Flexible printed circuit (FPC) structure capable of being bent

Abstract

The utility model discloses a bendable FPC (Flexible Printed Circuit) structure, which is characterized in that a single-layer wiring connection circuit is directly adopted in a bending area, compared with a double-layer wiring non-bending area, the thickness and the hardness of the bendable FPC structure are smaller, and meanwhile, as a grounding flat cable and a metal flat cable are positioned in the same layer of circuit, the bending stress is reduced, and the bending strength is improved. The grounding flat cable is locally provided with a circular metal block used for being in lap joint with the EMI film. The PI covering and exposing of the grounding flat cable are removed, the hardness of the PI layer is reduced, the softening effect is achieved, the thickness and hardness of the FPC are further reduced, the rebound force of the FPC after bending is reduced, and the softening effect is achieved.

Description

Technical Field

[0001] The utility model relates to the technical field of printed circuit boards, in particular to a bendable FPC structure. Background Art

[0002] FPC (Flexible Printed Circuit) is a bendable printed circuit board made of polyimide or polyester film as the substrate. It has the advantages of high wiring density, light weight, thin thickness, good bendability, etc. It is an important component of electronic appliances, such as touch screens, TFT display modules, etc.

[0003] The Chinese utility model with publication number CN 207039988 U in the prior art discloses an FPC board, including a plug-in part and a binding part and a fixing part connected between the plug-in part and the binding part, the fixing part includes a first connection part connected to the plug-in part and a second connection part connected to the binding part, a PI reinforcing plate is attached to one side of the first connection part, and the second connection part includes a substrate, a copper foil outside the substrate, and a softening layer outside the copper foil, and the softening layer is made of a metal with a ductility greater than that of the copper foil. The embodiment of the utility model enhances the flexibility of the FPC by arranging a metal layer with a ductility greater than that of the second connection part at the bending part of the FPC, so as to facilitate bending when the binding part is fixed.

[0004] In this solution, the flexibility of the FPC is enhanced by adding a ductile metal layer. However, in order to enhance the shielding effect, the FPC is covered with an EMI film, which further increases the thickness of the FPC and makes it too hard. The stress is too high after bending, and it is prone to problems such as warping or poor connection. Utility Model Content

[0005] In order to solve the above-mentioned deficiencies of the prior art, the utility model provides a bendable FPC structure, which directly adopts a single-layer wiring connection circuit in the bending area. Since the grounding cable and the metal cable are located in the same circuit layer, the bending stress will be reduced, and the grounding cable is partially made into a circular metal block to increase the connection with the EMI film. The PI covering of the grounding cable is removed and exposed, which reduces the hardness of the PI layer and plays a softening role, thereby reducing the thickness and hardness of the FPC, reducing the rebound force after the FPC is bent, and achieving a softening effect.

[0006] The technical problem to be solved by the utility model is achieved through the following technical solutions:

[0007] A bendable FPC structure, comprising: an FPC (1), comprising a bending area (12) and a non-bending area (11), wherein the bending area (12) is a single-layer wiring structure, and the non-bending area (11) is a double-layer wiring structure;

[0008] The bending area (12) comprises a metal busbar (21) and a ground busbar (23), the ground busbar (23) and the metal busbar (21) are arranged on the same side of the circuit layer, and the bending area (12) is connected to the non-bending area (11) via the metal busbar (21); and

[0009] A first interface end (3), the first interface end (3) being arranged at one end close to the bending area (12);

[0010] A second interface end (4), the second interface end (4) being arranged at an end close to the non-bending area (11);

[0011] A circular metal block (231) is provided on the grounding busbar (23), and the diameter of the circular metal block (231) is greater than the line width of the grounding busbar (23).

[0012] Furthermore, the FPC includes a base layer PI, an upper layer circuit, a lower layer circuit, an upper layer PI and a lower layer PI; the upper layer circuit and the lower layer circuit are respectively provided on the upper and lower surfaces of the base layer PI, and the upper layer PI and the lower layer PI are respectively provided on the side of the upper layer circuit and the lower layer circuit away from the base layer PI.

