Flexible bending-resistant circuit board

Abstract

The invention discloses a flexible bending-resistant circuit board, and relates to the technical field of electronic additive manufacturing. The flexible bending-resistant circuit board comprises a first flexible substrate and a second flexible substrate, the metal foil circuit is formed on the first flexible base material, and the metal foil circuit is provided with a hollow structure; the elastic conductive printed circuit is formed on the hollow structure of the metal foil circuit and is connected with the metal foil circuit; wherein the elastic conductive printed circuit comprises conductive particles and a resin film forming matter for binding the conductive particles, and the outage elongation of the elastic conductive printed circuit is not lower than 50%. According to the flexible bending-resistant circuit board provided by the embodiment of the invention, the elastic conductive printed circuit and the metal foil circuit are connected and combined, and the bending resistance of the flexible bending-resistant circuit board is far higher than that of the metal foil circuit, so that even if the metal foil circuit is bent and broken, the circuit conduction of the metal foil circuit can be ensured due to the connection with the elastic conductive printed circuit; and the bending-resistant performance of the flexible bending-resistant circuit board is further improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of electronic additive manufacturing, and in particular relates to a flexible, bend-resistant circuit board. Background Art

[0002] Flexible Printed Circuit (FPC), also known as soft circuit board or flexible circuit board, mainly uses a flexible substrate such as polyester film or polyimide as the base layer. Copper foil is attached to the base layer through sputtering, deposition, gluing, hot pressing and other processes to form a conductive layer. Finally, the conductive layer is wrapped with an encapsulation layer to form a flexible circuit board.

[0003] Although FPC flexible circuit boards are lighter, thinner, and more flexible than traditional printed circuit boards (PCBs), the bending resistance of existing FPC flexible circuit boards is still insufficient as usage demands continue to escalate and expand. Therefore, many manufacturers have begun to try various improved alternatives, but various problems still exist.

[0004] 1) Using room-temperature liquid metal (such as gallium or gallium-based alloys) to directly replace copper foil circuits significantly improves bending resistance, but the liquid metal has poor conductivity and the problem of liquid metal oxidation and deterioration is difficult to solve;

[0005] 2) Using room-temperature liquid metal and copper foil to form a self-healing composite conductive layer. In this solution, when the copper foil breaks, the liquid metal will penetrate the crack to repair it, thereby ensuring the reliability and bending resistance of the FPC. However, the problem of liquid metal oxidation and deterioration is difficult to solve.

[0006] Solutions (1) and (2) can indeed improve the bending resistance of FPC, but in actual applications, liquid metal is very easy to oxidize and deteriorate. Even if it is tightly sealed, it is difficult to completely solve the low stability and reliability of such products. In particular, the oxidation problem of liquid metal in the bending area will be particularly obvious. This is also the primary difficulty in the practical application of liquid metal circuits so far.

[0007] In summary, it is difficult for existing FPC flexible circuit boards to simultaneously achieve good bending resistance, conductivity, and stable reliability. Summary of the Invention

[0008] In view of this, an object of the present invention is to provide a flexible, bend-resistant circuit board to solve the problem in the prior art that FPC flexible circuit boards are difficult to simultaneously achieve good bend resistance, conductivity, and stable reliability.

[0009] In some illustrative embodiments, the flexible, bend-resistant circuit board includes: a first flexible substrate; a metal foil circuit formed on the first flexible substrate, the metal foil circuit having a hollow structure; and an elastic conductive printed circuit formed on the hollow structure of the metal foil circuit and connected to the metal foil circuit; wherein the elastic conductive printed circuit includes: conductive particles and a resin film that binds the conductive particles, and the elastic conductive printed circuit has an off-state elongation of not less than 50%.

[0010] In some optional embodiments, the metal foil circuit is formed of electrolytic metal foil or rolled metal foil.

[0011] In some optional embodiments, the metal foil circuit is a copper foil circuit, an aluminum foil circuit, a silver foil circuit, or a gold foil circuit.

[0012] In some optional embodiments, the power-off elongation of the elastic conductive printed circuit is not less than 150%.

[0013] In some optional embodiments, along the routing direction of the metal foil circuit, the elastic conductive printed circuit is continuously or discontinuously connected to the metal foil circuit.

[0014] In some optional embodiments, the running direction of the elastic conductive printed circuit is consistent with the running direction of the metal foil circuit connected thereto.

[0015] In some optional embodiments, a local area of the flexible bend-resistant circuit board is used as a bending area, the metal foil circuit located in the bending area has the hollow structure, and the elastic conductive printed circuit is formed on the metal foil circuit in the bending area.

[0016] In some optional embodiments, the connection structure between the elastic conductive printed circuit and the metal foil circuit includes: the elastic conductive printed circuit and the metal foil circuit are connected horizontally; or, the elastic conductive printed circuit and the metal foil circuit are connected horizontally, and the elastic conductive printed circuit and the metal foil circuit are stacked vertically.

[0017] In some optional embodiments, the metal foil circuit is a multi-circuit structure with an alternating arrangement; wherein a low-stress structure is formed on the first flexible substrate between adjacent metal foil circuits.

[0018] In some optional embodiments, the flexible bend-resistant circuit board further includes: a second flexible substrate, cooperating with the first flexible substrate to enclose at least a portion of the metal foil circuit and / or the elastic conductive printed circuit.

