Electromagnetic shielding film and circuit board

Abstract

The invention relates to the technical field of electronics, and discloses an electromagnetic shielding film and a circuit board, the electromagnetic shielding film comprises a substrate layer, a shielding layer and a bonding layer, and the substrate layer, the shielding layer and the bonding layer are stacked in sequence; the springback index of the electromagnetic shielding film is 0.2 GF-0. 9GF, the elongation at break of the two electromagnetic shielding films which are arranged in an oppositely-attached mode is 2%-15%, and the elastic modulus of the two electromagnetic shielding films which are arranged in an oppositely-attached mode is 0.7 GPA-3GPA. According to the electromagnetic shielding film, when the rebound index of the electromagnetic shielding film is in the range of 0.2 GF-0. 9GF, the elongation at break of the two electromagnetic shielding films which are oppositely attached is in the range of 2%-15%, and the elastic modulus of the electromagnetic shielding film is in the range of 0.7 GPA-3GPA, the electromagnetic shielding film not only has high bending resistance and segment difference resistance, but also can be used for manufacturing the electromagnetic shielding film. And meanwhile, the electromagnetic shielding film also has efficient shielding effectiveness and high adaptability.

Description

Technical Field

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

[0002] An electromagnetic shielding film is a key material for reducing electromagnetic interference, and it is widely used in various electronic devices such as mobile phones and computers. With the rapid development of folding screens, the requirements for electromagnetic shielding films are getting higher and higher. In order to enable folding mobile phones to operate normally and avoid electromagnetic interference generated by the outside and themselves, it is necessary to apply an electromagnetic shielding film on the surface of electronic devices such as folding mobile phones to ensure good electromagnetic shielding effect even in the folded state of the electronic device.

[0003] However, when the current electromagnetic shielding film is applied to folding mobile phone components, the electromagnetic shielding film cannot adapt to the high step difference and high-frequency bending of current folding mobile phone components. After multiple bendings, the shielding effectiveness of the electromagnetic shielding film often decreases or is lost; or the internal circuits of the circuit board or flexible board containing the electromagnetic shielding film are broken. Therefore, in order to overcome the defects in the prior art, an electromagnetic shielding film with bend resistance and high adaptability is urgently needed. Summary of the Invention

[0004] In view of this, the present invention provides an electromagnetic shielding film and a circuit board to solve the problems of bend resistance and high step difference resistance of the electromagnetic shielding film in the prior art, while maintaining the electromagnetic shielding film with high shielding effectiveness and high adaptability.

[0005] In a first aspect, the present invention provides an electromagnetic shielding film, comprising:

[0006] A base layer;

[0007] A shielding layer;

[0008] An adhesive layer, and the base layer, the shielding layer, and the adhesive layer are sequentially laminated;

[0009] The rebound index of the electromagnetic shielding film is 0.2 GF - 0.9 GF, the elongation at break of two oppositely pasted electromagnetic shielding films is 2% - 15%, and the elastic modulus of two oppositely pasted electromagnetic shielding films is 0.7 GPA - 3 GPA.

[0010] Among them, the base layer includes, but is not limited to, polystyrene-based resins, vinyl acetate resins, polyester resins, polyethylene resins, polyamide resins, rubber resins, acrylate resins, phenolic resins, epoxy resins, thermoplastic polyimide resins, urethane resins, melamine resins, alkyd resins, and ABF resins. Any resin that can meet the requirements of the carrier function is within the scope of this solution, and will not be elaborated here. 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; among them, 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 provided in one or more layers stacked on top of each other. When multiple layers are stacked, the materials between the layers can be the same or different.

[0011] The adhesive layer includes, but is not limited to, acrylate glue, silicone glue, polyurethane glue, and epoxy resin glue. It can also be made of the same material as the base layer. Any adhesive material that can meet the application requirements and environmental conditions is within the scope of this solution, and will not be elaborated here. The role of the adhesion is to bond the entire electromagnetic shielding film to the surface of the circuit board or component, playing a good adhesion role. The average thickness of the adhesive layer can be: 2μm - 8μm. Exemplarily, the average thickness of the adhesive layer can be: 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, or any interval composed of two values. Of course, the average thickness of the adhesive layer is not limited to the specific values listed above, and it can be set according to actual usage requirements, and will not be elaborated further here.