[0013] Furthermore, at least one of the upper layer circuit and the lower layer circuit includes the metal bus bar and the ground bus bar.

[0014] Furthermore, an upper layer PI on the surface of the bending area is provided with a window area and a square-shaped PI surrounding the window area, and the metal busbar and the ground busbar are exposed in the window area.

[0015] Furthermore, the grounding busbar is disposed in the middle area of ​​the bending area, the grounding busbar is separated by the metal busbar, and the width of the grounding busbar is 0.2-0.4 mm.

[0016] Furthermore, the diameter of the circular metal block is 0.8-1.2 mm.

[0017] Furthermore, two upper layers of EMI and lower layers of EMI are disposed on the front and back sides of the bending area, and the upper layer of EMI and the lower layer of EMI cover the upper layer of PI and the lower layer of PI.

[0018] Furthermore, the staggered spacing d between the upper layer EMI and the lower layer EMI is 0.5-1.0 mm.

[0019] Furthermore, the upper layer EMI is overlapped with the grounding cable of the upper layer circuit not covered by the upper layer PI.

[0020] Furthermore, auxiliary wings protruding outward are arranged on both sides of the edge of the interface end, and a plurality of normal gold fingers arranged in sequence are arranged on the edge of the interface end.

[0021] The utility model has the following beneficial effects: a bendable FPC structure, comprising: an FPC, comprising a bending area and a non-bending area; a bending area, the bending area is connected to the non-bending area through a metal cable; a first interface end, the first interface end is arranged at one end close to the bending area; a second interface end, the second interface end is arranged at one end close to the non-bending area. The bending area also includes a grounding cable, and a round metal block is arranged on the grounding cable. In the present invention, when in use, the first interface end and the second interface end are respectively connected to two components. Due to the positional relationship between different components, the FPC needs to be bent to ensure the stability of the connection. The present application directly uses a single-layer wiring connection line in the bending area. Compared with the non-bending area of ​​the double-layer wiring, its thickness and hardness are smaller. At the same time, since the grounding cable and the metal cable are located in the same circuit layer, the bending stress will be reduced. The grounding cable is partially provided with a circular metal block for overlapping with the EMI film; the PI covering of the grounding cable is removed and exposed, thereby reducing the hardness of the PI layer and softening it, thereby reducing the thickness and hardness of the FPC, reducing the rebound force after the FPC is bent, and achieving a softening effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the scheme in the present application, a brief introduction is given below to the drawings required for use in the description of the embodiments. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0023] Figure 1 A structural schematic diagram of a bendable FPC structure provided by the utility model;

[0024] Figure 2 A schematic diagram of a bendable FPC structure metal cable provided by the utility model;

[0025] Figure 3 A schematic diagram of the EMI coating of the bendable FPC structure provided by the utility model;

[0026] Figure 4 A schematic diagram of the stacking structure of the bendable FPC structure provided by the utility model;

[0027] Figure 5 A schematic diagram of the structure of the first interface end of the bendable FPC structure provided by the utility model;

[0028] Figure 6 This is a schematic diagram of the EMI film stacking structure of the bendable FPC structure provided by the utility model.

[0029] 1. FPC; 11. Non-bending area; 12. Bending area; 101. Base PI; 102. Upper circuit; 103. Lower circuit; 104. Upper PI; 105. Lower PI; 106. Upper EMI; 107. Lower EMI; 21. Metal cable; 23. Ground cable; 231. Round metal block; 3. First interface end; 31. Auxiliary wing; 32. Gold finger; 4. Second interface end. DETAILED DESCRIPTION

[0030] The present invention is described in detail below in conjunction with the accompanying drawings and embodiments, examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0031] In the description of the present invention, it should be understood that the terms "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0032] In addition, the terms "first", "second", and "third" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, a feature defined as "first", "second", and "third" may explicitly or implicitly include one or more of the features. In the description of the present utility model, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0033] In the present invention, unless otherwise clearly specified and limited, the terms "install", "connect", "connect", "fix", "set" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances. Example