[0019] Compared with the existing technology, this application has the following advantages:

[0020] The flexible bend-resistant circuit board in the embodiment of the present invention connects the elastic conductive printed circuit, which was originally mainly used in flexible stretchable circuits, with the traditional non-stretchable metal foil circuit, and the power-off elongation of the elastic conductive printed circuit is not less than 50%. The elastic stretchability of the elastic conductive printed circuit is deliberately ignored, and its bend resistance is mainly used instead. Since its bend resistance is much higher than that of the metal foil circuit, even if the metal foil circuit bends and breaks, its circuit conduction will be guaranteed due to the connection with the elastic conductive printed circuit, thereby improving the bend resistance of the flexible bend-resistant circuit board. In addition, the combination of the metal foil circuit and the elastic conductive printed circuit still has good conductivity guaranteed by the metal foil circuit, so that the flexible bend-resistant circuit board is compatible with good bend resistance, conductivity and stable reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a structural example 1 of the flexible bending-resistant circuit board in an embodiment of the present invention;

[0022] Figure 2 AA cross-sectional view of the first structural example of the flexible bending-resistant circuit board in an embodiment of the present invention;

[0023] Figure 3 This is a second structural example of the flexible bending-resistant circuit board in an embodiment of the present invention;

[0024] Figure 4 FIG2 is a cross-sectional view of the BB plane of the second structural example of the flexible bending-resistant circuit board in the embodiment of the present invention;

[0025] Figure 5 This is a third structural example of the flexible bending-resistant circuit board in an embodiment of the present invention;

[0026] Figure 6 This is a fourth structural example of the flexible bending-resistant circuit board in an embodiment of the present invention;

[0027] Figure 7 This is a fifth structural example of the flexible bending-resistant circuit board in an embodiment of the present invention;

[0028] Figure 8 This is a sixth structural example of the flexible bending-resistant circuit board in an embodiment of the present invention;

[0029] Figure 9 This is a seventh structural example of a flexible bending-resistant circuit board in an embodiment of the present invention;

[0030] Figure 10 This is a structural example eight of the flexible bending-resistant circuit board in an embodiment of the present invention;

[0031] Figure 11This is a ninth structural example of the flexible bending-resistant circuit board in an embodiment of the present invention;

[0032] Figure 12 This is a structural example 10 of the flexible bending-resistant circuit board in an embodiment of the present invention;

[0033] Figure 13 This is a structural example eleven of the flexible bending-resistant circuit board in an embodiment of the present invention;

[0034] Figure 14 This is a structural example 12 of the flexible bending-resistant circuit board in an embodiment of the present invention;

[0035] Figure 15 This is a thirteenth structural example of the flexible bending-resistant circuit board in an embodiment of the present invention;

[0036] Figure 16 This is a structural example 14 of the flexible bending-resistant circuit board in an embodiment of the present invention;

[0037] Figure 17 This is a structural example 15 of the flexible bending-resistant circuit board in an embodiment of the present invention;

[0038] Figure 18 This is the sixteenth structural example of the flexible bending-resistant circuit board in the embodiment of the present invention. DETAILED DESCRIPTION

[0039] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0040] Terminology Notes:

[0041] The power-off elongation refers to the maximum degree of stretching of an elastic conductive material (such as the elastic conductive printed circuit in this application) while maintaining its conductive properties (circuit conduction). The power-off elongation of the elastic conductive printed circuit in the embodiments of the present invention is measured based on an elastic conductive printed circuit with a width of 5000 μm and a thickness of 10 μm. Therefore, when measuring the power-off elongation of an elastic conductive printed circuit, those skilled in the art should require that the cross-sectional area (perpendicular to the stretching direction) of the elastic conductive printed circuit be no less than 5×10 4 μm 2 .

[0042] Example:

[0043] When a 10 cm long, 5000 μm wide, and 10 μm thick elastic conductive printed circuit is stretched to 15 cm along its length, the stretching degree reaches 50%, and the elastic conductive printed circuit still maintains its conductive properties, that is, the power-off elongation of the elastic conductive printed circuit reaches at least 50%.

[0044] It should be noted that the various technical features in the embodiments of the present invention can be combined with each other without conflict.

[0045] The embodiment of the present invention discloses a flexible bending-resistant circuit board, specifically, Figure 1-6 As shown, Figure 1 This is a structural example 1 of the flexible bending-resistant circuit board in an embodiment of the present invention; Figure 2 AA cross-sectional view of the first structural example of the flexible bending-resistant circuit board in an embodiment of the present invention; Figure 3 This is a second structural example of the flexible bending-resistant circuit board in an embodiment of the present invention; Figure 4 FIG2 is a cross-sectional view of the BB plane of the second structural example of the flexible bending-resistant circuit board in the embodiment of the present invention;

[0046] Figure 5 This is a third structural example of the flexible bending-resistant circuit board in an embodiment of the present invention; Figure 6 This is a fourth structural example of a flexible, bend-resistant circuit board according to an embodiment of the present invention. The flexible, bend-resistant circuit board comprises: a first flexible substrate 10; a metal foil circuit 20 formed on the first flexible substrate 10; and an elastic conductive printed circuit 30 formed on the first flexible substrate 10 and / or the metal foil circuit 20 and connected to the metal foil circuit 20. The elastic conductive printed circuit 30 comprises conductive particles and a resin film that binds the conductive particles. The elastic conductive printed circuit 30 has an off-state elongation of not less than 50%.

[0047] The elastic conductive printed circuit in the embodiment of the present invention is formed by a printing process of an elastic conductive paste (also known as a stretchable conductive paste); wherein the printing process is not limited to direct printing, inkjet printing, screen printing, transfer printing, lithography, gravure printing and other patterned molding processes, or it can be formed on the entire surface through a coating process, and then a circuit pattern is formed through a subtractive process.

