Rigid-flex board and preparation method thereof
By using double-sided adhesive film to block the flow glue of the adhesive sheet during the preparation of the soft-hard bonding plate, the problem of adhesive sheet overflow is solved, product reliability and yield rate is improved, production process is simplified and costs are reduced.
Patent Information
- Application Number
- CN202510727920.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-06-03
- Publication Date
- 2025-08-29
AI Technical Summary
When making a thin media hard and hard bonding plate with a 4-layer structure, the resin of the bonding sheet is prone to overflow to the soft plate area under high temperature and high pressure, resulting in surface contamination or line damage in the soft plate area, affecting product reliability and yield. The existing process is complex and costly.
Double-sided tape film is used instead of traditional covering film. The production process and cost are reduced by setting a window opening area on the adhesive sheet and using double-sided tape film to block the adhesive sheet flow during pressing.
Effectively block the flow of adhesive sheets, improve product reliability and yield, simplify process flow, and reduce production costs.
Smart Images
Figure CN120568627A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the field of rigid-flex boards, and in particular to a rigid-flex board and a preparation method thereof. Background Art
[0002] In some related technologies, when making a soft-hard combination board, a window is first opened on the bonding sheet at a position corresponding to the soft board area, and then the soft board, bonding sheet and hard board are pressed together. Finally, the window position is deep-processed to remove the unnecessary hard board, thereby exposing the soft board area.
[0003] For four-layer, thin-dielectric rigid-flex boards, due to the thin dielectric layer, the high temperature and high pressure during lamination can cause excessive resin flow from the bonding sheet, overflowing onto the flexible board area. This can cause surface contamination or circuit damage in this area, impacting product reliability and yield. To address this issue, an ink resist method is currently used. This involves pre-screening resist ink on the flexible board area. After lamination, the copper foil in this area is removed by etching, and then the ink is removed with an alkaline solution. However, this process requires additional screen printing ink, which is cumbersome to operate, increasing process complexity and production costs. Summary of the Invention
[0004] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention provides a method for preparing a rigid-flex board, which can simplify the production process and reduce production costs.
[0005] The present invention also provides a rigid-flex board prepared using the above preparation method.
[0006] A method for preparing a rigid-flex PCB according to a first embodiment of the present invention includes the following steps: Provide core board, copper foil layer, bonding sheet and double-sided adhesive film; Laminating the double-sided adhesive film on the core board; A window area is provided on the bonding sheet, wherein the window area corresponds to the soft board area of the core board; Stack the copper foil layer and the core board in order, place the bonding sheet between the copper foil layer and the core board, and place the double-sided adhesive film in the window area; Laminating the core board, the copper foil layer and the bonding sheet; The copper foil layer located in the soft board area of the core board is removed to expose the soft board area of the core board at the window area.
[0007] A method for preparing a rigid-flex board according to an embodiment of the present invention has at least the following beneficial effects: the present application adheres a double-sided adhesive film to the core board, and the double-sided adhesive film is arranged in the window area of the bonding sheet. During pressing, the double-sided adhesive film can prevent the adhesive flow of the bonding sheet from flowing to the soft board area of the core board, thereby playing the role of adhesive blocking. Compared with the traditional process of using ink adhesive blocking protection, there is no need for additional ink coating, which reduces the steps such as silk screen printing and ink fading, reduces the production process, and reduces the operation complexity and production cost.
[0008] According to some embodiments of the present invention, providing a core board, a copper foil layer, an adhesive sheet, and a double-sided adhesive film further includes preparing the double-sided adhesive film, including: The double-sided adhesive film is processed to form a base film, a first adhesive layer and a second adhesive layer, and the first adhesive layer and the second adhesive layer are respectively connected to the opposite sides of the base film, the first adhesive layer is used to be bonded to the copper foil layer, and the second adhesive layer is used to be bonded to the core board.
[0009] According to some embodiments of the present invention, processing the double-sided adhesive film to form a base film, a first adhesive layer, and a second adhesive layer includes: The thickness of the first adhesive layer is processed to be smaller than the thickness of the second adhesive layer.
[0010] According to some embodiments of the present invention, processing the double-sided adhesive film to form a base film, a first adhesive layer, and a second adhesive layer further includes: The thickness of the second adhesive layer is processed to be 0.8 to 1.2 times the thickness of the conductive layer of the core board.
[0011] According to some embodiments of the present invention, processing the double-sided adhesive film to form a base film, a first adhesive layer, and a second adhesive layer includes: Epoxy adhesive or modified polyimide adhesive is coated on two opposite sides of the base film to form the first adhesive layer and the second adhesive layer.
