Electromagnetic shield film and circuit board
By setting peaks and troughs on the side of the shielding layer near the adhesive film layer, and positioning the conductive particles opposite to the peaks, the problems of poor grounding performance and adhesive overflow in existing electromagnetic shielding films are solved, achieving better grounding effect and pressing stability.
Patent Information
- Application Number
- CN202211388437.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2022-11-08
- Publication Date
- 2025-11-25
- Estimated Expiration
- 2042-11-08
AI Technical Summary
The shielding layer of existing electromagnetic shielding films has a flat surface on the side near the adhesive layer, which results in less effective contact with conductive particles, poor grounding performance, and the adhesive layer is prone to overflow during the pressing process.
On the side of the shielding layer near the adhesive film layer, peaks and troughs are set, and conductive particles are set opposite to the peaks. The distance between adjacent peaks is 2-40μm, the peak height is 1-10μm, and the trough depth is 1-10μm. The surface of the conductive particles has a raised structure to ensure effective contact between the conductive particles and the circuit board ground layer.
The grounding performance of the electromagnetic shielding film was improved, the adhesive overflow of the film layer was avoided, and the good adhesion and appearance of the electromagnetic shielding film to the circuit board were ensured.
Smart Images
Figure CN115696899B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of electronic technology, and in particular to an electromagnetic shielding film and circuit board. Background Technology
[0002] As electronic products become lighter, smaller, thinner, and higher-performance, electromagnetic interference between electronic components can severely affect the communication signals of these products. To address these issues, electromagnetic shielding films are needed to shield against this interference. Currently, commonly used electromagnetic shielding films for circuit boards consist of an insulating layer, a shielding layer, and an adhesive film layer stacked sequentially. The shielding layer has a relatively flat surface, and the adhesive film layer contains conductive particles. Its grounding mechanism relies on the combined action of the shielding layer and the conductive particles. During use, the electromagnetic shielding film needs to be pressed onto the circuit board at high temperature. During this hot-pressing process, the shielding layer connects electrically to the ground plane of the circuit board through the conductive particles, thereby guiding the interference charge into the ground plane of the circuit board, thus achieving shielding. In the process of implementing this invention, the inventors discovered the following technical problem in the prior art: the side of the shielding layer near the adhesive film layer is a flat surface, resulting in less effective contact with the conductive particles during the pressing process, leading to poor grounding performance of the electromagnetic shielding film. Summary of the Invention
[0003] The purpose of this invention is to provide an electromagnetic shielding film and a circuit board that can improve the grounding performance of the electromagnetic shielding film and prevent adhesive overflow during the lamination process.
[0004] To achieve the above objectives, the present invention provides an electromagnetic shielding film, comprising a shielding layer and an adhesive film layer;
[0005] The shielding layer has peaks and troughs on the side near the adhesive film layer. The adhesive film layer contains conductive particles, and at least a portion of the conductive particles are positioned opposite to the peaks. The distance between two adjacent peaks is 2-40 μm.
[0006] As an improvement to the above scheme, the height of the wave peak is 1-10 μm.
[0007] As an improvement to the above scheme, the depth of the trough is 1-10 μm.
[0008] As an improvement to the above scheme, the ratio of the distance between two adjacent peaks to the distance between two adjacent troughs is 0.1-10.
[0009] As an improvement to the above solution, in the bulge where the wave crest is located, the ratio of the cross-sectional area at 3 / 4 of the distance from the bottom of the bulge to the cross-sectional area at the bottom of the bulge in the thickness direction of the electromagnetic shielding film is no more than 30%.
[0010] As an improvement to the above solution, in the bulge where the wave crest is located, the ratio of the cross-sectional area at 1 / 2 of the distance from the bottom of the bulge to the cross-sectional area at the bottom of the bulge in the thickness direction of the electromagnetic shielding film is not less than 65%.
[0011] As an improvement to the above scheme, at least 30% of the conductive particles are positioned opposite to the wave crest.
[0012] As an improvement to the above scheme, the conductive particles have a raised structure on their surface.
[0013] To achieve the above objectives, the present invention also provides a circuit board, including a circuit board body and an electromagnetic shielding film as described in any of the above embodiments; the electromagnetic shielding film is pressed together with the circuit board body; the side of the shielding layer near the adhesive film layer is electrically connected to the ground layer of the circuit board body through conductive particles.
