A manufacturing method for uncovering a rigid-flex printed circuit board

Abstract

The present invention discloses a manufacturing method for uncovering a rigid-flexible printed circuit board (R-F PCB), which includes the following steps: taking a first dielectric layer, opening a window in the first dielectric layer, attaching the first dielectric layer with the window opened to a flexible board, coating a release agent and printing resin ink at the window position of the first dielectric layer, the resin ink layer completely filling the window position of the first dielectric layer, stacking and laminating a second dielectric layer, a third dielectric layer, and a rigid board in sequence on the first dielectric layer to form a rigid-flexible printed circuit board to be uncovered, performing controlled-depth milling uncovering on the rigid-flexible printed circuit board to be uncovered, milling from the rigid board to the position where the resin ink layer is located, after the milling of the board is completed, performing uncovering, and peeling off the unpeeled resin ink layer and the release agent film layer at the window position of the first dielectric layer to form a rigid-flexible printed circuit board with the uncovering completed. The present invention can effectively improve the uncovering quality, form a neat uncovering cross-section, and prevent problems such as glue overflow and fracture at the uncovering position of the rigid-flexible printed circuit board.

Description

Technical Field

[0001] The present invention relates to the field of rigid-flexible printed circuit board manufacturing, and particularly to a manufacturing method for uncovering the cover of a rigid-flexible printed circuit board. Background Art

[0002] The flexible area of a rigid-flexible printed circuit board is formed by removing the rigid area of a specific layer from the rigid-flexible printed circuit board to expose the flexible area. The process of removing the rigid board of the specific layer is called the uncovering process.

[0003] Currently, for uncovering the cover of a rigid-flexible printed circuit board, generally, the inner dielectric layer is first windowed, then integrally laminated with a flexible board and a rigid board, and then the cover is uncovered by milling grooves.

[0004] For a structure with a relatively large rigid-flexible drop in design, since the dielectric layer is relatively thick, in order to prevent excessive glue overflow in the dielectric layer during the subsequent lamination process, a non-flowing prepreg needs to be used as the dielectric layer material. However, after the whole-board lamination, due to the poor glue filling property of the non-flowing dielectric layer, there will be a relatively obvious depression on the outer surface of the laminated circuit board.

[0005] Using the manufacturing method of windowing the dielectric layer, when manufacturing the outer layer circuit after lamination, due to the excessive depression on the outer surface corresponding to the windowed area, the board surface drop is too large, which will affect the processes such as film pasting and exposure in circuit manufacturing, and further affect circuit manufacturing, resulting in problems such as open circuits and short circuits.

[0006] Moreover, when uncovering the cover by milling grooves, due to the too large board surface drop, problems such as false deviation, inaccurate alignment, and inaccurate depth control are likely to occur at the cutting position, increasing the difficulty of uncovering the cover by milling grooves. If the depth control of the milling groove is too shallow, the cover body is difficult to uncover; if the control is too deep, it will damage the flexible board layer, and in severe cases, the product will be scrapped.

[0007] Therefore, it is necessary to explore a manufacturing method that can reduce the board surface drop, facilitate the manufacturing of the outer layer circuit, and improve the uncovering accuracy. Summary of the Invention

[0008] The technical problem to be solved by the present invention is to provide a manufacturing method for uncovering the cover of a rigid-flexible printed circuit board, which can effectively improve the uncovering quality, form a neat uncovering section, prevent problems such as glue overflow and fracture at the uncovering position of the rigid-flexible printed circuit board, and improve the product quality of the rigid-flexible printed circuit board.

[0009] The present invention provides a manufacturing method for uncovering the cover of a rigid-flexible printed circuit board, and the manufacturing method includes the following steps:

[0010] Step 1: Take a first dielectric layer, window the first dielectric layer, and the size of the window is the same as the size of the area to be uncovered subsequently.

[0011] Step 2: Attach the windowed first dielectric layer to the flexible board;

[0012] Step 3: Coat a release agent on the windowed position of the first dielectric layer to form a release agent film layer;

[0013] Step 4: Print resin ink on the windowed position of the first dielectric layer, bake the resin ink to form a resin ink layer, and the resin ink layer completely fills the windowed position of the first dielectric layer;

[0014] Step 5: Stack and press the second dielectric layer, the third dielectric layer, and the rigid board on the first dielectric layer in sequence to form a rigid-flex board to be uncovered;

[0015] Step 6: Perform controlled-depth milling and uncovering on the rigid-flex board to be uncovered, mill from the rigid board to the position where the resin ink layer is located, and after milling is completed, perform uncovering;

[0016] Step 7: Peel off the resin ink layer and the release agent film layer that are not peeled off at the windowed position of the first dielectric layer to form a rigid-flex board with uncovering completed.