[0012] According to some embodiments of the present invention, providing a window area on the bonding sheet includes: The edge of the window area is offset outward relative to the edge of the soft board area of the core board to form a safety area to prevent glue from flowing into the soft board area of the core board.
[0013] According to some embodiments of the present invention, the step of offsetting the edge of the window area outward relative to the edge of the soft board area of the core board to form a safety area includes: The width of the safety area is set to 0.2 mm to 0.3 mm.
[0014] According to some embodiments of the present invention, stacking the copper foil layer and the core board in sequence, disposing the bonding sheet between the copper foil layer and the core board, and disposing the double-sided adhesive film in the window area includes: The core board, the copper foil layer and the bonding sheet cooperate with the double-sided adhesive film to form a pressing unit, and buffer pads are arranged on the upper and lower surfaces of the pressing unit to ensure that the copper foil layer is in full contact with the double-sided adhesive film.
[0015] According to some embodiments of the present invention, the laminating of the core board, the copper foil layer, and the bonding sheet includes: Pressurizing is started at a temperature of 70° C. to 80° C., and pressing for a first preset time after pressurizing to bond the double-sided adhesive film to the copper foil layer; The temperature is above 190° C., and the pressing is performed for a second preset time, so that the bonding sheet is fully bonded to the core board and the copper foil layer.
[0016] According to some embodiments of the present invention, removing the copper foil layer located in the soft board area of the core board includes: The copper foil layer located in the soft board area of the core board is etched to realize opening of the cover.
[0017] The rigid-flex board according to the second embodiment of the present invention is prepared using the method for preparing the rigid-flex board according to the first embodiment.
[0018] The rigid-flex board according to the embodiment of the present invention has at least the following beneficial effects: the rigid-flex board of the present application meets the requirements of a thin dielectric rigid-flex board with a 4-layer structure, and there is no excessive glue flow in the soft board area of the rigid-flex board, thereby improving product reliability and yield.
[0019] Additional aspects and advantages of the present invention will be set forth in part in the description which follows and, in part, will be obvious from the description which follows, or may be learned by practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS
[0020] The present invention will be further described below with reference to the accompanying drawings and embodiments, in which: Figure 1 Schematic diagram of the process of preparing a rigid-flex PCB according to an embodiment of the present invention; Figure 2 Schematic diagram of copper foil layers and core boards stacked in sequence according to an embodiment of the present invention; Figure 3 This is a partial schematic diagram of the copper foil layer and the core board stacked in sequence according to an embodiment of the present invention; Figure 4 This is a schematic diagram of the structure of the double-sided adhesive film implemented in the present invention; Figure 5This is a schematic diagram of the position of the buffer pad during pressing in accordance with the present invention; Figure 6 Schematic diagram of the rigid-flex PCB manufacturing process when implementing the rigid-flex PCB manufacturing method according to an embodiment of the present application.
[0021] Reference numerals: 100, core board; 110, flexible board area; 200, copper foil layer; 300, bonding sheet; 310, window area; 400, double-sided adhesive film; 410, base film; 420, first adhesive layer; 430, second adhesive layer; 500, safety area; 600, buffer pad. DETAILED DESCRIPTION
[0022] The following describes embodiments of the present invention in detail. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended only to explain the present invention and are not to be construed as limiting the present invention.
[0023] In the description of the present invention, it should be understood that descriptions involving orientations, such as up, down, front, back, left, right, etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, they cannot be understood as limitations on the present invention.
[0024] In the description of the present invention, "several" means more than one, "plurality" means more than two, "greater than," "less than," and "exceed" are understood to exclude the number itself, while "above," "below," and "within" are understood to include the number itself. The use of "first" and "second" in the description is solely for the purpose of distinguishing technical features and should not be construed as indicating or implying relative importance, implicitly specifying the number of the indicated technical features, or implicitly specifying the order of the indicated technical features.
[0025] In the description of the present invention, unless otherwise clearly defined, terms such as setting, installing, and connecting should be understood in a broad sense, and technicians in the relevant technical field can reasonably determine the specific meanings of the above terms in the present invention based on the specific content of the technical solution.
[0026] In the description of the present invention, reference to terms such as "one embodiment," "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples" means that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the exemplary expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
[0027] Reference Figure 1 、 Figure 2 A first embodiment of the present invention provides a method for preparing a rigid-flex board, comprising the following steps: Step S100 : providing a core board 100 , a copper foil layer 200 , an adhesive sheet 300 and a double-sided adhesive film 400 .
[0028] In step S100 , the bonding sheet 300 is set to be a low-flow bonding sheet. Compared with a conventional bonding sheet, the low-flow bonding sheet can reduce the amount of glue flow.
