Polyimide flexible wiring board and intelligent terminal device

Abstract

The utility model belongs to the technical field of flexible circuit board, the utility model discloses a kind of polyimide flexible circuit board and intelligent terminal equipment.The polyimide flexible circuit board in the utility model includes: flexible circuit layer and protective layer;The flexible circuit layer can be single-sided flexible circuit layer, and can also be double-sided flexible circuit layer, the protective layer is arranged on one side or both sides of the flexible circuit layer, and the protective layer is attached to the flexible circuit layer arrangement.The utility model designs a kind of polyimide flexible circuit board of novel structure, and the organic component part in it is all polyimide material, the polyimide flexible circuit board prepared under the premise of guaranteeing electrical performance, mechanical property and heat resistance, is further thinned, and reliability is further improved, and simultaneously still has good cost advantage and production advantage.

Description

Technical Field

[0001] This utility model relates to the field of flexible circuit board technology, and in particular to a polyimide 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 FPC, or flexible circuit board, is showing a continuous growth trend. At the same time, flexible circuit boards are also trending towards miniaturization, lightweighting, integration, and flexibility. Utility Model Content

[0003] The main purpose of this invention is to design a polyimide flexible circuit board with a smaller thickness, better reliability, and lower production cost, while ensuring the electrical and mechanical performance of the flexible circuit board.

[0004] This utility model proposes a polyimide flexible circuit board, which includes: a flexible circuit layer, the flexible circuit layer including a substrate layer and a metal layer stacked sequentially; and a protective layer, the protective layer being disposed on one or both sides of the flexible circuit layer and attached to the flexible circuit layer.

[0005] In one embodiment, the substrate layer includes a first polyimide film, which is selected from either a thermosetting polyimide film or a thermoplastic polyimide film.

[0006] In one embodiment, the flexible circuit layer is a single-sided flexible circuit layer, which includes a substrate layer and a metal layer stacked sequentially; the protective layer is disposed on one side of the single-sided flexible circuit layer and is attached to the metal layer away from the substrate layer.

[0007] In one embodiment, the flexible circuit layer is a double-sided flexible circuit layer, which includes a first metal layer, a substrate layer and a second metal layer stacked sequentially; the protective layer is disposed on both sides of the double-sided flexible circuit layer and is attached to the first metal layer and the second metal layer.

[0008] In one embodiment, the protective layer is a polyimide-based adhesive-backed cover film; the polyimide-based adhesive-backed cover film includes a second polyimide film and an adhesive layer, the adhesive layer is bonded to the metal layer, and the second polyimide film is bonded to the adhesive layer and disposed opposite to the metal layer; the adhesive layer includes any one of epoxy resin, thermoplastic polyimide resin, phenolic resin, modified epoxy resin, polyacrylic acid resin, and polytetrafluoroethylene resin.

[0009] In one embodiment, in the polyimide-based adhesive cover film, the second polyimide film is selected from either a thermosetting polyimide film or a thermoplastic polyimide film.

[0010] In one embodiment, the metal layer is a metal foil.

[0011] In one embodiment, the thickness of the metal layer is 2 μm to 300 μm.

[0012] In one embodiment, the thickness of the substrate layer is 2 μm to 75 μm.

[0013] In one embodiment, the thickness of the protective layer is 10 μm to 75 μm.

[0014] This utility model also proposes an intelligent terminal device, which utilizes the flexible circuit board.

[0015] This invention designs a novel polyimide flexible circuit board, in which both the protective layer and the substrate layer in the flexible circuit layer are made of polyimide. The flexible circuit layer is a glue-free FCCL, and the metal layer and substrate layer can be composited in one step, which simplifies the production process and improves the precision of the resulting flexible circuit board. The resulting polyimide flexible circuit board is lighter and thinner while ensuring electrical performance, mechanical performance and heat resistance, and its reliability is further improved, without further increasing the manufacturing cost. Therefore, it has good cost advantages and production efficiency advantages. Attached Figure Description

[0016] 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.

[0017] Figure 1 This is a schematic diagram of the structure of the polyimide flexible circuit board in Embodiment 1 of this utility model; Figure 2 This is a schematic diagram of the structure of the polyimide flexible circuit board in Embodiment 2 of this utility model; Explanation of reference numerals in the attached figures: 1. Substrate layer; 2. Metal layer; 21. First metal layer; 22. Second metal layer; 3. Protective layer.

[0018] 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

[0019] 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.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] 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 FPC, or flexible circuit board, is showing a continuous growth trend. At the same time, flexible circuit boards are also trending towards miniaturization, lightweighting, integration, and flexibility.