[0014] Compared with the prior art, the electromagnetic shielding film and circuit board provided by the present invention have at least one of the following beneficial effects: by setting peaks and troughs on the side of the shielding layer near the adhesive film layer, the peaks have better piercing performance when penetrating the adhesive film layer, which can improve the contact degree with conductive particles and is beneficial to improving the grounding performance of the electromagnetic shielding film; by setting at least a portion of the conductive particles opposite to the peaks, the contact degree between the peaks and conductive particles 21 can be improved, increasing the interference charge introduced into the ground layer of the circuit board, which is beneficial to improving the grounding performance of the electromagnetic shielding film. Attached Figure Description
[0015] Figure 1 This is a schematic diagram of the structure of the first electromagnetic shielding film provided in the embodiments of the present invention;
[0016] Figure 2 This is a schematic diagram of the peaks and troughs in the electromagnetic shielding film provided in an embodiment of the present invention;
[0017] Figure 3 This is another schematic diagram of the wave crests and troughs in the electromagnetic shielding film provided in the embodiment of the present invention;
[0018] Figure 4 This is a schematic diagram of the structure of the second type of electromagnetic shielding film provided in an embodiment of the present invention;
[0019] Figure 5 This is a schematic diagram of the structure of the third type of electromagnetic shielding film provided in the embodiments of the present invention;
[0020] Figure 6 This is a schematic diagram of the structure of the third type of electromagnetic shielding film provided in the embodiments of the present invention;
[0021] Figure 7 This is a schematic diagram of the structure of a circuit board provided in an embodiment of the present invention.
[0022] Among them, 1. shielding layer; 2. adhesive film layer; 3. insulating layer; 4. carrier layer; 5. protective film layer; 6. circuit board body; 21. conductive particles. Detailed Implementation
[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0024] In the description of the specification and claims, it should be understood that the terms "upper", "lower", "left", "right", "front", "rear", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the embodiments of the present invention, and do not indicate or imply that the device or component referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the embodiments of the present invention.
[0025] Furthermore, the terms "first," "second," etc., used in the specification and claims are used only to distinguish the description of the same technical features and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated, nor necessarily the order of description or chronological sequence. Where appropriate, the terms are interchangeable. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature.
[0026] See Figure 1 An embodiment of the present invention provides an electromagnetic shielding film, including a shielding layer 1 and an adhesive film layer 2; the shielding layer 1 has a peak and a trough on the side near the adhesive film layer 2; the adhesive film layer 2 is provided with conductive particles 21, and at least a portion of the conductive particles 21 are arranged opposite to the peak.
[0027] In this invention, by setting peaks and troughs on the side of the shielding layer 1 near the adhesive film layer 2, the peaks have better piercing performance when penetrating the adhesive film layer 2. Under the premise that the distance parameter between two adjacent peaks is appropriate, the troughs have better adhesive-containing space, preventing the peaks from being too close together, which would reduce the adhesive capacity and cause the electromagnetic shielding film to detach from the circuit board during the peeling process of the carrier layer. Simultaneously, under the premise that the distance parameter between two adjacent peaks is appropriate, the peaks will not be too far apart, which would reduce the contact between the peaks and the conductive particles 21, thereby reducing the interference charge introduced into the circuit board ground layer and lowering the grounding performance of the electromagnetic shielding film. Furthermore, when at least some of the conductive particles 21 are arranged opposite to the peaks, the contact degree between the peaks and the conductive particles 21 can be increased, increasing the interference charge introduced into the circuit board ground layer, which is beneficial to improving the grounding performance of the electromagnetic shielding film.
[0028] For example, a wave crest is the maximum amplitude of a wave within a certain wavelength range, while the opposite minimum amplitude is called a wave trough. See also Figure 1 Point A is located at one of the wave peaks, and point B is located at one of the wave troughs.
[0029] In this invention, the distance between two adjacent peaks is 2-40 μm. Setting the distance between two adjacent peaks to 2-40 μm ensures that the troughs have sufficient space to accommodate the adhesive in the adhesive film layer 2 during the pressing process, preventing adhesive overflow from the adhesive film layer 2 during pressing.
[0030] In this design, the height of the wave crest is 1-10 μm. By setting the height of the wave crest to 1-10 μm, the shielding layer 1 and the adhesive film layer 2 can have sufficient contact area, thereby tightly binding the shielding layer 1 and the adhesive film layer 2 together through the wave crest. The wave crest acts like positioning nails between the two layers of the electromagnetic shielding film, firmly securing the two layers together and increasing the bonding force of the electromagnetic shielding film, thus preventing delamination during the pressing process.
