A method for controlling warping degree of asymmetric structure rigid-flex board

Abstract

The application relates to a control method for the warping degree of an asymmetric structure rigid-flex board. The rigid-flex board comprises a rigid plate, a flexible plate, a first adhesive layer and a second adhesive layer. A first side of the first adhesive layer is connected with the flexible plate, a second side of the first adhesive layer is connected with a first side of the rigid plate, and a first side of the second adhesive layer is connected with a second side of the rigid plate. The rigid-flex board provided in the embodiment of the application has the first adhesive layer between the rigid plate and the flexible plate and the second adhesive layer on the other side of the rigid plate, so that when the first adhesive layer and the second adhesive layer are heated in the pressing process, the first adhesive layer and the second adhesive layer both generate shrinkage stress towards the middle after cooling, and therefore the obtained rigid-flex board has symmetrical thermal expansion and contraction stress on both sides, and the warping degree of the rigid-flex board is reduced.

Description

Technical Field

[0001] This application relates to the field of PCB manufacturing technology, and in particular to a method for controlling the degree of warpage of an asymmetrical rigid-flex PCB. Background Technology

[0002] Currently, printed circuit boards (PCBs) on the market include the fabrication of rigid-flex boards.

[0003] In the existing technology, placing a PP sheet between a rigid plate and a flexible plate and then hot-pressing them together will result in a rigid-flex plate with an asymmetrical structure.

[0004] However, the warpage of the asymmetric rigid-flex plate obtained by this method is approximately 1.5%. When the warpage exceeds 0.75%, it affects the accuracy of mounting electronic component chips or other electronic parts onto the circuit rigid-flex plate. Therefore, how to reduce the warpage of the rigid-flex plate has become a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] Therefore, it is necessary to provide a method for controlling the warpage of asymmetric rigid-flex plates that can reduce the warpage of rigid-flex plates, addressing the aforementioned technical problems.

[0006] In a first aspect, this application provides a rigid-flex plate, which includes a rigid plate, a flexible plate, a first adhesive layer, and a second adhesive layer;

[0007] The first side of the first adhesive layer is connected to the flexible plate, the second side of the first adhesive layer is connected to the first side of the rigid plate, and the first side of the second adhesive layer is connected to the second side of the rigid plate.

[0008] In one embodiment, the rigid-flex plate further includes a first metal layer connected to a second side of the second adhesive layer.

[0009] In one embodiment, the rigid plate includes a rigid material layer and a second metal layer, the rigid material layer being connected to the second metal layer;

[0010] The second side of the first adhesive layer is connected to the second metal layer, and the first side of the second adhesive layer is connected to the rigid material layer.

[0011] In one embodiment, the flexible plate includes a flexible material layer, a third metal layer and a fourth metal layer, with a first side of the flexible material layer connected to the third metal layer and a second side of the flexible material layer connected to the fourth metal layer.

[0012] The first side of the first adhesive layer is connected to the fourth metal layer.

[0013] In one embodiment, the first adhesive layer and the second adhesive layer are PP sheets.

[0014] In one embodiment, the first metal layer is a copper foil.

[0015] Secondly, this application also provides a method for controlling the warpage of an asymmetric rigid-flexible plate, the rigid-flexible plate including the rigid-flexible plate in the above embodiments, the method comprising:

[0016] The first adhesive layer is disposed between the first side of the rigid plate and the flexible plate, and the second adhesive layer is disposed on the second side of the rigid plate to obtain the initial structure;

[0017] The rigid-flex plate is obtained based on this initial structure.

[0018] In one embodiment, obtaining the rigid-flex plate based on the initial structure includes:

[0019] The initial structure was hot-pressed together to obtain the rigid-flex plate.

[0020] In one embodiment, obtaining the rigid-flex plate based on the initial structure includes:

[0021] A first metal layer is disposed on the second side of the second adhesive layer in the initial structure to obtain an intermediate structure;

[0022] The intermediate structure is hot-pressed to obtain the rigid-flex plate.

