Large-bending-angle semi-flexible rigid-flex printed circuit board manufacturing method

Abstract

The invention discloses a manufacturing method of a large-bending-angle semi-flexible rigid-flexible combined board, which comprises the following steps of: taking a double-sided copper-clad board, and manufacturing a core board pattern to form a middle core board; a copper layer is divided into an upper surface copper layer and a lower surface copper layer, the first prepreg and the second prepreg are stacked with the middle core plate to form a stacked structure, and then the stacked structure is laminated to form a laminated plate; manufacturing a surface circuit pattern on the laminated plate, performing depth-controlled milling on the bending area to form a groove, milling the groove to form a trapezoid, and forming; the positioning mold is manufactured and fixed through the pins, the stability of the plate in the manufacturing process is ensured, and therefore the overall structural stability of a finished product is improved; by utilizing the guidance quality of the positioning die and setting the whole milling process to form a micro-current loop process, the milling precision is effectively improved, and the processing of a high-precision circuit board is facilitated.

Description

Technical Field

[0001] The present invention relates to the field of manufacturing rigid-flexible boards, and in particular to a method for manufacturing a semi-flexible rigid-flexible board with a large bending angle. Background Art

[0002] As a multi-layer circuit board that combines a rigid board and a flexible board, the semi-flexible rigid-flexible board has the characteristics of sequential bending or a small number of bending times. It plays an important role in some intelligent connected vehicle power modules or industrial control module applications due to its high integration and high space utilization.

[0003] However, for semi-flexible rigid-flexible panels where the thickness is greater than the width of the bending zone, it is often impossible to form an effective bend at a large angle (such as a 90-degree bend).

[0004] The processing method for the thicker rigid-flexible board mentioned above is usually as follows: when designing the circuit board stack, different layers are made with different window sizes, and after pressing, the stepped positions of the rigid board area and the bending area form a stepped structure; or the cover is opened gradually and multiple times from the board surface to the bottom of the bending area to form a bending area with a stepped structure.

[0005] However, both of the above processing methods have certain defects: if the processing method of opening the window first and then pressing is adopted, problems such as step deformation and glue overflow are likely to occur at the folding step position; if the processing method of opening the cover multiple times is adopted, the vibration, friction, expansion and contraction of the plate body caused by the processing process will be too great, which may easily lead to the process being more complicated and the processing cost being higher.

[0006] Therefore, in order to solve the above-mentioned problems, it is necessary to provide a method for manufacturing a semi-flexible rigid-flexible board with a large bending angle. Summary of the invention

[0007] The present invention aims to solve the problem that the semi-flexed rigid-flexible board of the prior art cannot achieve effective bending at a large angle when the thickness of the board is greater than the width of the bending zone. A method for manufacturing a semi-flexed rigid-flexible board with a large bending angle is proposed. The rigid-flexible board comprises a bending zone and a rigid zone. The width of the bending zone is less than or equal to the thickness of the rigid-flexible board. The manufacturing method comprises the following steps: S10: Take a double-sided copper clad laminate, make a core board pattern, and form an intermediate core board; S20: taking a copper layer, the copper layer being divided into an upper surface copper layer and a lower surface copper layer, and taking a first prepreg and a second prepreg, stacking them with the intermediate core board to form a stacked structure, and then pressing them together to form a pressed board; the stacked structure is stacking the upper surface copper layer, the second prepreg, the intermediate core board, the first prepreg and the lower surface copper layer from top to bottom; S30: making a surface circuit pattern on the pressed plate, and performing controlled depth milling on the bending area to form a groove, so that the whole plate becomes a grooved plate; S40: milling the groove to make it into a trapezoid, and then shaping it to form the semi-flexible rigid-flexible board with a large bending angle.

[0008] Furthermore, the manufacturing method includes attaching a first covering film to a region of the first prepreg corresponding to the bending region, and the first covering film in the stacked structure is arranged toward the middle core plate.

