Flexible circuit board, terminal device and manufacturing method of flexible circuit board

Abstract

The application discloses a flexible circuit board, which comprises a first dielectric layer, a second dielectric layer, a glue layer, a circuit layer and a reinforcing sheet, the glue layer is arranged between the first dielectric layer and the second dielectric layer, the circuit layer is embedded in the glue layer, and the reinforcing sheet is embedded in the glue layer and is arranged in a spaced mode with the circuit layer. The application further provides a terminal device and a manufacturing method of the flexible circuit board. The flexible circuit board provided by the application is beneficial to reducing the rebound of the reinforcing sheet, avoiding the cracking of the reinforcing sheet and the flexible circuit board and preventing interference and the like.

Description

Technical Field

[0001] This application relates to the field of circuit board technology, and in particular to a flexible circuit board, a terminal device, and a method for manufacturing a flexible circuit board. Background Technology

[0002] When flexible circuit boards are installed in terminal devices, reinforcing strips are typically required to shape the areas where the flexible circuit board bends. Existing methods of installing reinforcing strips can easily lead to their separation from the circuit board, and the reinforcing strips can also interfere with the installation of other components in the terminal device. Summary of the Invention

[0003] In a first aspect, this application provides a flexible circuit board, including a first dielectric layer, a second dielectric layer, an adhesive layer, a circuit layer, and a reinforcing sheet, wherein the adhesive layer is located between the first dielectric layer and the second dielectric layer; the circuit layer is embedded in the adhesive layer; and the reinforcing sheet is embedded in the adhesive layer and spaced apart from the circuit layer.

[0004] In some embodiments of this application, a portion of the surface of the circuit layer and a portion of the surface of the reinforcing sheet are connected to the surface of the first dielectric layer.

[0005] In some embodiments of this application, the flexible circuit board further includes an adhesive layer that bonds the first dielectric layer and the reinforcing sheet.

[0006] In some embodiments of this application, all surfaces of the circuit layer and the reinforcing sheet are covered with an adhesive layer.

[0007] In some embodiments of this application, the reinforcing sheet and the circuit layer are located on the same surface of the first dielectric layer.

[0008] Secondly, this application provides a terminal device, which includes a flexible circuit board.

[0009] Thirdly, this application provides a method for manufacturing a flexible circuit board, comprising the following steps: providing a circuit board substrate, including a first dielectric layer and a circuit layer disposed on the surface of the first dielectric layer; disposing a reinforcing sheet on the surface of the first dielectric layer, the reinforcing sheet being disposed at a distance from the circuit layer; and covering the surfaces of the circuit layer and the reinforcing sheet with a first protective layer to obtain a flexible circuit board.

[0010] In some embodiments of this application, the first protective layer includes a laminated adhesive layer and a second dielectric layer, the adhesive layer covering the circuit layer, the reinforcing sheet, and the surface of the first dielectric layer exposed to the circuit layer and the reinforcing sheet.

[0011] In some embodiments of this application, the manufacturing method further includes: before the step of covering the first protective layer, using an adhesive layer to bond the reinforcing sheet to the surface of the first dielectric layer.

[0012] Fourthly, this application provides a method for manufacturing a flexible circuit board, comprising the following steps: depositing a copper foil layer on the surface of a first carrier film layer; fabricating circuits on the copper foil layer to form a circuit layer; depositing a reinforcing sheet on the surface of a second carrier film layer, wherein the adhesiveness of the first carrier film layer and the second carrier film layer are different; pressing the first carrier film layer with the circuit layer and the second carrier film layer with the reinforcing sheet together, wherein the circuit layer and the reinforcing sheet are spaced apart; removing the one with less adhesiveness between the first carrier film layer and the second carrier film layer; covering the surface of the circuit layer and the reinforcing sheet with a first protective layer; and removing the one of the first carrier film layer and the second carrier film layer that was not removed, and covering the surface of the circuit layer and the reinforcing sheet with a second protective layer to obtain a flexible circuit board.

