Rigid-flex board with multiple layers of flexible boards and processing technology of superfine circuit in bending area of rigid-flex board

Abstract

The invention belongs to the technical field of printed circuit boards, and particularly relates to a rigid-flex board with multiple layers of flexible boards and a processing technology of a superfine circuit in a bending area of the rigid-flex board, which comprises the following steps: preparing a plurality of flexible boards, respectively manufacturing a circuit and pasting a cover film; preparing a bonding material and windowing; overlapping and pressing the soft board and the bonding material; drilling and copper plating are carried out on the laminated multilayer board, and then a bending area superfine circuit is manufactured and a cover film is pasted on the bending area superfine circuit; processing a protective film in a bending area of the multilayer board; preparing a semi-cured adhesive sheet, windowing a bending area, and laminating and pressing the semi-cured adhesive sheet and the multi-layer board; manufacturing a drill hole, plating copper and a circuit, and removing a protective film; processing a protective film in the bending area of the multilayer board; preparing a semi-cured adhesive sheet to open a window in the bending area, and overlapping and pressing; manufacturing drill holes, plating copper and circuits, removing a protective film, and producing to obtain a finished product. According to the invention, the height difference of the flexible board can be reduced, the flatness of the board surface can be ensured, and a superfine circuit can be processed in the bending area of the flexible board.

Description

Technical Field

[0001] The present invention belongs to the technical field of printed circuit boards, and specifically relates to a rigid-flexible board with a multi-layer flexible board and a processing technology for ultra-fine circuits in a bending area thereof, especially a rigid-flexible board for dynamically bending consumer electronic products. Background Art

[0002] With the continuous development of electronic technology, the market has higher and higher requirements for the performance and reliability of electronic products. Various electronic products are updated more and more frequently, which means that the performance requirements are getting higher and higher and the functions are getting more and more powerful. In order to meet these needs, the requirements for printed circuit boards are more stringent, and the rigid-flex board has advantages that cannot be replaced by the rigid circuit board. Therefore, more and more rigid-flex boards are used in electronic products. However, compared with rigid circuit boards, rigid-flex boards have obvious difficulties in production technology, such as ultra-fine lines in bending areas. Summary of the invention

[0003] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a rigid-flexible board with a multi-layer flexible board and a processing technology for ultra-fine circuits in the bending area thereof. The present invention can effectively increase the number of bending times of the multi-layer flexible board and can make ultra-fine circuits in the bending area of ​​the flexible board, further improving the performance and meeting the multi-functional requirements of electronic products.

[0004] In order to achieve the above technical objectives, the technical solution adopted by the embodiment of the present invention is: In a first aspect, an embodiment of the present invention provides a process for processing ultra-fine circuits in a bending area of ​​a rigid-flexible board having a multi-layer flexible board, comprising the following steps: Step S1, providing a first flexible board of a rigid-flex board, wherein the first flexible board comprises a first upper copper foil and a first lower copper foil, making circuit patterns on the first upper copper foil and the first lower copper foil as required and performing circuit quality inspection, and laminating a first upper covering film and a first lower covering film on the upper and lower circuit surfaces respectively; Step S2, providing a second flexible board of the rigid-flex board, wherein the second flexible board comprises a second upper copper foil, a circuit pattern is made on the second upper copper foil as required, and a circuit quality inspection is performed, and a second covering film is attached to the surface of the circuit; Step S3, providing a third soft board of a hard-flex board, wherein the third soft board comprises a third lower copper foil, making a circuit pattern on the third lower copper foil as required and performing a circuit quality inspection, and laminating a third covering film on the surface of the circuit; Step S4, providing a fourth soft board of the hard-flex board, wherein the fourth soft board comprises a fourth upper copper foil; Step S5, providing a fifth flexible board of the rigid-flexible board, wherein the fifth flexible board comprises a fifth lower copper foil; Step S6, providing adhesive material, opening a window corresponding to the bending area of ​​the first finished product, and not performing any treatment on the bending area of ​​the second finished product; Step S7, stacking and pressing the fifth soft board, the adhesive material, the third soft board, the adhesive material, the first soft board, the adhesive material, the second soft board, the adhesive material and the fourth soft board in order from bottom to top; Step S8, after lamination, making a first laser blind hole, a first mechanical through hole, copper plating according to the design data, and making circuits on the fifth lower copper foil and the fourth upper copper foil, and then laminating a fourth cover film on the circuit surface of the fourth flexible board, and laminating a fifth cover film on the circuit surface of the fifth flexible board; Step S9, processing a layer of first protective film on the first finished product bending area and the second finished product bending area of ​​the fourth covering film and the fifth covering film; Step S10, preparing a first semi-cured adhesive sheet, and opening windows at positions corresponding to the first finished product bending area and the second finished product bending area respectively; Step S11, preparing a first copper foil; Step S12, stacking and pressing the first copper foil, the first semi-cured adhesive sheet, the multi-layer soft board with the first protective film processed in step S9, the first semi-cured adhesive sheet and the first copper foil in order from bottom to top; Step S13, after lamination, laser second blind holes are made according to the design data, copper is plated, and circuits are made on the first copper foils on the upper and lower surfaces, and then the first protective film is removed; Step S14, processing a second protective film on the first finished product bending region and the second finished product bending region of the fourth covering film and the fifth covering film; Step S15, preparing a second semi-cured adhesive sheet, and opening windows at positions corresponding to the bending area of ​​the first finished product and the bending area of ​​the second finished product respectively; Step S16, preparing a second copper foil; Step S17, stacking and pressing the second copper foil, the second semi-cured adhesive sheet, the multilayer board with the second protective film processed in step S14, the second semi-cured adhesive sheet, and the second copper foil in order from bottom to top; Step S18, after lamination, make the third laser blind hole, the second mechanical through hole, copper plating, and the second copper foil on the upper and lower surfaces according to the design data, then remove the second protective film, and then produce according to the normal process to complete the production of the soft-rigid combination board.