[0009] Furthermore, a third semi-cured sheet is taken and a blind groove is made to form a blind groove semi-cured sheet, wherein the blind groove is located at the edge of the bending zone; the stacked structure includes a blind groove semi-cured sheet arranged between the intermediate core plate and the first semi-cured sheet; the blind groove is arranged toward the first semi-cured sheet.

[0010] Furthermore, the blind groove prepreg is attached with a second covering film in the corresponding bending area.

[0011] Furthermore, a single side of the first covering film is greater than or equal to the bending area.

[0012] Furthermore, the controlled depth milling is milling to the first covering film.

[0013] Furthermore, a single side of the second covering film is smaller than or equal to the bending area.

[0014] Furthermore, the milling is to make a positioning mold, the positioning mold having a load-bearing end and a fixed end, the load-bearing end being a two-sided structure connected to each other, and the intersection line of the two sides being the top edge; fixing the groove plate on the positioning mold, the bending area corresponding to the top edge, the groove facing away from the top edge, the rigid areas respectively fixed on the two sides, and the bending surfaces forming an apparent angle; forming a structure to be milled; fixing the structure to be milled on the table of a milling machine, the groove plate being separated from the table, and the rigid plate forming an acute angle with the milling cutter used for milling; and then performing the milling process.

[0015] Furthermore, the production of the groove plate also includes: drilling through holes and electroplating the pressed plate, the through holes forming positioning vias, and then producing the surface circuit pattern, the surface circuit pattern including a limiting circuit pattern, and the positioning vias are connected to the limiting circuit pattern.

[0016] Furthermore, the method of fixing the groove plate to the positioning mold includes: a first pin hole is made on the bearing end; a first pin is used to fix the groove plate to the surface of the bearing end through the first pin hole and the positioning conductive hole; a second pin hole is made on the fixed end, and a table top fixing hole is provided on the table top; a second pin is used to fix the milling structure to the table top through the second pin hole and the table top fixing hole; the table top is a conductive table top, and the milling machine has a control center, and the control center is electrically connected to the conductive table top and the milling cutter respectively.

[0017] The technical solution of the present invention ensures the position stability and processing accuracy of the plate during the manufacturing process by making a positioning mold and using pins to fix it as an auxiliary processing tool, thereby improving the overall structural stability of the finished product, reducing possible quality problems in the production process, and enhancing the reliability of the product in practical applications; by utilizing the guiding property of the mold, combining it with the control center and the conductive table to form an automatic control system for milling processing, and setting the overall milling process to form a micro-current loop process of "milling cutter → limiting circuit pattern → positioning conductive hole → pin → milling machine → control center → milling cutter", the milling accuracy is effectively improved, which is beneficial to the processing of high-precision circuit boards. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] 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 the structures shown in these drawings without paying creative work.

[0019] Figure 1 Schematic diagram of the process flow of an embodiment of the present invention; Figure 2 is a schematic cross-sectional view of a stacked structure according to an embodiment of the present invention; Figure 3 is a schematic cross-sectional view of a pressed plate according to an embodiment of the present invention; Figure 4 is a schematic diagram of the cross-sectional structure of a groove plate according to an embodiment of the present invention; Figure 5 for Figure 4 Schematic diagram of the plane structure; Figure 6 It is a structural schematic diagram of the milling process according to the embodiment of the present invention; Figure 7 It is a schematic diagram of the cross-sectional structure of a rigid-flex board according to an embodiment of the present invention.

[0020] Description of Figure Numbers:

[0021] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0022] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] It should be noted that all directional indications in the embodiments of the present invention (such as up, down, left, right, front, back, inside, outside...) are only used to explain the relative position relationship, movement status, etc. between the components in a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0024] In addition, in the present invention, descriptions such as "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" or "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0025] In addition, the technical solutions between the various embodiments of the present invention can be combined with each other, but it must be based on the fact that ordinary technicians in the field can implement it. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0026] See also Figure 1 , Figure 1 Schematic diagram of the process flow of an embodiment of the present invention.