[0024] Flexible printed circuit boards (FCCLs) are a crucial material in FPC production, while polyimide is a widely used insulating material in FPCs. In existing technologies, based on different manufacturing processes, FCCLs can be divided into hot-pressed FCCLs and vacuum-sputtered FCCLs. Hot-pressed FCCLs are typically made by hot-pressing electrolytic copper foil or rolled copper foil onto a polyimide film, and can be further divided into adhesive-coated FCCLs and adhesive-free FCCLs. Vacuum-sputtered FCCLs are made by directly depositing ultra-thin copper foil onto a polyimide film, and are therefore adhesive-free FCCLs. Hot-pressed FCCLs made using electrolytic or rolled copper foil have the technical problem of relatively large overall thickness, while vacuum-sputtered FCCLs, although having a thinner metal layer, have poorer bending resistance.

[0025] To address the aforementioned problems, this utility model proposes a polyimide flexible circuit board, comprising: a flexible circuit layer, the flexible circuit layer comprising a substrate layer and a metal layer stacked sequentially; and a protective layer, the protective layer being disposed on one or both sides of the flexible circuit layer and attached to the flexible circuit layer.

[0026] It should be noted that the flexible circuit layer is a polyimide-type flexible circuit board, namely a polyimide-type FCCL. The polyimide-type FCCL can be a single-sided polyimide-type FCCL or a double-sided polyimide-type FCCL. In this invention, the metal layer of the polyimide-type FCCL is directly bonded to the polyimide film constituting the substrate layer without the use of adhesive. The resulting adhesive-free FCCL can effectively reduce the thickness of the polyimide flexible circuit board while ensuring structural reliability, thereby achieving the thinning of the flexible circuit board. The adhesive-free FCCL has higher flatness and a smaller heat deformation shrinkage rate, so the flatness of the resulting flexible circuit board is much higher than that of traditional circuit boards. In addition, polyimide materials are among the most heat-resistant polymer materials and can withstand high temperatures of 350°C, while the high-temperature resistance of conventional adhesives is far lower than that of polyimide. Therefore, the adhesive-free FCCL has higher reliability and a longer service life at high temperatures compared to the adhesive-containing FCCL.

[0027] In one embodiment, the substrate layer includes a first polyimide film, which is selected from either a thermosetting polyimide film or a thermoplastic polyimide film.

[0028] It should be noted that thermosetting polyimide films, after heat treatment at 200℃~400℃, exhibit a network cross-linked polymer structure, resulting in higher strength and temperature resistance, but also poorer processability and non-reprocessability. In contrast, thermoplastic polyimide films, without high-temperature heat treatment, have a linear molecular structure and lower cross-linking, exhibiting better flexibility and processability. To achieve both flexibility and mechanical strength in polyimide films at low thicknesses, the thickness of the thermosetting polyimide film can be reduced, and it can be used as a substrate. At high temperatures, a softened thermoplastic polyimide is then laminated with the substrate to create a composite layer of thermosetting and thermoplastic polyimide films. This composite layer combines the high strength of thermosetting polyimide with the high flexibility of thermoplastic polyimide.

[0029] In one embodiment, the flexible circuit layer is a single-sided flexible circuit layer, such as... Figure 1As shown, the polyimide flexible circuit board includes a protective layer 3 and a single-sided flexible circuit layer. The single-sided flexible circuit layer includes a substrate layer 1 and a metal layer 2 stacked sequentially. The protective layer 3 is disposed on one side of the single-sided flexible circuit layer and is attached to the metal layer 2 away from the substrate layer 1.

[0030] In another embodiment, the flexible circuit layer is a double-sided flexible circuit layer, such as... Figure 2 As shown, the polyimide flexible circuit board includes a double-sided flexible circuit layer and a protective layer 3 disposed on both sides of the double-sided flexible circuit layer. The double-sided flexible circuit layer includes a first metal layer 21, a substrate layer 1, and a second metal layer 22 stacked sequentially. The protective layer 3 is disposed on both sides of the double-sided flexible circuit layer and is attached to the first metal layer 21 and the second metal layer 22.

[0031] It should be noted that in this invention, the flexible circuit layer constituting the polyimide flexible circuit board can be a single-sided flexible circuit layer, that is, the flexible circuit layer has a metal layer composited with the substrate layer; or it can be a double-sided flexible circuit layer, that is, the flexible circuit layer has two metal layers composited with the substrate layer respectively. The polyimide flexible circuit board made of a single-sided flexible circuit layer or a polyimide flexible circuit board made of a double-sided flexible circuit layer can be selected according to the actual application requirements.