[0023] In one embodiment, the method further includes:

[0024] The second metal layer in the rigid plate and the fourth metal layer in the flexible plate are etched.

[0025] The first adhesive layer is disposed between the etched second metal layer and the flexible plate including the etched fourth metal layer, and the second adhesive layer is disposed on the second side of the rigid plate to obtain the initial structure.

[0026] The aforementioned method for controlling the warpage of an asymmetric rigid-flex plate includes a rigid plate, a flexible plate, a first adhesive layer, and a second adhesive layer. The first side of the first adhesive layer is connected to the flexible plate, the second side of the first adhesive layer is connected to the first side of the rigid plate, and the first side of the second adhesive layer is connected to the second side of the rigid plate. In conventional techniques, a rigid-flex plate with a PP sheet placed between the rigid and flexible plates results in a significant warpage on one side due to the PP sheet being heated during pressing and generating shrinkage stress towards the center upon cooling. The flexible plate is typically thinner than the rigid plate. However, the rigid-flex plate provided in this embodiment has a first adhesive layer between the rigid and flexible plates, and a second adhesive layer on the other side of the rigid plate. Therefore, when the first and second adhesive layers are heated during pressing and generate shrinkage stress towards the center upon cooling, the resulting rigid-flex plate exhibits symmetrical thermal expansion and contraction stress on both sides, reducing the warpage of the rigid-flex plate. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments or related technologies of this application, the accompanying drawings used in the description of the embodiments or related technologies will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is a schematic diagram of an asymmetric rigid-flex plate in traditional technology.

[0029] Figure 2 This is one of the structural diagrams of an asymmetric rigid-flexible plate in one embodiment;

[0030] Figure 3 This is the second structural diagram of an asymmetric rigid-flexible plate in one embodiment;

[0031] Figure 4 This is the third structural diagram of an asymmetric rigid-flexible plate in one embodiment;

[0032] Figure 5 This is one of the flowcharts illustrating a method for controlling the warping degree of an asymmetric rigid-flexural plate in one embodiment;

[0033] Figure 6 This is a second flowchart illustrating a method for controlling the warping degree of an asymmetric rigid-flexural plate in one embodiment.

[0034] Figure 7 This is the fourth structural diagram of an asymmetric rigid-flexible plate in one embodiment.

[0035] Explanation of reference numerals in the attached figures:

[0036] 10 - Rigid-flexible sheet; 100 - Rigid sheet; 200 - Flexible sheet;

[0037] 300 - First adhesive layer; 400 - Second adhesive layer; 500 - First metal layer;

[0038] 101 - Rigid material layer; 102 - Second metal layer; 201 - Flexible material layer;

[0039] 202 - Third metal layer; 203 - Fourth metal layer. Detailed Implementation

[0040] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0041] Currently, printed circuit boards (PCBs) on the market typically use rigid-flex boards. In existing technology, a PP sheet is placed between a rigid board and a flexible board, and then thermo-pressed together to obtain the rigid-flex board. For example, ... Figure 1 As shown, the flexible board includes a flexible material and metal layers on both sides, while the rigid board consists of a rigid material and metal layers on both sides. The thickness of the metal layers is 18 μm, the thickness of the flexible material is 50 μm, and the thickness of the rigid material is 760 μm. A PP sheet is placed between the rigid and flexible boards and then hot-pressed to obtain a rigid-flex board. Because the PP sheet is heated during the pressing process, it generates shrinkage stress towards the center upon cooling. Therefore, the resulting rigid-flex board has thermal expansion and contraction stress on one side, leading to a greater degree of warping on the side with the thinner flexible board. The warping degree of the rigid-flex board obtained in this way is approximately 1.5%. When the warping degree of the rigid-flex board exceeds 0.75%, it will affect the accuracy of mounting electronic component chips or other electronic components onto the circuit rigid-flex board. Therefore, how to reduce the warping degree of the rigid-flex board has become an urgent problem to be solved by those skilled in the art.