[0027] The manufacturing process of the embodiment of the present invention includes using Figure 1 The following will implement the various steps in the process Figure 1 Each step in the process is further explained step by step.

[0028] See also Figure 2 , Figure 2 Schematic cross-sectional view of a stacked structure according to an embodiment of the present invention.

[0029] The rigid-flex board 10 of this embodiment includes a bending area 10A and a rigid area 10B. The width of the bending area 10A is less than or equal to the thickness of the rigid-flex board 10 .

[0030] Step S10: A double-sided copper clad laminate is used to make a core board pattern 1010 to form an intermediate core board 100, that is, a base layer of a multi-layer laminated structure, which provides a core board foundation for subsequent processing steps.

[0031] Please refer again Figure 2 , and see Figure 3 , Figure 3 It is a schematic cross-sectional view of a pressed plate according to an embodiment of the present invention.

[0032] Step S20: Take the copper layer, which is divided into an upper surface copper layer 200 and a lower surface copper layer 300, and take the first semi-cured sheet 400 and the second semi-cured sheet 500, and stack them with the intermediate core board 100 to form a stacked structure 20, and then press them together to form a pressed board 30; the stacked structure 20 is the upper surface copper layer 200, the second semi-cured sheet 500, the intermediate core board 100, the first semi-cured sheet 400 and the lower surface copper layer 300 stacked from top to bottom.

[0033] In this embodiment, the manufacturing method includes attaching a first covering film 4010 to the area of ​​the first semi-cured sheet 400 corresponding to the bending area 10A. Usually, the first covering film 4010 is made of polyimide. The covering film material of the flexible circuit board is used here. On the one hand, it can provide an additional flexible layer, which helps to disperse the stress of the bending area 10A of the rigid-flexible board 10 during use, plays a role in buffering stress, and reduces the risk of damage caused by stress concentration; on the other hand, the first covering film 4010 can increase the softness of the bending area 10A, thereby making it easier to achieve large-angle bending and maintain good performance even after multiple bending.

[0034] Furthermore, the first covering film 4010 in the stacked structure 20 is arranged toward the middle core board 10, that is, the inertia between the first covering film 4010 and the substrate is utilized to provide a structural basis for easy uncovering for the subsequent controlled deep milling processing. At the same time, a protective film is formed for the first semi-cured sheet 400 exposed in the bending area 10A, thereby preventing the first semi-cured sheet 400 from tearing or falling off when the rigid-flexible board 10 is used, thereby causing board surface pollution and other problems, thereby extending the service life of the rigid-flexible board 10.

[0035] Then take the third semi-cured sheet, make a blind groove 6010, and form a blind groove semi-cured sheet 600. The blind groove 6010 is located at the edge of the bending zone. At this time, the stacked structure 20 includes a blind groove semi-cured sheet 600 arranged between the middle core board 100 and the first semi-cured sheet 400; the blind groove 6010 is arranged toward the first semi-cured sheet 600 to form a pre-processing milling cut, which is effectively coordinated with the controlled depth milling cut in the subsequent process, that is, a controlled depth milling cut is formed around the edge of the bending zone 10A, and the depth of the controlled depth milling cut is from the board surface to the blind groove 6010. Then, the rigid plate in the controlled depth milling cut area is peeled off to avoid the controlled depth milling cut from reaching the position of the first covering film 4010, thereby effectively reducing the risk of the first semi-cured sheet 400 being damaged by milling cut, providing a larger milling error tolerance, and improving the processing accuracy of the circuit board. At the same time, it also effectively avoids excessive vibration and expansion and contraction effects on the circuit board caused by a large amount of controlled depth milling cuts.

[0036] Furthermore, a second covering film 6020 is attached to the blind groove semi-cured sheet 600 at the corresponding bending area 10A. Usually, the second covering film 6020 is also made of polyimide, and the covering film material of the flexible circuit board is also used. Combined with the setting of the above-mentioned first covering film 4010, a structure to be pressed corresponding to the second covering film 6020 and the first covering film 4010 is formed. The material of the covering film has strong inertness. When pressed, the first covering film 4010 and the second covering film 6020 form a good release effect with each other, which effectively cooperates with the depth-controlled milling and cover-lifting processing in the subsequent process.