[0031] In this design, the depth of the trough is 1-10 μm. By setting the depth of the trough to 1-10 μm, the adhesive material constituting the adhesive film layer 2 is squeezed into the recessed position where the trough of the shielding layer 1 is located, increasing the adhesive capacity. On the one hand, it reduces the likelihood of board bursting, avoiding the problem of high-temperature board bursting caused by insufficient adhesive capacity in existing electromagnetic shielding films, thus effectively ensuring the grounding of the electromagnetic shielding film and discharging interference charges. On the other hand, it prevents the adhesive from overflowing to the edge of the circuit board during lamination, thereby enabling the circuit board after laminating the shielding film to have a good appearance.
[0032] In this design, the ratio of the distance between two adjacent peaks to the distance between two adjacent troughs is 0.1-10. By setting this ratio to 0.1-10, the peaks distributed on the side of the shielding layer 1 closest to the adhesive film layer 2 have a better contact area with the adhesive film layer 2. This allows the peaks to penetrate into the adhesive film layer 2 during the lamination process and contact the conductive particles 21, thereby contacting the ground plane of the circuit board.
[0033] For example, see Figure 2 A1 to A4 represent the wave peaks in the shielding layer 1, and B1 to B3 represent the wave troughs. The distance S1 between two adjacent wave peaks is 2-40 μm, and the ratio of the distance S1 between two adjacent wave peaks to the distance S2 between two adjacent wave troughs is 0.1-10. When the distance S1 from wave peak A1 to wave peak A2 is 2 μm and the ratio is 0.1, the distance S2 from wave trough B1 to wave trough B2 is 20 μm; when S1 is 20 μm and the ratio is 0.1, S2 is 200 μm; when S1 is 40 μm and the ratio is 0.1, S2 is 400 μm. This indicates that there are two adjacent wave peaks that are very close together and two adjacent wave troughs that are far apart. When the distance S1 from wave crest A2 to wave crest A3 is 2 μm and the ratio is 10, the distance S2 from wave trough B2 to wave trough B3 is 0.2 μm. When S1 = 20 μm and the ratio is 10, S2 = 2 μm; when S1 = 40 μm and the ratio is 10, S2 = 4 μm. This indicates that there are two adjacent wave crests that are relatively far apart and two adjacent wave troughs that are relatively close together. When the ratio of the distance between two adjacent wave crests to the distance between two adjacent wave troughs is 0.1-10, the troughs between two adjacent wave crests that are relatively far apart have better adhesive space, preventing adhesive overflow in the adhesive layer 2 during the pressing process and preventing board bursting. When conductive particles are provided corresponding to adjacent and relatively close wave crests, after the electromagnetic shielding film is pressed, these two conductive particles can make close contact due to their sufficiently close distance, thereby improving the grounding performance of the electromagnetic shielding film.
[0034] In this scheme, in the bulge where the wave crest is located, the ratio of the cross-sectional area at 3 / 4 of the distance from the bottom of the bulge to the cross-sectional area at the bottom of the bulge in the thickness direction of the electromagnetic shielding film is not greater than 30%. In the bulge where the wave crest is located, the ratio of the cross-sectional area at 1 / 2 of the distance from the bottom of the bulge to the cross-sectional area at the bottom of the bulge in the thickness direction of the electromagnetic shielding film is not less than 65%.
[0035] It is worth noting that since the protrusion (the crest refers only to the highest point of the protrusion) may be surrounded by multiple recesses of varying heights (the locations of the troughs), a horizontal line corresponding to the highest trough is selected from the edge of the protrusion as the cross-sectional area of the bottom of the protrusion. Therefore, the midpoint from the bottom to the crest is the 1 / 2 mark. See also... Figure 3 The dashed box corresponding to 11 points to the protrusion where peak A1 is located. For peak A2, there are two valleys around it, namely valley B1 and valley B2. Since the height of valley B1 (relative to the side of the shielding layer 1 away from the adhesive film layer 2) is higher than that of valley B2, the horizontal line corresponding to valley B1 is selected as the cross-sectional area of the bottom of the protrusion where peak A2 is located. The cross-sectional area at 1 / 2 of the distance from the bottom of the protrusion and the cross-sectional area at 3 / 4 of the distance from the bottom of the protrusion are obtained in turn.
[0036] In this invention, by setting the ratio of the cross-sectional area at 3 / 4 of the distance from the bottom of the protrusion to the cross-sectional area at the bottom of the protrusion to no more than 30%, and setting the ratio of the cross-sectional area at 1 / 2 of the distance from the bottom of the protrusion to the cross-sectional area at the bottom of the protrusion to no less than 65%, it can be ensured that the protrusion is relatively thin, thereby giving the protrusion better puncture performance in the adhesive film layer 2.