[0042] To address the aforementioned issues, in one exemplary embodiment, such as Figure 2 As shown, a rigid-flex plate 10 is provided, which includes a rigid plate 100, a flexible plate 200, a first adhesive layer 300, and a second adhesive layer 400.

[0043] The first side of the first adhesive layer 300 is connected to the flexible plate 200, the second side of the first adhesive layer 300 is connected to the first side of the rigid plate 100, and the first side of the second adhesive layer 400 is connected to the second side of the rigid plate 100.

[0044] In this design, the rigid plate 100 can be a rigid substrate with a metal layer. The flexible plate 200 can be a flexible substrate with a metal layer. The first adhesive layer 300 can be made of materials such as acrylonitrile-butadiene-styrene copolymer, polyvinyl chloride, or polyethylene. The second adhesive layer 400 can also be made of materials such as acrylonitrile-butadiene-styrene copolymer, polyvinyl chloride, or polyethylene.

[0045] Optionally, the first and second adhesive layers are made of PP sheets, i.e., polypropylene material.

[0046] In this embodiment, the two sides of the first adhesive layer 300 can be connected to the flexible plate 200 and the rigid plate 100 respectively, and the second adhesive layer 400 can be connected to the side of the rigid plate 100 that is not connected to the first adhesive layer 300. That is, the first side of the first adhesive layer 300 is connected to the flexible plate 200, and the second side of the first adhesive layer 300 is connected to the first side of the rigid plate 100. The first side of the second adhesive layer 400 is connected to the second side of the rigid plate 100.

[0047] For example, the thicknesses of the rigid plate 100, flexible plate 200, first adhesive layer 300, and second adhesive layer 400 in the rigid-flex plate can be set as follows: the thickness of the first adhesive layer 300 is 100 μm, the thickness of the second adhesive layer 400 is 100 μm, the thickness of the rigid plate 100 is 678 μm, and the thickness of the flexible plate 200 is 86 μm.

[0048] The aforementioned rigid-flex plate 10 includes a rigid plate 100, a flexible plate 200, a first adhesive layer 300, and a second adhesive layer 400. The first side of the first adhesive layer 300 is connected to the flexible plate 200, the second side of the first adhesive layer 300 is connected to the first side of the rigid plate 100, and the first side of the second adhesive layer 400 is connected to the second side of the rigid plate 100. In conventional technology, a rigid-flex plate with a PP sheet placed between the rigid plate and the flexible plate suffers from thermal expansion and contraction stress on one side due to the PP sheet being heated during the pressing process and generating shrinkage stress towards the center after cooling. This results in a significant degree of warping on one side of the rigid-flex plate. The thickness of the flexible plate is typically less than the thickness of the rigid plate. The rigid-flex plate provided in this embodiment has a first adhesive layer between the rigid plate and the flexible plate, and a second adhesive layer on the other side of the rigid plate. Therefore, when the first adhesive layer and the second adhesive layer are heated during the pressing process, after cooling, both the first adhesive layer and the second adhesive layer generate shrinkage stress towards the middle. Thus, the resulting rigid-flex plate has symmetrical thermal expansion and contraction stress on both sides, which reduces the warping degree of the rigid-flex plate.

[0049] In one exemplary embodiment, such as Figure 3 As shown, the rigid-flex plate also includes a first metal layer 500, which is connected to the second side of the second adhesive layer 400.

[0050] Optionally, the first metal layer is copper foil.

[0051] In this embodiment, the rigid-flex plate further includes a first metal layer 500, a first side of the first adhesive layer 300 connected to the flexible plate 200, and a second side of the first adhesive layer 300 connected to the first side of the rigid plate 100. A first side of the second adhesive layer 400 is connected to the second side of the rigid plate 100. A second side of the second adhesive layer 400 is connected to the first metal layer 500.