[0048] The elastic conductive paste in the embodiment of the present invention is a low-temperature conductive paste with a resin as a binder phase, mainly including: conductive filler, resin and solvent. The resin system contains an elastic resin component, which gives it elastic and stretchable properties. After the elastic conductive paste is printed, formed and cured, the main structure of the elastic conductive printed circuit formed is conductive particles and a resin film that binds the conductive particles.

[0049] The conductive filler in the embodiment of the present invention is not limited to one or more of gold, silver, copper, iron, nickel, zinc, aluminum, palladium, conductive carbon black, and graphene; the elastic resin contained in the resin system in the embodiment of the present invention is not limited to one or more of silicone resin, TPU resin, SEBS resin, and SIS resin.

[0050] Those skilled in the art should note that although the elastic conductive paste referred to in this application is a low-temperature conductive paste, it is different from traditional ordinary low-temperature conductive pastes. Although after curing and molding, it also has the main structure of conductive particles and a resin film that binds the conductive particles, its resin system contains almost no elastic properties, or the elastic properties are relatively low, resulting in the entire structure after curing being brittle. Under repeated bending, the problem of circuit breakage and peeling is more likely to occur.

[0051] Since the elastic properties of the elastic conductive paste depend on its overall material system, such as the specific composition, component ratio, preparation process, etc., and the material system is too complex, the present invention does not limit the elastic conductive paste, and further specifically defines the elastic conductive printed circuit; specifically, the elastic conductive printed circuit in the embodiment of the present invention is a conductive printed circuit formed by a low-temperature conductive paste and having an off-state elongation of not less than 50%.

[0052] The elastic conductive printed circuit can be evaluated by referring to the definition of the power-off elongation in the embodiment of the present invention, which will not be described in detail here.

[0053] The flexible bend-resistant circuit board in the embodiment of the present invention connects the elastic conductive printed circuit, which was originally mainly used in flexible stretchable circuits, with the traditional non-stretchable metal foil circuit, and the power-off elongation of the elastic conductive printed circuit is not less than 50%. The elastic stretchability of the elastic conductive printed circuit is deliberately ignored, and its bend resistance is mainly used instead. Since its bend resistance is much higher than that of the metal foil circuit, even if the metal foil circuit bends and breaks, its circuit conduction will be guaranteed due to the connection with the elastic conductive printed circuit, thereby improving the bend resistance of the flexible bend-resistant circuit board. In addition, the combination of the metal foil circuit and the elastic conductive printed circuit still has good conductivity guaranteed by the metal foil circuit, so that the flexible bend-resistant circuit board is compatible with good bend resistance, conductivity and stable reliability.

[0054] Furthermore, the higher the off-state elongation of the elastic conductive printed circuit in the embodiment of the present invention, the better its bending resistance, and thus the better the bending resistance of the connection structure between the elastic conductive printed circuit and the metal foil circuit.

[0055] Preferably, the power-off elongation of the elastic conductive printed circuit in the embodiment of the present invention may be not less than 60%, not less than 70%, not less than 80%, not less than 90%, not less than 100%, not less than 110%, not less than 120%, not less than 130%, not less than 140%, not less than 150%, not less than 160%, not less than 170%, not less than 180%, not less than 190%, not less than 200%, not less than 220%, not less than 240%, not less than 260%, not less than 280%, or not less than 300%.

[0056] Furthermore, the power-off elongation of the elastic conductive printed circuit in the embodiment of the present invention is not less than 150%, which can achieve both the advantages of bending resistance and cost.

[0057] The thickness of the elastic conductive printed circuit in the embodiments of the present invention can range from 2 to 30 μm, including but not limited to 2 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, 25 μm, and 30 μm. Elastic conductive printed circuits within this thickness range can achieve both good electrical conductivity and flex resistance. If the thickness of the elastic conductive printed circuit is less than 2 μm, the electrical conductivity of the elastic conductive printed circuit is poor. If the thickness of the elastic conductive printed circuit is greater than 30 μm, the elastic conductive printed circuit is too thick, which in turn affects its flex resistance.

[0058] Preferably, the thickness of the elastic conductive printed circuit in the embodiment of the present invention may be in the range of 4 to 20 μm. The elastic conductive printed circuit in this thickness range has the best conductivity and bending resistance.

[0059] In the embodiment of the present invention, the first flexible substrate can be a flexible non-stretchable substrate and / or a flexible stretchable substrate, specifically including but not limited to PET, PVC, PU, PC, PP, PA, PI, CPI (transparent PI), TPE, TPU, TPV, etc.; wherein, the first flexible substrate is not limited to using any of the above-mentioned flexible substrates or a multi-layer composite substrate, as long as the first flexible substrate has flexible bending properties.

[0060] The thickness of the first flexible substrate in the embodiments of the present invention may be 5 to 50 μm, including but not limited to 5 μm, 6.5 μm, 7 μm, 8 μm, 10 μm, 12.5 μm, 13 μm, 15 μm, 16.5 μm, 17 μm, 18 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, and 50 μm. Preferably, the thickness of the first flexible substrate in the embodiments of the present invention may be 10 to 20 μm. This thickness of the first flexible substrate can combine the advantages of cost, structural strength, and low stress, further improving the bending resistance of the flexible flex-resistant circuit board.

[0061] The metal foil circuit in the embodiment of the present invention can be formed by electrolytic metal foil or rolled metal foil.

