A rigid-flex board preparation method

Abstract

The application provides a rigid-flex board preparation method, and belongs to the technical field of rigid-flex boards. The rigid-flex board preparation method comprises the following steps: obtaining an inner core board; first pressing, stacking a first copper layer, a first semi-cured insulating sheet, the inner core board, a second semi-cured insulating sheet and a second copper layer in sequence, and then placing the stack into a pressing device to press and form a mother board with a recessed area on the surface; flattening the mother board, stacking a semi-cured sheet with fluidity on the surface of the mother board, so that the semi-cured sheet fully fills each recessed area; second pressing, stacking a copper sheet on the surface of the semi-cured sheet covering layer, applying a preset pressure to the copper sheet at a preset temperature, and extruding the semi-cured sheet covering layer to a preset thickness; and removing the glue overflowing from the edge of the mother board after the second pressing by a milling machine to obtain a flat rigid-flex board. The semi-cured sheet with fluidity is stacked on the surface in the thickness direction of the mother board, and the recessed area is filled, and then the flat rigid-flex board is obtained by compaction and flattening.

Description

Technical Field

[0001] This application relates to the field of rigid-flex plate technology, and in particular to a method for preparing a rigid-flex plate. Background Technology

[0002] Rigid-flex PCBs are a type of special circuit board that combines the advantages of rigid and flexible core boards. They are flexible and can be assembled in three-dimensional space. Based on the different slotted areas of the flexible core board, they can be divided into two types: layered and non-layered structures. Due to impedance design requirements, most rigid-flex PCBs cannot accept the layered structure with air gaps between the flexible layers and must be manufactured using a non-layered method for the flexible part of the rigid-flex PCB.

[0003] The existing rigid-flex PCBs, when laminated with non-adhesive PP, are affected by the coating material, resulting in an uneven surface after lamination, which is not conducive to subsequent processing (film lamination, resin plugging). Summary of the Invention

[0004] In view of this, the purpose of this application is to overcome the shortcomings of the prior art and provide a method for preparing a rigid-flex plate.

[0005] This application provides the following technical solution: a method for preparing a rigid-flexible plate, comprising the following steps: Obtain the inner core board; In the first pressing, the first copper layer, the first semi-cured insulating sheet, the inner core board, the second semi-cured insulating sheet, and the second copper layer are stacked in sequence and placed in the pressing equipment to press and form a mother board with a recessed area on the surface. Flatten the base plate, then stack the fluid prepreg on the surface of the base plate, so that the prepreg fully fills each recessed area and continuously spreads on the surface of the base plate to form a uniform and flat prepreg covering layer. In the second pressing, the copper sheet is stacked on the surface of the prepreg cover layer. At a preset temperature, a preset pressure is applied to the copper sheet, and the prepreg cover layer is squeezed to a preset thickness. The edge is removed by a milling machine to remove the glue that overflows from the edge of the motherboard after the second pressing, so as to obtain a flat rigid-flex plate.

[0006] In some embodiments, the flat substrate includes the steps of: covering the surface of the first copper layer with the flowable prepreg, and continuously spreading it on the surface of the first copper layer to form a uniform and flat first prepreg cover layer.

[0007] In some embodiments, the second lamination includes the step of: laminating a copper sheet over the surface of the first prepreg cover layer.

[0008] In some embodiments, the flat substrate further includes the step of: covering the surface of the second copper layer with the flowable prepreg, and continuously spreading it on the surface of the second copper layer to form a uniform and flat second prepreg cover layer.

[0009] In some embodiments, the second lamination further includes the step of: laminating the copper sheet over the surface of the second prepreg cover layer.

[0010] In some embodiments, before the flattening of the motherboard, the method further includes the step of etching the first copper layer according to a first preset conductive line or etching away all of the first copper layer.

[0011] In some embodiments, before the flattening of the motherboard, the method further includes the step of etching the second copper layer according to the second preset conductive line or etching away the second copper layer entirely.

[0012] In some embodiments, after the second pressing, a portion of the fluid prepreg overflows from the edge of the motherboard near the first copper layer to form a first overflow adhesive layer, the first overflow adhesive layer surrounding the motherboard.