[0034] like Figure 1As shown, a bendable FPC structure includes: FPC1, including a bending area 12 and a non-bending area 11, the bending area 12 is a single-layer wiring structure, and the non-bending area 11 is a double-layer wiring structure;

[0035] The bending area 12 includes a metal bus line 21 and a ground bus line 23. The ground bus line 23 and the metal bus line 21 are arranged on the same circuit layer. The bending area 12 is connected to the non-bending area 11 through the metal bus line 21; and

[0036] A first interface end 3, wherein the first interface end 3 is disposed at one end close to the bending area 12;

[0037] A second interface end 4, the second interface end 4 is disposed at one end close to the non-bending area 11;

[0038] A circular metal block 231 is disposed on the grounding bus 23 . The diameter of the circular metal block 231 is greater than the width of the grounding bus 23 .

[0039] In the present invention, when in use, the first interface end 3 and the second interface end 4 are respectively connected to two components. Due to the positional relationship between different components, the FPC needs to be bent to ensure the stability of the connection. The present application directly uses a single-layer wiring connection line in the bending area 12. Compared with the non-bending area 11 of the double-layer wiring, its thickness and hardness are smaller. At the same time, since the grounding cable 23 and the metal cable 21 are located in the same circuit layer, the bending stress will be reduced. The grounding cable 23 is partially provided with a circular metal block 231 for overlapping with the EMI film.

[0040] In this embodiment, Figure 4 As shown, the FPC1 includes a base layer PI101, an upper layer circuit 102, a lower layer circuit 103, an upper layer PI104 and a lower layer PI105; the upper layer circuit 102 and the lower layer circuit 103 are respectively provided on the upper and lower surfaces of the base layer PI101, and the upper layer PI104 and the lower layer PI105 are respectively provided on the surface of the upper layer circuit 102 and the lower layer circuit 103 away from the base layer PI101.

[0041] Among them, the PI layer refers to a layer of polyimide material covered on the flexible printed circuit board. PI is a polymer material with high temperature resistance, chemical corrosion resistance and excellent mechanical properties. It is often used to cover the FPC to provide protection and enhance performance. Covering the PI layer can improve the mechanical strength, heat resistance and chemical resistance of the FPC, while also providing good insulation and corrosion resistance. This FPC covered with a PI layer is often used in electronic products that require high temperature, high humidity and high corrosion environments.

[0042] In another preferred implementation manner of the present embodiment, the upper layer circuit 102 or the lower layer circuit 103 includes the metal bus bar 21 and the ground bus bar 23, that is, when the upper layer circuit 102 forms the metal bus bar 21 and the ground bus bar 23 in the bending area 12, the lower layer circuit 103 avoids the bending area 12 and is not wired in the bending area 12; when the lower layer circuit 103 forms the metal bus bar 21 and the ground bus bar 23 in the bending area 12, the upper layer circuit 102 avoids the bending area 12 and is not wired in the bending area 12.

[0043] Preferably, the metal bus wire 21 and the ground bus wire 23 are formed by etching the same copper clad layer of the upper circuit 102 or the lower circuit 103 . In this embodiment, the metal bus wire 21 and the ground bus wire 23 are etched on the upper circuit 102 .

[0044] It should be noted that etching is a commonly used metal processing technology used to perform fine pattern and structure processing on metal surfaces. In the electronics industry, etching technology is often used to make circuit boards and microelectronic devices. When making circuit boards, etching technology is often used to remove excess metal from the surface of copper foil to form the desired circuit pattern. Etching technology usually uses chemical solutions or electrochemical methods to expose the metal surface to a specific etchant to remove excess metal. When making circuit boards, etching technology can accurately remove metal from the surface of copper foil to form the desired circuit pattern and structure. Etching technology has the advantages of high precision, high efficiency and low cost. It can realize complex circuit patterns and microstructure processing, providing an important processing means for the manufacture of electronic devices.

