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

Abstract

A flexible circuit board comprises a first dielectric layer, a second dielectric layer, an adhesive layer, a circuit layer and a reinforcing sheet, and the adhesive layer is located between the first dielectric layer and the second dielectric layer; the circuit layer is embedded in the adhesive layer; the reinforcing sheet is embedded in the adhesive layer, and the reinforcing sheet and the circuit layer are arranged at intervals. The invention further provides a terminal device and a manufacturing method of the flexible circuit board. According to the flexible circuit board provided by the invention, the rebound of the reinforcing sheet is reduced, the reinforcing sheet and the flexible circuit board are prevented from cracking, and interference and the like are prevented.

Description

Technical Field

[0001] The present application relates to the technical field of circuit boards, and in particular to a flexible circuit board, a terminal device, and a method for manufacturing the flexible circuit board. Background Art

[0002] When the flexible circuit board is installed in the terminal device, a reinforcing sheet is usually required to be shaped in the bending area of ​​the flexible circuit board. The existing installation method of the reinforcing sheet is easy to separate from the circuit board, and the reinforcing sheet is easy to interfere with the installation of other components in the terminal device. Summary of the invention

[0003] In a first aspect, the present application provides a flexible circuit board, comprising a first dielectric layer, a second dielectric layer, a glue layer, a circuit layer and a reinforcing sheet, wherein the glue layer is located between the first dielectric layer and the second dielectric layer; the circuit layer is buried in the glue layer; the reinforcing sheet is buried in the glue layer and spaced apart from the circuit layer.

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

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

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

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

[0008] In a second aspect, the present application provides a terminal device, which includes a flexible circuit board.

[0009] In a third aspect, the present application provides a method for manufacturing a flexible circuit board, comprising the following steps: providing a circuit substrate, comprising a first dielectric layer and a circuit layer arranged on the surface of the first dielectric layer; arranging a reinforcing sheet on the surface of the first dielectric layer, the reinforcing sheet and the circuit layer being spaced apart; and covering the surface of the circuit layer and the reinforcing sheet with a first protective layer to obtain a flexible circuit board.

[0010] In some embodiments of the present application, the first protective layer includes a glue layer and a second dielectric layer stacked together, and the glue layer covers 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 the present application, the manufacturing method further includes: before the step of covering the first protective layer, bonding the reinforcing sheet to the surface of the first dielectric layer using an adhesive layer.

[0012] In a fourth aspect, the present application provides a method for manufacturing a flexible circuit board, comprising the following steps: disposing a copper foil layer on the surface of a first carrier layer; performing circuit fabrication on the copper foil layer to form a circuit layer; disposing a reinforcing sheet on the surface of a second carrier layer, wherein the viscosity of the first carrier layer is different from that of the second carrier layer; pressing the first carrier layer provided with the circuit layer and the second carrier layer provided with the reinforcing sheet together, wherein the circuit layer and the reinforcing sheet are spaced apart, and removing the one with less viscosity between the first carrier layer and the second carrier layer; covering the surfaces of the circuit layer and the reinforcing sheet with a first protective layer; and removing the one of the first carrier layer and the second carrier layer that is not removed, and covering the surfaces of the circuit layer and the reinforcing sheet with a second protective layer to obtain a flexible circuit board.

[0013] In the flexible circuit board provided by the present application, the reinforcing sheet is embedded in the flexible circuit board. Due to the constraints of the glue layer, the first dielectric layer and the second dielectric layer, the restoring force of the reinforcing sheet can be reduced, which is beneficial to reducing the rebound of the reinforcing sheet. In addition, the surface of the reinforcing sheet is covered by the first dielectric layer and the glue layer, so the force between the reinforcing sheet and the first dielectric layer and the glue layer is strong, which can effectively avoid the problem of cracking of the reinforcing sheet and the flexible circuit board in the related art. Furthermore, the reinforcing sheet is embedded in the flexible circuit board and will not interfere with other components, thereby not affecting the installation of other components in the terminal device. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0015] Figure 2 A schematic cross-sectional view of a flexible circuit board with an embedded reinforcement sheet provided in an embodiment of the present application.

