Multi-layer flexible circuit board for wearable equipment

Abstract

The utility model discloses a multilayer flexible circuit board used for wearable equipment, and specifically relates to the circuit board technology field, the multilayer flexible circuit board comprises a base material layer, a signal reinforcing layer and a flexible layer, the signal reinforcing layer is divided into three layers, the outermost electromagnetic shielding layer is a copper foil with a moderate thickness, external electromagnetic interference is led to a grounding terminal by using excellent conductivity of copper, and the flexible layer is a flexible layer. The middle signal optimization layer is a polytetrafluoroethylene PTFE copper-clad plate, the dielectric constant and the loss factor of PTFE are low, the innermost grounding isolation layer is made of FR-4 materials and grounding copper foil, the FR-4 materials are good in mechanical performance and insulativity, the outer flexible buffer layer is made of thermoplastic polyurethane elastomer rubber, stress generated when the equipment is subjected to external force such as bending, stretching and extruding is buffered, and the service life of the equipment is prolonged. The middle flexible substrate layer is a polyimide film and a PI film which are resistant to high temperature and low temperature, good in flexibility and high in number of times of bending resistance, the innermost attaching reinforcing layer is made of silicon rubber and good in attaching performance, the circuit board can be stably installed in equipment, and the multi-layer flexible circuit board can guarantee signal quality, flexibility and durability.

Description

Technical Field

[0001] This utility model relates to the field of circuit board technology, specifically to a multilayer flexible circuit board for wearable devices. Background Technology

[0002] Currently, wearable devices such as wristbands and neckbands have become indispensable technological products in people's lives. In order to reduce the overall thickness of the devices, wearable devices use flexible circuit boards to make functional boards, such as heart rate boards. At the same time, in order to reliably fix the flexible circuit boards, conductive adhesive is usually used to press and fix the flexible circuit boards to the ground plane.

[0003] In current technology, wearable devices typically need to process multiple sensor signals and conduct wireless communication, requiring high stability in signal transmission. Ordinary flexible circuit boards (PCBs) are susceptible to external electromagnetic interference during signal transmission, leading to signal distortion or loss and affecting the normal operation of the wearable device. For example, when a smart bracelet monitors physiological data such as heart rate, unstable signal transmission from the flexible circuit board can result in inaccurate data. Wearable devices are subjected to various external forces during use, such as bending, stretching, and compression. The mechanical strength of ordinary flexible circuit boards may be insufficient to withstand these stresses, easily leading to problems such as circuit breakage and loose solder joints, affecting the device's lifespan. For instance, if a smartwatch's strap uses an ordinary flexible circuit board, frequent bending during daily wear may damage the board. Therefore, we propose a multi-layer flexible circuit board for wearable devices to address these issues. Utility Model Content

[0004] This utility model aims to solve one of the technical problems existing in the prior art or related technologies.

[0005] Therefore, the technical solution adopted by this utility model is as follows:

[0006] A multilayer flexible circuit board for wearable devices includes a substrate layer, signal enhancement layers for improving the anti-interference capability of the wearable device are disposed on both sides of the substrate layer, the signal enhancement layers on both sides are symmetrically distributed along the axis of the substrate layer, and flexible layers for improving the flexibility of the wearable device are disposed on the end faces of the signal enhancement layers on both sides that are far apart from each other, the flexible layers on both sides are symmetrically distributed along the axis of the substrate layer, and the substrate layer, signal enhancement layers and flexible layers together constitute the flexible circuit board body.

[0007] Preferably, the signal enhancement layer includes a grounding isolation layer, a signal optimization layer, and an electromagnetic shielding layer.

[0008] Preferably, the grounding isolation layer is disposed on both sides of the substrate layer, and the end faces of the grounding isolation layers on both sides that are far apart from each other are bonded to the signal optimization layer.

[0009] Preferably, the electromagnetic shielding layer is disposed on the side of the signal optimization layer away from the ground isolation layer, and the ground isolation layer, the signal optimization layer, and the electromagnetic shielding layer are arranged sequentially along the direction away from the substrate layer.

[0010] Preferably, the flexible layer includes an adhesion reinforcement layer, a flexible substrate layer, and a flexible buffer layer.

[0011] Preferably, the bonding reinforcement layer is disposed on both sides of the substrate layer, and the bonding reinforcement layers on both sides are symmetrically distributed along the axis of the substrate layer.

[0012] Preferably, the side of the bonding reinforcement layer closest to the substrate layer is in contact with and adhered to the electromagnetic shielding layer, while the side of the bonding reinforcement layer furthest from the electromagnetic shielding layer is in contact with the flexible substrate layer.

