Method for uncovering the cover of a rigid-flexible printed circuit board and rigid-flexible printed circuit board

Abstract

The present application relates to the technical field of printed circuit board processing, and provides a method for uncovering the cover of a rigid-flex board and a rigid-flex board. The rigid-flex board includes an adjacent flexure area and a rigid-flex connection area. The method for uncovering the cover of the rigid-flex board includes: providing a flexible board and a rigid board, the rigid board including a core board and a metal layer provided on the core board, the core board including an uncovering area corresponding to the flexure area and a rigid area corresponding to the rigid-flex connection area, blind vias being formed on the core board, and some of the blind vias being located at the junction of the uncovering area and the rigid area; stacking the rigid board on at least one side of the flexible board and performing lamination to form a laminated component; preparing a masking line at the junction of the uncovering area and the rigid area, the masking line corresponding to the blind vias; performing controlled-depth uncovering of the laminated component to remove the masking line and the uncovering area. The above method for uncovering the cover of the rigid-flex board is convenient for uncovering the cover and improves the product quality, effectively solving the technical problems that when the thickness of the rigid layer of the existing rigid-flex board is relatively thin, it is difficult to uncover the cover and the blind vias are prone to ingress of chemical solution, affecting the product quality.

Description

Technical Field

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

[0002] A rigid-flexible board, also known as a rigid-flex board, combines the strength of a rigid board and the flexibility of a flexible board. It can be applied in more and more fields, such as automobiles, drones, industrial control, various consumer electronic products, etc., and has excellent market prospects. In the manufacturing method, a rigid-flexible board usually takes a flexible circuit board as the core layer, stacks a rigid circuit board on at least one side of the flexible circuit board, and then removes the rigid circuit board corresponding to the flexure area to form a flexure area, and the overlapping part of the flexible circuit board and the rigid circuit board serves as the rigid-flexible bonding area. Among them, to remove the rigid circuit board corresponding to the flexure area, it can be cut and removed in a specified area first and then laminated, or laminated first and then the specified area is removed. The currently commonly used method is the latter, which is called the "uncovering method" in the industry.

[0003] In the uncovering method, blind vias are usually pre-routed at the boundary between the rigid-flexible bonding area and the flexure area before laminating the rigid core board. After laminating, the depth is controlled to the position of the blind vias on the outer layer to remove the rigid layer in the flexure area. With the high density and multi-functionality of printed circuit boards, the thickness of rigid-flexible boards tends to be thinner and lighter. When the thickness of the rigid board is relatively thin, the difficulty of uncovering will increase significantly. If the blind vias are pre-routed too shallowly, it is easy to cause difficulty in uncovering after controlling the depth on the outer layer; if the blind vias are pre-routed too deeply, the blind via area is prone to cracking, and it is easy for the etching solution to enter during circuit etching, affecting the quality of the inner-layer flexible board. Summary of the Invention

[0004] The purpose of the present application is to provide a method for uncovering a rigid-flexible board and a rigid-flexible board to solve the technical problems that when the thickness of the rigid layer of the existing rigid-flexible board is relatively thin, it is difficult to uncover and the blind via position is prone to etching solution entry, affecting the product quality.

[0005] An embodiment of the first aspect of the present application provides a method for uncovering a rigid-flexible board. The rigid-flexible board includes adjacent flexure areas and rigid-flexible bonding areas. The method for uncovering the rigid-flexible board includes:

[0006] Providing a flexible board and a rigid board. The rigid board includes a core board and a metal layer provided on the core board. The core board includes an uncovering area corresponding to the flexure area and a rigid area corresponding to the rigid-flexible bonding area. Blind vias are formed on the core board, and part of the blind vias are located at the junction of the uncovering area and the rigid area;

[0007] Stacking the rigid board on at least one side of the flexible board and performing lamination to form a laminated part, and making the opening of the blind via face the flexible board;

[0008] A shielding line is prepared at the junction of the uncovering area and the rigid area, and the shielding line corresponds to the blind groove;

[0009] The pressing part is uncovered with controlled depth, and cutting is performed from the shielding line to the blind groove to remove the shielding line and the uncovering area.

[0010] In one embodiment, the shielding line is prepared at the junction of the uncovering area and the rigid area, comprising: making the metal layer on the side of the core board facing away from the flexible board into a graphic circuit, wherein the graphic circuit forms the shielding line at the junction of the uncovering area and the rigid area.