[0016] Figure 3 for Figure 2 The structural schematic diagram of the arrangement of the reinforcement sheet and the circuit layer is shown.

[0017] Figure 4 A schematic structural diagram of the arrangement of reinforcement sheets and circuit layers provided in other embodiments of the present application.

[0018] Figure 5 for Figure 2 The flexible circuit board shown along Figure 3 The schematic cross-sectional view along the BB direction after bending along the AA direction is shown.

[0019] Figure 6 A schematic cross-sectional view of a single-sided copper clad laminate provided in an embodiment of the present application.

[0020] Figure 7 For Figure 6 The cross-sectional schematic diagram of a circuit substrate formed by circuit fabrication of a copper foil layer is shown.

[0021] Figure 8 For Figure 6 The cross-sectional schematic diagram shown is after the reinforcing sheet is bonded to the surface of the first dielectric layer.

[0022] Fig. 9 For Figure 8 The schematic cross-sectional view of the flexible printed circuit board obtained after the circuit layer and the surface of the reinforcing sheet are covered with the first protective layer.

[0023] Fig.10 A cross-sectional schematic diagram of disposing a copper foil layer on the surface of a first carrier layer provided for the implementation of the present application.

[0024] Fig.11 For etching Fig.10 The cross-sectional view of the copper foil layer after forming the circuit layer is shown.

[0025] Fig.12 The reinforcing sheet provided for the implementation of this application is arranged on the surface of the second carrier film layer and Fig.11 The cross-sectional schematic diagram of the structure after combination is shown.

[0026] Fig.13 To remove Fig.12 A schematic cross-sectional view of the first carrier film layer is shown.

[0027] Fig.14 A schematic cross-sectional view of the circuit layer and the reinforcing sheet after the first protective layer is covered on the surface.

[0028] Fig.15 Schematic cross-sectional view of a flexible circuit board with an embedded reinforcement sheet provided in some other embodiments of the present application.

[0029] Main component symbols

[0030]

[0031] DETAILED DESCRIPTION

[0032] In order to more clearly understand the above-mentioned purposes, features and advantages of the present application, the present application is described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be noted that, in the absence of conflict, the embodiments of the present application and the features in the embodiments can be combined with each other. In the following description, many specific details are set forth to facilitate a full understanding of the present application, and the described embodiments are only a part of the embodiments of the present application, rather than all of the embodiments.

[0033] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used in the specification of this article are only for the purpose of describing specific embodiments and are not intended to limit this application. The term "and / or" used herein includes all and any combination of one or more related listed items.

[0034] In the embodiments of the present application, for the convenience of description and not to limit the present application, the term "connection" used in the patent application specification and claims of the present application is not limited to physical or mechanical connection, whether direct or indirect. "Up", "down", "above", "below", "left", "right", etc. are only used to indicate relative position relationship. When the absolute position of the described object changes, the relative position relationship also changes accordingly.

[0035] See also Figure 1 The related art provides a method for installing a reinforcing sheet 20', wherein the reinforcing sheet 20' is located on the outer surface of the flexible circuit board 100' and is located in the bending area of ​​the flexible circuit board 100'. As time goes by, under the action of their respective stresses, the reinforcing sheet 20' and the flexible circuit board 100' are easily separated from each other; and the reinforcing sheet 20' is located on the outer surface of the flexible circuit board 100', which is equivalent to increasing the overall thickness, and the reinforcing sheet 20' is also easy to interfere with the installation of other components.

[0036] The present application embodiment provides a terminal device (not shown), which includes a main body component (not shown) and a flexible circuit board 100 (see Figures 2 to 5 ), flexible circuit board 100 (see Figure 5 ) is located on the surface of the main component in a bent shape.

