Flexible circuit board and intelligent terminal device

Abstract

The utility model discloses a flexible circuit board and intelligent terminal equipment, the flexible circuit board in the utility model comprises a base layer and a protective layer, the base layer comprises a first metal layer, a first silica gel layer and a second metal layer which are sequentially overlapped, and the protective layer at least comprises a second silica gel layer. The flexible circuit board provided by the utility model belongs to a full silica gel type flexible circuit board, has a lower dielectric constant, and can have a higher signal transmission rate in a high-frequency circuit when being applied to terminal equipment; the flexible circuit board is suitable for various extreme environments and has high reliability. Compared with a conventional flexible circuit board, the flexible circuit board provided by the utility model is thinner in overall thickness, accords with the trend of miniaturization, light weight and integration of a flexible electronic technology, and has a better application prospect.

Description

Technical Field

[0001] This utility model relates to the field of flexible circuit board technology, and in particular to a flexible circuit board and a smart terminal device. Background Technology

[0002] With the large-scale development of portable smart terminal products such as mobile phones, smartwatches, and smart bands, as well as new energy vehicles and AI devices, the application of flexible circuit boards is showing a continuous growth trend. At the same time, flexible circuit boards are also trending towards miniaturization, lightweighting, integration, and flexibility. In order to improve communication efficiency, the manufactured flexible circuit boards need to have a smaller size and lower transmission loss. Utility Model Content

[0003] The main objective of this invention is to design a flexible circuit board that is thinner, more reliable, and less expensive.

[0004] This utility model proposes a flexible circuit board, which includes: a base layer, the base layer including a first metal layer, a first silicone layer and a second metal layer stacked sequentially; and a protective layer, the protective layer being disposed on both sides of the base layer and attached to the first metal layer and the second metal layer, the protective layer including at least a second silicone layer.

[0005] In one embodiment, the first silicone layer bonds the first metal layer and the second metal layer, and the first metal layer, the second metal layer and the first silicone layer are directly laminated without the use of adhesives.

[0006] In one embodiment, the second silicone layer is attached to the first metal layer and the second metal layer, and covers the circuit patterns of the first metal layer and the second metal layer.

[0007] In one embodiment, the thickness of the first silicone layer is 10 μm to 100 μm.

[0008] In one embodiment, both the first metal layer and the second metal layer are metal foils.

[0009] In one embodiment, the thickness of the first metal layer is 1 μm to 100 μm.

[0010] In one embodiment, the thickness of the second metal layer is 1 μm to 100 μm.

[0011] In one embodiment, the second silicone layer includes a silicone film with a thickness of 1 μm to 50 μm.

[0012] In one embodiment, the second silicone layer further includes a plastic liner, the plastic liner and the silicone film being stacked; wherein the silicone film is attached to the first metal layer and the second metal layer, and the plastic liner is attached to the silicone film and facing away from the base layer; the plastic liner includes a plastic film; the thickness of the plastic liner is 1μm~450μm.

[0013] In one embodiment, the protective layer further includes a cover layer, which is attached to the second silicone layer and disposed away from the base layer.

[0014] In one embodiment, the covering layer includes any one of a polyimide film, a polyamide film, a polyethylene film, a polypropylene film, a polyetheretherketone film, a polyphenylene sulfide film, a polyethylene terephthalate film, a polycarbonate film, a polyethylene naphthalate film, and a polytetrafluoroethylene film.

[0015] In one embodiment, the thickness of the covering layer is 2 μm to 75 μm.

[0016] The present invention also proposes an intelligent terminal device, wherein the intelligent terminal device utilizes the flexible circuit board.

[0017] This invention presents a novel flexible circuit board structure, using a flexible copper-clad laminate as the base layer and covering it with a protective layer. Silicone layers are provided between metal layers and between the metal layers and the cover layer, making it an all-silicone flexible circuit board. This results in a lower dielectric constant and higher signal transmission rates in high-frequency circuits. Because silicone is more stable and durable than other polymers commonly used in flexible circuit boards, this all-silicone flexible circuit board is suitable for various extreme environments during flexible circuit board processing and application, exhibiting high reliability. Furthermore, this flexible circuit board is thinner than conventional flexible circuit boards, aligning with the miniaturization, lightweighting, and integration trends in flexible electronics technology, and demonstrating promising application prospects. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of the structure of a flexible circuit board according to an embodiment of the present invention; Attached image description:

[0021] 1. Base layer; 11. First silicone layer; 12. First metal layer; 13. Second metal layer; 2. Protective layer; 21. Second silicone layer; 22. Covering layer.