[0011] In one embodiment, the rigid board is stacked on at least one side of the flexible board and pressed to form a pressed part, comprising:

[0012] Providing an insulating dielectric layer, wherein a window is formed on the insulating dielectric layer, and the area of ​​the window is greater than or equal to the area of ​​the uncovering area;

[0013] The insulating medium layer and the rigid board are sequentially stacked on at least one side of the flexible board and pressed together to form the pressed part, so that the notch of the blind groove faces the flexible board and is connected with the window.

[0014] In one embodiment, the area of ​​the window is larger than the area of ​​the uncovering area, and the distance between each side edge of the window and the corresponding side edge of the uncovering area is 0.4 mm to 1.0 mm.

[0015] In one embodiment, the insulating medium layer is a low-flow prepreg.

[0016] In one embodiment, the core plate further comprises two waste areas corresponding to the flexing area and located at opposite sides of the uncovering area;

[0017] The blind groove includes a middle portion and two extension portions respectively located at two ends of the middle portion, the middle portion is located at the junction of the uncovering area and the rigid area, and one end of the two extension portions away from the middle portion respectively extends to the corresponding waste area.

[0018] In one embodiment, the controlling the depth of the cover on the pressed part comprises:

[0019] removing the waste area;

[0020] Cutting is performed along the boundary between the rigid area and the uncovering area, and cutting is performed through the shielding line toward the blind groove to remove the shielding line and the uncovering area.

[0021] In one embodiment, the depth of the blind groove is less than or equal to the thickness of the core board, and the distance between the bottom of the blind groove and the side of the core board facing away from the flexible board is 0 to 50 μm;

[0022] The depth of the controlled-depth cover opening is 1 / 3 to 2 / 3 of the thickness of the core board.

[0023] In one embodiment, before performing the controlled-depth cover opening on the pressed part, it further includes: stacking an additional rigid board on at least one side of the pressed part and performing pressing.

[0024] In the above-mentioned method for uncovering the cover of the rigid-flex board, first, a rigid board is stacked on at least one side of the flexible board and pressed to form a pressed part. A blind groove is formed on the side of the rigid board facing the flexible board. Then, a shielding line is prepared at a position on the side of the core board of the rigid board facing away from the flexible board and opposite to the blind groove. The shielding line can protect the blind groove and prevent the blind groove from breaking into the chemical solution during the circuit etching stage or subsequent wet processes, corroding the flexible board in the flexure area, thereby ensuring the product quality. Secondly, even if the blind groove penetrates the core board of the rigid board, there is no need to worry about the chemical solution entering in the later stage, and the depth of the subsequent cover opening and depth control is also better controlled, facilitating the cover opening, effectively solving the technical problems that when the thickness of the rigid layer of the existing rigid-flex board is relatively thin, it is difficult to uncover the cover and the blind groove is prone to enter the chemical solution, affecting the product quality.

[0025] An embodiment of the second aspect of the present application provides a rigid-flex board, which is manufactured by using the method for uncovering the cover of the rigid-flex board according to any one of the embodiments of the first aspect.

[0026] The rigid-flex board manufactured by the above manufacturing method has high product quality and low cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0028] Figure 1 It is a schematic structural diagram of the rigid-flex board before pressing provided by an embodiment of the present application;

[0029] Figure 2 is Figure 1 A schematic structural diagram of the pressed part formed after pressing the shown rigid-flex board;

[0030] Figure 3 is Figure 2 A schematic structural diagram of the pressed part of the shown rigid-flex board after making the graphic circuit;

[0031] Figure 4 is Figure 1 The distribution schematic diagram of the cover-lifting area, rigid area and waste area on the rigid board in the shown rigid-flexible printed circuit board;

[0032] Figure 5 is Figure 1 The distribution schematic diagram of the blind vias on the rigid board in the shown rigid-flexible printed circuit board;

[0033] Figure 6 The structural schematic diagram of the press-fitted component formed after press-fitting the rigid-flexible printed circuit board provided by another embodiment of the present application;

[0034] Figure 7 The flowchart of the cover-lifting method for the rigid-flexible printed circuit board provided by an embodiment of the present application.

[0035] The meanings of the marks in the figure are as follows:

[0036] 100, rigid-flexible printed circuit board; 101, flexure area; 102, rigid-flexible connection area

[0037] 10, flexible printed circuit board;

[0038] 20, rigid board; 21, core board; 211, cover-lifting area; 212, rigid area; 213, waste area; 22, blind via; 221, middle part; 222, extension part; 23, metal layer; 231, shielding line;

[0039] 30, insulating dielectric layer; 31, window;

[0040] 40, build-up rigid board. Detailed implementation manners

[0041] In order to make the purpose, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application, and are not used to limit the present application.

