Flexible circuit board radio frequency transmission line applied to folding screen terminal

Abstract

The utility model discloses a flexible circuit board radio frequency transmission line applied to a folding screen terminal, which is provided with a non-bending area and a dynamic bending area, the transmission line is composed of two layers of base material bodies and lines arranged on the base materials, the first base material body and the second base material body are hollowed out in the dynamic bending area, and the flexible circuit board radio frequency transmission line is formed. The hollow area is well conducted with the conductive silver coatings of the first protection layer and the second protection layer respectively, and a reference ground and a shielding layer are provided for the signal line of the dynamic bending area, so that the radio frequency transmission loss is reduced, the microstrip line is suitable for various radio frequency transmission requirements, the stability and continuity of characteristic impedance of the microstrip line are ensured, and the service life of the microstrip line is prolonged. The printing ink layers in the two protective layers ensure the film resistance and reliability of the silver conductive layer, a radio frequency transmission line which meets the high-frequency transmission requirement and is low in loss is provided for the folding screen terminal, the bending life of the dynamic bending area is greatly prolonged at the same time, and the good market prospect is achieved.

Description

Technical Field

[0001] This utility model belongs to the field of radio frequency transmission line technology, and in particular relates to a flexible circuit board radio frequency transmission line for use in foldable screen terminals. Background Technology

[0002] In recent years, with continuous breakthroughs in screen technology, hinge technology, and battery technology, the display effect, durability, and battery life of foldable screen phones will be further improved, leading to explosive growth in foldable screen devices. Driven by technological advancements and economies of scale, continued technological progress and cost reductions will further fuel market growth, which is expected to maintain a high growth rate in the coming years.

[0003] However, due to the high integration requirements of folding phones' RF transmission lines and the need to pass through the hinge, conventional coaxial transmission lines cannot meet the dynamic bending requirements of folding phones. Therefore, microstrip transmission lines on flexible circuit boards are used for the RF transmission lines passing through the hinge of folding phones. However, there is a significant market prospect for designing transmission lines that can meet both the low loss requirements of RF and the dynamic bending requirements of the hinge area. Utility Model Content

[0004] To address the aforementioned issues, this invention provides a flexible circuit board radio frequency transmission line for foldable screen terminals, which increases the number of bends that can be made in the dynamic bending zone and reduces the usage loss of the radio frequency transmission line.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] This utility model provides a flexible circuit board radio frequency transmission line for foldable screen terminals. The flexible circuit board radio frequency transmission line has a non-bending area and a dynamic bending area adjacent to the non-bending area along its length direction. The flexible circuit board radio frequency transmission line includes a first substrate body and a second substrate body. The first substrate body and the second substrate body are connected by an adhesive layer located in the non-bending area. Both the first substrate body and the second substrate body have a layered structure. The dynamic bending area has a gap located between the adhesive layers. The first substrate body and the second substrate body corresponding to the gap are both hollowed out.

[0007] As a preferred embodiment of the above technical solution, the first substrate body includes a first protective layer, a first conductive layer, a first substrate layer and a second conductive layer stacked sequentially, wherein the first substrate layer extends from the non-bending area to the dynamic bending area, and both the first protective layer and the second conductive layer are located in the dynamic bending area.

[0008] As a preferred embodiment of the above technical solution, both the first conductive layer and the second conductive layer are copper-clad layers. The first conductive layer is used to provide a signal trace layer for the non-bending area, and the second conductive layer is used to provide a signal trace layer for the dynamic bending area.

[0009] As a preferred embodiment of the above technical solution, the first substrate body further includes first conductive vias located on the lower surface of the first protective layer and arranged at intervals, and the first substrate layer is made of MPI material.

[0010] As a preferred embodiment of the above technical solution, the first protective layer comprises an EMI layer composed of silver conductive material and ink material, and the first protective layer is used to provide a reference ground and shielding layer for the signal line in the dynamic bending area.

[0011] As a preferred embodiment of the above technical solution, the second substrate body includes a second substrate layer, a third conductive layer and a second protective layer stacked sequentially. The second substrate layer extends from the non-bending area to the dynamic bending area, the third conductive layer is located in the non-bending area and the second protective layer is located in the dynamic bending area.

[0012] As a preferred embodiment of the above technical solution, the second substrate layer is made of MPI material, the third conductive layer is a copper-clad layer, and the second protective layer includes an EMI layer composed of silver conductive material and ink material.

[0013] As a preferred embodiment of the above technical solution, the third conductive layer is used to provide a reference ground for the signal line in the non-bending area, and the second protective layer is used to provide a reference ground and a shielding layer for the signal line in the dynamic bending area.

