Novel double-sided FPC board VIP hole manufacturing process

Abstract

The invention discloses a novel double-sided FPC (Flexible Printed Circuit) board VIP hole manufacturing process, which belongs to the field of PCB (Printed Circuit Board) processing devices, and comprises the following steps of: (a) forming funnel-shaped micropores in a double-sided FPC substrate by adopting laser drilling through laser drilling equipment; (b) carrying out vacuum plasma treatment on the micropores obtained in the step (a); (c) plating copper on the micropores by adopting a vertical continuous electroplating (VCP) process, wherein the TP value is gt; the current density is controlled to be 1.5-2.5 ASD in a 1: 1 acidic copper plating solution, so that the unilateral copper thickness of the lower aperture is larger than or equal to 10 microns, and the hole bottom is completely filled; and (d) carrying out surface anti-oxidation treatment and laminated packaging on the copper-plated FPC board. After the scheme is adopted, the hole pattern of the micro hole is controlled by adjusting laser parameters, so that the hole pattern of the micro hole is funnel-shaped, VIP holes can be manufactured under the condition that a common VCP copper-plated wire is used, and the problems of high requirements on production equipment, hole opening sinking and liquid medicine core wrapping in the conventional laser blind hole and laser micro hole process can be avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of PCB processing devices, and in particular to a novel process for manufacturing VIP holes in double-sided FPC boards. Background Art

[0002] The fabrication of VIP holes (typically conductive through-holes achieved through plated through-hole technology) on double-sided FPCs (Flexible Printed Circuits) is a key step in their manufacturing. Double-sided FPCs are flexible printed circuits with two conductive layers, electrically connected via VIP holes. This structure enables more complex circuit layouts within limited space, making them widely used in electronic products requiring high density, miniaturization, and high reliability, such as those in aerospace, military, mobile communications, laptop computers, and digital cameras.

[0003] The VIP hole production process involves multiple key steps, including cutting, drilling, hole metallization (electroplated through-hole), pre-treatment, circuit production, etching, protective film application, lamination and curing, surface treatment, and electrical testing. Currently, in the PCB industry, VIP holes in double-layer FPC boards are generally filled with laser blind vias + via-filling copper plating or laser micro-vias + VCP copper plating. Laser blind vias + via-filling copper plating must use via-filling copper plating wire, which requires high equipment and has high quality risks (blind via depression / fluid core wrapping). It is also prone to defects such as blind via depression and fluid core wrapping, which limits the yield rate. The laser micro-via + VCP solution has the risk of glue residue blocking the hole and fluid core wrapping. In addition, due to the poor uniformity of the micro-via aperture, core wrapping may still occur after copper plating, affecting the conductivity reliability.

[0004] The above process places stringent demands on equipment precision and is difficult to meet the processing requirements of ultra-thin FPC boards (total substrate thickness ≤ 50μm). To address these issues, a low-cost, highly reliable process for producing VIP holes in double-sided FPC boards is urgently needed. Summary of the Invention

[0005] The purpose of the present invention is to solve the problems of the existing laser micro-via + VCP solution in the hole blocking and the risk of core encapsulation by the filling solution, and to propose a new double-sided FPC board VIP hole production process.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions: A new double-sided FPC board VIP hole production process includes the following steps: (a) forming funnel-shaped microholes on a double-sided FPC substrate using a laser drilling device, wherein the lower pore diameter of the microhole is 20-25 μm, the upper pore diameter is 40-60 μm, and the pore depth is consistent with the total thickness of the substrate and is ≤50 μm; (b) performing vacuum plasma treatment on the micropores obtained in step (a) to remove residual carbon at the pore openings and increase the pore wall roughness to Ra ≤ 0.5 μm; (c) Copper plating of the microvias using a vertical continuous electroplating (VCP) process, using an acidic copper plating solution with a TP value > 1:1 and a current density of 1.5-2.5 ASD, ensuring that the copper thickness on one side of the lower aperture is ≥ 10 μm and the bottom of the aperture is completely filled, and the depression depth of the upper aperture is ≤ 5 μm; (d) The copper-plated FPC board is subjected to surface anti-oxidation treatment and laminated packaging.

[0007] Preferably, the laser drilling parameters in step (a) include: The laser wavelength is 355nm or 532nm; Energy density is 1.0-1.5J / cm²; The pulse frequency is 3-8kHz; The focused spot diameter is 15-25μm.

