Method for manufacturing a rigid-flex printed circuit board

Abstract

The application provides a preparation method of a rigid-flexible combination board, which comprises the following steps: stacking to form a first composite board, the first composite board having a functional area and a cutting-off area, the cutting-off area being annularly arranged at the periphery of the functional area, comprising the following steps: covering a sub-board layer on the top layer of the first composite front plate, the first adhesive sheet of the outer layer having a first window, filling an elastic body in the mounting hole, and then forming the first composite front plate on the top layer of the sub-board layer, the projection of the combination of the sub-board area and the flexible area being coincident with each adjacent first window; manufacturing the first composite board into a first pretreatment board; removing the part of the first pretreatment board corresponding to the first window, and then removing the part of the first pretreatment board corresponding to the cutting-off area. The preparation method provided by the application can solve the pollution problem caused by hole cracking, and is also beneficial to reducing the production cost and controlling the product quality.

Description

Technical Field

[0001] This invention relates to the technical field of circuit boards, and more specifically to a method for preparing a rigid-flex board. Background Technology

[0002] Currently, to adapt rigid-flex PCBs to different performance requirements, the main board and sub-board areas are typically made with different thicknesses. This is usually achieved through multiple lamination processes using release film, requiring repeated adjustments to process parameters. This is detrimental to reducing production costs and makes it difficult to control product quality. Furthermore, when the sub-board area has mounting holes, the lamination process can easily lead to cracking and chemical injection, causing contamination. Summary of the Invention

[0003] In order to overcome the shortcomings of the prior art, the present invention aims to provide a method for preparing a rigid-flexible plate. The preparation method of the rigid-flexible plate can solve the pollution problem caused by hole fracturing. In addition, the preparation method is also conducive to reducing production costs and controlling product quality.

[0004] To solve the above problems, the technical solution adopted by the present invention is as follows: A method for manufacturing a rigid-flex plate, the rigid-flex plate comprising a main plate region, a secondary plate region, and a flexible region connecting the two, the secondary plate region having mounting holes, the manufacturing method comprising the following steps: A first composite board is formed by stacking materials. The first composite board has a functional area and a cut-off area. The cut-off area is arranged around the periphery of the functional area. The step of stacking to form the first composite board includes: covering a sub-board layer on the top layer of a first composite front board. The sub-board layer has the flexible area and the sub-board area. The first composite front board includes a stacked rigid circuit board and a first adhesive film. The outer layer of the first adhesive film has a first window. After filling the mounting hole with an elastomer, the first composite front board is formed on the top layer of the sub-board layer. The outer layer of the first adhesive film of each first composite front board is adjacent to the sub-board layer. The conductive layer of the rigid circuit board on the outer layer of each first composite front board forms the outer layer of the first composite board. The combined projection of the sub-board area and the flexible area coincides with each adjacent first window. The first composite board is made into a first pre-processed board. The steps of forming the first pre-processed board include at least sequential lamination, hole opening, copper plating, forming the outermost circuit layer, and solder mask. The elastomer is a thermosetting elastomer, or the plasticizing temperature of the elastomer is higher than the lamination temperature. Remove the portion of the first pre-processed plate corresponding to the first window, exposing the sub-plate area and the flexible area to the surface. Then remove the portion of the first pre-processed plate corresponding to the cut-off area, so that the portion other than the sub-plate area and the flexible area forms the main plate area, thus obtaining a rigid-flexible bonded plate.

[0005] In some possible implementations, the preparation of the first adhesive film having the first window includes: After placing the second adhesive film at the pre-positioned position of the first adhesive film on the outer layer, remove the portion of the second adhesive film corresponding to the combined projection of the flexible area and the sub-plate area, thereby forming the first window to obtain the first adhesive film.

[0006] In some possible implementations, the top surface of the elastomer is positioned below the outer edge of the mounting hole.

[0007] In some possible implementations, the step of forming the first pretreatment plate further includes: Before the pressing step, each layer of the first composite board is fixed with rivets, and the rivets are fixed in the cutting area.