[0037] Furthermore, a single side of the first covering film 4010 is greater than or equal to the bending zone 10A, forming a structure in which the first covering film 4010 penetrates deep into the interior of the circuit board, that is, utilizing the advantages of the first covering film 4010 material such as high reliability, bendability, and not prone to cracking or chipping, to provide a covering and protective effect on the first semi-cured sheet 600 exposed after milling, thereby preventing the first semi-cured sheet 600 from tearing or chipping when bent, causing contamination of the board surface, and extending the service life of the circuit board.

[0038] Furthermore, the second covering film 6020 has a single side that is less than or equal to the bending zone 10A. On the one hand, it can effectively reduce unnecessary material usage and lower production costs. On the other hand, it can avoid the formation of a structure in which the first covering film 4010 and the second covering film 6020 simultaneously penetrate into the interior of the circuit board. In the case of large-angle bending, the first covering film 4010 and the second covering film 6020 have a certain thickness and form a release effect with each other, which may easily lead to the first covering film 4010 and the second covering film 6020. The bonding force between the substrate may not be sufficient to resist the bending stress. During the application process, the rigid-flexible board 10 may crack at the junction of the bending zone 10A and the rigid zone 10B.

[0039] See also Figure 4 and Figure 5 , Figure 4is a schematic diagram of the cross-sectional structure of a groove plate according to an embodiment of the present invention; Figure 5 for Figure 4 Schematic diagram of the plane structure; Step S30: A surface circuit pattern 410 is made on the laminated plate 30, and the bending area 10A is subjected to controlled depth milling, wherein the controlled depth milling is to mill to the first covering film 4010 to form a groove 420, and the entire plate is formed into a groove plate 40, which provides a plate material basis for subsequent milling processing.

[0040] The controlled depth milling operation can reduce the effective thickness of the bending zone 10A, making the bending zone 10A easier to deform without damaging the internal circuit. In addition, the controlled depth milling operation only mills to the position of the first covering film 4010, which can effectively avoid affecting the underlying structural layer and ensure the stability and reliability of the overall structure.

[0041] See also Figure 6 and Figure 7 , Figure 6 It is a structural schematic diagram of the milling process according to the embodiment of the present invention; Figure 7 It is a schematic diagram of the cross-sectional structure of a rigid-flex board according to an embodiment of the present invention.

[0042] Step S40: The groove 420 is milled 50 to form a trapezoid 440, and then formed along a forming line 700 to form a semi-flexible rigid-flexible board 10 with a large bending angle.

[0043] Milling can reduce the material thickness during bending, making it easier to achieve the desired bending angle. In the present embodiment, since the width of the bending zone 10A is less than or equal to the thickness of the rigid-flexible board 10, the most critical processing step is the milling process 50 to further process the groove 420 into a trapezoid, so that the board surface can form a larger bending angle, thereby improving the design, processing and application accuracy of the rigid-flexible board 10.

[0044] In this embodiment, the milling process 50 requires the production of a positioning mold 510 to provide auxiliary functions. The positioning mold 510 has a load-bearing end 5110 and a fixed end 5120. The load-bearing end 5110 is a two-sided structure connected to each other, and the intersection line of the two sides is the top edge. The groove plate 40 is fixed on the positioning mold 510, and the bending area 10A corresponds to the top edge. The groove 420 faces away from the top edge, and the rigid area 10B is fixed on the two sides respectively. At this time, the bending surface formed by the bending area 10A forms an angle, that is, an angle greater than 180° and less than 360°, which is preferably 190° to 330°, or 210°, or 225°, or 270°, to form a structure to be milled as a whole.