[0013] Preferably, the flexible substrate layer on both sides away from the bonding reinforcement layer is in contact with and bonded to the flexible buffer layer, and the bonding reinforcement layer, the flexible substrate layer and the flexible buffer layer are arranged sequentially along the direction of the signal reinforcement layer away from the substrate layer.

[0014] By adopting the above technical solution, the beneficial effects achieved by this utility model are as follows:

[0015] In this invention, the circuit board consists of a substrate layer, a signal enhancement layer, and a flexible layer. The outermost electromagnetic shielding layer is a copper foil of moderate thickness. Utilizing the excellent conductivity of copper, external electromagnetic interference is directed to the grounding terminal, ensuring accurate and stable transmission of signals such as heart rate, motion sensors, and Bluetooth signals in wearable devices like smart bracelets under complex electromagnetic environments. The middle signal optimization layer is a polytetrafluoroethylene (PTFE) copper-clad laminate. PTFE has a low dielectric constant and loss factor, which is beneficial for high-frequency signal optimization. Careful wiring planning can reduce signal reflection and crosstalk, ensuring high-quality transmission of high-speed wireless communication signals such as Bluetooth and Wi-Fi. The innermost grounding isolation layer is made of FR-4 material with grounding copper foil. FR-4 has good mechanical properties and insulation. By connecting the grounding copper foil and the device ground plane through grounding vias, crosstalk can be isolated, providing a stable potential for multi-sensor signals such as accelerometers and gyroscopes, and maintaining the stability of the circuit board structure.

[0016] The flexible layer also consists of three layers, symmetrically distributed outside the signal reinforcement layer. The outermost flexible buffer layer is thermoplastic polyurethane elastomer rubber (TPU). TPU has good elasticity, wear resistance, and corrosion resistance, resisting scratches and impacts, and buffering stress from bending, stretching, and compression, protecting the circuit board circuitry and solder joints. Its thickness can be adjusted as needed. The middle flexible substrate layer is a polyimide film. PI film is resistant to high and low temperatures, has good flexibility, and high bending resistance, adapting to different temperature environments and providing a flexible foundation for the circuit board. The innermost bonding reinforcement layer is silicone rubber. It has good adhesion, ensuring stable installation of the circuit board within the device. It provides additional support under stress, enhancing the circuit board's resistance to external damage. This multi-layer flexible circuit board ensures signal quality, flexibility, and durability, meeting the complex requirements of wearable devices. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the overall structure of this utility model.

[0018] Figure 2 This utility model Figure 1 Enlarged structural diagram at point A in the middle.

[0019] Figure 3 This is a schematic diagram of the multi-layer material bonding structure of this utility model.

[0020] Figure 4 This is a schematic diagram of the signal enhancement layer structure of this utility model.

[0021] Figure 5 This is a schematic diagram of the flexible layer structure of this utility model.

[0022] In the diagram: 1. Substrate layer; 2. Signal reinforcement layer; 201. Grounding isolation layer; 202. Signal optimization layer; 203. Electromagnetic shielding layer; 3. Flexible layer; 301. Adhesion reinforcement layer; 302. Flexible substrate layer; 303. Flexible buffer layer; 4. Flexible circuit board body. 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 protection scope of the present utility model.

[0024] Example: Figures 1-5As shown, this utility model provides a multilayer flexible circuit board for wearable devices, including a substrate layer 1. Signal reinforcement layers 2 are disposed on both sides of the substrate layer 1 to enhance the anti-interference capability of the wearable device. The two signal reinforcement layers 2 are symmetrically distributed along the axis of the substrate layer 1. Flexible layers 3 are disposed on the opposite ends of the two signal reinforcement layers 2 to enhance the flexibility of the wearable device. The two flexible layers 3 are symmetrically distributed along the axis of the substrate layer 1. The substrate layer 1, signal reinforcement layers 2, and flexible layers 3 together form the flexible circuit board body 4. The three-layer structure of different materials respectively constructs the signal reinforcement layer 2 and the flexible layer 3, which enables the multilayer flexible circuit board to ensure high-quality signal transmission in wearable devices while also possessing good flexibility and durability, meeting the complex usage requirements of wearable devices.