[0008] In some possible implementations, the step of forming the first pretreatment plate further includes: After the solder resist step, surface treatment is performed.

[0009] In some possible implementations, the preparation of the sub-plate layer includes the following steps: Stacking to form a second composite board includes: covering a flexible circuit board on top of a second composite front board, the flexible circuit board having the flexible area, the second composite front board including stacked circuit boards and a third adhesive film, the outer layer of the third adhesive film having a second window, forming the second composite front board on top of the flexible circuit board, the projection of the flexible area coinciding with each adjacent second window, the outer layer of the third adhesive film of the second composite front board adjacent to the flexible circuit board, and the conductive layer of the outer layer of the circuit board of each second composite front board forming the outer layer of the second composite board; The second composite board is made into a second pre-processed board by at least sequentially performing processes of lamination, drilling, copper plating, and forming the outermost circuit layer; Remove the portion of the second pre-processing plate corresponding to the second window, thereby exposing the flexible area to the surface.

[0010] In some possible implementations, the preparation of the third adhesive film having the second window includes: After placing the fourth adhesive film at the pre-positioned position of the outer third adhesive film, the portion of the fourth adhesive film corresponding to the projection of the flexible area is removed, thereby forming the second window to obtain the third adhesive film.

[0011] In some possible implementations, the first composite board has a plurality of said functional areas, and the step of removing the portion of the first pre-treated board corresponding to the cut-off area includes: First, remove the outer portion of the cut-off area, and then remove the portion of the cut-off area between two adjacent functional areas.

[0012] In some possible implementations, the fabrication of the sub-plate layer further includes: Apply peelable adhesive to the top and bottom of the flexible area; The peelable adhesive is removed after browning treatment.

[0013] Compared with the prior art, the beneficial effects of the present invention are as follows: In this application, an elastomer is filled into the mounting hole before lamination. This elastomer acts as a lamination buffer, preventing stress cracking of the mounting hole during multi-layer lamination. Therefore, the preparation method provided in this application solves the contamination problem caused by hole cracking. Furthermore, by setting up functional areas and separation areas, and cooperating with a first adhesive film with a first window, this application allows for the formation of main board areas, sub-board areas, and flexible areas of different thicknesses through a single lamination process. That is, the lamination thickness of the board remains constant in a single step. Therefore, the preparation method provided in this application does not require multiple adjustments to process parameters based on the varying thicknesses of the laminated boards from multiple multi-layer laminations. This preparation method also helps reduce production costs and facilitates quality control.

[0014] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. Attached Figure Description

[0015] Figure 1 A flowchart of a method for preparing a rigid-flexible plate according to an embodiment of this application is provided; Figure 2 This is a side view of a rigid-flexible plate. Figure 3 for Figure 2 A top view of the solid sub-plate area and flexible area shown; Figure 4 Top view showing the layout of the functional areas and cutting areas of the first composite panel; Figure 5 A top view showing another arrangement of the functional areas and cutting areas of the first composite panel; Figure 6 This is a simplified cross-sectional view of the first composite plate; Figure 7 This is a simplified cross-sectional view of the second composite plate.

[0016] Explanation of reference numerals in the attached figures: 10- Rigid-flexible composite board; 11- Main board area; 12- Sub-board area; 13- Flexible area; 120- Mounting hole; 20- Elastomer; 30- First composite board; 31- Functional area; 32- Cutting area; 40- First composite front board; 41- Rigid circuit board; 42- First adhesive film; 420- First window; 50- Sub-board layer; 60- Second composite front board; 61- Circuit board; 62- Third adhesive film; 620- Second window; 70- Flexible circuit board; 80- Second composite board. Detailed Implementation

[0017] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0018] The terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are constructed to distinguish different objects, not to describe a particular order. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. It should be noted that when an element is referred to as "fixed to" another element, it can be directly on the other element or there may be an intervening element. When an element is referred to as "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The accompanying drawings only depict the stacking relationship between different layers and do not limit their thickness relationships.