[0042] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it can be directly on the other element or indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element.

[0043] It should be understood that the orientation or positional relationship indicated by terms such as "length", "width", "upper", "lower", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present application 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 application. In the description of the present application, the meaning of "a plurality" is two or more, unless otherwise specifically defined.

[0044] In the present application, unless otherwise clearly specified and limited, terms such as "installed", "connected", "connected to", "fixed", etc. should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or integrated; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific circumstances.

[0045] In order to illustrate the technical solutions described in the present application, the following will be described in conjunction with specific drawings and embodiments.

[0046] An embodiment of the first aspect of the present application provides a method for uncovering a rigid-flex board, which is particularly applicable to the case where the thickness of the rigid board is relatively thin, such as the case where the core board thickness of the rigid board ≤ 0.5 mm.

[0047] Please refer to Figure 1 、 Figure 2 and Figure 7 , in an embodiment of the present application, the rigid-flex board 100 includes adjacent flexure areas 101 and rigid-flex bonding areas 102. The method for uncovering the rigid-flex board includes the steps:

[0048] Step S1: Provide a flexible board 10 and a rigid board 20.

[0049] The flexible board 10 is a double-sided flexible copper clad laminate, that is, the flexible board 10 includes a flexible substrate and copper foils provided on opposite sides of the flexible substrate. The flexible substrate can be a flexible insulating material such as a polyester film or a polyimide film. It can be understood that in other embodiments of the present application, the flexible board 10 can also be a single-sided flexible copper clad laminate, which is not limited herein.

[0050] The rigid board 20 includes a core board 21 and a metal layer 23 disposed on the core board 21. The rigid board 20 is a double-sided copper-clad board, that is, metal layers 23 are disposed on opposite sides of the core board 21, where the metal layer 23 is a copper layer. It can be understood that the core board 21 is a rigid board insulating medium, and one side of the core board 21 is used to dock with the flexible board 10, defined as the inner side. The copper layer on the inner side is pre-made into a graphic circuit before the blind groove 22 is prepared. The depth of the blind groove 22 is less than or equal to the thickness of the core board 21 to avoid cutting through the copper layer and causing the subsequent process to introduce chemicals. The core board 21 includes a uncovering area 211 corresponding to the flexing area 101 and a rigid area 212 corresponding to the rigid-flexible combination area 102. A blind groove 22 is provided on the core board 21, wherein the blind groove 22 can be prepared by mechanically controlled deep milling or laser ablation or a combination of the two. Optionally, the blind groove 22 is formed by UV laser ablation. Part of the blind groove 22 is located at the junction a between the uncovering area 211 and the rigid area 212, that is, the blind groove 22 is provided at the junction of the rigid-flexible combination area 102 and the flexure area 101. Specifically, the main part of the blind groove 22 is located at the junction a between the uncovering area 211 and the rigid area 212, and the end of the blind groove 22 can be inclined with the main part and extend to the outside of the uncovering area 211, for example, it can extend to the waste area to facilitate cutting.

[0051] It can be understood that in other embodiments of the present application, the rigid board 20 can also be a single-sided copper-clad board, that is, the core board 21 has a copper layer on only one side, and the blind groove 22 is opened on the side not covered by the copper layer, which is not limited here.

[0052] Step S2 : stacking the rigid board 20 on at least one side of the flexible board 10 and pressing them together to form a pressed part, with the opening of the blind groove 22 facing the flexible board 10 .

[0053] In this embodiment, please refer to Figure 2 , the rigid board 20 is a double-sided copper-clad board, and the rigid board 20 can be stacked on both sides of the flexible board 10 and pressed to form a pressed part. It can be understood that in other embodiments of the present application, the rigid board 20 is a single-sided copper-clad board, and the rigid board 20 is only stacked on one side of the flexible board 10 and pressed, at this time, the flexible board 10 is pressed with the side of the rigid board 20 that is not copper-clad; in another embodiment, the rigid board 20 can also be a multi-layer board, which is not limited here.

[0054] Step S3: preparing a shielding line 231 at the junction of the uncovering area 211 and the rigid area 212 .