[0025] The signal enhancement layer 2 includes a ground isolation layer 201, a signal optimization layer 202, and an electromagnetic shielding layer 203. The ground isolation layer 201 is disposed on both sides of the substrate layer 1, with the ends of the ground isolation layers 201 facing away from each other bonded to the signal optimization layer 202. The electromagnetic shielding layer 203 is disposed on the side of the signal optimization layer 202 away from the ground isolation layer 201. The ground isolation layer 201, signal optimization layer 202, and electromagnetic shielding layer 203 are arranged sequentially along the direction away from the substrate layer 1. The electromagnetic shielding layer 203 is made of metal foil, using copper foil of appropriate thickness as the material for the outer electromagnetic shielding layer 203. Copper has excellent conductivity and can efficiently guide external electromagnetic interference to the ground end, thus shielding external electromagnetic waves and preventing them from interfering with the signal transmission inside the circuit board. In wearable device scenarios, such as smart bracelets being in various complex electromagnetic environments, when near mobile phones or wireless chargers, this copper foil can protect heart rate, motion, and other sensor signals, as well as Bluetooth and other wireless communication signals, from external electromagnetic interference, ensuring the accuracy and stability of signal transmission. Its thickness can usually be selected between tens of micrometers and hundreds of micrometers depending on the actual electromagnetic shielding requirements. If it is too thin, the shielding effect may be poor, and if it is too thick, it will affect the overall flexibility of the circuit board.

[0026] The signal optimization layer 202 is made of polytetrafluoroethylene (PTFE) copper-clad laminate, using PTFE as the base material. PTFE has extremely low dielectric constant and loss factor, making it ideal for optimizing high-frequency signal transmission. On this layer, signal routing is carefully planned. For high-speed wireless communication signals, microstrip or stripline routing is used, with strict control over parameters such as signal line width, spacing, and distance from the ground plane to reduce signal reflection and crosstalk. For example, when wearable devices transmit Bluetooth data or connect via Wi-Fi, the signal can be transmitted at this layer with lower loss and higher quality, ensuring smooth and stable communication. Simultaneously, the copper foil circuit layer of this copper-clad laminate is tightly bonded to the PTFE board, able to withstand bending and other actions during daily use of wearable devices, preventing issues such as circuit detachment.

[0027] The innermost grounding isolation layer 201 is made of FR-4 material combined with grounding copper foil. FR-4 is used as the substrate material; it is a common and stable epoxy fiberglass cloth laminate with good mechanical properties and insulation. A thin copper foil is laid on the FR-4 substrate as a grounding layer, and this grounding copper foil is connected to the device's ground plane through a large number of evenly distributed grounding vias. In a multilayer flexible circuit board, this layer can effectively isolate crosstalk that may occur between different signal layers, providing a stable reference potential for each signal layer. This ensures that multiple sensor signals, such as those from accelerometers and gyroscopes, can be transmitted independently and stably when multiple sensor signals coexist, avoiding data inaccuracies caused by mutual interference between signals. Moreover, the relative rigidity of FR-4 material also helps to maintain the stability of the entire circuit board structure to a certain extent, ensuring orderly signal transmission even under complex stress environments.

[0028] Furthermore, the flexible layer 3 includes an adhesion reinforcement layer 301, a flexible substrate layer 302, and a flexible buffer layer 303. The adhesion reinforcement layer 301 is disposed on both sides of the substrate layer 1, and the two sides of the adhesion reinforcement layer 301 are symmetrically distributed along the axis of the substrate layer 1. The side of the two sides of the adhesion reinforcement layer 301 closer to the substrate layer 1 is in contact with and adhered to the electromagnetic shielding layer 203, and the side of the two sides of the adhesion reinforcement layer 301 away from the electromagnetic shielding layer 203 is in contact with the flexible substrate layer 302. The side of the two sides of the flexible substrate layer 302 away from the adhesion reinforcement layer 301 is in contact with and adhered to the flexible buffer layer 303. The adhesion reinforcement layer 301, the flexible substrate layer 302, and the flexible buffer layer 303 are arranged sequentially along the direction of the signal reinforcement layer 2 away from the substrate layer 1. Among them, the flexible buffer layer 303 is made of thermoplastic polyurethane elastomer rubber (TPU) as the material of the outer flexible protective buffer layer. TPU has excellent elasticity, abrasion resistance, and chemical corrosion resistance, and it can effectively resist various external physical damages such as scratches and collisions suffered by wearable devices in daily use. More importantly, when the device is subjected to external forces such as bending, stretching, or compression, the TPU layer can effectively absorb and disperse stress due to its high elasticity, preventing stress from being directly transmitted to the circuitry and solder joints inside the circuit board, thus providing excellent buffering protection. For example, in the flexible circuit board of a smartwatch strap, the stress generated by the frequent bending of the strap is largely buffered by the TPU layer, greatly reducing the risk of circuit board damage. The thickness of the TPU layer can be adjusted according to specific protection requirements, generally ranging from a few tenths of a millimeter to several millimeters.