[0062] Preferably, the metal foil circuit in the embodiment of the present invention may be made of rolled metal foil. Compared with electrolytic metal foil, rolled metal foil has better bending resistance.

[0063] The material of the metal foil circuit in the embodiment of the present invention includes, but is not limited to, one or more metals such as copper, aluminum, silver, gold, nickel, iron, and palladium.

[0064] Furthermore, the metal foil circuit in the embodiment of the present invention is a copper foil circuit, an aluminum foil circuit, a silver foil circuit or a gold foil circuit. Preferably, the metal foil circuit in the embodiment of the present invention can be a copper foil circuit, which has cost and mature process advantages compared to other metals.

[0065] The thickness of the metal foil circuit in the embodiment of the present invention can be 5 to 30 μm, including but not limited to 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, 21 μm, 22 μm, 23 μm, 24 μm, 25 μm, 26 μm, 27 μm, 28 μm, 29 μm, and 30 μm. Preferably, the thickness of the metal foil circuit in the embodiment of the present invention can be 12 to 25 μm. Metal foil circuits in this thickness range have better bending resistance.

[0066] In some embodiments, a first adhesive layer 50 may be provided between the metal foil circuit and the first flexible substrate; in other embodiments, no first adhesive layer 50 may be provided between the metal foil circuit and the first flexible substrate.

[0067] In some embodiments, the flexible, bend-resistant circuit board according to the present invention may further include a second flexible substrate 40 that cooperates with the first flexible substrate 10 to enclose at least a portion of the metal foil circuit 20 and / or the elastic conductive printed circuit 30. Specifically, the second flexible substrate may fully cooperate with the first flexible substrate to encapsulate the entire metal foil circuit and the elastic conductive printed circuit, or may encapsulate a portion of the metal foil circuit and the elastic conductive printed circuit, or may include a window in the second flexible substrate to expose a portion of the metal foil circuit and / or the elastic conductive printed circuit. The exposed portion of the metal foil circuit and / or the elastic conductive printed circuit may be used as a solder pad, an external electrode (e.g., a gold finger), and / or for other functional purposes.

[0068] In some embodiments, the elastic conductive printed circuit 30 can be formed after the second flexible substrate 40 is formed, connecting to the metal foil circuit 20. For example, a window exposing a portion of the metal foil circuit can be provided on the second flexible substrate, and the elastic conductive printed circuit 30 can be formed only on the metal foil circuit 20 within the window. Alternatively, the elastic conductive printed circuit 30 can be formed on the second flexible substrate, covering the metal foil circuit 20 within the window. Alternatively, the window provided on the second flexible substrate can be used to expose a portion of the metal foil circuit 20 and a portion of the first flexible substrate surrounding the window, and the elastic conductive printed circuit 30 can be formed within the window.

[0069] In other embodiments, the windows may be formed on the first flexible substrate (and / or the second flexible substrate), and the elastic conductive printed circuit may be formed from the side of the first flexible substrate (having the windows).

[0070] The second flexible substrate in the embodiment of the present invention can be a flexible non-stretchable substrate and / or a flexible stretchable substrate, specifically including but not limited to PET, PVC, PU, PC, PP, PA, PI, CPI (transparent PI), TPE, TPU, TPV, etc.; wherein, the second flexible substrate is not limited to using any of the above-mentioned flexible substrates or a multi-layer composite substrate, as long as the second flexible substrate has flexible bending properties.

[0071] The thickness of the second flexible substrate in the embodiments of the present invention may be 5 to 50 μm, including but not limited to 5 μm, 6.5 μm, 7 μm, 8 μm, 10 μm, 12.5 μm, 13 μm, 15 μm, 16.5 μm, 17 μm, 18 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, and 50 μm. Preferably, the thickness of the second flexible substrate in the embodiments of the present invention may be 10 to 20 μm. This thickness of the second flexible substrate can combine the advantages of cost, structural strength, and low stress, further improving the bending resistance of the flexible flex-resistant circuit board.

[0072] In some embodiments, the second flexible substrate 40 in the embodiment of the present invention can be combined with the first flexible substrate 10 via a second adhesive layer 60 .

[0073] In some embodiments of the present invention, along the routing direction of the metal foil circuit, the elastic conductive printed circuit is continuously or discontinuously connected to the metal foil circuit.

[0074] Those skilled in the art should understand that the function of the elastic conductive printed circuit in the embodiment of the present invention is mainly to improve the bending resistance of the metal foil circuit connected thereto. Therefore, whether the elastic conductive printed circuit is fully or partially connected to the metal foil circuit along the routing direction of the metal foil circuit, the bending resistance of the flexible bend-resistant circuit board can be improved.

[0075] In some embodiments, the routing direction of the elastic conductive printed circuit in the embodiments of the present invention is consistent with the routing direction of the metal foil circuit connected thereto. In this embodiment, the routing direction of the elastic conductive printed circuit is consistent with the routing direction of the metal foil circuit connected thereto, meaning that the circuit patterns of the elastic conductive printed circuit and the metal foil circuit connected thereto are substantially consistent, which helps reduce the complexity of the routing design of the elastic conductive printed circuit and maintains the overall circuit aesthetics.

[0076] In other embodiments, the routing direction of the elastic conductive printed circuit and the routing direction of the metal foil circuit connected thereto may also be different. Designing different circuit patterns for the elastic conductive printed circuit and the metal foil circuit can also improve the overall circuit aesthetics.