[0029] Reference Figure 4 In step S100, a double-sided adhesive film 400 is prepared. Specifically, the double-sided adhesive film 400 is processed to form a base film 410, a first adhesive layer 420, and a second adhesive layer 430. The first adhesive layer 420 and the second adhesive layer 430 are respectively connected to opposite sides of the base film 410. The first adhesive layer 420 is used to adhere to the copper foil layer 200, and the second adhesive layer 430 is used to adhere to the core board 100.
[0030] Reference Figure 2 、 Figure 3 In some embodiments, the base film 410 is made of polyimide film, and a double-sided adhesive film 400 is used to replace the traditional cover film to be attached to the core board 100. The double-sided adhesive film 400 also has the bending and insulation properties of the cover film, meeting the requirements of the soft board area 110 (such as Figure 2 The area between the dotted lines A and B in the figure represents the basic performance requirements.
[0031] Reference Figure 3 、 Figure 4In some embodiments, the core board 100 is set as a soft board, and epoxy glue or modified polyimide glue is applied to the opposite sides of the base film 410 to form a first glue layer 420 and a second glue layer 430. The epoxy glue and the modified polyimide glue have good bonding properties and can form a bond between the core board 100 and the copper foil layer 200, thereby improving the reliability of the product structure. In addition, the epoxy glue and the modified polyimide glue also have good insulation properties, which can enhance the electrical performance of the rigid-flex board and enable the rigid-flex board to operate stably in complex environments such as high temperature and humidity. Of course, in actual design, the material of the first glue layer 420 and the material of the second glue layer 430 can be designed according to actual needs.
[0032] Reference Figure 4 In some embodiments, the thickness D1 of the first adhesive layer 420 is processed to be smaller than the thickness D2 of the second adhesive layer 430. The first adhesive layer 420 and the second adhesive layer 430 are designed asymmetrically, so that the double-sided adhesive film 400 has both bending and adhesive resistance properties. This not only meets the bending requirements of the flexible board area 110 of the core board 100, but also solves the adhesive flow problem during the lamination of the rigid-flex board with thin dielectric layers, simplifies the process flow, and improves product yield.
[0033] Reference Figure 3 、 Figure 4 In some embodiments, the thickness D1 of the first adhesive layer 420 is set to 3μm to 6μm in order to control the thickness of the double-sided adhesive film 400, so that the double-sided adhesive film 400 has good bending performance, reduces the stress impact on the circuit of the soft board area 110 of the core board 100, and ensures the flexibility of the soft board area 110 of the core board 100 when bending. At the same time, a conductive layer is provided on the surface of the core board 100, and the conductive layer is copper foil. The thickness D2 of the second adhesive layer 430 is processed to 0.8 to 1.2 times the thickness of the conductive layer of the core board 100, so that the second adhesive layer 430 can completely fill the gap between the double-sided adhesive film 400 and the core board 100, enhance the interlayer bonding tightness, and improve the stability of the overall structure of the soft-rigid board. If the thickness of the conductive layer is set to 20μm, the thickness D2 of the second adhesive layer 430 is set to 16μm to 24μm. Of course, in actual design, the thickness D1 of the first adhesive layer 420 and the thickness D2 of the second adhesive layer 430 can be designed according to actual needs.
[0034] Step S200: Attaching double-sided adhesive film 400 to core substrate 100. During lamination, double-sided adhesive film 400 blocks adhesive from flowing from adhesive sheet 300 toward soft substrate area 110 of core substrate 100, thereby acting as an adhesive barrier. Compared to conventional processes using ink adhesive barrier protection, this eliminates the need for additional ink application, reduces screen printing and ink fading steps, and streamlines the production process, reducing operational complexity and production costs.
[0035] Reference Figure 1 、 Figure 2 Step S300 : setting a window area 310 on the bonding sheet 300 , where the window area 310 corresponds to the soft board area 110 of the core board 100 .
[0036] In step S300, the window area 310 can be avoided for the placement of the double-sided adhesive film 400, so that the double-sided adhesive film 400 can enter the window area 310, blocking the glue flow of the adhesive sheet 300 during the lamination process, avoiding glue overflowing to unnecessary areas, and preventing glue flow from contaminating other components or affecting the performance of the soft-hard junction board.
[0037] Reference Figure 2 In step S300, the edge of the window area 310 is offset outward relative to the edge of the soft board area 110 of the core board 100 to form a safety area 500 to prevent glue from flowing into the soft board area 110 of the core board 100. Specifically, a safety area 500 is set on both sides of the soft board area 110 of the core board 100. The safety area 500 is used to compensate for the amount of glue flowing out of the bonding sheet 300, so that the glue of the bonding sheet 300 can fully fill the required area during subsequent lamination.