[0013] The flexible circuit board provided in this application has a reinforcing sheet embedded within it. Due to the binding effect of the adhesive layer, the first dielectric layer, and the second dielectric layer, the restoring force of the reinforcing sheet can be reduced, thereby helping to reduce the springback of the reinforcing sheet. In addition, the surface of the reinforcing sheet is covered by the first dielectric layer and the adhesive layer, so the interaction force between the reinforcing sheet and the first dielectric layer and the adhesive layer is strong, which can effectively avoid the problem of cracking of the reinforcing sheet and the flexible circuit board in related technologies. Furthermore, since the reinforcing sheet is embedded in the flexible circuit board, it will not interfere with other components, thus not affecting the installation of other components in the terminal device. Attached Figure Description

[0014] Figure 1 A cross-sectional schematic diagram of a reinforcing sheet provided for the related technology of this application mounted on the surface of a flexible circuit board.

[0015] Figure 2 This is a cross-sectional schematic diagram of the flexible circuit board with an embedded reinforcing sheet provided in an embodiment of this application.

[0016] Figure 3 for Figure 2 The diagram shows the structural arrangement of the reinforcing sheet and the circuit layer.

[0017] Figure 4 This is a schematic diagram of the arrangement of reinforcing sheets and circuit layers provided in other embodiments of this application.

[0018] Figure 5 for Figure 2 The flexible circuit board shown is along Figure 3 The diagram shows a cross-section along the BB direction after bending in the AA direction.

[0019] Figure 6 This is a cross-sectional schematic diagram of a single-sided copper-clad laminate provided in an embodiment of this application.

[0020] Figure 7 To Figure 6 The diagram shows a cross-sectional view of a circuit board formed by fabricating circuits using copper foil layers.

[0021] Figure 8 In order to be in Figure 6 The diagram shows a cross-section of the first dielectric layer surface after the reinforcing sheet has been bonded.

[0022] Figure 9 In order to be in Figure 8 The diagram shows a cross-sectional view of the flexible circuit board obtained after the circuit layer and the surface of the reinforcing sheet are covered with the first protective layer.

[0023] Figure 10 A cross-sectional schematic diagram showing the copper foil layer disposed on the surface of the first carrier film layer for implementation of this application.

[0024] Figure 11 For etching Figure 10 The diagram shows a cross-sectional view of the copper foil layer after it has been used to form the circuit layer.

[0025] Figure 12 The reinforcing sheet provided for implementation of this application is disposed on the surface of the second carrier film layer and is in contact with it. Figure 11 The diagram shows a cross-sectional view of the combined structure.

[0026] Figure 13 To remove Figure 12 The diagram shows a cross-section behind the first carrier film layer.

[0027] Figure 14 A cross-sectional view of the circuit layer and the surface of the reinforcing sheet after the first protective layer has been applied.

[0028] Figure 15 A cross-sectional schematic diagram of a flexible circuit board with an embedded reinforcing sheet provided for other embodiments of this application.

[0029] Explanation of main component symbols

[0030]

[0031] Detailed Implementation

[0032] To better understand the above-mentioned objectives, features, and advantages of this application, the application will be described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. Many specific details are set forth in the following description to provide a thorough understanding of this application; the described embodiments are merely a part of the embodiments of this application, and not all of them.

[0033] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. The term "and / or" as used herein includes all and any combination of one or more of the associated listed items.

[0034] In the various embodiments of this application, for ease of description and not limitation, the term "connection" used in the patent application specification and claims is not limited to physical or mechanical connections, whether direct or indirect. Terms such as "upper," "lower," "above," "below," "left," and "right" are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship also changes accordingly.

[0035] Please see Figure 1 Related technology provides a method for mounting a reinforcing piece 20', which is located on the outer surface of a flexible circuit board 100' and in the bending area of ​​the flexible circuit board 100'. Over time, under their respective stresses, the reinforcing pieces 20' and the flexible circuit board 100' are prone to separating from each other; furthermore, the reinforcing pieces 20' being located on the outer surface of the flexible circuit board 100' effectively increases the overall thickness, and the reinforcing pieces 20' can also easily interfere with the mounting of other components.