[0014] As a preferred embodiment of the above technical solution, the second substrate body further includes second conductive vias located on the upper surface of the second protective layer and arranged at intervals.

[0015] As a preferred embodiment of the above technical solution, the adhesive layer comprises AD adhesive or UV adhesive.

[0016] Compared with the prior art, the beneficial effects of this utility model are as follows:

[0017] 1. By setting non-bending areas and dynamic bending areas, the transmission line consists of two substrate bodies and lines set on the substrate. The first substrate body and the second substrate body are connected by an adhesive layer located in the non-bending area. The GND of the first substrate body and the second substrate body is hollowed out in the dynamic bending area, so that the hollowed-out area is well connected to the conductive silver plating layer of the first protective layer and the second protective layer, respectively, providing a reference ground and shielding layer for the signal line in the dynamic bending area.

[0018] 2. The layered structure and hollowing treatment in the dynamic bending area greatly increase the number of dynamic bends of the RF transmission line. In the non-bending area, the RF transmission line is a coplanar waveguide microstrip line structure, which reduces the overall RF transmission loss. In the dynamic bending area, it is a strip line, which reduces the impact of the rotating shaft on the impedance continuity of the transmission line.

[0019] 3. Applicable to various RF transmission needs, ensuring the stability and continuity of the characteristic impedance of the microstrip line. The ink layer in the two protective layers ensures the film resistance and reliability of the silver conductive layer, providing RF transmission lines that meet the requirements of high-frequency transmission and low loss for foldable screen terminals. At the same time, it significantly improves the bending life of the dynamic bending area and has a strong market prospect. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the structure of the flexible circuit board radio frequency transmission line for foldable screen terminals proposed in this utility model;

[0021] Figure 2 This is a schematic diagram of the structure of the flexible circuit board radio frequency transmission line proposed in this utility model;

[0022] Figure 3 This is a schematic diagram of the dynamic bending zone proposed in this utility model.

[0023] The symbols for the main components are explained below:

[0024] 1-Non-bending area; 2-Dynamically bending area; 11-First substrate body; 111-First substrate layer; 112-First conductive layer; 113-Second conductive layer; 114-First protective layer; 21-First conductive via; 12-Second substrate body; 121-Second substrate layer; 122-Third conductive layer; 123-Second protective layer; 13-Adhesive layer; 22-Gap; 23-Second conductive via. Detailed Implementation

[0025] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present utility model. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments.

[0026] In the description of this utility model, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this utility model and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model.

[0027] See Figure 1 , Figure 2 and Figure 3 This utility model provides a flexible circuit board radio frequency transmission line for foldable screen terminals. The flexible circuit board radio frequency transmission line has a non-bending area 1 and a dynamic bending area 2 adjacent to the non-bending area 1 along its length direction. The flexible circuit board radio frequency transmission line includes a first substrate body 11 and a second substrate body 12. The first substrate body 11 and the second substrate body 12 are connected by an adhesive layer 13 located in the non-bending area 1. The first substrate body 11 and the second substrate body 12 are both layered structures. The dynamic bending area 2 is provided with a gap 22 located between the adhesive layers 13. The first substrate body 11 and the second substrate body 12 corresponding to the gap 22 are both hollowed out.

[0028] Specifically, the first substrate body 11 includes a first protective layer 114, a first conductive layer 112, a first substrate layer 111, and a second conductive layer 113 stacked sequentially. The first substrate layer 111 extends from the non-bending region 1 to the dynamic bending region 2. Both the first protective layer 114 and the second conductive layer 113 are located in the dynamic bending region 2. Both the first conductive layer 112 and the second conductive layer 113 are copper-clad layers. The first conductive layer 112 provides a signal line routing layer for the non-bending region 1, and the second conductive layer 113 provides a signal line routing layer for the dynamic bending region 2. The first substrate body 11 also includes first conductive vias 21 arranged at intervals on the lower surface of the first protective layer 114. The first substrate layer 111 is made of MPI material. The first protective layer 113 includes an EMI layer composed of silver conductive material and ink material. The first protective layer 114 provides a reference ground and shielding layer for the signal lines in the dynamic bending region 2. The EMI layer is an EMI protection layer, i.e., it provides electromagnetic interference protection.