[0045] Furthermore, the upper layer PI 201 on the surface of the bending zone 12 is provided with a window area and a U-shaped PI surrounding the window area, and the window area exposes the metal busbar 21 and the ground busbar 23. The window can reduce the hardness of the PI layer and soften the FPC, while the U-shaped PI left on the periphery of the window area ensures the strength of the bending zone 12 to a certain extent to avoid bending and tearing.

[0046] In this embodiment, the upper layer PI 104 covering the grounding cable 23 is removed and exposed, which plays a softening role, thereby reducing the thickness and hardness, and reducing the rebound force of the FPC after bending, thereby achieving a softening effect. Example

[0047] like Figure 2As shown, the grounding cable 23 is arranged in the middle area of ​​the bending area 12, the grounding cable 23 is separated by the metal cable 21, and the width of the grounding cable 23 is 0.2-0.4mm. By increasing the width of the grounding cable 23 and providing a circular metal block 231 on the grounding cable 23 in the cable gap so as to fully contact with the upper layer EMI 106, the grounding cable 23 is separated by the metal cable 21 to avoid unnecessary interference.

[0048] In another preferred implementation manner of this embodiment, the diameter of the circular metal block 231 is 0.8-1.2 mm.

[0049] Among them, the bending area 12 is a single-layer circuit routing, and at least one layer of the bending area 12 is also provided with a metal busbar 21 and the ground busbar 23. The ground busbar 23 is spaced apart from the metal busbar 21. In this embodiment, the bending area 12 is a single-layer metal busbar, and the non-bending area 11 is a double-layer metal busbar.

[0050] Furthermore, if Figure 6 As shown, two upper layers EMI 106 and lower layers EMI 107 are disposed on the front and back sides of the bending area 12 , which are staggered with each other. The upper layer EMI 106 and the lower layer EMI 107 cover the ground busbar 23 and the metal busbar 21 .

[0051] Furthermore, the upper EMI 106 is overlapped with the grounding cable 23 of the upper circuit 102 that is not covered by the upper PI 104, thereby isolating the interference of electromagnetic waves on the FPC electronic components.

[0052] It should be noted that EMI is a commonly used electromagnetic shielding material, which is used to isolate electromagnetic wave interference from electronic equipment, lines and antennas. The main components of EMI are metal foil and plastic film. By covering the metal foil on the plastic film to form a thin film, and then applying it to the electronic equipment or lines that need to be shielded, it can isolate electromagnetic wave interference. The use of EMI can not only improve the anti-interference ability of electronic equipment and lines, but also improve the electromagnetic compatibility of equipment and reduce the level of electromagnetic radiation. EMI is widely used in electronic equipment, aerospace, military industry and other fields to ensure the normal operation and service life of equipment. The role of EMI is achieved by preventing the propagation of electromagnetic waves, so it has a high effect in electromagnetic isolation. At the same time, EMI is low in production cost and easy to process and install, so it is widely used in the protection and isolation of various electronic equipment and lines.

[0053] like Figure 3As shown, the staggered spacing d of the upper EMI106 and the lower EMI107 is 0.5-1.0mm. The staggered arrangement of the upper EMI106 and the lower EMI107 can disperse the stress distribution on the FPC at the edge of the upper EMI106 and the lower EMI107. When the FPC is bent, the stress is dispersed, which can reduce the risk of copper layer fracture, thereby improving the yield and reducing costs. Example

[0054] like Figure 5 As shown, auxiliary wings 31 protruding outward are provided on both sides of the edge of the first interface end 3, and a plurality of gold fingers 32 arranged in sequence are provided on the edge of the first interface end 3. The auxiliary wings 31 can enhance the anti-twist strength of the side of the first interface end 3 of the FPC, and can better plug and unplug the gold fingers 32.

