Flexible wiring board structure

Abstract

The utility model discloses a flexible circuit board structure, include: substrate, the upside and downside of the substrate are provided with first circuit layer and second circuit layer respectively, the side of first circuit layer is provided with first reinforcing sheet away from the substrate, and one end of first reinforcing sheet is located the edge position of first circuit layer, the position of corresponding first reinforcing sheet is provided with ink layer on the side of second circuit layer away from the substrate, the distance from first circuit layer to the edge of substrate is less than the distance from second circuit layer to the edge of substrate in one end of the substrate provided with first reinforcing sheet, make the edge of circuit layer of one side of setting up reinforcing sheet in the pressing process of double -sided circuit board, can more effectively disperse the stress on second circuit layer, thereby reduce the pulling force that ink layer on second circuit layer suffered, and then solve the problem of edge ink crack.

Description

Technical Field

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

[0002] In the field of flexible printed circuit board (FPC) manufacturing technology, double-sided FPCs with steel sheet lamination have been widely used in various electronic devices due to their excellent flexibility and structural stability. These products typically consist of a steel sheet, a circuit layer, and an ink layer, with the ink layer serving to insulate and protect the circuitry.

[0003] However, in actual production and use, these products commonly suffer from edge ink cracking. Edge ink cracking not only damages the product's appearance but can also affect the insulation performance and mechanical strength of the circuitry, reducing product reliability and lifespan, and increasing defect rates and production costs. Utility Model Content

[0004] The technical problem to be solved by this utility model is to provide a flexible circuit board structure that solves the problem of edge ink cracking.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by this utility model is as follows: A flexible circuit board structure includes: a substrate, wherein a first circuit layer and a second circuit layer are respectively disposed on the upper and lower sides of the substrate; a first reinforcing sheet is disposed on the side of the first circuit layer away from the substrate, and one end of the first reinforcing sheet is disposed at the edge of the first circuit layer; an ink layer is disposed on the side of the second circuit layer away from the substrate at a position corresponding to the first reinforcing sheet; at the end of the substrate where the first reinforcing sheet is disposed, the distance from the first circuit layer to the edge of the substrate is less than the distance from the second circuit layer to the edge of the substrate.

[0006] Furthermore, at the end of the substrate where the first reinforcing sheet is disposed, the distance from the first circuit layer to the edge of the substrate is 0.12-0.2 mm.

[0007] Furthermore, at the end of the substrate where the first reinforcing sheet is disposed, the distance difference between the distance from the first circuit layer to the edge of the substrate and the distance from the second circuit layer to the edge of the substrate is 0.05-0.1 mm.

[0008] Furthermore, at the end of the substrate where the first reinforcing sheet is disposed, the distance from the second circuit layer to the edge of the substrate is not greater than the distance from the first reinforcing sheet to the edge of the substrate.

[0009] Furthermore, a second reinforcing sheet is provided on the side of the second circuit layer away from the substrate, and one end of the second reinforcing sheet is located at the edge of the second circuit layer; the second reinforcing sheet and the first reinforcing sheet are located at different ends of the substrate; the ink layer is provided on the side of the first circuit layer away from the substrate at a position corresponding to the second reinforcing sheet; at the end of the substrate where the second reinforcing sheet is provided, the distance from the second circuit layer to the edge of the substrate is less than the distance from the first circuit layer to the edge of the substrate.

[0010] Furthermore, at the end of the substrate where the second reinforcing sheet is disposed, the distance from the second circuit layer to the edge of the substrate is 0.12-0.2 mm.

[0011] Furthermore, at the end of the substrate where the second reinforcing sheet is disposed, the distance difference between the distance from the second circuit layer to the edge of the substrate and the distance from the first circuit layer to the edge of the substrate is 0.05-0.1 mm.

[0012] Furthermore, it also includes a first protective layer and a second protective layer; the first protective layer is disposed between the first circuit layer and the first reinforcing sheet, and the first protective layer covers the first circuit layer; the second protective layer covers the second circuit layer.

[0013] Furthermore, the first reinforcing sheet comprises a steel sheet.

[0014] Furthermore, both the first and second circuit layers comprise copper.