[0019] Reference Figure 1 One embodiment of this application provides a method for preparing a rigid-flexible plate, referring to... Figure 2 The rigid-flex plate 10 includes a main plate area 11, a secondary plate area 12, and a flexible area 13 connecting the two, as shown in the reference. Figure 3 The sub-plate area 12 is provided with mounting holes 120. For example, the main plate area 11 and the flexible area 13 can both be rigid structures. The preparation method includes the following steps.

[0020] Step S101, stacking to form the first composite plate 30, referring to... Figures 3 to 6 The first composite panel 30 has a functional area 31 and a cutting area 32, with the cutting area 32 surrounding the functional area 31.

[0021] Among them, the first composite plate 30 is formed by stacking (refer to) Figure 7The steps include the following.

[0022] A sub-board layer 50 is covered on top of the first composite front panel 40. The sub-board layer 50 has a flexible region 13 and a sub-board region 12. The first composite front panel 40 includes a stacked rigid circuit board 41 and a first adhesive film 42. The outer layer of the first adhesive film 42 has a first window 420. Exemplarily, the number of both the rigid circuit board 41 and the first adhesive film 42 can be one or more. The number of both the rigid circuit board 41 and the first adhesive film 42 can be adjusted according to the thickness requirements and the thickness of the sub-board layer 50. For example, if the first composite front panel 40 with a layer of rigid circuit board 41 and a layer of first adhesive film 42 can meet the thickness requirements of the main board region 11, then the number of both the rigid circuit board 41 and the first adhesive film 42 can be one. If the requirements cannot be met, the alternating number of layers of rigid circuit board 41 and first adhesive film 42 can be increased. In this embodiment, the first composite front panel 40 includes a stacked rigid circuit board 41 and a first adhesive film 42. Reducing the number of laminating films in the board assembly is beneficial for appropriately reducing the lamination temperature.

[0023] Elastomer 20 is filled into mounting hole 120 (see reference). Figure 3 After that, a first composite front panel 40 is formed on the top layer of the sub-panel layer 50. The outer first adhesive film 42 of each first composite front panel 40 is adjacent to the sub-panel layer 50. That is, the first adhesive film 42 adjacent to the sub-panel layer 50 has a first window 420, which facilitates the removal of part of the structure in subsequent steps to expose part of the area to the surface. The conductive layer of the outer rigid circuit board 41 of each first composite front panel 40 forms the outer layer of the first composite board 30. The combined projection of the sub-panel area 12 and the flexible area 13 coincides with each adjacent first window 420.

[0024] In some embodiments, the preparation of the first adhesive film 42 having a first window 420, as shown in the figure, includes the following steps: after placing a second adhesive film at a pre-positioned position on the outer first adhesive film 42, the portion of the second adhesive film corresponding to the combined projection of the flexible region 13 and the sub-plate region 12 is removed, thereby forming the first window 420 to obtain the first adhesive film 42. Specifically, for the bottom first composite front plate 40, the step of forming the first adhesive film 42 having the first window 420 is as follows: after the second adhesive film forms the top layer of the first composite front plate 40, the portion of the second adhesive film corresponding to the combined projection of the flexible region 13 and the sub-plate region 12 is removed, thereby forming the first window 420. For the top-layer first composite front panel 40, the second adhesive film is first covered on the sub-panel layer 50, and then the portion of the second adhesive film corresponding to the combined projection of the flexible area 13 and the sub-panel area 12 is removed to form the first window 420. Then, the rigid circuit board 41 is stacked. If it is necessary to increase the number of circuit board layers in the first composite front panel 40, the first adhesive film 42 (without the first window 420) and the rigid circuit board 41 are stacked sequentially. Using a covering-and-opening method to form the first adhesive film 42 with the first window 420 improves operational convenience and stacking accuracy.

[0025] In another embodiment, the first adhesive film 42 with the first window 420 can be directly attached to the corresponding rigid circuit board 41 or the corresponding sub-board layer 50.