[0029] The flexible substrate layer 302 is made of polyimide film, serving as the core layer of the intermediate flexible substrate. PI film possesses excellent high and low temperature resistance and superior flexibility, maintaining good physical and chemical properties over a wide temperature range. It can adapt to various environmental temperature conditions that wearable devices may face, functioning normally from cold outdoor environments to hot indoor environments. Furthermore, PI film has extremely high bending resistance. After special processing, even under prolonged and frequent bending of wearable devices, such as the multiple bending actions of a smart bracelet daily, the substrate can still prevent cracking, delamination, or other damage, providing a solid flexible foundation for the entire circuit board. It supports the attachment of upper and lower functional layers and the laying of internal circuitry. The innermost bonding reinforcement layer 301 is made of silicone rubber. Silicone rubber, with its good flexibility, biocompatibility, and excellent adhesion, can tightly adhere to the device's casing or other fixed components, ensuring stable installation of the circuit board inside the wearable device. Meanwhile, the flexibility of silicone rubber allows it to deform accordingly when the equipment is subjected to force, without restricting the overall flexibility of the circuit board. It can also provide auxiliary support for the internal structure of the circuit board to a certain extent, enhancing the overall resistance of the circuit board to external damage. For example, when subjected to compression, silicone rubber can share some of the pressure through its own deformation, protecting the circuit board's lines and solder joints from damage.

[0030] Obviously, those skilled in the art can make various modifications and variations to this utility model without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this utility model and their equivalents, this utility model also intends to include these modifications and variations.

Claims

1. A multilayer flexible circuit board for wearable devices, characterized in that, The device includes a substrate layer (1), on both sides of which signal enhancement layers (2) are provided to enhance the anti-interference capability of the wearable device. The signal enhancement layers (2) on both sides are symmetrically distributed along the axis of the substrate layer (1). Flexible layers (3) for enhancing the flexibility of the wearable device are provided on the end faces of the signal enhancement layers (2) that are far apart from each other. The flexible layers (3) on both sides are symmetrically distributed along the axis of the substrate layer (1). The substrate layer (1), signal enhancement layers (2) and flexible layers (3) together form a flexible circuit board body (4).

2. The multilayer flexible circuit board for wearable devices according to claim 1, characterized in that, The signal enhancement layer (2) includes a ground isolation layer (201), a signal optimization layer (202), and an electromagnetic shielding layer (203).

3. A multilayer flexible circuit board for wearable devices according to claim 2, characterized in that, The grounding isolation layer (201) is disposed on both sides of the substrate layer (1), and the end faces of the grounding isolation layers (201) on both sides that are far apart from each other are bonded to the signal optimization layer (202).

4. A multilayer flexible circuit board for wearable devices according to claim 3, characterized in that, The electromagnetic shielding layer (203) is disposed on the side of the signal optimization layer (202) away from the ground isolation layer (201), and the ground isolation layer (201), the signal optimization layer (202) and the electromagnetic shielding layer (203) are arranged sequentially in the direction away from the substrate layer (1).

5. A multilayer flexible circuit board for wearable devices according to claim 1, characterized in that, The flexible layer (3) includes an adhesive reinforcement layer (301), a flexible substrate layer (302), and a flexible buffer layer (303).

6. A multilayer flexible circuit board for wearable devices according to claim 5, characterized in that, The bonding reinforcement layer (301) is disposed on both sides of the substrate layer (1), and the bonding reinforcement layer (301) on both sides is symmetrically distributed along the axis of the substrate layer (1).

7. A multilayer flexible circuit board for wearable devices according to claim 6, characterized in that, The bonding reinforcement layer (301) on both sides is in contact with the electromagnetic shielding layer (203) on the side closer to the substrate layer (1), and the bonding reinforcement layer (301) away from the electromagnetic shielding layer (203) is in contact with the flexible substrate layer (302).

8. A multilayer flexible circuit board for wearable devices according to claim 7, characterized in that, The flexible substrate layer (302) on both sides away from the bonding reinforcement layer (301) is in contact with and bonded to the flexible buffer layer (303). The bonding reinforcement layer (301), the flexible substrate layer (302) and the flexible buffer layer (303) are arranged sequentially along the direction of the signal reinforcement layer (2) away from the substrate layer (1).

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