[0045] The structure to be milled is then fixed on the table of the milling machine 520, with the groove plate 40 separated from the table, and the plate surface of the rigid area 10B and the milling cutter 530 used for milling at an acute angle; then the milling process is performed to ensure that there is a certain distance between the groove plate 40 and the table, while allowing the rigid plate surface to contact the milling cutter 530 at an acute angle. This step is to ensure that the milling cutter 530 can accurately cut into the material during the milling process without being interfered by the table, and the direction of the milling cutter 530 can be effectively controlled.

[0046] Furthermore, the production of the groove plate 40 also includes: drilling holes and electroplating the pressed plate 30, the holes forming positioning vias 430, the main function of the positioning vias 430 is to provide electrical connection for the entire milling process 50, and also to provide a positioning reference for the subsequent process of using pins to fix the structure to be milled. Then the surface circuit pattern 410 is produced, the surface circuit pattern 410 not only includes the routing required for the actual circuit, but also includes a specially designed limit circuit pattern 410A. It is worth noting that the limit circuit pattern 410A is calculated to determine the specific wiring position of the limit circuit pattern 410A, and supports the connection between the positioning via and the limit circuit pattern, providing milling position limitation for the subsequent milling of the rigid board surface, and effectively cooperating with the current feedback position control milling to avoid excessive milling damage to the circuit pattern 410.

[0047] In this embodiment, fixing the groove plate 40 on the positioning mold 510 includes: a first pin hole is made on the load-bearing end 5110; a first pin 540 is used to fix the groove plate 40 to the surface of the load-bearing end 5110 through the first pin hole and the positioning conductive hole 430; a second pin hole is made on the fixed end 5120, and a table fixing hole is provided on the table; a second pin 550 is used to fix the milling structure on the table through the second pin hole and the table fixing hole, thereby ensuring the stability and accuracy of the groove plate 40 during the entire processing process, and preventing displacement during the processing.

[0048] In this embodiment, the table top is a conductive table top 560, and the milling machine 520 has a control center 5210, which is electrically connected to the conductive table top 560 and the milling cutter 530, respectively. This allows the control center 5210 to control the entire processing process through the conductive table top 560, forming a current loop of "milling cutter 530 → limiting circuit 410A → positioning conductive hole 430 → first pin 540 → second pin 550 → conductive table top 560 → → wire 570 → control center 5210 → milling cutter 530", realizing the process of current feedback control milling to achieve the purpose of high-precision processing.

[0049] For circuit boards with high precision and large bending angles, such a fixing and control system can better adapt to their special processing requirements, can achieve more complex shape cutting without damaging the material, significantly improve the positioning accuracy during the milling process, and thus achieve high-precision processing of the rigid-flex board 10, increasing the stability and reliability of the rigid-flex board 10 in practical applications. The entire process from positioning to fixing to the final milling forms a semi-automatic system processing, reduces errors caused by human factors, and improves the processing accuracy of the circuit board.

[0050] To summarize, by manufacturing a positioning mold 510 as an auxiliary processing tool, fixing it on the table of the milling machine 520, and then when the milling mechanism is fixed on the positioning mold 510, the bending area 10A corresponds to the top edge, and the rigid area 10B is fixed on the two sides respectively. At this time, the bending area 10A is bent in the opposite direction to form a protruding top angle, so that the circuit board forms an effective processable state; and by utilizing the guiding property of the positioning mold 510, the overall milling process is set to form a current return path of "milling cutter 530→limiting circuit 410A→positioning conductive hole 430→first pin 540→second pin 550→conductive table 560→wire 570→control center 5210→milling cutter 530", which meets the needs of high-precision milling processing, effectively improves the milling accuracy, and is conducive to the processing of high-precision rigid-flex boards.