[0008] Preferably, the vacuum plasma treatment in step (b) uses an Ar / O2 mixed gas, with an O2 volume ratio of 20-40%, a treatment pressure of 30-80 Pa, a radio frequency power of 200-500 W, and a treatment time of 60-120 s.

[0009] Preferably, the acid copper plating solution in step (c) comprises the following components: Copper sulfate: 80-120g / L; Sulfuric acid: 80-150g / L; Chloride ion: 30-80ppm; Organic additives: including leveling agents, wetting agents and inhibitors, with a total concentration of 2-8mL / L; In step (c), the circulation rate of the copper plating solution is 3-8 m / min, and the plating solution temperature is 22-28°C.

[0010] Preferably, the surface anti-oxidation treatment in step (d) is a chemical nickel-gold deposition or OSP organic solder paste process, and the laminated package adopts a polyimide cover film or epoxy resin prepreg; The double-sided FPC substrate is made of polyimide PI, polyester PET or liquid crystal polymer LCP, and the total thickness of the substrate is 25-50 μm; The VIP hole conduction resistance is ≤0.5Ω, the hole copper density is ≥98%, and the bonding strength between the hole wall and the plating is ≥1.5N / mm; After step (c) is completed, an X-ray inspection is performed to ensure that the lower aperture is filled without voids, and that the upper aperture is allowed to have a concave depth of ≤5 μm without cracks.

[0011] Preferably, the laser drilling equipment includes a machine base, a laser is provided at the upper end of the machine base, an optical system for focusing, expanding and collimating the laser beam is provided inside the laser, a connecting base is fixedly installed outside the laser, the lower end of the connecting base is slidably set on the machine base, a spring is fixedly connected between the machine base and the connecting base, and two symmetrically distributed support plates are fixedly installed on the top of the machine base.

[0012] Preferably, a driving component is provided in the machine base, a connecting shaft is fixedly installed at the bottom of the driving component, the connecting shaft is rotatably installed in the machine base, a servo motor is fixedly installed on the machine base, the output shaft of the servo motor is fixedly connected to the connecting shaft, a laser protection plate is provided at the upper end of the machine base, the laser protection plate is located below the laser, one end of the laser protection plate is inserted into the machine base and can slide horizontally, and also includes a through-hole, which passes through the laser protection plate and the machine base from top to bottom.

[0013] Preferably, the bottom of the driving component is hinged with a laser reflecting plate, and both sides of the driving component pass through a limit block, the limit block is an iron block, one end of the limit block can be inserted into the hinge shaft of the laser reflecting plate, and an elastic sheet is fixedly connected between the limit block and the driving component, and an electromagnet is fixedly installed on both sides of the driving component, and the electromagnet is arranged towards the limit block, and a support rod is placed on the machine base, and the lower end of the support rod is hollow and one end is connected to the outside world. One end of the support rod is fixedly installed with a heat conductive member, and a hole for the laser beam to pass through is opened on the heat conductive member, and one end of the heat conductive member extends into the inner cavity of the lower end of the support rod, and a piston is slidably provided in the inner cavity of the lower end of the support rod, and the piston divides the inner cavity of the lower end of the support rod into two independent spaces, and an elastic member is fixedly connected between the piston and the heat conductive member, and a travel switch is provided on one side of the piston, and the travel switch is used to control the on and off of the electromagnet circuit, and the independent space of the piston facing the heat conductive member is filled with thermosensitive gas.

[0014] Preferably, the outer shell of the heat conducting element is provided with a heat insulating sleeve, the inner side of the heat insulating sleeve is open and the heat conducting element is in contact with the outside air through the inner opening of the heat insulating sleeve.

[0015] Preferably, a vertical pipe is fixedly installed on the machine base, and the vertical pipe is made of aluminum alloy. The friction coefficient of the inner wall of the vertical pipe increases segmentally from top to bottom, and the lower end of the vertical pipe is opened. A fan facing the inner hole of the heat conductor is installed on the machine base, and a driving mechanism is installed between the fan shaft of the fan and the vertical pipe, and the driving mechanism is used to drive the fan shaft of the fan to rotate.

[0016] Compared with the prior art, the present invention has the following beneficial effects: After adopting this solution, the micropore shape is controlled by adjusting the laser parameters to make the micropore shape "funnel-shaped". VIP holes can be produced using ordinary VCP copper-plated wire, avoiding the high requirements for production equipment and the problems of hole depression and syrup core coating in conventional laser blind holes and laser micropore processes.