[0055] Among them, the gold finger 32 is a connection form on the electronic component connector, which is usually used to connect the circuit board to other circuit boards or plugs. It is a metal contact point protruding from the edge of the circuit board, usually made of metal materials such as copper, nickel or gold. The number and arrangement of the gold fingers 32 can be designed according to the needs of the circuit board. During the manufacturing process of the circuit board, the gold fingers 32 are usually formed by exposing the inner copper foil of the first interface end 3 through methods such as chemical corrosion or mechanical processing. After the manufacture of the gold fingers 32 is completed, it is also necessary to perform surface treatment on it, such as gold plating, to improve the conductivity and corrosion resistance of the connection. The advantages of the gold fingers 32 are high connection reliability, large contact area, and ability to withstand large currents and voltages. At the same time, the shape and arrangement of the gold fingers 32 can also be designed according to the needs of the circuit board, with high flexibility.

[0056] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the embodiments of the utility model rather than to limit them. Although the embodiments of the utility model are described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the embodiments of the utility model can still be modified or replaced by equivalents, and these modifications or equivalent replacements cannot cause the modified technical solutions to deviate from the scope of the technical solutions of the embodiments of the utility model.

Claims

1. A bendable FPC structure, characterized in that: include: The FPC (1) comprises a bending area (12) and a non-bending area (11), wherein the bending area (12) is a single-layer wiring structure, and the non-bending area (11) is a double-layer wiring structure; The bending area (12) comprises a metal busbar (21) and a ground busbar (23), the ground busbar (23) and the metal busbar (21) are arranged on the same side of the circuit layer, and the bending area (12) is connected to the non-bending area (11) via the metal busbar (21); and A first interface end (3), the first interface end (3) being arranged at one end close to the bending area (12); A second interface end (4), the second interface end (4) being arranged at an end close to the non-bending area (11); A circular metal block (231) is provided on the grounding busbar (23), and the diameter of the circular metal block (231) is greater than the line width of the grounding busbar (23).

2. The bendable FPC structure according to claim 1, characterized in that: The FPC (1) comprises a base layer PI (101), an upper layer circuit (102), a lower layer circuit (103), an upper layer PI (104) and a lower layer PI (105); the upper layer circuit (102) and the lower layer circuit (103) are respectively arranged on the upper and lower surfaces of the base layer PI (101); and the upper layer PI (104) and the lower layer PI (105) are respectively arranged on the surface of the upper layer circuit (102) and the lower layer circuit (103) away from the base layer PI (101).

3. The bendable FPC structure according to claim 2, wherein: The upper layer circuit (102) or the lower layer circuit (103) comprises the metal bus wire (21) and a ground bus wire (23).

4. The bendable FPC structure according to claim 1, wherein: The upper layer PI (201) on the surface of the bending area (12) is provided with a window area and a square-shaped PI surrounding the window area, and the metal busbar (21) and the ground busbar (23) are exposed in the window area.

5. The bendable FPC structure according to claim 1, wherein: The grounding busbar (23) is arranged in the middle area of ​​the bending area (12), the grounding busbar (23) is separated by the metal busbar (21), and the grounding busbar (23) has a width of 0.2-0.4 mm.

6. The bendable FPC structure according to claim 1, wherein: The diameter of the circular metal block (231) is 0.8-1.2 mm.

7. The bendable FPC structure according to claim 1, wherein: Two upper EMI layers (106) and lower EMI layers (107) are arranged staggered on the front and back sides of the bending area (12); the upper EMI layer (106) and lower EMI layer (107) cover the grounding busbar (23) and the metal busbar (21).

8. The bendable FPC structure according to claim 7, wherein: The upper layer EMI (106) and the lower layer EMI (107) are staggered by a distance d of 0.5-1.0 mm.

9. The bendable FPC structure according to claim 7, wherein: The upper layer EMI (106) is overlapped with the grounding cable (23) of the upper layer circuit (102) not covered by the upper layer PI (104).

10. The bendable FPC structure according to claim 1, wherein: Auxiliary wings (31) protruding outwards are arranged on both sides of the edge of the interface end (3), and a plurality of gold fingers (32) arranged in sequence are arranged on the edge of the interface end (3).

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