[0037] In this scheme, at least 30% of the conductive particles 21 are positioned opposite to the wave crest. For example, 30%, 40%, 50%, 60%, 70%, 80%, 90%, or 100% of the conductive particles 21 are positioned opposite to the wave crest. By positioning at least 30% of the conductive particles 21 opposite to the wave crest, a sufficient number of conductive particles 21 are distributed on the opposite side of the wave crest, thereby ensuring that more conductive particles 21 contact the ground plane of the circuit board after lamination. This increases the interference charge introduced into the ground plane of the circuit board, thereby improving the grounding performance of the electromagnetic shielding film.
[0038] In this invention, the conductive particles 21 have a raised structure on their surface. To prevent the conductive particles 21 from failing to effectively penetrate the adhesive film layer 2 and contact the shielding layer 1 and the circuit board ground layer during the pressing process, thus reducing the interference charge introduced by the shielding layer 1 to the circuit board ground layer and lowering the grounding performance of the electromagnetic shielding film, a raised structure is provided on the surface of the conductive particles 21. The raised structure can effectively penetrate the adhesive in the adhesive film layer 2, thereby ensuring that the conductive particles 21 can contact the ground layer of the circuit board, increasing the contact area between the shielding layer 1 and the conductive particles 21. At the same time, it can also ensure that the conductive particles 21 can contact the ground layer of the circuit board, increasing the contact area between the ground layer of the circuit board and the conductive particles 21, thereby increasing the interference charge introduced to the ground layer of the circuit board and improving the grounding performance of the electromagnetic shielding film.
[0039] In this design, the conductive particles 21 have a particle size of 0.1-20 μm, and the film layer 2 has a thickness of 2-30 μm. By setting the particle size of the conductive particles 21 to 0.1-20 μm and the thickness of the film layer 2 to 2-30 μm, the conductive particles 21 can achieve a denser filling within the film layer 2, and there can be more contact points between the conductive particles 21, forming a conductive network with a greater number of connections, thus achieving better conductivity.
[0040] In this scheme, the shielding layer 1 includes one or more of the following: 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; wherein the single-metal shielding layer is made of any one of the following materials: aluminum, titanium, zinc, iron, nickel, chromium, cobalt, copper, silver, and gold; and the alloy shielding layer is made of any two or more of the following materials: aluminum, titanium, zinc, iron, nickel, chromium, cobalt, copper, silver, and gold. The composition and shape of the conductive particles 21 are not limited; for example, the conductive particles 21 may be made of any one or more of the following materials: copper, aluminum, titanium, zinc, iron, nickel, chromium, cobalt, silver, and gold.
[0041] In this scheme, the materials used for the adhesive film layer 2 are selected from the following: modified epoxy resin, acrylic resin, modified rubber, and modified thermoplastic polyimide.
[0042] See Figure 4 The electromagnetic shielding film of the present invention is further provided with an insulating layer 3. The insulating layer 3 is disposed on the side of the shielding layer 1 away from the adhesive film layer 2. The insulating layer 3 can effectively electrically isolate the shielding layer 1 from the outside world, thereby ensuring the electromagnetic shielding effect of the shielding layer 1.
[0043] See Figure 5 The electromagnetic shielding film of the present invention further includes a carrier layer 4, which is disposed on the side of the insulating layer 3 away from the shielding layer 1. The carrier layer 4 protects the insulating layer 3 from damage caused by external contact or impact. A thickness of 50 micrometers for the carrier layer 4 provides excellent protection, effectively preventing damage to the insulating layer 3 from external contact or impact. Furthermore, the carrier layer 4 can serve as a base film for forming the insulating layer 3; that is, the insulating layer 3 can be formed on one side of the carrier layer 4.
[0044] See Figure 6The electromagnetic shielding film in this solution also includes a protective film layer 5, which is disposed on the side of the adhesive film layer 2 away from the shielding layer 1. The protective film layer 5 provides protection, ensuring that the adhesive film layer 2 is not scratched or damaged during use. The protective film layer 5 may be a PPS film layer, a PEN film layer, a polyester film layer, a polyimide film layer, a film layer formed by curing epoxy resin ink, a film layer formed by curing polyurethane ink, a film layer formed by curing modified acrylic resin, or a film layer formed by curing polyimide resin. When pressing the electromagnetic shielding film onto the circuit board, the protective film layer 5 needs to be peeled off first.
