Flexible circuit board structure

Abstract

The invention discloses a flexible circuit board structure, and the structure comprises a circuit board body which comprises a first surface and a second surface which are opposite to each other; the first covering layer is positioned on the first surface of the circuit board body; the second covering layer is positioned on the second surface of the circuit board body; wherein in the direction from the first surface to the second surface, the circuit board body comprises at least two conductive layers arranged at intervals and a stress shear layer located between the two adjacent conductive layers; stress neutral layers generated when the flexible circuit board structure is bent are on the conductive layers, and each conductive layer corresponds to one stress neutral layer; the stress shear layer is used for blocking stress between two adjacent conductive layers. According to the technical scheme provided by the embodiment of the invention, the problem that the internal circuit is broken when the flexible circuit board is bent for a long time is solved.

Description

Technical Field

[0001] The embodiments of the present invention relate to the technical field of circuit boards, and in particular to a flexible circuit board structure. Background Art

[0002] Flexible Printed Circuit Board (FPCB) is a printed circuit board that can be bent, folded and stretched, made of a flexible insulating substrate through precision manufacturing. Flexible circuit boards are widely used in industries such as mobile phones, cameras, laptops, smart wearable devices and other electronic products.

[0003] For flexible circuit boards composed of different numbers of polymer layers and copper layers, in addition to the characteristics of the material itself affecting the bending resistance, the interaction between the layers will also affect the internal stress of the material. When the existing flexible circuit boards are in a bent state for a long time, the copper wires inside the flexible circuit boards will bear greater stress and there will be a risk of breakage, affecting the normal use of electronic products. Summary of the invention

[0004] The embodiment of the present invention provides a flexible circuit board structure to improve the problem of internal circuit breakage of the flexible circuit board when it is bent for a long time.

[0005] An embodiment of the present invention provides a flexible circuit board structure, including:

[0006] The circuit board body comprises a first surface and a second surface which are arranged opposite to each other;

[0007] A first covering layer, located on a first surface of the circuit board body;

[0008] A second covering layer, located on the second surface of the circuit board body;

[0009] Among them, in the direction pointing from the first surface to the second surface, the circuit board body includes at least two conductive layers arranged at intervals and a stress shear layer located between two adjacent conductive layers; the stress neutral layer generated by the flexible circuit board structure when bending is on the conductive layer, and each conductive layer corresponds to a stress neutral layer; the stress shear layer is used to block the stress between two adjacent conductive layers.

[0010] Optionally, substrate layers are provided on the surfaces of the two opposite sides of each of the conductive layers, which are respectively a first substrate layer and a second substrate layer; the first substrate layer is located on the surface of the conductive layer facing the first side, and the second substrate layer is located on the surface of the conductive layer facing the second side; each of the conductive layers and the substrate layers located on the surfaces of the two opposite sides of the conductive layer constitute a film layer system;

[0011] When the flexible circuit board structure is bent, one of the first substrate layer and the second substrate layer is used as a tensile stress layer, and the other is used as a compressive stress layer; the stress shear layer is located between two adjacent film layer systems and / or within the film layer system.

[0012] Optionally, the radius of curvature of the stress neutral layer generated when each of the film layer systems is bent is determined based on the radius of curvature of the side of the compressive stress layer in the film layer system away from the tensile stress layer, the thickness of the film layer system, and the neutral layer position coefficient; wherein the neutral layer position coefficient is in the range of 0.2 to 0.5;

[0013] The thickness of each conductive layer in the film layer system is determined based on the curvature radius of the stress-neutral layer.

[0014] Optionally, the material of the stress shear layer includes at least one of silicone rubber, epoxy glue, polyurethane glue, stress relief glue and strong recycled glue;

[0015] and / or, in each of the film layer systems, the thickness of the first substrate layer is equal to the thickness of the second substrate layer;

[0016] And / or, the sum of the thickness of the first substrate layer and the second substrate layer is less than the thickness of the conductive layer.

[0017] Optionally, the first substrate layer located on the surface of the conductive layer closest to the first surface reuses the first covering layer, and the second substrate layer located on the surface of the conductive layer closest to the second surface reuses the second covering layer;

[0018] And / or, the Young's modulus of the first covering layer is less than or equal to 10 GPa, and the Young's modulus of the second covering layer is less than or equal to 10 GPa.