[0032] It should also be noted that in the flexible circuit layer, the substrate layer and the metal layer are directly bonded together without the use of adhesives.

[0033] It should be noted that in this invention, the flexible circuit layer constituting the polyimide flexible circuit board is an adhesive-free FCCL. The metal layer and the polyimide constituting the substrate layer are directly bonded without adhesive. This effectively reduces the thickness of the polyimide flexible circuit board while ensuring structural reliability, thus achieving a thinner flexible circuit board. Adhesive-free FCCL has a lower heat distortion and shrinkage rate, resulting in a significantly higher flatness of the resulting flexible circuit board compared to traditional circuit boards. Furthermore, polyimide is one of the most heat-resistant polymer materials, capable of withstanding temperatures up to 350°C, while conventional adhesives have much lower high-temperature resistance than polyimide. Therefore, adhesive-free FCCL exhibits higher reliability and a longer service life at high temperatures compared to adhesive-bonded FCCL.

[0034] In one embodiment, the protective layer is a polyimide-based adhesive cover film; the polyimide-based adhesive cover film includes a second polyimide film and an adhesive layer, the adhesive layer is bonded to the metal layer, and the second polyimide film is bonded to the adhesive layer and disposed opposite to the metal layer; the adhesive layer includes any one of epoxy resin, thermoplastic polyimide resin, phenolic resin, modified epoxy resin, polyacrylic acid resin, and polytetrafluoroethylene resin.

[0035] It should be noted that the polyimide-based adhesive cover film is an existing adhesive-backed cover film. The adhesive in the bonding layer is responsible for bonding the metal layer to the second polyimide film. The protective layer and the flexible circuit layer can be bonded using the traditional FPC production process, thereby improving production efficiency and reducing production costs.

[0036] In one embodiment, in the polyimide-based adhesive cover film, the second polyimide film is selected from either a thermosetting polyimide film or a thermoplastic polyimide film.

[0037] It should be noted that the second polyimide film in the polyimide-based adhesive cover film can be made of the same material as the first polyimide film or a different material. The main function of the polyimide-based adhesive cover film is to protect the circuits in the metal layer and to support the flexible circuit layer. Therefore, under the premise of ensuring strength, a polyimide material with lower thickness and lower production cost can be flexibly selected.

[0038] In one embodiment, the metal layer is a metal foil. Optionally, the metal foil can be a copper foil or a stainless steel sheet. This invention does not limit the specific type of metal layer, as long as the strength and bending resistance at a specific thickness meet the requirements.

[0039] In one embodiment, the thickness of the metal layer is 2 μm to 300 μm.

[0040] In one embodiment, the thickness of the substrate layer is 2μm to 75μm.

[0041] In one embodiment, the thickness of the protective layer is 10 μm to 75 μm.

[0042] This utility model also proposes an intelligent terminal device, which utilizes the flexible circuit board.

[0043] The present invention will be further described below through specific embodiments: Example 1 Reference Figure 1The polyimide flexible circuit board in Example 1 includes a protective layer 3, a substrate layer 1, and a metal layer 2; the protective layer 3 is disposed on one side of the single-sided flexible circuit layer, and the protective layer 3 is attached to the metal layer 2 away from the substrate layer 1.

[0044] In Example 1, the substrate layer 1 is a first polyimide film, and the material of the first polyimide film is thermoplastic polyimide; the thickness of the substrate layer 1 is 10 μm.

[0045] In Example 1, the metal layer 2 is a copper foil with a thickness of 12.5 μm.

[0046] In Example 1, protective layer 3 is a polyimide-based adhesive-backed cover film. The polyimide-based adhesive-backed cover film is a composite structure of a second polyimide film and an adhesive layer. The adhesive in the adhesive layer is a thermoplastic polyimide resin. The thickness of the second polyimide film in protective layer 3 is 12.5 μm, and the thickness of the adhesive layer in protective layer 3 is 12.5 μm.

[0047] The preparation method of the polyimide flexible circuit board in Example 1 includes the following steps: S1. The metal layer and the substrate layer are rolled together at high temperature (350℃, 120s, 12MPa) to obtain a single-sided flexible circuit layer. S2. The protective layer is hot-pressed to the metal layer in the single-sided flexible circuit layer obtained in step S1. The bonding temperature is 230 degrees Celsius, the time is 180s, and the pressure is 12MPa to obtain a polyimide flexible circuit board.

[0048] The organic components of the polyimide flexible circuit board in Example 1 are all polyimide materials, which have good temperature resistance and mechanical properties.