[0038] Reference Figure 2 In some embodiments, the width D of the safety area 500 is set to 0.2 mm to 0.3 mm based on the fact that the adhesive flow of the adhesive sheet 300 is 0.5 mm to 0.8 mm. In actual design, the width D of the safety area 500 can be designed according to actual needs.
[0039] Reference Figure 2 Step S400 : stack the copper foil layer 200 and the core board 100 in sequence, set the bonding sheet 300 between the copper foil layer 200 and the core board 100 , and set the double-sided adhesive film 400 in the window area 310 .
[0040] Reference Figure 2 In some embodiments, the copper foil layer 200, the bonding sheet 300, the core board 100, the bonding sheet 300, and the copper foil layer 200 are stacked in this order, and the core board 100, the copper foil layer 200 and the bonding sheet 300 cooperate with the double-sided adhesive film 400 to form a pressing unit.
[0041] Reference Figure 5 In some embodiments, cushioning pads 600 are positioned on the upper and lower surfaces of the lamination unit. The cushioning pads 600 are made of a highly conformable, cushioning material, ensuring sufficient contact between the copper foil layer 200 and the double-sided adhesive film 400, thereby providing a barrier to adhesive adhesion. The cushioning pads 600 ensure the proper filling of the adhesive sheet 300, preventing excessive adhesive flow from the adhesive sheet 300 and causing it to overflow onto the double-sided adhesive film 400, thereby ensuring a barrier to adhesive adhesion at the bonding point between the copper foil layer 200 and the double-sided adhesive film 400.
[0042] Step S500 : Laminating the core board 100 , the copper foil layer 200 and the bonding sheet 300 .
[0043] In some embodiments, the base film 410 of the double-sided adhesive film 400 is a polyimide film, and the first adhesive layer 420 and second adhesive layer 430 are epoxy adhesive or modified polyimide adhesive. The glass transition temperature of the double-sided adhesive film 400 is 60°C to 70°C. Furthermore, the dynamic viscosity curve data of the adhesive sheet 300 indicates that the adhesive sheet 300 begins to exhibit fluidity at 80°C, and the glass transition temperature of the adhesive sheet 300 is 190°C to 200°C. Therefore, a laminating procedure (as shown in the table below) is established based on the material properties to improve the laminating effect of the laminating unit. It should be noted that the dynamic viscosity curve data of the adhesive sheet 300 is prior art, and the present invention also improves upon this aspect, so the principles and processes will not be described in detail.
[0044]
[0045] In the lamination process, pressurization is started at a temperature of 70° C. to 80° C. and the pressing is continued for 8 minutes to bond the double-sided adhesive film 400 to the copper foil layer 200 , ie, the first adhesive of the double-sided adhesive film 400 to the copper foil layer 200 .
[0046] During the lamination process, the temperature is above 120° C., and when the fluidity of the bonding sheet 300 is the best, the pressure is increased to the maximum to allow the bonding sheet 300 to fully flow.
[0047] During the lamination process, the temperature is above 190° C. and the lamination is performed for 60 minutes to fully bond and solidify the bonding sheet 300 , the core board 100 , and the copper foil layer 200 .
[0048] It is understood that, under the lamination process and the action of the buffer pad 600, the first adhesive layer 420 of the double-sided adhesive film 400 is fully bonded to the copper foil layer 200 before the adhesive sheet 300 begins to flow. Therefore, when the adhesive sheet 300 begins to flow, the first adhesive layer 420 and the copper foil layer 200 cooperate to block the adhesive flow of the adhesive sheet 300, leaving no space for the adhesive sheet 300 to flow toward the double-sided adhesive film 400, thereby preventing the adhesive from flowing into the soft board area 110 of the core board 100.
[0049] In traditional screen printing ink resist protection methods, after lamination, the ink does not adhere to the copper foil layer 200, resulting in a cavity between the ink and the copper foil layer 200. During the subsequent baking process, bubbling and delamination are prone to occur in the screen printing ink area. In the present application, after lamination, the double-sided adhesive film 400 is bonded to the copper foil layer 200, and there is no cavity between the double-sided adhesive film 400 and the copper foil layer 200, which can avoid the problem of poor bubbling during the baking process.
[0050] Step S600 : removing the copper foil layer 200 located in the flexible board area 110 of the core board 100 to expose the flexible board area 110 of the core board 100 at the window area 310 .