[0019] Optionally, the first substrate layer includes a thermally conductive silicone layer, and the second substrate layer includes a thermally conductive silicone layer; the stress shear layer is located between two adjacent film layer systems;

[0020] Alternatively, in the film layer system, the first substrate layer includes the stress shear layer, and the second substrate layer includes the stress shear layer; and the stress shear layer is located in the film layer system.

[0021] Optionally, in the film layer system, one of the first substrate layer and the second substrate layer includes a thermally conductive silicone layer and a stress shear layer located between the thermally conductive silicone layer and the conductive layer, and the other includes a thermally conductive silicone layer and an OCA adhesive layer located between the thermally conductive silicone layer and the conductive layer; wherein at least one substrate layer located between two adjacent conductive layers includes the stress shear layer;

[0022] The stress shear layer is located in at least one of the adjacent film layer systems, or the stress shear layer is located in at least one of the adjacent film layer systems and between adjacent film layer systems.

[0023] Optionally, the substrate layer between two adjacent conductive layers shares the thermally conductive silicone layer, and the stress shear layer is located between the shared thermally conductive silicone layer and the conductive layer.

[0024] Optionally, in the direction from the first surface to the second surface, the circuit board body includes a first conductive layer, a first stress shear layer, a base thermal conductive silicone layer, a second stress shear layer, and a second conductive layer stacked in sequence; the first covering layer includes a first covering thermal conductive silicone layer and a first OCA adhesive layer located between the first covering thermal conductive silicone layer and the first conductive layer, and the second covering layer includes a second covering thermal conductive silicone layer and a second OCA adhesive layer located between the second covering thermal conductive silicone layer and the second conductive layer;

[0025] Wherein, the first substrate layer of the first conductive layer reuses the first covering layer, and the second substrate layer of the first conductive layer includes the first stress shear layer and the substrate thermal conductive silicone layer;

[0026] The first substrate layer of the second conductive layer includes the substrate thermal conductive silicone layer and the first stress shearing layer; the second substrate layer of the second conductive layer reuses the second covering layer.

[0027] Optionally, in the circuit board body, the thickness range of the first conductive layer and the thickness range of the second conductive layer are both 30um to 35um; the thickness range of the first stress shear layer and the second stress shear layer are both 10um to 15um; the thickness range of the substrate thermal conductive silicone layer is 20 to 25um;

[0028] In the first covering layer, the thickness of the first thermal conductive silicone layer is in the range of 10um to 15um; the thickness of the first OCA adhesive layer is in the range of 20um to 25um;

[0029] In the second covering layer, the thickness of the second thermal conductive silicone layer is in the range of 10um to 15um; the thickness of the second OCA layer is in the range of 20um to 25um.

[0030] The technical solution provided by the embodiment of the present invention can reduce the risk of conductive layers being fractured due to stress by setting multiple stress-neutral layers in the flexible circuit board structure and placing each conductive layer in a corresponding stress-neutral layer, and set a stress shear layer between adjacent conductive layers. The stress shear layer has the ability of high shear strain, that is, the stress shear layer can produce a large deformation when subjected to shear force, so that the film layers located on the two layers opposite to the stress shear layer can slide in a relatively independent space, blocking the transfer of stress between the film layers, further improving the problem of internal circuit fracture when the flexible circuit board is bent for a long time, and improving the durability and stability of the flexible circuit board.

[0031] It should be understood that the contents described in this section are not intended to identify the key or important features of the embodiments of the present invention, nor are they intended to limit the scope of the present invention. Other features of the present invention will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0033] Figure 1 is a simplified structural schematic diagram of a flexible circuit board structure provided by an embodiment of the present invention;

[0034] Figure 2 It is a schematic structural diagram of a tensile stress layer, a stress center layer and a compressive stress layer during a bending process provided by an embodiment of the present invention;

[0035] Figure 3 It is a force analysis diagram of a tensile stress layer, a stress center layer and a compressive stress layer provided by an embodiment of the present invention;

[0036] Figure 4 is a structural schematic diagram of another flexible circuit board structure provided by an embodiment of the present invention;

[0037] Figure 5 is a structural schematic diagram of another flexible circuit board structure provided by an embodiment of the present invention;

[0038] Figure 6 is a comparison diagram of a shear strain layer provided by an embodiment of the present invention before and after deformation by shear force;

[0039] Figure 7 is a structural schematic diagram of another flexible circuit board structure provided by an embodiment of the present invention;

[0040] Figure 8is a structural schematic diagram of another flexible circuit board structure provided by an embodiment of the present invention;

[0041] Fig. 9 is a structural schematic diagram of another flexible circuit board structure provided by an embodiment of the present invention;

[0042] Fig.10 is a structural schematic diagram of another flexible circuit board structure provided by an embodiment of the present invention;

[0043] Fig.11 It is a structural schematic diagram of another flexible circuit board structure provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0044] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only embodiments of a part of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of the substrate of the present invention.

