A manufacturing process of a rigid-flex printed circuit board

Abstract

The application provides a soft and hard combined board and a manufacturing process thereof, and relates to the technical field of circuit board manufacturing.The manufacturing process comprises the following steps: S10, material selection, selecting a soft board, a hard board and a PP sheet according to the thickness of the soft and hard combined board; S20, positioning and processing of a PIN hole, a first depth control groove and a hollowed-out part; S30, vacuum pressing, placing the PP sheet between the soft board and the hard board; the area of the soft board corresponding to the hollowed-out part of the PP sheet is inwardly recessed; S40, drilling, chemical copper deposition and copper plating, drilling through holes in the pressed board according to needs, then performing chemical copper deposition and copper plating; S50, printing of corrosion-resistant photosensitive ink; S60, dry film, double-sidedly attaching a photosensitive dry film to the pre-cured board, then performing line exposure, development and etching; and S70, secondary depth control, forming a through window on the hard board.The application has the beneficial effects of reducing production cost, high production efficiency and avoiding damage to the inner soft board when the window is opened on the hard board.

Description

Technical Field

[0001] This invention relates to the field of circuit board technology, and more specifically, to a manufacturing process for a rigid-flex PCB. Background Technology

[0002] Based on the different properties of the dielectric layer, printed circuit boards (PCBs) include rigid PCBs (hard boards), flexible PCBs (flex boards), and rigid-flex PCBs (hard-flex boards). Generally speaking, a rigid-flex board is a printed circuit board composed of both flexible and rigid PCBs, combining the flexibility of flexible PCBs with the strength of rigid PCBs. With the rapid compression of internal space in electronic products, rigid-flex boards provide maximum flexibility for component connection and assembly, therefore they are frequently used as component carriers in electronic products.

[0003] Current rigid-flex PCB manufacturing processes still present some challenges. These include the need for dedicated vacuum laminators, which are expensive (approximately 5 million RMB per unit) and have relatively low production efficiency. Furthermore, controlling the cutting depth during the windowing process for the rigid PCB is difficult, easily damaging the inner flexible PCB and affecting yield. Summary of the Invention

[0004] To overcome the shortcomings of the existing technology, the present invention provides a manufacturing process for a rigid-flex PCB, which can reduce production costs, increase production efficiency, and avoid damaging the inner flexible PCB when opening windows in the rigid PCB.

[0005] The technical solution adopted by this invention to solve its technical problem is: a manufacturing process for a rigid-flex PCB, the improvement of which is that the manufacturing process includes the following steps:

[0006] S10. Material selection: Choose flexible board, rigid board, and PP sheet according to the thickness of the flexible-rigid bonding board.

[0007] S20. The processing of positioning PIN holes, first depth control grooves and hollow parts involves drilling positioning PIN holes on the edges of the rigid board, flexible board and PP sheet, performing laser depth control on the upper surface of the rigid board to form two parallel first depth control grooves, and laser cutting the PP sheet to form hollow parts, with the width of the hollow parts being equal to the width of the two first depth control grooves.

[0008] S30. Vacuum pressing: Place the PP sheet between the flexible board and the rigid board. The PP sheet is attached to the upper surface of the rigid board. The three are riveted together by the positioning pin hole. Then, the riveted board is put into the vacuum pressing machine for vacuum pressing. After the PP sheet melts, the flexible board and the rigid board are pressed together.

[0009] The flexible board has an inward recess in the area corresponding to the cutout part of the PP sheet, with a recess depth of 80-100μm;

[0010] S40, drilling, chemical copper plating and electroplating: The laminated board is drilled with through holes as needed, followed by chemical copper plating and electroplating.

[0011] For the printing of S50 anti-corrosion photosensitive ink, screen printing is used to screen print 15-20μm anti-corrosion photosensitive ink in the recessed area of ​​the flexible board. After that, the board is placed in an oven for pre-curing.

[0012] S60, dry film: The pre-cured board is coated with photosensitive dry film on both sides, and then the circuit is exposed, developed and etched.