[0077] The metal foil circuit in the embodiment of the present invention may be provided with a first low-stress structure 70. This low-stress structure, for example, is a hollow structure. The hollow pattern is not limited to regular or irregular patterns such as triangles, circles, quadrilaterals, pentagons, and hexagons. Its purpose is to reduce the integrated stress structure of the metal foil circuit, thereby reducing the integrated stress of the metal foil circuit and further improving the bendability of the metal foil circuit.

[0078] In embodiments of the present invention, the first and / or second flexible substrates may also be provided with a second low-stress structure 80. This low-stress structure can be a hollow structure or a slit structure, similarly improving the bendability of the first flexible substrate. The low-stress structure on the first and / or second flexible substrates can avoid the metal foil circuit and / or the elastic conductive printed circuit.

[0079] In some embodiments, the metal foil circuits in the embodiments of the present invention are a multi-circuit structure with an alternate arrangement; wherein a low stress structure is formed on the first flexible substrate and / or the second flexible substrate between adjacent metal foil circuits.

[0080] In some embodiments, a local area of the flexible bend-resistant circuit board in the embodiments of the present invention is used as a bending area, and the elastic conductive printed circuit is formed on the first flexible substrate and / or metal foil circuit in the bending area and is connected to the metal foil circuit in the bending area.

[0081] Exemplary, continue to exhibit Figure 6 The middle section of the flexible bend-resistant circuit board is set as the bending area L2, while the two sides of the middle section are the non-bending areas L1. The metal foil circuit 20 is also located in the middle section of the bending area. In this case, the elastic conductive printed circuit 30 can only be used to improve the bending resistance of the metal foil circuit 20 in the bending area L2, and therefore only needs to be connected to the metal foil circuit 20 in this area.

[0082] In addition, the low stress structures ( 70 , 80 ) for the metal foil circuit 20 , the first flexible substrate 10 , and the second flexible substrate 40 may also be disposed only within the bending region L2 of the flexible bending-resistant circuit board.

[0083] In some embodiments, the connection structure between the elastic conductive printed circuit 30 and the metal foil circuit 20 in the embodiments of the present invention includes: the elastic conductive printed circuit 30 and the metal foil circuit 20 are horizontally connected; and / or, the elastic conductive printed circuit and the metal foil circuit are vertically stacked.

[0084] Specifically, continue to participate in the exhibition Figure 4 ( Figure 4 The second flexible substrate 40 is not shown), wherein:

[0085] The elastic conductive printed circuit and the metal foil circuit are connected in a horizontal direction (the horizontal direction is the direction in which the flexible substrate is unfolded). Specifically, the elastic conductive printed circuit 30 and the metal foil circuit 20 form a horizontally connected structure LC.

[0086] The elastic conductive printed circuit and the metal foil circuit are stacked in a vertical direction (the vertical direction is perpendicular to the direction in which the flexible substrate is unfolded). Specifically, the elastic conductive printed circuit 30 is formed on the metal foil circuit 20 and has an overlapping structural relationship SC with the metal foil circuit 20 .

[0087] In the embodiments of the present invention, the elastic conductive printed circuit and the metal foil circuit are horizontally connected. Because the elastic conductive printed circuit is primarily formed on the first flexible substrate, this portion of the elastic conductive printed circuit is less susceptible to breakage caused by the metal foil circuit. It remains stably attached to the first flexible substrate and maintains a relatively stable connection with the metal foil circuit. The elastic conductive printed circuit formed on the metal foil circuit improves the contact surface with the metal foil circuit, minimizing contact resistance between the metal foil circuit and the elastic conductive printed circuit in the event of a break in the metal foil circuit, thereby ensuring the conductive performance of the flexible, flex-resistant circuit board. Furthermore, the elastic conductive printed circuit acts as a structural constraint on the metal foil circuit, ensuring that, in the event of a break in the metal foil circuit, the broken metal foil circuit remains connected as closely as possible.

[0088] Therefore, the structure in which the elastic conductive printed circuit and the metal foil circuit are both horizontally connected and vertically stacked in the embodiment of the present invention is most effective in improving the bending resistance of the flexible bending-resistant circuit board.

[0089] Example 1

[0090] like Figure 7 As shown, Figure 7 This is a fifth structural example of a flexible, bend-resistant circuit board according to an embodiment of the present invention. The flexible, bend-resistant circuit board comprises: a first flexible substrate 10, a metal foil circuit 20, an elastic conductive printed circuit 30, and a second flexible substrate 40. The elastic conductive printed circuit 30 is formed so as to completely cover only the metal foil circuit 20 (i.e., the width of the elastic conductive printed circuit 30 is equal to the width of the metal foil circuit 20). The metal foil circuit is formed of rolled copper.

[0091] Example 2

[0092] like Figure 8 As shown, Figure 8 This is a sixth structural example of a flexible, bend-resistant circuit board according to an embodiment of the present invention. The flexible, bend-resistant circuit board comprises a first flexible substrate 10, a metal foil circuit 20, an elastic conductive printed circuit 30, and a second flexible substrate 40. The elastic conductive printed circuit 30 has a greater line width than the metal foil circuit 20 and is formed not only overlying the metal foil circuit 20 but also on the first flexible substrate 10 surrounding the metal foil circuit 20. The metal foil circuit is formed of rolled copper.

[0093] Comparative Example 1

[0094] The FPC flexible circuit board in the prior art specifically includes: a first flexible substrate, a metal foil circuit and a second flexible substrate; wherein the metal foil circuit is made of electrolytic copper.

[0095] Comparative Example 2

[0096] The only difference between Comparative Example 2 and Comparative Example 1 is that the metal foil circuit uses rolled copper.