[0052] For example, when the thickness of the first adhesive layer 300 is 100µm, the thickness of the second adhesive layer 400 is 100µm, the thickness of the rigid plate 100 is 678µm, and the thickness of the flexible plate 200 is 86µm, the thickness of the first metal layer 500 in the rigid-flex plate can be 18µm.

[0053] In this embodiment, the rigid-flex plate further includes a first metal layer 500, which is connected to the second side of the second adhesive layer 400, and the first metal layer 500 enables the interlayer wires to be interconnected.

[0054] In one exemplary embodiment, such as Figures 2-4 As shown, the rigid plate 100 includes a rigid material layer 101 and a second metal layer 102, and the rigid material layer 101 and the second metal layer 102 are connected.

[0055] The second side of the first adhesive layer 300 is connected to the second metal layer 102, and the first side of the second adhesive layer 400 is connected to the rigid material layer 101.

[0056] The second metal layer 102 can be copper foil.

[0057] In this embodiment, the rigid plate 100 may include a rigid material layer 101 and a second metal layer 102. The second metal layer 102 may be a metal layer with etched circuitry. The rigid material layer 101 may be connected to the second metal layer 102 with etched circuitry, the second side of the first adhesive layer 300 may be connected to the second metal layer 102 with etched circuitry, and the first side of the second adhesive layer 400 may be connected to the rigid material layer 101.

[0058] It should be noted that when manufacturing the rigid plate 100 in the embodiments of this application, one side of the metal layer on both sides of the ordinary rigid plate (such as the rigid plate in the conventional technology) can be completely etched away to obtain a rigid plate that only includes the second metal layer and the rigid material layer.

[0059] For example, the thickness of the rigid material layer 101 is 660 μm, and the thickness of the second metal layer 102 is 18 μm. That is, the sum of the thickness of the rigid plate 100, the thickness of the second adhesive layer 400, and the thickness of the first metal layer 500 in this embodiment is equal to the thickness of a normal rigid plate.

[0060] In one exemplary embodiment, such as Figure 4 As shown, the flexible plate 200 includes a flexible material layer 201, a third metal layer 202 and a fourth metal layer 203. The first side of the flexible material layer 201 is connected to the third metal layer 202, and the second side of the flexible material layer 201 is connected to the fourth metal layer 203.

[0061] The first side of the first adhesive layer 300 is connected to the fourth metal layer 203.

[0062] The third metal layer 202 and the fourth metal layer 203 can be copper foil.

[0063] In this embodiment, the flexible board 200 includes a flexible material layer 201, a third metal layer 202, and a fourth metal layer 203. The fourth metal layer 203 may be a metal layer with etched circuitry. A first side of the flexible material layer 201 can be connected to the third metal layer 203, a second side of the flexible material layer 201 can be connected to the fourth metal layer 203 with etched circuitry, and a first side of the first adhesive layer 300 can be connected to the fourth metal layer 203 with etched circuitry. The third and fourth metal layers, located on opposite sides of the flexible material layer, effectively provide conductivity to the insulating material.

[0064] For example, the thickness of the flexible material layer 201 is 50 μm, the thickness of the third metal layer 202 is 18 μm, and the thickness of the fourth metal layer 203 is 18 μm.

[0065] In one exemplary embodiment, a method for controlling the warpage of an asymmetric rigid-flexible plate is provided for fabricating the rigid-flexible plate 10 in the above embodiment. For example... Figure 5 As shown, the method includes the following steps:

[0066] S501. A first adhesive layer is placed between the first side of the rigid plate and the flexible plate, and a second adhesive layer is placed on the second side of the rigid plate to obtain an initial structure.