[0015] The beneficial effects of this utility model are as follows: by setting a first circuit layer and a second circuit layer on the upper and lower sides of the substrate respectively, a double-sided circuit board is formed; and when a first reinforcing sheet is set at the edge of the first circuit layer, the distance from the first circuit layer to the edge of the substrate is set to be less than the distance from the second circuit layer to the edge of the substrate, so that during the lamination process of the double-sided circuit board, the edge of the circuit layer on the side with the reinforcing sheet is closer to the edge of the substrate, which can more effectively disperse the stress on the second circuit layer, thereby reducing the tensile force on the ink layer on the second circuit layer, and thus solving the problem of edge ink cracking. Attached Figure Description

[0016] Figure 1 This is a structural schematic diagram of a flexible circuit double-sided board-FPC-steel sheet laminated product in related technologies; Figure 2 This is a schematic diagram of ink cracking in flexible circuit double-sided board-FPC-steel sheet laminated products in related technologies. Figure 3This is a schematic diagram of another ink crack in flexible circuit double-sided board-FPC-steel sheet laminated products in related technologies; Figure 4 This is a schematic diagram of a flexible circuit board structure according to the present invention; Figure 5 This is a schematic diagram of ink optimization for a flexible circuit board structure according to this utility model; Figure 6 This is another ink optimization diagram of a flexible circuit board structure according to the present invention; Label Explanation: 1. Substrate; 2. First circuit layer; 3. Second circuit layer; 4. First reinforcing sheet; 5. Ink layer; 6. Second reinforcing layer; 7. First protective layer; 8. Second protective layer. Detailed Implementation

[0017] To explain in detail the technical content, objectives, and effects of this utility model, the following description is provided in conjunction with the embodiments and accompanying drawings.

[0018] However, in actual production and use, these products commonly exhibit edge ink cracking. The main reason is that during product processing (such as die-cutting) and subsequent use, significant stress concentration occurs at the edges, causing the ink layer to be subjected to considerable tensile force. When this tensile force exceeds the ink's withstand limit, cracks appear. Please refer to... Figure 1 After FPC bonding and reinforcement, during the lamination process, the height difference created by the press auxiliary materials (resinforcement to the FPC with a 0.1-0.15mm suspended state) causes both ink 1 and ink 2 to sink during the lamination process, resulting in ink cracks (such as...). Figure 2 and Figure 3 (As shown). Edge ink cracks not only damage the product's appearance, but can also affect the insulation performance and mechanical strength of the circuit, reduce the product's reliability and lifespan, and increase the product's defect rate and production costs.

[0019] Please refer to Figure 4 A flexible circuit board structure includes: a substrate, wherein a first circuit layer and a second circuit layer are respectively disposed on the upper and lower sides of the substrate; a first reinforcing sheet is disposed on the side of the first circuit layer away from the substrate, and one end of the first reinforcing sheet is disposed at the edge of the first circuit layer; an ink layer is disposed on the side of the second circuit layer away from the substrate at a position corresponding to the first reinforcing sheet; at the end of the substrate where the first reinforcing sheet is disposed, the distance from the first circuit layer to the edge of the substrate is less than the distance from the second circuit layer to the edge of the substrate.

[0020] As can be seen from the above description, the beneficial effects of this utility model are as follows: by setting a first circuit layer and a second circuit layer on the upper and lower sides of the substrate respectively, a double-sided circuit board is formed; and when a first reinforcing sheet is set at the edge of the first circuit layer, the distance from the first circuit layer to the edge of the substrate is set to be less than the distance from the second circuit layer to the edge of the substrate, so that during the lamination process of the double-sided circuit board, the edge of the circuit layer on the side with the reinforcing sheet is closer to the edge of the substrate, which can more effectively disperse the stress on the second circuit layer, thereby reducing the tensile force on the ink layer on the second circuit layer, and thus solving the problem of edge ink cracking.

[0021] In an optional embodiment, at the end of the substrate where the first reinforcing sheet is disposed, the distance from the first circuit layer to the edge of the substrate is 0.12-0.2 mm.