[0055] Please refer to Figure 1 and Figure 3, a shielding line 231 is formed at the junction of the uncovering area 211 and the rigid area 212, and the shielding line 231 corresponds to the blind groove 22. The shielding line 231 can be a copper wire prepared by film pasting, exposure, development, and etching processes; or, the shielding line 231 can also be a material such as a protective tape that does not react with the medicine in the subsequent process. The shielding line 231 is laid on the side of the core board 21 of the rigid board 20 away from the flexible board 10, and the width of the shielding line 231 is slightly larger than the width of the blind groove 22 to completely cover the blind groove 22 area, thereby protecting the blind groove 22 and preventing the blind groove 22 from breaking and entering the medicine during the circuit etching stage or the subsequent wet process, corroding the flexible board 10 in the flexure area 101, and affecting the product quality. It can be understood that even if the blind groove 22 runs through the core board 21 of the rigid board 20, there is no need to worry about the medicine entering the later stage, and the depth of the subsequent uncovering control is also better controlled, which is convenient for uncovering.

[0056] Step S4: Control the depth of the pressed parts and uncover them.

[0057] Cutting is performed from the shielding line 231 to the blind groove 22 to remove the shielding line 231 and the uncovering area 211. Specifically, cutting is performed from the side of the rigid board 20 opposite to the blind groove 22 to the side where the blind groove 22 is located to remove the shielding line 231 opposite to the blind groove 22, and to connect with the blind groove 22 to form a through groove in the core board 21, so as to remove the uncovering area 211 of the rigid board 20, expose the internal flexible board 10, and form the flexing area 101. The cutting can be completed by mechanical controlled deep milling or laser ablation or a combination of the two.

[0058] In the above-mentioned uncovering method of the rigid-flexible board, a rigid board 20 is first stacked on at least one side of the flexible board 10 and pressed together to form a pressed part. A blind groove 22 is provided on the side of the rigid board 20 facing the flexible board 10. Then, a shielding line 231 is prepared at a position opposite to the blind groove 22 on the side of the core board 21 of the rigid board 20 away from the flexible board 10. The shielding line 231 can protect the blind groove 22 to prevent the blind groove 22 from breaking and entering the liquid medicine during the circuit etching stage or the subsequent wet process, thereby corroding the flexible board 10 in the flexure area 101, thereby ensuring product quality. Secondly, even if the blind groove 22 passes through the core board 21 of the rigid board 20, there is no need to worry about the liquid medicine entering in the later stage, and the depth of the subsequent uncovering control is also better controlled, which is convenient for uncovering, and effectively solves the technical problems of the existing rigid-flexible board 100 that when the rigid layer thickness is thin, it is difficult to uncover and the blind groove 22 is easy to enter the liquid medicine, which affects the product quality.

[0059] Please refer to Figures 1 to 3In one embodiment of the present application, step S3: preparing a shielding line 231 at the junction of the uncovering area 211 and the rigid area 212, including: making the metal layer 23 on the side of the core board 21 away from the flexible board 10 into a graphic circuit. Among them, the graphic circuit is formed with a shielding line 231 at the junction of the uncovering area 211 and the rigid area 212, and the shielding line 231 corresponds to the blind groove 22. In this way, the remaining normal graphic circuits and the shielding line 231 on the side of the core board 21 away from the flexible board 10 are etched together, and the depth control path is adjusted during the subsequent depth control uncovering, and the shielding line 231 can be removed while uncovering, which is consistent with the existing processing flow of the rigid-flexible board 100, without adding new processes and costs.

[0060] Specifically, through the process of lamination, exposure, development and etching, the metal layer 23 on the side of the core board 21 facing away from the flexible board 10 is made into a graphic circuit, wherein the graphic circuit forms a shielding line 231, i.e., a copper wire, at the junction of the uncovering area 211 and the rigid area 212.

[0061] It is understood that in other embodiments of the present application, the shielding line 231 may not be completed together with other graphic circuits. For example, the shielding line 231 may be a material that does not react with the solution in the subsequent process, such as a protective tape, and is pasted on the corresponding position of the blind groove 22 to protect the blind groove 22, which is not limited here.

[0062] Please refer to Figure 1 and Figure 2 In one embodiment of the present application, step S2: stacking a rigid board 20 on at least one side of the flexible board 10 and pressing the rigid board 20 to form a pressed part comprises:

[0063] First, an insulating dielectric layer 30 is provided. A window 31 is formed on the insulating dielectric layer 30 . The area of ​​the window 31 is greater than or equal to the area of ​​the uncovering area 211 .