[0017] Optionally, in Step 2, after attaching the windowed first dielectric layer to the flexible board, attach a support layer on the side of the flexible board opposite to the first dielectric layer, and remove the support layer after Step 7 is completed. The support layer is used to enhance the strength of the flexible board and the first dielectric layer during subsequent processing.

[0018] Optionally, the manufacturing method further includes, after Step 2 is completed, attaching a dry film layer on the side of the first dielectric layer away from the flexible board, performing windowing production on the dry film layer by exposure and development according to the window pattern of the first dielectric layer, and removing the dry film layer by film stripping after Step 4 is completed.

[0019] Optionally, nano carbon black powder is added to the resin ink. Adding carbon black powder to the resin ink is for subsequent controlled-depth milling. When the milling cutter probes down to the resin ink layer containing nano carbon black powder, it can be observed that black resin is discharged from the chip evacuation groove of the milling cutter, so as to facilitate positioning the probing depth of the milling cutter, facilitate milling of the board by the milling cutter, and prevent the milling cutter from probing insufficiently or excessively.

[0020] Optionally, the volume ratio of the nano carbon black powder to the resin ink is 1-5%.

[0021] Optionally, the release agent is a silicone release agent or a fluorine-based release agent.

[0022] Optionally, the first dielectric layer is a non-flowing prepreg, and the second dielectric layer and the third dielectric layer are flowing prepregs.

[0023] Optionally, the support layer is made of polyimide or polytetrafluoroethylene.

[0024] By adopting the above technical solution, a dielectric layer is divided into three layers, and the two layers close to the rigid board are made of flowing semi-cured sheet dielectric layers, and the layer close to the flexible board is made of non-flowing semi-cured sheet dielectric layer. This can effectively provide the supporting force of the flexible board during pressing, and can prevent the flexible board from expanding and contracting too much due to excessive expansion and contraction of the dielectric layer during pressing. It can also provide a relatively hard foundation for the subsequent production of a release agent film layer and printed resin ink. A release agent is applied to the window position of the first dielectric layer, providing an effective and easy-to-peel release agent film layer for subsequent uncovering. Resin ink is printed at the window position of the first dielectric layer, and nano-carbon black powder is added to the resin ink, which is beneficial for detecting the depth when the milling cutter mills the board. The discharge of black resin ink can be used as a sign of qualified depth. The production method can effectively improve the quality of uncovering, form a neat uncovering section, and prevent problems such as glue overflow and breakage at the uncovering position of the rigid-flexible board. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0026] Figure 1 A flowchart of a method for manufacturing a rigid-flex board cover according to an embodiment of the present invention;

[0027] Figure 2 A flowchart of a method for manufacturing a rigid-flex board cover according to another embodiment of the present invention;

[0028] Figure 3 This is a schematic structural diagram of a first dielectric layer attached to a flexible board according to an embodiment of the present invention;

[0029] Figure 4 for Figure 3 Schematic diagram of the structure after the support layer and the dry film layer are attached;

[0030] Figure 5 for Figure 4 Schematic diagram of the structure after coating the release agent;

[0031] Figure 6 for Figure 5 Schematic diagram of the structure after printing resin ink;

[0032] Figure 7 for Figure 6Schematic diagram of the structure after removing the dry film layer;

[0033] Figure 8 Schematic diagram of the pressing state of the rigid-flex printed circuit board;

[0034] Figure 9 is Figure 8 Schematic diagram of the structure after the controlled-depth milling and cover removal of the rigid-flex printed circuit board after pressing;

[0035] Figure 10 Schematic diagram of the structure after the controlled-depth milling and cover removal of the embodiment of the present invention;

[0036] Figure 11 Schematic diagram of the structure after the peeling of the resin ink layer and the release film layer of the embodiment of the present invention;

[0037] Figure 12 Schematic diagram of the structure of the rigid-flex printed circuit board after the cover removal is completed in the embodiment of the present invention.