[0022] The realization of the purpose, functional features and advantages of this utility model will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0023] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present utility model.

[0024] It should be noted that if the embodiments of this utility model involve directional indicators (such as up, down, left, right, front, back, etc.), the directional indicators are only used to explain the relative positional relationship and movement of the components in a specific posture. If the specific posture changes, the directional indicators will also change accordingly.

[0025] Furthermore, if the embodiments of this utility model involve descriptions such as "first" or "second," such descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features.

[0026] Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by this utility model.

[0027] The technical problem solved by this utility model is that with the large-scale development of portable smart terminal products such as mobile phones, smartwatches, and smart bracelets, as well as new energy vehicles and AI devices, the application of flexible circuit boards has shown a continuous growth trend. At the same time, flexible circuit boards are also trending towards miniaturization, lightweighting, integration, and flexibility. In order to improve communication efficiency, the manufactured flexible circuit boards need to have a smaller size and lower transmission loss.

[0028] It should be noted that the substrate of the flexible circuit board is FCCL, which is flexible copper clad laminate. FCCL is mainly made by laminating an insulating layer with a metal circuit layer. A cover film is then laminated onto the outer surface of the FCCL to obtain the flexible circuit board.

[0029] In the existing technology, FCCLs can be divided into different types according to their insulating layer materials. Commonly used insulating layer materials include PI (polyimide), PET (polyester), and fluoropolymers. When using conventional polyimide as the insulating layer, the dielectric constant of the resulting flexible circuit board is above 3. Since the signal transmission rate is inversely proportional to the square root of the material's dielectric constant, a high dielectric constant can easily cause signal transmission delay. When using fluorinated polyimide as the insulating layer, the dielectric constant of the resulting flexible circuit board in high-frequency circuits can be reduced to 2.8, but the cost is too high. When using PET as the insulating layer, the resulting flexible circuit board cannot withstand conventional reflow soldering processes, resulting in poor product reliability. When using fluoropolymers as the insulating layer, the dielectric constant of the resulting flexible circuit board in high-frequency circuits can be below 2.2, but the coefficient of thermal expansion of fluoropolymers is as high as 100 ppm or more, making it unable to withstand the thermal shock during conventional manufacturing processes, and the cost is also too high.

[0030] To address the aforementioned problems, this utility model proposes a flexible circuit board, comprising: a base layer, the base layer comprising a first metal layer, a first silicone layer, and a second metal layer stacked sequentially; and a protective layer, the protective layer being disposed on both sides of the base layer and attached to the first metal layer and the second metal layer, the protective layer comprising at least a second silicone layer.

[0031] It should be noted that the flexible circuit board includes a base layer and protective layers disposed on both sides of the base layer. The base layer is a silicone-based flexible copper-clad laminate, including a first silicone layer and two metal layers disposed on the first silicone layer. Unlike conventional PI-type flexible copper-clad laminates, PET-type flexible copper-clad laminates, and fluoropolymer-type flexible copper-clad laminates, the flexible copper-clad laminate in this invention uses silicone to bond the two metal circuits, combining the mechanical and dielectric properties of silicone, and exhibiting a low dielectric constant in high-frequency circuits. In addition, the first silicone layer has a high thermal conductivity, which can promptly release the heat generated in the flexible circuit board and ensure the stability of its signal transmission.

[0032] It should also be noted that the protective layer also contains silicone, including a second silicone layer. This second silicone layer comprises a soft silicone film, primarily used to protect the circuit patterns on the first and second metal layers. The second silicone layer has good elasticity, effectively buffering and dispersing external impacts, thereby preventing damage to the circuit patterns on the first and second metal layers. In summary, the design of the first and second silicone layers in this invention contributes to efficient, stable, and low-latency signal transmission.

