire electromagnetic shielding film are maintained within a certain range, so that the electromagnetic shielding film has a certain strength, the step resistance performance of the electromagnetic shielding film is stable, and the overall structure of the electromagnetic shielding film has high adaptability.

[0011] In order to optimize the above technical effects, in some embodiments, the elongation δ of the substrate layer and the elongation δ of the electromagnetic shielding film are t The relationship between them is 0.01≤δ / δ t ≤0.06. Exemplarily, the elongation δ of the substrate layer and the elongation δ of the electromagnetic shielding film t The relationship between them satisfies δ / δ t It can be 0.01, 0.02, 0.03, 0.04, 0.05, 0.06 or an interval consisting of any two values. The proportional relationship between the elongation of the substrate layer and the electromagnetic shielding film is specifically limited, and the elongation of the substrate layer and the elongation of the entire electromagnetic shielding film are kept within a certain range, which is conducive to the transmission and uniform distribution of internal stress of the electromagnetic shielding film, and further improves the step resistance performance of the electromagnetic shielding film. At the same time, it enables effective stress transmission between the electromagnetic shielding film and the circuit board or FPC board, which is conducive to improving the step resistance performance of the circuit board or FPC board containing the electromagnetic shielding film.

[0012] In some embodiments, the elongation δ of the electromagnetic shielding film is t Satisfy the relationship, 1000δ t / E 2 =A×(δ / E 1)+B, wherein A and B are correlation coefficients, the value range of A is 1.9-2.1, and the value range of B is 0.152-0.199. Exemplarily, the value range of the correlation coefficient A can be 1.9, 1.95, 2.0, 2.05, 2.1 or an interval consisting of any two values, and the value range of the correlation coefficient B can be 0.152, 0.160, 0.175, 0.183, 0.190, 0.199 or an interval consisting of any two values. Specifically limit the elongation of the electromagnetic shielding film and the elastic modulus E of the electromagnetic shielding film 2 , the relationship between the elongation of the base layer and the elastic modulus of the base layer. The electromagnetic shielding film that meets the above relationship has better performance in terms of step resistance and shielding effectiveness. At the same time, the circuit board or FPC board containing the electromagnetic shielding film has better bending resistance.

[0013] In some embodiments, the tensile strength σ of the base layer 1 14 to 30 MPa. 1 It can be 14Mpa, 16Mpa, 17Mpa, 22Mpa, 25Mpa, 30Mpa or an interval consisting of any two values. In the present invention, the tensile strength of the base layer is further limited, and the elasticity of the base layer will not be too large or too brittle due to the tensile strength of the base layer being too low or too high, which is convenient for preparing the shielding layer on the surface of the base layer in the subsequent process. At the same time, the appropriate tensile strength of the base layer can improve the adaptability of the electromagnetic shielding film. Therefore, the present invention limits the tensile strength of the base layer σ 1 The pressure is 14-30 MPa, which can further improve the step resistance performance on the one hand, and improve the application performance of the electromagnetic shielding film on the other hand.

[0014] In order to optimize the above technical effects, the tensile strength σ of the substrate layer 1 and the tensile strength σ of the electromagnetic shielding film 2 The relationship between them satisfies 0.7≤σ 1 / σ 2 ≤2.3. Exemplarily, the tensile strength of the base layer σ 1 and the tensile strength σ of the electromagnetic shielding film 2 The relationship between them satisfies 1 / σ 2 It can be 0.7, 1.0, 1.2, 1.5, 1.8, 2.0, 2.3 or any interval consisting of two values. The tensile strength of the substrate layer σ 1 and the tensile strength of the electromagnetic shielding film σ 2 The relationship between them is mainly to allow the base layer and the overall structure of the electromagnetic shielding film to adapt to each other.

[0015] In some embodiments, the thickness of the base layer is 2-20 μm. Preferably, the thickness of the base 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.

[0016] In some embodiments, the thickness of the shielding layer is 2 With the base layer thickness T 1 Satisfy the relationship 0.2≤T 2 / T 1 ≤0.7. Exemplarily, the thickness of the shielding layer T 2 With the base layer thickness T 1 Satisfy the relationship T 2 / T 1 It can be 0.2, 0.3, 0.4, 0.5, 0.6, 0.7 or any interval consisting of two values. By limiting the proportional relationship between the thickness of the shielding layer and the base layer, the step resistance performance and shielding effectiveness of the electromagnetic shielding film can be optimized. Among them, the thickness of the shielding layer is the average thickness of the shielding layer.