[0064] Under high temperature and high pressure conditions, the insulating dielectric layer 30 can bond the flexible board 10 and the rigid board 20 together to form a pressed part of the rigid-flexible board 100. The insulating dielectric layer 30 used to bond the flexible board 10 and the rigid board 20 needs to open a window 31 in advance, that is, remove the part of the insulating dielectric layer 30 opposite to the uncovering area 211 to prevent the insulating dielectric layer 30 from melting and flowing to the flexing area 101 during lamination, bonding the flexible board 10 and the rigid board 20 located in the flexing area 101, and making it impossible to uncover in the subsequent process. Among them, the insulating dielectric layer 30 is a semi-cured sheet. Optionally, the insulating dielectric layer 30 is a low-flow semi-cured sheet, which can effectively improve the problem of glue flow during the lamination process and ensure product quality.

[0065] Then, an insulating dielectric layer 30 and a rigid board 20 are sequentially stacked on at least one side of the flexible board 10 and pressed together to form a pressed part, so that the opening of the blind groove 22 faces the flexible board 10 and communicates with the window 31 .

[0066] In this embodiment, an insulating dielectric layer 30 and a rigid board 20 are stacked on opposite sides of the flexible board 10 , so that a 6-layer rigid-flexible board 100 can be manufactured.

[0067] Please refer to Figure 1 In one embodiment of the present application, the area of ​​the window 31 is larger than the area of ​​the uncovering area 211, and the distance between each side of the window 31 and the corresponding side of the uncovering area 211 is 0.4mm-1.0mm, that is, relative to the junction a between the uncovering area 211 and the rigid area 212, the single side of the window 31 is retracted by 0.4mm-1.0mm. In other words, the area of ​​the insulating dielectric layer 30 that needs to be removed in advance is slightly larger than the area of ​​the uncovering area 211, so that it can be avoided that the dielectric layer melts and flows to the flexing area 101 during lamination, and the flexible board 10 and the rigid board 20 in the flexing area 101 are bonded.

[0068] It can be understood that in other embodiments of the present application, the size of the window 31 can also be adjusted according to the fluidity of the insulating dielectric layer 30. When the fluidity of the insulating dielectric layer 30 is relatively high, the size of the window 31 can be appropriately increased; when the fluidity of the insulating dielectric layer 30 is relatively small, the size of the window 31 can be appropriately reduced.

[0069] Please refer to Figures 1 to 5 In one embodiment of the present application, the core board 21 further includes two waste areas 213 corresponding to the flexing area 101 and located on opposite sides of the uncovering area 211. That is, the waste area 213 on the core board 21 of the rigid board 20 is also located on the flexing area 101.

[0070] The blind groove 22 includes a middle portion 221 and two extension portions 222 located at both ends of the middle portion 221 . The middle portion 221 is located at the junction a between the uncovering area 211 and the rigid area 212 . One end of the two extension portions 222 away from the middle portion 221 extends to the corresponding waste area 213 .

[0071] In this embodiment, the boundary line between the cover-lifting area 211 and the rigid area 212 is a straight line segment, and the slotting path of the blind slot 22 is a straight line in the middle, and ends in an arc shape, that is, the middle part 221 is a straight line segment, wherein the arc-shaped cutting path goes deep into the waste area 213. With such a design, the entry and exit of the tool during cutting are completed in the waste area 213, which can reduce the formation of burrs on the edge of the cover-lifting area 211, and ensure that the edge of the cover-lifting area 211 is neat and burr-free. It can be understood that the subsequent depth-controlled cover-lifting path corresponds to the blind slot 22 cutting path, so as to connect the blind slot 22, finally form a through slot and complete the cover-lifting.

[0072] In one embodiment of the present application, step S4: controlling the depth of the pressed part to be uncovered comprises:

[0073] First, remove the scrap area 213. That is to say, the scrap area 213 is removed during the forming stage and will not appear on the finished product.

[0074] Then, cut along the junction of the rigid area 212 and the cover-lifting area 211, and cut through the shielding line 231 towards the blind slot 22 to remove the shielding line 231 and the cover-lifting area 211.

[0075] In this way, when performing depth-controlled cover-lifting on the laminated part, first remove the scrap area 213 on the core board 21 of the rigid board 20, then the two sides at the junction of the cover-lifting area 211 and the scrap area 213 are first milled and formed. Then, cut along the junction of the rigid-flexible bonding area 102 and the flexure area 101, that is, cut along the junction of the rigid area 212 and the cover-lifting area 211, cut through the shielding line 231 towards the blind slot 22 to remove the shielding line 231, and connect with the blind slot 22 to form a through slot in the core board 21, thereby removing the cover-lifting area 211. The cutting can be performed by methods such as mechanical depth-controlled milling, laser ablation, or a combination of both. Among them, the cutting starting point should be such that it can remove the shielding line 231 and can connect to the blind slot 22 downward.