[0017] In this application, laser drilling equipment is used for layered penetration, which suppresses heat accumulation, improves hole wall quality, and prevents carbonization. By drilling in stages (e.g., treating each layer separately), the intervals between laser pulses increase heat dissipation, preventing localized overheating of the substrate and carbonization of organic materials such as polyimide (PI) due to high temperatures. For multi-layer materials, laser penetration can be performed in stages, first penetrating the copper layer, then processing the PI layer, and finally completing the hole in the bottom copper layer. This avoids the problem of energy overload in a single drilling operation, which can lead to spattering or overheating of the bottom metal. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a schematic diagram of the effect of a new double-sided FPC board VIP hole manufacturing process proposed by the present invention; Figure 2 This is a schematic diagram of the structure of a new laser drilling equipment in the double-sided FPC board VIP hole production process proposed by the present invention. Figure 1 ; Figure 3 This is a side view of a new laser drilling device in a double-sided FPC board VIP hole manufacturing process proposed by the present invention; Figure 4 This is a schematic diagram of the structure of a new laser drilling equipment in the double-sided FPC board VIP hole production process proposed by the present invention. Figure 2 ; Figure 5 This is an enlarged schematic diagram of a portion of the structure of the driving component in a laser drilling device in a novel double-sided FPC board VIP hole manufacturing process proposed by the present invention; Figure 6 This is a partial enlarged schematic diagram of the structure of the laser protection plate in the laser drilling equipment in the novel double-sided FPC board VIP hole manufacturing process proposed by the present invention; Figure 7 This is an exploded view of the driving components and connecting shaft in the laser drilling equipment in the novel double-sided FPC board VIP hole production process proposed by the present invention; Figure 8 This is an enlarged cross-sectional view of a portion of the structure of the support rod in a laser drilling device in a novel double-sided FPC board VIP hole manufacturing process proposed by the present invention; Figure 9This is an enlarged schematic diagram of a portion of the structure of the synchronous belt mechanism in the laser drilling equipment in a novel double-sided FPC board VIP hole manufacturing process proposed by the present invention; Figure 10 This is an enlarged cross-sectional view of part of the structure of the vertical pipe in the laser drilling equipment in the novel double-sided FPC board VIP hole manufacturing process proposed by the present invention.

[0019] In the figure: machine base 1, laser 2, connecting base 3, spring 4, support plate 5, driving component 6, connecting shaft 7, servo motor 8, laser protection plate 9, through-hole 10, laser reflector 11, limit block 12, elastic sheet 13, electromagnet 14, support rod 15, heat conducting member 16, piston 17, elastic member 18, travel switch 19, thermal insulation sleeve 20, vertical pipe 21, fan 22, slider 23, vegetable wax 24, driving bar 25, first rotating shaft 26, driven wheel 27, second rotating shaft 28, bevel gear 29, synchronous belt mechanism 30. DETAILED DESCRIPTION

[0020] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. Example

[0021] Reference Figure 1 A new double-sided FPC board VIP hole production process includes the following steps: (a) Funnel-shaped microholes are formed on the double-sided FPC substrate using a laser drilling device. The lower pore diameter of the microhole is 20-25μm, the upper pore diameter is 40-60μm, and the hole depth is consistent with the total thickness of the substrate and is ≤50μm; (b) performing vacuum plasma treatment on the micropores obtained in step (a) to remove residual carbon at the pore openings and increase the pore wall roughness to Ra ≤ 0.5 μm; (c) Copper plating of the microvias using a vertical continuous plating (VCP) process, using an acidic copper plating solution with a TP value > 1:1 and a current density of 1.5-2.5 ASD, ensuring that the copper thickness on one side of the lower aperture is ≥ 10 μm and the bottom of the aperture is completely filled, and the depression depth of the upper aperture is ≤ 5 μm; (d) The copper-plated FPC board is subjected to surface anti-oxidation treatment and laminated packaging.

[0022] The laser drilling parameters in step (a) include: The laser wavelength is 355nm or 532nm; Energy density is 1.0-1.5J / cm²; The pulse frequency is 3-8kHz; The focused spot diameter is 15-25μm.

[0023] In step (b), the vacuum plasma treatment uses an Ar / O2 mixed gas, with the volume proportion of O2 being 20-40%, the treatment pressure being 30-80 Pa, the radio frequency power being 200-500 W, and the treatment time being 60-120 s.