[0045] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0046] An embodiment of the present invention provides a flexible circuit board structure. Figure 1 is a simplified schematic diagram of a flexible circuit board structure provided by an embodiment of the present invention, with reference to Figure 1 , the flexible circuit board structure includes:

[0047] The circuit board body 3 comprises a first surface and a second surface which are arranged opposite to each other;

[0048] A first covering layer 1, located on a first surface of a circuit board body 3;

[0049] A second covering layer 2, located on a second surface of the circuit board body 3;

[0050] Among them, in the direction from the first surface to the second surface, the circuit board body 3 includes at least two conductive layers arranged at intervals and a stress shear layer located between two adjacent conductive layers; the stress neutral layer generated by the flexible circuit board structure when bending is on the conductive layer, and each conductive layer corresponds to a stress neutral layer; the stress shear layer is used to block the stress between two adjacent conductive layers.

[0051] Specifically, the first covering layer 1 and the second covering layer 2 are used to prevent the internal circuit board body 3 from being worn by the outside, and play an electrical insulation role for the circuit of the circuit board body 3. In addition, the circuit board body 3 is arranged between the first covering layer 1 and the second covering layer 2. When the flexible circuit board structure is bent, the first covering layer 1 and the second covering layer 2 can be used as a tensile stress layer and a compressive stress layer, so that a strain neutral layer can be generated in the circuit board body 3. Then, by adjusting the matching between the film layers in the circuit board body 3 and the position of the conductive layer, the flexible circuit board structure can generate multiple layers of stress neutral layers when bent, and each stress neutral layer corresponds to a conductive layer.

[0052] Among them, tensile stress refers to the stress generated inside an object to resist stretching when it is subjected to external force. Specifically, when an object is subjected to tension at both ends, the stress along its axial direction is tensile stress. Tensile stress will increase the size of the object. Compressive stress refers to the stress generated inside an object to resist compression when it is subjected to external force. When an object is subjected to pressure, the stress is positive in the compression direction and negative in the tension direction. The stress neutral layer is a film layer that appears during the bending process of the material. When the material is bent, the outer layer is stretched and the inner layer is squeezed. There must be a transition layer inside it that is neither stretched nor compressed, and the stress is almost zero. This transition layer is called the stress neutral layer of the material. The position of the stress neutral layer is not fixed, it will change with the changes in the properties of the material and the degree of bending. Figure 2 is a schematic structural diagram of a tensile stress layer, a stress neutral layer and a compressive stress layer during a bending process provided by an embodiment of the present invention, Figure 3 is a force analysis diagram of a tensile stress layer, a stress neutral layer and a compressive stress layer provided by an embodiment of the present invention; Figure 2 and Figure 3 When a bending piece is bent, the tensile stress layer 01 is located on the outside of the bending piece, the compressive stress layer 02 is located on the inside of the bending piece, and the stress neutral layer 03 is generated between the tensile stress layer 01 and the compressive stress layer 02.

[0053] The technical solution provided by the embodiment of the present invention can reduce the risk of conductive layers being fractured due to stress by setting multiple stress-neutral layers in the flexible circuit board structure and placing each conductive layer in a corresponding stress-neutral layer, and a stress shear layer is set between adjacent conductive layers. The stress shear layer has the ability of high shear strain, that is, the stress shear layer can produce a large deformation when subjected to shear force, so that the film layers located on the two layers opposite to the stress shear layer can slide in a relatively independent space, blocking the transfer of stress between the film layers and preventing interference with the stress-neutral layer. The problem of internal circuit fracture during long-term bending of the flexible circuit board can be further improved, thereby improving the durability and stability of the flexible circuit board.

[0054] The above is the core inventive concept of the present invention. The film layer structure in the circuit board body is described in detail below.