[0076] Please refer to Figure 1 and Figure 3 , in an embodiment of the present application, the depth of the blind slot 22 is less than or equal to the thickness of the core board 21, so as to avoid cutting through the metal layer 23 on the side of the core board 21 away from the flexible board 10, thereby avoiding the entry of chemical solution in the subsequent manufacturing process. The distance between the bottom of the blind slot 22 and the side of the core board 21 away from the flexible board 10 is 0 - 50 μm, that is, the allowance between the core board 21 at the bottom of the slot and the closest adjacent copper foil layer is 0 - 50 μm.

[0077] It can be understood that if the blind slot 22 is pre-milled too shallowly, it is easy to cause difficulty in removing the cover after depth control of the outer layer; if the blind slot 22 is pre-milled too deeply, the blind slot 22 is prone to cracking, and it is easy for chemical solution to enter after circuit etching, affecting the quality of the inner-layer flexible board.

[0078] In this embodiment, the depth of the blind slot 22 has approached the thickness of the core board 21 of the rigid board 20. Therefore, the depth of depth-controlled cover-lifting can be adjusted more conveniently. As long as it is ensured that the core board 21 of the cover-lifting area 211 can be removed by connecting to the blind slot 22, there is no need to precisely control the depth control accuracy, nor to worry about insufficient depth to complete the cover-lifting. The cutting path is opposite to the blind slot 22 opening path, and the arc-shaped cutting paths at both ends can ensure that there are no burrs and flash on the cover-lifting edge.

[0079] In one embodiment, please refer to Figure 3 , the depth b of depth-controlled cover-lifting is less than the thickness of the core board 21. Specifically, the depth b of depth-controlled cover-lifting is 1 / 3 - 2 / 3 of the thickness of the core board 21. In this way, it can be ensured that the blind slot 22 can be connected and the core board 21 of the cover-lifting area 211 can be removed; in addition, it can also avoid excessive cutting depth during cover-lifting and affecting the internal flexible board 10.

[0080] In one embodiment of the present application, before step S4: controlling the depth and uncovering the cover of the pressed component, it further includes: stacking an additional rigid board 40 on at least one side of the pressed component and performing pressing to obtain a rigid-flexible printed circuit board 100 with multiple layers. In this way, the rigid-flexible printed circuit board 100 with the required number of layers can be designed according to user requirements.

[0081] In this embodiment, please refer to Figure 3 and Figure 6 , after the flexible board 10 and the rigid board 20 are pressed together once to obtain a pressed component, before uncovering the cover, additional rigid boards 40 can be further stacked and pressed on the opposite sides of the pressed component respectively for layer addition. The additional rigid board 40 can also be a double-sided copper clad laminate or a single-sided copper clad laminate. It can be understood that an insulating dielectric layer 30 is still required between the secondarily stacked additional rigid board 40 and the original rigid board 20 for bonding, so as to obtain a 10-layer rigid-flexible printed circuit board 100. When uncovering the cover, it is necessary to consider the thickness of the secondarily stacked additional rigid board 40 and the core board 21 of the original rigid board 20, and mill them out together with controlled depth. It can be understood that the controlled-depth uncovering depth c of the 10-layer rigid-flexible printed circuit board 100 needs to include the thickness of the secondarily stacked additional rigid board 40, the thickness of the insulating dielectric layer 30 between the secondarily stacked additional rigid board 40 and the first-stacked rigid board 20, and the original cutting thickness required for the original rigid board 20. In addition, the process of repeatedly stacking the additional rigid board 40 and performing pressing can also be carried out according to needs to obtain a rigid-flexible printed circuit board with more layers, which is not limited here.

[0082] It can be understood that in other embodiments of the present application, after the flexible board 10 and the rigid board 20 are pressed together once to obtain a pressed component, before uncovering the cover, an additional rigid board 40 can be further stacked and pressed on one side of the pressed component for layer addition.

[0083] An embodiment of the second aspect of the present application provides a rigid-flexible printed circuit board 100, which is manufactured by using the uncovering method of the rigid-flexible printed circuit board provided in any embodiment of the first aspect.

[0084] The rigid-flexible printed circuit board 100 can be any multi-layer board. The product quality of the rigid-flexible printed circuit board 100 manufactured by the above manufacturing method is high and the cost is low.