[0033] It should also be noted that, compared to conventional polyimide films and polyester films, silicone layers not only have a lower dielectric constant, but also better high-temperature resistance, aging resistance, and corrosion resistance, resulting in flexible circuit boards with higher reliability.

[0034] In one embodiment, the first silicone layer is used to bond the first metal layer and the second metal layer, and the first metal layer, the second metal layer, and the first silicone layer are directly bonded together without the use of adhesive. It should be noted that the first silicone layer not only bonds the first metal layer and the second metal layer but also serves as insulation, preventing short circuits in the circuits within the first metal layer and the second metal layer.

[0035] In one embodiment, the second silicone layer is attached to the first metal layer and the second metal layer, and covers the circuit patterns of the first metal layer and the second metal layer.

[0036] It should be noted that the second silicone layer is used to protect the circuit patterns in the first metal layer and the second metal layer; the materials of the first silicone layer and the second silicone layer are different, and their functions are also different; the first silicone layer needs higher adhesion to stably bond the first metal layer and the second metal layer; the second silicone layer needs better flexibility to buffer and disperse external impacts and protect the circuit.

[0037] It should also be noted that the first silicone layer and the second silicone layer also have some similar properties, such as a high thermal conductivity, which can release the heat generated in the first metal layer and the second metal layer in a timely manner to prevent heat accumulation from affecting the transmission efficiency of the line; and a low dielectric constant, which ensures efficient signal transmission.

[0038] In a preferred embodiment, the first metal layer includes a smooth surface and a rough surface; the second metal layer includes a smooth surface and a rough surface.

[0039] In a preferred embodiment, the first silicone layer bonds the rough surfaces of the first metal layer and the second metal layer respectively, and the first metal layer and the second metal layer are directly composited through the first silicone layer.

[0040] In a preferred embodiment, the second silicone layer is attached to the smooth surfaces of the first metal layer and the second metal layer, and covers the circuit patterns of the first metal layer and the second metal layer.

[0041] It should be noted that by setting smooth and rough surfaces in the first and second metal layers, the adhesion between the first metal layer, the first silicone layer and the second metal layer in the base layer is enhanced. At the same time, the process difficulty of bonding the base layer and the protective layer is reduced, production costs are reduced and production efficiency is improved.

[0042] In one embodiment, the thickness of the first silicone layer is 10 μm to 100 μm.

[0043] In one embodiment, both the first metal layer and the second metal layer are metal foils.

[0044] In one embodiment, the thickness of the first metal layer is 1 μm to 100 μm.

[0045] In one embodiment, the thickness of the second metal layer is 1 μm to 100 μm.

[0046] It should be noted that the first metal layer and the second metal layer include circuit patterns for signal transmission. In order to ensure stable and efficient signal transmission, the first metal layer and the second metal layer should use the same metal material, for example, both the first metal layer and the second metal layer should use copper foil.

[0047] In one embodiment, the second silicone layer includes a silicone film with a thickness of 1 μm to 50 μm.

[0048] In one embodiment, the second silicone layer further includes a plastic liner, the plastic liner and the silicone film being stacked; wherein the silicone film is attached to the first metal layer and the second metal layer, and the plastic liner is attached to the silicone film and facing away from the base layer; the plastic liner includes a plastic film; the thickness of the plastic liner is 1μm~450μm.

[0049] It should be noted that the second silicone layer can be made of pure silicone or a composite layer of silicone and a plastic liner stacked sequentially. The plastic liner includes plastic films, such as PET film, polyimide film, polyamide film, polyethylene film, and polypropylene film. The plastic liner is used to provide stiffness to the second silicone layer. Because the silicone film is too thin and soft, it is not easy for the machine to grip during the flexible circuit board manufacturing process. Therefore, a plastic liner is needed to make the second silicone layer easier to grip as a whole, so as to proceed to the next step of bonding the surface of the silicone film of the second silicone layer with the surface of the metal layer.