[0067] In this embodiment, a first adhesive layer can be placed between the first side of the rigid plate and the flexible plate, and a second adhesive layer can be bonded to the second side of the rigid plate to obtain an initial structure. That is, the initial structure is obtained by bonding the flexible plate, the first adhesive layer, the rigid plate, and the second adhesive layer in that order.

[0068] S502. Obtain the rigid-flex plate based on the initial structure.

[0069] In this embodiment of the application, the initial structure can be press-fitted to obtain a rigid-flex plate.

[0070] Optionally, a copper foil layer can be bonded to the second side of the second adhesive layer of the initial structure to obtain an intermediate structure, and then the intermediate structure can be pressed to obtain a rigid-flex plate.

[0071] The aforementioned method for controlling the warpage of asymmetric rigid-flexible plates involves placing a first adhesive layer between the first side of the rigid plate and the flexible plate, and placing a second adhesive layer on the second side of the rigid plate to obtain an initial structure, from which a rigid-flexible plate is obtained. In conventional techniques, rigid-flexible plates with a PP sheet placed between a rigid and flexible plate suffer from thermal expansion and contraction stress on one side due to the PP sheet being heated during pressing and generating inward shrinkage stress upon cooling. This results in significant warpage on the flexible plate side. The flexible plate is typically thinner than the rigid plate. However, the rigid-flexible plate provided in this embodiment has a first adhesive layer between the rigid and flexible plates, and a second adhesive layer on the other side of the rigid plate. Therefore, when the first and second adhesive layers are heated during pressing and generate inward shrinkage stress upon cooling, both layers exhibit symmetrical thermal expansion and contraction stress, reducing the warpage of the rigid-flexible plate.

[0072] Optionally, the pressing process can be hot pressing, that is, the initial structure can be hot pressed to obtain a rigid-flex plate.

[0073] Optionally, the first metal layer can be placed on the second side of the second adhesive layer in the initial structure to obtain an intermediate structure, and then the intermediate structure can be hot-pressed to obtain a rigid-flex plate.

[0074] In one exemplary embodiment, such as Figure 6 As shown, the method also includes:

[0075] S601, Etch the second metal layer in the rigid plate and the fourth metal layer in the flexible plate.

[0076] Specifically, the second metal layer in the rigid board and the fourth metal layer in the flexible board can be etched before the initial structure is constructed, thereby creating the circuitry required for the circuit board.

[0077] S602. A first adhesive layer is disposed between an etched second metal layer and a flexible plate including an etched fourth metal layer, and a second adhesive layer is disposed on the second side of a rigid plate to obtain an initial structure.

[0078] In this embodiment, a first adhesive layer can be disposed between an etched second metal layer and a flexible plate including an etched fourth metal layer, and a second adhesive layer can be disposed on the second side of a rigid plate to obtain an initial structure, thereby making the rigid-flexible plate obtained based on the initial structure practical.

[0079] For example, a detailed rigid-flex plate structure can be as follows: Figure 7 As shown. The thickness of the first adhesive layer in the rigid-flex plate is 100µm, and the thickness of the second adhesive layer is 100µm. The thickness of the rigid plate is 678µm, the thickness of the rigid material layer in the rigid plate is 660µm, the thickness of the flexible plate is 86µm, the thickness of the flexible material layer in the flexible plate is 50µm, the thickness of the third metal layer is 18µm, and the thickness of the fourth metal layer is 18µm. The thickness of the first metal layer 500 can be 18µm. The thickness of the second metal layer is 18µm. The rigid-flex plate 10 is obtained by laminating the third metal layer, the flexible material layer, the third metal layer, the first adhesive layer (PP sheet), the second metal layer, the rigid material layer, the second adhesive layer (PP sheet), and the first metal layer in that order, followed by hot pressing.

[0080] It should be understood that although the steps in the flowcharts of the above embodiments are shown sequentially according to the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless explicitly stated herein, there is no strict order restriction on the execution of these steps, and they can be executed in other orders. Moreover, at least some steps in the flowcharts of the above embodiments may include multiple steps or multiple stages. These steps or stages are not necessarily completed at the same time, but can be executed at different times. The execution order of these steps or stages is not necessarily sequential, but can be performed alternately or in turn with other steps or at least some of the steps or stages of other steps.