[0055] Based on the above embodiments, Figure 4 is a schematic structural diagram of another flexible circuit board structure provided by an embodiment of the present invention, Figure 5 is a schematic diagram of another flexible circuit board structure provided by an embodiment of the present invention, referring to Figure 4 and Figure 5 Optionally, substrate layers are disposed on the surfaces of opposite sides of each conductive layer 30, which are respectively a first substrate layer 10 and a second substrate layer 20; the first substrate layer 10 is located on the surface of the conductive layer 30 facing the first surface, and the second substrate layer 20 is located on the surface of the conductive layer 30 facing the second surface; each conductive layer 30 and the substrate layers located on the surfaces of opposite sides of the conductive layer 30 constitute a film layer system 100;

[0056] When the flexible circuit board structure is bent, one of the first substrate layer 10 and the second substrate layer 20 is used as a tensile stress layer 01, and the other is used as a compressive stress layer 02; the stress shear layer 40 is located between two adjacent film layer systems 100 and / or within the film layer system 100.

[0057] Specifically, when the flexible circuit board structure is bent in such a way that the first covering layer 1 is located at the outermost side of the entire bending piece (flexible circuit board structure), and the second covering layer 2 is located at the innermost side of the entire bending piece; then for each film layer system 100, the first substrate layer 10 in the film layer system 100 is located at the outermost side, used as the tensile stress layer 01, the second substrate layer 20 is located at the innermost side, used as the compressive stress layer 02, and the stress neutral layer 03 generated in each film layer system 100 is located in the conductive layer 30. When the flexible circuit board structure is bent in such a way that the first covering layer 1 is located at the innermost side of the bending piece, and the second covering layer 2 is located at the outermost side of the bending piece; then for each film layer system 100, the first substrate layer 10 in the film layer system 100 is located at the innermost side, used as the compressive stress layer 02, the second substrate layer 20 is located at the outermost side, used as the tensile stress layer 01, and the stress neutral layer 03 generated in each film layer system 100 is located in the conductive layer 30. Arranging multiple film layer systems 100 in the circuit board body can generate multiple stress neutral layers accordingly. Among them, Figure 4 and Figure 5 It is exemplarily shown that three film layer systems 100 are arranged in the circuit board body.

[0058] Figure 6 is a comparison diagram of a shear strain layer before and after being deformed by shear force provided by an embodiment of the present invention, with reference to Figure 6 A stress shear layer 40 is arranged between adjacent conductive layers 30. The stress shear layer 40 has the ability of high shear strain, that is, the stress shear layer 40 can produce a large deformation when subjected to shear force, so that the film layers located on the two layers opposite to the stress shear layer 40 can slide in a relatively independent space, blocking the transmission of stress between the film layers and preventing the influence on the stress neutral layer 03. This can improve the problem of internal circuit breakage when the flexible circuit board is bent for a long time, thereby improving the durability and stability of the flexible circuit board.

[0059] The stress shear layer 40 between two adjacent conductive layers 30 may have one or more layers. When the number of the stress shear layer 40 between two adjacent conductive layers 30 is one, the stress shear layer 40 may be located between the film layer systems 100 to which the two conductive layers 30 belong (see Figure 4 ); or, when the number of the stress shear layer 40 between two adjacent conductive layers 30 is one, the stress shear layer 40 can be located in one of the film layer systems 100 to which the two conductive layers 30 belong respectively, and reused as a substrate layer (refer to Figure 5 ).

[0060] When the number of stress shear layers 40 between two adjacent conductive layers 30 is two, one of the stress shear layers 40 can be located between the film systems 100 to which the two conductive layers 30 respectively belong, and the other stress shear layer 40 can be located in one of the film systems 100 to which the two conductive layers 30 respectively belong. The number of stress shear layers 40 between two adjacent conductive layers 30 can also be three, which are located between two adjacent film systems 100 and in two film systems 100, respectively. The number and position of the stress shear layers 40 between two adjacent conductive layers 30 can be set according to actual needs. The material of the stress shear layer 40 can include at least one of silicone rubber, epoxy glue, polyurethane glue, stress evacuation glue and strong recycled glue. The materials of the stress shear layers 40 at different positions can be the same or different.

[0061] Based on the above embodiments, optionally, refer to Figure 4 and Figure 5 , and combined with Figure 2 The curvature radius of the stress neutral layer 03 generated when each film layer system 100 is bent is determined based on the curvature radius of the side of the compressive stress layer 02 in the film layer system 100 away from the tensile stress layer 01, the thickness of the film layer system 100 and the position coefficient of the neutral layer 03; the thickness of the conductive layer 30 in each film layer system 100 is determined based on the curvature radius of the stress neutral layer 03; wherein, the position coefficient of the neutral layer 03 ranges from 0.2 to 0.5.