[0050] In one embodiment, when the second silicone layer is a composite layer of silicone and plastic liner, the second silicone layer can be formed by coating a silicone solution onto one surface of a plastic film and then curing it, or it can be formed by hot-pressing the silicone film and the plastic film together.

[0051] In another embodiment, the second silicone layer includes a silicone film, but in the process of preparing the flexible circuit board, the silicone film needs to be laminated with a release film first, so that the machine can more easily pick up the silicone film after laminating the release film, then attach it to the surface of the metal layer, and finally remove the release film; in this case, the second silicone layer obtained goes through the process of laminating the silicone film with the plastic liner and then removing the plastic liner, and the final second silicone layer only includes the silicone film.

[0052] In one embodiment, the protective layer further includes a cover layer, which is attached to the second silicone layer and disposed opposite to the base layer.

[0053] In one embodiment, the covering layer includes any one of a polyimide film, a polyamide film, a polyethylene film, a polypropylene film, a polyetheretherketone film, a polyphenylene sulfide film, a polyethylene terephthalate film, a polycarbonate film, a polyethylene naphthalate film, and a polytetrafluoroethylene film.

[0054] In one embodiment, the thickness of the cover layer is 2 μm to 75 μm. Optionally, the thickness of the cover layer can be 2 μm, 5 μm, 10 μm, 30 μm, 50 μm, and 75 μm, and the thickness of the cover layer includes, but is not limited to, the values ​​listed above, and can be within the above range.

[0055] In one embodiment, the base layer is a flexible copper-clad laminate, which includes a first metal layer, a first silicone layer, and a second metal layer stacked sequentially.

[0056] It should be noted that the signal transmission performance of the flexible circuit board in this invention is mainly determined by the flexible copper-clad laminate. The structure of the flexible copper-clad laminate in this invention is also different from that of conventional PI-type flexible copper-clad laminates, PET-type flexible copper-clad laminates, and fluoropolymer-type flexible copper-clad laminates. This invention uses silicone to bond two metal layers, combining the mechanical and dielectric properties of silicone, and has a low dielectric constant in high-frequency circuits. In addition, the first silicone layer has a high thermal conductivity, which can release the heat generated in the flexible circuit board in a timely manner and ensure the stability of its signal transmission.

[0057] In one embodiment, the fabrication process of the flexible copper-clad laminate includes the following steps:

[0058] S11. Two copper foils are provided, and a primer is applied to one surface of the two copper foils using a microgravure coating process. The mixture is left to stand at room temperature for 24 hours to obtain a primer coating.

[0059] S12. Apply the silicone adhesive to the base layer obtained in step S2 using a microgravure coating process, and bake at 120°C for 3 minutes to allow it to dry to the surface, thus obtaining the bonding surface.

[0060] S13. The two copper foils obtained in step S3 are bonded together, hot-pressed at 180°C for 1 minute, and then baked at 150°C for 30 minutes to obtain the flexible copper-clad laminate.

[0061] In one embodiment, the fabrication process of the flexible circuit board includes the following steps:

[0062] S11. Two copper foils are provided, and a primer is applied to one surface of the two copper foils using a microgravure coating process. The mixture is left to stand at room temperature for 24 hours to obtain a primer coating.

[0063] S12. Apply the silicone adhesive to the base layer obtained in step S2 using a microgravure coating process, and bake at 120°C for 3 minutes to allow it to dry to the surface, thus obtaining the bonding surface.

[0064] S13. The two copper foils obtained in step S3 are bonded together, hot-pressed at 180°C for 1 minute, and then baked at 150°C for 30 minutes to obtain the flexible copper-clad laminate.

[0065] S21. Stir and filter the silicone adhesive, and use a micro-gravure coating process to coat the silicone adhesive onto one surface of the cover layer to form a second silicone pre-composite layer. Then, attach the second silicone pre-composite layer to the other surface of the two copper foils in the flexible copper clad laminate, and let it stand at room temperature for 2 hours to obtain the flexible circuit board.

[0066] In another embodiment, the fabrication process of the flexible circuit board includes the following steps:

[0067] S11. Two copper foils are provided, one side of which is smooth and the other side is rough.