[0012] In addition, the resilience index of the electromagnetic shielding film refers to the ability of the material to return to its original shape or original size after being stressed, and the resilience index is also measured by the method of facing and pasting. Exemplarily, the resilience index of the electromagnetic shielding film in the present invention can be: 0.2 GF, 0.3 GF, 0.4 GF, 0.5 GF, 0.6 GF, 0.7 GF, 0.8 GF, 0.9 GF, or an interval composed of any two values. The elongation at break of two facing and pasting electromagnetic shielding films refers to the elongation ratio experienced by the material from the start of stretching to breakage when two layers of electromagnetic shielding films are placed together in a relatively adhered manner. Exemplarily, the elongation at break of two facing and pasting electromagnetic shielding films in the present invention can be: 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, or an interval composed of any two values. The elastic modulus of two facing and pasting electromagnetic shielding films refers to the ability of the material to undergo elastic deformation when stressed when two layers of electromagnetic shielding films are placed together in a relatively adhered manner. Exemplarily, the elastic modulus of two facing and pasting electromagnetic shielding films in the present invention can be 0.7 GPA, 0.8 GPA, 0.9 GPA, 1 GPA, 1.1 GPA, 1.2 GPA, 1.3 GPA, 1.4 GPA, 1.5 GPA, 1.6 GPA, 1.7 GPA, 1.8 GPA, 1.9 GPA, 2 GPA, 2.1 GPA, 2.2 GPA, 2.3 GPA, 2.4 GPA, 2.5 GPA, 2.6 GPA, 2.7 GPA, 2.8 GPA, 2.9 GPA, 3 GPA, or an interval composed of any two values. Of course, the resilience index, elongation at break, and elastic modulus of the electromagnetic shielding film are not limited to the specific values listed above. According to the average thickness, material, etc. of the actually set base layer, shielding layer, and adhesive layer, the corresponding resilience index, elongation at break, and elastic modulus can be obtained.

[0013] When the resilience index of the electromagnetic shielding film is in the range of 0.2 GF - 0.9 GF, the elongation at break of two facing and pasting electromagnetic shielding films is in the range of 2% - 15%, and the elastic modulus is in the range of 0.7 GPA - 3 GPA, the electromagnetic shielding film has high bending resistance and step difference resistance, and at the same time, the circuit board or flexible board containing the electromagnetic shielding film also has good bending resistance. Further, it can meet the application requirements of existing circuit boards or flexible boards and has high adaptability. If the resilience index, elastic modulus, and elongation at break of the electromagnetic shielding film are outside the above ranges, the bending resistance of the electromagnetic shielding film and the circuit board or flexible board containing the electromagnetic shielding film is poor.

[0014] In an alternative embodiment, the average thickness T1 of the base layer and the average thickness T2 of the shielding layer satisfy: T1 ≥ T2.

[0015] When the average thickness of the base layer is greater than or equal to the average thickness of the shielding layer, the laminated structure can be well protected and the laminated structure can be well stabilized. At the same time, when the average thickness of the base layer is greater than the average thickness of the shielding layer, the base layer can absorb the stress generated inside, can improve the elongation at break of the overall electromagnetic shielding film, and keep the resilience index and elastic modulus of the electromagnetic shielding film within a suitable range, so that the electromagnetic shielding film and the circuit board or flexible board containing the electromagnetic shielding film have better bending resistance performance, and the step difference resistance performance of the electromagnetic shielding film is also improved.

[0016] In an alternative embodiment, the average thickness T1 of the base layer and the average thickness T2 of the shielding layer satisfy the relationship: 0.1 ≤ T2 / T1 ≤ 0.95.

[0017] Wherein, in the present invention, T2 / T1 can be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 0.91, 0.92, 0.93, 0.94, 0.95 or an interval composed of any two numerical values. By selecting a suitable average thickness ratio, the laminated structure between the base layer and the shielding layer can be made more firm, and the bending resistance performance of the electromagnetic shielding film and the circuit board and flexible board containing the electromagnetic shielding film can be improved.

[0018] In an alternative embodiment, the average thickness T1 of the base layer and the average thickness T3 of the adhesive layer satisfy: T1 ≥ T3. Ensuring that the average thickness of the base layer is greater than or equal to the average thickness of the adhesive layer helps to improve the structural stability and enhance the bonding strength between the electromagnetic shielding film and the circuit board or flexible board; at the same time, it further improves the bending resistance performance of the electromagnetic shielding film and the circuit board and flexible board containing the electromagnetic shielding film.

[0019] In an alternative embodiment, the average thickness T1 of the base layer and the average thickness T3 of the adhesive layer satisfy the relationship: 0.35 ≤ T3 / T1 ≤ 1.7.

[0020] Wherein, in the present invention, T3 / T1 can be 0.35, 0.36, 0.37, 0.38, 0.39, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7 or an interval composed of any two numerical values. By selecting a suitable average thickness ratio, the bending resistance performance of the electromagnetic shielding film and the circuit board and flexible board containing the electromagnetic shielding film can be made more stable.

[0021] In an alternative embodiment, the average thickness of the shielding layer is 1 μm - 8 μm. Exemplarily, the average thickness of the shielding layer can be: 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, or an interval composed of any two values. Of course, the average thickness of the shielding layer is not limited to the specific values listed above, and it can be set according to actual usage requirements, and no more details will be elaborated here.