[0013] In some embodiments, after the second pressing, a portion of the fluid prepreg overflows from the edge of the motherboard near the second copper layer to form a second overflow adhesive layer, which surrounds the motherboard.

[0014] In some embodiments, the process after the milling process includes: drilling, electroplating, resin plugging, ceramic grinding plate, electroplating, outer layer circuitry, and post-processing.

[0015] The embodiments of this application have the following advantages: By stacking a flowable prepreg on the surface of the motherboard in the thickness direction, this application allows the prepreg to flow on the surface of the motherboard under the action of gravity, filling the recessed areas and forming a flat prepreg cover layer in the thickness direction of the motherboard. Furthermore, excess flowable prepreg overflows from the edge of the motherboard, ensuring that every area in the thickness direction of the motherboard is filled with the prepreg, thus guaranteeing the flatness of each area in the thickness direction of the motherboard. By controlling a preset temperature, the prepreg cover layer is cured at this preset temperature after being compacted and flattened, thereby obtaining a flat rigid-flex plate.

[0016] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 A one-view flowchart of a method for fabricating a rigid-flex plate according to some embodiments of this application is shown; Figure 2 The diagram shows a structural schematic of a rigid-flex plate in a method for preparing a rigid-flex plate according to some embodiments of this application.

[0019] Explanation of key component markings: 110 - Inner core board; 120 - First copper layer; 130 - First semi-cured insulating sheet; 140 - Second semi-cured insulating sheet; 150 - Second copper layer; 100 - Mother board; 200 - First semi-cured sheet cover layer; 300 - Copper sheet; 400 - Second semi-cured sheet cover layer. Detailed Implementation

[0020] The embodiments of this application are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application.

[0021] It should be noted that when an element is said to be "fixed to" another element, it can be directly on the other element or there may be an intervening element. When an element is said to be "connected to" another element, it can be directly connected to the other element or there may be an intervening element. Conversely, when an element is said to be "directly on" another element, there is no intervening element. The terms "vertical," "horizontal," "left," "right," and similar expressions used in this document are for illustrative purposes only.

[0022] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0023] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0024] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the template description is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0025] like Figure 1 and Figure 2 As shown, some embodiments of this application provide a method for preparing a rigid-flex plate, which includes the following steps: S100, Obtain the inner core board.

[0026] The inner core board 110 includes an upper copper foil, an insulating layer, and a lower copper foil stacked sequentially.

[0027] S200, the first pressing, involves sequentially stacking the first copper layer, the first semi-cured insulating sheet, the inner core board, the second semi-cured insulating sheet, and the second copper layer, and then pressing them together in a pressing device to form a motherboard with a recessed area on the surface.

[0028] Understandably, before the first pressing step, a first copper layer 120, a first semi-cured insulating sheet 130, a second semi-cured insulating sheet 140, and a second copper layer 150 are obtained. The first semi-cured insulating sheet 130 completely covers one side of the inner core board 110 in the thickness direction, the second semi-cured insulating sheet 140 completely covers the other side of the inner core board 110 in the thickness direction, the first copper layer 120 completely covers the first semi-cured insulating sheet 130, and the second copper layer 150 completely covers the second semi-cured insulating sheet 140.

[0029] In this embodiment, both the first semi-cured insulating sheet 130 and the second semi-cured insulating sheet 140 are non-flowing PP (Polypropylene) resin. "Non-flowing" means that the resin system has excellent viscosity control, strong anti-sagging properties after construction, and uniform solvent evaporation during the curing process, without the phenomenon of resin components precipitating to the surface (turning white and sticky) or flowing downward.

[0030] It should be noted that, due to the extremely low fluidity of the non-flowing PP resin, a height difference is formed between the copper surface of the inner layer circuit pattern in the inner core board 110 and the surface of the inner core board 110 during hot pressing. This results in an uneven imprint on the surface of the inner core board 110 after pressing, thus forming a recessed area on the surface of the inner core board 110.

[0031] It is understandable that, since the first semi-cured insulating sheet 130 and the second semi-cured insulating sheet 140 are respectively pressed on both sides of the inner core board 110 in the thickness direction, uneven overprints are formed on the two back sides of the inner core board 110 in the thickness direction, that is, the two back sides of the inner core board 110 in the thickness direction have recessed areas.