[0062] Specifically, the curvature radius of the stress-neutral layer 03 generated when each film layer system 100 is bent can be determined based on the following calculation formula:

[0063] p = r + kt;

[0064] Among them, p is the curvature radius of the stress neutral layer 03 generated when the film system 100 is bent; r is the curvature radius of the side of the compressive stress layer 02 away from the tensile stress layer 01 (the inner side of the film system 100) when the film system 100 is bent; k is the neutral layer position coefficient; t is the thickness of the film system 100.

[0065] The magnitude of the neutral layer position coefficient k is related to factors such as the thickness t of the film system 100, the curvature radius r and the bending angle when the film system 100 is bent; when the curvature radius r is large and the bending angle is small, the deformation degree of the film system 100 is small, and the position of the stress neutral layer 03 is close to the center of the thickness of the film system 100, and k can be approximately 0.5 at this time; when the bending radius r becomes smaller and the bending angle increases, the deformation degree of the film system 100 increases accordingly, and the position of the stress neutral layer 03 gradually moves toward the inside of the bending center, and k gradually decreases. In the embodiment of the present invention, the range of the neutral layer position coefficient k is set to 0.2~0.5 to prevent k from being too small and causing the position of the stress neutral layer 03 to deviate from the conductive layer 30.

[0066] Furthermore, in each film system 100 , the thickness of the first substrate layer 10 can be set equal to the thickness of the second substrate layer 20 , so that when the film system 100 begins to bend, the stress-neutral layer 03 moves from the center of the thickness of the conductive layer 30 .

[0067] Furthermore, in each film layer system 100, the sum of the thickness of the first substrate layer 10 and the second substrate layer 20 is less than the thickness of the conductive layer 30. The sum of the thickness of the first substrate layer 10 and the second substrate layer 20 in the same film layer system 100 is set to be less than the thickness of the conductive layer 30, so that the thickness of the conductive layer 30 accounts for more than 50% of the thickness of the film layer system 100, thereby preventing the position of the stress-neutral layer 03 from deviating from the conductive layer 30 when the film layer system 100 is bent too much.

[0068] Based on the above embodiments, Figure 7 is a schematic diagram of another flexible circuit board structure provided by an embodiment of the present invention, referring to Figure 7 Optionally, the first substrate layer 10 located on the surface of the conductive layer 30 closest to the first surface reuses the first covering layer 1, and the second substrate layer 20 located on the surface of the conductive layer 30 closest to the second surface reuses the second covering layer 2. The number of film layers in the flexible circuit board structure can be reduced, thereby reducing the thickness of the flexible circuit board structure.

[0069] On the basis of the above embodiments, optionally, the Young's modulus of the first covering layer 1 is less than or equal to 10Gpa, and the Young's modulus of the second covering layer 2 is less than or equal to 10Gpa, so as to prevent the Young's modulus of the first covering layer 1 and the Young's modulus of the second covering layer 2 from being too large, which may cause the first covering layer 1 and the second covering layer 2 to be too hard and unfavorable for the bending of the flexible circuit board structure. Among them, the thickness of the first covering layer 1 may be equal to the thickness of the second covering layer 2, so that when the flexible circuit board structure begins to bend, the stress neutral layer starts to move from the center position of the thickness of the circuit board body 3; and the thickness of the circuit board body 3 may be set to be greater than the thickness of the covering layer, so that the thickness of the circuit board body 3 accounts for more than 50% of the thickness of the flexible circuit board structure, so as to prevent the position of the stress neutral layer from deviating from the circuit board body 3 when the bending degree of the flexible circuit board structure is too large. Optionally, the thickness ratio of the first covering layer 1, the thickness of the circuit board body 3 and the thickness of the second covering layer 2 can be 1:2.5:1, 1:3:1, 1:4:1, 1:5:1, 1:6:1, 1:8:1, 1:10:1. Exemplarily, the thickness ratio of the first covering layer 1, the thickness of the circuit board body 3 and the thickness of the second covering layer 2 can be 17.5:61:17.5.

