Bending circuit board

Abstract

The utility model discloses a kind of bending circuit boards, including epoxy resin layer, copper layer, the copper layer inside etching forms the wire of intercommunication;Epoxy resin layer is equipped with recess in correspondence with circuit board bending area;The thickness of the epoxy resin layer of bending area is locally thinned to 10%-50% of original thickness.The utility model uses FR4 hard base material, and realizes bending by local thinning, without complex structure or flexible material.Bending circuit board also metal substrate enhances overall strength, avoids the fracture caused by bending stress.Groove design can be realized by laser cutting or mechanical engraving, and the process is simple.Metal substrate is combined with hard base plate, and the heat dissipation efficiency of car lamp LED assembly is improved.

Description

Technical Field

[0001] This utility model relates to the field of printed circuit boards, and more specifically, it relates to a bent circuit board. Background Technology

[0002] Printed circuit boards (PCBs), also known as printed circuit boards, are important electronic components. They serve as the support for electronic components and the carrier for electrical connections between them. Because they are manufactured using electronic printing techniques, they are called "printed" circuit boards. The metal base is generally made of materials such as aluminum, iron, copper, copper alloy, tungsten-molybdenum-aluminum alloy, etc. The insulating layer commonly uses modified epoxy resin, polyphenylene ether, polyimide, etc., while the circuit layer is made of copper layers, etc., forming a series of components. A metal-based PCB is a PCB with a metal substrate. With the continuous advancement of automotive lighting technology, the use of LED light sources is becoming increasingly widespread, and the shapes of automotive lights are becoming more diverse and free. The LED carrier PCB has become a common component of automotive lights. However, the carrier components that support the PCB are increasingly no longer limited to planar structures due to the constraints of automotive light shapes. The carrier surface has become a bent surface, requiring a bendable metal-based PCB.

[0003] Common PCB types include: Metal Core Printed Circuit Board (MCPCB), Flexible Printed Circuit Board (FPC), and Epoxy Retardant 4 (FR4). Among these, MCPCB is a special type of printed circuit board with a metal substrate, widely used in electronic applications requiring high thermal conductivity and heat dissipation performance. Its advantages include: ① Excellent heat dissipation: The metal substrate of MCPCB has excellent thermal conductivity, effectively transferring heat from electronic components to the external environment, making it ideal for heat dissipation applications. ② High electrical insulation: MCPCB typically uses an insulating layer on the metal substrate to ensure electrical isolation between circuit components and the metal substrate, thus preventing short circuits. ③ Good mechanical strength: The metal substrate gives MCPCB excellent mechanical strength, enabling it to withstand vibration and shock, suitable for various application environments. ④ High temperature resistance: MCPCB can typically operate in high-temperature environments, making it suitable for high-temperature electronic applications. ⑤ Space saving: Due to its excellent heat dissipation performance, MCPCB can dissipate heat from high-power electronic components in a relatively small space, thus reducing the size of the circuit board.

[0004] Its disadvantages include: ① Relatively high cost: MCPCBs are generally more expensive than traditional FR4 PCBs, mainly due to the use of metal substrates and special materials. ② Heavier: The metal substrate makes MCPCBs relatively heavy, which may not be ideal for some lightweight designs. ③ Design complexity: MCPCB design is relatively complex, requiring consideration of the correct layout between the metal substrate, insulating layers, and circuit components to ensure performance and reliability. Overall, MCPCBs perform well in electronic applications requiring high thermal conductivity and heat dissipation. However, their high cost and heavier characteristics may limit their use in certain applications. Its structure is as follows... Figure 1 As shown, the light-emitting diode (LED) is the light source, the circuit traces are below it with a copper layer thickness of about 1mm, the insulating layer is below that, and the bottom layer is a metal substrate, usually an aluminum plate.

[0005] Unlike traditional rigid circuit boards, FPCs are made of flexible insulating materials, typically polyester or polyimide films. These films have excellent bending and flexibility, allowing FPCs to be bent and folded to meet the space requirements of specific applications. FPCs (Flexible Printed Circuit Boards) offer the following advantages: ① High flexibility: FPCs can be bent into various complex three-dimensional shapes, making them suitable for compact space designs. ② Thin and light: FPCs are very thin, reducing the thickness and weight of devices. ③ Lightweight: Due to their thin and light characteristics, FPCs help reduce the overall weight of end devices. ④ High density: FPCs can support high-density circuit wiring, contributing to improved performance and functionality.