[0085] Taking a 6-layer rigid-flexible printed circuit board 100 as an example, the uncovering method of the rigid-flexible printed circuit board provided by the present application is described below. Please refer to Figures 1 to 7 , the uncovering method of the rigid-flexible printed circuit board specifically includes the following steps:

[0086] First, provide a flexible board 10, a rigid board 20, and an insulating dielectric layer 30.

[0087] The main process of the flexible board 10 includes: engineering design, cutting, inner layer graphic circuit, inner layer AOI, covering film on the flexure area 101, browning, and transfer and pressing. The main process of the rigid board 20 includes: engineering design, cutting, inner layer graphic circuit, inner layer AOI, blind groove 22, browning, and transfer and pressing. The insulating dielectric layer 30 is a prepreg with low fluidity, and its main process includes: cutting and milling window opening.

[0088] Engineering design optimizes the pattern circuit manufacturing data of the rigid board 20 facing away from the flexible board 10 in advance to ensure that the shielding line 231 is retained at the position corresponding to the blind groove 22 after etching.

[0089] Cut the flexible copper clad laminate, rigid copper clad laminate and PP large material into preset sizes according to the production panel size requirements.

[0090] The inner layer pattern circuit is made according to conventional processes, and the pattern circuit of the flexible board 10 and the pattern circuit on the side where the blind groove 22 of the rigid board 20 is located, that is, the pattern circuit on the side of the rigid board 20 facing the flexible board 10 are made normally. Specifically, the pattern circuit is made through the process of laminating (photoresist material), exposure, development, and etching.

[0091] Inner layer AOI (Automatic Optical Inspection) uses optical principles to compare the etched graphic circuit with the pre-designed circuit to check whether the circuit has open circuit, short circuit and other defects.

[0092] A blind groove 22 is formed on the rigid board 20 in an area corresponding to the junction of the rigid-flexible combination area 102 and the flexure area 101, that is, the junction of the rigid area 212 and the cover area 211 on the core board 21, using laser ablation to form the blind groove 22. The two ends of the path of the blind groove 22 are arc-shaped, extending into the waste area 213 along the edge of the cover area 211. The depth of the blind groove 22 should be less than or equal to the thickness of the core board 21 of the rigid board 20.

[0093] Browning increases the roughness of the copper surface by chemical reaction, thereby enhancing the bonding force between the insulating dielectric layer 30 and the copper surface during subsequent lamination.

[0094] The window 31 is opened on the insulating medium layer 30 by milling, and the area of ​​the window 31 is greater than or equal to the area of ​​the uncovering area 211.

[0095] Next, press fit.

[0096] Using a press, under high temperature and high pressure, the insulating dielectric layer 30 is pressed and melted, so as to press and bond multiple core boards 21 and the prepregs between layers together to form a pressed component with a preset number of layers. During pressing, different pressing parameters are selected according to different materials. The differences in pressing parameters are mainly conditions such as the heating rate, the maximum temperature, the maximum pressure, and the duration of the high temperature and high pressure section. Since the insulating dielectric layer 30 is a low-flow prepreg, it is necessary to open a window in advance at the position corresponding to the cover-lifting area 211 to prevent the flexible board 10 and the rigid board 20 in the cover-lifting area 211 from being bonded after pressing and unable to lift the cover.

[0097] Next, drill holes.

[0098] According to the design data, use a laser drilling machine to drill blind holes at designated positions on the pressed component and / or use a mechanical drilling machine to drill through holes, etc.

[0099] Then, carry out electroless copper plating and panel plating.

[0100] Using the principle of electrochemical reaction, deposit and electroplate a copper layer with a specified thickness in the holes processed in the previous process to make it conduct with the circuits of each layer. Non-metallized holes do not need to be plated with a copper layer in this process.

[0101] Next, fabricate the outer layer graphic circuit.

[0102] According to the conventional process, normally fabricate the graphic circuit of the outermost layer of the pressed component. Among them, the shielding line 231 on the opposite side of the blind groove 22 and the rest of the graphic circuit are etched and formed together. The shielding line 231 needs to cover the blind groove 22 and be slightly wider than the width of the blind groove 22 to ensure that no chemical solution penetrates during etching and subsequent wet processes. However, the shielding line 231 cannot be too wide, otherwise it will be inconvenient to mill and remove during subsequent depth-controlled cover lifting.

[0103] Then, perform solder mask, printing, surface treatment, and then perform milling and cover lifting with depth control.