[0051] Reference Figure 6 After the core board 100, copper foil layer 200 and bonding sheet 300 are pressed together, the process also includes drilling, electroplating, pattern transfer and other processes. During the pattern transfer process, the copper foil layer 200 located in the soft board area 110 of the core board 100 is etched to realize the opening of the cover, and the soft board area 110 of the soft and rigid board is exposed at the window area 310, which is simple and efficient. It should be noted that the soft board area 110 of the soft and rigid board is Figure 6 The area within the dotted box.
[0052] The rigid-flex board according to the second embodiment of the present invention is prepared using the method for preparing the rigid-flex board according to the first embodiment, meeting the requirements of a thin dielectric rigid-flex board with a four-layer structure. The flexible board area 110 of the rigid-flex board does not have excessive glue flow, thereby improving product reliability and yield.
[0053] While the embodiments of the present invention have been described in detail above with reference to the accompanying drawings, the present invention is not limited to the embodiments described above. Various modifications may be made within the scope of knowledge possessed by a person skilled in the art without departing from the spirit of the present invention. Furthermore, the embodiments of the present invention and the features thereof may be combined with one another unless there is a conflict.
Claims
1. A method for preparing a rigid-flex board, characterized in that: The following steps are involved: Provide core board, copper foil layer, bonding sheet and double-sided adhesive film; Laminating the double-sided adhesive film on the core board; A window area is provided on the bonding sheet, wherein the window area corresponds to the soft board area of the core board; Stack the copper foil layer and the core board in order, place the bonding sheet between the copper foil layer and the core board, and place the double-sided adhesive film in the window area; Laminating the core board, the copper foil layer and the bonding sheet; The copper foil layer located in the soft board area of the core board is removed to expose the soft board area of the core board at the window area.
2. The method for preparing a rigid-flex PCB according to claim 1, wherein: The core board, copper foil layer, bonding sheet and double-sided adhesive film are provided, including: The double-sided adhesive film is processed to form a base film, a first adhesive layer and a second adhesive layer, and the first adhesive layer and the second adhesive layer are respectively connected to the opposite sides of the base film, the first adhesive layer is used to be bonded to the copper foil layer, and the second adhesive layer is used to be bonded to the core board.
3. The method for preparing a rigid-flex PCB according to claim 2, wherein: The step of processing the double-sided adhesive film to form a base film, a first adhesive layer, and a second adhesive layer comprises: The thickness of the first adhesive layer is processed to be smaller than the thickness of the second adhesive layer.
4. The method for preparing a rigid-flex PCB according to claim 2, wherein: The step of processing the double-sided adhesive film to form a base film, a first adhesive layer, and a second adhesive layer further includes: The thickness of the second adhesive layer is processed to be 0.8 to 1.2 times the thickness of the conductive layer of the core board.
5. The method for preparing a rigid-flex PCB according to claim 2, wherein: The step of processing the double-sided adhesive film to form a base film, a first adhesive layer, and a second adhesive layer comprises: Epoxy adhesive or modified polyimide adhesive is coated on two opposite sides of the base film to form the first adhesive layer and the second adhesive layer.
6. The method for preparing a rigid-flex PCB according to claim 1, wherein: The step of providing a window area on the bonding sheet comprises: The edge of the window area is offset outward relative to the edge of the soft board area of the core board to form a safety area to prevent glue from flowing into the soft board area of the core board.
7. The method for preparing a rigid-flex PCB according to claim 6, wherein: The step of offsetting the edge of the window area outward relative to the edge of the soft board area of the core board to form a safety area includes: The width of the safety area is set to 0.2 mm to 0.3 mm.
8. The method for preparing a rigid-flex PCB according to claim 1, wherein: The method comprises stacking the copper foil layer and the core board in sequence, placing the bonding sheet between the copper foil layer and the core board, and placing the double-sided adhesive film in the window area, comprising: The core board, the copper foil layer and the bonding sheet cooperate with the double-sided adhesive film to form a pressing unit, and buffer pads are arranged on the upper and lower surfaces of the pressing unit to ensure that the copper foil layer is in full contact with the double-sided adhesive film.
9. The method for preparing a rigid-flex PCB according to claim 1, wherein: The laminating of the core board, the copper foil layer and the bonding sheet comprises: Pressurizing is started at a temperature of 70° C. to 80° C., and pressing for a first preset time after pressurizing to bond the double-sided adhesive film to the copper foil layer; The temperature is above 190° C., and the pressing is performed for a second preset time, so that the bonding sheet is fully bonded to the core board and the copper foil layer.
10. A rigid-flex board, characterized in that: The rigid-flex board is manufactured by the method for manufacturing the rigid-flex board according to any one of claims 1 to 9.