[0006] The disadvantages are: ① Complex manufacturing: The manufacturing process of FPC is relatively complex, resulting in higher costs. ② Susceptible to damage: Compared to rigid circuit boards, FPC is more susceptible to mechanical damage. ③ Limited current capacity: The current capacity of FPC is relatively low, making it unsuitable for high-current applications. ④ Usually requires customization: Due to varying application requirements, FPC usually requires custom manufacturing, leading to longer production cycles. ⑤ Electrostatic sensitivity: FPC materials are generally sensitive to electrostatic discharge (ESD), requiring special attention to anti-ESD measures. Its structure is shown in Figure 2, where the LED is the light source, below which is a copper layer for circuit traces, typically 1mm thick, and below that is an insulating layer.

[0007] FR4 is a common glass fiber reinforced epoxy resin-based surface mount material widely used in the manufacture of printed circuit boards (PCBs). Its advantages include: ① High mechanical strength: FR4 possesses excellent mechanical strength, capable of withstanding vibration and shock, maintaining stability in various environments. ② Electrical insulation properties: FR4 exhibits good electrical insulation properties, effectively preventing short circuits between circuit components. ③ Chemical stability: It has strong resistance to some chemical substances and can resist the corrosive effects of some chemical solvents. ④ Wide availability: FR4 is a widely available material, readily available, and suitable for various PCB applications.

[0008] However, it also has some drawbacks, such as its poor thermal conductivity: FR4 has relatively poor thermal conductivity, which means it may not be suitable for applications requiring efficient heat dissipation. Overall, FR4 is a common and reliable PCB material suitable for most general applications. Its structure is shown in Figure 3, where the LED is the light source, the middle layer is a copper layer for circuit traces, typically 1mm thick, and below is epoxy resin as an insulating layer.

[0009] The trapezoidal shape of vehicle lights (such as headlights or taillights on two-wheeled vehicles) typically relies on flexible printed circuit boards (FPCs) to achieve bending functionality. However, flexible circuit boards have drawbacks such as high cost and susceptibility to fatigue damage after prolonged use. While rigid printed circuit boards (such as MCPCBs and FR4s) are cheaper, traditional rigid boards cannot be bent, making it difficult to meet the design requirements of vehicle lights.

[0010] Prior art document CN219536397U proposes a metal substrate structure adjustable via hinges and bolts, but it relies on mechanical components for bending, resulting in a complex structure that is unsuitable for thin and lightweight designs. Prior art document CN220210677U achieves bending through a combination of multiple rigid plates and partial material removal, but the processing is complex and requires the addition of polyimide material, leading to higher costs.

[0011] For example, a bendable metal-based printed circuit board, such as the one described in announcement number CN203151860 U with an authorization announcement date of August 21, 2013, includes: a metal base layer; a PI insulating layer, one surface of which is adhered to the metal base layer; copper layer circuitry formed on the other surface of the PI insulating layer; and a solder resist layer, also formed on the other surface of the PI insulating layer, with windows on the solder resist layer exposing the copper layer circuitry at the windows to form electrical connection areas; a V-groove is formed on the other surface of the metal base layer not adhered to the PI insulating layer, the depth of the V-groove being less than the thickness of the metal base layer. Essentially, it utilizes the ductility of the metal base layer (such as aluminum / copper), allowing bending through metal deformation even after slotting. Its core design leverages the plasticity of metal. This means the PI insulating layer provides support, but to achieve large-angle bending, a deeper V-groove is needed. Since the PI insulating layer is a flexible material, this affects its supporting effect.

[0012] Therefore, there is an urgent need for a rigid bendable circuit board with a simple structure and low cost that can be bent within a specific angle range while possessing good heat dissipation and mechanical strength. Summary of the Invention

[0013] This invention solves the problems of traditional rigid FR4 boards being unable to be bent and flexible FPC boards being expensive and having poor heat dissipation.