[0104] Taking the cover-lifting area 211 as the boundary, first remove the waste area 213 on the core board 21, then mill and form the two sides where the cover-lifting area 211 intersects with the waste area 213; then, cut along the junction of the rigid-flexible bonding area 102 and the flexure area 101, that is, cut along the junction of the rigid area 212 and the cover-lifting area 211. The cutting starting point should be such that it can remove the copper wire and can connect to the blind groove 22 downward. The cutting path is opposite to the blind groove 22 windowing path, and the arc-shaped cutting paths at both ends ensure that there are no burrs and flash on the cover-lifting edge.

[0105] Complete the subsequent processes according to the conventional process until packaging and shipping.

[0106] The above-described embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present application, and should all be included within the protection scope of the present application.

Claims

1. A method for uncovering a rigid-flexible printed circuit board, characterized in that, The rigid-flex board includes adjacent flexing areas and rigid-flex combining areas, and the method for uncovering the rigid-flex board includes: A flexible board and a rigid board are provided, wherein the rigid board comprises a core board and a metal layer arranged on the core board, the core board comprises a cover area corresponding to the flexure area and a rigid area corresponding to the rigid-flex combination area, and a blind groove is provided on the core board, and part of the blind groove is located at the junction of the cover area and the rigid area; The rigid plate is stacked on at least one side of the flexible plate and pressed to form a pressed part, and the notch of the blind groove faces the flexible plate; A shielding line is prepared at the junction of the uncovering area and the rigid area, and the shielding line corresponds to the blind groove; The pressing piece is uncovered with controlled depth, and cutting is performed from the shielding line to the blind groove to remove the shielding line and the uncovering area.

2. The method for uncovering a rigid-flexible printed circuit board according to claim 1, characterized in that, The step of preparing a shielding line at the boundary between the uncovering area and the rigid area comprises: making the metal layer on the side of the core board away from the flexible board into a graphic circuit, wherein the graphic circuit forms the shielding line at the boundary between the uncovering area and the rigid area.

3. The method for uncovering a rigid-flexible printed circuit board according to claim 1, characterized in that, The rigid plate is stacked on at least one side of the flexible plate and pressed to form a pressed part, comprising: Providing an insulating dielectric layer, wherein a window is formed on the insulating dielectric layer, and the area of ​​the window is greater than or equal to the area of ​​the uncovering area; The insulating medium layer and the rigid board are sequentially stacked on at least one side of the flexible board and pressed together to form the pressed part, so that the notch of the blind groove faces the flexible board and is connected with the window.

4. The method for uncovering a rigid-flexible printed circuit board according to claim 3, characterized in that, The area of ​​the window is larger than the area of ​​the uncovering area, and the distance between each side edge of the window and the corresponding side edge of the uncovering area is 0.4 mm to 1.0 mm.

5. The method for uncovering a rigid-flexible printed circuit board according to claim 3, characterized in that, The insulating medium layer is a low-fluidity prepreg.

6. The method for uncovering a rigid-flexible printed circuit board according to claim 3, characterized in that, The core plate further comprises two waste areas corresponding to the flexing area and located at opposite sides of the uncovering area; The blind groove includes a middle portion and two extension portions respectively located at two ends of the middle portion, the middle portion is located at the junction of the uncovering area and the rigid area, and one end of the two extension portions away from the middle portion respectively extends to the corresponding waste area.

7. The method for uncovering a rigid-flexible printed circuit board according to claim 6, characterized in that, The controlling the depth of the cover on the pressed part comprises: removing the waste area; Cutting is performed along the boundary between the rigid area and the uncovering area, and cutting is performed through the shielding line toward the blind groove to remove the shielding line and the uncovering area.

8. The method for uncovering a rigid-flexible printed circuit board according to claim 3, characterized in that, The depth of the blind groove is less than or equal to the thickness of the core plate, and the distance between the bottom of the blind groove and the side of the core plate away from the flexible plate is 0 to 50 μm; The depth of the controlled depth cover is 1 / 3 to 2 / 3 of the thickness of the core board.

9. The preparation method of the method for uncovering a rigid-flexible printed circuit board according to any one of claims 1-8, characterized in that, Before the controlled depth uncovering of the pressing piece, the method further includes: stacking a build-up rigid board on at least one side of the pressing piece and pressing it.

10. A rigid-flexible printed circuit board, characterized in that, The rigid-flexible board is manufactured by the uncovering method of any one of claims 1 to 9.

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