[0005] Furthermore, in step S6, the thickness specification of the adhesive material is 0.01-0.05mm. The greater the thickness, the greater the overall height difference of the bending area of ​​the first finished product, which is not conducive to the production of ultra-fine circuits on the fourth upper copper foil and the fifth lower copper foil. The window size corresponding to the bending area position of the first finished product is 0.1-0.2mm smaller than the size of the bending area of ​​the first finished product on one side.

[0006] Furthermore, in steps S7, S12 and S17, buffer materials and mirror steel plates are placed on the upper and lower surfaces respectively during stacking to ensure the filling performance between the soft board materials and the adhesive materials and the flatness of the board surface.

[0007] Furthermore, in step S7, the heating rate during pressing is 1.5-4°C / min, the pressing pressure is 250-350psi, the maximum temperature is 160-185°C, and the holding time in the highest temperature section is 40-100 minutes.

[0008] Furthermore, when making the circuit in step S8, a vacuum laminating machine is used to laminar the dry film dedicated to the ultra-fine circuit, so as to meet the filling performance of the dry film in the bending area of ​​the first finished product and avoid laminating bubbles. The vacuum laminating temperature is 60-120° C., the vacuum degree is 0-2 hPa, and the pressurization time is 15-35 seconds. And the circuit is made using LDI exposure machine, with exposure energy of 9-12 grids.

[0009] Furthermore, in step S9, when the first protective film is processed in the first finished product bending area and the second finished product bending area, the size of the first protective film is 0.125-0.5 mm smaller than the size of the first finished product bending area and the second finished product bending area. Step S14: when processing the second protective film in the first finished product bending area and the second finished product bending area, the size of the second protective film is 0.125-0.25 mm smaller than the size of the first finished product bending area and the second finished product bending area; Both the first protective film and the second protective film can be dissolved and removed by chemical reagents.

[0010] Furthermore, in step S10, the first prepreg adhesive sheet is a prepreg adhesive sheet with low adhesive flow, and the window size is 0.1-0.2 mm larger than the size of the first finished product bending area and the second finished product bending area; In step S15, the second prepreg adhesive sheet is a prepreg adhesive sheet with low adhesive flow, and the window size is 0.05-0.1 mm larger than the size of the first finished product bending area and the second finished product bending area.

[0011] Furthermore, in step S12 and step S17, the heating rate of the pressing is 1.5-4°C / min, the pressing pressure is 350-450psi, the maximum temperature is 180-215°C, and the holding time in the highest temperature section is 90-120 minutes.

[0012] Furthermore, when manufacturing the circuits in step S13 and step S18, the copper foils in the bending area of ​​the first finished product and the bending area of ​​the second finished product are all etched away to expose the first protective film or the second protective film, and a special stripping device is used to remove the first protective film and the second protective film, with a stripping speed of 1.0-2.0 m / min and a stripping temperature of 50-58°C.

[0013] In a second aspect, an embodiment of the present invention provides a rigid-flexible board having multiple layers of flexible boards, which is manufactured using the processing technology described in the first aspect.