[0045] Specifically, when the electromagnetic shielding film includes a carrier layer 4, an insulating layer 3, a shielding layer 1, an adhesive film layer 2, and a protective film layer 5, the method for preparing the electromagnetic shielding film includes:
[0046] 1) Prepare carrier layer 4;
[0047] 2) An insulating layer 3 is formed on one side of the carrier layer 4;
[0048] 3) A shielding layer 1 is formed on the side of the insulating layer 3 that is away from the carrier layer 4;
[0049] 4) Apply adhesive to the side of the shielding layer 1 away from the insulating layer 3 to form an adhesive film layer 2, and form conductive particles 21 in the adhesive film layer;
[0050] 5) Attach the protective film layer 5 to the side of the adhesive film layer 2 that is away from the shielding layer 1.
[0051] To facilitate understanding of the above-described invention, the following four specific embodiments are provided and tested: Specific Implementation Example 1:
[0053] An electromagnetic shielding film includes a shielding layer 1 and an adhesive film layer 2. The shielding layer 1 has peaks and troughs on the side adjacent to the adhesive film layer 2. Conductive particles 21 are disposed in the adhesive film layer 2, and the conductive particles 21 are not positioned opposite to the peaks. The distance between two adjacent peaks is greater than 40 μm. The electromagnetic shielding film is then subjected to pressing (185℃, 10 min, 120 kg / cm²). 2 The film was covered with a step height of 38 μm, cured (160℃, 1.5 h), and subjected to thermal shock (288℃, 10 s, 3 times) before being tested for grounding.
[0054] Test results: After testing, the electromagnetic shielding film of this embodiment has a grounding resistance of 900-2000 milliohms when it is pressed onto a circuit board with a PAD (pad) diameter of 1mm. Specific Implementation Example 2:
[0056] An electromagnetic shielding film includes a shielding layer 1 and an adhesive film layer 2. The shielding layer 1 has peaks and troughs on the side adjacent to the adhesive film layer 2. Conductive particles 21 are disposed in the adhesive film layer 2, with 30% of the conductive particles 21 positioned opposite the peaks. The distance between two adjacent peaks is 2-40 μm. The electromagnetic shielding film is then subjected to pressing (185℃, 10 min, 120 kg / cm²). 2 The film was covered with a step height of 38 μm, cured (160℃, 1.5 h), and subjected to thermal shock (288℃, 10 s, 3 times) before being tested for grounding.
[0057] Test results: After testing, the electromagnetic shielding film of this embodiment has a grounding resistance of 158-200 milliohms when it is pressed onto a circuit board with a PAD (pad) diameter of 1mm.
[0058] Therefore, by applying the electromagnetic shielding film described in this embodiment, the grounding performance of the electromagnetic shielding film can be improved. Specific Implementation Example 3:
[0060] An electromagnetic shielding film includes a shielding layer 1 and an adhesive film layer 2. The shielding layer 1 has peaks and troughs on the side adjacent to the adhesive film layer 2. Conductive particles 21 are disposed in the adhesive film layer 2, with 65% of the conductive particles 21 positioned opposite the peaks. The distance between two adjacent peaks is 2-40 μm. The electromagnetic shielding film is then subjected to pressing (185℃, 10 min, 120 kg / cm²). 2 The film was covered with a step height of 38 μm, cured (160℃, 1.5 h), and subjected to thermal shock (288℃, 10 s, 3 times) before being tested for grounding.
[0061] Test results: After testing, the electromagnetic shielding film of this embodiment has a grounding resistance of 120-150 milliohms when it is laminated to a circuit board with a PAD (pad) diameter of 1mm.
[0062] Therefore, by applying the electromagnetic shielding film described in this embodiment, the grounding performance of the electromagnetic shielding film can be improved. Specific Implementation Example 4:
[0064] An electromagnetic shielding film includes a shielding layer 1 and an adhesive film layer 2. The shielding layer 1 has peaks and troughs on the side adjacent to the adhesive film layer 2. Conductive particles 21 are disposed in the adhesive film layer 2, with 100% of the conductive particles 21 positioned opposite the peaks. The distance between two adjacent peaks is 2-40 μm. The electromagnetic shielding film is then subjected to pressing (185℃, 10 min, 120 kg / cm²). 2The film was covered with a step height of 38 μm, cured (160℃, 1.5 h), and subjected to thermal shock (288℃, 10 s, 3 times) before being tested for grounding.