[0013] S70, Secondary depth control: Laser depth control is performed on the lower surface of the rigid board to form a second depth control groove. Then, the connection between the first and second depth control grooves is cut off to form a through window on the rigid board.

[0014] Furthermore, in step S20, the diameter of the positioning PIN hole is 3.175mm;

[0015] The depth of the two first depth control grooves is 0.15-0.2mm, the width of the first depth control grooves is 0.1-0.15mm, and the distance between the two first depth control grooves is 15-20mm.

[0016] Furthermore, in step S30, before vacuum pressing, a silicone sheet is laid on the carrier plate of the hot press, and after the riveted plate is placed on the silicone sheet, another silicone sheet is laid on the riveted plate.

[0017] Furthermore, in step S30, the internal temperature of the vacuum press is 205-210℃, the pressing time is 1.5-2 hours, and the pressing force is 35-38 kg / cm². 2 .

[0018] Furthermore, in step S40, a conductive copper layer of 0.3-0.5 μm is deposited inside the through hole. During the copper plating process, the copper layer thickness inside the through hole is 10-20 μm, and the copper plating layer thickness on the surface of the board is 35-45 μm.

[0019] Furthermore, in step S50, the temperature inside the oven is 75°C, and the baking time is 18-20 minutes;

[0020] In step S60, the temperature for attaching the photosensitive dry film is 120℃, and the pressure is 1.5-5.5 kg / cm². 2 .

[0021] Furthermore, following step S60, the following steps are also included:

[0022] A cover film is attached to the area where the photosensitive ink is printed on the flexible circuit board.

[0023] On the other hand, the present invention also provides a rigid-flex board, which is improved in that it includes a flexible board, a rigid board, a PP sheet and an anti-corrosion photosensitive ink.

[0024] The upper surface of the rigid plate is provided with two parallel first depth control grooves, and the PP sheet is provided with through holes to form a hollow part, and the width of the hollow part is equal to the width of the two first depth control grooves.

[0025] The PP sheet is disposed between the upper surface of the rigid plate and the flexible plate, and the hollow part of the PP sheet is located directly above the two first depth control grooves. After vacuum pressing, the flexible plate is recessed inward in the area corresponding to the hollow part.

[0026] The upper surface of the flexible circuit board is provided with an electroplated copper layer, and the recessed area of ​​the flexible circuit board is screen-printed with anti-corrosion photosensitive ink; a photosensitive dry film is attached to the flexible circuit board, and conductive lines are formed on the photosensitive dry film.

[0027] The lower surface of the rigid plate is provided with a second depth control groove corresponding to the position of the first depth control groove. After the connection position between the first depth control groove and the second depth control groove is cut off, a through window is formed on the rigid plate.

[0028] In the above structure, the flexible board, rigid board and PP sheet are provided with multiple positioning pin holes, and the three are riveted together through the positioning pin holes.

[0029] The beneficial effects of this invention are: the use of positioning holes ensures the alignment of the flexible board and the rigid board, prevents misalignment, and improves the lamination effect; this production process significantly reduces production costs compared to the existing technology that requires the purchase of a vacuum laminating machine; at the same time, by controlling the depth of the two surfaces of the rigid board, it is easy to open windows in the rigid board, avoiding damage to the inner flexible board, thereby improving the product yield. Attached Figure Description

[0030] Figure 1 This is a process flow diagram illustrating the manufacturing process of a rigid-flex PCB according to the present invention.

[0031] Figure 2 This is a schematic diagram of the structure before pressing in step S30 of the manufacturing process of a rigid-flex plate according to the present invention.

[0032] Figure 3 This is a schematic diagram of the structure after pressing in step S30 of the manufacturing process of a rigid-flex PCB according to the present invention.

[0033] Figure 4 This is a schematic diagram of the product structure in step S50 of the manufacturing process of a rigid-flex PCB according to the present invention.

[0034] Figure 5 This is a schematic diagram of the product structure in step S60 of the manufacturing process of a rigid-flex PCB according to the present invention.