[0014] Compared with the prior art, the technical solution of the embodiment of the present invention has the following beneficial effects: The present invention provides a hard-soft combination board with a multi-layer soft board. Buffer materials and mirror steel plates are used during lamination, which can reduce the height difference of the soft board and ensure the flatness of the board surface. Vacuum lamination and LDI exposure are used during circuit production. Vacuum lamination can completely attach a dry film to a bending area of ​​the soft board with a height difference, thereby solving the problem of lamination bubbles. The high depth of field function of the LDI exposure machine directly transfers images in the bending area of ​​the soft board with a height difference, thereby solving the problem of poor exposure, and can produce ultra-fine circuits in the bending area of ​​the soft board. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a schematic diagram of the structure after the first flexible board is attached to the cover film in step S1 of embodiment 1.

[0016] Figure 2 It is a schematic diagram of the structure after the second flexible board is attached to the cover film in step S2 of embodiment 1.

[0017] Figure 3 It is a schematic diagram of the structure after the third flexible board is attached to the cover film in step S3 of embodiment 1.

[0018] Figure 4 It is a schematic diagram of the structure of the fourth flexible board in step S4 of Example 1.

[0019] Figure 5 It is a schematic diagram of the structure of the fifth flexible board in step S5 of Example 1.

[0020] Figure 6 It is a schematic diagram of the structure after the window is opened in the adhesive material in step S6 of Example 1.

[0021] Figure 7 It is a schematic diagram of the structure obtained through stacking and pressing in step S7 of Example 1.

[0022] Figure 8 It is a schematic diagram of the structure obtained after the fifth covering film is attached in step S8 of Example 1.

[0023] Fig. 9 It is a schematic diagram of the structure obtained after processing the first protective film in step S9 of Example 1.

[0024] Fig.10 It is a schematic diagram of the structure after the first semi-cured adhesive sheet is opened with a window in step S10 of Example 1.

[0025] Fig.11 It is a schematic diagram of the structure of the first copper foil in step S11 of Example 1.

[0026] Fig.12 It is a schematic diagram of the structure obtained through stacking and pressing in step S12 of Example 1.

[0027] Fig.13 It is a schematic diagram of the structure obtained by removing the first protective film in step S13 of Example 1.

[0028] Fig.14 It is a schematic diagram of the structure obtained by processing the second protective film in step S14 of Example 1.

[0029] Fig.15 It is a schematic diagram of the structure after the second semi-cured adhesive sheet is opened with a window in step S15 of Example 1.

[0030] Fig.16 It is a schematic diagram of the structure of the second copper foil in step S16 of Example 1.

[0031] Fig.17 It is a schematic diagram of the structure obtained through stacking and pressing in step S17 of Example 1.

[0032] Fig.18 It is a schematic structural diagram of the finished rigid-flexible board obtained in step S18 of Example 1.

[0033] Fig.19 It is a schematic structural diagram of the finished rigid-flex board obtained in step S19 of Example 2.

[0034] Explanation of reference numerals: 1-fourth soft board; 2-second soft board; 3-first soft board; 4-third soft board; 5-fifth soft board; 6-adhesive material; 7-first semi-cured adhesive sheet; 8-first copper foil; 9-second semi-cured adhesive sheet; 10-second copper foil; 11-first blind hole; 12-first mechanical through hole; 13-second blind hole; 14-third blind hole; 15-second mechanical through hole; 16-first protective film; 17-second protective film; 18-buffer material; 19-mirror steel plate; A-first finished product bending area; B-second finished product bending area; 1-1-fourth upper copper foil; 1-2-fourth covering film; 2-1-second upper copper foil; 2-2-second covering film; 3-1-first upper copper foil; 3-2-first lower copper foil; 3-3-first upper covering film; 3-4-first lower covering film; 4-1-third lower copper foil; 4-2-third covering film; 5-1-fifth lower copper foil; 5-2-fifth covering film. DETAILED DESCRIPTION

[0035] In the description of the present invention, it is necessary to understand that the directions or positional relationships indicated by directional words such as "inside, outside", "up, down", "left, right", etc. are usually based on the directions or positional relationships shown in the drawings. They are only for the convenience of describing the present invention and simplifying the description. Unless otherwise specified, these directional words do not indicate or imply that the device or element referred to must have a specific direction or be constructed and operated in a specific direction. Therefore, they cannot be understood as limiting the scope of protection of the present invention.

