A method for processing the shape of a soft board of a hard-flex board

Abstract

The present invention belongs to the technical field of printed circuit boards, and specifically relates to a method for processing the shape of a flexible board of a rigid-flexible board, comprising the following steps: S1. providing a flexible rigid-flexible printed circuit board, and making circuit patterns on the upper and lower copper foils of the flexible board; S2. laminating a cover film in the bending area after browning treatment, and performing rapid pressing and baking on the circuits protecting the bending area; S3. punching the flexible board; S4. preparing a semi-cured adhesive sheet, opening a window in the bending area of ​​the flexible board, and drilling holes; S5. making an alignment jig, and setting spring pins at the punching position of the flexible board; S6. pre-aligning the flexible board and the semi-cured adhesive sheet; S7. setting copper foil on the upper and lower surfaces of the pre-laminated flexible board for pressing, and forming the shape; S8. when the forming milling cutter is used to fish out the shape, the milling cutter fishes in the hard board area; S9. processing the shape of the flexible board. The present invention can solve the problem of burrs caused by the milling cutter fishing into the flexible board during the forming of the rigid-flexible board.

Description

Technical Field

[0001] The present invention belongs to the technical field of printed circuit boards, and specifically relates to a method for processing the shape of a soft board of a hard-flex board, and is particularly suitable for a hard-flex board of a camera module or a hard-flex board of a consumer electronic product. Background Art

[0002] Rigid-flex PCBs for camera modules and consumer electronics are characterized by thin thickness, small size, and high precision. The curved areas of the flexible PCB are typically processed using methods such as laser cutting or die stamping. During forming, the milling cutter can pick up PI material from the flexible PCB, resulting in burrs. Laser cutting can cause these burrs to prevent the laser from cutting through, and increasing the power consumption can lead to severe carbonization. Die stamping can also cause these burrs to stick to the mold and cause defects such as dents and scratches. Laser cutting or die stamping followed by forming presents two challenges: First, when the flexible PCB is processed in a single linear shape, the PI material can wrap around the milling cutter, resulting in poor PCB removal. Second, when the flexible PCB is processed in a circular shape, the waste generated during this process is time-consuming and difficult to clean, directly increasing production time. Furthermore, the circular shape process is longer than a linear one, further increasing production costs. Summary of the Invention

[0003] The present invention aims to overcome the shortcomings of the prior art and provide a method for processing the outer shape of a rigid-flex board. By strictly controlling the window size of the prepreg adhesive sheet and the alignment accuracy between the prepreg adhesive sheet and the flexible board, the present invention allows the forming milling cutter to be located in the rigid board area. This method can eliminate the burrs caused by the milling cutter touching the flexible board during the forming of the rigid-flex board, and can also address the quality issues caused by burrs that can cause damage or scratches to the flexible board. The method is particularly suitable for the production of rigid-flex boards for camera modules or consumer electronics.

[0004] To achieve the above technical objectives, the technical solution adopted in the embodiment of the present invention is: a method for processing the shape of a flexible board of a rigid-flex board, comprising the following steps:

[0005] Step S1: providing a rigid-flexible printed circuit board (FPCB), wherein the upper and lower surfaces of the FPCB respectively have an upper copper foil and a lower copper foil, producing circuit patterns on the upper and lower copper foils as required, and performing a circuit quality inspection;

[0006] Step S2: After the flexible circuit board with the circuit pattern formed in step S1 is browned, an upper cover film and a lower cover film are attached to the bending area to protect the circuit in the bending area, and the flexible circuit board is quickly pressed and baked;

[0007] Step S3: Punching holes at selected positions on the soft board as required to form no less than four first circular holes, and measuring the expansion / contraction ratio R of the soft board layer;

[0008] Step S4: prepare a semi-cured adhesive sheet, open a window in the corresponding bending area of ​​the flexible board, and simultaneously drill a second circular hole in the corresponding punching position of the flexible board. The number and size of the second circular holes are the same as those of the first circular holes.

[0009] Step S5: Prepare an alignment jig, and drill third circular holes on the jig at positions corresponding to the first circular holes. The third circular holes have the same number and size as the first circular holes. Spring pins are set at the drilling positions. The size of the spring pins is 0.05 mm smaller than that of the first circular holes.