[0070] Based on the above embodiments, optionally, refer to Figure 4 and 7 The first substrate layer 10 includes a thermally conductive silicone layer 11 , and the second substrate layer 20 includes a thermally conductive silicone layer 11 ; the stress shear layer 40 is located between two adjacent film layer systems 100 .

[0071] Specifically, thermally conductive silicone is a thermally conductive compound with resistance to hot and cold alternation, aging resistance, electrical insulation, and certain adhesion. The materials of the first substrate layer 10 and the second substrate layer 20 are set to thermally conductive silicone, and the first substrate layer 10 and the second substrate layer 20 can achieve heat dissipation, electrical isolation and protection of the conductive layer 30, and can also ensure the firmness between the film layers. The stress shear layer 40 is set between two adjacent film layer systems 100. The stress shear layer 40 can produce a large deformation when subjected to shear force, so that the film layer systems 100 located on the opposite sides of the stress shear layer 40 can slide in a relatively independent space, blocking the transmission of stress between the film layer systems 100, so that each film layer system 100 can be relatively independent, preventing each film layer system 100 from interfering with the generation of the stress neutral layer 03 in the film layer system 100 adjacent to it when the flexible circuit board structure is bent, and also preventing the stress of the adjacent film layer system 100 from interfering with the generation of the stress neutral layer 03 inside it. This improves the problem of internal circuit breakage when the flexible circuit board is bent for a long time, and improves the durability and stability of the flexible circuit board.

[0072] In other embodiments of the present invention, optionally, Figure 8 is a schematic diagram of another flexible circuit board structure provided by an embodiment of the present invention, referring to Figure 8 The first substrate layer 10 and the second substrate layer 20 on the two opposite sides of each conductive layer 30 are both set as stress shear layers 40, and the same stress shear layer 40 is shared between two adjacent conductive layers 30, which can further block the transfer of stress between the film layer systems 100 and reduce the thickness of the flexible circuit board structure.

[0073] Based on the above embodiments, optionally, Fig. 9 is a schematic structural diagram of another flexible circuit board structure provided by an embodiment of the present invention, Fig.10 is a schematic structural diagram of another flexible circuit board structure provided by an embodiment of the present invention, Fig.11 is a schematic diagram of another flexible circuit board structure provided by an embodiment of the present invention, referring to Figures 9 to 11 In each film layer system 100, one of the first substrate layer 10 and the second substrate layer 20 includes a thermally conductive silicone layer 11 and a stress shear layer 40 located between the thermally conductive silicone layer 11 and the conductive layer 30, and the other includes a thermally conductive silicone layer 11 and an OCA adhesive layer 12 located between the thermally conductive silicone layer 11 and the conductive layer 30; wherein at least one substrate layer located between two adjacent conductive layers 30 includes a stress shear layer 40.

[0074] refer to Fig.10 and Fig.11 , the stress shear layer 40 is located in at least one of the adjacent film layer systems 100, or, referring to Fig. 9 The stress shear layer 40 is located in at least one of the adjacent film layer systems 100 and between the adjacent film layer systems 100 .

[0075] Specifically, the first substrate layer 10 and the second substrate layer 20 are both double-layer film structures, and a thermally conductive silicone layer 11 is provided in each of the first substrate layer 10 and the second substrate layer 20, so that the first substrate layer 10 and the second substrate layer 20 can have a heat dissipation effect on the conductive layer 30; a stress shear layer 40 is provided in one of the first substrate layer 10 and the second substrate layer 20 between the thermally conductive silicone layer 11 and the conductive layer 30, which can block the stress between the thermally conductive silicone layer 11 and the conductive layer 30. At this time, the thickness of the thermally conductive silicone layer 11 close to the conductive layer 30 can be used as a tensile stress layer 01 or a compressive stress layer 02; an OCA adhesive layer 12 with good adhesion is provided in one of the first substrate layer 10 and the second substrate layer 20 between the thermally conductive silicone layer 11 and the conductive layer 30, which can reduce the risk of cracking of the flexible circuit board structure; the thickness of the OCA adhesive layer 12 is set to at least 20μm, which can prevent the OCA adhesive layer 12 from being too thin and having poor adhesion, and can also ensure the sliding ability between the film layers when bending, thereby realizing the role of the stress shear layer.

[0076] Based on the above embodiments, optionally, refer to Fig.10 and Fig.11 The substrate layer between two adjacent conductive layers 30 shares the thermal conductive silicone layer 11, and the stress shear layer 40 is located between the shared thermal conductive silicone layer 11 and the conductive layer 30, which can further reduce the thickness of the flexible circuit board structure.