[0022] As can be seen from the above description, setting the distance from the first circuit layer to the edge of the substrate to 0.12-0.2mm can ensure that the circuit will not be damaged during the product's shape stamping.

[0023] In an optional embodiment, at the end of the substrate where the first reinforcing sheet is disposed, the distance difference between the distance from the first circuit layer to the edge of the substrate and the distance from the second circuit layer to the edge of the substrate is 0.05-0.1 mm.

[0024] As can be seen from the above description, by setting the interlayer distance difference between the first circuit layer and the second circuit layer to 0.05-0.1mm at the end of the substrate where the first reinforcing sheet is provided, the edge of the circuit layer on the side where the reinforcing sheet is provided is closer to the edge of the substrate, which can more effectively disperse the stress on the circuit layer on the back of the reinforcing sheet.

[0025] In an optional embodiment, at the end of the substrate where the first reinforcing sheet is disposed, the distance from the second circuit layer to the edge of the substrate is not greater than the distance from the first reinforcing sheet to the edge of the substrate.

[0026] As described above, at the end of the substrate where the first reinforcing sheet is provided, the range of the second circuit layer does not exceed the support range of the first reinforcing sheet, thereby effectively supporting the first circuit layer and the second circuit layer, and ensuring that the second circuit layer has no exposed portion relative to the first reinforcing sheet, thus more effectively dispersing the stress on the second circuit layer.

[0027] In an optional embodiment, a second reinforcing sheet is disposed on the side of the second circuit layer away from the substrate, and one end of the second reinforcing sheet is disposed at the edge of the second circuit layer; the second reinforcing sheet and the first reinforcing sheet are located at different ends of the substrate; the ink layer is disposed on the side of the first circuit layer away from the substrate at a position corresponding to the second reinforcing sheet; at the end of the substrate where the second reinforcing sheet is disposed, the distance from the second circuit layer to the edge of the substrate is less than the distance from the first circuit layer to the edge of the substrate.

[0028] As described above, the product has reinforcing sheets on both sides; and based on the position of the reinforcing sheets, the distance between the corresponding first and second circuit layers and the edge of the substrate is adjusted, thereby reducing the tensile force on the ink layers on both sides of the product and thus solving the problem of ink cracks on the edges of both sides of the product.

[0029] In an optional embodiment, at one end of the substrate where the second reinforcing sheet is disposed, the distance from the second circuit layer to the edge of the substrate is 0.12-0.2 mm.

[0030] As can be seen from the above description, setting the distance from the second circuit layer to the edge of the substrate to 0.12-0.2mm can ensure that the circuit will not be damaged during the product's shape stamping.

[0031] In an optional embodiment, at the end of the substrate where the second reinforcing sheet is disposed, the distance difference between the distance from the second circuit layer to the edge of the substrate and the distance from the first circuit layer to the edge of the substrate is 0.05-0.1 mm.

[0032] As can be seen from the above description, by setting the interlayer distance difference between the second circuit layer and the first circuit layer to 0.05-0.1mm at the end of the substrate where the second reinforcing sheet is provided, the edge of the circuit layer on the side where the reinforcing sheet is provided is closer to the edge of the substrate, which can more effectively disperse the stress on the circuit layer on the back of the reinforcing sheet.

[0033] In an optional embodiment, the system further includes a first protective layer and a second protective layer; the first protective layer is disposed between the first circuit layer and the first reinforcing sheet, and the first protective layer covers the first circuit layer; the second protective layer covers the second circuit layer.

[0034] As can be seen from the above description, by setting protective layers on both the first and second circuit layers, the circuit layers can be protected while preventing ink and reinforcing sheets from affecting the circuit performance.

[0035] In an alternative embodiment, the first reinforcing sheet comprises a steel sheet.

[0036] As can be seen from the above description, using steel sheets as reinforcing sheets not only provides support but also has a certain degree of elasticity, making them more suitable for flexible circuit board applications.

[0037] In an alternative embodiment, the first and second line layers include copper layers.

[0038] As can be seen from the above description, using copper layers as the first and second circuit layers not only provides effective conductivity but also has a lower cost compared to other materials.