[0049] Example 2 Reference Figure 2 The polyimide flexible circuit board in Example 2 includes a protective layer 3, a first metal layer 21, a substrate layer 1, a second metal layer 22, and the protective layer 3 stacked sequentially. The first metal layer 21, the substrate layer 1, and the second metal layer 22 stacked sequentially constitute a double-sided flexible circuit layer; the protective layer 3 is disposed on both sides of the double-sided flexible circuit layer and is attached to the first metal layer 21 and the second metal layer 22.

[0050] In Example 2, the substrate layer 1 is a first polyimide film, which is a composite layer of thermosetting polyimide film and thermoplastic polyimide film; the thickness of the substrate layer 1 is 12.5 μm.

[0051] In Example 2, the metal layer 2 is a copper foil with a thickness of 35 μm.

[0052] In Example 2, the protective layer 3 is a polyimide-based adhesive-backed cover film. This film is a composite structure of a second polyimide film and an adhesive layer. The adhesive layer is used to bond the protective layer 3 to either the first metal layer 21 or the second metal layer 22. The adhesive in the adhesive layer is a thermoplastic polyimide resin. The thickness of the second polyimide film in the protective layer 3 is 12.5 μm, and the thickness of the adhesive layer in the protective layer 3 is 17.5 μm.

[0053] The preparation method of the polyimide flexible circuit board in Example 2 includes the following steps: S1. Coat the surfaces of two copper foils with polyimide paste and treat them at 300°C for 5 minutes to obtain two single-sided flexible circuit layers. S2. Roll-press the polyimide surfaces of the two single-sided flexible circuit layers from step S1 together at a pressure of 25 MPa, a temperature of 360°C, and a time of 180 s to obtain a double-sided flexible circuit layer. S3. Thermoplastic polyimide resin is coated on the surface of the second polyimide film and dried to form a protective layer. The protective layer is then rolled and bonded to the metal surface of the double-sided flexible circuit layer obtained in step S2. The rolling temperature is 260°C, the pressure is 16MPa, and the time is 150s to obtain a polyimide flexible circuit board.

[0054] In Example 2, the organic components of the polyimide flexible circuit board are all polyimide materials, which have good temperature resistance and mechanical properties.

[0055] 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 polyimide flexible wiring board, characterized by, The polyimide flexible circuit board includes: A flexible circuit layer, the flexible circuit layer comprising a substrate layer and a metal layer stacked sequentially; and A protective layer is disposed on one or both sides of the flexible circuit layer and is attached to the flexible circuit layer.

2. The polyimide flexible wiring board according to claim 1, wherein The substrate layer includes a first polyimide film, which is selected from either a thermosetting polyimide film or a thermoplastic polyimide film.

3. The polyimide flexible wiring board according to claim 1, wherein The flexible circuit layer is a single-sided flexible circuit layer, which includes a substrate layer and a metal layer stacked sequentially; the protective layer is disposed on one side of the single-sided flexible circuit layer and is attached to the metal layer away from the substrate layer.

4. The polyimide flexible wiring board according to claim 1, wherein The flexible circuit layer is a double-sided flexible circuit layer, which includes a first metal layer, a substrate layer and a second metal layer stacked in sequence; the protective layer is disposed on both sides of the double-sided flexible circuit layer and is attached to the first metal layer and the second metal layer.

5. The polyimide flexible wiring board according to claim 1, wherein The protective layer is a polyimide-based adhesive-backed cover film; The polyimide-based adhesive cover film includes a second polyimide film and an adhesive layer, wherein the adhesive layer is bonded to the metal layer and the second polyimide film is bonded to the adhesive layer and disposed opposite to the metal layer; The adhesive layer includes any one of epoxy resin, thermoplastic polyimide resin, phenolic resin, modified epoxy resin, polyacrylic resin, and polytetrafluoroethylene resin.

6. The polyimide flexible wiring board according to claim 5, wherein In the polyimide-based adhesive cover film, the second polyimide film is selected from either thermosetting polyimide film or thermoplastic polyimide film.

7. The polyimide flexible circuit board as described in claim 1, characterized in that, The metal layer is a metal foil; And / or, the thickness of the metal layer is 2μm to 300μm.

8. The polyimide flexible circuit board as described in claim 1, characterized in that, The thickness of the substrate layer is 2μm~75μm; And / or, the thickness of the protective layer is 10μm~75μm.

9. An intelligent terminal device, characterized by The intelligent terminal device uses the flexible circuit board according to any one of claims 1 to 8.

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