[0014] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0015] A bent circuit board includes an epoxy resin layer and a copper layer, wherein interconnecting conductors are etched inside the copper layer.

[0016] The epoxy resin layer has grooves corresponding to the bending areas of the circuit board.

[0017] The epoxy resin layer thickness in the bending area is locally reduced to 10%-50% of its original thickness.

[0018] Preferably, the depth of the groove is 50%-90% of the thickness of the epoxy resin layer, and the minimum distance between the bottom of the groove and the copper layer is not less than 1mm.

[0019] Preferably, the bending area is configured to allow the circuit board to bend within a range of 10° to 30°.

[0020] Preferably, the groove is U-shaped, V-shaped, arc-shaped, or trapezoidal.

[0021] Preferably, the system further includes a metal substrate, wherein the copper layer is bonded to the metal substrate.

[0022] Preferably, the metal substrate is an aluminum substrate or a copper substrate, bonded to the copper layer by thermosetting adhesive, and the thickness of the metal substrate is greater than 5 mm. A safety spacing (≥0.1 mm) is maintained between the copper layers to prevent damage to the copper layer due to processing errors.

[0023] Preferably, the width of the bending area is 5mm to 10mm to avoid insufficient mechanical strength due to excessive width or stress concentration due to insufficient width.

[0024] Preferably, the surface of the bending area is covered with a polyimide protective film with a thickness of 10-50 μm, and the protective film extends 1-3 mm beyond the edges on both sides of the bending area to avoid edge stress causing the protective film to peel off.

[0025] The beneficial effects are as follows:

[0026] 1. Low cost: It uses FR4 rigid substrate and achieves bending by local thinning, without the need for complex structures or flexible materials.

[0027] 2. High reliability: The metal substrate enhances the overall strength and avoids breakage caused by bending stress.

[0028] 3. Easy to process: The groove design can be achieved through laser cutting or mechanical engraving, which is a simple process.

[0029] 4. Heat dissipation optimization: The combination of metal substrate and rigid substrate improves the heat dissipation efficiency of automotive LED components. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the layered structure of an MCPCB circuit board;

[0031] Figure 2 This is a schematic diagram of the layered structure of an FPC circuit board;

[0032] Figure 3 This is a schematic diagram of the layered structure of the FR4 circuit board;

[0033] Figure 4 This is a schematic diagram of the bent circuit board structure provided by this utility model;

[0034] Figure 5 This is another perspective schematic diagram of the bent circuit board structure provided by this utility model;

[0035] In the diagram: 11, 21, 31 - LEDs; 12, 22, 32 - copper layers; 13, 23 - insulating layers; 14 - metal substrate; 33 - epoxy resin. Detailed Implementation

[0036] The present disclosure will be further described below with reference to the accompanying drawings and embodiments.

[0037] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0038] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0039] In this disclosure, terms such as "upper," "lower," "left," "right," "front," "back," "vertical," "horizontal," "side," and "bottom" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are merely relational terms determined for the convenience of describing the structural relationship of the various components or elements in this disclosure, and do not specifically refer to any component or element in this disclosure, nor should they be construed as limiting this disclosure.

[0040] In this disclosure, terms such as "fixed connection," "connected," and "linked" should be interpreted broadly, indicating a fixed connection, an integral connection, or a detachable connection; a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can determine the specific meaning of these terms in this disclosure based on the specific circumstances, and they should not be construed as limitations on this disclosure. Example

[0041] like Figure 4 and Figure 5 As shown, a bent circuit board, using FR4 circuit board, includes an epoxy resin layer with a thickness of 10mm and a copper layer 2 with a thickness of 1mm. The copper layer 2 has interconnected conductors etched inside. The epoxy resin layer 1 has grooves 4 corresponding to the bending area of ​​the circuit board. The thickness of the epoxy resin layer 1 in the bending area is locally thinned to 10%-50% of its original thickness. It also includes a metal substrate 3 with a thickness of 15mm, which is bonded to the copper layer 2.