[0036] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0037] Example 1 A process for processing ultra-fine circuits in a bending area of ​​a rigid-flexible board having a multi-layer flexible board comprises the following steps: Step S1, providing a first soft board 3 of a soft-rigid combination board, the supplier of the first soft board 3 is Taihong Electronic Materials Co., Ltd., the model is 0.001 T / T OZ, the first soft board 3 comprises a first upper copper foil 3-1 and a first lower copper foil 3-2, a circuit pattern is made on the first upper copper foil 3-1 and the first lower copper foil 3-2 as required and a circuit quality inspection is performed, and a first upper cover film 3-3 and a first lower cover film 3-4 are respectively attached to the upper and lower circuit surfaces, such as Figure 1 As shown; The supplier of the first upper cover film 3 - 3 and the first lower cover film 3 - 4 is Taihong Electronic Materials Co., Ltd., model number is FHK0315; Step S2, providing a second soft board 2 of a hard-flex board, the supplier of the second soft board 2 is Taihong Electronic Materials Co., Ltd., the model is 0.0008 T / T OZ, the second soft board 2 comprises a second upper copper foil 2-1, a circuit pattern is made on the second upper copper foil 2-1 as required and the circuit quality is inspected, and a second covering film 2-2 is attached to the surface of the circuit, such as Figure 2 As shown; The supplier of the second cover film 2-2 is Taihong Electronic Materials Co., Ltd., and the model number is FHK0315; Step S3, providing a third soft board 4 of a soft-rigid combination board, the supplier of the third soft board 4 is Taihong Electronic Materials Co., Ltd., the model is 0.0008 T / T OZ, the third soft board 4 includes a third lower copper foil 4-1, a circuit pattern is made on the third lower copper foil 4-1 according to the requirements and the circuit quality is inspected, and a third covering film 4-2 is attached to the surface of the circuit, such as Figure 3 As shown; The supplier of the third cover film 4-2 is Taihong Electronic Materials Co., Ltd., and the model number is FHK0315; Step S4, providing a fourth soft board 1 of a soft-rigid combination board, the supplier of the fourth soft board 1 is Taihong Electronic Materials Co., Ltd., the model is 0.0005 T / T OZ, the fourth soft board 1 includes a fourth upper copper foil 1-1, such as Figure 4 As shown; Step S5, providing a fifth soft board 5 of a hard-flex board, the supplier of the fifth soft board 5 is Taihong Electronic Materials Co., Ltd., the model is 0.0005 T / T OZ, the fifth soft board 5 includes a fifth lower copper foil 5-1, such as Figure 5 As shown; Step S6, providing adhesive material 6, which is pure glue, supplied by Taihong Electronic Materials Co., Ltd., model BT25, opening a window at the position of the first finished product bending area A, the size of the window opening is 0.125mm smaller than the size of the first finished product bending area A on one side, and no treatment is performed at the position of the second finished product bending area B, such as Figure 6 As shown; Step S7, stack the fifth soft board 5, the adhesive material 6, the third soft board 4, the adhesive material 6, the first soft board 3, the adhesive material 6, the second soft board 2, the adhesive material 6, and the fourth soft board 1 in order from bottom to top, and place the RCF buffer material 18 and the mirror steel plate 19 on the upper and lower surfaces respectively during stacking, and then press them together, with a pressing heating rate of 3°C / min, a pressing pressure of 300psi, a maximum temperature of 170°C, and a holding time of 90 minutes in the highest temperature section, as shown in FIG. Figure 7 As shown; Step S8, after lamination, the first laser blind hole 11 and the first mechanical through hole 12 are made according to the design data, copper is plated, and the circuit is made on the fifth lower copper foil 5-1 of the fifth flexible board 5 and the fourth upper copper foil 1-1 of the fourth flexible board 1, and then the fourth cover film 1-2 is attached to the circuit surface of the fourth flexible board 1 and the fifth cover film 5-2 is attached to the circuit surface of the fifth flexible board 5, as shown in FIG. Figure 8 As shown; When making the circuit, a vacuum laminator is used to laminate the dry film dedicated to the ultra-fine circuit to meet the dry film filling performance of the bending area A of the first finished product and avoid lamination bubbles. The vacuum lamination temperature is 80°C, the vacuum degree is 2hPa, and the pressurization time is 25 seconds. At the same time, an LDI exposure machine is used to avoid poor exposure caused