[0097] In order to facilitate those skilled in the art to quickly understand the technical solutions and effects of the present invention, the applicant conducted bending tests on the above-mentioned embodiments 1-2 and comparative examples 1-2 to verify the bending resistance of the flexible bending-resistant circuit boards in the embodiments of the present invention.

[0098] Among them, the bending test uses professional bending equipment for testing, and the test conditions are as follows:

[0099] ① The flexible circuit board is suspended vertically with a 200g weight on the bottom, and its vertical center is used as the bending point; ② Turn left 90 degrees first, then turn right 90 degrees, which counts as one bend. The equipment stops when the FPC breaks and fails to conduct electricity; ③ Bending radius 0.5mm; ④ Speed 60 times / minute; ⑤ Bending angle ±90°

[0100] The specific parameters and experimental data of Examples 1-2 and Comparative Examples 1-2 are shown in the following table:

[0101]

[0102] The above experimental data demonstrates that rolled copper exhibits superior flex resistance to electrolytic copper. Furthermore, the flexible, flex-resistant circuit board (PCB) in which metal foil circuitry is connected to an elastic conductive printed circuit in the embodiments of the present invention exhibits flex resistance superior to that of conventional copper foil FPCs, achieving a flex resistance improvement of over 100% compared to conventional copper foil FPCs. Furthermore, the flex resistance of the flexible conductive printed circuit board, in which the flexible conductive printed circuitry extends beyond the metal foil circuitry, is even greater than that of the flexible conductive printed circuit board in which the metal foil circuitry is merely overlaid.

[0103] In addition to the connection schemes shown in Examples 1 and 2, there are multiple connection schemes between the elastic conductive printed circuit and the metal foil circuit in the embodiments of the present invention, including but not limited to the following Examples 3-12.

[0104] Example 3

[0105] like Figure 9 As shown, Figure 9 This is the seventh structural example of a flexible bend-resistant circuit board in an embodiment of the present invention; the flexible bend-resistant circuit board includes: a first flexible substrate 10, a metal foil circuit 20, and an elastic conductive printed circuit 30; wherein the elastic conductive printed circuit 30 is formed on the metal foil circuit 20 and is arranged intermittently.

[0106] Example 4

[0107] like Figure 10 As shown, Figure 10 This is an eighth structural example of a flexible bend-resistant circuit board in an embodiment of the present invention; the flexible bend-resistant circuit board includes: a first flexible substrate 10, a metal foil circuit 20, and an elastic conductive printed circuit 30; wherein the elastic conductive printed circuit 30 and the metal foil circuit 20 are both formed on the first flexible substrate 10, and are connected only at the sides.

[0108] Example 5

[0109] like Figure 11 As shown, Figure 11 This is a ninth structural example of a flexible, bend-resistant circuit board according to an embodiment of the present invention. The flexible, bend-resistant circuit board comprises a first flexible substrate 10, a metal foil circuit 20, an elastic conductive printed circuit 30, and a second flexible substrate 40. The elastic conductive printed circuit 30 and the metal foil circuit 20 are both formed on the first flexible substrate 10. The elastic conductive printed circuit 30 is located on both sides of the metal foil circuit 20, and both sides are connected laterally.

[0110] Example 6

[0111] like Figure 12 As shown, Figure 12 This is a structural example ten of a flexible bend-resistant circuit board in an embodiment of the present invention; the flexible bend-resistant circuit board includes: a first flexible substrate 10, a metal foil circuit 20, an elastic conductive printed circuit 30, and a second flexible substrate 40; wherein the elastic conductive printed circuit 30 is formed on the metal foil circuit 20, and the line width of the elastic conductive printed circuit 30 is smaller than that of the metal foil circuit 20, and the elastic conductive printed circuit 30 is distributed obliquely on the metal foil circuit 20 in the line width direction of the metal foil circuit 30.

[0112] Example 7

[0113] like Figure 13 As shown, Figure 13 This is an eleventh structural example of a flexible bend-resistant circuit board in an embodiment of the present invention; the flexible bend-resistant circuit board includes: a first flexible substrate 10, a metal foil circuit 20, an elastic conductive printed circuit 30, and a second flexible substrate 40; wherein the elastic conductive printed circuit 30 is formed on both the metal foil circuit 20 and the first flexible substrate 10, and the line width of the elastic conductive printed circuit 30 is greater than that of the metal foil circuit 20. The elastic conductive printed circuit 30 is distributed obliquely on the metal foil circuit 20 in the line width direction of the metal foil circuit 30, and simultaneously forms a horizontal and vertical connection structure.

[0114] Example 8

[0115] like Figure 14 As shown, Figure 14This is a twelfth structural example of a flexible bend-resistant circuit board in an embodiment of the present invention; the flexible bend-resistant circuit board includes: a first flexible substrate 10, a metal foil circuit 20, and an elastic conductive printed circuit 30; wherein a hollow structure 70 is distributed on the metal foil circuit 20, and the elastic conductive printed circuit 30 is formed in the hollow structure of the metal foil circuit 20 and is horizontally connected to the metal foil circuit 20.

[0116] Example 9

[0117] like Figure 15 As shown, Figure 15 This is a thirteenth structural example of a flexible bend-resistant circuit board in an embodiment of the present invention; the flexible bend-resistant circuit board includes: a first flexible substrate 10, a metal foil circuit 20, an elastic conductive printed circuit 30, and a second flexible substrate 40; wherein, a hollow structure 80 is distributed on the metal foil circuit 20, and the elastic conductive printed circuit 20 is laid on the metal foil circuit 20 and the first flexible substrate 10 at the same time, and the elastic conductive printed circuit 30 covers the hollow structure, and forms a horizontal and vertical connection structure with the metal foil circuit 20 at the same time.