[0037] See also Figure 2 The flexible circuit board 100 may include a first dielectric layer 11, a glue layer 31, a second dielectric layer 33, a circuit layer 132, and a reinforcing sheet 20. The glue 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, the glue layer 31, the second dielectric layer 33, the circuit layer 132, and the reinforcing sheet 20 may be one or more layers.

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

[0039] The circuit layer 132 and the reinforcing sheet 20 are both buried in the adhesive layer 31, and the circuit layer 132 and the reinforcing sheet 20 are arranged at intervals. The circuit layer 132 and the reinforcing sheet 20 located in the same layer can be one or more. When both are multiple, please refer to Figure 3 , the reinforcing sheet 20 and the circuit layer 132 are arranged at intervals; please refer to Figure 4 (a) in the figure may be located on both sides of the circuit layer 132; see Figure 4 (b) in the figure can also be a combination of the above two arrangements.

[0040] In this embodiment, 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 is beneficial to reducing 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] See also Figure 5 When the flexible circuit board 100 is bent, it can be bent in a direction perpendicular to the reinforcing sheet 20 so that the reinforcing sheet 20 is bent. The reinforcing sheet 20 is embedded in the flexible circuit board 100. Due to the constraints 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 facilitating the reduction of the rebound 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 reinforcing sheet 20 has a strong force with the first dielectric layer 11 and the adhesive layer 31, which can effectively avoid the problem of cracking of 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 and will not interfere with other components, thereby not affecting the installation of other components in the terminal device.

[0043] In another embodiment, see Fig. 9 The reinforcing sheet 20 may also be bonded to the surface of the first dielectric layer 11 through the bonding layer 21 to increase the bonding force between the reinforcing sheet 20 and the first dielectric layer 11. The bonding layer 21 may be a thermosetting adhesive.

[0044] See also Fig.15 Another embodiment of the present application provides a flexible circuit board 100a. Different from the previous embodiment, the circuit layer 132 and all surfaces of the reinforcing sheet 20 in this embodiment 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] See also Figures 6 to 9 The present 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, comprising a first dielectric layer 11 and a copper foil layer 13 which are stacked.

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

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

[0049] In other embodiments, the structure of the circuit substrate 15 is not limited to one first dielectric layer 11 and one circuit layer 132 , and may be multiple layers.

[0050] The circuit layer 132 may be formed by etching the copper foil layer 13 or by die cutting. The cross section of the circuit layer 132 formed by the etching process may be a trapezoid.

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

[0052] The reinforcing sheet 20 can be bonded to the surface of the first dielectric layer 11 by 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 is beneficial to reducing the overall thickness of the flexible circuit board 100.

[0053] Step S14: Please refer to Fig. 9 , the first protection layer 30 is covered on the surface of the circuit layer 132 and the reinforcing sheet 20 to obtain the flexible circuit board 100 .

[0054] The first protective layer 30 includes a glue layer 31 and a second dielectric layer 33 which are stacked, the glue layer 31 covering the circuit layer 132 and the reinforcing sheet 20, and the glue layer 31 also covering 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 glue layer 31 away from the first dielectric layer 11. The material of the second dielectric layer 33 is a flexible material.

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

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

[0057] Step S22: Please refer to Fig.11 , the copper foil layer 13a is subjected to circuit fabrication to form a circuit layer 132 .

[0058] The circuit layer 132 may be formed by an etching process or a die-cutting process. The cross section of the circuit layer 132 formed by the etching process may be a trapezoid; the cross section of the circuit layer 132 formed by the die-cutting process may be a hexagon.

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

[0060] The viscosity of the first film carrier layer 50a is different from the viscosity of the second film carrier layer 55a. In this embodiment, the viscosity of the first film carrier layer 50a is smaller than the viscosity of the second film carrier layer 55a.

[0061] Step S24: Please refer to Fig.13 , press the first carrier layer 50a provided with the circuit layer 132 and the second carrier layer 55a provided with the reinforcement sheet 20 together so that the circuit layer 132 and the reinforcement sheet 20 are located between the first carrier layer 50a and the second carrier layer 55a, and remove the one with less viscosity between the first carrier layer 50a and the second carrier layer 55a.