[0077] by Fig.10 Taking the structure shown as an example, the structure of the flexible circuit board is described: in the direction from the first surface to the second surface, the circuit board body 3 includes a first conductive layer 30a, a first stress shear layer 40a, a substrate thermal conductive silicone layer 11b, a second stress shear layer 40b and a second conductive layer 30b which are stacked in sequence; the first covering layer 1 includes a first covering thermal conductive silicone layer 11a and a first OCA adhesive layer 12a located between the first covering thermal conductive silicone layer 11 and the first conductive layer 30a, and the second covering layer 2 includes a second covering thermal conductive silicone layer 11c and a second OCA adhesive layer 12b located between the second covering thermal conductive silicone layer 11c and the second conductive layer 30b; wherein, the first substrate layer 10 of the first conductive layer 30a reuses the first covering layer 1, and the second substrate layer 20 of the first conductive layer 30a includes the first stress shear layer 40a and the substrate thermal conductive silicone layer 11b; the first substrate layer 10 of the second conductive layer 30b includes the substrate thermal conductive silicone layer 11b and the first stress shear layer 40b; and the second substrate layer 20 of the second conductive layer 30b reuses the second covering layer 2.

[0078] In the circuit board body 3, the thickness range of the first conductive layer 30a and the thickness range of the second conductive layer 30b are both 30um~35um; the thickness range of the first stress shear layer 40a and the second stress shear layer 40b are both 10um~15um; the thickness range of the substrate thermal conductive silicone layer 11b is 20~25um; in the first covering layer 1, the thickness range of the first covering thermal conductive silicone layer 11a is 10um~15um; the thickness range of the first OCA adhesive layer 12a is 20um~25um; in the second covering layer 2, the thickness range of the second covering thermal conductive silicone layer 11c is 10um~15um; the thickness range of the second OCA adhesive layer 12b is 20um~25um.

[0079] The first substrate layer 10 and the second substrate layer 20 on the two opposite sides of the first conductive layer 30a and the second conductive layer 30b have the same thickness; the substrate layer between two adjacent conductive layers 30 shares the thermal conductive silicone layer 11b.

[0080] The thickness range of each film layer can be set to meet the requirements that the thickness range of the first cover film and the second cover film are the same, and the thickness of the circuit board body accounts for more than 50% of the thickness of the flexible circuit board structure. And the thickness range of each conductive layer relative to the substrate layer on both sides is equal, and the thickness of each conductive layer accounts for more than 50% of the thickness of its own film layer system. In addition, the thickness range of each film layer can also prevent the thickness of the flexible circuit board structure from being too large when the thickness of each film layer is too large, which is not conducive to bending; and prevent the thickness of each film layer (mainly referring to the stress shear layer and the OCA adhesive layer here) from being too small, which leads to weak relative sliding ability between film layers and is not conducive to bending.

[0081] Note that the above are only preferred embodiments of the present invention and the technical principles used. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and that various obvious changes, readjustments and substitutions can be made by those skilled in the art without departing from the scope of the substrate of the present invention. Therefore, although the present invention is described in more detail through the above embodiments, the present invention is not limited to the above embodiments, and may include more other equivalent embodiments without departing from the concept of the present invention, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. A flexible circuit board structure, characterized in that: include: The circuit board body comprises a first surface and a second surface which are arranged opposite to each other; A first covering layer, located on a first surface of the circuit board body; A second covering layer, located on the second surface of the circuit board body; Wherein, in the direction from the first surface to the second surface, the circuit board body includes at least two conductive layers spaced apart and a stress shearing layer between two adjacent conductive layers; the stress shearing layer is used to block the stress between two adjacent conductive layers.

2. The flexible circuit board structure according to claim 1, characterized in that: The surfaces of the two opposite sides of each conductive layer are provided with substrate layers, which are respectively a first substrate layer and a second substrate layer; the first substrate layer is located on the surface of the conductive layer facing the first side, and the second substrate layer is located on the surface of the conductive layer facing the second side; each conductive layer and the substrate layers located on the two opposite sides of the conductive layer constitute a film layer system; When the flexible circuit board structure is bent, one of the first substrate layer and the second substrate layer is used as a tensile stress layer, and the other is used as a compressive stress layer; the stress shear layer is located between two adjacent film layer systems and / or within the film layer system.