by the height difference in the bending area A of the first finished product. The exposure energy is 10 grids. Step S9, a first protective film 16 is attached to the surface of the fourth covering film 1-2 and the fifth covering film 5-2 by a vacuum laminator, and exposed and developed. After development, only the first protective film 16 of the first finished product bending area A and the second finished product bending area B is retained. The size of the first protective film 16 is 0.125 mm smaller than the size of the first finished product bending area A and the second finished product bending area B. Fig. 9 As shown; Step S10, prepare a first semi-cured adhesive sheet 7. The supplier of the first semi-cured adhesive sheet 7 is Taiguang Electronic Materials Co., Ltd., and the model is 1037 Low flow. Open windows at the positions corresponding to the first finished product bending area A and the second finished product bending area B, respectively. The size of the window is 0.15 mm larger than the size of the first finished product bending area A and the second finished product bending area B. Fig.10 As shown; Step S11, prepare the first copper foil 8, such as Fig.11 As shown; Step S12, stack the first copper foil 8, the first semi-cured adhesive sheet 7, the multi-layer soft board with the first protective film 16 processed in step S9, the first semi-cured adhesive sheet 7, and the first copper foil 8 in order from bottom to top, and place the RCF buffer material 18 and the mirror steel plate 19 on the upper and lower surfaces respectively during stacking, and then press them, the pressing heating rate is 3.5°C / min, the pressing pressure is 400psi, the maximum temperature is 195°C, and the holding time of the highest temperature section is 90 minutes, such as Fig.12 As shown; Step S13, after lamination, make the second laser blind hole 13 according to the design data, copper plate, and make circuits on the first copper foil 8 on the upper and lower surfaces, etch away all the copper foils in the first finished product bending area A and the second finished product bending area B to expose the first protective film 16, and then remove the first protective film 16 through the film stripping process, the film stripping speed: 1.0m / min, the film stripping temperature: 53℃, if Fig.13 As shown; Step S14: A second protective film 17 is attached to the surface of the fourth covering film 1-2 and the fifth covering film 5-2 by a vacuum laminator, and then exposed and developed. After development, only the second protective film 17 of the first finished product bending area A and the second finished product bending area B is retained. The size of the second protective film 17 is 0.2 mm smaller than that of the first finished product bending area A and the second finished product bending area B. Fig.14 As shown; Step S15, prepare a second semi-cured adhesive sheet 9. The supplier of the second semi-cured adhesive sheet 9 is Taiguang Electronic Materials Co., Ltd., and the model is 106 Low flow. Open windows at the positions corresponding to the first finished product bending area A and the second finished product bending area B, respectively. The size of the window is 0.1 mm larger than the size of the first finished product bending area A and the second finished product bending area B. Fig.15 As shown; Step S16: prepare a second copper foil 10, such as Fig.16 As shown; Step S17, stack the second copper foil 10, the second semi-cured adhesive sheet 9, the multilayer board with the second protective film 17 processed in step S14, the second semi-cured adhesive sheet 9, and the second copper foil 10 in order from bottom to top, and place the RCF buffer material 18 and the mirror steel plate 19 on the upper and lower surfaces respectively during stacking, and then press them together, with a pressing heating rate of 3.5°C / min, a pressing pressure of 400psi, a maximum temperature of 195°C, and a holding time of 90 minutes in the highest temperature section, as shown in FIG. Fig.17 As shown; Step S18, after lamination, make the third laser blind hole 14, the second mechanical through hole 15 according to the design data, copper plating, and make circuits on the second copper foil 10 on the upper and lower surfaces. When making the circuit, all the copper foils in the first finished product bending area A and the second finished product bending area B are etched away to expose the second protective film 17, and then the second protective film 17 is removed by the film stripping process. The film stripping speed is 1.5m / min and the film stripping temperature is 56°C. Then, the normal process is followed to complete the production of the rigid-flexible board. Fig.18 shown.