[0024] The acid copper plating solution in step (c) comprises the following components: Copper sulfate: 80-120g / L; Sulfuric acid: 80-150g / L; Chloride ion: 30-80ppm; Organic additives: including leveling agents, wetting agents and inhibitors, with a total concentration of 2-8mL / L; In step (c), the circulation rate of the copper plating solution is 3-8 m / min, and the plating solution temperature is 22-28°C.

[0025] In step (d), the surface anti-oxidation treatment is a chemical nickel-gold deposition process or an OSP organic solder paste process, and the laminated package adopts a polyimide cover film or an epoxy resin prepreg; The double-sided FPC substrate is made of polyimide (PI), polyester (PET) or liquid crystal polymer (LCP), with a total thickness of 25-50μm; VIP hole on-resistance ≤ 0.5Ω, hole copper density ≥ 98%, hole wall and plating bonding strength ≥ 1.5N / mm; After step (c) is completed, an X-ray inspection is performed to ensure that the lower aperture is filled without voids, and that the upper aperture is allowed to have a concave depth of ≤5 μm without cracks.

[0026] After adopting this solution, the micropore shape is controlled by adjusting the laser parameters to make the micropore shape "funnel-shaped". VIP holes can be produced using ordinary VCP copper-plated wire, avoiding the high requirements for production equipment and the problems of hole depression and molten core coating in conventional laser blind hole and laser micropore processes.

[0027] Example 2 proposed based on Example 1: Reference Figure 2-10 The laser drilling equipment includes a machine base 1, a laser 2 is provided at the upper end of the machine base 1, an optical system for focusing, expanding and collimating the laser beam is provided inside the laser 2, a connecting base 3 is fixedly installed outside the laser 2, and the lower end of the connecting base 3 is slidably set on the machine base 1, a spring 4 is fixedly connected between the machine base 1 and the connecting base 3, and two symmetrically distributed support plates 5 are fixedly installed on the top of the machine base 1.

[0028] A driving component 6 is provided in the machine base 1, and a connecting shaft 7 is fixedly installed at the bottom of the driving component 6. The connecting shaft 7 can be rotatably installed in the machine base 1. A servo motor 8 is fixedly installed on the machine base 1, and the output shaft of the servo motor 8 is fixedly connected to the connecting shaft 7. A laser protection plate 9 is provided at the upper end of the machine base 1, and the laser protection plate 9 is located below the laser 2. One end of the laser protection plate 9 is inserted into the machine base 1 and can slide horizontally. It also includes a through-hole 10, which passes through the laser protection plate 9 and the machine base 1 from top to bottom.

[0029] The working diagram of the device can be referred to Figure 2 As shown, the substrate is placed on two supporting plates 5, and the laser 2 is used to drill holes in the substrate below.

[0030] The servo motor 8 drives the connecting shaft 7 to rotate, and the driving component 6 on the connecting shaft 7 rotates about the axis of the connecting shaft 7 and toward the connecting base 3. The driving component 6 can push the connecting base 3 to move horizontally, and the spring 4 is compressed, so that the connecting base 3 and the laser 2 move synchronously, and the horizontal position of the laser 2 can be adjusted, so that different positions of the substrate can be drilled. When the servo motor 8 is reversed, the elastic force of the spring 4 resets the connecting base 3, and thus resets the laser 2. Under this adjustment function, if the laser shield 9 blocks the laser emitted by the laser 2, the laser shield 9 can be pushed away from the laser 2.

[0031] Among them, the bottom of the driving component 6 is hinged with a laser reflector 11, and both sides of the driving component 6 are penetrated by a limit block 12, the limit block 12 is an iron block, one end of the limit block 12 can be inserted into the hinge shaft of the laser reflector 11, and an elastic sheet 13 is fixedly connected between the limit block 12 and the driving component 6. Electromagnets 14 are fixedly installed on both sides of the driving component 6, and the electromagnets 14 are set toward the limit block 12. A support rod 15 is placed on the machine base 1. The lower end of the support rod 15 is hollow and one end is connected to the outside world. One end of the support rod 15 is fixedly installed There is a heat conductor 16, which has a hole for the laser beam to pass through. One end of the heat conductor 16 extends into the inner cavity of the lower end of the support rod 15. A piston 17 is slidably provided in the inner cavity of the lower end of the support rod 15. The piston 17 divides the inner cavity of the lower end of the support rod 15 into two independent spaces. An elastic member 18 is fixedly connected between the piston 17 and the heat conductor 16. A limit switch 19 is provided on one side of the piston 17. The limit switch 19 is used to control the on and off of the circuit of the electromagnet 14. The independent space on the side of the piston 17 facing the heat conductor 16 is filled with thermosensitive gas.