[0032] S300, flat master board, applies a flowable prepreg layer to the surface of the master board, allowing the prepreg to fully fill all recessed areas and continuously spread on the surface of the master board to form a uniform and flat prepreg cover layer.

[0033] It should be noted that when the fluid prepreg is laminated on the surface of the motherboard 100 in the thickness direction, it can flow on the surface of the motherboard 100 under the action of gravity, flowing from higher areas to lower areas and filling in the recessed areas, forming a smooth prepreg cover layer in the thickness direction of the motherboard 100. Understandably, excess fluid prepreg overflows from the edges of the motherboard 100 to ensure that every area in the thickness direction of the motherboard 100 is filled with the prepreg, thus ensuring the flatness of each area in the thickness direction of the motherboard 100.

[0034] The thickness of the fluid prepreg on the mother plate 100 can be specifically set according to the actual situation, and is not specifically limited in this embodiment.

[0035] S400, the second pressing, involves stacking a copper sheet on the surface of the prepreg cover layer, applying a preset pressure to the copper sheet at a preset temperature, and pressing the prepreg cover layer to a preset thickness.

[0036] It should be noted that by stacking copper sheets 300 layers on the surface of the prepreg cover layer, the prepreg cover layer is compacted and flattened by the copper layer, which further ensures the flatness of the surface of the prepreg cover layer and the tightness of the contact surface between the prepreg cover layer and the inner core board 110, avoiding gaps or unevenness.

[0037] In this embodiment, the thickness of the semi-cured coating is adjusted by controlling the pressure on the copper sheet 300, thereby meeting the design requirements.

[0038] In addition, by controlling the preset temperature, the semi-cured coating layer is cured at the preset temperature after being compacted and leveled, thereby ensuring the formation of a cured coating layer. This not only ensures the smoothness of the surface of the cured coating layer, but also its stability.

[0039] S500, edge milling, removes the adhesive that overflows from the edge of the motherboard after the second pressing by a milling machine to obtain a flat rigid-flex plate.

[0040] It should be noted that after the second pressing, the copper sheet 300 extrudes the excess prepreg from the edge of the motherboard 100, forming excess adhesive at the edge of the motherboard 100. The excess adhesive at the edge of the motherboard 100 is removed by a milling machine, thus obtaining a flat rigid-flex board.

[0041] like Figure 2 As shown, in some embodiments of this application, the flat motherboard 100 includes the step of: S310, covering the surface of the first copper layer 120 with the fluid semi-cured sheet, and continuously spreading it on the surface of the first copper layer 120 to form a uniform and flat first semi-cured sheet cover layer 200.

[0042] It should be noted that after the first pressing, due to the low fluidity of the first semi-cured insulating sheet 130, an uneven plane is formed on the surface of the first copper layer 120, that is, the surface of the first copper layer 120 has a first recessed area.

[0043] By covering the surface of the first copper layer 120 with a fluid semi-cured sheet, the first recessed area on the surface of the first copper layer 120 is filled by the fluid semi-cured sheet, thereby smoothing the surface of the first copper layer 120 and forming a uniform and smooth first semi-cured coating layer on the surface of the first copper layer 120.

[0044] In this embodiment, the first semi-cured capping layer overflows from the edge of the first copper layer 120 to ensure that the first semi-cured capping layer completely covers the first copper layer 120.

[0045] It should be noted that in step S310, the fluid prepreg is located above the first copper layer 120, so that the fluid prepreg can flow on the first copper layer 120 under the action of gravity and fill the first recessed area.

[0046] like Figure 2 As shown, in some embodiments of this application, the second pressing includes the step of: S410, stacking copper sheet 300 on the surface of the first prepreg cover layer 200.

[0047] In this process, along the thickness direction of the inner core board 110, the copper sheet 300 completely covers the first prepreg cover layer 200. By applying pressure along the thickness direction to the copper sheet 300, the first prepreg cover layer 200 is squeezed by the copper sheet 300. This not only further smooths the surface of the first prepreg cover layer 200, but also allows the first prepreg cover layer 200 to further fill the first recessed area through squeezing, avoiding gaps or pits and improving its flatness.