[0038] Example 2 A process for processing ultra-fine circuits in a bending area of ​​a rigid-flexible board having a multi-layer flexible board comprises the following steps: Step S1, providing a first soft board 3 of a soft-rigid combination board, the supplier of the first soft board 3 is Taihong Electronic Materials Co., Ltd., the model is 0.0008 T / T OZ, the soft board comprises a first upper copper foil 3-1 and a first lower copper foil 3-2, circuit patterns are made on the first upper copper foil 3-1 and the first lower copper foil 3-2 as required and the circuit quality inspection is performed, and a first upper covering film 3-3 and a first lower covering film 3-4 are respectively attached to the upper and lower circuit surfaces, the supplier of the first upper covering film 3-3 and the first lower covering film 3-4 is Taihong Electronic Materials Co., Ltd., the model is FHK0315; Step S2, providing a second soft board 2 of a hard-flex board, the supplier of the second soft board 2 is Taihong Electronic Materials Co., Ltd., the model is 0.0008T / T OZ, the second soft board 2 comprises a second upper copper foil 2-1, a circuit pattern is made on the second upper copper foil 2-1 as required and the circuit quality is inspected, and a second covering film 2-2 is attached to the surface of the circuit, the supplier of the second covering film 2-2 is Taihong Electronic Materials Co., Ltd., the model is FHK0315; Step S3, providing a third soft board 4 of a soft-rigid combination board, the supplier of the third soft board 4 is Taihong Electronic Materials Co., Ltd., the model is 0.0008 T / T OZ, the third soft board 4 includes a third lower copper foil 4-1, a circuit pattern is made on the third lower copper foil 4-1 as required and the circuit quality is inspected, and a third covering film 4-2 is attached to the surface of the circuit, the supplier of the third covering film 4-2 is Taihong Electronic Materials Co., Ltd., the model is FHK0315; Step S4, providing a fourth soft board 1 of a soft-rigid combination board, the supplier of the fourth soft board 1 is Taihong Electronic Materials Co., Ltd., the model is 0.0005 T / T OZ, and the fourth soft board 1 includes a fourth upper copper foil 1-1; Step S5, providing a fifth soft board 5 of a hard-flex board, the supplier of the fifth soft board 5 is Taihong Electronic Materials Co., Ltd., the model is 0.0005 T / T OZ, and the fifth soft board 5 includes a fifth lower copper foil 5-1; Step S6, providing adhesive material 6, which is pure glue, supplied by Taihong Electronic Materials Co., Ltd., model BT25, opening a window at the position corresponding to the bending area A of the first finished product, the size of the window opening is 0.125mm smaller than the size of the bending area A of the first finished product on one side, and no treatment is performed at the position corresponding to the bending area B of the second finished product; Step S7, stacking the fifth soft board 5, the adhesive material 6, the third soft board 4, the adhesive material 6, the first soft board 3, the adhesive material 6, the second soft board 2, the adhesive material 6, and the fourth soft board 1 in order from bottom to top, placing the RCF buffer material 18 and the mirror steel plate 19 on the upper and lower surfaces respectively during stacking, and then pressing, the pressing heating rate is 3°C / min, the pressing pressure is 280psi, the maximum temperature is 160°C, and the holding time of the highest temperature section is 90 minutes; Step S8, after lamination, make the first laser blind hole 11, the first mechanical through hole 12, and copper plating according to the design data, and make circuits on the fifth lower copper foil 5-1 of the fifth soft board 5 and the fourth upper copper foil 1-1 of the fourth soft board 1, and then stick the fourth cover film 1-2 on the circuit surface of the fourth soft board 1, and stick the fifth cover film 5-2 on the circuit surface of the fifth soft board 5; when making the circuit, use a vacuum laminating machine to laminarize the dry film dedicated to the ultra-fine circuit to meet the filling performance of the dry film in the bending area A of the first finished product and avoid the generation of laminating bubbles. The vacuum laminating temperature is 75°C, the vacuum degree is 2hPa, and the pressing time is 30 seconds. At the same time, an LDI exposure machine is used for production to avoid poor exposure caused by the height difference in the bending area A of the first finished product, and the exposure energy is 10 grids; Step S9, attaching a first protective film 16 to the surface of the fourth cover film 1-2 and the fifth cover film 5-2 by using a vacuum laminator, and performing exposure and development, and only retaining the first protective film 16 of the first finished product bending area A and the second finished product bending area B after development, and the size of the first protective film 16 is 0.125 mm smaller than the size of the first finished product bending area A and the second finished product bending area B; Step S10, prepare a first semi-cured adhesive sheet 7, the supplier of the first semi-cured adhesive sheet 7 is Taiguang Electronic Materials Co., Ltd., the model is 1037 Low flow, and open windows at positions corresponding to the first finished product bending area A and the second finished product bending area B, respectively. The size of the window is 0.15 mm larger than the size of the first finished product bending area A and the second finished product bending area B; Step S11, preparing a first copper foil 8; Step S12, stacking the first copper foil 8, the first semi-cured adhesive sheet 7, the multi-layer soft board with the first protective film 16 processed in step S9, the first semi-cured adhesive sheet 7 and the first copper foil 8 in order from bottom to top, placing RCF buffer material 18 + mirror steel plate 19 on the upper and lower surfaces respectively during stacking, and then pressing, the pressing heating rate is 3.8°C / min, the pressing pressure is 420psi, the maximum temperature is 195°C, and the holding time of the highest temperature section is 90 minutes; Step S13, after lamination, make the second laser blind hole 13 according to the design data, copper plate, and make circuits on the first copper foil 8 on the upper and lower surfaces, and etch away all the copper foils in the first finished product bending area A and the second finished product bending area B to expose the first protective film 16, and then remove the first protective film 16 through the film stripping process, the film stripping speed: 1.2m / min, the film stripping temperature 53°C; Step S14, a second protective film 17 is attached to the surface of the fourth cover film 1-2 and the fifth cover film 5-2 by using a vacuum laminator, and then exposed and developed. After development, only the second protective film 17 of the first finished product bending area A and the second finished product bending area B is retained, and the size of the second protective film 17 is 0.125 mm smaller than the size of the first finished product bending area A and the second finished product bending area B; Step S15, prepare a second semi-cured adhesive sheet 9, the supplier of the second semi-cured adhesive sheet 9 is Taiguang Electronic Materials Co., Ltd., the model is 106 Low flow, and windows are opened at positions corresponding to the first finished product bending area A and the second finished product bending area B, respectively. The size of the window is 0.075 mm larger than the size of the first finished product bending area A and the second finished product bending area B; Step S16, preparing a second copper foil 10; Step S17, stacking the second copper foil 10, the second semi-cured adhesive sheet 9, the multilayer board with the second protective film 17 processed in step S14, the second semi-cured adhesive sheet 9, and the second copper foil 10 in order from bottom to top, placing RCF buffer material 18 + mirror steel plate 19 on the upper and lower surfaces respectively during stacking, and then pressing, the pressing heating rate is 3.8°C / min, the pressing pressure is 420psi, the maximum temperature is 195°C, and the holding time of the highest temperature section is 90 minutes; Step S18, repeat steps S13 to S17 once; Step S19, after lamination, make the third laser blind hole 14, the second mechanical through hole 15 according to the design data, copper plating, and make circuits on the second copper foil 10 on the upper and lower surfaces. When making the circuit, all the copper foils in the first finished product bending area A and the second finished product bending area B are etched away to expose the second protective film 17, and then the second protective film 17 is removed by the film stripping process. The film stripping speed is 1.5m / min and the film stripping temperature is 56°C. Then, the normal process is followed to complete the production of the soft-rigid combination board. Fig.19 shown.