[0026] In some embodiments, the top surface of the elastomer 20 is set below the outer edge of the mounting hole 120, thereby preventing the elastomer 20 from bulging out and breaking through the upper structure during pressing. The construction of the elastomer 20 is conducive to further ensuring the quality of the finished board and to improving the adaptability of the first composite board 30 to process parameters, that is, it is not necessary to strictly control the pressing parameters to prevent the problem of breaking.

[0027] The rigid circuit board 41 may include a single-layer, double-layer, or multi-layer circuit board. The substrate of the rigid circuit board 41 may be made of a rigid material, such as glass fiber or ceramic, or the rigid circuit board 41 may be formed by stacking multiple flexible circuit boards to form a rigid structure. The rigid circuit board 41 can be obtained using conventional circuit board technology, so its specific manufacturing process will not be described in detail. For example, the mounting hole 120 may be a conductive hole or a non-conductive hole, and may be a blind hole or a through hole.

[0028] In some embodiments, the preparation of the sub-layer 50 includes the following steps.

[0029] Stacked to form a second composite board 80 (reference) Figure 7The specific steps include: covering the top of the second composite front panel 60 with a flexible circuit board 70, the flexible circuit board 70 having a flexible area 13, the second composite front panel 60 including a stacked circuit board 61 and a third adhesive film 62, the outer third adhesive film 62 having a second window 620, forming the second composite front panel 60 on top of the flexible circuit board 70, the projection of the flexible area 13 coinciding with each adjacent second window 620, the outer third adhesive film 62 of the second composite front panel 60 adjacent to the flexible circuit board 70, that is, the third adhesive film 62 having the second window 620 adjacent to the flexible circuit board 70, the conductive layer of the outer circuit board 61 of each second composite front panel 60 forming the outer layer of the second composite board 80. The second composite board 80 is made into a second pre-processed board by at least sequentially performing processes of lamination, drilling, copper plating, and forming the outermost circuit layer (e.g., forming the circuit layer through exposure, development, and etching processes). Lamination, drilling, copper plating, and forming the outermost circuit layer are conventional circuit board manufacturing process steps, and therefore will not be described in detail. The portion of the second pre-processed plate corresponding to the second window 620 is removed, exposing the flexible region 13 to the surface. Exemplarily, the flexible circuit board 70 may include one, two, or multiple circuit layers. The circuit board 61 may be a flexible structure circuit board or a rigid circuit board; in this embodiment, a flexible circuit board is chosen to reduce bonding stress. Typically, the flexible circuit board 70 can be obtained using conventional methods in the art, and therefore will not be described in detail.

[0030] In some embodiments, the preparation of the third adhesive film 62 having the second window 620 includes: placing a fourth adhesive film at a pre-positioned position on the outer third adhesive film 62, and then removing the portion of the fourth adhesive film corresponding to the projection of the flexible region 13, thereby forming the second window 620 to obtain the third adhesive film 62. Exemplarily, the adhesive film can be removed by mechanical cutting. Specifically, for the second composite front panel 60 located on the bottom side of the flexible circuit board 70, after forming the fourth adhesive film on the top layer of the second composite front panel 60, the portion of the fourth adhesive film corresponding to the projection of the flexible region can be removed. For the second composite front panel located on the top side of the flexible circuit board, the fourth adhesive film can be covered on the top layer of the flexible circuit board, and then the portion of the fourth adhesive film corresponding to the projection of the flexible region 13 can be removed.

[0031] In some embodiments, the preparation of the sub-layer 50 further includes: covering the top and bottom of the flexible region 13 with a peelable adhesive, performing a browning treatment, and then removing the peelable adhesive. The browning treatment increases the roughness of the surface conductive layer, thereby strengthening the connection between the sub-layer 50 and the first composite front board 40. Conventional browning processes and chemicals used in the circuit board industry can be used for the browning treatment, which will not be elaborated further.