[0068] S12. Apply the primer liquid to the rough surface of the copper foil using a micro-gravure coating process, and let it stand at room temperature for 24 hours to obtain the primer coating layer.

[0069] S13. Apply the silicone adhesive to the base layer obtained in step S2 using a microgravure coating process, and bake at 120°C for 3 minutes to allow it to dry to the surface, thus obtaining the bonding surface.

[0070] S14. The two copper foils obtained in step S3 are bonded together, hot-pressed at 180°C for 1 minute, and then baked at 150°C for 30 minutes to obtain the flexible copper-clad laminate.

[0071] S21. Stir and filter the silicone adhesive, and use a microgravure coating process to coat the silicone adhesive onto the smooth surface of one copper foil in the flexible copper clad laminate, and let it stand at room temperature for 2 hours; then use a microgravure coating process to coat the silicone adhesive onto the smooth surface of another copper foil in the flexible copper clad laminate, and let it stand at room temperature for 2 hours to obtain the flexible circuit board.

[0072] In another embodiment, the fabrication process of the flexible circuit board includes the following steps:

[0073] S11. Two copper foils are provided, one side of which is smooth and the other side is rough.

[0074] S12. Apply the primer liquid to the rough surface of the copper foil using a micro-gravure coating process, and let it stand at room temperature for 24 hours to obtain the primer coating layer.

[0075] S13. Apply the silicone adhesive to the base layer obtained in step S2 using a microgravure coating process, and bake at 120°C for 3 minutes to allow it to dry to the surface, thus obtaining the bonding surface.

[0076] S14. The two copper foils obtained in step S3 are bonded together, hot-pressed at 180°C for 1 minute, and then baked at 150°C for 30 minutes to obtain the flexible copper-clad laminate.

[0077] S21. The silicone film and PET film are hot-pressed together to obtain a second silicone layer; the second silicone layer and the cover layer are hot-pressed together to obtain a protective layer; the surface of the silicone film of the protective layer is hot-pressed together with the copper foil in the flexible copper clad laminate to obtain the flexible circuit board.

[0078] This utility model also proposes an intelligent terminal device, which utilizes the flexible circuit board.

[0079] The present invention will be further described below through specific embodiments:

[0080] Example 1

[0081] Reference Figure 1 The flexible circuit board in Embodiment 1 includes a base layer 1 and a protective layer 2. The base layer 1 includes a first silicone layer 11, a first metal layer 12 and a second metal layer 13 that are stacked in sequence. The protective layer 2 includes a second silicone layer 21 and a cover layer 22.

[0082] In Example 1, the thickness of the first silicone layer 11 is 100 μm; the thickness of the first metal layer 12 is 25 μm; the thickness of the second metal layer 13 is 25 μm; the thickness of the second silicone layer 21 is 5 μm; and the cover layer 22 is a PET film with a thickness of 36 μm.

[0083] The method for fabricating the flexible circuit board in Example 1 includes the following steps:

[0084] S11. Two copper foils are provided, and a primer is applied to one surface of the two copper foils using a microgravure coating process. The mixture is left to stand at room temperature for 24 hours to obtain a primer coating.

[0085] S12. Apply the silicone adhesive to the base layer obtained in step S11 using a microgravure coating process, and bake at 120°C for 3 minutes to allow it to dry to the surface, thus obtaining the bonding surface.

[0086] S13. The two copper foils obtained in step S12 are bonded together, hot-pressed at 180°C for 1 minute, and then baked at 150°C for 30 minutes to form the first silicone layer, thus obtaining the flexible copper-clad laminate.

[0087] S21. Stir and filter the silicone adhesive, and use a micro-gravure coating process to coat the silicone adhesive onto one surface of the cover layer to form a second silicone pre-composite layer. Then, attach the second silicone pre-composite layer to the other surface of the two copper foils in the flexible copper clad laminate, and let it stand at room temperature for 2 hours to obtain the flexible circuit board.

[0088] Example 2

[0089] Example 2 is based on Example 1, except that the thickness is different.