[0032] The heat conductor 16 is covered with an insulating sleeve 20. The inner side of the insulating sleeve 20 is open, and the heat conductor 16 is exposed to the outside air through the inner opening of the insulating sleeve 20. After the heat conductor 16 absorbs heat and heats up, the insulating sleeve 20 reduces the heat loss of the heat conductor 16 itself, allowing the heat conductor 16 to more completely transfer its heat to the heat-sensitive gas inside the support rod 15.

[0033] A vertical pipe 21 is fixedly installed on the machine base 1. The vertical pipe 21 is made of aluminum alloy. The friction coefficient of the inner wall of the vertical pipe 21 increases segmentally from top to bottom. The lower end of the vertical pipe 21 is opened. A fan 22 is installed on the machine base 1 facing the inner hole of the heat conductor 16. A driving mechanism is installed between the fan shaft of the fan 22 and the vertical pipe 21. The driving mechanism is used to drive the fan shaft of the fan 22 to rotate.

[0034] The driving mechanism includes a slider 23 slidably arranged in the vertical tube 21, the upper end of the interior of the vertical tube 21 is filled with vegetable wax 24, and the bottom of the slider 23 is fixedly connected to a driving bar 25 that runs through the bottom of the vertical tube 21. A first rotating shaft 26 is rotatably mounted on the vertical tube 21, and a driven wheel 27 is provided in the vertical tube 21. The driven wheel 27 is fixedly connected to the first rotating shaft 26, and the driving bar 25 and the driven wheel 27 are tightly fitted and transmitted by friction. A second rotating shaft 28 is rotatably mounted on the outside of the vertical tube 21, and bevel gears 29 are installed at the opposite ends of the second rotating shaft 28 and the first rotating shaft 26. The two bevel gears 29 are meshed and the second rotating shaft 28 and the first rotating shaft 26 are transmitted through two bevel gears 29. A synchronous belt mechanism 30 is installed between the second rotating shaft 28 and the fan shaft of the fan 22.

[0035] The laser passes through the inner hole of heat conductor 16 and then strikes the substrate. Heat is generated during laser drilling. By placing heat conductor 16 outside the hole machined in the substrate, surrounding it, it quickly and completely absorbs the heat generated by laser drilling. Heat conductor 16 heats up and transfers the heat to the thermosensitive gas within support rod 15. The thermosensitive gas expands due to the heat and pushes piston 17 toward limit switch 19. Limit switch 19 triggers and controls the circuit closure of electromagnet 14. Electromagnet 14 is energized and applies an attractive force to stop block 12. One end of stop block 12 is inserted into the hinged shaft of laser reflector 11. The resulting impact sound alerts the operator, synchronizing the movement of laser reflector 11 and drive unit 6. Servo motor 8 is then activated, operating intermittently and in both forward and reverse directions. At this point, the substrate is in a pre-set state, indicating excessively high additional temperature and a significant heat accumulation effect, affecting normal drilling. Targeted cooling of the substrate is required.

[0036] When the servo motor 8 is working, it first drives the driving component 6 to move toward the connecting seat 3 and pushes the laser 2 to move horizontally. The laser emitted by the laser 2 is immediately absorbed by the laser protection plate 9. At the same time, the laser reflector 11 rotates synchronously. Subsequently, the laser emitted by the laser 2 passes through the through-hole 10 and shoots toward the inclined laser reflector 11. The laser is reflected by the laser reflector 11 to the vertical tube 21. The vertical tube 21 is heated and heated. The temperature is transferred to the vegetable wax 24 therein. The vegetable wax 24 is melted by the heat and drips onto the slider 23. The slider 23 is in the initial state. The slider 23 is in a stationary state (its gravity is less than the friction force it receives from the inner wall of the vertical tube 21). When the liquid vegetable wax 24 on the slider 23 accumulates to a certain amount, the slider 23 moves downward and drives the driving bar 25 to move downward synchronously. The driving bar 25 drives the driven wheel 27 to rotate, and cooperates with the transmission action of the two bevel gears 29 to drive the second rotating shaft 28 to rotate, and then drives the fan 22 to rotate through the synchronous belt mechanism 30, so that the fan 22 generates an airflow blowing toward the drilling position of the substrate, and directionally dissipates heat to the drilling position of the substrate. The airflow is from top to bottom, and the heat dissipation effect is good.