[0032] Step S102 involves fabricating the first composite board 30 into a first pre-processed board. The steps for forming the first pre-processed board include at least sequential lamination, hole drilling, copper plating, formation of the outermost circuit layer (which can be formed through exposure, development, and etching processes), and solder resist (which can be applied to the required areas using solder resist ink). In other words, the above operations fabricate the first composite board 30 into a circuit board with interconnected circuit layers. The elastomer 20 is a thermosetting elastomer (e.g., it may include thermosetting polyurethane elastomers, thermosetting styrene-butadiene rubber elastomers, or thermosetting silicone rubber elastomers), or the plasticizing temperature of the elastomer is higher than the lamination temperature, thereby ensuring that the elastomer does not plasticize during hot lamination to provide elastic cushioning. It is understood that holes can be drilled only in the functional area, or holes can be drilled in both the functional area 31 and the cut-off area 32. Copper plating and the formation of the outer circuit layer can be performed in both the functional area 31 and the cut-off area 32. The purpose of setting the cut-off area 32 is to seal the window so that the chemical solution will not affect the inner sub-board layer 50 during the formation of the circuit layer. Therefore, the cut-off area 32 does not require each circuit layer to be conductive.

[0033] In some embodiments, the step of forming the first pre-treatment plate further includes: before the pressing step, fixing each layer of the first composite plate 30 with rivets, the rivets being fixed to the cut-off area 32. Adding the riveting step helps ensure that the layers do not move during the pressing process, thereby improving accuracy.

[0034] In some embodiments, the step of forming the first pretreatment board further includes: performing a surface treatment after the solder resist step. For example, the surface treatment may include one of the following: electroless nickel immersion gold plating (applying a nickel layer to the conductive areas of the surface followed by immersion gold to improve solderability and anti-diffusion capability), tin plating, or organic solderability protection treatment. The specific operations of the surface treatment are conventional in the art, and therefore will not be described in detail. The surface treatment can be selected according to the requirements for improved solderability, corrosion resistance, or electrical properties.

[0035] Step S103: Remove the portion of the first pre-processed plate corresponding to the first window 420, exposing the sub-plate area 12 and the flexible area 13 to the surface. Then, remove the portion of the first pre-processed plate corresponding to the cutting area 32, so that the portion other than the sub-plate area 12 and the flexible area 13 forms the main plate area 11, resulting in a rigid-flexible bonded plate 10. Accordingly, the rigid-flexible bonded plate 10 has main plate areas 11, flexible areas 13, and sub-plate areas 12 with different thicknesses (see details). Figure 2 ).

[0036] In some embodiments, in conjunction with reference Figure 5The first composite board 30 has multiple functional areas 31. The step of removing the portion of the first pre-processed board corresponding to the cutting area 32 includes: first removing the outer portion of the cutting area 32, and then removing the portion of the cutting area 32 between two adjacent functional areas 31. Setting multiple functional areas 31 is beneficial to improving production efficiency.

[0037] For example, the material of any of the above adhesive films may include polypropylene prepreg.

[0038] The removal of any of the above methods can be achieved through mechanical cutting or laser cutting.

[0039] In this application, an elastomer 20 is filled into the mounting hole 120 before lamination. Therefore, the elastomer 20 acts as a lamination buffer, preventing stress cracking of the mounting hole 120 during multi-layer lamination. Thus, the preparation method provided in this application solves the contamination problem caused by hole cracking. Furthermore, through the arrangement of the functional area 31 and the separation area 32, and the cooperation of the first adhesive film 42 with the first window 420, the main board area 11, the sub-board area 12, and the flexible area 13 with different thicknesses can be obtained through a single lamination process. That is, the lamination thickness of the board remains constant. Therefore, the preparation method provided in this application does not require multiple adjustments to process parameters based on the different thicknesses of the laminated boards from multiple multi-layer laminations. This preparation method also helps reduce production costs and facilitates product quality control.

[0040] The above embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention shall fall within the scope of protection claimed by the present invention.