[0022] In an alternative embodiment, the material of the shielding layer is at least one of aluminum, titanium, zinc, iron, nickel, chromium, cobalt, copper, silver, and gold. That is to say, the shielding layer can be a metal shielding layer, and the metal shielding layer can be a single shielding layer or an alloy shielding layer, that is, it can be supported by any one of the materials of aluminum, titanium, zinc, iron, nickel, chromium, cobalt, copper, silver, and gold, or made of any two or more materials. Using a metal shielding layer can ensure that the shielding layer has good electrical conductivity and at the same time make the electromagnetic shielding film have better shielding effectiveness.

[0023] In an alternative embodiment, the average thickness T1 of the base layer, the average thickness T2 of the shielding layer, and the average thickness T3 of the adhesive layer satisfy the relationship: T3 + T2 ≤ T1. In this way, it can effectively ensure that the sum of the average thicknesses of the adhesive layer and the shielding layer does not exceed the average thickness of the base layer, and the base layer can well distribute the stress inside the electromagnetic shielding film to ensure that the entire electromagnetic shielding film and the circuit board or flexible board containing the electromagnetic shielding film have high bending resistance; at the same time, the base layer can also play a good protective role for the electromagnetic shielding film.

[0024] In an alternative embodiment, the average thickness T1 of the base layer, the average thickness T2 of the shielding layer, and the average thickness T3 of the adhesive layer satisfy the relationship: 0.3 < T3 / (T2 + T1) ≤ 1.1.

[0025] Among them, in the present invention, T3 / (T2 + T1) can be 0.31, 0.35, 0.38, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, or an interval composed of any two values. Making the average thickness T3 of the adhesive layer divided by the sum of the average thickness T2 of the shielding layer and the average thickness T1 of the base layer greater than or equal to 0.3 and less than or equal to 1.1, by reasonably setting the ratio of the average thickness T3 of the adhesive layer relative to the base layer and the shielding layer, the overall structural stability of the electromagnetic shielding film can be effectively improved, the bending resistance of the electromagnetic shielding film and the circuit board or flexible board containing the electromagnetic shielding film can be improved, and at the same time, the bonding strength between the electromagnetic shielding film and the circuit board or flexible board can be ensured.

[0026] In an alternative embodiment, the side of the shielding layer away from the base layer has a protrusion.

[0027] In an alternative embodiment, the adhesive layer contains conductive particles.

[0028] In an alternative embodiment, the overall thickness of the electromagnetic shielding film is 5 μm - 25 μm, specifically, it can be any interval composed of any two values among 8 μm, 12 μm, 15 μm, 17 μm, 19 μm, 20 μm, 22 μm, and 25 μm.

[0029] In this embodiment, the adhesive layer containing conductive particles can effectively enhance the conduction path and improve the conductivity and shielding effectiveness of the shielding layer.

[0030] In a second aspect, the circuit board includes the electromagnetic shielding film in any of the above embodiments.

[0031] Compared with the prior art, the beneficial effects of the present invention are as follows: when the rebound index of the electromagnetic shielding film is in the range of 0.2 GF - 0.9 GF, the elongation at break of two oppositely attached electromagnetic shielding films is in the range of 2% - 15%, and the elastic modulus of the electromagnetic shielding film is in the range of 0.7 GPA - 3 GPA, the electromagnetic shielding film not only has high bending resistance performance, but also has high shielding effectiveness and high adaptability. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. Obviously, the following drawings are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0033] Figure 1 is a schematic structural diagram of the electromagnetic shielding film according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0034] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

[0035] In addition, the technical features involved in different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0036] Embodiment 1

[0037] See Figure 1As shown in the figure, it is a schematic structural diagram of an electromagnetic shielding film provided by an embodiment of the present invention.

[0038] In this embodiment, an electromagnetic shielding film is provided, including: a base layer, a shielding layer, and an adhesive layer, and the base layer, the shielding layer, and the adhesive layer are stacked in sequence. Among them, the average thickness of the base layer is 5 μm, and the materials used are epoxy resin and rubber; the average thickness of the shielding layer is 2.3 μm, and the material used is a copper shielding layer; the average thickness of the adhesive layer is 2.6 μm, and the material used is acrylic resin. The rebound index of the electromagnetic shielding film is 0.2 GF, the elongation at break of two oppositely attached electromagnetic shielding films is 8%, and the elastic modulus of two oppositely attached electromagnetic shielding films is 3 GPA.

[0039] Embodiment 2

[0040] Other technical features of this embodiment are the same as those of Embodiment 1. The difference is that: the rebound index of the electromagnetic shielding film is 0.5 GF, the elongation at break of two oppositely attached electromagnetic shielding films is 15%, and the elastic modulus of two oppositely attached electromagnetic shielding films is 0.7 GPA.