[0048] In addition, the thickness of the first semi-cured film cover layer 200 can be adjusted by controlling the pressure on the copper sheet 300 to meet user needs.

[0049] like Figure 2 As shown, in some embodiments of this application, the flat motherboard 100 further includes the step: S320, covering the surface of the second copper layer 150 with the fluid semi-cured sheet, and continuously spreading it on the surface of the second copper layer 150 to form a uniform and flat second semi-cured sheet cover layer 400.

[0050] It should be noted that after the first pressing, due to the low fluidity of the second semi-cured insulating sheet 140, an uneven plane is formed on the surface of the second copper layer 150, that is, the surface of the second copper layer 150 has a second recessed area.

[0051] By covering the surface of the second copper layer 150 with a fluid semi-cured sheet, the second recessed area on the surface of the second copper layer 150 is filled by the fluid semi-cured sheet, thereby smoothing the surface of the second copper layer 150 and forming a uniform and smooth second semi-cured coating layer on the surface of the second copper layer 150.

[0052] In this embodiment, the second semi-cured capping layer overflows from the edge of the second copper layer 150 to ensure that the second semi-cured capping layer completely covers the second copper layer 150.

[0053] It should be noted that in step S320, the fluid prepreg is located above the second copper layer 150, so that the fluid prepreg can flow on the second copper layer 150 under the action of gravity and fill the second recessed area.

[0054] like Figure 2 As shown, in some embodiments of this application, the second pressing further includes the step of: S420, stacking the copper sheet 300 on the surface of the second prepreg cover layer 400.

[0055] It should be noted that, along the thickness direction of the inner core board 110, the copper sheet 300 completely covers the second prepreg cover layer 400. By applying pressure along the thickness direction to the copper sheet 300, the second prepreg cover layer 400 is squeezed by the copper sheet 300. This not only further smooths the surface of the second prepreg cover layer 400, but also allows the second prepreg cover layer 400 to further fill the second recessed area through squeezing, avoiding gaps or pits and improving its flatness.

[0056] In addition, the thickness of the second semi-cured film cover layer 400 can be adjusted by controlling the pressure on the copper sheet 300 to meet user needs.

[0057] like Figure 1 As shown, in some embodiments of this application, the step of etching the first copper layer 120 or completely etching away the first copper layer 120 is included before the flat motherboard 100: according to the first preset conductive line.

[0058] In this embodiment, excess copper foil on the first copper layer 120 is selectively removed by chemical etching, leaving only the conductive lines required by the design, thereby achieving circuit conduction and regional insulation separation.

[0059] like Figure 2 As shown, in some embodiments of this application, the step of etching the second copper layer 150 or completely etching away the second copper layer 150 is included before the flat motherboard 100.

[0060] In this embodiment, excess copper foil on the second copper layer 150 is selectively removed by chemical etching, leaving only the conductive lines required by the design, thereby achieving circuit conduction and regional insulation separation.

[0061] In some embodiments of this application, after the second pressing, a portion of the fluid semi-cured sheet overflows from the edge of the mother plate 100 near the first copper layer 120 to form a first overflow adhesive layer, which surrounds the mother plate 100.

[0062] It is understandable that when the first overflow adhesive layer surrounds the motherboard 100, it means that the first semi-cured cover layer between the copper sheet 300 and the first copper layer 120 completely fills the first recessed area on the surface of the first copper layer 120 to ensure the flatness of the copper sheet 300 on the first copper layer 120.

[0063] In some embodiments of this application, after the second pressing, a portion of the fluid prepreg overflows from the edge of the motherboard 100 near the second copper layer 150 to form a second overflow adhesive layer, which surrounds the motherboard 100.

[0064] It is understandable that when the second overflow adhesive layer surrounds the motherboard 100, it means that the second semi-cured cover layer between the copper sheet 300 and the second copper layer 150 completely fills the second recessed area on the surface of the first copper layer 120 to ensure the flatness of the copper sheet 300 on the second copper layer 150.

[0065] In some embodiments of this application, the steps following the milling process include: drilling, electroplating, resin plugging, ceramic grinding plate, electroplating, outer layer circuitry, and post-processing.