[0035] Figure 6 This is a schematic diagram of the product structure in step S70 of the manufacturing process of a rigid-flex PCB according to the present invention. Detailed Implementation

[0036] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0037] The following will clearly and completely describe the concept, specific structure, and technical effects of the present invention in conjunction with embodiments and accompanying drawings, so as to fully understand the purpose, features, and effects of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are all within the scope of protection of the present invention. Furthermore, all connections / linkages involved in the patent do not simply refer to direct contact between components, but rather to the ability to form a better connection structure by adding or reducing connecting accessories according to specific implementation conditions. The various technical features in this invention can be combined interactively without contradicting each other.

[0038] Example 1

[0039] Reference Figure 1 As shown, the present invention provides a manufacturing process for a rigid-flex PCB, specifically, the manufacturing process includes the following steps:

[0040] S10. Material selection: Select flexible board 10, rigid board 20 and PP sheet 30 according to the thickness of the flexible-rigid bonding board. The thickness of flexible board 10 and rigid board 20 can be adjusted according to actual needs. No specific limitation is made in this embodiment.

[0041] The processing of S20, positioning PIN holes 101, first depth control grooves 301, and hollowed-out portions 201 involves drilling positioning PIN holes 101 on the edges of the rigid board 20, flexible board 10, and PP sheet 30; laser depth control is performed on the upper surface of the rigid board 20 to form two parallel first depth control grooves 301; the PP sheet 30 is laser-cut to form hollowed-out portions 201, and the width of the hollowed-out portions 201 is equal to the width of the two first depth control grooves 301; in this embodiment, the diameter of the positioning PIN holes 101 is 3.175mm; the depth of the two first depth control grooves 301 is 0.15mm, the width of the first depth control grooves 301 is 0.1mm, and the distance between the two first depth control grooves 301 is 15mm;

[0042] S30, Vacuum pressing: The PP sheet 30 is placed between the flexible board 10 and the rigid board 20. The PP sheet 30 is attached to the upper surface of the rigid board 20. The three parts are riveted together through the positioning pin hole 101. At this time, its structure is as follows: Figure 2 As shown; subsequently, the riveted plates are placed in a vacuum press for vacuum pressing. After the PP sheet 30 melts, the flexible plate 10 and the rigid plate 20 are pressed together; the flexible plate 10 is recessed inward in the area corresponding to the hollowed-out portion 201 of the PP sheet 30 to form a first recess 102, and the depth of the first recess 102 is 80μm; at this time, its structure is as follows. Figure 3 As shown;

[0043] In step S30, before vacuum pressing, a silicone sheet is laid on the carrier plate of the hot press. After the riveted plate is placed on the silicone sheet, another silicone sheet is laid on the riveted plate. In step S30, the temperature inside the vacuum press is 205℃, the pressing time is 2h, and the pressing force is 35kg / cm2.

[0044] S40, drilling, chemical copper plating and electroplating: The laminated board is drilled with through holes as needed, followed by chemical copper plating and electroplating.

[0045] In step S40, a 0.3 μm conductive copper layer is deposited inside the through hole 102. During the copper plating process, the copper layer thickness inside the through hole is 10 μm, and the copper plating layer 103 on the surface of the board is 35 μm thick.

[0046] The S50 anti-corrosion photosensitive ink is printed using screen printing. A 15-20μm layer of anti-corrosion photosensitive ink 104 is screen-printed onto the recessed areas of the flexible board 10. The board is then placed in an oven for pre-curing. The oven temperature is 75℃, and the baking time is 18 minutes. Its structure is as follows: Figure 4 As shown;

[0047] S60, Dry film: Apply photosensitive dry film 105 to both sides of the pre-cured board, and then perform circuit exposure, development and etching; In step S60, the temperature of applying photosensitive dry film 105 is 120℃ and the pressure is 1.5kg / cm2.