3. The flexible circuit board structure according to claim 2, characterized in that: The stress neutral layer generated when the flexible circuit board structure is bent is on the conductive layer, and each conductive layer corresponds to a stress neutral layer; the curvature radius of the stress neutral layer generated when each film layer system is bent is determined based on the curvature radius of the side of the compressive stress layer in the film layer system away from the tensile stress layer, the thickness of the film layer system, and the neutral layer position coefficient; wherein the neutral layer position coefficient is in the range of 0.2 to 0.5; The thickness of each conductive layer in the film layer system is determined based on the curvature radius of the stress-neutral layer.

4. The flexible circuit board structure according to claim 2, characterized in that: The material of the stress shear layer includes at least one of silicone rubber, epoxy glue, polyurethane glue, stress evacuation glue and strong regenerated glue; and / or, in each of the film layer systems, the thickness of the first substrate layer is equal to the thickness of the second substrate layer, And / or, in each of the film layer systems, the sum of the thickness of the first substrate layer and the second substrate layer is less than the thickness of the conductive layer.

5. The flexible circuit board structure according to claim 2, characterized in that: The first substrate layer located on the surface of the conductive layer closest to the first surface reuses the first covering layer, and the second substrate layer located on the surface of the conductive layer closest to the second surface reuses the second covering layer; And / or, the Young's modulus of the first covering layer is less than or equal to 10 GPa, and the Young's modulus of the second covering layer is less than or equal to 10 GPa.

6. The flexible circuit board structure according to claim 2, characterized in that: In the film layer system, the first substrate layer includes a thermally conductive silicone layer, and the second substrate layer includes a thermally conductive silicone layer; the stress shear layer is located between two adjacent film layer systems; Alternatively, in the film layer system, the first substrate layer includes the stress shear layer, and the second substrate layer includes the stress shear layer; The stress shear layer is located in the film layer system.

7. The flexible circuit board structure according to claim 2, characterized in that: In the film layer system, one of the first substrate layer and the second substrate layer includes a thermally conductive silicone layer and a stress shear layer located between the thermally conductive silicone layer and the conductive layer, and the other includes a thermally conductive silicone layer and an OCA adhesive layer located between the thermally conductive silicone layer and the conductive layer; wherein at least one substrate layer located between two adjacent conductive layers includes the stress shear layer; The stress shear layer is located in at least one of the adjacent film layer systems, or the stress shear layer is located in at least one of the adjacent film layer systems and between adjacent film layer systems.

8. The flexible circuit board structure according to claim 7, characterized in that: The substrate layer between two adjacent conductive layers shares the thermally conductive silicone layer, and the stress shear layer is located between the shared thermally conductive silicone layer and the conductive layer.

9. The flexible circuit board structure according to claim 8, characterized in that: In the direction from the first surface to the second surface, the circuit board body includes a first conductive layer, a first stress shear layer, a base thermal conductive silicone layer, a second stress shear layer, and a second conductive layer stacked in sequence; the first covering layer includes a first covering thermal conductive silicone layer and a first OCA adhesive layer located between the first covering thermal conductive silicone layer and the first conductive layer, and the second covering layer includes a second covering thermal conductive silicone layer and a second OCA adhesive layer located between the second covering thermal conductive silicone layer and the second conductive layer; Wherein, the first substrate layer of the first conductive layer reuses the first covering layer, and the second substrate layer of the first conductive layer includes the first stress shear layer and the substrate thermal conductive silicone layer; The first substrate layer of the second conductive layer includes the substrate thermal conductive silicone layer and the first stress shearing layer; the second substrate layer of the second conductive layer reuses the second covering layer.

10. The flexible circuit board structure according to claim 9, characterized in that: In the circuit board body, the thickness range of the first conductive layer and the thickness range of the second conductive layer are both 30um to 35um; the thickness range of the first stress shear layer and the second stress shear layer are both 10um to 15um; the thickness range of the substrate thermal conductive silicone layer is 20 to 25um; In the first covering layer, the thickness of the first covering thermal conductive silicone layer ranges from 10um to 15um; The thickness of the first OCA adhesive layer ranges from 20um to 25um; In the second covering layer, the thickness of the second covering thermal conductive silicone layer ranges from 10um to 15um; The thickness of the second OCA adhesive layer is in the range of 20um to 25um.

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