[0090] Reference Figure 1 The flexible circuit board in Embodiment 2 includes a base layer 1 and a protective layer 2. The base layer 1 includes a first silicone layer 11, a first metal layer 12 and a second metal layer 13 that are stacked in sequence. The protective layer 2 includes a second silicone layer 21 and a cover layer 22.

[0091] In Example 2, the thickness of the first silicone layer 11 is 100 μm; the thickness of the first metal layer 12 is 15 μm; the thickness of the second metal layer 13 is 10 μm; the thickness of the second silicone layer 21 is 20 μm; and the cover layer 22 is a PET film with a thickness of 36 μm.

[0092] The method for preparing the flexible circuit board in Example 2 includes the following steps:

[0093] S11. Two copper foils are provided, one side of which is smooth and the other side is rough.

[0094] S12. Apply the primer liquid to the rough surface of the copper foil using a micro-gravure coating process, and let it stand at room temperature for 24 hours to obtain the primer coating layer.

[0095] S13. Apply the silicone adhesive to the base layer obtained in step S2 using a microgravure coating process, and bake at 120°C for 3 minutes to allow it to dry to the surface, thus obtaining the bonding surface.

[0096] S14. The two copper foils obtained in step S3 are bonded together, hot-pressed at 180°C for 1 minute, and then baked at 150°C for 30 minutes to form the first silicone layer, thus obtaining the flexible copper-clad laminate.

[0097] S21. Stir and filter the silicone adhesive, apply the silicone adhesive to one surface of the cover layer using a micro-gravure coating process, place it at 100°C for 2 minutes for semi-curing treatment to form a second silicone pre-composite layer, attach the second silicone pre-composite layer to the smooth surface of the copper foil in the flexible copper clad laminate, place it at 150°C for 30 minutes for curing treatment to obtain the flexible circuit board.

[0098] The above description is merely an exemplary embodiment of the present utility model and does not limit the patent scope of the present utility model. Any equivalent structural transformations made based on the technical concept of the present utility model and the contents of the present utility model specification and drawings, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present utility model.

Claims

1. A flexible circuit board, characterized in that, The flexible circuit board includes: The base layer comprises a first metal layer, a first silicone layer, and a second metal layer stacked sequentially; and A protective layer is disposed on both sides of the base layer and is attached to the first metal layer and the second metal layer. The protective layer includes at least a second silicone layer.

2. The flexible circuit board as described in claim 1, characterized in that, The first silicone layer bonds the first metal layer and the second metal layer; And / or, the second silicone layer is attached to the first metal layer and the second metal layer, and covers the circuit patterns of the first metal layer and the second metal layer.

3. The flexible circuit board as described in claim 1, characterized in that, The thickness of the first silicone layer is 10μm to 100μm.

4. The flexible circuit board as described in claim 1, characterized in that, Both the first metal layer and the second metal layer are metal foils; And / or, the thickness of the first metal layer is 1 μm to 100 μm; And / or, the thickness of the second metal layer is 1 μm to 100 μm.

5. The flexible circuit board as described in claim 1, characterized in that, The second silicone layer includes a silicone film with a thickness of 1 μm to 50 μm.

6. The flexible circuit board as described in claim 5, characterized in that, The second silicone layer further includes at least one plastic liner; the plastic liner and the silicone film are stacked together. The silicone film is attached to the first metal layer and the second metal layer, and the plastic liner is attached to the silicone film and faces away from the base layer. The plastic liner includes a plastic film; The thickness of the plastic liner is 1 μm to 450 μm.

7. The flexible circuit board as described in claim 1, characterized in that, The protective layer further includes a cover layer, which is attached to the second silicone layer and disposed facing away from the base layer.

8. The flexible circuit board as described in claim 7, characterized in that, The covering layer includes any one of polyimide film, polyamide film, polyethylene film, polypropylene film, polyetheretherketone film, polyphenylene sulfide film, polyethylene terephthalate film, polycarbonate film, polyethylene naphthalate film, and polytetrafluoroethylene film.

9. The flexible circuit board as described in claim 8, characterized in that, The thickness of the cover layer is 2μm to 75μm.

10. A smart terminal device, characterized in that, The intelligent terminal device uses the flexible circuit board according to any one of claims 1 to 9.

Images