[0048] Following step S60, the following step is performed: attaching a cover film 106 to the position of the photosensitive ink printed on the flexible board 10; its structure is as follows Figure 5 As shown;

[0049] S70, Secondary depth control: Laser depth control is performed on the lower surface of the rigid plate 20 to form a second depth control groove. Then, the connection between the first depth control groove 301 and the second depth control groove is cut off to form a through window 302 on the rigid plate 20; its structure is as follows. Figure 6 As shown.

[0050] In addition, the present invention also provides a rigid-flex PCB, which combines... Figure 6 As shown, the rigid-flex board includes a flexible board 10, a rigid board 20, a PP sheet 30, and an anti-corrosion photosensitive ink 104. The upper surface of the rigid board 20 has two parallel first depth control grooves 301. The PP sheet 30 has through holes forming a perforated portion 201, the width of which is equal to the width of the two first depth control grooves 301. The PP sheet 30 is disposed between the upper surface of the rigid board 20 and the flexible board 10, with the perforated portion 201 of the PP sheet 30 located between the two first depth control grooves 301. Directly above, after vacuum pressing, the area of ​​the flexible board 10 corresponding to the cutout portion 201 is recessed inward; the upper surface of the flexible board 10 is provided with an electroplated copper layer, and the recessed position of the flexible board 10 is screen-printed with anti-corrosion photosensitive ink 104; a photosensitive dry film 105 is attached to the flexible board 10, and conductive lines are formed on the photosensitive dry film 105; the lower surface of the rigid board 20 is provided with a second depth control groove corresponding to the position of the first depth control groove 301, and after cutting off the connection position between the first depth control groove 301 and the second depth control groove, a through window 302 is formed on the rigid board 20.

[0051] In addition, the flexible board 10, the rigid board 20 and the PP sheet 30 are provided with a plurality of positioning pin holes 101, and the three are riveted together through the positioning pin holes 101; the area of ​​the flexible board 10 corresponding to the hollow part 201 is recessed inward to a depth of 80μm.

[0052] Through the above-described process and structure, the positioning holes used in this invention can ensure the alignment of the flexible board 10 and the rigid board 20, prevent misalignment, and improve the pressing effect. Compared with the existing technology that requires the purchase of a vacuum laminating machine, this production process significantly reduces production costs. At the same time, by controlling the depth of the two surfaces of the rigid board 20, it is easy to open the window in the rigid board 20, avoiding damage to the inner flexible board 10, thereby improving the product yield.

[0053] Example 2

[0054] Reference Figure 1 As shown, the present invention provides a manufacturing process for a rigid-flex PCB, specifically, the manufacturing process includes the following steps:

[0055] S10. Material selection: Select flexible board 10, rigid board 20 and PP sheet 30 according to the thickness of the flexible-rigid bonding board. The thickness of flexible board 10 and rigid board 20 can be adjusted according to actual needs. No specific limitation is made in this embodiment.

[0056] The processing of S20, positioning PIN holes 101, first depth control grooves 301, and hollowed-out portions 201 involves drilling positioning PIN holes 101 on the edges of the rigid board 20, flexible board 10, and PP sheet 30; laser depth control is performed on the upper surface of the rigid board 20 to form two parallel first depth control grooves 301; the PP sheet 30 is laser-cut to form hollowed-out portions 201, and the width of the hollowed-out portions 201 is equal to the width of the two first depth control grooves 301; in this embodiment, the diameter of the positioning PIN holes 101 is 3.175mm; the depth of the two first depth control grooves 301 is 0.2mm, the width of the first depth control grooves 301 is 0.15mm, and the distance between the two first depth control grooves 301 is 20mm;

[0057] S30, Vacuum pressing: The PP sheet 30 is placed between the flexible board 10 and the rigid board 20. The PP sheet 30 is attached to the upper surface of the rigid board 20. The three parts are riveted together through the positioning pin hole 101. At this time, its structure is as follows: Figure 2 As shown; subsequently, the riveted plates are placed in a vacuum press for vacuum pressing. After the PP sheet 30 melts, the flexible plate 10 and the rigid plate 20 are pressed together; the flexible plate 10 is recessed inward in the area corresponding to the hollowed-out portion 201 of the PP sheet 30 to form a first recess 102, and the depth of the first recess 102 is 100μm; at this time, its structure is as follows. Figure 3 As shown;