[0039] The flexible circuit board structure provided by this utility model can be applied to the fabrication of double-sided flexible circuit boards. The following is a detailed description of the specific implementation method: Please refer to Figure 4 A flexible circuit board structure includes: a substrate 1, with a first circuit layer 2 and a second circuit layer 3 respectively disposed on the upper and lower sides of the substrate 1; a first reinforcing sheet 4 disposed on the side of the first circuit layer 2 away from the substrate 1, with one end of the first reinforcing sheet 4 disposed at the edge of the first circuit layer 2; an ink layer 5 disposed on the side of the second circuit layer 3 away from the substrate 1 at a position corresponding to the first reinforcing sheet 4; at the end of the substrate 1 where the first reinforcing sheet 4 is disposed, the distance from the first circuit layer 2 to the edge of the substrate 1 is less than the distance from the second circuit layer 3 to the edge of the substrate 1. A second reinforcing sheet 6 disposed on the side of the second circuit layer 3 away from the substrate 1, with one end of the second reinforcing sheet 6 disposed at the edge of the second circuit layer 3; the second reinforcing sheet 6 and the first reinforcing sheet 4 are located at different ends of the substrate 1; an ink layer 5 disposed on the side of the first circuit layer 2 away from the substrate 1 at a position corresponding to the second reinforcing sheet 6; at the end of the substrate 1 where the second reinforcing sheet 6 is disposed, the distance from the second circuit layer 3 to the edge of the substrate 1 is less than the distance from the first circuit layer 2 to the edge of the substrate 1. Meanwhile, a first protective layer 7 and a second protective layer 8 are also provided; the first protective layer 7 is disposed between the first circuit layer 2 and the first reinforcing sheet 4, and the first protective layer 7 covers the first circuit layer 2; the second protective layer 8 covers the second circuit layer 3.

[0040] In this embodiment, both the first reinforcing sheet 4 and the second reinforcing sheet 6 are steel sheets. In other optional embodiments, other materials can also be used to make the reinforcing sheets, such as alloys. Both the first circuit layer 2 and the second circuit layer 3 are copper layers. The first protective layer 7 and the second protective layer 8 are made of coverlay film (CVL), whose main function is to protect the conductive lines on the flexible circuit board and prevent the lines from being damaged by external environmental factors; it can be made of polymer materials such as polyimide (PI) and polyester (PET).

[0041] Specifically, at the end of substrate 1 where the reinforcing sheet is located, the distance from the circuit layer on the corresponding side of the reinforcing sheet (i.e., on which the reinforcing sheet is located) to the edge of substrate 1 is 0.12-0.2 mm, and the distance from the circuit layer on the non-corresponding side of the reinforcing sheet to the edge of substrate 1 is no greater than the distance from the first reinforcing sheet 4 to the edge of substrate 1. Simultaneously, the distance difference between the distance from the circuit layer on the corresponding side of the reinforcing sheet to the edge of substrate 1 and the distance from the circuit layer on the non-corresponding side of the reinforcing sheet to the edge of substrate 1 is 0.05-0.1 mm, meaning the interlayer misalignment distance between circuit layers is 0.05-0.1 mm. The specific value depends on the alignment accuracy during circuit exposure and is adjusted to the maximum range according to the actual product structure.

[0042] For example, with Figure 1 Based on the structure shown, in the original design, the distance between the copper layer and the product outline was 0.2mm. The copper layer size on the corresponding side of the steel sheet was increased by 0.05mm, resulting in a distance of 0.15mm from the product outline; the copper layer size on the non-corresponding side of the steel sheet was reduced by 0.05mm. By increasing the size of the copper layer on the corresponding side of the steel sheet, the structural strength of the front edge of the steel sheet is enhanced, allowing for better stress dispersion and reducing stress concentration under external forces. Simultaneously, reducing the inward movement of the copper layer on the back of the steel sheet compared to the front alters the stress distribution at the edges, reducing the tensile force on the ink layer 5 and effectively reducing edge ink cracking. Furthermore, this structural design is simple, easy to implement in production, and requires no large-scale modification of existing production equipment, demonstrating good economic efficiency and practicality.