[0039] Finally, it should be noted that the above specific implementation methods are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the spirit and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A process for processing ultra-fine circuits in the bending area of ​​a rigid-flexible board with multiple layers of flexible boards, characterized in that: The following steps are involved: Step S1, providing a first soft board (3) of a hard-flex board, wherein the first soft board (3) comprises a first upper copper foil (3-1) and a first lower copper foil (3-2), producing circuit patterns on the first upper copper foil (3-1) and the first lower copper foil (3-2) as required and performing circuit quality inspection, and laminating a first upper covering film (3-3) and a first lower covering film (3-4) on the upper and lower circuit surfaces respectively; Step S2, providing a second flexible board (2) of a rigid-flexible board, wherein the second flexible board (2) comprises a second upper copper foil (2-1), producing a circuit pattern on the second upper copper foil (2-1) as required, performing a circuit quality inspection, and laminating a second covering film (2-2) on the surface of the circuit; Step S3, providing a third soft board (4) of a hard-flex board, the third soft board (4) comprising a third lower copper foil (4-1), making a circuit pattern on the third lower copper foil (4-1) as required and performing a circuit quality inspection, and laminating a third covering film (4-2) on the surface of the circuit; Step S4, providing a fourth soft board (1) of a hard-flex board, wherein the fourth soft board (1) comprises a fourth upper copper foil (1-1); Step S5, providing a fifth soft board (5) of a hard-flex board, wherein the fifth soft board (5) comprises a fifth lower copper foil (5-1); Step S6, providing adhesive material (6), opening a window at the position corresponding to the bending area (A) of the first finished product, and not performing any treatment at the position corresponding to the bending area (B) of the second finished product; Step S7, stacking and pressing the fifth soft board (5), the adhesive material (6), the third soft board (4), the adhesive material (6), the first soft board (3), the adhesive material (6), the second soft board (2), the adhesive material (6) and the fourth soft board (1) in order from bottom to top; Step S8, after lamination, a laser first blind hole (11) and a first mechanical through hole (12) are made according to the design data, copper is plated, and a circuit is made on the fifth lower copper foil (5-1) and the fourth upper copper foil (1-1), and then a fourth covering film (1-2) is attached to the circuit surface of the fourth flexible board (1), and a fifth covering film (5-2) is attached to the circuit surface of the fifth flexible board (5); Step S9, processing a layer of first protective film (16) on the first finished product bending region (A) and the second finished product bending region (B) of the fourth covering film (1-2) and the fifth covering film (5-2); Step S10, preparing a first semi-cured adhesive sheet (7), and opening windows at positions corresponding to the first finished product bending area (A) and the second finished product bending area (B); Step S11, preparing a first copper foil (8); Step S12, stacking and pressing the first copper foil (8), the first semi-cured adhesive sheet (7), the multi-layer soft board on which the first protective film (16) is processed in step S9, the first semi-cured adhesive sheet (7) and the first copper foil (8) in order from bottom to top; Step S13, after lamination, laser second blind holes (13) are made according to the design data, copper is plated, and circuits are made on the first copper foils (8) on the upper and lower surfaces, and then the first protective film (16) is removed; Step S14, processing a layer of second protective film (17) on the first finished product bending region (A) and the second finished product bending region (B) of the fourth covering film (1-2) and the fifth covering film (5-2); Step S15, preparing a second semi-cured adhesive sheet (9), and opening windows at positions corresponding to the first finished product bending area (A) and the second finished product bending area (B); Step S16, preparing a second copper foil (10); Step S17, stacking and pressing the second copper foil (10), the second semi-cured adhesive sheet (9), the multilayer board on which the second protective film (17) has been processed in step S14, the second semi-cured adhesive sheet (9), and the second copper foil (19) in order from bottom to top; Step S18, after lamination, laser third blind holes (14), second mechanical through holes (15) are made according to the design data, copper is plated, and circuits are made on the second copper foil (10) on the upper and lower surfaces, and then the second protective film (17) is removed, and then the normal production process is followed to complete the production of the rigid-flexible board.