[0017] 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. The shielding layer can be a single layer or multiple layers, and the materials between the layers in a multilayer structure can be the same or different.

[0018] Preferably, the base layer 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, polyimide resins, carbamate resins, melamine resins, alkyd resins, and ABF resins. Any base layer that can meet the requirements of the carrier is within the scope of the present invention, and will not be listed in detail here. Exemplarily, the base 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 polymers, polyoxadiazole, epoxy glass cloth, and BT resin. Other base layers that can meet the performance requirements are within the scope of the present invention, and will not be listed in detail here.

[0019] Please continue to see Figure 1The shielding layer is stacked with a bonding layer 3 on the surface away from the base layer. Preferably, the bonding layer includes at least one of vinyl acetate, polyester, polyethylene, polyamide, rubber, acrylate, phenolic, epoxy, polyimide, urethane, melamine, alkyd, ABF and other resins. The bonding layer mainly plays a bonding role and can bond the overall structure of the electromagnetic shielding film to the surface of the circuit board or components.

[0020] The thickness of the bonding layer is 2-20 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. The thickness of the bonding layer will affect the overall thickness of the electromagnetic shielding film, thereby limiting the thickness of the bonding layer.

[0021] In some embodiments, the bonding layer contains conductive particles or does not contain conductive particles.

[0022] Preferably, when the adhesive layer does not contain conductive particles, grounding can be achieved by piercing the adhesive layer through the protrusions arranged on the surface of the shielding layer away from the base 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. Figure 2 The bonding layer contains conductive particles, which can be separated conductive particles or large particles aggregated together; when the conductive particles are separated conductive particles, the grounding conductivity of the bonding layer can be further improved; and when the conductive particles are large particles aggregated together, the piercing strength can be increased. The height of the protrusion is 1-9 μm.

[0023] In order to solve the same problem, on the other hand, the present invention provides a circuit board composed of the above-mentioned electromagnetic shielding film. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] 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.

[0025] Figure 1 It is a schematic diagram of the structure of an electromagnetic shielding film according to a first embodiment of the present invention;

[0026] Figure 2 is a schematic diagram of the structure of an electromagnetic shielding film in a second embodiment of the present invention;

[0027] Reference numerals:

[0028] 1-shielding layer; 2-base layer; 3-adhesive layer; 4-protrusion; 5-conductive particles. DETAILED DESCRIPTION

[0029] 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.

[0030] 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.

[0031] Example 1

[0032] See also Figure 1 As shown, this embodiment provides an electromagnetic shielding film, the structure of which includes a base layer 2, a shielding layer 1 and an adhesive layer 3 which are stacked.

[0033] The shielding layer is made of copper with a thickness of 1.5 μm, the base layer is made of epoxy resin and polyimide with a thickness of 6.5 μm, and the bonding layer is made of acrylic acid with a thickness of 7.0 μm.

[0034] Among them, the elongation δ of the base layer is 124%, and the elastic modulus E of the base layer is 1 It is 121MPa.

[0035] Example 2

[0036] This embodiment provides an electromagnetic shielding film, whose structure, material and parameters are the same as those of embodiment 1, except that the elongation δ of the base layer is 65%, and the elastic modulus E of the base layer is 1 It is 83MPa.

[0037] Example 3

[0038] This embodiment provides an electromagnetic shielding film, whose structure, material and parameters are the same as those of embodiment 1, except that the elongation δ of the base layer is 138%, and the elastic modulus E of the base layer is 1 It is 134MPa.

[0039] Example 4

[0040] This embodiment provides an electromagnetic shielding film, whose structure, material and parameters are the same as those of embodiment 1, except that the elastic modulus E of the base layer is 1The elastic modulus E of the electromagnetic shielding film 2 The relationship between them is 0.06≤E 1 / E 2 ≤0.12.

[0041] Example 5

[0042] This embodiment provides an electromagnetic shielding film, whose structure, material and parameters are the same as those of embodiment 1, except that the elastic modulus E of the base layer is 1 The elastic modulus E of the electromagnetic shielding film 2 The relationship between them satisfies 0.11≤E 1 / E 2 ≤0.16.

[0043] Example 6

[0044] This embodiment provides an electromagnetic shielding film, whose structure, material and parameters are the same as those of embodiment 1, except that the elongation δ of the base layer is the same as the elongation δ of the electromagnetic shielding film. t The relationship between them is 0.01≤δ / δ t ≤0.04.