[0029] Specifically, the second substrate body 12 includes a second substrate layer 121, a third conductive layer 122, and a second protective layer 123 stacked sequentially. The second substrate layer 121 extends from the non-bending region 1 to the dynamic bending region 2. The third conductive layer 122 is located in the non-bending region 1, and the second protective layer 123 is located in the dynamic bending region 2. The second substrate layer 121 is made of MPI material, the third conductive layer 122 is a copper-clad layer, and the second protective layer 123 includes an EMI layer composed of silver conductive material and ink material. The third conductive layer 122 is used to provide a reference ground for the signal lines in the non-bending region 1, and the second protective layer 123 is used to provide a reference ground and a shielding layer for the signal lines in the dynamic bending region 2. The second substrate body 12 also includes second conductive vias 23 located on the upper surface of the second protective layer 123 and arranged at intervals.

[0030] In this embodiment, the adhesive layer 13 includes AD adhesive or UV adhesive. The flexible circuit board extends to form a thick strip structure, and both ends can be connected to BTB (Board to Board) connectors (not shown). The two ends of the flexible circuit board are connected to the first device and the second device respectively through the BTB connectors. The flexible circuit board has a length direction and a width direction. The length direction of the flexible circuit board can be the direction from one end of the flexible circuit board to the other end, and the thickness direction of the flexible circuit board can be the direction of the stacking of the internal layers of the flexible circuit board. The non-bending area 1 and the dynamic bending area 2 can be understood as being divided along the length direction. The dynamic bending area 2 is located between the non-bending areas 1. The dynamic bending area 2 and the two non-bending areas 1 work together to make the flexible circuit board "U" or "W" shaped, so as to adapt to the shape of the housing of the two rotating connections of the foldable electronic device. The adhesive layer 13 can be made of acrylic or epoxy resin. Acrylic adhesives have excellent heat resistance and high bonding strength. Although epoxy resin adhesives have lower heat resistance than acrylic, all other properties are relatively balanced and good.

[0031] The first substrate body 11 is a double-sided copper-clad MPI stacked structure, and the second substrate body 12 is a single-sided copper-clad MPI stacked structure. The MPI is modified polyimide. The first protective layer 114 and the second protective layer 123 are located on the outermost side of the RF transmission line of the flexible circuit board and in the dynamic bending region 2. Both the first protective layer 114 and the second protective layer 123 contain a silver conductive layer and an ink layer. They only cover the dynamic bending region 2, have good conductivity with the copper cladding in the non-bending region 1, and provide a reference ground and shielding layer for the signal lines in the dynamic bending region 2. The first substrate layer 111 and the second substrate layer 121 are arranged opposite to each other. In other words, by using two layers of MPI material with low dielectric constant and low loss factor as the substrate, the RF transmission line achieves lower loss to meet RF transmission requirements, especially at high frequencies. The first conductive via 21 and the second conductive via 23 can be arranged in a one-to-one correspondence. They are both prepared by etching technology. The first conductive layer 112 and the second conductive layer 113 are respectively formed on the first substrate layer by electroplating, coating or lamination.

[0032] It should be noted that the layering treatment of the dynamic bending region 2 and the reference ground layers, namely the first conductive layer 112 and the third conductive layer 113, are all hollowed out, ensuring good conductivity with the conductive silver plating layers of the two protective layers. This provides a reference ground and shielding layer for the signal lines in the dynamic bending region 2, ensuring the stability and continuity of the characteristic impedance of the microstrip line, while significantly improving the bending life. The ink layer ensures the film resistance and reliability of the silver conductive layer. In other words, when the dynamic bending region of the flexible circuit board RF transmission line undergoes bending deformation, the presence of the first conductive via 21 and the second conductive via 23 prevents the first substrate layer 111 and the second substrate layer 121 from forming a stable connection in the dynamic bending region 2. This makes the dynamic bending region of the flexible circuit board RF transmission line more flexible, reducing the rigidity of the flexible circuit board RF transmission line and thus extending its bending life.