[0118] Example 10

[0119] like Figure 16 As shown, Figure 16 This is a fourteenth structural example of a flexible bend-resistant circuit board in an embodiment of the present invention; the flexible bend-resistant circuit board includes: a first flexible substrate 10, a metal foil circuit 20, a second flexible substrate 40 and an elastic conductive printed circuit 30; wherein, a window 90 is provided on the second flexible substrate 40 (and / or the first flexible substrate) to expose a portion of the metal foil circuit 20, and then an elastic conductive printed circuit 30 is formed on a side of the second flexible substrate 40 formed with the window 90 away from the metal foil circuit 20; wherein, the elastic conductive printed circuit 30 covers the window 90 and is vertically connected to the metal foil circuit 20.

[0120] Example 11

[0121] like Figure 17 As shown, Figure 17 This is a fifteenth structural example of a flexible, bend-resistant circuit board according to an embodiment of the present invention. The flexible, bend-resistant circuit board comprises: a first flexible substrate 10, a metal foil circuit 20, a second flexible substrate 40, and an elastic conductive printed circuit 30. A window is provided on the second flexible substrate 40 to expose a portion of the metal foil circuit 20 and the first flexible substrate 10. The elastic conductive printed circuit 30 is formed on a side of the second flexible substrate 40 away from the metal foil circuit 20. The elastic conductive printed circuit 30 covers the window 90 and is horizontally and vertically connected to the metal foil circuit 20.

[0122] Example 12

[0123] like Figure 18 As shown, Figure 18 This is a sixteenth structural example of a flexible bend-resistant circuit board in an embodiment of the present invention; the flexible bend-resistant circuit board includes: a first flexible substrate 10, a metal foil circuit 20, an elastic conductive printed circuit 30, and a second flexible substrate 40; wherein the metal foil circuit 20 is a multi-circuit structure distributed at intervals, and low-stress structures 80 are formed on the first flexible substrate 10 and / or the second flexible substrate 40 at intervals between the metal foil circuits 20.

[0124] It should be understood by those skilled in the art that the above embodiments can be arbitrarily combined with each other when the technical features do not conflict with each other.

[0125] With reference to the above embodiments, the present invention specifically discloses a flexible, bend-resistant circuit board, comprising: a first flexible substrate 10; a metal foil circuit 20 formed on the first flexible substrate 10, the metal foil circuit 10 having a hollow structure (such as a first low-stress structure 70); and an elastic conductive printed circuit 30 formed on the hollow structure 70 of the metal foil circuit 20 and connected to the metal foil circuit 20. The elastic conductive printed circuit 30 includes conductive particles and a resin film that binds the conductive particles, and the elastic conductive printed circuit has an off-state elongation of not less than 50%.

[0126] In the embodiments of the present invention, the elastic conductive printed circuit and the metal foil circuit are horizontally connected. Because the elastic conductive printed circuit is primarily formed on the first flexible substrate, this portion of the elastic conductive printed circuit is less susceptible to breakage caused by the metal foil circuit. It remains stably attached to the first flexible substrate and maintains a relatively stable connection with the metal foil circuit. The elastic conductive printed circuit formed on the metal foil circuit improves the contact surface with the metal foil circuit, minimizing contact resistance between the metal foil circuit and the elastic conductive printed circuit in the event of a break in the metal foil circuit, thereby ensuring the conductive performance of the flexible, flex-resistant circuit board. Furthermore, the elastic conductive printed circuit acts as a structural constraint on the metal foil circuit, ensuring that, in the event of a break in the metal foil circuit, the broken metal foil circuit remains connected as closely as possible.

[0127] In some embodiments, the metal foil circuit is formed from electrolytic metal foil or rolled metal foil.

[0128] In some embodiments, the metal foil circuit is a copper foil circuit, an aluminum foil circuit, a silver foil circuit, or a gold foil circuit.

[0129] In some embodiments, the elastic conductive printed circuit has an off-state elongation of not less than 150%.

[0130] In some embodiments, along the routing direction of the metal foil circuit, the elastic conductive printed circuit is continuously or discontinuously connected to the metal foil circuit.

[0131] In some embodiments, the running direction of the elastic conductive printed circuit is consistent with the running direction of the metal foil circuit connected thereto.

[0132] In some embodiments, a local area of the flexible bend-resistant circuit board is used as a bending area, the metal foil circuit in the bending area has a hollow structure, and the elastic conductive printed circuit is formed on the metal foil circuit in the bending area.

[0133] In some embodiments, the connection structure between the elastic conductive printed circuit and the metal foil circuit includes: the elastic conductive printed circuit and the metal foil circuit are connected horizontally; or, the elastic conductive printed circuit and the metal foil circuit are connected horizontally, and the elastic conductive printed circuit and the metal foil circuit are stacked vertically.

[0134] In some embodiments, the metal foil circuit is a multi-circuit structure with an alternate arrangement; wherein a low-stress structure is formed on the first flexible substrate between adjacent metal foil circuits.

[0135] In some embodiments, the flexible bend-resistant circuit board further includes: a second flexible substrate, cooperating with the first flexible substrate to enclose at least a portion of the metal foil circuit and / or the elastic conductive printed circuit.