[0066] It should be noted that drilling opens up interlayer channels in the multilayer board to form subsequent conductive vias. Plasma treatment and alkaline potassium permanganate solution remove resin residue generated during the high temperatures of drilling, preventing copper layer detachment and hole breakage. After chemical copper plating, electroplating ensures the integrity of the conductive layer on the via walls. Resin is used to fill the inside of the holes to avoid damaging the conductive copper layer. The resin bumps after plugging are ground smooth to ensure the pads are completely flat. Additionally, a hot-pressed photosensitive dry film is used to cover the entire outer copper layer, followed by UV exposure, sodium carbonate development, and then copper electroplating. Pure tin is then electroplated as an anti-corrosion protective layer. The outer layer circuitry is etched in an alkaline ammonia etching bath, and nitric acid is used to remove the tin protective layer from the circuit surface, forming the final outer conductive circuitry.

[0067] The post-process includes solder mask printing, pre-baking, exposure and development, surface treatment, character silkscreen printing, forming and grooving, electrical testing, final inspection (FQC), V-Cut board separation, cleaning, vacuum packaging and shipping.

[0068] In all examples shown and described herein, any specific values ​​should be interpreted as merely exemplary and not as limitations; therefore, other examples of exemplary embodiments may have different values.

[0069] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0070] 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 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 modifications and improvements all fall within the protection scope of this application.

Claims

1. A method for preparing a rigid-flexible plate, characterized in that, Including the following steps: Obtain the inner core board; In the first pressing, the first copper layer, the first semi-cured insulating sheet, the inner core board, the second semi-cured insulating sheet, and the second copper layer are stacked in sequence and placed in the pressing equipment to press and form a mother board with a recessed area on the surface. Flatten the base plate, then stack the fluid prepreg on the surface of the base plate, so that the prepreg fully fills each recessed area and continuously spreads on the surface of the base plate to form a uniform and flat prepreg covering layer. In the second pressing, the copper sheet is stacked on the surface of the prepreg cover layer. At a preset temperature, a preset pressure is applied to the copper sheet, and the prepreg cover layer is squeezed to a preset thickness. The edge is removed by a milling machine to remove the glue that overflows from the edge of the motherboard after the second pressing, so as to obtain a flat rigid-flex plate.

2. The method for preparing a rigid-flexible plate according to claim 1, characterized in that, The flat substrate includes the steps of: covering the surface of the first copper layer with the fluid prepreg, and continuously spreading it on the surface of the first copper layer to form a uniform and flat first prepreg cover layer.

3. The method for preparing a rigid-flexible plate according to claim 2, characterized in that, The second pressing includes the step of: stacking copper sheets over the surface of the first prepreg cover layer.

4. The method for preparing a rigid-flexible plate according to claim 1, characterized in that, The flat substrate further includes the step of: covering the surface of the second copper layer with the fluid prepreg, and continuously spreading it on the surface of the second copper layer to form a uniform and flat second prepreg cover layer.

5. The method for preparing a rigid-flexible plate according to claim 4, characterized in that, The second pressing also includes the step of: stacking the copper sheet over the surface of the second semi-cured sheet cover layer.

6. The method for preparing a rigid-flexible plate according to claim 1, characterized in that, Before the flattening of the motherboard, the process includes the following steps: etching the first copper layer according to the first preset conductive line or etching away all of the first copper layer.

7. The method for preparing a rigid-flexible plate according to claim 1, characterized in that, Before the flattening of the motherboard, the process includes the following steps: etching the second copper layer according to the second preset conductive line or etching away the second copper layer completely.

8. The method for preparing a rigid-flexible plate according to any one of claims 1 to 7, characterized in that, After the second pressing, a portion of the fluid semi-cured sheet overflows from the edge of the motherboard near the first copper layer to form a first overflow adhesive layer, which surrounds the motherboard.

9. The method for preparing a rigid-flexible plate according to any one of claims 1 to 7, characterized in that, After the second pressing, a portion of the fluid prepreg overflows from the edge of the motherboard near the second copper layer to form a second overflow adhesive layer, which surrounds the motherboard.

10. The method for preparing a rigid-flexible plate according to claim 1, characterized in that, The process after the serger edge includes the following steps: drilling, electroplating, resin plugging, ceramic grinding plate, electroplating, outer layer circuitry, and post-processing.

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