[0058] In step S30, before vacuum pressing, a silicone sheet is laid on the carrier plate of the hot press. After the riveted plate is placed on the silicone sheet, another silicone sheet is laid on the riveted plate. In step S30, the internal temperature of the vacuum press is 210℃, the pressing time is 1.5h, and the pressing force is 38kg / cm2.

[0059] S40, drilling, chemical copper plating and electroplating: The laminated board is drilled with through holes as needed, followed by chemical copper plating and electroplating.

[0060] In step S40, a 0.5 μm conductive copper layer is deposited inside the through hole 102. During the copper plating process, the copper layer thickness inside the through hole is 20 μm, and the copper plating layer 103 on the surface of the board is 45 μm thick.

[0061] The S50 anti-corrosion photosensitive ink is printed using screen printing. A 15-20μm layer of anti-corrosion photosensitive ink 104 is screen-printed onto the recessed areas of the flexible board 10. The board is then placed in an oven for pre-curing. The oven temperature is 75℃, and the baking time is 20 minutes. Its structure is as follows: Figure 4 As shown;

[0062] S60, Dry film: Apply photosensitive dry film 105 to both sides of the pre-cured board, and then perform circuit exposure, development and etching; In step S60, the temperature for applying photosensitive dry film 105 is 120℃ and the pressure is 5.5kg / cm2.

[0063] Following step S60, the following step is performed: attaching a cover film 106 to the position of the photosensitive ink printed on the flexible board 10; its structure is as follows Figure 5 As shown;

[0064] S70, Secondary depth control: Laser depth control is performed on the lower surface of the rigid plate 20 to form a second depth control groove. Then, the connection between the first depth control groove 301 and the second depth control groove is cut off to form a through window 302 on the rigid plate 20; its structure is as follows. Figure 6 As shown.

[0065] In addition, the present invention also provides a rigid-flex PCB, which combines... Figure 6 As shown, the rigid-flex board includes a flexible board 10, a rigid board 20, a PP sheet 30, and an anti-corrosion photosensitive ink 104. The upper surface of the rigid board 20 has two parallel first depth control grooves 301. The PP sheet 30 has through holes forming a perforated portion 201, the width of which is equal to the width of the two first depth control grooves 301. The PP sheet 30 is disposed between the upper surface of the rigid board 20 and the flexible board 10, with the perforated portion 201 of the PP sheet 30 located between the two first depth control grooves 301. Directly above, after vacuum pressing, the area of ​​the flexible board 10 corresponding to the cutout portion 201 is recessed inward; the upper surface of the flexible board 10 is provided with an electroplated copper layer, and the recessed position of the flexible board 10 is screen-printed with anti-corrosion photosensitive ink 104; a photosensitive dry film 105 is attached to the flexible board 10, and conductive lines are formed on the photosensitive dry film 105; the lower surface of the rigid board 20 is provided with a second depth control groove corresponding to the position of the first depth control groove 301, and after cutting off the connection position between the first depth control groove 301 and the second depth control groove, a through window 302 is formed on the rigid board 20.

[0066] In addition, the flexible board 10, the rigid board 20 and the PP sheet 30 are provided with a plurality of positioning pin holes 101, and the three are riveted together through the positioning pin holes 101; the area of ​​the flexible board 10 corresponding to the hollow part 201 is recessed inward to a depth of 80μm.

[0067] Through the above-described process and structure, the positioning holes used in this invention can ensure the alignment of the flexible board 10 and the rigid board 20, prevent misalignment, and improve the pressing effect. Compared with the existing technology that requires the purchase of a vacuum laminating machine, this production process significantly reduces production costs. At the same time, by controlling the depth of the two surfaces of the rigid board 20, it is easy to open the window in the rigid board 20, avoiding damage to the inner flexible board 10, thereby improving the product yield.