[0081] Those skilled in the art will understand that all or part of the processes in the above embodiments can be implemented by a computer program instructing related hardware. The computer program can be stored in a non-volatile computer-readable storage medium. When executed, the computer program can include the processes of the embodiments described above. Any references to memory, databases, or other media used in the embodiments provided in this application can include at least one of non-volatile and volatile memory. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetic random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory can include random access memory (RAM) or external cache memory, etc. By way of illustration and not limitation, RAM can take many forms, such as Static Random Access Memory (SRAM) or Dynamic Random Access Memory (DRAM). The databases involved in the embodiments provided in this application may include at least one type of relational database and non-relational database. Non-relational databases may include, but are not limited to, blockchain-based distributed databases. The processors involved in the embodiments provided in this application may be general-purpose processors, central processing units, graphics processing units, digital signal processors, programmable logic devices, quantum computing-based data processing logic devices, etc., and are not limited to these.

[0082] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0083] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

Claims

1. A rigid-flex plate, characterized in that, The rigid-flex plate includes a rigid plate, a flexible plate, a first adhesive layer, and a second adhesive layer; the first adhesive layer and the second adhesive layer are PP sheets; The first side of the first adhesive layer is connected to the flexible plate, the second side of the first adhesive layer is connected to the first side of the rigid plate, and the first side of the second adhesive layer is connected to the second side of the rigid plate; the thickness of the rigid plate is 678 micrometers, the thickness of the flexible plate is 86 micrometers, the thickness of the first adhesive layer is 100 micrometers, and the thickness of the second adhesive layer is 100 micrometers.

2. The rigid-flex plate according to claim 1, characterized in that, The rigid-flex plate further includes a first metal layer, which is connected to a second side of the second adhesive layer.

3. The rigid-flex plate according to claim 1, characterized in that, The rigid plate includes a rigid material layer and a second metal layer, wherein the rigid material layer is connected to the second metal layer; The second side of the first adhesive layer is connected to the second metal layer, and the first side of the second adhesive layer is connected to the rigid material layer.

4. The rigid-flex plate according to claim 1, characterized in that, The flexible board includes a flexible material layer, a third metal layer, and a fourth metal layer. A first side of the flexible material layer is connected to the third metal layer, and a second side of the flexible material layer is connected to the fourth metal layer. The first side of the first adhesive layer is connected to the fourth metal layer.

5. The rigid-flex plate according to claim 2, characterized in that, The first metal layer is copper foil.

6. A method for controlling the warpage of an asymmetric rigid-flexural plate, characterized in that, The rigid-flex plate includes the rigid-flex plate as described in any one of claims 1-5, and the method includes: The first adhesive layer is disposed between the first side of the rigid plate and the flexible plate, and the second adhesive layer is disposed on the second side of the rigid plate to obtain the initial structure; The rigid-flex plate is obtained based on the initial structure.

7. The method according to claim 6, characterized in that, The process of obtaining the rigid-flexible plate based on the initial structure includes: The initial structure is hot-pressed to obtain the rigid-flex plate.

8. The method according to claim 6, characterized in that, The process of obtaining the rigid-flexible plate based on the initial structure includes: A first metal layer is disposed on the second side of the second adhesive layer in the initial structure to obtain an intermediate structure; The intermediate structure is hot-pressed to obtain the rigid-flex plate.

9. The method according to claim 6, characterized in that, The method further includes: The second metal layer in the rigid plate and the fourth metal layer in the flexible plate are etched. The first adhesive layer is disposed between the etched second metal layer and the flexible plate including the etched fourth metal layer, and the second adhesive layer is disposed on the second side of the rigid plate to obtain the initial structure.

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