[0036] This application provides a terminal device (not shown in the figures), which includes a main component (not shown in the figures) and a flexible circuit board 100 (see [link to relevant documentation]). Figures 2 to 5 Flexible circuit board 100 (see also) Figure 5 It is located on the surface of the main component in a bent shape.

[0037] Please see Figure 2 The flexible circuit board 100 may include a first dielectric layer 11, an adhesive layer 31, a second dielectric layer 33, a circuit layer 132, and a reinforcing sheet 20. The adhesive layer 31 is located between the first dielectric layer 11 and the second dielectric layer 33 and bonds the first dielectric layer 11 and the second dielectric layer 33. The number of layers of the first dielectric layer 11, adhesive layer 31, second dielectric layer 33, circuit layer 132, and reinforcing sheet 20 may be one or more.

[0038] Both the first dielectric layer 11 and the second dielectric layer 33 can be selected from flexible materials such as polyimide (PI), liquid crystal polymer (LCP), and modified polyimide (MPI).

[0039] Both the circuit layer 132 and the reinforcing sheet 20 are embedded in the adhesive layer 31, with the circuit layer 132 and the reinforcing sheet 20 spaced apart. There can be one or more circuit layers 132 and reinforcing sheets 20 located in the same layer. For cases involving multiple reinforcing sheets 20, please refer to [reference needed]. Figure 3 The reinforcing sheet 20 is arranged alternately with the circuit layer 132; please refer to Figure 4 (a) in the diagram can be located on either side of the line in line layer 132; please refer to [link / reference]. Figure 4 (b) in the above arrangement can also be a combination of the two arrangements mentioned above.

[0040] In this embodiment, both the circuit layer 132 and the reinforcing sheet 20 are connected to the first dielectric layer 11, and the surfaces not connected to the first dielectric layer 11 are connected to the adhesive layer 31. In other embodiments, all surfaces of the circuit layer 132 and / or the reinforcing sheet 20 are connected to the adhesive layer 31.

[0041] In this embodiment, the circuit layer 132 and the reinforcing sheet 20 are located on the same surface of the first dielectric layer 11, which helps to reduce the overall thickness of the flexible circuit board 100. In other embodiments, the circuit layer 132 and the reinforcing sheet 20 may also be located on different surfaces of the first dielectric layer 11.

[0042] Please see Figure 5 When the flexible circuit board 100 is bent, it can be bent along a direction perpendicular to the reinforcing sheet 20, so that the reinforcing sheet 20 can be bent. The reinforcing sheet 20 is embedded in the flexible circuit board 100. Due to the restraint of the adhesive layer 31, the first dielectric layer 11 and the second dielectric layer 33, the restoring force of the reinforcing sheet 20 can be reduced, thereby helping to reduce the springback of the reinforcing sheet 20. In addition, the surface of the reinforcing sheet 20 is covered by the first dielectric layer 11 and the adhesive layer 31, so the interaction force between the reinforcing sheet 20 and the first dielectric layer 11 and the adhesive layer 31 is strong, which can effectively avoid the problem of cracking of the reinforcing sheet 20' and the flexible circuit board 100' in related technologies. Furthermore, the reinforcing sheet 20 is embedded in the flexible circuit board 100 and will not interfere with other components, thereby not affecting the installation of other components in the terminal device.

[0043] In another embodiment, please refer to Figure 9 The reinforcing sheet 20 can also be bonded to the surface of the first dielectric layer 11 via the adhesive layer 21 to increase the bonding force between the reinforcing sheet 20 and the first dielectric layer 11. The adhesive layer 21 can be a thermosetting adhesive.

[0044] Please see Figure 15 Another embodiment of this application provides a flexible circuit board 100a. Unlike the previous embodiment, in this embodiment, all surfaces of the circuit layer 132 and the reinforcing sheet 20 are connected to the adhesive layer 31, which can further increase the binding force of the adhesive layer (i.e., the first adhesive layer 35a and the second adhesive layer 41a) on the reinforcing sheet 20.