[0051] The above description is only a preferred embodiment of the present invention, and does not limit the patent scope of the present invention. All equivalent structural changes made by using the contents of the present invention specification and drawings under the inventive concept of the present invention, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A method for manufacturing a semi-flexible rigid-flexible board with a large bending angle, characterized in that: The rigid-flex board comprises a bending area and a rigid area, the width of the bending area is less than or equal to the thickness of the rigid-flex board, and the manufacturing method comprises the following steps: S10: Take a double-sided copper clad laminate, make a core board pattern, and form an intermediate core board; S20: taking a copper layer, the copper layer being divided into an upper surface copper layer and a lower surface copper layer, and taking a first prepreg and a second prepreg, stacking them with the intermediate core board to form a stacked structure, and then pressing them together to form a pressed board; The stacking structure is stacking the upper surface copper layer, the second prepreg, the middle core board, the first prepreg and the lower surface copper layer from top to bottom; S30: making a surface circuit pattern on the pressed plate, and performing controlled depth milling on the bending area to form a groove, so that the whole plate becomes a grooved plate; S40: milling the groove to make it into a trapezoid, and then shaping it to form the semi-flexible rigid-flexible board with a large bending angle.

2. A method for manufacturing a semi-flexible rigid-flexible board with a large bending angle as claimed in claim 1, characterized in that: The manufacturing method includes attaching a first covering film to a region of the first prepreg corresponding to the bending region, The first cover film in the stacked structure is disposed toward the middle core plate.

3. The method for manufacturing a semi-flexible rigid-flexible board with a large bending angle as claimed in claim 1, characterized in that: Take the third prepreg, make a blind groove, and form a blind groove prepreg, wherein the blind groove is located at the edge of the bending area; The stacked structure includes a blind groove prepreg sheet disposed between the middle core plate and the first prepreg sheet; the blind groove is disposed toward the first prepreg sheet.

4. The method for manufacturing a semi-flexible rigid-flexible board with a large bending angle as claimed in claim 3, characterized in that: The blind groove prepreg is attached with a second covering film in the corresponding bending area.

5. The method for manufacturing a semi-flexible rigid-flexible board with a large bending angle as claimed in claim 2, characterized in that: A single side of the first covering film is larger than or equal to the bending area.

6. A method for manufacturing a semi-flexible rigid-flexible board with a large bending angle as claimed in claim 2 or 5, characterized in that: The controlled depth milling is performed by milling to the first covering film.

7. The method for manufacturing a semi-flexible rigid-flexible board with a large bending angle as claimed in claim 4, characterized in that: A single side of the second covering film is smaller than or equal to the bending area.

8. The method for manufacturing a semi-flexible rigid-flexible board with a large bending angle as claimed in claim 1, characterized in that: The milling is: Making a positioning mold, the positioning mold having a bearing end and a fixed end, the bearing end being a two-sided structure connected to each other, and the intersection line of the two sides being the top edge; The groove plate is fixed on the positioning mold, the bending area corresponds to the top edge, the groove faces away from the top edge, the rigid area is fixed on the two surfaces respectively, and the bending surface forms an apparent angle; forming a structure to be milled; The structure to be milled is fixed on the table of a milling machine, the groove plate is separated from the table, and the rigid plate and the milling cutter for milling form an acute angle; then the milling process is performed.

9. A method for manufacturing a semi-flexible rigid-flexible board with a large bending angle as claimed in claim 8, characterized in that: The production of the groove plate also includes: drilling through holes and electroplating the pressed plate, the through holes forming positioning vias, and then producing the surface circuit pattern, the surface circuit pattern including a limiting circuit pattern, the positioning vias being connected to the limiting circuit pattern.

10. The method for manufacturing a semi-flexible rigid-flexible board with a large bending angle as claimed in claim 9, characterized in that: The step of fixing the groove plate on the positioning mold comprises: The load-bearing end is provided with a first pin hole; the groove plate is fixed to the surface of the load-bearing end by using a first pin through the first pin hole and the positioning through hole; The fixed end is provided with a second pin hole, and the table top is provided with a table top fixing hole; a second pin is used to pass through the second pin hole and the table top fixing hole to fix the milling structure on the table top; The table top is a conductive table top, and the milling machine has a control center, which is electrically connected to the conductive table top and the milling cutter respectively.

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