[0068] The above is a detailed description of the preferred embodiments of the present invention. However, the present invention is not limited to the embodiments described. Those skilled in the art can make various equivalent modifications or substitutions without departing from the spirit of the present invention. All such equivalent modifications or substitutions are included within the scope defined by the claims of this application.

Claims

1. A manufacturing process for a rigid-flex PCB, characterized in that, The manufacturing process includes the following steps: S10. Material selection: Choose flexible board, rigid board, and PP sheet according to the thickness of the flexible-rigid bonding board. S20. The processing of positioning PIN holes, first depth control grooves and hollow parts involves drilling positioning PIN holes on the edges of the rigid board, flexible board and PP sheet, performing laser depth control on the upper surface of the rigid board to form two parallel first depth control grooves, and laser cutting the PP sheet to form hollow parts, with the width of the hollow parts being equal to the width of the two first depth control grooves. S30. Vacuum pressing: Place the PP sheet between the flexible board and the rigid board. The PP sheet is attached to the upper surface of the rigid board. The three are riveted together by the positioning pin hole. Then, the riveted board is put into the vacuum pressing machine for vacuum pressing. After the PP sheet melts, the flexible board and the rigid board are pressed together. The flexible board is recessed inward in the area corresponding to the cutout part of the PP sheet to form the first recessed part; S40, drilling, chemical copper plating and electroplating: The laminated board is drilled with through holes as needed, followed by chemical copper plating and electroplating. S50, the anti-corrosion photosensitive ink is printed by screen printing. The anti-corrosion photosensitive ink is screen printed on the first recess of the flexible board, and then the board is placed in an oven for pre-curing. S60, dry film: The pre-cured board is coated with photosensitive dry film on both sides, and then the circuit is exposed, developed and etched. S70, Secondary depth control: Laser depth control is performed on the lower surface of the rigid board to form a second depth control groove. Then, the connection between the first and second depth control grooves is cut off to form a through window on the rigid board.

2. The manufacturing process of a rigid-flex PCB according to claim 1, characterized in that, In step S20, the diameter of the positioning PI N hole is 3.175mm; The depth of the two first depth control grooves is 0.15-0.2mm, the width of the first depth control grooves is 0.1-0.15mm, and the distance between the two first depth control grooves is 15-20mm.

3. The manufacturing process of a rigid-flex PCB according to claim 1, characterized in that, In step S30, before vacuum pressing, a silicone sheet is laid on the carrier plate of the hot press. After the riveted plate is placed on the silicone sheet, another silicone sheet is laid on the riveted plate.

4. The manufacturing process of a rigid-flex PCB according to claim 1, characterized in that, In step S30, the temperature inside the vacuum press is 205-210℃, the pressing time is 1.5-2 hours, and the pressing force is 35-38 kg / cm². 2 .

5. The manufacturing process of a rigid-flex PCB according to claim 1, characterized in that, In step S30, the depth of the first recess is 80-100μm; in step S50, the thickness of the screen-printed anti-corrosion photosensitive ink is 15-20μm.

6. The manufacturing process of a rigid-flex PCB according to claim 1, characterized in that, In step S40, a conductive copper layer of 0.3-0.5 μm is deposited inside the through hole. During the copper plating process, the copper layer thickness inside the through hole is 10-20 μm, and the copper plating layer thickness on the surface of the board is 35-45 μm.

7. The manufacturing process of a rigid-flex PCB according to claim 1, characterized in that, In step S50, the oven temperature is 75℃ and the baking time is 18-20 minutes. In step S60, the temperature for attaching the photosensitive dry film is 120℃, and the pressure is 1.5-5.5 kg / cm². 2 .

8. The manufacturing process of a rigid-flex PCB according to claim 1, characterized in that, Following step S60, the following steps are also included: A cover film is attached to the area where the photosensitive ink is printed on the flexible circuit board.

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