[0038] The description of the reference numerals is as follows:

[0039] 1 - First dielectric layer, 2 - Flexible board, 3 - Support layer, 4 - Dry film layer, 5 - Release film layer, 6 - Resin ink layer, 7 - Second dielectric layer, 8 - Third dielectric layer, 9 - Rigid board, 10 - Milling cutter, 11 - Window opening. Detailed implementation manners

[0040] The following further describes the detailed implementation manners of the present invention with reference to the accompanying drawings. It should be noted here that the description of these implementation manners is used to help understand the present invention, but does not constitute a limitation to the present invention. In addition, the technical features involved in the various implementation manners of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0041] The present invention provides a method for making a rigid-flex printed circuit board with cover removal. Please refer to Figure 1 , Figure 1 is the flowchart of the method for making a rigid-flex printed circuit board with cover removal in the embodiment of the present invention. The method includes the following steps:

[0042] S101: Take the first dielectric layer, and open a window on the first dielectric layer. The size of the window is the same as the size of the area to be covered and removed later;

[0043] S102: Attach the first dielectric layer with the window opened to the flexible board;

[0044] S103: Coat a release agent at the window opening position of the first dielectric layer to form a release film layer;

[0045] S104: Print resin ink at the windowing position of the first dielectric layer, bake the resin ink to form a resin ink layer, and the resin ink layer completely fills the windowing position of the first dielectric layer;

[0046] S105: Stack and press the second dielectric layer, the third dielectric layer, and the rigid board on the first dielectric layer in sequence to form a rigid-flex printed circuit board to be uncovered;

[0047] S106: Perform depth-controlled milling and uncovering on the rigid-flex printed circuit board to be uncovered, mill from the rigid board to the position where the resin ink layer is located, and uncover it after milling;

[0048] S107: Peel off the unpeeled resin ink layer and the release agent film layer at the windowing position of the first dielectric layer to form a rigid-flex printed circuit board with uncovering completed.

[0049] The present invention further provides a manufacturing method for uncovering a rigid-flex printed circuit board. Please refer to Figure 2 , Figure 2 which is a flowchart of the manufacturing method for uncovering a rigid-flex printed circuit board according to another embodiment of the present invention. The manufacturing method includes the following steps:

[0050] S201: Take a first dielectric layer, perform windowing on the first dielectric layer, and the size of the windowing is consistent with the size of the area to be uncovered subsequently;

[0051] S202: Attach the windowed first dielectric layer to a flexible board, and attach a support layer to the side of the flexible board opposite to the first dielectric layer;

[0052] S203: Attach a dry film layer to the side of the first dielectric layer away from the flexible board, and perform exposure and development windowing production on the dry film layer according to the windowing pattern of the first dielectric layer.

[0053] S204: Coat a release agent at the windowing position of the first dielectric layer to form a release agent film layer;

[0054] S205: Print resin ink at the windowing position of the first dielectric layer, bake the resin ink to form a resin ink layer, and the resin ink layer completely fills the windowing position of the first dielectric layer;

[0055] S206: Remove the dry film layer by means of film stripping;

[0056] S207: Stack and press the second dielectric layer, the third dielectric layer, and the rigid board on the first dielectric layer in sequence to form a rigid-flex printed circuit board to be uncovered;

[0057] S208: Perform controlled-depth milling to uncover the rigid-flex board to be uncovered, milling from the rigid board to the position where the resin ink layer is located. After the milling of the board is completed, uncover it.

[0058] S209: Peel off the resin ink layer and the release agent film layer that are not peeled off at the windowing position of the first dielectric layer to form a rigid-flex board with the uncovering completed.

[0059] S210: Remove the support layer.

[0060] In the present invention, a dielectric layer is divided into three layers for stacked lamination, and pre-windowing and coating with a release agent are adopted to provide an effective release agent film layer for subsequent uncovering, which can effectively improve the uncovering quality, form a neat uncovering cross-section, and prevent problems such as glue overflow and fracture at the uncovering position of the rigid-flex board.

[0061] The present invention will be described in detail below with reference to the accompanying drawings.

[0062] As Figure 3 shown, take the first dielectric layer 1, window the first dielectric layer 1 at 11, and the size of the window 11 is the same as the size of the area to be uncovered subsequently. In this embodiment, the first dielectric layer 1 is a non-flowing prepreg.