[0043] For example, in another practical application, the copper plating is designed with interlayer staggering. The copper plating on the reinforced side is 0.12mm from the edge of the product, while the copper plating on the non-reinforced side is 0.2mm from the edge, resulting in a 0.08mm stagger. The copper plating on both sides forms a trapezoidal shape, which enhances the support of the board edge during lamination, improves the bending resistance of the FPC, and effectively ensures product quality. Figure 5 and Figure 6 The image shows the optimized ink structure. Among them, Figure 2 , Figure 3 , Figure 5 and Figure 6 It is a double-sided structure. The image shows a cross-section of the ink fracture. From top to bottom, it is ink-substrate copper-substrate PI-substrate copper-covering film-steel sheet. This type of flexible circuit board component is divided into two areas (BTB (Board-to-Board) connector area / chip area). Reinforcing steel sheet 1 and reinforcing steel sheet 2 represent the two areas of the FPC respectively.

[0044] The above description is merely an embodiment of this utility model and does not limit the patent scope of this utility model. Any equivalent modifications made based on the content of this utility model specification and drawings, or direct or indirect applications in related technical fields, are similarly included within the patent protection scope of this utility model.

Claims

1. A flexible circuit board structure, characterized in that, include: A substrate, wherein a first circuit layer and a second circuit layer are respectively disposed on the upper and lower sides of the substrate; A first reinforcing sheet is provided on the side of the first circuit layer away from the substrate, and one end of the first reinforcing sheet is located at the edge of the first circuit layer. An ink layer is provided on the side of the second circuit layer away from the substrate at a position corresponding to the first reinforcing sheet; At the end of the substrate where the first reinforcing sheet is disposed, the distance from the first circuit layer to the edge of the substrate is less than the distance from the second circuit layer to the edge of the substrate.

2. The flexible circuit board structure according to claim 1, characterized in that, At the end of the substrate where the first reinforcing sheet is disposed, the distance from the first circuit layer to the edge of the substrate is 0.12-0.2 mm.

3. The flexible circuit board structure according to claim 1, characterized in that, At the end of the substrate where the first reinforcing sheet is disposed, the distance difference between the distance from the first circuit layer to the edge of the substrate and the distance from the second circuit layer to the edge of the substrate is 0.05-0.1 mm.

4. The flexible circuit board structure according to claim 1, characterized in that, At the end of the substrate where the first reinforcing sheet is disposed, the distance from the second circuit layer to the edge of the substrate is not greater than the distance from the first reinforcing sheet to the edge of the substrate.

5. A flexible circuit board structure according to claim 1, characterized in that, A second reinforcing sheet is provided on the side of the second circuit layer away from the substrate, and one end of the second reinforcing sheet is located at the edge of the second circuit layer; the second reinforcing sheet and the first reinforcing sheet are located at different ends of the substrate; The ink layer is disposed on the side of the first circuit layer away from the substrate at a position corresponding to the second reinforcing sheet; At one end of the substrate where the second reinforcing sheet is disposed, the distance from the second circuit layer to the edge of the substrate is less than the distance from the first circuit layer to the edge of the substrate.

6. A flexible circuit board structure according to claim 5, characterized in that, At one end of the substrate where the second reinforcing sheet is disposed, the distance from the second circuit layer to the edge of the substrate is 0.12-0.2 mm.

7. A flexible circuit board structure according to claim 5, characterized in that, At one end of the substrate where the second reinforcing sheet is disposed, the distance difference between the distance from the second circuit layer to the edge of the substrate and the distance from the first circuit layer to the edge of the substrate is 0.05-0.1 mm.

8. A flexible circuit board structure according to claim 1, characterized in that, It also includes a first protective layer and a second protective layer; The first protective layer is disposed between the first circuit layer and the first reinforcing sheet, and the first protective layer covers the first circuit layer; The second protective layer covers the second circuit layer.

9. A flexible circuit board structure according to claim 1, characterized in that, The first reinforcing sheet comprises a steel sheet.

10. A flexible circuit board structure according to claim 1, characterized in that, The first and second line layers include copper layers.

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