[0010] Step S6: Use an alignment jig to pre-align the flexible board and the semi-cured adhesive sheet, with the pre-lamination temperature at 80-150°C and the time for 10-60 seconds;

[0011] Step S7: Copper foils are placed on the upper and lower surfaces of the semi-cured adhesive sheet in step S6, and pressed together, and then formed into an outer shape according to the required process;

[0012] Step S8: When the forming milling cutter is fishing, a fishing path is set 0.6-1.0 mm away from the outer shape of the soft board so that the milling cutter is fished in the hard board area to avoid the milling cutter directly fishing the soft board and causing burrs;

[0013] Step S9: Processing the shape of the flexible board to complete the processing of the shape of the flexible board of the rigid-flex board.

[0014] Furthermore, the expansion and contraction ratio of the window in step S4 is the same as the measured expansion and contraction ratio R of the flexible board, and the size of the window is 0.5 mm larger than the outer shape of the flexible board.

[0015] Furthermore, the expansion / contraction ratio of the third circular hole in step S5 is the same as the measured expansion / contraction ratio R of the flexible board.

[0016] Furthermore, in step S2, the quick pressing pressure of the upper covering film and the lower covering film is: 70-150kg, the quick pressing temperature is: 160-210℃, the quick pressing time is: 1-4 minutes, the baking temperature is: 100-190℃, and the baking time is 60-200 minutes.

[0017] Furthermore, the semi-cured adhesive sheet in step S4 is a low-glue semi-cured adhesive sheet, and the glue flow rate thereof is less than 0.5 mm when the rigid-flex board is pressed together.

[0018] The technical solutions in the embodiments of the present invention have the following beneficial effects:

[0019] Without increasing the process flow and cost, the present invention takes into account the characteristic of the semi-cured adhesive sheet of the soft and rigid combination board that the glue flow is less than 0.5mm during pressing. The special design is made when opening the window. This can ensure that the semi-cured adhesive sheet will not flow onto the soft board, and can also ensure that the milling cutter will not pick up the soft board PI material during molding, avoiding the defects caused by the burrs of the soft board. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Schematic diagram of the cross-sectional structure of a rigid-flex board in an embodiment of the present invention.

[0021] Figure 2 Schematic diagram of the planar structure of a rigid-flex board in an embodiment of the present invention.

[0022] Figure 3 yes Figure 1 Schematic diagram of the cross-sectional structure of the medium-soft board layer.

[0023] Figure 4 yes Figure 1 Schematic diagram of the planar structure of the medium-soft board layer.

[0024] Figure 5 yes Figure 1 Schematic diagram of the cross-sectional structure of the covering film.

[0025] Figure 6 yes Figure 1 Schematic diagram of the planar structure of the covering membrane.

[0026] Figure 7 yes Figure 1 Schematic diagram of the cross-sectional structure of the semi-cured adhesive sheet.

[0027] Figure 8 yes Figure 1 Schematic diagram of the planar structure of the semi-cured adhesive sheet.

[0028] Figure 9 yes Figure 1 Schematic diagram of the cross-sectional structure of the copper foil.

[0029] Figure 10 yes Figure 1 Schematic diagram of the cross-sectional structure of the middle fixture.

[0030] Figure 11 yes Figure 1 Schematic diagram of the plane structure of the middle fixture.

[0031] Figure 12 yes Figure 1 Schematic diagram of the cross-sectional structure of the spring pin.

[0032] Figure 13 Schematic diagram of the planar structure of the rigid-flex board in an embodiment of the present invention.

[0033] Figure 14 Schematic diagram of laser cutting of the flexible circuit board of the present invention.

[0034] Explanation of the reference numerals: 1-flexible board; 1-1-upper copper foil; 1-2-lower copper foil; 1-3-upper cover film; 1-4-lower cover film; 2-first circular hole; 3-semi-cured adhesive sheet; 4-second circular hole; 5-copper foil; 6-spring pin; 7-third circular hole. DETAILED DESCRIPTION

[0035] In the description of the present invention, it should be understood 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 accompanying 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 solutions and advantages of the present invention more clearly understood, the present invention 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 invention and are not intended to limit the present invention.

[0037] Example 1

[0038] A method for processing the shape of a flexible board of a rigid-flex board comprises the following steps:

[0039] Step S1. Figure 3 and 4 As shown, a rigid-flexible printed circuit board (FPCB) 1 is provided. The upper and lower surfaces of the FPCB 1 respectively have an upper copper foil 1-1 and a lower copper foil 1-2. Circuit patterns are produced on the upper and lower copper foils 1-1, 1-2 as required and circuit quality inspection is performed.