[0063] As Figure 4 shown, attach the windowed first dielectric layer 1 to the flexible board 2, and attach a support layer 3 to the side of the flexible board 2 opposite to the first dielectric layer 1.

[0064] The first dielectric layer 1 can be attached to the flexible board 2 by means of micro-lamination, adhesive layer adhesion, etc. In this embodiment, the support layer 3 is used to enhance the strength of the flexible board 2 and the first dielectric layer 1 during subsequent processing. The material of the support layer 3 is polyimide or polytetrafluoroethylene, which is convenient for peeling after the manufacturing process is completed. Since the support layer 3 only serves to increase the strength, in other embodiments, the support layer 3 can be not provided, and not providing the support layer 3 does not affect the realization of this manufacturing method.

[0065] Please continue to refer to Figure 4 , attach a dry film layer 4 to the side of the first dielectric layer 1 away from the flexible board 2, and perform exposure and development windowing production on the dry film layer 4 according to the windowing pattern of the first dielectric layer 1.

[0066] As Figure 5 shown, apply a release agent at the windowing position of the first dielectric layer 1 to form a release agent film layer 5. The release agent is a silicone oil release agent or a fluorine-based release agent, and the formed release agent film layer 5 is easy to peel off, providing an effective peeling effect for subsequent uncovering.

[0067] As Figure 6 and Figure 9 shown, resin ink is printed at the window opening position of the first dielectric layer 1, and the resin ink is baked. Optionally, the baking parameters are 120°C × 30 min to form a resin ink layer 6, and the resin ink layer 6 completely fills the window opening position of the first dielectric layer 1.

[0068] In this embodiment, the resin ink needs to be specially formulated. First, the resin ink is stirred evenly, and then nano-carbon black powder is added to the resin ink. Optionally, the volume ratio of the nano-carbon black powder to the resin ink is 1-5%. Adding carbon black powder to the resin ink is to facilitate the positioning of the depth of the cutter 10 when the cutter 10 drills down to the resin ink layer 6 containing nano-carbon black powder during controlled-depth milling. When black resin is observed to be discharged from the chip evacuation groove of the cutter 10, it is convenient to position the depth of the cutter 10 for milling the board and prevent the cutter 10 from under-drilling or over-drilling.

[0069] As Figure 7 shown, the dry film layer 4 is removed by a film stripping method. The dry film layer 4 can be directly removed with a film stripping solution without damaging the first dielectric layer 1, the release agent film layer 5, and the resin ink layer 6. The dry film layer 4 can prevent the release agent from being coated on the first dielectric layer 1 when the release agent is coated, and can also prevent the printed resin ink from being coated on the first dielectric layer 1 when the resin ink is printed. The dry film layer 4 plays a role in protecting the first dielectric layer 1. Therefore, in other embodiments, the dry film layer 4 may not be provided, and the absence of the dry film layer 4 does not affect the implementation of this manufacturing method.

[0070] As Figure 8 shown, the second dielectric layer 7, the third dielectric layer 8, and the rigid board 9 are stacked and pressed in sequence on the first dielectric layer 1 to form a rigid-flex printed circuit board to be uncovered as shown in Figure 9 shown. In this embodiment, the second dielectric layer 7 and the third dielectric layer 8 are flowable semi-cured sheets.

[0071] As Figure 9 shown, controlled-depth milling and uncovering are performed on the rigid-flex printed circuit board to be uncovered, milling from the rigid board 9 to the position where the resin ink layer 6 is located. When the cutter 10 detects the depth and black debris is discharged, it proves that the detected depth has reached the position where the resin ink layer 6 is located. At this time, milling can be performed according to the milling pattern for uncovering, and after milling is completed, uncovering is carried out.

[0072] As Figure 10 and Figure 11As shown, the resin ink layer 6 and the release film layer 5 that are not peeled off at the window opening position of the first dielectric layer 1 are peeled off. If it is difficult to peel off the resin ink during the peeling process, appropriate heating can be carried out before peeling again. The heating temperature and time are generally 75°C × 10 min to form a rigid-flexible printed circuit board with the cover removed. The support layer 3 is removed to obtain the rigid-flexible printed circuit board as shown in Figure 12 the figure.