[0041] Embodiment 3

[0042] Other technical features of this embodiment are the same as those of Embodiment 1. The difference is that: the rebound index of the electromagnetic shielding film is 0.9 GF, the elongation at break of two oppositely attached electromagnetic shielding films is 2%, and the elastic modulus of two oppositely attached electromagnetic shielding films is 1.8 GPA.

[0043] Comparative Example 1

[0044] This comparative example provides an electromagnetic shielding film, whose structure and the materials of each structure are the same as those of Embodiment 1. The difference is that: the rebound index of the electromagnetic shielding film is 1.2 GF, the elongation at break of two oppositely attached electromagnetic shielding films is 5%, and the elastic modulus of two oppositely attached electromagnetic shielding films is 3.1 GPA.

[0045] Test Example

[0046] In this test example, the test method for the bending resistance of the electromagnetic shielding film is as follows: for the bending resistance test, two electromagnetic shielding films of the same model to be tested are attached to the two surfaces of a bending plate (the bending plate contains circuits) and pressed (pre-pressing time: 10 seconds, forming time: 180 seconds, forming pressure: 120 kg, pressing temperature: 185 °C); after pressing, it is baked and cured (baking temperature: 160 °C, baking time: 90 min); the width of the sample strip is 1.5 cm, and the bending conditions are: R angle 0.8 mm, speed 60 revolutions / min, angle ±135 degrees, load 500 g. When the change in the resistance of the bent circuit exceeds 10%, the test is stopped. The shielding effectiveness of the electromagnetic shielding film is detected in accordance with GB / T 30142-2013; for the step resistance test, the electromagnetic shielding film is pressed onto a test plate with a corresponding height, and a scanning electron microscope is used to observe the corresponding height at which the shielding layer breaks. Among them, in the test results, the test results in Comparative Example 1 are used as the benchmark (poor), and the test results are divided into poor, good, and excellent. As shown in Table 1, they are the performance parameters between the examples and the comparative examples.

[0047] Table 1

[0048] Flexural resistance Resistance to step difference Electromagnetic shielding effectiveness Example 1 Good Good Good Example 2 Good Good Good Example 3 Good Good Good Comparative example 1 Poor Poor Poor

[0049] It can be seen that when the springback index of the electromagnetic shielding film is in the range of 0.2 GF - 0.9 GF, the elongation at break of two oppositely attached electromagnetic shielding films is in the range of 2% - 15%, and the elastic modulus of the electromagnetic shielding film is in the range of 0.7 GPA - 3 GPA, the electromagnetic shielding film not only has high bending resistance performance and step resistance performance, but also has high shielding effectiveness and high adaptability.

[0050] Although the embodiments of the present invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the present invention, and such modifications and variations all fall within the scope defined by the appended claims.

Claims

1. An electromagnetic shielding film, characterized in that: include: basal layer; Shielding layer; A bonding layer, wherein the base layer, the shielding layer and the bonding layer are stacked in sequence; The rebound index of the electromagnetic shielding film is 0.2GF-0.9GF, the elongation at break of the two electromagnetic shielding films arranged opposite to each other is 2%-15%, and the elastic modulus of the two electromagnetic shielding films arranged opposite to each other is 0.7GPA-3GPA.

2. The electromagnetic shielding film according to claim 1, characterized in that The average thickness T1 of the base layer and the average thickness T2 of the shielding layer satisfy: T1≥T2, or satisfy the relationship: 0.1≤T2 / T1≤0.

95.

3. The electromagnetic shielding film according to claim 1, characterized in that The average thickness T1 of the base layer and the average thickness T3 of the bonding layer satisfy: T1≥T3, or satisfy the relationship: 0.35≤T3 / T1≤1.

7.

4. The electromagnetic shielding film according to claim 1, characterized in that The average thickness of the shielding layer is 1 μm-8 μm.

5. The electromagnetic shielding film according to claim 1, characterized in that The material of the shielding layer is at least one of gold, silver or copper.

6. The electromagnetic shielding film according to claim 1, characterized in that The average thickness T1 of the base layer, the average thickness T2 of the shielding layer, and the average thickness T3 of the bonding layer satisfy the relationship: T3+T2≤T1.

7. The electromagnetic shielding film according to claim 1, characterized in that The average thickness T1 of the base layer, the average thickness T2 of the shielding layer, and the average thickness T3 of the bonding layer satisfy the relationship: 0.3<T3 / (T2+T1)≤1.

1.

8. The electromagnetic shielding film according to claim 1, characterized in that The shielding layer has a protrusion on a side away from the base layer.

9. The electromagnetic shielding film according to claim 1, characterized in that The adhesive layer contains conductive particles.

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

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