2. The ultra-fine circuit processing process of the bending area of ​​the rigid-flexible board with multi-layer flexible board according to claim 1 is characterized in that: In step S6, the thickness specification of the adhesive material (6) is 0.01-0.05 mm, and the window size corresponding to the first finished product bending area (A) is 0.1-0.2 mm smaller than the size of the first finished product bending area (A) on one side.

3. The ultra-fine circuit processing process of the bending area of ​​the rigid-flexible board with multi-layer flexible board according to claim 1 is characterized in that: In steps S7, S12 and S17, a buffer material (18) and a mirror steel plate (19) are placed on the upper and lower surfaces respectively during stacking to ensure the filling performance between the soft board material and the adhesive material (6) and the flatness of the board surface.

4. The ultra-fine circuit processing process of the bending area of ​​the rigid-flexible board with multi-layer flexible board according to claim 1, characterized in that: The heating rate during pressing in step S7 is 1.5-4°C / min, the pressing pressure is 250-350psi, the maximum temperature is 160-185°C, and the holding time in the highest temperature section is 40-100 minutes.

5. The ultra-fine circuit processing process of the bending area of ​​the rigid-flexible board with multi-layered flexible board according to claim 1, characterized in that: When making the circuit in step S8, a vacuum laminating machine is used to laminar the dry film dedicated to the ultra-fine circuit to meet the filling performance of the dry film in the bending area (A) of the first finished product, the vacuum laminating temperature is 60-120°C, the vacuum degree is 0-2hPa, and the pressing time is 15-35 seconds; And the circuit is made using LDI exposure machine, with exposure energy of 9-12 grids.

6. The ultra-fine circuit processing process of the bending area of ​​the rigid-flexible board with multi-layered flexible board according to claim 1, characterized in that: Step S9: when processing the first protective film (16) in the first finished product bending region (A) and the second finished product bending region (B), the size of the first protective film (16) is 0.125-0.5 mm smaller than the size of the first finished product bending region (A) and the second finished product bending region (B); Step S14: when processing the second protective film (17) in the first finished product bending region (A) and the second finished product bending region (B), the size of the second protective film (17) is 0.125-0.25 mm smaller than the size of the first finished product bending region (A) and the second finished product bending region (B); Both the first protective film (16) and the second protective film (17) can be dissolved and removed by chemical reagents.

7. The ultra-fine circuit processing process of the bending area of ​​the rigid-flexible board with multi-layered flexible board according to claim 1, characterized in that: In step S10, the first prepreg adhesive sheet (7) is a prepreg adhesive sheet with low adhesive flow, and the window size is 0.1-0.2 mm larger than the size of the first finished product bending area (A) and the second finished product bending area (B); In step S15, the second semi-cured adhesive sheet (9) is a semi-cured adhesive sheet with low adhesive flow, and the window size is 0.05-0.1 mm larger than the size of the first finished product bending area (A) and the second finished product bending area (B).

8. The ultra-fine circuit processing process of the bending area of ​​the rigid-flexible board with multi-layered flexible board according to claim 1, characterized in that: The heating rate of the pressing in step S12 and step S17 is 1.5-4°C / min, the pressing pressure is 350-450psi, the maximum temperature is 180-215°C, and the holding time in the highest temperature section is 90-120 minutes.

9. The ultra-fine circuit processing process of the bending area of ​​the rigid-flexible board with multi-layered flexible board according to claim 1, characterized in that: During the circuit production in step S13 and step S18, the copper foils in the first finished product bending area (A) and the second finished product bending area (B) are all etched away to expose the first protective film (16) or the second protective film (17), and the first protective film (16) and the second protective film (17) are removed using a dedicated film stripping device, with a film stripping speed of 1.0-2.0 m / min and a film stripping temperature of 50-58°C.

10. A rigid-flex board with multiple layers of flexible boards, characterized in that: The invention is prepared by the processing technology described in any one of claims 1 to 9.

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