[0073] In the method for manufacturing a rigid-flexible printed circuit board with the cover removed according to the present invention, a dielectric layer is divided into three layers, which can prevent the excessive shrinkage and expansion of the flexible printed circuit board during the lamination process due to the excessive shrinkage and expansion of the dielectric layer. The release film layer provides an effective basis for subsequent peeling, and adding nano-carbon black powder to the resin ink can use the discharge of the black resin ink as a sign of qualified depth. The entire manufacturing method can effectively improve the quality of the cover removal, form a neat cross-section of the cover removal, and prevent problems such as glue overflow and fracture at the cover removal position of the rigid-flexible printed circuit board.

[0074] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to the described embodiments. For those skilled in the art, without departing from the principle and spirit of the present invention, various changes, modifications, substitutions, and variations to these embodiments still fall within the protection scope of the present invention.

[0075] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", "row", "column", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention.

[0076] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one of these features. In the description of the present invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise specifically defined.

[0077] In a patent for invention, unless otherwise clearly stipulated or limited, terms such as "installed", "connected", "joined", "fixed", "secured", etc. shall be construed broadly. For example, it may be a fixed connection, a detachable connection, or integrated; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the communication inside two elements or the interaction relationship between two elements, unless otherwise clearly limited. For those of ordinary skill in the art, the specific meanings of the above terms in this patent for invention may be understood according to specific circumstances.

[0078] In this patent for invention, unless otherwise clearly stipulated or limited, a first feature being "on" or "under" a second feature may be that the first and second features are in direct contact, or the first and second features are indirectly in contact through an intermediate medium. Moreover, a first feature being "above", "over" and "on top of" a second feature may be that the first feature is directly above or obliquely above the second feature, or merely indicates that the first feature has a higher horizontal height than the second feature. A first feature being "under", "beneath" and "underneath" a second feature may be that the first feature is directly below or obliquely below the second feature, or merely indicates that the first feature has a lower horizontal height than the second feature.

Claims

1. A manufacturing method for uncovering a rigid-flex printed circuit board, characterized in that, Including the following steps: Step 1: Take the first dielectric layer and open a window in the first dielectric layer, the size of the window being the same as the size of the area to be uncovered subsequently; Step 2: Attach the first dielectric layer with the window opened to a flexible board, then attach a support layer on the side of the flexible board facing away from the first dielectric layer, then attach a dry film layer on the side of the first dielectric layer facing away from the flexible board, and perform exposure and development window making on the dry film layer according to the window pattern of the first dielectric layer; Step 3: Coat a release agent at the window position of the first dielectric layer to form a release agent film layer; Step 4: Print resin ink at the window position of the first dielectric layer, add nano carbon black powder to the resin ink, bake the resin ink to form a resin ink layer, the resin ink layer completely filling the window position of the first dielectric layer; Remove the dry film layer by the method of film stripping; Step 5: Stack and press a second dielectric layer, a third dielectric layer and a rigid board in sequence on the first dielectric layer to form a rigid-flexible printed circuit board to be uncovered; Step 6: Perform controlled-depth milling and uncovering on the rigid-flexible printed circuit board to be uncovered, milling from the rigid board to the position where the resin ink layer is located, and after the milling of the board is completed, perform uncovering; Step 7: Peel off the resin ink layer and the release agent film layer that are not peeled off at the window position of the first dielectric layer, and then remove the support layer, the support layer being used to enhance the strength of the flexible board and the first dielectric layer during subsequent processing, to form a rigid-flexible printed circuit board with uncovering completed.

2. The manufacturing method of uncovering a rigid-flex printed circuit board according to claim 1, wherein The volume ratio of the nano carbon black powder to the resin ink is 1-5%.

3. The manufacturing method of a rigid-flex printed circuit board lid opening according to claim 1, characterized in that, The release agent is a silicone release agent or a fluorine-based release agent.

4. The manufacturing method of a rigid-flex printed circuit board lid lifting according to claim 1, characterized in that, The first dielectric layer is a non-flowing prepreg, and the second dielectric layer and the third dielectric layer are flowing prepregs.

5. The manufacturing method of a rigid-flex printed circuit board cover opening according to claim 1, characterized in that, The material of the support layer is polyimide or polytetrafluoroethylene.

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