[0037] After cooling for a period of time, the temperature at the drilling position of the substrate returns to normal, the servo motor 8 reverses, and the laser continues to shoot towards the drilling position of the substrate, while the vegetable wax 24 in the vertical tube 21 is no longer heated, and the liquid vegetable wax 24 on the slider 23 no longer accumulates. At the same time, as the slider 23 moves down to the area with high friction on the inner wall of the vertical tube 21, the slider 23 remains stationary, the fan 22 no longer rotates, and the drilling position of the substrate does not need to continue to cool.

[0038] The drilling work is continued for a period of time, and the above work is repeated. The servo motor 8 rotates forward. Similarly, the fan 22 rotates and cools the drilling position of the substrate. The device continues to repeat the work until the drilling work is completed.

[0039] This drilling process, performed as a layered penetration process, suppresses heat accumulation, improves hole wall quality, and prevents carbonization. By drilling in stages (e.g., treating each layer of material separately), the interval between laser pulses increases the heat dissipation process, keeping the local temperature rise of the substrate within ΔT ≤ 5°C. This prevents high-temperature carbonization of organic materials like polyimide (PI), ensuring a hole wall roughness Ra ≤ 0.5μm.

[0040] The first drilling is done with low energy (e.g. 50% rated power) to pre-drill the hole, and then the energy is gradually increased to the target value to form a smooth funnel-shaped hole profile, thus avoiding hole edge collapse or residual glue at the bottom caused by a single high-energy impact.

[0041] The above drilling process is a layered penetration work. For multi-layer materials (such as copper-PI-copper structure), laser penetration can be performed in batches. The first time, the copper layer is penetrated (using 355nm UV laser); the second time, the PI layer is processed (switching to CO2 laser); and finally the bottom copper layer is opened, avoiding the problem of single drilling energy overload causing the bottom metal to splash or overheat.

[0042] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A new double-sided FPC board VIP hole production process, characterized in that: The following steps are involved: (a) forming funnel-shaped microholes on a double-sided FPC substrate using a laser drilling device, wherein the lower pore diameter of the microhole is 20-25 μm, the upper pore diameter is 40-60 μm, and the pore depth is consistent with the total thickness of the substrate and is ≤50 μm; (b) performing vacuum plasma treatment on the micropores obtained in step (a) to remove residual carbon at the pore openings and increase the pore wall roughness to Ra ≤ 0.5 μm; (c) Copper plating of the microvias using a vertical continuous plating (VCP) process, using an acidic copper plating solution with a TP value > 1:1 and a current density of 1.5-2.5 ASD, ensuring that the copper thickness on one side of the lower aperture is ≥ 10 μm and the bottom of the aperture is completely filled, and the depression depth of the upper aperture is ≤ 5 μm; (d) The copper-plated FPC board is subjected to surface anti-oxidation treatment and laminated packaging.

2. A novel double-sided FPC board VIP hole manufacturing process according to claim 1, characterized in that: The laser drilling parameters in step (a) include: The laser wavelength is 355nm or 532nm; Energy density is 1.0-1.5J / cm²; The pulse frequency is 3-8kHz; The focused spot diameter is 15-25μm.

3. A novel double-sided FPC board VIP hole manufacturing process according to claim 1, characterized in that: The vacuum plasma treatment in step (b) uses an Ar / O2 mixed gas, with an O2 volume ratio of 20-40%, a treatment pressure of 30-80 Pa, a radio frequency power of 200-500 W, and a treatment time of 60-120 s.

4. A novel double-sided FPC board VIP hole manufacturing process according to claim 1, characterized in that: The acid copper plating solution in step (c) comprises the following components: Copper sulfate: 80-120g / L; Sulfuric acid: 80-150g / L; Chloride ion: 30-80ppm; Organic additives: including leveling agents, wetting agents and inhibitors, with a total concentration of 2-8mL / L; In step (c), the circulation rate of the copper plating solution is 3-8 m / min, and the plating solution temperature is 22-28°C.