[0045] Example 7

[0046] This embodiment provides an electromagnetic shielding film, whose structure, material and parameters are the same as those of embodiment 1, except that the elongation δ of the base layer is the same as the elongation δ of the electromagnetic shielding film. t The relationship between them is 0.03≤δ / δ t ≤0.06.

[0047] Example 8

[0048] This embodiment provides an electromagnetic shielding film, whose structure, material and parameters are the same as those of embodiment 1, except that the elongation δ of the electromagnetic shielding film is t Satisfy the relationship, 1000δ t / E 2 =A×(δ / E 1 )+B, where the correlation coefficient A is 1.9 and the correlation coefficient B is 0.199.

[0049] Example 9

[0050] This embodiment provides an electromagnetic shielding film, whose structure, material and parameters are the same as those of embodiment 1, except that the elongation δ of the electromagnetic shielding film is t Satisfy the relationship, 1000δ t / E 2 =A×(δ / E 1 )+B, where the correlation coefficient A is 2.1 and the correlation coefficient B is 0.152.

[0051] Example 10

[0052] This embodiment provides an electromagnetic shielding film, whose structure, material and parameters are the same as those of embodiment 1, except that the tensile strength σ of the base layer is 1 and the tensile strength σ of the electromagnetic shielding film 2 The relationship between them satisfies 0.7≤σ 1 / σ 2 ≤1.5.

[0053] Embodiment 11

[0054] This embodiment provides an electromagnetic shielding film, whose structure, material and parameters are the same as those of embodiment 1, except that the tensile strength σ of the base layer is 1 and the tensile strength σ of the electromagnetic shielding film 2 The relationship between them satisfies 1.2≤σ 1 / σ 2 ≤2.3.

[0055] Comparative Example

[0056] This comparative example provides an electromagnetic shielding film, whose structure, material and parameters are the same as those of Example 1, except that the elongation δ of the base layer is 52%, and the elastic modulus E of the base layer is 1 It is 74MPa.

[0057] Experimental example

[0058] The electromagnetic shielding performance, step resistance, adhesion performance and bending resistance of the electromagnetic shielding films of Examples 1-11 and the comparative example were tested. The test results are shown in Table 1.

[0059] Among them, the shielding effectiveness of the electromagnetic shielding film is tested in accordance with GB / T30142-2013; 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 circuits) and press them (pre-pressing time 10 seconds, molding time 180 seconds, molding pressure 120kg, pressing temperature 185°C); baking and curing after pressing (baking temperature 160°C, 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, when the resistance change of the bending line exceeds 10%, stop the test; the high-break 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 fail if it exceeds 1 ohm.

[0060] Table 1 Performance test results of electromagnetic shielding film

[0061]

[0062]

[0063] It can be seen from Table 1 that the circuit board or FPC board of the electromagnetic shielding film provided by the embodiment of the present invention performs well in bending resistance, step resistance of the electromagnetic shielding film and electromagnetic shielding effectiveness.

[0064] 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. An electromagnetic shielding film, characterized in that: The electromagnetic shielding film comprises a base layer and a shielding layer which are stacked, the elongation δ of the base layer is between 60% and 140%, and the elastic modulus E1 of the base layer is between 80 and 130 MPa.

2. The electromagnetic shielding film according to claim 1, characterized in that The elastic modulus E1 of the base layer and the elastic modulus E2 of the electromagnetic shielding film satisfy the relationship of 0.06≤E1 / E2≤0.

16.

3. The electromagnetic shielding film according to claim 1, characterized in that The elongation δ of the base layer and the elongation δ of the electromagnetic shielding film t The relationship between them satisfies 0.01≤δ t / δ≤0.

06.

4. The electromagnetic shielding film according to claim 2 or 3, characterized in that: The elongation δ of the electromagnetic shielding film t Satisfy the relationship, 1000δ t / E2=A×(δ / E1)+B, where A and B are correlation coefficients, the value range of A is 1.9~2.1, and the value range of B is 0.152~0.

199.

5. The electromagnetic shielding film according to claim 4, characterized in that The tensile strength σ1 of the base layer is 14-30 MPa.

6. The electromagnetic shielding film according to claim 5, characterized in that The tensile strength σ1 of the base layer and the tensile strength σ2 of the electromagnetic shielding film satisfy the relationship 0.7≤σ1 / σ2≤2.

3.

7. The electromagnetic shielding film according to claim 1, characterized in that The thickness T1 of the base layer is 2-20 μm.

8. The electromagnetic shielding film according to claim 7, characterized in that The thickness T2 of the shielding layer and the average thickness T1 of the base layer satisfy the relationship 0.2≤T2 / T1≤0.

7.

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

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

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