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

[0063] Step S25: Please refer to Fig.14 The first protection layer 30 a is covered on 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 which are stacked. The first adhesive layer 35a covers the circuit layer 132 and the reinforcing sheet 20, and the first adhesive layer 35a also covers the surface of the first carrier layer 50a exposed to 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 away from the second carrier layer 55a.

[0065] Step S26: Please refer to Fig.15 , remove the second carrier layer 55a, and cover the surface of the circuit layer 132 and the reinforcing sheet 20 with the second protection layer 40a to obtain the flexible circuit board 100a.

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

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

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

[0069] The above implementation modes are only used to illustrate the technical solutions of the present application and are not intended to limit the present application. Although the present application has been described in detail with reference to the above preferred implementation modes, a person skilled in the art should understand that the technical solutions of the present application may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present application.

Claims

1. A flexible circuit board, characterized in that: include: a first dielectric layer; a second dielectric layer; A glue layer, located between the first dielectric layer and the second dielectric layer; A circuit layer, buried in the adhesive layer; The reinforcing sheet is embedded in the adhesive layer and spaced apart from the circuit layer.

2. The flexible circuit board according to claim 1, characterized in that: Part of the surface of the circuit layer and part of the surface of the reinforcing sheet are connected to the surface of the first dielectric layer.

3. The flexible circuit board according to claim 2, characterized in that: The flexible circuit board further includes a bonding layer, and the bonding layer bonds the first dielectric layer and the reinforcing sheet.

4. The flexible circuit board according to claim 1, characterized in that: All surfaces of the circuit layer and the reinforcing sheet are covered by the adhesive layer.

5. The flexible circuit board according to any one of claims 1 to 4, characterized in that: The reinforcing sheet and the circuit layer are located on the same surface of the first dielectric layer.

6. A terminal device, characterized in that: The terminal device comprises the flexible circuit board as claimed in any one of claims 1 to 5.

7. A method for manufacturing a flexible circuit board, characterized in that: The following steps are involved: Providing a circuit substrate, comprising a first dielectric layer and a circuit layer arranged on a surface of the first dielectric layer; A reinforcing sheet is arranged on the surface of the first dielectric layer, and the reinforcing sheet is arranged at a distance from the circuit layer; as well as A first protective layer is covered on the surface of the circuit layer and the reinforcing sheet to obtain the flexible circuit board.

8. The method for manufacturing a flexible circuit board according to claim 7, characterized in that: The first protective layer includes a glue layer and a second dielectric layer which are stacked, and the glue layer covers the circuit layer, the reinforcing sheet, and a surface of the first dielectric layer exposed to the circuit layer and the reinforcing sheet.

9. The method for manufacturing a flexible circuit board according to claim 7 or 8, characterized in that: The manufacturing method further comprises: before the step of covering the first protective layer, bonding the reinforcing sheet to the surface of the first dielectric layer using a bonding layer.

10. A method for manufacturing a flexible circuit board, characterized in that: The following steps are involved: Disposing a copper foil layer on the surface of the first carrier layer; Performing circuit fabrication on the copper foil layer to form a circuit layer; The reinforcing sheet is arranged on the surface of the second carrier film layer, and the viscosity of the first carrier film layer is different from the viscosity of the second carrier film layer; The first carrier film layer provided with the circuit layer and the second carrier film layer provided with the reinforcing sheet are pressed together, the circuit layer and the reinforcing sheet are spaced apart, and the one with less viscosity between the first carrier film layer and the second carrier film layer is removed; Covering the surface of the circuit layer and the reinforcing sheet with a first protective layer; as well as The first carrier film layer and the second carrier film layer that are not removed are removed, and a second protective layer is covered on the surface of the circuit layer and the reinforcing sheet to obtain the flexible circuit board.

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