[0136] With reference to the above embodiments, the present invention further discloses a flexible, bend-resistant circuit board, comprising: a first flexible substrate 10; a metal foil circuit 20 formed on the first flexible substrate 10; a window 90 provided on the first flexible substrate 10 to expose a portion of the metal foil circuit 20; and a flexible conductive printed circuit 30 formed on a side of the first flexible substrate 10 away from the metal foil circuit 20. At least a portion of the flexible conductive printed circuit 30 is connected to the metal foil circuit 20 through the window 90. The flexible conductive printed circuit 30 includes conductive particles and a resin film that binds the conductive particles. The flexible conductive printed circuit has a power-off elongation of no less than 50%.

[0137] In the embodiments of the present invention, the elastic conductive printed circuit and the metal foil circuit are horizontally connected. Because the elastic conductive printed circuit is primarily formed on the first flexible substrate, this portion of the elastic conductive printed circuit is less susceptible to breakage caused by the metal foil circuit. It remains stably attached to the first flexible substrate and maintains a relatively stable connection with the metal foil circuit. The elastic conductive printed circuit formed on the metal foil circuit improves the contact surface with the metal foil circuit, minimizing contact resistance between the metal foil circuit and the elastic conductive printed circuit in the event of a break in the metal foil circuit, thereby ensuring the conductive performance of the flexible, flex-resistant circuit board. Furthermore, the elastic conductive printed circuit acts as a structural constraint on the metal foil circuit, ensuring that, in the event of a break in the metal foil circuit, the broken metal foil circuit remains connected as closely as possible.

[0138] In some embodiments, the metal foil circuit is formed from electrolytic metal foil or rolled metal foil.

[0139] In some embodiments, the metal foil circuit is a copper foil circuit, an aluminum foil circuit, a silver foil circuit, or a gold foil circuit.

[0140] In some embodiments, the elastic conductive printed circuit has an off-state elongation of not less than 150%.

[0141] In some embodiments, along the routing direction of the metal foil circuit, the elastic conductive printed circuit is continuously or discontinuously connected to the metal foil circuit.

[0142] In some embodiments, the running direction of the elastic conductive printed circuit is consistent with the running direction of the metal foil circuit connected thereto.

[0143] In some embodiments, a local area of the flexible bend-resistant circuit board is used as a bending area, and the elastic conductive printed circuit is formed on the first flexible substrate and / or metal foil circuit in the bending area and connected to the metal foil circuit in the bending area.

[0144] In some embodiments, the connection structure between the elastic conductive printed circuit and the metal foil circuit includes: the elastic conductive printed circuit and the metal foil circuit are horizontally connected; and / or the elastic conductive printed circuit and the metal foil circuit are vertically stacked.

[0145] In some embodiments, the metal foil circuit is a multi-circuit structure with an alternate arrangement; wherein a low-stress structure is formed on the first flexible substrate between adjacent metal foil circuits.

[0146] In some embodiments, the flexible bend-resistant circuit board further includes: a second flexible substrate, cooperating with the first flexible substrate to enclose at least a portion of the metal foil circuit and / or the elastic conductive printed circuit.

[0147] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A flexible bending-resistant circuit board, characterized in that: include: a first flexible substrate; a metal foil circuit formed on the first flexible substrate, wherein the metal foil circuit has a hollow structure; An elastic conductive printed circuit is formed on the hollow structure of the metal foil circuit and connected to the metal foil circuit; wherein the elastic conductive printed circuit includes: conductive particles and a resin film that binds the conductive particles, and the power-off elongation of the elastic conductive printed circuit is not less than 50%.

2. The flexible bending-resistant circuit board according to claim 1, characterized in that: The metal foil circuit is formed of electrolytic metal foil or rolled metal foil.

3. The flexible bending-resistant circuit board according to claim 1, characterized in that: The metal foil circuit is a copper foil circuit, an aluminum foil circuit, a silver foil circuit or a gold foil circuit.

4. The flexible bending-resistant circuit board according to claim 1, characterized in that: The power-off elongation of the elastic conductive printed circuit is not less than 150%.

5. The flexible bending-resistant circuit board according to claim 1, characterized in that: Along the routing direction of the metal foil circuit, the elastic conductive printed circuit is continuously or discontinuously connected to the metal foil circuit.

6. The flexible bending-resistant circuit board according to claim 1, characterized in that: The running direction of the elastic conductive printed circuit is consistent with the running direction of the metal foil circuit connected thereto.

7. The flexible bending-resistant circuit board according to claim 1, characterized in that: A local area of the flexible bending-resistant circuit board is used as a bending area, the metal foil circuit located in the bending area has the hollow structure, and the elastic conductive printed circuit is formed on the metal foil circuit in the bending area.

8. The flexible bending-resistant circuit board according to claim 1, characterized in that: The connection structure between the elastic conductive printed circuit and the metal foil circuit includes: The elastic conductive printed circuit and the metal foil circuit are connected in a horizontal direction; or, the elastic conductive printed circuit and the metal foil circuit are connected in a horizontal direction, and the elastic conductive printed circuit and the metal foil circuit are stacked in a vertical direction.

9. The flexible bending-resistant circuit board according to claim 1, characterized in that: The metal foil circuit is a multi-circuit structure with an interval arrangement; wherein a low stress structure is formed on the first flexible substrate between adjacent metal foil circuits.

10. The flexible bending-resistant circuit board according to claim 1, characterized in that: Also includes: The second flexible substrate cooperates with the first flexible substrate to enclose at least a portion of the metal foil circuit and / or the elastic conductive printed circuit.

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