5. A novel double-sided FPC board VIP hole manufacturing process according to claim 1, characterized in that: The surface anti-oxidation treatment in step (d) is a chemical nickel-gold deposition process or an OSP organic solder paste process, and the laminated package adopts a polyimide cover film or an epoxy resin prepreg; The double-sided FPC substrate is made of polyimide (PI), polyester (PET) or liquid crystal polymer (LCP), and the total thickness of the substrate is 25-50 μm; The VIP hole conduction resistance is ≤0.5Ω, the hole copper density is ≥98%, and the bonding strength between the hole wall and the plating is ≥1.5N / mm; After step (c) is completed, an X-ray inspection is performed to ensure that the lower aperture is filled without voids, and that the upper aperture is allowed to have a concave depth of ≤5 μm without cracks.

6. A novel double-sided FPC board VIP hole manufacturing process according to claim 1, characterized in that: The laser drilling equipment comprises a machine base (1), a laser (2) is provided at the upper end of the machine base (1), an optical system for focusing, expanding and collimating the laser beam is provided inside the laser (2), a connecting seat (3) is fixedly installed outside the laser (2), the lower end of the connecting seat (3) is slidably arranged on the machine base (1), a spring (4) is fixedly connected between the machine base (1) and the connecting seat (3), and two symmetrically distributed supporting plates (5) are fixedly installed on the top of the machine base (1).

7. A novel double-sided FPC board VIP hole manufacturing process according to claim 6, characterized in that: A driving component (6) is provided in the machine base (1), a connecting shaft (7) is fixedly installed at the bottom of the driving component (6), and the connecting shaft (7) is rotatably installed in the machine base (1). A servo motor (8) is fixedly installed on the machine base (1), and the output shaft of the servo motor (8) is fixedly connected to the connecting shaft (7). A laser protection plate (9) is provided at the upper end of the machine base (1), and the laser protection plate (9) is located below the laser (2). One end of the laser protection plate (9) is inserted into the machine base (1) and can slide horizontally, and also includes a through-hole (10), and the through-hole (10) passes through the laser protection plate (9) and the machine base (1) from top to bottom.

8. A novel double-sided FPC board VIP hole manufacturing process according to claim 7, characterized in that: The bottom of the driving component (6) is hinged with a laser reflector plate (11), and both sides of the driving component (6) are penetrated by a limit block (12), and the limit block (12) is an iron block. One end of the limit block (12) can be inserted into the hinge shaft of the laser reflector plate (11), and an elastic sheet (13) is fixedly connected between the limit block (12) and the driving component (6). Electromagnets (14) are fixedly installed on both sides of the driving component (6), and the electromagnets (14) are arranged toward the limit block (12). A support rod (15) is placed on the machine base (1), and the lower end of the support rod (15) is hollow and one end is connected to the outside world. One end of the support rod (15) is fixedly installed. A heat conducting member (16) is provided, wherein a hole for the laser beam to pass through is provided on the heat conducting member (16), one end of the heat conducting member (16) extends into the inner cavity of the lower end of the support rod (15), a piston (17) is slidably provided in the inner cavity of the lower end of the support rod (15), and the piston (17) divides the inner cavity of the lower end of the support rod (15) into two independent spaces, an elastic member (18) is fixedly connected between the piston (17) and the heat conducting member (16), a travel switch (19) is provided on one side of the piston (17), and the travel switch (19) is used to control the on-off of the circuit of the electromagnet (14), and the independent space on the side of the piston (17) facing the heat conducting member (16) is filled with a thermosensitive gas.

9. A novel double-sided FPC board VIP hole manufacturing process according to claim 8, characterized in that: The outer shell of the heat-conducting element (16) is provided with a heat-insulating sleeve (20), the inner side of the heat-insulating sleeve (20) is open, and the heat-conducting element (16) is in contact with the outside air through the inner side opening of the heat-insulating sleeve (20).

10. A novel double-sided FPC board VIP hole manufacturing process according to claim 8, characterized in that: A vertical pipe (21) is fixedly mounted on the machine base (1), and the vertical pipe (21) is made of aluminum alloy. The friction coefficient of the inner wall of the vertical pipe (21) increases in sections from top to bottom. The lower end of the vertical pipe (21) is opened. A fan (22) facing the inner hole of the heat conducting member (16) is mounted on the machine base (1), and a driving mechanism is installed between the fan shaft of the fan (22) and the vertical pipe (21), and the driving mechanism is used to drive the fan shaft of the fan (22) to rotate.

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