[0040] Step S2. Figure 5 and 6 As shown, the flexible circuit board 1 with the circuit pattern formed in step S1 is subjected to browning treatment and then the upper cover film 1-3 and the lower cover film 1-4 are attached to the bending area to protect the circuit in the bending area. The flexible circuit board 1 is then subjected to rapid pressing and baking. The rapid pressing temperature is 170°C, the rapid pressing time is 180s, the pressure is 80kg, and the baking temperature is 150°C, and the baking time is 90 minutes.

[0041] Step S3. Use a CCD puncher to punch out first circular holes 2 at selected locations on the flexible circuit board 1 for alignment with the prepreg adhesive sheet 3. The diameter of the first circular holes 2 is 2.0 mm, and there are 20 of them. Simultaneously measure the expansion and contraction ratio of the flexible circuit board to 50 ppm.

[0042] Step S4. Figure 7 and 8 As shown, a low-flow semi-cured adhesive sheet 3 is prepared, and windows are simultaneously opened on the semi-cured adhesive sheet 3 corresponding to the bending area of ​​the flexible board 1. The window expansion and contraction ratio is 50ppm, and the window size is 0.5mm larger than the outer shape of the flexible board 1. At the same time, second circular holes 4 are drilled on the semi-cured adhesive sheet 3 corresponding to the punching positions of the flexible board. The number of second circular holes 4 is 20, and the hole diameter is 2.0mm.

[0043] Step S5. Figure 10 and 11 As shown, a positioning jig is made, and a third circular hole 7 is drilled on the jig at the position corresponding to the first circular hole 2. The expansion and contraction ratio of the third circular hole 7 is 50ppm. A spring pin 6 is set at the drilling position. The size of the spring pin 6 is 1.95mm. Figure 12 and 13 As shown;

[0044] Step S6. Align the flexible board 1 in step S3 and the semi-cured adhesive sheet 3 in step S4 using the alignment fixture in step S5, with the pre-lamination temperature at 100°C and the time for 20 seconds;

[0045] Step S7. Figure 9 As shown, in step S6, copper foil 5 is set on the upper and lower surfaces of the semi-cured adhesive sheet 3, and pressed together, and then formed into an outer shape according to the required process;

[0046] Step S8. When the forming milling cutter is fishing, a fishing path is set 0.65mm away from the soft board shape, so that the milling cutter is fished in the hard board area, which solves the problem of the milling cutter directly fishing the soft board and generating burrs. Figure 14 As shown;

[0047] Step S9. Use laser cutting technology to process the side shape of the flexible board 1 to complete the processing of the flexible board shape of the flexible board. Figure 1 、 2 and 13.

[0048] Example 2

[0049] A method for processing the shape of a flexible board of a rigid-flex board, comprising the following steps:

[0050] Step S1. Providing a rigid-flexible printed circuit board (FPCB) 1, wherein the upper and lower surfaces of the FPCB 1 have an upper copper foil 1-1 and a lower copper foil 1-2, respectively. Circuit patterns are produced on the upper and lower copper foils 1-1 and 1-2 as required and the circuit quality is inspected.

[0051] Step S2: After the flexible circuit board 1 with the circuit pattern formed in step S1 is browned, the upper cover film 1-3 and the lower cover film 1-4 are applied to the bend area to protect the circuit in the bend area. The flexible circuit board 1 is then subjected to rapid pressing and baking. The rapid pressing temperature is 180°C, the rapid pressing time is 170 seconds, the pressure is 100kg, and the baking temperature is 170°C, and the baking time is 60 minutes.

[0052] Step S3. Use a CCD puncher to punch out first circular holes 2 for alignment with the prepreg adhesive sheet 3 at selected locations on the flexible substrate 1. The diameter of the first circular holes 2 is 2.55 mm, and the number is 30. Simultaneously measure the expansion and contraction rate of the flexible substrate to be 80 ppm.

[0053] Step S4. Prepare a low-flow prepreg adhesive sheet 3 and simultaneously create windows on the prepreg adhesive sheet 3 corresponding to the bend area of ​​the flexible circuit board 1. The window expansion and contraction ratio is 80 ppm, and the window size is 0.6 mm larger than the outer shape of the flexible circuit board 1. Simultaneously, drill 30 second circular holes 4 on the prepreg adhesive sheet 3 at the locations corresponding to the punching holes of the flexible circuit board 1. The number of second circular holes 4 is 2.55 mm.