[0045] Please see Figures 6 to 9 This application also provides a method for manufacturing a flexible circuit board 100, which may include the following steps:

[0046] Step S11: Please refer to Figure 6 A single-sided copper-clad laminate 10 is provided, including a first dielectric layer 11 and a copper foil layer 13 stacked together.

[0047] The first dielectric layer 11 is made of a flexible material.

[0048] Step S12: Please refer to Figure 7 The copper foil layer 13 is fabricated to form a circuit layer 132, thereby forming a circuit substrate 15.

[0049] In other embodiments, the structure of the circuit board 15 is not limited to a first dielectric layer 11 and a circuit layer 132, but can be multilayered.

[0050] The circuit layer 132 can be formed by etching the copper foil layer 13 or by die cutting. The cross-section of the circuit layer 132 formed by etching can be trapezoidal.

[0051] Step S13: Please refer to Figure 8 A reinforcing sheet 20 is provided on the surface of the first dielectric layer 11, and the reinforcing sheet 20 is provided at intervals from the circuit layer 132.

[0052] The reinforcing sheet 20 can be bonded to the surface of the first dielectric layer 11 using an adhesive layer 21, which can be a thermosetting adhesive. The reinforcing sheet 20 and the circuit layer 132 are located on the same surface of the first dielectric layer 11, which helps to reduce the overall thickness of the flexible circuit board 100.

[0053] Step S14: Please refer to Figure 9 A first protective layer 30 is applied to the surface of the circuit layer 132 and the reinforcing sheet 20 to obtain a flexible circuit board 100.

[0054] The first protective layer 30 includes an adhesive layer 31 and a second dielectric layer 33 stacked together. The adhesive layer 31 covers the circuit layer 132 and the reinforcing sheet 20, and also covers the surface of the first dielectric layer 11 exposed to the circuit layer 132 and the reinforcing sheet 20. The second dielectric layer 33 is located on the surface of the adhesive layer 31 facing away from the first dielectric layer 11. The second dielectric layer 33 is made of a flexible material.

[0055] Please see Figures 10 to 15 Another embodiment of this application provides a method for manufacturing a flexible circuit board 100a, which may include the following steps:

[0056] Step S21: Please refer to Figure 10A copper foil layer 13a is disposed on the surface of the first carrier film layer 50a.

[0057] Step S22: Please refer to Figure 11 The copper foil layer 13a is fabricated to form the circuit layer 132.

[0058] The circuit layer 132 can be formed by etching or die-cutting. The cross-section of the circuit layer 132 formed by etching can be trapezoidal; the cross-section of the circuit layer 132 formed by die-cutting can be hexagonal.

[0059] Step S23: Please refer to Figure 12 The reinforcing sheet 20 is disposed on the surface of the second carrier film layer 55a.

[0060] The adhesiveness of the first carrier film layer 50a differs from that of the second carrier film layer 55a. In this embodiment, the adhesiveness of the first carrier film layer 50a is less than that of the second carrier film layer 55a.

[0061] Step S24: Please refer to Figure 13 The first carrier film layer 50a, on which the circuit layer 132 is provided, and the second carrier film layer 55a, on which the reinforcing sheet 20 is provided, are pressed together so that the circuit layer 132 and the reinforcing sheet 20 are located between the first carrier film layer 50a and the second carrier film layer 55a, and the one with less adhesion between the first carrier film layer 50a and the second carrier film layer 55a is removed.

[0062] In this embodiment, the circuit layer 132 and the reinforcing sheet 20 are both bonded to the surfaces of the first carrier film layer 50a and the second carrier film layer 55a, with the circuit layer 132 and the reinforcing sheet 20 spaced apart from each other. The first carrier film layer 50a, which has less adhesion, is peeled off.

[0063] Step S25: Please refer to Figure 14 A first protective layer 30a is applied to the surface of the circuit layer 132 and the reinforcing sheet 20.

[0064] The first protective layer 30a includes a first adhesive layer 35a and a first dielectric layer 11a stacked together. The first adhesive layer 35a covers the circuit layer 132 and the reinforcing sheet 20, and also covers the first carrier film layer 50a exposed on the surfaces of the circuit layer 132 and the reinforcing sheet 20. The first dielectric layer 11a is located on the surface of the first adhesive layer 35a facing away from the second carrier film layer 55a.