[0042] In one embodiment, a rectangular groove is formed in the bending area by laser cutting, with a depth of 90% of the epoxy resin layer thickness, i.e., the maximum depth of the groove is 9mm. A 1mm layer of epoxy resin is left to encapsulate the copper layer, preventing damage from excessive cutting and preventing the copper layer from rusting due to prolonged direct contact with air. The metal substrate 3 is a 15mm thick aluminum plate, bonded to the back of the rigid substrate with thermosetting adhesive. The metal substrate 3 is used to conduct heat from the copper layer 2 and to reinforce fixation. The bending angle is 10°, and the remaining epoxy resin thickness after laser cutting in the bending area is 1mm. A bending test (1000 repeated bends at 10°) showed no breakage. Since epoxy resin is a thermosetting polymer with high rigidity, excellent adhesion, and chemical resistance, but inherently brittle and with low elongation at break (typically <5%), directly bending the untreated epoxy resin layer can easily lead to cracks or delamination due to stress concentration. By locally thinning the epoxy resin layer, the rigidity of the bending area can be specifically reduced while preserving the structural strength of the non-bending areas. The specific principles are as follows: Thinning by 10%-30% reduces local rigidity. With a reduced epoxy resin layer thickness, deformation stress is more evenly distributed during bending, reducing the risk of brittle fracture. It also maintains structural integrity; the remaining thickness (70%-90%) still provides sufficient support to prevent overall structural collapse during bending. Thinning by 30%-50% significantly improves flexibility. The substantial reduction in epoxy resin layer thickness lowers the external force required for bending, allowing for larger angle deformations (e.g., 30°). Critical thickness control: When thinning exceeds 50%, the remaining epoxy resin layer is too thin (<50%), potentially leading to insufficient interfacial adhesion strength and increased risk of delamination. 10% thinning (lower limit) is suitable for small-angle bending (10°-15°), such as the slightly curved shape of automotive headlights. This reduces the stress concentration factor by 30%-40% and increases bending life by 2-3 times (compared to an unthinned substrate). 50% thinning (upper limit) is suitable for larger-angle bending (25°-30°), such as irregularly shaped structures in industrial equipment. This reduces the bending modulus by 60%-70%, while compensating for the strength loss through bonding with a metal substrate.

[0043] In one embodiment, the surface of the bending area is covered with a 20μm polyimide film, allowing the circuit board to be bent up to 25° for use in two-wheeled vehicle headlights, meeting the trapezoidal shape requirements. The bending area is a 2mm wide straight groove, and the epoxy resin layer is thinned to 30% of its original thickness. The metal substrate has heat dissipation fins extending to the external environment. This design is suitable for high-power LED automotive lights, improving heat dissipation efficiency by 40%.

[0044] The embodiments described above are merely preferred solutions of this utility model and are not intended to limit this utility model in any way. Other variations and modifications are possible without departing from the technical solutions described in the claims.

Claims

1. A bent circuit board, characterized in that, It includes an epoxy resin layer (1) and a copper layer (2), wherein a connected wire is etched inside the copper layer (2); The epoxy resin layer (1) has a groove (4) corresponding to the bending area of ​​the circuit board; The epoxy resin layer (1) in the bending area is locally thinned to 10%-50% of its original thickness.

2. A bent circuit board according to claim 1, characterized in that, The depth of the groove (4) is 50%-90% of the thickness of the epoxy resin layer (1), and the minimum distance between the bottom of the groove (4) and the copper layer (2) is not less than 1mm.

3. A bent circuit board according to claim 2, characterized in that, The bending area is configured to allow the circuit board to bend within the range of 10° to 30°.

4. A bent circuit board according to claim 3, characterized in that, The groove (4) is U-shaped, V-shaped, arc-shaped, or trapezoidal.

5. A bent circuit board according to claim 1, characterized in that, It also includes a metal substrate (3) to which the copper layer (2) is bonded.

6. A bent circuit board according to claim 5, characterized in that, The metal substrate (3) is an aluminum substrate or a copper substrate, which is bonded to the copper layer (2) by thermosetting adhesive, and the thickness of the metal substrate is greater than 5 mm.

7. A bent circuit board according to claim 1, characterized in that, The surface of the bending area is covered with a polyimide protective film with a thickness of 10-50 μm, and the protective film extends 1-3 mm beyond the outer edges of both sides of the bending area.

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