[0033] It should be understood that, by setting a non-bending region 1 and a dynamic bending region 2, the RF transmission line consists of two substrate bodies and lines disposed on the substrates. The first substrate body 11 and the second substrate body 12 are bonded in the non-bending region 1 and are layered in the dynamic bending region 2. The GND of the first substrate body 11 and the second substrate body 12 are both hollowed out in the dynamic bending region 2. An EMI layer is added on the hollowed-out layer, and the hollowed-out areas are well connected to the conductive silver-plated layer of the EMI layer, providing a reference ground and shielding layer for the signal lines in the dynamic bending region 2. The layered structure and hollowed-out design of the dynamic bending region 2... This technology significantly improves the dynamic bending lifespan of RF transmission lines. In the non-bending region 1, the RF transmission line uses a coplanar waveguide microstrip line structure to reduce overall RF transmission loss. In the dynamic bending region 2, it uses a stripline to reduce the impact of the pivot on the impedance continuity of the transmission line. Suitable for various RF transmission requirements, it ensures the stability and continuity of the microstrip line's characteristic impedance. The ink layer in the two protective layers ensures the film resistance and reliability of the silver conductive layer. This provides foldable screen terminals with RF transmission lines that meet high-frequency transmission requirements and have low loss, while significantly improving the bending lifespan in the dynamic bending region, demonstrating strong market potential. In other words, by setting the flexible circuit board RF transmission line along its length as a non-bending region 1 and a dynamic bending region 2, the first substrate body 11 and the second substrate body 12 are connected by an adhesive layer 2 located in the non-bending region 1. Both the first substrate body 11 and the second substrate body 12 are layered structures. Both the first substrate body 11 and the second substrate body 12 are hollowed out in the dynamic bending region 2, so that the hollowed-out areas are well connected to the conductive silver plating layers of the first protective layer 114 and the second protective layer 123, respectively, providing a reference ground and shielding layer for the signal line in the dynamic bending region 2, thereby reducing RF transmission loss, making it suitable for various RF transmission requirements, and ensuring the stability and continuity of the characteristic impedance of the microstrip line.

[0034] The above description is only a preferred embodiment of the present utility model, but the protection scope of the present utility model is not limited thereto. Any equivalent substitutions or changes made by those skilled in the art within the technical scope disclosed in the present utility model, based on the technical solution and the inventive concept of the present utility model, should be included within the protection scope of the present utility model.

Claims

1. A flexible circuit board radio frequency transmission line for use in foldable screen terminals, characterized in that, The flexible circuit board radio frequency transmission line has a non-bending area and a dynamic bending area adjacent to the non-bending area along its length. The flexible circuit board radio frequency transmission line includes a first substrate body and a second substrate body. The first substrate body and the second substrate body are connected by an adhesive layer located in the non-bending area. Both the first substrate body and the second substrate body have a layered structure. The dynamic bending area has a gap located between the adhesive layers. The first substrate body and the second substrate body corresponding to the gap are both hollowed out.

2. The flexible circuit board radio frequency transmission line for foldable screen terminals according to claim 1, characterized in that, The first substrate body includes a first protective layer, a first conductive layer, a first substrate layer and a second conductive layer stacked sequentially. The first substrate layer extends from the non-bending area to the dynamic bending area, and the first protective layer and the second conductive layer are both located in the dynamic bending area.

3. The flexible circuit board radio frequency transmission line for foldable screen terminals according to claim 2, characterized in that, Both the first conductive layer and the second conductive layer are copper-clad layers. The first conductive layer is used to provide a signal trace layer for the non-bending area, and the second conductive layer is used to provide a signal trace layer for the dynamic bending area.

4. The flexible circuit board radio frequency transmission line for foldable screen terminals according to claim 3, characterized in that, The first substrate body also includes first conductive vias located on the lower surface of the first protective layer and arranged at intervals, and the first substrate layer is made of MPI material.

5. The flexible circuit board radio frequency transmission line for foldable screen terminals according to claim 2, characterized in that, The first protective layer comprises an EMI layer composed of silver conductive material and ink material, and the first protective layer is used to provide a reference ground and shielding layer for the signal line in the dynamic bending area.

6. The flexible circuit board radio frequency transmission line for foldable screen terminals according to claim 1, characterized in that, The second substrate body includes a second substrate layer, a third conductive layer and a second protective layer stacked sequentially. The second substrate layer extends from the non-bending area to the dynamic bending area. The third conductive layer is located in the non-bending area and the second protective layer is located in the dynamic bending area.

7. The flexible circuit board radio frequency transmission line for a foldable screen terminal according to claim 6, characterized in that, The second substrate layer is made of MPI material, the third conductive layer is a copper-clad layer, and the second protective layer includes an EMI layer composed of silver conductive material and ink material.

8. The flexible circuit board radio frequency transmission line for a foldable screen terminal according to claim 7, characterized in that, The third conductive layer is used to provide a reference ground for the signal line in the non-bending area, and the second protective layer is used to provide a reference ground and a shielding layer for the signal line in the dynamic bending area.

9. The flexible circuit board radio frequency transmission line for a foldable screen terminal according to claim 6, characterized in that, The second substrate body also includes second conductive vias located on the upper surface of the second protective layer and arranged at intervals.

10. The flexible circuit board radio frequency transmission line for a foldable screen terminal according to claim 1, characterized in that, The adhesive layer includes AD adhesive or UV adhesive.

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