Claims

1. A method for preparing a rigid-flexible composite plate, characterized in that, The rigid-flex plate includes a main plate area, a secondary plate area, and a flexible area connecting the two. The secondary plate area is provided with mounting holes. The manufacturing method includes the following steps: A first composite board is formed by stacking materials. The first composite board has a functional area and a cut-off area. The cut-off area is arranged around the periphery of the functional area. The step of stacking to form the first composite board includes: covering a sub-board layer on the top layer of a first composite front board. The sub-board layer has the flexible area and the sub-board area. The first composite front board includes a stacked rigid circuit board and a first adhesive film. The outer layer of the first adhesive film has a first window. After filling the mounting hole with an elastomer, the first composite front board is formed on the top layer of the sub-board layer. The outer layer of the first adhesive film of each first composite front board is adjacent to the sub-board layer. The conductive layer of the rigid circuit board on the outer layer of each first composite front board forms the outer layer of the first composite board. The combined projection of the sub-board area and the flexible area coincides with each adjacent first window. The first composite board is made into a first pre-processed board. The steps of forming the first pre-processed board include at least sequential lamination, hole opening, copper plating, forming the outermost circuit layer, and solder mask. The elastomer is a thermosetting elastomer, or the plasticizing temperature of the elastomer is higher than the lamination temperature. Remove the portion of the first pre-processed plate corresponding to the first window, exposing the sub-plate area and the flexible area to the surface. Then remove the portion of the first pre-processed plate corresponding to the cut-off area, so that the portion other than the sub-plate area and the flexible area forms the main plate area, thus obtaining a rigid-flexible bonded plate.

2. The preparation method according to claim 1, characterized in that, The preparation of the first adhesive film having the first window includes: After placing the second adhesive film at the pre-positioned position of the first adhesive film on the outer layer, remove the portion of the second adhesive film corresponding to the combined projection of the flexible area and the sub-plate area, thereby forming the first window to obtain the first adhesive film.

3. The preparation method according to claim 1, characterized in that, The top surface of the elastomer is positioned below the outer edge of the mounting hole.

4. The preparation method according to claim 1, characterized in that, The step of forming the first pretreatment plate further includes: Before the pressing step, each layer of the first composite board is fixed with rivets, and the rivets are fixed in the cutting area.

5. The preparation method according to any one of claims 1 to 4, characterized in that, The step of forming the first pretreatment plate further includes: After the solder resist step, surface treatment is performed.

6. The preparation method according to claim 1, characterized in that, The preparation of the sub-plate layer includes the following steps: Stacking to form a second composite board includes: covering a flexible circuit board on top of a second composite front board, the flexible circuit board having the flexible area, the second composite front board including stacked circuit boards and a third adhesive film, the outer layer of the third adhesive film having a second window, forming the second composite front board on top of the flexible circuit board, the projection of the flexible area coinciding with each adjacent second window, the outer layer of the third adhesive film of the second composite front board adjacent to the flexible circuit board, and the conductive layer of the outer layer of the circuit board of each second composite front board forming the outer layer of the second composite board; The second composite board is made into a second pre-processed board by at least sequentially performing processes of lamination, drilling, copper plating, and forming the outermost circuit layer; Remove the portion of the second pre-processing plate corresponding to the second window, thereby exposing the flexible area to the surface.

7. The preparation method according to claim 6, characterized in that, The preparation of the third adhesive film with the second window includes: After placing the fourth adhesive film at the pre-positioned position of the outer third adhesive film, the portion of the fourth adhesive film corresponding to the projection of the flexible area is removed, thereby forming the second window to obtain the third adhesive film.

8. The preparation method according to claim 1, characterized in that, The first composite board has multiple functional areas, and the step of removing the portion of the first pre-treated board corresponding to the cut-off area includes: First, remove the outer portion of the cut-off area, and then remove the portion of the cut-off area between two adjacent functional areas.

9. The preparation method according to claim 6 or 7, characterized in that, The preparation of the sub-plate layer also includes: Apply peelable adhesive to the top and bottom of the flexible area; The peelable adhesive is removed after browning treatment.

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