[0065] Step S26: Please refer to Figure 15 The second carrier film layer 55a is removed, and a second protective layer 40a is applied to the surface of the circuit layer 132 and the reinforcing sheet 20 to obtain the flexible circuit board 100a.

[0066] After removing the second carrier film layer 55a, the surfaces of the circuit layer 132, the reinforcing sheet 20, and the first adhesive layer 35a facing away from the first dielectric layer 11a are exposed. The second protective layer 40a includes a second adhesive layer 41a and a second dielectric layer 33a stacked together. The second adhesive layer 41a covers the surfaces of the circuit layer 132, the reinforcing sheet 20, and the first adhesive layer 35a facing away from the first dielectric layer 11a; the second dielectric layer 33a is located on the surface of the second adhesive layer 41a facing away from the first protective layer 30a.

[0067] The first adhesive layer 35a and the second adhesive layer 41a are bonded together to form an adhesive layer (not shown in the figure).

[0068] The flexible circuit board 100 (or 100a) manufactured using the manufacturing method of the present application embodiment can reduce the restoring force of the reinforcing sheet 20, thereby helping to reduce the springback of the reinforcing sheet 20; in addition, it can effectively avoid the problem of cracking between the reinforcing sheet 20' and the flexible circuit board 100' in the related art; furthermore, the reinforcing sheet 20 is embedded in the flexible circuit board 100, which will not affect the installation of other components in the terminal device.

[0069] The above embodiments are only used to illustrate the technical solutions of this application and are not intended to limit it. Although this application has been described in detail with reference to the above preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions to the technical solutions of this application should not depart from the spirit and scope of the technical solutions of this application.

Claims

1. A flexible circuit board, characterized in that, include: First dielectric layer; Second dielectric layer; An adhesive layer is located between the first dielectric layer and the second dielectric layer; The circuit layer is embedded in the adhesive layer; A reinforcing sheet is embedded in the adhesive layer and extends along the direction of the flexible circuit board. The reinforcing sheet is spaced apart from the circuit layer. The circuit layer and the reinforcing sheet are located in the same layer and are both located on the same side of the first dielectric layer. All surfaces of the reinforcing sheet are covered by the adhesive layer.

2. A terminal device, characterized in that, The terminal device includes the flexible circuit board as described in claim 1.

3. A method for manufacturing a flexible circuit board, characterized in that, Includes the following steps: A copper foil layer is disposed on the surface of the first carrier film layer; The copper foil layer is fabricated to form a circuit layer; A reinforcing sheet is disposed on the surface of the second carrier film layer, wherein the adhesiveness of the first carrier film layer is different from that of the second carrier film layer; The first carrier film layer with the circuit layer and the second carrier film layer with the reinforcing sheet are pressed together. Along the direction of extension of the first carrier film layer, the circuit layer and the reinforcing sheet are spaced apart. The one with less adhesion between the first carrier film layer and the second carrier film layer is removed. A first protective layer is applied to the surface of the circuit layer and the reinforcing sheet. The first protective layer includes a first adhesive layer and a first dielectric layer stacked together. The first adhesive layer covers the circuit layer and the reinforcing sheet. The first adhesive layer also covers the first carrier film layer exposed on the surface of the circuit layer and the reinforcing sheet. as well as Remove one of the first and second carrier layers that was not removed, and cover the surface of the circuit layer and the reinforcing sheet with a second protective layer. The second protective layer includes a second adhesive layer and a second dielectric layer stacked together. The second adhesive layer covers the surface of the circuit layer, the reinforcing sheet, and the surface of the first adhesive layer away from the first dielectric layer. The second dielectric layer is located on the surface of the second adhesive layer away from the first protective layer. The first adhesive layer and the second adhesive layer are bonded to each other to form an adhesive layer, thereby obtaining the flexible circuit board. The circuit layer and the reinforcing sheet are located in the same layer and are both located on the same side of the first dielectric layer. All surfaces of the reinforcing sheet are covered by the adhesive layer.

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