[0065] Test results: After testing, the electromagnetic shielding film of this embodiment, after being pressed onto a circuit board with a PAD (pad) diameter of 1mm, has a grounding resistance of 80-120 milliohms.
[0066] Therefore, by applying the electromagnetic shielding film described in this embodiment, the grounding performance of the electromagnetic shielding film can be improved.
[0067] In summary, by setting peaks and troughs on the side of the shielding layer 1 near the adhesive film layer 2, and by setting at least a portion (30%, 65%, 100%) of the conductive particles 21 opposite to the peaks, and by setting the distance between two adjacent peaks to 2-40 μm, the peaks have better piercing performance when penetrating the adhesive film layer 2, and can improve the degree of contact with the conductive particles 21, thereby improving the grounding performance of the electromagnetic shielding film.
[0068] See Figure 7 Another embodiment of the present invention provides a circuit board, which includes a circuit board body 6 and an electromagnetic shielding film as described in any of the above embodiments; the electromagnetic shielding film is pressed together with the circuit board body 6; the side of the shielding layer 1 near the adhesive film layer 2 is electrically connected to the ground layer of the circuit board body 6 through conductive particles 21.
[0069] Preferably, the circuit board body 6 is one of a flexible single-sided board, a flexible double-sided board, a flexible multilayer board, or a rigid-flex board.
[0070] Specifically, by setting peaks and troughs on the side of the shielding layer 1 near the adhesive film layer 2, with a distance of 2-40 μm between adjacent peaks, the peaks have better piercing performance when penetrating the adhesive film layer 2. With a suitable distance between adjacent peaks, the side of the shielding layer 1 near the adhesive film layer 2 has better adhesive-containing space, preventing the peaks from being too close together, which would reduce the adhesive capacity and cause the electromagnetic shielding film to detach from the circuit board during the peeling off of the carrier layer 4. Simultaneously, with a suitable distance between adjacent peaks, the peaks are also not too far apart, which would reduce the contact between the shielding layer 1 and the ground layer, thus reducing the interference charge introduced into the circuit board ground layer and lowering the grounding performance of the electromagnetic shielding film. Furthermore, setting the distance between adjacent peaks to 2-40 μm, with at least some conductive particles 21 positioned opposite the peaks, increases the contact between the peaks and conductive particles 21, increasing the interference charge introduced into the circuit board ground layer and improving the grounding performance of the electromagnetic shielding film. In addition, the distance between two adjacent peaks is set to 2-40μm, so that there is enough space to accommodate the adhesive in the adhesive film layer 2 during the pressing process, and the adhesive film layer 2 will not overflow during the pressing process.
[0071] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention.
Claims
1. An electromagnetic shielding film, characterized in that, Includes a shielding layer and an adhesive film layer; The shielding layer has peaks and troughs on the side near the adhesive film layer; The adhesive film layer contains conductive particles, and at least a portion of the conductive particles are arranged opposite to the wave peaks, with the distance between two adjacent wave peaks being 2-40 μm. In the bulge where the wave crest is located, the ratio of the cross-sectional area at 3 / 4 of the distance from the bottom of the bulge to the cross-sectional area at the bottom of the bulge in the thickness direction of the electromagnetic shielding film is no greater than 30%.
2. The electromagnetic shielding film as described in claim 1, characterized in that, The height of the wave crest is 1-10 μm.
3. The electromagnetic shielding film as described in claim 1, characterized in that, The depth of the trough is 1-10 μm.
4. The electromagnetic shielding film as described in claim 1, characterized in that, The ratio of the distance between two adjacent peaks to the distance between two adjacent troughs is 0.1-10.
5. The electromagnetic shielding film as described in claim 1, characterized in that, In the bulge where the wave crest is located, the ratio of the cross-sectional area at half the distance from the bottom of the bulge to the cross-sectional area at the bottom of the bulge in the thickness direction of the electromagnetic shielding film is not less than 65%.
6. The electromagnetic shielding film as described in claim 1, characterized in that, At least 30% of the conductive particles are positioned opposite the wave crest.
7. The electromagnetic shielding film as described in claim 1, characterized in that, The conductive particles have a raised structure on their surface.
8. A circuit board, characterized in that, It includes a circuit board body and an electromagnetic shielding film as described in any one of claims 1-7; the electromagnetic shielding film is pressed together with the circuit board body; the side of the shielding layer near the adhesive film layer is electrically connected to the ground layer of the circuit board body through conductive particles.
Citation Information
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