[0054] Step S5. Make an alignment jig and drill a third circular hole 7 on the jig at the position corresponding to the first circular hole 2. The expansion and contraction ratio of the third circular hole 7 is 80 ppm. Set a spring pin 6 at the drilling position. The size of the spring pin 6 is 2.5 mm.

[0055] Step S6. Align the flexible board 1 in step S3 and the semi-cured adhesive sheet 3 in step S4 using the alignment fixture in step S5, with the pre-lamination temperature at 110°C and the time for 15 seconds;

[0056] Step S7. Copper foil 5 is provided on the upper and lower surfaces of the semi-cured adhesive sheet 3 in step S6, and pressed together, and formed into a shape according to the required process;

[0057] Step S8. When the forming milling cutter is fishing, a fishing path is set at 0.75 mm away from the outer shape of the soft board, so that the milling cutter is fished in the hard board area, which solves the problem of the milling cutter directly fishing the soft board and causing burrs;

[0058] Step S9: Finally, the side profile of the flexible board 1 is processed by laser cutting technology to complete the processing of the flexible board profile of the rigid-flex board.

[0059] Finally, it should be noted that the above specific implementation methods are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that the technical solutions of the present invention can be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A method for processing the shape of a soft board of a hard-flex board, characterized in that: The following steps are involved: Step S1, providing a rigid-flexible printed circuit board (1), wherein the upper and lower surfaces of the flexible board (1) respectively have an upper copper foil (1-1) and a lower copper foil (1-2), and circuit patterns are produced on the upper copper foil (1-1) and the lower copper foil (1-2) as required and circuit quality inspection is performed; Step S2, after the flexible board (1) on which the circuit pattern is produced in step S1 is subjected to browning treatment, an upper covering film (1-3) and a lower covering film (1-4) are attached to the bending area to protect the circuit in the bending area, and quick pressing and baking are performed; Step S3, punching holes at selected positions on the soft board (1) according to requirements to form no less than four first circular holes (2), and measuring the expansion / contraction ratio R of the soft board (1); Step S4, preparing a semi-cured adhesive sheet (3), and opening a window in the corresponding bending area of ​​the soft board, and simultaneously drilling a second circular hole (4) at the corresponding punching position of the soft board, wherein the second circular holes (4) are the same in number and size as the first circular holes (2), and the expansion and contraction ratio of the window is the same as the measured expansion and contraction ratio R of the soft board (1), so as to ensure that the semi-cured adhesive sheet (3) does not flow glue to the soft board (1) during lamination; Step S5, making a positioning jig, drilling a third circular hole (7) on the jig at a position corresponding to the first circular hole (2), the third circular holes (7) having the same number and size as the first circular holes (2), the expansion and contraction ratio of the third circular holes (7) being the same as the measured expansion and contraction ratio R of the flexible board (1), setting a spring pin (6) at the drilling position, the size of the spring pin (6) being 0.05 mm smaller than the size of the first circular hole (2); Step S6: Pre-laminating the soft board (1) and the semi-cured adhesive sheet (3) using a positioning jig, with the pre-lamination temperature being 80-150° C. and the time being 10-60 seconds; Step S7, placing copper foil (5) on the upper and lower surfaces of the semi-cured adhesive sheet (3) in step S6, pressing them together, and shaping them into an outer shape according to the required process; Step S8: When the forming milling cutter is fishing, a fishing path is set at 0.6-1.0 mm away from the outer shape of the soft board, so that the milling cutter is fished in the hard board area to avoid the milling cutter directly fishing the soft board and causing burrs; Step S9: using a laser cutting process to process the shape of the flexible board (1), thereby completing the processing of the shape of the flexible board of the rigid-flexible board.

2. The method for processing the shape of a flexible board of a rigid-flex board according to claim 1, characterized in that: In step S4, the window size is 0.5 mm larger than the outer shape of the soft board (1).

3. The method for processing the shape of a flexible board of a rigid-flex board according to claim 1, characterized in that: In step S2, the quick pressing pressure of the upper covering film (1-3) and the lower covering film (1-4) is: 70-150 kg, the quick pressing temperature is: 160-210°C, the quick pressing time is: 1-4 minutes, the baking temperature is: 100-190°C, and the baking time is: 60-200 minutes.

4. The method for processing the shape of a flexible board of a rigid-flex board according to claim 1, characterized in that: The semi-cured adhesive sheet (3) in step S4 is a low-glue semi-cured adhesive sheet, and its glue flow is less than 0.5 mm when the rigid-flex board is pressed together.

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